Unravelling the effects of melt depletion and secondary infiltration on mantle Re-Os isotopes beneath the French Massif Central

NASA Astrophysics Data System (ADS)

Harvey, J.; Gannoun, A.; Burton, K. W.; Schiano, P.; Rogers, N. W.; Alard, O.

2010-01-01

Spinel lherzolite xenoliths from Mont Briançon, French Massif Central, retain evidence for multiple episodes of melt depletion and melt/fluid infiltration (metasomatism). Evidence for primary melt depletion is still preserved in the co-variation of bulk-rock major elements (MgO 38.7-46.1 wt.%; CaO 0.9-3.6 wt.%), and many samples yield unradiogenic bulk-rock Os isotope ratios ( 187Os/ 188Os = 0.11541-0.12626). However, many individual xenoliths contain interstitial glasses and melt inclusions that are not in equilibrium with the major primary minerals. Incompatible trace element mass balance calculations demonstrate that metasomatic components comprise a significant proportion of the bulk-rock budget for these elements in some rocks, ranging to as much as 25% of Nd and 40% of Sr Critically, for Re-Os geochronology, melt/fluid infiltration is accompanied by the mobilisation of sulfide. Consequently, bulk-rock isotope measurements, whether using lithophile (e.g. Rb-Sr, Sm-Nd) or siderophile (Re-Os) based isotope systems, may only yield a perturbed and/or homogenised average of these multiple events. Osmium mass balance calculations demonstrate that bulk-rock Os in peridotite is dominated by contributions from two populations of sulfide grain: (i) interstitial, metasomatic sulfide with low [Os] and radiogenic 187Os/ 188Os, and (ii) primary sulfides with high [Os] and unradiogenic 187Os/ 188Os, which have been preserved within host silicate grains and shielded from interaction with transient melts and fluid. The latter can account for >97% of bulk-rock Os and preserve geochronological information of the melt from which they originally precipitated as an immiscible liquid. The Re-depletion model ages of individual primary sulfide grains preserve evidence for melt depletion beneath the Massif Central from at least 1.8 Gyr ago despite the more recent metasomatic event(s).

Petrology of Impact-Melt Rocks at the Chicxulub Multiring Basin, Yucatan, Mexico

NASA Technical Reports Server (NTRS)

Schuraytz, Benjamin C.; Sharpton, Virgil L.; Marin, Luis E.

1994-01-01

Compositions and textures of melt rocks from the upper part of the Chicxulub structure are typical of melt rocks at other large terrestrial impact structures. Apart from variably elevated iridium concentrations (less than 1.5 to 13.5 +/- 0.9 ppb) indicating nonuniform dissemination of a meteoritic component, bulk rock and phenocryst compositions imply that these melt rocks were derived exclusively from continental crust and platform-sediment target lithologies. Modest differences in bulk chemistry among samples from wells located approximately 40 km apart suggest minor variations in relative contributions of these target lithologies to the melts. Subtle variations in the compositions of early-formed pyroxene and plagioclase also support minor primary differences in chemistry between the melts. Evidence for pervasive hydrothermal alteration of the porous mesostasis includes albite, K-feldspar, quartz, epidote, chlorite, and other phyllosilicates, as well as siderophile element-enriched sulfides, suggesting the possibility that Chicxulub, like Sudbury, may host important ore deposits.

Preliminary results of thermal conductivity and elastic wave velocity measurements of various rock samples collected from outcrops in hanging wall of the Alpine Fault

NASA Astrophysics Data System (ADS)

Lin, W.; Tadai, O.; Shigematsu, N.; Nishikawa, O.; Mori, H.; Townend, J.; Capova, L.; Saito, S.; Kinoshita, M.

2015-12-01

The Alpine Fault is a mature active fault zone likely to rupture in the near future and DFDP aims to measure physical and chemical conditions within the fault. DFDP-2B borehole was drilled into hanging wall of the Alpine Fault. Downhole temperature measurements carried out in DFDP-2B borehole showed that the geothermal gradient in the hanging wall of the fault is very high, likely reaching to 130-150 °C/km (Sutherland et al., 2015 AGU Fall Meeting). To explain this abnormal feature, the determination of thermal properties of all the rock types in the hanging wall of the Alpine Fault is essential. To measure thermal properties and elastic wave velocities, we collected six typical rock block samples from outcrops in Stony creek and Gaunt creek. These include ultramylonite, mylonite, muscovite schist, garnet amphibolite, protomylonite and schist, which are representative of the hanging wall of the Alpine Fault. Their wet bulk densities are 2.7 - 2.8 g/cm3, and porosities are 1.4 - 3.0%. We prepared a pair of 4 cm cube specimens of each rock type with one flat plane parallel to the foliation. First, we measured thermal conductivity by the transient plane heat source (hot disc) method in a bulk mode, i.e. to deal with the rock as an isotropic material. However, several samples have clearly visible foliation and are likely to be anisotropic. Thus, the data measured in bulk mode provided an average value of the rocks in the range of approximately 2.4 - 3.2 W/mK. The next step will be to measure thermal conductivity in an anisotropic mode. We also measured P wave velocity (Vp) using the same samples, but in two directions, i.e. parallel and perpendicular to the foliation, respectively. Our preliminary results suggested that Vp is anisotropic in all the six rocks. Generally, Vp parallel to foliation is higher than that in the perpendicular direction. Vp in the parallel direction ranged in 5.5 - 6.0 km/s, whereas in the perpendicular direction it was 4.4 - 5.5 km/s. We thank the PIs and onsite staffs of the DFDP-2 project for their helps to collecting rock samples, and the financial support by JSPS (Japan-New Zealand Joint Research Program).

Treated and untreated rock dust: Quartz content and physical characterization.

PubMed

Soo, Jhy-Charm; Lee, Taekhee; Chisholm, William P; Farcas, Daniel; Schwegler-Berry, Diane; Harper, Martin

2016-11-01

Rock dusting is used to prevent secondary explosions in coal mines, but inhalation of rock dusts can be hazardous if the crystalline silica (e.g., quartz) content in the respirable fraction is high. The objective of this study is to assess the quartz content and physical characteristics of four selected rock dusts, consisting of limestone or marble in both treated (such as treatment with stearic acid or stearates) and untreated forms. Four selected rock dusts (an untreated and treated limestone and an untreated and treated marble) were aerosolized in an aerosol chamber. Respirable size-selective sampling was conducted along with particle size-segregated sampling using a Micro-Orifice Uniform Deposit Impactor. Fourier Transform Infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) analyses were used to determine quartz mass and particle morphology, respectively. Quartz percentage in the respirable dust fraction of untreated and treated forms of the limestone dust was significantly higher than in bulk samples, but since the bulk percentage was low the enrichment factor would not have resulted in any major change to conclusions regarding the contribution of respirable rock dust to the overall airborne quartz concentration. The quartz percentage in the marble dust (untreated and treated) was very low and the respirable fractions showed no enrichment. The spectra from SEM-EDX analysis for all materials were predominantly from calcium carbonate, clay, and gypsum particles. No free quartz particles were observed. The four rock dusts used in this study are representative of those presented for use in rock dusting, but the conclusions may not be applicable to all available materials.

Estimates of olivine-basaltic melt electrical conductivity using a digital rock physics approach

NASA Astrophysics Data System (ADS)

Miller, Kevin J.; Montési, Laurent G. J.; Zhu, Wen-lu

2015-12-01

Estimates of melt content beneath fast-spreading mid-ocean ridges inferred from magnetotelluric tomography (MT) vary between 0.01 and 0.10. Much of this variation may stem from a lack of understanding of how the grain-scale melt geometry influences the bulk electrical conductivity of a partially molten rock, especially at low melt fraction. We compute bulk electrical conductivity of olivine-basalt aggregates over 0.02 to 0.20 melt fraction by simulating electric current in experimentally obtained partially molten geometries. Olivine-basalt aggregates were synthesized by hot-pressing San Carlos olivine and high-alumina basalt in a solid-medium piston-cylinder apparatus. Run conditions for experimental charges were 1.5 GPa and 1350 °C. Upon completion, charges were quenched and cored. Samples were imaged using synchrotron X-ray micro-computed tomography (μ-CT). The resulting high-resolution, 3-dimensional (3-D) image of the melt distribution constitutes a digital rock sample, on which numerical simulations were conducted to estimate material properties. To compute bulk electrical conductivity, we simulated a direct current measurement by solving the current continuity equation, assuming electrical conductivities for olivine and melt. An application of Ohm's Law yields the bulk electrical conductivity of the partially molten region. The bulk electrical conductivity values for nominally dry materials follow a power-law relationship σbulk = Cσmeltϕm with fit parameters m = 1.3 ± 0.3 and C = 0.66 ± 0.06. Laminar fluid flow simulations were conducted on the same partially molten geometries to obtain permeability, and the respective pathways for electrical current and fluid flow over the same melt geometry were compared. Our results indicate that the pathways for flow fluid are different from those for electric current. Electrical tortuosity is lower than fluid flow tortuosity. The simulation results are compared to existing experimental data, and the potential influence of volatiles and melt films on electrical conductivity of partially molten rocks is discussed.

Ion microprobe mass analysis of plagioclase from 'non-mare' lunar samples

NASA Technical Reports Server (NTRS)

Meyer, C., Jr.; Anderson, D. H.; Bradley, J. G.

1974-01-01

The ion microprobe was used to measure the composition and distribution of trace elements in lunar plagioclase, and these analyses are used as criteria in determining the possible origins of some nonmare lunar samples. The Apollo 16 samples with metaclastic texture and high-bulk trace-element contents contain plagioclase clasts with extremely low trace-element contents. These plagioclase inclusions represent unequilibrated relicts of anorthositic, noritic, or troctolitic rocks that have been intermixed as a rock flour into the KREEP-rich matrix of these samples. All of the plagioclase-rich inclusions which were analyzed in the KREEP-rich Apollo 14 breccias were found to be rich in trace elements. This does not seem to be consistent with the interpretation that the Apollo 14 samples represent a pre-Imbrium regolith, because such an ancient regolith should have contained many plagioclase clasts with low trace-element contents more typical of plagioclase from the pre-Imbrium crust. Ion-microprobe analyses for Ba and Sr in large plagioclase phenocrysts in 14310 and 68415 are consistent with the bulk compositions of these rocks and with the known distribution coefficients for these elements. The distribution coefficient for Li (basaltic liquid/plagioclase) was measured to be about 2.

The Surface Chemical Composition of Lunar Samples and Its Significance for Optical Properties

NASA Technical Reports Server (NTRS)

Gold, T.; Bilson, E.; Baron, R. L.

1976-01-01

The surface iron, titanium, calcium, and silicon concentration in numerous lunar soil and rock samples was determined by Auger electron spectroscopy. All soil samples show a large increase in the iron to oxygen ratio compared with samples of pulverized rock or with results of the bulk chemical analysis. A solar wind simulation experiment using 2 keV energy alpha -particles showed that an ion dose corresponding to approximately 30,000 years of solar wind increased the iron concentration on the surface of the pulverized Apollo 14 rock sample 14310 to the concentration measured in the Apollo 14 soil sample 14163, and the albedo of the pulverized rock decreased from 0.36 to 0.07. The low albedo of the lunar soil is related to the iron + titanium concentration on its surface. A solar wind sputter reduction mechanism is discussed as a possible cause for both the surface chemical and optical properties of the soil.

Endolithic Boring Enhance the Deep-sea Carbonate Lithification on the Southwest Indian Ridge

NASA Astrophysics Data System (ADS)

Peng, X.; Xu, H.

2017-12-01

Deep-sea carbonates represent an important type of sedimentary rock due to their effect on the composition of upper oceanic crust and their contribution to deep-sea geochemical cycles. However, the lithification of deep-sea carbonates at the seafloor has remained a mystery for many years. A large lithified carbonate area, characterized by thriving benthic faunas and tremendous amount of endolithic borings, was discovered in 2008, blanketed on the seafloor of ultraslow spreading Southwest Indian Ridge (SWIR). Macrofaunal inhabitants including echinoids, polychaetes, gastropods as well as crustaceans, are abundant in the sample. The most readily apparent feature of the sample is the localized enhancement of density around the borings. The boring features of these carbonate rocks and factors that may enhance deep-sea carbonate lithification are reported. The δ13CPDB values of 46 bulk samples are -0.37 to 1.86‰, while these samples have a relatively narrow δ18OPDB range of 1.35 to 3.79‰. The bulk δ13CPDB values of chalk and gray excrements are positively correlated with bulk δ18OPDB values (r = 0.91) (Fig. 8), which reflects that endolithic boring is possibly a critical factor influence the lithification. We suggest that active boring may trigger the dissolution of the original calcite and thus accelerate deep-sea carbonate lithification on mid-ocean ridges. Our study reports an unfamiliar phenomenon of non-burial carbonate lithification and interested by the observation that it is often associated with boring feature. These carbonate rocks may provide a novel mechanism for deep-sea carbonate lithification at the deep-sea seafloor and also illuminate the geological and biological importance of deep-sea carbonate rocks on mid-ocean ridges.

The Chemical Structure of the Hawaiian Mantle Plume

NASA Astrophysics Data System (ADS)

Ren, Z.; Hirano, N.; Hirata, T.; Takahashi, E.; Ingle, S.

2004-12-01

Numerous geochemical studies of Hawaiian basaltic lavas have shown that the Hawaiian mantle plume is isotopically heterogeneous. However, the distribution and scale of these heterogeneities remain unknown. This is essentially due to the complex interactions created by melting a heterogeneous source, subsequent aggregation of the melts on their way to the surface, and mixing that takes place in shallow magma chambers prior to eruption. In sum, the measured compositions of bulk lavas may represent only _eaverage_f compositions that do not fully reflect the complexity of either the mantle source heterogeneity and/or chemical structure. Melt inclusions, or samples of the local magma frozen in olivine phenocrysts during their formation, are better at recording the complex magmatic history than are the bulk samples. Here, we report major and trace element compositions of olivine-hosted melt inclusions from submarine Haleakala lavas that were collected by 2001-2002 JAMSTEC cruises measured by EPMA and LA-ICP-MS after homogenization at 1250° C, QFM for 20min. Melt inclusions from the submarine Hana Ridge (Haleakala volcano) show large ranges in CaO/Al2O3 (0.92-1.50), TiO2/Na2O (0.79-1.60) and Sr/Nb (14.56-36.60), Zr/Nb (6.48-16.95), ranging from Kilauea-like to Mauna Loa-like compositions within separately-sampled lavas as well as in a single host lava sample. Bulk rocks geochemistry shows that major element composition and trace element ratios such as Zr/Nb, Sr/Nb (Ren et al., 2004a, in press, J. Petrol.) together with Pb, Nd and Sr isotopic ratios (Ren et al., 2004b, submitted to J. Petrol.) of Haleakala shield volcano also display systematic compositional variation changing from a Kilauea-like in the submarine Hana Ridge (main shield stage) to Kilauea-Mauna Loa-like in the subaerial Honomanu stage (late shield stage, data from Chen and Frey, 1991). Some of the compositional variations in melt inclusions in single rocks are wider range than over-all variation observed in bulk rocks. It is important that both Kilauea-like and Mauna Loa-like compositions co-exist in melt inclusions in single submarine Hana Ridge rocks which are identified as Kilauea-like based on bulk geochemistry. These observations are inconsistent with the current interpretation that magma compositions are controlled by concentric zonation of the Hawaiian mantle plume (e.g. Kea component and Loa component), manifested as the Kea trend and the Loa trend volcanoes (e.g. Hauri, 1996; Lassiter et al., 1996). Our new data from olivine-hosted melt inclusions imply that the chemical structure of the Hawaiian mantle plume is significantly more complicated than previously modeled and the length-scale of chemical heterogeneity must be remarkably smaller than estimated based on bulk rock geochemistry.

The determination of the acoustic parameters of volcanic rocks from compressional velocity measurements

USGS Publications Warehouse

Carroll, R.D.

1969-01-01

A statistical analysis was made of the relationship of various acoustic parameters of volcanic rocks to compressional wave velocities for data obtained in a volcanic region in Nevada. Some additional samples, chiefly granitic rocks, were also included in the study to extend the range of parameters and the variety of siliceous rock types sampled. Laboratory acoustic measurements obtained on 62 dry core samples were grouped with similar measurements obtained from geophysical logging devices at several depth intervals in a hole from which 15 of the core samples had been obtained. The effects of lithostatic and hydrostatic load on changing the rock acoustic parameters measured in the hole were noticeable when compared with the laboratory measurements on the same core. The results of the analyses determined by grouping all of the data, however, indicate that dynamic Young's, shear and bulk modulus, shear velocity, shear and compressional characteristic impedance, as well as amplitude and energy reflection coefficients may be reliably estimated on the basis of the compressional wave velocities of the rocks investigated. Less precise estimates can be made of density based on the rock compressional velocity. The possible extension of these relationships to include many siliceous rocks is suggested. ?? 1969.

Northwest Africa 8535 and Northwest Africa 10463: New Insights into the Angrite Parent Body

NASA Technical Reports Server (NTRS)

Santos, A. R.; Agee, C. B.; Shearer, C. K.; McCubbin, F. M.

2016-01-01

The angrite meteorites are valuable samples of igneous rocks formed early in Solar System history (approx.4.56 Ga, summarized in [1]). This small meteorite group (approx.24 individually named specimens) consists of rocks with somewhat exotic mineral compositions (e.g., high Ca olivine, Al-Ti-bearing diopside-hedenbergite, calcium silico-phosphates), resulting in exotic bulk rock compositions. These mineral assemblages remain fairly consistent among angrite samples, which suggests they formed due to similar processes from a single mantle source. There is still debate over the formation process for these rocks (see summary in [1]), and analysis of additional angrite samples may help to address this debate. Toward this end, we have begun to study two new angrites, Northwest Africa 8535, a dunite, and Northwest Africa 10463, a basaltic angrite.

Empirical relations of rock properties of outcrop and core samples from the Northwest German Basin for geothermal drilling

NASA Astrophysics Data System (ADS)

Reyer, D.; Philipp, S. L.

2014-09-01

Information about geomechanical and physical rock properties, particularly uniaxial compressive strength (UCS), are needed for geomechanical model development and updating with logging-while-drilling methods to minimise costs and risks of the drilling process. The following parameters with importance at different stages of geothermal exploitation and drilling are presented for typical sedimentary and volcanic rocks of the Northwest German Basin (NWGB): physical (P wave velocities, porosity, and bulk and grain density) and geomechanical parameters (UCS, static Young's modulus, destruction work and indirect tensile strength both perpendicular and parallel to bedding) for 35 rock samples from quarries and 14 core samples of sandstones and carbonate rocks. With regression analyses (linear- and non-linear) empirical relations are developed to predict UCS values from all other parameters. Analyses focus on sedimentary rocks and were repeated separately for clastic rock samples or carbonate rock samples as well as for outcrop samples or core samples. Empirical relations have high statistical significance for Young's modulus, tensile strength and destruction work; for physical properties, there is a wider scatter of data and prediction of UCS is less precise. For most relations, properties of core samples plot within the scatter of outcrop samples and lie within the 90% prediction bands of developed regression functions. The results indicate the applicability of empirical relations that are based on outcrop data on questions related to drilling operations when the database contains a sufficient number of samples with varying rock properties. The presented equations may help to predict UCS values for sedimentary rocks at depth, and thus develop suitable geomechanical models for the adaptation of the drilling strategy on rock mechanical conditions in the NWGB.

The petrology and geochemistry of Miller Range 05035: A new lunar gabbroic meteorite

NASA Astrophysics Data System (ADS)

Joy, K. H.; Crawford, I. A.; Anand, M.; Greenwood, R. C.; Franchi, I. A.; Russell, S. S.

2008-08-01

Miller Range (MIL) 05035 is a lunar gabbroic meteorite. The mineralogy, Fe/Mn ratios in olivine and pyroxene, bulk-rock chemical composition and the bulk oxygen isotope values (δ 17O = 2.86-2.97‰ and δ 18O = 5.47-5.71‰) are similar to those of other mare basalts, and are taken as supporting evidence for a lunar origin for this meteorite. The sample is dominated by pyroxene grains (54-61% by area mode of thin section) along with large plagioclase feldspar (25-36% by mode) and accessory quartz, ilmenite, spinel, apatite and troilite. The bulk-rock major element composition of MIL 05035 indicates that the sample has a very low-Ti (VLT) to low-Ti lunar heritage (we measure bulk TiO 2 to be 0.9 Wt.%) and has low bulk incompatible trace element (ITE) concentrations, akin to samples from the VLT mare basalt suite. To account for these geochemical characteristics we hypothesize that MIL 05035's parental melt was derived from a mantle region dominated by early cumulates of the magma ocean (comprised principally of olivine and orthopyroxene). MIL 05035 is likely launch paired with the Asuka-881757 and Yamato-793169 basaltic lunar meteorites and the basaltic regolith breccia MET 01210. This group of meteorites (Y/A/M/M) therefore may be a part of a stratigraphic column consisting of an upper regolith environment underlain by a coarsening downwards basalt lava flow.

Origin of heavy Fe isotope compositions in high-silica igneous rocks: A rhyolite perspective

NASA Astrophysics Data System (ADS)

Du, De-Hong; Wang, Xiao-Lei; Yang, Tao; Chen, Xin; Li, Jun-Yong; Li, Weiqiang

2017-12-01

The origin of heavy Fe isotope compositions in high-silica (>70 wt% SiO2) igneous rocks remains a highly controversial topic. Considering that fluid exsolution in eruptive rocks is more straight-forward to constrain than in plutonic rocks, this study addresses the problem of Fe isotope fractionation in high-silica igneous rocks by measuring Fe isotope compositions of representative rhyolitic samples from the Neoproterozoic volcanic-sedimentary basins in southern China and the Triassic Tu Le Basin in northern Vietnam. The samples show remarkably varied δ56FeIRMM014 values ranging from 0.05 ± 0.05‰ to 0.55 ± 0.05‰, which is among the highest values reported from felsic rocks. The extensional tectonic setting and short melt residence time in magma chambers for the studied rhyolites rule out Soret diffusion and thermal migration processes as causes of the high δ56Fe values. Effects of volcanic degassing and fluid exsolution on bulk rock δ56Fe values for the rhyolites are also assessed using bulk rock geochemical indicators and Rayleigh fractionation models, and these processes are found to be insufficient to produce resolvable changes in Fe isotope compositions of the residual melt. The most probable mechanism accounting for heavy Fe isotope compositions in the high-silica rhyolites is narrowed down to fractional crystallization processes in the magma before rhyolite eruption. Removal of isotopically light Fe-bearing minerals (i.e. ulvöspinel-rich titanomagnetite, ilmenite and biotite) is proposed as the main cause of Fe isotope variation in silicic melts during magmatic evolution. This study implies that crystal fractionation is the dominant mechanism that controls Fe isotope fractionation in eruptive rocks and Fe isotopes could be used to study magmatic differentiation of high-silica magmas.

Selected physical properties of rocks from the Baid al Jimalah West tungsten deposit, Kingdom of Saudi Arabia, and recommendations for geophysical surveys

USGS Publications Warehouse

Gettings, M.E.

1983-01-01

Bulk density and magnetic susceptibility of 11 outcrop samples representing the Proterozoic lithologic units at the Baid al Jimalah West tungsten deposit, Kingdom of Saudi Arabia were measured. Induced polarization response, apparent resistivity, and electromagnetic conductivity were determined for four specimens of the sample suite. Measurements show that there is a negative density contrast of about -0.17 g-cm^-3 between metasedimentary rocks of the Murdama group and the Bald al Jimalah graaite and that this contrast decreases with increasing mineralization of the granite. Similarly, the bulk magnetic susceptibility of the granite is about one-third that of the Murdama rocks for this sample suite; however, magnetic susceptibility increases with increasing mineralization in the granite specimens. Electromagnetic conductivities are uniformly low, in part because the specimens are weathered, but probably also because intense silicification accompanies the mineralization. Induced polarization chargeability increases in the granitic specimens with increasing mineralization and reflects higher percentages of sulfide minerals. Chargeability for the mineralized rocks is about four times higher than for the Murdama host rocks, and apparent resistivity values are about one-fifth the values of host rocks. Based on these results, it is recommended that during reconnaissance exploration of the area 15 detailed high-precision gravity profiles at 10 m to 50 m station spacing and eight induced polarization dipole-dipole profiles at 25 m dipole spacing and maximum 'n' of 6 be measured. To help define subsurface structure, a high-precision, ground-magnetic survey (map at 2-gamma contour interval) and a four-channel gamma ray spectrometric survey on a 25x50 m grid covering the area of the profiles are recommended.

High-resolution Campanian-Maastrichtian carbon and oxygen stable isotopes of bulk-rock and skeletal components: palaeoceanographic and palaeoenvironmental implications for the Boreal shelf sea

NASA Astrophysics Data System (ADS)

Wilmsen, Markus; Niebuhr, Birgit

2017-03-01

A high-resolution latest Early Campanian to Early Maastrichtian carbon and oxygen stable isotope record from the northern German Boreal shelf sea based on 537 analyses of co-occurring belemnites, brachiopods, inoceramids, oysters, and bulk rock samples is presented. All samples are precisely related to their stratigraphic, systematic and facies backgrounds and form an integrated, nearly 10-myr-long dataset with considerable palaeoenvironmental and palaeoceanographical implications. Petrographic studies indicate that low-magnesium calcitic coccoliths and calcispheres (i.e., planktic carbonate) predominate the bulk-rock data (marl-limestone rhythmites and chalks), thus representing a sea-surface water signal, and that only minor diagenetic alteration of the carbonate muds took place. Based on TL and CL microscopy, the investigated belemnites are extraordinarily well preserved, which may in part be explained by their early diagenetic surficial silicification (container effect), while the other macroinvertebrate groups are all less well preserved. The (plankton-dominated) δ13C values of the marl-limestone rhythmites and chalks (+1.1 to +2.5 ‰), recording a surface water signal, compare well with the δ18C data of inoceramids while δ13Cbrach. values (+1.5 to +3.0 ‰) are heavier than the bulk rock data. The large variation in the δ13Cbel. (-0.1 to +3.6 ‰) is attributed to isotopic disequilibrium of the biogenic carbonate formed by the belemnite animal. The bulk rock δ18O values show a remarkable low scatter, supporting petrographic observation of only minor diagenetic stabilisation/cementation, and can be approximated with northern German shelf sea-surface temperatures of ca. 20°C for the Late Campanian (ca. -2 ‰ δ18O), being slightly cooler during the Early Maastrichtian. The δ18O values of the belemnite rostra are even less variable and quite rich in heavier 18O (-0.7 to +0.6 with a mean of -0.1 ‰ δ18Obel.) in comparison to bulk rock and other skeletal components. Based on their excellent microstructural preservation and non-luminescence, we conclude that the belemnite rostra are diagenetically unaltered and have preserved the primary δ18O signal of ambient seawater (12 ± 2°C). In the absence of any indication for migration from cooler water masses and evidence for authochtonous populations we assume that the belemnites of the genera Belemnitella and Belemnella lived as nektobenthos near the sea-floor and thus record the temperature of the bottom mixed layer of the seasonally weakly stratified north German shelf sea at water depths of 100 to 150 m; the temperature gradient was thus 12.5-18.75 m/1°C. A conspicuous latest Campanian cooling event is evident in both sea-surface and bottom-water temperatures. The δ18O values of nearly all investigated benthic fossils lie between the isotope values of pristine belemnites and bulk rock, and, therefore, should be used for palaeotemperature reconstructions only with great care.

Paleomagnetism of a primitive achondrite parent body: The acapulcoite-lodranites

NASA Astrophysics Data System (ADS)

Schnepf, N. R.; Weiss, B. P.; Andrade Lima, E.; Fu, R. R.; Uehara, M.; Gattacceca, J.; Wang, H.; Suavet, C. R.

2014-12-01

Primitive achondrites are a recently recognized meteorite grouping with textures and compositions intermediate between unmelted meteorites (chondrites) and igneous meteorites (achondrites). Their existence demonstrates prima facie that some planetesimals only experienced partial rather than complete melting. We present the first paleomagnetic measurements of acapulcoite-lodranite meteorites to determine the existence and intensity of ancient magnetic fields on their parent body. Our paleomagnetic study tests the hypothesis that their parent body had an advecting metallic core, with the goal of providing one of the first geophysical constraints on its large-scale structure and the extent of interior differentiation. In particular, by analyzing samples whose petrologic textures require an origin on a partially differentiated body, we will be able to critically test a recent proposal that some achondrites and chondrite groups could have originated on a single body (Weiss and Elkins-Tanton 2013). We analyzed samples of the meteorites Acapulco and Lodran. Like other acapulcoites and lodranites, these meteorites are granular rocks containing large (~0.1-0.3 mm) kamacite and taenite grains along with similarly sized silicate crystals. Many silicate grains contain numerous fine (1-10 μm) FeNi metal inclusions. Our compositional measurements and rock magnetic data suggest that tetrataenite is rare or absent. Bulk paleomagnetic measurements were done on four mutually oriented bulk samples of Acapulco and one bulk sample of Lodran. Alternating field (AF) demagnetization revealed that the magnetization of the bulk samples is highly unstable, likely due to the large (~0.1-0.3 mm) interstitial kamacite grains throughout the samples. To overcome this challenge, we are analyzing individual ~0.2 mm mutually oriented silicate grains extracted using a wire saw micromill. Preliminary SQUID microscopy measurements of a Lodran silicate grain suggest magnetization stable to AF levels of at least 25-40 mT.

The Canadian space agency planetary analogue materials suite

NASA Astrophysics Data System (ADS)

Cloutis, Edward A.; Mann, Paul; Izawa, Matthew R. M.; Applin, Daniel M.; Samson, Claire; Kruzelecky, Roman; Glotch, Timothy D.; Mertzman, Stanley A.; Mertzman, Karen R.; Haltigin, Timothy W.; Fry, Christopher

2015-12-01

The Canadian Space Agency (CSA) recently commissioned the development of a suite of over fifty well-characterized planetary analogue materials. These materials are terrestrial rocks and minerals that are similar to those known or suspected to occur on the lunar or martian surfaces. These include: Mars analogue sedimentary, hydrothermal, igneous and low-temperature alteration rock suites; lunar analogue basaltic and anorthositic rock suites; and a generic impactite rock suite from a variety of terrestrial impact structures. Representative thin sections of the materials have been characterized by optical microscopy and electron probe microanalysis (EPMA). Reflectance spectra have been collected in the ultraviolet, visible, near-infrared and mid-infrared, covering 0.2-25 μm. Thermal infrared emission spectra were collected from 5 to 50 μm. Raman spectra with 532 nm excitation, and laser-induced fluorescence spectra with 405 nm excitation were also measured. Bulk chemical analysis was carried out using X-ray fluorescence, with Fe valence determined by wet chemistry. Chemical and mineralogical data were collected using a field-portable Terra XRD-XRF instrument similar to CheMin on the MSL Curiosity rover. Laser-induced breakdown spectroscopy (LIBS) data similar to those measured by ChemCam on MSL were collected for powdered samples, cut slab surfaces, and as depth profiles into weathered surfaces where present. Three-dimensional laser camera images of rock textures were collected for selected samples. The CSA intends to make available sample powders (<45 μm and 45-1000 μm grain sizes), thin sections, and bulk rock samples, and all analytical data collected in the initial characterisation study to the broader planetary science community. Aiming to complement existing planetary analogue rock and mineral libraries, the CSA suite represents a new resource for planetary scientists and engineers. We envision many potential applications for these materials in the definition, development and testing of new analytical instruments for use in planetary missions, as well as possible calibration and ground-truthing of remote sensing data sets. These materials may also be useful as reference materials for cross-calibration between different instruments and laboratories. Comparison of the analytical data for selected samples is useful for highlighting the relative strengths, weaknesses and synergies of different analytical techniques.

Analysis of terrestrial and Martian volcanic compositions using thermal emission spectroscopy

NASA Astrophysics Data System (ADS)

Wyatt, Michael Bruce

2002-11-01

This dissertation comprises four separate parts that address the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) investigation objective of determining and mapping the composition and distribution of surface minerals and rocks on Mars from orbit. In Part 1, laboratory thermal infrared spectra (5 25 μm, at 2 cm-1 spectral sampling), deconvolved modal mineralogies, and derived mineral and bulk rock chemistries of basalt, basaltic andesite, andesite, and dacite were used to evaluate and revise volcanic rock classification schemes. Multiple steps of classification were required to distinguish volcanic rocks, reflecting the mineralogic diversity and continuum of compositions that exists in volcanic rock types. In Part 2, laboratory spectral data were convolved to TES 10 cm-1 sampling to ascertain whether adequate results for volcanic rock classification can be obtained with lower spectral resolution, comparable to that obtained from Mars orbit. Modeled spectra, modeled modal mineralogies, and derived bulk rock chemistries at low (10 cm-1) spectral sampling provide good matches to measured and high (2 cm-1) spectral sampling modeled values. These results demonstrate the feasibility of using similar techniques and classification schemes for the interpretation of terrestrial laboratory samples and TES-resolution data. In Part 3, new deconvolved mineral abundances from TES data and terrestrial basalts using a spectral end-member set representing minerals common in unaltered and low-temperature aqueously altered basalts were used to reclassify martian surface lithologies. The new formulations maintain the dominance of unaltered basalt in the southern highlands, but indicate the northern lowlands can be interpreted as weathered basalt. The coincidence between locations of altered basalt and a previously suggested northern ocean basin implies that lowland plains materials may be basalts altered under submarine conditions and/or weathered basaltic sediment transported into this depocenter. In Part 4, results from the previous parts are applied to examine the distribution of TES-derived surface compositions in the Oxia Palus region on Mars through high-spatial resolution mapping. Features of interest within Oxia Palus include volcanic/sedimentary materials in southern Acidalia Planitia, low-albedo crater floors and wind streaks in western Arabia Terra, and channel outflow deposits of the Mars Pathfinder (MP) landing site.

Process parameters, orientation, and functional properties of melt-processed bulk Y-Ba-Cu-O superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zakharchenko, I.V.; Terryll, K.M.; Rao, K.V.

1995-03-01

This study compared the microstructure, texturing, and functional properties (critical currents) of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}-based bulk pellets that were prepared by the quench-melt-growth-process (QMGP), melt-textured growth (MTG), and conventional solid-state reaction (SSR) approaches. Using two X-ray diffraction (XRD) methods, {theta}-2{theta}, and rocking curves, the authors found that the individual grains of two melt-processed pellets exhibited remarkable preferred orientational alignment (best rocking curve width = 3.2{degree}). However, the direction of the preferred orientation among the grains was random. Among the three types of bulk materials studied, the QMGP sample was found to have the best J{sub c} values, {approx} 4,500more » A/cm{sup 2} at 77 K in a field of 2 kG, as determined from SQUID magnetic data.« less

Characteristics of amorphous kerogens fractionated from terrigenous sedimentary rocks

NASA Astrophysics Data System (ADS)

Suzuki, Noriyuki

1984-02-01

A preliminary attempt to fractionate amorphous kerogens from terrigenous bulk kerogen by a benzene-water two phase partition method under acidic condition was made. Microscopic observation revealed that amorphous kerogens and structured kerogens were fractionated effectively by this method. Characteristics of the amorphous and structured kerogens fractionated by this method were examined by some chemical analyses and compared with those of the bulk kerogen and humic acid isolated from the same rock sample (Haizume Formation, Pleistocene, Japan). The elemental and infrared (IR) analyses showed that the amorphous kerogen fraction had the highest atomic H/C ratio and the lowest atomic N/C ratio and was the richest in aliphatic structures and carbonyl and carboxyl functional groups. Quantities of fatty acids from the saponification products of each geopolymer were in agreement with the results of elemental and IR analyses. Distribution of the fatty acids was suggestive that more animal lipids participate in the formation of amorphous kerogens because of the abundance of relatively lower molecular weight fatty acids (such as C 16 and C 18 acids) in saponification products of amorphous kerogens. On the other hand, although the amorphous kerogen fraction tends to be rich in aliphatic structures compared with bulk kerogen of the same rock samples, van Krevelen plots of elemental compositions of kerogens from the core samples (Nishiyama Oil Field, Tertiary, Japan) reveal that the amorphous kerogen fraction is not necessarily characterized by markedly high atomic H/C ratio. This was attributed to the oxic environment of deposition and the abundance of biodegraded terrestrial amorphous organic matter in the amorphous kerogen fraction used in this work.

Potential Hydrogen Yields from Ultramafic Rocks of the Coast Range Ophiolite and Zambales Ophiolite: Inferences from Mössbauer Spectroscopy

NASA Astrophysics Data System (ADS)

Stander, A.; Nelms, M.; Wilkinson, K.; Dyar, M. D.; Cardace, D.

2013-12-01

The reduced status of mantle rocks is a possible controller and indicator of deep life habitat, due to interactions between water and ultramafic (Fe, Mg-rich) minerals, which, under reducing conditions, can yield copious free hydrogen, which is an energy source for rock-hosted chemosynthetic life. In this work, Mössbauer spectroscopy was used to parameterize the redox status of Fe in altering peridotites of the Coast Range Ophiolite (CRO) in California, USA and Zambales Ophiolite (ZO) in the Philippines. Fe-bearing minerals were identified and data were collected for the percentages of Fe(III)and Fe(II)and bulk Fe concentration. Thin section analysis shows that relict primary olivines and spinels generally constitute a small percentage of the ZO and CRO rock, and given satisfactory estimates of the volume of the ultramafic units of the ZO and CRO, a stoichiometric H2 production can be estimated. In addition, ZO serpentinites are ~63,000 ppm Fe in bulk samples; they contain ~41-58% Fe(III)and ~23-34% Fe(II) in serpentine and relict minerals along with ~8-30% of the total Fe as magnetite. CRO serpentinites are ~42,000 ppm Fe in bulk samples; they contain ~15-50% Fe(III), ~22-88% Fe(II) in serpentine and relict minerals, and ~0-52% of total Fe is in magnetite (Fe(II)Fe(III)2O4). Assuming stoichiometric production of H2, and given the following representation of serpentinization 2(FeO)rock + H2O → (Fe2O3)rock +H2, we calculated the maximum quantity of hydrogen released and yet to be released through the oxidation of Fe(II). Given that relatively high Fe(III)/Fetotal values can imply higher water:rock ratios during rock alteration (Andreani et al., 2013), we can deduce that ZO ultramafics in this study have experienced a net higher water:rock ratio than CRO ultramafics. We compare possible H2 yields and contrast the tectonic and alteration histories of the selected ultramafic units. (M. Andreani, M. Muñoz, C. Marcaillou, A. Delacour, 2013, μXANES study of iron redox state in serpentine during oceanic serpentinization, Lithos, Available online 20 April 2013)

Do Hf isotopes in magmatic zircons represent those of their host rocks?

NASA Astrophysics Data System (ADS)

Wang, Di; Wang, Xiao-Lei; Cai, Yue; Goldstein, Steven L.; Yang, Tao

2018-04-01

Lu-Hf isotopic system in zircon is a powerful and widely used geochemical tracer in studying petrogenesis of magmatic rocks and crustal evolution, assuming that zircon Hf isotopes can represent initial Hf isotopes of their parental whole rock. However, this assumption may not always be valid. Disequilibrium partial melting of continental crust would preferentially melt out non-zircon minerals with high time-integrated Lu/Hf ratios and generate partial melts with Hf isotope compositions that are more radiogenic than those of its magma source. Dissolution experiments (with hotplate, bomb and sintering procedures) of zircon-bearing samples demonstrate this disequilibrium effect where partial dissolution yielded variable and more radiogenic Hf isotope compositions than fully dissolved samples. A case study from the Neoproterozoic Jiuling batholith in southern China shows that about half of the investigated samples show decoupled Hf isotopes between zircons and the bulk rocks. This decoupling could reflect complex and prolonged magmatic processes, such as crustal assimilation, magma mixing, and disequilibrium melting, which are consistent with the wide temperature spectrum from ∼630 °C to ∼900 °C by Ti-in-zircon thermometer. We suggest that magmatic zircons may only record the Hf isotopic composition of their surrounding melt during crystallization and it is uncertain whether their Hf isotopic compositions can represent the primary Hf isotopic compositions of the bulk magmas. In this regard, using zircon Hf isotopic compositions to trace crustal evolution may be biased since most of these could be originally from disequilibrium partial melts.

Fluid-rock Interactions recorded in Serpentinites subducted to 60-80 km Depth

NASA Astrophysics Data System (ADS)

Peters, D.; John, T.; Scambelluri, M.; Pettke, D. T.

2016-12-01

The HP metamorphic serpentinised peridotites of Erro-Tobbio (ET, Italy) offer a unique possibility to study fluid-rock interactions in subducted ultrabasic rocks that reached 550-650°C at 2-2.5 GPa. They contain metamorphic olivine + Ti-clinohumite in both the serpentinite matrix and veins cutting the rock foliation, interpreted to represent partial serpentinite dehydration fluid pathways [1,2] being variably retrogressed as e.g., indicated by chrysotile/lizardite mesh textures in vein olivine in strongly altered samples. This study aims to constraining the origin of fluid(s) and the scale(s) of fluid-rock interaction based on major to trace element systematics employing detailed bulk rock (nanoparticulate pressed powder pellet LA-ICP-MS [3] and ion chromatography / liquid ICP-MS analysis), and in situ mineral analysis (work in progress). Bulk data show moderate fluid-mobile element (FME) enrichment for Cs, Rb, Ba, Pb, As, and Sb (up to 100 times primitive mantle (PM)), W (1000 PM), and B (10000 PM). Alkali over U ratios of compiled serpentinite data (n ˜ 620) reveal distinctive global FME enrichment trends for MOR vs. forearc (FA) serpentinisation. ET serpentinites fall into the latter, indicating both sediment-equilibrated fluids and the preservation of characteristic FME enrichment patterns in HP serpentinites. Petrography reveals a multiphase evolution of the HP veins including retrograde serpentinisation, whereas serpentinite hosts have remained largely unaffected by retrogression. Comparison of vein vs. wall rock bulk data indicate vein-forming fluids in equilibrium with wall rocks, however, without evidence for external fluid ingress. The preservation of multiple fluid-rock interaction episodes and the lack of external fluid ingress in the ET HP serpentinites indicate near-closed system behaviour throughout subduction and imprint of characteristic fluid signatures onto the mantle. [1] Scambelluri et al. (1995) Geology, 23, 459-462. [2] John et al. (2011) Earth Planet Sci Lett 308, 65-76. [3] Peters and Pettke (2016) GGR, DOI: 10.1111/ggr.12125.

Freeze-Thaw Cycle Test on Basalt, Diorite and Tuff Specimens with the Simulated Ground Temperature of Antarctica

NASA Astrophysics Data System (ADS)

Park, J.; Hyun, C.; Cho, H.; Park, H.

2010-12-01

Physical weathering caused by freeze-thaw action in cold regions was simulated with artificial weathering simulator in laboratory. Physical weathering of rock in cold regions usually depends on the temperature, rock type and moisture content. Then these three variables were considered in this study. The laboratory freeze-thaw tests were conducted on the three types of rocks, e.g. diorite, basalt and tuff, which are the major rock types around Sejong Station, King George Island, Antarctica. Nine core samples composed of three samples from each rock type were prepared in NX core, and 50 cycles of freeze-thaw test was carried out under dried and saturated water conditions. In this study, the physical weathering of rocks was investigated after each 10 cycles by measuring P-wave velocity, bulk density, effective porosity, Schmidt hardness and uniaxial compression strength(UCS). The experimental result of the diorite and the tuff specimens showed that P-wave velocity, bulk density, effective porosity, Schmidt hardness and UCS were gradually decreased as weathering progresses, but the result of the basalt specimens did not show typical trends due to the characteristics of irregular pore distribution and various pore sizes. Scanning electron microscopy(SEM) photographs of diorite, basalt and tuff specimens weathered in dried and saturated conditions were also acquired to investigate the role of water during physical weathering processes. The number and size of microcracks were increased as weathering progresses. This work was supported by the National Research Foundation of Korea(NRF) Grant(NRF-2010-0027753).

K-Ca and Rb-Sr Dating of Lunar Granite 14321 Revisited

NASA Technical Reports Server (NTRS)

Simon, Justin I.; Shih, C.-Y.; Nyquist, L. E.

2011-01-01

K-Ca and Rb-Sr age determinations were made for a bulk feldspar-rich portion of an Apollo rock fragment of the pristine lunar granite clast (14321,1062), an acid-leached split of the sample, and the leachate. K-Ca and Rb-Sr data were also obtained for a whole rock sample of Apollo ferroan anorthosite (FAN, 15415). The recent detection [1] of widespread intermediate composition plagioclase indicates that the generation of a diversity of evolved lunar magmas maybe more common and therefore more important to our understanding of crust formation than previously believed. Our new data strengthen the K-Ca and Rb-Sr internal isochrons of the well-studied Apollo sample 14321 [2], which along with a renewed effort to study evolved lunar magmas will provide an improved understanding of the petrogenetic history of evolved rocks on the Moon.

Complex conductivity of volcanic rocks and the geophysical mapping of alteration in volcanoes

NASA Astrophysics Data System (ADS)

Ghorbani, A.; Revil, A.; Coperey, A.; Soueid Ahmed, A.; Roque, S.; Heap, M. J.; Grandis, H.; Viveiros, F.

2018-05-01

Induced polarization measurements can be used to image alteration at the scale of volcanic edifices to a depth of few kilometers. Such a goal cannot be achieved with electrical conductivity alone, because too many textural and environmental parameters influence the electrical conductivity of volcanic rocks. We investigate the spectral induced polarization measurements (complex conductivity) in the frequency band 10 mHz-45 kHz of 85 core samples from five volcanoes: Merapi and Papandayan in Indonesia (32 samples), Furnas in Portugal (5 samples), Yellowstone in the USA (26 samples), and Whakaari (White Island) in New Zealand (22 samples). This collection of samples covers not only different rock compositions (basaltic andesite, andesite, trachyte and rhyolite), but also various degrees of alteration. The specific surface area is found to be correlated to the cation exchange capacity (CEC) of the samples measured by the cobalthexamine method, both serving as rough proxies of the hydrothermal alteration experienced by these materials. The in-phase (real) conductivity of the samples is the sum of a bulk contribution associated with conduction in the pore network and a surface conductivity that increases with alteration. The quadrature conductivity and the normalized chargeability are two parameters related to the polarization of the electrical double layer coating the minerals of the volcanic rocks. Both parameters increase with the degree of alteration. The surface conductivity, the quadrature conductivity, and the normalized chargeability (defined as the difference between the in-phase conductivity at high and low frequencies) are linearly correlated to the CEC normalized by the bulk tortuosity of the pore space. The effects of temperature and pyrite-content are also investigated and can be understood in terms of a physics-based model. Finally, we performed a numerical study of the use of induced polarization to image the normalized chargeability of a volcanic edifice. Induced polarization tomography can be used to map alteration of volcanic edifices with applications to geohazard mapping.

Chondrules in the Sharps H3 chondrite - Evidence for intergroup compositional differences among ordinary chondrite chondrules

NASA Technical Reports Server (NTRS)

Rubin, Alan E.; Pernicka, Ernst

1989-01-01

Bulk compositions of 19 chondrules and one matrix-rich sample from H3.4 Sharps were determined by instrumental neutron activation analysis. Samples were characterized petrographically, and mineral compositions were determined by electron microprobe analysis. There is constancy among ordinary chondrite (OC) groups in the compositional interrelationships of different chondrule types; e.g., in H3 as well as L3 and LL3 chondrites, porphyritic chondrules are more refractory than nonporphyritic chondrules. Precursor components of H3 chondrules are closely related to those of LL3 chondrules. The mean Ir/Ni, Ir/Co, and Ir/Au ratios of H3 chondrules differ from the corresponding ratios of LL3 chondrules at the 99, 90, and 79 percent confidence levels, respectively. The ratios in H3 chondrules exceed those in LL3 chondrules by amounts similar to those by which H whole-rocks exceed LL whole-rocks. These data suggest that there are primary systematic differences in bulk composition between H and LL chondrules. These differences support the inference that chondrule formation occurred after major nebular fractionation events had established the observed bulk compositional differences among OC groups.

A Future Moon Mission: Curatorial Statistics on Regolith Fragments Applicable to Sample Collection by Raking

NASA Technical Reports Server (NTRS)

Allton, J. H.; Bevill, T. J.

2003-01-01

The strategy of raking rock fragments from the lunar regolith as a means of acquiring representative samples has wide support due to science return, spacecraft simplicity (reliability) and economy [3, 4, 5]. While there exists widespread agreement that raking or sieving the bulk regolith is good strategy, there is lively discussion about the minimum sample size. Advocates of consor-tium studies desire fragments large enough to support petrologic and isotopic studies. Fragments from 5 to 10 mm are thought adequate [4, 5]. Yet, Jolliff et al. [6] demonstrated use of 2-4 mm fragments as repre-sentative of larger rocks. Here we make use of cura-torial records and sample catalogs to give a different perspective on minimum sample size for a robotic sample collector.

An integrated study of geochemistry and mineralogy of the Upper Tukau Formation, Borneo Island (East Malaysia): Sediment provenance, depositional setting and tectonic implications

NASA Astrophysics Data System (ADS)

Nagarajan, Ramasamy; Roy, Priyadarsi D.; Kessler, Franz L.; Jong, John; Dayong, Vivian; Jonathan, M. P.

2017-08-01

An integrated study using bulk chemical composition, mineralogy and mineral chemistry of sedimentary rocks from the Tukau Formation of Borneo Island (Sarawak, Malaysia) is presented in order to understand the depositional and tectonic settings during the Neogene. Sedimentary rocks are chemically classified as shale, wacke, arkose, litharenite and quartz arenite and consist of quartz, illite, feldspar, rutile and anatase, zircon, tourmaline, chromite and monazite. All of them are highly matured and were derived from a moderate to intensively weathered source. Bulk and mineral chemistries suggest that these rocks were recycled from sedimentary to metasedimentary source regions with some input from granitoids and mafic-ultramafic rocks. The chondrite normalized REE signature indicates the presence of felsic rocks in the source region. Zircon geochronology shows that the samples were of Cretaceous and Triassic age. Comparable ages of zircon from the Tukau Formation sedimentary rocks, granitoids of the Schwaner Mountains (southern Borneo) and Tin Belt of the Malaysia Peninsular suggest that the principal provenance for the Rajang Group were further uplifted and eroded during the Neogene. Additionally, presence of chromian spinels and their chemistry indicate a minor influence of mafic and ultramafic rocks present in the Rajang Group. From a tectonic standpoint, the Tukau Formation sedimentary rocks were deposited in a passive margin with passive collisional and rift settings. Our key geochemical observation on tectonic setting is comparable to the regional geological setting of northwestern Borneo as described in the literature.

The effect of rock particles and D2O replacement on the flow behaviour of ice.

PubMed

Middleton, Ceri A; Grindrod, Peter M; Sammonds, Peter R

2017-02-13

Ice-rock mixtures are found in a range of natural terrestrial and planetary environments. To understand how flow processes occur in these environments, laboratory-derived properties can be extrapolated to natural conditions through flow laws. Here, deformation experiments have been carried out on polycrystalline samples of pure ice, ice-rock and D 2 O-ice-rock mixtures at temperatures of 263, 253 and 233 K, confining pressure of 0 and 48 MPa, rock fraction of 0-50 vol.% and strain-rates of 5 × 10 -7 to 5 × 10 -5  s -1 Both the presence of rock particles and replacement of H 2 O by D 2 O increase bulk strength. Calculated flow law parameters for ice and H 2 O-ice-rock are similar to literature values at equivalent conditions, except for the value of the rock fraction exponent, here found to be 1. D 2 O samples are 1.8 times stronger than H 2 O samples, probably due to the higher mass of deuterons when compared with protons. A gradual transition between dislocation creep and grain-size-sensitive deformation at the lowest strain-rates in ice and ice-rock samples is suggested. These results demonstrate that flow laws can be found to describe ice-rock behaviour, and should be used in modelling of natural processes, but that further work is required to constrain parameters and mechanisms for the observed strength enhancement.This article is part of the themed issue 'Microdynamics of ice'. © 2016 The Author(s).

The effect of rock particles and D2O replacement on the flow behaviour of ice

PubMed Central

Grindrod, Peter M.

2017-01-01

Ice–rock mixtures are found in a range of natural terrestrial and planetary environments. To understand how flow processes occur in these environments, laboratory-derived properties can be extrapolated to natural conditions through flow laws. Here, deformation experiments have been carried out on polycrystalline samples of pure ice, ice–rock and D2O-ice–rock mixtures at temperatures of 263, 253 and 233 K, confining pressure of 0 and 48 MPa, rock fraction of 0–50 vol.% and strain-rates of 5 × 10−7 to 5 × 10−5 s−1. Both the presence of rock particles and replacement of H2O by D2O increase bulk strength. Calculated flow law parameters for ice and H2O-ice–rock are similar to literature values at equivalent conditions, except for the value of the rock fraction exponent, here found to be 1. D2O samples are 1.8 times stronger than H2O samples, probably due to the higher mass of deuterons when compared with protons. A gradual transition between dislocation creep and grain-size-sensitive deformation at the lowest strain-rates in ice and ice–rock samples is suggested. These results demonstrate that flow laws can be found to describe ice–rock behaviour, and should be used in modelling of natural processes, but that further work is required to constrain parameters and mechanisms for the observed strength enhancement. This article is part of the themed issue ‘Microdynamics of ice’. PMID:28025298

Scanning SQUID microscope with an in-situ magnetization/demagnetization field for geological samples

NASA Astrophysics Data System (ADS)

Du, Junwei; Liu, Xiaohong; Qin, Huafeng; Wei, Zhao; Kong, Xiangyang; Liu, Qingsong; Song, Tao

2018-04-01

Magnetic properties of rocks are crucial for paleo-, rock-, environmental-magnetism, and magnetic material sciences. Conventional rock magnetometers deal with bulk properties of samples, whereas scanning microscope can map the distribution of remanent magnetization. In this study, a new scanning microscope based on a low-temperature DC superconducting quantum interference device (SQUID) equipped with an in-situ magnetization/demagnetization device was developed. To realize the combination of sensitive instrument as SQUID with high magnetizing/demagnetizing fields, the pick-up coil, the magnetization/demagnetization coils and the measurement mode of the system were optimized. The new microscope has a field sensitivity of 250 pT/√Hz at a coil-to-sample spacing of ∼350 μm, and high magnetization (0-1 T)/ demagnetization (0-300 mT, 400 Hz) functions. With this microscope, isothermal remanent magnetization (IRM) acquisition and the according alternating field (AF) demagnetization curves can be obtained for each point without transferring samples between different procedures, which could result in position deviation, waste of time, and other interferences. The newly-designed SQUID microscope, thus, can be used to investigate the rock magnetic properties of samples at a micro-area scale, and has a great potential to be an efficient tool in paleomagnetism, rock magnetism, and magnetic material studies.

Experimental results of temperature response to stress change: An indication of the physics of earthquake rupture propagation

NASA Astrophysics Data System (ADS)

Lin, W.; Yang, X.; Tadai, O.; Zeng, X.; Yeh, E. C.; Yu, C.; Hatakeda, K.; Xu, H.; Xu, Z.

2016-12-01

As a result of the earthquake rupture propagation, stress on the earthquake fault and in the hanging wall and in the footwall coseismically drops. Based on the thermo-elasticity theory, the temperature of rocks may change associated with coseismic stress change at the same time as their elastic deformation. This coseismic temperature change is one of the physics of earthquake rupture propagation, however has not been noted and expressly addressed before. To understand this temperature issue, we conducted laboratory experiments to quantitatively investigate temperatures response of rocks to rapid stress change of various typical rocks. Consequently, we developed a hydrostatic compression experimental equipment for rock samples with a high resolution temperature measuring system. This enable us to rapidly load and/or unload the confining pressure. As experimental rock samples, we collected 15 representative rocks from various scientific drilling projects and outcrops of earthquake faults, and quarries in the world. The rock types include sandstone, siltstone, limestone, granite, basalt, tuff etc. Based on the classical thermo-elastic theory, a conventional relationship between the temperature change (dT) of rock samples and the confining pressure change (dP) in the hydrostatic compression system under adiabatic condition can be expressed as a linear function. Therefore, we can measure the adiabatic pressure derivative of temperature (dT/dP) directly by monitoring changes of rock sample temperature and confining pressure during the rapidly loading and unloading processes. As preliminary results of the experiments, the data of 15 rock samples showed that i) the adiabatic pressure derivative of temperature (dT/dP) of most rocks are about 1.5 6.2 mK/MPa; ii) the dT/dP of sedimentary rocks is larger than igneous and metamorphic rocks; iii) a good linear correlation between dT/dP and the rock's bulk modulus was recognized.

Elastic wave velocities, chemistry and modal mineralogy of crustal rocks sampled by the Outokumpu scientific drill hole: Evidence from lab measurements and modeling

NASA Astrophysics Data System (ADS)

Kern, H.; Mengel, K.; Strauss, K. W.; Ivankina, T. I.; Nikitin, A. N.; Kukkonen, I. T.

2009-07-01

The Outokumpu scientific deep drill hole intersects a 2500 m deep Precambrian crustal section comprising a 1300 m thick biotite-gneiss series (mica schists) at top, followed by a 200 m thick meta-ophiolite sequence, underlain again by biotite gneisses (mica schists) (500 m thick) with intercalations of amphibolite and meta-pegmatoids (pegmatitic granite). From 2000 m downward the dominating rock types are meta-pegmatoids (pegmatitic granite). Average isotropic intrinsic P- and S-wave velocities and densities of rocks were calculated on the basis of the volume fraction of the constituent minerals and their single crystal properties for 29 core samples covering the depth range 198-2491 m. The modal composition of the rocks is obtained from bulk rock (XRF) and mineral chemistry (microprobe), using least squares fitting. Laboratory seismic measurements on 13 selected samples representing the main lithologies revealed strong anisotropy of P- and S-wave velocities and shear wave splitting. Seismic anisotropy is strongly related to foliation and is, in particular, an important property of the biotite gneisses, which dominate the upper and lower gneiss series. At in situ conditions, velocity anisotropy is largely caused by oriented microcracks, which are not completely closed at the pressures corresponding to the relatively shallow depth drilled by the borehole, in addition to crystallographic preferred orientation (CPO) of the phyllosilicates. The contribution of CPO to bulk anisotropy is confirmed by 3D velocity calculations based on neutron diffraction texture measurements. For vertical incidence of the wave train, the in situ velocities derived from the lab measurements are significantly lower than the measured and calculated intrinsic velocities. The experimental results give evidence that the strong reflective nature of the ophiolite-derived rock assemblages is largely affected by oriented microcracks and preferred crystallographic orientation of major minerals, in addition to the lithologic control.

Regional geophysical expression of a carbonatite terrane in the eastern Mojave Desert, California

USGS Publications Warehouse

Ponce, David A.; Denton, Kevin M.; Miller, David M.

2013-01-01

A world-class, rare earth element carbonatite deposit is located near Mountain Pass, in the eastern Mojave Desert of California and is hosted by Proterozoic rocks that extend along the eastern margins of the Clark Mountain Range, Mescal Range, and Ivanpah Mountains in a north-northwest trending fault-bounded block. This Proterozoic block is generally composed of a complex of 1.7 - 1.6 Ga gneisses and schists that are intruded by ~1.4 Ga carbonatite and ultrapotassic mafic dikes. In the latter suite, common intrusive rock types include shonkinite, syenite, and alkali granites that are associated with carbonatite dikes. Regional geophysical data reveal that the carbonatite deposit itself occurs along the northeast edge of a prominent magnetic high with an amplitude of 200 nanoteslas, which appears to be related to the surrounding Proterozoic block. More than 340 gravity stations and 155 physical property samples were collected to augment existing geophysical data to determine the geophysical and geologic setting of the eastern Mojave Desert carbonatite terrane. Physical properties of representative rock types in the area show that 23 samples of carbonatite ore have an average saturated bulk density of 2,866 with a range of 2,440 to 3,192 kg/m3 and a magnetic susceptibility of 0.22 with a range of 0.03 to 0.61x 10-3 SI units, 17 samples of syenite have an average saturated bulk density of 2,670 with a range of 2,555 to 2,788 kg/m3 and a magnetic susceptibility of 3.50 with a range of 0.19 to 11.46 x 10-3 SI units, 19 samples of shonkinite dike have an average saturated bulk density of 2,800 with a range of 2,603 to 3,000 kg/m3 and a magnetic susceptibility of 0.71 with a range of 0.00 to 4.44 x 10-3 SI units, and 28 samples of Proterozoic gneiss have an average saturated bulk density of 2,734 with a range of 2,574 to 3,086 kg/m3 and a magnetic susceptibility of 1.23 with a range of 0.01 to 7.48 x 10-3 SI units. In general, carbonatites have distinctive gravity, magnetic, and radiometric signatures because these deposits are relatively dense, have primary magnetite, and are enriched in thorium or uranium. In this case, because the carbonatite rocks in this Proterozoic terrane are themselves essentially nonmagnetic, they are not the source of the magnetic high associated with the Clark Mountain and Mescal Ranges. Instead, we suggest that weakly to moderately magnetic syenite intrusions or other granitic or metamorphic rocks in the region are the source of the magnetic high. Gravity data indicate that basins within the eastern Mojave carbonatite terrane are complicated. For example, a gravity high in the northern part of Ivanapah Valley suggest that the basin is underlain by shallow basement rocks, whereas the southern part of Ivanpah Valley extends to a depth of about 2 km. Combined gravity, magnetic, and geologic studies improve the current geophysical framework and structural interpretation of the eastern Mojave Desert carbonatite terrane.

Geomechanical Anisotropy and Rock Fabric in Shales

NASA Astrophysics Data System (ADS)

Huffman, K. A.; Connolly, P.; Thornton, D. A.

2017-12-01

Digital rock physics (DRP) is an emerging area of qualitative and quantitative scientific analysis that has been employed on a variety of rock types at various scales to characterize petrophysical, mechanical, and hydraulic rock properties. This contribution presents a generic geomechanically focused DRP workflow involving image segmentation by geomechanical constituents, generation of finite element (FE) meshes, and application of various boundary conditions (i.e. at the edge of the domain and at boundaries of various components such as edges of individual grains). The generic workflow enables use of constituent geological objects and relationships in a computational based approach to address specific questions in a variety of rock types at various scales. Two examples are 1) modeling stress dependent permeability, where it occurs and why it occurs at the grain scale; 2) simulating the path and complexity of primary fractures and matrix damage in materials with minerals or intervals of different mechanical behavior. Geomechanical properties and fabric characterization obtained from 100 micron shale SEM images using the generic DRP workflow are presented. Image segmentation and development of FE simulation composed of relatively simple components (elastic materials, frictional contacts) and boundary conditions enable the determination of bulk static elastic properties. The procedure is repeated for co-located images at pertinent orientations to determine mechanical anisotropy. The static moduli obtained are benchmarked against lab derived measurements since material properties (esp. frictional ones) are poorly constrained at the scale of investigation. Once confidence in the input material parameters is gained, the procedure can be used to characterize more samples (i.e. images) than is possible from rock samples alone. Integration of static elastic properties with grain statistics and geologic (facies) conceptual models derived from core and geophysical logs enables quantification of the impact that variations in rock fabric and grain interactions have on bulk mechanical rock behavior. When considered in terms of the stratigraphic framework of two different shale reservoirs it is found that silica distribution, clay content and orientation play a first order role in mechanical anisotropy.

K-Ar constraints on fluid-rock interaction and dissolution-precipitation events within the actively creeping shear zones from SAFOD cores

NASA Astrophysics Data System (ADS)

Ali, S.; Hemming, S. R.; Torgersen, T.; Fleisher, M. Q.; Cox, S. E.; Stute, M.

2009-12-01

The San Andreas Fault Observatory at Depth (SAFOD) was drilled to study the physical and chemical processes responsible for faulting and earthquake generation along an active, plate-bounding fault at depth. SAFOD drill cores show multiple zones of alteration and deformation due to fluid-rock interaction in the fault rocks(Schleicher et al. 2008). In context of fluid studies in the SAFZ, noble gas and potassium measurements were performed on solid samples of sedimentary rocks obtained from drill cores across the fault (3050-4000m-MD). We used a combination of 40Ar/39Ar and K-Ar methods on crushed samples of mudrock with variable amounts of visible slickensides to constrain the degree of resetting of the K-Ar system across the San Andreas Fault zone. 40Ar/39Ar was analyzed from small fragments (sand sized grains) while K-Ar was measured in crushed bulk rock samples (100-250 mg for Ar, and 5-10 mg for K analyses). The apparent 40Ar/39Ar ages based on single step laser fusion of small fragments corresponding to the detrital component in the coarse fraction, show varying ages ranging from the provenance age to <13Ma. Although more data are needed to make detailed comparisons, the apparent K-Ar ages of bulk samples in the fault zone are biased toward authigenic materials contained in the fine fraction, similar to the 40Ar/39Ar ages reported for mineralogical separates from very fine size fractions of samples obtained from 3065.98m-MD and 3294.89m-MD (Schleicher et al., submitted to Geology). The small samples measured for 40Ar/39Ar show scatter in the apparent ages, generally bracketing the bulk ages. However they are picked from sieved portions of the samples, and it is likely that there may be a loss of the younger (finer) material. Detrital provenance ages appear to be 50-60Ma in the Pacific Plate, and 100Ma in the North American Plate. 40Ar/39Ar ages within the SAFZ, as defined by geophysical logs (3200-3400m MD), are dominated by apparent detrital ages of ˜100Ma. More work is needed to test whether this is a real provenance age, or if there could be some systematic process that could lead to age bias towards older values. We observe nearly complete resetting of K-Ar ages, indicating that the K content is dominated by newly formed authigenic minerals as a result of fluid rock interaction in the SAFZ. Because the authigenic minerals are subject to successive dissolution-precipitation events over a range of time (3 to 0 Ma) and because the detrital component may not be fully reset, the K-Ar apparent ages (<300,000 years) in the SAFZ provide a maximum age on the resetting event. Similar trends of relatively young ages across the SAFZ compared to the surrounding country rock in the Pacific and North American Plates are also observed in the apparent fluid ‘ages’, corresponding to the fluid event responsible for the fluid-rock interaction in the fault (Ali et al. this session).

Green and Fast Laser Fusion Technique for Bulk Silicate Rock Analysis by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry.

PubMed

Zhang, Chenxi; Hu, Zhaochu; Zhang, Wen; Liu, Yongsheng; Zong, Keqing; Li, Ming; Chen, Haihong; Hu, Shenghong

2016-10-18

Sample preparation of whole-rock powders is the major limitation for their accurate and precise elemental analysis by laser ablation inductively-coupled plasma mass spectrometry (ICPMS). In this study, a green, efficient, and simplified fusion technique using a high energy infrared laser was developed for major and trace elemental analysis. Fusion takes only tens of milliseconds for each sample. Compared to the pressed pellet sample preparation, the analytical precision of the developed laser fusion technique is higher by an order of magnitude for most elements in granodiorite GSP-2. Analytical results obtained for five USGS reference materials (ranging from mafic to intermediate to felsic) using the laser fusion technique generally agree with recommended values with discrepancies of less than 10% for most elements. However, high losses (20-70%) of highly volatile elements (Zn and Pb) and the transition metal Cu are observed. The achieved precision is within 5% for major elements and within 15% for most trace elements. Direct laser fusion of rock powders is a green and notably simple method to obtain homogeneous samples, which will significantly accelerate the application of laser ablation ICPMS for whole-rock sample analysis.

Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

NASA Astrophysics Data System (ADS)

Hassanzadegan, Alireza; Guérizec, Romain; Reinsch, Thomas; Blöcher, Guido; Zimmermann, Günter; Milsch, Harald

2016-08-01

The static and poroelastic moduli of a porous rock, e.g., the drained bulk modulus, can be derived from stress-strain curves in rock mechanical tests, and the dynamic moduli, e.g., dynamic Poisson's ratio, can be determined by acoustic velocity and bulk density measurements. As static and dynamic elastic moduli are different, a correlation is often required to populate geomechanical models. A novel poroelastic approach is introduced to correlate static and dynamic bulk moduli of outcrop analogues samples, representative of Upper-Malm reservoir rock in the Molasse basin, southwestern Germany. Drained and unjacketed poroelastic experiments were performed at two different temperature levels (30 and 60°C). For correlating the static and dynamic elastic moduli, a drained acoustic velocity ratio is introduced, corresponding to the drained Poisson's ratio in poroelasticity. The strength of poroelastic coupling, i.e., the product of Biot and Skempton coefficients here, was the key parameter. The value of this parameter decreased with increasing effective pressure by about 56 ~% from 0.51 at 3 MPa to 0.22 at 73 MPa. In contrast, the maximum change in P- and S-wave velocities was only 3 % in this pressure range. This correlation approach can be used in characterizing underground reservoirs, and can be employed to relate seismicity and geomechanics (seismo-mechanics).

Large Carbonate Associated Sulfate isotopic variability between brachiopods, micrite, and other sedimentary components in Late Ordovician strata

NASA Astrophysics Data System (ADS)

Present, Theodore M.; Paris, Guillaume; Burke, Andrea; Fischer, Woodward W.; Adkins, Jess F.

2015-12-01

Carbonate Associated Sulfate (CAS) is trace sulfate incorporated into carbonate minerals during their precipitation. Its sulfur isotopic composition is often assumed to track that of seawater sulfate and inform global carbon and oxygen budgets through Earth's history. However, many CAS sulfur isotope records based on bulk-rock samples are noisy. To determine the source of bulk-rock CAS variability, we extracted CAS from different internal sedimentary components micro-drilled from well-preserved Late Ordovician and early Silurian-age limestones from Anticosti Island, Quebec, Canada. Mixtures of these components, whose sulfur isotopic compositions vary by nearly 25‰, can explain the bulk-rock CAS range. Large isotopic variability of sedimentary micrite CAS (34S-depleted from seawater by up to 15‰) is consistent with pore fluid sulfide oxidation during early diagenesis. Specimens recrystallized during burial diagenesis have CAS 34S-enriched by up to 9‰ from Hirnantian seawater, consistent with microbial sulfate reduction in a confined aquifer. In contrast to the other variable components, brachiopods with well-preserved secondary-layer fibrous calcite-a phase independently known to be the best-preserved sedimentary component in these strata-have a more homogeneous isotopic composition. These specimens indicate that seawater sulfate remained close to about 25‰ (V-CDT) through Hirnantian (end-Ordovician) events, including glaciation, mass extinction, carbon isotope excursion, and pyrite-sulfur isotope excursion. The textural relationships between our samples and their CAS isotope ratios highlight the role of diagenetic biogeochemical processes in setting the isotopic composition of CAS.

Mineralogy and source rock evaluation of the marine Oligo-Miocene sediments in some wells in the Nile Delta and North Sinai, Egypt

NASA Astrophysics Data System (ADS)

El sheikh, Hassan; Faris, Mahmoud; Shaker, Fatma; Kumral, Mustafa

2016-06-01

This paper aims to study the mineralogical composition and determine the petroleum potential of source rocks of the Oligocene-Miocene sequence in the Nile Delta and North Sinai districts. The studied interval in the five wells can be divided into five rock units arranged from the top to base; Qawasim, Sidi Salem, Kareem, Rudeis, and Qantara formations. The bulk rock mineralogy of the samples was investigated using X-Ray Diffraction technique (XRD). The results showed that the sediments of the Nile Delta area are characterized by the abundance of quartz and kaolinite with subordinate amounts of feldspars, calcite, gypsum, dolomite, and muscovite. On the other hand, the data of the bulk rock analysis at the North Sinai wells showed that kaolinite, quartz, feldspar and calcite are the main constituents associated with minor amounts of dolomite, gypsum, mica, zeolite, and ankerite. Based on the organic geochemical investigations (TOC and Rock-Eval pyrolysis analyses), all studied formations in both areas are thermally immature but in the Nile delta area, Qawasim, Sidi Salem and Qantara formations (El-Temsah-2 Well) are organically-rich and have a good petroleum potential (kerogen Type II-oil-prone), while Rudeis Formation is a poor petroleum potential source rock (kerogen Type III-gas-prone). In the North Sinai area, Qantara Formation has a poor petroleum potential (kerogen Type III-gas-prone) and Sidi Salem Formation (Bardawil-1 Well) is a good petroleum potential source rock (kerogen Type II-oil-prone).

Chlorine isotope constraints on fluid-rock interactions during subduction and exhumation of the Zermatt-Saas ophiolite

NASA Astrophysics Data System (ADS)

Selverstone, J.; Sharp, Z. D.

2013-10-01

Chlorine isotope compositions of high-pressure (˜2.3 GPa) serpentinite, rodingite, and hydrothermally altered oceanic crust (AOC) differ significantly from high- and ultrahigh-pressure (> 3.2 GPa) metasedimentary rocks in the Aosta region, Italy. Texturally early serpentinites, rodingites, and AOC have bulk δ37Cl values indistinguishable from those of modern seafloor analogues (δ37Cl = -1.0 to +1.0‰). In contrast, serpentinites and AOC samples that recrystallized during exhumation have low δ37Cl values (-2.7 to -0.5‰); 37Cl depletion correlates with progressive changes in bulk chemistry. HP/UHP metasediments have low δ37Cl values (median = -2.5‰) that differ statistically from modern marine sediments (median = -0.6‰). Cl in metasedimentary rocks is concentrated in texturally early minerals, indicating modification of seafloor compositions early in the subduction history. The data constrain fluid sources during both subduction and exhumation-related phases of fluid-rock interaction: (1) marine sediments at the top of the downgoing plate likely interacted with isotopically light pore fluids from the accretionary wedge in the early stages of subduction. (2) No pervasive interaction with externally derived fluid occurred during subsequent subduction to the maximum depths of burial. (3) Localized mixing between serpentinites and fluids released by previously isotopically modified metasediments occurred during exhumation in the subduction channel. Most samples, however, preserved protolith signatures during subduction to near-arc depths.

Physical and hydraulic properties of volcanic rocks from Yucca Mountain, Nevada

USGS Publications Warehouse

Flint, Lorraine E.

2003-01-01

A database of physical and hydraulic properties was developed for rocks in the unsaturated zone at Yucca Mountain, Nevada, a site under consideration as a geologic repository for high-level radioactive waste. The 5320 core samples were collected from 23 shallow (<100 m) and 10 deep (500-1000 m) vertical boreholes. Hydrogeologic units have been characterized in the unsaturated zone [Flint, 1998] that represent rocks with ranges of welding, lithophysae, and high and low temperature alteration (as a result of the depositional, cooling, and alterational history of the lithostratigraphic layers). Lithostratigraphy, the hydrogeologic unit, and the corresponding properties are described. In addition, the physical properties of bulk density, porosity, and particle density; the hydraulic properties of saturated hydraulic conductivity and moisture retention characteristics; and the field water content were measured and compiled for each core sample.

Geophysical Signatures to Monitor Fluids and Mineralization for CO2 Sequestration in Basalts

NASA Astrophysics Data System (ADS)

Otheim, L. T.; Adam, L.; Van Wijk, K.; Batzle, M. L.; Mcling, T. L.; Podgorney, R. K.

2011-12-01

Carbon dioxide sequestration in large reservoirs can reduce emissions of this green house gas into the atmosphere. Basalts are promising host rocks due to their volumetric extend, worldwide distribution, and recent observations that CO2-water mixtures react with basalt minerals to precipitate as carbonate minerals, trapping the CO2. The chemical reaction between carbonic acid and minerals rich in calcium, magnesium and iron precipitates carbonates in the pore space. This process would increase the elastic modulus and velocity of the rock. At the same time, the higher compressibility of CO2 over water changes the elastic properties of the rock, decreasing the saturated rock bulk modulus and the P-wave velocity. Reservoirs where the rock properties change as a result of fluid or pressure changes are commonly monitored with seismic methods. Here we present experiments to study the feasibility of monitoring CO2 migration in a reservoir and CO2-rock reactions for a sequestration scenario in basalts. Our goal is to measure the rock's elastic response to mineralization with non-contacting ultrasonic lasers, and the effect of fluid substitution at reservoir conditions at seismic and ultrasonic frequencies. For the fluid substitution experiment we observe changes in the P- and S-wave velocities when saturating the sample with super-critical (sc) CO2, CO2-water mixtures and water alone for different pore and confining pressures. The bulk modulus of the rock is significantly dependent on frequency in the 2~to 106~Hz range, for CO2-water mixtures and pure water saturations. Dry and pure CO2 (sc or gas) do not show a frequency dependence on the modulus. Moreover, the shear wave modulus is not dispersive for either fluid. The frequency dependence of the elastic parameters is related to the attenuation (1/Q) of the rock. We will show the correlation between frequency dependent moduli and attenuation data for the different elastic moduli of the rocks. Three other basalt samples were stored in a pressure chamber with a sc CO2-water solution to study the effect of mineralization on the elastic properties of the rock. The rock elastic properties are recorded with non-contacting ultrasonic lasers at room conditions. After 15 weeks the first post-mineralization scan showed differences in the rock velocities with respect to the pre-mineralization scan. The analysis is done through coda wave interferometry and direct arrivals. The samples were inserted back into the pressure vessel for continuing mineralization and subsequent scans. Finally, we will discuss the applicability of Gassmann's equation and how the combination of mineralization together with CO2-water mixture affects the velocity of waves in basalt rocks.

Characterization of rock thermal conductivity by high-resolution optical scanning

USGS Publications Warehouse

Popov, Y.A.; Pribnow, D.F.C.; Sass, J.H.; Williams, C.F.; Burkhardt, H.

1999-01-01

We compared thress laboratory methods for thermal conductivity measurements: divided-bar, line-source and optical scanning. These methods are widely used in geothermal and petrophysical studies, particularly as applied to research on cores from deep scientific boreholes. The relatively new optical scanning method has recently been perfected and applied to geophysical problems. A comparison among these methods for determining the thermal conductivity tensor for anisotropic rocks is based on a representative collection of 80 crystalline rock samples from the KTB continental deep borehole (Germany). Despite substantial thermal inhomogeneity of rock thermal conductivity (up to 40-50% variation) and high anisotropy (with ratios of principal values attaining 2 and more), the results of measurements agree very well among the different methods. The discrepancy for measurements along the foliation is negligible (<1%). The component of thermal conductivity normal to the foliation reveals somewhat larger differences (3-4%). Optical scanning allowed us to characterize the thermal inhomogeneity of rocks and to identify a three-dimensional anisotropy in thermal conductivity of some gneiss samples. The merits of optical scanning include minor random errors (1.6%), the ability to record the variation of thermal conductivity along the sample, the ability to sample deeply using a slow scanning rate, freedom from constraints for sample size and shape, and quality of mechanical treatment of the sample surface, a contactless mode of measurement, high speed of operation, and the ability to measure on a cylindrical sample surface. More traditional methods remain superior for characterizing bulk conductivity at elevated temperature.Three laboratory methods including divided-bar, line-source and optical scanning are widely applied in geothermal and petrophysical studies. In this study, these three methods were compared for determining the thermal conductivity tensor for anisotropic rocks. For this study, a representative collection of 80 crystalline rock samples from the KTB continental deep borehole was used. Despite substantial thermal inhomogeneity of rock thermal conductivity and high anisotropy, measurement results were in excellent agreement among the three methods.

The harzburgites-lherzolite cycle: depletion and refertilization processes

NASA Astrophysics Data System (ADS)

Dijkstra, A. H.

2011-12-01

Lherzolites or clinopyroxene-rich harzburgites sampled at the ocean floor are now generally interpreted as refractory harzburgites refertilized by melt-rock reaction or melt impregnation at the spreading center, rather than as relatively undepleted bulk upper mantle. The key evidence for a melt refertilization origin is often textural. Critically, the refertilization can mask the underlying very refractory character: oceanic peridotites prior to melt refertilization at the ridge are often too refractory to be simple mantle residues of bulk upper mantle that was melted at the ridge. This suggests that the upper mantle contains large domains that record prior melting histories. This is supported by ancient rhenium-depletion ages that are common in oceanic peridotites. In this presentation, I will discuss some key examples (e.g., Macquarie Island [1], Pindos, Totalp, Lanzarote) of refertilized oceanic peridotites, which all have recorded previous, ancient depletions. I will show the textural and geochemical evidence for melt refertilization. It has often been assumed that melt refertilization occurs by interaction with mantle melts. However, there is now evidence for melt refertilization through a reaction with eclogite-derived melts, probably at the base of the melting column underneath the ridge system. These eclogitic mantle heterogeneities themselves do not normally survive the melting underneath the spreading center, but their isotopic signature can be recognized in the reacted peridotites. In summary, we have moved away from the idea that oceanic mantle rocks are simple melting residues of homogeneous bulk upper mantle. The picture that emerges is a rich and complex one, suggesting that oceanic mantle rocks record dynamic histories of melting and refertilization. In particular, the melting event in refertilized peridotites can be much older than the age of the ridge system at which they are sampled. Many oceanic peridotites contain evidence for a Mesoproterozoic melting event of perhaps global significance. Regardless of the nature of these melting events, it is now clear that in their complex overprinting history, oceanic peridotites more and more resemble polygenetic metamorphic rocks.

The effect of oriented microcracks and crystallographic and shape preferred orientation on bulk elastic anisotropy of a foliated biotite gneiss from Outokumpu

NASA Astrophysics Data System (ADS)

Kern, H.; Ivankina, T. I.; Nikitin, A. N.; Lokajíček, T.; Pros, Z.

2008-10-01

Elastic anisotropy is an important property of crustal and mantle rocks. This study investigates the contribution of oriented microcracks and crystallographic (LPO) and shape preferred orientation (SPO) to the bulk elastic anisotropy of a strongly foliated biotite gneiss, using different methodologies. The rock is felsic in composition (about 70 vol.% SiO 2) and made up by about 40 vol.% quartz, 37 vol.% plagioclase and 23 vol.% biotite. Measurements of compressional (Vp) and shear wave (Vs) velocities on a sample cube in the three foliation-related structural directions (up to 600 MPa) and of the 3D P-wave velocity distribution on a sample sphere (up to 200 MPa) revealed a strong pressure sensitivity of Vp, Vs and P-wave anisotropy in the low pressure range. A major contribution to bulk anisotropy is from biotite. Importantly, intercrystalline and intracrystalline cracks are closely linked to the morphologic sheet plane (001) of the biotite minerals, leading to very high anisotropy at low pressure. Above about 150 MPa the effect of cracks is almost eliminated, due to progressive closure of microcracks. The residual (pressure-independent) part of velocity anisotropy is mainly caused by the strong alignment of the platy biotite minerals, displaying a strong SPO and LPO. Calculation of the 3D velocity distribution based on neutron diffraction texture measurements of biotite, quartz, and plagioclase and their single-crystal properties give evidence for an important contribution of the biotite LPO to the intrinsic velocity anisotropy, confirming the experimental findings that maximum and minimum velocities and shear wave splitting are closely related to foliation. Comparison of the LPO-based calculated anisotropy (about 8%) with measured intrinsic anisotropy (about 15% at 600 MPa) give hints for a major contribution of SPO to the bulk anisotropy of the rock.

Origin of Pseudotachylites during slow creep experiments

NASA Astrophysics Data System (ADS)

Peč, M.; Stünitz, H.; Heilbronner, R.; Drury, M.; De Capitani, C.

2012-04-01

Pseudotachylites are interpreted as solidified friction induced melts which form exclusively during seismic or impact events and are thus accepted as 'unequivocal evidence' of paleo-earthquakes on exhumed faults. However, we found in experiments that pseudotachylites can form under clearly aseismic conditions at confining pressures and temperatures typical of mid crustal levels (Pc = 500 MPa, T = 300° C). The starting material consists of granitoid powder crushed to a size of ≤ 200 μm in diameter. This material (0.1 g), with 0.2 wt% water added, is placed between alumina forcing blocks pre-cut at 45° , weld-sealed in platinum jackets with an inner nickel foil insert and deformed in a solid medium deformation apparatus (modified Griggs rig). We applied displacement rates of (10-8 ms-1 < dotγ < 10-6 ms-1) which approximate typical tectonic plate velocities of a few cm/a. In the 0.7 mm thick layer of fault rock, this produces a bulk shear strain rate of ( 10-5s-1 < γdot < 10-3s-1). The samples reach a peak shear strength of ( 1200 MPa < τ < 1500 MPa) at bulk sample strains of (1.5 < γ < 2.3). Only at the highest displacement rates ( 10-6ms-1), the samples fail abruptly shortly after reaching peak strength, possibly due to fracturing of the forcing blocks. However, at slower displacement rates (10-7ms-1 to 10-8ms-1) the samples reach a peak strength of 1200 - 1400 MPa, then weaken slightly (by 30 MPa), and continue to deform at approximately constant stress without any abrupt stress drops. The weakening is accompanied by a transient increase of the measured displacement rate of the forcing piston by 25%. The friction coefficient, μ, on the 45° pre-cut is 0.6, which is in the range of values typical of intact rock materials. After the experiment, the fault rock consists of a S-C-C' fabric with a percolating, multiply connected layer of pseudotachylites decorating the C'- C shears. Microstructures indicative for pseudotachylites are: injection veins, flow structures, bubbles, and bubble trains following the local flow pattern, corroded clasts and amorphous glass identified by TEM. The chemical composition of the pseudotachylites varies depending on the precursor material and is in general more ferromagnesian and basic compared to the bulk rock indicating preferred melting of biotite. The calculated temperature increase due to shear heating is at the most 5°C. High stresses cause pervasive comminution: the smallest crystalline fragments within the bubbly melt have a grain diameter of 10 nm. Nanomaterials exhibit a 'melting point depression' (dependence of melting point on grain size) which allows melting well below bulk melting temperatures. Thus, it seems that melting is a continuation of the comminution once the rock has reached small enough grain size. We therefore suggest that pseudotachylites may also form as 'mechanical melts' at slow displacement rates without the necessity of reaching high temperatures.

Quantifying Rock Weakening Due to Decreasing Calcite Mineral Content by Numerical Simulations

PubMed Central

2018-01-01

The quantification of changes in geomechanical properties due to chemical reactions is of paramount importance for geological subsurface utilisation, since mineral dissolution generally reduces rock stiffness. In the present study, the effective elastic moduli of two digital rock samples, the Fontainebleau and Bentheim sandstones, are numerically determined based on micro-CT images. Reduction in rock stiffness due to the dissolution of 10% calcite cement by volume out of the pore network is quantified for three synthetic spatial calcite distributions (coating, partial filling and random) using representative sub-cubes derived from the digital rock samples. Due to the reduced calcite content, bulk and shear moduli decrease by 34% and 38% in maximum, respectively. Total porosity is clearly the dominant parameter, while spatial calcite distribution has a minor impact, except for a randomly chosen cement distribution within the pore network. Moreover, applying an initial stiffness reduced by 47% for the calcite cement results only in a slightly weaker mechanical behaviour. Using the quantitative approach introduced here substantially improves the accuracy of predictions in elastic rock properties compared to general analytical methods, and further enables quantification of uncertainties related to spatial variations in porosity and mineral distribution. PMID:29614776

Quantifying Rock Weakening Due to Decreasing Calcite Mineral Content by Numerical Simulations.

PubMed

Wetzel, Maria; Kempka, Thomas; Kühn, Michael

2018-04-01

The quantification of changes in geomechanical properties due to chemical reactions is of paramount importance for geological subsurface utilisation, since mineral dissolution generally reduces rock stiffness. In the present study, the effective elastic moduli of two digital rock samples, the Fontainebleau and Bentheim sandstones, are numerically determined based on micro-CT images. Reduction in rock stiffness due to the dissolution of 10% calcite cement by volume out of the pore network is quantified for three synthetic spatial calcite distributions (coating, partial filling and random) using representative sub-cubes derived from the digital rock samples. Due to the reduced calcite content, bulk and shear moduli decrease by 34% and 38% in maximum, respectively. Total porosity is clearly the dominant parameter, while spatial calcite distribution has a minor impact, except for a randomly chosen cement distribution within the pore network. Moreover, applying an initial stiffness reduced by 47% for the calcite cement results only in a slightly weaker mechanical behaviour. Using the quantitative approach introduced here substantially improves the accuracy of predictions in elastic rock properties compared to general analytical methods, and further enables quantification of uncertainties related to spatial variations in porosity and mineral distribution.

Distribution of manganese between coexisting biotite and hornblende in plutonic rocks

USGS Publications Warehouse

Greenland, L.P.; Gottfried, D.; Tilling, R.I.

1968-01-01

The distribution of manganese between coexisting biotite and hornblende for 80 mineral pairs from igneous rocks of diverse provenance (including Southern California, Sierra Nevada, Boulder, and Boulder Creek batholiths and the Jemez Mountains volcanics) has been determined by neutron activation analysis. Data on the distribution ratio (Kd = Mnhornblende Mnbiotite) indicate that an equilibrium distribution of Mn is closely approached, though not completely attained, in most samples from plutonic environments. Comparison of Kd values of mineral pairs with bulk chemical composition of host rocks reveals no correlation. Because initial crystallization temperatures vary with rock composition, the lack of correlation of composition with Kd suggests that the equilibrium distribution of Mn between biotite and hornblende reflects exchange at subsolidus temperatures rather than initial crystallization temperatures. The highest Kd values are for volcanic rocks, in which rapid quenching prevents subsolidus redistribution of Mn. For sample pairs from the Southern California and Sierra Nevada batholiths there is a positive correlation of Kd with TiO2 content of biotite. Though the evidence is not compelling, Kd may also correlate with the rate of cooling and/or the presence or absence of sphene in the rock. ?? 1968.

Direct laboratory observation of fluid distribution and its influence on acoustic properties of patchy saturated rocks

NASA Astrophysics Data System (ADS)

Lebedev, M.; Clennell, B.; Pervukhina, M.; Shulakova, V.; Mueller, T.; Gurevich, B.

2009-04-01

Porous rocks in hydrocarbon reservoirs are often saturated with a mixture of two or more fluids. Interpretation of exploration seismograms requires understanding of the relationship between distribution of the fluids patches and acoustic properties of rocks. The sizes of patches as well as their distribution affect significantly the seismic response. If the size of the fluid patch is smaller than the diffusion wavelength then pressure equilibration is achieved and the bulk modulus of the rock saturated with a mixture is defined by the Gassmann equations (Gassmann, 1951) with the saturation-weighted average of the fluid bulk modulus given by Wood's law (Wood, 1955, Mavko et al., 1998). If the fluid patch size is much larger than the diffusion wavelength then there is no pressure communication between different patches. In this case, fluid-flow effects can be neglected and the overall rock may be considered equivalent to an elastic composite material consisting of homogeneous parts whose properties are given by Gassmann theory with Hill's equation for the bulk modulus (Hill, 1963, Mavko et al., 1998). At intermediate values of fluid saturation the velocity-saturation relationship is significantly affected by the fluid patch distribution. In order to get an improved understanding of factors influencing the patch distribution and the resulting seismic wave response we performed simultaneous measurements of P-wave velocities and rock sample CT imaging. The CT imaging allows us to map the fluid distribution inside rock sample during saturation (water imbibition). We compare the experimental results with theoretical predictions. In this paper we will present results of simultaneous measurements of longitudinal wave velocities and imaging mapping of fluid distribution inside rock sample during sample saturation. We will report results of two kinds of experiments: "dynamic" and "quasi static" saturation. In both experiments Casino Cores Otway Basin sandstone, Australia core samples (38 mm in diameter, approximately 60 mm long) were dried in oven under reduced pressure. In dynamic saturation experiments, samples were jacketed in the experimental cell, made from transparent for X-radiation material (PMMA). Distillate water was injected into the sample from the one side. Fluid distribution in such "dynamic" experiment: both spatial and time dependant was measured using X-ray Computer Tomograph (CT) with resolution 0.2 x 0.2 x 1 mm3. Velocities (Vp, and Vs) at ultrasonic frequency of 1 MHz, were measured in the direction perpendicular to initial direction of the fluid flow injection. Sample saturation was estimated from the CT results. In "quasi static" experiments samples were saturated during long period of time (over 2 weeks) to achieve uniform distribution of liquid inside the sample. Saturation was determined by measurement of the weight of water fraction. All experiments were performed at laboratory environments at temperature 25 C. Ultrasonic velocities and fluid saturations were measured simultaneously during water injection into sandstone core samples. The experimental results obtained on low-permeability samples show that at low saturation values the velocity-saturation dependence can be described by the Gassmann-Wood relationship. However, with increasing saturation a sharp increase of P-wave velocity is observed, eventually approaching the Gassmann-Hill relationship. We connect the characteristics of the transition behavior of the velocity-saturation relationships to the increasing size of the patches inside the rock sample. In particular, we show that for relatively large fluid injection rate this transition occurs at smaller degrees of saturation as compared with high injection rate. We model the experimental data using the so-called White model (Toms 2007) that assumes fluid patch distribution as a periodic assemblage of concentric spheres. We can observe reasonable agreement between experimental results and theoretical predictions of White's model. The results illustrate the non-unique relationships between saturation and velocity in sandstones dependent on texture and fluid displacement history: fuller understanding of these phenomena is needed for accurate assessment of time lapse seismic measurements, be they for oil and gas recovery or for CO2 disposal purposes. Gassmann, F., 1951, Elastic waves through a packing of spheres. Geophysics 16, 673-685; Mavko, G., T. Mukerji, and J. Dvorkin, 1998, The Rock Physics Handbook: Tools for seismic analysis in porous media: Cambridge University Press. Wood, A. W., 1955, A Textbook of Sound, The MacMillan Co., New York, 360 pp. Hill, R., 1963, Elastic properties of reinforced solids: some theoretical principles. J. Mech. Phys. Solids, 11, 357-372. Hill, R., 1952, The elastic behavior of crystalline aggregates. Proc. Physical Soc., London, A65, 349-354. J. Toms, T.M. Mueller, B. Gurevich, 2007 Seismic attenuation in porous rocks with random patchy saturation. Geophysical Prospecting, 55, 671-678.

Petrophysical Properties (Density and Magnetization) of Rocks from the Suhbaatar-Ulaanbaatar-Dalandzadgad Geophysical Profile in Mongolia and Their Implications

PubMed Central

Gao, Jintian; Gu, Zuowen; Dagva, Baatarkhuu; Tserenpil, Batsaikhan

2013-01-01

Petrophysical properties of 585 rock samples from the Suhbaatar-Ulaanbaatar-Dalandzadgad geophysical profile in Mongolia are presented. Based on the rock classifications and tectonic units, petrophysical parameters (bulk density, magnetic susceptibility, intensity of natural remanent magnetization, and Köenigsberger ratio) of these rocks are summarized. Results indicate that (1) significant density contrast of different rocks would result in variable gravity anomalies along the profile; (2) magnetic susceptibility and natural remanent magnetization of all rocks are variable, covering 5-6 orders of magnitude, which would make a variable induced magnetization and further links to complex magnetic anomalies in ground surface; (3) the distribution of rocks with different lithologies controls the pattern of lithospheric magnetic anomaly along the profile. The petrophysical database thus provides not only one of the keys to understand the geological history and structure of the profile, but also essential information for analysis and interpretation of the geophysical (e.g., magnetic and gravity) survey data. PMID:24324382

Petrophysical properties (density and magnetization) of rocks from the Suhbaatar-Ulaanbaatar-Dalandzadgad geophysical profile in Mongolia and their implications.

PubMed

Yang, Tao; Gao, Jintian; Gu, Zuowen; Dagva, Baatarkhuu; Tserenpil, Batsaikhan

2013-01-01

Petrophysical properties of 585 rock samples from the Suhbaatar-Ulaanbaatar-Dalandzadgad geophysical profile in Mongolia are presented. Based on the rock classifications and tectonic units, petrophysical parameters (bulk density, magnetic susceptibility, intensity of natural remanent magnetization, and Köenigsberger ratio) of these rocks are summarized. Results indicate that (1) significant density contrast of different rocks would result in variable gravity anomalies along the profile; (2) magnetic susceptibility and natural remanent magnetization of all rocks are variable, covering 5-6 orders of magnitude, which would make a variable induced magnetization and further links to complex magnetic anomalies in ground surface; (3) the distribution of rocks with different lithologies controls the pattern of lithospheric magnetic anomaly along the profile. The petrophysical database thus provides not only one of the keys to understand the geological history and structure of the profile, but also essential information for analysis and interpretation of the geophysical (e.g., magnetic and gravity) survey data.

Measurements of unjacketed moduli of porous rock

NASA Astrophysics Data System (ADS)

Tarokh, A.; Makhnenko, R. Y.; Labuz, J.

2017-12-01

Coupling of stress and pore pressure appears in a number of applications dealing with subsurface (sedimentary) rock, including petroleum exploration and waste storage. Poroelastic analyses consider the compressibility of the solid constituents forming the rock, and often times solid bulk modulus Ks is assumed to be the same as the dominant mineral bulk modulus. In fact, there are two different parameters describing solid compressibility of a porous rock: the unjacketed bulk modulus Ks' and the unjacketed pore modulus Ks". Experimental techniques are developed to measure the two poroelastic parameters of fluid-saturated porous rock under the unjacketed condition. In an unjacketed experiment, the rock without a membrane is loaded by the fluid in a pressure vessel. The confining fluid permeates the connected pore space throughout the interior of the rock. Therefore, changes in mean stress P will produce equal changes in pore pressure p, i.e. ΔP = Δp. The test can also be performed with a jacketed rock specimen by applying equal increments of mean stress and pore pressure. The unjacketed bulk modulus, Ks', is obtained by measuring the bulk strain with resistive strain gages. The unjacketed pore modulus, Ks", the pore volume counterpart to Ks', is a measure of the change in pore pressure per unit pore volume strain under the unjacketed condition. Several indirect estimates of Ks" have been reported but limitations of these approaches do not provide an accurate value. We present direct measurements of Ks" with detailed calibration on the system volumetric response. The results indicate that for Dunnville sandstone Ks' and Ks" are equal while for Berea sandstone, a difference between the two moduli exists, which is explained by the presence of non-connected pores. The experiments also strongly suggest that both Ks' and Ks" are independent of effective stress.

Multifractal magnetic susceptibility distribution models of hydrothermally altered rocks in the Needle Creek Igneous Center of the Absaroka Mountains, Wyoming

USGS Publications Warehouse

Gettings, M.E.

2005-01-01

Magnetic susceptibility was measured for 700 samples of drill core from thirteen drill holes in the porphyry copper-molybdenum deposit of the Stinkingwater mining district in the Absaroka Mountains, Wyoming. The magnetic susceptibility measurements, chemical analyses, and alteration class provided a database for study of magnetic susceptibility in these altered rocks. The distribution of the magnetic susceptibilities for all samples is multi-modal, with overlapping peaked distributions for samples in the propylitic and phyllic alteration class, a tail of higher susceptibilities for potassic alteration, and an approximately uniform distribution over a narrow range at the highest susceptibilities for unaltered rocks. Samples from all alteration and mineralization classes show susceptibilities across a wide range of values. Samples with secondary (supergene) alteration due to oxidation or enrichment show lower susceptibilities than primary (hypogene) alteration rock. Observed magnetic susceptibility variations and the monolithological character of the host rock suggest that the variations are due to varying degrees of alteration of blocks of rock between fractures that conducted hydrothermal fluids. Alteration of rock from the fractures inward progressively reduces the bulk magnetic susceptibility of the rock. The model introduced in this paper consists of a simulation of the fracture pattern and a simulation of the alteration of the rock between fractures. A multifractal model generated from multiplicative cascades with unequal ratios produces distributions statistically similar to the observed distributions. The reduction in susceptibility in the altered rocks was modelled as a diffusion process operating on the fracture distribution support. The average magnetic susceptibility was then computed for each block. For the purpose of comparing the model results with observation, the simulated magnetic susceptibilities were then averaged over the same interval as the measured data. Comparisons of the model and data from drillholes show good but not perfect agreement. ?? 2005 Author(s). This work is licensed under a Creative Commons License.

Catalog of Apollo 17 rocks. Volume 1: Stations 2 and 3 (South Massif)

NASA Technical Reports Server (NTRS)

Ryder, Graham

1993-01-01

The Catalog of Apollo 17 Rocks is a set of volumes that characterize each of 334 individually numbered rock samples (79 larger than 100 g) in the Apollo 17 collection, showing what each sample is and what is known about it. Unconsolidated regolith samples are not included. The catalog is intended to be used by both researchers requiring sample allocations and a broad audience interested in Apollo 17 rocks. The volumes are arranged geographically, with separate volumes for the South Massif and Light Mantle, the North Massif, and two volumes for the mare plains. Within each volume, the samples are arranged in numerical order, closely corresponding with the sample collection stations. The present volume, for the South Massif and Light Mantle, describes the 55 individual rock fragments collected at Stations two, two-A, three, and LRV-five. Some were chipped from boulders, others collected as individual rocks, some by raking, and a few by picking from the soil in the processing laboratory. Information on sample collection, petrography, chemistry, stable and radiogenic isotopes, rock surface characteristics, physical properties, and curatorial processing is summarized and referenced as far as it is known up to early 1992. The intention has been to be comprehensive: to include all published studies of any kind that provide information on the sample, as well as some unpublished information. References which are primarily bulk interpretations of existing data or mere lists of samples are not generally included. Foreign language journals were not scrutinized, but little data appears to have been published only in such journals. We have attempted to be consistent in format across all of the volumes, and have used a common reference list that appears in all volumes. Where possible, ages based on Sr and Ar isotopes have been recalculated using the 'new' decay constants recommended by Steiger and Jager; however, in many of the reproduced diagrams the ages correspond with the 'old' decay constants. In this volume, mg' or Mg' = atomic Mg/(Mg +Fe).

Chlorine Isotope Evidence for Syn-Subduction Modification of Serpentinites by Interaction with Sediment-Derived Fluid

NASA Astrophysics Data System (ADS)

Selverstone, J.; Sharp, Z. D.

2012-12-01

High-pressure serpentinites and rodingites and high- to ultrahigh-pressure metasedimentary rocks from the Aosta region, Italy, preserve strikingly different chlorine isotope compositions that can be used to constrain the nature of fluid-rock interactions during subduction. Serpentinites and rodingitized gabbroic dikes subducted to 70-80 km have bulk δ37Cl values between -1.6 and +0.9‰ (median= -0.5‰, n=26 plus 5 replicates; one amphibole-vein outlier at -2.9‰). Serpentinite δ37Cl values are positively correlated with Cr ± Cl contents (r2= 0.97 and 0.58) and negatively correlated with CaO (r2=0.72). BSE imaging and X-ray mapping reveal up to three generations of compositionally distinct serpentine and chlorite in single samples. The youngest generation, which is most abundant, has the lowest chlorine content. Three rodingite samples contain abundant texturally early fluid inclusions. These samples were finely crushed and leached in 18 MΩ H2O to extract water-soluble chlorides. The leachates, which are assumed to record the compositions of the fluid inclusions, have δ37Cl values that are 0.7-1.5‰ lower than the corresponding bulk rock values. Leachate from the outlier amph-magnesite vein is indistinguishable from the bulk value at -2.7‰. There is almost no overlap between the Cl isotope compositions of HP serp/rod samples and associated HP/UHP metasedimentary rocks. Calcmica schists, diamond-bearing Mn nodules, and impure marbles subducted to >130 km and calcmica schists and Mn crusts transported to 70-80 km have δ37Cl values between -4.5 and -1.5‰ (median= -2.7‰, n=25 plus 7 replicates; two outlier points at -0.5‰). Primary fluid inclusions in the diamondiferous samples contain carbonate- and silicate-bearing aqueous fluids with very low chloride contents (Frezzotti et al., 2011, Nature Geosci). Taken together, these data record a history of progressive modification of serpentinites and rodingites by mixing with low-δ37Cl, low-Cl, high-Ca fluids during subduction and metamorphism. Serpentinites with the highest Cr contents have Cl isotopic compositions identical to those of modern seafloor serpentinites (δ37Cl=0.2-0.6‰), consistent with primary serpentinization by seawater (e.g., Barnes et al. 2009, Lithos). Low-Cr serpentinites record significant interaction with a Ca-rich fluid that shifted the rocks to lower δ37Cl values and diluted the original Cr and Cl contents. The fluid was likely derived from continuous devolatilization reactions in associated low-δ37Cl, calcareous metasedimentary rocks. These data have important implications for models of subduction mass transfer associated with antigorite breakdown. If serpentinites are commonly modified by interaction with metasedimentary fluids prior to antigorite dehydration, chemical signatures imparted during deserpentinization will reflect the integrated history of fluid-rock interaction in the subduction channel rather than an endmember "serpentinite signature". The data further suggest that Cl may be hydrophobic in HP/UHP carbonate-bearing aqueous fluids, resulting in generation of low-Cl fluid during metamorphic devolatilization.

A method for the concentration of fine-grained rutile (TiO2) from sediment and sedimentary rocks by chemical leaching

USGS Publications Warehouse

Commeau, Judith A.; Valentine, Page C.

1991-01-01

Most of the sample analyzed by the method described were marine muds collected from the Gulf of Maine (Valentine and Commeau, 1990). The silt and clay fraction (up to 99 wt% of the sediment) is composed of clay minerals (chiefly illite-mica and chlorite), silt-size quartz and feldspar, and small crystals (2-12 um) of rutile and hematite. The bulk sediment samples contained an average of 2 to 3 wt percent CaCO3. Tiher samples analyzed include red and gray Carboniferous and Triassic sandstones and siltstones exposed around the Bay of Fundy region and Paleozoic sandstones, siltstones, and shales from northern Maine and New Brunswick. These rocks are probable sources for the fine-grained rutile found in the Gulf of Maine.

Dissolution-Assisted Pattern Formation During Olivine Carbonation

NASA Astrophysics Data System (ADS)

Lisabeth, Harrison; Zhu, Wenlu; Xing, Tiange; De Andrade, Vincent

2017-10-01

Olivine and pyroxene-bearing rocks in the oceanic crust react with hydrothermal fluids producing changes in the physical characteristics and behaviors of the altered rocks. Notably, these reactions tend to increase solid volume, reducing pore volume, permeability, and available reactive surface area, yet entirely hydrated and/or carbonated rocks are commonly observed in the field. We investigate the evolution of porosity and permeability of fractured dunites reacted with CO2-rich solutions in laboratory experiments. The alteration of crack surfaces changes the mechanical and transport properties of the bulk samples. Analysis of three-dimensional microstructural data shows that although precipitation of secondary minerals causes the total porosity of the sample to decrease, an interconnected network of porosity is maintained through channelized dissolution and coupled carbonate precipitation. The observed microstructure appears to be the result of chemo-mechanical coupling, which may provide a mechanism of porosity maintenance without the need to invoke reaction-driven cracking.

New observations on the quartz monzodiorite-granite suite. [in lunar soil

NASA Technical Reports Server (NTRS)

Marvin, U. B.; Holmberg, B. B.; Lindstrom, M. M.; Martinez, R. R.

1991-01-01

Five new fragments of quartz monzodiorite (QMD) were identified in particles from soil 15403, which was collected from the boulder sampled as rock 15405, an impact-melt breccia containing clasts of KREEP basalt, QMD, granite, and a more primitive alkali norite. Petrographic and geochemical studies of the fragments show considerable variation in modal proportions and bulk composition. This heterogeneity is due to unrepresentative sampling in small fragments of coarse-grained rocks. Variations in the proportions of accessory minerals have marked effects on incompatible-trace-element concentrations and ratios. Semiquantitative calculations support the derivation of QMD from 60-percent fractional crystallization of a KREEP basalt magma as suggested by Hess (1989). Apollo 15 KREEP basalt cannot be the actual parent magma because the evolved rocks predate volcanic KREEP basalts. It is suggested that ancient KREEP basalt magmas have crystallized as plutons, with alkali norite clasts offering the only direct evidence of this precursor.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lisabeth, Harrison; Zhu, Wenlu; Xing, Tiange

Olivine and pyroxene bearing rocks in the oceanic crust react with hydrothermal fluids producing changes in the physical characteristics and behaviors of the altered rocks. Notably, these reactions tend to increase solid volume, reducing pore volume, permeability and available reactive surface area; yet, entirely hydrated and/or carbonated rocks are commonly observed in the field. We investigate the evolution of porosity and permeability of fractured dunites reacted with CO 2-rich solutions in laboratory experiments. The alteration of crack surfaces changes the mechanical and transport properties of the bulk samples. Analysis of three-dimensional microstructural data shows that although precipitation of secondary mineralsmore » causes the total porosity of the sample to decrease, an interconnected network of porosity is maintained through channelized dissolution and coupled carbonate precipitation. Lastly, the observed microstructure appears to be the result of chemo-mechanical coupling, which may provide a mechanism of porosity maintenance without the need to invoke reaction-driven cracking.« less

Dissolution-Assisted Pattern Formation During Olivine Carbonation

DOE PAGES

Lisabeth, Harrison; Zhu, Wenlu; Xing, Tiange; ...

2017-08-31

Olivine and pyroxene bearing rocks in the oceanic crust react with hydrothermal fluids producing changes in the physical characteristics and behaviors of the altered rocks. Notably, these reactions tend to increase solid volume, reducing pore volume, permeability and available reactive surface area; yet, entirely hydrated and/or carbonated rocks are commonly observed in the field. We investigate the evolution of porosity and permeability of fractured dunites reacted with CO 2-rich solutions in laboratory experiments. The alteration of crack surfaces changes the mechanical and transport properties of the bulk samples. Analysis of three-dimensional microstructural data shows that although precipitation of secondary mineralsmore » causes the total porosity of the sample to decrease, an interconnected network of porosity is maintained through channelized dissolution and coupled carbonate precipitation. Lastly, the observed microstructure appears to be the result of chemo-mechanical coupling, which may provide a mechanism of porosity maintenance without the need to invoke reaction-driven cracking.« less

Consortium reports on lunar meteorites Yamato 793169 and Asuka 881757, a new type of mare basalt

NASA Technical Reports Server (NTRS)

Yanai, Keizo; Takeda, Hiroshi; Lindstrom, M. M.; Tatsumoto, M.; Torigoe, N.; Misawa, K.; Warren, P. H.; Kallemeyn, G. W.; Koeberl, C.; Kojima, H.

1993-01-01

Consortium studies on lunar meteorites Yamato 793169 and Asuka 881757 (formerly Asuka-31) were performed to characterize these new samples from unknown locations in the lunar mare. Both meteorites are coarse-grained mare rocks having low Mg/Fe ratios (bulk mg'=30-35) and low TiO2 (1.5-2.5 percent in homogenized bulk samples). They are intermediate between VLT and low-Ti mare basalts. Although these meteorites are not identical to each other, their mineral and bulk compositions, isotopic systematics, and crystallization ages are remarkably similar and distinct from those of all other mare basalts. They appear to represent a new type of low-Ti mare basalt that crystallized at about 3.9Ga. These meteorites are inconsistent with the canonical correlation between the TiO2 contents and ages of mare basalts and suggest that our knowledge of lunar volcanism is far from complete.

Integrating isotopic fingerprinting with petrology: how do igneous rocks evolve?

NASA Astrophysics Data System (ADS)

Davidson, J. P.

2002-12-01

In the title of his seminal work, N.L. Bowen recognized the fundamental importance of magmatic evolution in producing the spectrum of igneous rocks. Indeed it is difficult to imagine a hot highly reactive fluid passing through c. 100 km of a chemically distinct medium (lithosphere) without evolving through cooling, crystallization and interaction with the wall rocks. The fact that magmas evolve - almost invariably through open system processes - has been largely marginalized in the past 30 years by the desire to use them as probes of mantle source regions. This perspective has been driven principally by advances offered by isotope geochemistry, through which components and sources can be effectively fingerprinted. Two fundamental observations urge caution in ignoring differentiation effects; 1) the scarcity of truly primary magmas according to geochemical criteria (recognized long ago by petrologists), and 2) the common occurrence of petrographic criteria attesting to open system evolution. Recent advances in multicollector mass spectrometry permit integration of the powerful diagnostic tools of isotope geochemistry with petrographic observations through accurate and precise analysis of small samples. Laser ablation and microdrilling enable sampling within and between mineral phases. The results of our microsampling investigations give widespread support for open system evolution of magmas, and provide insights into the mechanisms and timescales over which this occurs. For example; 1) core-rim decreases in 87Sr/86Sr in zoned plagioclase crystals from 1982 lavas of El Chichon volcano, Mexico, argue that the zoning and isotopic changes are in response to magma recharge mixing with an originally contaminated resident magma; 2) Single grain and intra-grain isotopic analyses of mineral phases from Ngauruhoe andesites (New Zealand) are highly variable, arguing that bulk rock data reflect mechanical aggregations of components which have evolved in discrete domains of the magma storage and delivery system; 3) 87Sr/86Sr variations within feldspars from a single ignimbrite exceed the entire rhyolite bulk rock range of 87Sr/86Sr recorded from the Taupo volcanic zone, New Zealand; arguing that the isotopic heterogeneity encountered during differentiation is greater than that erupted; and 4) Gabbros from the Rum intrusion (NW Scotland) exhibit inter and intra-grain isotopic heterogeneity arguing that accumulation involved mixing of crystal populations which evolved in different domains of an open system magma chamber. These studies suggest that isotopic modification of magmas in the crust (according to P-T estimates of plagiocalse stability) is the rule rather than the exception. Although it is conceivable that isotopic signatures are all inherited from mantle-derived melts which interacted before, during and after crystal growth, it is more likely that the isotopic diversity reflects contamination and mixing which obscures the signature of the mantle contributions. Furthermore, it is perhaps unrealistic to think of the evolution of a particular igneous rock. Rather each rock appears to be an aggregate of components with separate evolutionary histories. Because isotopic composition is leveraged by the mass balance of these components (Sr is typically concentrated in plagioclase, Nd in glass and accessories, Hf in zircon, Pb in feldspar and glass), the isotopic systematics of bulk rocks can become decoupled from each other. Thus the isotope characteristics of the rock components give a more faithful record of evolution processes than the bulk rock itself.

Production of hybrid granitic magma at the advancing front of basaltic underplating: Inferences from the Sesia Magmatic System (south-western Alps, Italy)

NASA Astrophysics Data System (ADS)

Sinigoi, Silvano; Quick, James E.; Demarchi, Gabriella; Klötzli, Urs S.

2016-05-01

The Permian Sesia Magmatic System of the southwestern Alps displays the plumbing system beneath a Permian caldera, including a deep crustal gabbroic complex, upper crustal granite plutons and a bimodal volcanic field dominated by rhyolitic tuff filling the caldera. Isotopic compositions of the deep crustal gabbro overlap those of coeval andesitic basalts, whereas granites define a distinct, more radiogenic cluster (Sri ≈ 0.708 and 0.710, respectively). AFC computations starting from the best mafic candidate for a starting melt show that Nd and Sr isotopic compositions and trace elements of andesitic basalts may be modeled by reactive bulk assimilation of ≈ 30% of partially depleted crust and ≈ 15%-30% gabbro fractionation. Trace elements of the deep crustal gabbro cumulates require a further ≈ 60% fractionation of the andesitic basalt and loss of ≈ 40% of silica-rich residual melt. The composition of the granite plutons is consistent with a mixture of relatively constant proportions of residual melt delivered from the gabbro and anatectic melt. Chemical and field evidence leads to a conceptual model which links the production of the two granitic components to the evolution of the Mafic Complex. During the growth of the Mafic Complex, progressive incorporation of packages of crustal rocks resulted in a roughly steady state rate of assimilation. Anatectic granite originates in the hot zone of melting crust located above the advancing mafic intrusion. Upward segregation of anatectic melts facilitates the assimilation of the partially depleted restite by stoping. At each cycle of mafic intrusion and incorporation, residual and anatectic melts are produced in roughly constant proportions, because the amount of anatectic melt produced at the roof is a function of volume and latent heat of crystallization of the underplated mafic melt which in turn produces proportional amounts of hybrid gabbro cumulates and residual melt. Such a process can explain the restricted range in isotopic compositions of most rhyolitic and granitic rocks of the Permo-Carboniferous province of Europe and elsewhere. Sheet labelled "XRF standard analyses" reports replicate analyses normalized to 100 obtained by XRF on international standards analyzed along with our samples. Sheet labelled "XRF replicate sample analyses" reports replicate XRF analyses on two samples of our data set. ICP-MS analyses from Acme Analytical Laboratories Ltd. are shown for comparison. Sheet labelled "ICP-MS analyses" reports replicate analyses of trace elements on standard SO18, its official value and replicate analyses of two our samples provided by Acme Analytical Laboratories Ltd. Sheet labelled "kinzigite". Major and trace elements of amphibolite-facies paragneiss samples of the Kinzigite Formation from the roof of the Mafic Complex. In bold data by ICP-MS, other data by XRF. For Ba, Rb and Sr XRF data were included in the average estimate to increase the statistics. The last column reports the average data of amphibolite-facies rocks from the Kinzigite Formation from Schnetger (1994). Sheet labelled "PBB paragneiss". Data for granulite-facies paragneiss samples in the septa of the paragneiss bearing belt (PBB). XRF data for Ba and Sr were included in the average estimate to increase the statistics (Rb excluded because close to detection limit for XRF in many samples). The last column reports the average data of granulite-facies rocks from Val Strona (stronalite) from Schnetger (1994). Sheet labelled "PBB charnockite". Data for charnockitic rocks included in paragneiss septa. XRF data for Ba and Sr were included in the average estimate to increase the statistics (Rb excluded because close to detection limit for XRF in many samples). Sheet labelled "computed crustal assimilant". Reports the average compositions of paragneiss in amphibolite and granulite facies from this work and from Schnetger (1994). The bulk composition of the septa is computed as 70% paragneiss and 30% charnockite, as roughly estimated in the field. The partially depleted assimilant is computed as a 50/50 mixture of amphibolite- and granulite facies rocks. Sheet labelled "anatectic products" includes leucosomes at the roof of the Mafic Complex, anatectic granites from this work and from the Atesina Volcanic district (Rottura et al., 1998). In bold data by ICP-MS, other data by XRF. Sheet labelled "Valle Mosso granite" reports the whole rock compositions of granitic rocks of the pluton, distinguishing samples from upper and lower granite. XRF data for Ba, Rb and Sr were included in the average estimate to increase the statistics. The last column reports the bulk composition of the pluton, estimated as 70% lower and 30% upper granite. Sheet labelled "Rhyolite" reports whole rock and average compositions of rhyolite. Sheet labelled "UMC gabbro" reports whole rock compositions of gabbros from the upper Mafic Complex. Samples are grouped as pertaining to the "Upper Zone" and "Main Gabbro" according the subdivision of Rivalenti et al. (1975). Gt gabbro = garnet-bearing gabbro. In bold data by ICP-MS, other data by XRF. For Ba and Sr XRF data were included in the average estimate to increase the statistics. Sheet labelled "computed average UMC" reports the whole composition of upper Mafic complex, estimated as 30% Upper Zone and 70% Main Gabbro. Sheet labelled "mafic rocks in middle crust" reports the whole rock compositions from the mafic pod PST262, intruded at the boundary between Ivrea Zone and Serie dei Laghi at 287 ± 5 Ma (Klötzli et al., 2014) and mafic dikes and an enclave intruded in the lower Valle Mosso granite. Sheet labelled "mafic volcanic rocks" reports the whole rock compositions of basaltic andesite and andesite from the Sesia Magmatic System. The average composition is computed excluding altered samples and XRF data for trace elements. Sr and Nd isotope data from this work and previous publications. Sheet labelled "compositions for modelling" reports a summary of the average compositions of the components used for the computations. Sheet labelled "Kd used for AFC and FC modelling" reports the Kd values and percent of mineral phases used in the AFC and FC computations (from Claeson and Meurer, 2004; Rollinson, 1993; Green et al., 2000; Namur et al., 2011). Sheet labelled "trace elements modelling" reports the results of AFC, bulk mixing and FC computations on trace elements. The enclosed figure illustrates the bulk mixing lines between Campore and average crust or anatectic granite respectively. Mixing required getting the composition of andesitic basalt with average crust and anatectic granite varies from 33 to 63% respectively (see text for consequences). The AFC path from Campore to andesitic basalts overlaps the bulk mixing lines. The shape of the mixing line between residual and anatectic melt results in the poor sensibility of Nd to the addition of anatectic melt to the residual one (εNd remains within the field of mafic rocks up to 80% addition of anatectic melt). Sheet labelled "major elements modelling" reports the results of mass balance computations on major-elements based on bulk mixing and XL-FRAC (Stormer and Nicholls, 1978). Sheet labelled "EC-RAXFC modelling" reports input data and results obtained by EC-RAXFC code (Bohrson and Spera, 2007) to simulate the energy constrained AFC from Campore to andesitic basalt. Liquidus temperature and specific heat of magma and assimilant (tlm, tla, cpm, cpa) as well as heat of crystallization and fusion (hm, ha) were obtained by Rhyolite-Melts code (Gualda et al., 2012) at P = 6 kbar (intermediate pressure between the roof and the deepest rocks of the Mafic Complex; Demarchi et al., 1998), assuming QFM + 2, and H2O content = 0.5 for Campore and = 1.0 for assimilant (intermediate between kinzigite and stronalite from Schnetger, 1994). Initial temperature of assimilant (tlo) was assumed equal to the solidus temperature (ts), which results around 850° from the experimental melting of natural metapelite (Vielzeuf and Holloway, 1988). Non-linear melting functions were chosen within the range of values suggested by Bohrson and Spera (2007). Recharge magma (R) was set = 0 because the homogeneity of the Upper Mafic Complex is best explained if each new mafic pulse is injected at the new neutral buoyancy level, above a dense and partially depleted restite, and may be treated as a single pulse. X was set = 1 assuming that all anatectic melt enters the mafic magma. Different simulations were run using alternatively bulk partition coefficients of Sr and Nd for the assimilant (Da) reported for "standard" upper crust by Bohrson and Spera (2001; 1.5 and 0.25, respectively), Da estimated from our data set (2.15 and 2.6, respectively) and intermediate values. For the mafic magma, the bulk D values (Dm) of 0.77 for Sr and 0.34 for Nd result from the Kd and percent of mineral phases used in the AFC computation. Lat-long grid for samples reported in OS tables.

Effective Elastic and Neutron Capture Cross Section Calculations Corresponding to Simulated Fluid Properties from CO2 Push-Pull Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chugunov, Nikita; Altundas, Bilgin

The submission contains a .xls files consisting of 10 excel sheets, which contain combined list of pressure, saturation, salinity, temperature profiles from the simulation of CO2 push-pull using Brady reservoir model and the corresponding effective compressional and shear velocity, bulk density, and fluid and time-lapse neutron capture cross section profiles of rock at times 0 day (baseline) through 14 days. First 9 sheets (each named after the corresponding CO2 push-pull simulation time) contains simulated pressure, saturation, temperature, salinity profiles and the corresponding effective elastic and neutron capture cross section profiles of rock matrix at the time of CO2 injection. Eachmore » sheet contains two sets of effective compressional velocity profiles of the rock, one based on Gassmann and the other based on Patchy saturation model. Effective neutron capture cross section calculations are done using a proprietary neutron cross-section simulator (SNUPAR) whereas for the thermodynamic properties of CO2 and bulk density of rock matrix filled with fluid, a standalone fluid substitution tool by Schlumberger is used. Last sheet in the file contains the bulk modulus of solid rock, which is inverted from the rock properties (porosity, sound speed etc) based on Gassmann model. Bulk modulus of solid rock in turn is used in the fluid substitution.« less

Martian regolith in Elephant Moraine 79001 shock melts? Evidence from major element composition and sulfur speciation

NASA Astrophysics Data System (ADS)

Walton, E. L.; Jugo, P. J.; Herd, C. D. K.; Wilke, M.

2010-08-01

Shock veins and melt pockets in Lithology A of Martian meteorite Elephant Moraine (EETA) 79001 have been investigated using electron microprobe (EM) analysis, petrography and X-ray Absorption Near Edge Structure (XANES) spectroscopy to determine elemental abundances and sulfur speciation (S 2- versus S 6+). The results constrain the materials that melted to form the shock glasses and identify the source of their high sulfur abundances. The XANES spectra for EETA79001 glasses show a sharp peak at 2.471 keV characteristic of crystalline sulfides and a broad peak centered at 2.477 keV similar to that obtained for sulfide-saturated glass standards analyzed in this study. Sulfate peaks at 2.482 keV were not observed. Bulk compositions of EETA79001 shock melts were estimated by averaging defocused EM analyses. Vein and melt pocket glasses are enriched in Al, Ca, Na and S, and depleted in Fe, Mg and Cr compared to the whole rock. Petrographic observations show preferential melting and mobilization of plagioclase and pyrrhotite associated with melt pocket and vein margins, contributing to the enrichments. Estimates of shock melt bulk compositions obtained from glass analyses are biased towards Fe- and Mg- depletions because, in general, basaltic melts produced from groundmass minerals (plagioclase and clinopyroxene) will quench to a glass, whereas ultramafic melts produced from olivine and low-Ca pyroxene megacrysts crystallize during the quench. We also note that the bulk composition of the shock melt pocket cannot be determined from the average composition of the glass but must also include the crystals that grew from the melt - pyroxene (En 72-75Fs 20-21Wo 5-7) and olivine (Fo 75-80). Reconstruction of glass + crystal analyses gives a bulk composition for the melt pocket that approaches that of lithology A of the meteorite, reflecting bulk melting of everything except xenolith chromite. Our results show that EETA79001 shock veins and melt pockets represent local mineral melts formed by shock impedance contrasts, which can account for the observed compositional anomalies compared to the whole rock sample. The observation that melts produced during shock commonly deviate from the bulk composition of the host rock has been well documented from chondrites, rocks from terrestrial impact structures and other Martian meteorites. The bulk composition of shock melts reflects the proportions of minerals melted; large melt pockets encompass more minerals and approach the whole rock whereas small melt pockets and thin veins reflect local mineralogy. In the latter, the modal abundance of sulfide globules may reach up to 15 vol%. We conclude the shock melt pockets in EETA79001 lithology A contain no significant proportion of Martian regolith.

Exploring the Utilization of Low-Pressure, Piston-Cylinder Experiments to Determine the Bulk Compositions of Finite, Precious Materials

NASA Technical Reports Server (NTRS)

Vander Kaaden, K. E.; McCubbin, F. M.; Harrington, A. D.

2017-01-01

Determining the bulk composition of precious materials with a finite mass (e.g., meteorite samples) is extremely important in the fields of Earth and Planetary Science. From meteorite studies we are able to place constraints on large scale planetary processes like global differentiation and subsequent volcanism, as well as smaller scale processes like crystallization in a magma chamber or sedimentary compaction at the surface. However, with meteorite samples in particular, far too often we are limited by how precious the sample is as well as its limited mass. In this study, we have utilized aliquots of samples previously studied for toxicological hazards, including both the fresh samples (lunar mare basalt NWA 4734, lunar regolith breccia NWA 7611, martian basalt Tissint, martian regolith breccia NWA 7034, a vestian basalt Berthoud, a vestian regolith breccia NWA 2060, and a terrestrial mid-ocean ridge basalt (MORB)), and those that underwent iron leaching (Tissint, NWA 7034, NWA 4734, MORB). With these small masses of material, we performed low pressure (approx. 0.75 GPa), high temperature (greater than 1600 degrees Celsius) melting experiments. Each sample was analyzed using a JEOL 8530F electron microprobe to determine the bulk composition of the materials that were previously examined. When available, the results of our microprobe data were compared with bulk rock compositions in the literature. The results of this study show that with this technique, only approx. 50 mg of sample is required to accurately determine the bulk composition of the materials of interest.

Heterogeneity in small aliquots of Apolllo 15 olivine-normative basalt: Implications for breccia clast studies

NASA Astrophysics Data System (ADS)

Lindstrom, Marilyn M.; Shervais, John W.; Vetter, Scott K.

1993-05-01

Most of the recent advances in lunar petrology are the direct result of breccia pull-apart studies, which have identified a wide array of new highland and mare basalt rock types that occur only as clasts within the breccias. These rocks show that the lunar crust is far more complex than suspected previously, and that processes such as magma mixing and wall-rock assimilation were important in its petrogenesis. These studies are based on the implicit assumption that the breccia clasts, which range in size from a few mm to several cm across, are representative of the parent rock from which they were derived. In many cases, the aliquot allocated for analysis may be only a few grain diameters across. While this problem is most acute for coarse-grained highland rocks, it can also cause considerable uncertainty in the analysis of mare basalt clasts. Similar problems arise with small aliquots of individual hand samples. Our study of sample heterogeneity in 9 samples of Apollo 15 olivine normative basalt (ONB) which exhibit a range in average grain size from coarse to fine are reported. Seven of these samples have not been analyzed previously, one has been analyzed by INAA only, and one has been analyzed by XRF+INAA. Our goal is to assess the effects of small aliquot size on the bulk chemistry of large mare basalt samples, and to extend this assessment to analyses of small breccia clasts.

Heterogeneity in small aliquots of Apolllo 15 olivine-normative basalt: Implications for breccia clast studies

NASA Technical Reports Server (NTRS)

Lindstrom, Marilyn M.; Shervais, John W.; Vetter, Scott K.

1993-01-01

Most of the recent advances in lunar petrology are the direct result of breccia pull-apart studies, which have identified a wide array of new highland and mare basalt rock types that occur only as clasts within the breccias. These rocks show that the lunar crust is far more complex than suspected previously, and that processes such as magma mixing and wall-rock assimilation were important in its petrogenesis. These studies are based on the implicit assumption that the breccia clasts, which range in size from a few mm to several cm across, are representative of the parent rock from which they were derived. In many cases, the aliquot allocated for analysis may be only a few grain diameters across. While this problem is most acute for coarse-grained highland rocks, it can also cause considerable uncertainty in the analysis of mare basalt clasts. Similar problems arise with small aliquots of individual hand samples. Our study of sample heterogeneity in 9 samples of Apollo 15 olivine normative basalt (ONB) which exhibit a range in average grain size from coarse to fine are reported. Seven of these samples have not been analyzed previously, one has been analyzed by INAA only, and one has been analyzed by XRF+INAA. Our goal is to assess the effects of small aliquot size on the bulk chemistry of large mare basalt samples, and to extend this assessment to analyses of small breccia clasts.

Hematite, pyroxene, and phyllosilicates on Mars: Implications from oxidized impact melt rocks from Manicouagan Crater, Quebec, Canada

NASA Technical Reports Server (NTRS)

Morris, Richard V.; Golden, D. C.; Bell, James F., III; Lauer, H. V., Jr.

1995-01-01

Visible and near-IR reflectivity, Mossbauer, and X ray diffraction data were obtained on powders of impact melt rock from the Manicouagan Impact Crater located in Quebec, Canada. The iron mineralogy is dominated by pyroxene for the least oxidized samples and by hematite for the most oxidized samples. Phyllosilicate (smectite) contents up to 15 wt % were found in some heavily oxidized samples. Nanophase hematite and/or paramagnetic ferric iron is observed in all samples. No hydrous ferric oxides (e.g., goethite, lepidocrocite, and ferrihydrite) were detected, which implies the alteration occurred above 250 C. Oxidative alteration is thought to have occurred predominantly during late-stage crystallization and subsolidus cooling of the impact melt by invasion of oxidizing vapors and/or solutions while the impact melt rocks were still hot. The near-IR band minimum correlated with the extent of aleration (Fe(3+)/Fe(sub tot)) and ranged from approx. 1000 nm (high-Ca pyroxene) to approx. 850 nm (bulk, well-crystalline hematite) for least and most oxidized samples, respectively. Intermediate band positions (900-920 nm) are attributed to low-Ca pyroxene and/or a composite band from hematite-pyroxene assemblages. Manicouagan data are consistent with previous assignments of hematite and pyroxene to the 850 and 1000 nm bands observed in Martian reflectivity spectra. Manicouagan data also show that possible assignments for intermediate band positions (900-920 nm) in Martian spectra are pyroxene and/or hematite-pyroxene assemblages. By analogy with impact melt sheets and in agreement with observables for Mars, oxidative alteration of Martian impact melt sheets above 250 C and subsequent erosion could produce rocks and soils with variable proportions of hematite (both bulk and nanophase), pyroxene, and phyllosilicates as iron-bearing mineralogies. If this process is dominant, these phases on Mars were formed rapidly at relatively high temperatures on a sporadic basis throughout the history of the planet. The Manicouagan samples also show that this mineralogical diversity can be accomplished at constant chemical composition, which is also indicated for Mars from analyses of soil at the two Viking landing sites.

Hematite, pyroxene, and phyllosilicates on Mars: Implications from oxidized impact melt rocks from Manicouagan Crater, Quebec, Canada

NASA Technical Reports Server (NTRS)

Morris, Richard V.; Golden, D. C.; Bell, James F., III; Lauer, H. V., Jr.

1995-01-01

Visible and near-IR refectivity, Moessbauer, and X ray diffraction data were obtained on powders of impact melt rock from the Manicouagan Impact Crater located in Quebec, Canada. The iron mineralogy is dominated by pyroxene for the least oxidized samples and by hematite for the most oxidized samples. Phyllosilicate (smectite) contents up to approximately 15 wt % were found in some heavily oxidized samples. Nanophase hematite and/or paramagnetic ferric iron is observed in all samples. No hydrous ferric oxides (e.g., goethite, lepidocrocite, and ferrihydrite) were detected, which implies the alteration occurred above 250 C. Oxidative alteration is thought to have occurred predominantly during late-stage crystallization and subsolidus cooling of the impact melt by invasion of oxidizing vapors and/or solutions while the impact melt rocks were still hot. The near-IR band minimum correlated with the extent of aleration Fe(3+)/Fe(sub tot) and ranged from approximately 1000 nm (high-Ca pyroxene) to approximately 850 nm (bulk, well-crystalline hematite) for least and most oxidized samples, respectively. Intermediate band positions (900-920 nm) are attributed to low-Ca pyroxene and/or a composite band from hematite-pyroxene assemblages. Manicouagan data are consistent with previous assignments of hematite and pyroxene to the approximately 850 and approximately 1000nm bands observed in Martian reflectivity spectra. Manicouagan data also show that possible assignments for intermediate band positions (900-920 nm) in Martian spectra are pyroxene and/or hematite-pyroxene assemblages. By analogy with impact melt sheets and in agreement with observables for Mars, oxidative alteration of Martian impact melt sheets above 250 C and subsequent erosion could produce rocks and soils with variable proportions of hematite (both bulk and nanophase), pyroxene, and phyllosilicates as iron-bearing mineralogies. If this process is dominant, these phases on Mars were formed rapidly at relativly high temperatures on a sporadic basis throughout the history of the planet. The Manicouagan samples also show that this mineralogical diversity can be accomplished at constant chemical composition, which is also indicated for Mars from the analyses of soil at the two Viking landing sites.

Lower continental crust formation through focused flow in km-scale melt conduits: The zoned ultramafic bodies of the Chilas Complex in the Kohistan island arc (NW Pakistan)

NASA Astrophysics Data System (ADS)

Jagoutz, O.; Müntener, O.; Burg, J.-P.; Ulmer, P.; Jagoutz, E.

2006-02-01

Whole-rock and Sm-Nd isotopic data of the main units of the Chilas zoned ultramafic bodies (Kohistan paleo-island arc, NW Pakistan) indicate that ultramafic rocks and gabbronorite sequences stem from a common magma. However, field observations rule out formation of both ultramafic and mafic sequences in terms of gravitational crystal settling in a large magma chamber. Contacts between ultramafic and gabbronorite sequences show emplacement of the dunitic bodies into a semi-consolidated gabbronoritic crystal-mush, which in turn has intruded and reacted with the ultramafic rocks to produce concentric zoning. Field and petrological observations indicate a replacive origin of the dunite. Bulk Mg#'s of dunitic rocks range from 0.87-0.81 indicating that the dunite-forming melt underwent substantial fractionation-differentiation and that percolative fractional crystallization probably generated the dunitic core. The REE chemistry of clinopyroxene in primitive dunite samples and the Nd isotopic composition of ultramafic rocks are in equilibrium with the surrounding gabbronorite. Accordingly, liquids that formed the dunitic rocks and later the mafic sequence derived from a similar depleted source ( ɛNd˜4.8). We propose a mechanism for the comagmatic emplacement, where km-scale ultramafic bodies represent continuous channels reaching down into the upper mantle. The melt-filled porosity in these melt channels diminishes the mean-depth-integrated density difference to the surrounding rocks. Due to buoyancy forces, melt channels raise into the overlying crustal sequence. In the light of such processes, the ultramafic bodies are interpreted as melt channels through which the Chilas gabbronorite sequence was fed. The estimated basaltic-andesitic, low Mg# (˜0.53) bulk composition of the Chilas gabbronorite sequence closely matches estimates of lower crustal compositions. Since the mafic sequence originated from a primary, high Mg# (> 0.7) basaltic arc magma, differentiation of such high Mg# magmas within km-scale isolated melt conduits may explain the "Mg#-gap" between bulk estimates of the continental crust and primary basaltic magmas, a major paradox in the andesite model of crust formation.

Integrated approach for quantification of fractured tight reservoir rocks: Porosity, permeability analyses and 3D fracture network characterisation on fractured dolomite samples

NASA Astrophysics Data System (ADS)

Voorn, Maarten; Barnhoorn, Auke; Exner, Ulrike; Baud, Patrick; Reuschlé, Thierry

2015-04-01

Fractured reservoir rocks make up an important part of the hydrocarbon reservoirs worldwide. A detailed analysis of fractures and fracture networks in reservoir rock samples is thus essential to determine the potential of these fractured reservoirs. However, common analyses on drill core and plug samples taken from such reservoirs (including hand specimen analysis, thin section analysis and laboratory porosity and permeability determination) suffer from various problems, such as having a limited resolution, providing only 2D and no internal structure information, being destructive on the samples and/or not being representative for full fracture networks. In this study, we therefore explore the use of an additional method - non-destructive 3D X-ray micro-Computed Tomography (μCT) - to obtain more information on such fractured samples. Seven plug-sized samples were selected from narrowly fractured rocks of the Hauptdolomit formation, taken from wellbores in the Vienna Basin, Austria. These samples span a range of different fault rocks in a fault zone interpretation, from damage zone to fault core. 3D μCT data is used to extract porosity, fracture aperture, fracture density and fracture orientations - in bulk as well as locally. The 3D analyses are complemented with thin sections made to provide some 2D information with a much higher detail than the μCT data. Finally, gas- and water permeability measurements under confining pressure provide an important link (at least in order of magnitude) of the µCT results towards more realistic reservoir conditions. Our results show that 3D μCT can be applied efficiently on plug-sized samples of naturally fractured rocks, and that several important parameters can be extracted. μCT can therefore be a useful addition to studies on such reservoir rocks, and provide valuable input for modelling and simulations. Also permeability experiments under confining pressure provide important additional insights. Combining these and other methods can therefore be a powerful approach in microstructural analysis of reservoir rocks, especially when applying the concepts that we present (on a small set of samples) in a larger study, in an automated and standardised manner.

The permeability of fault zones in the upper continental crust: statistical analysis from 460 datasets, updated depth-trends, and permeability contrasts between fault damage zones and protoliths.

NASA Astrophysics Data System (ADS)

Scibek, J.; Gleeson, T. P.; Ingebritsen, S.; McKenzie, J. M.

2017-12-01

Fault zones are an important part of the hydraulic structure of the Earth's crust and influence a wide range of Earth processes and a large amount of test data has been collected over the years. We conducted a meta-analysis of global of fault zone permeabilities in the upper brittle continental crust, using about 10,000 published research items from a variety of geoscience and engineering disciplines. Using 460 datasets at 340 localities, the in-situ bulk permeabilities (>10's meters scale, including macro-fractures) and matrix permeabilities (drilled core samples or outcrop spot tests) are separated, analyzed, and compared. The values have log-normal distributions and we analyze the log-permeability values. In the fault damage zones of plutonic and metamorphic rocks the mean bulk permeability was 1x10-14m2, compared to matrix mean of 1x10-16m2. In sedimentary siliciclastic rocks the mean value was the same for bulk and matrix permeability (4x10-14m2). More useful insights were determined from the regression analysis of paired permeability data at all sites (fault damage zone vs. protolith). Much of the variation in fault permeability is explained by the permeability of protolith: in relatively weak volcaniclastic and clay-rich rocks up to 70 to 88% of the variation is explained, and only 20-30% in plutonic and metamorphic rocks. We propose a revision at shallow depths for previously published upper-bound curves for the "fault-damaged crust " and the geothermal-metamorphic rock assemblage outside of major fault zones. Although the bounding curves describe the "fault-damaged crust" permeability parameter space adequately, the only statistically significant permeability-depth trend is for plutonic and metamorphic rocks (50% of variation explained). We find a depth-dependent systematic variation of the permeability ratio (fault damage zone / protolith) from the in-situ bulk permeability global data. A moving average of the log-permeability ratio value is 2 to 2.5 (global mean is 2.2). Although the data is unevenly distributed with depth, the present evidence is that the permeability ratio is at a maximum at depths 1 to 2 kilometers, decreases with depth below 2km, and is also lower near the ground surface.

Rock magnetic properties estimated from coercivity - blocking temperature diagram: application to recent volcanic rocks

NASA Astrophysics Data System (ADS)

Terada, T.; Sato, M.; Mochizuki, N.; Yamamoto, Y.; Tsunakawa, H.

2013-12-01

Magnetic properties of ferromagnetic minerals generally depend on their chemical composition, crystal structure, size, and shape. In the usual paleomagnetic study, we use a bulk sample which is the assemblage of magnetic minerals showing broad distributions of various magnetic properties. Microscopic and Curie-point observations of the bulk sample enable us to identify the constituent magnetic minerals, while other measurements, for example, stepwise thermal and/or alternating field demagnetizations (ThD, AFD) make it possible to estimate size, shape and domain state of the constituent magnetic grains. However, estimation based on stepwise demagnetizations has a limitation that magnetic grains with the same coercivity Hc (or blocking temperature Tb) can be identified as the single population even though they could have different size and shape. Dunlop and West (1969) carried out mapping of grain size and coercivity (Hc) using pTRM. However, it is considered that their mapping method is basically applicable to natural rocks containing only SD grains, since the grain sizes are estimated on the basis of the single domain theory (Neel, 1949). In addition, it is impossible to check thermal alteration due to laboratory heating in their experiment. In the present study we propose a new experimental method which makes it possible to estimate distribution of size and shape of magnetic minerals in a bulk sample. The present method is composed of simple procedures: (1) imparting ARM to a bulk sample, (2) ThD at a certain temperature, (3) stepwise AFD on the remaining ARM, (4) repeating the steps (1) ~ (3) with ThD at elevating temperatures up to the Curie temperature of the sample. After completion of the whole procedures, ARM spectra are calculated and mapped on the HC-Tb plane (hereafter called HC-Tb diagram). We analyze the Hc-Tb diagrams as follows: (1) For uniaxial SD populations, theoretical curve for a certain grain size (or shape anisotropy) is drawn on the Hc-Tb diagram. The curves are calculated using the single domain theory, since coercivity and blocking temperature of uniaxial SD grains can be expressed as a function of size and shape. (2) Boundary between SD and MD grains are calculated and drawn on the Hc-Tb diagram according to the theory by Butler and Banerjee (1975). (3) Theoretical predictions by (1) and (2) are compared with the obtained ARM spectra to estimate quantitive distribution of size, shape and domain state of magnetic grains in the sample. This mapping method has been applied to three samples: Hawaiian basaltic lava extruded in 1995, Ueno basaltic lava formed during Matsuyama chron, and Oshima basaltic lava extruded in 1986. We will discuss physical states of magnetic grains (size, shape, domain state, etc.) and their possible origins.

Evolution of strength and physical properties of carbonate and ultramafic rocks under hydrothermal conditions

NASA Astrophysics Data System (ADS)

Lisabeth, Harrison Paul

Interaction of rocks with fluids can significantly change mineral assemblage and structure. This so-called hydrothermal alteration is ubiquitous in the Earth's crust. Though the behavior of hydrothermally altered rocks can have planet-scale consequences, such as facilitating oceanic spreading along slow ridge segments and recycling volatiles into the mantle at subduction zones, the mechanisms involved in the hydrothermal alteration are often microscopic. Fluid-rock interactions take place where the fluid and rock meet. Fluid distribution, flux rate and reactive surface area control the efficiency and extent of hydrothermal alteration. Fluid-rock interactions, such as dissolution, precipitation and fluid mediated fracture and frictional sliding lead to changes in porosity and pore structure that feed back into the hydraulic and mechanical behavior of the bulk rock. Examining the nature of this highly coupled system involves coordinating observations of the mineralogy and structure of naturally altered rocks and laboratory investigation of the fine scale mechanisms of transformation under controlled conditions. In this study, I focus on fluid-rock interactions involving two common lithologies, carbonates and ultramafics, in order to elucidate the coupling between mechanical, hydraulic and chemical processes in these rocks. I perform constant strain-rate triaxial deformation and constant-stress creep tests on several suites of samples while monitoring the evolution of sample strain, permeability and physical properties. Subsequent microstructures are analyzed using optical and scanning electron microscopy. This work yields laboratory-based constraints on the extent and mechanisms of water weakening in carbonates and carbonation reactions in ultramafic rocks. I find that inundation with pore fluid thereby reducing permeability. This effect is sensitive to pore fluid saturation with respect to calcium carbonate. Fluid inundation weakens dunites as well. The addition of carbon dioxide to pore fluid enhances compaction and partial recovery of strength compared to pure water samples. Enhanced compaction in CO2-rich fluid samples is not accompanied by enhanced permeability reduction. Analysis of sample microstructures indicates that precipitation of carbonates along fracture surfaces is responsible for the partial restrengthening and channelized dissolution of olivine is responsible for permeability maintenance.

Mineralogy, petrology and chemistry of ANT-suite rocks from the lunar highlands

NASA Technical Reports Server (NTRS)

Prinz, M.; Keil, K.

1977-01-01

Anorthositic-noritic-troctolitic (ANT) rocks are the oldest and most abundant rocks of the lunar surface, and comprise about 90% of the suite of the lunar highlands. Consideration is given to the mineralogy, petrology, bulk chemistry, and origin of ANT-suite rocks. Problems associated in classifying and labeling lunar highland rocks because of textural complexities occurring from impact modifications are discussed. The mineralogy of ANT-suite rocks, dominated by plagioclase, olivine and pyrozene, and containing various minor minerals, is outlined. The petrology of ANT-suite rocks is reviewed along with the major element bulk composition of these rocks, noting that they are extremely depleted in K2O and P2O5. Various models describing the origin of ANT-suite rocks are summarized, and it is suggested that this origin involves a parental liquid of high-alumina basalt with low Fe/Fe+Mg.

Manicouagan impact melt, Quebec. I - Stratigraphy, petrology, and chemistry

NASA Technical Reports Server (NTRS)

Floran, R. J.; Grieve, R. A. F.; Dence, M. R.; Phinney, W. C.; Warner, J. L.; Blanchard, D. P.; Simonds, C. H.

1978-01-01

A sheet of clast-laden impact melt 230 m thick and 55 km in diameter forms an annular plateau surrounding an uplift of shocked anorthosite within the moderately eroded Manicouagan structure. Three gradational units of the melt sheet are characterized with respect to grain size, inclusions, texture, and mineralogy. The melt rocks as a group are chemically homogeneous with a bulk composition similar to that of latite and with no statistically significant regional chemical variations. The melt is not completely chemically homogeneous as a local mafic variant represented by two samples with poikilitic texture was found. These poikilitic rocks texturally resemble some Apollo 17 impact melt rocks and are inferred to have had a similar origin and thermal history.

Lunar highland meteorite Dhofar 026 and Apollo sample 15418: Two strongly shocked, partially melted, granulitic breccias

USGS Publications Warehouse

Cohen, B. A.; James, O.B.; Taylor, L.A.; Nazarov, M.A.; Barsukova, L.D.

2004-01-01

Studies of lunar meteorite Dhofar 026, and comparison to Apollo sample 15418, indicate that Dhofar 026 is a strongly shocked granulitic breccia (or a fragmental breccia consisting almost entirely of granulitic breccia clasts) that experienced considerable post-shock heating, probably as a result of diffusion of heat into the rock from an external, hotter source. The shock converted plagioclase to maskelynite, indicating that the shock pressure was between 30 and 45 GPa. The post-shock heating raised the rock's temperature to about 1200 ??C; as a result, the maskelynite devitrified, and extensive partial melting took place. The melting was concentrated in pyroxene-rich areas; all pyroxene melted. As the rock cooled, the partial melts crystallized with fine-grained, subophitic-poikilitic textures. Sample 15418 is a strongly shocked granulitic breccia that had a similar history, but evidence for this history is better preserved than in Dhofar 026. The fact that Dhofar 026 was previously interpreted as an impact melt breccia underscores the importance of detailed petrographic study in interpretation of lunar rocks that have complex textures. The name "impact melt" has, in past studies, been applied only to rocks in which the melt fraction formed by shock-induced total fusion. Recently, however, this name has also been applied to rocks containing melt formed by heating of the rocks by conductive heat transfer, assuming that impact is the ultimate source of the heat. We urge that the name "impact melt" be restricted to rocks in which the bulk of the melt formed by shock-induced fusion to avoid confusion engendered by applying the same name to rocks melted by different processes. ?? Meteoritical Society, 2004.

Investigation of Usability as Aggregate of Different Originated Rocks

NASA Astrophysics Data System (ADS)

Başpinar Tuncay, Ebru; Kilinçarslan, Şemsettin; Yağmurlu, Fuzuli

2016-10-01

The general properties of aggregate can determine the performance and durability of the concrete. In this study, mineralogical, petrographic, mechanical, physical and chemical properties of the rock samples of different origin (limestone, recrystallized limestone, dolomite, sand and gravel, tephra-phonolite, trachybasalt) were determined. Samples were obtained from different origin rocks units and they have been classified in three different sizes of aggregate with crushing and screening method. Grading, classification of particle, loose bulk density, water absorption ratio, flakiness index, coefficient of Los Angeles, resistance to freeze-loosening and alkali-silica reaction of aggregates and organic matter determination has been determined. The rocks have been investigated in compliance with the relevant standards. Trachybasalt and dolomite have higher particle density than other rocks. In addition, strength and flexural strength of these rocks are higher than other rocks. Tephra-phonolite has the lowest water absorption rate. At the same time resistance to freeze loosening of Tephra- phonolite is lower than the other rocks. Resistance to fragmentation and the resistance to wear of all of rocks are quite high. Sand and gravel, tephra-phonolite and trachybasalt are evaluated in terms of alkali-silica reaction. Sand and gravel are more reactive than the other aggregates. Organic matter content of the aggregates is low for the quality of aggregate. Also high correlation between some properties of aggregates was observed. For example, high correlation between compressive strength and flexural strength, water absorption and porosity, resistance to fragmentation and the resistance to ware (Micro-Deval).

Thermal Inertia of Rocks and Rock Populations

NASA Technical Reports Server (NTRS)

Golombek, M. P.; Jakosky, B. M.; Mellon, M. T.

2001-01-01

The effective thermal inertia of rock populations on Mars and Earth is derived from a model of effective inertia versus rock diameter. Results allow a parameterization of the effective rock inertia versus rock abundance and bulk and fine component inertia. Additional information is contained in the original extended abstract.

What is the iron isotope composition of the Moon?

NASA Astrophysics Data System (ADS)

Poitrasson, F.; Zambardi, T.; Magna, T.; Neal, C. R.

2016-12-01

It is difficult to estimate the bulk chemical and isotopic composition of the Moon because of severe limitations in our sampling. As a result, there is currently a debate on the bulk Fe isotope composition of the Moon despite the constraints on the lunar accretion modes or differentiation processes it may provide. For this, a proper mass balance estimation of essential planetary reservoirs is required. For instance, the dichotomy in δ57Fe between low- and high-Ti mare basalt varieties as a consequence of differences in degree of fractional crystallization of their respective lunar mantle sources should be rigorously tested. To investigate this, we performed new iron isotope measurements of 33 bulk lunar mare basalts and highland rocks, including KREEP-related materials. The new data show significant Fe isotope differences between high-Ti and low-Ti mare basalts, yielding mean δ57FeIRMM-014=0.277±0.020‰ and δ57FeIRMM-014=0.127±0.020‰, respectively. Assuming that lunar basalts mirror the iron isotope composition of their respective mantle protoliths, the estimated relative proportion of the low-Ti and high-Ti mantle source suggests that the lunar upper mantle should be close to δ57Fe=0.14±0.03‰. At present, it is unclear whether the bulk lunar Fe isotope composition is indistinguishable from that of the Earth (δ57FeIRMM-014=0.10±0.03‰), when estimated solely from mare basalts data, or if it is twice as heavy relative to chondrites, as initially proposed. A large scatter at δ57Fe=0.08±0.19‰ for ferroan anorthosites, Mg-suite rocks and a KREEP basalt imparts more complexities for global isotopic view of the Moon. A better understanding of the cause of Fe isotope heterogeneity among the lunar highland rocks will likely allow to better estimate the bulk Moon composition, and possibly to improve our knowledge about the genesis of the lunar crust itself.

Acid-neutralizing potential of minerals in intrusive rocks of the Boulder batholith in northern Jefferson County, Montana

USGS Publications Warehouse

Desborough, George A.; Briggs, Paul H.; Mazza, Nilah; Driscoll, Rhonda

1998-01-01

Experimental studies show that fresh granitic rocks of the Boulder batholith in the Boulder River headwaters near Basin, Montana have significant acid-neutralizing potential and are capable of neutralizing acidic water derived from metal-mining related wastes or mine workings. Laboratory studies show that in addition to the acidneutralizing potential (ANP) of minor amounts of calcite in these rocks, biotite, tremolite, and feldspars will contribute significantly to long-term ANP. We produced 0.45 micrometer-filtered acidic (pH = 2.95) leachate for use in these ANP experiments by exposing metal-mining related wastes to deionized water in a waste:leachate ratio of 1:20. We then exposed these leachates to finely-ground and sized fractions of batholith rocks, and some of their mineral fractions for extended and repeated periods, for which results are reported here. The intent was to understand what reactions of metal-rich acidic water and fresh igneous rocks would produce. The reactions between the acidic leachates and the bulk rocks and mineral fractions are complex. Factors such as precipitation of phases like Fe-hydroxides and Alhydroxides and the balance between dissolved cations and anions that are sulfate dominated complicate analysis of the results. Research by others of acid neutralization by biotite and tremolite attributed a rise in pH to proton (H+) adsorption in sites vacated by K, Mg, and Ca. Destruction of the silicate framework and liberation of associated structural hydroxyl ions may contribute to ANP. Studies by others have indicated that the conversion of biotite to a vermiculite-type structure by removal of K at a pH of 4 consumes about six protons for every mole of biotite, but at a pH of 3 there is pronounced dissolution of the tetrahedral lattice. The ANP of fresh granitic rocks is much higher than anticipated. The three bulk Boulder igneous rock samples studied have minimum ANP equivalent to about 10-14 weight percent calcite. This ANP is in addition to that provided by the 0.36-1.4 weight percent calcite present in these samples. The total rock ANP is thus equivalent to that of many sedimentary rocks that are generally believed to be among the most efficient for attenuation of acidic waters. The long-term ANP contributed by biotite, tremolite, feldspars, and possibly unidentified minerals in these rocks, as well as calcite, are all important with regard to their natural remediation of degraded water quality originating from Fe-sulfide rich mineral deposits and the associated mine wastes and acid-mine drainage water.

Compaction Characteristics of Earth-Rock Mixtures. Report 1. Vicksburg Silty Clay and Degray Dam Clayey Sandy Gravel

DTIC Science & Technology

1973-05-01

dry density of total sample Yf = dry unit weight of finer fraction G = bulk specific gravity of coarser fraction (based on ovendry weightq). Same as G...ttl~o o 40 oe o Fig. ii. Theoretical and experimental densities of eclayey sandy gravel (GC) DeGray meterial expressions require tests performed on

Porosity, permeability and 3D fracture network characterisation of dolomite reservoir rock samples

PubMed Central

Voorn, Maarten; Exner, Ulrike; Barnhoorn, Auke; Baud, Patrick; Reuschlé, Thierry

2015-01-01

With fractured rocks making up an important part of hydrocarbon reservoirs worldwide, detailed analysis of fractures and fracture networks is essential. However, common analyses on drill core and plug samples taken from such reservoirs (including hand specimen analysis, thin section analysis and laboratory porosity and permeability determination) however suffer from various problems, such as having a limited resolution, providing only 2D and no internal structure information, being destructive on the samples and/or not being representative for full fracture networks. In this paper, we therefore explore the use of an additional method – non-destructive 3D X-ray micro-Computed Tomography (μCT) – to obtain more information on such fractured samples. Seven plug-sized samples were selected from narrowly fractured rocks of the Hauptdolomit formation, taken from wellbores in the Vienna basin, Austria. These samples span a range of different fault rocks in a fault zone interpretation, from damage zone to fault core. We process the 3D μCT data in this study by a Hessian-based fracture filtering routine and can successfully extract porosity, fracture aperture, fracture density and fracture orientations – in bulk as well as locally. Additionally, thin sections made from selected plug samples provide 2D information with a much higher detail than the μCT data. Finally, gas- and water permeability measurements under confining pressure provide an important link (at least in order of magnitude) towards more realistic reservoir conditions. This study shows that 3D μCT can be applied efficiently on plug-sized samples of naturally fractured rocks, and that although there are limitations, several important parameters can be extracted. μCT can therefore be a useful addition to studies on such reservoir rocks, and provide valuable input for modelling and simulations. Also permeability experiments under confining pressure provide important additional insights. Combining these and other methods can therefore be a powerful approach in microstructural analysis of reservoir rocks, especially when applying the concepts that we present (on a small set of samples) in a larger study, in an automated and standardised manner. PMID:26549935

Porosity, permeability and 3D fracture network characterisation of dolomite reservoir rock samples.

PubMed

Voorn, Maarten; Exner, Ulrike; Barnhoorn, Auke; Baud, Patrick; Reuschlé, Thierry

2015-03-01

With fractured rocks making up an important part of hydrocarbon reservoirs worldwide, detailed analysis of fractures and fracture networks is essential. However, common analyses on drill core and plug samples taken from such reservoirs (including hand specimen analysis, thin section analysis and laboratory porosity and permeability determination) however suffer from various problems, such as having a limited resolution, providing only 2D and no internal structure information, being destructive on the samples and/or not being representative for full fracture networks. In this paper, we therefore explore the use of an additional method - non-destructive 3D X-ray micro-Computed Tomography (μCT) - to obtain more information on such fractured samples. Seven plug-sized samples were selected from narrowly fractured rocks of the Hauptdolomit formation, taken from wellbores in the Vienna basin, Austria. These samples span a range of different fault rocks in a fault zone interpretation, from damage zone to fault core. We process the 3D μCT data in this study by a Hessian-based fracture filtering routine and can successfully extract porosity, fracture aperture, fracture density and fracture orientations - in bulk as well as locally. Additionally, thin sections made from selected plug samples provide 2D information with a much higher detail than the μCT data. Finally, gas- and water permeability measurements under confining pressure provide an important link (at least in order of magnitude) towards more realistic reservoir conditions. This study shows that 3D μCT can be applied efficiently on plug-sized samples of naturally fractured rocks, and that although there are limitations, several important parameters can be extracted. μCT can therefore be a useful addition to studies on such reservoir rocks, and provide valuable input for modelling and simulations. Also permeability experiments under confining pressure provide important additional insights. Combining these and other methods can therefore be a powerful approach in microstructural analysis of reservoir rocks, especially when applying the concepts that we present (on a small set of samples) in a larger study, in an automated and standardised manner.

The effect of grain size and cement content on index properties of weakly solidified artificial sandstones

NASA Astrophysics Data System (ADS)

Atapour, Hadi; Mortazavi, Ali

2018-04-01

The effects of textural characteristics, especially grain size, on index properties of weakly solidified artificial sandstones are studied. For this purpose, a relatively large number of laboratory tests were carried out on artificial sandstones that were produced in the laboratory. The prepared samples represent fifteen sandstone types consisting of five different median grain sizes and three different cement contents. Indices rock properties including effective porosity, bulk density, point load strength index, and Schmidt hammer values (SHVs) were determined. Experimental results showed that the grain size has significant effects on index properties of weakly solidified sandstones. The porosity of samples is inversely related to the grain size and decreases linearly as grain size increases. While a direct relationship was observed between grain size and dry bulk density, as bulk density increased with increasing median grain size. Furthermore, it was observed that the point load strength index and SHV of samples increased as a result of grain size increase. These observations are indirectly related to the porosity decrease as a function of median grain size.

Separation of Diamagnetic and Paramagnetic Fabrics Reveals Strain Directions in Carbonate Rocks

NASA Astrophysics Data System (ADS)

Issachar, R.; Levi, T.; Marco, S.; Weinberger, R.

2018-03-01

We present a new procedure for separating magnetic fabrics in coccolith-bearing chalk samples, demonstrated in the case studies of three sites located within the Dead Sea Fault (DSF) plate boundary. The separation is achieved by combining measurements of room temperature and low-temperature anisotropy of magnetic susceptibility (RT-AMS and LT-AMS, respectively) with anisotropy of anhysteretic remanence magnetization (AARM). The LT-AMS, measured at 77 K, enhances the fabric of paramagnetic clay minerals. The AARM represents the fabric of ferromagnetic Fe oxides. By subtracting the paramagnetic and ferromagnetic fabrics from the RT-AMS, the diamagnetic fabric is separated. In the studied samples, we found that the ferromagnetic contribution to the bulk magnetic fabric is negligible and could be excluded from the subtraction procedure. Our analysis indicates that in chalks with a negligible ferromagnetic contribution, diamagnetic fabric predominates the rock bulk magnetic fabric, if the mean susceptibility is <-6 × 10-6 SI, whereas with a mean susceptibility >11 × 10-6 SI, paramagnetic fabric predominates. In the studied rocks, the paramagnetic clay minerals preserve the original depositional fabric, whereas the diamagnetic minerals show a tectonic fabric. We propose a mechanism by which coccolith rotation under tectonic strain contributes to the development of the diamagnetic fabric parallel to the shortening direction. We infer that the diamagnetic fabrics of the studied rocks indicate strain regime of approximately N-S horizontal shortening near strands of the DSF system. This suggests a deflection of the regional principal strain axes near the DSF. The diamagnetic fabric is more sensitive to tectonic strain than paramagnetic fabric in chalks and provides a valuable strain indicator near major faults.

Petrography, mineralogy, and geochemistry of lunar meteorite Sayh al Uhaymir 300

NASA Astrophysics Data System (ADS)

Hsu, Weibiao; Zhang, Aicheng; Bartoschewitz, Rainer; Guan, Yunbin; Ushikubo, Takayuki; KrńHenbÜHl, Urs; Niedergesaess, Rainer; Pepelnik, Rudolf; Reus, Ulrich; Kurtz, Thomas; Kurtz, Paul

2008-08-01

We report here the petrography, mineralogy, and geochemistry of lunar meteorite Sayh al Uhaymir 300 (SaU 300). SaU 300 is dominated by a fine-grained crystalline matrix surrounding mineral fragments (plagioclase, pyroxene, olivine, and ilmenite) and lithic clasts (mainly feldspathic to noritic). Mare basalt and KREEPy rocks are absent. Glass melt veins and impact melts are present, indicating that the rock has been subjected to a second impact event. FeNi metal and troilite grains were observed in the matrix. Major element concentrations of SaU 300 (Al2O3 21.6 wt% and FeO 8.16 wt%) are very similar to those of two basalt-bearing feldspathic regolith breccias: Calcalong Creek and Yamato (Y-) 983885. However, the rare earth element (REE) abundances and pattern of SaU 300 resemble the patterns of feldspathic highlands meteorites (e.g., Queen Alexandra Range (QUE) 93069 and Dar al Gani (DaG) 400), and the average lunar highlands crust. It has a relatively LREE-enriched (7 to 10 x CI) pattern with a positive Eu anomaly (˜11 x CI). Values of Fe/Mn ratios of olivine, pyroxene, and the bulk sample are essentially consistent with a lunar origin. SaU 300 also contains high siderophile abundances with a chondritic Ni/Ir ratio. SaU 300 has experienced moderate terrestrial weathering as its bulk Sr concentration is elevated compared to other lunar meteorites and Apollo and Luna samples. Mineral chemistry and trace element abundances of SaU 300 fall within the ranges of lunar feldspathic meteorites and FAN rocks. SaU 300 is a feldspathic impact-melt breccia predominantly composed of feldspathic highlands rocks with a small amount of mafic component. With a bulk Mg# of 0.67, it is the most mafic of the feldspathic meteorites and represents a lunar surface composition distinct from any other known lunar meteorites. On the basis of its low Th concentration (0.46 ppm) and its lack of KREEPy and mare basaltic components, the source region of SaU 300 could have been within a highland terrain, a great distance from the Imbrium impact basin, probably on the far side of the Moon.

Characterization of the Fault Core and Damage Zone of the Borrego Fault, 2010 M7.2 Rupture

NASA Astrophysics Data System (ADS)

Dorsey, M. T.; Rockwell, T. K.; Girty, G.; Ostermeijer, G.; Mitchell, T. M.; Fletcher, J. M.

2017-12-01

We collected a continuous sample of the fault core and 23 samples of the damage zone out to 52 m across the rupture trace of the 2010 M7.2 El Mayor-Cucapa earthquake to characterize the physical damage and chemical transformations associated with this active seismic source. In addition to quantifying fracture intensity from macroscopic analysis, we cut a continuous thin section through the fault core and from various samples in the damage zone, and ran each sample for XRD analyses for clay mineralogy, XRF for bulk geochemical analyses, and bulk and grain density from which porosity and volumetric strain were derived. The parent rock is a hydrothermally-altered biotite tonalite, with biotite partially altered to chlorite. The presence of epidote with chlorite suggests that these rocks were subjected to relatively high temperatures of 300-400° C. Adjacent to the outermost damage zone is a chaotic breccia zone with distinct chemical and physical characteristics, indicating possible connection to an ancestral fault to the southwest. The damage zone consists of an outer zone of protocataclasite, which grades inward towards mesocataclasite with seams of ultracataclasite. The fault core is anomalous in that it is largely composed of a sliver of marble that has been translated along the fault, so direct comparison with the damage zone is impaired. From collected data, we observe that chloritization increases into the breccia and damage zones, as does the presence of illite. Porosity reaches maximum values in the damage zone adjacent to the core, and closely follows trends in fracture intensity. Statistically significant gains in Mg, Na, K, Mn, and total bulk mass occurred within the inner damage zone, with losses of Ca and P mass, which led to the formation of chlorite and albite. The outer damage zone displays gains in Mg and Na mass with losses in Ca and P mass. The breccia zone shows gains in mass of Mg and Mn and loss in total bulk mass. A gain in LOI in both the breccia and damage zones is attributed to formation of clay. Volumetric strain tracks porosity, as expected, and increases towards the core. Notably, damage appears to be superposed on chemical alterations, which supports the idea that much of the hydrothermal alteration occurred at depth followed by brecciation and cataclasis once the fault zone rocks were exhumed closer to the surface.

Characterization of rock samples and mineralogical controls on leachates

USGS Publications Warehouse

Hammarstrom, Jane M.; Cravotta, Charles A.; Galeone, Daniel G.; Jackson, John C.; Dulong, Frank T.; Hornberger, Roger J.; Brady, Keith B.C.

2009-01-01

Rocks associated with coal beds typically include shale, sandstone, and (or) limestone. In addition to common rock-forming minerals, all of these rock types may contain sulfide and sulfate minerals, various carbonate minerals, and organic material. These different minerals have inherently different solubility characteristics, as well as different acid-generating or acid-neutralizing potentials. The abundance and composition of sulfur- and carbonate-bearing minerals are of particular interest in interpreting the leaching column data because (1) pyrite and carbonate minerals are the primary controls on the acid-base account of a sample, (2) these minerals incorporate trace metals that can be released during weathering, and (3) these minerals readily react during weathering due to mineral dissolution and oxidation of iron.Rock samples were collected by the Pennsylvania Department of Environmental Protection (PaDEP) from five different sites to assess the draft standardized leaching column method (ADTI-WP2) for the prediction of weathering rates and water quality at coal mines. Samples were sent to USGS laboratories for mineralogical characterization and to ActLabs for chemical analysis. The samples represent a variety of rock types (shales, sandstones, and coal refuse) that are typical of coal overburden in the eastern United States. These particular samples were chosen for testing the weathering protocols because they represent a range of geochemical and lithologic characteristics, sulfur contents, and acid-base accounting characteristics (Hornberger et al., 2003). The rocks contain variable amounts of pyrite and carbonate minerals and vary in texture.This chapter includes bulk rock chemical data and detailed mineralogical and textural data for unweathered starting materials used in the interlaboratory validation study, and for two samples used in the early phases of leaching column tests (Wadesville Sandstone, Leechburg Coal Refuse). We also characterize some of the post-weathering rock samples, report trace-element content in leachate, and discuss mineralogical controls on leachate quality based on data from one of the participating laboratories. Table 5.1 lists the samples described in this chapter, the sample numbers, and comments on the characteristics of each lithology. Sample locations are plotted in Figure 5.1. Chapters 2 and 3 describe the sample locations, sample preparation protocols, ABA characteristics, and rationale for selection of rock samples for testing. Microprobe data for pyrite and carbonate minerals are tabulated in Appendix 5.1. Leachate data, along with a series of graphs showing concentration and cumulative transport trends, for the laboratory data discussed in this chapter are included as Excel spreadsheets in Appendices 5.2 and 5.3. Leach column data for the interlaboratory study are evaluated and interpreted in Chapters 7 -11.

Iron isotope behavior during fluid/rock interaction in K-feldspar alteration zone - A model for pyrite in gold deposits from the Jiaodong Peninsula, East China

NASA Astrophysics Data System (ADS)

Zhu, Zhi-Yong; Jiang, Shao-Yong; Mathur, Ryan; Cook, Nigel J.; Yang, Tao; Wang, Meng; Ma, Liang; Ciobanu, Cristiana L.

2018-02-01

Mechanisms for Fe isotope fractionation in hydrothermal mineral deposits and in zones of associated K-feldspar alteration remain poorly constrained. We have analyzed a suite of bulk samples consisting of granite displaying K-feldspar alteration, Precambrian metamorphic rocks, and pyrite from gold deposits of the Jiaodong Peninsula, East China, by multi-collector inductively-coupled plasma mass spectrometry. Pyrites from disseminated (J-type) ores show a δ56Fe variation from +0.01 to +0.64‰, overlapping with the signature of the host granites (+0.08 to +0.39‰). In contrast, pyrites from quartz veins (L-type ores) show a wide range of Fe-isotopic composition from -0.78 to +0.79‰. Negative values are never seen in the J-type pyrites. The Fe isotope signature of the host granite with K-feldspar alteration is significantly heavier than that of the bulk silicate Earth. The Fe isotopic compositions of Precambrian metamorphic rocks across the district display a narrow range between -0.16‰ and +0.19‰, which is similar to most terrestrial rocks. Concentrations of major and trace elements in bulk samples were also determined, so as to evaluate any correlation between Fe isotope composition and degree of alteration. We note that during progressive K-feldspar alteration to rocks containing >70 wt% SiO2, >75 ppm Rb, and <1.2 wt% total Fe2O3, the Fe isotope composition of the granite changes systematically. The Fe isotope signature becomes heavier as the degree of alteration increases. The extremely light Fe isotopic compositions in L-type gold deposits may be explained by Rayleigh fractionation during pyrite precipitation in an open fracture system. We note that the sulfur isotopic compositions of pyrite in the two types of ores are also different. Pyrite from J-type ores has a systematically 3.5‰-higher δ34S value (11.2‰) than those of pyrite from the L-type ores (7.7‰). There is, however, no correlation between Fe and S isotope signatures. The isotopic fractionation of sulfur is used to constrain a change in the fO2 of the hydrothermal fluids from which pyrite precipitated. This work demonstrates that the Fe isotope composition of pyrite displays a significant response to the process of pyrite precipitation in hydrothermal systems, and that systematic fractionation of iron isotopes occurs during fluid/rock reaction in the K-feldspar alteration zone of the Linglong granite. The implications of the results are that processes of mineralization and associated fluid-rock interaction, which are ubiquitously observed in porphyry-style Cu-Au-Mo and other hydrothermal deposits, may be readily traceable using Fe isotopes.

Questa baseline and pre-mining ground-water quality investigation. 19. Leaching characteristics of composited materials from mine waste-rock piles and naturally altered areas near Questa, New Mexico

USGS Publications Warehouse

Smith, Kathleen S.; Hageman, Philip L.; Briggs, Paul H.; Sutley, Stephen J.; McCleskey, R. Blaine; Livo, K. Eric; Verplanck, Philip L.; Adams, Monique G.; Gemery-Hill, Pamela A.

2007-01-01

The goal of this study is to compare and contrast the leachability of metals and the acidity from individual mine waste-rock piles and natural erosional scars in the study area near Questa, New Mexico. Surficial multi-increment (composite) samples less than 2 millimeters in diameter from five waste-rock piles, nine erosional-scar areas, a less-altered site, and a tailings slurry-pipe sample were analyzed for bulk chemistry and mineralogy and subjected to two back-to-back leaching procedures. The first leaching procedure, the U.S. Geological Survey Field Leach Test (FLT), is a short-duration leach (5-minute shaking and 10-minute settling) and is intended to leach readily soluble materials. The FLT was immediately followed by an 18-hour, end-over-end rotation leaching procedure. Comparison of results from the back-to-back leaching procedures can provide information about reactions that may take place upon migration of leachates through changing geochemical conditions (for example, pH changes), both within the waste-rock and scar materials and away from the source materials. For the scar leachates, the concentrations of leachable metals varied substantially between the scar areas sampled. The scar leachates have low pH (pH 3.2-4.1). Under these low-pH conditions, cationic metals are solubilized and mobile, but anionic species, such as molybdenum, are less soluble and less mobile. Generally, metal concentrations in the waste-rock leachates did not exceed the upper range of those metal concentrations in the erosional-scar leachates. One exception is molybdenum, which is notably higher in the waste-rock leachates compared with the scar leachates. Most of the waste-rock leachates were at least mildly acidic (pH 3.0-6.2). The pH values in the waste-rock leachates span a large pH range that includes some pH-dependent solubility and metal-attenuation reactions. An increase in pH with leaching time and agitation indicates that there is pH-buffering capacity in some of the waste-rock piles. As pH increased in the waste-pile leachates, concentrations of several metals decreased with increasing time and agitation. Similar pH-dependent reactions may take place upon migration of the leachates in the waste-rock piles. Bulk chemistry, mineralogy, and leachate sulfur-isotope data indicate that the Capulin and Sugar Shack West waste-rock piles are compositionally different from the younger Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles. The Capulin and Sugar Shack West piles have the lowest-pH leachates (pH 3.0-4.1) of the waste-pile samples, and the source material for the Capulin and Sugar Shack West piles appears to be similar to the source material for the erosional-scar areas. Calcite dissolution, in addition to gypsum dissolution, appears to produce the calcium and sulfate concentrations in leachates from the Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles.

Calculated in situ rock density from gravity observations, UA-1 (Cannikin) emplacement hole, Amchitka Island, Alaska

USGS Publications Warehouse

Healey, D.L.

1971-01-01

Gravity observations were made on the ground surface and at a depth of 5,854 feet in drill hole UA-1. Two attempts to measure the free-air gradient utilizing the headframe over the drill hole were unsuccessful owing to mechanical vibrations in the structure. Because of the uncertainty in the measured free-air gradients these values were discarded and the average value (0.09406 mgal/ft) was used in the calculations. The calculated in situ bulk density is 2.36 g/cc. The weighted average bulk density determined from 47 core samples taken in the adjacent UAE-1 drill hole is also 2.36 g/cc. An analysis of selected portions of density logs provides an in situ bulk density of 2.37 g/cc.

Iron isotopes in ancient and modern komatiites: Evidence in support of an oxidised mantle from Archean to present

NASA Astrophysics Data System (ADS)

Hibbert, K. E. J.; Williams, H. M.; Kerr, A. C.; Puchtel, I. S.

2012-03-01

The mantle of the modern Earth is relatively oxidised compared to the initially reducing conditions inferred for core formation. The timing of the oxidation of the mantle is not conclusively resolved but has important implications for the timing of the development of the hydrosphere and atmosphere. In order to examine the timing of this oxidation event, we present iron isotope data from three exceptionally well preserved komatiite localities, Belingwe (2.7 Ga), Vetreny (2.4 Ga) and Gorgona (0.089 Ga). Measurements of Fe isotope compositions of whole-rock samples are complemented by the analysis of olivine, spinel and pyroxene separates. Bulk-rock and olivine Fe isotope compositions (δ57Fe) define clear linear correlations with indicators of magmatic differentiation (Mg#, Cr#). The mean Fe isotope compositions of the 2.7-2.4 Ga and 0.089 Ga samples are statistically distinct and this difference can be explained by greater extent of partial melting represented by the older samples and higher mantle ambient temperatures in the Archean and early Proterozoic relative to the present day. Significantly, samples of all ages define continuous positive linear correlations between bulk rock δ57Fe and V/Sc and δ57Fe and V, and between V/Sc and V with TiO2, providing evidence for the incompatible behaviour of V (relative to Sc) and of isotopically heavy Fe. Partial melting models calculated using partition coefficients for V at oxygen fugacities (fO2s) of 0 and + 1 relative to the fayalite-magnetite-quartz buffer (FMQ) best match the data arrays, which are defined by all samples, from late Archean to Tertiary. These data, therefore, provide evidence for komatiite generation under moderately oxidising conditions since the late Archean, and argue against a change in mantle fO2 concomitant with atmospheric oxygenation at ~ 2.4 Ga.

Contrasted glass-whole rock compositions and phenocryst re-distribution, IPOD Sites 417 and 418

NASA Astrophysics Data System (ADS)

Staudigel, H.; Bryan, W. B.

1982-01-01

Major element composition ranges of closely associated basalt glass-whole rock pairs from individual small cooling units approach the total known range of basalt glass and whole rock compositions at IPOD sites 417 and 418. The whole rock samples fall into two groups: one is depleted in MgO and distinctly enriched in plagioclase but has lost some olivine and/or pyroxene relative to its corresponding glass; and the other is enriched in MgO and in phenocrysts of olivine and pyroxene as well as plagioclase compared to its corresponding glass. By analogy with observed phenocryst distributions in lava pillows, tubes, and dikes, and with some theoretical studies, we infer that bulk rock compositions are strongly affected by phenocryst redistribution due to gravity settling, flotation, and dynamic sorting after eruption, although specific models are not well constrained by the one-dimensional geometry of drill core. Compositional trends or groupings in whole rock data resulting from such late-stage processes should not be confused with more fundamental compositional effects produced in deep chambers or during partial melting.

A Mars Sample Return Sample Handling System

NASA Technical Reports Server (NTRS)

Wilson, David; Stroker, Carol

2013-01-01

We present a sample handling system, a subsystem of the proposed Dragon landed Mars Sample Return (MSR) mission [1], that can return to Earth orbit a significant mass of frozen Mars samples potentially consisting of: rock cores, subsurface drilled rock and ice cuttings, pebble sized rocks, and soil scoops. The sample collection, storage, retrieval and packaging assumptions and concepts in this study are applicable for the NASA's MPPG MSR mission architecture options [2]. Our study assumes a predecessor rover mission collects samples for return to Earth to address questions on: past life, climate change, water history, age dating, understanding Mars interior evolution [3], and, human safety and in-situ resource utilization. Hence the rover will have "integrated priorities for rock sampling" [3] that cover collection of subaqueous or hydrothermal sediments, low-temperature fluidaltered rocks, unaltered igneous rocks, regolith and atmosphere samples. Samples could include: drilled rock cores, alluvial and fluvial deposits, subsurface ice and soils, clays, sulfates, salts including perchlorates, aeolian deposits, and concretions. Thus samples will have a broad range of bulk densities, and require for Earth based analysis where practical: in-situ characterization, management of degradation such as perchlorate deliquescence and volatile release, and contamination management. We propose to adopt a sample container with a set of cups each with a sample from a specific location. We considered two sample cups sizes: (1) a small cup sized for samples matching those submitted to in-situ characterization instruments, and, (2) a larger cup for 100 mm rock cores [4] and pebble sized rocks, thus providing diverse samples and optimizing the MSR sample mass payload fraction for a given payload volume. We minimize sample degradation by keeping them frozen in the MSR payload sample canister using Peltier chip cooling. The cups are sealed by interference fitted heat activated memory alloy caps [5] if the heating does not affect the sample, or by crimping caps similar to bottle capping. We prefer cap sealing surfaces be external to the cup rim to prevent sample dust inside the cups interfering with sealing, or, contamination of the sample by Teflon seal elements (if adopted). Finally the sample collection rover, or a Fetch rover, selects cups with best choice samples and loads them into a sample tray, before delivering it to the Earth Return Vehicle (ERV) in the MSR Dragon capsule as described in [1] (Fig 1). This ensures best use of the MSR payload mass allowance. A 3 meter long jointed robot arm is extended from the Dragon capsule's crew hatch, retrieves the sample tray and inserts it into the sample canister payload located on the ERV stage. The robot arm has capacity to obtain grab samples in the event of a rover failure. The sample canister has a robot arm capture casting to enable capture by crewed or robot spacecraft when it returns to Earth orbit

Composition of Impact Melt Debris from the Eltanin Impact Strewn Field, Bellingshausen Sea

NASA Technical Reports Server (NTRS)

Kyte, Frank T.

2002-01-01

The impact of the km-sized Eltanin asteroid into the Bellingshausen Sea produced mm- to cm-sized vesicular impact melt-rock particles found in sediment cores across a large area of the ocean floor. These particles are composed mainly of olivine and glass with minor chromite and traces of NiFe-sulfides. Some particles have inclusions of unmelted mineral and rock fragments from the precursor asteroid. Although all samples of melt rock examined have experienced significant alteration since their deposition in the late Pliocene, a significant portion of these particles have interiors that remain pristine and can be used to estimate the bulk composition of the impact melt. The bulk composition of the melt-rock particles is similar to the composition of basaltic meteorites such as howardites or mesosiderite silicates, with a contribution from seawater salts and a siderophile-rich component. There is no evidence that the Eltanin impact melt contains a significant terrestrial silicate component that might have been incorporated by mixing of the projectile with oceanic crust. If terrestrial silicates were incorporated into the melt, then their contribution must be much less than 10 wt%. Since excess K, Na, and CI are not present in seawater proportions, uptake of these elements into the melt must have been greatest for K and least for CI, producing a K/CI ratio about 4 times that in seawater. After correcting for the seawater component, the bulk composition of the Eltanin impact melt provides the best estimate of the bulk composition of the Eltanin asteroid. Excess Fe in the impact melt, relative to that in howardites, must be from a significant metal phase in the parent asteroid. Although the estimated Fe:Ni:Ir ratios (8:1:4 x 10(exp -5)) are similar to those in mesosiderite metal nodules (10:1:6 x 10(exp -5), excess Co and Au by factors of about 2 and 10 times, respectively, imply a metal component distinct from that in typical mesosiderites. An alternative interpretation, that siderophiles have been highly fractionated from a mesosiderite source, would require loss of about 90% of the original metal from the impact melt and the sediments, and is unsupported by any observational data. More likely, the excess Fe in the melt rocks is 'representative of the amount of metal in the impacting asteroid, which is estimated to be 4+/- 1 wt%.

Computation of fluid flow and pore-space properties estimation on micro-CT images of rock samples

NASA Astrophysics Data System (ADS)

Starnoni, M.; Pokrajac, D.; Neilson, J. E.

2017-09-01

Accurate determination of the petrophysical properties of rocks, namely REV, mean pore and grain size and absolute permeability, is essential for a broad range of engineering applications. Here, the petrophysical properties of rocks are calculated using an integrated approach comprising image processing, statistical correlation and numerical simulations. The Stokes equations of creeping flow for incompressible fluids are solved using the Finite-Volume SIMPLE algorithm. Simulations are then carried out on three-dimensional digital images obtained from micro-CT scanning of two rock formations: one sandstone and one carbonate. Permeability is predicted from the computed flow field using Darcy's law. It is shown that REV, REA and mean pore and grain size are effectively estimated using the two-point spatial correlation function. Homogeneity and anisotropy are also evaluated using the same statistical tools. A comparison of different absolute permeability estimates is also presented, revealing a good agreement between the numerical value and the experimentally determined one for the carbonate sample, but a large discrepancy for the sandstone. Finally, a new convergence criterion for the SIMPLE algorithm, and more generally for the family of pressure-correction methods, is presented. This criterion is based on satisfaction of bulk momentum balance, which makes it particularly useful for pore-scale modelling of reservoir rocks.

Carbon and nutrient contents in soils from the Kings River Experimental Watersheds, Sierra Nevada Mountains, California

Treesearch

D.W. Johnson; C.T. Hunsaker; D.W. Glass; B.M. Rau; B.A. Roath

2011-01-01

Soil C and nutrient contents were estimated for eight watersheds in two sites (one high elevation, Bull, and one low elevation, Providence) in the Kings River Experimental Watersheds in the western Sierra Nevada Mountains of California. Eighty-seven quantitative pits were dug to measure soil bulk density and total rock content, while three replicate surface samples...

Catalog of Mount St. Helens 2004-2007 Dome Samples with Major- and Trace-Element Chemistry

USGS Publications Warehouse

Thornber, Carl R.; Pallister, John S.; Rowe, Michael C.; McConnell, Siobhan; Herriott, Trystan M.; Eckberg, Alison; Stokes, Winston C.; Cornelius, Diane Johnson; Conrey, Richard M.; Hannah, Tammy; Taggart, Joseph E.; Adams, Monique; Lamothe, Paul J.; Budahn, James R.; Knaack, Charles M.

2008-01-01

Sampling and analysis of eruptive products at Mount St. Helens is an integral part of volcano monitoring efforts conducted by the U.S. Geological Survey?s Cascades Volcano Observatory (CVO). The objective of our eruption sampling program is to enable petrological assessments of pre-eruptive magmatic conditions, critical for ascertaining mechanisms for eruption triggering and forecasting potential changes in eruption behavior. This report provides a catalog of near-vent lithic debris and new dome-lava collected during 34 intra-crater sampling forays throughout the October 2004 to October 2007 (2004?7) eruptive interval at Mount St. Helens. In addition, we present comprehensive bulk-rock geochemistry for a time-series of representative (2004?7) eruption products. This data, along with that in a companion report on Mount St. Helens 2004 to 2006 tephra by Rowe and others (2008), are presented in support of the contents of the U.S. Geological Survey Professional Paper 1750 (Sherrod and others, eds., 2008). Readers are referred to appropriate chapters in USGS Professional Paper 1750 for detailed narratives of eruptive activity during this time period and for interpretations of sample characteristics and geochemical data. The suite of rock samples related to the 2004?7 eruption of Mount St. Helens and presented in this catalog are archived at the David A. Johnson Cascades Volcano Observatory, Vancouver, Wash. The Mount St. Helens 2004?7 Dome Sample Catalogue with major- and trace-element geochemistry is tabulated in 3 worksheets of the accompanying Microsoft Excel file, of2008-1130.xls. Table 1 provides location and sampling information. Table 2 presents sample descriptions. In table 3, bulk-rock major and trace-element geochemistry is listed for 44 eruption-related samples with intra-laboratory replicate analyses of 19 dacite lava samples. A brief overview of the collection methods and lithology of dome samples is given below as an aid to deciphering the dome sample catalog. This is followed by an explanation of the categories of sample information (column headers) in Tables 1 and 2. A summary of the analytical methods used to obtain the geochemical data in this report introduces the presentation of major- and trace-element geochemistry of 2004?7 Mount St. Helens dome samples in table 3. Intra-laboratory results for the USGS AGV-2 standard are presented (tables 4 and 5), which demonstrate the compatibility of chemical data from different sources.

Pre-eruptive volatile content, melt-inclusion chemistry, and microthermometry of interplinian Vesuvius lavas (pre-AD 1631)

USGS Publications Warehouse

Belkin, H.E.; de Vivo, B.; Torok, K.; Webster, J.D.

1998-01-01

Silicate-melt inclusions from lavas and pyroclastics from a selected suite of pre-A.D. 1631 interplinian Mt. Somma-Vesuvius lavas and scoria have been experimentally homogeneized and studied by microthermometry, electron microprobe (EMPA) and secondary-ion mass spectrometry (SIMS) to examine pre-eruptive volatile content and magma evolution. The melt inclusions have a bubble about 0.06% their volume, uncommonly contain non-condensable gas but do not contain any dense fluid phases. Clinopyroxene-hosted inclusions yield homogenization temperatures (Th) from 1170 to 1260??C, most between 1220 and 1240??C; plagiclase-hosted inclusions have Th from 1210 to 1230??C; these values are typical for the Vesuvius environment. The dominant factor controlling major element variability in the inclusions is clinopyroxene fractionation; MgO varies from 5 to 3 wt%, SiO2 varies from 60 to 48 wt%. total alkalis vary from 15 to 4 wt%, and CaO varies from 13 to 5 wt%. H2O varies from 2.7 to 0.6 wt% and is decoupled from incompatible element evolution suggesting vapor saturation during trapping. Chlorine and F vary from 1.- wt% to 0 and 0.63 to 0 wt%, respectively. Bulk rock and limited matrix glass analyses show that the lavas lost about half of their F and Cl content except for the A.D. 472-1631 lava which contains similar Cl abundances as the bulk rock. SO3 varies from 0.5 to 0 wt% and compared with matrix glass and bulk rock demonstrate that the lavas have lost essentially all sulfur. The samples can be classified into three age groups, ??? 25 000 yr B.P., 25 000-17 000 yr B.P., and A.D. 472-1631. There is a systematic increase in some components, e.g., total alkalis, SO3, Cl, Li, B, and Sr with the youth of the sample and a decrease in others, e.g., Zr and Y. However, on average these samples seem less evolved than later A.D. 1631-1944 lavas.

Quantitative analysis of major and trace elements in NH4HF2-modified silicate rock powders by laser ablation - inductively coupled plasma mass spectrometry.

PubMed

Zhang, Wen; Hu, Zhaochu; Liu, Yongsheng; Yang, Wenwu; Chen, Haihong; Hu, Shenghong; Xiao, Hongyan

2017-08-29

In this paper, we described a NH 4 HF 2 digestion method as sample preparation for the rapid determination of major and trace elements in silicate rocks using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Sample powders digested by NH 4 HF 2 at 230 °C for 3 h form ultrafine powders with a typical grain size d 80  < 8.5 μm, and various silicate rocks have a consistent grain morphology and size, allowing us to produce pressed powder pellets that have excellent cohesion and homogeneity suitable for laser ablation micro-analysis without the addition of binder. The influences of the digestion parameters were investigated and optimized, including the evaporation stage of removing residual NH 4 HF 2 , sample homogenization, selection of the digestion vessel and calibration strategy of quantitative analysis. The optimized NH 4 HF 2 digestion method was applied to dissolve six silicate rock reference materials (BCR-2, BHVO-2, AGV-2, RGM-2, GSP-2, GSR-1) covering a wide range of rock types. Ten major elements and thirty-five trace elements were simultaneously analyzed by LA-ICP-MS. The analytical results of the six reference materials generally agreed with the recommended values, with discrepancies of less than 10% for most elements. The analytical precision is within 5% for most major elements and within 10% for most trace elements. Compared with previous methods of LA-ICP-MS bulk analysis, our method enables the complete dissolution of refractory minerals, such as zircon, in intermediate-acidic intrusive rocks and limits contamination as well as the loss of volatile elements. Moreover, there are many advantages for the new technique, including reducing matrix effects between reference materials and samples, spiking the internal standard simply and feasibly and sample batch processing. The applicability filed of the new technique in this study was focused on the whole-rock analysis of igneous rock samples, which are from basic rocks to acid rocks (45% < SiO 2  < 73%). However, we thought that the NH 4 HF 2 digestion method can be used as a new alternative in LA-ICP-MS for a wider range of geological samples, and will significantly accelerate the application of LA-ICP-MS for the whole-rock analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Shear-enhanced compaction in viscoplastic rocks

NASA Astrophysics Data System (ADS)

Yarushina, V. M.; Podladchikov, Y. Y.

2012-04-01

The phenomenon of mutual influence of compaction and shear deformation was repeatedly reported in the literature over the past years. Dilatancy and shear-enhanced compaction of porous rocks were experimentally observed during both rate-independent and rate-dependent inelastic deformation. Plastic pore collapse was preceding the onset of dilatancy and shear-enhanced compaction. Effective bulk viscosity is commonly used to describe compaction driven fluid flow in porous rocks. Experimental data suggest that bulk viscosity of a fluid saturated rock might be a function of both the effective pressure and the shear stress. Dilatancy and shear-enhanced compaction can alter the transport properties of rocks through their influence on permeability and compaction length scale. Recent investigations show that shear stresses in deep mantle rocks can be responsible for spontaneous development of localized melt-rich bands and segregation of small amounts of melt from the solid rock matrix through shear channeling instability. Usually it is assumed that effective viscosity is a function of porosity only. Thus coupling between compaction and shear deformation is ignored. Spherical model which considers a hollow sphere subjected to homogeneous tractions on the outer boundary as a representative elementary volume succeeded in predicting the volumetric compaction behavior of porous rocks and metals to a hydrostatic pressure in a wide range of porosities. Following the success of this simple model we propose a cylindrical model of void compaction and decompaction due to the non-hydrostatic load. The infinite viscoplastic layer with a cylindrical hole is considered as a representative volume element. The remote boundary of the volume is subjected to a homogeneous non-hydrostatic load such that plane strain conditions are fulfilled through the volume. At some critical values of remote stresses plastic zone develops around the hole. The dependence of the effective bulk viscosity on the properties of individual components as well as on the stress state is examined. We show that bulk viscosity is a function of porosity, effective pressure and shear stress. Decreasing porosity tends to increase bulk viscosity whereas increasing shear stress and increasing effective pressure reduce it.

Dynamic bulk and shear moduli due to grain-scale local fluid flow in fluid-saturated cracked poroelastic rocks: Theoretical model

NASA Astrophysics Data System (ADS)

Song, Yongjia; Hu, Hengshan; Rudnicki, John W.

2016-07-01

Grain-scale local fluid flow is an important loss mechanism for attenuating waves in cracked fluid-saturated poroelastic rocks. In this study, a dynamic elastic modulus model is developed to quantify local flow effect on wave attenuation and velocity dispersion in porous isotropic rocks. The Eshelby transform technique, inclusion-based effective medium model (the Mori-Tanaka scheme), fluid dynamics and mass conservation principle are combined to analyze pore-fluid pressure relaxation and its influences on overall elastic properties. The derivation gives fully analytic, frequency-dependent effective bulk and shear moduli of a fluid-saturated porous rock. It is shown that the derived bulk and shear moduli rigorously satisfy the Biot-Gassmann relationship of poroelasticity in the low-frequency limit, while they are consistent with isolated-pore effective medium theory in the high-frequency limit. In particular, a simplified model is proposed to quantify the squirt-flow dispersion for frequencies lower than stiff-pore relaxation frequency. The main advantage of the proposed model over previous models is its ability to predict the dispersion due to squirt flow between pores and cracks with distributed aspect ratio instead of flow in a simply conceptual double-porosity structure. Independent input parameters include pore aspect ratio distribution, fluid bulk modulus and viscosity, and bulk and shear moduli of the solid grain. Physical assumptions made in this model include (1) pores are inter-connected and (2) crack thickness is smaller than the viscous skin depth. This study is restricted to linear elastic, well-consolidated granular rocks.

Geochemical characterization of slags, other mines wastes, and their leachates from the Elizabeth and Ely mines (Vermont), the Ducktown mining district (Tennessee), and the Clayton smelter site (Idaho)

USGS Publications Warehouse

Piatak, Nadine M.; Seal, Robert R.; Hammarstrom, Jane M.; Meier, Allen L.; Briggs, Paul H.

2003-01-01

Waste-rock material produced at historic metal mines contains elevated concentrations of potentially toxic trace elements. Two types of mine waste were examined in this study: sintered waste rock and slag. The samples were collected from the Elizabeth and Ely mines in the Vermont copper belt (Besshi-type massive sulfide deposits), from the Copper Basin mining district near Ducktown, Tennessee (Besshi-type massive sulfide deposits), and from the Clayton silver mine in the Bayhorse mining district, Idaho (polymetallic vein and replacement deposits). The data in this report are presented as a compilation with minimal interpretation or discussion. A detailed discussion and interpretation of the slag data are presented in a companion paper. Data collected from sintered waste rock and slag include: (1) bulk rock chemistry, (2) mineralogy, (3) and the distribution of trace elements among phases for the slag samples. In addition, the reactivity of the waste material under surficial conditions was assessed by examining secondary minerals formed on slag and by laboratory leaching tests using deionized water and a synthetic solution approximating precipitation in the eastern United States.

Classes of organic molecules targeted by a methanogenic microbial consortium grown on sedimentary rocks of various maturities

PubMed Central

Meslé, Margaux; Dromart, Gilles; Haeseler, Frank; Oger, Philippe M.

2015-01-01

Organic-rich shales are populated by methanogenic consortia that are able to degrade the fossilized organic matter into methane gas. To identify the organic fraction effectively degraded, we have sequentially depleted two types of organic-rich sedimentary rocks, shale, and coal, at two different maturities, by successive solvent extractions to remove the most soluble fractions (maltenes and asphaltenes) and isolate kerogen. We show the ability of the consortia to produce methane from all rock samples, including those containing the most refractory organic matter, i.e., the kerogen. Shales yielded higher methane production than lignite and coal. Mature rocks yielded more methane than immature rocks. Surprisingly, the efficiency of the consortia was not influenced by the removal of the easily biodegradable fractions contained in the maltenes and asphaltenes. This suggests that one of the limitations of organic matter degradation in situ may be the accessibility to the carbon and energy source. Indeed, bitumen has a colloidal structure that may prevent the microbial consortia from reaching the asphaltenes in the bulk rock. Solvent extractions might favor the access to asphaltenes and kerogen by modifying the spatial organization of the molecules in the rock matrix. PMID:26136731

Modelling the diffusion-available pore space of an unaltered granitic rock matrix using a micro-DFN approach

NASA Astrophysics Data System (ADS)

Svensson, Urban; Löfgren, Martin; Trinchero, Paolo; Selroos, Jan-Olof

2018-04-01

In sparsely fractured rock, the ubiquitous heterogeneity of the matrix, which has been observed in different laboratory and in situ experiments, has been shown to have a significant influence on retardation mechanisms that are of importance for the safety of deep geological repositories for nuclear waste. Here, we propose a conceptualisation of a typical heterogeneous granitic rock matrix based on micro-Discrete Fracture Networks (micro-DFN). Different sets of fractures are used to represent grain-boundary pores as well as micro fractures that transect different mineral grains. The micro-DFN model offers a great flexibility in the way inter- and intra-granular space is represented as the different parameters that characterise each fracture set can be fine tuned to represent samples of different characteristics. Here, the parameters of the model have been calibrated against experimental observations from granitic rock samples taken at Forsmark (Sweden) and different variant cases have been used to illustrate how the model can be tied to rock samples with different attributes. Numerical through-diffusion simulations have been carried out to infer the bulk properties of the model as well as to compare the computed mass flux with the experimental data from an analogous laboratory experiment. The general good agreement between the model results and the experimental observations shows that the model presented here is a reliable tool for the understanding of retardation mechanisms occurring at the mm-scale in the matrix.

Cogenetic Rock Fragments from a Lunar Soil: Evidence of a Ferroan Noritic-Anorthosite Pluton on the Moon

NASA Technical Reports Server (NTRS)

Jolliff, B. L.; Haskin, L. A.

1995-01-01

The impact that produced North Ray Crater, Apollo 16 landing site, exhumed rocks that include relatively mafic members of the lunar ferroan anorthositic suite. Bulk and mineral compositions indicate that a majority of 2-4 mm lithic fragments from sample 67513, including impact breccias and monomict igneous rocks, are related to a common noritic-anorthosite precursor. Compositions and geochemical trends of these lithic fragments and of related samples collected along the rim of North Ray Crater suggest that these rocks derived from a single igneous body. This body developed as an orthocumulate from a mixture of cumulus plagioclase and mafic intercumulus melt, after the plagioclase had separated from any cogenetic mafic minerals and had become concentrated into a crystal mush (approximately 70 wt% plagioclase, 30 wt% intercumulus melt). We present a model for the crystallization of the igneous system wherein "system" is defined as cumulus plagioclase and intercumulus melt. The initial accumulation of plagioclase is analogous to the formation of thick anorthosites of the terrestrial Stillwater Complex; however, a second stage of formation is indicated, involving migration of the cumulus-plagioclase-intercumulus-melt system to a higher crustal level, analogous to the emplacement of terrestrial massif anorthosites. Compositional variations of the lithic fragments from sample 67513 are consistent with dominantly equilibrium crystallization of intercumulus melt. The highly calcic nature of orthocumulus pyroxene and plagioclase suggests some reaction between the intercumulus melt and cumulus plagioclase, perhaps facilitated by some recrystallization of cumulus plagioclase. Bulk compositions and mineral assemblages of individual rock fragments also require that most of the mafic minerals fortned in close contact with cumulus plagioclase, not as separate layers. The distribution of compositions (and by inference, modes) has a narrow peak at anorthosite and a broader, larger peak at noritic anoilhosite. Characteristics of the samples and their geochemical trends imply an origin in a system that was large relative to the (unknown) size of the impact that produced the breccias of ferroan noritic-anorthosite composition that were excavated later by the formation of North Ray Crater, and they appear to be consistent with an origin of the suite within a perched plagioclase cumulate. If the Moon's crust formed by accumulation of plagioclase in a magma ocean, ferroan noritic anothosite, formed as an orthocumulate, is an alternative to extensive adcumulus formation of ferroan anorthosite (greater than 90 vol% plagiclase). This provides a relatively mafic ferroan anorthositic component (approximately 15 vol% mafics), which is required by mass-balance models of compositions of polymict lunar-crustal materials. The inferred bulk composition of the system of cumulus plagioclase and intercumulus melt is similar to that of ferroan regolith breccia MacAlpine Hills 88104/5, a lunar-highland meteorite, and may represent a common and widespread component of the Moon's early highland crust.

Biogenicity and Syngeneity of Organic Matter in Ancient Sedimentary Rocks: Recent Advances in the Search for Evidence of Past Life

NASA Astrophysics Data System (ADS)

Oehler, Dorothy Z.; Cady, Sherry L.

2014-08-01

The past decade has seen an explosion of new technologies for assessment of biogenicity and syngeneity of carbonaceous material within sedimentary rocks. Advances have been made in techniques for analysis of in situ organic matter as well as for extracted bulk samples of soluble and insoluble (kerogen) organic fractions. The in situ techniques allow analysis of micrometer-to-sub-micrometer-scale organic residues within their host rocks and include Raman and fluorescence spectroscopy/imagery, confocal laser scanning microscopy, and forms of secondary ion/laser-based mass spectrometry, analytical transmission electron microscopy, and X-ray absorption microscopy/spectroscopy. Analyses can be made for chemical, molecular, and isotopic composition coupled with assessment of spatial relationships to surrounding minerals, veins, and fractures. The bulk analyses include improved methods for minimizing contamination and recognizing syngenetic constituents of soluble organic fractions as well as enhanced spectroscopic and pyrolytic techniques for unlocking syngenetic molecular signatures in kerogen. Together, these technologies provide vital tools for the study of some of the oldest and problematic carbonaceous residues and for advancing our understanding of the earliest stages of biological evolution on Earth and the search for evidence of life beyond Earth. We discuss each of these new technologies, emphasizing their advantages and disadvantages, applications, and likely future directions.

Carbonate-silicate melt immiscibility, REE mineralising fluids, and the evolution of the Lofdal Intrusive Suite, Namibia

NASA Astrophysics Data System (ADS)

Bodeving, Sarah; Williams-Jones, Anthony E.; Swinden, Scott

2017-01-01

The Lofdal Intrusive Suite, Namibia, consists of calcio-carbonatite and silica-undersaturated alkaline intrusive rocks ranging in composition from phono-tephrite to phonolite (and nepheline syenite). The most primitive of these rocks is the phono-tephrite, which, on the basis of its Y/Ho and Nb/Ta ratios, is interpreted to have formed by partial melting of the mantle. Roughly linear trends in major and trace element contents from phono-tephrite to phonolite and nepheline syenite indicate that the latter two rock types evolved from the phono-tephrite by fractional crystallisation. The nepheline syenite, however, has a lower rare earth element (REE) content than the phonolite. The carbonatite has a primitive mantle-normalised REE profile roughly parallel to that of the silica-undersaturated alkaline igneous rocks, although the absolute REE concentrations are higher. Like the phono-tephrite, it also has a mantle Y/Ho ratio. However, the Nb/Ta and Zr/Hf ratios are significantly higher. Moreover, the carbonatite displays strong negative Ta, Zr and Hf anomalies on spidergrams, whereas the silicate rocks display positive anomalies for these elements. Significantly, this behaviour is predicted by the corresponding carbonatite-silicate melt partition coefficients, as is the behaviour of the REE. Based on these observations, we interpret the carbonatite to represent an immiscible liquid that exsolved from the phono-tephrite or possibly the phonolite melt. The result was a calcio-carbonatite that is enriched in the heavy REE (HREE) relative to most other carbonatites. Fluids released from the corresponding magma are interpreted to have been the source of the REE mineralisation that is currently the target of exploration. 2. The composition of feldspar in nepheline syenite, fenite, calcio-carbonatite and phonolite plotted on the feldspar ternary classification diagram modified after Schairer (1950) in terms of the components albite (Ab), orthoclase (Or) and anorthite (An). Note: ANO = anorthosite, SAN = sanidine, OLI = oligoclase, AND = andesine, LAB = labradorite, BYT = bytownite. 3. Composition of the Lofdal mica plotted on the biotite classification diagram of Rieder et al. (1998). 4. Clinopyroxene composition in nepheline syenite and calcio-carbonatite phenocrysts illustrated on the classification ternary for sodic pyroxenes (after Morimoto; 1989). Quad (Q) represents wollastonite, enstatite and ferrosilite of the Mg-Ca-Fe group of pyroxenes. 5. The range of carbonatite compositions illustrated on the carbonatite classification diagram of Gittins and Harmer (1997). 6. Composition of the Lofdal nepheline syenite on the plutonic Total-Alkali-Silica diagram of Wilson (1989). 7. a. A binary plot showing the concentration of Y versus that of Ho in bulk rock samples of the phono-tephrites, phonolites, nepheline syenites and carbonatites. The trend-line represents the mantle value of approximately 27.7 (Sun and McDonough, 1989). b. A binary plot showing the concentration of Nb versus that of Ta in bulk rock samples of the phono-tephrites, phonolites, nepheline syenites and carbonatites. The trend-line represents the mantle value of approximately 17.4 (Sun and McDonough, 1989). c. A binary plot showing the concentration of Zr versus that of Hf in bulk rock samples of the phono-tephrites, phonolites, nepheline syenites and carbonatites. The trend-line represents the mantle value of approximately 36.2 (Sun and McDonough, 1989). 8. A binary plot showing the concentration of K2O versus Na2O in nepheline syenite and fenite.

Formation of an Anti-Core–Shell Structure in Layered Oxide Cathodes for Li-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hanlei; Omenya, Fredrick; Whittingham, M. Stanley

The layered → rock-salt phase transformation in the layered dioxide cathodes for Li-ion batteries is believed to result in a “core-shell” structure of the primary particles, in which the core region maintains as the layered phase while the surface region undergoes the phase transformation to the rock-salt phase. Using transmission electron microscopy, here we demonstrate the formation of an “anti-core-shell” structure in cycled primary particles with a formula of LiNi0.80Co0.15Al0.05O2, in which the surface and subsurface regions remain as the layered structure while the rock-salt phase forms as domains in the bulk with a thin layer of the spinel phasemore » between the rock-salt core and the skin of the layered phase. Formation of this anti-core-shell structure is attributed to the oxygen loss at the surface that drives the migration of oxygen from the bulk to the surface, thereby resulting in localized areas of significantly reduced oxygen levels in the bulk of the particle, which subsequently undergoes the phase transformation to the rock-salt domains. The formation of the anti-core-shell rock-salt domains is responsible for the reduced capacity, discharge voltage and ionic conductivity in cycled cathode.« less

Elastic anisotropy of layered rocks: Ultrasonic measurements of plagioclase-biotite-muscovite (sillimanite) gneiss versus texture-based theoretical predictions (effective media modeling)

NASA Astrophysics Data System (ADS)

Ivankina, T. I.; Zel, I. Yu.; Lokajicek, T.; Kern, H.; Lobanov, K. V.; Zharikov, A. V.

2017-08-01

In this paper we present experimental and theoretical studies on a highly anisotropic layered rock sample characterized by alternating layers of biotite and muscovite (retrogressed from sillimanite) and plagioclase and quartz, respectively. We applied two different experimental methods to determine seismic anisotropy at pressures up to 400 MPa: (1) measurement of P- and S-wave phase velocities on a cube in three foliation-related orthogonal directions and (2) measurement of P-wave group velocities on a sphere in 132 directions The combination of the spatial distribution of P-wave velocities on the sphere (converted to phase velocities) with S-wave velocities of three orthogonal structural directions on the cube made it possible to calculate the bulk elastic moduli of the anisotropic rock sample. On the basis of the crystallographic preferred orientations (CPOs) of major minerals obtained by time-of-flight neutron diffraction, effective media modeling was performed using different inclusion methods and averaging procedures. The implementation of a nonlinear approximation of the P-wave velocity-pressure relation was applied to estimate the mineral matrix properties and the orientation distribution of microcracks. Comparison of theoretical calculations of elastic properties of the mineral matrix with those derived from the nonlinear approximation showed discrepancies in elastic moduli and P-wave velocities of about 10%. The observed discrepancies between the effective media modeling and ultrasonic velocity data are a consequence of the inhomogeneous structure of the sample and inability to perform long-wave approximation. Furthermore, small differences between elastic moduli predicted by the different theoretical models, including specific fabric characteristics such as crystallographic texture, grain shape and layering were observed. It is shown that the bulk elastic anisotropy of the sample is basically controlled by the CPO of biotite and muscovite and their volume proportions in the layers dominated by phyllosilicate minerals.

Carbon and nitrogen isotopic analysis of coral-associated nitrogen in rugose corals of the Middle Devonian, implications for paleoecology and paleoceanography.

NASA Astrophysics Data System (ADS)

Hickey, A. N.; Junium, C. K.; Uveges, B. T.; Ivany, L. C.; Martindale, R. C.

2017-12-01

The Middle Devonian Appalachian Basin of Central New York hosts an extraordinary diversity of well-studied fossil invertebrates within the shallow marine sequences of the Givetian Age, Hamilton Group. Of particular interest are a series of aerially expansive coral beds with diverse assemblages of rugose corals. These well-preserved specimens provide an excellent opportunity to test the feasibility of δ15N and δ13C analyses in rugose corals in an effort to resolve outstanding issues regarding their paleoecology and ontogeny as well environmental dynamics within the Devonian Appalachian Basin. Here we present carbon and nitrogen isotope analyses of the rugose corals Heliophyllum and Siphonophrentis from the Joshua Coral Bed. Corals were cleaned of the host calcareous shale and sonicated sequentially in deionized water and methanol, and then oxidatively cleaned. Cleaned corals were sectioned into 0.5cm billets to obtain enough residual organic material for analysis. The organic content of the corals is low, but nanoEA allows for serial sampling of 5-10 samples per coral. Coral sections were decarbonated and the residual organic material is filtered and dried prior to analysis. Coral organic matter is analyzed in triplicate using nanoEA, which is a cryo-trapping, capillary focusing technique for δ15N and δ13C. The δ15N of organic matter extracted from rugose corals is, on average, enriched by 2-4‰ relative to the bulk nitrogen in the host rock. As well, the δ13C of organic carbon from the corals is 13C-enriched relative to the bulk rock, but to a lesser degree (no more than 1.5‰). Assuming that the bulk rock carbon and nitrogen are largely representative of the long-term primary production background, the modest enrichment is consistent with a trophic effect, and that rugose corals are likely planktivores. In an individual coral, δ15N ranges by 3-4‰ over its length, and when adjusted for trophic enrichment varies around the average δ15N of bulk sedimentary organic matter (+2.0‰). There is no apparent trajectory in the isotopic composition of organic matter, which suggests that over the sampled life history of the corals we cannot resolve any ontogenetic trends. Therefore, the variability in the δ15N of the coral organic matter likely reflects short-term variability in basinal conditions or changes in coral food supply.

Characterizing and quantifying superparamagnetic magnetite particles in serpentinized mantle peridotite observed in continental ophiolite complexes.

NASA Astrophysics Data System (ADS)

Ortiz, E.; Vento, N. F. R.; Tominaga, M.; Beinlich, A.; Einsle, J. F.; Buisman, I.; Ringe, E.; Schrenk, M. O.; Cardace, D.

2017-12-01

Serpentinization of mantle peridotite has been recognized as one of the most important energy factories for the deep biosphere. To better evaluate the habitability of the deep biosphere, it is crucial to understand the link between in situ peridotite serpentinization processes and associated magnetite and hydrogen production. Previous efforts in correlating magnetite and hydrogen production during serpentinization processes are based primarily on laboratory experiments and numerical modeling, being challenged to include the contribution of superparamagnetic-sized magnetites (i.e., extremely fine-grained magnetite, petrographically observed as a "pepper flake" like texture in many natural serpentinized rock samples). To better estimate the abundance of superparamagnetic grains, we conducted frequency-dependent susceptibility magnetic measurements at the Institute of Rock Magnetism on naturally serpentinized rock samples from the Coast Range Ophiolite Microbial Observatory (CROMO) in California, USA and the Atlin Ophiolite (British Columbia). In addition, we conducted multiscale EDS phase mapping, BackScattered Electron (BSE) scanning, FIB-nanotomography and STEM-EELS to identify and quantify the superparamagnetic minerals that contribute to the measured magnetic susceptibility signals in our rock samples. Utilizing a multidisciplinary approach, we aim to improve the estimation of hydrogen production based on the abundance of magnetite, that includes the contribution of superparamagnetic particle size magnetite, to ultimately provide a more accurate estimation of bulk deep-biomass hosted by in situ serpentinization processes.

Permeability and microstructural changes due to weathering of pyroclastic rocks in Cappadocia, central Turkey

NASA Astrophysics Data System (ADS)

Sato, M.; Takahashi, M.; Anma, R.; Shiomi, K.

2014-12-01

Studies of permeability changes of rocks during weathering are important to understand the processes of geomorphological development and how they are influenced by cyclic climatic conditions. Especially volcanic tuffs and pyroclastic flow deposits are easily affected by water absorption and freezing-thawing cycle (Erguler. 2009, Çelik and Ergül 2014). Peculiar erosional landscapes of Cappadocia, central Turkey, with numerous underground cities and carved churches, that made this area a world heritage site, are consists of volcanic tuffs and pyroclastic flow deposits. Understanding permeability changes of such rocks under different conditions are thus important not only to understand fundamental processes of weathering, but also to protect the landscapes of the world heritage sites and archaeological remains. In this study, we aim to evaluate internal void structures and bulk permeability of intact and weathered pyroclastic rocks from Cappadocia using X-ray CT, mercury intrusion porosimetry data and permeability measurement method of flow pump test. Samples of pyroclastic deposits that comprise the landscapes of Rose Valley and Ihlara Valley, were collected from the corresponding strata outside of the preservation areas. Porosity and pore-size distribution for the same samples measured by mercury intrusion porosimetry, indicate that the intact samples have lower porosity than weathered samples and pore sizes were dominantly 1-10μm in calculated radii, whereas weathered samples have more micropores (smaller than 1 μm). X-ray CT images were acquired to observe internal structure of samples. Micro-fractures, probably caused by repeated expansion and contraction due to temperature changes, were observed around clast grains. The higher micropore ratio in weathered samples could be attributed to the development of the micro-farctures. We will discuss fundamental processes of weathering and geomorphological development models using these data.

Mineral chemistry of the Tissint meteorite: Indications of two-stage crystallization in a closed system

NASA Astrophysics Data System (ADS)

Liu, Yang; Baziotis, Ioannis P.; Asimow, Paul D.; Bodnar, Robert J.; Taylor, Lawrence A.

2016-12-01

The Tissint meteorite is a geochemically depleted, olivine-phyric shergottite. Olivine megacrysts contain 300-600 μm cores with uniform Mg# ( 80 ± 1) followed by concentric zones of Fe-enrichment toward the rims. We applied a number of tests to distinguish the relationship of these megacrysts to the host rock. Major and trace element compositions of the Mg-rich core in olivine are in equilibrium with the bulk rock, within uncertainty, and rare earth element abundances of melt inclusions in Mg-rich olivines reported in the literature are similar to those of the bulk rock. Moreover, the P Kα intensity maps of two large olivine grains show no resorption between the uniform core and the rim. Taken together, these lines of evidence suggest the olivine megacrysts are phenocrysts. Among depleted olivine-phyric shergottites, Tissint is the first one that acts mostly as a closed system with olivine megacrysts being the phenocrysts. The texture and mineral chemistry of Tissint indicate a crystallization sequence of: olivine (Mg# 80 ± 1) → olivine (Mg# 76) + chromite → olivine (Mg# 74) + Ti-chromite → olivine (Mg# 74-63) + pyroxene (Mg# 76-65) + Cr-ulvöspinel → olivine (Mg# 63-35) + pyroxene (Mg# 65-60) + plagioclase, followed by late-stage ilmenite and phosphate. The crystallization of the Tissint meteorite likely occurred in two stages: uniform olivine cores likely crystallized under equilibrium conditions; and a fractional crystallization sequence that formed the rest of the rock. The two-stage crystallization without crystal settling is simulated using MELTS and the Tissint bulk composition, and can broadly reproduce the crystallization sequence and mineral chemistry measured in the Tissint samples. The transition between equilibrium and fractional crystallization is associated with a dramatic increase in cooling rate and might have been driven by an acceleration in the ascent rate or by encounter with a steep thermal gradient in the Martian crust.

Miniature Neutron-Alpha Activation Spectrometer

NASA Astrophysics Data System (ADS)

Rhodes, E.; Goldsten, J.

2001-01-01

We are developing a miniature neutron-alpha activation spectrometer for in situ analysis of samples including rocks, fines, ices, and drill cores, suitable for a lander or Rover platform, that would meet the severe mass, power, and environmental constraints of missions to the outer planets. In the neutron-activation mode, a gamma-ray spectrometer will first perform a penetrating scan of soil, ice, and loose material underfoot (depths to 10 cm or more) to identify appropriate samples. Chosen samples will be analyzed in bulk in neutron-activation mode, and then the sample surfaces will be analyzed in alpha-activation mode using Rutherford backscatter and x-ray spectrometers. The instrument will provide sample composition over a wide range of elements, including rock-forming elements (such as Na, Mg, Si, Fe, and Ca), rare earths (Sm and Eu for example), radioactive elements (K, Th, and U), and light elements present in water, ices, and biological materials (mainly H, C, O, and N). The instrument is expected to have a mass of about l kg and to require less than 1 W power. Additional information is contained in the original extended abstract.

Sm-Nd systematics of lunar ferroan anorthositic suite rocks: Constraints on lunar crust formation

NASA Astrophysics Data System (ADS)

Boyet, Maud; Carlson, Richard W.; Borg, Lars E.; Horan, Mary

2015-01-01

We have measured Sm-Nd systematics, including the short-lived 146Sm-142Nd chronometer, in lunar ferroan anorthositic suite (FAS) whole rocks (15415, 62236, 62255, 65315, 60025). At least some members of the suite are thought to be primary crystallization products formed by plagioclase flotation during crystallization of the lunar magma ocean (LMO). Most of these samples, except 62236, have not been exposed to galactic cosmic rays for a long period and thus require minimal correction to their 142Nd isotope composition. These samples all have measured deficits in 142Nd relative to the JNdi-1 terrestrial standard in the range -45 to -21 ppm. The range is -45 to -15 ppm once the 62236 142Nd/144Nd ratio is corrected from neutron-capture effects. Analyzed FAS samples do not define a single isochron in either 146Sm-142Nd or 147Sm-143Nd systematics, suggesting that they either do not have the same crystallization age, come from different sources, or have suffered isotopic disturbance. Because the age is not known for some samples, we explore the implications of their initial isotopic compositions for crystallization ages in the first 400 Ma of solar system history, a timing interval that covers all the ages determined for the ferroan anorthositic suite whole rocks as well as different estimates for the crystallization of the LMO. 62255 has the largest deficit in initial 142Nd and does not appear to have followed the same differentiation path as the other FAS samples. The large deficit in 142Nd of FAN 62255 may suggest a crystallization age around 60-125 Ma after the beginning of solar system accretion. This result provides essential information about the age of the giant impact forming the Moon. The initial Nd isotopic compositions of FAS samples can be matched either with a bulk-Moon with chondritic Sm/Nd ratio but enstatite-chondrite-like initial 142Nd/144Nd (e.g. 10 ppm below modern terrestrial), or a bulk-Moon with superchondritic Sm/Nd ratio and initial 142Nd/144Nd similar to ordinary chondrites.

Sm-Nd systematics of lunar ferroan anorthositic suite rocks: Constraints on lunar crust

DOE PAGES

Boyet, Maud; Carlson, Richard W.; Borg, Lars E.; ...

2014-09-28

Here, we have measured Sm–Nd systematics, including the short-lived 146Sm– 142Nd chronometer, in lunar ferroan anorthositic suite (FAS) whole rocks (15415, 62236, 62255, 65315, 60025). At least some members of the suite are thought to be primary crystallization products formed by plagioclase flotation during crystallization of the lunar magma ocean (LMO). Most of these samples, except 62236, have not been exposed to galactic cosmic rays for a long period and thus require minimal correction to their 142Nd isotope composition. These samples all have measured deficits in 142Nd relative to the JNdi-1 terrestrial standard in the range –45 to –21 ppm.more » The range is –45 to –15 ppm once the 62236 142Nd/ 144Nd ratio is corrected from neutron-capture effects. Analyzed FAS samples do not define a single isochron in either 146Sm– 142Nd or 147Sm– 143Nd systematics, suggesting that they either do not have the same crystallization age, come from different sources, or have suffered isotopic disturbance. Because the age is not known for some samples, we explore the implications of their initial isotopic compositions for crystallization ages in the first 400 Ma of solar system history, a timing interval that covers all the ages determined for the ferroan anorthositic suite whole rocks as well as different estimates for the crystallization of the LMO. 62255 has the largest deficit in initial 142Nd and does not appear to have followed the same differentiation path as the other FAS samples. The large deficit in 142Nd of FAN 62255 may suggest a crystallization age around 60–125 Ma after the beginning of solar system accretion. This result provides essential information about the age of the giant impact forming the Moon. The initial Nd isotopic compositions of FAS samples can be matched either with a bulk-Moon with chondritic Sm/Nd ratio but enstatite-chondrite-like initial 142Nd/ 144Nd (e.g. 10 ppm below modern terrestrial), or a bulk-Moon with superchondritic Sm/Nd ratio and initial 142Nd/ 144Nd similar to ordinary chondrites.« less

Exploring the Utilization of Low-Pressure, Piston-Cylinder Experiments to Determine the Bulk Compositions of Finite, Precious Materials

NASA Astrophysics Data System (ADS)

Vander Kaaden, K. E.; McCubbin, F. M.; Harrington, A.

2017-12-01

Determining the bulk composition of precious materials with a finite mass (e.g., meteorite samples) is extremely important in the fields of Earth and Planetary Science. From meteorite studies we are able to place constraints on large scale planetary processes like global differentiation and subsequent volcanism, as well as smaller scale processes like crystallization in a magma chamber or sedimentary compaction at the surface. However, with meteorite samples in particular, far too often we are limited by how precious the sample is as well as its limited mass. In this study, we have utilized aliquots of samples previously studied for toxicological hazards [1] including both the fresh samples (lunar mare basalt NWA 4734, lunar regolith breccia NWA 7611, martian basalt Tissint, martian regolith breccia NWA 7034, a vestian basalt Berthoud, a vestian regolith breccia NWA 2060, and a terrestrial mid-ocean ridge basalt (MORB)), and those that underwent iron leaching (Tissint, NWA 7034, NWA 4734, MORB). With these small masses of material, we performed low pressure ( 0.75 GPa), high temperature (>1600°C) melting experiments. Each sample was analyzed using a JEOL 8530F electron microprobe to determine the bulk composition of the materials that were previously examined in [1]. When available, the results of our microprobe data were compared with bulk rock compositions in the literature. The results of this study show that with this technique, only 50 mg of sample is required to accurately determine the bulk composition of the materials of interest. [1] Harrington, A.D., McCubbin, F.M., Kaur, J., Smirnov, A., Galdanes, K., Schoonen, M.A.A., Chen, L.C., Tsirka, S.E., and Gordon, T. (2017) Pulmonary inflammatory responses to acute meteroite dust exposures - Implications for human space exploration. 48th Lunar and Planetary Science Conference, The Woodlands, TX, #2922.

Volatiles in High-K Lunar Basalts

NASA Technical Reports Server (NTRS)

Barnes, Jessica J.; McCubbin, Francis M.; Messenger, Scott R.; Nguyen, Ann; Boyce, Jeremy

2017-01-01

Chlorine is an unusual isotopic system, being essentially unfractionated ((delta)Cl-37 approximately 0 per mille ) between bulk terrestrial samples and chondritic meteorites and yet showing large variations in lunar (approximately -4 to +81 per mille), martian, and vestan (HED) samples. Among lunar samples, the volatile-bearing mineral apatite (Ca5(PO4)3[F,Cl,OH]) has been studied for volatiles in K-, REE-, and P (KREEP), very high potassium (VHK), low-Ti and high-Ti basalts, as well as samples from the lunar highlands. These studies revealed a positive correlation between in-situ (delta)Cl-37 measurements and bulk incompatible trace elements (ITEs) and ratios. Such trends were interpreted to originate from Cl isotopic fractionation during the degassing of metal chlorides during or shortly after the differentiation of the Moon via a magma ocean. In this study, we investigate the volatile inventories of a group of samples for which new-era volatile data have yet to be reported - the high-K (greater than 2000 ppm bulk K2O), high-Ti, trace element-rich mare basalts. We used isotope imaging on the Cameca NanoSIMS 50L at JSC to obtain the Cl isotopic composition [((Cl-37/(35)Clsample/C-37l/(35)Clstandard)-1)×1000, to get a value in per thousand (per mille)] which ranges from approximately -2.7 +/- 2 per mille to +16.1 +/- 2 per mille (2sigma), as well as volatile abundances (F & Cl) of apatite in samples 10017, 10024 & 10049. Simply following prior models, as lunar rocks with high bulk-rock abundances of ITEs we might expect the high-K, high-Ti basalts to contain apatite characterized by heavily fractionated (delta)Cl-37 values, i.e., Cl obtained from mixing between unfractionated mantle Cl (approximately 0 per mille) and the urKREEP reservoir (possibly fractionated to greater than +25 per mille.). However, the data obtained for the studied samples do not conform to either the early degassing or mixing models. Existing petrogentic models for the origin of the high-K, high-Ti basalts do not include urKREEP assimilation into their LMO cumulate sources. Therefore, Cl in these basalts either originated from source region heterogeneity or through assimilation or metasomatism by volatile and incompatible trace element rich materials. The new data presented here could provide evidence for the existence of region(s) in the lunar interior that are ITE-enriched and contain Cl that does not share isotopic affinities with lunar urKREEP, possibly representing the composition of the purported 'neuKREEP'.

A reconnaissance view of tungsten reservoirs in some crustal and mantle rocks: Implications for interpreting W isotopic compositions and crust-mantle W cycling

NASA Astrophysics Data System (ADS)

Liu, Jingao; Pearson, D. Graham; Chacko, Thomas; Luo, Yan

2018-02-01

High-precision measurements of W isotopic ratios have enabled increased exploration of early Earth processes. However, when applying W isotopic data to understand the geological processes, it is critical to recognize the potential mobility of W and hence evaluate whether measured W contents and isotopic compositions reflect the primary petrogenetic processes or instead are influenced by the effects of secondary inputs/mobility. Furthermore, if we are to better understand how W is partitioned between different minerals during melting and metasomatic processes it is important to document the likely sinks for W during these processes. In addition, an understanding of the main hosts for W in the crust and mantle is critically important to constrain how W is cycled and stored in the crust-mantle geochemical cycle. As a first step to investigate these issues, we have carried out in situ concentration measurements of W and other HFSEs in mineral phases within a broad spectrum of crustal and mantle rocks, along with whole-rock concentration measurements. Mass balance shows that for tonalitic gneiss and amphibolite, the major rock-forming minerals can adequately account for the bulk W budget, and for the pristine ultramafic rocks, olivine and orthopyroxene are the major controlling phases for W whereas for metasomatized ultramafic rocks, significant W is hosted in Ti-bearing trace phases (e.g., rutile, lindsleyite) along grain boundaries or is inferred to reside in cryptic W-bearing trace phases. Formation or decomposition of these phases during secondary processes could cause fractionation of W from other HFSEs, and also dramatically modify bulk W concentrations in rocks. For rocks that experienced subsequent W enrichment/alteration, their W isotopic compositions may not necessarily represent their mantle sources, but could reflect later inputs. The relatively small suite of rocks analyzed here serves as a reconnaissance study but allows some preliminary speculations on their significance for crust-mantle HFSE and siderophile element budgets - to be tested in future studies. The significant concentration of W, as well as Nb and Ta hosted in rutile and titanite has interesting implications for the budget of W during crust-mantle recycling. Crust-mantle recycling models invoking the recycling of rutile-bearing eclogites to satisfy the mantle Nb/Ta ratio carry the penalty that the very high W/U and W/Th ratios of these rocks results in a concomitant large deviation from the primitive mantle-like ratios estimated for bulk continental crust. Similarly, data from the single amphibolite sample investigated in this study are inconsistent with models implicating the partial melting of amphibolite-bearing subducted slabs as a major process for formation of continental crust in the Earth's early history. Either the current widely accepted estimates for bulk continental crust W/U and W/Th ratios are in error, or partial melting or other processes lowers the W/U or W/Th of melt residues during their return to the mantle. The present small dataset cannot properly evaluate this, requiring further investigation. Finally, the lithospheric mantle has the potential to store substantial amounts of W, for example via infiltration by W-rich melts/fluids, and thus may act as a source for W mineralization in the crust.

Strontium Isotopic Composition of Paleozoic Carbonate Rocks in the Nevada Test Site Vicinity, Clark, Lincoln, and Nye Counties, Nevada and Inyo County, California.

DOE Office of Scientific and Technical Information (OSTI.GOV)

James B. Paces; Zell E. Peterman; Kiyoto Futa

2007-08-07

Ground water moving through permeable Paleozoic carbonate rocks represents the most likely pathway for migration of radioactive contaminants from nuclear weapons testing at the Nevada Test Site, Nye County, Nevada. The strontium isotopic composition (87Sr/86Sr) of ground water offers a useful means of testing hydrochemical models of regional flow involving advection and reaction. However, reaction models require knowledge of 87Sr/86Sr data for carbonate rock in the Nevada Test Site vicinity, which is scarce. To fill this data gap, samples of core or cuttings were selected from 22 boreholes at depth intervals from which water samples had been obtained previously aroundmore » the Nevada Test Site at Yucca Flat, Frenchman Flat, Rainier Mesa, and Mercury Valley. Dilute acid leachates of these samples were analyzed for a suite of major- and trace-element concentrations (MgO, CaO, SiO2, Al2O3, MnO, Rb, Sr, Th, and U) as well as for 87Sr/86Sr. Also presented are unpublished analyses of 114 Paleozoic carbonate samples from outcrops, road cuts, or underground sites in the Funeral Mountains, Bare Mountain, Striped Hills, Specter Range, Spring Mountains, and ranges east of the Nevada Test Site measured in the early 1990's. These data originally were collected to evaluate the potential for economic mineral deposition at the potential high-level radioactive waste repository site at Yucca Mountain and adjacent areas (Peterman and others, 1994). Samples were analyzed for a suite of trace elements (Rb, Sr, Zr, Ba, La, and Ce) in bulk-rock powders, and 87Sr/86Sr in partial digestions of carbonate rock using dilute acid or total digestions of silicate-rich rocks. Pre-Tertiary core samples from two boreholes in the central or western part of the Nevada Test Site also were analyzed. Data are presented in tables and summarized in graphs; however, no attempt is made to interpret results with respect to ground-water flow paths in this report. Present-day 87Sr/86Sr values are compared to values for Paleozoic seawater present at the time of deposition. Many of the samples have 87Sr/86Sr compositions that remain relatively unmodified from expected seawater values. However, rocks underlying the northern Nevada Test Site as well as rocks exposed at Bare Mountain commonly have elevated 87Sr/86Sr values derived from post-depositional addition of radiogenic Sr most likely from fluids circulating through rubidium-rich Paleozoic strata or Precambrian basement rocks.« less

Strontium Isotopic Composition of Paleozoic Carbonate Rocks in the Nevada Test Site Vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California

USGS Publications Warehouse

Paces, James B.; Peterman, Zell E.; Futo, Kiyoto; Oliver, Thomas A.; Marshall, Brian D.

2007-01-01

Ground water moving through permeable Paleozoic carbonate rocks represents the most likely pathway for migration of radioactive contaminants from nuclear weapons testing at the Nevada Test Site, Nye County, Nevada. The strontium isotopic composition (87Sr/86Sr) of ground water offers a useful means of testing hydrochemical models of regional flow involving advection and reaction. However, reaction models require knowledge of 87Sr/86Sr data for carbonate rock in the Nevada Test Site vicinity, which is scarce. To fill this data gap, samples of core or cuttings were selected from 22 boreholes at depth intervals from which water samples had been obtained previously around the Nevada Test Site at Yucca Flat, Frenchman Flat, Rainier Mesa, and Mercury Valley. Dilute acid leachates of these samples were analyzed for a suite of major- and trace-element concentrations (MgO, CaO, SiO2, Al2O3, MnO, Rb, Sr, Th, and U) as well as for 87Sr/86Sr. Also presented are unpublished analyses of 114 Paleozoic carbonate samples from outcrops, road cuts, or underground sites in the Funeral Mountains, Bare Mountain, Striped Hills, Specter Range, Spring Mountains, and ranges east of the Nevada Test Site measured in the early 1990's. These data originally were collected to evaluate the potential for economic mineral deposition at the potential high-level radioactive waste repository site at Yucca Mountain and adjacent areas (Peterman and others, 1994). Samples were analyzed for a suite of trace elements (Rb, Sr, Zr, Ba, La, and Ce) in bulk-rock powders, and 87Sr/86Sr in partial digestions of carbonate rock using dilute acid or total digestions of silicate-rich rocks. Pre-Tertiary core samples from two boreholes in the central or western part of the Nevada Test Site also were analyzed. Data are presented in tables and summarized in graphs; however, no attempt is made to interpret results with respect to ground-water flow paths in this report. Present-day 87Sr/86Sr values are compared to values for Paleozoic seawater present at the time of deposition. Many of the samples have 87Sr/86Sr compositions that remain relatively unmodified from expected seawater values. However, rocks underlying the northern Nevada Test Site as well as rocks exposed at Bare Mountain commonly have elevated 87Sr/86Sr values derived from post-depositional addition of radiogenic Sr most likely from fluids circulating through rubidium-rich Paleozoic strata or Precambrian basement rocks.

Bulk Hydrogen Content OF High-Silica Rocks in Gale Crater With the Active Dynamic Albedo of Neutrons Experiment

NASA Technical Reports Server (NTRS)

Gabriel, T. S. J.; Hardgrove, C.; Litvak, M.; Mitrofanov, I.; Boynton, W. V.; Fedosov, F.; Golovin, D.; Jun, I.; Mischna, M.; Tate, C. G.;

Properties of Clay for Ceramics with Rock Waste for Production Structural Block by Pressing and Firing

NASA Astrophysics Data System (ADS)

Cerqueira, N. A.; Choe, D.; Alexandre, J.; Azevedo, A. R. G.; Xavier, C. G.; Souza, V. B.

Building work requires optimization of materials and labor, so that the execution of its subsystems contribute to the quality, reduce costs, decrease waste in buildings, productivity, practicality and especially agility. Thus, the fitting blocks can contribute in this direction. This work therefore consists of physical characterization (determination of fitness levels, grain size and bulk density), chemical (EDX) and thermal (DTA and TGA) sample clay Campos dos Goytacazes-RJ and waste rock ornamental Cachoeiro de Itapemirim-ES, to verify potential for producing red ceramic blocks, pressed and burned, male and female type. The output of block will be with different pe rcentages of incorporation of residues of ornamental rocks (0%, 5% and 10%). With the results obtained, it was found that the raw materials under consideration has the potential for application in the production of ceramic articles.

Geochemistry of lunar crustal rocks from breccia 67016 and the composition of the moon

NASA Technical Reports Server (NTRS)

Norman, Marc D.; Taylor, Stuart R.

1992-01-01

The geochemistry of anorthositic clasts from an Apollo 16 breccia 67016 is studied in order to investigate the role of these rock types in lunar crustal evolution. The samples have aluminous, alkali-poor compositions and varied FeO and MgO contents. Three compositional groups are recognized. One group is poor in mafic constituents with low abundances of lithophile trace elements typical of lunar anorthosites, while the other two groups are more mafic and are distinguished from each other by FeO/MgO ratios greater than one in the case of ferroan noritic and less than one in the case of magnesian troctolitic. These mafic-enriched varieties have considerably higher lithophile element concentrations, at levels similar to that of the bulk lunar crust. The ferroan noritic clasts may represent a fundamental type of igneous rock in the lunar crust which has not been widely recognized.

Archean upper crust transition from mafic to felsic marks the onset of plate tectonics.

PubMed

Tang, Ming; Chen, Kang; Rudnick, Roberta L

2016-01-22

The Archean Eon witnessed the production of early continental crust, the emergence of life, and fundamental changes to the atmosphere. The nature of the first continental crust, which was the interface between the surface and deep Earth, has been obscured by the weathering, erosion, and tectonism that followed its formation. We used Ni/Co and Cr/Zn ratios in Archean terrigenous sedimentary rocks and Archean igneous/metaigneous rocks to track the bulk MgO composition of the Archean upper continental crust. This crust evolved from a highly mafic bulk composition before 3.0 billion years ago to a felsic bulk composition by 2.5 billion years ago. This compositional change was attended by a fivefold increase in the mass of the upper continental crust due to addition of granitic rocks, suggesting the onset of global plate tectonics at ~3.0 billion years ago. Copyright © 2016, American Association for the Advancement of Science.

Dielectric constant as a predictor of porosity in dry volcanic rocks

NASA Astrophysics Data System (ADS)

Rust, A. C.; Russell, J. K.; Knight, R. J.

1999-07-01

Measurements of dielectric constant ( K') are made on 34 samples of volcanic rocks at frequencies of 0.01 to 10 MHz under ambient atmospheric conditions. Bulk density ( ρT), total porosity ( ΦT) and connected porosity ( ΦConn) are also measured. The samples derive from two dacitic lava flows (˜60-62 and 68 wt.% SiO 2), dacitic pyroclastic deposits (˜66-68 wt.% SiO 2) and two basalt lava flows (˜49-52 wt.% SiO 2). Each locality provided a suite of samples with similar mineralogy and composition but a range of porosities. Porosity measurements indicate that as much as 17% of pumice pore space can be unconnected. The data show a strong correlation between K' and ΦT and the dacitic rocks show a 2.5-fold decrease in K' over a porosity range of 8-79%. The data are fitted to a time propagation (TP) model and to a more general two-parameter model based on the Lichtenecker-Rother equation. For dacitic rocks, the dielectric constant is best related to porosity by: (K') 0.96=Φ+6.51(1-Φ). K' and ρT are also strongly correlated in these sample sets. The trend formed by samples of dacite in ( K', ρT) space is linear and the data compare well with published values for other non-basaltic rocks. Samples of basalt show greater variance in measured values of K', due perhaps to higher and more variable modes of Fe-Ti oxide minerals. These new data suggest the possibility of inverting radar velocity data to obtain estimates of porosity in dry volcanic successions. Inversion of radar data for porosity could be useful in discriminating between units of an eruption cycle (e.g., lava flow, pyroclastic flow, airfall) and mapping porosity variations within deposits such as welded pyroclastic flows.

Obtaining higher-accuracy estimates of water-rich rocks and water-poor sand dunes on Mars in active neutron experiments

NASA Astrophysics Data System (ADS)

Gabriel, T. S. J.; Hardgrove, C.; Litvak, M. L.; Nowicki, S.; Mitrofanov, I. G.; Boynton, W. V.; Fedosov, F.; Golovin, D.; Jun, I.; Mischna, M.; Tate, C. G.; Moersch, J.; Harshman, K.; Kozyrev, A.; Malakhov, A. V.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Vostrukhin, A.; Thompson, L. M.

2017-12-01

The Dynamic Albedo of Neutrons (DAN) experiment on the Mars Science Laboratory Curiosity Rover delivers high-energy (14.1 MeV) pulses of neutrons into the surface when operating in "active" mode. Neutrons are moderated in the subsurface and return to two detectors to provide a time-of-flight profile in 64 time-bins in epithermal and thermal energy ranges. Results are compared to simulations of the experiment in the Monte Carlo N-Particle Transport Code where several aspects are modeled including the DAN detectors, neutron source, rover components, and underlying rock. Models can be improved by increasing the fidelity of the rock geochemistry as informed by instruments including the Alpha Particle X-Ray Spectrometer (APXS). Furthermore, increasing the fidelity of the rock morphology in models is enabled by the suite of imaging instruments on the rover.To rapidly interpret DAN data a set of pre-simulated generic rock density and bulk geochemistry models are compared to several DAN active observations. While, to first order, this methodology provides an indication of significant geochemical changes in the subsurface, higher-fidelity models should be used to provide accurate constraints on water content, depth of geologic layers, or abundance of neutron absorbers. For example, in high-silicon, low-iron rocks observed along the rover's traverse, generic models can differ by several wt%H2O from models that use APXS measurements of nearby drill samples. Accurate measurements of high-silicon targets are necessary in outlining the extent of aqueous alteration and hydrothermal activity in Gale Crater. Additionally, we find that for DAN active experiments over sand dunes best-fit models can differ by greater than 0.5 wt%HO when the upper layer density is reduced by 0.6 g/cm3 to account for the low-bulk density of sand. In areas where the rock geochemistry differs little from generic models the difference in results is expectedly less disparate. We report refined wt%HO values for high-silicon, aqueously-altered rock and comparatively dry sand dunes along the rover traverse. We also outline the methodology for providing accurate geochemical and morphological constraints using DAN active measurements.

Unexpected mechanical properties of very dry Berea sandstone near 45°C

NASA Astrophysics Data System (ADS)

Miller, R. A.; Darling, T. W.; TenCate, J. A.; Johnson, P. A.

2011-12-01

An understanding of the nonlinear and hysteretic behavior of porous rocks is important for seismic studies and geologic carbon sequestration applications. However, the fundamental processes responsible for such behavior are poorly understood, including interactions involving adsorbed water and bulk carbon dioxide. Water has been shown to affect the nonlinear mechanical properties of porous rocks, both in high humidity conditions and in low pressure conditions where only a monolayer of water is present on rock grain surfaces [1, 2]. To study the impact of small quantities of adsorbed water on the nonlinear behavior of sandstone, we compare nonlinear resonant ultrasound spectroscopy (NRUS) and time-of-flight modulation (TOFM) measurements [3] on a Berea sandstone core before and after removing bulk water from the sample. Water is removed through extended exposure to ultra high vacuum (UHV) conditions. At the sample's driest state, we achieve a partial pressure of water below 10-8 Torr at room temperature. Periodic measurements record acoustic data as the rock is slowly heated from room temperature to 55°C in UHV. Measurements made after several months of exposure to UHV conditions show behavior we have not previously observed. We report an unexpected sharp increase in Q-1 above 45°C, suggesting we have reduced the concentration of water to a low enough level to affect the sample's mechanical properties. Nonlinear effects are still present when the sample is at its driest state below 45°C, in agreement with previous work [4], which indicates water is not the sole contributor to nonlinearity in porous rock. We are also studying the effect of adding carbon dioxide or argon gas to the dry specimen. We present our acoustic data and propose a model for the impact of adsorbed water on the attenuation of porous rock. [We gratefully acknowledge support from the Nevada Terawatt Facility at the University of Nevada, Reno, and from the Geosciences Research Program of the DOE Office of Basic Energy Sciences]. [1] B. R. Tittmann, L. Ahlberg, and J. Curnow, "Internal friction and velocity measurements," Proc. of 7th Lunar Science Conference , pp. 3123-3132, 1997. [2] K. E.-A. Van Den Abeele, J. Carmeliet, P. A. Johnson, and B. Zinszner, "Influence of water saturation on the nonlinear elastic mesoscopic response in Earth materials and the implications to the mechanism of nonlinearity," Journal of Geophysical Research 107, p. 2121, June 2002. [3] "Dynamic Measures of Elastic Nonlinear (Anelastic) Behavior: Dynamic Acousto-Elasticity Testing (DAET)," G. Renaud, P-Y Le Bas, J. A. TenCate, T. J. Ulrich, J. W. Carey, J. Han, T.W. Darling and P. A. Johnson, AGU Fall Meeting, Dec. 2011. [4] "Water and CO2 chemistry influences on the mechanical integrity of rocks," T.W. Darling, P-Y Le Bas, J. W. Carey, P. A. Johnson and R. A. Miller, AGU Fall Meeting, Dec. 2010.

POWTEX Neutron Diffractometer at FRM II - New Perspectives for In-Situ Rock Deformation Analysis

NASA Astrophysics Data System (ADS)

Walter, J. M.; Stipp, M.; Ullemeyer, K.; Klein, H.; Leiss, B.; Hansen, B. T.; Kuhs, W. F.

2012-04-01

In Geoscience quantitative texture analysis here defined as the quantitative analysis of the crystallographic preferred orientation (CPO), is a common tool for the investigation of fabric development in mono- and polyphase rocks, their deformation histories and kinematics. Bulk texture measurements also allow the quantitative characterisation of the anisotropic physical properties of rock materials. A routine tool to measure bulk sample volumes is neutron texture diffraction, as neutrons have large penetration capabilities of several cm in geological sample materials. The new POWTEX (POWder and TEXture) Diffractometer at the neutron research reactor FRM II in Garching, Germany is designed as a high-intensity diffractometer by groups from the RWTH Aachen, Forschungszentrum Jülich and the University of Göttingen. Complementary to existing neutron diffractometers (SKAT at Dubna, Russia; GEM at ISIS, UK; HIPPO at Los Alamos, USA; D20 at ILL, France; and the local STRESS-SPEC and SPODI at FRM II) the layout of POWTEX is focused on fast time-resolved experiments and the measurement of larger sample series as necessary for the study of large scale geological structures. POWTEX is a dedicated beam line for geoscientific research. Effective texture measurements without sample tilting and rotation are possible firstly by utilizing a range of neutron wavelengths simultaneously (Time-of-Flight technique) and secondly by the high detector coverage (9.8 sr) and a high flux (~1 - 107 n/cm2s) at the sample. Furthermore the instrument and the angular detector resolution is designed also for strong recrystallisation textures as well as for weak textures of polyphase rocks. These instrument characteristics allow in-situ time-resolved texture measurements during deformation experiments on rocksalt, ice and other materials as large sample environments will be implemented at POWTEX. The in-situ deformation apparatus is operated by a uniaxial spindle drive with a maximum axial load of 250 kN, which will be redesigned to minimize shadowing effects inside the cylindrical detector. The HT deformatione experiments will be carried out in uniaxial compression or extension and an upgrade to triaxial deformation conditions is envisaged. The load frame can alternatively be used for ice deformation by inserting a cryostat cell for temperatures down to 77 K with a triaxial apparatus allowing also simple shear experiments on ice. Strain rates range between 10-8 and 10-3 s-1 reaching to at least 50 % axial strain. The deformation apparatus is designed for continuous long-term deformation experiments and can be exchanged between in-situ and ex-situ placements during continuous operation inside and outside the neutron detector.

Ce(III) and Ce(IV) (re)distribution and fractionation in a laterite profile from Madagascar: Insights from in situ XANES spectroscopy at the Ce LIII-edge

NASA Astrophysics Data System (ADS)

Janots, Emilie; Bernier, Felix; Brunet, Fabrice; Muñoz, Manuel; Trcera, Nicolas; Berger, Alfons; Lanson, Martine

2015-03-01

The distribution of trivalent and tetravalent cerium, Ce(III) and Ce(IV) respectively, in a lateritic profile from Madagascar, has been characterized by X-ray-absorption near-edge structure (XANES) spectroscopy at the Ce LIII-edge on the LUCIA beamline (SOLEIL synchrotron, France). XANES spectra were acquired on bulk-rock samples as well as on specific lateritic minerals or polymineral zones (in-situ measurements) of the tonalite bedrock and the three overlying weathered horizons (C-, B- and A-horizons). Geochemically, the bedrock, and the A- and C-horizons show similar rare earth element content (REE = 363-405 mg/kg). They also display the same positive Ce-anomaly (CeCN/Ce∗ = 1.12-1.45), which is therefore likely to be inherited from the bedrock. In the B-horizon, the higher REE content (REE = 2194 mg/kg) and the larger Ce-anomaly (CeCN/Ce∗ = 4.26) are consistent with an accumulation zone caused by the evaporation of groundwater during the dry season. There is a good agreement between the Ce(III)/Cetotal ratio (XCe(III)) deduced from the positive Ce-anomaly (bulk-rock geochemical data) and that derived from XANES spectroscopy on the same bulk-rock samples (BR-XCe(III)-XANES) in the bedrock, and the C- and B-horizons. In the A-horizon, XANES measurements on bulk rock and minerals revealed a higher BR-XCe(III)-XANES (up to 100%) compared to the XCe(III) deduced from geochemical data (XCe(III) = 79%). The preservation of a positive Ce-anomaly in the A-horizon suggests that the Ce mobilization and redistribution during weathering occurred with no significant Ce fractionation from other trivalent REE. Remarkably, the only investigated sample where cerianite is observed belongs to the B-horizon. Within this horizon, Ce oxidation state varies depending on the microstructural position (porosity, cracks, clay-rich groundmass). The highest Ce(IV) concentrations are measured in cerianite (and aluminophosphates) localized in pores at the vicinity of Mn-rich domains (XCe(III)-XANES = 30-51%). Therefore, Ce fractionation from other REE is attributed to a Ce oxidation and precipitation potentially assisted by oxyhydroxide scavenging. In the C-horizon, Ce(III) and Ce(IV) are mainly distributed in REE-minerals of the rhabdophane group found in pores and cracks. The similarity between the Ce(III) proportion of rhabdophane grains (XCe(III)-XANES = 74-89%) with that of the bedrock (BR-XCe(III)-XANES = 79%) suggests no significant fractionation of Ce(III) and Ce(IV) between solution and mineral during the successive stages of primary REE-mineral alteration, transport in solution and secondary precipitation in the incipient stages of weathering. Overall, our novel spectroscopic approach shows that Ce is not necessarily oxidized nor fractionated from other REE during weathering in lateritic conditions. This implies that like Ce(III), Ce(IV) can be mobilized in aqueous fluids during weathering, possibly thanks to complexation with organic molecules, and can precipitate together with Ce(III) in secondary REE-bearing minerals. The corollary is that (paleo)redox reconstructions in soils and/or sediments based on Ce-anomaly in weathered rocks or minerals must be interpreted with caution.

Hardrock Elastic Physical Properties: Birch's Seismic Parameter Revisited

NASA Astrophysics Data System (ADS)

Wu, M.; Milkereit, B.

2014-12-01

Identifying rock composition and properties is imperative in a variety of fields including geotechnical engineering, mining, and petroleum exploration, in order to accurately make any petrophysical calculations. Density is, in particular, an important parameter that allows us to differentiate between lithologies and estimate or calculate other petrophysical properties. It is well established that compressional and shear wave velocities of common crystalline rocks increase with increasing densities (i.e. the Birch and Nafe-Drake relationships). Conventional empirical relations do not take into account S-wave velocity. Physical properties of Fe-oxides and massive sulfides, however, differ significantly from the empirical velocity-density relationships. Currently, acquiring in-situ density data is challenging and problematic, and therefore, developing an approximation for density based on seismic wave velocity and elastic moduli would be beneficial. With the goal of finding other possible or better relationships between density and the elastic moduli, a database of density, P-wave velocity, S-wave velocity, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio was compiled based on a multitude of lab samples. The database is comprised of isotropic, non-porous metamorphic rock. Multi-parameter cross plots of the various elastic parameters have been analyzed in order to find a suitable parameter combination that reduces high density outliers. As expected, the P-wave velocity to S-wave velocity ratios show no correlation with density. However, Birch's seismic parameter, along with the bulk modulus, shows promise in providing a link between observed compressional and shear wave velocities and rock densities, including massive sulfides and Fe-oxides.

Pristine Igneous Rocks and the Early Differentiation of Planetary Materials

NASA Technical Reports Server (NTRS)

Warren, Paul H.

1998-01-01

Our studies are highly interdisciplinary, but are focused on the processes and products of early planetary and asteroidal differentiation, especially the genesis of the ancient lunar crust. Most of the accessible lunar crust consists of materials hybridized by impact-mixing. Rare pristine (unmixed) samples reflect the original genetic diversity of the early crust. We studied the relative importance of internally generated melt (including the putative magma ocean) versus large impact melts in early lunar magmatism, through both sample analysis and physical modeling. Other topics under investigation included: lunar and SNC (martian?) meteorites; igneous meteorites in general; impact breccias, especially metal-rich Apollo samples and polymict eucrites; effects of regolith/megaregolith insulation on thermal evolution and geochronology; and planetary bulk compositions and origins. We investigated the theoretical petrology of impact melts, especially those formed in large masses, such as the unejected parts of the melts of the largest lunar and terrestrial impact basins. We developed constraints on several key effects that variations in melting/displacement ratio (a strong function of both crater size and planetary g) have on impact melt petrology. Modeling results indicate that the impact melt-derived rock in the sampled, megaregolith part of the Moon is probably material that was ejected from deeper average levels than the non-impact-melted material (fragmental breccias and unbrecciated pristine rocks). In the largest lunar impacts, most of the impact melt is of mantle origin and avoids ejection from the crater, while most of the crust, and virtually all of the impact-melted crust, in the area of the crater is ejected. We investigated numerous extraordinary meteorites and Apollo rocks, emphasizing pristine rocks, siderophile and volatile trace elements, and the identification of primary partial melts, as opposed to partial cumulates. Apollo 15 sample 15434,28 is an extraodinarily large glass spherule, nearly if not entirely free of meteoritic contamination, and provides insight into the diversity of mare basalts in the Hadley-Apennine region. Apollo 14 sample 14434 is in many respects a new rock type, intermediate between nonmare gabbronorites and mare basalts. We helped to both plan and implement a consortium to study the Yamato-793605 SNC/martian meteorite.

Biogenicity and Syngeneity of Organic Matter in Ancient Sedimentary Rocks: Recent Advances in the Search for Evidence of Past Life

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oehler, Dorothy Z.; Cady, Sherry L.

2014-12-01

he past decade has seen an explosion of new technologies for assessment of biogenicity and syngeneity of carbonaceous material within sedimentary rocks. Advances have been made in techniques for analysis of in situ organic matter as well as for extracted bulk samples of soluble and insoluble (kerogen) organic fractions. The in situ techniques allow analysis of micrometer-to-sub-micrometer-scale organic residues within their host rocks and include Raman and fluorescence spectroscopy/imagery, confocal laser scanning microscopy, and forms of secondary ion/laser-based mass spectrometry, analytical transmission electron microscopy, and X-ray absorption microscopy/spectroscopy. Analyses can be made for chemical, molecular, and isotopic composition coupled withmore » assessment of spatial relationships to surrounding minerals, veins, and fractures. The bulk analyses include improved methods for minimizing contamination and recognizing syngenetic constituents of soluble organic fractions as well as enhanced spectroscopic and pyrolytic techniques for unlocking syngenetic molecular signatures in kerogen. Together, these technologies provide vital tools for the study of some of the oldest and problematic carbonaceous residues and for advancing our understanding of the earliest stages of biological evolution on Earth and the search for evidence of life beyond Earth. We discuss each of these new technologies, emphasizing their advantages and disadvantages, applications, and likely future directions.« less

Petrology and Geochemistry of Unbrecciated Harzburgitic Diogenite MIL 07001: A Window Into Vestan Geological Evolution

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Peng, Z. X.; Mertzman, S. A.; Mertzman, K. R.

2014-01-01

There is a strong case that asteroid 4 Vesta is the parent of the howardite, eucrite and diogenite (HED) meteorites. Models developed for the geological evolution of Vesta can satisfy the compositions of basaltic eucrites that dominate in the upper crust. The bulk compositional characteristics of diogenites - cumulate harzburgites and orthopyroxenites from the lower crust - do not fit into global magma ocean models that can describe the compositions of basaltic and cumulate eucrites. Recent more detailed formation models do make provision for a more complicated origin for diogenites, but this model has yet to be completely vetted. Compositional studies of bulk samples has led to the hypothesis that many diogenites were formed late by interaction of their parent melts with a eucritic crust, but those observations may alternatively be explained by subsolidus equilibration of trace elements between orthopyroxene and plagioclase and Ca-phosphate in the rocks. Differences in radiogenic Mg-26 content between diogenites and eucrites favors early formation of the former, not later formation. Understanding the origin of diogenites is crucial for understanding the petrologic evolution of Vesta. We have been doing coordinated studies of a suite of diogenites including petrologic investigations, bulk rock major and trace element studies, and in situ trace element analyses of orthopyroxene. Here we will focus on an especially unusual, and potentially key, diogenite, MIL 07001.

Major to ultra trace element bulk rock analysis of nanoparticulate pressed powder pellets by LA-ICP-MS

NASA Astrophysics Data System (ADS)

Peters, Daniel; Pettke, Thomas

2016-04-01

An efficient, clean procedure for bulk rock major to trace element analysis by 193 nm Excimer LA-ICP-MS analysis of nanoparticulate pressed powder pellets (PPPs) employing a binder is presented. Sample powders are milled in water suspension in a planetary ball mill, reducing average grain size by about one order of magnitude compared to common dry milling protocols. Microcrystalline cellulose (MCC) is employed as a binder, improving the mechanical strength of the PPP and the ablation behaviour, because MCC absorbs 193 nm laser light well. Use of MCC binder allows for producing cohesive pellets of materials that cannot be pelletized in their pure forms, such as quartz powder. Rigorous blank quantification was performed on synthetic quartz treated like rock samples, demonstrating that procedural blanks are irrelevant except for a few elements at the 10 ng g-1 concentration level. The LA-ICP-MS PPP analytical procedure was optimised and evaluated using six different SRM powders (JP-1, UB-N, BCR-2, GSP-2, OKUM, and MUH-1). Calibration based on external standardization using SRM 610, SRM 612, BCR-2G, and GSD-1G glasses allows for evaluation of possible matrix effects during LA-ICP-MS analysis. The data accuracy of the PPP LA-ICP-MS analytical procedure compares well to that achieved for liquid ICP-MS and LA-ICP-MS glass analysis, except for element concentrations below ˜30 ng g-1, where liquid ICP-MS offers more precise data and in part lower limits of detection. Uncertainties on the external reproducibility of LA-ICP-MS PPP element concentrations are of the order of 0.5 to 2 % (1σ standard deviation) for concentrations exceeding ˜1 μg g-1. For lower element concentrations these uncertainties increase to 5-10% or higher when analyte-depending limits of detection (LOD) are approached, and LODs do not significantly differ from glass analysis. Sample homogeneity is demonstrated by the high analytical precision, except for very few elements where grain size effects can rarely still be resolved analytically. Matrix effects are demonstrated for PPP analysis of diverse rock compositions and basalt glass analysis when externally calibrated based on SRM 610 and SRM 612 glasses; employing basalt glass GSD-1G or BCR-2G for external standardisation basically eliminates these problems. Perhaps the most prominent progress of the LA-ICP-MS PPP analytical procedure presented here is the fact that trace elements not commonly analysed, i.e. new, unconventional geochemical tracers, can be measured straightforwardly, including volatile elements, the flux elements Li and B, the chalcophile elements As, Sb, Tl, Bi, and elements that alloy with metal containers employed in conventional glass production approaches. The method presented here thus overcomes many common problems and limitations in analytical geochemistry and is shown to be an efficient alternative for bulk rock trace elements analysis.

Quantitative Vectorial Magnetic Imaging of Multi Domain Rock Forming Minerals using Nitrogen-Vacancy Centers in Diamond

NASA Astrophysics Data System (ADS)

Shaar, R.; Farchi, E.; Farfurnik, D.; Ebert, Y.; Haim, G.; Bar-Gill, N.

2017-12-01

Magnetization in rock samples is crucial for paleomagnetometry research, as it harbors valuable geological information on long term processes, such as tectonic movements and the formation of oceans and continents. Nevertheless, current techniques are limited in their ability to measure high spatial resolution and high-sensitivity quantitative vectorial magnetic signatures from individual minerals and micrometer scale samples. As a result, our understanding of bulk rock magnetization is limited, specifically for the case of multi-domain minerals. In this work we use a newly developed nitrogen-vacancy magnetic microscope, capable of quantitative vectorial magnetic imaging with optical resolution. We demonstrate direct imaging of the vectorial magnetic field of a single, multi-domain dendritic magnetite, as well as the measurement and calculation of the weak magnetic moments of an individual grain on the micron scale. Our results were measured in a standoff distance of 3-10 μm, with 350 nm spatial resolution, magnetic sensitivity of 6 μT/√(Hz) and a field of view of 35 μm. The results presented here show the capabilities and the future potential of NV microscopy in measuring the magnetic signals of individual micrometer scale grains. These outcomes pave the way for future applications in paleomagnetometry, and for the fundamental understanding of magnetization in multi-domain samples.

Fe (hydro) oxide controls Mo isotope fractionation during the weathering of granite

NASA Astrophysics Data System (ADS)

Wang, Zhibing; Ma, Jinlong; Li, Jie; Wei, Gangjian; Zeng, Ti; Li, Lei; Zhang, Le; Deng, Wenfeng; Xie, Luhua; Liu, Zhifeng

2018-04-01

Understanding the fractionation mechanisms of Mo isotopes and seeking the main hosts of light δ98/95Mo during chemical weathering of continental rocks is a prerequisite for constraining heavy δ98/95Mo input into rivers. This study investigates the Mo concentrations and δ98/95Mo values of bulk samples, chemical extractions, and clay fractions of weathering products in a granite weathering profile in Guangdong province, South China, as well as in surrounding stream water. Results from bulk samples show that the τ MoTiO2 values systematically decrease from 59.1% to -77.0%, and δ98/95Mo values systematically increase from -1.46‰ to -0.17‰, upwards in the profile (from 30 to 0 m depth). Atmospheric input has a limited effect on δ98/95Mo variations in the weathering profile. Adsorption and desorption processes of Fe (hydro) oxide are the dominant factors controlling the variations in δ98/95Mo, with light Mo isotopes preferentially adsorbed by Fe (hydro) oxide, and released during desorption process, whereas the incongruent dissolution of primary minerals has little effect. Organic materials and the clay fraction are not the main hosts of light δ98/95Mo, as indicated by the results of chemical extractions, which show that a large proportion (41.5-86.2%) of total Mo with light δ98/95Mo (-1.57‰ to -0.59‰) is associated with Fe (hydro) oxide. Moreover, a significant positive correlation exists between Mo concentrations and δ98/95Mo in the Fe (hydro) oxide extractions from bulk samples. Finally, δ98/95Mo in stream water indicates the release of heavier δ98/95Mo into river water during the chemical weathering of granite rock. The results advance our understanding the mechanisms of Mo isotope fractionation during chemical weathering and its isotopic mass balance in Earth's surface system.

The Northwest Africa 8159 martian meteorite: Expanding the martian sample suite to the early Amazonian

NASA Astrophysics Data System (ADS)

Herd, Christopher D. K.; Walton, Erin L.; Agee, Carl B.; Muttik, Nele; Ziegler, Karen; Shearer, Charles K.; Bell, Aaron S.; Santos, Alison R.; Burger, Paul V.; Simon, Justin I.; Tappa, Michael J.; McCubbin, Francis M.; Gattacceca, Jérôme; Lagroix, France; Sanborn, Matthew E.; Yin, Qing-Zhu; Cassata, William S.; Borg, Lars E.; Lindvall, Rachel E.; Kruijer, Thomas S.; Brennecka, Gregory A.; Kleine, Thorsten; Nishiizumi, Kunihiko; Caffee, Marc W.

2017-12-01

Northwest Africa (NWA) 8159 is an augite-rich shergottite, with a mineralogy dominated by Ca-, Fe-rich pyroxene, plagioclase, olivine, and magnetite. NWA 8159 crystallized from an evolved melt of basaltic composition under relatively rapid conditions of cooling, likely in a surface lava flow or shallow sill. Redox conditions experienced by the melt shifted from relatively oxidizing (with respect to known Martian lithologies, ∼QFM) on the liquidus to higher oxygen fugacity (∼QFM + 2) during crystallization of the groundmass, and under subsolidus conditions. This shift resulted in the production of orthopyroxene and magnetite replacing olivine phenocryst rims. NWA 8159 contains both crystalline and shock-amorphized plagioclase (An50-62), often observed within a single grain; based on known calibrations we bracket the peak shock pressure experienced by NWA 8159 to between 15 and 23 GPa. The bulk composition of NWA 8159 is depleted in LREE, as observed for Tissint and other depleted shergottites; however, NWA 8159 is distinct from all other martian lithologies in its bulk composition and oxygen fugacity. We obtain a Sm-Nd formation age of 2.37 ± 0.25 Ga for NWA 8159, which represents an interval in Mars geologic time which, until recently, was not represented in the other martian meteorite types. The bulk rock 147Sm/144Nd value of 0.37 ± 0.02 is consistent with it being derived directly from its source and the high initial ε143Nd value indicates this source was geochemically highly depleted. Cr, Nd, and W isotopic compositions further support a unique mantle source. While the rock shares similarities with the 2.4-Ga NWA 7635 meteorite, there are notable distinctions between the two meteorites that suggest differences in mantle source compositions and conditions of crystallization. Nevertheless, the two samples may be launch-paired. NWA 8159 expands the known basalt types, ages and mantle sources within the Mars sample suite to include a second igneous unit from the early Amazonian.

High Spatial Resolution 40Ar/39Ar Geochronology of Lunar Impact Melt Rocks

NASA Astrophysics Data System (ADS)

Mercer, Cameron Mark

Impact cratering has played a key role in the evolution of the solid surfaces of Solar System bodies. While much of Earth’s impact record has been erased, its Moon preserves an extensive history of bombardment. Quantifying the timing of lunar impact events is crucial to understanding how impacts have shaped the evolution of early Earth, and provides the basis for estimating the ages of other cratered surfaces in the Solar System. Many lunar impact melt rocks are complex mixtures of glassy and crystalline “melt” materials and inherited clasts of pre-impact minerals and rocks. If analyzed in bulk, these samples can yield complicated incremental release 40Ar/39Ar spectra, making it challenging to uniquely interpret impact ages. Here, I have used a combination of high-spatial resolution 40Ar/39Ar geochronology and thermal-kinetic modeling to gain new insights into the impact histories recorded by such lunar samples. To compare my data to those of previous studies, I developed a software tool to account for differences in the decay, isotopic, and monitor age parameters used for different published 40Ar/39Ar datasets. Using an ultraviolet laser ablation microprobe (UVLAMP) system I selectively dated melt and clast components of impact melt rocks collected during the Apollo 16 and 17 missions. UVLAMP 40Ar/39Ar data for samples 77135, 60315, 61015, and 63355 show evidence of open-system behavior, and provide new insights into how to interpret some complexities of published incremental heating 40Ar/39Ar spectra. Samples 77115, 63525, 63549, and 65015 have relatively simple thermal histories, and UVLAMP 40Ar/39Ar data for the melt components of these rocks indicate the timing of impact events—spanning hundreds of millions of years—that influenced the Apollo 16 and 17 sites. My modeling and UVLAMP 40Ar/39Ar data for sample 73217 indicate that some impact melt rocks can quantitatively retain evidence for multiple melt-producing impact events, and imply that such polygenetic rocks should be regarded as high-value sampling opportunities during future exploration missions to cratered planetary surfaces. Collectively, my results complement previous incremental heating 40Ar/39Ar studies, and support interpretations that the Moon experienced a prolonged period of heavy bombardment early in its history.

Effects of mother lode-type gold mineralization on 187Os/188Os and platinum group element concentrations in peridotite: Alleghany District, California

USGS Publications Warehouse

Walker, R.J.; Böhlke, J.K.; McDonough, W.F.; Li, Ji

2007-01-01

Osmium isotope compositions and concentrations of Re, platinum group elements (PGE), and Au were determined for host peridotites (serpentinites and barzburgites) and hydrothermally altered ultramafic wall rocks associated with Mother Lode-type hydrothermal gold-quartz vein mineralization in the Alleghany district, California. The host peridotites have Os isotope compositions and Re, PGE, and Au abundances typical of the upper mantle at their presumed formation age during the late Proterozoic or early Paleozoic. The hydrothermally altered rocks have highly variable initial Os isotope compositions with ??os, values (% deviation of 187OS/188OS from the chondritic average calculated for the approx. 120 Ma time of mineralization) ranging from -1.4 to -8.3. The lowest Os isotope compositions are consistent with Re depletion of a chondritic source (e.g., the upper mantle) at ca. 1.6 Ga. Most of the altered samples are enriched in Au and have depleted and fractionated abundances of Re and PGE relative to their precursor peridotites. Geoehemical characteristics of the altered samples suggest that Re and some PGE were variably removed from the ultramafic rocks during the mineralization event. In addition to Re, the Pt and Pd abundances of the most intensely altered rocks appear to have been most affected by mineralization. The 187Os-depleted isotopic compositions of some altered rocks are interpreted to be a result of preferential 187Os loss via destruction of Re-rich phases during the event. For these rocks, Os evidently is not a useful tracer of the mineralizing fluids. The results do, however, provide evidence for differential mobility of these elements, and mobility of 187Os relative to the initial bulk Os isotope composition during hydrothermal metasomatic alteration of ultramafic rocks. ?? 2007 Society of Economic Geologists, Inc.

Approach of automatic 3D geological mapping: the case of the Kovdor phoscorite-carbonatite complex, NW Russia.

PubMed

Kalashnikov, A O; Ivanyuk, G Yu; Mikhailova, J A; Sokharev, V A

2017-07-31

We have developed an approach for automatic 3D geological mapping based on conversion of chemical composition of rocks to mineral composition by logical computation. It allows to calculate mineral composition based on bulk rock chemistry, interpolate the mineral composition in the same way as chemical composition, and, finally, build a 3D geological model. The approach was developed for the Kovdor phoscorite-carbonatite complex containing the Kovdor baddeleyite-apatite-magnetite deposit. We used 4 bulk rock chemistry analyses - Fe magn , P 2 O 5 , CO 2 and SiO 2 . We used four techniques for prediction of rock types - calculation of normative mineral compositions (norms), multiple regression, artificial neural network and developed by logical evaluation. The two latter became the best. As a result, we distinguished 14 types of phoscorites (forsterite-apatite-magnetite-carbonate rock), carbonatite and host rocks. The results show good convergence with our petrographical studies of the deposit, and recent manually built maps. The proposed approach can be used as a tool of a deposit genesis reconstruction and preliminary geometallurgical modelling.

Role of lichens in weathering of granodiorite in the Sila uplands (Calabria, southern Italy)

NASA Astrophysics Data System (ADS)

Scarciglia, Fabio; Saporito, Natalina; La Russa, Mauro F.; Le Pera, Emilia; Macchione, Maria; Puntillo, Domenico; Crisci, Gino M.; Pezzino, Antonino

2012-12-01

This paper explores the role of five recurrent epilithic lichen species (Aspicilia intermutans (Nyl.) Arnold, Xanthoparmelia pulla (Ach.) O. Blanco, A. Crespo, Elix, D. Hawksw. & Lumbsch, Rhizocarpon lecanorinum Anders, Tephromela atra (Huds.) Hafellner and Lecanora bolcana (Pollini) Poelt), which encrust granodiorite spheroidal boulders exposed in the Sila uplands (Calabria, southern Italy), in weathering of plutonic rocks in a typical mountainous Mediterranean environment. A detailed investigation was carried out on the lichen-rock interface of each species, by comparing them mutually and with lichen-free granodiorite samples. For this purpose, the lichen species were sampled together with the encrusted rock surface for detailed mineral-petrographic analyses performed in thin and ultra-thin sections. Optical and scanning electron microscopy of these sections and of bulk samples permitted us to highlight the peculiar modes of physical and chemical attacks of lichen thalli and hyphae on and into the substratum for each species. Crack systems often parallel to the outer rock surface appear often intruded by hyphae, which cause rupture of primary minerals, with detachment and progressive incorporation of their fragments into the thallus. In particular, the species L. bolcana and T. atra revealed an unexpected, partly endolithic behavior, presumably enhanced by the presence of rock fractures earlier generated by other physical breakage processes already affecting the spheroidal boulders in the Sila mountains. Dissolution features often affect primary minerals (even quartz), that may show very peculiar patterns which are suggestive of a biologically-induced control. Various phyllosilicate clay minerals were identified using SEM-EDS microprobe analyses and FT-IR spectroscopy, which also enabled the identification of possible amorphous silica (or quartz micrograins), rhizocarpic acid and carotenoid at the encrusted granodiorite interface. In contrast, neither oxalic acids nor oxalates were detected.

Quantitative models for aggregate: some types and examples from Oklahoma carbonate rocks

USGS Publications Warehouse

Bliss, James D.

1999-01-01

Evaluation of data for three engineering variable--absorption, bulk specific gravity, and freeze-thaw durability (350 cycles)--was made for quarries in carbonate rocks in Oklahoma that supply aggregate. It was found that lower Palrozoic carbonate rocks (Cambrian through Devonian) are likely to make a better quality aggregate than upper Paleozoic (Mississippian to Permian) carbonate rocks. In addition, freeze-thaw durability can be forecast from absorption and is exemplary for lower Paleozoic carbonate rocks.

Petrography and geochemistry of precambrian rocks from GT-2 and EE-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laughlin, A.W.; Eddy, A.

1977-08-01

During the drilling of GT-2 and EE-1, 27 cores totaling about 35 m were collected from the Precambrian section. Samples of each different lithology in each core were taken for petrographic and whole-rock major- and trace-element analyses. Whole-rock analyses are now completed on 37 samples. From these data four major Precambrian units were identified at the Fenton Hill site. Geophysical logs and cuttings were used to extrapolate between cores. The most abundant rock type is an extremely variable gneissic unit comprising about 75% of the rock penetrated. This rock is strongly foliated and may range compositionally from syenogranitic to tonaliticmore » over a few centimeters. The bulk of the unit falls within the monzogranite field. Interlayered with the gneiss is a ferrohastingsite-biotite schist which compositionally resembles a basaltic andesite. A fault contact between the schist and gneiss was observed in one core. Intrusive into this metamorphic complex are two igneous rocks. A leucocratic monzogranite occurs as at least two 15-m-thick dikes, and a biotite-granodiorite body was intercepted by 338 m of drill hole. Both rocks are unfoliated and equigranular. The biotite granodiorite is very homogeneous and is characterized by high modal contents of biotite and sphene and by high K/sub 2/O, TiO/sub 2/, and P/sub 2/O/sub 5/ contents. Although all of the cores examined show fractures, most of these are tightly sealed or healed. Calcite is the most abundant fracture filling mineral, but epidote, quartz, chlorite, clays or sulfides have also been observed. The degree of alteration of the essential minerals normally increases as these fractures are approached. The homogeneity of the biotite granodiorite at the bottom of GT-2 and the high degree of fracture filling ensure an ideal setting for the Hot Dry Rock Experiment.« less

The Regolith of 4 Vesta - Inferences from Howardites

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Herrin, J. S.; Cartwright, J. A.

2011-01-01

Asteroid 4 Vesta is quite likely the parent asteroid of the howardite, eucrite and diogenite meteorites - the HED clan. Eucrites and diogenites are the products of igneous processes; the former are basaltic composition rocks from flows, and shallow and deep intrusive bodies, whilst the latter are cumulate orthopyroxenites thought to have formed deep in the crust. Impact processes have excavated these materials and mixed them into a suite of polymict breccias. Howardites are polymict breccias composed mostly of clasts and mineral fragments of eucritic and diogenitic parentage, with neither end-member comprising more than 90% of the rock. Early work interpreted howardites as representing the lithified regolith of their parent asteroid. Recently, howardites have been divided into two subtypes; fragmental howardites, being a type of non-regolithic polymict breccia, and regolithic howardites, being lithified remnants of the active regolith of 4 Vesta. We are in the thralls of a collaborative investigation of the record of impact mixing contained within howardites, which includes studies of their mineralogy, petrology, bulk rock compositions, and bulk rock and clast noble gas contents. One goal of our investigation is to test the hypothesis that some howardites represent breccias formed from an ancient, well-mixed regolith on Vesta. Another is to use our results to further understand regolith processing on differentiated asteroids as compared to what has been learned from the Moon. We have made petrographic observations and electron microprobe analyses on 21 howardites and 3 polymict eucrites. We have done bulk rock analyses using X-ray fluorescence spectrometry and are completing inductively coupled plasma mass spectrometry analyses. Here, we discuss our petrologic and bulk compositional results in the context of regolith formation. Companion presentations describe the noble gas results and compositional studies of low-Ca pyroxene clasts.

Heterogeneous vesiculation of 2011 El Hierro xeno-pumice revealed by X-ray computed microtomography

NASA Astrophysics Data System (ADS)

Berg, S. E.; Troll, V. R.; Deegan, F. M.; Burchardt, S.; Krumbholz, M.; Mancini, L.; Polacci, M.; Carracedo, J. C.; Soler, V.; Arzilli, F.; Brun, F.

2016-12-01

During the first week of the 2011 El Hierro submarine eruption, abundant light-coloured pumiceous, high-silica volcanic bombs coated in dark basanite were found floating on the sea. The composition of the light-coloured frothy material (`xeno-pumice') is akin to that of sedimentary rocks from the region, but the textures resemble felsic magmatic pumice, leaving their exact mode of formation unclear. To help decipher their origin, we investigated representative El Hierro xeno-pumice samples using X-ray computed microtomography for their internal vesicle shapes, volumes, and bulk porosity, as well as for the spatial arrangement and size distributions of vesicles in three dimensions (3D). We find a wide range of vesicle morphologies, which are especially variable around small fragments of rock contained in the xeno-pumice samples. Notably, these rock fragments are almost exclusively of sedimentary origin, and we therefore interpret them as relicts an the original sedimentary ocean crust protolith(s). The irregular vesiculation textures observed probably resulted from pulsatory release of volatiles from multiple sources during xeno-pumice formation, most likely by successive release of pore water and mineral water during incremental heating and decompression of the sedimentary protoliths.

Correlation of the Rock Mass Rating (RMR) System with the Unified Soil Classification System (USCS): Introduction of the Weak Rock Mass Rating System (W-RMR)

NASA Astrophysics Data System (ADS)

Warren, Sean N.; Kallu, Raj R.; Barnard, Chase K.

2016-11-01

Underground gold mines in Nevada are exploiting increasingly deeper ore bodies comprised of weak to very weak rock masses. The Rock Mass Rating (RMR) classification system is widely used at underground gold mines in Nevada and is applicable in fair to good-quality rock masses, but is difficult to apply and loses reliability in very weak rock mass to soil-like material. Because very weak rock masses are transition materials that border engineering rock mass and soil classification systems, soil classification may sometimes be easier and more appropriate to provide insight into material behavior and properties. The Unified Soil Classification System (USCS) is the most likely choice for the classification of very weak rock mass to soil-like material because of its accepted use in tunnel engineering projects and its ability to predict soil-like material behavior underground. A correlation between the RMR and USCS systems was developed by comparing underground geotechnical RMR mapping to laboratory testing of bulk samples from the same locations, thereby assigning a numeric RMR value to the USCS classification that can be used in spreadsheet calculations and geostatistical analyses. The geotechnical classification system presented in this paper including a USCS-RMR correlation, RMR rating equations, and the Geo-Pick Strike Index is collectively introduced as the Weak Rock Mass Rating System (W-RMR). It is the authors' hope that this system will aid in the classification of weak rock masses and more usable design tools based on the RMR system. More broadly, the RMR-USCS correlation and the W-RMR system help define the transition between engineering soil and rock mass classification systems and may provide insight for geotechnical design in very weak rock masses.

Apollo 15 coarse fines (4-10 mm): Sample classification, description and inventory

NASA Technical Reports Server (NTRS)

Powell, B. N.

1972-01-01

A particle by particle binocular microscopic examination of all of the Apollo 15 4-10 mm fines samples is reported. These particles are classified according to their macroscopic lithologic features in order to provide a basis for sample allocations and future study. The relatively large size of these particles renders them too vaulable to permit treatment along with the other bulk fines, yet they are too small (and numerous) to practically receive full individual descriptive treatment as given the larger rock samples. This examination, classification and description of subgroups represents a compromise treatment. In most cases and for many types of investigation the individual particles should be large enough to permit the application of more than one type of analysis.

Unraveling multiple phases of sulfur cycling during the alteration of ancient ultramafic oceanic lithosphere

NASA Astrophysics Data System (ADS)

Schwarzenbach, Esther M.; Gill, Benjamin C.; Johnston, David T.

2018-02-01

Ultramafic-hosted hydrothermal systems - characterized by ongoing serpentinization reactions - exert an important influence on the global sulfur cycle. Extensive water-rock interaction causes elemental exchange between seawater and the oceanic lithosphere, effectively removing sulfate from seawater through both abiogenic and biogenic processes. Here, we use bulk rock multiple sulfur isotope signatures (32S, 33S, 34S) and in situ sulfide analyses together with petrographic observations to track the sulfur cycling processes and the hydrothermal evolution of ancient peridotite-hosted hydrothermal systems. We investigate serpentinized peridotites from the Northern Apennine ophiolite in Italy and the Santa Elena ophiolite in Costa Rica and compare those with the Iberian Margin (Ocean Drilling Program (ODP) Leg 149 and 173) and the 15°20‧N Fracture Zone along the Mid-Atlantic Ridge (ODP Leg 209). In situ measurements of sulfides in the Northern Apennine serpentinites preserve a large range in δ34Ssulfide of -33.8 to +13.3‰ with significant heterogeneities within single sulfide grains and depending on mineralogy. Detailed mineralogical investigation and comparison with bulk rock Δ33Ssulfide and in situ δ34Ssulfide data implies a thermal evolution of the system from high temperatures (∼350 °C) that allowed thermochemical sulfate reduction and input of hydrothermal sulfide to lower temperatures (<120 °C) that permitted microbial activity. The change in temperature regime is locally preserved in individual samples and correlates with the progressive uplift and exposure of mantle rock associated with detachment faulting along a mid-ocean ridge spreading center. The Santa Elena peridotites preserve distinct signatures for fluid circulation at high temperatures with both closed system thermochemical sulfate reduction and input of mafic-derived sulfur. In addition, the peridotites provide strong evidence that low Ca2+ concentrations in peridotite-hosted systems can limit sulfate removal during anhydrite precipitation at temperatures above 150 °C. This may play a central role for the availability of sulfate to microbial communities within these systems. Overall, the combined application of in situ and bulk rock multiple sulfur isotope measurements with petrographic observations allows us to resolve the different episodes of sulfur cycling during alteration of the oceanic lithosphere and the temporal changes between abiogenic and biogenic processes that control the sulfur cycling in these systems.

Laboratory Study of Aliphatic Organic Spectral Signatures and Applications to Ceres and Primitive Asteroids

NASA Astrophysics Data System (ADS)

Kaplan, H. H.; Milliken, R.

2017-12-01

Aliphatic organics were recently discovered on the surface of Ceres with Dawn's Visible and InfraRed (VIR) mapping spectrometer, which has implications for prebiotic chemistry of Ceres and other asteroids. An absorption in the spectrum at 3.4 µm was used to identify and provide initial estimates of the amount of organic material. We have studied the 3.4 µm absorption in reflectance spectra of bulk rock and meteorite powders and isolated organic materials in the NASA RELAB facility at Brown University to determine how organic composition and abundance affects absorption strength. Reflectance spectra of insoluble organic matter (IOM) extracted from carbonaceous chondrites were measured from 0.35 - 25 µm. These IOM have known elemental (H, C, N, O) and isotopic compositions that were compared with spectral properties. Bulk meteorites were measured as chips and particulates over the same wavelength range. Despite overall low reflectance values (albedo <0.01), the 3.4 µm absorption is observed for some IOM samples, specifically those with a H/C ratio greater than 0.4. The absorption strength (band depth) increases with increasing H/C ratio, which corroborates similar findings in our previous study of sedimentary rocks and isolated kerogens. The absorption strength in the bulk meteorites reflects both H/C of the IOM and the concentration of IOM in the inorganic (mineral) matrix. Overlapping absorptions from carbonates and phyllosilicates (OH/H2O) can also influence the aliphatic organic bands in bulk rocks and meteorites. This laboratory work provides a foundation that can be used to constrain the composition of Ceres' aliphatic organic matter using band depth as a proxy for H/C. Reflectance spectra collected for this work will also be used to model the Dawn VIR data and obtain abundance and H/C estimates assuming that the organic material on Ceres' surface is similar to carbonaceous chondrite IOM. These spectra and findings can aid interpretation of reflectance data from Ceres and other asteroid missions, such as OSIRIS-REx and Hayabusa2.

The Viking X ray fluorescence experiment - Analytical methods and early results

NASA Technical Reports Server (NTRS)

Clark, B. C., III; Castro, A. J.; Rowe, C. D.; Baird, A. K.; Rose, H. J., Jr.; Toulmin, P., III; Christian, R. P.; Kelliher, W. C.; Keil, K.; Huss, G. R.

1977-01-01

Ten samples of the Martian regolith have been analyzed by the Viking lander X ray fluorescence spectrometers. Because of high-stability electronics, inclusion of calibration targets, and special data encoding within the instruments the quality of the analyses performed on Mars is closely equivalent to that attainable with the same instruments operated in the laboratory. Determination of absolute elemental concentrations requires gain drift adjustments, subtraction of background components, and use of a mathematical response model with adjustable parameters set by prelaunch measurements on selected rock standards. Bulk fines at both Viking landing sites are quite similar in composition, implying that a chemically and mineralogically homogeneous regolith covers much of the surface of the planet. Important differences between samples include a higher sulfur content in what appear to be duricrust fragments than in fines and a lower iron content in fines taken from beneath large rocks than those taken from unprotected surface material. Further extensive reduction of these data will allow more precise and more accurate analytical numbers to be determined and thus a more comprehensive understanding of elemental trends between samples.

Thermal maturity of northern Appalachian Basin Devonian shales: Insights from sterane and terpane biomarkers

USGS Publications Warehouse

Hackley, Paul C.; Ryder, Robert T.; Trippi, Michael H.; Alimi, Hossein

2013-01-01

To better estimate thermal maturity of Devonian shales in the northern Appalachian Basin, eleven samples of Marcellus and Huron Shale were characterized via multiple analytical techniques. Vitrinite reflectance, Rock–Eval pyrolysis, gas chromatography (GC) of whole rock extracts, and GC–mass spectrometry (GCMS) of extract saturate fractions were evaluated on three transects that lie across previously documented regional thermal maturity isolines. Results from vitrinite reflectance suggest that most samples are immature with respect to hydrocarbon generation. However, bulk geochemical data and sterane and terpane biomarker ratios from GCMS suggest that almost all samples are in the oil window. This observation is consistent with the presence of thermogenic gas in the study area and higher vitrinite reflectance values recorded from overlying Pennsylvanian coals. These results suggest that vitrinite reflectance is a poor predictor of thermal maturity in early mature areas of Devonian shale, perhaps because reported measurements often include determinations of solid bitumen reflectance. Vitrinite reflectance interpretations in areas of early mature Devonian shale should be supplanted by evaluation of thermal maturity information from biomarker ratios and bulk geochemical data.

New constraints on the formation of shergottite Elephant Moraine 79001 lithology A

NASA Astrophysics Data System (ADS)

Liu, Yang; Balta, J. Brian; Goodrich, Cyrena A.; McSween, Harry Y.; Taylor, Lawrence A.

2013-05-01

Previous studies of Elephant Moraine (EET) 79001 disagreed upon the nature of the magnesian olivine and orthopyroxene grains, and generally considered the formation of EET 79001 at low pressure conditions. New observations on mineral associations, and trace-element abundances of olivine-hosted melt inclusions, in lithology A (EET-A) of EET 79001 lead to new constraints on the formation of this meteorite. The abundances and chondrite-normalized REE pattern of the average melt inclusions in olivine of Mg# 75-61 are similar to those of the bulk-rock composition of lithology A, suggesting that the Mg# <77 olivines are phenocrysts. We also report the widespread occurrence of round orthopyroxene (En78.9-77.9Wo2.2-2.5) inclusions in disequilibrium contact with their olivine hosts (Mg# 73-68). Compositions of these inclusions are similar to xenocrystic cores (Mg# ⩾77; Wo ⩽4) in pyroxene megacrysts. These observations indicate that orthopyroxene xenocrysts were being resorbed while Mg# 77-73 olivine was crystallizing. Combined, these observations suggest that only small portions of the megacrysts are xenocrystic, namely orthopyroxene of Mg# ⩾77 and Wo ⩽4, and possibly also olivine of Mg# ⩾77. The volume percentages of the xenocrystic materials in the rock are small (⩽1 vol.% for each mineral). Compositions of the xenocrystic minerals are similar to cores of megacrysts in olivine-phyric shergottite Yamato (Y) 980459 and Northwest Africa (NWA) 5789. Considering the small fraction of xenocrysts and the similarity between REE abundances of the early-trapped melt and those in bulk EET-A, we re-evaluated the possibility that the bulk-rock composition of EET-A is close to that of its parent melt. Results of pMELTS modeling indicate that polybaric crystallization of the EET-A bulk composition (corrected by removal of xenocryst material) can reproduce the crystallization sequence of EET-A, in contrast to the conclusions of previous workers. We estimate that the EET-A parent magma began crystallizing at ∼0.7 GPa (∼60 km depth), followed a near-isobaric path at 0.5-0.7 GPa during crystallization of most olivine and pyroxene megacrysts, and then crystallized at shallower depth during the formation of megacryst rims and groundmass. Combined with recent reports of high-pressure crystallization for three other olivine-phyric samples, our results strongly support the interpretation that these relatively primitive samples may have begun to crystallize at much greater depths than previously inferred, at the base of martian crust.

The influence of shale depositional fabric on the kinetics of hydrocarbon generation through control of mineral surface contact area on clay catalysis

NASA Astrophysics Data System (ADS)

Rahman, Habibur M.; Kennedy, Martin; Löhr, Stefan; Dewhurst, David N.; Sherwood, Neil; Yang, Shengyu; Horsfield, Brian

2018-01-01

Accurately assessing the temperature and hence the depth and timing of hydrocarbon generation is a critical step in the characterization of a petroleum system. Clay catalysis is a potentially significant modifier of hydrocarbon generation temperature, but experimental studies of clay catalysis show inconsistent or contradictory results. This study tests the hypothesis that source rock fabric itself is an influence on clay mineral catalysis as it controls the extent to which organic matter and clay minerals are physically associated. Two endmember clay-organic fabrics distinguish the source rocks studied: (1) a particulate fabric where organic matter is present as discrete, >5 μm particles and (2) a nanocomposite fabric in which amorphous organic matter is associated with clay mineral surfaces at sub-micron scale. High-resolution electron imaging and bulk geochemical characterisation confirm that samples of the Miocene Monterey Formation (California) are representative of the nanocomposite source rock endmember, whereas samples from the Permian Stuart Range Formation (South Australia) represent the particulate source rock endmember. Kinetic experiments are performed on paired whole rock and kerogen isolate samples from these two formations using open system, non-isothermal pyrolysis at three different heating rates (0.7, 2 and 5 K/min) to determine the effects of the different shale fabrics on hydrocarbon generation kinetics. Extrapolation to a modelled geological heating rate shows a 20 °C reduction in the onset temperature of hydrocarbon generation in Monterey Formation whole rock samples relative to paired kerogen isolates. This result is consistent with the Monterey Formations's nanocomposite fabric where clay catalysis can proceed because reactive clay minerals are intimately associated with organic matter. By contrast, there is no significant difference in the modelled hydrocarbon generation temperature of paired whole rock and kerogen isolates from the Stuart Range Formation. This is consistent with its particulate fabric, where relatively large, discrete organic particles have limited contact with the mineral matrix and the clay minerals are mainly diagenetic and physically segregated within pores. While heating rate may have a control on mineral matrix effects, this result shows that the extent to which organic matter and clay minerals are physically associated could have a significant effect on the timing of hydrocarbon generation, and is a function of the depositional environment and detrital vs diagenetic origin of clay minerals in source rocks.

Detachment Faulting, Serpentinization, Fluids and Life: Preliminary Results of IODP Expedition 357 (Atlantis Massif, MAR 30°N)

NASA Astrophysics Data System (ADS)

Fruh-Green, G. L.; Orcutt, B.; Green, S.; Cotterill, C.

2016-12-01

We present an overview of IODP Expedition 357, which successfully used two seabed rock drills to core 17 shallow holes at 9 sites across Atlantis Massif (Mid-Atlantic Ridge 30°N). A major goal of this expedition is to investigate serpentinization processes and microbial activity in the shallow subsurface of highly altered ultramafic and mafic sequences that have been uplifted to the seafloor along a major detachment fault zone. More than 57 m of core were recovered, with borehole penetration ranging from 1.3 to 16.4 meters below seafloor, and core recovery as high as 75% of total penetration. The cores show highly heterogeneous rock type, bulk rock chemistry and alteration that reflect multiple phases of magmatism and fluid-rock interaction within the detachment fault zone. In cores along an E-W transect of the southern wall, recovered mantle peridotites are locally intruded by gabbroic and doleritic dikes and veins. The proportion of mafic rocks are volumetrically less than the amount of mafic rocks recovered previously in the central dome at IODP Site U1309, suggesting a lower degree of melt infiltration into mantle peridotite at the ridge-transform intersection. New technologies were developed and successfully applied for the first time: (1) an in-situ sensor package and water sampling system on each seabed drill measured real-time variations in dissolved methane, oxygen, pH, oxidation reduction potential, temperature, and conductivity during drilling and took water samples after drilling; (2) a borehole plug system to seal the boreholes was successfully deployed at two sites to allow access for future sampling; and (3) delivery of chemical tracers into the drilling fluids for contamination testing. We will provide an overview of the drilling strategy and preliminary results of Expedition 357, and highlight the role of serpentinization in sustaining microbial communities in a region of active serpentinization and low temperature hydrothermal alteration.

Elephant Moraine 87521: The first lunar meteorite composed of predominantly mare material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warren, P.H.; Kallemeyn, G.W.

1989-12-01

The trace-element chemistry and detailed petrography of brecciated Antarctic meteorite EET87521 reveal that it is not, as originally classified, a eucrite. Its Fe/Mn ratio and bulk Co content are fair higher than expected for a eucrite. Only one known type of extraterrestrial material resembles EET87521 in all important respects for which constraints exist: very-low-Ti (VLT) lunar mare basalts. Even compared to VLT basalts, EET87521 is enriched in REE. However, other varieties of high-alumina, low-Ti mare basalt are known that contain REE at even higher concentrations than EET87521. Several clasts in EET87521 preserve clear vestiges of coarse-grained igneous, possibly orthocumulate, textures.more » Mineralogically, these coarse-grained clasts are diverse; e.g., olivine ranges from Fo{sub 15} in one to Fo{sub 67} in another. One clast with an anomalously fine-grained texture is anorthositic and contains exceptionally Mg-rich pyroxene and Na-poor plagioclase, along with the only FeNi-metal in the thin section. Its FeNi-metals have compositions typical of metals incorporated into lunar soils and polymict breccias as debris from metal-rich meteorites. However, the low Ni and Ir contents of our bulk-rock analysis imply that the proportion of impact-projectile matter in our chip sample is probably small. The moderate degree of lithologic diversity among the lithic lasts and the bulk composition in general indicate that EET87521 is dominated by a single rock type: VLT mare basalt.« less

Heterogeneity of shales in different scales and its implications to laboratory analyses - examples from sedimentology and organic geochemistry study of the Lower Paleozoic shales from shale gas exploration well located in the Baltic Basin, Poland.

NASA Astrophysics Data System (ADS)

Roszkowska-Remin, Joanna; Janas, Marcin

2017-04-01

We present the litho-sedimentological, organic geochemical results and organic porosity estimation of the Ordovician and Silurian shales in the SeqWell (shale gas exploration well located in the Pomerania region, Poland). The most perspective black and bituminous shales of the Upper Ordovician and the Lower Silurian may seem to be homogeneous. However, our results reveal that these shales show heterogeneity at different scales (m to mm). For example, in most cases the decrease of TOC content in the m scale is related to pyroclastic rock intercalations and "dark bioturbations" with no color difference when compared with surrounding sediments. While in cm scale heterogeneity is related to bioturbations, density of organic-rich laminas, or abundance of carbonates and pyrite. Without a detailed sedimentological study of polished core surfaces and Rock-Eval analyses those observations are rather invisible. The correct interpretation of results requires the understanding of rock's heterogeneity in different scales. It has a critical importance for laboratory tests applied on few cm long samples, especially if the results are to be extrapolated to wider intervals. Therefore in ShaleSeq project, a detailed sedimentological core logging and analysis of geochemical parameters of perspective formations in m to mm scale was performed for the first time. The results show good correlation between bioturbation index (BI) and organic geochemical indicators like organic carbon content (TOC) or oxic deposition conditions indicator (oxygen index - OI) leading to the assumption that environmental conditions may have played a crucial role in organic carbon preservation. The geochemical analyses of 12 samples showed that even within the few cm long sections shale can be really diversified. Eight out of twelve analyzed samples were considered geochemically mostly homogeneous, whilst four of them showed evident heterogeneity. Concluding, the sampling should be preceded by detailed sedimentological study, as it allows to control if the chosen samples are representative for wider intervals and give opportunity to place the laboratory results in the wider context. An attempt to estimate organic porosity using Rock-Eval data was based on Marathon Oil company study of the Polish Lower Paleozoic shales. The results of this study and suggested equations were used to calculate hypothetical organic porosity of the most perspective shales in the SeqWell. Calculated organic porosities in % bulk volume of rock suggested that organic porosity for Upper Ordovician and Lower Silurian shales in SeqWell may be at the level of 0,1-2,9% in bulk volume of rock. These results would suggest that organic porosity doesn't play a major role in total porosity system in these shales at the certain thermal maturity level. The hypothetical organic porosity values were not validated by the microscopic study though. Our study are part of the ShaleSeq Project co-funded by Norway Grants of the Polish-Norwegian Research Programme operated by the National Centre for Research and Development.

Zircon U-Pb ages and Hf isotopic compositions indicate multiple sources for Grenvillian detrital zircon deposited in western Laurentia

NASA Astrophysics Data System (ADS)

Howard, Amanda L.; Farmer, G. Lang; Amato, Jeffrey M.; Fedo, Christopher M.

2015-12-01

Combined U-Pb ages and Hf isotopic data from 1.0 Ga to 1.3 Ga (Grenvillian) detrital zircon in Neoproterozoic and Cambrian siliciclastic sedimentary rocks in southwest North America, and from igneous zircon in potential Mesoproterozoic source rocks, are used to better assess the provenance of detrital zircon potentially transported across Laurentia in major river systems originating in the Grenville orogenic highlands. High-precision hafnium isotopic analyses of individual ∼1.1 Ga detrital zircon from Neoproterozoic siliciclastic sedimentary rocks in Sonora, northern Mexico, reveal that these zircons have low εHf (0) (-22 to -26) and were most likely derived from ∼1.1 Ga granitic rocks embedded in local Mojave Province Paleoproterozoic crust. In contrast, Grenvillian detrital zircons in Cambrian sedimentary rocks in Sonora, the Great Basin, and the Mojave Desert, have generally higher εHf (0) (-15 to -21) as demonstrated both by high precision solution-based, and by lower precision laser ablation, ICPMS data and were likely derived from more distal sources further to the east/southeast in Laurentia. Comparison to new and existing zircon U-Pb geochronology and Hf isotopic data from Grenvillian crystalline rocks from the Appalachian Mountains, central and west Texas, and from Paleoproterozoic terranes throughout southwest North America reveals that zircon in Cambrian sandstones need not entirely represent detritus transported across the continent from Grenville province rocks in the vicinity of the present-day southern Appalachian Mountains. Instead, these zircons could have been derived from more proximal, high εHf (0), ∼1.1 Ga, crystalline rocks such as those exposed today in the Llano Uplift in central Texas and in the Franklin Mountains of west Texas. Regardless of the exact source(s) of the Grenvillian detrital zircon, new and existing whole-rock Nd isotopic data from Neoproterozoic to Cambrian siliciclastic sedimentary rocks in the Mojave Desert demonstrate that the occurrences of higher εHf (0), Grenvillian detrital zircons are decoupled from the sources of the bulk of the sedimentary detritus in which the zircons are entrained. The Cambrian Wood Canyon Formation and the underlying ;off craton; Neoproterozoic Johnnie Formation and Stirling Quartzite all contain higher εHf (0), Grenvillian detrital zircon, in some cases as the dominant detrital zircon population. However, only portions of the Wood Canyon Formation have whole rock Nd isotopic compositions consistent with a bulk sediment source in ∼1.1 Ga sources rocks. Whole rock Nd isotopic compositions of the remaining portions of this unit, and all of the Johnnie Formation and Stirling Quartzite, require bulk sediment sources principally in Paleoproterozoic continental crust. We consider the observed decoupling in the sources of Grenvillian detrital zircon and bulk sediment in the Wood Canyon Formation and underlying siliciclastic sediments as a demonstration that detrital zircon U-Pb and Hf isotopic data alone can provide an incomplete picture of the source of sediments that comprise a given siliciclastic stratigraphic unit.

Melt rock components in KREEPy breccia 15205: Petrography and mineral chemistry of KREEP basalts and quartz-normative mare basalts

NASA Astrophysics Data System (ADS)

Shervais, John W.; Vetter, Scott K.

1993-05-01

Many current models for the origin of lunar highland rocks feature as an essential component the assimilation of KREEPy material by primitive magmas parental to the Mg-rich suite and alkali suite plutonic rocks. Similar models have also been proposed for the origin of various mare basalt suites. However, any model which considers assimilation of KREEP an important petrologic process must sooner-or-later deal with the question: what is KREEP? Because pristine KREEP basalts are rare, and most known samples are small (e.g., 15382/15386), the geochemical variability of KREEP basalts is poorly known. Other KREEP compositions which are commonly used in these models include the hypothetical 'high-K KREEP' component of Warren and Wasson, which is derived from Apollo 14 soil data, and the 'superKREEP' quartz-monzodiorite 15405. Lunar breccia 15205 is a polymict regolith breccia that consists of approximately 20% KREEP basalt clasts and 20% quartz-normative basalt clasts in a KREEP-rich matrix. Bulk rock mixing calculations show that this sample comprises about 84% KREEP. The clasts range up to 1 cm in size, but most are considerably smaller. The primary aim is to characterize pristine KREEP basalts petrographically, to establish the range in chemical compositions of KREEP basalts, and to test models that were proposed for their origin. In addition, we may be able to extend the compositional range recognized in the quartz-normative basalt suite and cast some light on its origin as well. Preliminary whole rock geochemical data on the KREEP basalts are presented in a companion paper by M.M. Lindstrom and co-workers. Concentration is on petrography and mineral chemistry of these clasts, and the implications these data have for the origin of the different melt rock suites.

Melt rock components in KREEPy breccia 15205: Petrography and mineral chemistry of KREEP basalts and quartz-normative mare basalts

NASA Technical Reports Server (NTRS)

Shervais, John W.; Vetter, Scott K.

1993-01-01

Many current models for the origin of lunar highland rocks feature as an essential component the assimilation of KREEPy material by primitive magmas parental to the Mg-rich suite and alkali suite plutonic rocks. Similar models have also been proposed for the origin of various mare basalt suites. However, any model which considers assimilation of KREEP an important petrologic process must sooner-or-later deal with the question: what is KREEP? Because pristine KREEP basalts are rare, and most known samples are small (e.g., 15382/15386), the geochemical variability of KREEP basalts is poorly known. Other KREEP compositions which are commonly used in these models include the hypothetical 'high-K KREEP' component of Warren and Wasson, which is derived from Apollo 14 soil data, and the 'superKREEP' quartz-monzodiorite 15405. Lunar breccia 15205 is a polymict regolith breccia that consists of approximately 20% KREEP basalt clasts and 20% quartz-normative basalt clasts in a KREEP-rich matrix. Bulk rock mixing calculations show that this sample comprises about 84% KREEP. The clasts range up to 1 cm in size, but most are considerably smaller. The primary aim is to characterize pristine KREEP basalts petrographically, to establish the range in chemical compositions of KREEP basalts, and to test models that were proposed for their origin. In addition, we may be able to extend the compositional range recognized in the quartz-normative basalt suite and cast some light on its origin as well. Preliminary whole rock geochemical data on the KREEP basalts are presented in a companion paper by M.M. Lindstrom and co-workers. Concentration is on petrography and mineral chemistry of these clasts, and the implications these data have for the origin of the different melt rock suites.

Alteration of immature sedimentary rocks on Earth and Mars. Recording Aqueous and Surface-atmosphere Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cannon, Kenneth M.; Mustard, John F.; Salvatore, Mark R.

The rock alteration and rind formation in analog environments like Antarctica may provide clues to rock alteration and therefore paleoclimates on Mars. Clastic sedimentary rocks derived from basaltic sources have been studied in situ by martian rovers and are likely abundant on the surface of Mars. Moreover, how such rock types undergo alteration when exposed to different environmental conditions is poorly understood compared with alteration of intact basaltic flows. Here we characterize alteration in the chemically immature Carapace Sandstone from Antarctica, a terrestrial analog for martian sedimentary rocks. We employ a variety of measurements similar to those used on previousmore » and current Mars missions. Laboratory techniques included bulk chemistry, powder X-ray diffraction (XRD), hyperspectral imaging and X-ray absorption spectroscopy. Through these methods we find that primary basaltic material in the Carapace Sandstone is pervasively altered to hydrated clay minerals and palagonite as a result of water–rock interaction. A thick orange rind is forming in current Antarctic conditions, superimposing this previous aqueous alteration signature. The rind exhibits a higher reflectance at visible-near infrared wavelengths than the rock interior, with an enhanced ferric absorption edge likely due to an increase in Fe 3+ of existing phases or the formation of minor iron (oxy)hydroxides. This alteration sequence in the Carapace Sandstone results from decreased water–rock interaction over time, and weathering in a cold, dry environment, mimicking a similar transition early in martian history. This transition may be recorded in sedimentary rocks on Mars through a similar superimposition mechanism, capturing past climate changes at the hand sample scale. These results also suggest that basalt-derived sediments could have sourced significant volumes of hydrated minerals on early Mars due to their greater permeability compared with intact igneous rocks.« less

Quantification of Biogenic Magnetite by Synchrotron X-ray Microscopy During the PETM

NASA Astrophysics Data System (ADS)

Wang, H.; Wang, J.; Kent, D. V.; Chen-Wiegart, Y. C. K.

2014-12-01

Exceptionally large biogenic magnetite crystals, including spearhead-like and spindle-like ones up to 4 microns, have been reported in clay-rich sediments recording the ~56 Ma Paleocene-Eocene thermal maximum (PETM) and carbon isotope excursion (CIE) in a borehole at Ancora, NJ and along with magnetotactic bacteria (MTB) chains, were suggested [Schumann et al. 2008 PNAS; Kopp et al. 2009 Paleoceanography] to account for the distinctive single domain (SD) rock magnetic properties of these sediments [Lanci et al. 2002 JGR]. However, because uncalibrated magnetic extraction techniques were used to provide material for TEM imaging of the biogenic magnetite, it is difficult to quantitatively analyze their concentration in the bulk clay. In this study, we use a synchrotron transmission X-ray microscope to image bulk CIE clay. We first take mosaic images of sub-millimeter-sized bulk clay samples, in which we can identify many of the various types of giant biogenic magnetite crystals, as well as several other types of iron minerals, such as pyrite framboids, siderite, and detrital magnetite. However, limited by the instrument resolution (~50 nm), we are not able to identify MTB chains let alone isolated magnetic nanoparticles that may be abundant the clay. To quantitatively estimate the concentration of the giant biogenic magnetite, we re-deposited the bulk clay sample in an alcohol solution on a silicon nitride membrane for 2D X-ray scans. After scanning a total area of 0.55 mm2 with average clay thickness of 4 μm, we identified ~40 spearheads, ~5 spindles and a few elongated rods and estimated their total magnetization as SD particles to be less than about 10% of the mass normalized clay for the scanned area. This result suggests that the giant biogenic magnetite is not a major source of the SD signal for the clay and is in good agreement with rock magnetic analyses using high-resolution first-order reversal curves and thermal fluctuation tomography on bulk CIE clay showing that most of the magnetite occurs as isolated, near-equant SD particles [Wang et al. 2013 PNAS]. This would also exclude a significant contribution from MTB chains and points to a non-biogenic origin, such as a comet impact plume condensate, for the magnetic nanoparticles [Kent et al. 2003 EPSL] in the very rapidly deposited CIE clays [Wright & Schaller 2014 PNAS].

Reconnaissance geochemical survey of Al Jurdhawiyah and Wadi al Jarir quadrangles, sheets 25/42 D and 25/42 C, Kingdom of Saudia Arabia

USGS Publications Warehouse

Samater, Rashid M.

1983-01-01

A reconnaissance wadi-sediment geochemical survey was conducted in the Al Jurdhawiyah (sheet 28/42 D) and Wadi al Jarir (sheet 2G/42 C) quadrangles in order to identify anomalies potentially related to mineralized rock. Sieved bulk-sediment fractions and pan concentrates were created from the original samples collected from wadis in the two quadrangles. A semiquantitative 30-element spectrographic analysis was completed on both the sieved bulk-sediment fraction and the pan concentrate of each sample. The results were statistically analyzed in an attempt to identify anomalous regions. Anomaly threshold values were calculated for most elements; the threshold value of an element in a data set is defined as the geometric mean value plus two standard deviations. The Bald al Jimalah West tin-tungsten deposit (MODS 02661) in the southern part of the Al Jurdhawiyah quadrangle was identified by one pan-concentrate sample containing anomalous concentrations of tin and tungsten. Samples near the Bald al Jimalah East ancient lead-zinc-silver mines (MODS 00960) contain strongly anomalous concentrations of tin and lead and to a lesser extent of tungsten and copper. Both of these regions and other regions containing anomalous concentrations of certain elements are recommended for additional studies. A comparison of results obtained from sieved bulk-sediment fractions and pan concentrates indicates that the latter is the better medium for these geochemical investigations.

In Situ Carbon and Sulfur Isotope Analysis of Archean Organic Matter and Pyrite

NASA Technical Reports Server (NTRS)

Williford, K. H.; Ushikubo, T.; LePot, K.; Kitajima, K.; Spicuzza, M. J.; Valley, J. W.; Hallman, C.; Summons, R.; Eigenbrode, J. L.

2012-01-01

Stable isotopic compositions of biologically important elements (e.g., C and S) in sedimentary rocks are valuable biosignatures to the extent that they indicate the presence and variable expression of microbial metabolisms in space and time. Strong interactions between the carbon and sulfur cycles (e.g., via organic matter remineralization during microbial sulfate reduction) make coordinated, in situ C and S isotope analysis by secondary ion mass spectrometry (SIMS) a particularly powerful tool. In rocks ranging in age from 2.7-2.5 Ga, expansions in the ranges of delta C-13 of organic matter and delta S-34 of pyrite likely reflect the increasing influence of oxygenic photosynthesis in the surface ocean (as well as methane and sulfur metabolisms in deeper waters), whereas the large range of mass independent sulfur isotope fractionation (Delta S-33) suggests that the atmosphere remained anoxic until approx 2.4 Gyr ago. We report in situ delta C-13 measurements of organic matter in the approx 2.7-2.6 Ga Carawine Dolomite, Marra Mamba Iron Formation, and Jeerinah, Wittenoom, and Tumbiana Formations, as well as the approx 2.5 Ga Mount McRae Shale. We also report in situ delta S-24 and Delta S-33 measurements of pyrite associated with organic matter in a subset of these samples. In a single square cm sample of the Tumbiana Formation with bulk delta C-13(sub org) of -49.7% (VPDB), two distinct kerogen types have delta C-13 values, measured in situ, consistent with oxygenic photosynthesis (-33%) and methane metabolism (-52%). In a sample from the ABDP-9 core, radiobitumen associated with a uraniferous mineral grain is C-13-enriched by 8% (-26.8%0) relative to average in situ kerogen (-34.9%0) and similar in delta C-13 to solvent extractable hydrocarbons from the Mount McRae Shale (avg delta C-13 = -27.1 %). Average reproducibility for delta C-13 was 0.4% (2 SD) using a 6 micron spot and 0.8% using a 3 micron spot. In situ sulfur isotope analyses of 33 authigenic pyrite grains in 3 samples of the ABDP-9 core using a 10 micron spot (2 SD reproducibility = 0.4% for delta S-34 and -0.1% for Delta S-33) show a range of 28.1 % in delta S-34 (-10.3 to 17.8%) and 13.3%0 in Delta S-33 (-3.8 to 9.5%), whereas the range from 132 bulk analyses across 84 m of core is 19.4% for delta S-34 and 11.5% for Delta S-33. Coordinated, in situ carbon and sulfur isotope analyses in one ABDP-9 sample are shown. In situ values from this kerogen-pyrite association are within 0.1% of the bulk value in the case of delta C-13 and higher by several permil in the case of delta S-34 and Delta S-33. Coordinated in situ carbon and sulfur isotope analyses in rocks deposited during key intervals of environmental change (e.g., the Great Oxidation Event) can refine our understanding of the mode and tempo of change. In Earth's oldest sedimentary rocks, and in extraterrestrial samples, these coordinated in situ analyses may reveal biosignatures in the form of isotopic correlations at the scale of individual microorganisms and their microhabitats.

Experimental observation of water saturation effects on shear wave splitting in synthetic rock with fractures aligned at oblique angles

NASA Astrophysics Data System (ADS)

Amalokwu, Kelvin; Chapman, Mark; Best, Angus I.; Sothcott, Jeremy; Minshull, Timothy A.; Li, Xiang-Yang

2015-01-01

Fractured rocks are known to exhibit seismic anisotropy and shear wave splitting (SWS). SWS is commonly used for fractured rock characterization and has been shown to be sensitive to fluid type. The presence of partial liquid/gas saturation is also known to affect the elastic properties of rocks. The combined effect of both fractures and partial liquid/gas saturation is still unknown. Using synthetic, silica-cemented sandstones with aligned penny-shaped voids, we conducted laboratory ultrasonic experiments to investigate the effect fractures aligned at an oblique angle to wave propagation would have on SWS under partial liquid/gas saturation conditions. The result for the fractured rock shows a saturation dependence which can be explained by combining a fractured rock model and a partial saturation model. At high to full water saturation values, SWS decreases as a result of the fluid bulk modulus effect on the quasi-shear wave. This bulk modulus effect is frequency dependent as a result of wave-induced fluid flow mechanisms, which would in turn lead to frequency dependent SWS. This result suggests the possible use of SWS for discriminating between full liquid saturation and partial liquid/gas saturation.

A textural and compositional investigation on the source and timing of iron oxidation and titanium enrichment in high-pressure serpentinites

NASA Astrophysics Data System (ADS)

Crossley, R.; Evans, K. A.; Reddy, S.; Lester, G. W.

2016-12-01

The redox state, quantity and composition of subduction zone fluids influence the transport and precipitation of elements including those which are redox-sensitive, of economic importance such as Cu, Au and Ag, and those considered to be immobile, which include Fe3+. However, subduction zone fluids remain poorly understood. The redox state of Fe in high-pressure ultramafic rocks, which host a significant proportion of Fe3+, can be used to provide an insight into Fe cycling and constrain the composition and possible source of subduction zone fluids. In this work, we use a combination of oxide mineral textures, mineral parageneses, mineral composition data, and whole rock geochemistry of high-pressure retrogressed ultramafic rocks from the Zermatt-Saas Zone to constrain the distribution and oxidation state of iron, and to provide insights on the nature of fluids at depth within subduction zones. Oxide minerals host the bulk of the iron, particularly Fe3+. The increase in mode of magnetite during initial retrogression is most consistent with oxidation of existing iron via the infiltration of an oxidising fluids since it is difficult to reconcile addition of Fe3+ with the known limited solubility of this species. In addition, fluid-mediated or mechanical mixing with other lithologies in the slab could introduce elements and alter the bulk composition of serpentinites. However, the high Ti content of one sample cannot be explained by simple mixing of a depleted mantle protolith with the nearby Allalin gabbros, and provides the tantalising possibility that Ti, an element generally perceived as immobile, has been added to the rock. While we cannot completely exclude the possibility of pre-subduction Ti addition, textural analysis of Ti-rich minerals suggest mobilisation of Ti during subduction on at least a centimetre scale. If Ti addition has occurred, then the introduction of Fe3+, also generally considered to be immobile, cannot be disregarded. The Al-rich nature of the sample may be consistent with aluminosilicate complexing as the transport vector for Ti and/or Fe3+.

Modeling KBOs Charon, Orcus and Salacia by means of a new equation of state for porous icy bodies

NASA Astrophysics Data System (ADS)

Malamud, U.; Prialnik, D.

2015-10-01

We use a one-dimensional adaptive-grid thermal evolution code to model intermediate sized Kuiper belt objects Charon, Orcus and Salacia and compare their measured bulk densities with those resulting from evolutionary calculations at the end of 4.6 Gyr. Our model assumes an initial homogeneous composition of mixed ice and rock, and follows the multiphase flow of water through the porous rocky medium, consequent differentiation and aqueous chemical alterations in the rock. Heating sources include long-lived radionuclides, serpentinization reactions, release of gravitational potential energy due to compaction, and crystallization of amorphous ice. The density profile is calculated by assuming hydrostatic equilibrium to be maintained through changes in composition, pressure and temperature. To this purpose, we construct an equation of state suitable for porous icy bodies with radii of a few hundred km, based on the best available empirical studies of ice and rock compaction, and on comparisons with rock porosities in Earth analog and Solar System silicates. We show that the observed bulk densities can be reproduced by assuming the same set of initial and physical parameters, including the same rock/ice mass ratio for all three bodies. We conclude that the mass of the object uniquely determines the evolution of porosity, and thus explains the observed differences in bulk density. The final structure of all three objects is differentiated, with an inner rocky core, and outer ice-enriched mantle. The degree of differentiation, too, is determined by the object's mass.

Modeling Kuiper belt objects Charon, Orcus and Salacia by means of a new equation of state for porous icy bodies

NASA Astrophysics Data System (ADS)

Malamud, Uri; Prialnik, Dina

2015-01-01

We use a one-dimensional adaptive-grid thermal evolution code to model Kuiper belt objects Charon, Orcus and Salacia and compare their measured bulk densities with those resulting from evolutionary calculations at the end of 4.6 Gyr. Our model assumes an initial homogeneous composition of mixed ice and rock, and follows the multiphase flow of water through the porous rocky medium, consequent differentiation and aqueous chemical alterations in the rock. Heating sources include long-lived radionuclides, serpentinization reactions, release of gravitational potential energy due to compaction, and crystallization of amorphous ice. The density profile is calculated by assuming hydrostatic equilibrium to be maintained through changes in composition, pressure and temperature. To this purpose, we construct an equation of state suitable for porous icy bodies with radii of a few hundred km, based on the best available empirical studies of ice and rock compaction, and on comparisons with rock porosities in Earth analog and Solar System silicates. We show that the observed bulk densities can be reproduced by assuming the same set of initial and physical parameters, including the same rock/ice mass ratio for all three bodies. We conclude that the mass of the object uniquely determines the evolution of porosity, and thus explains the observed differences in bulk density. The final structure of all three objects is differentiated, with an inner rocky core, and outer ice-enriched mantle. The degree of differentiation, too, is determined by the object's mass.

Spatial and Temporal Variations in CHLORINE-36 Deposition in the Northern United States

NASA Astrophysics Data System (ADS)

Hainsworth, Laura J.

Chlorine-36, a cosmogenic radioisotope, has been developed for use as a tracer in hydrological systems. The deposition of atmospheric ^{36} Cl, although of primary importance to hydrological applications, has not been well studied. To begin to address this problem, ^{36}Cl has been measured in monthly, wet-only, precipitation samples collected from February, 1991, to January, 1993, at the Elms Environmental Education Center in St. Mary's County, Maryland. In addition, bulk deposition samples were collected over a 1 y period at seven sites across the Northern United States and analyzed for ^{36} Cl. The mean, wet-only ^{36} Cl/Cl ratio for the 2 y sampling period is 68 +/- 19 (x10^{-15} ) and the mean ^{36}Cl concentration is 1.2 +/- 0.1 (x10 ^6) atoms/L. The ^ {36}Cl wet deposition flux data reveal a distinct seasonal deposition pattern, with peaks occurring in March and April. This pattern is attributed to stratospheric/tropospheric exchange. The mean ^{36}Cl wet deposition flux is 38.2 +/- 5 atoms/m^2s. Comparison between wet-only and bulk deposition samples indicates that the difference accounts for approximately 25% of the total ^{36}Cl deposition flux at the Elms site. A new model, using ^{90} Sr to predict the ^{36} Cl deposition pattern, is developed to predict ^{36}Cl/Cl ratios across the United States. Chlorine-36/Cl ratios in bulk deposition samples collected across the northern United States agree well with the model predictions. A mean global ^{36}Cl production rate of approximately 28 to 38 atoms/m^2s is indicated by these samples. A comparison between ^{36 }Cl concentrations in the Aquia and Magothy aquifers in southern Maryland and bulk deposition samples collected at the Elms, MD, site indicated that modern precipitation can account for the ^{36}Cl content in the youngest water in these aquifers. Surface water samples from the Susquehanna River basin reveal ^{36}Cl and stable chloride concentrations an order of magnitude higher than in bulk deposition samples collected at State College, PA. The source of excess ^{36}Cl in the Susquehanna is not known. Possible explanations include 'bomb-pulse' ^{36}Cl and in-situ ^{36}Cl production in surface rocks.

Potentially exploitable supercritical geothermal resources in the ductile crust

USGS Publications Warehouse

Watanabe, Noriaki; Numakura, Tatsuya; Sakaguchi, Kiyotoshi; Saishu, Hanae; Okamoto, Atsushi; Ingebritsen, Steven E.; Tsuchiya, Noriyoshi

2017-01-01

The hypothesis that the brittle–ductile transition (BDT) drastically reduces permeability implies that potentially exploitable geothermal resources (permeability >10−16 m2) consisting of supercritical water could occur only in rocks with unusually high transition temperatures such as basalt. However, tensile fracturing is possible even in ductile rocks, and some permeability–depth relations proposed for the continental crust show no drastic permeability reduction at the BDT. Here we present experimental results suggesting that the BDT is not the first-order control on rock permeability, and that potentially exploitable resources may occur in rocks with much lower BDT temperatures, such as the granitic rocks that comprise the bulk of the continental crust. We find that permeability behaviour for fractured granite samples at 350–500 °C under effective confining stress is characterized by a transition from a weakly stress-dependent and reversible behaviour to a strongly stress-dependent and irreversible behaviour at a specific, temperature-dependent effective confining stress level. This transition is induced by onset of plastic normal deformation of the fracture surface (elastic–plastic transition) and, importantly, causes no ‘jump’ in the permeability. Empirical equations for this permeability behaviour suggest that potentially exploitable resources exceeding 450 °C may form at depths of 2–6 km even in the nominally ductile crust.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Connolly, J.R.

Petrologic, bulk chemical, and mineralogic data are presented for 49 samples of tuffaceous rocks from core holes USW G-1 and UE-25a{number_sign}1 at Yucca Mountain, Nevada. Included, in descending stratigraphic order, are 11 samples from the Topopah Spring Member of the Paintbrush Tuff, 12 samples from the Tuffaceous Beds of Calico Hills, 3 samples from the Prow Pass Member of the Crater Flat Tuff, 20 samples from the Bullfrog Member of the Crater Flat Tuff and 3 samples from the Tram Member of the Crater Flat Tuff. The suite of samples contains a wide variety of petrologic types, including zeolitized, glassy,more » and devitrified tuffs. Data vary considerably between groups of samples, and include thin section descriptions (some with modal analyses for which uncertainties are estimated), electron microprobe analyses of mineral phases and matrix, mineral identifications by X-ray diffraction, and major element analyses with uncertainty estimates.« less

Petrogenesis of Franciscan Complex and Coast Range Ophiolite Serpentinites in northern California

NASA Astrophysics Data System (ADS)

Eldam, R.; Barnes, J.; Lee, C.; Errico, J. C.; Loewy, S. L.; Cisneros, M.

2012-12-01

Franciscan Complex serpentinites have been interpreted as eroded pieces of the overriding Coast Range Ophiolite (CRO), off-scraped pieces of the subducting oceanic plate, and as sedimentary serpentinites (e.g., Wakabayashi, 2004); however, most of these interpretations are based on tectonic models and field relationships. Here we present bulk rock major and trace element geochemistry, pyroxene and spinel geochemistry, and stable isotope data (O, H, Cl) for serpentinite samples with the goal of determining protolith origin and subsequent serpentinizing fluid sources of several metasomatized Franciscan and CRO ultramafic rocks in order to decipher the tectonic setting of serpentinization. We focused on serpentinite bodies found in the Franciscan Complex (west of Cuesta Ridge; south of San Francisco; Tiburon Peninsula; Healdsburg) (n = 12). Three samples from Cuesta Ridge (CRO) were also analyzed for comparison. All samples are >~95% serpentinized and consist of lizardite +/- chrysotile. Relict grains are rarely preserved. Franciscan serpentinites (Tiburon Peninsula, west of Cuesta Ridge) show positive-sloped REE patterns. This depletion in LREE is typical of abyssal peridotites. Relict clinopyroxenes from Tiburon Peninsula have high HREE concentrations, also supporting an abyssal origin. 2 of the 3 samples from the Cuesta Ridge show flat REE patterns; whereas, one is U-shaped. This enrichment in LREE is similar to forearc peridotites. Spinels from Cuesta Ridge have Cr# > 0.60 also implying a forearc setting; whereas, Franciscan localities have typically have lower Cr# (0.21 to 0.51). All samples show remarkable positive Ce and Y anomalies. We speculate that these anomalies may be due to interaction with ferromanganese nodules and crusts (also high in Ce and Y) on the seafloor prior to subduction. Cuesta Ridge samples have δ18O values between +6.0 to +6.6‰. Franciscan serpentinites (except those south of San Francisco) have δ18O values of +5.4 to +7.9‰. These δ18O values are similar to typical oceanic serpentinites and likely represent low-T seawater hydration on the seafloor. δD values of all samples are extremely low (-107 to -90‰) and likely result from post-serpentinization, post-emplacement interaction with meteoric water at low temperature. Samples south of San Francisco lie on the San Andreas fault and have high δ18O values (+7.2 to +9.5‰) and low δD values (-107 to -104‰) likely due to low-T interaction with meteoric water at high fluid-rock ratios. Most of the serpentinites (12 of the 15) have δ37Cl values between +0.2 and +0.9‰, typical values for serpentinites formed by interaction with seawater. Based on bulk rock geochemistry and pyroxene and spinel compositions, serpentinites located within the Franciscan Complex have geochemical characteristics of abyssal peridotites; whereas, those from Cuesta Ridge are more chemically heterogeneous with most having affinity to forearc peridotites. All stable isotope geochemistry indicates seafloor serpentinization by seawater. Wakabayashi, J., 2004, International Geology Review, 46, 1103-1118.

The Neogene Ogallala Formation in Southwestern Kansas and Northeastern New Mexico: Preliminary Magnetostratigraphic Analyses for the High Plains-Ogallala Drilling Program

NASA Astrophysics Data System (ADS)

Zeigler, K. E.; Petronis, M. S.; Smith, J. J.; Ludvigson, G. A.; Doveton, J.

2012-12-01

A better understanding of the Ogallala Formation is critical in terms of refining groundwater flow models and management policies for communities relying on aquifers in heterolithic sequences around the globe. The High Plains aquifer remains under increasing stress with the growth of both urban and agricultural areas and therefore, developing the best groundwater management policies will depend on the most accurate characterization of the aquifer, the aquifer materials and their stratigraphic and geochronologic framework. Although mammalian faunal assemblages and volcanic ash bed tephrochronology provide a basic geochronologic framework for the Ogallala Formation, better precision in terms of correlation is needed in order to understand formative processes and depositional histories for the primary water-bearing units in the High Plains aquifer and confining strata. The High Plains-Ogallala Drilling Program (HPODP) was developed to advance understanding of sedimentary facies, stratigraphic framework, and chronostratigraphy of the Ogallala Formation and overlying units that comprise the central High Plains aquifer. The drilling program began in the early summer of 2011 in Haskell Co., western Kansas. By early fall 2011; the drill crew was at 92 m with about 32 m to go until they expect to hit bedrock. The final 32 meters of core was extracted during the summer 2012. Here we report the preliminary magnetostratigraphic and rock magnetic data from the first section of core. We scanned the entire 92 meters of core using an ASC Core Analysis System with a Bartington Instruments MS2C magnetic susceptibility coil allowing for bulk susceptibility measurements to be obtained along the length of the core. In addition, we collected 40 sub samples for paleomagnetic and rock magnetic. Bulk susceptibility data reveal depth dependent changes in rock magnetic properties that we interpret to reflect either climatic driven variations impacting the depositional system or a change in provenance of the sediments. Bulk susceptibility of the sediments decreases by an order of magnitude from the surface to the base of the measured core suggesting a change in detrital magnetic influx. Curie point estimates indicate that the dominant magnetic mineral in all samples is cubic, titanomagnetite phase of variable composition; whether a systemic change with depth exist is as of yet to be revealed. Preliminary paleomagnetic data are encouraging with many sub samples yielding a single component magnetization that decays near univectorally to the origin during both alternating field and thermal demagnetization.

Coupling geodynamic with thermodynamic modelling for reconstructions of magmatic systems

NASA Astrophysics Data System (ADS)

Rummel, Lisa; Kaus, Boris J. P.; White, Richard

2016-04-01

Coupling geodynamic with petrological models is fundamental for understanding magmatic systems from the melting source in the mantle to the point of magma crystallisation in the upper crust. Most geodynamic codes use very simplified petrological models consisting of a single, fixed, chemistry. Here, we develop a method to better track the petrological evolution of the source rock and corresponding volcanic and plutonic rocks by combining a geodynamic code with a thermodynamic model for magma generation and evolution. For the geodynamic modelling a finite element code (MVEP2) solves the conservation of mass, momentum and energy equations. The thermodynamic modelling of phase equilibria in magmatic systems is performed with pMELTS for mantle-like bulk compositions. The thermodynamic dependent properties calculated by pMELTS are density, melt fraction and the composition of the liquid and solid phase in the chemical system: SiO2-TiO2-Al2O3-Fe2O3-Cr2O3-FeO-MgO-CaO-Na2O-K2O-P2O5-H2O. In order to take into account the chemical depletion of the source rock with increasing melt extraction events, calculation of phase diagrams is performed in two steps: 1) With an initial rock composition density, melt fraction as well as liquid and solid composition are computed over the full upper mantle P-T range. 2) Once the residual rock composition (equivalent to the solid composition after melt extraction) is significantly different from the initial rock composition and the melt fraction is lower than a critical value, the residual composition is used for next calculations with pMELTS. The implementation of several melt extraction events take the change in chemistry into account until the solidus is shifted to such high temperatures that the rock cannot be molten anymore under upper mantle conditions. An advantage of this approach is that we can track the change of melt chemistry with time, which can be compared with natural constraints. In the thermo-mechanical code the thermodynamic dependent properties from pre-computed phase diagrams are carried by each particle using marker-in-cell method . Thus the physical and chemical properties can change locally as a function of previous melt extraction events, pressure and temperature conditions. After each melt extraction event, the residual rock composition is compared with the bulk composition of previous computed phase diagrams, so that the used phase diagram is replaced by the phase diagram with the closest bulk chemistry. In the thermo-mechanical code, the melt is extracted directly to the surface as volcanites and within the crust as plutonites. The density of the crust and new generated crust is calculated with the thermodynamic modelling tool Perple_X. We have investigated the influence of several input parameters on the magma composition to compare it with real rock samples from Eifel (West-Germany). In order to take the very inhomogeneous chemistry of European mantle into account, we include not only primitive mantle but also metasomatised mantle fragments in the melting source of a plume (Eifel plume).

Discrete Element Modeling of Micro-scratch Tests: Investigation of Mechanisms of CO2 Alteration in Reservoir Rocks

NASA Astrophysics Data System (ADS)

Sun, Zhuang; Espinoza, D. Nicolas; Balhoff, Matthew T.; Dewers, Thomas A.

2017-12-01

The injection of CO2 into geological formations leads to geochemical re-equilibrium between the pore fluid and rock minerals. Mineral-brine-CO2 reactions can induce alteration of mechanical properties and affect the structural integrity of the storage formation. The location of alterable mineral phases within the rock skeleton is important to assess the potential effects of mineral dissolution on bulk geomechanical properties. Hence, although often disregarded, the understanding of particle-scale mechanisms responsible for alterations is necessary to predict the extent of geomechanical alteration as a function of dissolved mineral amounts. This study investigates the CO2-related rock chemo-mechanical alteration through numerical modeling and matching of naturally altered rocks probed with micro-scratch tests. We use a model that couples the discrete element method (DEM) and the bonded particle model (BPM) to perform simulations of micro-scratch tests on synthetic rocks that mimic Entrada sandstone. Experimental results serve to calibrate numerical scratch tests with DEM-BPM parameters. Sensitivity analyses indicate that the cement size and bond shear strength are the most sensitive microscopic parameters that govern the CO2-induced alteration in Entrada sandstone. Reductions in cement size lead to decrease in scratch toughness and an increase in ductility in the rock samples. This work demonstrates how small variations of microscopic bond properties in cemented sandstone can lead to significant changes in macroscopic large-strain mechanical properties.

High-resolution delineation of chlorinated volatile organic compounds in a dipping, fractured mudstone: Depth- and strata-dependent spatial variability from rock-core sampling

NASA Astrophysics Data System (ADS)

Goode, Daniel J.; Imbrigiotta, Thomas E.; Lacombe, Pierre J.

2014-12-01

Synthesis of rock-core sampling and chlorinated volatile organic compound (CVOC) analysis at five coreholes, with hydraulic and water-quality monitoring and a detailed hydrogeologic framework, was used to characterize the fine-scale distribution of CVOCs in dipping, fractured mudstones of the Lockatong Formation of Triassic age, of the Newark Basin in West Trenton, New Jersey. From these results, a refined conceptual model for more than 55 years of migration of CVOCs and depth- and strata-dependent rock-matrix contamination was developed. Industrial use of trichloroethene (TCE) at the former Naval Air Warfare Center (NAWC) from 1953 to 1995 resulted in dense non-aqueous phase liquid (DNAPL) TCE and dissolved TCE and related breakdown products, including other CVOCs, in underlying mudstones. Shallow highly weathered and fractured strata overlie unweathered, gently dipping, fractured strata that become progressively less fractured with depth. The unweathered lithology includes black highly fractured (fissile) carbon-rich strata, gray mildly fractured thinly layered (laminated) strata, and light-gray weakly fractured massive strata. CVOC concentrations in water samples pumped from the shallow weathered and highly fractured strata remain elevated near residual DNAPL TCE, but dilution by uncontaminated recharge, and other natural and engineered attenuation processes, have substantially reduced concentrations along flow paths removed from sources and residual DNAPL. CVOCs also were detected in most rock-core samples in source areas in shallow wells. In many locations, lower aqueous concentrations, compared to rock core concentrations, suggest that CVOCs are presently back-diffusing from the rock matrix. Below the weathered and highly fractured strata, and to depths of at least 50 meters (m), groundwater flow and contaminant transport is primarily in bedding-plane-oriented fractures in thin fissile high-carbon strata, and in fractured, laminated strata of the gently dipping mudstones. Despite more than 18 years of pump and treat (P&T) remediation, and natural attenuation processes, CVOC concentrations in aqueous samples pumped from these deeper strata remain elevated in isolated intervals. DNAPL was detected in one borehole during coring at a depth of 27 m. In contrast to core samples from the weathered zone, concentrations in core samples from deeper unweathered and unfractured strata are typically below detection. However, high CVOC concentrations were found in isolated samples from fissile black carbon-rich strata and fractured gray laminated strata. Aqueous-phase concentrations were correspondingly high in samples pumped from these strata via short-interval wells or packer-isolated zones in long boreholes. A refined conceptual site model considers that prior to P&T remediation groundwater flow was primarily subhorizontal in the higher-permeability near surface strata, and the bulk of contaminant mass was shallow. CVOCs diffused into these fractured and weathered mudstones. DNAPL and high concentrations of CVOCs migrated slowly down in deeper unweathered strata, primarily along isolated dipping bedding-plane fractures. After P&T began in 1995, using wells open to both shallow and deep strata, downward transport of dissolved CVOCs accelerated. Diffusion of TCE and other CVOCs from deeper fractures penetrated only a few centimeters into the unweathered rock matrix, likely due to sorption of CVOCs on rock organic carbon. Remediation in the deep, unweathered strata may benefit from the relatively limited migration of CVOCs into the rock matrix. Synthesis of rock core sampling from closely spaced boreholes with geophysical logging and hydraulic testing improves understanding of the controls on CVOC delineation and informs remediation design and monitoring.

High-resolution delineation of chlorinated volatile organic compounds in a dipping, fractured mudstone: depth- and strata-dependent spatial variability from rock-core sampling

USGS Publications Warehouse

Goode, Daniel J.; Imbrigiotta, Thomas E.; Lacombe, Pierre J.

2014-01-01

Synthesis of rock-core sampling and chlorinated volatile organic compound (CVOC) analysis at five coreholes, with hydraulic and water-quality monitoring and a detailed hydrogeologic framework, was used to characterize the fine-scale distribution of CVOCs in dipping, fractured mudstones of the Lockatong Formation of Triassic age, of the Newark Basin in West Trenton, New Jersey. From these results, a refined conceptual model for more than 55 years of migration of CVOCs and depth- and strata-dependent rock-matrix contamination was developed. Industrial use of trichloroethene (TCE) at the former Naval Air Warfare Center (NAWC) from 1953 to 1995 resulted in dense non-aqueous phase liquid (DNAPL) TCE and dissolved TCE and related breakdown products, including other CVOCs, in underlying mudstones. Shallow highly weathered and fractured strata overlie unweathered, gently dipping, fractured strata that become progressively less fractured with depth. The unweathered lithology includes black highly fractured (fissile) carbon-rich strata, gray mildly fractured thinly layered (laminated) strata, and light-gray weakly fractured massive strata. CVOC concentrations in water samples pumped from the shallow weathered and highly fractured strata remain elevated near residual DNAPL TCE, but dilution by uncontaminated recharge, and other natural and engineered attenuation processes, have substantially reduced concentrations along flow paths removed from sources and residual DNAPL. CVOCs also were detected in most rock-core samples in source areas in shallow wells. In many locations, lower aqueous concentrations, compared to rock core concentrations, suggest that CVOCs are presently back-diffusing from the rock matrix. Below the weathered and highly fractured strata, and to depths of at least 50 meters (m), groundwater flow and contaminant transport is primarily in bedding-plane-oriented fractures in thin fissile high-carbon strata, and in fractured, laminated strata of the gently dipping mudstones. Despite more than 18 years of pump and treat (P&T) remediation, and natural attenuation processes, CVOC concentrations in aqueous samples pumped from these deeper strata remain elevated in isolated intervals. DNAPL was detected in one borehole during coring at a depth of 27 m. In contrast to core samples from the weathered zone, concentrations in core samples from deeper unweathered and unfractured strata are typically below detection. However, high CVOC concentrations were found in isolated samples from fissile black carbon-rich strata and fractured gray laminated strata. Aqueous-phase concentrations were correspondingly high in samples pumped from these strata via short-interval wells or packer-isolated zones in long boreholes. A refined conceptual site model considers that prior to P&T remediation groundwater flow was primarily subhorizontal in the higher-permeability near surface strata, and the bulk of contaminant mass was shallow. CVOCs diffused into these fractured and weathered mudstones. DNAPL and high concentrations of CVOCs migrated slowly down in deeper unweathered strata, primarily along isolated dipping bedding-plane fractures. After P&T began in 1995, using wells open to both shallow and deep strata, downward transport of dissolved CVOCs accelerated. Diffusion of TCE and other CVOCs from deeper fractures penetrated only a few centimeters into the unweathered rock matrix, likely due to sorption of CVOCs on rock organic carbon. Remediation in the deep, unweathered strata may benefit from the relatively limited migration of CVOCs into the rock matrix. Synthesis of rock core sampling from closely spaced boreholes with geophysical logging and hydraulic testing improves understanding of the controls on CVOC delineation and informs remediation design and monitoring.

Frictional Behavior of Altered Basement Approaching the Nankai Trough

NASA Astrophysics Data System (ADS)

Saffer, D. M.; Ikari, M.; Rooney, T. O.; Marone, C.

2017-12-01

The frictional behavior of basement rocks plays an important role in subduction zone faulting and seismicity. This includes earthquakes seaward of the trench, large megathrust earthquakes where seamounts are subducting, or where the plate interface steps down to basement. In exhumed subduction zone rocks such as the Shimanto complex in Japan, slivers of basalt are entrained in mélange which is evidence of basement involvement in the fault system. Scientific drilling during the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) recovered basement rock from two reference sites (C0011 and C0012) located seaward of the trench offshore the Kii Peninsula during Integrated Ocean Discovery Program (IODP) Expeditions 322 and 333. The basement rocks are pillow basalts that appear to be heterogeneously altered, resulting in contrasting dense blue material and more vesicular gray material. Major element geochemistry shows differences in silica, calcium oxides and loss-on-ignition between the two types of samples. Minor element geochemistry reveals significant differences in vanadium, chromium, and barium. X-ray diffraction on a bulk sample powder representing an average composition shows a phyllosilicate content of 20%, most of which is expandable clays. We performed laboratory friction experiments in a biaxial testing apparatus as either intact sample blocks, or as gouge powders. We combine these experiments with measurements of Pennsylvania slate for comparison, including a mixed-lithology intact block experiment. Intact Nankai basement blocks exhibit a coefficient of sliding friction of 0.73; for Nankai basement powder, slate powder, slate blocks and slate-on-basement blocks the coefficient of sliding friction ranges from 0.44 to 0.57. At slip rates ranging from 3x10-8 to 3x10-4 m/s we observe predominantly velocity-strengthening frictional behavior, indicating a tendency for stable slip. At rates of < 1x10-6 m/s some velocity-weakening was observed, specifically in intact rock-on-rock experiments. Our results show that basement alteration tends to reduce the tendency for unstable slip, but that the altered Nankai basement may still exhibit seismogenic behavior in the case of localized slip in competent rock.

Digenetic Changes in Macro- to Nano-Scale Porosity in the St. Peter Sandstone:L An (Ultra) Small Angle Neutron Scattering and Backscattered Electron Imagining Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anovitz, Lawrence; Cole, David; Rother, Gernot

2013-01-01

Small- and Ultra-Small Angle Neutron Scattering (SANS and USANS) provide powerful tools for quantitative analysis of porous rocks, yielding bulk statistical information over a wide range of length scales. This study utilized (U)SANS to characterize shallowly buried quartz arenites from the St. Peter Sandstone. Backscattered electron imaging was also used to extend the data to larger scales. These samples contain significant volumes of large-scale porosity, modified by quartz overgrowths, and neutron scattering results show significant sub-micron porosity. While previous scattering data from sandstones suggest scattering is dominated by surface fractal behavior over many orders of magnitude, careful analysis of ourmore » data shows both fractal and pseudo-fractal behavior. The scattering curves are composed of subtle steps, modeled as polydispersed assemblages of pores with log-normal distributions. However, in some samples an additional surface-fractal overprint is present, while in others there is no such structure, and scattering can be explained by summation of non-fractal structures. Combined with our work on other rock-types, these data suggest that microporosity is more prevalent, and may play a much more important role than previously thought in fluid/rock interactions.« less

Modern Subsurface Bacteria in Pristine 2.7 Ga-Old Fossil Stromatolite Drillcore Samples from the Fortescue Group, Western Australia

PubMed Central

Gérard, Emmanuelle; Moreira, David; Philippot, Pascal; Van Kranendonk, Martin J.; López-García, Purificación

2009-01-01

Background Several abiotic processes leading to the formation of life-like signatures or later contamination with actual biogenic traces can blur the interpretation of the earliest fossil record. In recent years, a large body of evidence showing the occurrence of diverse and active microbial communities in the terrestrial subsurface has accumulated. Considering the time elapsed since Archaean sedimentation, the contribution of subsurface microbial communities postdating the rock formation to the fossil biomarker pool and other biogenic remains in Archaean rocks may be far from negligible. Methodology/Principal Findings In order to evaluate the degree of potential contamination of Archean rocks by modern microorganisms, we looked for the presence of living indigenous bacteria in fresh diamond drillcores through 2,724 Myr-old stromatolites (Tumbiana Formation, Fortescue Group, Western Australia) using molecular methods based on the amplification of small subunit ribosomal RNA genes (SSU rDNAs). We analyzed drillcore samples from 4.3 m and 66.2 m depth, showing signs of meteoritic alteration, and also from deeper “fresh” samples showing no apparent evidence for late stage alteration (68 m, 78.8 m, and 99.3 m). We also analyzed control samples from drilling and sawing fluids and a series of laboratory controls to establish a list of potential contaminants introduced during sample manipulation and PCR experiments. We identified in this way the presence of indigenous bacteria belonging to Firmicutes, Actinobacteria, and Alpha-, Beta-, and Gammaproteobacteria in aseptically-sawed inner parts of drillcores down to at least 78.8 m depth. Conclusions/Significance The presence of modern bacterial communities in subsurface fossil stromatolite layers opens the possibility that a continuous microbial colonization had existed in the past and contributed to the accumulation of biogenic traces over geological timescales. This finding casts shadow on bulk analyses of early life remains and makes claims for morphological, chemical, isotopic, and biomarker traces syngenetic with the rock unreliable in the absence of detailed contextual analyses at microscale. PMID:19396360

The Northwest Africa 8159 martian meteorite: Expanding the martian sample suite to the early Amazonian

DOE PAGES

Herd, Christopher D. K.; Walton, Erin L.; Agee, Carl B.; ...

2017-09-01

Northwest Africa (NWA) 8159 is an augite-rich shergottite, with a mineralogy dominated by Ca-, Fe-rich pyroxene, plagioclase, olivine, and magnetite. NWA 8159 crystallized from an evolved melt of basaltic composition under relatively rapid conditions of cooling, likely in a surface lava flow or shallow sill. Redox conditions experienced by the melt shifted from relatively oxidizing (with respect to known Martian lithologies, ~QFM) on the liquidus to higher oxygen fugacity (~QFM + 2) during crystallization of the groundmass, and under subsolidus conditions. This shift resulted in the production of orthopyroxene and magnetite replacing olivine phenocryst rims. NWA 8159 contains both crystallinemore » and shock-amorphized plagioclase (An 50–62), often observed within a single grain; based on known calibrations we bracket the peak shock pressure experienced by NWA 8159 to between 15 and 23 GPa. The bulk composition of NWA 8159 is depleted in LREE, as observed for Tissint and other depleted shergottites; however, NWA 8159 is distinct from all other martian lithologies in its bulk composition and oxygen fugacity. Here, we obtain a Sm-Nd formation age of 2.37 ± 0.25 Ga for NWA 8159, which represents an interval in Mars geologic time which, until recently, was not represented in the other martian meteorite types. The bulk rock 147Sm/ 144Nd value of 0.37 ± 0.02 is consistent with it being derived directly from its source and the high initial ε 143Nd value indicates this source was geochemically highly depleted. Cr, Nd, and W isotopic compositions further support a unique mantle source. While the rock shares similarities with the 2.4-Ga NWA 7635 meteorite, there are notable distinctions between the two meteorites that suggest differences in mantle source compositions and conditions of crystallization. Nevertheless, the two samples may be launch-paired. Finally, NWA 8159 expands the known basalt types, ages and mantle sources within the Mars sample suite to include a second igneous unit from the early Amazonian.« less

Causes of 142Nd Variation in Earth

NASA Astrophysics Data System (ADS)

Boyet, M.; Bouvier, A.; Gannoun, A.; Carlson, R.

2015-12-01

Variability of the 142Nd/144Nd ratio can reflect Sm/Nd fractionation during the lifetime of 146Sm, i.e. the first 500 Ma of Solar System history1 and nucleosynthetic heterogeneity inherited from the solar nebula. Deciphering the message carried by 142Nd variability requires a detailed examination of the data for Earth and meteorites. The elevated 142Nd/144Nd in terrestrial samples relative to average chondrites suggests that all terrestrial rocks sampled by volcanism over the Earth's history come from a geochemical reservoir characterized by a superchondritic Sm/Nd ratio. The chemical compliment to this reservoir, however, has never been seen, so it either was lost during Earth's accretion2,3, or is preserved in a deep hidden reservoir 1,4. These models are based on a comparison of Earth rocks and O-chondrites because they do not show any variation in stable Sm and Nd isotopic composition compared to Earth6-8. The first analyzed E-chondrites with terrestrial 142Nd/144Nd showed 144Sm excesses that reflect an excess p-process contribution. Although 142Nd is mainly produced by s-process, there is a direct p-process component estimated to be lower than 4 %. We will present new Sm and Nd isotopic data on meteoritic materials. CAIs show deficits in both r- and p-process isotopes that would lead to elevated 142Nd, yet the bulk C-chondrites in which they are contained show excesses in r-process isotopes and hence 142Nd/144Nd lower than terrestrial. The new E-chondrites data do not confirm the 142Nd-144Sm correlation observed in bulk chondrites In light of these results and using 146Sm-142Nd isochrons for constraining the bulk 142Nd/144Nd ratio of planetary bodies, we will discuss the 142Nd signature of terrestrial samples (from Hadean to present). 1Boyet & Carlson, Science 2005; 2O'Neill & Palme, Phil. Trans. R. Soc 2008; 3Caro et al. Nature 2008; 4Andreasen et al. EPSL 2008; 6Andreasen & Sharma, Science 2006; 7Carlson et al., Science 2007; 8Gannoun et al. PNAS 2011.

The Northwest Africa 8159 martian meteorite: Expanding the martian sample suite to the early Amazonian

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herd, Christopher D. K.; Walton, Erin L.; Agee, Carl B.

Northwest Africa (NWA) 8159 is an augite-rich shergottite, with a mineralogy dominated by Ca-, Fe-rich pyroxene, plagioclase, olivine, and magnetite. NWA 8159 crystallized from an evolved melt of basaltic composition under relatively rapid conditions of cooling, likely in a surface lava flow or shallow sill. Redox conditions experienced by the melt shifted from relatively oxidizing (with respect to known Martian lithologies, ~QFM) on the liquidus to higher oxygen fugacity (~QFM + 2) during crystallization of the groundmass, and under subsolidus conditions. This shift resulted in the production of orthopyroxene and magnetite replacing olivine phenocryst rims. NWA 8159 contains both crystallinemore » and shock-amorphized plagioclase (An 50–62), often observed within a single grain; based on known calibrations we bracket the peak shock pressure experienced by NWA 8159 to between 15 and 23 GPa. The bulk composition of NWA 8159 is depleted in LREE, as observed for Tissint and other depleted shergottites; however, NWA 8159 is distinct from all other martian lithologies in its bulk composition and oxygen fugacity. Here, we obtain a Sm-Nd formation age of 2.37 ± 0.25 Ga for NWA 8159, which represents an interval in Mars geologic time which, until recently, was not represented in the other martian meteorite types. The bulk rock 147Sm/ 144Nd value of 0.37 ± 0.02 is consistent with it being derived directly from its source and the high initial ε 143Nd value indicates this source was geochemically highly depleted. Cr, Nd, and W isotopic compositions further support a unique mantle source. While the rock shares similarities with the 2.4-Ga NWA 7635 meteorite, there are notable distinctions between the two meteorites that suggest differences in mantle source compositions and conditions of crystallization. Nevertheless, the two samples may be launch-paired. Finally, NWA 8159 expands the known basalt types, ages and mantle sources within the Mars sample suite to include a second igneous unit from the early Amazonian.« less

Confirmation of a meteoritic component in impact-melt rocks of the Chesapeake Bay impact structure, Virginia, USA - Evidence from osmium isotopic and PGE systematics

USGS Publications Warehouse

Lee, S.R.; Horton, J. Wright; Walker, R.J.

2006-01-01

The osmium isotope ratios and platinum-group element (PGE) concentrations of impact-melt rocks in the Chesapeake Bay impact structure were determined. The impact-melt rocks come from the cored part of a lower-crater section of suevitic crystalline-clast breccia in an 823 m scientific test hole over the central uplift at Cape Charles, Virginia. The 187Os/188Os ratios of impact-melt rocks range from 0.151 to 0.518. The rhenium and platinum-group element (PGE) concentrations of these rocks are 30-270?? higher than concentrations in basement gneiss, and together with the osmium isotopes indicate a substantial meteoritic component in some impact-melt rocks. Because the PGE abundances in the impact-melt rocks are dominated by the target materials, interelemental ratios of the impact-melt rocks are highly variable and nonchondritic. The chemical nature of the projectile for the Chesapeake Bay impact structure cannot be constrained at this time. Model mixing calculations between chondritic and crustal components suggest that most impact-melt rocks include a bulk meteoritic component of 0.01-0.1% by mass. Several impact-melt rocks with lowest initial 187Os/188Os ratios and the highest osmium concentrations could have been produced by additions of 0.1%-0.2% of a meteoritic component. In these samples, as much as 70% of the total Os may be of meteoritic origin. At the calculated proportions of a meteoritic component (0.01-0.1% by mass), no mixtures of the investigated target rocks and sediments can reproduce the observed PGE abundances of the impact-melt rocks, suggesting that other PGE enrichment processes operated along with the meteoritic contamination. Possible explanations are 1) participation of unsampled target materials with high PGE abundances in the impact-melt rocks, and 2) variable fractionations of PGE during syn- to post-impact events. ?? The Meteoritical Society, 2006.

Asbestos quantification in track ballast, a complex analytical problem

NASA Astrophysics Data System (ADS)

Cavallo, Alessandro

2016-04-01

Track ballast forms the trackbeb upon which railroad ties are laid. It is used to bear the load from the railroad ties, to facilitate water drainage, and also to keep down vegetation. It is typically made of angular crushed stone, with a grain size between 30 and 60 mm, with good mechanical properties (high compressive strength, freeze - thaw resistance, resistance to fragmentation). The most common rock types are represented by basalts, porphyries, orthogneisses, some carbonatic rocks and "green stones" (serpentinites, prasinites, amphibolites, metagabbros). Especially "green stones" may contain traces, and sometimes appreciable amounts of asbestiform minerals (chrysotile and/or fibrous amphiboles, generally tremolite - actinolite). In Italy, the chrysotile asbestos mine in Balangero (Turin) produced over 5 Mt railroad ballast (crushed serpentinites), which was used for the railways in northern and central Italy, from 1930 up to 1990. In addition to Balangero, several other serpentinite and prasinite quarries (e.g. Emilia Romagna) provided the railways ballast up to the year 2000. The legal threshold for asbestos content in track ballast is established in 1000 ppm: if the value is below this threshold, the material can be reused, otherwise it must be disposed of as hazardous waste, with very high costs. The quantitative asbestos determination in rocks is a very complex analytical issue: although techniques like TEM-SAED and micro-Raman are very effective in the identification of asbestos minerals, a quantitative determination on bulk materials is almost impossible or really expensive and time consuming. Another problem is represented by the discrimination of asbestiform minerals (e.g. chrysotile, asbestiform amphiboles) from the common acicular - pseudo-fibrous varieties (lamellar serpentine minerals, prismatic/acicular amphiboles). In this work, more than 200 samples from the main Italian rail yards were characterized by a combined use of XRD and a special SEM-EDS analytical procedure. The first step consists in the macroscopic petrographic description of the rock fragments, in order to identify and quantify the "green stones". The second step is represented by the "self-grinding" of the clasts (Los Angeles rattle test), and the powders (< 2 mm) are characterized by XRD (main rock-forming minerals) and quantitative SEM-EDS. Especially in serpentinic clasts with superficial slip-fibre chrysotile mineralizations, the "self-grinding" procedure allows to release a large part of the fibers. The third and last step consists in the total grinding of the bulk ballast sample ("self grinding" powders + remaining rock fragments), followed by quantitative SEM-EDS procedure. The most important aspects in the SEM-EDS procedure are represented by an accurate sample preparation (e.g. using ultrasound and a surfactant to avoid fiber agglomeration), as well as effective criteria for the distinction of asbestos fibers and non-asbestiform/pseudo-fibrous varieties (presence of fibril bundles, fibril diameter, splayed ends). The results show a great variability in the lithological composition of the ballast samples, and some critical issues in serpentinite-rich ballast, sometimes exceeding the legal threshold of 1000 ppm. On the other hand, the presence of metabasites (prasinites, amphibolites) is much less critical, because the presence of asbestiform amphiboles (especially tremolite - actinolite) is really rare.

Thermo-mechanical Properties of Upper Jurassic (Malm) Carbonate Rock Under Drained Conditions

NASA Astrophysics Data System (ADS)

Pei, Liang; Blöcher, Guido; Milsch, Harald; Zimmermann, Günter; Sass, Ingo; Huenges, Ernst

2018-01-01

The present study aims to quantify the thermo-mechanical properties of Neuburger Bankkalk limestone, an outcrop analog of the Upper Jurassic carbonate formation (Germany), and to provide a reference for reservoir rock deformation within future enhanced geothermal systems located in the Southern German Molasse Basin. Experiments deriving the drained bulk compressibility C were performed by cycling confining pressure p c between 2 and 50 MPa at a constant pore pressure p p of 0.5 MPa after heating the samples to defined temperatures between 30 and 90 °C. Creep strain was then measured after each loading and unloading stage, and permeability k was obtained after each creep strain measurement. The drained bulk compressibility increased with increasing temperature and decreased with increasing differential pressure p d = p c - p p showing hysteresis between the loading and unloading stages above 30 °C. The apparent values of the indirectly calculated Biot coefficient α ind containing contributions from inelastic deformation displayed the same temperature and pressure dependencies. The permeability k increased immediately after heating and the creep rates were also temperature dependent. It is inferred that the alteration of the void space caused by temperature changes leads to the variation of rock properties measured under isothermal conditions while the load cycles applied under isothermal conditions yield additional changes in pore space microstructure. The experimental results were applied to a geothermal fluid production scenario to constrain drawdown and time-dependent effects on the reservoir, overall, to provide a reference for the hydromechanical behavior of geothermal systems in carbonate, and more specifically, in Upper Jurassic lithologies.

Rb-Sr and Sm-Nd isotopic and REE studies of igneous components in the bulk matrix domain of Martian breccia Northwest Africa 7034

NASA Astrophysics Data System (ADS)

Nyquist, Laurence E.; Shih, Chi-Yu; McCubbin, Francis M.; Santos, Alison R.; Shearer, Charles K.; Peng, Zhan X.; Burger, Paul V.; Agee, Carl B.

2016-03-01

The bulk matrix domain of the Martian breccia NWA 7034 was examined petrographically and isotopically to better understand the provenance and age of the source material that make up the breccia. Both 147Sm-143Nd and 146Sm-142Nd age results for mineral separates from the bulk matrix portion of breccia NWA 7034 suggest that various lithological components in the breccia probably formed contemporaneously ~4.44 Ga ago. This old age is in excellent agreement with the upper intersection ages (4.35-4.45 Ga) for U-Pb discordia and also concordia defined by zircon and baddeleyite grains in matrix and igneous-textured clasts. Consequently, we confirm an ancient age for the igneous components that make up the NWA 7034 breccia. Substantial disturbance in the Rb-Sr system was detected, and no age significance could be gleaned from our Rb-Sr data. The disturbance to the Rb-Sr system may be due to a thermal event recorded by bulk-rock K-Ar ages of 1.56 Ga and U-Pb ages of phosphates at about 1.35-1.5 Ga, which suggest partial resetting from an unknown thermal event(s), possibly accompanying breccia formation. The NWA 7034 bulk rock is LREE enriched and similar to KREEP-rich lunar rocks, which indicates that the earliest Martian crust was geochemically enriched. This enrichment supports the idea that the crust is one of the enriched geochemical reservoirs on Mars that have been detected in studies of other Martian meteorites.

The miniaturized Raman system and detection of traces of life in halite from the Atacama Desert: some considerations for the search for life signatures on Mars.

PubMed

Vítek, Petr; Jehlička, Jan; Edwards, Howell G M; Hutchinson, Ian; Ascaso, Carmen; Wierzchos, Jacek

2012-12-01

Raman spectroscopy is being adopted as a nondestructive instrumentation for the robotic exploration of Mars to search for traces of life in the geological record. Here, miniaturized Raman spectrometers of two different types equipped with 532 and 785 nm lasers for excitation, respectively, were compared for the detection of microbial biomarkers in natural halite from the hyperarid region of the Atacama Desert. Measurements were performed directly on the rock as well as on the homogenized, powdered samples prepared from this material-the effects of this sample preparation and the excitation wavelength employed in the analysis are compared and discussed. From these results, 532 nm excitation was found to be superior for the analysis of powdered specimens due to its high sensitivity toward carotenoids and hence a higher capability for their detection at relatively low concentration in bulk powdered specimens. For the same reason, this wavelength was a better choice for the detection of carotenoids in direct measurements made on the rock samples. The 785 nm excitation wavelength, in contrast, proved to be more sensitive toward the detection of scytonemin.

Isolating magnetic moments from individual grains within a magnetic assemblage

NASA Astrophysics Data System (ADS)

Béguin, A.; Fabian, K.; Jansen, C.; Lascu, I.; Harrison, R.; Barnhoorn, A.; de Groot, L. V.

2017-12-01

Methods to derive paleodirections or paleointensities from rocks currently rely on measurements of bulk samples (typically 10 cc). The process of recording and storing magnetizations as function of temperature, however, differs for grains of various sizes and chemical compositions. Most rocks, by their mere nature, consist of assemblages of grains varying in size, shape, and chemistry. Unraveling the behavior of individual grains is a holy grail in fundamental rock magnetism. Recently, we showed that it is possible to obtain plausible magnetic moments for individual grains in a synthetic sample by a micromagnetic tomography (MMT) technique. We use a least-squares inversion to obtain these magnetic moments based on the physical locations and dimensions of the grains obtained from a MicroCT scanner and a magnetic flux density map of the surface of the sample. The sample used for this proof of concept, however, was optimized for success: it had a low dispersion of the grains, and the grains were large enough so they were easily detected by the MicroCT scanner. Natural lavas are much more complex than the synthetic sample analyzed so far: the dispersion of the magnetic markers is one order of magnitude higher, the grains differ more in composition and size, and many small (submicron) magnetic markers may be present that go undetected by the MicroCT scanner. Here we present the first results derived from a natural volcanic sample from the 1907-flow at Hawaii. To analyze the magnetic flux at the surface of the sample at room temperature, we used the Magnetic Tunneling Junction (MTJ) technique. We were able to successfully obtain MicroCT and MTJ scans from the sample and isolate plausible magnetic moments for individual grains in the top 70 µm of the sample. We discuss the potential of the MMT technique applied to natural samples and compare the MTJ and SSM methods in terms of work flow and quality of the results.

Re-Os systematics of komatiites and komatiitic basalts at Dundonald Beach, Ontario, Canada: Evidence for a complex alteration history and implications of a late-Archean chondritic mantle source

NASA Astrophysics Data System (ADS)

Gangopadhyay, Amitava; Sproule, Rebecca A.; Walker, Richard J.; Lesher, C. Michael

2005-11-01

Osmium isotopic compositions, and Re and Os concentrations have been examined in one komatiite unit and two komatiitic basalt units at Dundonald Beach, part of the 2.7 Ga Kidd-Munro volcanic assemblage in the Abitibi greenstone belt, Ontario, Canada. The komatiitic rocks in this locality record at least three episodes of alteration of Re-Os elemental and isotope systematics. First, an average of 40% and as much as 75% Re may have been lost due to shallow degassing during eruption and/or hydrothermal leaching during or immediately after emplacement. Second, the Re-Os isotope systematics of whole rock samples with 187Re/ 188Os ratios >1 were reset at ˜2.5 Ga, possibly due to a regional metamorphic event. Third, there is evidence for relatively recent gain and loss of Re in some rocks. Despite the open-system behavior, some aspects of the Re-Os systematics of these rocks can be deciphered. The bulk distribution coefficient for Os (D Ossolid/liquid) for the Dundonald rocks is ˜3 ± 1 and is well within the estimated D values obtained for komatiites from the nearby Alexo area and stratigraphically-equivalent komatiites from Munro Township. This suggests that Os was moderately compatible during crystal-liquid fractionation of the magmas parental to the Kidd-Munro komatiitic rocks. Whole-rock samples and chromite separates with low 187Re/ 188Os ratios (<1) yield a precise chondritic average initial 187Os/ 188Os ratio of 0.1083 ± 0.0006 (γ Os = 0.0 ± 0.6) for their well-constrained ˜2715 Ma crystallization age. The chondritic initial Os isotopic composition of the mantle source for the Dundonald rocks is consistent with that determined for komatiites in the Alexo area and in Munro Township, suggesting that the mantle source region for the Kidd-Munro volcanic assemblage had evolved with a long-term chondritic Re/Os before eruption. The chondritic initial Os isotopic composition of the Kidd-Munro komatiites is indistinguishable from that of the projected contemporaneous convective upper mantle. The uniform chondritic Os isotopic composition of the Kidd-Munro komatiites contrasts with the typical large-scale Os isotopic heterogeneity in the mantle sources for ca. 89 Ma komatiites from the Gorgona Island, arc-related rocks and present-day ocean island basalts. This suggests that the Kidd-Munro komatiites sampled a late-Archean mantle source region that was significantly more homogeneous with respect to Re/Os relative to most modern mantle-derived rocks.

Stimuli Responsive/Rheoreversible Hydraulic Fracturing Fluids for Enhanced Geothermal Energy Production (Part II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonneville, Alain; Jung, Hun Bok; Shao, Hongbo

We have used an environmentally friendly and recyclable hydraulic fracturing fluid - diluted aqueous solutions of polyallylamine or PAA – for reservoir stimulation in Enhanced Geothermal System (EGS). This fluid undergoes a controlled and large volume expansion with a simultaneous increase in viscosity triggered by CO2 at EGS temperatures. We are presenting here the results of laboratory-scale hydraulic fracturing experiment using the fluid on small cylindrical rock cores (1.59 cm in diameter and 5.08 cm in length) from the Coso geothermal field in California. Rock samples consisted of Mesozoic diorite metamorphosed to greenschist facies. The experiments were conducted on 5more » samples for realistic ranges of pressures (up to 275 bar) and temperatures (up to 210 °C) for both the rock samples and the injected fluid. After fracturing, cores were subjected to a CO2 leakage test, injection of KI solution, and X-ray microtomography (XMT) scanning to examine the formation and distribution of fractures. The design and conduct of these experiments will be presented and discussed in details. Based on the obtained XMT images, Computational Fluid Dynamics (CFD) simulations were then performed to visualize hydraulic fractures and compute the bulk permeability. OpenFOAM (OpenCFD Ltd., Reading, UK), was used to solve the steady state simulation. The flow predictions, based upon the laminar, 3-D, incompressible Navier-Stokes equations for fluid mass and momentum, show the remarkable stimulation of the permeability in the core samples and demonstrate the efficiency of such a CO2 triggered fluid in EGS.« less

Extrapolation of bulk rock elastic moduli of different rock types to high pressure conditions and comparison with texture-derived elastic moduli

NASA Astrophysics Data System (ADS)

Ullemeyer, Klaus; Lokajíček, Tomás; Vasin, Roman N.; Keppler, Ruth; Behrmann, Jan H.

2018-02-01

In this study elastic moduli of three different rock types of simple (calcite marble) and more complex (amphibolite, micaschist) mineralogical compositions were determined by modeling of elastic moduli using texture (crystallographic preferred orientation; CPO) data, experimental investigation and extrapolation. 3D models were calculated using single crystal elastic moduli, and CPO measured using time-of-flight neutron diffraction at the SKAT diffractometer in Dubna (Russia) and subsequently analyzed using Rietveld Texture Analysis. To define extrinsic factors influencing elastic behaviour, P-wave and S-wave velocity anisotropies were experimentally determined at 200, 400 and 600 MPa confining pressure. Functions describing variations of the elastic moduli with confining pressure were then used to predict elastic properties at 1000 MPa, revealing anisotropies in a supposedly crack-free medium. In the calcite marble elastic anisotropy is dominated by the CPO. Velocities continuously increase, while anisotropies decrease from measured, over extrapolated to CPO derived data. Differences in velocity patterns with sample orientation suggest that the foliation forms an important mechanical anisotropy. The amphibolite sample shows similar magnitudes of extrapolated and CPO derived velocities, however the pattern of CPO derived velocity is closer to that measured at 200 MPa. Anisotropy decreases from the extrapolated to the CPO derived data. In the micaschist, velocities are higher and anisotropies are lower in the extrapolated data, in comparison to the data from measurements at lower pressures. Generally our results show that predictions for the elastic behavior of rocks at great depths are possible based on experimental data and those computed from CPO. The elastic properties of the lower crust can, thus, be characterized with an improved degree of confidence using extrapolations. Anisotropically distributed spherical micro-pores are likely to be preserved, affecting seismic velocity distributions. Compositional variations in the polyphase rock samples do not significantly change the velocity patterns, allowing the use of RTA-derived volume percentages for the modeling of elastic moduli.

Variation in 142Nd/144Nd of Archean rocks from southwest Greenland : Implications for early Earth mantle dynamics

NASA Astrophysics Data System (ADS)

Rizo, H.; Boyet, M.; Blichert-Toft, J.; Rosing, M.; Paquette, J. L.

2012-04-01

The short-lived 146Sm-142Nd chronometer (half-life = 103 Ma) has proven successful in bringing constraints on the dynamics of the early Earth mantle. Since the parent isotope, 146Sm, was extant only during the first 300 Ma of the history of the Solar System, the positive 142Nd anomalies measured in southwest Greenland Archean rocks imply that their incompatible element-depleted mantle source formed during the Hadean. Interestingly, the magnitude of these anomalies seems to decrease over time. 3.7-3.8 Ga old rocks from the Amitsoq Complex have revealed +10 to +20 ppm 142Nd anomalies [1, 2, 3, 4, 5, 6, 7], whereas younger 3.0 Ga old samples from the Ivisaartoq greenstone belt yield smaller positive anomalies, ranging from +5.5 to +8.5 ppm [8]. Thus, the chemical heterogeneities detected in the southwest Greenland mantle were formed during the first 150 Ma of Earth's history, and seem to have resisted re-mixing by mantle convection until 3.0 Ga. In this study, we investigate the evolution of the southwest Greenland mantle during the time period of 3.3-3.4 Ga. The samples analyzed come from both the ~3.3 Ga amphibolite unit and the ~3.4 Ga Ameralik basic dyke swarm from the Amitsoq Complex. Coupled Sm-Nd and Lu-Hf bulk-rock ages obtained for seven amphibolites are in good agreement (3351 ± 210 Ma and 3302 ± 260 Ma, respectively) and consistent with the minimum age found by Nutman and Friend (2009) [9] for this formation. We further obtained coherent bulk-rock 147Sm-143Nd and zircon+baddeleyite 207Pb/206Pb ages for the Ameralik dykes (3428 ± 250 Ma and 3421 ± 34 Ma, respectively), in line with ages suggested by Nielsen at al., (2002) [10] and Nutman et al., (2004) [11]. We are currently in the process of analyzing these samples for 142Nd isotopic compositions and the results will be compared with the existing southwest Greenland data in order to shed new light on the evolution and destruction of heterogeneities in the early Earth mantle. [1] Rizo et al., (2011) Earth Planet. Sci. Lett. [2] Bennett et al., (2007b) Science. [3] Boyet et al., (2003) Earth Planet. Sci. Lett. [4] Boyet and Carlson (2006) Earth Planet. Sci. Lett. [5] Caro et al., (2003) Nature. [6] Caro et al., (2006) Geochim. Cosmochim. Acta. [7] Harper and Jacobsen (1992) Nature. [8] Bennett et al., (2010) Goldschmidt 2010. [9] Nutman and Friend (2009) Precamb. Res. [10] Nielsen et al., (2002) Precamb. Res. [11] Nutman et al., (2004) J. Geol. Soc. Lond.

Understanding physical rock properties and their relation to fluid-rock interactions under supercritical conditions

NASA Astrophysics Data System (ADS)

Kummerow, Juliane; Raab, Siegfried; Meyer, Romain

2017-04-01

The electrical conductivity of rocks is, in addition to lithological factors (mineralogy, porosity) and physical parameters (temperature, pressure) sensitive to the nature of pore fluids (phase, salinity), and thus may be an indicative measure for fluid-rock interactions. Especially near the critical point, which is at 374.21° C and 22.12 MPa for pure water, the physico-chemical properties of aqueous fluids change dramatically and mass transfer and diffusion-controlled chemical reactivity are enhanced, which in turn leads to the formation of element depletion/ enrichment patterns or cause mineral dissolution. At the same time, the reduction of the dielectric constant of water promotes ion association and consequently mineral precipitation. All this cause changes in the electrical conductivity of geothermal fluids and may have considerable effects on the porosity and hydraulic properties of the rocks with which they are in contact. In order to study the impact of fluid-rock interactions on the physical properties of fluids and rocks in near- and supercritical geological settings in more detail, in the framework of the EU-funded project "IMAGE" (Integrated Methods for Advanced Geothermal Exploration) hydraulic and electrical properties of rock cores from different active and exhumed geothermal areas on Iceland were measured up to supercritical conditions (Tmax = 380° C, pfluid = 23 MPa) during long-term (2-3 weeks) flow-through experiments in an internally heated gas pressure vessel at a maximum confining pressure of 42 MPa. In a second flow-through facility both the intrinsic T-dependent electrical fluid properties as well as the effect of mineral dissolution/ precipitation on the fluid conductivity were measured for increasing temperatures in a range of 24 - 422° C at a constant fluid pressure of 31 MPa. Petro- and fluid physical measurements were supplemented by a number of additional tests, comprising microstructural investigations as well as the chemical analysis of fluid samples, which were taken at every temperature level. Both physical and chemical data indicate only slight fluid-rock interactions at T < 250° C and the increase in bulk conductivity is most probably dominated by a T-dependence of the surface conductance. At higher temperatures, the decreasing fluid density causes the decrease of dielectric constant, which in turn leads to the precipitation of minerals due to a promoted association between oppositely charged ions. This is intensified at the critical point, indicated by a sharp decrease in conductivity, when regarding pure fluids. The opposite was observed in experiments, where fluid-solid interaction was allowed. In this case, the conductivity of the bulk system has increased within seconds nearly by factor 7. This points to a massive release of charge carriers due to an extensive and spontaneous increase in rock solubility, what counterbalances the effect of mineral precipitation. Moreover, the permanent oscillation of conductivities at supercritical conditions may indicate a dynamic interplay of ion depletion by mineral precipitation and the input of new charge carriers due to mineral dissolution. Regarding the permeability we can resolve the influence of mineral precipitation only, which is indicated by a decrease in rock permeability by about 5 % after the sample was exposed to supercritical conditions for 4 hours. Especially, for Si a continuous increase of ion concentration in the fluid samples is revealed for increasing temperatures, indicating a beginning mineral dissolution above 150° C. At near-critical conditions also Al and Pb as well as the rare earth elements (REE) are more intensively dissolved. From SEM analyses it is apparent that the alteration of the solid material is most effective where fresh fluid is continuously flowing around the solid, while stagnant fluids led to a much less pervasive alteration of the material. In this case, solid dissolution seems to slow down considerably or even comes to an end, what can be explained by the adjustment of a chemical equilibrium and the stabilisation of the reaction front.

Water Content of Lunar Alkali Fedlspar

NASA Technical Reports Server (NTRS)

Mills, R. D.; Simon, J. I.; Wang, J.; Alexander, C. M. O'D.; Hauri, E. H.

2016-01-01

Detection of indigenous hydrogen in a diversity of lunar materials, including volcanic glass, melt inclusions, apatite, and plagioclase suggests water may have played a role in the chemical differentiation of the Moon. Spectroscopic data from the Moon indicate a positive correlation between water and Th. Modeling of lunar magma ocean crystallization predicts a similar chemical differentiation with the highest levels of water in the K- and Th-rich melt residuum of the magma ocean (i.e. urKREEP). Until now, the only sample-based estimates of water content of KREEP-rich magmas come from measurements of OH, F, and Cl in lunar apatites, which suggest a water concentration of < 1 ppm in urKREEP. Using these data, predict that the bulk water content of the magma ocean would have <10 ppm. In contrast, estimate water contents of 320 ppm for the bulk Moon and 1.4 wt % for urKREEP from plagioclase in ferroan anorthosites. Results and interpretation: NanoSIMS data from granitic clasts from Apollo sample 15405,78 show that alkali feldspar, a common mineral in K-enriched rocks, can have approx. 20 ppm of water, which implies magmatic water contents of approx. 1 wt % in the high-silica magmas. This estimate is 2 to 3 orders of magnitude higher than that estimated from apatite in similar rocks. However, the Cl and F contents of apatite in chemically similar rocks suggest that these melts also had high Cl/F ratios, which leads to spuriously low water estimates from the apatite. We can only estimate the minimum water content of urKREEP (+ bulk Moon) from our alkali feldspar data because of the unknown amount of degassing that led to the formation of the granites. Assuming a reasonable 10 to 100 times enrichment of water from urKREEP into the granites produces an estimate of 100-1000 ppm of water for the urKREEP reservoir. Using the modeling of and the 100-1000 ppm of water in urKREEP suggests a minimum bulk silicate Moon water content between 2 and 20 ppm. However, hydrogen loss was likely very significant in the evolution of the lunar mantle. Conclusions: Lunar granites crystallized between 4.3-3.8 Ga from relatively wet melts that degassed upon crystallization. The formation of these granites likely removed significant amounts of water from some mantle source regions, e.g. later mare basalts predicting derivation from a mantle with <10 ppm water. However, this would have been a heterogeneous pro-cess based on K distribution. Thus some, if not most of the mantle may not have been devolatilized by this process; as seen by water in volcanic glasses and melt inclusions.

Sembar Goru/Ghazij Composite Total Petroleum System, Indus and Sulaiman-Kirthar Geologic Provinces, Pakistan and India

USGS Publications Warehouse

Wandrey, C.J.; Law, B.E.; Shah, Haider Ali

2004-01-01

Geochemical analyses of rock samples and produced oil and gas in the Indus Basin have shown that the bulk of the hydrocarbons produced in the Indus Basin are derived from the Lower Cretaceous Sembar Formation and equivalent rocks. The source rocks of the Sembar are composed of shales that were deposited in shallow marine environments, are of mixed type-II and type-III kerogen, with total organic carbon (TOC) content ranging from less than 0.5 percent to more than 3.5 percent; the average TOC of the Sembar is about 1.4 percent. Vitrinite reflectance (Ro) values range from immature (1.35 percent Ro). Thermal generation of hydrocarbons in the Sembar Formation began 65 to 40 million years ago, (Mya) during Paleocene to Oligocene time. Hydrocarbon expulsion, migration, and entrapment are interpreted to have occurred mainly 50 to 15 Mya, during Eocene to Miocene time, prior to and contemporaneously with the development of structural traps in Upper Cretaceous and Tertiary reservoirs. The principal reservoirs in the Sembar-Goru/Ghazij Composite Total Petroleum System are Upper Cretaceous through Eocene sandstones and limestones.

Characterization of seismic properties across scales: from the laboratory- to the field scale

NASA Astrophysics Data System (ADS)

Grab, Melchior; Quintal, Beatriz; Caspari, Eva; Maurer, Hansruedi; Greenhalgh, Stewart

2016-04-01

When exploring geothermal systems, the main interest is on factors controlling the efficiency of the heat exchanger. This includes the energy state of the pore fluids and the presence of permeable structures building part of the fluid transport system. Seismic methods are amongst the most common exploration techniques to image the deep subsurface in order to evaluate such a geothermal heat exchanger. They make use of the fact that a seismic wave caries information on the properties of the rocks in the subsurface through which it passes. This enables the derivation of the stiffness and the density of the host rock from the seismic velocities. Moreover, it is well-known that the seismic waveforms are modulated while propagating trough the subsurface by visco-elastic effects due to wave induced fluid flow, hence, delivering information about the fluids in the rock's pore space. To constrain the interpretation of seismic data, that is, to link seismic properties with the fluid state and host rock permeability, it is common practice to measure the rock properties of small rock specimens in the laboratory under in-situ conditions. However, in magmatic geothermal systems or in systems situated in the crystalline basement, the host rock is often highly impermeable and fluid transport predominately takes place in fracture networks, consisting of fractures larger than the rock samples investigated in the laboratory. Therefore, laboratory experiments only provide the properties of relatively intact rock and an up-scaling procedure is required to characterize the seismic properties of large rock volumes containing fractures and fracture networks and to study the effects of fluids in such fractured rock. We present a technique to parameterize fractured rock volumes as typically encountered in Icelandic magmatic geothermal systems, by combining laboratory experiments with effective medium calculations. The resulting models can be used to calculate the frequency-dependent bulk modulus K(ω) and shear modulus G(ω), from which the P- and S-wave velocities V P(ω) and V S(ω) and the quality factors QP(ω) and QS(ω) of fluid saturated fractured rock volumes can be estimated. These volumes are much larger and contain more complex structures than the rock samples investigated in the laboratory. Thus, the derived quantities describe the elastic and anelastic (energy loss due to wave induced fluid flow) short-term deformation induced by seismic waves at scales that are relevant for field-scale seismic exploration projects.

Visual classification of very fine-grained sediments: Evaluation through univariate and multivariate statistics

USGS Publications Warehouse

Hohn, M. Ed; Nuhfer, E.B.; Vinopal, R.J.; Klanderman, D.S.

1980-01-01

Classifying very fine-grained rocks through fabric elements provides information about depositional environments, but is subject to the biases of visual taxonomy. To evaluate the statistical significance of an empirical classification of very fine-grained rocks, samples from Devonian shales in four cored wells in West Virginia and Virginia were measured for 15 variables: quartz, illite, pyrite and expandable clays determined by X-ray diffraction; total sulfur, organic content, inorganic carbon, matrix density, bulk density, porosity, silt, as well as density, sonic travel time, resistivity, and ??-ray response measured from well logs. The four lithologic types comprised: (1) sharply banded shale, (2) thinly laminated shale, (3) lenticularly laminated shale, and (4) nonbanded shale. Univariate and multivariate analyses of variance showed that the lithologic classification reflects significant differences for the variables measured, difference that can be detected independently of stratigraphic effects. Little-known statistical methods found useful in this work included: the multivariate analysis of variance with more than one effect, simultaneous plotting of samples and variables on canonical variates, and the use of parametric ANOVA and MANOVA on ranked data. ?? 1980 Plenum Publishing Corporation.

Green glass vitrophyre 78526 - An impact of very low-Ti mare basalt composition

NASA Technical Reports Server (NTRS)

Warner, R. D.; Taylor, G. J.; Kiel, K.; Planner, H. H.; Nehru, C. E.; Ma, M.-S.; Schmitt, R. A.

1978-01-01

Rake sample 78526 is an 8.77 g rock consisting primarily of vitrophyric pale green glass with subordinate mineral and lithic relics. Petrographic and compositional evidence leads to the following conclusions: (1) the bulk composition represents that of a mixture formed by impact melting of at least two different textural and compositional varieties of VLT mare basalt that are now present in the rock as lithic relics and a poorly defined low-Ti mare basalt component observed in thin section only in the form of isolated mineral relics; (2) the admixed VLT mare basalts had REE abundances lower than those found in other mare basalts (but probably higher than emerald green glass) and REE patterns showing significant enrichment of the heavy relative to light REE's, suggesting that they were derived by comparatively high degrees of partial melting of a clinopyroxene-rich source region; and (3) the impact melt supercooled to produce the vitrophyre, with rather sharply contrasting textural domains present in the vitrophyre resulting from differences in nucleation kinetics and degrees of supercooling in various portions of the sample.

The rare earth element compositions of the Changjiang (Yangtze) and Huanghe (Yellow) river sediments

NASA Astrophysics Data System (ADS)

Yang, Shou Ye; Jung, Hoi Soo; Choi, Man Sik; Li, Cong Xian

2002-07-01

Thirty-four samples from the Changjiang and Huanghe were analyzed to characterize their rare earth element (REE) compositions. Although REE concentrations in the Changjiang sediments are higher than those of the Huanghe sediments, the former are less variable. Bulk samples and acid-leachable fractions have convex REE patterns and middle REE enrichments relative to upper continental crust, whereas flat patterns are present in the residual fractions. Source rock composition is the primary control on REE composition, and weathering processes play a minor role. Grain size exerts some influence on REE composition, as demonstrated by the higher REE contents of clay minerals in sediments from both rivers. Heavy minerals contribute about 10-20% of the total REE in the sediments. Apatite is rare in the river sediments, and contributes less than 2% of the REE content, but other heavy minerals such as sphene, allanite and zircon are important reservoirs of residual REE fractions. The Fe-Mn oxides phase accounts for about 14% of bulk REE content in the Changjiang sediments, which could be one of the more important factors controlling REE fractionation in the leachable fraction.

Determining Individual Particle Magnetizations in Assemblages of Micrograins

NASA Astrophysics Data System (ADS)

de Groot, Lennart V.; Fabian, Karl; Béguin, Annemarieke; Reith, Pim; Barnhoorn, Auke; Hilgenkamp, Hans

2018-04-01

Obtaining reliable information from even the most challenging paleomagnetic recorders, such as the oldest igneous rocks and meteorites, is paramount to open new windows into Earth's history. Currently, such information is acquired by simultaneously sensing millions of particles in small samples or single crystals using superconducting quantum interference device magnetometers. The obtained rock-magnetic signal is a statistical ensemble of grains potentially differing in reliability as paleomagnetic recorder due to variations in physical dimensions, chemistry, and magnetic behavior. Here we go beyond bulk magnetic measurements and combine computed tomography and scanning magnetometry to uniquely invert for the magnetic moments of individual grains. This enables us to select and consider contributions of subsets of grains as a function of particle-specific selection criteria and avoid contributions that arise from particles that are altered or contain unreliable magnetic carriers. This new, nondestructive, method unlocks information from complex paleomagnetic recorders that until now goes obscured.

Worldwide occurrence of silica-rich melts in sub-continental and sub-oceanic mantle minerals

NASA Astrophysics Data System (ADS)

Schiano, P.; Clocchiatti, R.

1994-04-01

ROCK samples derived from the Earth's upper mantle commonly show indirect evidence for chemical modification. Such modification, or 'metasomatism', can be recognized by the precipitation of exotic minerals such as phlogopite, amphibole or apatite1, and by the overprinting of the bulk compositions of the mantle rocks by a chemical signature involving the enrichment of potassium and other 'incompatible' elements2. Here we study the composition of the metasomatic agents more directly by examining melt and fluid inclusions trapped in mantle minerals. These inclusions are secondary, forming trails along healed fracture planes. A systematic study of the chemical compositions and entrapment temperatures and pressures of inclusions from 14 ultramaflc peridotites from both continental and oceanic intraplate regions shows that volatile- and silica-rich metasomatic melts are present throughout the litho-sphere. Their compositions, which differ dramatically from those of erupted, mantle-derived magmas, are more akin to continental than to oceanic crust.

The regolith at the Apollo 15 site and its stratigraphic implications

USGS Publications Warehouse

Carr, M.H.; Meyer, C.E.

1974-01-01

Regolith samples from the Apollo 15 landing site are described in terms of two major fractions, a homogeneous glass fraction and a non-homogeneous glass fraction. The proportions of different components in the homogeneous glass fraction were determined directly by chemical analyses of individual particles. They are mainly green glass, a mare-like glass, and different types of Fra Mauro and Highland type glasses. The proportions of various components in the remainder of each of the soils were determined indirectly by finding the mix of components that best fits their bulk compositions. The mixing model suggests that the Apennine Front consists mainly of rocks of low-K Fra Mauro basalt composition. These may overlie rocks with the composition of anorthositic gabbro. Green glass, which occurs widely throughout the site is believed to be derived from a green glass layer which darkens upland surfaces and lies beneath the local mare surface. ?? 1974.

New Insights From Whole Rock and Mineral Data on the Magmatic and Tectonic Evolution of the Columbia River Basalt Group (USA)

NASA Astrophysics Data System (ADS)

Caprarelli, G.; Reidel, S. P.

2004-12-01

The Miocene Columbia River Basalt Group (CRBG) of north-western USA was emplaced in a geologically dynamic setting characterized by a close association between magmatism and lithospheric thinning and rifting. We present and discuss electron probe microanalysis and XRFA data obtained from samples spanning the entire sequence of the CRBG. The examined basalts have near-aphyric textures. No glass is present, and plagioclase and augitic clinopyroxene are dominant matrix and groundmass phases. Plagioclase microcrysts are labradoritic to bytownitic. Whole rock compositions were taken as proxies of the liquid compositions. Application of plagioclase / melt and clinopyroxene / melt geothermobarometers indicated that during crustal ascent the magmas were dry, and that pre-eruptive pressures and temperatures ranged from 0 to 0.66 GPa and 1393 to 1495 K, respectively. In a P-T diagram most of the samples are distributed along a general CRBG trend, while some samples plot along a parallel higher temperature trend. The calculated P-T values, the positive correlation between calculated P and T, and no horizontal alignment of the data, exclude the presence of upper crustal solidification fronts, and indicate that magma aggregation zones were located deeper than 25 km, plausibly immediately below the Moho, that in this region is at a depth of approximately 35 km. Episodic stretching of the lithosphere best explains the observed parallel P-T trends. Whole rock major element abundances resulted from fractional crystallization of the magmas during ascent. To retrieve the compositions of the primitive melts we added to the bulk rock compositions variable amounts of magnesian olivine [Mg/(Mg+Fe) = 0.88], and derived the evolution of olivine fractionating magmas in equilibrium with mantle harzburgite. Two groups of samples were found, corresponding to the parallel P-T trends obtained from mineral / melt calculations. The highest temperature trend corresponds to samples whose calculated primitive compositions are in agreement with those obtained from peridotite melting experiments (as published in the relevant literature). Interpretation of results for rocks belonging to the general CRBG trend suggests, either: (a) that higher forsteritic content olivine should be used in the calculations; or, (b) that melt / ol / opx reactions occurred. Investigation of the CRBG primitive compositions has relevance with regard to the geodynamic evolution models of this region. We are currently undertaking melt inclusion studies of suitable CRBG samples.

Magnetic mineralogy and rock magnetic properties of silicate and carbonatite rocks from Oldoinyo Lengai volcano (Tanzania)

NASA Astrophysics Data System (ADS)

Mattsson, H. B.; Balashova, A.; Almqvist, B. S. G.; Bosshard-Stadlin, S. A.; Weidendorfer, D.

2018-06-01

Oldoinyo Lengai, a stratovolcano in northern Tanzania, is most famous for being the only currently active carbonatite volcano on Earth. The bulk of the volcanic edifice is dominated by eruptive products produced by silica-undersaturated, peralkaline, silicate magmas (effusive, explosive and/or as cumulates at depth). The recent (2007-2008) explosive eruption produced the first ever recorded pyroclastic flows at this volcano and the accidental lithics incorporated into the pyroclastic flows represent a broad variety of different rock types, comprising both extrusive and intrusive varieties, in addition to various types of cumulates. This mix of different accidental lithics provides a unique insight into the inner workings of the world's only active carbonatite volcano. Here, we focus on the magnetic mineralogy and the rock magnetic properties of a wide selection of samples spanning the spectrum of Oldoinyo Lengai rock types compositionally, as well from a textural point of view. Here we show that the magnetic properties of most extrusive silicate rocks are dominated by magnetite-ulvöspinel solid solutions, and that pyrrhotite plays a larger role in the magnetic properties of the intrusive silicate rocks. The natrocarbonatitic lavas, for which the volcano is best known for, show distinctly different magnetic properties in comparison with the silicate rocks. This discrepancy may be explained by abundant alabandite crystals/blebs in the groundmass of the natrocarbonatitic lavas. A detailed combination of petrological/mineralogical studies with geophysical investigations is an absolute necessity in order to understand, and to better constrain, the overall architecture and inner workings of the subvolcanic plumbing system. The results presented here may also have implications for the quest in order to explain the genesis of the uniquely natrocarbonatitic magmas characteristic of Oldoinyo Lengai.

Fe-Distribution and Hydrogen Generation During Serpentinization

NASA Astrophysics Data System (ADS)

Klein, F.; Bach, W.; Jöns, N.; McCollom, T.; Berquó, T.; Moskowitz, B.

2009-04-01

Serpentinization of peridotite generates large amounts of dihydrogen (H2,aq), indicated by the presence of Ni-Fe alloys and low-sulfur-fugacity sulfides, e. g. awaruite and pentlandite, in serpentinites. Hydrogen is produced when ferrous iron in olivine is oxidized by water to ferric iron in secondary magnetite and serpentine. This process is strongly dependent on bulk rock composition, water-to-rock ratio and temperature. These relations were examined in thermodynamic reaction path models (using the EQ3/6 computer code) with dunitic and harzburgitic rock compositions. The model results were compared with electron microprobe analyses, bulk magnetization measurements, and Mößbauer spectroscopy of partially to fully serpentinized dunites and harzburgites from Ocean Drilling Program Leg 209, Hole 1274A, Mid-Atlantic Ridge 15 °N. These samples have mesh rims that reveal a distinct in-to-out zoning, starting with brucite (Mg# 80) at the interface with olivine, then a zone of serpentine (Mg# 95) + brucite ± magnetite, and finally serpentine + magnetite in the outermost mesh rim. The composition of co-existing serpentine and brucite in pseudomorphic mesh rims is virtually constant in most samples from 32 to 147 meters below seafloor, suggesting similar alteration conditions of olivine downhole. Bulk magnetization measurements of microdrilled mesh rims in combination with thin section petrography revealed a positive correlation of magnetite content with extent of serpentinization. Where relic olivine is present, the magnetite content is significantly lower then in fully serpentinized rocks. In these domains with sparse magnetite, Mößbauer spectra revealed Fe3+/‘ Fe values between 0.30 and 0.48 for paramagnetic minerals in the mesh rims (i. e., secondary hydrous phases). In heavily to completely serpentinized rocks with abundant magnetite, Fe3+/‘ Fe values of the paramagnetic phases are consistently higher and range from 0.53 to 0.68. In the EQ3/6 runs, a serpentine solid solution model that includes greenalite and hisingerite (Fe2Si2O5(OH)4) was used in investigating the distribution of iron between serpentine and magnetite and its oxidation state in serpentine. Our model computations predict that above 330 °C and water activities near unity, the dissolution of olivine and coeval formation of serpentine, magnetite and dihydrogen is significantly obstructed by the dearth of silica. At these temperatures, hydrogen fugacities are too low for awaruite and pentlandite to be stable. When temperatures drop below 320-330 °C, brucite becomes stable and hydrogen generation is facilitated, because the reaction of olivine to serpentine, magnetite and brucite requires no external silica. The MgO-FeO-Fe2O3-SiO2-H2O and Fe-Ni-Co-O-S phase relations observed in the mesh rims suggest that serpentine and brucite from Hole 1274A likely formed at temperatures between 150 and 250 °C and water-to-rock ratios (w/r) between 5 and 0.1. However, formation of awaruite must have taken place during main stage serpentinization at temperatures between 200-250 °C and w/r < 1, when alteration conditions were sufficiently reducing. Likewise, the model predicts the Fe3+/‘ Fe ratios of mesh-rim serpentine/brucite observed in incompletely serpentinized rocks of serpentine (0.3 to 0.5) at low w/r ratios and T < 250 °C. The calculation results furthermore indicate that elevated Fe3+/‘ Fe ratios (0.5 to 0.7) measured in fully serpentinized rocks appear to correspond to higher w/r ratios and less reducing conditions. Our study indicates that unprecedented details about the reaction sequences during serpentinization may be obtained from merging careful petrographic, magnetic, and spectroscopic analyses with comprehensive thermodynamic modeling.

Natural Serpentinite Carbonation at Linnajavri, N-Norway (Invited)

NASA Astrophysics Data System (ADS)

Beinlich, A.; Tominaga, M.; Pluemper, O.; Hoevelmann, J.; Tivey, M.; Andrade Lima, E.; Weiss, B. P.; Austrheim, H.; Jamtveit, B.

2013-12-01

Investigation of natural mafic and ultramafic rock carbonation driven by the infiltration of CO2-bearing fluids into a solid rock unit provides insight into feedback mechanisms that may become important for in situ sequestration schemes of anthropogenic CO2. We present observations from massively carbonated serpentinites at Linnajavri, N-Norway, where completely serpentinized fragments of the dismembered ophiolite are hydrothermally altered on a km-scale to ophicarbonate (serpentine + Mg-carbonate), soapstone (talc + Mg-carbonate) and listvenite (quartz + Mg-carbonate). Field observations indicate that tectonic preprocessing of the serpentinite facilitated fluid infiltration. Listvenite is indicative of the most intense carbonation and is present along the tectonic contact of the ophiolite with the underlying carbonate-mica schist. Soapstone/steatite is indicative of less intense carbonation, forms m-wide reaction halos around fractures within the serpentinite and is also present as massive body between the listvenite and unaltered serpentinite. Sharp reaction interfaces between the soapstone and serpentinite can be traced for several hundred meters and are defined by the breakdown of antigorite to form magnesite and talc. The soapstone-listvenite transition zones are not entirely exposed in the field and are less than 5 m wide. 18O thermometry using the isotopic composition of quartz/talc and coexisting magnesite derived from veins and bulk rock samples indicate an isothermal formation of listvenite and soapstone at ~275°C. The corresponding isotopic signature of the fluid (δ13CVPDB = 2.2(5) ‰) derived from the δ13C composition of magnesite suggests an interaction with crustal rocks and devolatilization of associated overthrusted sediments as a possible source for the CO2. He- and Hg-porosimetry data, mass-balance calculations, and the preservation of serpentinite structures imply an isovolumetric alteration, which indicates that the carbonation declined due to the cessation of externally supplied CO2. The presence of sharp alteration fronts implies that reaction rates were fast relative to CO2 transport rates. Carbonation at Linnajavri was accompanied by partial dissolution of (Cr)-magnetite and incorporation of the released Fe in precipitating carbonate minerals. SQUID microscopy mapping of both natural remanence magnetization (NRM) and anhysteretic remanence magnetization (ARM) confirms different bulk intensities for the serpentinite, soapstone and listvenite samples. The alteration dependent distribution of ferromagnetic minerals suggests that magnetic surface mapping may represent a powerful tool to localize the position of reaction fronts between pristine and carbonated rock types and hence the spatial extent of the carbonation progress.

Subsurface Evolution: Weathering and Mechanical Strength Reduction in Bedrock of Lower Gordon Gulch, Colorado Front Range

NASA Astrophysics Data System (ADS)

Kelly, P. J.; Anderson, S. P.; Anderson, R. S.; Blum, A.; Foster, M. A.; Langston, A. L.

2011-12-01

Weathering processes drive mobile regolith production at the surface of the earth. Chemical and physical weathering weakens rock by creating porosity, opening fractures, and transforming minerals. Increased porosity provides habitat for living organisms, which aid in further breakdown of the rock, leaving it more susceptible to displacement and transport. In this study, we test mechanical and chemical characteristics of weathered profiles to better understand weathering processes. We collect shallow bedrock cores from tors and isovolumetrically weathered bedrock in lower Gordon Gulch to characterize the mechanical strength, mineralogy, and bulk chemistry of samples to track changes in the subsurface as bedrock weathers to mobile regolith. Gordon Gulch is a small (2.7 km2), E-W trending catchment within the Boulder Creek Critical Zone Observatory underlain by Pre-Cambrian gneiss and granitic bedrock. The basin is typical of the "Rocky Mountain Surface" of the Front Range, characterized by low relief, a lack of glacial or fluvial incision, and deep weathering. Although the low-curvature, low-relief Rocky Mountain Surface would appear to indicate a landscape roughly in steady-state, shallow seismic surveys (Befus et al., 2011, Vadose Zone Journal) indicate depth to bedrock is highly variable. Block style release of saprolite into mobile regolith could explain this high variability and should be observable in geotechnical testing. Gordon Gulch also displays a systematic slope-aspect dependent control on weathering, with N-facing hillslopes exhibiting deeper weathering profiles than the S-facing hillslope. We believe comparisons of paired geotechnical-testing, XRD, and XRF analyses may explain this hillslope anisotropy. Rock quality designation (RQD) values, a commonly used indicator of rock mass quality (ASTM D6032), from both N- and S- facing aspects in Gordon Gulch indicate that granitic bedrock in both outcrop and saprolitic rock masses is poor to very poor. Brazilian tensile testing of outcrop core samples show relatively low tensile failure forces, and exhibit a roughly logarithmic increase in failure force, and hence tensile strength, with depth. For many of the granitic strength profiles, the point of greatest curvature is around 0.5 m depth. Tests reveal small-scale variation in the tensile strength, suggesting that the tight fracture-spacing bounding blocks of saprolite plays an important role in regolith production. The origin of the micro- and macro-fractures is unclear. Preliminary results do not correlate clear depth-trends in mineralogy or bulk chemistry with mechanical strength. The lack of a strong signature from chemical or mineralogical weathering suggests that mechanical processes, such as frost cracking or biotite hydration, may dominate.

Assessment of gamma radiation exposure of beach sands in highly touristic areas associated with plutonic rocks of the Atticocycladic zone (Greece).

PubMed

Papadopoulos, A; Koroneos, A; Christofides, G; Papadopoulou, L; Tzifas, I; Stoulos, S

2016-10-01

This study aims to evaluate the activity concentrations of 238 U, 226 Ra, 232 Th, 228 Th and 40 K along beaches close to the plutonic rocks of the Atticocycladic zone that ranged from 15 to 628, 12-2292, 16-10,143, 14-9953 and 191-1192 Bq/kg respectively. A sample from island of Mykonos contained the highest 232 Th content measured in sediments of Greece. The heavy magnetic fraction and the heavy non-magnetic fraction as well as the total heavy fraction, were correlated with the concentrations of the measured radionuclides in the bulk samples. The heavy fractions seem to control the activity concentrations of 238 U and 232 Th of all the samples, showing some local differences in the main 238 U and 232 Th mineral carrier. Similar correlations have been found between 238 U, 232 Th content and rare earth elements concentrations. The measured radionuclides in the beach sands were normalized to the respective values measured in the granitic rocks, which at least in most cases are their most probable parental rocks, so as to provide data upon their enrichment or depletion. Since the Greek beaches are among the most popular worldwide the annual effective dose equivalent received due to sand exposure has been estimated and found to vary between 0.002 and 0.379 mSv y -1 for tourists and from 0.018 to 3.164 mSv y -1 for local people working on the beach. The values corresponding to ordinary sand samples are orders of magnitude lower than the limit of 1 mSv y -1 , only in the case of heavy minerals-rich sands the dose could reach or exceed the recommended maximum limit. Copyright © 2016 Elsevier Ltd. All rights reserved.

Redistribution of iron and titanium in subduction zones: insights from high-pressure serpentinites

NASA Astrophysics Data System (ADS)

Crossley, Rosalind; Evans, Katy; Reddy, Steven; Lester, Gregory

2017-04-01

The redox state, quantity and composition of subduction zone fluids influence the transport and precipitation of elements including those which are redox-sensitive, of economic importance such as Cu, Au and Ag, and those considered to be immobile, which include Fe3+. However, subduction zone fluids remain poorly understood. The redox state of Fe in high-pressure ultramafic rocks, which host a significant proportion of Fe3+, can be used to provide an insight into Fe cycling and constrain the composition of subduction zone fluids. In this work, a combination of the study of oxide and silicate mineral textures, interpretation of mineral parageneses, mineral composition data, and the whole rock geochemistry of high-pressure retrogressed ultramafic rocks from the Zermatt-Saas Zone constrains the distribution of iron and titanium, and oxidation state of iron, to provide constraints on fluids at depth in subduction zones. Oxide minerals host the bulk of the iron, particularly Fe3+. The increase in mode of magnetite during initial retrogression is most consistent with oxidation of existing iron within the samples during the infiltration of an oxidising fluid since it is difficult to reconcile addition of Fe3+ with the known limited solubility of this species. These fluids may be sourced from hybrid samples and/or serpentinites at greater depths. However, high Ti contents are not typical of serpentinites and additionally cannot be accounted for by simple mixing of a depleted mantle protolith with the nearby Allalin gabbro. Titanium-rich samples are suggested to result from fluid-facilitated hybridisation of gabbro and serpentinite protoliths prior to peak metamorphism, and provides the tantalising possibility that Ti, an element generally perceived as immobile, has been added to the rock during this process. If Ti addition has occurred, then the introduction of Fe3+, also generally considered to be immobile, cannot be disregarded. Aluminosilicate complexing could provide a transport vector for Ti where this mechanism of Ti transport is consistent with the Al-rich nature of the sample.

Comparison of Geochemical, Grain-Size, and Magnetic Proxies for Rock Flour and Ice- Rafted Debris in the Late Pleistocene Mono Basin, CA

NASA Astrophysics Data System (ADS)

Zimmerman, S. H.; Hemming, S. R.; Kent, D. V.

2008-12-01

Advance and retreat of mountain glaciers are important indicators of climate variability, but the most direct proxy record, mapping and dating of moraines, is by nature discontinous. The Sierra Nevada form the western boundary of the Mono Lake basin, and the proximity of the large Pleistocene lake to the glacial canyons of the Sierra presents a rare opportunity to examine glacial variability in a continuous, well-dated lacustrine sequence. We have applied a geochemical proxy for rock flour to the glacial silts of the late Pleistocene Wilson Creek Formation, but because it is time- and sample-intensive, another method is required for a high-resolution record. Previous microscopic examination, thermomagnetic measurements, XRD analysis, and new isothermal remnant magnetization (IRM) acquisition curves show that the magnetic mineralogy is dominated by fine-grained, unaltered magnetite. Bulk measurements show strong susceptibility (mean ~ 16 x 10- 6 m3/kg) and remanent magnetization (mean IRM ~ 10-2 Am2/kg) compared to diluting components (carbonate, smectite, rhyolitic ash). The Wilson Creek type section sediments also contain a coarse lithic fraction, quantified by counting the >2cm clasts in outcrop and the >425 μm fraction in the bulk sediment. Susceptibility, IRM, and ARM (anhysteretic remnant magnetization) are quite similar throughout the type section, with the abundance of coarse lithic fraction correlative to the ratio k/IRM. Because the magnetic fraction of the rock flour is fine-grained magnetite, IRM should capture the changes in concentration of flour through time, and the major features of the (low-resolution) geochemical flour proxy record are identifiable in the IRM record. Flux-correction of the IRM results in a rock flour proxy record with major peaks between 36 and 48 ka, similar to a rock flour record from neighboring Owens Lake. This regional glacial signal contrasts with peaks in coarse lithics between 58 and 68 ka in the Wilson Creek record; coupled with coeval high lake levels and a lack of geomorphic evidence of glacier-lake interaction, this is taken to indicate that the rafting was due to shore ice, rather than glacial icebergs.

Oxygen Isotopes and the Cooling History of the Mount Barcroft Area, Central White Mountains, Easternmost California

NASA Astrophysics Data System (ADS)

Ernst, W. G.; Rumble, D.

2001-12-01

The White-Inyo Range + Owens Valley marks the western limit of the Basin and Range province, directly east of the Sierra Nevada. At Mount Barcroft, mid-Mesozoic, alkaline, bimodal White Mountain Peak metavolcanic + metaclastic rocks on the N are separated from Lower Cambrian siliciclastic + carbonate metasedimentary strata on the S by the NE-trending Middle Jurassic Barcroft mafic granodioritic pluton. It consists of mineralogically/chemically intergradational gabbro/diorite, granodiorite, metadiorite, and alaskite. Eastward, the section is intruded by the Late Cretaceous, ternary-minimum McAfee Creek Granite. Ignoring altered dikes, bulk-rock analyses of plutonic rocks indicate that metaluminous, I-type rocks of the Barcroft comagmatic suite possess an av(12) d18O value of 7.5. Slightly peraluminous, apparently S-type granitic rocks sensu stricto of the McAfee Creek series have an av(8) d18O value of 8.6. Evidence is lacking for large-scale bulk-rock interaction with near-surface waters, suggesting intermediate crustal depths of intrusion and cooling for these plutons. Coexisting Barcroft minerals exhibit consistent oxygen isotopic partitioning from high to low d18O in the sequence quartz > plagioclase > K-feldspar >> amphibole = biotite. Wall-rock quartz and biotite are richer in 18O than analogous phases in the plutonic rocks, and show slightly greater fractionations than igneous counterparts. Along its borders, late-stage exchange with heated aqueous fluids, derived from recrystallized wall rocks due to emplacement of the Middle Jurassic magma, increased 18O/16O ratios of dikes, and some Barcroft igneous plagioclase and subsolidus tremolite-actinolite. Oxygen isotope geothermometry for Barcroft quartz-amphibole and quartz-biotite pairs yields broadly similar temperatures; the combined average of 13 pairs is 519oC. A single quartz-biotite pair analyzed from a Lower Cambrian quartzite within the inner metamorphic aureole of the Barcroft pluton yields a temperature of 511oC, in agreement with values based on wall-rock metamorphic parageneses. Barcroft quartz, feldspars, biotite, and clinoamphiboles were subjected to exchange with deuteric fluid, and re-equilibrated under subsolidus conditions. Quartz-plagioclase pairs from two Barcroft granodiorites possess similar temperatures of 519 and 515oC, so also re-equilibrated at subsolidus temperatures. Areal distributions for quartz-plagioclase, quartz-clinoamphibole, and quartz-biotite pairs reveal that annealing temperatures are lowest in axial portions of the Barcroft granodioritic pluton. Late Cretaceous emplacement of the McAfee Creek Granite had little effect on d18O values of Barcroft minerals and bulk rocks.

High-temperature rapid pyrometamorphism induced by a charcoal pit burning: The case of Ricetto, central Italy

NASA Astrophysics Data System (ADS)

Capitanio, Flavio; Larocca, Francesco; Improta, Salvatore

Bulk chemistry and mineralogy of the peculiar rock of Ricetto (Carseolani Mts., Central Apennines, Italy) was studied to resolve its controversial origin: igneous dyke or anthropic product. This hybrid rock consists of a colorless, felsic component made up of glass plus quartz, and a brown, femic component made up of fans and spherulites of diopside, calcic plagioclase, wollastonite, and melilite. Textural relationships indicate very rapid cooling and immiscibility phenomena. The bulk chemistry of the rock is the same as that of the surrounding siliciclastic sandstone. The 14C analysis of a coal fragment from bottom of the body yields the conventional age of 227(+/-50) years. The Ricetto occurrence is an example of pyrometamorphism of a siliceous limestone induced by a charcoal pit burning. The small size of the heat source at Ricetto caused an intense but short-lived melting of the country rock. Prograde metamorphism caused a temperature increase up to 1,000-1,100 °C when melilite crystallization conditions were reached at appreciable P(CO2) and high f(O2). Melting occurred in a close system represented by the simplified equation: 3Cal+16.5Qtz+Ms+Bt-->Mel+Melt+2H2O+3CO2+0.5O2. Diopside+calcic plagioclase+wollastonite formed by melilite breakdown during rapid cooling, through the reaction: 6Mel+6Qtz+0.5O2-->3Di+2An+7Wo. Liquid immiscibility caused the separation between the felsic melt component and the femic melilite-bearing component. Immiscibility was characterized by different fractionation of alumina and alkalies between these two phases. Differences in bulk, glass, and mineral chemistry between the Ricetto and other melilite-bearing pyrometamorphic rocks can be attributed mainly to different protoliths.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyet, Maud; Carlson, Richard W.; Borg, Lars E.

Here, we have measured Sm–Nd systematics, including the short-lived 146Sm– 142Nd chronometer, in lunar ferroan anorthositic suite (FAS) whole rocks (15415, 62236, 62255, 65315, 60025). At least some members of the suite are thought to be primary crystallization products formed by plagioclase flotation during crystallization of the lunar magma ocean (LMO). Most of these samples, except 62236, have not been exposed to galactic cosmic rays for a long period and thus require minimal correction to their 142Nd isotope composition. These samples all have measured deficits in 142Nd relative to the JNdi-1 terrestrial standard in the range –45 to –21 ppm.more » The range is –45 to –15 ppm once the 62236 142Nd/ 144Nd ratio is corrected from neutron-capture effects. Analyzed FAS samples do not define a single isochron in either 146Sm– 142Nd or 147Sm– 143Nd systematics, suggesting that they either do not have the same crystallization age, come from different sources, or have suffered isotopic disturbance. Because the age is not known for some samples, we explore the implications of their initial isotopic compositions for crystallization ages in the first 400 Ma of solar system history, a timing interval that covers all the ages determined for the ferroan anorthositic suite whole rocks as well as different estimates for the crystallization of the LMO. 62255 has the largest deficit in initial 142Nd and does not appear to have followed the same differentiation path as the other FAS samples. The large deficit in 142Nd of FAN 62255 may suggest a crystallization age around 60–125 Ma after the beginning of solar system accretion. This result provides essential information about the age of the giant impact forming the Moon. The initial Nd isotopic compositions of FAS samples can be matched either with a bulk-Moon with chondritic Sm/Nd ratio but enstatite-chondrite-like initial 142Nd/ 144Nd (e.g. 10 ppm below modern terrestrial), or a bulk-Moon with superchondritic Sm/Nd ratio and initial 142Nd/ 144Nd similar to ordinary chondrites.« less

Evaluating the cause(s) of Ti, Ta, and Nb (TITAN) enrichment in ocean island basalts using LA-ICP-MS

NASA Astrophysics Data System (ADS)

Lyakov, J.; Durkin, K.; Hirsch, L.; Peters, B.; Hattingh, R.; Day, J. M.

2017-12-01

Titanium, Ta, and Nb (TITAN) enrichments in some ocean island basalt (OIB) lavas have been attributed to mantle source, or to partial melting and fractional crystallization Iprocesses. TITAN anomalies in the mantle sources of OIB would imply these trace elements can be used to track mantle heterogeneity in a manner similar to some isotopic tracers (e.g., He, Os, W), whereas a petrogenetic process to account for TITAN anomalies would be more prosaic. To further evaluate this issue, we have performed laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of phenocryst phases and matrix on petrographically well-characterized polished-sections of OIB samples. These samples come from five ocean island archipelagos (Canary Islands, the Azores, Samoa, Tubuai'i, Réunion), and are used to assess the citing of Ti, Ta, Nb and associated trace-elements within bulk-rocks. We find poorly-defined but broadly positive correlations between olivine and clinopyroxene modal abundance and Ta/Ta*, Nb/Nb*, but no correlation with Ti/Ti* (where, for example, Ti/Ti* is the primitive mantle normalized ratio, written as: Ti/√[Sm × Tb]). Abundances of olivine and clinopyroxene with samples spanned a wide-range, from 0-70 modal %. We determined trace-element abundances by LA-ICP-MS in a sub-set of samples for major (olivine, clinopyroxene) and minor (e.g., magnetite) phenocryst phases, and for the typically vitrophyric to partly crystallized matrices of samples. Modal reconstruction relative to the bulk rock are broadly similar, although the Ta/Ta*, Nb/Nb* and, especially Ti/Ti* anomalies cannot always be reproduced, especially if Fe-Ti oxide phases were not analyzed due to their limited presence within polished sections. LA-ICP-MS analyses reveal that, while TITAN anomalies are dominantly preserved in the matrix and oxide phases, the role of fractional crystallization of olivine and clinopyroxene is a controlling factor in the magnitude of TITAN anomaly generated. Our results support suggestions that Ti, Ta and Nb are affected by partial melting, assimilation and fractional crystallization processes during magma evolution, generating more prominent TITAN anomalies in volcanic samples than their mantle sources.

Interpreting Assemblages with Titanite (Sphene): It Does not have to be Greek to You.

NASA Technical Reports Server (NTRS)

Xirouchakis, Dimitrios M.; Lindsley, Donald H.; McKay, Gordon A. (Technical Monitor)

2000-01-01

Assemblages with titanite, pyroxene(s), olivine, ilmenite, magnetite, and quartz can be used to constrain the intensive and compositional variables that operate during crystallization. Such assemblages are relatively rare in metamorphic rocks, but they are more common in igneous rocks and more frequently reported in plutonic than volcanic rocks. We used the program QUILF, enhanced with thermodynamic data for titanite, to compute stable reactions among titanite (CaTiOSiO4), Fe-Mg-Ti ilmenite and magnetite (hereafter ilmenite and magnetite), Ca-Mg-Fe pyroxenes and olivine, and quartz, and to evaluate some of the factors that control titanite stability. Calculations at 1, 3, and 6 Kbar and 650, 850, 1100 0 C, in the system CaO - MgO - FeO Fe2O3 - TiO2 - SiO2, suggest that the reactions: Augitc + Ilmenite = Titanite + Magnetite + Quartz and Augite + Ilmenite + Quartz = Titanite + Orthopyroxene, impose well defined fugacity of O2, alpha(sub SiO2), , and compositional restrictions to the assemblages: (1) Titanite + Magnetite + Quartz, (2) Titanite + Orthopyroxene, (3) Augite + Ilmenite, and consequently titanite stability. From our calculations in this system we can draw the following general conclusions: (1) The assemblage Titanite + Magnetite + Quartz is always a good indicator of relatively high fugacity of O2, and it is likely more common in relatively iron-rich bulk compositions and for decreasing temperature and pressure conditions. (2) At high temperatures (>= 650 C) titanite is not stable in quartz-saturated rocks that contain the assemblage Orthopyroxene + Augite + Ilmenite + Magnetite. (3) In quartz-saturated rocks the coexistence of titanite and magnetite with either orthopyroxene or olivine requires a confluence of conditions relating bulk composition, fugacity of O2, and slow cooling. Thus, such assemblages must be rare. (4) Regardless of T and fugacity of O2 conditions, and bulk-composition, titanite is not stable in quartz-absent rocks that contain Olivine + Orthopyroxene + Augite + Ilmenite + Magnetite. Decreasing temperature and pressure conditions appear to favor titanite crystallization, thus, it is not unsurprising that titanite is frequently observed in slowly cooled rocks, albeit, in association with amphibole. We argue that the titanite + amphibole association is likely favored by high water activity, regardless of oxygen fugacity. Because water activity increases during crystallization of a pluton, the association titanite + amphibole, and consequently titanite, is likely to be more common in plutonic rocks than in volcanic rocks.

An experimental study of the carbonation of serpentinite and partially serpentinised peridotites

NASA Astrophysics Data System (ADS)

Lacinska, Alicja M.; Styles, Michael T.; Bateman, Keith; Hall, Matthew; Brown, Paul D.

2017-06-01

In situ sequestration of CO2 in mantle peridotites has been proposed as a method to alleviate the amount of anthropogenic CO2 in the atmosphere. This study presents the results of eight-month long laboratory fluid-rock experiments on representative mantle rocks from the Oman-United Arab Emirates ophiolite to investigate this process. Small core samples (3 cm long) were reacted in wet supercritical CO2 and CO2-saturated brine at 100 bar and 70°C. The extent of carbonate formation, and hence the degree of carbon sequestration, varied greatly depending on rock type, with serpentinite (lizardite-dominated) exhibiting the highest capacity, manifested by the precipitation of magnesite MgCO3 and ferroan magnesite (Mg,Fe)CO3. The carbonate precipitation occurred predominantly on the surface of the core and subordinately within cross-cutting fractures. The extent of the CO2 reactions appeared to be principally controlled by the chemical and mineralogical composition of the rock, as well as the rock texture, with all these factors influencing the extent and rate of mineral dissolution and release of Mg and Fe for subsequent reaction with the CO2. It was calculated that ≈ 0.7 g of CO2 was captured by reacting ≈ 23 g of serpentinite, determined by the mass of magnesite formed. This equates to ≈ 30 kg CO2 per tonne of host rock, equivalent to ≈ 3% carbonation in half a year. However, recycling of carbonate present in veins within the original rock sample could mean that the overall amount is around 2%. The increased reactivity of serpentinite was associated with preferential dissolution of more reactive types of serpentine minerals and brucite, that were mainly present in the cross-cutting veins. The bulk of the serpentinite rock was little affected. This study, using relatively short term experiments, suggests that serpentinite might be a good host rock for CO2 sequestration, although long term experiments might prove that dunite and harzburgite could be an effective in an engineered system of CCSM. Wet scCO2 proved to be chemically aggressive than CO2-saturated brine and its ingress along fractures and grain boundaries resulted in greater host rock dissolution and subsequent carbonate precipitation.

Predicted bulk composition of petroleum generated by Lower Cretaceous Wealden black shales, Lower Saxony Basin, Germany

NASA Astrophysics Data System (ADS)

Ziegs, Volker; Mahlstedt, Nicolaj; Bruns, Benjamin; Horsfield, Brian

2015-09-01

The Berriasian Wealden Shale provides the favourable situation of possessing immature to overmature source rock intervals due to differential subsidence within the Lower Saxony Basin. Hydrocarbon generation kinetics and petroleum physical properties have been investigated on four immature Wealden Shale samples situated in different depth intervals and following the PhaseKinetics approach of di Primio and Horsfield (AAPG Bull 90(7):1031-1058, 2006). Kinetic parameters and phase prediction were applied to a thermally calibrated 1D model of the geodynamic evolution at the location of an overmature well. The immature source rocks of all depth intervals comprise kerogen type I being derived from the lacustrine algae Botryococcus braunii. Bulk kinetics of the lower three depth intervals (sample 2-4) can be described by one single activation energy E a, typical for homogeneous, lacustrine organic matter (OM), whereas sample 1 from the uppermost interval shows a slightly broader E a distribution which hints to a more heterogeneous, less stable OM, but still of lacustrine origin. Predicted physical properties of the generated petroleum fluids are characteristic of variably waxy, black oil possessing GOR's below 100 Sm3/Sm3 and saturations pressures below 150 bar. Petroleum fluids from the more heterogeneous OM-containing sample 1 can always be described by slightly higher values. Based on the occurrence of paraffinic, free hydrocarbons in the uppermost horizon of the overmature well and gas/condensate in the lower 3 depth intervals, two scenarios have been discussed. From the first and least realistic scenario assuming no expulsion from the source rock, it can be deduced that phase separation in the course of uplift can only have occurred in the uppermost interval containing the slightly less stable OM but not in the lower intervals being composed of a more stable OM. Therefore and taking secondary cracking into account, all depth intervals should contain gas/condensate. The free hydrocarbons in the upper horizon are interpreted as impregnation from migrated hydrocarbons. The second scenario assumes nearly complete expulsion due to fracturing by the so-called generation overpressure (Mann et al. in Petroleum and basin evolution. Springer, Berlin, 1997). The expelled petroleum might migrate into lower pressurised source rock horizons and reach bubble-point pressures leading to the exsolution of gas and "precipitation" of very high molecular weight bitumen unable to migrate. Subsequent burial of the latter in the course of the basin evolution would lead to secondary cracking and remaining pyrobitumen explaining the high amounts of pyrobitumen in the overmature well Ex-B and relatively enhanced TOC contents at such high maturity levels.

Deformation mechanisms in experimentally deformed Boom Clay

NASA Astrophysics Data System (ADS)

Desbois, Guillaume; Schuck, Bernhard; Urai, Janos

2016-04-01

Bulk mechanical and transport properties of reference claystones for deep disposal of radioactive waste have been investigated since many years but little is known about microscale deformation mechanisms because accessing the relevant microstructure in these soft, very fine-grained, low permeable and low porous materials remains difficult. Recent development of ion beam polishing methods to prepare high quality damage free surfaces for scanning electron microscope (SEM) is opening new fields of microstructural investigation in claystones towards a better understanding of the deformation behavior transitional between rocks and soils. We present results of Boom Clay deformed in a triaxial cell in a consolidated - undrained test at a confining pressure of 0.375 MPa (i.e. close to natural value), with σ1 perpendicular to the bedding. Experiments stopped at 20 % strain. As a first approximation, the plasticity of the sample can be described by a Mohr-Coulomb type failure envelope with a coefficient of cohesion C = 0.117 MPa and an internal friction angle ϕ = 18.7°. After deformation test, the bulk sample shows a shear zone at an angle of about 35° from the vertical with an offset of about 5 mm. We used the "Lamipeel" method that allows producing a permanent absolutely plane and large size etched micro relief-replica in order to localize and to document the shear zone at the scale of the deformed core. High-resolution imaging of microstructures was mostly done by using the BIB-SEM method on key-regions identified after the "Lamipeel" method. Detailed BIB-SEM investigations of shear zones show the following: the boundaries between the shear zone and the host rock are sharp, clay aggregates and clastic grains are strongly reoriented parallel to the shear direction, and the porosity is significantly reduced in the shear zone and the grain size is smaller in the shear zone than in the host rock but there is no evidence for broken grains. Comparison of microstructures within the host rock and the undeformed sample shows that the sample underwent compaction prior shearing that results in a change of power law exponent of the pore size distribution within the clay matrix and a slight reorientation of clastic grains' long axis perpendicular to σ1. Microstructures in the shear zone indicate ductile behavior before the specimen's failure. Deformation mechanisms are bending of clay plates and sliding along clay-clay contacts. Strain is strongly localised in thin, anastomosing zones of strong preferred orientation, producing slickensided shear surfaces common in shallow clays. There is no evidence for intragranular cracking.We propose that the deformation localizes in regions without hard quartz grains.

Petrified lightning: the role of bubbles in the physical and chemical processes leading to formation of rock fulgurites

NASA Astrophysics Data System (ADS)

Chen, J.; Elmi, C.; Goldsby, D. L.; Giere, R.

2016-12-01

Fulgurite is a vitrified soil, sand or rock resulting from lightning strikes. The thunderbolt, which can have an energy density of 3.3 ×106 J/m, is associated with air temperatures of up to 30,000 K and a current of up to 10 kA, which can heat the rock to >2000 K within tens of ms. The rapid fusing and subsequent quenching of the surface of the rock leaves a distinctive thin garbled coating comprised of glassy to fine-grained porous material. Similar materials and structures result from atomic bomb tests (trinitite) and from meteorite impacts (tektite). Chemical analysis of rock fulgurite samples on granites collected near Baveno, Italy reveals a glass composition of mainly SiO2 and Al2O3. A porosity of about 10% in the analyzed fulgurite was determined. The presence of newly-formed cristobalite and relict quartz in a relatively chemically homogenous glass matrix indicates induced temperatures >1700 ºC. The residual organic matter in the glass suggests that rapid cooling of the melt trapped NOx and COx gases vaporized during the lightning event. Tiny spheres mainly made of Fe and rich in Si point to reducing conditions. To better understand the formation of the porous glass matrix during intense Joule heating and subsequent rapid cooling, idealized physical models were developed to simulate bubble nucleation and redox reactions inside the bubbles. Preliminary results suggest that a weathered surface layer of higher electrical conductivity than the bulk rock results in strong Joule heating near the surface, facilitating the formation of a dense population of bubbles in the 10 mm-thick glass layer. Experiments to generate fulgurites in the laboratory, with well controlled energy input and sample properties, will aid our understanding of the physics of fulgurite formation and corroborate theoretical models. The results of such experiments, which are underway, will be presented.

Comprehensive Interpretation of the Laboratory Experiments Results to Construct Model of the Polish Shale Gas Rocks

NASA Astrophysics Data System (ADS)

Jarzyna, Jadwiga A.; Krakowska, Paulina I.; Puskarczyk, Edyta; Wawrzyniak-Guz, Kamila; Zych, Marcin

2018-03-01

More than 70 rock samples from so-called sweet spots, i.e. the Ordovician Sa Formation and Silurian Ja Member of Pa Formation from the Baltic Basin (North Poland) were examined in the laboratory to determine bulk and grain density, total and effective/dynamic porosity, absolute permeability, pore diameters size, total surface area, and natural radioactivity. Results of the pyrolysis, i.e., TOC (Total Organic Carbon) together with S1 and S2 - parameters used to determine the hydrocarbon generation potential of rocks, were also considered. Elemental composition from chemical analyses and mineral composition from XRD measurements were also included. SCAL analysis, NMR experiments, Pressure Decay Permeability measurements together with water immersion porosimetry and adsorption/ desorption of nitrogen vapors method were carried out along with the comprehensive interpretation of the outcomes. Simple and multiple linear statistical regressions were used to recognize mutual relationships between parameters. Observed correlations and in some cases big dispersion of data and discrepancies in the property values obtained from different methods were the basis for building shale gas rock model for well logging interpretation. The model was verified by the result of the Monte Carlo modelling of spectral neutron-gamma log response in comparison with GEM log results.

Evolution of depleted mantle: The lead perspective

NASA Astrophysics Data System (ADS)

Tilton, George R.

1983-07-01

Isotopic data have established that, compared to estimated bulk earth abundances, the sources of oceanic basaltic lavas have been depleted in large ion lithophile elements for at least several billions of years. Various data on the Tertiary-Mesozoic Gorgona komatiite and Cretaceous Oka carbonatite show that those rocks also sample depleted mantle sources. This information is used by analogy to compare Pb isotopic data from 2.6 billion year old komatiite and carbonatite from the Suomussalmi belt of eastern Finland and Munro Township, Ontario that are with associated granitic rocks and ores that should contain marked crustal components. Within experimental error no differences are detected in the isotopic composition of initial Pb in either of the rock suites. These observations agree closely with Sr and Nd data from other laboratories showing that depleted mantle could not have originated in those areas more than a few tenths of billions of years before the rocks were emplaced. On a world-wide basis the Pb isotope data are consistent with production of depleted mantle by continuous differentiation processes acting over approximately the past 3 billion years. The data show that Pb evolution is more complex than the simpler models derived from the Rb-Sr and Sm-Nd systems. The nature of the complexity is still poorly understood.

Scaling craters in carbonates: Electron paramagnetic resonance analysis of shock damage

NASA Technical Reports Server (NTRS)

Polanskey, Carol A.; Ahrens, Thomas J.

1994-01-01

Carbonate samples from the 8.9-Mt nuclear (near-surface explosion) crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron paramagnetic resonance (EPR). Samples from below the OAK apparent crater floor were obtained from six boreholes, as well as ejecta recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to the spectra of Solenhofen and Kaibab limestone, which had been skocked to known pressures. Analysis of the OAK Crater borehole samples has identified a thin zone of allocthonous highly shocked (10-13 GPa) carbonate material underneath the apparent crater floor. This approx. 5- to 15-m-thick zone occurs at a maximum depth of approx. 125 m below current seafloor at the borehole, sited at the initial position of the OAK explosive, and decreases in depth towards the apparent crater edge. Because this zone of allocthonous shocked rock delineates deformed rock below, and a breccia of mobilized sand and collapse debris above, it appears to outline the transient crater. The transient crater volume inferred in this way is found to by 3.2 +/- 0.2 times 10(exp 6)cu m, which is in good agreement with a volume of 5.3 times 10(exp 6)cu m inferred from gravity scaling of laboratory experiments. A layer of highly shocked material is also found near the surface outside the crater. The latter material could represent a fallout ejecta layer. The ejecta boulders recovered from the present crater floor experienced a range of shock pressures from approx. 0 to 15 GPa with the more heavily shocked samples all occurring between radii of 360 and approx. 600 m. Moreover, the fossil content, lithology and Sr isotopic composition all demonstrate that the initial position of the bulk of the heavily shocked rock ejecta sampled was originally near surface rock at initial depths in the 32 to 45-m depth (below sea level) range. The EPR technique is also sensitive to prehistoric shock damage. This is demonstrated by our study of shocked Kaibab limestone from the 49,000-year-old Meteor (Barringer) Crater Arizona.

Evidence of biological activity in Hawaiian subsurface basalts

NASA Astrophysics Data System (ADS)

Fisk, M. R.; Storrie-Lombardi, M. C.; Douglas, S.; Popa, R.; McDonald, G.; di Meo-Savoie, C.

2003-12-01

The Hawaii Scientific Drilling Program (HSDP) cored and recovered igneous rock from the surface to a depth of 3109 m near Hilo, Hawaii. Much of the deeper parts of the hole is composed of hyaloclastite (fractured basalt glass that has been cemented in situ with secondary minerals). Some hyaloclastite units have been altered in a manner attributed to microorganisms in volcanic rocks. Samples from one such unit (1336 m to 1404 m below sea level) were examined to test the hypothesis that the alteration was associated with microorganisms. Deep ultraviolet native fluorescence and resonance Raman spectroscopy indicate that nucleic acids and aromatic amino acids are present in clay inside spherical cavities (vesicles) within basalt glass. Chemical mapping shows that phosphorus and carbon were enriched at the boundary between the clay and volcanic glass of the vesicles. Environmental scanning electron microscopy (ESEM) reveals two to three micrometer coccoid structures in these same boundaries. ESEM-linked energy dispersive spectroscopy demonstrated carbon, phosphorous, chloride, and magnesium in these bodies significantly differing from unoccupied neighboring regions of basalt. These observations taken together indicate the presence of microorganisms at the boundary between primary volcanic glass and secondary clays. Amino acids and nucleic acids were extracted from bulk samples of the hyaloclastite unit. Amino acid abundance was low, and if the amino acids are derived from microorganisms in the rock, then there are less than 100,000 cells per gram of rock. Most nucleic acid sequences extracted from the unit were closely related to sequences of Crenarchaeota collected from the subsurface of the ocean floor.

Geochemical characterisation of Tithonian-Berriasian Chia Gara organic-rich rocks in northern Iraq with an emphasis on organic matter enrichment and the relationship to the bioproductivity and anoxia conditions

NASA Astrophysics Data System (ADS)

Mohialdeen, Ibrahim M. J.; Hakimi, Mohammed Hail

2016-02-01

Tithonian-Berriasian Chia Gara organic-rich rocks, located in Kurdistan (northern Iraq), were analysed based on inorganic and organic geochemistry to define the origin, type of organic matter, and the influencing factors of organic matter (OM) enrichment, including the OM input and preservation, and their relationship to the paleoenvironment conditions. The δ13Corg values of the Chia Gara rocks range from -29.99‰ to -26.93‰, with average values of approximately -28.8‰, indicating that the organic matter has a predominantly marine origin. Enhanced biological productivity within the photic zone of the water column during deposition of the Chia Gara Fm. is indicated by consistently high organic carbon content in most samples (average 3 wt.%), as well as by bulk geochemical and biomarker characteristics. Major contributions by aquatic algae and microorganisms with a minor terrigenous organic matter contribution are indicated by the n-alkane distribution patterns and the composition of the hopanoids, steroids, and tricyclic terpenoids. Strongly reducing bottom water is indicated by low pristane/phytane ratios, homohopane distribution patterns, and the redox-sensitive trace elements geochemistry. Salinity stratification with alkaline bottom waters is indicated by high Sr/Ba ratios and the presence of gammacerane in the analysed Chia Gara samples. These data indicate that OM enrichment in the Tithonian-Berriasian Chia Gara rocks results from the combination of enhanced biological productivity and salinity stratification with anoxic bottom water conditions, which favoured OM preservation.

Rock Magnetic Properties and Paleointensity Determinations of Basalts From the Emperor Seamounts

NASA Astrophysics Data System (ADS)

Carvallo, C.; Dunlop, D. J.; Ozdemir, O.

2002-12-01

Thellier-Thellier paleointensity experiments were carried out on sixty-six basaltic samples coming from three Emperor seamounts (Detroit, Nintoku and Koko) drilled during ODP Leg 197. Seventeen samples yielded reliable results. One sample from Detroit Seamount (81 Ma) gives a VADM of 3.0+/-0.2x1022Am2. Ten samples from Nintoku (56 Ma) give VADMs between 1.6+/-0.1x1022 and 4.7+/-0.2x1022Am2. Six samples from Koko seamount (44 Ma) give VADMs between 0.6+/-0.1x1022 and 1.8+/-0.1x1022Am2. Assuming that the accepted samples did not undergo any maghemitization, the generally low VADM values we measured are in agreement with other records of paleointensities in this time range. The low success rate was due to chemical changes during the heatings. Samples have a wide distribution of unblocking temperatures and bulk susceptibility variations during heating, revealing an important variation in oxidation state and titanium content with depth and between seamounts. Other rock magnetic properties such as low-temperature measurements and thermomagnetic curves also indicate that the magnetic composition of the basalt varies from almost pure magnetite to titanomagnetite (x=0.4) within the same hole. Identification of magnetic minerals is important in order to assess the reliability of paleointensity and paleomagnetic measurements. It might also provide some information on parameters such as cooling rate of the lava flows or alteration.

Plagioclase-Hosted Magnetite Inclusions From the Bushveld Complex

NASA Astrophysics Data System (ADS)

Feinberg, J. M.; Scott, G. R.; Renne, P. R.; Wenk, H.

2004-12-01

Gabbros from the Main Zone of the 2.064 Ga Bushveld Complex have long been known to possess unusually stable magnetizations due to the presence of high coercivity, exsolved magnetite inclusions in plagioclase and clinopyroxene. The paleomagnetic pole for these rocks has been used to anchor apparent polar wander paths for the Kaapval craton during the Early-Mid Proterozoic. To better understand the rock magnetic properties of silicate-hosted magnetite inclusions, oriented paleomagnetic samples of gabbro were collected from quarries near Belfast and Rustenberg, South Africa, sampling the eastern and western limbs of the Complex, respectively. Plagioclase composition at both sites ranges from An55 (rims) to An65 (cores) based on optical and electron microprobe data. Four kinds of inclusions are present within the plagioclase: elongate magnetite needles, nanometer-scale magnetite particles (responsible for the "cloudy" appearance of some crystals), translucent brown hematite/ilmenite platelets, and colorless euhedral inclusions of pyroxene and/or feldspar. Magnetite inclusions are most abundant at the cores of the plagioclase crystals. Orientations of the needles and the platelets are crystallographically controlled by the silicate host. Although the elongation direction of the magnetite inclusions can occur in any of five possible orientations, only two or three of these directions dominates each plagioclase crystal. Alternating field demagnetization of bulk samples (NRM = 1.5 x 101 A m-1) shows univectorial remanence with average median destructive fields (MDF) of 115 mT (Belfast) and 90 mT (Rustenberg). AF demagnetization of single plagioclase crystals (NRM = 100 A m-1) also shows single component remanence with average MDFs >150 mT. The NRM coercivity spectra of single plagioclase crystals are indistinguishable from that of the bulk samples. When normalized to their abundance in bulk samples the magnetite-bearing plagioclase fully accounts for the NRM of Bushveld gabbros at both sites. Close examination of the inclusions' interiors using magnetic force microscopy shows no ulvöspinel exsolution as observed in other silicate exsolved titanomagnetites with comparably high coercivities. Consequently, we interpret the high coercivities of the inclusions to be a product of their small size and extreme shape anisotropy. Single crystals of plagioclase demonstrate a strong anisotropy of IRM acquisition (see Scott, et al. this conference). Additionally, electron backscatter diffraction (EBSD) orientation indexing shows a strongly preferred orientation for plagioclase and pyroxene (with (010)plag and (100)pyr parallel to subhorizontal layering) consistent with gravitational settling within a magma chamber. Thus, there are two anisotropies (silicate preferred orientation and magnetite inclusion remanence) to consider when describing the ancient magnetic field present during the emplacement of the Bushveld.

Permeability of gypsum samples dehydrated in air

NASA Astrophysics Data System (ADS)

Milsch, Harald; Priegnitz, Mike; Blöcher, Guido

2011-09-01

We report on changes in rock permeability induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air (dry) for up to 800 h at ambient pressure and temperatures between 378 and 423 K. Subsequently, the reaction kinetics, so induced changes in porosity, and the concurrent evolution of sample permeability were constrained. Weighing the heated samples in predefined time intervals yielded the reaction progress where the stoichiometric mass balance indicated an ultimate and complete dehydration to anhydrite regardless of temperature. Porosity showed to continuously increase with reaction progress from approximately 2% to 30%, whilst the initial bulk volume remained unchanged. Within these limits permeability significantly increased with porosity by almost three orders of magnitude from approximately 7 × 10-19 m2 to 3 × 10-16 m2. We show that - when mechanical and hydraulic feedbacks can be excluded - permeability, reaction progress, and porosity are related unequivocally.

Characterization of LIBS emission lines for the identification of chlorides, carbonates, and sulfates in salt/basalt mixtures for the application to MSL ChemCam data: LIBS OF CL, C, S IN SALT-BASALT MIXTURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, D. E.; Ehlmann, B. L.; Forni, O.

Ancient environmental conditions on Mars can be probed through the identification of minerals on its surface, including water-deposited salts and cements dispersed in the pore space of sedimentary rocks. Laser-induced breakdown spectroscopy (LIBS) analyses by the Martian rover Curiosity's ChemCam instrument can indicate salts, and ChemCam surveys aid in identifying and selecting sites for further, detailed in situ analyses. Here, we performed laboratory LIBS experiments under simulated Mars conditions with a ChemCam-like instrument on a series of mixtures containing increasing concentrations of salt in a basaltic background to investigate the potential for identifying and quantifying chloride, carbonate, and sulfate saltsmore » found only in small amounts, dispersed in bulk rock with ChemCam, rather than concentrated in veins. The data then indicate that the presence of emission lines from the basalt matrix limited the number of Cl, C, and S emission lines found to be useful for quantitative analysis; nevertheless, several lines with intensities sensitive to salt concentration were identified. Detection limits for the elements based on individual emission lines ranged from ~20 wt % carbonate (2 wt % C), ~5–30 wt % sulfate (1–8 wt % S), and ~5–10 wt % chloride (3–6 wt % Cl) depending on the basaltic matrix and/or salt cation. Absolute quantification of Cl, C, and S in the samples via univariate analysis depends on the cation-anion pairing in the salt but appears relatively independent of matrices tested, following normalization. Our results are promising for tracking relative changes in the salt content of bulk rock on the Martian surface with ChemCam.« less

Characterization of LIBS emission lines for the identification of chlorides, carbonates, and sulfates in salt/basalt mixtures for the application to MSL ChemCam data: LIBS OF CL, C, S IN SALT-BASALT MIXTURES

DOE PAGES

Anderson, D. E.; Ehlmann, B. L.; Forni, O.; ...

2017-04-24

Ancient environmental conditions on Mars can be probed through the identification of minerals on its surface, including water-deposited salts and cements dispersed in the pore space of sedimentary rocks. Laser-induced breakdown spectroscopy (LIBS) analyses by the Martian rover Curiosity's ChemCam instrument can indicate salts, and ChemCam surveys aid in identifying and selecting sites for further, detailed in situ analyses. Here, we performed laboratory LIBS experiments under simulated Mars conditions with a ChemCam-like instrument on a series of mixtures containing increasing concentrations of salt in a basaltic background to investigate the potential for identifying and quantifying chloride, carbonate, and sulfate saltsmore » found only in small amounts, dispersed in bulk rock with ChemCam, rather than concentrated in veins. The data then indicate that the presence of emission lines from the basalt matrix limited the number of Cl, C, and S emission lines found to be useful for quantitative analysis; nevertheless, several lines with intensities sensitive to salt concentration were identified. Detection limits for the elements based on individual emission lines ranged from ~20 wt % carbonate (2 wt % C), ~5–30 wt % sulfate (1–8 wt % S), and ~5–10 wt % chloride (3–6 wt % Cl) depending on the basaltic matrix and/or salt cation. Absolute quantification of Cl, C, and S in the samples via univariate analysis depends on the cation-anion pairing in the salt but appears relatively independent of matrices tested, following normalization. Our results are promising for tracking relative changes in the salt content of bulk rock on the Martian surface with ChemCam.« less

Eclogites and garnet pyroxenites from Kimberley, Kaapvaal craton, South Africa: their diverse origins and complex metasomatic signatures

NASA Astrophysics Data System (ADS)

Shu, Qiao; Brey, Gerhard P.; Pearson, D. Graham

2018-06-01

We describe the petrography and mineral chemistry of sixteen eclogite and garnet pyroxenite xenoliths from the reworked Boshof road dump (Kimberley) and define three groups that stem from different depths. Group A, the shallowest derived, has low HREE (heavy rare earth element) abundances, flat middle to heavy REE patterns and high Mg# [= 100·Mg/(Mg + Fe)]. Their protoliths probably were higher pressure cumulates ( 0.7 GPa) of mainly clinopyroxene (cpx) and subordinate orthopyroxene (opx) and olivine (ol). Group B1 xenoliths, derived from the graphite/diamond boundary and below show similarities to present-day N-MORB that were modified by partial melting (higher Mg# and positively inclined MREE (middle REE) and HREE (heavy REE) patterns of calculated bulk rocks). Group B2 samples from greatest depth are unique amongst eclogites reported so far worldwide. The calculated bulk rocks have humped REE patterns with very low La and Lu and prominent maxima at Sm or Eu and anomalously high Na2O (up to 5 wt%) which makes protolith identification difficult. The complex trace element signatures of the full spectrum of Kimberley eclogites belie a multi-stage history of melt depletion and metasomatism with the introduction of new phases especially of phlogopite (phlog). Phlogopite appears to be characteristic for Kimberley eclogites and garnet peridotites. Modelling the metasomatic overprint indicates that groups A and B1 were overprinted by volatile- and potassium-rich melts probably by a process of chromatographic fractionation. Using constraints from other metasomatized Kimberley mantle rocks suggest that much of the metasomatic phlogopite in the eclogites formed during an intense episode of metasomatism that affected the mantle beneath this region 1.1 Gyr ago.

The sedimentary organic matter from a Lake Ichkeul core (far northern Tunisia): Rock-Eval and biomarker approach

NASA Astrophysics Data System (ADS)

Affouri, Hassène; Sahraoui, Olfa

2017-05-01

The vertical distributions of bulk and molecular biomarker composition in samples from a ca. 156 cm sediment core from Lake Ichkeul were determined. Bulk analysis (Rock-Eval pyrolysis, carbonate, lipid extraction) and molecular analysis of saturated fractions were used to characterize the nature, preservation conditions and input of sedimentary organic matter (OM) to this sub-wet lake environment. The sediments are represented mainly by gray-black silty-clay facies where the carbonate (CaCO3) content varies in a range of 10-30% dry sediment. Rock-Eval pyrolysis revealed a homogeneous total organic carbon (TOC) content of ca. 1% sediment, but with down core fluctuation, indicating different anoxic conditions at different depths and material source variation. The values show three periods of relative enrichment, exceeding ca. 1%, at 146-134 cm, 82 cm and 14-0 cm depth. The low Hydrogen Index (HI) values [<119 mg hydrocarbon (HC)/g TOC)] were characteristic of continental Type III OM. The Tmax values in the range 415-420 °C were characteristic of immature OM at an early diagenetic stage. The distributions of n-alkanes (C17 to C34), isoprenoid (iso) alkanes (pristane and phytane), terpanes and steranes showed that the OM is a mixture of marine algal and bacterial source and emergent and floating higher plant origin. In addition, the distributions, as well as several biomarker ratios (n-alkanes, iso-alkanes/n-alkanes), showed that the OM is a mixture of immature and mature. Significant downcore fluctuation was observed in the molecular composition. This indicates intense microbial activity below ca. 50 cm core depth under an anoxic and brackish environment.

Geohydrologic data from test hole USW UZ-7, Yucca Mountain area, Nye County, Nevada

USGS Publications Warehouse

Kume, Jack; Hammermeister, D.P.

1990-01-01

This report contains a description of the methods used in drilling and coring of the test-hole USW UZ-7, a description of the methods used in collecting, handling, and testing of test-hole samples; Lithologic information from the test hole; and water-content, water-potential, bulk-density, grain-density, porosity, and tritium data for the test hole. Test-hole USW UZ-7 was drilled and cored to a total depth of 62.94 m. The drilling was done using air as a drilling fluid to minimize disturbance to the water content of cores, drill-bit cuttings, and borehole wall-rock. Beginning at the land surface, the unsaturated-zone rock that was penetrated consisted of alluvium; welded and partially to nonwelded ash-flow tuff; bedded and reworked ash-fall tuff; nonwelded ash-flow tuff; and welded ash-flow tuff. Values of gravimetric water content and water potential of alluvium were intermediate between the extreme values in welded and nonwelded units of tuff. Gravimetric water content was largest in bedded and nonwelded ash-fall tuffs and was smallest in welded ash-flow tuff. Values of water potential were more negative in densely welded ash-flow tuffs and were less negative in bedded and nonwelded ash-fall tuffs. Bulk density was largest in densely welded ash-flow tuffs and smallest in nonwelded and bedded ash-fall tuffs. Grain density was uniform but was slightly larger in nonwelded and bedded ash-fall tuffs than in welded ash-flow tuffs. Porosity trends were opposite to bulk-density trends. Tritium content in alluvium was smallest near the alluvium-bedrock contact, markedly increased in the middle of the deposit, and decreased in the near-surface zone of the deposit. (Author 's abstract)

Water Content in the SW USA Mantle Lithosphere: FTIR Analysis of Dish Hill and Kilbourne Hole Pyroxenites

NASA Technical Reports Server (NTRS)

Gibler, Robert; Peslier, Anne H.; Schaffer, Lillian Aurora; Brandon, Alan D.

2014-01-01

Kilbourne Hole (NM, USA) and Dish Hill (CA, USA) mantle xenoliths sample continental mantle in two different tectonic settings. Kilbourne Hole (KH) is located in the Rio Grande rift. Dish Hill (DH) is located in the southern Mojave province, an area potentially affected by subduction of the Farallon plate beneath North America. FTIR analyses were obtained on well characterized pyroxenite, dunite and wehrlite xenoliths, thought to represent crystallized melts at mantle depths. PUM normalized REE patterns of the KH bulk-rocks are slightly LREE enriched and consistent with those of liquids generated by < 5% melting of a spinel peridotite source. Clinopyroxenes contain from 272 to 313 ppm weight H2O similar to the lower limit of KH peridotite clinopyroxenes (250-530 ppm H2O). This is unexpected as crystallized melts like pyroxenites should concentrate water more than residual mantle-like peridotites, given that H is incompatible. PUM normalized bulk REE of the DH pyroxenites are characterized by flat to LREE depleted REE profiles consistent with > 6% melting of a spinel peridotite source. Pyroxenite pyroxenes have no detectable water but one DH wehrlite, which bulk-rock is LREE enriched, has 4 ppm H2O in orthopyroxene and <1ppm in clinopyroxene. The DH pyroxenites may thus come from a dry mantle source, potentially unaffected by the subduction of the Farallon plate. These water-poor melts either originated from shallow oceanic lithosphere overlaying the Farallon slab or from continental mantle formed > 2 Ga. The Farallon subduction appears to have enriched in water the southwestern United States lithospheric mantle further east than DH, beneath the Colorado plateau.

The evolution of pore connectivity in volcanic rocks

NASA Astrophysics Data System (ADS)

Colombier, Mathieu; Wadsworth, Fabian B.; Gurioli, Lucia; Scheu, Bettina; Kueppers, Ulrich; Di Muro, Andrea; Dingwell, Donald B.

2017-03-01

Pore connectivity is a measure of the fraction of pore space (vesicles, voids or cracks) in a material that is interconnected on the system length scale. Pore connectivity is fundamentally related to permeability, which has been shown to control magma outgassing and the explosive potential of magma during ascent in the shallowest part of the crust. Here, we compile a database of connectivity and porosity from published sources and supplement this with additional measurements, using natural volcanic rocks produced in a broad range of eruptive styles and with a range of bulk composition. The database comprises 2715 pairs of connectivity C and porosity ϕ values for rocks from 35 volcanoes as well as 116 products of experimental work. For 535 volcanic rock samples, the permeability k was also measured. Data from experimental studies constrain the general features of the relationship between C and ϕ associated with both vesiculation and densification processes, which can then be used to interpret natural data. To a first order, we show that a suite of rocks originating from effusive eruptive behaviour can be distinguished from rocks originating from explosive eruptive behaviour using C and ϕ. We observe that on this basis, a particularly clear distinction can be made between scoria formed in fire-fountains and that formed in Strombolian activity. With increasing ϕ, the onset of connectivity occurs at the percolation threshold ϕc which in turn can be hugely variable. We demonstrate that C is an excellent metric for constraining ϕc in suites of porous rocks formed in a common process and discuss the range of ϕc values recorded in volcanic rocks. The percolation threshold is key to understanding the onset of permeability, outgassing and compaction in shallow magmas. We show that this threshold is dramatically different in rocks formed during densification processes than in rocks formed in vesiculating processes and propose that this value is the biggest factor in controlling the evolution of permeability at porosities above ϕc.

Physical properties of the surface materials at the Viking landing sites on Mars

USGS Publications Warehouse

Moore, H.J.; Hutton, R.E.; Clow, G.D.; Spitzer, C.R.

1987-01-01

This report summarizes the results of the Physical Properties Investigation of the Viking '75 Project, activities of the surface samplers, and relevant results from other investigations. The two Viking Landers operated for nearly four martian years after landing on July 20 (Lander 1) and Sept. 3 (Lander 2), 1976; Lander 1 acquired its last pictures on or about Nov. 5, 1982. Lander 1 rests on a smooth, cratered plain at the west edge of Chryse Planitia (22.5 ? N, 48.0? W), and Lander 2 rests 200 km west of the crater Mie in Utopia Planitia (48.0? N, 225.7? W). Lander 1 views showed that dune-like deposits of drift material were superposed on rock-strewn surfaces. Soil-like material from the rock-strewn areas was called blocky material. Lander 2 views also showed a rock-strewn surface. Polygonal to irregular features, etched by the wind, revealed crusty to cloddy material among rocks. Both landers descended to the surface along nearly vertical trajectories. Velocities at touchdown were about 2 m/s for both landers. Footpad 2 of Lander 1 penetrated drift material 0.165 m, and footpad 3 penetrated blocky material 0.036 m. The two visible footpads of Lander 2 struck rocks. Erosion by exhausts from the forward engines produced craters with rims of mixed fine-grained material and platy to equidimensional clods, crusts, and fragments. Comparison of engine-exhaust erosion on Mars with terrestrial data suggested that drift material behaved like a weakly cohesive material with a grain size less than 3-9 /-lm. Although not sand, blocky and crusty to cloddy materials eroded like sand-with grain sizes of 0.01 or 0.2 cm. The surface samplers accomplished an impressive number of tasks. All experiments that required samples received samples. Deep holes, as much as 0.22 m deep, were excavated by both landers. Lander 2 successfully pushed rocks and collected samples from areas originally beneath the rocks. Tasks specifically accomplished for the Physical Properties Investigation include: (1) acquiring motor-current data while excavating trenches, (2) performing surface-bearing tests, (3) performing backhoe touchdowns, (4) attempting to chip or scratch rocks, (5) comminuting samples, (6) measuring subsurface diurnal temperatures, and (7) constructing conical piles of materials on and among rocks. Sample trenches in the three major types of soil-like materials were different from one another. Trenches in drift material, which were typically 0.06 m deep, had steep walls along much of their lengths, lumpy tailings and floors, and smooth domed surfaces with sparse fine fractures around their tips. Trenches in blocky material, which were typically 0.03-0.04 m deep, had steep walls near their tips, and surfaces around their tips were displaced upward and some appeared blocky. Trenches in crusty to cloddy material, which were typically 0.04-0.05 m deep, had steep and often irregular slopes near their tips, clods and slabs of crust in their tailings, and disrupted areas around their tips composed of mixed fine-grained material and slabs of crust or thick polygonal clods that had been displaced upwards. Data acquired during landing, trenching, surface-bearing tests, backhoe touchdowns, and from other science experiments were used to determine the mechanical properties of drift, blocky, and crusty to cloddy materials. Drift material appeared to be very fine grained, with local planes of weakness; in general, the drift material was consistent with a material having an angle of internal friction about 18?, a cohesion ranging from 0.7 to 3.0 kPa, and a bulk density of 1,200 kg/m 3 . Blocky material was consistent with a material having an angle of internal friction about 30?, cohesions from 1.5 to 16 kPa, and a bulk density of 1,600 kg/m 3 . Crusty to cloddy material had variable properties. For chiefly crusty to cloddy material, angles of internal friction were about 35 ? , and cohesions were from 0.5 to 5.2 kPa. For mixed fines and crusts, a

Characterizing Mobile/Less-Mobile Porosity and Solute Exchange in Dual-Domain Media Using Tracer Experiments and Electrical Measurements in a Hassler-Type Core Holder

NASA Astrophysics Data System (ADS)

Falzone, S.; Slater, L. D.; Day-Lewis, F. D.; Parker, B. L.; Keating, K.; Robinson, J.

2017-12-01

Mass transfer is the process by which solute is retained in less-mobile porosity domains, and later released into the mobile porosity domain. This process is often responsible for the slow arrival and gradual release of contaminants and solute tracers. Recent studies have outlined methods using dual-domain mass transfer (DDMT) models for characterizing this phenomenon. These models use the non-linear relationship of bulk (σb) and fluid (σf) conductivity, collected from electrical methods during tracer experiments, to characterize the less-mobile/mobile porosity ratio (β) and the mass-transfer rate coefficient (α). DDMT models use the hysteretic σb-σf relationship observed while solute tracers are injected and then flushed from a sample media. Due to limitations in observing the hysteretic σb-σf relationship, this method has not been used to characterize low permeability samples. We have developed an experimental method for testing porous rock cores that allows us to develop a fundamental understanding of contaminant storage and release in consolidated rock. We test the approach on cores from sedimentary rock sites where mass transfer is expected to occur between hydraulically connected fractures and the adjacent low permeability rock matrix. Our method uses a Hassler-type core holder, designed to apply confining pressure around the outside of a sample core, which hydraulically isolates the sample core, allowing water to be injected into it at increased pressures. The experimental apparatus was also designed to measure σb with spectral induced polarization (SIP) measurements, and σf from a sampling port located at the center of the core. Cores were initially saturated with a solution with high electrical conductivity ( 80000 μS/cm). DI water was then injected into the cores at elevated pressures (>60 psi) and the saturating solution was flushed from the cores, in order to generate flow rates fast enough to capture the non-linear σb-σf relationship expected when DDMT occurs. Our initial results demonstrate the existence of a non-linear σb-σf relationship indicative of DDMT for a tight sandstone core from a contaminated fractured rock site. Integrating the electrical results with known physical characteristics of the cores, we are able to quantify the mass transfer characteristics of the cores.

Susceptibility of volcanic ash-influenced soil in northern Idaho to mechanical compaction

Treesearch

Deborah S. Page-Dumroese

1993-01-01

Timber harvesting and mechanical site preparation can reduce site productivity if they excessively disturb or compact the soil. Volcanic ash-influenced soils with low undisturbed bulk densities and rock content are particularly susceptible. This study evaluates the effects of harvesting and site preparation on changes in the bulk density of ash-influenced forest soils...

Crystallography of some lunar plagioclases

USGS Publications Warehouse

Stewart, D.B.; Appleman, D.E.; Huebner, J.S.; Clark, J.R.

1970-01-01

Crystals of calcic bytownite from type B rocks have space group U with c ??? 14 angstroms. Bytownite crystals from type A rocks are more sodic and have space group C1, c ??? 7 angstroms. Cell parameters of eight bulk feldspar separates from crystalline rocks indicate that the range of angle gamma is about 23 times the standard error of measurement, and its value might be useful for estimation of composition. Cell parameters of seven ilmenites are close to those of pure FeTiO3.

Frequency-Based Precursory Acoustic Emission Failure Sequences In Sedimentary And Igneous Rocks Under Uniaxial Compression

NASA Astrophysics Data System (ADS)

Colin, C.; Anderson, R. C.; Chasek, M. D.; Peters, G. H.; Carey, E. M.

2016-12-01

Identifiable precursors to rock failure have been a long pursued and infrequently encountered phenomena in rock mechanics and acoustic emission studies. Since acoustic emissions in compressed rocks were found to follow the Gutenberg-Richter law, failure-prediction strategies based on temporal changes in b-value have been recurrent. In this study, we extend on the results of Ohnaka and Mogi [Journal of Geophysical Research, Vol. 87, No. B5, p. 3873-3884, (1982)], where the bulk frequency characteristics of rocks under incremental uniaxial compression were observed in relation to changes in b-value before and after failure. Based on the proposition that the number of low-frequency acoustic emissions is proportional to the number of high-amplitude acoustic emissions in compressed rocks, Ohnaka and Mogi (1982) demonstrated that b-value changes in granite and andesite cores under incremental uniaxial compression could be expressed in terms of the percent abundance of low-frequency events. In this study, we attempt to demonstrate that the results of Ohnaka and Mogi (1982) hold true for different rock types (basalt, sandstone, and limestone) and different sample geometries (rectangular prisms). In order to do so, the design of the compression tests was kept similar to that of Ohnaka and Mogi (1982). Two high frequency piezoelectric transducers of 1 MHz and a 500 kHz coupled to the sides of the samples detected higher and lower frequency acoustic emission signals. However, rather than gathering parametric data from an analog signal using a counter as per Ohnaka and Mogi (1982), we used an oscilloscope as an analog to digital converter interfacing with LabVIEW 2015 to record the complete waveforms. The digitally stored waveforms were then processed, detecting acoustic emission events using a statistical method, and filtered using a 2nd order Butterworth filter. In addition to calculating the percent abundance of low-frequency events over time, the peak frequency of the acoustic emissions over time was observable due to the digital method of waveform capture. This allows for a more direct comparison between frequency characteristics and b-values of rocks under compression and investigates the viability of observing frequency behavior over time as a method of rock failure prediction.

Characteristics and origin of rock varnish from the hyperarid coastal deserts of northern Peru

NASA Astrophysics Data System (ADS)

Jones, Charles E.

1991-01-01

The characteristics of a new type of rock varnish from the hyperarid coastal deserts of northern Peru, combined with laboratory experiments on associated soil materials, provide new insights into the formation of rock varnish. The Peruvian varnish consists of an Fe-rich, Mn-poor component covering up to 95% of a varnished surface and a Fe-rich, Mn-rich component found only in pits and along cracks and ridges. The alkaline soils plus the catalytic Fe oxyhydroxides that coat much of the varnish surfaces make the Peruvian situation ideal for physicochemical precipitation of Mn. However, the low Mn content of the dominant Fe-rich, Mn-poor component suggests that such precipitation is minor. This, plus the presence of abundant bacteria in the Mn-rich varnish and the recorded presence of Mn-precipitating bacteria in varnish elsewhere, suggests that bacteria are almost solely responsible for Mn-precipitation in rock varnish. A set of experiments involving Peruvian soil samples in contact with water-CO 2 solutions indicates that natural fogs or dews release Mn but not Fe when they come in contact with eolian materials on rock surfaces. This mechanism may efficiently provide Mn to bacteria on varnishing surfaces. The lack of Fe in solution suggests that a large but unknown proportion of Fe in varnish may be in the form of insoluble Fe oxyhydroxides sorbed onto the clay minerals that form the bulk of rock varnish. The results of this study do not substantively change R. I. Dorn's paleoenvironmental interpretations of varnish Mn:Fe ratios, but they do suggest areas for further inquiry.

The earliest Lunar Magma Ocean differentiation recorded in Fe isotopes

NASA Astrophysics Data System (ADS)

Wang, Kun; Jacobsen, Stein B.; Sedaghatpour, Fatemeh; Chen, Heng; Korotev, Randy L.

2015-11-01

Recent high-precision isotopic measurements show that the isotopic similarity of Earth and Moon is unique among all known planetary bodies in our Solar System. These observations provide fundamental constraints on the origin of Earth-Moon system, likely a catastrophic Giant Impact event. However, in contrast to the isotopic composition of many elements (e.g., O, Mg, Si, K, Ti, Cr, and W), the Fe isotopic compositions of all lunar samples are significantly different from those of the bulk silicate Earth. Such a global Fe isotopic difference between the Moon and Earth provides an important constraint on the lunar formation - such as the amount of Fe evaporation as a result of a Giant Impact origin of the Moon. Here, we show through high-precision Fe isotopic measurements of one of the oldest lunar rocks (4.51 ± 0.10 Gyr dunite 72 415), compared with Fe isotope results of other lunar samples from the Apollo program, and lunar meteorites, that the lunar dunite is enriched in light Fe isotopes, complementing the heavy Fe isotope enrichment in other lunar samples. Thus, the earliest olivine accumulation in the Lunar Magma Ocean may have been enriched in light Fe isotopes. This new observation allows the Fe isotopic composition of the bulk silicate Moon to be identical to that of the bulk silicate Earth, by balancing light Fe in the deep Moon with heavy Fe in the shallow Moon rather than the Moon having a heavier Fe isotope composition than Earth as a result of Giant Impact vaporization.

The Miniaturized Raman System and Detection of Traces of Life in Halite from the Atacama Desert: Some Considerations for the Search for Life Signatures on Mars

PubMed Central

Jehlička, Jan; Edwards, Howell G.M.; Hutchinson, Ian; Ascaso, Carmen; Wierzchos, Jacek

2012-01-01

Abstract Raman spectroscopy is being adopted as a nondestructive instrumentation for the robotic exploration of Mars to search for traces of life in the geological record. Here, miniaturized Raman spectrometers of two different types equipped with 532 and 785 nm lasers for excitation, respectively, were compared for the detection of microbial biomarkers in natural halite from the hyperarid region of the Atacama Desert. Measurements were performed directly on the rock as well as on the homogenized, powdered samples prepared from this material—the effects of this sample preparation and the excitation wavelength employed in the analysis are compared and discussed. From these results, 532 nm excitation was found to be superior for the analysis of powdered specimens due to its high sensitivity toward carotenoids and hence a higher capability for their detection at relatively low concentration in bulk powdered specimens. For the same reason, this wavelength was a better choice for the detection of carotenoids in direct measurements made on the rock samples. The 785 nm excitation wavelength, in contrast, proved to be more sensitive toward the detection of scytonemin. Key Words: Miniaturized portable Raman—Atacama—Mars—Biomarker detection. Astrobiology 12, 1095–1099. PMID:23151300

X-Ray Amorphous Phases in Terrestrial Analog Volcanic Sediments: Implications for Amorphous Phases in Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Smith, R. J.; Horgan, B.; Rampe, E.; Dehouck, E.; Morris, R. V.

2017-01-01

X-ray diffraction (XRD) amorphous phases have been found as major components (approx.15-60 wt%) of all rock and soil samples measured by the CheMin XRD instrument in Gale Crater, Mars. The nature of these phases is not well understood and could be any combination of primary (e.g., glass) and secondary (e.g., allophane) phases. Amorphous phases form in abundance during surface weathering on Earth. Yet, these materials are poorly characterized, and it is not certain how properties like composition and structure change with formation environment. The presence of poorly crystalline phases can be inferred from XRD patterns by the appearance of a low angle rise (< or approx.10deg 2(theta)) or broad peaks in the background at low to moderate 2(theta) angles (amorphous humps). CheMin mineral abundances combined with bulk chemical composition measurements from the Alpha Particle X-ray Spectrometer (APXS) have been used to estimate the abundance and composition of the XRD amorphous materials in soil and rock samples on Mars. Here we apply a similar approach to a diverse suite of terrestrial samples - modern soils, glacial sediments, and paleosols - in order to determine how formation environment, climate, and diagenesis affect the abundance and composition of X-ray amorphous phases.

Chemical and Sr isotopic characterization of North America uranium ores: Nuclear forensic applications

DOE PAGES

Balboni, Enrica; Jones, Nina; Spano, Tyler; ...

2016-08-31

This study reports major, minor, and trace element data and Sr isotope ratios for 11 uranium ore (uraninite, UO 2+x) samples and one processed uranium ore concentrate (UOC) from various U.S. deposits. The uraninite investigated represent ores formed via different modes of mineralization (e.g., high- and low-temperature) and within various geological contexts, which include magmatic pegmatites, metamorphic rocks, sandstone-hosted, and roll front deposits. In situ trace element data obtained by laser ablation-ICP-MS and bulk sample Sr isotopic ratios for uraninite samples investigated here indicate distinct signatures that are highly dependent on the mode of mineralization and host rock geology. Relativemore » to their high-temperature counterparts, low-temperature uranium ores record high U/Th ratios (>1000), low total rare earth element (REE) abundances (<1 wt%), high contents (>300 ppm) of first row transition metals (Sc, Ti, V, Cr, Mn, Co, Ni), and radiogenic 87Sr/ 86Sr ratios (>0.7200). Comparison of chondrite normalized REE patterns between uraninite and corresponding processed UOC from the same locality indicates identical patterns at different absolute concentrations. Lastly, this result ultimately confirms the importance of establishing geochemical signatures of raw, uranium ore materials for attribution purposes in the forensic analysis of intercepted nuclear materials.« less

Chemical and Sr isotopic characterization of North America uranium ores: Nuclear forensic applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balboni, Enrica; Jones, Nina; Spano, Tyler

This study reports major, minor, and trace element data and Sr isotope ratios for 11 uranium ore (uraninite, UO 2+x) samples and one processed uranium ore concentrate (UOC) from various U.S. deposits. The uraninite investigated represent ores formed via different modes of mineralization (e.g., high- and low-temperature) and within various geological contexts, which include magmatic pegmatites, metamorphic rocks, sandstone-hosted, and roll front deposits. In situ trace element data obtained by laser ablation-ICP-MS and bulk sample Sr isotopic ratios for uraninite samples investigated here indicate distinct signatures that are highly dependent on the mode of mineralization and host rock geology. Relativemore » to their high-temperature counterparts, low-temperature uranium ores record high U/Th ratios (>1000), low total rare earth element (REE) abundances (<1 wt%), high contents (>300 ppm) of first row transition metals (Sc, Ti, V, Cr, Mn, Co, Ni), and radiogenic 87Sr/ 86Sr ratios (>0.7200). Comparison of chondrite normalized REE patterns between uraninite and corresponding processed UOC from the same locality indicates identical patterns at different absolute concentrations. Lastly, this result ultimately confirms the importance of establishing geochemical signatures of raw, uranium ore materials for attribution purposes in the forensic analysis of intercepted nuclear materials.« less

The composition of secondary amorphous phases under different environmental conditions

NASA Astrophysics Data System (ADS)

Smith, R.; Rampe, E. B.; Horgan, B. H. N.; Dehouck, E.; Morris, R. V.

2017-12-01

X-ray diffraction (XRD) patterns measured by the CheMin instrument on the Mars Science Laboratory Curiosity rover demonstrate that amorphous phases are major components ( 15-60 wt%) of all rock and soil samples in Gale Crater. The nature of these phases is not well understood and could be any combination of primary (e.g., glass) and secondary (e.g., silica, ferrihydrite) phases. Secondary amorphous phases are frequently found as weathering products in soils on Earth, but these materials remain poorly characterized. Here we study a diverse suite of terrestrial samples including: sediments from recently de-glaciated volcanoes (Oregon), modern volcanic soils (Hawaii), and volcanic paleosols (Oregon) in order to determine how formation environment, climate, and diagenesis affect the abundance and composition of amorphous phases. We combine bulk XRD mineralogy with bulk chemical compositions (XRF) to calculate the abundance and bulk composition of the amorphous materials in our samples. We then utilize scanning transmission electron microscopy (STEM) and energy dispersive x-ray spectroscopy (EDS) to study the composition of individual amorphous phases at the micrometer scale. XRD analyses of 8 samples thus far indicate that the abundance of amorphous phases are: modern soils (20-80 %) > paleosols (15-40 %) > glacial samples (15-30 %). Initial calculations suggest that the amorphous components consist primarily of SiO2, Al2O3, TiO2, FeO and Fe2O3, with minor amounts of other oxides (e.g., MgO, CaO, Na2O). Compared to their respective crystalline counterparts, calculations indicate bulk amorphous components enriched in SiO2 for the glacial sample, and depleted in SiO2 for the modern soil and paleosol samples. STEM analyses reveal that the amorphous components consist of a number of different phases. Of the two samples analyzed using STEM thus far, the secondary amorphous phases have compositions with varying ratios of SiO2, Al2O3, TiO2, and Fe-oxides, consistent with mass balance calculation results, but inconsistent with well-known amorphous phase compositions (e.g., allophane, ferrihydrite). These results show that a number of secondary amorphous phases can form within a single soil environment. Continued analysis can help determine whether compositional trends can be linked to environmental factors.

Thermo-hydro-mechanical coupling in long-term sedimentary rock response

NASA Astrophysics Data System (ADS)

Makhnenko, R. Y.; Podladchikov, Y.

2017-12-01

Storage of nuclear waste or CO2 affects the state of stress and pore pressure in the subsurface and may induce large thermal gradients in the rock formations. In general, the associated coupled thermo-hydro-mechanical effect on long-term rock deformation and fluid flow have to be studied. Principles behind mathematical models for poroviscoelastic response are reviewed, and poroviscous model parameter, the bulk viscosity, is included in the constitutive equations. Time-dependent response (creep) of fluid-filled sedimentary rocks is experimentally quantified at isotropic stress states. Three poroelastic parameters are measured by drained, undrained, and unjacketed geomechanical tests for quartz-rich Berea sandstone, calcite-rich Apulian limestone, and clay-rich Jurassic shale. The bulk viscosity is calculated from the measurements of pore pressure growth under undrained conditions, which requires time scales 104 s. The bulk viscosity is reported to be on the order of 1015 Pa•s for the sandstone, limestone, and shale. It is found to be decreasing with the increase of pore pressure despite corresponding decrease in the effective stress. Additionally, increase of temperature (from 24 ºC to 40 ºC) enhances creep, where the most pronounced effect is reported for the shale with bulk viscosity decrease by a factor of 3. Viscous compaction of fluid-filled porous media allows a generation of a special type of fluid flow instability that leads to formation of high-porosity, high-permeability domains that are able to self-propagate upwards due to interplay between buoyancy and viscous resistance of the deforming porous matrix. This instability is known as "porosity wave" and its formation is possible under conditions applicable to deep CO2 storage in reservoirs and explains creation of high-porosity channels and chimneys. The reported experiments show that the formation of high-permeability pathways is most likely to occur in low-permeable clay-rich materials (caprock representatives) at elevated temperatures.

Oxygen-Carbon and Strontium Isotope Evidence for the Origin and Evolution of CO2-rich Volatiles from Oligocene to Miocene Mantle Magmas, Southwestern Colorado and Northwestern New Mexico

NASA Astrophysics Data System (ADS)

Gonzales, D. A.; Zbrozek, M.

2012-12-01

Oligocene to Miocene, alkaline mafic to ultramafic, rocks that are exposed in the Navajo volcanic field and dikes on the northern San Juan basin (NVSJ) contain calcite in vugs, veins, and breccias. Oxygen-carbon and Sr isotope signatures of bulk carbonate samples from these rocks were used to test hypotheses on the history of volatiles related to this pulse of mantle magmatism. Elevated fluorine in rocks, and fluorite-calcite breccias in some outcrops, indicate that magmatic volatiles were released by NVSJ melts. Oxygen and carbon isotope data for carbonate samples record a complex paragenetic history. δ13C values are mostly -8‰ to -4‰ with a mean value of -5.3 ± 2.0‰, similar to δ13C for primary mantle-derived carbonate. A subset of δ18O values are +5‰ to +10‰ which are within the accepted range of δ18O values for magmatic carbonate in carbonatite and kimberlite. A majority of δ18O values, however, range from +10‰ to +24‰ revealing that low-δ18O magmatic volatiles were overprinted by processes that caused enrichment of 18O at some stage during melt generation and emplacement. A subset of 87Sr/86Sri data from carbonate samples are nearly identical to 87Sr/86Sri for related rocks, hinting that the melts and volatiles came from the same source. Generally, NVSJ calcite samples have higher 87Sr/86Sri ratios than those of rocks, reflecting different melt-volatile sources or crustal contamination from Paleozoic limestone. Field and petrologic evidence does not lend convincing support for crustal contamination. Limestone fragments comprise less than 1% of xenoliths in NVSJ rocks. Also, rock samples do not show elevated CaO, MgO, FeO, Ba or Sr with increasing δ18O calcite which is expected for contamination of magmas with limestone. We propose that CO2-H2O-F volatiles in NVSJ magmas came from distinct melt-volatile sources, similar to the interpretation of Nowell (1993). Our assertion is that CO2-rich volatiles that exsolved from low δ18O mafic melts interacted with volatiles and melts from carbonate-bearing metasomatized lithospheric mantle. This is consistent with the subtle increase of 87Sr/86Sri rock and fluorine over the +6‰ to +24‰ range of δ18Ocalcite values recorded in minette samples. This hypothesis is supported by other studies that document +21‰ to +25‰ δ18O for carbonate in mantle xenoliths from Pliocene alkaline basalts in the region. Incipient to extensive alteration of olivine and phlogopite phenocrysts in NVSJ rocks reveals that deuteric isotopic exchange with H2O-CO2 magmatic fluids was a plausible factor for some of the variation in δ18O of calcite samples. In addition, melt contamination with limestone cannot be ruled out, but it requires nearly complete digestion of xenoliths in feeder dikes that had relatively low volumes of magma and cooled quickly. Overall, the isotope data combined with field and petrologic results are not consistent with models that invoke groundwater as the main source of volatiles in NVSJ magmas.

Initial report of the physical property measurement, ChikyuOman core description Phase I: sheeted dike and gabbro boundary from ICDP Holes GT1A, GT2A and GT3A

NASA Astrophysics Data System (ADS)

Abe, N.; Okazaki, K.; Hatakeyama, K.; Ildefonse, B.; Leong, J. A. M.; Tateishi, Y.; Teagle, D. A. H.; Takazawa, E.; Kelemen, P. B.; Michibayashi, K.; Coggon, J. A.; Harris, M.; de Obeso, J. C.

2017-12-01

We report results on the physical property measurements of the core samples from ICDP Holes GT1A, GT2A and GT3A drilled at Samail Ophiolite, Sultanate of Oman. Cores from Holes GT1A and GT2A in the lower crust section are mainly composed of gabbros (gabbro and olivine gabbro), and small amounts of ultramafic rocks (wehrlite and dunite), while cores from Hole GT3A at the boundary between sheeted dikes and gabbro are mainly composed of basalt and diabase, followed by gabbros (gabbro, olivine gabbro and oxide gabbro), and less common felsic dikes, trondhjemite and tonalite, intrude the mafic rocks. Measurements of physical properties were undertaken to characterize recovered core material. Onboard the Drilling Vessel Chikyu, whole-round measurements included X-ray CT image, natural gamma radiation, and magnetic susceptibility for Leg 1, and additional P-wave velocity, gamma ray attenuation density, and electrical resistivity during Leg 2. Split-core point magnetic susceptibility and color spectroscopy were measured for all core sections. P-wave velocity, bulk/grain density and porosity of more than 500 discrete cube samples, and thermal conductivity on more than 240 pieces from the working half of the split core sections were also measured. Physical Properties of gabbroic rocks from Holes GT1A and GT2A are similar to typical oceanic gabbros from ODP and IODP expeditions at Atlantis Bank, Southwestern Indian Ridge (ODP Legs 118, 176 and 179; IODP Exp 360) and at Hess Deep, Eastern Pacific (ODP Leg 147 and IODP Exp. 345). Average P-wave velocity, bulk density, grain density, porosity and thermal conductivity are 6.7 km/s, 2.92 g/cm^3, 2.93 g/cm^3, 0.98% and 2.46 W/m/K, respectively. P-wave velocity of samples from all three holes is inversely correlated with porosity. No clear correlation between the original lithology and physical properties is observed. GT3A cores show a wider range (e.g., Vp from 2.2 to 7.1 km/s) of values for the measured physical properties, compared to gabbros from Holes GT1A and GT2A.

Inferences from Microfractures and Geochemistry in Dynamic Shale-CO2 Packed Bed Experiments

NASA Astrophysics Data System (ADS)

Radonjic, M.; Olabode, A.

2016-12-01

Subsurface storage of large volumes of carbondioxide (CO2) is expected to have long term rock-fluid interactions impact on reservoir and seal rocks properties. Caprocks, particularly sedimentary types, are the ultimate hydraulic barrier in carbon sequestration. The mineralogical components of sedimentary rocks are geochemically active under enormous earth stresses, which generate high pressure and temperature conditions. It has been postulated that in-situ mineralization can lead to flow impedance in natural fractures in the presence of favorable geochemical and thermodynamic conditions. This experimental modelling research investigated the impact of in-situ geochemical precipitation on conductivity of fractures. Geochemical analyses were performed on four different samples of shale rocks, effluent fluids and recovered precipitates both before and after CO2-brine flooding of crushed shale rocks at moderately high temperature and pressure conditions. The results showed that most significant diagenetic changes in shale rocks after flooding with CO2-brine, reflected in the effluent fluid with predominantly calcium based minerals dissolving and precipitating under experimental conditions. Major and trace elements in the effluent (using ICP-OES analysis) indicated that multiple geochemical reactions are occurring with almost all of the constituent minerals participating. The geochemical composition of precipitates recovered after the experiments showed diagenetic carbonates and opal as the main constituents. The bulk rock showed little changes in composition except for sharper and more refined peaks on XRD analysis, suggesting that a significant portion of the amorphous content of the rocks have been removed via dissolution by the slightly acid CO2-brine fluid that was injected. Micro-indentation results captured slight reduction in the hardness of the shale rocks and this reduction appeared dependent on diagenetic quartz content. It can be inferred that convective reactive transport of dissolved minerals are involved in nanoscale precipitation-dissolution processes in shale. This reactive transport of dissolved minerals can occlude micro-fracture flow paths, thereby improving shale caprock seal integrity with respect to leakage risk under CO2 sequestration conditions.

The magmatic evolution and genesis of the Quaternary basanite-trachyphonolite suite of Itasy (Madagascar) as inferred by geochemistry, Sr-Nd-Pb isotopes and trace element distribution in coexisting phases

NASA Astrophysics Data System (ADS)

Melluso, L.; Tucker, R. D.; Cucciniello, C.; le Roex, A. P.; Morra, V.; Zanetti, A.; Rakotoson, R. L.

2018-06-01

The Itasy is a Pleistocene-Holocene volcanic field in central Madagascar, located to the west of the Ankaratra volcanic complex. It comprises scoria cones and lava domes (>120), with associated pyroclastic fall and mafic lava flows, covering an area of ab. 400 km2. The last volcanic episodes probably dated ca. 6000-7100 y BP; warm springs and geysers are active. The juvenile samples comprise a peculiar, almost bimodal, rock suite ranging from potassic leucite-kaersutite-bearing basanites, tephrites and phonotephrites, to benmoreites and titanite-haüyne-bearing trachyphonolites (MgO from 9-10 wt% to 0.1 wt%). These rocks show continuous and overlapping variations in the bulk-rock and phase composition (olivine, clinopyroxene, amphibole, feldspar, leucite, haüyne, nepheline, oxides, apatite, titanite, glass and other accessories). The basanites have homogeneous isotopic composition (87Sr/86Sr = 0.70366-0.70378, 143Nd/144Nd = 0.51274-0.51277, 206Pb/204Pb = 18.7-18.9, 207Pb/204Pb = 15.53-15.56; 208Pb/204Pb = 38.89-39.01), and a marked enrichment in the most incompatible elements (LILE and HFSE reach 100-215 times primitive mantle). These features are consistent with low degrees of partial melting of a volatile-, LILE- and HFSE-rich, amphibole-bearing peridotitic mantle induced by uplift during an E-W-directed extensional regime, as is found in central Madagascar. The marked changes in the geochemical composition, and small variations of the Sr-Nd-Pb isotopes in the trachyphonolites (87Sr/86Sr = 0.70425-0.70446, 143Nd/144Nd = 0.51266-0.51269, 206Pb/204Pb = 18.18-18.39, 207Pb/204Pb = 15.49-15.51; 208Pb/204Pb = 38.38-39.57) with respect to basanites and tephrites point to a limited amount of crustal contamination by the relatively low-206Pb/204Pb, low-143Nd/144Nd, high-87Sr/86Sr Precambrian basement rocks (of Middle Archean to Late Proterozoic age), and highlight the geochemical effects of titanite and anorthoclase removal on the trace element fractionation trends, a feature also shown in the trace element composition of the phenocrysts in trachyphonolites. Supplementary Table S2: synopsis of the mineral assemblages of the main lithotypes of the Itasy complex. Supplementary Table S3: composition of olivine of the Itasy rocks. Supplementary Table S4: composition of oxides of the Itasy rocks. Supplementary Table S5: composition of pyroxene of the Itasy rocks. Supplementary Table S6: composition of amphibole, biotite and rhönite of the Itasy rocks. Supplementary Table S7: composition of feldspar and glass of the Itasy rocks. Supplementary Table S8: composition of feldspathoids of the Itasy rocks. Supplementary Table S9: composition of titanite, apatite, other accessories of the Itasy rocks. Supplementary Table S10: Recapitulation of mass balance calculations between rocks of different degree of magmatic evolution, and detailed results. The composition of the phases is reported in the supplementary tables. Supplementary Table S11: average REE mineral/bulk rock ratios for titanite, amphibole and clinopyroxene. The partition coefficients of titanite, clinopyroxene, apatite and amphibole are taken from Olin and Wolff (2012), Fedele et al. (2009, 2015) and Tiepolo et al. (2007). Note that amphibole of RT-06I-355 could not be considered in equilibrium with the host rock (cf. Supplementary Figs. S1a, S1b, S1c).

Preliminary report on the coal resources of the National Petroleum Reserve in Alaska

USGS Publications Warehouse

Martin, G.C.; Callahan, J.E.

1978-01-01

NPR-A, located on the Arctic slope of Northern Alaska, is underlain by a thick sequence of sedimentary rocks of Cretaceous age which attain a thickness of as much as 4600 m (15,000 feet). The bulk of the coal resources occurs in rocks of the Nanushuk Group of Early and Late Cretaceous age. The Nanushuk Group is a wedge-shaped unit of marginal marine and nonmarine rocks that is as thick as 3300 m (11,000 feet) just west of NPR-A. Within the reserve, coal occurs primarily in the middle and thicker portions of this clastic wedge and occurs stratigraphically in the upper half of the section. Specific data on individual coal beds or zones are scarce, and estimates of identified coal resources of about 49.5 billion tons represent a sampling of coal resources too small to give a realistic indication of the potential resources for an area so large. Estimates of undiscovered resources suggest hypothetical resources of between 330 billion and 3.3 trillion tons. The wide range in the undiscovered resource estimates reflects the scarcity and ambiguity of the available data but also suggests the presence of a potentially large coal resource.

Characterization of Rock Types at Meridiani Planum, Mars using MER 13-Filter Pancam Spectra

NASA Technical Reports Server (NTRS)

Nuding, D. L.; Cohen, B. A.

2009-01-01

The Mars Exploration Rover Opportunity has traversed more than 13 km across Meridiani Planum, finding evidence of ancient aqueous environments that, in the past, may have been suitable for life. Meridiani bedrock along the rover traverse is a mixture in composition and bulk mineralogy between a sulfate-rich sedimentary rock and hematite spherules ("blueberries"). On top of the bedrock, numerous loose rocks exist. These rocks consist of both local bedrock and "cobbles" of foreign origin. The cobbles provide a window into lithologic diversity and a chance to understand other types of martian rocks and meteorites. This study was also an attempt to establish a method to expand upon those of Mini-TES to remotely identify rocks of interest to make efficient use of the rover s current resources.

Fabrication and convergent X-ray nanobeam diffraction characterization of submicron-thickness SrTiO 3 crystalline sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tilka, J. A.; Park, J.; Sampson, K. C.

The creation of thin SrTiO3 crystals from (001)-oriented SrTiO3 bulk single crystals using focused ion beam milling techniques yields sheets with submicron thickness and arbitrary orientation within the (001) plane. Synchrotron x-ray nanodiffraction rocking curve widths of these SrTiO3 sheets are less than 0.02 degrees, less than a factor of two larger than bulk SrTiO3, making these crystals suitable substrates for epitaxial thin film growth. The change in the rocking curve width is sufficiently small that we deduce that dislocations are not introduced into the SrTiO3 sheets. Observed lattice distortions are consistent with a low concentration of point defects.

Monte Carlo Analysis of Reservoir Models Using Seismic Data and Geostatistical Models

NASA Astrophysics Data System (ADS)

Zunino, A.; Mosegaard, K.; Lange, K.; Melnikova, Y.; Hansen, T. M.

2013-12-01

We present a study on the analysis of petroleum reservoir models consistent with seismic data and geostatistical constraints performed on a synthetic reservoir model. Our aim is to invert directly for structure and rock bulk properties of the target reservoir zone. To infer the rock facies, porosity and oil saturation seismology alone is not sufficient but a rock physics model must be taken into account, which links the unknown properties to the elastic parameters. We then combine a rock physics model with a simple convolutional approach for seismic waves to invert the "measured" seismograms. To solve this inverse problem, we employ a Markov chain Monte Carlo (MCMC) method, because it offers the possibility to handle non-linearity, complex and multi-step forward models and provides realistic estimates of uncertainties. However, for large data sets the MCMC method may be impractical because of a very high computational demand. To face this challenge one strategy is to feed the algorithm with realistic models, hence relying on proper prior information. To address this problem, we utilize an algorithm drawn from geostatistics to generate geologically plausible models which represent samples of the prior distribution. The geostatistical algorithm learns the multiple-point statistics from prototype models (in the form of training images), then generates thousands of different models which are accepted or rejected by a Metropolis sampler. To further reduce the computation time we parallelize the software and run it on multi-core machines. The solution of the inverse problem is then represented by a collection of reservoir models in terms of facies, porosity and oil saturation, which constitute samples of the posterior distribution. We are finally able to produce probability maps of the properties we are interested in by performing statistical analysis on the collection of solutions.

Extreme isotopic variations in the upper mantle: evidence from Ronda

NASA Astrophysics Data System (ADS)

Reisberg, Laurie; Zindler, Alan

1986-12-01

The Ronda Ultramafic Complex in southern Spain represents a piece of the Earth's mantle which has been tectonically emplaced into the crust. Nd and Sr isotopic analyses are presented for leached, hand-picked Cr-diopside separates prepared from 15 rock and 18 river sediment samples from Ronda. These results demonstrate that within this small, contiguous body there exists the entire range of Nd isotopic compositions, and much of the range of Sr compositions, found in rocks derived from the sub-oceanic mantle. The sediment cpx samples show that the average isotopic composition of the massif becomes progressively less "depleted" moving from SW to NE along the long axis of the massif. The rock cpx samples document 143Nd/ 144Nd variations from 0.5129 to 0.5126 and 87Sr/ 86Sr variations from 0.7031 to 0.7039 within a uniform outcrop less than 10 m in extent. Thus, extreme isotopic fluctuations exist over a wide range of wavelengths. Sr and Nd isotopes are generally inversely correlated, forming a trend on a Nd-Sr diagram that sharply crosscuts that of the "mantle array". Many of the 143Nd/ 144Nd values, and all of the Sm/Nd values, from one section of the massif are lower than that SCV015SCV0 of the bulk earth, implying that this region existed, or was influenced by a component which existed, in a LREE-enriched environment for a significant period of time. Among the sediment cpxs there is a positive correlation between 143Nd/ 144Nd and 147Sm/ 144Nd. The rock cpx separates display considerably more scatter. A simple, single-stage differentiation event starting with a uniform mantle source cannot explain these results. At least one episode of mixing with a LREE-enriched component is required. If these results from Ronda are typical of the upper mantle, basalts with different isotopic compositions need not derive from spatially separated mantle sources.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kayzar, Theresa M.; Villa, Adam C.; Lobaugh, Megan L.

The uranium concentrations and isotopic compositions of waters, sediment leachates and sediments from Red Rock Creek in the Stanislaus National Forest of California were measured to investigate the transport of uranium from a point source (the Juniper Uranium Mine) to a natural surface stream environment. Furthermore, we alter the (234U)/(238U) composition of Red Rock Creek downstream of the Juniper Mine. As a result of mine-derived contamination, water (234U)/(238U) ratios are 67% lower than in water upstream of the mine (1.114–1.127 ± 0.009 in the contaminated waters versus 1.676 in the clean branch of the stream), and sediment samples have activitymore » ratios in equilibrium in the clean creek and out of equilibrium in the contaminated creek (1.041–1.102 ± 0.007). Uranium concentrations in water, sediment and sediment leachates are highest downstream of the mine, but decrease rapidly after mixing with the clean branch of the stream. Uranium content and compositions of the contaminated creek headwaters relative to the mine tailings of the Juniper Mine suggest that uranium has been weathered from the mine and deposited in the creek. The distribution of uranium between sediment surfaces (leachable fraction) and bulk sediment suggests that adsorption is a key element of transfer along the creek. In clean creek samples, uranium is concentrated in the sediment residues, whereas in the contaminated creek, uranium is concentrated on the sediment surfaces (~70–80% of uranium in leachable fraction). Furthermore, contamination only exceeds the EPA maximum contaminant level (MCL) for drinking water in the sample with the closest proximity to the mine. Isotopic characterization of the uranium in this system coupled with concentration measurements suggest that the current state of contamination in Red Rock Creek is best described by mixing between the clean creek and contaminated upper branch of Red Rock Creek rather than mixing directly with mine sediment.« less

Thallium isotope variations in an ore-bearing continental igneous setting: Collahuasi Formation, northern Chile

NASA Astrophysics Data System (ADS)

Baker, R. G. A.; Rehkämper, M.; Ihlenfeld, C.; Oates, C. J.; Coggon, R.

2010-08-01

Thallium is a highly incompatible element and a large fraction of the bulk silicate Earth Tl budget is, therefore, expected to reside in the continental crust. Nonetheless, the Tl isotope systematics of continental rocks are essentially unexplored at present. Here, we present new Tl isotope composition and concentration data for a suite of 36 intrusive and extrusive igneous rocks from the vicinity of porphyry Cu deposits in the Collahuasi Formation of the Central Andes in northern Chile. The igneous lithologies of the rocks are variably affected by the hydrothermal alteration that accompanied the formation of the Cu deposits. The samples display Tl concentrations that vary by more than an order of magnitude, from 0.1 to 3.2 μg/g, whilst ɛ 205Tl ranges between -5.1 and +0.1 (ɛ 205Tl is the deviation of the 205Tl/ 203Tl isotope ratio of a sample from a standard in parts per 10 4). These variations are primarily thought to be a consequence of hydrothermal alteration processes, including metasomatic transport of Tl, and formation/breakdown of Tl-bearing minerals, which are associated with small but significant Tl isotope effects. The Tl abundances show excellent correlations with both K and Rb concentrations but no co-variation with Cu. This demonstrates that Tl displays only limited chalcophile affinity in the continental crust of the Collahuasi Formation, but behaves as a lithophile element with a distribution that is primarily governed by partitioning of Tl + into K +-bearing phases. Collahuasi samples with propylitic alteration features, which are derived from the marginal parts of the hydrothermal systems, have, on average, slightly lighter Tl isotope compositions than rocks from the more central sericitic and argillic alteration zones. This small but statistically significant difference most likely reflects preferential retention of isotopically heavy Tl in alteration phases, such as white micas and clays, which formed during sericitic and argillic alteration.

A mineralogical perspective on the recovery of platinum group elements from Merensky Reef and UG2 at the Two Rivers mine on the Eastern limb of the Bushveld Complex in South Africa

NASA Astrophysics Data System (ADS)

Rose, Derek H.; Viljoen, K. S.; Mulaba-Bafubiandi, Antoine

2018-06-01

Published studies dealing with the process mineralogy of Pt mines on the Bushveld Complex is generally limited to the Western Bushveld. The recognition by mine management that another resource, in addition to the Upper Group 2 (UG2) reef currently being mined at the Two Rivers platinum mine (TRP), is urgently required in order to extend the life of mine, presented an opportunity to conduct such a study on the Eastern Limb of the Bushveld Complex. A process mineralogical investigation was undertaken on ore from the Merensky Reef (MR) and the UG2 at TRP. This was conducted on a suite of geological samples (channel samples) collected from the underground workings, as well as metallurgical samples obtained from the rougher circuits at the concentrator plant during the processing of MR and UG2 ore. The geological and metallurgical samples were analysed for bulk composition and quantitative mineralogy, while the geological samples were also subjected to laboratory-scale milling and flotation tests. This study shows that, although mineralogically distinct, the MR and UG2 behave similarly in terms of metallurgical performance. This holds promise for the proposed blending of MR and UG2 ores at TRP. An evaluation of the bulk rock (ore) Pt/Pd ratio as a possible indicator of the level of hydrothermal alteration of the ore, demonstrates that this may be of use in predicting recovery plant performance.

Elemental depletions in Antarctic micrometeorites and Arctic cosmic spherules: Comparison and relationships

NASA Technical Reports Server (NTRS)

Presper, T.; Kurat, G.; Koeberl, C.; Palme, H.; Maurette, Michel

1993-01-01

Antarctic micrometeorites (MM's) and Arctic cosmic spherules (CS's) have bulk compositions comparable to those of chondritic meteorites. However, abundance of Na, Ca, Mn, Ni, Co, and S are commonly lower in MM's and CS's as compared to chondrites. Our SEM, EMP, and INAA studies suggest that these elemental depletions in unmelted MM's are likely to be due to leaching of soluble components from the MM's in the upper atmosphere and the melt ice water. Depletions in CS's appear to be mainly due to volatilization during melting in the atmosphere or to sampling bias during aggregate formation or parent rock break-up.

SM-ND Age and REE Systematics of Larkman Nunatek 06319: Closed System Fractional Crystallization of a Shergottite Magma

NASA Technical Reports Server (NTRS)

Shafer, J. T.; Brandon, A. D.; Lapen T. J.; Righter, M.; Peslier, A. H.

2010-01-01

Sm-Nd isotopic data were collected on mineral separates and bulk rock powders of LAR 06319, yielding an age of 180+/-13 Ma (2(sigma)). This age is concordant with the Lu-Hf age (197+/-29 Ma, [1]) determined in conjunction with these data and the Sm-Nd age (190+/-26 Ma) of Shih et al., 2009 [2]. The Sm-Nd data form at statistically significant isochron (Fig. 1) that is controlled largely by leachate-residue pairs (samples with the R suffix are residues after leaching in cold 2N HCl for 10 minutes).

Noble metals in ferromanganese crusts from marginal seas of the Northwest Pacific

NASA Astrophysics Data System (ADS)

Astakhova, N. V.

2017-07-01

Based on data on the concentration of noble metals (Au, Ag, Pt, Os, Ir, and Ru) in bulk samples of ferromanganese crusts, the presence of inclusions of micro- and nanosized grains of Ag, Au, Pd, and Pt, often with impurities of other elements, as well as their chaotic distribution, three sources of incorporation of these metals into ore crusts of Far Eastern seas are suggested: seawater, postvolcanic gas-hydrothermal fluids, and hydrothermal plumes. The presence of grains of platinoids and gold in ferromanganese crusts on only some mounts may result from peculiarities in the formation of volcanic rocks on the ancient continental basement.

Calculating Effective Elastic Properties of Berea Sandstone Using Segmentation-less Method without Targets

NASA Astrophysics Data System (ADS)

Ikeda, K.; Goldfarb, E. J.; Tisato, N.

2017-12-01

Digital rock physics (DRP) allows performing common laboratory experiments on numerical models to estimate, for example, rock hydraulic permeability. The standard procedure of DRP involves turning a rock sample into a numerical array using X-ray micro computed tomography (micro-CT). Each element of the array bears a value proportional to the X-ray attenuation of the rock at the element (voxel). However, the traditional DRP methodology, which includes segmentation, over-predicts rock moduli by significant amounts (e.g., 100%). Recently, a new methodology - the segmentation-less approach - has been proposed leading to more accurate DRP estimate of elastic moduli. This new method is based on homogenization theory. Typically, segmentation-less approach requires calibration points from known density objects, known as targets. Not all micro-CT datasets have these reference points. Here, we describe how we perform segmentation- and target-less DRP to estimate elastic properties of rocks (i.e., elastic moduli), which are crucial parameters to perform subsurface modeling. We calculate the elastic properties of a Berea sandstone sample that was scanned at a resolution of 40 microns per voxel. We transformed the CT images into density matrices using polynomial fitting curve with four calibration points: the whole rock, the center of quartz grains, the center of iron oxide grains, and the center of air-filled volumes. The first calibration point is obtained by assigning the density of the whole rock to the average of all CT-numbers in the dataset. Then, we locate the center of each phase by finding local extrema point in the dataset. The average CT-numbers of these center points are assigned the density equal to either pristine minerals (quartz and iron oxide) or air. Next, density matrices are transformed to porosity and moduli matrices by means of an effective medium theory. Finally, effective static bulk and shear modulus are numerically calculated by using a Matlab code derived from the elas3D NIST code. The calculated quasi-static P- and S-wave speed overestimates the laboratory result by 37% and 5%, respectively. In fact, our approach predicts wave speeds more accurately than traditional DRP methods. Nevertheless, the presented methodology need to be further investigated and improved.

Redistribution of Iron and Titanium in High-Pressure Ultramafic Rocks

NASA Astrophysics Data System (ADS)

Crossley, Rosalind J.; Evans, Katy A.; Reddy, Steven M.; Lester, Gregory W.

2017-11-01

The redox state of iron in high-pressure serpentinites, which host a significant proportion of Fe3+ in subduction zones, can be used to provide an insight into iron cycling and constrain the composition of subduction zone fluids. In this study, we use oxide and silicate mineral textures, interpretation of mineral parageneses, mineral composition data, and whole rock geochemistry of high-pressure retrogressed ultramafic rocks from the Zermatt-Saas Zone to constrain the distribution of iron and titanium, and iron oxidation state. These data provide an insight on the oxidation state and composition of fluids at depth in subduction zones. Oxide minerals host the bulk of iron, particularly Fe3+. The increase in mode of magnetite and observation of magnetite within antigorite veins in the investigated ultramafic samples during initial retrogression is most consistent with oxidation of existing iron within the samples during the infiltration of an oxidizing fluid since it is difficult to reconcile addition of Fe3+ with the known limited solubility of this species. However, high Ti contents are not typical of serpentinites and also cannot be accounted for by simple mixing of a depleted mantle protolith with the nearby Allalin gabbro. Titanium-rich phases coincide with prograde metamorphism and initial exhumation, implying the early seafloor and/or prograde addition and late mobilization of Ti. If Ti addition has occurred, then the introduction of Fe3+, also generally considered to be immobile, cannot be disregarded. We explore possible transport vectors for Ti and Fe through mineral texture analysis.

Role of coupled cataclasis-pressure solution deformation in microearthquake activity along the creeping segment of the SAF: Inferences from studies of the SAFOD core samples

NASA Astrophysics Data System (ADS)

Hadizadeh, J.; Gratier, J.; Renard, F.; Mittempregher, S.; di Toro, G.

2009-12-01

Rocks encountered in the SAFOD drill hole represent deformation in the southern-most extent of the creeping segment of the SAF north of the Parkfield. At the site and toward the northwest the SAF is characterized by aseismic creep as well as strain release through repeating microearthquakes M<3. The activity is shown to be mostly distributed as clusters aligned in the slip direction, and occurring at depths of between 3 to 5 kilometers. It has been suggested that the events are due to frequent moment release from high strength asperities constituting only about 1% or less of the total fault surface area within an otherwise weak fault gouge. We studied samples selected from the SAFOD phase 3 cores (3142m -3296m MD) using high resolution scanning electron microscopy, cathodoluminescence imaging, X-ray fluorescence mapping, and energy dispersive X-ray spectroscopy. The observed microstructural deformation that is apparently relevant to the seismological data includes clear evidence of cyclic deformation events, cataclastic flow, and pressure solution creep with attendant vein sealing and fracture healing fabrics. Friction testing of drill cuttings and modeling by others suggest that the overall creep behavior in shale-siltstone gouge may be due to low bulk friction coefficient of 0.2-0.4 for the fault rock. Furthermore, the low resistivity zone extending to about 5km beneath the SAFOD-Middle Mountain area is believed to consist of a pod of fluid-filled fractured and porous rocks. Our microstructural data indicate that the foliated shale-siltstone cataclasites are, in a highly heterogeneous way, more porous and permeable than the host rock and therefore provide for structurally controlled enhanced fluid-rock interactions. This is consistent with the observed pressure solution deformation and the microstructural indications of transiently high fluid pressures. We hypothesize that while the friction laws defining stable sliding are prevalent in bulk deformation of the creeping segment, there exist the possibility of steady conditions for repetitive healing, dilation, and rupture of populations of stress-oriented patches due to operation of pressure solution creep along the fault zone. The limitation on the total area of the locked patches at any given time would be controlled primarily by the imposed tectonic and near field rates of slip and fluid flux within the local permeability structure. The available geophysical data for the creeping section of the SAF including hypocenter cluster distribution, moment release rate, seismic rupture area (∝ healed patch size), stress drop and return time characteristics point to a highly heterogeneous internal structure at the SAFOD site, and could be used to test the proposed coupled cataclasis-pressure solution microstructural model.

Rare earth element abundances in rocks and minerals from the Fiskenaesset Complex, West Greenland. [comparison with lunar anorthosites

NASA Technical Reports Server (NTRS)

Henderson, P.; Fishlock, S. J.; Laul, J. C.; Cooper, T. D.; Conard, R. L.; Boynton, W. V.; Schmitt, R. A.

1976-01-01

The paper reports activation-analysis determinations of rare-earth-element (REE) and other trace-element concentrations in selected rocks, plagioclase, and mafic separates from the Fiskenaesset Complex. The REE abundances are found to be very low and atypical in comparison with other terrestrial anorthosites. The plagioclases are shown to be characterized by a deficiency in heavy RE elements relative to light ones and a positive Eu anomaly, while the mafic separates are enriched in heavy rare earths and have no Eu anomaly, except in one sample. It is found that the bulk and trace-element abundances of the plagioclases are similar to those observed in some lunar anorthosites, but the degree of Eu anomaly is less in the plagioclases. The data are taken as confirmation of the idea that fractionation processes were involved in the origin of the Complex, and it is concluded that the Complex may have been produced from a magma generated by partial melting of a garnet-bearing source.

Petrology and geochemistry of feldspathic impact-melt breccia Abar al' Uj 012, the first lunar meteorite from Saudi Arabia

NASA Astrophysics Data System (ADS)

Mészáros, Marianna; Hofmann, Beda A.; Lanari, Pierre; Korotev, Randy L.; Gnos, Edwin; Greber, Nicolas D.; Leya, Ingo; Greenwood, Richard C.; Jull, A. J. Timothy; Al-Wagdani, Khalid; Mahjoub, Ayman; Al-Solami, Abdulaziz A.; Habibullah, Siddiq N.

2016-10-01

Abar al' Uj (AaU) 012 is a clast-rich, vesicular impact-melt (IM) breccia, composed of lithic and mineral clasts set in a very fine-grained and well-crystallized matrix. It is a typical feldspathic lunar meteorite, most likely originating from the lunar farside. Bulk composition (31.0 wt% Al2O3, 3.85 wt% FeO) is close to the mean of feldspathic lunar meteorites and Apollo FAN-suite rocks. The low concentration of incompatible trace elements (0.39 ppm Th, 0.13 ppm U) reflects the absence of a significant KREEP component. Plagioclase is highly anorthitic with a mean of An96.9Ab3.0Or0.1. Bulk rock Mg# is 63 and molar FeO/MnO is 76. The terrestrial age of the meteorite is 33.4 ± 5.2 kyr. AaU 012 contains a 1.4 × 1.5 mm2 exotic clast different from the lithic clast population which is dominated by clasts of anorthosite breccias. Bulk composition and presence of relatively large vesicles indicate that the clast was most probably formed by an impact into a precursor having nonmare igneous origin most likely related to the rare alkali-suite rocks. The IM clast is mainly composed of clinopyroxenes, contains a significant amount of cristobalite (9.0 vol%), and has a microcrystalline mesostasis. Although the clast shows similarities in texture and modal mineral abundances with some Apollo pigeonite basalts, it has lower FeO and higher SiO2 than any mare basalt. It also has higher FeO and lower Al2O3 than rocks from the FAN- or Mg-suite. Its lower Mg# (59) compared to Mg-suite rocks also excludes a relationship with these types of lunar material.

Magma genesis at Gale Crater: Evidence for Pervasive Mantle Metasomatism

NASA Astrophysics Data System (ADS)

Filiberto, J.

2017-12-01

Basaltic rocks have been analyzed at Gale Crater with a larger range in bulk chemistry than at any other landing site [1]. Therefore, the rocks may have experienced significantly different formation conditions than those experienced by magmas at Gusev Crater or Meridiani Planum. Specifically, the rocks at Gale Crater have higher potassium than other Martian rocks, with a potential analog of the Nakhlite parental magma, and are consistent with forming from a metasomatized mantle source [2-4]. Mantle metasomatism would not only affect the bulk chemistry but mantle melting conditions, as metasomatism fluxes fluids into the source region. Here I will combine differences in bulk chemistry between Martian basalts to calculate formation conditions in the interior and investigate if the rocks at Gale Crater experienced magma genesis conditions consistent with metasomatism - lower temperatures and pressures of formation. To calculate average formation conditions, I rely on experimental results, where available, and silica-activity and Mg-exchange thermometry calculations for all other compositions following [5, 6]. The results show that there is a direct correlation between the calculated mantle potential temperature and the K/Ti ratio of Gale Crater rocks. This is consistent with fluid fluxed metasomatism introducing fluids to the system, which depressed the melting temperature and fluxed K but not Ti to the system. Therefore, all basalts at Gale Crater are consistent with forming from a metasomatized mantle source, which affected not only the chemistry of the basalts but also the formation conditions. References: [1] Cousin A. et al. (2017) Icarus. 288: 265-283. [2] Treiman A.H. et al. (2016) Journal of Geophysical Research: Planets. 121: 75-106. [3] Treiman A.H. and Medard E. (2016) Geological Society of America Abstracts with Programs. 48: doi: 10.1130/abs/2016AM-285851. [4] Schmidt M.E. et al. (2016) Geological Society of America Abstracts with Programs. 48: doi: 10.1130/abs/2016AM-285651. [5] Filiberto J. and Dasgupta R. (2011) Earth and Planetary Science Letters. 304: 527-537. [6] Filiberto J. and Dasgupta R. (2015) Journal of Geophysical Research: Planets. 120: DOI: 10.1002/2014JE004745.

Ultrasonic Acoustic Velocities During Partial Melting of a Mantle Peridotite KLB-1

NASA Astrophysics Data System (ADS)

Weidner, Donald J.; Li, Li; Whitaker, Matthew L.; Triplett, Richard

2018-02-01

Knowledge of the elastic properties of partially molten rocks is crucial for understanding low-velocity regions in the interior of the Earth. Models of fluid and solid mixtures have demonstrated that significant decreases in seismic velocity are possible with small amounts of melt, but there is very little available data for testing these models, particularly with both P and S waves for mantle compositions. We report ultrasonic measurements of P and S velocities on a partially molten KLB-1 sample at mantle conditions using a multi-anvil device at a synchrotron facility. The P, S, and bulk sound velocities decrease as melting occurs. We find that the quantity, ∂lnVS/∂lnVB (where VB is the bulk sound velocity) is lower than mechanical models estimate. Instead, our data, as well as previous data in the literature, are consistent with a dynamic melting model in which melting and solidification interact with the stress field of the acoustic wave.

Constraints on the Parental Melts of Enriched Shergottites from Image Analysis and High Pressure Experiments

NASA Technical Reports Server (NTRS)

Collinet, M.; Medard, E.; Devouard, B.; Peslier, A.

2012-01-01

Martian basalts can be classified in at least two geochemically different families: enriched and depleted shergottites. Enriched shergottites are characterized by higher incompatible element concentrations and initial Sr-87/Sr-86 and lower initial Nd-143/Nd-144 and Hf-176/Hf-177 than depleted shergottites [e.g. 1, 2]. It is now generally admitted that shergottites result from the melting of at least two distinct mantle reservoirs [e.g. 2, 3]. Some of the olivine-phyric shergottites (either depleted or enriched), the most magnesian Martian basalts, could represent primitive melts, which are of considerable interest to constrain mantle sources. Two depleted olivine-phyric shergottites, Yamato (Y) 980459 and Northwest Africa (NWA) 5789, are in equilibrium with their most magnesian olivine (Fig. 1) and their bulk rock compositions are inferred to represent primitive melts [4, 5]. Larkman Nunatak (LAR) 06319 [3, 6, 7] and NWA 1068 [8], the most magnesian enriched basalts, have bulk Mg# that are too high to be in equilibrium with their olivine megacryst cores. Parental melt compositions have been estimated by subtracting the most magnesian olivine from the bulk rock composition, assuming that olivine megacrysts have partially accumulated [3, 9]. However, because this technique does not account for the actual petrography of these meteorites, we used image analysis to study these rocks history, reconstruct their parent magma and understand the nature of olivine megacrysts.

Evaluation of frictional melting on the basis of trace element analyses of fault rocks

NASA Astrophysics Data System (ADS)

Ishikawa, T.; Ujiie, K.

2016-12-01

Pseudotachylytes (solidified frictional melts produced during seismic slip) found in exhumed accretionary complexes are considered to have formed originally at seismogenic depths, and help our understanding of the dynamics of earthquake faulting in subduction zones. The frictional melting should affect rock chemistry. Actually, major element compositions of unaltered pseudotachylyte matrix in the Shimanto accretionary complex are reported to be similar to that of illite, implying disequilibrium melting in the slip zone (Ujiie et al., 2007). Bulk-rock trace element analyses of the pseudotachylyte-bearing fault rocks also revealed their shift to the clay-mineral-like compositions (Honda et al., 2011). Toward better understanding of the frictional melting using chemical means, we carried out detailed major and trace element analyses for pseudotachylyte-bearing dark veins and surrounding host rocks from the Mugi area of the Shimanto accretionary complex (Ujiie et al., 2007). About one milligram each of samples was collected from a rock chip along the microstructure by using the PC-controlled micro-drilling apparatus, and then analyzed by ICP-MS. Host rocks showed a series of compositional trends controlled by mixing of detrital sedimentary components. Unaltered part of the pseudotachylyte vein, on the other hand, showed striking enrichment of fluid-immobile trace elements, consistent with selective melting of fine-grained, clay-rich matrix of the fault rock. Importantly, completely altered parts of the dark veins exhibit essentially the same characteristics as the unaltered part, indicating that the trace element composition of the pseudotachylyte is well preserved even after considerable alteration in the later stages. These results demonstrate that trace element and structural analyses are useful to detect preexistence of pseudotachylytes resulting from selective frictional melting of clay minerals. It has been controversial that pseudotachylytes are rarely formed or rarely preserved. Trace element analyses on clay-rich localized slipping zones shed light on this topic. References: Ujiie et al. (2007) J. Struct. Geol. 29, 599-613; Honda et al. (2011) GRL 38, L06310.

Extremely magnetized abyssal lavas erupted in active back-arc of the Okinawa Trough

NASA Astrophysics Data System (ADS)

Fujii, M.; Sato, H.; Okino, K.

2017-12-01

Although high-amplitude of marine magnetic anomalies have been utilized for understanding for seafloor dynamics, the causal link between intensity of natural remanent magnetization and physical and chemical processes of extrusive rocks are still unclear. In addition, we essentially lack rock magnetic data of arc-back-arc lavas, which potentially provide strong constraints for understanding time- and spatial-dependent diversity of lava magnetization including mid-ocean ridge basalts. Here, we present new rock magnetic data of strongly magnetized basaltic rocks, which rank among the most magnetized in known oceanic basaltic rocks, from active back-arc region of the Okinawa Trough. We analyzed 27 non-oxidized (fresh) basaltic rock samples obtained from the active back-arc volcanoes, located at the segment boundary along back-arc rift. Their natural remanent magnetization ranges 7 A/m to >200 A/m, and has clear nonlinear relationship with both magnetic hysteresis signatures and titanomagnetite amount. The strongly magnetized lavas show large contribution of appropriate amount of SD titanomagnetite grains formed in proper crystal growth environments. The high-temperature thermomagnetic experiments demonstrate reversible curves in both heating and cooling with single Curie temperature. The Curie temperature shows up to 480°C for strongly magnetized lavas, which is much higher than that of mid-ocean ridge basalts mainly containing TM60, indicating that rich Fe and low Ti contents of titanomagnetite grains are main magnetic carrier. These observations clearly demonstrate that intensity of natural remanent magnetization is primarily controlled by cooling rate of lavas and ratio of Fe to Ti of titanomagnetite grains as well as bulk iron contents, with important implications towards marine magnetic anomalies and arc-back-arc volcanism.

Pre-Elsonian mafic magmatism in the Nain Igneous Complex, Labrador: the bridges layered intrusion

USGS Publications Warehouse

Ashwal, L.D.; Wiebe, R.A.; Wooden, J.L.; Whitehouse, M.J.; Snyder, Diane

1992-01-01

Decades of work on the pristine, unmetamorphosed, and well exposed anorthositic, mafic and granitic rocks of the Nain igneous complex, Labrador, have led to the conclusion that all plutonic rocks in that area were emplaced in a short time intercal at about 1300 ?? 10 Ma). We report here new isotopic data for mafic intrusive rocks that appear to have crystallized several hundred Ma earlier than the bulk of the plutonic activity in the Nain complex. The Bridges layered intrusion (BLI) is a small (15-20 km2) lens of layered mafic rocks about 1.5 km thick, surrounded and intruded by anorthositic, leuconoritic and leucotroctolitic plutons in the middle of the coastal section of the Nain igneous complex. BLI shows very well developed magmatic structures, including channel scours, slump structures, and ubiquitous modally graded layering. Most rocks, however, show granular textures indicative of recrystallization, presumably caused by emplacement of younger anorthositic rocks. BLI contains cumulate rocks with slightly more primitive mineral compositions (An60-83, Fo66-71) than those of other mafic intrusions in the Nain igneous complex, including Kiglapait. SmNd isotopic data for 7 BLI whole-rocks ranging in composition between olivine melagabbro and olivine leucogabbro yield an age of 1667 ?? 75 Ma, which we interpret as the time of primary crystallization. The internal isotopic systematics of the BLI have been reset, probably by intrusion of adjacent anorthositic plutons. A SmNd mineral isochron (plag, whole-rock, mafics) for a BLI olivine melagabbro gives an age of 1283 ?? 22 Ma, equivalent within error of a mineral array (plag, whole-rock, opx, cpx) for an adjacent, igneous-textured, leuconorite vein (1266 ?? 152 Ma). The initial Nd ratio for BLI corresponds to ??{lunate}Nd = -3.18 ?? 0.44. Other whole-rock samples, however, some with vein-like alteration (Chlorite, serpentine, amphiboles), show ??{lunate}Nd values as low as -9.1, suggesting variable contamination by direct assimilation of early Archean crustal rocks and/or by fluids that have interacted with such crust. Adjacent anorthositic rocks also show variable ??{lunate}Nd some as low as -14.7, implying larger degrees if crustal assimilation, perhaps by parental magmas during lower crustal ponding prior to emplacement. These contamination effects preclude straightforward determination of the isotopic character of mantle sources for both BLI and the anorthositic rocks. ?? 1992.

Lithium elemental and isotopic disequilibrium in minerals from peridotite xenoliths from far- east Russia: product of recent melt/fluid-rock reaction

NASA Astrophysics Data System (ADS)

Rudnick, R. L.; Ionov, D. A.

2006-12-01

Peridotite xenoliths from the Tok and Barhatny localities in far-east Russia are characterized by strong Li elemental and isotopic disequilibria caused by addition of Li to the rocks via diffusion from a small-volume grain boundary fluid or melt. Because Li diffuses rapidly at mantle temperatures, the disequilibrium is a transient feature and its preservation in these samples indicates that Li addition occurred shortly before or even during the entrainment of the xenoliths in the host basalts. δ&^{7}Licpx is consistently lower than that of coexisting olivines and Δ&^{7}Liol-cpx, which ranges from 2.8 to 22.9‰,correlates with bulk rock composition. The most refractory samples experienced the greatest overall Li addition and most closely approximate elemental and isotopic equilibrium due to longer equilibration times and probably also greater infiltration of the Li-bearing melt or fluid. The variable but often extreme isotopic compositions produced by this process (δ&^{7}Licpx down to -15 and δ&^{7}Liol up to +12) do not reflect the presence of an isotopically exotic recycled component, as has been previously inferred for xenoliths from this region. The best estimate for the δ&^{7}Li of the source of the Li in the Tok xenoliths is δ&^{7}Li = +1.4, which is identical to that of the host basalt. A single sample from the Koppy locality, which is situated closest to the paleo-Pacific subduction zone, shows both elemental and isotopic equilibration of Li and has a "normal" δ&^{7}Licpx of +3.5. The analytically identical δ&^{7}Li of olivine and cpx from this sample, coupled with its relatively low equilibration temperature of 990°C suggests that there is no discernible Li isotopic fractionation between coexisting minerals at mantle temperatures. This study highlights the very large isotopic effects that can be produced via kinetic fractionation in peridotite xenoliths at high temperatures and associated with host-rock xenolith interactions.

Granulite sulphides as tracers of lower crustal origin and evolution: An example from the Slave craton, Canada

NASA Astrophysics Data System (ADS)

Aulbach, Sonja; Krauss, Cristen; Creaser, Robert A.; Stachel, Thomas; Heaman, Larry M.; Matveev, Sergei; Chacko, Thomas

2010-09-01

We carried out a detailed study of sulphide minerals, a ubiquitous mineral group in lower crustal mafic to peraluminous granulite xenoliths from the Diavik kimberlites, to assess their use in constraining the origin and tectonothermal evolution of the deep crust, and to obtain additional data on the composition of lower crust beneath ancient continents. Sulphides are overwhelmingly pyrrhotite with minor Ni (0.7-3.9 at.%), Co (0.1-0.7 at.%), and Cu contents (0.4-3.9 at.%). Sulphide modes in mafic granulites range from 0.14 to 0.55 vol%, translating into bulk rock S contents from ˜600 to 2000 ppm, similar to S contents in other mafic igneous rocks and indicating preservation of primary igneous S contents. In mafic granulites, Re and Os abundances in sulphides range from 42.5 to 726 ppb and 3.2 to 180 ppb, respectively, whereas those in peraluminous granulites are distinctly lower (36.1-282 ppb and 1.8-7.2 ppb, respectively), suggestive of Re and Os loss to fractionating sulphides in the more evolved precursors of these rocks. The significant within-sample variability of 187Os/ 188Os and correlation with 187Re/ 188Os indicates the preservation of primary Re-Os isotope systematics and time-integrated decay of the measured 187Re. Within the large uncertainties inherent in the nature of the samples and technique, sulphides in some granulites may record major tectonothermal events in the central Slave craton spanning several billion years of evolution. Multiple generations of sulphide can occur in a single sample. These data attest to the heterogeneous composition and complex history of the Slave craton lower crust.

Stochastic multicomponent reactive transport analysis of low quality drainage release from waste rock piles: Controls of the spatial distribution of acid generating and neutralizing minerals

NASA Astrophysics Data System (ADS)

Pedretti, Daniele; Mayer, K. Ulrich; Beckie, Roger D.

2017-06-01

In mining environmental applications, it is important to assess water quality from waste rock piles (WRPs) and estimate the likelihood of acid rock drainage (ARD) over time. The mineralogical heterogeneity of WRPs is a source of uncertainty in this assessment, undermining the reliability of traditional bulk indicators used in the industry. We focused in this work on the bulk neutralizing potential ratio (NPR), which is defined as the ratio of the content of non-acid-generating minerals (typically reactive carbonates such as calcite) to the content of potentially acid-generating minerals (typically sulfides such as pyrite). We used a streamtube-based Monte-Carlo method to show why and to what extent bulk NPR can be a poor indicator of ARD occurrence. We simulated ensembles of WRPs identical in their geometry and bulk NPR, which only differed in their initial distribution of the acid generating and acid neutralizing minerals that control NPR. All models simulated the same principal acid-producing, acid-neutralizing and secondary mineral forming processes. We show that small differences in the distribution of local NPR values or the number of flow paths that generate acidity strongly influence drainage pH. The results indicate that the likelihood of ARD (epitomized by the probability of occurrence of pH< 4 in a mixing boundary) within the first 100 years can be as high as 75% for a NPR = 2 and 40% for NPR = 4. The latter is traditionally considered as a ;universally safe; threshold to ensure non-acidic waters in practical applications. Our results suggest that new methods that explicitly account for mineralogical heterogeneity must be sought when computing effective (upscaled) NPR values at the scale of the piles.

The Petrology and Geochemistry of Feldspathic Granulitic Breccia NWA 3163: Implications for the Lunar Crust

NASA Technical Reports Server (NTRS)

McLeod, C. L.; Brandon, A. D.; Lapen, T. J.; Shafer, J. T.; Peslier, A. H.; Irvine, A. J.

2013-01-01

Lunar meteorites are crucial to understand the Moon s geological history because, being samples of the lunar crust that have been ejected by random impact events, they potentially originate from areas outside the small regions of the lunar surface sampled by the Apollo and Luna missions. The Apollo and Luna sample sites are contained within the Procellarum KREEP Terrain (PKT, Jolliff et al., 2000), where KREEP refers to potassium, rare earth element, and phosphorus-rich lithologies. The KREEP-rich rocks in the PKT are thought to be derived from late-stage residual liquids after approx.95-99% crystallization of a lunar magma ocean (LMO). These are understood to represent late-stage liquids which were enriched in incompatible trace elements (ITE) relative to older rocks (Snyder et al., 1992). As a consequence, the PKT is a significant reservoir for Th and KREEP. However, the majority of the lunar surface is likely to be significantly more depleted in ITE (84%, Jolliff et al., 2000). Lunar meteorites that are low in KREEP and Th may thus sample regions distinct from the PKT and are therefore a valuable source of information regarding the composition of KREEP-poor lunar crust. Northwest Africa (NWA) 3163 is a thermally metamorphosed ferroan, feldspathic, granulitic breccia composed of igneous clasts with a bulk anorthositic, noritic bulk composition. It is relatively mafic (approx.5.8 wt.% FeO; approx.5 wt.% MgO) and has some of the lowest concentrations of ITEs (17ppm Ba) compared to the feldspathic lunar meteorite (FLM) and Apollo sample suites (Hudgins et al., 2011). Localized plagioclase melting and incipient melting of mafic minerals require localized peak shock pressures in excess of 45 GPa (Chen and El Goresy, 2000; Hiesinger and Head, 2006). NWA 3163, and paired samples NWA 4481 and 4883, have previously been interpreted to represent an annealed micro-breccia which was produced by burial metamorphism at depth in the ancient lunar crust (Fernandes et al., 2009). This is in contrast to the interpretation of Hudgins et al. (2009) where NWA 3163 was interpreted to have formed through contact metamorphism. To further constrain its origin, we examine the petrogenesis of NWA 3163 with a particular emphasis on in-situ measurement of trace elements within constituent minerals, Sm-Nd and Rb-Sr isotopic systematics on separated mineral fractions and petrogenetic modeling.

Unraveling complex nonlinear elastic behaviors in rocks using dynamic acousto-elasticity

NASA Astrophysics Data System (ADS)

Riviere, J.; Guyer, R.; Renaud, G.; TenCate, J. A.; Johnson, P. A.

2012-12-01

In comparison with standard nonlinear ultrasonic methods like frequency mixing or resonance based measurements that allow one to extract average, bulk variations of modulus and attenuation versus strain level, dynamic acousto-elasticity (DAE) allows to obtain the elastic behavior over the entire dynamic cycle, detailing the full nonlinear behavior under tension and compression, including hysteresis and memory effects. This method consists of exciting a sample in Bulk-mode resonance at strains of 10-7 to 10-5 and simultaneously probing with a sequence of high frequency, low amplitude pulses. Time of flight and amplitudes of these pulses, respectively related to nonlinear elastic and dissipative parameters, can be plotted versus vibration strain level. Despite complex nonlinear signatures obtained for most rocks, it can be shown that for low strain amplitude (< 10-6), the nonlinear classical theory issued from a Taylor decomposition can explain the harmonic content. For higher strain, harmonic content becomes richer and the material exhibits more hysteretic behaviors, i.e. strain rate dependencies. Such observations have been made in the past (e.g., Pasqualini et al., JGR 2007), but not with the extreme detail of elasticity provided by DAE. Previous quasi-static measurements made in Berea sandstone (Claytor et al, GRL 2009), show that the hysteretic behavior disappears when the protocol is performed at a very low strain-rate (static limit). Therefore, future work will aim at linking quasi-static and dynamic observations, i.e. the frequency or strain-rate dependence, in order to understand underlying physical phenomena.

Use of colliery spoil for infilling mine workings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghataora, G.S.; Jarvis, S.T.

1996-12-31

Colliery spoil has been used as a major constituent of rock paste, a controlled low-strength bulk infill material, to infill abandoned limestone mines in the West Midlands of England since the early 1980s. During this time the design of colliery spoil rock paste has been modified and improved to ensure that strengths are achieved and consolidation is minimized. This paper describes the methods used for measuring and monitoring the development of the strength of rock paste used to infill the Littleton Street Mine in Walsall, England. The mine had a volume of about 500,000 m{sup 3} and is possibly themore » largest underground void to be infilled with rock paste.« less

Depositional environment and distribution of Late Cretaceous [open quotes]source rocks[close quotes] from Costa Rica to West Africa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erlich, R.N.; Sofer, Z.; Pratt, L.M.

1993-02-01

Late Cretaceous [open quotes]source rocks[close quotes] from Costa Rica, western and eastern Venezuela, and Trinidad were studied using organic and inorganic geochemistry, biostratigraphy, and sedimentology in order to determine their depositional environments. Bulk mineralogy and major element geochemistry for 304 samples were combined with Rock Eval data and extract biomaker analysis to infer the types and distributions of the various Late Cretaceous productivity systems represented in the dataset. When data from this study are combined with published and proprietary data from offshore West Africa, Guyana/Suriname, and the central Caribbean, they show that these Late Cretaceous units can be correlated bymore » their biogeochemical characteristics to establish their temporal and spatial relationships. Paleogeographic maps constructed for the early to late Cenomanian, Turonian, Coniacian to middle Santonian, and late Santonian to latest Campanian show that upwelling and excessive fluvial runoff were probably the dominant sources of nutrient supply to the coastal productivity systems. The late Santonian to Maastrichtian rocks examined in this study indicate that organic material was poorly preserved after deposition, even though biologic productivity remained constant or changed only slightly. A rapid influx of oxygenated bottom water may have occurred following the opening of a deep water connection between the North and South Atlantic oceans, and/or separation of India from Africa and the establishment of an Antarctic oceanic connection. This study suggests that the most important factors that controlled source rock quality in northern South America were productivity, preservation, degree of clastic dilution, and subsurface diagenesis.« less

Tectonic origin of serpentinites on Syros, Greece: Geochemical signatures of abyssal origin preserved in a HP/LT subduction complex

NASA Astrophysics Data System (ADS)

Cooperdock, Emily H. G.; Raia, Natalie H.; Barnes, Jaime D.; Stockli, Daniel F.; Schwarzenbach, Esther M.

2018-01-01

This study combines whole rock trace and major element geochemistry, and stable isotope (δD and δ18O) analyses with petrographic observations to deduce the origin and tectonic setting of serpentinization of ultramafic blocks from the exhumed HP/LT Aegean subduction complex on Syros, Greece. Samples are completely serpentinized and are characterized by mineral assemblages that consist of variable amounts of serpentine, talc, chlorite, and magnetite. δD and δ18O values of bulk rock serpentinite powders and chips (δD = - 64 to - 33‰ and δ18O = + 5.2 to + 9.0‰) reflect hydration by seawater at temperatures < 250 °C in an oceanic setting pre-subduction, or by fluids derived from dehydrating altered oceanic crust during subduction. Fluid-mobile elements corroborate the possibility of initial serpentinization by seawater, followed by secondary fluid-rock interactions with a sedimentary source pre- or syn-subduction. Whole rock major element, trace element, and REE analyses record limited melt extraction, exhibit flat REE patterns, and do not show pronounced Eu anomalies. The geochemical signatures preserved in these serpentinites argue against a mantle wedge source, as has been previously speculated for ultramafic rocks on Syros. Rather, the data are consistent with derivation from abyssal peridotites in a hyper-extended margin setting or mid-ocean ridge and fracture zone environment. In either case, the data suggest an extensional and/or oceanic origin associated with the Cretaceous opening of the Pindos Ocean and not a subduction-related derivation from the mantle wedge.

Mobility of gold during metamorphism of the Dalradian in Scotland

NASA Astrophysics Data System (ADS)

Pitcairn, I. K.; Skelton, A. D. L.; Wohlgemuth-Ueberwasser, C. C.

2015-09-01

Mobility of Au and related metals during metamorphism has been suggested to be the source of metals enriched in orogenic Au deposits. This study investigates the mobility of Au, As, and Sb during metamorphism of the Dalradian metasedimentary rocks of Scotland. The metamorphic processes in the Dalradian of Scotland are extremely well studied, and the terrane is an ideal area to investigate mobility of these metals. Our results show that of the 25 major and trace elements analysed, only Au, As, Sb, S and volatile contents as shown by loss on ignition (LOI) values show systematic variation with the metamorphic grade of the samples. Average Au concentrations decrease from 1.1 ± 0.55 ppb and 0.72 ± 0.34 ppb in chlorite and biotite zone rocks down to 0.4 ± 0.22 ppb and 0.34 ± 0.13 ppb in kyanite and sillimanite zone rocks. Average As concentrations decrease from 4.8 ppm (range 0.5 to 17.8 ppm) and 1.96 ± 1.9 ppm in chlorite and biotite zone rocks down to 0.24 ± 0.15 ppm and 0.2 ± 0.12 ppm in kyanite and sillimanite zone rocks. Average Sb concentrations decrease from 0.18 ± 0.15 ppm and 0.11 ± 0.10 ppm in chlorite and biotite zone rocks down to 0.04 ± 0.02 ppm in both kyanite and sillimanite zone rocks. Sulphur and LOI concentrations also show significant decreases. Mass balance calculations indicate that compared to chlorite and biotite zone samples, sillimanite zone samples have an average mass loss of 62 ± 14%, 94 ± 4% and 74 ± 14% for Au, As, and Sb respectively. Every 1 km3 of chlorite-biotite zone mixed psammitic-pelitic protolith rock that is metamorphosed to sillimanite zone conditions would release 1.5 t Au, 8613 t As, 270 t Sb, and 1.02 Mt S. The mobility of these elements is strongly controlled by the paragenesis of sulphide minerals. Pyrite, sphalerite, galena and cobaltite (as well as gersdorffite) decrease in abundance with increasing metamorphic grade in the Dalradian metasedimentary rocks. A critical aspect of the sulphide paragenesis is the transition of pyrite to pyrrhotite. This transition is complete by mid greenschist facies in the Loch Lomond samples but is more gradual at Glen Esk occurring between biotite and sillimanite zones. The Au, As, and Sb content of the sulphide assemblage also decreases with increasing metamorphic grade, and we suggest that this is a controlling factor on the mobility of these metals from the Dalradian metasedimentary rocks during metamorphism. Chlorite may be an important host mineral for As in the greenschist facies rocks. Breakdown of chlorite indirectly drives the mobility of Au, As, and Sb, as this produces the bulk of metamorphic fluid that drives transition between pyrite and pyrrhotite. We suggest that there is potential for significant undiscovered mineralisation in the Central and SW Highlands of Scotland. However, as the total mass of gold mobilised is lower than observed in other metasedimentary terranes such as the Otago and Alpine Schist's, New Zealand, very efficient fluid focussing and trapping mechanisms would be required to form large deposits in the Dalradian of Scotland.

The Chlorine Isotopic Composition Of Lunar UrKREEP

NASA Technical Reports Server (NTRS)

Barnes, J. J.; Tartese, R.; Anand, M.; McCubbin, F. M.; Neal, C. R.; Franchi, I. A.

2016-01-01

Since the long standing paradigm of an anhydrous Moon was challenged there has been a renewed focus on investigating volatiles in a variety of lunar samples. However, the current models for the Moon’s formation have yet to fully account for its thermal evolution in the presence of H2O and other volatiles. When compared to chondritic meteorites and terrestrial rocks, lunar samples have exotic chlorine isotope compositions, which are difficult to explain in light of the abundance and isotopic composition of other volatile species, especially H, and the current estimates for chlorine and H2O in the bulk silicate Moon. In order to better understand the processes involved in giving rise to the heavy chlorine isotope compositions of lunar samples, we have performed a comprehensive in situ high precision study of chlorine isotopes, using NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) of lunar apatite from a suite of Apollo samples covering a range of geochemical characteristics and petrologic types.

Strain partitioning in shales during elastic and creep deformation observed by synchrotron X-ray micro-tomography.

NASA Astrophysics Data System (ADS)

Sone, H.; Cheung, C.; Rivers, M. L.; Wang, Y.; Yu, T.

2016-12-01

Knowledge about the ductile time-dependent constitutive behavior of geological materials is essential when evaluating the long-term integrity of subsurface structures and predicting the long-term geomechanical response of the surrounding formations. To this end, it is not only important to measure the bulk time-dependent behavior but also essential to understand the microscale mechanism by which rocks exhibit time-dependence, because laboratory data needs to be extrapolated to time-scales much beyond laboratory experiments. We conducted long-term creep experiments using Green River shale samples and obtained synchrotron X-ray images during the tests in an attempt to capture the microscale strain-partitioning that occurs within the sample. Shale samples of few millimeter dimensions were stressed up to several tens of MPa by a spring-loaded device within an X-ray transparent load frame, and the load was held constant for up to several months to allow creep deformation. Tomographic images of about 5 micron resolution were reconstructed from images collected at different timings of the experiment, which allows us to investigate where and how much strain localized during elastic and creep deformation. Tracking the position of some outstanding features in the rock texture (e.g. pyrite grains, organic material patches) indicate that strain magnitudes expected from the sample elastic and relaxation modulus can be successfully recovered from the tomographic images. We also attempt to use digital volume correlation to track sub-voxel displacements and to characterize the spatial heterogeneity of the deformation.

Consortium study of lunar meteorites Yamato-793169 and Asuka-881757: Geochemical evidence of mutual similarity, and dissimilarity versus other mare basalts

NASA Technical Reports Server (NTRS)

Warren, Paul H.; Lindstrom, Marilyn M.

1993-01-01

Compositions of bulk powders and separated minerals from two meteorites derived from the mare lava plains of the Earth's Moon, Yamato-793169 and Asuka-881757, indicate a remarkable degree of similarity to one another, and clearly favor lunar origin. However, these meteorites are unlike any previously studied lunar rock. In both cases, the bulk-rock TiO2 content is slightly greater than the level separating VLT from low-Ti mare basalt, yet the Sc content is much higher than previously observed except among high-Ti mare basalts. Conceivably, the Sc enrichment in A881757 reflects origin of this rock as a cumulate from a mare magma of 'normal' Sc content, but this seems unlikely. Mineral-separate data suggest that most of the Sc is in pyroxene, and a variety of evidence weighs against the cumulus hypothesis as a major cause for the high Sc. The remarkable similarity between Y793169 and A881757 suggests the possibility that they were derived from a single source crater on the Moon.

Finite-element modelling of thermal micracking in fresh and consolidated marbles

NASA Astrophysics Data System (ADS)

Weiss, T.; Fuller, E.; Siegesmund, S.

2003-04-01

The initial stage of marble weathering is supposed to be controlled by thermal microcracking. Due to the anisotropy of the thermal expansion coefficients of calcite, the main rock forming mineral in marble, stresses are caused which lead to thermally-induced microcracking, especially along the grain boundaries. The so-called "granular disintegration" is a frequent weathering phenomenon observed for marbles. The controlling parameters are the grain size, grain shape and grain orientation. We use a finite-element approach to constrain magnitude and directional dependence of thermal degradation. Therefore, different assumptions are validated including the fracture toughness of the grain boundaries, the effects of the grain-to-grain orientation and bulk lattice preferred orientation (here referred to as texture). The resulting thermal microcracking and bulk rock thermal expansion anisotropy are validated. It is evident that thermal degradation depends on the texture. Strongly textured marbles exhibit a clear directional dependence of thermal degradation and a smaller bulk thermal degradation than randomly oriented ones. The effect of different stone consolidants in the pore space of degraded marble is simulated and its influence on mechanical properties such as tensile strength are evaluated.

Estimation of Dry Fracture Weakness, Porosity, and Fluid Modulus Using Observable Seismic Reflection Data in a Gas-Bearing Reservoir

NASA Astrophysics Data System (ADS)

Chen, Huaizhen; Zhang, Guangzhi

2017-05-01

Fracture detection and fluid identification are important tasks for a fractured reservoir characterization. Our goal is to demonstrate a direct approach to utilize azimuthal seismic data to estimate fluid bulk modulus, porosity, and dry fracture weaknesses, which decreases the uncertainty of fluid identification. Combining Gassmann's (Vier. der Natur. Gesellschaft Zürich 96:1-23, 1951) equations and linear-slip model, we first establish new simplified expressions of stiffness parameters for a gas-bearing saturated fractured rock with low porosity and small fracture density, and then we derive a novel PP-wave reflection coefficient in terms of dry background rock properties (P-wave and S-wave moduli, and density), fracture (dry fracture weaknesses), porosity, and fluid (fluid bulk modulus). A Bayesian Markov chain Monte Carlo nonlinear inversion method is proposed to estimate fluid bulk modulus, porosity, and fracture weaknesses directly from azimuthal seismic data. The inversion method yields reasonable estimates in the case of synthetic data containing a moderate noise and stable results on real data.

State-of-the-Art for Assessing Earthquake Hazards in the United States. Report 19. The Evidence for Reservoir-Induced Macroearthquakes.

DTIC Science & Technology

1982-06-01

pore pressures are dissipating. 232. The question of deep fluid communication is unresolved. Koyna is situated in flow basalt known as the Deccan Traps ...The trap rock formation is about 1200 m thick near Koyna. The basalt flows are irregular and at the damsite seven flows have been mapped. Some of the...ranges from 0 to about 30 km but is generally 2 to 8 km in depth. This places the bulk of the seismicity below the trap rock in a basement rock of unknown

Magnetic and elastic wave anisotropy in partially molten rocks: insight from experimental melting of synthetic quartz-mica schist (Invited)

NASA Astrophysics Data System (ADS)

Almqvist, B.; Misra, S.; Biedermann, A. R.; Mainprice, D.

2013-12-01

We studied the magnetic and elastic wave speed anisotropy of a synthetically prepared quartz-mica schist, prior to, during and after experimental melting. The synthetic rock was manufactured from a mixture of powders with equal volumes of quartz and muscovite. The powders were initially compacted with 200 MPa uniaxial stress at room temperature and sealed in a stainless steel canister. Subsequently the sealed canister was isostatically pressed at 180 MPa and 580 °C for 24 hours. This produced a solid medium with ~25 % porosity. Mica developed a preferred grain-shape alignment due to the initial compaction with differential load, where mica flakes tend to orient perpendicular to the applied stress and hence define a synthetic foliation plane. In the last stage we used a Paterson gas-medium apparatus, to pressurize and heat the specimens up to 300 MPa and 750 °C for a six hour duration. This stage initially compacted the rock, followed by generation of melt, and finally crystallization of new minerals from the melt. Elastic wave speed measurements were performed in situ at pressure and temperature, with a transducer assembly mounted next to the sample. Magnetic measurements were performed before and after the partial melt experiments. Anisotropy was measured in low- and high-field, using a susceptibility bridge and torsion magnetometer, respectively. Additionally we performed measurements of hysteresis, isothermal remanent magnetization (IRM) and susceptibility as a function of temperature, to investigate the magnetic properties of the rock. The elastic wave speed, before the melting-stage of the experiment, exhibits a distinct anisotropy with velocities parallel to the foliation being about 15 % higher than normal to the foliation plane. Measurements of the magnetic anisotropy in the bulk sample show that anisotropy is originating from the preferred orientation of muscovite, with a prominent flattening fabric. In contrast, specimens that underwent partial melting display a weaker elastic and magnetic anisotropy, because muscovite preferentially melts due to dehydration melting at 750 °C. The decrease in anisotropy can be inferred from in situ observation of elastic wave anisotropy, but also from comparison of measurements of magnetic anisotropy prior to and subsequent to experiment. A distinct anisotropy is however identified after the experiments both in susceptibility and remanence, which appears to be controlled by the original foliation. As muscovite undergoes dehydration melting a small amount of Fe is released into the melt. Crystallization from the melt indicates that the Fe is bound in biotite and Fe-oxides. The bulk susceptibility and saturation remanence increase by more than one order of magnitude in samples after the melting experiment. The newly formed ferrimagnetic phase, identified through hysteresis, IRM and thermomagnetic measurements, have a tight grouping in the magnetite pseudo-single-domain field on a Day plot. Our experiments are pertinent to the study of partially molten rocks and provide an opportunity to help guide research in magnetic and elastic wave anisotropy of migmatite and granite. In particular the results from experiments apply to the understanding of generation and percolation of melt prior to, or coeval to, the onset of deformation.

Paleomagnetic Analysis Using SQUID Microscopy

NASA Technical Reports Server (NTRS)

Weiss, Benjamin P.; Lima, Eduardo A.; Fong, Luis E.; Baudenbacher, Franz J.

2007-01-01

Superconducting quantum interference device (SQUID) microscopes are a new generation of instruments that map magnetic fields with unprecedented spatial resolution and moment sensitivity. Unlike standard rock magnetometers, SQUID microscopes map magnetic fields rather than measuring magnetic moments such that the sample magnetization pattern must be retrieved from source model fits to the measured field data. In this paper, we presented the first direct comparison between paleomagnetic analyses on natural samples using joint measurements from SQUID microscopy and moment magnetometry. We demonstrated that in combination with apriori geologic and petrographic data, SQUID microscopy can accurately characterize the magnetization of lunar glass spherules and Hawaiian basalt. The bulk moment magnitude and direction of these samples inferred from inversions of SQUID microscopy data match direct measurements on the same samples using moment magnetometry. In addition, these inversions provide unique constraints on the magnetization distribution within the sample. These measurements are among the most sensitive and highest resolution quantitative paleomagnetic studies of natural remanent magnetization to date. We expect that this technique will be able to extend many other standard paleomagnetic techniques to previously inaccessible microscale samples.

Uranium in granites from the Southwestern United States: actinide parent-daughter systems, sites and mobilization. First year report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silver, L T; Williams, I S; Woodhead, J A

1980-10-01

Some of the principal findings of the study on the Lawler Peak Granite are: the granite is dated precisely by this work at 1411 +- 3 m.y., confirming its synchroneity with a great regional terrane of granites. Uranium is presently 8-10 times crustal abundance and thorium 2-3 times in this granite. Uranium is found to be enriched in at least eight, possibly ten, primary igneous mineral species over the whole-rock values. Individual mineral species show distinct levels in, and characteristics ranges of, uranium concentration. It appears that in a uraniferous granite such as this, conventional accuracy mineral suites probably cannotmore » account for most of the uranium in the rock, and more rare, high U-concentration phases also are present and are significant uranium hosts. It appears that at least two different geological episodes have contributed to the disturbance of the U-Th-Pb isotope systems. Studies of various sites for transient dispersal of uranium, thorium, and radiogenic lead isotopes indicate a non-uniform dispersal of these components. It appears that the bulk rock has lost at least 24 percent of its original uranium endowment, accepting limited or no radiogenic lead or thorium migration from the sample.« less

Effects of varying environmental conditions on emissivity spectra of bulk lunar soils: Application to Diviner thermal infrared observations of the Moon

NASA Astrophysics Data System (ADS)

Donaldson Hanna, K. L.; Greenhagen, B. T.; Patterson, W. R.; Pieters, C. M.; Mustard, J. F.; Bowles, N. E.; Paige, D. A.; Glotch, T. D.; Thompson, C.

2017-02-01

Currently, few thermal infrared measurements exist of fine particulate (<63 μm) analogue samples (e.g. minerals, mineral mixtures, rocks, meteorites, and lunar soils) measured under simulated lunar conditions. Such measurements are fundamental for interpreting thermal infrared (TIR) observations by the Diviner Lunar Radiometer Experiment (Diviner) onboard NASA's Lunar Reconnaissance Orbiter as well as future TIR observations of the Moon and other airless bodies. In this work, we present thermal infrared emissivity measurements of a suite of well-characterized Apollo lunar soils and a fine particulate (<25 μm) San Carlos olivine sample as we systematically vary parameters that control the near-surface environment in our vacuum chamber (atmospheric pressure, incident solar-like radiation, and sample cup temperature). The atmospheric pressure is varied between ambient (1000 mbar) and vacuum (<10-3 mbar) pressures, the incident solar-like radiation is varied between 52 and 146 mW/cm2, and the sample cup temperature is varied between 325 and 405 K. Spectral changes are characterized as each parameter is varied, which highlight the sensitivity of thermal infrared emissivity spectra to the atmospheric pressure and the incident solar-like radiation. Finally spectral measurements of Apollo 15 and 16 bulk lunar soils are compared with Diviner thermal infrared observations of the Apollo 15 and 16 sampling sites. This comparison allows us to constrain the temperature and pressure conditions that best simulate the near-surface environment of the Moon for future laboratory measurements and to better interpret lunar surface compositions as observed by Diviner.

The parent magma of xenoliths in shergottite EETA79001: Bulk and trace element composition inferred from magmatic inclusions

NASA Technical Reports Server (NTRS)

Treiman, Allan H.; Lindstrom, David J.; Martinez, Rene R.

1994-01-01

The SNC meteorites are samples of the Martian crust, so inferences about their origins and parent magmas are of wide planetologic significance. The EETA79001 shergottite, a basalt, contains xenoliths of pyroxene-olivine cumulate rocks which are possibly related to the ALHA77005 and LEW88516 SNC lherzolites. Olivines in the xenoliths contain magmatic inclusions, relics of magma trapped within the growing crystals. The magmatic inclusions allow a parent magma composition to be retrieved; it is similar to the composition reconstructed from xenolith pyroxenes by element distribution coefficients. The xenolith parent magma is similar but not identical to parent magmas for the shergottite lherzolites.

Assessment of dynamic material properties of intact rocks using seismic wave attenuation: an experimental study

PubMed Central

Wanniarachchi, W. A. M.; Perera, M. S. A.; Rathnaweera, T. D.; Lyu, Q.; Mahanta, B.

2017-01-01

The mechanical properties of any substance are essential facts to understand its behaviour and make the maximum use of the particular substance. Rocks are indeed an important substance, as they are of significant use in the energy industry, specifically for fossil fuels and geothermal energy. Attenuation of seismic waves is a non-destructive technique to investigate mechanical properties of reservoir rocks under different conditions. The attenuation characteristics of five different rock types, siltstone, shale, Australian sandstone, Indian sandstone and granite, were investigated in the laboratory using ultrasonic and acoustic emission instruments in a frequency range of 0.1–1 MHz. The pulse transmission technique and spectral ratios were used to calculate the attenuation coefficient (α) and quality factor (Q) values for the five selected rock types for both primary (P) and secondary (S) waves, relative to the reference steel sample. For all the rock types, the attenuation coefficient was linearly proportional to the frequency of both the P and S waves. Interestingly, the attenuation coefficient of granite is more than 22% higher than that of siltstone, sandstone and shale for both P and S waves. The P and S wave velocities were calculated based on their recorded travel time, and these velocities were then used to calculate the dynamic mechanical properties including elastic modulus (E), bulk modulus (K), shear modulus (µ) and Poisson's ratio (ν). The P and S wave velocities for the selected rock types varied in the ranges of 2.43–4.61 km s−1 and 1.43–2.41 km h−1, respectively. Furthermore, it was observed that the P wave velocity was always greater than the S wave velocity, and this confirmed the first arrival of P waves to the sensor. According to the experimental results, the dynamic E value is generally higher than the static E value obtained by unconfined compressive strength tests. PMID:29134090

Study of the Nankai seismogenic fault using dynamic wave propagation modelling of digital rock from the Nobeoka Fault

NASA Astrophysics Data System (ADS)

Eng, Chandoeun; Ikeda, Tatsunori; Tsuji, Takeshi

2018-10-01

To understand the characteristics of the Nankai seismogenic fault in the plate convergent margin, we calculated the P- and S-wave velocities (VP and VS) of digital rock models constructed from core samples of an ancient plate boundary fault at Nobeoka, Kyushu Island, Japan. We first constructed 3D digital rock models from microcomputed tomography images and identified their heterogeneous textures such as cracks and veins. We replaced the cracks and veins with air, water, quartz, calcite and other materials with different bulk and shear moduli. Using the Rotated Staggered Grid Finite-Difference Method, we performed dynamic wave propagation simulations and quantified the effective VP, VS and the ratio of VP to VS (VP/VS) of the 3D digital rock models with different crack-filling minerals. Our results demonstrate that the water-saturated cracks considerably decreased the seismic velocity and increased VP/VS. The VP/VS of the quartz-filled rock model was lower than that in the water-saturated case and in the calcite-filled rock model. By comparing the elastic properties derived from the digital rock models with the seismic velocities (e.g. VP and VP/VS) around the seismogenic fault estimated from field seismic data, we characterised the evolution process of the deep seismogenic fault. The high VP/VS and low VP observed at the transition from aseismic to coseismic regimes in the Nankai Trough can be explained by open cracks (or fractures), while the low VP/VS and high VP observed at the deeper coseismic fault zone suggests quartz-filled cracks. The quartz-rich fault zone characterised as low VP/VS and high VP in this study could partially relate to the coseismic behaviour as suggested by previous studies, because quartz exhibits slip-weakening behaviour (i.e. unstable coseismic slip).

Assessment of dynamic material properties of intact rocks using seismic wave attenuation: an experimental study.

PubMed

Wanniarachchi, W A M; Ranjith, P G; Perera, M S A; Rathnaweera, T D; Lyu, Q; Mahanta, B

2017-10-01

The mechanical properties of any substance are essential facts to understand its behaviour and make the maximum use of the particular substance. Rocks are indeed an important substance, as they are of significant use in the energy industry, specifically for fossil fuels and geothermal energy. Attenuation of seismic waves is a non-destructive technique to investigate mechanical properties of reservoir rocks under different conditions. The attenuation characteristics of five different rock types, siltstone, shale, Australian sandstone, Indian sandstone and granite, were investigated in the laboratory using ultrasonic and acoustic emission instruments in a frequency range of 0.1-1 MHz. The pulse transmission technique and spectral ratios were used to calculate the attenuation coefficient ( α ) and quality factor ( Q ) values for the five selected rock types for both primary ( P ) and secondary ( S ) waves, relative to the reference steel sample. For all the rock types, the attenuation coefficient was linearly proportional to the frequency of both the P and S waves. Interestingly, the attenuation coefficient of granite is more than 22% higher than that of siltstone, sandstone and shale for both P and S waves. The P and S wave velocities were calculated based on their recorded travel time, and these velocities were then used to calculate the dynamic mechanical properties including elastic modulus ( E ), bulk modulus ( K ), shear modulus ( µ ) and Poisson's ratio ( ν ). The P and S wave velocities for the selected rock types varied in the ranges of 2.43-4.61 km s -1 and 1.43-2.41 km h -1 , respectively. Furthermore, it was observed that the P wave velocity was always greater than the S wave velocity, and this confirmed the first arrival of P waves to the sensor. According to the experimental results, the dynamic E value is generally higher than the static E value obtained by unconfined compressive strength tests.

Assessment of dynamic material properties of intact rocks using seismic wave attenuation: an experimental study

NASA Astrophysics Data System (ADS)

Wanniarachchi, W. A. M.; Ranjith, P. G.; Perera, M. S. A.; Rathnaweera, T. D.; Lyu, Q.; Mahanta, B.

2017-10-01

The mechanical properties of any substance are essential facts to understand its behaviour and make the maximum use of the particular substance. Rocks are indeed an important substance, as they are of significant use in the energy industry, specifically for fossil fuels and geothermal energy. Attenuation of seismic waves is a non-destructive technique to investigate mechanical properties of reservoir rocks under different conditions. The attenuation characteristics of five different rock types, siltstone, shale, Australian sandstone, Indian sandstone and granite, were investigated in the laboratory using ultrasonic and acoustic emission instruments in a frequency range of 0.1-1 MHz. The pulse transmission technique and spectral ratios were used to calculate the attenuation coefficient (α) and quality factor (Q) values for the five selected rock types for both primary (P) and secondary (S) waves, relative to the reference steel sample. For all the rock types, the attenuation coefficient was linearly proportional to the frequency of both the P and S waves. Interestingly, the attenuation coefficient of granite is more than 22% higher than that of siltstone, sandstone and shale for both P and S waves. The P and S wave velocities were calculated based on their recorded travel time, and these velocities were then used to calculate the dynamic mechanical properties including elastic modulus (E), bulk modulus (K), shear modulus (µ) and Poisson's ratio (ν). The P and S wave velocities for the selected rock types varied in the ranges of 2.43-4.61 km s-1 and 1.43-2.41 km h-1, respectively. Furthermore, it was observed that the P wave velocity was always greater than the S wave velocity, and this confirmed the first arrival of P waves to the sensor. According to the experimental results, the dynamic E value is generally higher than the static E value obtained by unconfined compressive strength tests.

Involvement of magmatic fluids at the Laloki and Federal Flag massive sulfide Cu-Zn-Au-Ag deposits, Astrolabe mineral district, Papua New Guinea: sulfur isotope evidence

NASA Astrophysics Data System (ADS)

Noku, Shadrach K.; Espi, Joseph O.; Matsueda, Hiroharu

2015-01-01

We present the first sulfur (S) isotope data of sulfides, sulfates, pyrite in host mudstone, and bulk sulfur of gabbroic rocks from the Laloki and Federal Flag massive Cu-Zn-Au-Ag deposits in the Astrolabe mineral district, Papua New Guinea. Early-stage pyrite-marcasite, chalcopyrite, and sphalerite from Laloki display wide range of δ34S values from -4.5 to +7.0 ‰ ( n = 16). Late-stage pyrite, chalcopyrite, and sphalerite have restricted δ34S values of -1.9 to +4.7 ‰ ( n = 16). The mineralizing stage these correspond to had moderately saline (5.9-8.4 NaCl eq. wt%) mineralizing fluids of possible magmatic origin. A single analysis of late-stage barite has a value of δ34S +17.9 ‰, which is likely similar to coexisting seawater sulfate. Pyrite from the foot-wall mudstone at Laloki has very light δ34S values of -36.1 to -33.8 ‰ ( n = 2), which suggest an organic source for S. Pyrite-marcasite and chalcopyrite from Federal Flag show δ34S values of -2.4 to -1.9 ‰ ( n = 2), consistent with a magmatic origin, either leached from intrusive magmatic rocks or derived from magmatic-hydrothermal fluids. The very narrow range and near-zero δ34S values (-1.0 to +0.6 ‰) of bulk gabbroic samples is consistent with mantle-derived magmatic S. Sulfur isotope characteristics of sulfides and sulfates are, however, very similar to base metal sulfide accumulations associated with modern volcanic arcs and sedimented mid-ocean ridges. The most reasonable interpretation is that the range of the sulfide and sulfate δ34S values from both Laloki and Federal Flag massive sulfide deposits is indicative of the complex interaction of magmatic fluids, seawater, gabbroic rocks, and mudstone.

High-resolution (SIMS) versus bulk sulfur isotope patterns of pyrite in Proterozoic microbialites with diverse mat textures

NASA Astrophysics Data System (ADS)

Gomes, M. L.; Fike, D. A.; Bergmann, K.; Knoll, A. H.

2015-12-01

Sulfur (S) isotope signatures of sedimentary pyrite preserved in marine rocks provide a rich suite of information about changes in biogeochemical cycling associated with the evolution of microbial metabolisms and oxygenation of Earth surface environments. Conventionally, these S isotope records are based on bulk rock measurements. Yet, in modern microbial mat environments, S isotope compositions of sulfide can vary by up to 40‰ over a spatial range of ~ 1 mm. Similar ranges of S isotope variability have been found in Archean pyrite grains using both Secondary Ion Mass Spectrometry and other micro-analytical techniques. These micron-scale patterns have been linked to changes in rates of microbial sulfate reduction and/or sulfide oxidation, isotopic distillation of the sulfate reservoir due to microbial sulfate reduction, and post-depositional alteration. Fine-scale mapping of S isotope compositions of pyrite can thus be used to differentiate primary environmental signals from post-depositional overprinting - improving our understanding of both. Here, we examine micron-scale S isotope patterns of pyrite in microbialites from the Mesoproterozoic-Neoproterozoic Sukhaya Tunguska Formation and Neoproterozoic Draken Formation in order to explore S isotope variability associated with different mat textures and pyrite grain morphologies. A primary goal is to link modern observations of how sulfide spatial isotope distributions reflect active microbial communities present at given depths in the mats to ancient processes driving fine-sale pyrite variability in microbialites. We find large (up to 60‰) S isotope variability within a spatial range of less than 2.5cm. The micron-scale S isotope measurements converge around the S isotope composition of pyrite extracted from bulk samples of the same microbialites. These micron-scale pyrite S isotope patterns have the potential to reveal important information about ancient biogeochemical cycling in Proterozoic mat environments with implications for interpreting S isotope signatures from the geological record.

Water content in the SW USA mantle lithosphere: FTIR analysis of Dish Hill and Kilbourne Hole pyroxenites

NASA Astrophysics Data System (ADS)

Gibler, R.; Peslier, A. H.; Schaffer, L. A.; Brandon, A. D.

2014-12-01

Kilbourne Hole (NM, USA) and Dish Hill (CA, USA) mantle xenoliths sample continental mantle in two different tectonic settings. Kilbourne Hole (KH) is located in the Rio Grande rift. Dish Hill (DH) is located in the southern Mojave province, an area potentially affected by subduction of the Farallon plate beneath North America [1]. FTIR analyses were obtained on well characterized pyroxenite, dunite and wehrlite xenoliths, thought to represent crystallized melts at mantle depths. PUM normalized REE patterns of the KH bulk-rocks are slightly LREE enriched and consistent with those of liquids generated by < 5% melting of a spinel peridotite source [2]. Clinopyroxenes contain from 272 to 313 ppm weight H2O similar to the lower limit of KH peridotite clinopyroxenes (250-530 ppm H2O, [3]). This is unexpected as crystallized melts like pyroxenites should concentrate water more than residual mantle-like peridotites, given that H is incompatible. PUM normalized bulk REE of the DH pyroxenites are characterized by flat to LREE depleted REE profiles consistent with > 6% melting of a spinel peridotite source. Pyroxenite pyroxenes have no detectable water but one DH wehrlite, which bulk-rock is LREE enriched, has 4 ppm H2O in orthopyroxene and <1ppm in clinopyroxene. The DH pyroxenites may thus come from a dry mantle source, potentially unaffected by the subduction of the Farallon plate. These water-poor melts either originated from shallow oceanic lithosphere overlaying the Farallon slab [4] or from continental mantle formed > 2 Ga [5]. The Farallon subduction appears to have enriched in water the southwestern United States lithospheric mantle further east than DH, beneath the Colorado plateau [6]. [1] Atwater, 1970 Tectonophysics 31, 145-165. [2] Shaw, 2000 CM 38, 1041-1064. [3] Schaffer et al, 2013 AGU Fall Meeting. [4] Luffi et al, 2009 JGR 114, 1-36. [5] Armytage et al, 2013 GCA 137, 113-133. [6] Li et al, 2008 JGR 113, 1-22.

Magmatic evolution of lunar highland rocks estimated from trace elements in plagioclase: A new bulk silicate Moon model with sub-chondritic Ti/Ba, Sr/Ba, and Sr/Al ratios

NASA Astrophysics Data System (ADS)

Togashi, Shigeko; Kita, Noriko T.; Tomiya, Akihiko; Morishita, Yuichi

2017-08-01

The compositions of host magmas of ferroan anorthosites (FAN-host magmas) were estimated from secondary ion mass spectrometry analyses of plagioclase in lunar highland rocks. The evolution of the magmas was investigated by considering phase relations based on the MELTS algorithm and by re-examining partition coefficients for trace elements between plagioclase and melts. Data little affected by post-magmatic processes were selected by using plagioclase with relatively primitive Sc and Co contents. The FAN-host magma contained 90-174 ppm Sr, 40-119 ppm Ba and 0.5-1.3% TiO2, and had sub-chondritic Sr/Ba and Ti/Ba ratios. It is difficult to account for the formation of FAN-host magma on the basis of magma evolution processes of previously proposed bulk silicate Moon models with chondritic ratios for refractory elements at global scale. Therefore, the source of the FAN-host magma must have had primordial sub-chondritic Sr/Ba and Ti/Ba ratios. The FAN-host magmas were consistent in refractory elements with the estimated host mafic magma for feldspathic crust based on lunar meteorites, and some very-low-Ti mare rocks from lunar meteorites. Here, we propose an alternative bulk silicate Moon model (the cBSM model), which is enriched in crustal components of proto-bodies relative to the present whole Earth-Moon system.

Bulk magnetic domain stability controls paleointensity fidelity

NASA Astrophysics Data System (ADS)

Paterson, Greig A.; Muxworthy, Adrian R.; Yamamoto, Yuhji; Pan, Yongxin

2017-12-01

Nonideal, nonsingle-domain magnetic grains are ubiquitous in rocks; however, they can have a detrimental impact on the fidelity of paleomagnetic records—in particular the determination of ancient magnetic field strength (paleointensity), a key means of understanding the evolution of the earliest geodynamo and the formation of the solar system. As a consequence, great effort has been expended to link rock magnetic behavior to paleointensity results, but with little quantitative success. Using the most comprehensive rock magnetic and paleointensity data compilations, we quantify a stability trend in hysteresis data that characterizes the bulk domain stability (BDS) of the magnetic carriers in a paleomagnetic specimen. This trend is evident in both geological and archeological materials that are typically used to obtain paleointensity data and is therefore pervasive throughout most paleomagnetic studies. Comparing this trend to paleointensity data from both laboratory and historical experiments reveals a quantitative relationship between BDS and paleointensity behavior. Specimens that have lower BDS values display higher curvature on the paleointensity analysis plot, which leads to more inaccurate results. In-field quantification of BDS therefore reflects low-field bulk remanence stability. Rapid hysteresis measurements can be used to provide a powerful quantitative method for preselecting paleointensity specimens and postanalyzing previous studies, further improving our ability to select high-fidelity recordings of ancient magnetic fields. BDS analyses will enhance our ability to understand the evolution of the geodynamo and can help in understanding many fundamental Earth and planetary science questions that remain shrouded in controversy.

Bulk magnetic domain stability controls paleointensity fidelity

PubMed Central

Muxworthy, Adrian R.; Yamamoto, Yuhji; Pan, Yongxin

2017-01-01

Nonideal, nonsingle-domain magnetic grains are ubiquitous in rocks; however, they can have a detrimental impact on the fidelity of paleomagnetic records—in particular the determination of ancient magnetic field strength (paleointensity), a key means of understanding the evolution of the earliest geodynamo and the formation of the solar system. As a consequence, great effort has been expended to link rock magnetic behavior to paleointensity results, but with little quantitative success. Using the most comprehensive rock magnetic and paleointensity data compilations, we quantify a stability trend in hysteresis data that characterizes the bulk domain stability (BDS) of the magnetic carriers in a paleomagnetic specimen. This trend is evident in both geological and archeological materials that are typically used to obtain paleointensity data and is therefore pervasive throughout most paleomagnetic studies. Comparing this trend to paleointensity data from both laboratory and historical experiments reveals a quantitative relationship between BDS and paleointensity behavior. Specimens that have lower BDS values display higher curvature on the paleointensity analysis plot, which leads to more inaccurate results. In-field quantification of BDS therefore reflects low-field bulk remanence stability. Rapid hysteresis measurements can be used to provide a powerful quantitative method for preselecting paleointensity specimens and postanalyzing previous studies, further improving our ability to select high-fidelity recordings of ancient magnetic fields. BDS analyses will enhance our ability to understand the evolution of the geodynamo and can help in understanding many fundamental Earth and planetary science questions that remain shrouded in controversy. PMID:29187534

Tectonic Origin of Serpentinites on Syros, Greece: Geochemical Signatures of Seafloor Serpentinization Preserved in the HP/LT Subduction Complex

NASA Astrophysics Data System (ADS)

Raia, N. H.; Cooperdock, E. H. G.; Barnes, J.; Stockli, D. F.; Schwarzenbach, E. M.

2016-12-01

Serpentinized ultramafic rocks are commonly found in exhumed HP/LT subduction complexes, but their tectonic origins (i.e., setting of serpentinization) are difficult to decipher due to extensive alteration. Growing literature and geochemical datasets demonstrate that immobile elements (REE, HFSE) in serpentinites can retain magmatic signatures indicative of the tectonic setting of parent peridotite, while fluid-mobile elements and stable isotopic signatures shed light on the fluids causing serpentinization. This study combines whole-rock trace and major element geochemistry, stable isotope (δD and δO) analyses with petrographic observation to determine the tectonic origin of ultramafic rocks in the HP/LT Aegean subduction complex. The best-preserved HP rocks of the Cycladic Blueschist Unit (CBU) are found on Syros, Greece, where serpentinized ultramafic rocks within the CBU are closely associated with metamorphosed remnants of subducted oceanic crust. All samples are completely serpentinized, lacking relict pyroxene or spinel grains, with typical assemblages consisting of serpentine, talc, chlorite, magnetite, and minor carbonate. The serpentinizing fluid was characterized using stable isotopes. δD and δO values of bulk-rock serpentinite powders and chips, respectively, suggest seafloor serpentinites hydrated by seawater at low T, typical of alteration at mid-ocean ridges and hyper-extended margins (δD = -64 to -33‰ and δO = 5.2 to 9.0‰). To fingerprint a tectonic origin, whole rock serpentinite REE patterns are compared to a global database of whole rock serpentinite analyses from fore-arc mantle wedge, mid-ocean ridge, and hyper-extended margin tectonic settings. Whole rock major element, trace element, and REE analyses are consistent with limited melt extraction, flat REE patterns (LaN/SmN = 0.2-2.6, SmN/YbN = 0.3-3.5; N= C1 normalized), and do not show pronounced Eu anomalies. These data are consistent with abyssal peridotites derived from hyper-extended margin settings, although some overlap with mid-ocean ridge serpentinites makes it difficult to rule out. In any case, the geochemical signatures retained in these serpentinites indicate they are unlikely sourced from the mantle wedge, as has been historically speculated.

Eclogitic metatrondhjemites from metaophiolites of the Western Alps

NASA Astrophysics Data System (ADS)

Martin, Silvana; Tartarotti, Paola; Meyzen, Chrstine; Benciolini, Luca; Toffolo, Luca

2016-04-01

Eclogitic metatrondhjemites from metaophiolites of the Western Alps Martin S.**, Tartarotti P.*, Meyzen C. **, Benciolini L.***, Toffolo L. ** *Dipartimento di Scienze della Terra, Università degli Studi di Milano ** Dipartimento di Geoscienze, Università di Padova *** Dipartimento di Chimica, Fisica e Ambiente, Università di Udine In the Urtier valley (southern Aosta Valley, Italy), the Piemonte metaophiolites mainly consist of serpentinized peridotites including pods and boudinaged layers of Fe-metagabbro and trondhjemite transposed in the main eclogitic foliation. The contact between serpentinized peridotites and Fe-metagabbro/trondhjemite is locally lined by chloriteschist and rodingite. The high pressure parageneses in the Fe-metagabbro are omphacite-garnet-rutile-glaucophane-phengite, and in the metatrondhjemite plagioclase-quartz-phengite-clinozoisite-epidote-garnet, respectively. Bulk-rock major and trace elements in addition to O isotope analyses were performed in both rock types. Fe-metagabbros are characterized by MgO wt% ranging between 6.11 and 9.63%, ∑REE= 20-101 ppm, (La/Yb)N = 0.22-0.91; trondhjemites have SiO2 43%, Al2O3 ranging between 21 and 24%, CaO ranging between 17 and 20%, ∑REE = 172 - 272 ppm, (La/Yb)N ranging between 7.78 and 13.70. The δ18O is 5.9 ‰ in a Fe-metagabbro sample and 7.4 ‰ in a trondhjemite sample, suggesting that these rocks have been affected by a weak oceanic low temperature alteration. The high CaO content may indicate a metasomatic process which could have occurred during the oceanic stage or at high pressure conditions.

Summary of the development of a signature for detection of residual dust from collapse of the World Trade Center buildings

PubMed Central

Lowers, Heather A; Meeker, Gregory P; Lioy, Paul J; Lippmann, Morton

2014-01-01

The collapse of the World Trade Center (WTC) towers on September 11, 2001, caused lower Manhattan and adjacent areas to be covered in millimeters to centimeters of dust. WTC dust penetrated into indoor spaces, and public health concerns remain regarding exposure to possible residual dust in the affected areas. The goal of the studies outlined in this review was to determine which, if any, components of the bulk WTC dust are sufficiently above typical background dust levels in New York City to develop an analytical method to screen for the component(s). Components of the <150-µm-size fraction of the dust are gypsum, phases compatible with crushed concrete, man-made vitreous fibers (MMVFs), silica, lead, chrysotile asbestos, and other materials. Slag wool was the most common WTC MMVF, whereas soda-lime glass and rock wool were minor to trace constituents. Most background samples also contained gypsum, phases compatible with concrete, and MMVF. However, the proportions of the various MMVF in background samples are typically unlike those characteristic of bulk WTC dust. Results indicate that slag wool can be used as a signature marker to identify areas that contain potential residual WTC dust contamination at concentrations that are less than average background levels for the material. PMID:18478046

Origins of chromite and magnetite in sedimentary rocks deposited in a shallow water environment in the 3.2 Ga Moodies Group, South Africa

NASA Astrophysics Data System (ADS)

Otake, T.; Sakamoto, Y.; Itoh, S.; Yurimoto, H.; Kakegawa, T.

2012-12-01

*Otake, T. totake@eng.hokudai.ac.jp Div. of Sustainable Resources Engineering, Hokkaido Univ., Sapporo, Japan Sakamoto, Y. yu.sakamoto12@gmail.com Dep. of Earth Science, Tohoku Univ., Sendai, Japan Itoh, S. sitoh@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Yurimoto. H. yuri@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Kakegawa, T. kakegawa@m.tohoku.ac.jp Dep. of Earth Science, Tohoku Univ., Sendai, Japan Geochemical data from ferruginous chemical sedimentary rocks (e.g., Banded Iron Formation: BIF) have been used to reconstruct the surface environments of early Earth. However, only a few studies have investigated the geochemical characteristics of BIFs deposited in a shallow water environment during the Archean, which may have differed from those deposited in a deep water environment. Therefore, we investigated geological, petrographic and geochemical characteristics of ferruginous rocks deposited in a shallow water environment in the Moodies group, in the Barberton Greenstone Belt, South Africa. We obtained ferruginous rock samples in the Moodies group from both an outcrop and underground gold mine, and compared the characteristics of these samples. The 70 sedimentary rock samples were divided into groups based on the dominant Fe minerals they contain: Hematite-rich jaspilite (HM group), Magnetite-rich iron formation/shale/sandstone (MT group), and Siderite-rich sandstone (SD group). Samples in the HM group are predominantly composed of fine-grained quartz (< 20 μm) and hematite (< 5 μm), which are interpreted to be chemical precipitates. Samples in the MT group contain quartz, magnetite, siderite, ankerite, chlorite, biotite and chromite. The grain size of magnetite is much larger (20-150 μm) than that of hematite in the HM group. The magnetite is interpreted as a secondary mineral transformed from hematite during early diagenesis. Results of in situ oxygen isotope analysis by SIMS showed that magnetite in the Moodies group has similar δ18O values to those in the least metamorphosed BIFs. All chromite observed in the MT group is overgrown by magnetite. Samples in the SD group contain quartz, siderite, chlorite, biotite, and chromite; the chromite is included in Mg-rich siderite or silicate minerals (e.g., chlorite and biotite). Oxygen isotope compositions indicate that chromite in both the MT and SD groups, was hydrothermally altered. Results of geochemical analyses of the bulk outcrop samples showed that FeTotal/Ti and Cr/Ti ratios of outcrop samples increase concordantly in the ferruginous zone, particularly in the MT group. The Cr/Ti ratios of the underground samples also increase with increasing the Fetotal/Ti ratios. On the other hand, Th/U ratios of both the outcrop and underground samples decrease with increasing FeTotal/Ti ratios. The correlations of Fetotal/Ti ratios with U/Th and Cr/Ti ratios indicate that dissolved Cr and U species in the ocean were coprecipitated with ferric (hydr)oxides during the formation of ferruginous rocks of the Moodies Group. These results suggest that Cr and U were chemically mobile, possibly as oxidized species, in the Earth's surface environment at ~3.2 Ga.

Returning from the deep: Archean atmospheric fingerprints in modern hotspot lavas (Invited)

NASA Astrophysics Data System (ADS)

Jackson, M. G.; Cabral, R. A.; Rose-Koga, E. F.; Koga, K. T.; Whitehouse, M. J.; Antonelli, M. A.; Farquhar, J.; Day, J. M.; Hauri, E. H.

2013-12-01

Ocean plates transport surface materials, including oceanic crust and sediment, into the mantle at subduction zones. However, the fate of the subducted package--oceanic crust and sediment--in the mantle is poorly understood. A long-standing hypothesis maintains that subducted materials reside in the mantle for an extended, but unknown, period of time and are then recycled back to the Earth's surface in regions of buoyantly upwelling mantle and melted beneath hotspots. Sulfur isotopes provide an important new tool to evaluate the presence of ancient recycled materials in hotspot lavas. Widespread terrestrial mass independently fractionated sulfur (MIF-S) isotope signatures were generated exclusively through atmospheric photochemical reactions until ~2.45 Ga. In fact, the only significant reservoirs of MIF-S containing rocks documented so far are sediments and hydrothermal rocks older than ~2.45 Ga. Armed with this insight, we examined sulfur isotopes in olivine phenocrysts and olivine-hosted sulfides in lavas from the island of Mangaia, Cook Islands. Lavas from this location host unusually radiogenic Pb-isotopic compositions--referred to as a HIMU (high U/Pb) component--and this has been attributed to ancient recycled oceanic crust in the mantle source. In Cabral et al. (2013), we report MIF-S in olivine phenocrysts and olivine-hosted sulfides. The discovery of MIF-S isotopic signatures in young hotspot lavas appears to provide a "timestamp" and "signature" for preservation of subducted Archean surface materials in the mantle sourcing Mangaia lavas. We report new sulfur isotope data on olivine-hosted sulfides from the Mangaia lavas that reinforce our discovery of MIF-S anomalies reported in Cabral et al. (2013). We also report new sulfur isotopic data on Mangaia whole rock powders, and we find no evidence of MIF-S signatures. It is not yet clear why the individual Mangaia sulfides and the olivine separates have more extreme MIF-S than the whole rocks. We consider it likely that the MIF-S anomaly measured in the olivine separates was diminished relative to the olivine-hosted sulfides by incorporation of modern sulfur into the olivine separates by low-temperature processes operating on the rocks during the 20 Ma since eruption: The absence of a MIF-S anomaly in the whole rock that has olivine-hosted sulfides with MIF-S anomalies may be a result of near-complete replacement of the magmatic sulfur (with a MIF-S anomaly) with modern sulfur (with no MIF-S anomaly) during surficial weathering over 20 Ma. The sulfur in the olivine-hosted sulfides with the largest MIF-S anomalies represents a very small proportion of the sulfur in a bulk basaltic rock and therefore do not impart a clear MIF-S anomaly on the bulk rock analysis. Very few data are available to evaluate this hypothesis. Therefore, pairing sulfur isotope measurements with whole rocks, mineral separates and olivine-hosted sulfides with careful petrographic and electron probe analyses of the samples will be critical for evaluating the origin of the sulfides--primary magmatic or secondary--and the origin and distribution of the sulfur-isotopic signatures in OIB.

Northwest Africa 5738: Multistage fluid-driven secondary alteration in an extraordinarily evolved eucrite

NASA Astrophysics Data System (ADS)

Warren, Paul H.; Rubin, Alan E.; Isa, Junko; Gessler, Nicholas; Ahn, Insu; Choi, Byeon-Gak

2014-09-01

The Northwest Africa 5738 eucrite contains a record of unprecedented geochemical complexity for a sample from the HED asteroid. It originated with a uniquely evolved (Stannern Trend) primary igneous composition, combining ultra-high bulk incompatible element and Na2O concentrations with a relatively low mg. Its bulk oxygen-isotopic composition (Δ‧17O = -0.27‰), as well as its trace element composition (e.g., Ga/Al), confirm other evidence for classification as a eucrite. Pyroxene mg equilibration, exsolution and ;cloudy; inclusions, all reflect a typical eucritic degree of thermal metamorphism. The rock contains an unprecedented array of microscopic fluid-metasomatic vein deposits. Most common are curvy microveins within pyroxene, which consist dominantly of Ca-plagioclase (typically An95, in stark contrast with the rock's An68-78 primary-igneous plagioclase), with Fe-olivine (Fo14) and Cr-spinel as additional major constituents. Likely related to these microveins are small masses of intergrown Ca-plagioclase (again roughly An95) and silica (or high-Si glass). Analyses of the microvein Cr-spinels show stoichiometry implying a significant Fe3+ content (Fe2O3 0.7-2.3 wt.%), and fO2 up to roughly IW+3; clearly elevated in comparison to the normal HED fO2 of about IW-1. The fO2 results show an anticorrelation with equilibration T (and with Mg/Fe), which suggests the parent fluid system became more oxidizing as it cooled. NWA 5738 also contains apparent secondary iron metal. The Fe-metals are very pure, with Ni consistently below an EPMA detection limit of ∼0.01 wt.%. The vein-like shapes of roughly 1/3 of the largest Fe-metals suggest origin by deposition from a fluid. The role of pyroxene exsolution as template for a denticular (sawtooth) Fe-metal edge shape, and the survival of Fo14 olivine in a rock with abundant silica and a far higher bulk mg, suggest that the most intense thermal metamorphism occurred no later than the secondary alteration. Near-complete lack of spatial association suggests that the Fe-metals formed during a distinct time period from the curvy microveins. The immediate cause of Fe-metal deposition was most plausibly (or anyway, least implausibly) an abrupt downshift in the fluid fO2. Considering the extremely evolved bulk composition, the fluid(s) may have been largely deuteric. However, more likely the main source of fluid was a nearby buried mass of volatile-rich impactor matter, such as carbonaceous chondrite, that hit the asteroid at low enough velocity to remain mostly intact. We further speculate that the abrupt drop in fluid fO2 may have been caused by a process of carbon-fueled ;smelting; (cf. ureilites), triggered by an impact-effected shift of the carbonaceous material to a changed environment, with higher T and/or lower P. These and other recent eucrite results point to a need for greater scrutiny regarding the absence of comparable alteration-veining in rocks from the lunar highland crust, a mysterious lack in view of recent evidence for abundant lunar water.

Helium-oxygen-osmium isotopic and elemental constraints on the mantle sources of the Deccan Traps

NASA Astrophysics Data System (ADS)

Peters, Bradley J.; Day, James M. D.; Greenwood, Richard C.; Hilton, David R.; Gibson, Jennifer; Franchi, Ian A.

2017-11-01

The Deccan Traps, a 65 million-year-old continental flood basalt province located in western India, is the result of one of the largest short-lived magmatic events to have occurred on Earth. The nature and composition of its mantle source(s), however, have been difficult to resolve due to extensive assimilation of continental crust into the ascending Traps magmas. To circumvent this issue, using high-precision electron microprobe analysis, we have analyzed olivine grains from MgO-rich (up to 15.7 wt.%) lavas that likely erupted before substantial crustal assimilation occurred. We compare olivine, pyroxene and plagioclase mineral chemistry and He-O-Os isotope compositions with bulk rock major- and trace-element abundances and 187Os/188Os for both bulk-rocks and mineral separates. Helium isotope compositions for the olivine grains generally show strong influence from crustal assimilation (<3 RA), but one ankaramite from the Pavagadh volcanic complex has a 3He/4He ratio of 10.7 RA, which is slightly lower than the range of 3He/4He measured for present-day Réunion Island volcanism (∼12-14 RA). Olivine-dominated mineral separates span a more restricted range in 187Os/188Os (0.1267 to 0.1443) compared with their host lavas (0.1186 to 0.5010), with the separates reflecting a parental magma composition less affected by lithospheric or crustal interaction than for the bulk-rocks. Despite significant He-Os isotopic variations, Δ17O is relatively invariant (- 0.008 ± 0.014 ‰) and indistinguishable from the bulk mantle, consistent with high-3He/4He hotspots measured to-date. Compositions of olivine grains indicate the presence of up to 25% of a pyroxenite source for Deccan parental magmas, in good agreement with ∼20% predicted from isotopic data for the same samples. Modeled pyroxenite signatures are similar to geochemical signatures expected to arise due to other types of mantle differentiation or due to assimilation of continental crust; however, we show that crustal assimilation cannot account for all of the compositional features of the olivine. Weak correlations exist between a global compilation of Xpx (Deccan: 0.2-0.7) and 3He/4He, δ18O (Deccan olivine: 4.9-5.2‰) and 187Os/188Os. Robust relationships between these parameters may be precluded due to a lack of two-reservoir source mixing, instead involving multiple mantle domains with distinct compositions, or because Xpx may reflect both source features and crustal assimilation. Notwithstanding, geochemical similarities exist between Deccan Traps olivine (3He/4He = 10.7 RA; 187Os/188Osi = 0.1313 ± 45, 2σ) and Réunion igneous rocks (3He/4He = 12-14 RA; 187Os/188Osi = 0.1324 ± 14). These relationships imply that a characteristic geochemical 'fingerprint' may have persisted in the mantle plume that fed the Deccan Traps, since its inception at 65 Ma, to ongoing eruptions occurring on Réunion up to the present-day.

Northwest Africa 7034: New Unique Water-rich Martian Meteorite from the Early Amazonian Epoch

NASA Astrophysics Data System (ADS)

Agee, C. B.; Wilson, N.; Ziegler, K. G.; McCubbin, F. M.; Polyak, V.; Nunn, M.; Sharp, Z. D.; Asmerom, Y.; Thiemens, M. H.

2012-12-01

Northwest Africa (NWA) 7034 is a porphyritic basaltic breccia that shares some geochemical characterstics with known martian meteorites (SNC), but also possesses some unique characteristics that would exclude it from the current SNC grouping. Instead, it has a major and minor element composition that is a remarkably good match with the geochemistry of the rocks and soil at Gusev Crater measured by the Spirit rover and the average martian crust composition from the Odyssey Orbiter gamma ray spectrometer. The mismatch of orbiter and rover data with SNC meteorites has been a perplexing enigma, however with the discovery of NWA 7034 we may now have found a "missing link" between martian meteorites and space craft data. A five-point isochon gives an Rb-Sr age for NWA 7034 of 2.089±0.081 Ga (2σ) (MSWD=6.6) and an initial 87Sr/86Sr ratio of 0.71359±54. The Sm-Nd data for the same samples show more scatter, with an isochron of 2.19±1.4 Ga (2σ). NWA 7034 is REE enriched crustal rock (La x58 CI) and strongly light REE over heavy REE enriched (La/Yb)N=2.3, with negative-Eu anomaly (Eu/Eu*=0.67). The whole rock has 143Nd/144Nd=0.511756 and 147Sm/144Nd=0.1664, giving a calculated initial (source value) 143Nd/144Nd=0.509467 (initial ɛNd=-9.1) which requires that it be derived from an enriched martian reservoir, with an inferred time-integrated 147Sm/144Nd=0.1689, assuming separation from a chondrite-like martian mantle 4.5 Ga. An age of ~2.1 Ga for NWA 7034 would make it the first meteorite sample from the early Amazonian or late Hesperian epoch in Mars geologic history. Oxygen isotope analyses of NWA 7034 were performed by laser fluorination at UNM on acid-washed bulk sample and at UCSD on vacuum pre-heated (1000°C) bulk sample and give mean values Δ17O=0.57±0.05‰ n=10 and Δ17O=0.50±0.03‰ n=2, respectively. These interlab values are in good agreement, but are significantly higher than literature values for SNC meteorites (Δ17O range 0.15-0.45‰). There may be several possible explanations for the relatively high oxygen isotope values of NWA 7034. One possibility is that two or more distinct oxygen isotope reservoirs exist on Mars - for example a reservoir represented by the SNC meteorites and another martian reservoir with higher δ18O, δ17O, and Δ17O that we see in NWA 7034. The existence of multiple oxygen isotopic reservoirs within the silicate portion of Mars, as indicated by the new data from NWA 7034, is difficult to reconcile in the context of a global magma ocean and may indicate incomplete planetary differentiation on Mars. NWA 7034 has an order of magnitude more indigenous water than most SNC meteorites. Six whole-rock combustion measurements yielded a bulk water content for NWA 7034 of 6190±620 ppm with δD=+46.3±8.6. The maximum δD value in three separate stepwise heating experiments was +276, +327, and +319‰ reached at 1050°C, 1014°C, and 804°C respectively. The mean amount of water released at high temperature (>320°C) is 3280±720 ppm. The comparatively high water content of NWA 7034 may be giving a glimpse of conditions in its source on Mars 2.1 billion years ago.

Core Cutting Test with Vertical Rock Cutting Rig (VRCR)

NASA Astrophysics Data System (ADS)

Yasar, Serdar; Osman Yilmaz, Ali

2017-12-01

Roadheaders are frequently used machines in mining and tunnelling, and performance prediction of roadheaders is important for project economics and stability. Several methods were proposed so far for this purpose and, rock cutting tests are the best choice. Rock cutting tests are generally divided into two groups which are namely, full scale rock cutting tests and small scale rock cutting tests. These two tests have some superiorities and deficiencies over themselves. However, in many cases, where rock sampling becomes problematic, small scale rock cutting test (core cutting test) is preferred for performance prediction, since small block samples and core samples can be conducted to rock cutting testing. Common problem for rock cutting tests are that they can be found in very limited research centres. In this study, a new mobile rock cutting testing equipment, vertical rock cutting rig (VRCR) was introduced. Standard testing procedure was conducted on seven rock samples which were the part of a former study on cutting rocks with another small scale rock cutting test. Results showed that core cutting test can be realized successfully with VRCR with the validation of paired samples t-test.

The rocks of Gusev Crater as viewed by the Mini-TES instrument

USGS Publications Warehouse

Ruff, S.W.; Christensen, P.R.; Blaney, D.L.; Farrand, W. H.; Johnson, J. R.; Michalski, J.R.; Moersch, J.E.; Wright, S.P.; Squyres, S. W.

2006-01-01

The Miniature Thermal Emission Spectrometer (Mini-TES) on board the Mars Exploration Rover Spirit is part of a payload designed to investigate whether a lake once existed in Gusev Crater. Mini-TES has observed hundreds of rocks along the rover's traverse into the Columbia Hills, yielding information on their distribution, bulk mineralogy, and the potential role of water at the site. Although dust in various forms produces contributions to the spectra, we have established techniques for dealing with it. All of the rocks encountered on the plains traverse from the lander to the base of the Columbia Hills share common spectral features consistent with an olivine-rich basaltic rock known as Adirondack Class. Beginning at the base of the West Spur of the Columbia Hills and across its length, the rocks are spectrally distinct from the plains but can be grouped into a common type called Clovis Class. These rocks, some of which appear as in-place outcrop, are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration. The northwest flank of Husband Hill is covered in float rocks known as Wishstone Class with spectral features that can be attributed uniquely to plagioclase feldspar, a phase that represents more than half of the bulk mineralogy. Rare exceptions are three classes of basaltic "exotics" found scattered across Husband Hill that may represent impact ejecta and/or float derived from local intrusions within the hills. The rare outcrops observed on Husband Hill display distinctive spectral characteristics. The outcrop called Peace shows a feature attributable to molecular bound water, and the outcrop that hosts the rock called Watchtower displays a dominant basaltic glass component. Despite evidence from the rover's payload for significant alteration of some of the rocks, no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by Mini-TES. The mineralogical results supplied by Mini-TES provide no clear evidence that a lake once existed in Gusev Crater. Copyright 2006 by the American Geophysical Union.

Geochemistry of the Shuksan greenschists and blueschists, North Cascades, Washington: Variably fractionated and altered metabasalts of oceanic affinity

NASA Astrophysics Data System (ADS)

Dungan, M. A.; Vance, J. A.; Blanchard, D. P.

1983-06-01

The Shuksan schist comprises a structurally coherent, metabasaltic member of the Easton Formation, the uppermost allochthon (Shuksan thrust plate) in the thrust system of the western North Cascades of Washington State. Late Jurassic metamorphism at moderately high P/T produced interlayering of actinolite-bearing greenschist assemblages with blue amphibole-bearing rocks. Major and trace element analyses of twelve greenschist and blueschist samples have been used to establish similarities between the basaltic protolith and moderately to strongly fractionated Type I MORB, to distinguish the effects of seafloor alteration superimposed on the primary igneous chemistry, and to evaluate the origin and nature of the chemical controls which produced the two mineral assemblages. The twelve analyzed samples exhibit moderate to strong LREE depletion, and characteristically low concentrations of other non-labile trace elements such as Nb, Th and Hf. The highly to moderately incompatible elements Ti, P, Nb, Zr, Hf, Y, Sc, and the REE vary by factors of 1.5 to 3.5 within the suite in a systematic pattern, increasing smoothly with increasing total iron. The relative enrichments of these elements are inversely proportional to bulk partition coefficients estimated for fractionation of basaltic magmas. The magnitude of the negative europium anomaly increases with overall incompatible element enrichment. These variations are consistent with the production of a wide spectrum of compositions by different degrees of low pressure fractionation of similar Type I MORB parent magmas. The concentrations of Sr, Rb, Na, and K vary irregularly and do not correlate with the non-labile trace elements. K and Rb are substantially elevated over typical MORB values in most samples and exhibit a consistently lower ratio (K/Rb=400 vs 1000) than fresh MORB. Concentrations of these four elements are believed to have been modified by low temperature seafloor alteration (pre-metamorphic) characterized by the formation of K-rich celadonitic clays, palagonite and minor potassium feldspar. The critical chemical variables that control the occurrence of actinolite and blue amphibole in the Shuksan schists are total iron, Fe2O3-content and Na/Ca (all high in blueschists). The chemical features were largely established by magmatic processes and inherited from the igneous parent rocks; the chemically more evolved samples are blueschists. The Fe2O3-content and Na/Ca, however, may be modified during alteration, rendering initial bulk compositions near the chemical boundary susceptible to changes which may shift rock compositions from one compatibility field to the other. Heterogeneous alteration of pillow lavas and other fragmental deposits, followed by intense flattening during metamorphism, provides a mechanism for generating blueschists and greenschists interlayered on the cm scale.

Transition Metal Systematics of Opx-Enriched Harzburgites From the Cascades Arc With Implications for the Origin of Cratonic Peridotites

NASA Astrophysics Data System (ADS)

Turner, S. J.

2007-12-01

A number of peridotite xenoliths collected from the Simcoe volcanic field region of the Cascades arc exhibit notable enrichment of modal orthopyroxene. The process driving this enrichment is most likely metasomatism of the mantle wedge by Si-rich fluids derived ultimately from the underlying slab. By investigating the resultant elemental systematics associated with subduction zone metasomatism of this type, we hope to shed light on the origin of other opx-rich peridotites, such as those seen in many cratonic xenolith suites. The xenoliths found in the Simcoe volcanic field provide a rare opportunity to examine the composition of sub arc mantle, as it is unusual to find mantle xenoliths in volcanic arc lavas. The samples were analyzed using laser ablation ICPMS and their bulk compositions were reconstructed from point-counted mineral modes. Two-pyroxene mineral thermometry of the samples yield temperatures of approximately 1000 degrees C, corresponding to a depth of origin at uppermost mantle pressures if typical arc geotherms are assumed. Most of the peridotites are harzburgites or olivine-orthopyroxenites (Mg#s 0.88-0.9; opx mode 0.15-0.9), with small amounts of clinopyroxene (<0.02). Clinopyroxenes are significantly enriched in the light rare earths, consistent with a metasomatic origin for these opx-rich harzburgites. Of note is the counterintuitive systematics of Zn. Whole-rock Zn decreases with opx, but Zn in olivine also decreases with opx mode while Zn in opx increases with opx mode, hence the decrease in whole- rock Zn is not simply due to mechanical segregation of harzburgite into opx- and ol-rich zones. In summary, the REE signatures suggest the subducting slab as the most likely candidate for the source of the fluids that caused the opx enrichment. The opx-enrichment itself and the unusual trends in Zn suggest a reaction between a silicic fluid and normal harzburgite. Moreover, the concomitant decrease in olivine and whole-rock Zn with opx mode suggests significant leaching of Zn from the peridotite during this process. Because the bulk partitioning of Zn in anhydrous peridotite melting is unity, low Zn contents are anomalous. The best explanation for these low values is that Zn partition coefficients decrease in hydrous environments. Many opx-enriched Archean cratonic peridotite xenoliths have anomalously low Zn contents, supporting the suggestion that such peridotites formed in arc environments.

Magmatic and Crustal Differentiation History of Granitic Rocks from Hf-O Isotopes in Zircon

NASA Astrophysics Data System (ADS)

Kemp, , A. I. S.; Hawkesworth, , C. J.; Foster, , G. L.; Paterson, , B. A.; Woodhead, , J. D.; Hergt, , J. M.; Gray, , C. M.; Whitehouse, M. J.

2007-02-01

Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust.

Multivariate Statistical Analysis of MSL APXS Bulk Geochemical Data

NASA Astrophysics Data System (ADS)

Hamilton, V. E.; Edwards, C. S.; Thompson, L. M.; Schmidt, M. E.

2014-12-01

We apply cluster and factor analyses to bulk chemical data of 130 soil and rock samples measured by the Alpha Particle X-ray Spectrometer (APXS) on the Mars Science Laboratory (MSL) rover Curiosity through sol 650. Multivariate approaches such as principal components analysis (PCA), cluster analysis, and factor analysis compliment more traditional approaches (e.g., Harker diagrams), with the advantage of simultaneously examining the relationships between multiple variables for large numbers of samples. Principal components analysis has been applied with success to APXS, Pancam, and Mössbauer data from the Mars Exploration Rovers. Factor analysis and cluster analysis have been applied with success to thermal infrared (TIR) spectral data of Mars. Cluster analyses group the input data by similarity, where there are a number of different methods for defining similarity (hierarchical, density, distribution, etc.). For example, without any assumptions about the chemical contributions of surface dust, preliminary hierarchical and K-means cluster analyses clearly distinguish the physically adjacent rock targets Windjana and Stephen as being distinctly different than lithologies observed prior to Curiosity's arrival at The Kimberley. In addition, they are separated from each other, consistent with chemical trends observed in variation diagrams but without requiring assumptions about chemical relationships. We will discuss the variation in cluster analysis results as a function of clustering method and pre-processing (e.g., log transformation, correction for dust cover) and implications for interpreting chemical data. Factor analysis shares some similarities with PCA, and examines the variability among observed components of a dataset so as to reveal variations attributable to unobserved components. Factor analysis has been used to extract the TIR spectra of components that are typically observed in mixtures and only rarely in isolation; there is the potential for similar results with data from APXS. These techniques offer new ways to understand the chemical relationships between the materials interrogated by Curiosity, and potentially their relation to materials observed by APXS instruments on other landed missions.

Experiments in Ice Contaminant Remanent Magnetization of Dusty Frost Deposits

NASA Astrophysics Data System (ADS)

Grossman, Y.; Aharonson, O.; Shaar, R.

2017-12-01

Sedimentary rocks can acquire magnetization in the presence of an external field as grains settle out of suspension in a water column - a process known as Depositional Remanent Magnetization (DRM). In analogy with this, here we propose and experimentally demonstrate a new mechanism for acquisition of magnetization by ice and particulate mixtures which we term Ice Contaminant Remanent Magnetization (ICRM). This phenomenon results from the settling of atmospheric dust containing magnetic particles (e.g. magnetite or other iron oxides). Upon freezing, magnetic dust particles assume a preferential orientation that depends on the external planetary field, resulting in bulk magnetization of the dusty ice. Hence over geologic timescales, the ice stratigraphy is expected to record the geomagnetic history. To test this hypothesis, we designed a set of experiments in which mixtures of ice and dust were deposited in a controlled ambient magnetic field environment. We measured the ratio between the volume normalized magnetization of the dusty ice (m) and the applied field (H) during deposition of the mixture, which is expressed as the effective ICRM susceptibility: m=χICRMH. A magnetic field was applied by a 3-axis Helmholtz coil at the Weizmann Simulating Planetary Ices & Environments Laboratory, and the frozen samples were analyzed in a 2G-Entreprises SQUID Rock Magnetometer at the Hebrew University Institute for Earth Sciences. We measured a clear correlation in amplitude and direction between the ambient magnetic field applied during deposition and the remanent magnetic moment of the resulting samples. We studied various concentrations and particle sizes (diameters 5 µm to 50 µm) of iron and magnetite particles. Effective bulk susceptibilities show a range of values, starting from 10-3 and up to values that saturate the analytical instrument. Our preliminary results indicate that natural ice deposits may acquire variable magnetization due to ICRM, which may in turn be interpreted as paleomagnetic records on Earth and other planets.

Mantle Water Contents Beneath the Rio Grande Rift (NM, USA): FTIR Analysis of Rio Puerco and Kilbourne Hole Peridotite Xenoliths

NASA Technical Reports Server (NTRS)

Schaffer, L. A.; Peslier, A. H.; Brandon, A.; Selverstone, J.

2015-01-01

Peridotite xenoliths from the Rio Grande Rift (RGR) are being analyzed for H (sub 2) O contents by FTIR (Fourier Transform Infrared) as well as for major and trace element compositions. Nine samples are from the Rio Puerco Volcanic Field (RP) which overlaps the central RGR and southeastern Colorado Plateau; seventeen samples are from Kilbourne Hole (KH) in the southern RGR. Spinel Cr# (Cr/(Cr+Al)) (0.08-0.46) and olivine Mg# (Mg/(Mg plus Fe)) (0.883-0.911) of all RGR samples fall within the olivine-spinel mantle array from [1], an indicator that peridotites are residues of partial melting. Pyroxene H (sub 2) O in KH correlate with bulk rock and pyroxene Al (sub 2) O (sub 3).The KH clinopyroxene rare earth element (REE) variations fit models of 0-13 percent fractional melting of a primitive upper mantle. Most KH peridotites have bulk-rock light REE depleted patterns, but five are enriched in light REEs consistent with metasomatism. Variation in H (sub 2) O content is unrelated to REE enrichment. Metasomatism is seen in RP pyroxenite xenoliths [2] and will be examined in the peridotites studied here. Olivine H (sub 2) O contents are low (less than or equal to 15 parts per million), and decrease from core to rim within grains. This is likely due to H loss during xenolith transport by the host magma [3]. Diffusion models of H suggest that mantle H (sub 2) O contents are still preserved in cores of KH olivine, but not RP olivine. The average H (sub 2) O content of Colorado Plateau clinopyroxene (670 parts per million) [4] is approximately 300 parts per million higher than RGR clinopyroxene (350 parts per million). This upholds the hypothesis that hydration-induced lithospheric melting occurred during flat-slab subduction of the Farallon plate [5]. Numerical models indicate hydration via slab fluids is possible beneath the plateau, approximately 600 kilometers from the paleo-trench, but less likely approximately 850 kilometers away beneath the rift [6].

Proposed moduli of dry rock and their application to predicting elastic velocities of sandstones

USGS Publications Warehouse

Lee, Myung W.

2005-01-01

Velocities of water-saturated isotropic sandstones under low frequency can be modeled using the Biot-Gassmann theory if the moduli of dry rocks are known. On the basis of effective medium theory by Kuster and Toksoz, bulk and shear moduli of dry sandstone are proposed. These moduli are related to each other through a consolidation parameter and provide a new way to calculate elastic velocities. Because this parameter depends on differential pressure and the degree of consolidation, the proposed moduli can be used to calculate elastic velocities of sedimentary rocks under different in-place conditions by varying the consolidation parameter. This theory predicts that the ratio of P-wave to S-wave velocity (Vp/Vs) of a dry rock decreases as differential pressure increases and porosity decreases. This pattern of behavior is similar to that of water-saturated sedimentary rocks. If microcracks are present in sandstones, the velocity ratio usually increases as differential pressure increases. This implies that this theory is optimal for sandstones having intergranular porosities. Even though the accurate behavior of the consolidation parameter with respect to differential pressure or the degree of consolidation is not known, this theory presents a new way to predict S-wave velocity from P-wave velocity and porosity and to calculate elastic velocities of gas-hydrate-bearing sediments. For given properties of sandstones such as bulk and shear moduli of matrix, only the consolidation parameter affects velocities, and this parameter can be estimated directly from the measurements; thus, the prediction of S-wave velocity is accurate, reflecting in-place conditions.

Petrography and Origin of the Unique Achondrite GRA 06128 and 06129: Preliminary Results

NASA Technical Reports Server (NTRS)

Treiman, A. H.; Morris, R. V.; Kring, D. A.; Mittlefehldt, D. W.; Jones, J. H.

2008-01-01

GRA 06128 & 06129 are paired achondrites [1], with unique mineral proportions (75% oligoclase), mineral compositions, and oxygen isotope ratios. They appear to represent alkalic igneous rock from a hitherto unsampled differentiated parent body, modified significantly by thermal and shock metamorphism. Samples and Methods: Bulk samples were examined at JSC during splitting for consortium analyses. Microscope and BSE images here are on thick section GRA06128,40. Chemical analyses of minerals were acquired at Johnson Space Center with the Cameca SX100, operated at 15 kV. Feldspar was analyzed with a defocused 5 micron beam @ 5 nA; other minerals were analyzed with a focused beam @ 20 nA. Moessbauer spectra were obtained at ARES, JSC [2]. Intrinsic radioactivity was measured in the low-level counting facility at ARES JSC [3]. An estimated abundance of Al-26 of approx. 70 dpm/kg is within the range determined for eucrites.

Predicting the Sources and Formation Mechanisms of Evolved Lunar Crust by Linking K/Ca Ratios of Lunar Granites to Analogous Terrestrial Igneous Rocks

NASA Technical Reports Server (NTRS)

Mills, R. D.; Simon, J. I.

2012-01-01

Although silicic rocks (i.e. granites and rhyolites) comprise a minor component of the sampled portion of the lunar crust, recent remote sensing studies [e.g., 1-4] indicate that several un-sampled regions of the Moon have significantly higher concentrations of silicic material (also high in [K], [U], and [Th]) than sampled regions. Within these areas are morphological features that are best explained by the existence of chemically evolved volcanic rocks. Observations of silicic domes [e.g., 1-5] suggest that sizable networks of silicic melt were present during crust formation. Isotopic data indicate that silicic melts were generated over a prolonged timespan from 4.3 to 3.9 Ga [e.g., 6-8]. The protracted age range and broad distribution of silicic rocks on the Moon indicate that their petrogenesis was an important mechanism for secondary crust formation. Understanding the origin and evolution of such silicic magmas is critical to determining the composition of the lunar crustal highlands and will help to distinguish between opposing ideas for the Moon's bulk composition and differentiation. The two main hypotheses for generating silicic melts on Earth are fractional crystallization or partial melting. On the Moon silicic melts are thought to have been generated during extreme fractional crystallization involving end-stage silicate liquid immiscibility (SLI) [e.g. 9, 10]. However, SLI cannot account for the production of significant volumes of silicic melt and its wide distribution, as reported by the remote global surveys [1, 2, 3]. In addition, experimental and natural products of SLI show that U and Th, which are abundant in the lunar granites and seen in the remote sensing data of the domes, are preferentially partitioned into the depolymerized ferrobasaltic magma and not the silicic portion [11, 12]. If SLI is not the mechanism that generated silicic magmas on the Moon then alternative processes such as fractional crystallization (only crystal-liquid separation) or partial melting should be considered as viable possibilities to be tested.

Investigating uranium distribution in surface sediments and waters: a case study of contamination from the Juniper Uranium Mine, Stanislaus National Forest, CA.

PubMed

Kayzar, Theresa M; Villa, Adam C; Lobaugh, Megan L; Gaffney, Amy M; Williams, Ross W

2014-10-01

The uranium concentrations and isotopic compositions of waters, sediment leachates and sediments from Red Rock Creek in the Stanislaus National Forest of California were measured to investigate the transport of uranium from a point source (the Juniper Uranium Mine) to a natural surface stream environment. The ((234)U)/((238)U) composition of Red Rock Creek is altered downstream of the Juniper Mine. As a result of mine-derived contamination, water ((234)U)/((238)U) ratios are 67% lower than in water upstream of the mine (1.114-1.127 ± 0.009 in the contaminated waters versus 1.676 in the clean branch of the stream), and sediment samples have activity ratios in equilibrium in the clean creek and out of equilibrium in the contaminated creek (1.041-1.102 ± 0.007). Uranium concentrations in water, sediment and sediment leachates are highest downstream of the mine, but decrease rapidly after mixing with the clean branch of the stream. Uranium content and compositions of the contaminated creek headwaters relative to the mine tailings of the Juniper Mine suggest that uranium has been weathered from the mine and deposited in the creek. The distribution of uranium between sediment surfaces (leachable fraction) and bulk sediment suggests that adsorption is a key element of transfer along the creek. In clean creek samples, uranium is concentrated in the sediment residues, whereas in the contaminated creek, uranium is concentrated on the sediment surfaces (∼70-80% of uranium in leachable fraction). Contamination only exceeds the EPA maximum contaminant level (MCL) for drinking water in the sample with the closest proximity to the mine. Isotopic characterization of the uranium in this system coupled with concentration measurements suggest that the current state of contamination in Red Rock Creek is best described by mixing between the clean creek and contaminated upper branch of Red Rock Creek rather than mixing directly with mine sediment. Published by Elsevier Ltd.

Investigating uranium distribution in surface sediments and waters: a case study of contamination from the Juniper Uranium Mine, Stanislaus National Forest, CA

DOE PAGES

Kayzar, Theresa M.; Villa, Adam C.; Lobaugh, Megan L.; ...

2014-06-07

The uranium concentrations and isotopic compositions of waters, sediment leachates and sediments from Red Rock Creek in the Stanislaus National Forest of California were measured to investigate the transport of uranium from a point source (the Juniper Uranium Mine) to a natural surface stream environment. Furthermore, we alter the (234U)/(238U) composition of Red Rock Creek downstream of the Juniper Mine. As a result of mine-derived contamination, water (234U)/(238U) ratios are 67% lower than in water upstream of the mine (1.114–1.127 ± 0.009 in the contaminated waters versus 1.676 in the clean branch of the stream), and sediment samples have activitymore » ratios in equilibrium in the clean creek and out of equilibrium in the contaminated creek (1.041–1.102 ± 0.007). Uranium concentrations in water, sediment and sediment leachates are highest downstream of the mine, but decrease rapidly after mixing with the clean branch of the stream. Uranium content and compositions of the contaminated creek headwaters relative to the mine tailings of the Juniper Mine suggest that uranium has been weathered from the mine and deposited in the creek. The distribution of uranium between sediment surfaces (leachable fraction) and bulk sediment suggests that adsorption is a key element of transfer along the creek. In clean creek samples, uranium is concentrated in the sediment residues, whereas in the contaminated creek, uranium is concentrated on the sediment surfaces (~70–80% of uranium in leachable fraction). Furthermore, contamination only exceeds the EPA maximum contaminant level (MCL) for drinking water in the sample with the closest proximity to the mine. Isotopic characterization of the uranium in this system coupled with concentration measurements suggest that the current state of contamination in Red Rock Creek is best described by mixing between the clean creek and contaminated upper branch of Red Rock Creek rather than mixing directly with mine sediment.« less

Rotary bulk solids divider

DOEpatents

Maronde, Carl P.; Killmeyer, Jr., Richard P.

1992-01-01

An apparatus for the disbursement of a bulk solid sample comprising, a gravity hopper having a top open end and a bottom discharge end, a feeder positioned beneath the gravity hopper so as to receive a bulk solid sample flowing from the bottom discharge end, and a conveyor receiving the bulk solid sample from the feeder and rotating on an axis that allows the bulk solid sample to disperse the sample to a collection station.

ROTARY BULK SOLIDS DIVIDER

DOEpatents

Maronde, Carl P.; Killmeyer JR., Richard P.

1992-03-03

An apparatus for the disbursement of a bulk solid sample comprising, a gravity hopper having a top open end and a bottom discharge end, a feeder positioned beneath the gravity hopper so as to receive a bulk solid sample flowing from the bottom discharge end, and a conveyor receiving the bulk solid sample from the feeder and rotating on an axis that allows the bulk solid sample to disperse the sample to a collection station.

Variable magma reservoir depths for Tongariro Volcanic Complex eruptive deposits from 10,000 years to present

NASA Astrophysics Data System (ADS)

Arpa, Maria Carmencita; Zellmer, Georg F.; Christenson, Bruce; Lube, Gert; Shellnutt, Gregory

2017-07-01

Mineral, groundmass and bulk rock chemical analyses of samples from the Tongariro Volcanic Complex were made to estimate depths of magma reservoirs for selected eruptive deposits. The sample set consists of two units from the 11,000 cal. years bp Mangamate Formation (Te Rato and Wharepu) and more recent deposits from near 1717 cal. years bp (Ngauruhoe and Red Crater) to 1975 (Ngauruhoe). The depths of crystallization were determined by established thermobarometers. Results show that the Mangamate eruptions of Te Rato and Wharepu originated from a deeper magma reservoir of about 28-35 km and likely ascended rapidly, whereas explosive eruption deposits from Ngauruhoe have depths of crystallization in the lower to mid-crust or about 7 to 22 km depth. A Red Crater lava flow had a possible magma reservoir depth from 4 to 9 km. The different eruptions sampled for this study tapped different reservoir levels, and the oldest and largest eruptions were sourced from the deepest reservoir.

Rock pushing and sampling under rocks on Mars

USGS Publications Warehouse

Moore, H.J.; Liebes, S.; Crouch, D.S.; Clark, L.V.

1978-01-01

Viking Lander 2 acquired samples on Mars from beneath two rocks, where living organisms and organic molecules would be protected from ultraviolet radiation. Selection of rocks to be moved was based on scientific and engineering considerations, including rock size, rock shape, burial depth, and location in a sample field. Rock locations and topography were established using the computerized interactive video-stereophotogrammetric system and plotted on vertical profiles and in plan view. Sampler commands were developed and tested on Earth using a full-size lander and surface mock-up. The use of power by the sampler motor correlates with rock movements, which were by plowing, skidding, and rolling. Provenance of the samples was determined by measurements and interpretation of pictures and positions of the sampler arm. Analytical results demonstrate that the samples were, in fact, from beneath the rocks. Results from the Gas Chromatograph-Mass Spectrometer of the Molecular Analysis experiment and the Gas Exchange instrument of the Biology experiment indicate that more adsorbed(?) water occurs in samples under rocks than in samples exposed to the sun. This is consistent with terrestrial arid environments, where more moisture occurs in near-surface soil un- der rocks than in surrounding soil because the net heat flow is toward the soil beneath the rock and the rock cap inhibits evaporation. Inorganic analyses show that samples of soil from under the rocks have significantly less iron than soil exposed to the sun. The scientific significance of analyses of samples under the rocks is only partly evaluated, but some facts are clear. Detectable quantities of martian organic molecules were not found in the sample from under a rock by the Molecular Analysis experiment. The Biology experiments did not find definitive evidence for Earth-like living organisms in their sample. Significant amounts of adsorbed water may be present in the martian regolith. The response of the soil from under a rock to the aqueous nutrient in the Gas Exchange instrument indicates that adsorbed water and hydrates play an important role in the oxidation potential of the soil. The rock surfaces are strong, because they did not scratch, chip or spall when the sampler pushed them. Fresh surfaces of soil and the undersides of rocks were exposed so that they could be imaged in color. A ledge of soil adhered to one rock that tilted, showing that a crust forms near the surface of Mars. The reason for low amounts of iron in the sampIes from under the rocks is not known at this time.

Crustal Rock: Recorder of Oblique Impactor Meteoroid Trajectories

NASA Astrophysics Data System (ADS)

Ahrens, Thomas J.

2005-07-01

Oblique impact experiments in which 2g lead bullets strike samples of San Marcos granite and Bedford limestone at 1.2 km/s induce zones of increased crack density (termed shocked damage) which result in local decreases in bulk and shear moduli that results in maximum decreases of 30-40% in compressional and shear wave velocity (Budianski and O'Connell). Initial computer simulation of oblique impacts of meteorites (Pierazzo and Melosh) demonstrate the congruence of peak shock stress trajectory with the pre-impact meteoroid trajectory. We measure (Ai and Ahrens) via multi-beam (˜ 300) tomographic inversion, the sub-impact surface distribution of damage from the decreases in compressional wave velocity in the 20 x 20 x 15 cm rock target. The damage profiles for oblique impacts are markedly asymmetric (in plane of pre-impact meteoroid pre-impact trajectory) beneath the nearly round excavated craters. Thus, meteorite trajectory information can be recorded in planetary surfaces. Asymmetric sub-surface seismic velocity profiles beneath the Manson (Iowa) and Ries (Germany) impact craters demonstrate that pre-impact meteoroid trajectories records remain accessible for at least ˜ 10 ^ 8 years.

Mars Crust: Made of Basalt

NASA Astrophysics Data System (ADS)

Taylor, G. J.

2009-05-01

By combining data from several sources, Harry Y. (Hap) McSween (University of Tennessee), G. Jeffrey Taylor (University of Hawaii) and Michael B. Wyatt (Brown University) show that the surface of Mars is composed mostly of basalt not unlike those that make up the Earth's oceanic crust. McSween and his colleagues used data from Martian meteorites, analyses of soils and rocks at robotic landing sites, and chemical and mineralogical information from orbiting spacecraft. The data show that Mars is composed mostly of rocks similar to terrestrial basalts called tholeiites, which make up most oceanic islands, mid-ocean ridges, and the seafloor beneath sediments. The Martian samples differ in some respects that reflect differences in the compositions of the Martian and terrestrial interiors, but in general are a lot like Earth basalts. Cosmochemistst have used the compositions of Martian meteorites to discriminate bulk properties of Mars and Earth, but McSween and coworkers' synthesis shows that the meteorites differ from most of the Martian crust (the meteorites have lower aluminum, for example), calling into question how diagnostic the meteorites are for understanding the Martian interior.

The importance of bulk density determination in gravity data processing for structure interpretation

NASA Astrophysics Data System (ADS)

Wildan, D.; Akbar, A. M.; Novranza, K. M. S.; Sobirin, R.; Permadi, A. N.; Supriyanto

2017-07-01

Gravity method use rock density variation for determining subsurface lithology and geological structure. In the "green area" where measurement of rock density has not been done, an attemp to find density is usually performed by calculating using Parasnis method, or by using using the average of rock density in the earth's crust (2,67 gr/cm3) or by using theoritical value of dominant rock density in the survey area (2,90 gr/cm3). Those three values of densities are applied to gravity data analysis in the hilly "X" area. And we have compared all together in order to observed which value has represented the structure better. The result showed that the higher value of rock density, the more obvious structure in the Bouguer anomaly profile. It is due to the contrast of maximum and minimum value of Bouguer anomaly that will affect the exageration in distance vs Bouguer anomaly graphic.

Geothermal alteration of Kamchatka rock physical properties: experimental and pore-scale modeling study

NASA Astrophysics Data System (ADS)

Shanina, Violetta; Gerke, Kirill; Bichkov, Andrey; Korost, Dmitry

2013-04-01

Alternative renewable energy sources research is getting more and more attention due to its importance for future exploitation and low ecological impacts. Geothermal energy is quite abundant and represents a cheap and easily extractable power source for electricity generation or central heating. For these purposes naturally heated geothermal fluids are extracted via drilled wells; after cooling water is usually pumped back to the reservoir to create a circle, or dumped into local streams. In addition to fundamental interest in understanding natural geothermal processes inside the reservoir, in both cases fluids can significantly alter rock properties around the well or stream bed, which is of great practical and ecological importance for the geothermal industry. Detailed knowledge of these transformations is necessary for power plant construction and well design, geophysical modeling and the prediction of geological properties. Under natural conditions such processes occur within geological time frames and are hard to capture. To accelerate geothermal alteration and model deep reservoir high temperature and pressure conditions we use autoclave laboratory experiments. To represent different geothermal conditions, rock samples are autoclaved using a wide range of parameters: temperature (100-450°C), pressure (16-1000 Bars), solution chemistry (from acidic to alkali artificial solutions and natural geothermal fluids sampled in Kamchatka), duration (from weeks to 1 year). Rock samples represent unaltered andesite-dacite tuffs, basalts and andesite collected at the Kamchatka peninsula. Numerous rock properties, e.g., density (bulk and specific), porosity (total and effective), hygroscopicity, P/S wave velocities, geomechanical characteristics (compressive and tensile strength, elastic modulus), etc., were thoroughly analyzed before and after alteration in laboratory autoclave or natural conditions (in situ). To reveal structural changes, some samples were scanned using X-ray microtomography prior to any alteration and after the experiments. 3D images were used to quantify structural changes and to determine permeability values using a pore-scale modeling approach, as laboratory measurements with through flow are known to have a potential to modify the pore structure. Chemical composition and local mineral formations were investigated using a «Spectroscan Max GV» spectrometer and scanning electron microscope imaging. Our study revealed significant relationships between structure modifications, physical properties and alteration conditions. Main results and conclusions include: 1) initial porosity and its connectivity have substantial effect on alteration dynamics, rocks with higher porosity values and connected pore space exhibit more pronounced alterations; 2) under similar experimental conditions (pressure, temperature, duration) pH plays an important role, acidic conditions result in significant new mineral formation; 3) almost all physical properties, including porosity, permeability, and elastic properties, were seriously modified in the modeled geothermal processes within short (from geological point of view) time frames; 4) X-ray microtomography was found useful for mineral phases distribution and the pore-scale modeling approach was found to be a promising technique to numerically obtain rock properties based on 3D scans; 5) we conclude that alteration and change of reservoir rocks should be taken into account for re-injecting well and geothermal power-plant design.

Geologic and engineering properties investigations: Project Sulky

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lutton, R.J.; Girucky, F.E.

1966-09-01

The Sulky event was a nuclear cratering experiment in which a device yielding 85 + 15 tons was detonated at a depth of 90 ft in jointed basalt. The explosion produced a rubble-covered mound roughly circular in plan and extending approximately 24 ft above the original ground surface. Prior to the event the Sulky site was explored by means of 6 core borings and the emplacement calyx hole. Geophysical logging was conducted and laboratory tests were performed on representative samples. Postshot investigations consisted of trenching through the mound and drilling 3 core borings to determine the extent of the rupturemore » zone. The rock consists of vesicular basalt over dense basalt and each type is structurally modified by layering of vesicles resulting from viscous flow of the lava. Unconfined compressive strengths range from about 10,000 psi for vesicular basalt to about 20,000 psi for dense basalt. Bulk specific gravities for dense basalt are about 2.74, but with increasing vesicle content the bulk specific gravity reaches values as low as 2.40.« less

MicroCT vs. Hg porosimetry: microporosity in commercial stones

NASA Astrophysics Data System (ADS)

Fusi, N.; Martinez-Martinez, J.; Barberini, V.; Galimberti, L.

2009-04-01

Decay of rocks, due both to extrinsic and intrinsic factors, can show up in several different forms, such as neoformation of minerals, decohesion of grains and/or crystals, magnification of previous defects, new discontinuities, etc. Intrinsic factors include the type of material, its properties and microstructure, in particular porosity and microporosity. Extrinsic factors relate to atmosphere and usage of the material itself. Rock degradation has several heavy consequences for commercial stones, such as increase of permeability, loss of material, loss of mechanical strength; these consequences are of crucial importance for conservation of historical buildings. Aim of this study is to compare microporosity of some massive commercial stones by means of X ray microtomography, a non destructive technique, and Hg porosimetry. Nine of the most used Spanish limestones and dolostones have been analysed. The lithotypes have been chosen for their homogeneous mineralogical composition (calcitic or dolomitic) and for their low porosity; some of them have been widely used in Spain for historical buildings. Different lithotypes have been described in thin section: Ambarino (A) and Beige Serpiente (BS): brecciated dolostone, composed by microcrystalline dolomitic clasts, in a dolomitic and/or calcitic microcrystalline matrix. Amarillo Triana (AT): yellow dolomitic marble, with fissures filled up by calcite and Fe oxides. Blanco Alconera (BA): a white-pink homogeneous limestone, with veins. Blanco Tranco (BT): a homogeneous white calcitic marble, without any fissures and/or fractures. Crema Valencia (CV): a pinkish limestone, characterized by abundant stilolythes, filled mainly by quartz (80%) and kaolin (11%). Gris Macael (GM): a calcitic marble wiht darker and lighter beds, conferring a strong anisotropy. Rojo Cehegin (RC): a red fossiliferous limestone with white calcitic veins. Travertino Blanco (TB): a massive white calcitic travertine. Prismatic samples of about 2x1x1 cm have been cut and scanned by means of a X ray microCT system before and after mercury saturation with Hg porosimeter. The microCT system used is a BIR Actis 130/150 with nominal resolution of 5 micron; for our samples resolution is of 25 microns. Generator and detector are fixed, while the sample rotates; the scanning plane is horizontal. Samples reduce the X rays energy passing through, as a function of its density and atomic number. X rays are then collected on a detector, which converts them into light radiations; a digital camera collects light radiations in raw data and send them to the computer, where they are processed as black/white images. The Hg porosimeter used is a Pascal 140/240 Thermo Fisher. Samples were first degassed and then intruded by Hg. Apparent density, bulk density, porosity and open pore size distribution (pore diameter between 3.7 and 58000 nm) of each sample have been computed using the PASCAL (Pressurization with Automatic Speed-up by Continuous Adjustametnt Logic) method and the Washburn equation; this equation assumes: cylindrical pores, a contact angle between mercury and sample of 140°, a surface tension of mercury vacuum of 0,480 N/m and mercury density equal to 13.5 g/cm³. MicroCT images and porosity data from Hg porosimeter have been compared by several authors both for rocks (Klobes et alii, 1997) and for artificial materials with medical applications (Lin-Gibson et alii, 2007) In samples with no density/composition differences microCT images are homogeneous and gives no information on the internal structure of the sample. This is the case of massive samples (such as BA, BT, GM and TB) and of samples without any significant density differences between clasts and matrix (A and BS) or rock and veins (RC). MicroCT images of the same sample after mercury saturation offer a detailed map of microporosity of the rock, due to the high density contrast between mercury (13.6 g/cm3) and the rock (2.71 g/cm3 for calcite and 2.86 g/cm3 for dolomite). In some cases microporosity coincide with structural features of the rock, such as stylolythes (CV), fissures (AT) and veins (RC). This method works for samples with low porosity (less than 1%); on the other hand for samples with higher porosity (4%; A and BS) microCT images after Hg saturation present artefacts, due to the spreading of Hg within the sample, which obliterates the true structure of the rock. References Klobes, P., Riesemeier, H., Meyer, K., Goebbles, J. and Hellmuth, K.H. (1997). Rock porosity determination by combination of K-ray computerized tomography with mercury porosimetry. Fresenius J. Anal. Chem., 357, 543-547 Lin-Gibson, S., Cooper, J.A., Forrest, A.L. and Cicerone, M.T. (2007). Systematic investigation of porogen size and content on scaffold morphometric parameters and properties. Biomacromolecules, 8, 1511-1518.

Fault Damage Zone Permeability in Crystalline Rocks from Combined Field and Laboratory Measurements: Can we Predict Damage Zone Permeability?

NASA Astrophysics Data System (ADS)

Mitchell, T. M.; Faulkner, D. R.

2009-04-01

Models predicting crustal fluid flow are important for a variety of reasons; for example earthquake models invoking fluid triggering, predicting crustal strength modelling flow surrounding deep waste repositories or the recovery of natural resources. Crustal fluid flow is controlled by both the bulk transport properties of rocks as well as heterogeneities such as faults. In nature, permeability is enhanced in the damage zone of faults, where fracturing occurs on a wide range of scales. Here we analyze the contribution of microfracture damage on the permeability of faults that cut through low porosity, crystalline rocks by combining field and laboratory measurements. Microfracture densities surrounding strike-slip faults with well-constrained displacements ranging over 3 orders of magnitude (~0.12 m - 5000 m) have been analyzed. The faults studied are excellently exposed within the Atacama Fault Zone, where exhumation from 6-10 km has occurred. Microfractures in the form of fluid inclusion planes (FIPs) show a log-linear decrease in fracture density with perpendicular distance from the fault core. Damage zone widths defined by the density of FIPs scale with fault displacement, and an empirical relationship for microfracture density distribution throughout the damage zone with displacement is derived. Damage zone rocks will have experienced differential stresses that were less than, but some proportion of, the failure stress. As such, permeability data from progressively loaded, initially intact laboratory samples, in the pre-failure region provide useful insights into fluid flow properties of various parts of the damage zone. The permeability evolution of initially intact crystalline rocks under increasing differential load leading to macroscopic failure was determined at water pore pressures of 50 MPa and effective pressure of 10 MPa. Permeability is seen to increase by up to, and over, two orders of magnitude prior to macroscopic failure. Further experiments were stopped at various points in the loading history in order to correlate microfracture density within the samples with permeability. By combining empirical relationships determined from both quantitative fieldwork and experiments we present a new model that allows microfracture permeability distribution throughout the damage zone to be determined as function of increasing fault displacement.

Hematite Spherules of Meridiani Planum: Implications for Aqueous History at the Site

NASA Astrophysics Data System (ADS)

Calvin, W. M.

2004-12-01

The thermal infrared spectral signature of bulk, grey hematite was the chemical "beacon" that focused the selection of Meridiani Planum as the landing site for the Mars Exploration Rover Opportunity, and aqueous processes were favored for its formation. Orbital data suggesting more bound water in accessory minerals at this location also supported this interpretation. After landing January 24, 2004, the Mini-TES instrument rapidly confirmed the thermal spectral signature of bulk hematite in soils on the plains surrounding Eagle crater and unevenly distributed within the crater. Observations within Eagle crater soon uncovered unusual spherical grains in abundance surrounding the outcrop and Microscopic Imager (MI) showed these grains eroding from within these rocks. They were dubbed "blueberries" by the team due to their spherical nature and their grey or blue appearance compared to their surroundings in various color composites of Pancam images. Extensive observations with the Mössbauer, Alpha-Particle X-ray Spectrometer (APXS) and Mini-TES instruments, especially of the "Berry Bowl" (i.e. with berries and adjacent berry-free rock), confirmed that these spherules are dominantly composed of hematite. Pancam spectra of individual spheres also match laboratory spectra of hematite. These spheres are found within and around outcrop rocks, across the plains of Meridiani, and rolling into the interior of Endurance crater. They are ubiquitous and remarkably even in size and tone. Grains are spherical to subspherical typically 2 to 6 mm in diameter. Opportunity has performed numerous operations with the Rock Abrasion Tool (RAT), and has sliced through individual spherules. The appearance after ratting shows limited or no interior structure and they remain uniformly grey in color. They can preserve scratches from the grinding wheel or become dislodged by ratting, indicating they are harder than the host rock. Several lines of evidence suggest the spheres are post-depositional diagenetic products. On Earth, oolitic iron occurs as concretions in Utah and in the Clinton Formation outcropping from New York into Alabama. Ferromanganese nodules occur in abundance on the modern sea floor and are found in the Great Lakes. Although diagenetic in origin, these terrestrial analogs have strong contrasts with what is observed on Mars, including diverse size, shape and composition of terrestrial samples, significant interior lamination and presence of nucleation centers that are lacking in the Martian spheres. The uniformity of composition and size of the Martian examples provide clues to the redox state of fluids at the time of formation and by analogy with seafloor nodules a rough estimate of the time required for growth.

Thermodynamic modeling using BINGO-ANTIDOTE: A new strategy to investigate metamorphic rocks

NASA Astrophysics Data System (ADS)

Lanari, Pierre; Duesterhoeft, Erik

2016-04-01

BINGO-ANTIDOTE is a new program, combing the achievements of the two petrological software packages XMAPTOOLS[1] and THERIAK-DOMINO[2]. XMAPTOOLS affords information about compositional zoning in mineral and local bulk composition of domains at the thin sections scale. THERIAK-DOMINO calculates equilibrium phase assemblages from given bulk rock composition, temperature T and pressure P. Primarily BINGO-ANTIDOTE can be described as an inverse THERIAK-DOMINO, because it uses the information provided by XMAPTOOLS to calculate the probable P-T equilibrium conditions of metamorphic rocks. Consequently, the introduced program combines the strengths of forward Gibbs free energy minimization models with the intuitive output of inverse thermobarometry models. In order to get "best" P-T equilibrium conditions of a metamorphic rock sample and thus estimating the degree of agreement between the observed and calculated mineral assemblage, it is critical to define a reliable scoring strategy. BINGO uses the THERIAKD ADD-ON[3] (Duesterhoeft and de Capitani, 2013) and is a flexible model scorer with 3+1 evaluation criteria. These criteria are the statistical agreement between the observed and calculated mineral-assemblage, -proportions (vol%) and -composition (mol). Additionally, a total likelihood, consisting of the first three criteria, allows the user an evaluation of the most probable equilibrium P-T condition. ANTIDOTE is an interactive user interface, displaying the 3+1 evaluation criteria as probability P-T-maps. It can be used with and without XMAPTOOLS. As a stand-alone program, the user is able to give the program macroscopic observations (i.e., mineral names and proportions), which ANTIDOTE converts to a readable BINGO input. In this manner, the use of BINGO-ANTIDOTE opens up thermodynamics to students and people with only a basic knowledge of phase diagrams and thermodynamic modeling techniques. This presentation introduces BINGO-ANTIDOTE and includes typical examples of its functionality, such as the determination of P-T conditions of high-grade rocks. BINGO-ANTIDOTE is still under development and will soon be freely available online. References: [1] Lanari P., Vidal O., De Andrade V., Dubacq B., Lewin E., Grosch E. G. and Schwartz S. (2013) XMapTools: a MATLAB©-based program for electron microprobe X-ray image processing and geothermobarometry. Comput. Geosci. 62, 227-240. [2] de Capitani C. and Petrakakis K. (2010) The computation of equilibrium assemblage diagrams with Theriak/Domino software. Am. Mineral. 95, 1006-1016. [3] Duesterhoeft E. and de Capitani C. (2013) Theriak_D: An add-on to implement equilibrium computations in geodynamic models. Geochem. Geophys. Geosyst. 14, 4962-4967.

Characterization of the Basalt of Broken Tank, NM for the 'in situ' Calibration Target for the Alpha-Particle X-ray Spectrometer (APXS) on the Upcoming Mars Science Laboratory (MSL) Rover

NASA Astrophysics Data System (ADS)

Burkemper, L.; King, P. L.; Gellert, R.; Spilde, M. N.; Chamberlin, R. M.

2008-12-01

The MSL rover mission will launch in Fall 2009. It is equipped with an APXS for analyzing the bulk chemistry of rocks and soils. To monitor the APXS performance in situ on the martian surface over the extended mission, a calibration target will be included on the MSL rover. Engineering constraints led to a 4.2 cm diameter, 3 mm thick, homogeneous rock disc that would survive vibrations during launch. The basalt from Broken Tank, NM was chosen for the flight disc from ~200 volcanic rocks. The basalt is relatively homogeneous, fine- and even-grained, vesicle-free, and extremely dense and hard due to its ophitic texture. Other volcanic rocks - even well characterized samples of BCR - were ruled out due to vesicles, or high contents of glass, phenocrysts, secondary minerals, or fractures. The flight disc was prepared by hand- polishing to a 0.05 micron finish. We obtained scanning electron microscope back-scattered electron maps and X-ray maps (Al, Mg, Ca, Fe, Ti, Na, and K) on the polished, uncoated surface of the target. One pit (~0.03 mm2) and three tiny surface imperfections (<0.04 mm2) were observed on the surface. Electron microprobe analyses on two C-coated thin sections give the following compositions: olivine cores Fa23Fo77 and rims Fa40Fo60; plagioclase cores Ab42An56Or2 and discrete rims Ab62An7Or31; oxides Ilm67Hm33 and also trace chromite, apatite, chlorite, clays and devitrified glass. The NIH software Scion Image was used to determine the modal abundance of each phase in the basalt disk and in two thin sections. Bulk composition was established with multiple XRF laboratory analyses. There is no significant heterogeneity on the scale of the APXS analysis (~1.5 cm). Sulfides were not observed and XRF verified low Ni (<90 ppm) and S (70 ppm), making these elements ideal to monitor any Martian dust build-up during the surface operation. The rock slab is glued into a Ni frame, mounted vertically and accessible with a brush tool. The K- and L- X-ray lines of Ni can be used to monitor the energy efficiency of the X-ray detector. This work was supported by the Space Science Enhancement Program of the Canadian Space Agency and the New Mexico Space Grant Consortium.

Induced polarization of volcanic rocks - 1. Surface versus quadrature conductivity

NASA Astrophysics Data System (ADS)

Revil, A.; Le Breton, M.; Niu, Q.; Wallin, E.; Haskins, E.; Thomas, D. M.

2017-02-01

We performed complex conductivity measurements on 28 core samples from the hole drilled for the Humu'ula Groundwater Research Project (Hawai'i Island, HI, USA). The complex conductivity measurements were performed at 4 different pore water conductivities (0.07, 0.5, 1.0 or 2.0, and 10 S m-1 prepared with NaCl) over the frequency range 1 mHz to 45 kHz at 22 ± 1 °C. The in-phase conductivity data are plotted against the pore water conductivity to determine, sample by sample, the intrinsic formation factor and the surface conductivity. The intrinsic formation factor is related to porosity by Archie's law with an average value of the cementation exponent m of 2.45, indicating that only a small fraction of the connected pore space controls the transport properties. Both the surface and quadrature conductivities are found to be linearly related to the cation exchange capacity of the material, which was measured with the cobalt hexamine chloride method. Surface and quadrature conductivities are found to be proportional to each other like for sedimentary siliclastic rocks. A Stern layer polarization model is used to explain these experimental results. Despite the fact that the samples contain some magnetite (up to 5 per cent wt.), we were not able to identify the effect of this mineral on the complex conductivity spectra. These results are very encouraging in showing that galvanometric induced polarization measurements can be used in volcanic areas to separate the bulk from the surface conductivity and therefore to define some alteration attributes. Such a goal cannot be achieved with resistivity alone.

Helium measurements of pore fluids obtained from the San Andreas Fault Observatory at Depth (SAFOD, USA) drill cores

NASA Astrophysics Data System (ADS)

Ali, S.; Stute, M.; Torgersen, T.; Winckler, G.; Kennedy, B. M.

2011-02-01

4He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4-6 times on each sample, and indicate a bulk 4He diffusion coefficient of 3.5 ± 1.3 × 10-8 cm2 s-1 at 21°C, compared to previously published diffusion coefficients of 1.2 × 10-18 cm2 s-1 (21°C) to 3.0 × 10-15 cm2 s-1 (150°C) in the sands and clays. Correcting the diffusion coefficient of 4Hewater for matrix porosity (˜3%) and tortuosity (˜6-13) produces effective diffusion coefficients of 1 × 10-8 cm2 s-1 (21°C) and 1 × 10-7 (120°C), effectively isolating pore fluid 4He from the 4He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8 ± 0.4% (SD, n = 4) and mudstones 3.1 ± 0.8% (SD, n = 4).

Rhenium-osmium systematics of calcium-aluminium-rich inclusions in carbonaceous chondrites

USGS Publications Warehouse

Becker, H.; Morgan, J.W.; Walker, R.J.; MacPherson, G.J.; Grossman, J.N.

2001-01-01

The Re-Os isotopic systematics of calcium-aluminium-rich inclusions (CAIs) in chondrites were investigated in order to shed light on the behavior of the Re-Os system in bulk chondrites, and to constrain the timing of chemical fractionation in primitive chondrites. CAIs with relatively unfractionated rare earth element (REE) patterns (groups I, III, V, VI) define a narrow range of 187Re/188Os (0.3764-0.4443) and 187Os/188Os (0.12599-0.12717), and high but variable Re and Os abundances (3209-41,820 ppb Os). In contrast, CAIs that show depletions in highly refractory elements and strongly fractionated REE patterns (group II) also show a much larger range in 187Re/188Os (0.409-0.535) and 187Os/188Os (0.12695-0.13770), and greater than an order of magnitude lower Re and Os abundances than other groups (e.g., 75.7-680.2 ppb Os). Sixteen bulk CAIs and CAI splits plot within analytical uncertainty of a 4558 Ga reference isochron, as is expected for materials of this antiquity. Eight samples, however, plot off the isochron. Several possible reasons for these deviations are discussed. Data for multiple splits of one CAI indicate that the nonisochronous behavior for at least this CAI is the result of Re-Os reequilibration at approximately 1.6 Ga. Thus, the most likely explanation for the deviations of most of the nonisochronous CAIs is late-stage open-system behavior of Re and Os in the asteroidal environment. The 187Os/188Os-Os systematics of CAIs are consistent with previous models that indicate group II CAIs are mixtures of components that lost the bulk of their highly refractory elements in a previous condensation event and a minor second component that provided refractory elements at chondritic relative proportions. The high Re/Os of group II CAIs relative to other CAIs and chondrite bulk rocks may have been caused by variable mobilization of Re and Os during medium- to low-temperature parent body alteration ??4.5 Ga ago. This model is favored over nebular models, which pose several difficulties. The narrow range of 187Os/188Os in group I, III, V, and VI bulk CAIs, and the agreement with 187Os/188Os of whole rock carbonaceous chondrites suggest that on a bulk inclusion scale, secondary alteration only modestly fractionated Re/Os in these CAIs. The average of 187Os/188Os for group I, III, V, and VI CAIs is indistinguishable from average CI chondrites, indicating a modern solar system value for 187Os/188Os of 0.12650, corresponding to a 187Re/188Os of 0.3964. Copyright ?? 2001 Elsevier Science Ltd.

Surveying Clay Mineral Diversity in the Murray Formation, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Bristow, T.F.; Blake, D. F..; Vaniman, D. T.; Chipera, S. J.; Rampe, E. B.; Grotzinger, J. P.; McAdam, A. C.; Ming, D. W..; Morrison, S. M.; Yen, A. S.;

QA/QC requirements for physical properties sampling and analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Innis, B.E.

1993-07-21

This report presents results of an assessment of the available information concerning US Environmental Protection Agency (EPA) quality assurance/quality control (QA/QC) requirements and guidance applicable to sampling, handling, and analyzing physical parameter samples at Comprehensive Environmental Restoration, Compensation, and Liability Act (CERCLA) investigation sites. Geotechnical testing laboratories measure the following physical properties of soil and sediment samples collected during CERCLA remedial investigations (RI) at the Hanford Site: moisture content, grain size by sieve, grain size by hydrometer, specific gravity, bulk density/porosity, saturated hydraulic conductivity, moisture retention, unsaturated hydraulic conductivity, and permeability of rocks by flowing air. Geotechnical testing laboratories alsomore » measure the following chemical parameters of soil and sediment samples collected during Hanford Site CERCLA RI: calcium carbonate and saturated column leach testing. Physical parameter data are used for (1) characterization of vadose and saturated zone geology and hydrogeology, (2) selection of monitoring well screen sizes, (3) to support modeling and analysis of the vadose and saturated zones, and (4) for engineering design. The objectives of this report are to determine the QA/QC levels accepted in the EPA Region 10 for the sampling, handling, and analysis of soil samples for physical parameters during CERCLA RI.« less

Determining Individual Grains' Magnetic Moments by Micromagnetic Tomography

NASA Astrophysics Data System (ADS)

de Groot, L. V.; Fabian, K.; Béguin, A.; Reith, P.; Rastogi, A.; Barnhoorn, A.; Hilgenkamp, H.

2017-12-01

Methods to derive paleodirections or paleointensities from rocks currently rely on measurements of bulk samples (typically 10 cc). These samples contain many millions of magnetic remanence carrying grains, their statistical assemblage gives rise to a net magnetic moment for the entire sample. The magnetic properties of these grains, however, differ because of their sizes, shapes, and chemical composition. When dealing with lavas this complex magnetic behavior often hampers paleointensity experiments; while occasionally a reliable paleodirection is obscured. If we would be able to isolate the contribution of each magnetic grain in a sample to the bulk magnetic moment of that sample, a wealth of opportunities for highly detailed magnetic analysis would be opened, possibly leading to an entirely new approach in retrieving paleomagnetic signals from complex mineralogies. Here we take the first practical steps towards this goal by developing a new technique: 'micromagnetic tomography'. Firstly, the distribution and volume of the remanence carrying grains in the sample must be assessed; this is done using a MicroCT scanner capable of detecting grains 1 micron. Secondly, the magnetic stray field perpendicular to the surface of a thin sample is measured using a high-resolution DC SQUID microscope. A mathematical inversion of these measurements yields the isolated direction and magnitude of the magnetic moment of individual grains in the sample. As the measured strength of the magnetic field decreases with the third power as function of distance to the exerting grain (as a result of decay in three dimensions), grains in the top 30-40 microns of our synthetic sample with a relatively low dispersion of grains in a matrix can be assessed reliably. We will discuss the potential of our new inversion scheme, and current challenges we need to overcome for both the scanning SQUID and MicroCT techniques before we can analyse 'real' volcanic samples with our technique.

Stochastic multicomponent reactive transport analysis of low quality drainage release from waste rock piles: Controls of the spatial distribution of acid generating and neutralizing minerals.

PubMed

Pedretti, Daniele; Mayer, K Ulrich; Beckie, Roger D

2017-06-01

In mining environmental applications, it is important to assess water quality from waste rock piles (WRPs) and estimate the likelihood of acid rock drainage (ARD) over time. The mineralogical heterogeneity of WRPs is a source of uncertainty in this assessment, undermining the reliability of traditional bulk indicators used in the industry. We focused in this work on the bulk neutralizing potential ratio (NPR), which is defined as the ratio of the content of non-acid-generating minerals (typically reactive carbonates such as calcite) to the content of potentially acid-generating minerals (typically sulfides such as pyrite). We used a streamtube-based Monte-Carlo method to show why and to what extent bulk NPR can be a poor indicator of ARD occurrence. We simulated ensembles of WRPs identical in their geometry and bulk NPR, which only differed in their initial distribution of the acid generating and acid neutralizing minerals that control NPR. All models simulated the same principal acid-producing, acid-neutralizing and secondary mineral forming processes. We show that small differences in the distribution of local NPR values or the number of flow paths that generate acidity strongly influence drainage pH. The results indicate that the likelihood of ARD (epitomized by the probability of occurrence of pH<4 in a mixing boundary) within the first 100years can be as high as 75% for a NPR=2 and 40% for NPR=4. The latter is traditionally considered as a "universally safe" threshold to ensure non-acidic waters in practical applications. Our results suggest that new methods that explicitly account for mineralogical heterogeneity must be sought when computing effective (upscaled) NPR values at the scale of the piles. Copyright © 2017 Elsevier B.V. All rights reserved.

Re-Os and Lu-Hf isotopic constraints on the formation and age of mantle pyroxenites from the Bohemian Massif

NASA Astrophysics Data System (ADS)

Ackerman, Lukáš; Bizimis, Michael; Haluzová, Eva; Sláma, Jiří; Svojtka, Martin; Hirajima, Takao; Erban, Vojtěch

2016-07-01

We report on the Lu-Hf and Re-Os isotope systematics of a well-characterized suite of spinel and garnet pyroxenites from the Gföhl Unit of the Bohemian Massif (Czech Republic, Austria). Lu-Hf mineral isochrons of three pyroxenites yield undistinguishable values in the range of 336-338 Ma. Similarly, the slope of Re-Os regression for most samples yields an age of 327 ± 31 Ma. These values overlap previously reported Sm-Nd ages on pyroxenites, eclogites and associated peridotites from the Gföhl Unit, suggesting contemporaneous evolution of all these HT-HP rocks. The whole-rock Hf isotopic compositions are highly variable with initial εHf values ranging from - 6.4 to + 66. Most samples show a negative correlation between bulk rock Sm/Hf and εHf and, when taking into account other characteristics (e.g., high 87Sr/86Sr), this may be explained by the presence of recycled oceanic sediments in the source of the pyroxenite parental melts. A pyroxenite from Horní Kounice has decoupled Hf-Nd systematics with highly radiogenic initial εHf of + 66 for a given εNd of + 7.8. This decoupling is consistent with the presence of a melt derived from a depleted mantle component with high Lu/Hf. Finally, one sample from Bečváry plots close to the MORB field in Hf-Nd isotope space consistent with its previously proposed origin as metamorphosed oceanic gabbro. Some of the websterites and thin-layered pyroxenites have variable, but high Os concentrations paralleled by low initial γOs. This reflects the interaction of the parental pyroxenitic melts with a depleted peridotite wall rock. In turn, the radiogenic Os isotope compositions observed in most pyroxenite samples is best explained by mixing between unradiogenic Os derived from peridotites and a low-Os sedimentary precursor with highly radiogenic 187Os/188Os. Steep increase of 187Os/188Os at nearly uniform 187Re/188Os found in a few pyroxenites may be connected with the absence of primary sulfides, but the presence of minor late stage sulfide-bearing veinlets likely associated with HT-HP metamorphism at crustal conditions.

Global variations in abyssal peridotite compositions

NASA Astrophysics Data System (ADS)

Warren, Jessica M.

2016-04-01

Abyssal peridotites are ultramafic rocks collected from mid-ocean ridges that are the residues of adiabatic decompression melting. Their compositions provide information on the degree of melting and melt-rock interaction involved in the formation of oceanic lithosphere, as well as providing constraints on pre-existing mantle heterogeneities. This review presents a compilation of abyssal peridotite geochemical data (modes, mineral major elements, and clinopyroxene trace elements) for > 1200 samples from 53 localities on 6 major ridge systems. On the basis of composition and petrography, peridotites are classified into one of five lithological groups: (1) residual peridotite, (2) dunite, (3) gabbro-veined and/or plagioclase-bearing peridotite, (4) pyroxenite-veined peridotite, and (5) other types of melt-added peridotite. Almost a third of abyssal peridotites are veined, indicating that the oceanic lithospheric mantle is more fertile, on average, than estimates based on residual peridotites alone imply. All veins appear to have formed recently during melt transport beneath the ridge, though some pyroxenites may be derived from melting of recycled oceanic crust. A limited number of samples are available at intermediate and fast spreading rates, with samples from the East Pacific Rise indicating high degrees of melting. At slow and ultra-slow spreading rates, residual abyssal peridotites define a large (0-15% modal clinopyroxene and spinel Cr# = 0.1-0.6) compositional range. These variations do not match the prediction for how degree of melting should vary as a function of spreading rate. Instead, the compositional ranges of residual peridotites are derived from a combination of melting, melt-rock interaction and pre-existing compositional variability, where melt-rock interaction is used here as a general term to refer to the wide range of processes that can occur during melt transport in the mantle. Globally, 10% of abyssal peridotites are refractory (0% clinopyroxene, spinel Cr# > 0.5, bulk Al2O3 < 1 wt.%) and some ridge sections are dominated by harzburgites while lacking a significant basaltic crust. Abyssal ultramafic samples thus indicate that the mantle is multi-component, probably consisting of at least three components (lherzolite, harzburgite, and pyroxenite). Overall, the large compositional range among residual and melt-added peridotites implies that the oceanic lithospheric mantle is heterogeneous, which will lead to the generation of further heterogeneities upon subduction back into the mantle.

Composition and properties of the Pierre Shale and equivalent rocks, northern Great Plains region

USGS Publications Warehouse

Schultz, Leonard Gene; Tourtelot, H.A.; Gill, J.R.; Boerngen, J.G.

1980-01-01

The Pierre Shale and equivalent rocks of Late Cretaceous age consist in the east-central Dakotas of several hundred feet of offshore-marine shale and minor marl; in west-central Montana near the sediment source the equivalents of the Pierre Shale consist of several thousand feet of volcanic-rich and mostly nonmarine sediments; and in the area between, both types of rock are separated by tongues of nearshore-marine siltstone and sandstone that mark three major transgressions of the sea across the area. The major-, minor-, and trace-element composition was determined for 226 samples of these rocks, and the mineralogical composition was determined for 1,350 samples. Slurry pH, Atterberg limits, and grain and bulk densities were determined on some samples. The arithmetic mean, in percent, and standard deviation (in parentheses) of major and minor elements, mostly in shale and siltstone and excluding the 23 chemically analyzed bentonite samples, are as follows: SiO2 60.8 (7.9) Al2O3 14.4 (2.5) Fe2O3 3.4 (1.4) FeO 1.1 (1.2) MgO 2.2 (1.0) CaO 2.7 (0.48) Na2O 1.1 (0.56) K2O 2.4 (0.57) H2O- 3.2 (1.3) H2O+ 4.3 (1.2) TiO2 0.58 (0.12) P2O5 0.14 (0.073) S 0.37 (1.1) F 0.71 (0.15) Cl 0.16 (0.024) CO2 2.1 (7.0) C, organic 0.94 (1.8) The mean and standard deviation of minerals as determined by X-ray methods, excluding bentonite samples, is as follows: clay minerals, 53 (20); quartz, 24 (13); cristobalite, 1 (5); potassium-feldspar, 1 (2); plagioclase, 6 (7); anorthite content from 20 to 40 percent; calcite, 5 (14); dolomite, 4 (7); organic matter, 1 (2); and sparsely scattered gypsum, jarosite, pyrite, zeolites, augite, siderite, and probably minor amounts of hydrated iron-manganese (Fe-Mn) oxides. The mean and standard deviation of the clay-mineral fraction is as follows: mixed-layer illite-smectite, 70 (20); illite, 16 (9); chlorite, 3 (6); and kaolinite, 9 (13). The mixed-layer clay, except in the Montana disturbed belt, is a random interlayering of 20 to 60 percent illite-type layers, about 35 percent beidelite-type layers, and the remainder montmorillonite-type layers; chlorite or vermiculite layers are rare. Most bentonite differs from shale in its small quartz content, rarely more than a few percent, in the more calcic composition and hightemperature thermal state of its plagioclase, and in its rare kaolinite, near absence of chlorite, and lack of illite-either free or mixed layered with smectite. Bentonite commonly consists of more than 90 percent smectite in which montmorillonite is interlayered with a smaller amount of beidellite. The clay-mineral composition of marine rock, including proportions of layers in the dominant illite-smectite, averages about the same as in the nonmarine rock, though in the latter the composition is more variable. The average content of major chemical constituents also is closely similar, partly because the large clay content of fine-grained offshore-marine shale is balanced by the small clay content of nearshore-marine siltstone and sandstone. In addition, the alumina and alkalic elements in an average of 10 percent more clay in marine rock are partly balanced by these constituents in the 5 percent more feldspar in nonmarine rock. Much of the observed regional and stratigraphic variation in maj or constituents is the result of the three major east-west migrations of the depositional sites of nearshore-marine sandstone and siltstone. Dolomite is found almost exclusively in relatively coarse-grained rock, particularly in nearshore-marine siltstone where diagenetic dolomite is expected, but it is found almost as frequently in nonmarine siltstone. Amounts of minor constituents are nearly equal in marine and nonmarine rocks, except that pyrite and consequently sulfur are relatively sparse in nonmarine rock. Average amounts of organic matter found in marine and nonmarine rocks are nearly identical. However, organic matter in nonmarine rock occurs almost entirely in volumetric

Direct determination of halogens in powdered geological and environmental samples using isotope dilution laser ablation ICP-MS

NASA Astrophysics Data System (ADS)

Boulyga, Sergei F.; Heumann, Klaus G.

2005-04-01

Laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) with a special laser ablation system for bulk analyses (LINA-Spark(TM)-Atomiser) was applied for direct determinations of chlorine, bromine, and iodine in rock and sediment samples. Special attention was focused on possible inter-halogen fractionations and analyte/spike isotope fractionations by using LA-ICP-MS and LA-ICP-IDMS, respectively. A variation of Br/Cl and I/Cl element intensity ratios by a factor of 1.3-3 was observed when changing the nebulizer gas flow rate in the range of 0.84-1.0 L min-1 and the laser power density in the range of 2-10 GW cm-2, respectively. When using an internal standard for halogen quantification in LA-ICP-MS, this inter-element fractionation can cause systematic errors, which can be avoided by applying the isotope dilution technique. However, at high laser power densities (>5.7 GW cm-2 for iodine and >4.0 GW cm-2 for bromine and chlorine) the corresponding measured isotope ratio of the isotope-diluted sample deviates significantly from the target value. Under optimised conditions concentrations in the range of 30 [mu]g g-1-16 × 103 [mu]g g-1 for chlorine, <2-140 [mu]g g-1 for bromine, and <0.1-31 [mu]g g-1 for iodine were determined by LA-ICP-IDMS in two sediment reference materials (SRM 1646, SRM 2704) and three rock reference samples (GS-N, Granite; BX-N, Bauxite; DT-N, Disthene), which have not been certified for these halogens. The sediment results agree well within the given uncertainties with indicative values by different methods and the results of the rock samples with those obtained by negative thermal ionisation isotope dilution mass spectrometry. The detection limits of LA-ICP-IDMS are 8 [mu]g g-1 for chlorine, 1.7 [mu]g g-1 for bromine, and 0.1 [mu]g g-1 for iodine.

Gas Hydrate Estimation Using Rock Physics Modeling and Seismic Inversion

NASA Astrophysics Data System (ADS)

Dai, J.; Dutta, N.; Xu, H.

2006-05-01

ABSTRACT We conducted a theoretical study of the effects of gas hydrate saturation on the acoustic properties (P- and S- wave velocities, and bulk density) of host rocks, using wireline log data from the Mallik wells in the Mackenzie Delta in Northern Canada. We evaluated a number of gas hydrate rock physics models that correspond to different rock textures. Our study shows that, among the existing rock physics models, the one that treats gas hydrate as part of the solid matrix best fits the measured data. This model was also tested on gas hydrate hole 995B of ODP leg 164 drilling at Blake Ridge, which shows adequate match. Based on the understanding of rock models of gas hydrates and properties of shallow sediments, we define a procedure that quantifies gas hydrate using rock physics modeling and seismic inversion. The method allows us to estimate gas hydrate directly from seismic information only. This paper will show examples of gas hydrates quantification from both 1D profile and 3D volume in the deepwater of Gulf of Mexico.

An overview on source rocks and the petroleum system of the central Upper Rhine Graben

NASA Astrophysics Data System (ADS)

Böcker, Johannes; Littke, Ralf; Forster, Astrid

2017-03-01

The petroleum system of the Upper Rhine Graben (URG) comprises multiple reservoir rocks and four major oil families, which are represented by four distinct source rock intervals. Based on geochemical analyses of new oil samples and as a review of chemical parameter of former oil fields, numerous new oil-source rock correlations were obtained. The asymmetric graben resulted in complex migration pathways with several mixed oils as well as migration from source rocks into significantly older stratigraphic units. Oldest oils originated from Liassic black shales with the Posidonia Shale as main source rock (oil family C). Bituminous shales of the Arietenkalk-Fm. (Lias α) show also significant source rock potential representing the second major source rock interval of the Liassic sequence. Within the Tertiary sequence several source rock intervals occur. Early Tertiary coaly shales generated high wax oils that accumulated in several Tertiary as well as Mesozoic reservoirs (oil family B). The Rupelian Fish Shale acted as important source rock, especially in the northern URG (oil family D). Furthermore, early mature oils from the evaporitic-salinar Corbicula- and Lower Hydrobienschichten occur especially in the area of the Heidelberg-Mannheim-Graben (oil family A). An overview on potential source rocks in the URG is presented including the first detailed geochemical source rock characterization of Middle Eocene sediments (equivalents to the Bouxwiller-Fm.). At the base of this formation a partly very prominent sapropelic coal layer or coaly shale occurs. TOC values of 20-32 % (cuttings) and Hydrogen Index (HI) values up to 640-760 mg HC/g TOC indicate an extraordinary high source rock potential, but a highly variable lateral distribution in terms of thickness and source rock facies is also supposed. First bulk kinetic data of the sapropelic Middle Eocene coal and a coaly layer of the `Lymnäenmergel' are presented and indicate oil-prone organic matter characterized by low activation energies. These sediments are considered as most important source rocks of numerous high wax oils (oil family B) in addition to the coaly source rocks from the (Lower) Pechelbronn-Schichten (Late Eocene). Migration pathways are significantly influenced by the early graben evolution. A major erosion period occurred during the latest Cretaceous. The uplift center was located in the northern URG area, resulting in SSE dipping Mesozoic strata in the central URG. During Middle Eocene times a second uplift center in the Eifel area resulted in SW-NE-directed shore lines in the central URG and contemporaneous south-southeastern depocenters during marine transgression from the south. This structural setting resulted in a major NNW-NW-directed and topography-driven migration pattern for expelled Liassic oil in the fractured Mesozoic subcrop below sealing Dogger α clays and basal Tertiary marls.

Ab-initio study of electronic structure and elastic properties of ZrC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mund, H. S., E-mail: hmoond@gmail.com; Ahuja, B. L.

2016-05-23

The electronic and elastic properties of ZrC have been investigated using the linear combination of atomic orbitals method within the framework of density functional theory. Different exchange-correlation functionals are taken into account within generalized gradient approximation. We have computed energy bands, density of states, elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, lattice parameters and pressure derivative of the bulk modulus by calculating ground state energy of the rock salt structure type ZrC.

Rock sample brought to earth from the Apollo 12 lunar landing mission

NASA Technical Reports Server (NTRS)

1969-01-01

A scientist's gloved hand holds one of the numerous rock samples brought back to Earth from the Apollo 12 lunar landing mission. This sample is a highly shattered basaltic rock with a thin black-glass coating on five of its six sides. Glass fills fractures and cements the rock together. The rock appears to have been shattered and thrown out by a meteorite impact explosion and coated with molten rock material before the rock fell to the surface.

A compilation of whole-rock and glass major-element geochemistry of Kilauea Volcano, Hawai'i, near-vent eruptive products: January 1983 through September 2001

USGS Publications Warehouse

Thornber, Carl R.; Hon, Ken; Heliker, Christina; Sherrod, David A.

2003-01-01

This report presents major-element geochemical data from 652 glasses (~6,520 analyses) and 795 whole-rock aliquots from 1,002 fresh samples of olivine-tholeiitic lava collected throughout the near-continuous eruption of Kïlauea Volcano, Hawai'i, from January 1983 through September 2001. The data presented herein provide a unique temporal compilation of lava geochemistry that best reflects variations of pre-eruptive magma compositions during prolonged rift-zone eruption. This document serves as a repository for geochemical data referred to in U.S. Geological Survey Professional Paper 1676 (Heliker, Swanson, and Takahashi, eds., 2003) which includes multidisciplinary research papers pertaining to the first twenty years of Puu Oo-Kupaianaha eruption activity. Details of eruption characteristics and nomenclature are provided in the introductory chapter of that volume (Heliker and Mattox, 2003). Geochemical relations among all or portions of this data set are depicted and interpreted by Thornber (2003), Thornber and others (2003) and Thornber (2001). Trace element compositions and Nd, Sr and Pb isotopic analyses of representative samples of this select eruption suite will be provided in a separate and complimentary open file report. From 1983 to October 2001, approximately 2,500 eruption samples were collected and archived by the U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO). Geochemical data for 1,002 of these samples are included here. Previous reports present bulk-lava major- element chemistry for eruption samples collected from 1983 to 1986 and from 1990 to 1994 (Neal and others, 1988 and Mangan and others, 1995, respectively). Major element glass chemistry and thermometry data for samples collected from 1983 to 1994 is reported by Helz and Hearn (1998) and whole-rock and glass chemistry for samples collected from September 1994 to October 2001 is provided by Thornber and others (2002). This report is a compilation of previously published data along with unpublished whole-rock data for the 1986–1990 eruptive interval (episode 48, see Heliker and Mattox, 2003). The geochemical data in this report is mostly limited to well-quenched samples collected at or near their respective vents. The samples include tephra and spatter, in addition to lava dipped from lava lakes, lava tubes, and surface lava flows. The details of sample collection techniques as described by Thornber and others (2002) are generally applicable for this entire sampling interval. Specifically excluded from this database are samples of distal surface flows, many of which were collected for topical studies of emplacement dynamics (for example, Cashman and others, 1999). Samples of sluggish or crystal-laden tube flows collected during eruptive pauses were also excluded, because they bear visual, petrographic and geochemical evidence for crystal accumulation during surface-flow stagnation. In addition, the pre-1992 whole-rock major element data reported here has been corrected to compensate for minor analytical discrepancies between pre- and post-1991 XRF analyses. These discrepancies resulted from a change in instrumentation at the USGS Denver analytical laboratories. This select suite of time-constrained geochemical data is suitable for constructing petrologic models of pre-eruptive magmatic processes associated with prolong rift zone eruption of Hawaiian shield volcanoes.

Magma genesis in the lesser Antilles island arc

NASA Astrophysics Data System (ADS)

Hawkesworth, C. J.; Powell, M.

1980-12-01

143Nd/ 144Nd, 87Sr/ 86Sr and REE results are reported on volcanic rocks from the islands of Dominica and St. Kitts in the Lesser Antilles. Particular attention is given to the lavas and xenoliths of the Foundland (basalt-andesite) and the Plat Pays (andesite-dacite) volcanic centres on Dominica. Combined major and trace element [ 2] and isotope results suggest that the bulk of the andesites and dacites on Dominica, and by analogy in the rest of the arc, are produced by fractional crystallisation of basaltic magma. The differences in the erupted products of the two volcanoes do not appear to be related to any significant differences in the source rocks of the magmas. Along the arc 87Sr/ 86Sr ratios range from 0.7037 on St. Kitts, to 0.7041-0.7047 on Dominica, and 0.7039-0.7058 on Grenada [ 5], and these are accompanied by a parallel increase in K, Sr, Ba and the light REE's. Moreover, compared with LIL-element-enriched and -depleted rocks from MOR and intraplate environments, the basic rocks from the Lesser Antilles are preferentially enriched in alkaline elements (K, Ba, Rb, Sr) relative to less mobile elements such as the rare earths. 143Nd/ 144Nd varies from 0.51308 on St. Kitts, to 0.51286 on Dominica, and 0.51264-0.51308 on Grenada [ 5], and all these samples have relatively high 87Sr/ 86Sr ratios compared with the main trend of Nd and Sr isotopes for most mantle-derived volcanic rocks. Alkaline elements and 87Sr appear to have been introduced from the subducted ocean crust, but the results on other, less mobile elements are more ambiguous — island arc tholeiites (as on St. Kitts) do not appear to contain significant amounts of REE's, Zr, Y, etc., from the subducted oceanic crust, but such a contribution may be present in more LIL-element-enriched calc-alkaline rock types.

Northwest Africa 8159: An approximately 2.3 Billion Year Old Martian Olivine-Bearing Augite Basalt

NASA Technical Reports Server (NTRS)

Simon, J. I.; Peters, T. J.; Tappa, M. J.; Agee, C. B.

2014-01-01

Based on petrology, mineralogy, and bulk composition, the new NWA 8159 martian meteorite is distinct from all known samples from Mars. In particular, the augite compositional trends are unique, but most similar to those of nakhite intercumulus. Whether NWA 8159 represents a new lithology or is related to a known meteorite group remains to be determined. Sr and Nd isotopic analyses will allow comparison of source characteristics with SNC and other new ungrouped meteorites (e.g., NWA 7635). Here we report initial Rb-Sr and Sm-Nd isotopic results for NWA 8159 with the objective to determine its formation age and to potentially identify similarities and potential source affinities with other martian rocks.

Device Acquires and Retains Rock or Ice Samples

NASA Technical Reports Server (NTRS)

Giersch, Louis R.; Backes, Paul G.

2009-01-01

The Rock Baller is a sample acquisition tool that improves sample retention. The basic elements of the Rock Baller are the tool rotation axis, the hub, the two jaws, and the cutting blades, which are located on each of the jaws. The entire device rotates about the tool rotation axis, which is aligned parallel to the nominal normal direction of the parent rock surface. Both jaws also rotate about the jaw axis, which is perpendicular to the tool rotation axis, at a rate much slower than the rotation about the tool rotation axis. This movement gradually closes the jaws into a nearly continuous hemispherical shell that encloses the sample as it is cut from the parent rock. When required the jaws are opened to release the sample. The hemispherical cutting method eliminates the sample retention problems associated with existing sample acquisition methods that employ conventional cylindrical cutting. The resulting samples are hemispherical, or nearly hemispherical, and as a result the aspect ratio (sample depth relative to sample radius) is essentially fixed. This fixed sample aspect ratio may be considered a drawback of the Rock Baller method, as samples with a higher aspect ratio (more depth, less width) may be considered more scientifically valuable because such samples would allow for a broader inspection of the geological record. This aspect ratio issue can be ameliorated if the Rock Baller is paired with a device similar to the Rock Abrasion Tool (RAT) used on the Mars Exploration Rovers. The RAT could be used to first grind into the surface of the parent rock, after which the Rock Baller would extract a sample from a depth inside the rock that would not have been possible without first using the RAT. Other potential applications for this technology include medical applications such as the removal of tissue samples or tumors from the body, particularly during endoscopic, laparoscopic, or thoracoscopic surgeries.

Rock-Eval analysis of French forest soils: the influence of depth, soil and vegetation types on SOC thermal stability and bulk chemistry

NASA Astrophysics Data System (ADS)

Soucemarianadin, Laure; Cécillon, Lauric; Baudin, François; Cecchini, Sébastien; Chenu, Claire; Mériguet, Jacques; Nicolas, Manuel; Savignac, Florence; Barré, Pierre

2017-04-01

Soil organic matter (SOM) is the largest terrestrial carbon pool and SOM degradation has multiple consequences on key ecosystem properties like nutrients cycling, soil emissions of greenhouse gases or carbon sequestration potential. With the strong feedbacks between SOM and climate change, it becomes particularly urgent to develop reliable routine methodologies capable of indicating the turnover time of soil organic carbon (SOC) stocks. Thermal analyses have been used to characterize SOM and among them, Rock-Eval 6 (RE6) analysis of soil has shown promising results in the determination of in-situ SOC biogeochemical stability. This technique combines a phase of pyrolysis followed by a phase of oxidation to provide information on both the SOC bulk chemistry and thermal stability. We analyzed with RE6 a set of 495 soils samples from 102 permanent forest sites of the French national network for the long-term monitoring of forest ecosystems (''RENECOFOR'' network). Along with covering pedoclimatic variability at a national level, these samples include a range of 5 depths up to 1 meter (0-10 cm, 10-20 cm, 20-40 cm, 40-80 cm and 80-100 cm). Using RE6 parameters that were previously shown to be correlated to short-term (hydrogen index, HI; T50 CH pyrolysis) or long-term (T50 CO2 oxidation and HI) SOC persistence, and that characterize SOM bulk chemical composition (oxygen index, OI and HI), we tested the influence of depth (n = 5), soil class (n = 6) and vegetation type (n = 3; deciduous, coniferous-fir, coniferous-pine) on SOM thermal stability and bulk chemistry. Results showed that depth was the dominant discriminating factor, affecting significantly all RE6 parameters. With depth, we observed a decrease of the thermally labile SOC pool and an increase of the thermally stable SOC pool, along with an oxidation and a depletion of hydrogen-rich moieties of the SOC. Soil class and vegetation type had contrasted effects on the RE6 parameters but both affected significantly T50 CO2 oxidation with, for instance, entic Podzols and dystric Cambisols containing relatively more thermally stable SOC in the deepest layer than hypereutric/calcaric Cambisols. Moreover, soils in deciduous plots contained a higher proportion of thermally stable SOC than soils in coniferous plots. This study shows that RE6 analysis constitutes a fast and cost effective way to qualitatively estimate SOM turnover and to discuss its ecosystem drivers. It offers promising prospects towards a quantitative estimation of SOC turnover and the development of RE6-based indicators related to the size of the different SOC kinetic pools.

Partial reactive crystallization of variable CO2-bearing siliceous MORB-eclogite-derived melt in fertile peridotite and genesis of alkalic basalts with signatures of crustal recycling

NASA Astrophysics Data System (ADS)

Mallik, A.; Dasgupta, R.

2013-12-01

The presence of heterogeneity in the form of recycled altered oceanic crust (MORB-eclogite) has been proposed in the source of HIMU ocean island basalts (OIBs) [1]. Partial melts of recycled oceanic crust, however, are siliceous and Mg-poor and thus do not resemble the major element compositions of alkalic OIBs that are silica-poor and Mg-rich. In an upwelling heterogenous mantle, MORB-eclogite undergoes melting deeper than volatile-free peridotite, hence, andesitic partial melt derived from eclogite will react with subsolidus peridotite. We have examined the effect of such a melt-rock reaction under volatile-free conditions at 1375 °C, 3 GPa by varying the melt-rock ratio from 8 to 50 wt.% [2]. We concluded that the reacted melts reproduce certain major element characteristics of oceanic basanites, but not nephelinites. Also, the melt-rock reaction produces olivine and garnet-bearing websteritic residue. Because presence of CO2 has been invoked in the source of many HIMU ocean islands, the effect of CO2 on such a melt-rock reaction needs to be evaluated. Accordingly, we performed reaction experiments on mixtures of 25% and 33% CO2-bearing andesitic partial melt and peridotite at 1375 °C, 3 GPa by varying the dissolved CO2 content of the reacting melts from 1 to 5 wt.% (bulk CO2 from 0.25 to 1.6 wt.%) [3, this study]. Owing to melt-rock reaction, with increasing CO2 in the bulk mixture, (a) modes of olivine and cpx decrease while melt, opx and garnet increase, (b) reacted melts evolve to greater degree of Si-undersaturation (from andesite through basanite to nephelinite), (c) enhanced crystallization of garnet take place with higher CO2 in the melt, reducing alumina content of the reacted melts, and (d) CaO and MgO content of the reacted melts increase, without affecting FeO* and Na2O contents (indicating greater propensity of Ca2+ and Mg2+ over Fe2+ and Na+ to enter silicate melt as carbonate). For a given melt-MgO, the CO2-bearing reacted melts are a better match for alkalic basalts in terms of SiO2, Al2O3, CaO and CaO/Al2O3 than the CO2-free ones [3]. Using the experimental data, we have further developed an empirical model to predict mineral modes in residue and reacted melt compositions for olivine-opx saturated lithologies as a function of melt:rock ratio and bulk CO2 content. For example, in case of 5 wt.% eclogite melt infiltrating in fertile peridotite, with bulk CO2 from 0 to 2 wt.%, the derivative melts show an increase in CaO and MgO from 11 to 16 wt.%, 15 to 24 wt.%, respectively and decrease in SiO2 and Al2O3 from 45 to 39 wt.% and 14 to 5 wt.%, respectively. From this model, we have created a major element composition space of MORB-eclogite-derived reactive melt mass vs. bulk CO2 and we predict that primary HIMU-type magmas require <5 to 10 wt.% of MORB-eclogite melt input and up to 0.8 wt.% bulk CO2 in their source. Our model also allows determining the residual lithology at the source of alkalic basalts, produced owing to eclogite melt-peridotite reaction with or without CO2. [1] Jackson & Dasgupta (2008) EPSL 276, 175-186. [2] Mallik & Dasgupta (2012) EPSL 329-330, 97-108. [3] Mallik & Dasgupta (in press) JPetrol.

Computational study of Drucker-Prager plasticity of rock using microtomography

NASA Astrophysics Data System (ADS)

Liu, J.; Sarout, J.; Zhang, M.; Dautriat, J.; Veveakis, M.; Regenauer-Lieb, K.

2016-12-01

Understanding the physics of rocks is essential for the industry of mining and petroleum. Microtomography provides a new way to quantify the relationship between the microstructure and their mechanical and transport properties. Transport and elastic properties have been studied widely while plastic properties are still poorly understood. In this study, we analyse a synthetic sandstone sample for its up-scaled plastic properties from the micro-scale. The computations are based on the representative volume element (RVE). The mechanical RVE was determined by the upper and lower bound finite element computations of elasticity. By comparing with experimental curves, the parameters of the matrix (solid part), which consists of calcite-cemented quartz grains, were investigated and quite accurate values obtained. Analyses deduced the bulk properties of yield stress, cohesion and the angle of friction of the rock with pores. Computations of a series of models of volume-sizes from 240-cube to 400-cube showed almost overlapped stress-strain curves, suggesting that the mechanical RVE determined by elastic computations is valid for plastic yielding. Furthermore, a series of derivative models were created which have similar structure but different porosity values. The analyses of these models showed that yield stress, cohesion and the angle of friction linearly decrease with the porosity increasing in the range of porosity from 8% to 28%. The angle of friction decreases the fastest and cohesion shows the most stable along with porosity.

Nickel isotopic composition of the mantle

NASA Astrophysics Data System (ADS)

Gall, Louise; Williams, Helen M.; Halliday, Alex N.; Kerr, Andrew C.

2017-02-01

This paper presents a detailed high-precision study of Ni isotope variations in mantle peridotites and their minerals, komatiites as well as chondritic and iron meteorites. Ultramafic rocks display a relatively large range in δ60 Ni (permil deviation in 60 Ni /58 Ni relative to the NIST SRM 986 Ni isotope standard) for this environment, from 0.15 ± 0.07‰ to 0.36 ± 0.08‰, with olivine-rich rocks such as dunite and olivine cumulates showing lighter isotope compositions than komatiite, lherzolite and pyroxenite samples. The data for the mineral separates shed light on the origin of these variations. Olivine and orthopyroxene display light δ60 Ni whereas clinopyroxene and garnet are isotopically heavy. This indicates that peridotite whole-rock δ60 Ni may be controlled by variations in modal mineralogy, with the prediction that mantle melts will display variable δ60 Ni values due to variations in residual mantle and cumulate mineralogy. Based on fertile peridotite xenoliths and Phanerozoic komatiite samples it is concluded that the upper mantle has a relatively homogeneous Ni isotope composition, with the best estimate of δ60Nimantle being 0.23 ± 0.06‰ (2 s.d.). Given that >99% of the Ni in the silicate Earth is located in the mantle, this also defines the Ni isotope composition of the Bulk Silicate Earth (BSE). This value is nearly identical to the results obtained for a suite of chondrites and iron meteorites (mean δ60 Ni 0.26 ± 0.12‰ and 0.29 ± 0.10‰, respectively) showing that the BSE is chondritic with respect to its Ni isotope composition, with little to no Ni mass-dependent isotope fractionation resulting from core formation.

Trace element determination of zircons from adakites and granitoids: implications for petrogenetic processes

NASA Astrophysics Data System (ADS)

Chen, T. W.; Chu, M. F.; Chung, S. L.; Iizuka, Y.

2017-12-01

Zircon has long been proposed as a time capsule of crustal formation. Concerning of its high capacity of lithophile elements, the dramatic change of crustal chemical composition in late Archean, i.e. from TTG suites to granitoids, may be recorded in zircon remnants. In this study, major- and trace element contents of zircons from adakites, a modern analogue of TTG suites, in southern Tibet were determined by EPMA and LA-ICPMS, respectively, and compared with those in Gangdese granitoids and Sumatra high/low ΣREE granitoids in order to examine the hypothesis. The REE patterns of zircons in this study show little inter-sample discrepancy though there is significant difference in whole-rock HREE contents between adakites and granitoids. Since none of geochemical feature, including REE contents, of zircons correlates with SiO2 content or ASI of corresponding host rocks, fractional crystallization shows insignificant impact on the compositional variation in zircons. In addition to the influence of lattice strain and charge balance requirements, zircons in these rock samples are proposed to crystallize from the magma mush, so they record the composition with least composition difference, not that of the bulk melt. More specifically, the pre-/co-existing mineral phases, e.g. apatite, play a critical role in preferentially taking the LREE and MREE from melt, and eliminating the HREE depletion in residual melt and thus zircons of Gangdese adakites. With the aim of objectively identifying geochemical discriminants of zircons from adakites and granitoids, statistical analysis was used and then 8 parameters were selected, i.e. Ti, V, Yb, Hf, Sc/Yb, U/Yb, Eu/Eu*, ΣHREE. Despite the zircon populations of adakites- and granitoids-origins overlapping in any bivariate plot, the linear combination of discriminants provides a potential way to distinguish zircons from these two groups.

Stream-Sediment Geochemistry in Mining-Impacted Drainages of the Yankee Fork of the Salmon River, Custer County, Idaho

USGS Publications Warehouse

Frost, Thomas P.; Box, Stephen E.

2009-01-01

This reconnaissance study was undertaken at the request of the USDA Forest Service, Region 4, to assess the geochemistry, in particular the mercury and selenium contents, of mining-impacted sediments in the Yankee Fork of the Salmon River in Custer County Idaho. The Yankee Fork has been the site of hard-rock and placer mining, primarily for gold and silver, starting in the 1880s. Major dredge placer mining from the 1930s to 1950s in the Yankee Fork disturbed about a 10-kilometer reach. Mercury was commonly used in early hard-rock mining and placer operations for amalgamation and recovery of gold. During the late 1970s, feasibility studies were done on cyanide-heap leach recovery of gold from low-grade ores of the Sunbeam and related deposits. In the mid-1990s a major open-pit bulk-vat leach operation was started at the Grouse Creek Mine. This operation shut down when gold values proved to be lower than expected. Mercury in stream sediments in the Yankee Fork ranges from below 0.02 ppm to 7 ppm, with the highest values associated with old mill locations and lode and placer mines. Selenium ranges from below the detection limit for this study of 0.2 ppm to 4 ppm in Yankee Fork sediment samples. The generally elevated selenium content in the sediment samples reflect the generally high selenium contents in the volcanic rocks that underlie the Yankee Fork and the presence of gold and silver selenides in some of the veins that were exploited in the early phases of mining.

Formation of dome and basin structures: Results from scaled experiments using non-linear rock analogues

NASA Astrophysics Data System (ADS)

Zulauf, J.; Zulauf, G.; Zanella, F.

2016-09-01

Dome and basin folds are structures with circular or slightly elongate outcrop patterns, which can form during single- and polyphase deformation in various tectonic settings. We used power-law viscous rock analogues to simulate single-phase dome-and-basin folding of rocks undergoing dislocation creep. The viscosity ratio between a single competent layer and incompetent matrix was 5, and the stress exponent of both materials was 7. The samples underwent layer-parallel shortening under bulk pure constriction. Increasing initial layer thickness resulted in a decrease in the number of domes and basins and an increase in amplitude, A, arc-length, L, wavelength, λ, and layer thickness, Hf. Samples deformed incrementally show progressive development of domes and basins until a strain of eY=Z = -30% is attained. During the dome-and-basin formation the layer thickened permanently, while A, L, and λ increased. A dominant wavelength was not attained. The normalized amplitude (A/λ) increased almost linearly reaching a maximum of 0.12 at eY=Z = -30%. During the last increment of shortening (eY=Z = -30 to -40%) the domes and basins did not further grow, but were overprinted by a second generation of non-cylindrical folds. Most of the geometrical parameters of the previously formed domes and basins behaved stable or decreased during this phase. The normalized arc-length (L/Hf) of domes and basins is significantly higher than that of 2D cylindrical folds. For this reason, the normalized arc length can probably be used to identify domes and basins in the field, even if these structures are not fully exposed in 3D.

Euhedral metallic-Fe-Ni grains in extraterrestrial samples

NASA Technical Reports Server (NTRS)

Rubin, Alan E.

1993-01-01

Metallic Fe-Ni is rare in terrestrial rocks, being largely restricted to serpentinized peridotites and volcanic rocks that assimilated carbonaceous material. In contrast, metallic Fe-Ni is nearly ubiquitous among extraterrestrial samples (i.e., meteorites, lunar rocks, and interplanetary dust particles). Anhedral grains are common. For example, in eucrites and lunar basalts, most of the metallic Fe-Ni occurs interstitially between silicate grains and thus tends to have irregular morphologies. In many porphyritic chondrules, metallic Fe-Ni and troilite form rounded blebs in the mesostasis because their precursors were immiscible droplets. In metamorphosed ordinary chondrites, metallic Fe-Ni and troilite form coarse anhedral grains. Some of the metallic Fe-Ni and troilite grains has also been mobilized and injected into fractures in adjacent silicate grains where local shock-reheating temperatures reached the Fe-FeS eutectic (988 C). In interplanetary dust particles metallic Fe-Ni most commonly occurs along with sulfide as spheroids and fragments. Euhedral metallic Fe-Ni grains are extremely rare. Several conditions must be met before such grains can form: (1) grain growth must occur at free surfaces, restricting euhedral metallic Fe-Ni grains to systems that are igneous or undergoing vapor-deposition; (2) the metal (+/-) sulfide assemblage must have an appropriate bulk composition so that taenite is the liquidus phase in igneous systems or the stable condensate phase in vapor-deposition systems; and (3) metallic Fe-Ni grains must remain underformed during subsequent compaction, thermal metamorphism, and shock. Because of these restrictions, the occurrence of euhedral metallic Fe-Ni grains in an object can potentially provide important petrogenetic information. Despite its rarity, euhedral metallic Fe-Ni occurs in a wide variety of extraterrestrial materials. Some of these materials formed in the solar nebula; others formed on parent body surfaces by meteoroid impacts.

Infrared and Raman spectroscopic studies of structural variations in minerals from Apollo 11, 12, 14 and 15 samples, volume 3

NASA Technical Reports Server (NTRS)

Estep, P. A.; Kovach, J. J.; Waldstein, P.; Karr, C., Jr.

1972-01-01

Infrared and Raman vibrational spectroscopic data, yielding direct information on molecular structure, were obtained for single grains ( 150 microns) of minerals, basalts, and glasses isolated from Apollo 11, 12, 14, and 15 rock and dust samples, and for grains in Apollo 14 polished butt samples. From the vibrational data, specification substitutions were determined for the predominant silicate minerals of plagioclase, pyroxene, and olivine. Unique spectral variations for grains of K-feldspar, orthopyroxene, pyroxenoid, and ilmenite were observed to exceed the ranges of terrestrial samples, and these variations may be correlatable with formation histories. Alpha-quartz was isolated as pure single grains, in granitic grains composited with sanidine, and in unique grains that were intimately mixed with varying amounts of glass. Accessory minerals of chromite and ulvospinel were isolated as pure grains and structurally characterized from their distinctive infrared spectra. Fundamental vibrations of the SiO4 tetrahedra in silicate minerals were used to classify bulk compositions in dust sieved fractions, basalt grains and glass particles, and to compare modal characteristics for maria, highland and rille samples. No hydrated minerals were found in any of the samples studied, indicating anhydrous formation conditions.

Observationally Constraining Gas Giant Composition via Their Host Star Abundances

NASA Astrophysics Data System (ADS)

Teske, Johanna; Thorngren, Daniel; Fortney, Jonathan

2018-01-01

While the photospheric abundances of the Sun match many rock-forming elemental abundances in the Earth to within 10 mol%, as well as in Mars, the Moon, and meteorites, the Solar System giant planets are of distinctly non-stellar composition — Jupiter's bulk metallicity (inferred from its bulk density, measured from spacecraft data) is ∼ x5-10 solar, and Saturn is ∼ x10-20 solar. This knowledge has led to dramatic advances in understanding models of core accretion, which now match the heavy element enrichment of each of the Solar System's giant planets. However, we have thus far lacked similar data for exoplanets to use as a check for formation and composition models over a much larger parameter space. Here we present a study of the host stars of a sample of cool transiting gas giants with measured bulk metal fractions (as in Thorngren et al. 2016) to better constrain the relation Zplanet/Zstar — giant exoplanet metal enrichment relative to the host star. We add a new dimension of chemical variation, measuring C, O, Mg, Si, Ni, and well as Fe (on which previous Zplanet/Zstar calculations were based). Our analysis provides the best constraints to date on giant exoplanet interior composition and how this relates to formation environment, and make testable predictions for JWST observations of exoplanet atmospheres.

Heat transfer through particulated media in stagnant gases model and laboratory measurements: Application to Mars

NASA Astrophysics Data System (ADS)

Piqueux, Sylvain Loic Lucien

The physical characterization of the upper few centimeters to meters of the Martian surface has greatly benefited from remote temperature measurements. Typical grain sizes, rock abundances, subsurface layering, soil cementation, bedrock exposures, and ice compositions have been derived and mapped using temperature data in conjunction with subsurface models of heat conduction. Yet, these models of heat conduction are simplistic, precluding significant advances in the characterization of the physical nature of the Martian surface. A new model of heat conduction for homogeneous particulated media accounting for the grain size, porosity, gas pressure and composition, temperature, and the effect of any cementing phase is presented. The incorporation of the temperature effect on the bulk conductivity results in a distortion of the predicted diurnal and seasonal temperatures when compared to temperatures predicted with a temperature-independent conductivity model. Such distortions have been observed and interpreted to result from subsurface heterogeneities, but they may simply be explained by a temperature-dependency of the thermal inertia, with additional implications on the derived grain sizes. Cements are shown to significantly increase the bulk conductivity of a particulated medium and bond fractions <5% per volume are consistent with Martian thermal inertia data previously hypothesized to correspond to a global duricrust. A laboratory setup has been designed, built, calibrated and used to measure the thermal conductivity of particulated samples in order to test and refine the models mentioned above. Preliminary results confirm the influence of the temperature on the bulk conductivity, as well as the effect of changing the gas composition. Cemented samples are shown to conduct heat more efficiently than their uncemented counterparts.

Fabrics, Facies And Flow Through A Large-Volume Ignimbrite: Pampa De Oxaya, Chile.

NASA Astrophysics Data System (ADS)

Platzman, Ellen; Cooper, Frances

2016-04-01

Large volume pyroclastic currents form during some of the most destructive volcanic eruptions on the planet, yet because they are underrepresented in the geological record they remain poorly understood. The Miocene Oxaya ignimbrites, exposed along the western Andean slopes in northern Chile, form one of the largest ignimbrite provinces on earth. We use anisotropy of magnetic susceptibility (AMS) in conjunction with rock magnetic measurements to investigate flow behavior and depositional processes in one of the largest members of the Oxaya succession, the Cardones ignimbrite. Despite its prominence the location of the source caldera remains unknown and fundamental processes remain poorly constrained. During 2012 nearly 8km (7,773m) of core was recovered from the early Miocene ignimbrites in 11 holes at elevations ranging from 2336m to 3805m along the Andean escarpment east of Arica, Chile. The drill cores are remarkable in that they penetrate through the entirety of the ignimbrite sequence and into the basement below. Samples for this study were collected from a > 1 km long core drilled at an altitude 3692m. The core sampled 981 m of Cardones ignimbrite and 15 m of underlying sediments and volcaniclastics before penetrating 148 m of basement. Detailed measurements of the variation in bulk magnetic properties including natural remanent magnetization (NRM), susceptibility, ARM, and IRM, were used to monitor changes in concentration, composition and grainsize of the magnetic components though the ignimbrite. AMS in conjunction with detailed rock magnetic measurements were used to constrain flow processes. The data reveal a well-defined flow direction and systematic variations in flow processes with depth. Low field bulk magnetic susceptibility averages 3.2x10-3 SI. Rock magnetic studies and petrographic examination indicate that magnetite is likely to be the dominant magnetic phase although paramagnetic mineral phases also contribute to the magnetic fabric. The degree of anisotropy (P) ranges from 1.01- 1.1 with high P generally associated with predominately linear fabrics and higher bulk susceptibility. Petrofabric orientations, after correction for rotation about the core axis, are well grouped and imbricated revealing a well-defined transport direction down the paleo-slope towards the SW (247°), confirming the deformed Lauca caldera as the likely source of the eruption. Systematic variations in a fabric shape (T) and intensity (P) with depth were also observed with predominately oblate fabrics near the top and towards the base of the flow, and predominately prolate fabrics in the central section of the flow. These vertical changes in fabric show that this massive, apparently homogeneous deposit has a systematic layering that can be interpreted as the combined effect of subtle changes in clast populations related to source heterogeneities, temporal changes in the flow-boundary zone during deposition, and changes in post-depositional processes with depth.

Microstructural controls on the macroscopic behavior of geo-architected rock samples

NASA Astrophysics Data System (ADS)

Mitchell, C. A.; Pyrak-Nolte, L. J.

2017-12-01

Reservoir caprocks, are known to span a range of mechanical behavior from elastic granitic units to visco-elastic shale units. Whether a rock will behave elastically, visco-elastically or plastically depends on both the compositional and textural or microsctructural components of the rock, and how these components are spatially distributed. In this study, geo-architected caprock fabrication was performed to develop synthetic rock to study the role of rock rheology on fracture deformations, fluid flow and geochemical alterations. Samples were geo-architected with Portland Type II cement, Ottawa sand, and different clays (kaolinite, illite, and Montmorillonite). The relative percentages of these mineral components are manipulated to generate different rock types. With set protocols, the mineralogical content, texture, and certain structural aspects of the rock were controlled. These protocols ensure that identical samples with the same morphological and mechanical characteristics are constructed, thus overcoming issues that may arise in the presence of heterogeneity and high anisotropy from natural rock samples. Several types of homogeneous geo-architected rock samples were created, and in some cases the methods were varied to manipulate the physical parameters of the rocks. Characterization of rocks that the samples exhibit good repeatability. Rocks with the same mineralogical content generally yielded similar compressional and shear wave velocities, UCS and densities. Geo-architected rocks with 10% clay in the matrix had lower moisture content and effective porosities than rocks with no clay. The process by which clay is added to the matrix can strongly affect the resulting compressive strength and physical properties of the geo-architected sample. Acknowledgment: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Geosciences Research Program under Award Number (DE-FG02-09ER16022).

Full-waveform inversion of Crosshole GPR data: Implications for porosity estimation in chalk

NASA Astrophysics Data System (ADS)

Keskinen, Johanna; Klotzsche, Anja; Looms, Majken C.; Moreau, Julien; van der Kruk, Jan; Holliger, Klaus; Stemmerik, Lars; Nielsen, Lars

2017-05-01

The Maastrichtian-Danian chalk is a widely distributed hydrocarbon and groundwater reservoir rock in north-western Europe. Knowledge of lateral and vertical heterogeneity and porosity variation in this type of rock is essential, since they critically determine the reservoir properties. We have collected a densely sampled crosshole ground-penetrating radar (GPR) dataset from a highly heterogeneous section of the chalk and inverted it with a full-waveform inversion (FWI) approach. To date, successful crosshole FWI has only been reported for a handful of GPR field data, none of which include strongly heterogeneous environments like the one considered in this study. Testing different starting models shows that all FWI results converge to very similar subsurface structures indicating that the results are robust with regard to local variations in the permittivity starting models and are not very sensitive to the conductivity starting models. Compared to their ray-based counterparts, the obtained FWI models show significantly higher resolution and improved localization of fine-scale heterogeneity. The final FWI permittivity tomogram was converted to a bulk porosity model using the Complex Refractive Index Model (CRIM) and comparisons with plug sample porosities and televiewer image logs verify that variations in the obtained permittivity are related to facies and lithology changes. The inferred porosity varies from 30 to 54%, which is consistent with values in the chalk cores from the investigated boreholes and in agreement with other studies conducted in similar rocks onshore. Moreover, porosities vary significantly over scales of less than a meter both laterally and vertically. The FWI constrains porosity variation with decimeter scale resolution in our 5 m (horizontally) by 10 m (vertically) model section bridging the gap between what is measured on the core sample scale and the scale typical of hydrogeophysical field experiments conducted to characterize fluid flow in the subsurface. The results provide complementary knowledge to traditional chalk reservoir characterization.

Crustal Heterogeneity in the Basin and Range,

DTIC Science & Technology

1995-08-14

plutonism ). Seismic velocities are taken from laboratory measurements of rocks with similar compositions and are consistent with the bulk velocities... plutons intruded into Proterozoic North American crust in the Chocolate Mountains (Figure 2, upper crust) as describing the entire crustal column

Towards Solving the Conundrum of Fast-Spread Ocean Crust Formation: Insights from Textural Analysis of Gabbroic Rocks from Pito Deep and Hess Deep, East Pacific Rise

NASA Astrophysics Data System (ADS)

Brown, T. C.; Cheadle, M. J.; John, B. E.; Coogan, L. A.; Gee, J. S.; Karson, J. A.; Meyer, R.; Ceuleneer, G.; Swapp, S.

2014-12-01

Few examples of in situ fast-spread lower ocean crust exist for sampling. Here we present detailed textural analyses of two sample sets that formed at the East Pacific Rise, collected from tectonic windows at Pito (PD) and Hess (HD) deeps. PD samples (collected by ROV) span the upper ~900 m of lower crust. HD samples (collected by seafloor drilling during IODP Exp. 345) come from >1500 m below the sheeted dike gabbro transition (mbsd). PD gabbroic rock textures are consistent with a gabbro glacier flow model generating the uppermost plutonic crust. Shallow samples (41-72 mbsd) likely formed at the distal edge of the magma lens, analogous to similar rocks from Oman. These gabbros are relatively evolved (cpx Mg#75-77, An53-61 and 1-4% Fe-Ti oxides), and have elongate plagioclase grains (aspect ratios up to 1:2:10) exhibiting a strong shape preferred orientation (SPO) with <40% of grains showing dislocation creep textures. Deeper samples (177-876 mbsd) likely began crystallizing in the magma lens then subsided and 'flowed' through the underlying mush zone. These gabbros are more primitive below 386 mbsd (Fo83-88, cpx Mg# 85-89 and An70-82), and plagioclase grains have more equilibrated morphologies (aspect ratios < 1:2:6) that define ~vertical SPOs which increase in strength with depth. Plagioclase exhibits magmatic crystal-lattice preferred orientations (CPOs) which are also vertical. Significantly, the proportion of grains showing dislocation creep textures increases with depth, and plagioclase grain size distributions show a smaller range of sizes at depth; observations that perhaps reflect the effect of increasing strain with depth. IODP Hole U1415I at HD recovered gabbros and troctolitic gabbros from the mid lower crust that show distinctive cm-dm scale modal layering. Strong plagioclase SPOs parallel layering and magmatic CPOs vary dramatically in strength over just 4.5 m of core. Plagioclase grains are relatively equant (aspect ratios < 1:2:4), wrap around large cpx oikocrysts, and exhibit fewer dislocation creep textures than the PD gabbros. These observations perhaps suggest primary crystal accumulation rather than bulk strain/flow. The similar mineralogy and textures of these samples to those from the Rum layered intrusion suggest HD U1415I gabbros may have formed by mid-crust sill injection.

Petrographic and geochemical comparisons between the lower crystalline basement-derived section and the granite megablock and amphibolite megablock of the Eyreville B core, Chesapeake Bay impact structure, USA

USGS Publications Warehouse

Townsend, G.N.; Gibson, R.L.; Horton, J. Wright; Reimold, W.U.; Schmitt, R.T.; Bartosova, K.

2009-01-01

The Eyreville B core from the Chesapeake Bay impact structure, Virginia, USA, contains a lower basement-derived section (1551.19 m to 1766.32 m deep) and two megablocks of dominantly (1) amphibolite (1376.38 m to 1389.35 m deep) and (2) granite (1095.74 m to 1371.11 m deep), which are separated by an impactite succession. Metasedimentary rocks (muscovite-quartz-plagioclase-biotite-graphite ?? fibrolite ?? garnet ?? tourmaline ?? pyrite ?? rutile ?? pyrrhotite mica schist, hornblende-plagioclase-epidote-biotite- K-feldspar-quartz-titanite-calcite amphibolite, and vesuvianite-plagioclase- quartz-epidote calc-silicate rock) are dominant in the upper part of the lower basement-derived section, and they are intruded by pegmatitic to coarse-grained granite (K-feldspar-plagioclase-quartz-muscovite ?? biotite ?? garnet) that increases in volume proportion downward. The granite megablock contains both gneissic and weakly or nonfoliated biotite granite varieties (K-feldspar-quartz-plagioclase-biotite ?? muscovite ?? pyrite), with small schist xenoliths consisting of biotite-plagioclase-quartz ?? epidote ?? amphibole. The lower basement-derived section and both megablocks exhibit similar middleto upper-amphibolite-facies metamorphic grades that suggest they might represent parts of a single terrane. However, the mica schists in the lower basement-derived sequence and in the megablock xenoliths show differences in both mineralogy and whole-rock chemistry that suggest a more mafi c source for the xenoliths. Similarly, the mineralogy of the amphibolite in the lower basement-derived section and its association with calc-silicate rock suggest a sedimentary protolith, whereas the bulk-rock and mineral chemistry of the megablock amphibolite indicate an igneous protolith. The lower basement-derived granite also shows bulk chemical and mineralogical differences from the megablock gneissic and biotite granites. ?? 2009 The Geological Society of America.

Three-dimensional rocking curve imaging to measure the effective distortion in the neighbourhood of a defect within a crystal: an ice example

PubMed Central

Philip, Armelle; Meyssonnier, Jacques; Kluender, Rafael T.; Baruchel, José

2013-01-01

Rocking curve imaging (RCI) is a quantitative version of monochromatic beam diffraction topography that involves using a two-dimensional detector, each pixel of which records its own ‘local’ rocking curve. From these local rocking curves one can reconstruct maps of particularly relevant quantities (e.g. integrated intensity, angular position of the centre of gravity, FWHM). Up to now RCI images have been exploited in the reflection case, giving a quantitative picture of the features present in a several-micrometre-thick subsurface layer. Recently, a three-dimensional Bragg diffraction imaging technique, which combines RCI with ‘pinhole’ and ‘section’ diffraction topography in the transmission case, was implemented. It allows three-dimensional images of defects to be obtained and measurement of three-dimensional distortions within a 50 × 50 × 50 µm elementary volume inside the crystal with angular misorientations down to 10−5–10−6 rad. In the present paper, this three-dimensional-RCI (3D-RCI) technique is used to study one of the grains of a three-grained ice polycrystal. The inception of the deformation process is followed by reconstructing virtual slices in the crystal bulk. 3D-RCI capabilities allow the effective distortion in the bulk of the crystal to be investigated, and the predictions of diffraction theories to be checked, well beyond what has been possible up to now. PMID:24046486

Three-dimensional rocking curve imaging to measure the effective distortion in the neighbourhood of a defect within a crystal: an ice example.

PubMed

Philip, Armelle; Meyssonnier, Jacques; Kluender, Rafael T; Baruchel, José

2013-08-01

Rocking curve imaging (RCI) is a quantitative version of monochromatic beam diffraction topography that involves using a two-dimensional detector, each pixel of which records its own 'local' rocking curve. From these local rocking curves one can reconstruct maps of particularly relevant quantities ( e.g. integrated intensity, angular position of the centre of gravity, FWHM). Up to now RCI images have been exploited in the reflection case, giving a quantitative picture of the features present in a several-micrometre-thick subsurface layer. Recently, a three-dimensional Bragg diffraction imaging technique, which combines RCI with 'pinhole' and 'section' diffraction topography in the transmission case, was implemented. It allows three-dimensional images of defects to be obtained and measurement of three-dimensional distortions within a 50 × 50 × 50 µm elementary volume inside the crystal with angular misorientations down to 10 -5 -10 -6  rad. In the present paper, this three-dimensional-RCI (3D-RCI) technique is used to study one of the grains of a three-grained ice polycrystal. The inception of the deformation process is followed by reconstructing virtual slices in the crystal bulk. 3D-RCI capabilities allow the effective distortion in the bulk of the crystal to be investigated, and the predictions of diffraction theories to be checked, well beyond what has been possible up to now.

Composition of the lithospheric mantle in the Siberian craton : New constraints from fresh peridotites from the Udachnaya-East Kimberlite

NASA Astrophysics Data System (ADS)

Doucet, Luc-Serge; Ionov, Dmitri A.; Ashchepkov, Igor

2010-05-01

Peridotite xenoliths from the Udachnaya kimberlite pipe represent the major source of lithospheric mantle samples beneath central Siberian craton. An important problem with the availble data [1], however, is that the Udachnaya xenoliths, like many other kimberlite-hosted peridotite suites worldwide, are extensively altered due to interaction with host magma and post-eruption alteration. This alteration causes particular dificulties for whole-rock studies including microstructures, modal estimates and chemical compositions. We report petrographic data and major and trace element compositions for whole-rocks and minerals of some 30 unusually fresh peridotite xenolith from the Udachnaya-East kimberlite. Our study has two goals. The first is to present and discuss trace element data on rocks and minerals from Udachnaya, whose composition remains little known. The other one is to explore how the availability of the fresh peridotites improves our knowledge of petrology and geochemistry of cratonic mantle in relation to published data on altered samples [1]. The xenoliths are spinel, garnet-spinel and garnet facies peridotites including garnet- and cpx-rich lherzolites, garnet and spinel harzburgites and dunites. Thermobarometric estimates for garnet bearing rocks yield T = 800-1350°C and P = 20-70 kbar, low-T spinel facies rocks may originate from shallower levels. Thus, the suite represents a lithospheric profile from the sub-Moho mantle down to ~210 km. The deeper peridotites commonly have porphyroclastic microstructures with mainly neoblast olivine, opx porphyroclasts and cpx and garnet with broadly variable morphologies whereas rocks of shallow origin are commonly protogranular. Trace element compositions in bulk rocks appear to be affected by host magma contamination with enrichments in highly to moderately incompatible elements as well as in alkalis. Nevertheless, the kimberlite-related contamination cannot explain a combination of low Th and U and high Sr contents. The broad range of heavy REE appears to be controlled by the presence and the abundance of garnet and is also related to microstructures such that granular spinel harzburgites have lower HREE contents than "fertile" porphyroclastic garnet lherzolites. Trace elements in cpx and garnet have equilibrated patterns in porphyroclastic peridotites and complex sinusoidal shapes in granular peridotites. Bulk-rock major element compositions show important variations in Mg# (0.89 - 0.93), SiO2 (41.5 - 46.6%), Al2O3 (0.3 - 4%) and CaO (0.3 - 4%). As for compatible trace elements, the major element compositions appear to be related to microstructures. Calculated modal compositions show highly variable opx contents (4.5 - 24%), which are generally lower than in Kaapvaal peridotites but are similar to those from the North Atlantic craton [3]. Overall, modal compositions and the contents of low-mobility elements, are consistent with an origin by variable degrees of partial melting of fertile mantle [1-3]. The range in FeO contents (6-8.5%) may indicate either variable melting depths [2] or post-melting enrichments. Enrichments in SiO2 show some similarities to those in supra-subduction xenoliths [4]; enrichments in highly incompatible elements can be explained by metasomatism with possible involvement of subduction-related fluids. Strong correlations between chemical compositions and microstructures indicate the involvement of tectonic processes in melt percolation and metasomatism. We suggest that the cratonic lithosphere in Siberia was formed in three stages: (1) formation of proto-cratonic mantle by high-degree melting at variable depth, (2) accretion of the proto-craton domains in subduction-related settings, (3) metasomatism commonly accompanied by deformation. [1] Boyd et al (1997) Contrib. Mineral. Petrol. 128, 228-246. [2] Herzberg (2004) J. Petrol. 45, 2507-2530. [3] Wittig et al (2008) Lithos 71, 289-322. [4] Ionov (2009) J. Petrol. In press

Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

USGS Publications Warehouse

Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

2011-01-01

The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

Water quality and aquatic toxicity data of 2002 spring thaw conditions in the upper Animas River watershed, Silverton, Colorado

USGS Publications Warehouse

Fey, D.L.; Wirt, L.; Besser, J.M.; Wright, W.G.

2002-01-01

This report presents hydrologic, water-quality, and biologic toxicity data collected during the annual spring thaw of 2002 in the upper Animas River watershed near Silverton, Colorado. The spring-thaw runoff is a concern because elevated concentrations of iron oxyhydroxides can contain sorbed trace metals that are potentially toxic to aquatic life. Water chemistry of streams draining the San Juan Mountains is affected by natural acid drainage and weathering of hydrothermal altered volcanic rocks and by more than a century of mining activities. The timing of the spring-thaw sampling effort was determined by reviewing historical climate and stream-flow hydrographs and current weather conditions. Twenty-one water-quality samples were collected between 11:00 AM March 27, 2002 and 6:00 PM March 30, 2002 to characterize water chemistry at the A-72 gage on the upper Animas River below Silverton. Analyses of unfiltered water at the A-72 gage showed a relation between turbidity and total-recoverable iron concentrations, and showed diurnal patterns. Copper and lead concentrations were related to iron concentrations, indicating that these elements are probably sorbed to colloidal iron material. Calcium, strontium, and sulfate concentrations showed overall decreasing trends due to dilution, but the loads of those constituents increased over the sampling period. Nine water-quality samples were collected near the confluence of Mineral Creek with the Animas River, the confluence of Cement Creek with the Animas River, and on the upper Animas River above the confluence with Cement Creek (three samples at each site). A total of six bulk water-toxicity samples were collected before, during, and after the spring thaw from the Animas River at the A-72 gage site. Toxicity tests conducted with the bulk water samples on amphipods did not show strong differences in toxicity among the three sampling periods; however, toxicity of river water to fathead minnows showed a decreasing trend during the course of the study.

Nontronite Stability in Near-Surface Sediments

NASA Astrophysics Data System (ADS)

Home, C.; Baker, L.

2015-12-01

The purpose of this study is to examine how long nontronite clays persist in soil, by studying samples collected from a sediment cone weathering out of crack in a basalt outcrop near Moscow Idaho. Nontronite, a dioctahedral ferric smectite clay, is a frequent weathering product of basaltic rocks. However, it is rarely described in surface soils, even in basaltic terrains. At our field site, nontronite formed by basalt weathering is eroding from cracks in the basalt and forming small talus cones. We are examining samples collected from a trench and several soil cores to determine the clay mineralogy at different depths in the talus cone. Bulk and clay mineralogy is being determined using X-ray Diffractometry (XRD) analysis and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. Bulk chemical analyses, and selective extractions with acid oxalate and citrate-bicarbonate-dithionite reagents, are being used to analyze Fe mineralogy and amorphous constituents. Preliminary observations suggest that iron mineralogy may vary with depth in the sediments, and that older, deeper sediments may contain more Fe in oxide phases. We hypothesize that nontronite in the sediments is decomposing over time to form low-Fe smectites + Fe oxides. The results of this study will help determine whether nontronite is stable to erosion and redeposition in a surficial environment, as well as the timescale of its possible decomposition. These results may be useful in assessing proposed models of nontronite transport and redeposition on Mars.

Comparison of deformation mechanics for two different carbonates: oolitic limestone and laminites

NASA Astrophysics Data System (ADS)

Zihms, Stephanie; Lewis, Helen; Couples, Gary; Hall, Stephen; Somerville, Jim

2016-04-01

Carbonate rocks form under a range of conditions which leads to a diverse rock group. Even though carbonates are overall mineralogically simple, the solid-space distribution ranges from simple compositions such as oolitic limestones to highly complex networks of pores and solids as seen in coquinas. Their fundamental mechanical behaviour has been identified to be like clastic rocks (Vajdova 2004, Brantut, Heap et al. 2014). However it is very likely that this observation is not true for more complex carbonates. Triaxial tests were performed on cylindrical samples of two different carbonates; a) oolitic limestone (Bicqueley quarry, France) and b) laminite (Ariripe basin, Brazil). The samples were deformed under confining pressures of 8, 12 and 20MPa, and 20, 30 and 40MPa, respectively. All tests were stopped as soon as peak load was observed to preserve as many deformation characteristics as possible. Photographs of the samples were taken before and after deformation to allow surface analysis of deformation features. Additionally, samples were analysed post-deformation with X-ray tomography (XRT) (using the Zeiss XRadia XRM 520 at the 4D Imaging Lab at Lund University). The 3D tomography images represent the post-deformation samples' density distribution, allowing detailed, non-destructive, 3D analysis of the deformation features that developed in the triaxial testing, including the complex geometries and interactions of fractures, deformation bands and sedimentary layering. They also provide an insight into the complexity of deformation features produced due to the carbonate response. Initial results show that the oolitic limestone forms single shear bands almost the length of the sample, exhibiting similar characteristics to sandstones deformed under similar conditions. These features are observed for all three applied loads. The laminate sample deformed at the lowest confining pressure exhibits compactive features. However, the laminite samples deformed at the two higher confining pressures both show highly complex fracture networks comprising open fractures and fracture propagation. This suggests that the laminate changes from compactive to dilational responses over the selected confining conditions. The XRT analysis indicates that a more complex fracture distribution could be linked to rock component properties e.g. grain size and composition. For the laminite these are variable with the layers. This is in agreement with field observations of laminite microfabrics (Calvo, Rodriguez-Pascua et al. 1998). Additionally, the typical grain size of the laminate (μm) is much smaller than the oolitic limestone (mm), which suggests that fracture network complexity can also be linked to bulk system complexity i.e. pore & grain network. These deformation experiments show that, as previously observed, oolitic limestones seem to behave similarly to sandstones. However this observation is not true for laminites and it is very likely that more complex carbonates will develop even more complicated deformation behaviour. It is therefore necessary to systematically test different carbonate rocks to understand the impact of geometry and composition, as well as the interplay with the pore network. Brantut, N., et al. (2014). Journal of Geophysical Research: Solid Earth 119(7): 5444-5463. Calvo, J. P., et al. (1998). Sedimentology 45: 279-292. Vajdova, V. (2004). Journal of Geophysical Research 109(B5).

Study of sample drilling techniques for Mars sample return missions

NASA Technical Reports Server (NTRS)

Mitchell, D. C.; Harris, P. T.

1980-01-01

To demonstrate the feasibility of acquiring various surface samples for a Mars sample return mission the following tasks were performed: (1) design of a Mars rover-mounted drill system capable of acquiring crystalline rock cores; prediction of performance, mass, and power requirements for various size systems, and the generation of engineering drawings; (2) performance of simulated permafrost coring tests using a residual Apollo lunar surface drill, (3) design of a rock breaker system which can be used to produce small samples of rock chips from rocks which are too large to return to Earth, but too small to be cored with the Rover-mounted drill; (4)design of sample containers for the selected regolith cores, rock cores, and small particulate or rock samples; and (5) design of sample handling and transfer techniques which will be required through all phase of sample acquisition, processing, and stowage on-board the Earth return vehicle. A preliminary design of a light-weight Rover-mounted sampling scoop was also developed.

Undiscovered phosphate resources in the Caribbean region and their potential value for agricultural development

USGS Publications Warehouse

Sheldon, Richard Porter; Davidson, D.F.; Riggs, S.R.; Burnett, W.C.

1985-01-01

The countries of the world's humid tropical regions lack the soil fertility necessary for high agricultural productivity. A recently developed agricultural technology that increases soil fertility can make tropical agriculture highly productive, but the technique requires large inputs into the soil of phosphorus and other fertilizers and soil amendments. Use of fertilizers derived from phosphate rock is increasing greatly throughout the world, and fertilizer raw materials are being produced more and more frequently from phosphate rock deposits close to the areas of use. An increased understanding of the origin of phosphate rock in ancient oceans has enabled exploration geologists to target areas of potential mineral resource value and to search directly for deposits. However, because of the difficulty of prospecting for mineral deposits in forested tropical regions, phosphate rock deposits are not being explored for in the countries of the humid tropics, including most countries of the Caribbean region. As a result, the countries of the Caribbean must import phosphate rock or phosphorus fertilizer products. In the present trade market, imports of phosphate are too low for the initiation of new agricultural technology in the Caribbean and Central American region. A newly proposed program of discovery and development of undiscovered phosphate rock deposits revolves around reconnaissance studies, prospecting by core drilling, and analysis of bulk samples. The program should increase the chance of discovering economic phosphate rock deposits. The search for and evaluation of phosphate rock resources in the countries of the Caribbean region would take about 5 years and cost an average of $15 million per country. The program is designed to begin with high risk-low cost steps and end with low risk-high cost steps. A successful program could improve the foreign exchange positions of countries in the Caribbean region by adding earnings from agricultural product exports and by substituting domestically produced phosphate rock and fertilizer products for imported phosphate fertilizers. A successful program also could provide enough domestically produced phosphorus fertilizer products to allow initiation of new agricultural technology in the region and thus increase domestic food production. Finally, a new phosphorus fertilizer industry would create new jobs in the mining, chemical, and transportation industries of the Caribbean region.

Rock Content Influence on Soil Hydraulic Properties

NASA Astrophysics Data System (ADS)

Parajuli, K.; Sadeghi, M.; Jones, S. B.

2015-12-01

Soil hydraulic properties including the soil water retention curve (SWRC) and hydraulic conductivity function are important characteristics of soil affecting a variety of soil properties and processes. The hydraulic properties are commonly measured for seived soils (i.e. particles < 2 mm), but many natural soils include rock fragments of varying size that alter bulk hydraulic properties. Relatively few studies have addressed this important problem using physically-based concepts. Motivated by this knowledge gap, we set out to describe soil hydraulic properties using binary mixtures (i.e. rock fragment inclusions in a soil matrix) based on individual properties of the rock and soil. As a first step of this study, special attention was devoted to the SWRC, where the impact of rock content on the SWRC was quantified using laboratory experiments for six different mixing ratios of soil matrix and rock. The SWRC for each mixture was obtained from water mass and water potential measurements. The resulting data for the studied mixtures yielded a family of SWRC indicating how the SWRC of the mixture is related to that of the individual media, i.e., soil and rock. A consistent model was also developed to describe the hydraulic properties of the mixture as a function of the individual properties of the rock and soil matrix. Key words: Soil hydraulic properties, rock content, binary mixture, experimental data.

Composition of the Rex Chert and associated rocks of the Permian Phosphoria Formation: Soda Springs area, SE Idaho

USGS Publications Warehouse

Hein, James R.; McIntyre, Brandie; Perkins, Robert B.; Piper, David Z.; Evans, James

2002-01-01

This study, one in a series, reports bulk chemical and mineralogical compositions, as well as petrographic and outcrop descriptions of rocks collected from three measured outcrop sections of the Rex Chert member of the Phosphoria Formation in SE Idaho. The three measured sections were chosen from ten outcrops of Rex Chert that were described in the field. The Rex Chert overlies the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, the source of phosphate ore in the region. Rex Chert removed as overburden comprises part of the material disposed in waste-rock piles during phosphate mining. It has been proposed that the chert be used to cap and isolate waste piles, thereby inhibiting the leaching of potentially toxic elements into the environment. It is also used to surface roads in the mining district. The rock samples studied here constitute a set of individual chert beds that are representative of each stratigraphic section sampled. The informally named cherty shale member that overlies the Rex Chert in measured section 1 was also described and sampled. The upper Meade Peak and the transition zone to the Rex Chert were described and sampled in section 7. The cherts are predominantly spicularite composed of granular and mosaic quartz, and sponge spicules, with various but minor amounts of other fossils and detrital grains. The cherty shale member and transition rocks between the Meade Peak and Rex Chert are siliceous siltstones and argillaceous cherts with ghosts of sponge spicules and somewhat more detrital grains than the chert. The overwhelmingly dominant mineral is quartz, although carbonate beds are rare in each section and are composed predominantly of calcite and dolomite in addition to quartz. Feldspar, mica, clay minerals, calcite, dolomite, and carbonate fluorapatite are minor to trace minerals in the chert. The mean concentrations of oxides and elements in the Rex Chert and the cherty shale member are dominated by SiO2, which averages 94.6%. Organic-carbon contents are generally very low in the chert, but are up to 1.8 wt. % in cherty shale member samples and up to 3.3% in samples from the transition between the Meade Peak and Rex Chert. Likewise, phosphate (P2O5) is generally low in the chert, but can be up to 3.1% in individual beds. Selenium concentrations in Rex Chert and cherty shale member samples vary from Q-mode factors are interpreted to represent the following rock and mineral components: chert-silica component consisting of Si (± Ba); phosphorite-phosphate component composed of P, Ca, As, Y, V, Cr, Sr, and La (± Fe, Zn, Cu, Ni, Li, Se, Nd, Hg); shale component composed of Al, Na, Zr, K, Ba, Li, and organic C (± Ti, Mg, Se, Ni, Fe, Sr, V, Mn, Zn); carbonate component (dolomite, calcite, silicified carbonates) composed of carbonate C, Mg, Ca, and Si (± Mn); tentatively organic matter-hosted elements (and/or sulfide-sulfate phases) composed of Cu (± organic C, Zn, Mn Si, Ni, Hg, and Li). Selenium shows a dominant association with the shale component, but correlations and Qmode factors also indicate that organic matter (within the shale component) and carbonate fluorapatite may host a portion of the Se. Consideration of larger numbers of factors in Qmode analysis indicates that native Se (a factor containing Se (± Ba)) may also comprise a minor component of the Se compliment.

Lunar Samples - Apollo 12

NASA Image and Video Library

1969-11-28

S69-60354 (29 Nov. 1969) --- A scientist's gloved hand holds one of the numerous rock samples brought back to Earth from the Apollo 12 lunar landing mission. The rocks are under thorough examination in the Manned Spacecraft Center's (MSC) Lunar Receiving Laboratory (LRL). This sample is a highly shattered basaltic rock with a thin black-glass coating on five of its six sides. Glass fills fractures and cements the rock together. The rock appears to have been shattered and thrown out by a meteorite impact explosion and coated with molten rock material before the rock fell to the surface.

Early lunar petrogenesis, oceanic and extraoceanic

NASA Technical Reports Server (NTRS)

Warren, P. H.; Wasson, J. T.

1980-01-01

An attempt is made to ascertain which (if any) pristine nonmare rocks, other than KREEPy ones, are not cumulates from the magma ocean. It is noted that the only pristine rocks having bulk densities low enough to have formed by floating above the magma ocean are the ferroan anorthosites, which are easily recognizable as a discrete subset of pristine rocks in general, on the basis of mineral composition relationships. The other class of pristine nonmare rocks, the Mg-rich rocks, did not form from the same magma that produced the ferroan anorthosites. It is suggested that they were formed in layered noritic-troctolitic plutons. These plutons, it is noted, were apparently intruded at, or slightly above, the boundary between the floated ferroan anorthosite crust and the underlying complementary mafic cumulates. It is thought that the parental magmas of the plutons may have arisen by partial melting of either deep mafic cumulates from the magma ocean or a still deeper, undifferentiated primordial layer that was not molten during the magma ocean period.

Folded fabric tunes rock deformation and failure mode in the upper crust.

PubMed

Agliardi, F; Dobbs, M R; Zanchetta, S; Vinciguerra, S

2017-11-10

The micro-mechanisms of brittle failure affect the bulk mechanical behaviour and permeability of crustal rocks. In low-porosity crystalline rocks, these mechanisms are related to mineralogy and fabric anisotropy, while confining pressure, temperature and strain rates regulate the transition from brittle to ductile behaviour. However, the effects of folded anisotropic fabrics, widespread in orogenic settings, on the mechanical behaviour of crustal rocks are largely unknown. Here we explore the deformation and failure behaviour of a representative folded gneiss, by combining the results of triaxial deformation experiments carried out while monitoring microseismicity with microstructural and damage proxies analyses. We show that folded crystalline rocks in upper crustal conditions exhibit dramatic strength heterogeneity and contrasting failure modes at identical confining pressure and room temperature, depending on the geometrical relationships between stress and two different anisotropies associated to the folded rock fabric. These anisotropies modulate the competition among quartz- and mica-dominated microscopic damage processes, resulting in transitional brittle to semi-brittle modes under P and T much lower than expected. This has significant implications on scales relevant to seismicity, energy resources, engineering applications and geohazards.

A IAB-Complex Iron Meteorite Containing Low-Ca Clinopyroxene: Northwest Africa 468 and its Relationship to Iodranites and Formation by Impact Melting

NASA Technical Reports Server (NTRS)

Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.

2002-01-01

Northwest Africa 468 (NWA 468) is a new ungrouped, silicate-rich member of the IAB complex of nonmagmatic iron meteorites. The silicates contain relatively coarse (approximately 300 micron-size) grains of low-Ca clinopyroxene with polysynthetic twinning and inclined extinction. Low-Ca clinopyroxene is indicative of quenching from high temperatures (either from protoenstatite in a few seconds or high-temperature clinoenstatite in a few hours). It seems likely that NWA 468 formed by impact melting followed by rapid cooling to less than or equal to 660 C. After the loss of a metal-sulfide melt from the silicates, sulfide was reintroduced, either from impact-mobilized FeS or as an S2 vapor that combined with metallic Fe to produce FeS. The O-isotopic composition (delta O-17 = -1.39 %) indicates that the precursor material of NWA 468 was a metal-rich (e.g., CR) carbonaceous chondrite. Lodranites are similar in bulk chemical and O-isotopic composition to the silicates in NWA 468; the MAC 88177 lodranite (which also contains low-Ca clinopyroxene) is close in bulk chemical composition. Both NWA 468 and MAC 88177 have relatively low abundances of REE (rare earth elements) and plagiophile elements. Siderophiles in the metal-rich areas of NWA 468 are similar to those in the MAC 88177 whole rock; both samples contain low Ir and relatively high Fe, Cu and Se. Most unweathered lodranites contain approximately 20 - 38 wt. % metallic Fe-Ni. These rocks may have formed in an analogous manner to NWA 468 (i.e., by impact melting of metal-rich carbonaceous-chondrite precursors) but with less separation of metal-rich melts from silicates.

Sm-Nd and Ar-Ar Studies of DHO 908 and 489: Implications for Lunar Crustal History

NASA Technical Reports Server (NTRS)

Nyquist, L. E.; Shih, C. Y.; Reese, Y. D.; Park, J.; Bogard, D. D.; Garrison, D. H.; Yamaguchi, A.

2011-01-01

It is widely assumed that ferroan anorthosites (FANs) formed as flotation cumulates on a global lunar magma ocean (LMO). A corollary is that all FANs are approximately contemporaneous and formed with the same initial Nd-143/Nd-144 ratio. Indeed, a whole rock isochron for selected FANs (and An93 anorthosite) yields an isochron age of 4.42 +/- 0.13 Ga and initial Nd-143/Nd-144, expressed in epsilon-units, of epsilon(sub Nd,CHUR) = 0.3+/-0.3 relative to the CHondritic Uniform Reservoir , or epsilon(sub Nd,HEDPB)=-0.6+/-0.3 relative to the HED Parent Body. These values are in good agreement with the age (T) = 4.47+/-0.07 Ga, and epsilon(sub Nd,HEDPB) =-0.6 +/- 0.5 for FAN 67075. We also have studied anorthositic clasts in the Dhofar 908 and 489 lunar highland meteorites containing clasts of magnesian anorthosites (MAN) with Mg# approximately 75. Because of their relatively high Mg#, magnesian anorthosites should have preceded most FANs in crystallization from the LMO if both are LMO products. Thus, it is important to determine whether the Nd-isotopic data of MAN and FAN are consistent with a co-magmatic origin. We previously reported Sm-Nd data for white clast Dho 908 WC. Mafic minerals in this clast were too small to be physically separated for an isochron. However, we estimated initial Nd-143/Nd-144 for the clast by combining its bulk ("whole rock") Sm-Nd data with an Ar-39-Ar-40 age of 4.42+/-.04 Ga. Here we report additional Sm-Nd data for bulk samples of Dho 908 and its pair Dho 489.

Influence of Composition and Deformation Conditions on the Strength and Brittleness of Shale Rock

NASA Astrophysics Data System (ADS)

Rybacki, E.; Reinicke, A.; Meier, T.; Makasi, M.; Dresen, G. H.

2015-12-01

Stimulation of shale gas reservoirs by hydraulic fracturing operations aims to increase the production rate by increasing the rock surface connected to the borehole. Prospective shales are often believed to display high strength and brittleness to decrease the breakdown pressure required to (re-) initiate a fracture as well as slow healing of natural and hydraulically induced fractures to increase the lifetime of the fracture network. Laboratory deformation tests were performed on several, mainly European black shales with different mineralogical composition, porosity and maturity at ambient and elevated pressures and temperatures. Mechanical properties such as compressive strength and elastic moduli strongly depend on shale composition, porosity, water content, structural anisotropy, and on pressure (P) and temperature (T) conditions, but less on strain rate. We observed a transition from brittle to semibrittle deformation at high P-T conditions, in particular for high porosity shales. At given P-T conditions, the variation of compressive strength and Young's modulus with composition can be roughly estimated from the volumetric proportion of all components including organic matter and pores. We determined also brittleness index values based on pre-failure deformation behavior, Young's modulus and bulk composition. At low P-T conditions, where samples showed pronounced post-failure weakening, brittleness may be empirically estimated from bulk composition or Young's modulus. Similar to strength, at given P-T conditions, brittleness depends on the fraction of all components and not the amount of a specific component, e.g. clays, alone. Beside strength and brittleness, knowledge of the long term creep properties of shales is required to estimate in-situ stress anisotropy and the healing of (propped) hydraulic fractures.

Partial melting of TTG gneisses: crustal contamination and the production of granitic melts

NASA Astrophysics Data System (ADS)

Meade, F. C.; Masotta, M.; Troll, V. R.; Freda, C.; Johnson, T. E.; Dahren, B.

2011-12-01

Understanding partial melting of ancient TTG gneiss terranes is crucial when considering crustal contamination in volcanic systems, as these rocks are unlikely to melt completely at magmatic temperatures (1000-1200 °C) and crustal pressures (<500 MPa). Variations in the bulk composition of the gneiss, magma temperature, pressure (depth) and the composition and abundance of any fluids present will produce a variety of melt compositions, from partial melts enriched in incompatible elements to more complete melts, nearing the bulk chemistry of the parent gneiss. We have used piston cylinder experiments to simulate partial melting in a suite of 12 gneisses from NW Scotland (Lewisian) and Eastern Greenland (Ammassalik, Liverpool Land) under magma chamber temperature and pressure conditions (P=200 MPa, T=975 °C). These gneisses form the basement to much of the North Atlantic Igneous Province, where crustal contamination of magmas was commonplace but the composition of the crustal partial melts are poorly constrained [1]. The experiments produced partial melts in all samples (e.g. Fig 1). Electron microprobe analyses of glasses indicate they are compositionally heterogeneous and are significantly different from the whole rock chemistry of the parent gneisses. The melts have variably evolved compositions but are typically trachy-dacitic to rhyolitic (granitic). This integrated petrological, experimental and in-situ geochemical approach allows quantification of the processes of partial melting of TTG gneiss in a volcanic context, providing accurate major/trace element and isotopic (Sr, Pb) end-members for modeling crustal contamination. The experimental melts and restites will be compared geochemically with a suite of natural TTG gneisses, providing constraints on the extent to which the gneisses have produced and subsequently lost melt. [1] Geldmacher et al. (2002) Scottish Journal of Geology, v.38, p.55-61.

Formation of Apollo 16 impactites and the composition of late accreted material: Constraints from Os isotopes, highly siderophile elements and sulfur abundances

NASA Astrophysics Data System (ADS)

Gleißner, Philipp; Becker, Harry

2017-03-01

Fe-Ni metal-schreibersite-troilite intergrowths in Apollo 16 impact melt rocks and new highly siderophile element (HSE) and S abundance data indicate that millimeter-scale closed-system fractional crystallization processes during cooling of impactor-derived metal melt droplets in impact-melts are the main reason for compositional variations and strong differences in abundances and ratios of HSE in multiple aliquots from Apollo 16 impact melt rocks. Element ratios obtained from linear regression of such data are therefore prone to error, but weighted averages take into account full element budgets in the samples and thus represent a more accurate estimate of their impactor contributions. Modeling of solid metal-liquid metal partitioning in the Fe-Ni-S-P system and HSE patterns in impactites from different landing sites suggest that bulk compositions of ancient lunar impactites should be representative of impact melt compositions and that large-scale fractionation of the HSE by in situ segregation of solid metal or sulfide liquid in impact melt sheets most likely did not occur. The compositional record of lunar impactites indicates accretion of variable amounts of chondritic and non-chondritic impactor material and the mixing of these components during remelting of earlier ejecta deposits. The non-chondritic composition appears most prominently in some Apollo 16 impactites and is characterized by suprachondritic HSE/Ir ratios which increase from refractory to moderately volatile HSE and exhibit a characteristic enrichment of Ru relative to Pt. Large-scale fractional crystallization of solid metal from sulfur and phosphorous rich metallic melt with high P/S in planetesimal or embryo cores is currently the most likely process that may have produced these compositions. Similar materials or processes may have contributed to the HSE signature of the bulk silicate Earth (BSE).

Viking landing sites, remote-sensing observations, and physical properties of Martian surface materials

USGS Publications Warehouse

Moore, H.J.; Jakosky, B.M.

1989-01-01

Important problems that confront future scientific exploration of Mars include the physical properties of Martian surface materials and the geologic processes that formed the materials. The design of landing spacecraft, roving vehicles, and sampling devices and the selection of landing sites, vehicle traverses, and sample sites will be, in part, guided by the physical properties of the materials. Four materials occur in the sample fields of the Viking landers: (1) drift, (2) crusty to cloddy, (3) blocky, and (4) rock. The first three are soillike. Drift materials is weak, loose, and porous. We estimate that it has a dielectric constant near 2.4 and a thermal inertia near 1 ?? 10-3 to 3 ?? 10-3 (cal cm-2 sec 1 2 K-1) because of its low bulk density, fine grain size, and small cohesion. Crusty to cloddy material is expected to have a dielectric constant near 2.8 and a thermal inertia near 4 ?? 10-3 to 7 ?? 10-3 because of its moderate bulk density and cementation of grains. Blocky material should have a dielectric constant near 3.3 and a thermal inertia near 7 ?? 10-3 to 9 ?? 10-3 because of its moderate bulk density and cementation. Common basaltic rocks have dielectric constans near 8 and thermal inertias near 30 ?? 10-3 to 60 ?? 10-3. Comparisons of estimated dielectric constants and thermal inertias of the materials at the landing sites with those obtained remotely by Earth-based radars and Viking Orbiter thermal sensors suggest that the materials at the landing sites are good analogs for materials elsewhere on Mars. Correlation of remotely estimated dielectric constant and thermal inertias indicates two modal values for paired values of dielectric constants and thermal inertias near (A) 2 and 2 ?? 10-3 and (B) 3 and 6 ?? 10-3, respectively. These two modes are comparable to the dielectric constants and thermal inertias for drift and crusty to cloddy material, respectively. Dielectric constants and thermal inertias for blocky material are larger but conistent with values in the northern plains. Our interprertations are compatible with an aeolian origin for drift and similar materials elsewhere on Mars. The postulate that moderate dielectric constants and thermal inertias larger than 3 or 4 ?? 10-3 are produced by cementation of soillike materials is partly consistent with the data. The average dielectric constant and thermal inertia and their correlation with one another suggest that most of the surface of Mars should present few difficulties to future surface exploration, but some surfaces may present difficulties for spacecraft that are not suitably designed. ?? 1989.

D/H isotope ratios of kerogen, bitumen, oil, and water in hydrous pyrolysis of source rocks containing kerogen types I, II, IIS, and III

USGS Publications Warehouse

Schimmelmann, A.; Lewan, M.D.; Wintsch, R.P.

1999-01-01

Immature source rock chips containing different types of kerogen (I, II, IIS, III) were artificially matured in isotopically distinct waters by hydrous pyrolysis and by pyrolysis in supercritical water. Converging isotopic trends of inorganic (water) and organic (kerogen, bitumen, oil) hydrogen with increasing time and temperature document that water-derived hydrogen is added to or exchanged with organic hydrogen, or both, during chemical reactions that take place during thermal maturation. Isotopic mass-balance calculations show that, depending on temperature (310-381??C), time (12-144 h), and source rock type, between ca. 45 and 79% of carbon-bound hydrogen in kerogen is derived from water. Estimates for bitumen and oil range slightly lower, with oil-hydrogen being least affected by water-derived hydrogen. Comparative hydrous pyrolyses of immature source rocks at 330??C for 72 h show that hydrogen in kerogen, bitumen, and expelled oil/wax ranks from most to least isotopically influenced by water-derived hydrogen in the order IIS > II ~ III > I. Pyrolysis of source rock containing type II kerogen in supercritical water at 381 ??C for 12 h yields isotopic results that are similar to those from hydrous pyrolysis at 350??C for 72 h, or 330??C for 144 h. Bulk hydrogen in kerogen contains several percent of isotopically labile hydrogen that exchanges fast and reversibly with hydrogen in water vapor at 115??C. The isotopic equilibration of labile hydrogen in kerogen with isotopic standard water vapors significantly reduces the analytical uncertainty of D/H ratios when compared with simple D/H determination of bulk hydrogen in kerogen. If extrapolation of our results from hydrous pyrolysis is permitted to natural thermal maturation at lower temperatures, we suggest that organic D/H ratios of fossil fuels in contact with formation waters are typically altered during chemical reactions, but that D/H ratios of generated hydrocarbons are subsequently little or not affected by exchange with water hydrogen at typical reservoir conditions over geologic time. It will be difficult to utilize D/H ratios of thermally mature bulk or fractions of organic matter to quantitatively reconstruct isotopic aspects of paleoclimate and paleoenvironment. Hope resides in compound-specific D/H ratios of thermally stable, extractable biomarkers ('molecular fossils') that are less susceptible to hydrogen exchange with water-derived hydrogen.

Compaction Around a Spherical Inclusion in Partially Molten Rock

NASA Astrophysics Data System (ADS)

Alisic, Laura; Rhebergen, Sander; Rudge, John F.; Katz, Richard F.; Wells, Garth N.

2015-04-01

Conservation laws that describe the behavior of partially molten mantle rock have been established for several decades, but the associated rheology remains poorly understood. Constraints on the rheology may be obtained from recently published torsion experiments involving deformation of partially molten rock around a rigid, spherical inclusion. These experiments give rise to patterns of melt segregation that exhibit the competing effects of pressure shadows around the inclusion and melt-rich bands through the medium. Such patterns provide an opportunity to infer rheological parameters through comparison with models based on the conservation laws and constitutive relations that hypothetically govern the system. To this end, we have developed software tools using the automated code generation package FEniCS to simulate finite strain, two-phase flow around a rigid, spherical inclusion in a three-dimensional configuration that mirrors the laboratory experiments. The equations for compaction and advection-diffusion of a porous medium are solved utilising newly developed matrix preconditioning techniques. Simulations indicate that the evolution of porosity and therefore of melt distribution is predominantly controlled by the non-linear porosity-weakening exponent of the shear viscosity and the poorly known bulk viscosity. In the simulations presented here, we find that the balance of pressure shadows and melt-rich bands observed in experiments only occurs for bulk-to-shear viscosity ratio of less than about five. However, the evolution of porosity in simulations with such low bulk viscosity exceeds physical bounds at unrealistically small strain due to the unchecked, exponential growth of the porosity variations. Processes that limit or balance porosity localization will have to be incorporated in the formulation of the model to produce results that are consistent with the porosity evolution in experiments.

Four reference soil and rock samples for measuring element availability in the Western Energy Regions

USGS Publications Warehouse

Crock, J.G.; Severson, R.C.

1980-01-01

Attaining acceptable precision in extractable element determinations is more difficult than in total element determinations. In total element determinations, dissolution of the sample is qualitatively checked by the clarity of the solution and the absence of residues. These criteria cannot be used for extracts. Possibilities for error are introduced in virtually every step in soil extractions. Therefore, the use of reference materials whose homogeneity and element content are reasonably well known is essential for determination of extractable elements. In this report, estimates of homogeneity and element content are presented for four reference samples. Bulk samples of about 100 kilograms of each sample were ground to pass an 80-mesh sieve. The samples were homogenized and split using a Jones-type splitter. Fourteen splits of each reference sample were analyzed for total content of Ca, Co, Cu, Fe, K, Mg, Mn, Na, and Zn; DTPA-extractable Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn; exchangeable Ca, Mg, K, and Na; cation exchange capacity water-saturation-extractable Ca, Mg, K, Na, C1, and SO4; soil pH; and hot-water-extractable boron. Error measured between splits was small, indicating that the samples were homogenized adequately and that the laboratory procedure provided reproducible results.

Laboratory Evaluation of Remediation Alternatives for U.S. Coast Guard Small Arms Firing Ranges

DTIC Science & Technology

1999-11-01

S) is an immobilization process that involves the mixing of a contaminated soil with a binder material to enhance the physical and chemical...samples were shipped to WES for laboratory analysis. Phase III: Homogenization of the Bulk Samples. Each of the bulk samples was separately mixed to...produce uniform samples for testing. These mixed bulk soil samples were analyzed for metal content. Phase IV: Characterization of the Bulk Soils

Iron isotope biogeochemistry of Neoproterozoic marine shales

NASA Astrophysics Data System (ADS)

Kunzmann, Marcus; Gibson, Timothy M.; Halverson, Galen P.; Hodgskiss, Malcolm S. W.; Bui, Thi Hao; Carozza, David A.; Sperling, Erik A.; Poirier, André; Cox, Grant M.; Wing, Boswell A.

2017-07-01

Iron isotopes have been widely applied to investigate the redox evolution of Earth's surface environments. However, it is still unclear whether iron cycling in the water column or during diagenesis represents the major control on the iron isotope composition of sediments and sedimentary rocks. Interpretation of isotopic data in terms of oceanic redox conditions is only possible if water column processes dominate the isotopic composition, whereas redox interpretations are less straightforward if diagenetic iron cycling controls the isotopic composition. In the latter scenario, iron isotope data is more directly related to microbial processes such as dissimilatory iron reduction. Here we present bulk rock iron isotope data from late Proterozoic marine shales from Svalbard, northwestern Canada, and Siberia, to better understand the controls on iron isotope fractionation in late Proterozoic marine environments. Bulk shales span a δ 56Fe range from -0.45 ‰ to +1.04 ‰ . Although δ 56Fe values show significant variation within individual stratigraphic units, their mean value is closer to that of bulk crust and hydrothermal iron in samples post-dating the ca. 717-660 Ma Sturtian glaciation compared to older samples. After correcting for the highly reactive iron content in our samples based on iron speciation data, more than 90% of the calculated δ 56Fe compositions of highly reactive iron falls in the range from ca. -0.8 ‰ to +3 ‰ . An isotope mass-balance model indicates that diagenetic iron cycling can only change the isotopic composition of highly reactive iron by < 1 ‰ , suggesting that water column processes, namely the degree of oxidation of the ferrous seawater iron reservoir, control the isotopic composition of highly reactive iron. Considering a long-term decrease in the isotopic composition of the iron source to the dissolved seawater Fe(II) reservoir to be unlikely, we offer two possible explanations for the Neoproterozoic δ 56Fe trend. First, a decreasing supply of Fe(II) to the ferrous seawater iron reservoir could have caused the reservoir to decrease in size, allowing a higher degree of partial oxidation, irrespective of increasing environmental oxygen levels. Alternatively, increasing oxygen levels would have led to a higher proportion of Fe(II) being oxidized, without decreasing the initial size of the ferrous seawater iron pool. We consider the latter explanation as the most likely. According to this hypothesis, the δ 56Fe record reflects the redox evolution of Earth's surface environments. δ 56Fe values in pre-Sturtian samples significantly heavier than bulk crust and hydrothermal iron imply partial oxidation of a ferrous seawater iron reservoir. In contrast, mean δ 56Fe values closer to that of hydrothermal iron in post-Sturtian shales reflects oxidation of a larger proportion of the ferrous seawater iron reservoir, and by inference, higher environmental oxygen levels. Nevertheless, significant iron isotopic variation in post-Sturtian shales suggest redox heterogeneity and possibly a dominantly anoxic deep ocean, consistent with results from recent studies using iron speciation and redox sensitive trace metals. However, the interpretation of generally increasing environmental oxygen levels after the Sturtian glaciation highlights the need to better understand the sensitivity of different redox proxies to incremental changes in oxygen levels to enable us to reconcile results from different paleoredox proxies.

The neodymium stable isotope composition of the silicate Earth and chondrites

NASA Astrophysics Data System (ADS)

McCoy-West, Alex J.; Millet, Marc-Alban; Burton, Kevin W.

2017-12-01

The non-chondritic neodymium (Nd) 142Nd/144Nd ratio of the silicate Earth potentially provides a key constraint on the accretion and early evolution of the Earth. Yet, it is debated whether this offset is due to the Earth being formed from material enriched in s-process Nd isotopes or results from an early differentiation process such as the segregation of a late sulfide matte during core formation, collisional erosion or a some combination of these processes. Neodymium stable isotopes are potentially sensitive to early sulfide segregation into Earth's core, a process that cannot be resolved using their radiogenic counterparts. This study presents the first comprehensive Nd stable isotope data for chondritic meteorites and terrestrial rocks. Stable Nd measurements were made using a double spike technique coupled with thermal ionisation mass spectrometry. All three of the major classes of chondritic meteorites, carbonaceous, enstatite and ordinary chondrites have broadly similar isotopic compositions allowing calculation of a chondritic mean of δ146/144Nd = -0.025 ± 0.025‰ (±2 s.d.; n = 39). Enstatite chondrites yield the most uniform stable isotope composition (Δ146/144Nd = 26 ppm), with considerably more variability observed within ordinary (Δ146/144Nd = 72 ppm) and carbonaceous meteorites (Δ146/144Nd = 143 ppm). Terrestrial weathering, nucleosynthetic variations and parent body thermal metamorphism appear to have little measurable effect on δ146/144Nd in chondrites. The small variations observed between ordinary chondrite groups most likely reflect inherited compositional differences between parent bodies, with the larger variations observed in carbonaceous chondrites being linked to varying modal proportions of calcium-aluminium rich inclusions. The terrestrial samples analysed here include rocks ranging from basaltic to rhyolitic in composition, MORB glasses and residual mantle lithologies. All of these terrestrial rocks possess a broadly similar Nd isotope composition giving an average composition for the bulk silicate Earth of δ146/144Nd = -0.022 ± 0.034‰ (n = 30). In the samples here magmatic differentiation appears to only have an effect on stable Nd in highly evolved magmas with heavier δ146/144Nd values observed in samples with >70 wt% SiO2. The average stable Nd isotope composition of chondrites and the bulk silicate Earth are indistinguishable at the 95% confidence level. However, mantle samples do possess variable stable Nd isotope compositions (Δ146/144Nd = 75 ppm) with an average δ 146 / 144Nd value of -0.008‰. If these heavier values represent the true composition of pristine mantle then it is not possible to completely rule out some role for core formation in accounting for some of the offset between the mantle and chondrites. Overall, these results indicate that the mismatch of 142Nd between the Earth and chondrites is best explained by a higher proportion of s-process Nd in the Earth, rather than partitioning into sulfide or S-rich metal in the core.

Isotope analysis of crystalline impact melt rocks from Apollo 16 stations 11 and 13, North Ray Crater

NASA Technical Reports Server (NTRS)

Reimold, W. U.; Nyquist, L. E.; Bansal, B. M.; Shih, C.-Y.; Weismann, H.; Wooden, J. L.; Mackinnon, I. D. R.

1985-01-01

The North Ray Crater Target Rock Consortium was formed to study a large number of rake samples collected at Apollo 16 stations 11 and 13 with comparative chemical, mineralogical, and chronological techniques in order to provide a larger data base for the discussion of lunar highland evolution in the vicinity of the Apollo 16 landing region. The present investigation is concerned with Rb-Sr and Sm-Nd isotopic analyses of a number of whole-rock samples of feldspathic microporhyritic (FM) impact melt, a sample type especially abundant among the North Ray crater (station 11) sample collection. Aspects of sample mineralogy and analytical procedures are discussed, taking into account FM impact melt rocks 6715 and 63538, intergranular impact melt rock 67775, subophitic impact melt rock 67747, subophitic impact melt rock 67559, and studies based on the utilization of electron microscopy and mass spectroscopy.

A model for hydrostatic consolidation of Pierre shale

USGS Publications Warehouse

Savage, W.Z.; Braddock, W.A.

1991-01-01

This paper presents closed-form solutions for consolidation of transversely isotropic porous media under hydrostatic stress. The solutions are applied to model the time variation of pore pressure, volume strain and strains parallel and normal to bedding, and to obtain coefficients of consolidation and permeability, as well as other properties, and the bulk modulus resulting from hydrostatic consolidation of Pierre shale. It is found that the coefficients consolidation and permeability decrease and the bulk moduli increase with increasing confining pressure, reflecting the closure of voids in the rock. ?? 1991.

Rock sampling. [apparatus for controlling particle size

NASA Technical Reports Server (NTRS)

Blum, P. (Inventor)

1971-01-01

An apparatus for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The device includes grinding means for cutting grooves in the rock surface and to provide a grouping of thin, shallow, parallel ridges and cutter means to reduce these ridges to a powder specimen. Collection means is provided for the powder. The invention relates to rock grinding and particularly to the sampling of rock specimens with good size control.

Bedrock Geology of the DFDP-2 Drill-Site

NASA Astrophysics Data System (ADS)

Toy, V.; Sutherland, R.; Townend, J.

2015-12-01

Bedrock was encountered in DFDP-2B at drilled depths (MD) of 238.50-893.18 m (vertical depths of 238.40-818.00 m). Continuous sampling of cuttings revealed the bedrock is composed predominantly of ductilely sheared mylonite-series lithologies exhumed from the roots of the Alpine Fault zone. The protolith is interpreted to be amphibolite facies metasediments classified as part of the Aspiring Subdivision of the Torlesse Supergroup. Onsite description of whole cuttings and thin sections made within a few hours of sample recovery allowed identification of progressive structural changes. Fabrics were schistose in the upper part of the hole, but at greater depths we observed increasing indications that the rocks had been subjected to simple shear deformation. These macro-and micro-structural features are consistent with those that typify the Alpine Fault mylonite sequence previously described, and were used as input to drilling decisions. The structural features found to be the most useful indicators of ductile simple shear strain accommodated by the recovered rocks were the occurrence of shear bands; changes in mean quartz grain size; changes in maximum mica grain size; and redistribution of or changes in microstructural setting of accessory phases (e.g. graphite). The quartz:mica ratio based on mass was also determined but the extent to which this reflects true lithologic variations is unclear, as washing and winnowing of the samples (both by circulating drill fluids and during the sample collection process) probably modified bulk mineralogy in different particle size domains. Nevertheless, the quartz:mica dataset suggests a dramatic change in mineralogy at 730 m MD (vertical depth of 695 m). This coincides with a pronounced step in the temperature gradient, possibly related to large changes in hydrogeology.

Characterization of Martian Soil Fines Fraction in SNC Meteorites

NASA Technical Reports Server (NTRS)

Rao, M. N.; McKay, D. S.

2003-01-01

Some impact-melt glasses in shergottite meteorites contain large abundances of martian atmospheric noble gases with high (129)Xe/(132)Xe ratios, accompanied by varying (87)Sr/(86)Sr (initial) ratios. These glasses contain Martian Soil Fines (MSF) probably from young volcanic terrains such as Tharsis or Elysium Mons. The composition of the MSF bearing samples is different from the average bulk composition of the host rock. These samples show the following charecteristics: a) simultaeneous enrichment of the felsic component and depletion of the mafic component relative to the host phase and b) significant secondary sulfur/sulfate excesses over the host material. The degree of enrichment and associated depletion varies from one sample to another. Earlier, we found large enrichments of felsic (Al, Ca, Na and K) component and depletion of mafic (Fe, Mg, Mn and Ti) component in several impact melt glass veins and pods of samples ,77 ,78 , 18, and ,20A in EET79001 accompanied by large sulfur/sulfate excesses. Based on these results, we proposed a model where the comminution of basaltic rocks takes place by meteoroid bombardment on the martian surface, leading to the generation of fine-grained soil near the impact sites. This fine-grained soil material is subsequently mobilized by saltation and deflation processes on Mars surface due to pervasive aeolian activity. This movement results in mechanical fractionation leading to the felsic enrichment and mafic depletion in the martian dust. We report, here, new data on an impact-melt inclusion ,507 (PAPA) from EET79001, Lith B and ,506 (ALPHA) from EET79001, Lith A and compare the results with those obtained on Shergotty impact melt glass (DBS).

Is Tridymite at Gale Crater Evidence for Silicic Volcanism on Mars?

NASA Technical Reports Server (NTRS)

Morris, Richard V.; Vaniman, David T.; Ming, Douglas W.; Graff, Trevor G.; Downs, Robert T.; Fendrich, Kim; Mertzman, Stanley A.

2016-01-01

The X-ray diffraction (XRD) instrument (CheMin) onboard the MSL rover Curiosity detected 17 wt% of the SiO2 polymorph tridymite (relative to bulk sample) for the Buckskin drill sample (73 wt% SiO2) obtained from sedimentary rock in the Murray formation at Gale Crater, Mars. Other detected crystalline materials are plagioclase, sanidine, cristobalite, cation-deficient magnetite, and anhydrite. XRD amorphous material constitutes approx. 60 wt% of bulk sample, and the position of its broad diffraction peak near approx. 26 deg. 2-theta is consistent with opal-A. Tridymite is a lowpressure, high-temperature mineral (approx. 870 to 1670 deg. C) whose XRD-identified occurrence on the Earth is usually associated with silicic (e.g., rhyolitic) volcanism. High SiO2 deposits have been detected at Gale crater by remote sensing from martian orbit and interpreted as opal-A on the basis H2O and Si-OH spectral features. Proposed opal-A formation pathways include precipitation of silica from lake waters and high-SiO2 residues of acid-sulfate leaching. Tridymite is nominally anhydrous and would not exhibit these spectral features. We have chemically and spectrally analyzed rhyolitic samples from New Mexico and Iwodake volcano (Japan). The glassy (by XRD) NM samples have H2O spectral features similar to opal-A. The Iwodake sample, which has been subjected to high-temperature acid sulfate leaching, also has H2O spectral features similar to opal-A. The Iwodake sample has approx. 98 wt% SiO2 and 1% wt% TiO2 (by XRF), tridymite (>80 wt.% of crystalline material without detectable quartz by XRD), and H2O and Si-OH spectral features. These results open the working hypothesis that the opal-A-like high-SiO2 deposits at Gale crater detected from martian orbit are products of alteration associated with silicic volcanism. The presence or absence of tridymite will depend on lava crystallization temperatures (NM) and post crystallization alteration temperatures (Iwodake).

Combining Textural Techniques to Explore Effects of Diagenesis and Low-grade Metamorphism on Iron Mineralogy and Iron Speciation

NASA Astrophysics Data System (ADS)

Slotznick, S. P.; Webb, S.; Eiler, J. M.; Kirschvink, J. L.; Fischer, W. W.

2016-12-01

Iron chemistry and mineralogy in the sedimentary rocks provide a valuable tool for studying paleoenvironmental conditions due to the fact that iron atoms can take on either the +II or +III valence state under geological redox conditions. One method utilizing this redox chemistry is `iron speciation', a bulk chemical sequential extraction technique that maps proportions of iron species to redox conditions empirically calibrated from modern sediments. However, all Precambrian and many Phanerozoic rocks have experienced post-depositional processes; it is vital to explore their effects on iron mineralogy and speciation. We combined light and electron microscopy, magnetic microscopy, (synchrotron-based) microprobe x-ray spectroscopy, and rock magnetic measurements in order to deconvolve secondary overprints from primary phases and provide quantitative measurement of iron minerals. These techniques were applied to excellently-preserved shale and siltstone samples of the 1.4 Ga lower Belt Supergroup, Montana and Idaho, USA, spanning a metamorphic gradient from sub-biotite to garnet zone. Previously measured Silurian-Devonian shales, sandstones, and carbonates in Maine and Vermont, USA spanning from the chlorite to kyanite zone provided additional well-constrained, quantitative data for comparison and to extend our analysis. In all of the studied samples, pyrrhotite formation occurred at the sub-biotite or sub-chlorite zone. Pyrrhotite was interpreted to form from pyrite and/or other iron phases based on lithology; these reactions can affect the paleoredox proxy. Iron carbonates can also severely influence iron speciation results since they often form in anoxic pore fluids during diagenesis; textural analyses of the Belt Supergroup samples highlighted that iron-bearing carbonates were early diagenetic cements or later diagenetic overprints. The inclusion of iron from diagenetic minerals during iron speciation analyses will skew results by providing a view of pore-fluid redox, not ancient water column chemistry. While our analyses and biological indicators suggest that the studied samples of the lower Belt Supergroup and New England were deposited in oxic water columns, iron speciation results imply anoxic/ferruginous conditions due to diagenetic alterations affecting the record.

On the Serpentinization Degree (S) of IODP Expedition 357 Atlantis Massif Rocks: Insights from Rock Magnetic Properties and Microscopic Magnetic Mineralogy Study of six Sites

NASA Astrophysics Data System (ADS)

Herrero-Bervera, E.; Whattam, S. A.; Frederichs, T.

2016-12-01

We have studied the magnetic properties of 37 serpentinized samples recovered via drilling during IODP Expedition 357, Atlantis Massif. We have recovered various lithologies including ultamafic rocks (primarily extensively serpentinized), subordidate gabbros, dolerites (small-scale melt injections) and schists. We have conducted remanence and induced magnetic experiments on the samples to determine for instance the degree of serpentinization (S). Stepwise alternating field and thermal demagnetization experiments from 2.5 to 70 mT and from 28 to 700°C, respectively, yielded univectorial diagrams showing the removal of secondary components (e.g., VRM, IRM, CRM) by isolating a characteristic component (ChRM) at various fields and temperatures. The normalized intensity of demagnetization (J/Jo) shows that the decrease of the magnetization of the specimens where about 50% of the original magnetization and is lost at about 5 mT and 100°C (i.e., Median Destructive Field). The stereograms show magnetic stability of the specimens by determining the directional behavior after 4 demagnetization steps (from 7.5-10 mT fields and low temperatures). Induced magnetization such as SIRM's, hysteresis saturation loops, back-fields and FORC experiments were performed. Diagnostic values of Mrs/Ms and Brc/Bc determine the domain structure of a magnetic sample. The magnetic grain sizes were determined using the protocol of Dunlop [2000]. Most of the samples were distributed over the Single (SD), Pseudo-Single Domain (PSD) and a few over the Multi Domain (MD) ranges with a certain degree of clustering on the PSD range. Curie points were obtained by measuring their low-field susceptibility vs. temperature from 28°C up to 700°C in an Argon atmosphere showing a minimum of 1-4 magnetic mineral phases with temperatures ranging from 100°C up to 640°C. These phases are predominantly Ti-poor, Ti-rich magnetite, maghemite and magnetite as corroborated by microscopic analysis as well as the Verwey transition (Tv≈110-120K). Samples studied show appreciable variation in bulk susceptibility (77.8 x 10-3 to 0.31 x 10-3 SI units). The samples are characterized by low, intermediate and high degree of serpentinization based on the results of their magnetic properties (e,g, Kappa, density, magnetic stability and Mrs/Ms vs Bcr/Bc).

The Complex Stratigraphy of the Highland Crust in the Serenitatis Region of the Moon Inferred from Mineral Fragment Chemistry

NASA Technical Reports Server (NTRS)

Ryder, Graham; Norman, Marc D.; Taylor, G. Jeffrey

1997-01-01

Large impact basins are natural drill holes into the Moon, and their ejecta carries unique information about the rock types and stratigraphy of the lunar crust. We have conducted an electron microprobe study of mineral fragments in the poikilitic melt breccias collected from the Taurus Mountains at the Apollo 17 landing site. These breccias are virtually unanimously agreed to be impact melt produced in the Serenitatis impact event. They contain lithic fragments and much more abundant mineral fragments of crustal origin. We have made precise microprobe analyses of minor element abundances in fragments of olivine, pyroxene, and plagioclase to provide new information on the possible source rocks and the crustal stratigraphy in the Serenitatis region. These data were also intended to elucidate the nature of the cryptic geochemical component in breccias such as these with low-K Fra Mauro basalt compositions. We chose the finest-grained (i.e., most rapidly quenched) breccias for study, to avoid reacted and partly assimilated fragments as much as possible. Most of the mineral fragments appear to have been derived from rocks that would fall into the pristine igneous Mg-suite as represented by lithic fragments in the Apollo collection, or reasonable extensions of it. Gabbroic rocks were more abundant in the target stratigraphy than is apparent from the Apollo sample collection. Some pyroxene and plagiociase, but probably not much olivine, could be derived from feldspathic granulites, which are metamorphosed polymict breccias. Some mineral fragments are from previously unknown rocks. These include highly magnesian olivines (up to Fo(sub 94)), possibly volcanic in origin, that exacerbate the difficulty in explaining highly magnesian rocks in the lunar crust. It appears that some part of the lunar interior has an mg*(= 100 x Mg/(Mg/Fe) atomic) greater than the conventional bulk Moon value of 80-84. Other volcanic rocks, including mare basalts, and rapidly- cooled impact melt rocks do not contribute significantly to the fragment population. Nor do ferroan anorthosites contribute more than a tiny part of even the plagiociase fragment population. A few mineral fragments that are consistent with the cryptic low-K Fra Mauro chemical component were found, and these appear to be from gabbroic sources. The mineral fragment populations cannot be mixed in their observed proportions to produce the whole rock composition, because the fragments are more refractory and deficient in Ti, P, and alkalis. A preferential contribution to the melt from a rock similar to sodic ferrogabbro can partly resolve the discrepancy. The population of mineral fragments requires a very diverse population of igenous rocks that are not all related to each other, demonstrating the existence of a complex crust built of numerous separate igneous plutons. Many of these plutons may have crystallized at shallow depths. The chemical composition of the melt breccias, in combination with the mineral fragment data and an understanding of the cratering process, suggests that the deepest crust sampled by the Serenitatis impace (not necessarily the deepest crust) was basaltic in composition, including KREEP and gabbroic rocks like sodic ferrogabbro, and lacking abundant olivine-rich material. These were overlain by Mg-suite rocks of varied types, including norites and troctolites that supplied most of the olivine mineral fragments. Granulities, which are metamorphosed and more feldspathic breccias, were abundant near the surface. Remote sensing indicates that the entire Serenitatis region lacks ferroan anorthosite, consistent with the results of our study.

Fractal Analysis of Permeability of Unsaturated Fractured Rocks

PubMed Central

Jiang, Guoping; Shi, Wei; Huang, Lili

2013-01-01

A physical conceptual model for water retention in fractured rocks is derived while taking into account the effect of pore size distribution and tortuosity of capillaries. The formula of calculating relative hydraulic conductivity of fractured rock is given based on fractal theory. It is an issue to choose an appropriate capillary pressure-saturation curve in the research of unsaturated fractured mass. The geometric pattern of the fracture bulk is described based on the fractal distribution of tortuosity. The resulting water content expression is then used to estimate the unsaturated hydraulic conductivity of the fractured medium based on the well-known model of Burdine. It is found that for large enough ranges of fracture apertures the new constitutive model converges to the empirical Brooks-Corey model. PMID:23690746

Fractal analysis of permeability of unsaturated fractured rocks.

PubMed

Jiang, Guoping; Shi, Wei; Huang, Lili

2013-01-01

A physical conceptual model for water retention in fractured rocks is derived while taking into account the effect of pore size distribution and tortuosity of capillaries. The formula of calculating relative hydraulic conductivity of fractured rock is given based on fractal theory. It is an issue to choose an appropriate capillary pressure-saturation curve in the research of unsaturated fractured mass. The geometric pattern of the fracture bulk is described based on the fractal distribution of tortuosity. The resulting water content expression is then used to estimate the unsaturated hydraulic conductivity of the fractured medium based on the well-known model of Burdine. It is found that for large enough ranges of fracture apertures the new constitutive model converges to the empirical Brooks-Corey model.

Trace element partitioning between coexisting biotite and muscovite from metamorphic rocks, western Labrador: Structural, compositional and thermal controls

NASA Astrophysics Data System (ADS)

Yang, Panseok; Rivers, Toby

2000-04-01

Coexisting biotite and muscovite in ten metapelitic and quartzofeldspathic rocks from western Labrador have been analyzed by electron microprobe for major and minor elements and by a laser ablation microprobe coupled to ICP-MS (LAM-ICP-MS) for selected trace elements - Li, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Cs, Ba, REE, Hf and Ta. The samples have experienced a single prograde Grenvillian metamorphism ranging from 490 to 680°C and from 7 to 12 kbar. The trace element compositions of coexisting micas in the metamorphic rocks are used to assess the effects of crystal structure, major element composition and temperature on the partitioning of each element between biotite and muscovite. Overall, trace element distributions are systematic across the range of metamorphic grade and bulk composition, suggesting that chemical equilibrium was approached. Most distribution coefficients (biotite/muscovite) show good agreement with published data. However, distribution coefficients for Co and Sr are significantly different from previous determinations, probably because of contamination associated with older data obtained by bulk analysis techniques. The sequence of distribution coefficients is governed mainly by the ionic radii and charges of substituting cations compared to the optimum ionic radius of each crystallographic site in the micas. In particular, distribution coefficients exhibit the sequence Cr 3+ (0.615 Å) > V 3+ (0.64 Å) > Sc 3+ (0.745 Å) in VI-sites, and Ba 2+ (1.61 Å) > Sr 2+ (1.44 Å) and Cs + (1.88 Å) > K + (1.64 Å) > Rb + (1.72 Å) > Na + (1.39 Å) in XII-sites. The distributions of Li, Sc, Sr and Ba appear to be thermally sensitive but are also controlled by major element compositions of micas. V and Zr partitioning is dependent on T and may be used to cross-check thermometry calculations where the latter suffer from retrograde re-equilibration and/or high concentrations of Fe 3+. The ranges and dependence of distribution coefficients on major element compositions provide important constraints on the values that can be used in geochemical modeling.

Evolution of Fe redox state in serpentine during subduction

NASA Astrophysics Data System (ADS)

Debret, Baptiste; Andreani, Muriel; Muñoz, Manuel; Bolfan-Casanova, Nathalie; Carlut, Julie; Nicollet, Christian; Schwartz, Stéphane; Trcera, Nicolas

2014-08-01

Serpentinites are an important component of the oceanic lithosphere that formed at slow to ultra-slow spreading centers. Serpentine could thus be one of the most abundant hydrous minerals recycled into the mantle in subduction zones. Prograde metamorphism in subducted serpentinites is characterized by the destabilization of lizardite into antigorite, and then into secondary olivine. The nature of the fluid released during these phase transitions is controlled by redox reactions and can be inferred from oxidation state of Fe in serpentine minerals. We used bulk rock analyses, magnetic measurements, SEM observations and μXANES spectroscopy to establish the evolution of Fe2O3Tot(BR) and magnetite content in serpentinite and Fe oxidation state in serpentine minerals from ridge to subduction settings. At mid-ocean ridges, during the alteration of peridotite into serpentinite, iron is mainly redistributed between magnetite and oceanic serpentine (usually lizardite). The Fe3+/FeTotal ratio in lizardite and the modal percentage of magnetite progressively increase with the degree of local serpentinization to maxima of about 0.8 and 7 wt%, respectively, in fully serpentinized peridotites. During subduction, the Fe2O3Tot(BR) of serpentinite remains constant (∼7-10 wt%, depending on the initial Fe content of the peridotite) while the modal percentage of magnetite decreases to less than 2% in eclogite facies rocks. The Fe3+/FeTotal ratio in serpentine also decreases down to 0.2-0.4 in antigorite at eclogite facies. Our results show that, in the first 70 km of subduction, the transition from lizardite to antigorite is accompanied by a reduction of Fe in bulk rock samples and in serpentine minerals. This redox reaction might be coupled with the oxidation of reduced oceanic phases such as sulfides, and the formation of oxidized fluids (e.g. SOX, H2O, COX). At greater depths, the beginning of antigorite dehydration leads to an increase of Fe3+/FeTotal in relict antigorite, in agreement with the preferential partitioning of ferric iron into serpentine rather than into olivine.

Hydrothermal Habitats: Measurements of Bulk Microbial Elemental Composition, and Models of Hydrothermal Influences on the Evolution of Dwarf Planets

NASA Astrophysics Data System (ADS)

Neveu, Marc Francois Laurent

Finding habitable worlds is a key driver of solar system exploration. Many solar system missions seek environments providing liquid water, energy, and nutrients, the three ingredients necessary to sustain life. Such environments include hydrothermal systems, spatially-confined systems where hot aqueous fluid circulates through rock by convection. I sought to characterize hydrothermal microbial communities, collected in hot spring sediments and mats at Yellowstone National Park, USA, by measuring their bulk elemental composition. To do so, one must minimize the contribution of non-biological material to the samples analyzed. I demonstrate that this can be achieved using a separation method that takes advantage of the density contrast between cells and sediment and preserves cellular elemental contents. Using this method, I show that in spite of the tremendous physical, chemical, and taxonomic diversity of Yellowstone hot springs, the composition of microorganisms there is surprisingly ordinary. This suggests the existence of a stoichiometric envelope common to all life as we know it. Thus, future planetary investigations could use elemental fingerprints to assess the astrobiological potential of hydrothermal settings beyond Earth. Indeed, hydrothermal activity may be widespread in the solar system. Most solar system worlds larger than 200 km in radius are dwarf planets, likely composed of an icy, cometary mantle surrounding a rocky, chondritic core. I enhance a dwarf planet evolution code, including the effects of core fracturing and hydrothermal circulation, to demonstrate that dwarf planets likely have undergone extensive water-rock interaction. This supports observations of aqueous products on their surfaces. I simulate the alteration of chondritic rock by pure water or cometary fluid to show that aqueous alteration feeds back on geophysical evolution: it modifies the fluid antifreeze content, affecting its persistence over geological timescales; and the distribution of radionuclides, whose decay is a chief heat source on dwarf planets. Interaction products can be observed if transported to the surface. I simulate numerically how cryovolcanic transport is enabled by primordial and hydrothermal volatile exsolution. Cryovolcanism seems plausible on dwarf planets in light of images recently returned by spacecrafts. Thus, these coupled geophysical-geochemical models provide a comprehensive picture of dwarf planet evolution, processes, and habitability.

Elasticity of water-saturated rocks as a function of temperature and pressure.

NASA Technical Reports Server (NTRS)

Takeuchi, S.; Simmons, G.

1973-01-01

Compressional and shear wave velocities of water-saturated rocks were measured as a function of both pressure and temperature near the melting point of ice to confining pressure of 2 kb. The pore pressure was kept at about 1 bar before the water froze. The presence of a liquid phase (rather than ice) in microcracks of about 0.3% porosity affected the compressional wave velocity by about 5% and the shear wave velocity by about 10%. The calculated effective bulk modulus of the rocks changes rapidly over a narrow range of temperature near the melting point of ice, but the effective shear modulus changes gradually over a wider range of temperature. This phenomenon, termed elastic anomaly, is attributed to the existence of liquid on the boundary between rock and ice due to local stresses and anomalous melting of ice under pressure.

Elastic and electrical properties and permeability of serpentinites from Atlantis Massif, Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Falcon-Suarez, Ismael; Bayrakci, Gaye; Minshull, Tim A.; North, Laurence J.; Best, Angus I.; Rouméjon, Stéphane

2017-11-01

Serpentinized peridotites co-exist with mafic rocks in a variety of marine environments including subduction zones, continental rifts and mid-ocean ridges. Remote geophysical methods are crucial to distinguish between them and improve the understanding of the tectonic, magmatic and metamorphic history of the oceanic crust. But, serpentinite peridotites exhibit a wide range of physical properties that complicate such a distinction. We analysed the ultrasonic P- and S-wave velocities (Vp, Vs) and their respective attenuation (Qp-1, Qs-1), electrical resistivity and permeability of four serpentinized peridotite samples from the southern wall of the Atlantis Massif, Mid-Atlantic Ridge, collected during International Ocean Discovery Program Expedition 357. The measurements were taken over a range of loading-unloading stress paths (5-45 MPa), using ∼1.7 cm length, 5 cm diameter samples horizontally extracted from the original cores drilled on the seafloor. The measured parameters showed variable degrees of stress dependence, but followed similar trends. Vp, Vs, resistivity and permeability show good inter-correlations, while relationships that included Qp-1 and Qs-1 are less clear. Resistivity showed high contrast between highly serpentinized ultramafic matrix (>50 Ω m) and mechanically/geochemically altered (magmatic/hydrothermal-driven alteration) domains (<20 Ω m). This information together with the elastic constants (Vp/Vs ratio and bulk moduli) of the samples allowed us to infer useful information about the degree of serpentinization and the alteration state of the rock, contrasted by petrographic analysis. This study shows the potential of combining seismic techniques and controlled source electromagnetic surveys for understanding tectonomagmatic processes and fluid pathways in hydrothermal systems.

Chlorine in Lunar Basalts

NASA Technical Reports Server (NTRS)

Barnes, J. J.; Anand, M.; Franchi, I. A.

2017-01-01

In the context of the lunar magma ocean (LMO) model, it is anticipated that chlorine (and other volatiles) should have been concentrated in the late-stage LMO residual melts (i.e., the dregs enriched in incompatible elements such as K, REEs, and P, collectively called KREEP, and in its primitive form - urKREEP, [1]), given its incompatibility in mafic minerals like olivine and pyroxene, which were the dominant phases that crystallized early in the cumulate pile of the LMO (e.g., [2]). When compared to chondritic meteorites and terrestrial rocks (e.g., [3-4]), lunar samples often display heavy chlorine isotope compositions [5-9]. Boyce et al. [8] found a correlation between delta Cl-37 (sub Ap) and bulk-rock incompatible trace elements (ITEs) in lunar basalts, and used this to propose that early degassing of Cl (likely as metal chlorides) from the LMO led to progressive enrichment in remaining LMO melt in Cl-37over Cl-35- the early degassing model. Barnes et al. [9] suggested that relatively late degassing of chlorine from urKREEP (to yield delta Cl-37 (sub urKREEP greater than +25 per mille) followed by variable mixing between KREEPy melts and mantle cumulates (characterized by delta Cl-370 per mille) could explain the majority of Cl isotope data from igneous lunar samples. In order to better understand the processes involved in giving rise to the heavy chlorine isotope compositions of lunar samples, we have performed an in situ study of chlorine isotopes and abundances of volatiles in lunar apatite from a diverse suite of lunar basalts spanning a range of geochemical types.

Preliminary examination of lunar samples from apollo 14.

PubMed

1971-08-20

The major findings of the preliminary examination of the lunar samples are as follows: 1) The samples from Fra Mauro base may be contrasted with those from Tranquillity base and the Ocean of Storms in that about half the Apollo 11 samples consist of basaltic rocks, and all but three Apollo 12 rocks are basaltic, whereas in the Apollo 14 samples only two rocks of the 33 rocks over 50 grams have basaltic textures. The samples from Fra Mauro base consist largely of fragmental rocks containing clasts of diverse lithologies and histories. Generally the rocks differ modally from earlier lunar samples in that they contain more plagioclase and contain orthopyroxene. 2) The Apollo 14 samples differ chemically from earlier lunar rocks and from their closest meteorite and terrestrial analogs. The lunar material closest in composition is the KREEP component (potassium, rare earth elements, phosphorus), "norite," "mottled gray fragments" (9) from the soil samples (in particular, sample 12033) from the Apollo 12 site, and the dark portion of rock 12013 (10). The Apollo 14 material is richer in titanium, iron, magnesium, and silicon than the Surveyor 7 material, the only lunar highlands material directly analyzed (11). The rocks also differ from the mare basalts, having much lower contents of iron, titanium, manganese, chromium, and scandium and higher contents of silicon, aluminum, zirconium, potassium, uranium, thorium, barium, rubidium, sodium, niobium, lithium, and lanthanum. The ratios of potassium to uranium are lower than those of terrestrial rocks and similar to those of earlier lunar samples. 3) The chemical composition of the soil closely resembles that of the fragmental rocks and the large basaltic rock (sample 14310) except that some elements (potassium, lanthanum, ytterbium, and barium) may be somewhat depleted in the soil with respect to the average rock composition. 4) Rocks display characteristic surface features of lunar material (impact microcraters, rounding) and shock effects similar to those observed in rocks and soil from the Apollo 11 and Apollo 12 missions. The rocks show no evidence of exposure to water, and their content of metallic iron suggests that they, like the Apollo 11 and Apollo 12 material, were formed and have remained in an environment with low oxygen activity. 5) The concentration of solar windimplanted material in the soil is large, as was the case for Apollo 11 and Apollo 12 soil. However, unlike previous fragmental rocks, Apollo 14 fragmental rocks possess solar wind contents ranging from approximately that of the soil to essentially zero, with most rocks investigated falling toward one extreme of this range. A positive correlation appears to exist between the solar wind components, carbon, and (20)Ne, of fragmental rocks and their friability (Fig. 12). 6) Carbon contents lie within the range of carbon contents for Apollo 11 and Apollo 12 samples. 7) Four fragmental rocks show surface exposure times (10 x 10(6) to 20 x 10(6) years) about an order of magnitude less than typical exposure times of Apollo 11 and Apollo 12 rocks. 8) A much broader range of soil mechanics properties was encountered at the Apollo 14 site than has been observed at the Apollo 11, Apollo 12, and Surveyor landing sites. At different points along the traverses of the Apollo 14 mission, lesser cohesion, coarser grain size, and greater resistance to penetration was found than at the Apollo 11 and Apollo 12 sites. These variations are indicative of a very complex, heterogeneous deposit. The soils are more poorly sorted, but the range of grain size is similar to those of the Apollo 11 and Apollo 12 soils. 9) No evidence of biological material has been found in the samples to date.

Laboratory synthesis of silicate glass spherules: Application to impact ejecta

NASA Astrophysics Data System (ADS)

Stoddard, P. S.; Pahlevan, K.; Tumber, S.; Weber, R.; Lee, K. K.

2012-12-01

To investigate the process by which molten droplets of impact ejecta solidify into glassy spherule tektites, we employed laser levitation experiments to recreate the hot temperatures of falling molten rock. Following models for Earth composition based on enstatite chondrites, we levitated mixtures of oxide powders in a stream of gas and melted them with a laser, producing silicate glass beads. After quenching, we polished the ~1 mm diameter samples in cross-section and analyzed with electron probe microanalysis (EPMA). Fine and coarsely-spaced EPMA transects across each bead displayed diffusion profiles at their edges, particularly in their SiO2 and MgO content. Heating altered the beads' bulk composition as well; all of the glassy spherules were compositionally different from the initial combination of powders. By comparing these changes to the environmental factors acting on the bead (e.g., temperature, type of levitation gas, duration of heating and amount of rotation), we produced a model for how molten ejecta change chemically and physically as they solidify into a glass. We find that high temperatures likely generated on impact have a strong effect on the composition of tektites; therefore, attempts to correlate tektites to their parent rocks should correct for this effect.

Lunar material resources: An overview

NASA Technical Reports Server (NTRS)

Carter, James L.

1992-01-01

The analysis of returned lunar samples and a comparison of the physical and chemical processes operating on the Moon and on the Earth provide a basis for predicting both the possible types of material resources (especially minerals and rocks) and the physical characteristics of ore deposits potentially available on the Moon. The lack of free water on the Moon eliminates the classes of ore deposits that are most exploitable on Earth; namely, (1) hydrothermal, (2) secondary mobilization and enrichment, (3) precipitation from a body of water, and (4) placer. The types of lunar materials available for exploitation are whole rocks and their contained minerals, regolith, fumarolic and vapor deposits, and nonlunar materials, including solar wind implantations. Early exploitation of lunar material resources will be primarily the use of regolith materials for bulk shielding; the extraction from regolith fines of igneous minerals such as plagioclase feldspars and ilmenite for the production of oxygen, structural metals, and water; and possibly the separation from regolith fines of solar-wind-implanted volatiles. The only element, compound, or mineral, that by itself has been identified as having the economic potential for mining, processing, and return to Earth is helium-3.

Lateral variation of H2O/K2O ratios in Quaternary Magma of the Northeastern Japan arc

NASA Astrophysics Data System (ADS)

Miyagi, I.

2012-12-01

Water plays a fundamental role in the magma genesis beneath subduction zones. In order to estimate a spatial distribution of the density of water flux in the wedge mantle of the Northeastern Japan arc, this study examines a lateral variation of pre-eruptive bulk rock H2O/K2O contents among volcanoes located both in the frontal and in back arc settings. The analytical targets are the frontal volcanoes Nigorikawa (N42.12 E140.45), Zenikame (N41.74 E140.85), Adachi (N38.22 E140.65), and Nanashigure (N40.07 E141.11), and the back arc ones Hijiori (N38.61 E140.17) and Kanpu (N39.93 E139.88). The bulk magmatic H2O content (TH2O) is calculated from a mass balance of hydrogen isotopic ratios among three phases in a batch of magma; dissolved water in melt, excess H2O vapor, and hydrous phenocrysts such as amphiboles (Miyagi and Matsubaya, 2003). Since the amount of H2O in hydrous phenocryst is negligible, the bulk magmatic H2O content can be written as TH2O = (30 XD CD) / (15 - dT + dMW), where dMW is the measured hydrogen isotopic ratio of hydrous phenocrysts, XD is a melt fraction of magma, CD is a water concentration of the melt, and dT is hydrogen isotopic ratios of a bulk magma (assumed to be -50 per-mil). Both XD and CD are estimated from bulk rock chemistry of the sample using the MELTS program (Ghiorso and Sack, 1995). Hydrogen isotopic fractionation factors are assumed to be -15 and -30 per-mil for vapor and hydrous mineral, and vapor and silicate melt, respectively. There observed a clear difference among the H2O/K2O ratios of bulk magmas from the frontal and back arc volcanoes. For instance higher H2O/K2O wt ratios was observed in the frontal volcanoes (Nigorikawa 5.3, Zenikame 11-12, Adachi 8-10, and Nanashigure 4-18), while lower H2O/K2O wt ratios was observed in the back arc ones (Kanpu 0-2.5 and Hijiori 1.4). The lateral variation of H2O/K2O ratios infer the higher water flux through the frontal side of wedge mantle, which can be a potential cause of the larger quantity of volcanic products along the frontal side of the NE Japan arc. This research project has been conducted under the research contract with Nuclear and Industrial Safety Agency (NISA). I thank Drs. H. Kawaraya, D. Ishiyama, and O. Matsubaya at Akita univ. for their help in the analysis of hydrogen isotopic ratios.

Stratigraphy and geochemical characterization of the Oligocene Miocene Maikop series: Implications for the paleogeography of Eastern Azerbaijan

NASA Astrophysics Data System (ADS)

Hudson, Samuel M.; Johnson, Cari L.; Efendiyeva, Malakhat A.; Rowe, Harold D.; Feyzullayev, Akper A.; Aliyev, Chingiz S.

2008-04-01

The Oligocene-Miocene Maikop Series is a world-class source rock responsible for much of the oil and gas found in the South Caspian Basin. It is composed of up to 3 km of marine mudstone, and contains a nearly continuous record of deposition during progressive tectonic closure of the basin as the Arabian Peninsula converged northward into Eurasia. Historically, the stratigraphy of this interval has been difficult to define due to the homogenous nature of the fine-grained, clay-dominated strata. Outcrop exposures in eastern Azerbaijan allow direct observation and detailed sampling of the interval, yielding a more comprehensive stratigraphic context and a more advanced understanding of syndepositional conditions in the eastern Paratethys Sea. Specifically, the present investigation reveals that coupling field-based stratigraphic characterization with geochemical analyses (e.g., bulk elemental geochemistry, Rock-Eval pyrolysis, bulk stable isotope geochemistry) yields a more robust understanding of internal variations within the Maikop Series. Samples from seven sections located within the Shemakha-Gobustan oil province reveal consistent stratigraphic and spatial geochemical trends. It is proposed that the Maikop Series be divided into three members based on these data along with lithostratigraphic and biostratigraphic data reported herein. When comparing Rupelian (Early Oligocene) and Chattian (Late Oligocene) strata, the Rupelian-age strata commonly possess higher TOC values, more negative δ 15N tot values, more positive δ 13C org values, and higher radioactivity relative to Chattian-age rocks. The trace metals Mo and V (normalized to Al) are positively correlated with TOC, with maximum values occurring at the Rupelian-Chattian boundary and overall higher average values in the Rupelian. Across the Oligocene-Miocene boundary, a slight drop in V/Al, Mo/Al ratios is observed, along with drops in %S and TOC. These results indicate that geochemical signatures of the Maikop Series are regional in nature, and furthermore that analogous fine-grained sections may be better characterized and subdivided using similar techniques. In general, geochemical indicators suggest that the basin was in limited communication with the Tethys Sea throughout the Oligocene-Early Miocene, with suboxic to anoxic conditions present during the Oligocene and to a lesser extent in the Miocene. This increased isolation was likely due to tectonic uplift to both the south and north of the study area, and greatly enhanced by global sea-level fluctuations. These data serve as the basis for a more detailed understanding of the tectonic evolution of the region, and support a standardized chemostratigraphic division of the important petroleum source interval.

Efficient mixing of the solar nebula from uniform Mo isotopic composition of meteorites.

PubMed

Becker, Harry; Walker, Richard J

2003-09-11

The abundances of elements and their isotopes in our Galaxy show wide variations, reflecting different nucleosynthetic processes in stars and the effects of Galactic evolution. These variations contrast with the uniformity of stable isotope abundances for many elements in the Solar System, which implies that processes efficiently homogenized dust and gas from different stellar sources within the young solar nebula. However, isotopic heterogeneity has been recognized on the subcentimetre scale in primitive meteorites, indicating that these preserve a compositional memory of their stellar sources. Small differences in the abundance of stable molybdenum isotopes in bulk rocks of some primitive and differentiated meteorites, relative to terrestrial Mo, suggest large-scale Mo isotopic heterogeneity between some inner Solar System bodies, which implies physical conditions that did not permit efficient mixing of gas and dust. Here we report Mo isotopic data for bulk samples of primitive and differentiated meteorites that show no resolvable deviations from terrestrial Mo. This suggests efficient mixing of gas and dust in the solar nebula at least to 3 au from the Sun, possibly induced by magnetohydrodynamic instabilities. These mixing processes must have occurred before isotopic fractionation of gas-phase elements and volatility-controlled chemical fractionations were established.

An internally consistent pressure calibration of geobarometers applicable to the Earth’s upper mantle using in situ XRD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beyer, Christopher; Rosenthal, Anja; Myhill, Robert

We have performed an experimental cross calibration of a suite of mineral equilibria within mantle rock bulk compositions that are commonly used in geobarometry to determine the equilibration depths of upper mantle assemblages. Multiple barometers were compared simultaneously in experimental runs, where the pressure was determined using in-situ measurements of the unit cell volumes of MgO, NaCl, Re and h-BN between 3.6 and 10.4 GPa, and 1250 and 1500 °C. The experiments were performed in a large volume press (LVPs) in combination with synchrotron X-ray diffraction. Noble metal capsules drilled with multiple sample chambers were loaded with a range ofmore » bulk compositions representative of peridotite, eclogite and pyroxenite lithologies. By this approach, we simultaneously calibrated the geobarometers applicable to different mantle lithologies under identical and well determined pressure and temperature conditions. We identified discrepancies between the calculated and experimental pressures for which we propose simple linear or constant correction factors to some of the previously published barometric equations. As a result, we establish internally-consistent cross-calibrations for a number of garnet-orthopyroxene, garnet-clinopyroxene, Ca-Tschermaks-in-clinopyroxene and majorite geobarometers.« less

Effects of dispersed particulates on the rheology of water ice at planetary conditions

NASA Technical Reports Server (NTRS)

Durham, William B.; Kirby, Stephen H.; Stern, Laura A.

1992-01-01

Effects of the initial grain size and the hard particulate impurities on the transient and the steady state flows of water ice I were investigated under laboratory conditions selected as appropriate for simulating those of the surfaces and interiors of large moons. The samples were molded with particulate volume fraction, phi, of 0.001 to 0.56 and particle sizes of 1 to 150 microns; deformation experiments were conducted at constant shortening rates of 4.4 x 10 exp -7 to 4.9 x 10 exp -4 per sec at pressures of 50 and 100 MPa and temperatures 77 to 223 K. The results obtained suggest that viscous drag occurs in the ice as it flows around hard particulates. Mixed-phase ice was found to be tougher than pure ice, extending the range of bulk plastic deformation vs. faulting to lower temperatures and higher strain rates. It is suggested that bulk planetary compositions of ice + rock (phi = 0.4-0.5) are roughly 2 orders of magnitude more viscous than pure ice, leading to thermal instability inside giant icy moons and possibly explaining the retention of crater topography on icy planetary surfaces.

A multi-proxy isotope study (δ41K, δ26Mg, 87Sr/86Sr) of low-temperature oceanic crust alteration: the Troodos Ophiolite and Ocean Drilling Program Hole 801C

NASA Astrophysics Data System (ADS)

Santiago Ramos, D. P.; Higgins, J. A.

2017-12-01

Low-temperature alteration of oceanic crust plays an important role in a number of geochemical cycles, thus modulating the chemical composition of the oceans. In particular, it has been established that low-temperature (<150oC) alteration of basalt is a major sink of seawater potassium. However, little is known about the effects of this process on the potassium isotope composition of seawater, which is 0.5‰ enriched relative to bulk silicate Earth (δ41KBSE=-0.54‰). Here we measure a number of isotope systems (δ41K, δ26Mg, 87Sr/86Sr) in both host rock and vein material from the upper volcanic section of Cretaceous (Troodos Ophiolite) and Jurassic (ODP 801C) oceanic crust using a MC-ICP-MS. The goal is to estimate the K isotopic fractionation associated with basalt alteration in low-temperature conditions, and how it might affect the K isotope enrichment of seawater relative to BSE. We find that marine hydrothermal samples from Troodos and ODP site 801C are enriched in potassium relative to the unaltered glass compositions and have δ41K values both higher and lower than BSE, ranging from -0.45‰ to -0.69‰ (n = 9) and -0.32‰ to -0.71‰ (n = 5), respectively. The low measured δ41K values could represent 1) fractionation (α<1) of K isotopes during uptake from seawater (δ41KSW 0‰), or 2) remobilized mantle-sourced K (δ41KBSE=-0.54‰) from deeper within the ophiolite sequence. Measurements of δ26Mg (n=15) and 87Sr/86Sr (n=12) in these samples yield enriched values relative to bulk silicate Earth, suggesting that alteration of oceanic crust likely happened under high water-to-rock ratios in both Troodos and ODP 801C, and that the added potassium is seawater-sourced. We thus suggest that the isotopically light δ41K values measured in both sites are associated with the formation of secondary clays enriched in the 39K isotope. This light isotope enrichment could be intensified if seawater K sourcing is a diffusion-limited process, as aqueous potassium diffusion has been associated with K isotope fractionations between 0.9967 and 0.9984. Our results indicate that the uptake of potassium in altered oceanic crust could be responsible, in part, for the observed K isotope enrichment of seawater relative to bulk silicate Earth.

Pristine Igneous Rocks and the Early Differentiation of Planetary Materials

NASA Technical Reports Server (NTRS)

Warren, Paul H.

2005-01-01

Our studies are highly interdisciplinary, but are focused on the processes and products of early planetary and asteroidal differentiation, especially the genesis of the ancient lunar crust. The compositional diversity that we explore is the residue of process diversity, which has strong relevance for comparative planetology. Most of the accessible lunar crust consists of materials hybridized by impact-mixing. Our lunar research concentrates on the rare pristine (unmixed) samples that reflect the original genetic diversity of the early crust. Among HED basalts (eucrites and clasts in howardites), we distinguish as pristine the small minority that escaped the pervasive thermal metamorphism of the parent asteroid's crust. We have found a correlation between metamorphically pristine HED basalts and the similarly small minority of compositionally evolved "Stannern trend" samples, which are enriched in incompatible elements and titanium compared to main group eucrites, and yet have relatively high mg ratios. Other topics under investigation included: lunar and SNC (martian?) meteorites; igneous meteorites in general; impact breccias, especially metal-rich Apollo samples and polymict eucrites; siderophile compositions of the lunar and martian mantles; and planetary bulk compositions and origins.

Introduction to the Apollo collections. Part 1: Lunar igneous rocks

NASA Technical Reports Server (NTRS)

Mcgee, P. E.; Warner, J. L.; Simonds, C. H.

1977-01-01

The basic petrographic, chemical, and age data is presented for a representative suite of igneous rocks gathered during the six Apollo missions. Tables are given for 69 samples: 32 igneous rocks and 37 impactites (breccias). A description is given of 26 basalts, four plutonic rocks, and two pyroclastic samples. The textural-mineralogic name assigned each sample is included.

The evolution, argon diffusion properties, and 40Argon/39Argon ages of detachment-related fault rocks in the footwalls of the Whipple and Chemehuevi Mountains, Southeastern, California

NASA Astrophysics Data System (ADS)

Hazelton, Garrett Blaine

Furnace and laser spot methods of obtaining 40Ar/ 39Ar ages from fine-grained cataclasite and pseudotachylyte are compared and evaluated in terms of protolith, faulting, and cooling age components. These methods are applied to fault rocks from outcrop-scale, small-displacement, brittle detachment faults (minidetachments or MDF's) that cut mid-crustal rocks from the footwalls of brittle, large-displacement (>20 km), top-to-the-NE, low-angle normal (i.e., detachment) faults in the Whipple (WM) and Chemehuevi Mountains (CM), SE California. Mid-Tertiary extension affected both areas from ˜26 Ma to ˜11--8 Ma. Rapid footwall cooling began at ˜22 Ma. WM-CM furnace ages range from 22.0 +/- 1.3 to 14.6 +/- 0.6 Ma, CM laser ages from 29.9 +/- 3.7 to 15.7 +/- 1.2 Ma. These ages are younger than host protolith formation and record detachment faulting or footwall cooling. At least 50 MDF's were mapped; they typically cut all basement fabrics. Brittle MDFand detacriment-generated fault rocks are texturally similar, but some in the WM are plastically deformed. Fault rock matrix was mechanically extracted, optically studied, probed to characterize bulk mineralogy. K-feldspar grains are the primary source of fault rock-derived Ar. The laser provides high spatial resolution and the furnace method yields the Ar diffusion properties of fault rock matrix. Both methods yield reproducible results, but ages are difficult to interpret without an established geothermochronologic context. Fault rock 40Ar/39Ar measurements reveal: (1) closure temperatures of 140--280°C (at 100°C/Myr); (2) activation energies ranging from 33--50 kcal/mol; (3) individual K-feldspar grain ages of 55--5 Ma; (4) unanticipated and poorly understood low-temperature diffusion behavior; (5) little difference between pseudotachylyte and cataclasite matrix diffusion and age results; (6) that pre-analysis sample characterization is requisite. The diffusion properties of prepared glasses (47--84% SiO2) were also measured. Those with fault rock-like compositions yield activation energies of 25--39 kca/mol and average diffusivity of 4.63 · 10-3 cm2/sec. Network-forming Ca, Fe, and Mg partly cause certain low-temperature diffusion behaviors that, if unaccounted for, could allow an underestimation of Ar diffusion rates in some glass-bearing materials. Numerical models show that ambient temperature, grain size, and cooling rate strongly influence the Ar retention rate and interpretability of fault rock 40Ar/39Ar ages.

Data Validation Package September 2016 Groundwater and Surface Water Sampling at the Slick Rock, Colorado, Processing Sites January 2017

DOE Office of Scientific and Technical Information (OSTI.GOV)

Traub, David; Nguyen, Jason

The Slick Rock, Colorado, Processing Sites are referred to as the Slick Rock West Processing Site (SRK05) and the Slick Rock East Processing Site (SRK06). This annual event involved sampling both sites for a total of 16 monitoring wells and 6 surface water locations as required by the 2006 Draft Final Ground Water Compliance Action Plan for the Slick Rock, Colorado, Processing Sites (GCAP). A domestic well was also sampled at a property adjacent to the Slick Rock East site at the request of the landowner.

Petrophysical Properties of Twenty Drill Cores from the Los Azufres, Mexico, Geothermal Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iglesias, E.R.; Contreras L., E.; Garcia G., A.

1987-01-20

For this study we selected 20 drill cores covering a wide range of depths (400-3000 m), from 15 wells, that provide a reasonable coverage of the field. Only andesite, the largely predominant rock type in the field, was included in this sample. We measured bulk density, grain (solids) density, effective porosity and (matrix) permeability on a considerable number of specimens taken from the cores; and inferred the corresponding total porosity and fraction of interconnected total porosity. We characterized the statistical distributions of the measured and inferred variables. The distributions of bulk density and grain density resulted approximately normal; the distributionsmore » of effective porosity, total porosity and fraction of total porosity turned out to be bimodal; the permeability distribution resulted highly skewed towards very small (1 mdarcy) values, though values as high as 400 mdarcies were measured. We also characterized the internal inhomogeneity of the cores by means of the ratio (standard deviation/mean) corresponding to the bulk density in each core (in average there are 9 specimens per core). The cores were found to present clearly discernible inhomogeneity; this quantitative characterization will help design new experimental work and interpret currently available and forthcoming results. We also found statistically significant linear correlations between total density and density of solids, effective porosity and total density, total porosity and total density, fraction of interconnected total porosity and the inverse of the effective porosity, total porosity and effective porosity; bulk density and total porosity also correlate with elevation. These results provide the first sizable and statistically detailed database available on petrophysical properties of the Los Azufres andesites. 1 tab., 16 figs., 4 refs.« less

Two-dimensional Coupled Petrological-tectonic Modelling of Extensional Basins

NASA Astrophysics Data System (ADS)

Kaus, B. J. P.; Podladchikov, Y. Y.; Connolly, J. A. D.

Most numerical codes that simulate the deformation of a lithosphere assume the den- sity of the lithosphere to be either constant or depend only on temperature and pres- sure. It is, however, well known that rocks undergo phase transformations in response to changes in pressure and temperature. Such phase transformations may substantially alter the bulk properties of the rock (i.e., density, thermal conductivity, thermal ex- pansivity and elastic moduli). Several previous studies demonstrated that the density effects due to phase transitions are indeed large enough to have an impact on the litho- sphere dynamics. These studies were however oversimplified in that they accounted for only one or two schematic discontinuous phase transitions. The current study there- fore takes into account all the reactions that occur for a realistic lithospheric composi- tion. Calculation of the phase diagram and bulk physical properties of the stable phase assemblages for the crust and mantle within the continental lithosphere was done ac- counting for mineral solution behaviour using a free energy minimization program for natural rock compositions. The results of these calculations provide maps of the varia- tions in rock properties as a function of pressure and temperature that are easily incor- porated in any dynamic model computations. In this contribution we implemented a density map in the two-dimensional basin code TECMOD2D. We compare the results of the model with metamorphic reactions with a model without reactions and define some effective parameters that allow the use of a simpler model that still mimics most of the density effects of the metamorphic reactions.

Spatially-resolved isotopic study of carbon trapped in ∼3.43 Ga Strelley Pool Formation stromatolites

NASA Astrophysics Data System (ADS)

Flannery, David T.; Allwood, Abigail C.; Summons, Roger E.; Williford, Kenneth H.; Abbey, William; Matys, Emily D.; Ferralis, Nicola

2018-02-01

The large isotopic fractionation of carbon associated with enzymatic carbon assimilation allows evidence for life's antiquity, and potentially the early operation of several extant metabolic pathways, to be derived from the stable carbon isotope record of sedimentary rocks. Earth's organic carbon isotope record extends to the Late Eoarchean-Early Paleoarchean: the age of the oldest known sedimentary rocks. However, complementary inorganic carbon reservoirs are poorly represented in the oldest units, and commonly reported bulk organic carbon isotope measurements do not capture the micro-scale isotopic heterogeneities that are increasingly reported from younger rocks. Here, we investigated the isotopic composition of the oldest paired occurrences of sedimentary carbonate and organic matter, which are preserved as dolomite and kerogen within textural biosignatures of the ∼3.43 Ga Strelley Pool Formation. We targeted least-altered carbonate phases in situ using microsampling techniques guided by non-destructive elemental mapping. Organic carbon isotope values were measured by spatially-resolved bulk analyses, and in situ using secondary ion mass spectrometry to target microscale domains of organic material trapped within inorganic carbon matrixes. Total observed fractionation of 13C ranges from -29 to -45‰. Our data are consistent with studies of younger Archean rocks that host biogenic stromatolites and organic-inorganic carbon pairs showing greater fractionation than expected for Rubisco fixation alone. We conclude that organic matter was fixed and/or remobilized by at least one metabolism in addition to the CBB cycle, possibly by the Wood-Ljungdahl pathway or methanogenesis-methanotrophy, in a shallow-water marine environment during the Paleoarchean.

77 FR 40087 - Manufacturer of Controlled Substances; Notice of Registration; Cerilliant Corporation

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-06

... DEPARTMENT OF JUSTICE Drug Enforcement Administration Manufacturer of Controlled Substances... Rock, Texas 78665-2402, made application by letter to the Drug Enforcement Administration (DEA) to be registered as a bulk manufacturer of the following basic classes of controlled substances: Drug Schedule 4...

Trace elements quantified by the APXS on Mars

NASA Astrophysics Data System (ADS)

Gellert, R.; Berger, J. A.; Boyd, N.; O'Connell-Cooper, C.; Desouza, E.; Thompson, L. M.; VanBommel, S.; Yen, A.

2017-12-01

The APXS accurately quantifies many trace elements within the dime-sized sample: Ni, Cu, Zn, Ga, Ge, Pb, Br, Se, As, and Y with 20 ppm detection limit (DL) and Rb, Sr, Zr, Co, Cr, and Mn with 200 ppm DL. Together with the major and minor elements, this gives important constraints for a variety of formation processes of the investigated soils, floats or extensive bedrock on Mars. The global soil, found at all rover landing sites, was used to define an average Mars value for Ni, Zn, Cr and Mn, with a consistent value of Fe/Mn 50 for soils and igneous rocks. All other APXS trace elements are below DL. Strong enrichments or depletions can both give evidence for the formation processes and link together groups of rocks and indicate their common diagenetic origin. Felsic rocks at Gale and Gusev have Cr, Ni and Zn far below soil, indicating their likely igneous origin. Further, similarly low values are found in elevated silica samples in the Murray Fm. at Gale where these elements have been mobilized and leached by fluids. High Sr and Ga was found in the host rock surrounding the Garden City vein system, which contains also high Ge, Mn and Cu, indicating mobilization in high temperature and/or acidic fluids after the Murray was lithified. The fracture fill sample Stephen at Windjana is high in Zn, Co and Cu. Germanium is enriched in the Murray Fm with very consistent values of about 100 ppm over many kilometers and 200 meters elevation, similar to perviously found bedrock at Yellowknife Bay and Windjana in Gale. Zinc is highly elevated but changes significantly with elevation in Murray, often correlated with Fe/Mn, possibly indicating changing redox conditions. Pb and Se are highly enriched at Pahrump (150, 75 ppm, resp.), drop first to low values and increase again uphill towards HematiteRidge. Nodules found at Pahrump show striking evidence for (Mg, Ni)-sulfates with Nickel up to 4% in the sulfates. All together these trends might indicate hydrothermal activity. The MER APXS instruments with somewhat higher DL found similar patterns. Elevated Ge was found at Home plate, Gusev crater, and at the rim of Endeavour crater at Meridiani Planum. Together with detailed investigations of SNC meteorites, the APXS detected trace elements supplement the bulk chemistry significantly and allow new insights into the formation processes encountered on Mars

Stable isotope analysis of Dacryoconarid carbonate microfossils: a new tool for Devonian oxygen and carbon isotope stratigraphy.

PubMed

Frappier, Amy Benoit; Lindemann, Richard H; Frappier, Brian R

2015-04-30

Dacryoconarids are extinct marine zooplankton known from abundant, globally distributed calcite microfossils in the Devonian, but their shell stable isotope composition has not been previously explored. Devonian stable isotope stratigraphy is currently limited to less common invertebrates or bulk rock analyses of uncertain provenance. As with Cenozoic planktonic foraminifera, isotopic analysis of dacryoconarid shells could facilitate higher-resolution, geographically widespread stable isotope records of paleoenvironmental change, including marine hypoxia events, climate changes, and biocrises. We explored the use of Dacryoconarid isotope stratigraphy as a viable method in interpreting paleoenvironments. We applied an established method for determining stable isotope ratios (δ(13) C, δ(18) O values) of small carbonate microfossils to very well-preserved dacryoconarid shells. We analyzed individual calcite shells representing five common genera using a Kiel carbonate device coupled to a MAT 253 isotope ratio mass spectrometer. Calcite shell δ(13) C and δ(18) O values were compared by taxonomic group, rock unit, and locality. Single dacryoconarid calcite shells are suitable for stable isotope analysis using a Kiel-IRMS setup. The dacryoconarid shell δ(13) C values (-4.7 to 2.3‰) and δ(18) O values (-10.3 to -4.8‰) were consistent across taxa, independent of shell size or part, but varied systematically through time. Lower fossil δ(18) O values were associated with warmer water temperature and more variable δ(13) C values were associated with major bioevents. Dacryoconarid δ(13) C and δ(18) O values differed from bulk rock carbonate values. Dacryoconarid individual microfossil δ(13) C and δ(18) O values are highly sensitive to paleoenvironmental changes, thus providing a promising avenue for stable isotope chemostratigraphy to better resolve regional to global paleoceanographic changes throughout the upper Silurian to the upper Devonian. Our results warrant further exploration of dacryoconarid stable isotope proxy sensitivity, the isotopic contrast among dacryoconarids, other taxa, and bulk rock, as well as other potential dacryoconarid proxies (Mg/Ca, Sr/Ca, (87) Sr/(86) Sr, microlaser and ion microprobe isotope techniques, and clumped isotopes) for stratigraphic research. Copyright © 2015 John Wiley & Sons, Ltd.

Distinctly different parental magmas for plutons and lavas in the central Aleutian arc

NASA Astrophysics Data System (ADS)

Cai, Y.; Rioux, M. E.; Kelemen, P. B.; Goldstein, S. L.; Bolge, L.; Kylander-Clark, A. R.

2014-12-01

While it is generally agreed that continental crust is generated by arc magmatism, average arc lavas are basaltic while the bulk continental crust is andesitic, and this has led to many models for secondary reprocessing of the arc crust in order to form continental crust. We report new data on calc-alkaline plutons in the central Aleutians showing that they have distinctly different sources compared to Holocene tholeiitic lavas. Therefore the lavas are not representative of the net magmatic transfer from the mantle into the arc crust. Eocene to Miocene (9-39 Ma) intermediate to felsic plutonic rocks from the central Aleutian arc show higher SiO2 at a given Mg#, higher ɛNd- and ɛHf-values, and lower Pb isotope ratios than Holocene volcanic rocks from the same region. Instead, the plutonic rocks resemble volcanics from the western Aleutians isotopically, and have chemical compositions similar to bulk continental crust. These data could reflect temporal variation of Aleutian magma source compositions, from Eocene-Miocene "isotopically depleted" and predominantly calc-alkaline to Holocene "isotopically enriched" and predominantly tholeiitic. Alternatively, they may reflect different transport and emplacement processes for the magmas that form plutons and lavas: calc-alkaline magmas with higher Si content and high viscosity may preferentially form plutons, perhaps after extensive mid-crustal degassing of initially high water contents. The latter case implies that the upper and middle arc crust is more like the calc-alkaline bulk composition of the continental crust than the lavas alone. Crustal reprocessing mechanisms that preserve upper and middle arc crust, while removing lower arc crust, can account for the genesis and evolution of continental crust. Since gabbroic lower arc crust extends from ca 20-40 km depth, and is density stable over most of this depth range, "delamination" of dense lithologies [1] may not be sufficient to accomplish this. Alternatively, subduction erosion of arc crust followed by "relamination" [2] of buoyant calc-alkaline rocks may be more effective. [1] e.g. Ringwood & Green, Tectonophysics 1966; Herzberg et al. Contributions to mineralogy and petrology 1983; [2] e.g. Hacker et al. Earth and Planetary Science Letters 2011.

The Usability of Rock-Like Materials for Numerical Studies on Rocks

NASA Astrophysics Data System (ADS)

Zengin, Enes; Abiddin Erguler, Zeynal

2017-04-01

The approaches of synthetic rock material and mass are widely used by many researchers for understanding the failure behavior of different rocks. In order to model the failure behavior of rock material, researchers take advantageous of different techniques and software. But, the majority of all these instruments are based on distinct element method (DEM). For modeling the failure behavior of rocks, and so to create a fundamental synthetic rock material model, it is required to perform related laboratory experiments for providing strength parameters. In modelling studies, model calibration processes are performed by using parameters of intact rocks such as porosity, grain size, modulus of elasticity and Poisson ratio. In some cases, it can be difficult or even impossible to acquire representative rock samples for laboratory experiments from heavily jointed rock masses and vuggy rocks. Considering this limitation, in this study, it was aimed to investigate the applicability of rock-like material (e.g. concrete) to understand and model the failure behavior of rock materials having complex inherent structures. For this purpose, concrete samples having a mixture of %65 cement dust and %35 water were utilized. Accordingly, intact concrete samples representing rocks were prepared in laboratory conditions and their physical properties such as porosity, pore size and density etc. were determined. In addition, to acquire the mechanical parameters of concrete samples, uniaxial compressive strength (UCS) tests were also performed by simultaneously measuring strain during testing. The measured physical and mechanical properties of these extracted concrete samples were used to create synthetic material and then uniaxial compressive tests were modeled and performed by using two dimensional discontinuum program known as Particle Flow Code (PFC2D). After modeling studies in PFC2D, approximately similar failure mechanism and testing results were achieved from both experimental and artificial simulations. The results obtained from these laboratory tests and modelling studies were compared with the other researcher's studies in respect to failure mechanism of different type of rocks. It can be concluded that there is similar failure mechanism between concrete and rock materials. Therefore, the results obtained from concrete samples that would be prepared at different porosity and pore sizes can be used in future studies in selection micro-mechanical and physical properties to constitute synthetic rock materials for understanding failure mechanism of rocks having complex inherent structures such as vuggy rocks or heavily jointed rock masses.

7 CFR 201.40 - Bulk.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Sampling in the Administration of the Act § 201.40 Bulk. Bulk seeds or screenings shall be sampled by inserting a long probe or thrusting the hand into the bulk as circumstances require in at least seven... 7 Agriculture 3 2011-01-01 2011-01-01 false Bulk. 201.40 Section 201.40 Agriculture Regulations of...

7 CFR 201.40 - Bulk.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Sampling in the Administration of the Act § 201.40 Bulk. Bulk seeds or screenings shall be sampled by inserting a long probe or thrusting the hand into the bulk as circumstances require in at least seven... 7 Agriculture 3 2010-01-01 2010-01-01 false Bulk. 201.40 Section 201.40 Agriculture Regulations of...

Rock Around the World: International Outreach for Scientific Education Using Infrared Spectroscopy

NASA Astrophysics Data System (ADS)

Rogers, L. D.; Klug, S. L.; Christensen, P. R.; Rogers, T. A.; Daub, G.

2005-12-01

Since the creation of the Rock Around the World (RATW) program in January 2004, we have received 6,861 (to date) rocks from children and adults alike from around the world. RATW is an educational outreach device to inspire and teach children about science. In addition, the accumulation of almost 7,000 rock samples has exponentially expanded the Arizona State University earth-based rock library into a large collection of samples useful for scientific investigation of Earth and Mars. This library currently supports research that is being conducted by the Mars Global Surveyor Thermal Emission Spectrometer (TES), the Mars Odyssey Thermal Emission Imaging System (THEMIS) and the two Mini-Thermal Emission Spectrometer (Mini-TES) instruments that are onboard the Mars Exploration Rovers. Currently, we have 3 undergraduate students working on the RATW project. As each rock sample arrives, appropriate information that was received with the sample is entered into our web-based RATW database. The information received with the rock sample is directly input into the RATW website. The information is publicly available for each sample at http://ratw.asu.edu. The sample is photographed, and then sent to the spectrometer for analysis. Once the spectrum is taken, calibration is performed. Then the sample is filed away in our rock archive room. Our website has several interactive tools which enhance the learning process. These tools include an interactive world map where the visitor can click on a rock location and preview all of the rocks sent from that geographical area of the world. In addition RATW has also put four virtual mineral libraries online. This enables any visitor to the RATW website to deconvolve or "unmix" their spectrum to see the mineral composition, using the same techniques that scientists use on the TES, THEMIS, and mini-TES data. The 6,861 rock samples we have received have been very geographically widespread. Participants have sent rocks from such places as Greenland, India, Switzerland and the Falkland Islands. We have received submissions that have included maps, drawings, pictures, stories, GPS readings and scientific literature and research about their rock sample and collection area. The number of RATW participants, and the enthusiasm with which they have participated, has shown that educational and scientific programs in Earth and Planetary Science draw worldwide interest among students and adults alike.

Influence of Melting and Hydrothermal Alteration on Lead in Abyssal Peridotites

NASA Astrophysics Data System (ADS)

Warren, J. M.; D'Errico, M. E.; Godard, M.; Coble, M. A.; Horan, M.

2017-12-01

The lead isotopic system is a key tracer of mantle convection, yet the abundance and mineralogical hosts of Pb in the upper mantle are poorly constrained. To address this, we analyzed the concentration of Pb in minerals and bulk rock powders of abyssal peridotites. These samples represent the oceanic upper mantle following melt extraction. They can be used to explore the mantle Pb budget, assuming that the amount of Pb lost during mantle melting and gained during seafloor alteration can be determined. We performed in situ analysis of the three main silicate phases (olivine, orthopyroxene, and clinopyroxene), which yield Pb concentrations of 2-30 ppb. Olivine is the main mineralogical host of Pb, unlike other trace elements, which are predominantly hosted in clinopyroxene. Sulfide contains an average of 3 ppm Pb, but these high concentrations are offset by low modal abundances (<0.01%), making this mineral a minor source of peridotite Pb. Whole rock Pb concentrations of abyssal peridotites measured by thermal ionization mass spectrometry range from 3 to 38 ppb. These values are close to the reconstructed whole rock values of 2 to 14 ppb, calculated from the mineral concentrations of Pb multiplied by their modes. In contrast, the average value among literature data for whole rock abyssal peridotites is >100 ppb [1, 2], measured by inductively-coupled plasma mass spectrometry. The higher values among literature data may reflect a combination of lower analytical sensitivity and effects of alteration. Samples in this study include an unaltered peridotite from the Gakkel Ridge, which shows the closest agreement between reconstructed and measured whole rock values. We estimate that our peridotites have undergone 5 to 9% melting [3], based on non-modal fractional melt modeling of rare earth element abundances. Assuming 18 to 23 ppb Pb in the depleted source mantle [4, 5], expected concentrations in abyssal peridotites after melting are <1 ppb. However, as suggested by [5], mantle Pb abundance is poorly constrained by the Ce/Pb ratio of mid-ocean ridge basalt and the amount of Pb in the depleted mantle may be higher than current estimates. [1] Niu, 2004, J. Pet.; [2] Paulick et al., 2006, Chem. Geol.; [3] D'Errico et al., 2016, GCA; [4] Salters and Stracke, 2004, G-Cubed; [5] Workman and Hart, 2005 EPSL.

Mantle water contents beneath the Rio Grande Rift (NM, USA): FTIR analysis of Rio Puerco and Kilbourne Hole peridotite xenoliths

NASA Astrophysics Data System (ADS)

Schaffer, L. A.; Peslier, A. H.; Brandon, A. D.; Selverstone, J.

2015-12-01

Peridotite xenoliths from the Rio Grande Rift (RGR) are being analyzed for H2O contents by FTIR as well as for major and trace element compositions. Nine samples are from the Rio Puerco Volcanic Field (RP) which overlaps the central RGR and southeastern Colorado Plateau; seventeen samples are from Kilbourne Hole (KH) in the southern RGR. Spinel Cr# (Cr/(Cr+Al) = 0.08-0.46) and olivine Mg# (Mg/(Mg+Fe) = 0.883-0.911) of samples fall within the olivine-spinel mantle array from [1], an indicator that these are residues of partial melting. Pyroxene H2O contents in KH correlate with bulk rock and pyroxene Al2O3 contents. The KH clinopyroxene rare earth element (REE) variations fit models of 0-13% fractional melting of a primitive upper mantle. Most KH peridotites have bulk-rock light REE depleted patterns, but five are enriched in light REEs consistent with metasomatism. Variation in H2O content seems unrelated to REE enrichment. Metasomatism is seen in RP pyroxenite xenoliths [2] and will be examined in the peridotites studied here. Olivine H2O contents are low (≤20 ppm), and decrease from core to rim within grains. This is likely due to H loss during xenolith transport by the host magma [3]. Diffusion models of H suggest that mantle H2O contents are still preserved in cores of KH olivine, but not those of RP olivine. The average H2O content of Colorado Plateau clinopyroxene (670 ppm) [4] is ~300 ppm higher than RGR clinopyroxene (350 ppm). This upholds the hypothesis that hydration-induced lithospheric melting occurred during flat-slab subduction of the Farallon plate [5]. Numerical models indicate hydration via slab fluids is possible beneath the plateau, ~600 km from the paleo-trench, but less likely ~850 km away beneath the rift [6]. [1]Arai, 1994 CG 113, 191-204.[2]Porreca et al., 2006 Geosp 2, 333-351.[3]Peslier and Luhr, 2006 EPSL 242, 302-319.[4]Li et al., 2008 JGR 113, 1978-2012.[5]Humphreys et al., 2003 Int Geol Rev 45, 575-595.[6]English et al., 2003 EPSL 214, 619-632.

Petrogenesis of the Alaskan-type mafic-ultramafic complex in the Makkah quadrangle, western Arabian Shield, Saudi Arabia

NASA Astrophysics Data System (ADS)

Habtoor, Abdelmonem; Ahmed, Ahmed Hassan; Harbi, Hesham

2016-10-01

The Makkah quadrangle is a part of the Jeddah terrane in the Precambrian basement, Western Arabian Shield of Saudi Arabia. Gabal Taftafan mafic-ultramafic complex lies within the central part of the Makkah quadrangle. The Taftafan mafic-ultramafic complex is a well-differentiated rock association which comprises of dunite core, hornblende- and plagioclase-bearing peridotites, troctolite, clinopyroxenite and marginal gabbro, in a distinctive zonal structure. The bulk-rock geochemistry of the Taftafan mafic-ultramafic rocks is characterized by a tholeiitic/sub-alkaline affinity with high Mg in the ultramafic core (0.84) and is systematically decreased towards the marginal gabbro (0.60). The patterns of trace elements show enrichment in the fluid-mobile elements (Sr, Ba) and a pronounced negative Nb anomaly which reflect a hydrous parental magma generated in a subduction tectonic setting. The mafic-ultramafic rocks of the Taftafan complex have low total rare earth elements (REE) displaying sub-parallel patterns leading to the assumption that these rocks are comagmatic and are formed by fractional crystallization from a common magma type. The platinum-group elements (PGE) content of all rock types in the Taftafan complex is very low, with ∑ PPGE > ∑ IPGE; displaying slightly positive slopes of the PGE distribution patterns. The chemistry of ferromagnesian minerals is characterized by a high forsterite (Fo) olivine with wide range (Fo91-67), from ultramafic core to the marginal gabbro, Ca-rich diopsidic clinopyroxene, and calcic hornblende. Orthopyroxene is almost absent from all rock types, or very rare when present. Hornblende and Ca-plagioclase possess the longest crystallization history since they are present in almost all rock types of the complex. Spinels in the dunite and hornblende-bearing peridotite core show homogeneous composition with intermediate Cr# (0.53-0.67). Plagioclase-bearing peridotite and troctolite have two exsolved types of spinel; Al-rich and Fe-rich varieties. All spinel varieties in the mafic-ultramafic rocks have high Fe3 + and TiO2 contents. The estimated melt composition in equilibrium with Gabal Taftafan complex is mostly similar to that of the SSZ boninitic magmas. The Taftafan mafic-ultramafic rocks show many similarities with the Alaskan-type mafic-ultramafic complexes, including the internal zonal lithology, bulk rock geochemistry, and mineral chemistry. Thus, it is neither related to a fragment of ophiolite sequence nor to the stratiform mafic-ultramafic intrusion. The location of the Taftafan complex along a major fracture zone parallel to the suture between Jeddah and Asir terranes in addition to the aforementioned striking similarities to the Alaskan-type complexes, suggests a formation in subduction-related setting from a common hydrous mafic magma.

Origin Of Extreme 3He/4He Signatures In Icelandic Lavas: Insights From Melt Inclusion Studies

NASA Astrophysics Data System (ADS)

Harlou, R.; Kent, A. J.; Breddam, K.; Davidson, J. P.; Pearson, D. G.

2003-12-01

Helium isotopes are considered a powerful tool for tracking different mantle domains. Yet, the origin of He isotope variations in many basaltic suites remains enigmatic and often difficult to link with more lithophile chemical and isotopic tracers. One problem is that He isotope ratios are measured from crushed olivines and thus reflect prior fluid and melt fluxes trapped in inclusions within the olivine grains, whereas the lithophile elements mainly reflect the host lava. In an attempt to link He and lithophile element variations, we have characterized the major and trace element composition including volatile elements, of olivine-hosted melt inclusions from three ankaramitic lavas from Vestfirdir, NW-Iceland. Previous studies have reported extreme 3He/4He ratios from NW-Iceland and one ankaramite (SEL97) has been suggested to provide the most precise estimate of the radiogenic (Sr-Nd-Pb) isotopic composition of a relatively undegassed (high 3He/4He) mantle component (C or FOZO) common to several ocean islands (Hilton et al. 1999, EPSL 173, 53-60). The samples investigated here exhibit amongst the highest 3He/4He ratios observed in terrestrial rocks (42.9 and 34.8 R/Ra). A detailed account of the trace element signature of melt inclusions in these samples may thus help explain the origin of FOZO. One sample of similar composition to these, has a lower He content and a relatively poorly defined He isotope composition of 8.15 +/- 5.1 R/Ra (Breddam & Kurz, 2001, EOS, 82, F1315). In terms of major elements, the whole rock data reflect olivine accumulation, whereas the melt inclusion data reflect ol + cpx fractionation. The melt inclusions are generally basaltic (Mg#: 52-62), with primitive mantle normalised trace element concentrations that are broadly parallel the host lavas. There is little compositional difference between melt inclusion populations from high and low 3He/4He lavas, although inclusions of the low 3He/4He lava have lower S and moderately lower Cl. The observed range of trace element ratios: [La/Sm]N 1-4, [La/Yb]N 1-5, Sr/Nd 14-24, Ba/Rb 9-23, and Ce/Pb 5-46, covers much of the range observed in Icelandic alkali basalts. The compositional similarities between inclusions and host lavas suggests that bulk rock compositions are petrogenetically related to the melts sampled by melt inclusions. If He predominantly resides in these inclusions, it suggests that the whole rock composition is an aggregate derived from the same melts that contain the measured He.

Uranium in NIMROC standard igneous rock samples

NASA Technical Reports Server (NTRS)

Rowe, M. W.; Herndon, J. M.

1976-01-01

Results are reported for analysis of the uranium in multiple samples of each of six igneous-rock standards (dunite, granite, lujavrite, norite, pyroxenite, and syenite) prepared as geochemical reference standards for elemental and isotopic compositions. Powdered rock samples were examined by measuring delayed neutron emission after irradiation with a flux of the order of 10 to the 13th power neutrons/sq cm per sec in a nuclear reactor. The measurements are shown to compare quite favorably with previous uranium determinations for other standard rock samples.

Negative ?Nd in Anorthositic Clasts in Yamato 86032 and MAC88105: Evidence for the LMO?

NASA Astrophysics Data System (ADS)

Nyquist, L. E.; Bogard, D. D.; Shih, C. Y.; Wiesmann, H.

2002-03-01

The LMO model predicts flotation cumulates with negative epsilon Nd values, but Apollo 16 FANs have positive epsilon Nd values. Ar-Ar ages plus bulk-rock Sm-Nd data for two FAN breccias from two lunar meteorites give negative epsilon Nd values.

U.S. Geological Survey silicate rock standards

USGS Publications Warehouse

Flanagan, F.J.

1967-01-01

The U.S. Geological Survey has processed six silicate rocks to provide new reference samples to supplement G-1 and W-1. Complete conventional, rapid rock, and spectrochemical analyses by the U.S. Geological Survey are reported for a granite (replacement for G-1), a granodiorite, an andesite, a peridotite, a dunite, and a basalt. Analyses of variance for nickel, chromium, copper, and zirconium in each rock sample showed that for these elements, the rocks can be considered homogeneous. Spectrochemical estimates are given for the nickel, chromium, copper, and zirconium contents of the samples. The petrography of five of the six rocks is described and CIPW norms are presented. ?? 1967.

Design and development of a dust dispersion chamber to quantify the dispersibility of rock dust.

PubMed

Perera, Inoka E; Sapko, Michael J; Harris, Marcia L; Zlochower, Isaac A; Weiss, Eric S

2016-01-01

Dispersible rock dust must be applied to the surfaces of entries in underground coal mines in order to inert the coal dust entrained or made airborne during an explosion and prevent propagating explosions. 30 CFR. 75.2 states that "… [rock dust particles] when wetted and dried will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air …" However, a proper definition or quantification of "light blast of air" is not provided. The National Institute for Occupational Safety and Health (NIOSH) has, consequently, designed a dust dispersion chamber to conduct quantitative laboratory-scale dispersibility experiments as a screening tool for candidate rock dusts. A reproducible pulse of air is injected into the chamber and across a shallow tray of rock dust. The dust dispersed and carried downwind is monitored. The mass loss of the dust tray and the airborne dust measurements determine the relative dispersibility of the dust with respect to a Reference rock dust. This report describes the design and the methodology to evaluate the relative dispersibility of rock dusts with and without anti-caking agents. Further, the results of this study indicate that the dispersibility of rock dusts varies with particle size, type of anti-caking agent used, and with the untapped bulk density. Untreated rock dusts, when wetted and dried forming a cake that was much less dispersible than the reference rock dust used in supporting the 80% total incombustible content rule.

Eclogite-facies metamorphic reactions under stress and faulting in granulites from the Bergen Arcs, Norway: an experimental investigation

NASA Astrophysics Data System (ADS)

Incel, Sarah; Hilairet, Nadège; Labrousse, Loïc; Andersen, Torgeir B.; Wang, Yanbin; Schubnel, Alexandre

2017-04-01

Field observations from the Bergen Arcs, Norway, demonstrate a network of pseudotachylites quenched under eclogite-facies conditions in mafic granulites. In these nominally anhydrous high-pressure high-temperature (HP/HT) rocks the formation of pseudotachylites, believed to represent fossilized earthquakes, cannot be explained by processes akin to dehydration embrittlement. On the contrary, the transition to eclogite is expected to involve hydration of the initial rock. To experimentally investigate the underlying mechanisms leading to brittle failure in HP/HT rocks, we performed deformation experiments on natural granulite samples from the Bergen Arcs. The experiments were conducted under eclogite-facies conditions (2-3 GPa, 990-1220 K) to trigger the breakdown of plagioclase - the main constituent of granulite. For these experiments, both a D-DIA and a Griggs apparatus were used. The D-DIA press is mounted on a synchrotron beamline, enabling us to monitor strain, stress, and phase changes in-situ while contemporaneously recording acoustic emissions. The Griggs experiments were performed on a new device installed at ENS Paris, in which only stress-strain were recorded, and post-mortem microstructures investigated. The initial material consisted of a fine grain size granulite powder (< 38 µm) composed of mainly plagioclase and minor amount of pyroxene. Hydrous phases are phlogopite and epidote group minerals that make up less than 1 vol. % of the total bulk rock powder plus the adhesion water on grain surfaces. Mechanical data together with XRD observations and the record of acoustic emissions demonstrate a correlation between stress drops, the growth of plagioclase breakdown products and the onset of acoustic emissions during deformation of our specimen within the eclogitic field. Microstructural analysis show remarkable similarities with that of the natural ecoligitic pseudotachylites of the Bergen arcs. The plagioclase decomposition products form narrow conjugated shear bands, along which dissected and displaced crystals are found in the samples. The lack of microstructural evidence for macroscopic brittle failure in our microstructures could be due to plastic overprinting of early brittle structures. Nevertheless, our preliminary experimental results show a strong correlation between strain localization, dynamic fracture propagation (rapid enough to produce AEs) and the eclogitization of granulite.

Magnetic mapping of (carbonated) oceanic crust-mantle boundary: New insights from Linnajavri, northern Norway

NASA Astrophysics Data System (ADS)

Tominaga, M.; Beinlich, A.; Tivey, M.; Andrade Lima, E.; Weiss, B. P.

2012-12-01

The contribution of lower oceanic crust and upper mantle to marine magnetic anomalies has long been recognized, but the detailed magnetic character of this non-volcanic source layer remains to be fully defined. Here, we report preliminary results of a magnetic survey and source characterization of a "carbonated" oceanic Moho (petrological "Mohorovicic discontinuity") sequence observed at the Linnajavri Serpentinite Complex (LSC), northern Norway. The LSC is located at 67° 36'N and 16° 24'E within the upper Allochthon of the Norwegian Caledonides and represents a dismembered ophiolite. Particularly in the southern ("Ridoalggicohkka") area of the LSC, gabbro, serpentinite and its talc-carbonate (soapstone) and quartz-carbonate (listvenite) altered equivalents are extraordinarily well-exposed [1]. An intact oceanic Moho is exposed here, despite its complex tectonic setting. The small degree of arctic rock weathering (≤ 2 mm weathering surface) allowed for detailed regional-scale surface magnetic mapping across alteration fronts (serpentinite-soapstone; soapstone-listvenite) and lithological contacts (soapstone-gabbro). Magnetic mapping was conducted using a handheld 3-axis magnetometer, surface-towed resistivity meter and Teka surface magnetic susceptometer with sample spacing of 1 m. Geophysical field mapping was combined with petrological observations and scanning SQUID microscopy (SM) mapping conducted on thin sections from rock samples that were drilled along the survey lines. Regional scale magnetic mapping indicates that the total magnetic field across both the "carbonated" Moho and the soapstone-serpentinite interfaces show higher frequency changes in their magnetic anomaly character and amplitudes than the surface-towed resistivity data. SQUID microscopy mapping of both natural remanence magnetization (NRM) and anhysteretic remanence magnetization (ARM) on gabbro, serpentinite, soapstone, and listvenite samples, with a sensor-sample separation of ˜190 μm, show that the distribution of microscopically measurable ferromagnetic and possibly sulfide minerals produces a different bulk intensity for each of the rock types. SM vector magnetic field maps of these samples also reveal that the magnetization associated with these grains (observed as dipole-like fields in SM maps) is variable in direction from grain to grain, which may result from different alteration histories for each grain. These complex magnetization patterns acquired through thermal and chemical alteration history may explain the short wavelength magnetic anomalies observed along our traverse lines. [1] Beinlich, A., Plümper, O., Hövelmann, J., Austrheim, H. and Jamtveit, B. (2012), Terra Nova, in press.

Reflection spectra and magnetochemistry of iron oxides and natural surfaces

NASA Technical Reports Server (NTRS)

Wasilewski, P.

1978-01-01

The magnetic properties and spectral characteristics of iron oxides are distinctive. Diagnostic features in reflectance spectra (0.5 to 2.4 micron) for alpha Fe2O3, gamma Fe2O3, and FeOOH include location of Fe3(+) absorption features, intensity ratios at various wavelengths, and the curve shape between 1.2 micron and 2.4 micron. The reflection spectrum of natural rock surfaces are seldom those of the bulk rock because of weathering effects. Coatings are found to be dominated by iron oxides and clay. A simple macroscopic model of rock spectra (based on concepts of stains and coatings) is considered adequate for interpretation of LANDSAT data. The magnetic properties of materials associated with specific spectral types and systematic changes in both spectra and magnetic properties are considered.

40 CFR 761.265 - Sampling bulk PCB remediation waste and porous surfaces.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Sampling bulk PCB remediation waste..., DISTRIBUTION IN COMMERCE, AND USE PROHIBITIONS Cleanup Site Characterization Sampling for PCB Remediation Waste in Accordance with § 761.61(a)(2) § 761.265 Sampling bulk PCB remediation waste and porous surfaces...

A method for development of a system of identification for Appalachian coal-bearing rocks

USGS Publications Warehouse

Ferm, J.C.; Weisenfluh, G.A.; Smith, G.C.

2002-01-01

The number of observable properties of sedimentary rocks is large and numerous classifications have been proposed for describing them. Some rock classifications, however, may be disadvantageous in situations such as logging rock core during coal exploration programs, where speed and simplicity are the essence. After experimenting with a number of formats for logging rock core in the Appalachian coal fields, a method of using color photographs accompanied by a rock name and numeric code was selected. In order to generate a representative collection of rocks to be photographed, sample methods were devised to produce a representative collection, and empirically based techniques were devised to identify repeatedly recognizable rock types. A number of cores representing the stratigraphic and geographic range of the region were sampled so that every megascopically recognizable variety was included in the collection; the frequency of samples of any variety reflects the frequency with which it would be encountered during logging. In order to generate repeatedly recognizable rock classes, the samples were sorted to display variation in grain size, mineral composition, color, and sedimentary structures. Class boundaries for each property were selected on the basis of existing, widely accepted limits and the precision with which these limits could be recognized. The process of sorting the core samples demonstrated relationships between rock properties and indicated that similar methods, applied to other groups of rocks, could yield more widely applicable field classifications. ?? 2002 Elsevier Science B.V. All rights reserved.

Effect of Different Loading Conditions on the Nucleation and Development of Shear Zones Around Material Heterogeneities

NASA Astrophysics Data System (ADS)

Rybacki, E.; Nardini, L.; Morales, L. F.; Dresen, G.

2017-12-01

Rock deformation at depths in the Earth's crust is often localized in high temperature shear zones, which occur in the field at different scales and in a variety of lithologies. The presence of material heterogeneities has long been recognized to be an important cause for shear zones evolution, but the mechanisms controlling initiation and development of localization are not fully understood, and the question of which loading conditions (constant stress or constant deformation rate) are most favourable is still open. To better understand the effect of boundary conditions on shear zone nucleation around heterogeneities, we performed a series of torsion experiments under constant twist rate (CTR) and constant torque (CT) conditions in a Paterson-type deformation apparatus. The sample assemblage consisted of copper-jacketed Carrara marble hollow cylinders with one weak inclusion of Solnhofen limestone. The CTR experiments were performed at maximum bulk strain rates of 1.8-1.9*10-4 s-1, yielding shear stresses of 19-20 MPa. CT tests were conducted at shear stresses between 18.4 and 19.8 MPa resulting in shear strain rates of 1-2*10-4 s-1. All experiments were run at 900 °C temperature and 400 MPa confining pressure. Maximum bulk shear strains (γ) were ca. 0.3 and 1. Strain localized within the host marble in front of the inclusion in an area termed process zone. Here grain size reduction is intense and local shear strain (estimated from markers on the jackets) is up to 8 times higher than the applied bulk strain, rapidly dropping to 2 times higher at larger distance from the inclusion. The evolution of key microstructural parameters such as average grain size and average grain orientation spread (GOS, a measure of lattice distortion) within the process zone, determined by electron backscatter diffraction analysis, differs significantly as a function of loading conditions. Both parameters indicate that, independent of bulk strain and distance from the inclusion, the contribution of small strain-free recrystallized grains is larger in CTR than in CT samples. Our results suggest that loading conditions substantially affect material heterogeneity-induced localization in its nucleation and transient stages.

Frictional behaviour of sandstone: A sample-size dependent triaxial investigation

NASA Astrophysics Data System (ADS)

Roshan, Hamid; Masoumi, Hossein; Regenauer-Lieb, Klaus

2017-01-01

Frictional behaviour of rocks from the initial stage of loading to final shear displacement along the formed shear plane has been widely investigated in the past. However the effect of sample size on such frictional behaviour has not attracted much attention. This is mainly related to the limitations in rock testing facilities as well as the complex mechanisms involved in sample-size dependent frictional behaviour of rocks. In this study, a suite of advanced triaxial experiments was performed on Gosford sandstone samples at different sizes and confining pressures. The post-peak response of the rock along the formed shear plane has been captured for the analysis with particular interest in sample-size dependency. Several important phenomena have been observed from the results of this study: a) the rate of transition from brittleness to ductility in rock is sample-size dependent where the relatively smaller samples showed faster transition toward ductility at any confining pressure; b) the sample size influences the angle of formed shear band and c) the friction coefficient of the formed shear plane is sample-size dependent where the relatively smaller sample exhibits lower friction coefficient compared to larger samples. We interpret our results in terms of a thermodynamics approach in which the frictional properties for finite deformation are viewed as encompassing a multitude of ephemeral slipping surfaces prior to the formation of the through going fracture. The final fracture itself is seen as a result of the self-organisation of a sufficiently large ensemble of micro-slip surfaces and therefore consistent in terms of the theory of thermodynamics. This assumption vindicates the use of classical rock mechanics experiments to constrain failure of pressure sensitive rocks and the future imaging of these micro-slips opens an exciting path for research in rock failure mechanisms.

Mg isotope systematics during magmatic processes: Inter-mineral fractionation in mafic to ultramafic Hawaiian xenoliths

NASA Astrophysics Data System (ADS)

Stracke, A.; Tipper, E. T.; Klemme, S.; Bizimis, M.

2018-04-01

Observed differences in Mg isotope ratios between bulk magmatic rocks are small, often on a sub per mill level. Inter-mineral differences in the 26Mg/24Mg ratio (expressed as δ26Mg) in plutonic rocks are on a similar scale, and have mostly been attributed to equilibrium isotope fractionation at magmatic temperatures. Here we report Mg isotope data on minerals in spinel peridotite and garnet pyroxenite xenoliths from the rejuvenated stage of volcanism on Oahu and Kauai, Hawaii. The new data are compared to literature data and to theoretical predictions to investigate the processes responsible for inter-mineral Mg isotope fractionation at magmatic temperatures. Theory predicts up to per mill level differences in δ26Mg between olivine and spinel at magmatic temperatures and a general decrease in Δ26Mgolivine-spinel (=δ26Mgolivine - δ26Mgspinel) with increasing temperature, but also with increasing Cr# in spinel. For peridotites with a simple petrogenetic history by melt depletion, where increasing depletion relates to increasing melting temperatures, Δ26Mgolivine-spinel should thus systematically decrease with increasing Cr# in spinel. However, most natural peridotites, including the Hawaiian spinel peridotites investigated in this study, are overprinted by variable extents of melt-rock reaction, which disturb the systematic primary temperature and compositionally related olivine-spinel Mg isotope systematics. Diffusion, subsolidus re-equilibration, or surface alteration may further affect the observed olivine-spinel Mg isotope fractionation in peridotites, making Δ26Mgolivine-spinel in peridotites a difficult-to-apply geothermometer. The available Mg isotope data on clinopyroxene and garnet suggest that this mineral pair is a more promising geothermometer, but its application is restricted to garnet-bearing igneous (garnet pyroxenites) and metamorphic rocks (eclogites). Although the observed δ26Mg variation is on a sub per mill range in bulk magmatic rocks, the clearly resolvable inter-mineral Mg isotope differences imply that crystallization or preferential melting of isotopically distinct minerals such garnet, spinel, and clinopyroxene should cause Mg isotope fractionation between bulk melt and residue. Calculated Mg isotope variations during partial mantle melting indeed predict differences between melt and residue, but these are analytically resolvable only for melting of mafic lithologies, that is, garnet pyroxenites. Contributions from garnet pyroxenite melts may thus account for some of the isotopically light δ26Mg observed in ocean island basalts and trace lithological mantle heterogeneity. Consequently, applications for high-temperature Mg isotope fractionations are promising and diverse, and recent advances in analytical precision may allow the full petrogenetic potential inherent in the sub per mill variations in δ26Mg in magmatic rocks to be exploited.

ESR signals in a core from the lake Baikal: implications for climate change

NASA Astrophysics Data System (ADS)

Toyoda, S.; Hidaka, K.; Takamatsu, N.

2002-12-01

Electron spin resonance dating method has been used for obtaining ages of Quaternary events using speleothem, corals, shells, hydroxyapatite in tooth enamel, gypsum, and quartz (Ikeya, 1993). Recently, it was also found that an ESR signal in quartz of loess is useful to discuss the variation of its origin (e. g. Ono et al., 1998). The method is based on the signal intensity of the heat treated (gamma ray irradiation and heating, Toyoda and Ikeya, 1991) E 1_f center (an unpaired electron at an oxygen vacancy) correlates the original (crystallization) age of quartz (e.g. Toyoda and Hattori, 2000). If there is variation in ages of basement rocks (origin of loess), ESR signal intensity may differentiate the origins. We applied the present method to sediments taken from the core of the lake Baikal with the length of 600m. The ESR intensity of the heat treated E1_f center was determined by an ESR measurement at room temperature for about 100 mg of the bulk samples, with a microwave power of 0.01 mW, field modulation amplitude of 0.1 mT, and with a scan range of 5 mT around g=2.001 after gamma ray irradiation to 1 kGy and subsequent heating at 300C. The ESR signal of the E1_f center was clearly observed although other minerals are also included in the bulk sample. The peak to peak height was taken as the signal intensity after normalizing the height with the gain (the instrumental setting at the time of measurement), mass, and the intensity of the standard simultaneously measured with the sample. The concentrations of the quartz in the bulk samples were obtained by the X ray diffraction study, normalizing the peak intensity with a standard CeO sample. The variation of the ESR signal intensity with depth of the core will be presented together with the possible climate change which may have caused the variation. References M. Ikeya (1993) New applications of electron spin resonance, dating, dosimetry and imaging, World Scientific. Y. Ono, T. Naruse, M. Ikeya, H. Kohno, and S. Toyoda (1998) Global Planet. Change, 18, 129-135. S. Toyoda and M. Ikeya (1991) Geochem. J. 25, 437-445. S. Toyoda and W. Hattori (2000) Appl. Radiat. Isot., 52, 1351-1356.

Clumped isotopologue constraints on the origin of methane at seafloor hot springs

NASA Astrophysics Data System (ADS)

Wang, David T.; Reeves, Eoghan P.; McDermott, Jill M.; Seewald, Jeffrey S.; Ono, Shuhei

2018-02-01

Hot-spring fluids emanating from deep-sea vents hosted in unsedimented ultramafic and mafic rock commonly contain high concentrations of methane. Multiple hypotheses have been proposed for the origin(s) of this methane, ranging from synthesis via reduction of aqueous inorganic carbon (∑CO2) during active fluid circulation to leaching of methane-rich fluid inclusions from plutonic rocks of the oceanic crust. To further resolve the process(es) responsible for methane generation in these systems, we determined the relative abundances of several methane isotopologues (including 13CH3D, a "clumped" isotopologue containing two rare isotope substitutions) in hot-spring source fluids sampled from four geochemically-distinct hydrothermal vent fields (Rainbow, Von Damm, Lost City, and Lucky Strike). Apparent equilibrium temperatures retrieved from methane clumped isotopologue analyses average 310-42+53 °C, with no apparent relation to the wide range of fluid temperatures (96-370 °C) and chemical compositions (pH, [H2], [∑CO2], [CH4]) represented. Combined with very similar bulk stable isotope ratios (13C/12C and D/H) of methane across the suite of hydrothermal fluids, all available geochemical and isotopic data suggest a common mechanism of methane generation at depth that is disconnected from active fluid circulation. Attainment of equilibrium amongst methane isotopologues at temperatures of ca. 270-360 °C is compatible with the thermodynamically-favorable reduction of CO2 to CH4 at temperatures at or below ca. 400 °C under redox conditions characterizing intrusive rocks derived from sub-ridge melts. Collectively, the observations support a model where methane-rich aqueous fluids, known to be trapped in rocks of the oceanic lithosphere, are liberated from host rocks during hydrothermal circulation and perhaps represent the major source of methane venting with thermal waters at unsedimented hydrothermal fields. The results also provide further evidence that water-rock reactions occurring at temperatures lower than 200 °C do not contribute significantly to the quantities of methane venting at mid-ocean ridge hot springs.

Characterizing a Mississippian Carbonate Reservoir for CO2-EOR and Carbon Geosequestration: Applicability of Existing Rock Physics Models and Implications to Feasibility of a Time Lapse Monitoring Program in the Wellington Oil Field, Sumner County, Kansas.

NASA Astrophysics Data System (ADS)

Lueck, A. J.; Raef, A. E.

2015-12-01

This study will focus on characterizing subsurface rock formations of the Wellington Field, in Sumner County, Kansas, for both geosequestration of carbon dioxide (CO2) in the saline Arbuckle formation and enhanced oil recovery of a depleting Mississippian oil reservoir. Multi-scale data including lithofacies core samples, X-ray diffraction, digital rock physics scans, scanning electron microscope (SEM) imaging, well log data including sonic and dipole sonic, and surface 3D seismic reflection data will be integrated to establish and/or validate a new or existing rock physics model that best represents our reservoir rock types and characteristics. We will acquire compressional wave velocity and shear wave velocity data from Mississippian and Arbuckle cores by running ultrasonic tests using an Ult 100 Ultrasonic System and a 12 ton hydraulic jack located in the geophysics lab in Thompson Hall at Kansas State University. The elastic constants Young's Modulus, Bulk Modulus, Shear (Rigidity) Modulus and Poisson's Ratio will be extracted from these velocity data. Ultrasonic velocities will also be compared to sonic and dipole sonic log data from the Wellington 1-32 well. These data will be integrated to validate a lithofacies classification statistical model, which will be and partially has been applied to the largely unknown saline Arbuckle formation, with hopes for a connection, perhaps via Poisson's ratio, allowing a time-lapse seismic feasibility assessment and potentially developing a transformation of compressional wave sonic velocities to shear wave sonic for all wells, where compressional wave sonic is available. We will also be testing our rock physics model by predicting effects of changing effective (brine + CO2 +hydrocarbon) fluid composition on seismic properties and the implications on feasibility of seismic monitoring. Lessons learned from characterizing the Mississippian are essential to understanding the potential of utilizing similar workflows for the much less known saline aquifer of the Arbuckle in south central Kansas.

Experimental research on rock fracture failure characteristics under liquid nitrogen cooling conditions

NASA Astrophysics Data System (ADS)

Gao, Feng; Cai, Chengzheng; Yang, Yugui

2018-06-01

As liquid nitrogen is injected into a wellbore as fracturing fluid, it can rapidly absorb heat from warmer rock and generate cryogenic condition in downhole region. This will alter the physical conditions of reservoir rocks and further affect rock failure characteristics. To investigate rock fracture failure characteristics under liquid nitrogen cooling conditions, the fracture features of four types of sandstones and one type of marble were tested on original samples (the sample without any treatment) and cryogenic samples (the samples just taken out from the liquid nitrogen), respectively. The differences between original samples and cryogenic samples in load-displacement curves, fracture toughness, energy evolution and the crack density of ruptured samples were compared and analyzed. The results showed that at elastic deformation stage, cryogenic samples presented less plastic deformation and more obvious brittle failure characteristics than original ones. The average fracture toughness of cryogenic samples was 10.47%-158.33% greater than that of original ones, indicating that the mechanical strength of rocks used were enhanced under cooling conditions. When the samples ruptured, the cryogenic ones were required to absorb more energy and reserve more elastic energy. In general, the fracture degree of cryogenic samples was higher than that of original ones. As the samples were entirely fractured, the crack density of cryogenic samples was about 536.67% at most larger than that of original ones. This indicated that under liquid nitrogen cooling conditions, the stimulation reservoir volume is expected to be improved during fracturing. This work could provide a reference to the research on the mechanical properties and fracture failure of rock during liquid nitrogen fracturing.

Analyses and description of geochemical samples, Mill Creek Wilderness Study Area, Giles County, Virginia

USGS Publications Warehouse

Mei, Leung; Lesure, Frank Gardner

1978-01-01

Semiquantitative emission spectrographic analyses for 64 elements on 62 stream sediment and 71 rock samples from Mill Creek Wilderness Study area, Giles County, Virginia, are reported here in detail. Locations for all samples are given in Universal Transverse Mercator (UTM) coordinates. Brief descriptions of rock samples are also included. Rocks analysed are mostly sandstone. Samples of hematitic sandstone of the Rose Hill Formation and limonite-cemented sandstone of the Rocky Gap Sandstone contain high values of iron; these rocks are submarginal iron resources. Some of the same iron-rich samples have a little more barium, copper, cobalt, lead, silver, and/or zinc then is in average sandstone, but they do not suggest the presence of economic deposits of these metals. No other obviously anomalous values related to mineralized rock are present in the data.

Analyses and description of geochemical samples, Peters Mountain Wilderness Study Area, Giles County, Virginia

USGS Publications Warehouse

Rait, Norma; Lesure, Frank Gardner

1978-01-01

Semiquantitative emission spectrographic analyses for 64 elements on 43 stream sediment and 73 rock samples from Peters Mountain Wilderness Study area, Giles County, Virginia, are reported here in detail. Locations for all samples are in Universal Transverse Mercator (UTM) coordinates. Brie[ descriptions of rock samples are also included. Rocks analysed are mostly sandstone. Samples of hematitic sandstone of the Rose Hill Formation and limonite-cemented sandstone of the Rocky Gap Sandstone contain high values of iron; these rocks are submarginal iron resources. Some of the same iron-rich samples have a little more barium, copper, cobalt, lead, silver, and/or zinc then average sandstone, but they do not suggest the presence of economic deposits of these metals. No other obviously anomalous values related to mineralized rock are present in the data.

"MERAPIDATA": New Petrologic and Geochemical Database of the Merapi Volcano, Central Java, Indonesia

NASA Astrophysics Data System (ADS)

Borisova, A. Y.; Martel, C.; Pratomo, I.; Toutain, J.; Sumarti, S.; Surono, S.

2011-12-01

Petrologic and geochemical databases of erupted products are critical for monitoring and predicting the evolution of active volcanoes. To monitor the activity of one of the most dangerous volcanoes in the world, Merapi Volcano in Indonesia, in the framework of the new instrumental site VELI (Volcans Explosifs - Laboratoires Indonésiens labelled by INSU in 2009 in France), we generated "MERAPIDATA", a complete database of available petrologic and geochemical data published in the literature on pyroclastic flows, tephra, lavas and xenoliths coupled with the exact ages of historical flows [1] or estimated ages based on 14C geochronology [2]. "MERAPIDATA" permits to access complete petrologic, geochemical, and geochronological information (e.g., major, trace element and Sr-Nd-Pb-O isotopic composition of the bulk volcanic rocks, xenoliths, minerals and glasses; textural information; type of eruption; classification) of a given volcanic product or series. In addition to ~300 published volcanic products, new data on 2 pyroclastic flows, 1 tephra and 4 ash samples collected on northern and western slopes of the volcano in October and November 2010 during subplinian type eruption have been added to "MERAPIDATA". The 2010 ash sample chemistry allows classifying them as high-K basaltic andesite. The ash samples demonstrate major and trace element compositions typical for the high-K series. For the first time, we obtained complete data on the Merapi ash samples which characterized by low L.O.I. ≤ 0.58 wt%, CO2total ≤ 0.05 wt%, H2Ototal = 0.3 - 0.5 wt%, Stotal ≤ 0.13 wt% and moderate Cl (550 - 1120 ppm) contents. The ash-leachates produced by leaching experiments demonstrate constant F/Cl ratios (0.05 ± 0.01) and Ca-Na-K enrichment (Ca/Na= 3 - 7, Na/K = 1 - 5). Sr-Nd-Pb-O isotopic analyses on the 2010 Merapi products are in progress. New petrologic (e.g., melt and fluid inclusion data, T - P - fO2 - aH2O - aCO2) and geochemical (e.g., volatile, major, trace element and isotopic composition of the bulk volcanic rocks and glassy matrix) data will permit to explain unexpected subplinian type of the 2010 eruption. The complete "MERAPIDATA" programmed with MS Access 2007 will be available in English version for open access at the website of the Observatory of Midi-Pyrénées (Toulouse, France): "http://www.get.obs-mip.fr/index.php/Annuaire/Borisova-Anastassia/MERAPIDATA". [1] Camus et al., (2000). JVGR 100, 139-163. [2] Gertisser & Keller (2003). JVGR 123, 1-23.

Digitally available interval-specific rock-sample data compiled from historical records, Nevada National Security Site and vicinity, Nye County, Nevada

USGS Publications Warehouse

Wood, David B.

2007-11-01

Between 1951 and 1992, 828 underground tests were conducted on the Nevada National Security Site, Nye County, Nevada. Prior to and following these nuclear tests, holes were drilled and mined to collect rock samples. These samples are organized and stored by depth of borehole or drift at the U.S. Geological Survey Core Library and Data Center at Mercury, Nevada, on the Nevada National Security Site. From these rock samples, rock properties were analyzed and interpreted and compiled into project files and in published reports that are maintained at the Core Library and at the U.S. Geological Survey office in Henderson, Nevada. These rock-sample data include lithologic descriptions, physical and mechanical properties, and fracture characteristics. Hydraulic properties also were compiled from holes completed in the water table. Rock samples are irreplaceable because pre-test, in-place conditions cannot be recreated and samples can not be recollected from the many holes destroyed by testing. Documenting these data in a published report will ensure availability for future investigators.

An integrated magnetic and geological study of cataclasite- dominated pseudotachylytes in the Chiapas Massif, Mexico: a snapshot of stress orientation following slip

NASA Astrophysics Data System (ADS)

Garza, Roberto S. Molina; Geissman, John; Wawrzyniec, Tim; Weber, Bodo; Martínez, Margarita López; Aranda-Gómez, Jorge

2009-06-01

The Permian age Chiapas Massif in southeast Mexico is locally host to well-exposed pseudotachylyte vein networks. The veins are black to dark grey and aphanitic in appearance, and consist mostly of microbreccia of angular fragments of plagioclase, K-feldspar, biotite and quartz, in a cryptocrystalline (microscopically irresolvable) matrix. Evidence of melting is present in the form of glass seams, dikelets, glass clasts included in cataclasite and a distinct chemistry in the pseudotachylite veins; pristine glass represents a relatively small volume of the pseudotachylite veins. At an exposure along the Tablón River valley, where the host rock is a medium to coarse-grained equigranular quartz diorite, individual veins are consistently oriented about 280°, are up to 16 mm wide, tens of cm apart, display a consistent left-lateral offset and can be traced for several metres. Individual pseudotachylyte veins rarely cross each other, and they cannot be directly linked to a regional-scale fault. Pseudotachylytes are apparently formed by a combination of crushing, comminution and frictional melting, but they are cataclasite dominated. Textures indicate that cataclasis continued after frictional melting had ceased. A 40Ar/39Ar age determination from whole rock chips of one vein shows a climbing Ar release spectrum with a date of ~114 Ma as the most reliable age estimate for Ar retention. This result is interpreted in the context of pseudotachylyte formation, recrystallization and resetting of K-bearing minerals for the K-Ar system in the late Early Cretaceous. Ten veins were sampled for palaeomagnetic and magnetic fabric studies, with samples collected from both the veins and their host rock. Remanence data give moderate natural remanent magnetization (NRM) intensities for both the veins (e.g. NRM mean 6.6 × 10-3 A m-1 σ = 5.5) and host rock (mean 7.7 × 10-3 A m-1 σ = 10.8). Many samples of host rock yield an ill-defined east-west directed and shallow magnetization, which we interpret as a Late Permian magnetization based on previous studies of the Chiapas Massif. This magnetization resides in haematite. Veins, as well as immediately adjacent host rock, typically have well-defined, single polarity magnetizations of north-northwest declination and moderate positive inclination and these resemble the Cretaceous expected field direction. The overall mean of the veins is of Dec = 348.7° and Inc = 33.6° (k = 30.5 and α95 = 12.3° n = 6 site means). Rock magnetic parameters suggest that the remanence in the veins principally resides in low-Ti pseudo-single domain magnetite and maghemite grains, but haematite, coarse-grained magnetite, rutile, Fe-Cr-Ni oxides and ilmenite are also present in the veins. Bulk magnetic susceptibility values range between ~0.3 and 1.1 * 10-3 SI volume units, and host rock values do not differ significantly from vein values. The orientations of the principal susceptibility axes in the host rock and the veins are indistinguishable. In both, magnetic foliations are near vertical and are essentially parallel to the nearly east-west orientation of the veins. Nonetheless, host rock fabrics are predominantly prolate, whereas vein fabrics are oblate. The mean susceptibility tensors of host rocks and pseudotachylyte are characterized by P'/T values of 1.041/-0.327 and 1.033/+0.302, respectively. This result suggests that the fabric reflected by magnetic susceptibility anisotropy in the veins was formed under pure shear stress, during cooling of the veins. The lack of evidence of fabric rotation supports models that associate partial melt with viscous break during fault slip.

An experimental investigation of the effect of impact generated micro-deformations in Moenkopi and Coconino Sandstone from Meteor Crater, Arizona on subsequent weathering

NASA Astrophysics Data System (ADS)

Verma, A.; Bourke, M. C.; Osinski, G.; Viles, H. A.; Blanco, J. D. R.

2017-12-01

Impact cratering is an important geological process that affects all planetary bodies in our solar system. As rock breakdown plays an important role in the evolution of landforms and sediments, it is important to assess the role of inheritance in the subsequent breakdown of impacted rocks.The shock pressure of several gigapascals generated during the impact can exceed the effective strength of target lithology by three to four orders of magnitude and is responsible for melting, vaporisation, shock metamorphism, fracturing and fragmentation of rocks. Environmental conditions and heterogeneities in rock properties exert an important control in rock breakdown. Similar to other subaerial rocks, impacted rocks are affected by a range of rock breakdown processes. In order to better understand the role of inheritance of the impact on rock breakdown, a rock breakdown experiment was conducted in a simulated environmental cabinet under conditions similar to the arid conditions found at the Meteor Crater site. We sampled Moenkopi and Coconino Sandstone from the Meteor Crater impact site in Arizona. For comparison, samples were also collected at control sites close by that have similar rock formations but did not undergo impact. Several established techniques (X-ray CT, SEM, Equotip, SfM) were used to characterise the rock samples before the environmental cabinet experiments. Our laboratory analysis (XRD, SEM, optical microscopy, X-ray CT) on impacted rock samples from Meteor Crater, show that rock porosity and permeability changes due to compaction and fracturing during impact. There were no high-pressure polymorphs of quartz or glass detected in XRD analysis. We ran the experiments on a total of 28 petrophysically characterised 5x5x5 cm sample blocks of Coconino and Moenkopi Sandstone (24 impacted rocks and 4 non-impacted). The results will be presented at the AGU Fall meeting 2017.

Nuclear chemistry of returned lunar samples: Nuclide analysis by gamma-ray spectrometry

NASA Technical Reports Server (NTRS)

Kelley, G. D.; Eldridge, J. S.

1972-01-01

Concentrations of primordial radioelements and of cosmogenic radionuclides in crystalline rocks, breccias, and soils from the Ocean of Storms were determined. Concentrations of K, Th, U, Al-26, and Na-22 were determined for seven clastic or brecciated rocks, three sieved samples of fines, and one composite sample of sawdust from the cutting of a fragmental rock, all from samples obtained on the Apollo 14 mission. The K, Th, and U concentrations and cogmogenic radionuclide abundances in rocks and soils from Apollo 15 are also discussed.

Electromagnetic Emissions During Rock-fracturing Experiments Inside Magnetic Field Free Space

NASA Astrophysics Data System (ADS)

Wang, H.; Zhou, J.; Zhu, T.; Jin, H.

2012-12-01

Abnormal electromagnetic emission (EME) signal is one type of the most important precursors before earthquake, which has been widely observed and recorded before large earthquake, but the physical mechanism underlying the phenomenon is unclear and under controversy. Monitoring the EME signals during rock-fracturing experiments in laboratory is an effective way to study the phenomena and their underlying mechanism. Electromagnetic noise is everywhere because industrial and civilian electrical equipments have been widely used, which make difficulties to the in-lab experiments and field monitoring. To avoid the interference from electromagnetic noise, electromagnetic experiments must be carried out inside shielded space. Magnetic Field Free Space (MFFS) was constructed by Institute of Geophysics, China Earthquake Administration in 1980s. MFFS is a near-spherical polyhedron 'space' with 26 faces and inside diameter about 2.3 m. It is enclosed by 8-layer permalloy 1J85 for shielding magnetic field and 2-layer purified aluminium for shielding electric field. MFFS mainly shields static magnetic field by a factor of 160-4000 for the magnetic signals with the frequencies ranging from 0.01 Hz to 10 Hz. The intensity of magnetic field inside the space is less than 20 nT and its fluctuation is less than 0.3 nT in 90 hours. MFFS can dramatically shield EME signals in the frequency range of EME antennas utilized in our experiments, (several to ~320) kHz, by at least 90%, based on observation. Rock specimens (granite, marble) were fractured by two ways inside MFFS. 1) Cuboid bulk specimens were drilled, filled with static cracking agent, and then dilated from inside until fracture. 2) Cylindrical rock specimens were stressed until fracture by using a non-magnetic rock testing machine with the maximum testing force 300kN. EME, acoustic emission (AE) and strain signals were collected synchronously by the same data acquisitor, Acoustic Emission Workstation made by Physical Acoustics Corporation in America. EME and AE signals were collected at sampling rate larger than 1 MHz, while strain signals at sampling interval of 0.1 second. Abnormal strong EME signals were usually observed at the same moment with the main crack indicated by strain signals. There are too many AE signals but too little EME signals collected during the rock-cracking experiments. Even AE signals with amplitude larger than 60dB were hardly found accompanied by EME signals. Few data indicate that EME and AE signals occur simultaneously. Abnormal EME signals were always detected after rock specimens were cracked, indicated by the torn strain gauges. The lag of EME signals behind the cracking signals revealed by strain gauges may indicate that EME signals were caused by the fast movement of charged rock fragments. This study was sponsored by National Natural Science Foundation of China (NSFC, grant 41004029) and Institute of Geophysics, CEA (Project No.: DQJB10B14). We would like to thank Shuqing Qian, Zhiwei Guo and Zhengyi Liu to take part in the experiments.

Petrographic and geochemical comparisons between the lower crystalline basement-derived section and the granite megablock and amphibolite megablock of the Eyreville-B core, Chesapeake Bay impact structure

USGS Publications Warehouse

Townsend, Gabrielle N.; Gibson, Roger L.; Horton, J. Wright; Reimold, Wolf Uwe; Schmitt, Ralf T.; Bartosova, Katerina

2009-01-01

The Eyreville B core from the Chesapeake Bay impact structure, Virginia, USA, contains a lower basement-derived section (1551.19 m to 1766.32 m deep) and two megablocks of dominantly (1) amphibolite (1376.38 m to 1389.35 m deep) and (2) granite (1095.74 m to 1371.11 m deep), which are separated by an impactite succession. Metasedimentary rocks (muscovite-quartz-plagioclase-biotite-graphite ± fibrolite ± garnet ± tourmaline ± pyrite ± rutile ± pyrrhotite mica schist, hornblende-plagioclase-epidote-biotite-K-feldspar-quartz-titanite-calcite amphibolite, and vesuvianite-plagioclase-quartz-epidote calc-silicate rock) are dominant in the upper part of the lower basement-derived section, and they are intruded by pegmatitic to coarse-grained granite (K-feldspar-plagioclase-quartz-muscovite ± biotite ± garnet) that increases in volume proportion downward. The granite megablock contains both gneissic and weakly or nonfoliated biotite granite varieties (K-feldspar-quartz-plagioclase-biotite ± muscovite ± pyrite), with small schist xenoliths consisting of biotite-plagioclase-quartz ± epidote ± amphibole. The lower basement-derived section and both megablocks exhibit similar middle- to upper-amphibolite-facies metamorphic grades that suggest they might represent parts of a single terrane. However, the mica schists in the lower basement-derived sequence and in the megablock xenoliths show differences in both mineralogy and whole-rock chemistry that suggest a more mafic source for the xenoliths. Similarly, the mineralogy of the amphibolite in the lower basement-derived section and its association with calc-silicate rock suggest a sedimentary protolith, whereas the bulk-rock and mineral chemistry of the megablock amphibolite indicate an igneous protolith. The lower basement-derived granite also shows bulk chemical and mineralogical differences from the megablock gneissic and biotite granites.

The Polar Rock Repository: Rescuing Polar Collections for New Research

NASA Astrophysics Data System (ADS)

Grunow, A.

2016-12-01

Geological field expeditions in polar regions are logistically difficult, financially expensive and can have a significant environmental impact on pristine regions. The scarcity of outcrop in Antarctica (98% ice-covered) makes previously collected rock samples very valuable to the science community. NSF recognized the need for preserving rock, dredge, and terrestrial core samples from polar areas and created the Polar Rock Repository (PRR). The PRR collection allows for full and open access to both samples and metadata via the PRR website. In addition to the physical samples and their basic metadata, the PRR archives supporting materials from the collector, field notebooks, images of the samples, field maps, air photos, thin sections and any associated bibliography/DOI's. Many of these supporting materials are unique. More than 40,000 samples are available from the PRR for scientific analysis to researchers around the globe. Most of the samples cataloged at the PRR were collected more than 30 years ago, some more than 100 years ago. The rock samples and metadata are made available online through an advanced search engine for the PRR website. This allows scientists to "drill down" into search results using categories and look-up object fields similar to websites like Amazon. Results can be viewed in a table, downloaded as a spreadsheet, or plotted on an interactive map that supports display of satellite imagery and bathymetry layers. Samples can be requested by placing them in the `shopping cart'. These old sample collections have been repeatedly used by scientists from around the world. One data request involved locating coal deposits in Antarctica for a global compilation and another for looking at the redox state of batholithic rocks from the Antarctic Peninsula using magnetic susceptibilities of PRR rocks. Sample usage has also included non-traditional geologic studies, such as a search for monopoles in Cenozoic volcanic samples, and remote sensing/spectral imaging of Transantarctic Mountains rocks. Rescuing these collections from universities that no longer want to store the rocks or from researchers who no longer need the samples has resulted in many new publications, new proposals and enormous cost and environmental savings to the U.S. Antarctic science program.

Influence of Bulk Carbonaceous Matter on Pluto's Structure and Evolution

NASA Astrophysics Data System (ADS)

McKinnon, W. B.; Stern, S. A.; Weaver, H. A., Jr.; Spencer, J. R.; Moore, J. M.; Young, L. A.; Olkin, C.

2017-12-01

The rock/ice mass ratio of the Pluto system is about 2/1 (McKinnon et al., Icarus 287, 2017) [1], though this neglects the potential role of bulk carbonaceous matter ("CHON"), an important cometary component and one likely important in the ancestral Kuiper belt. The wealth of measurements at comet 67P/Churyumov-Gerasimenko (a Jupiter-family comet and thus one formed in the same region of the outer Solar System as Pluto) by Rosetta are particularly instructive. E.g., Davidsson et al. (A&A 592, 2016) [2] propose in their "composition A" that 67P/Ch-G is 25% metal/sulfides, 42% rock/organics, and 32% ice by mass. For their assumed component densities, the overall grain density is 1820 kg/m3. Fulle et al. (MNRAS 462, 2016) [3] posit 5 ± 2 volume % Fe-sulfides of density 4600 kg/m3, 28 ± 5% Mg,Fe-olivines and -pyroxenes of density 3200 kg/m3, 52 ± 12% hydrocarbons of density 1200 kg/m3, and 15 ± 6% ices of 917 kg/m3. This composition yields a primordial grain density (dust + ice) of 1885 ± 240 kg/m3. Both of these cometary density estimates [2,3] are consistent with Pluto-Charon, especially as Pluto's uncompressed (STP) density is close to 1820 kg/m3 and that of the system as a whole is close to 1800 kg/m3 [1]. We consider the potential compositional and structural implications of these proposed 67P/Ch-G compositions when applied to Pluto and Charon. The amount of ice in model A of [2] is a good match to Pluto structural models. Their rock/organics component, however, is taken to be half graphite (2000 kg/m3) by volume. The composition in [3] is more divergent: very ice poor, and on the order of 50% light hydrocarbons by volume. Regardless of the differences between [2] and [3], the possibility of massive internal graphite or carbonaceous layers within Pluto is real. We discuss the possible consequences for Pluto's structure, rock/ice ratio, thermal and chemical evolution, and even interpretation of its gravity field from tectonics. For example, radiogenic heat flows could be lessened in comparison with pure ice+rock±ocean interior models. And could the inferred gravity high at Sputnik Planitia (Nimmo et al., Nature 540, 2016) actually be due to an uplifted graphite-rich layer? A bulk carbonaceous contribution to icy satellites is also possible, and may behind the rich organic chemistry in Enceladus' plume vapor (Waite et al., Nature 460, 2009).