Hydrocarbon Source Rocks in the Deep River and Dan River Triassic Basins, North Carolina

USGS Publications Warehouse

Reid, Jeffrey C.; Milici, Robert C.

2008-01-01

This report presents an interpretation of the hydrocarbon source rock potential of the Triassic sedimentary rocks of the Deep River and Dan River basins, North Carolina, based on previously unpublished organic geochemistry data. The organic geochemical data, 87 samples from 28 drill holes, are from the Sanford sub-basin (Cumnock Formation) of the Deep River basin, and from the Dan River basin (Cow Branch Formation). The available organic geochemical data are biased, however, because many of the samples collected for analyses by industry were from drill holes that contained intrusive diabase dikes, sills, and sheets of early Mesozoic age. These intrusive rocks heated and metamorphosed the surrounding sediments and organic matter in the black shale and coal bed source rocks and, thus, masked the source rock potential that they would have had in an unaltered state. In places, heat from the intrusives generated over-mature vitrinite reflectance (%Ro) profiles and metamorphosed the coals to semi-anthracite, anthracite, and coke. The maximum burial depth of these coal beds is unknown, and depth of burial may also have contributed to elevated thermal maturation profiles. The organic geochemistry data show that potential source rocks exist in the Sanford sub-basin and Dan River basin and that the sediments are gas prone rather than oil prone, although both types of hydrocarbons were generated. Total organic carbon (TOC) data for 56 of the samples are greater than the conservative 1.4% TOC threshold necessary for hydrocarbon expulsion. Both the Cow Branch Formation (Dan River basin) and the Cumnock Formation (Deep River basin, Sanford sub-basin) contain potential source rocks for oil, but they are more likely to have yielded natural gas. The organic material in these formations was derived primarily from terrestrial Type III woody (coaly) material and secondarily from lacustrine Type I (algal) material. Both the thermal alteration index (TAI) and vitrinite reflectance data (%Ro) indicate levels of thermal maturity suitable for generation of hydrocarbons. The genetic potential of the source rocks in these Triassic basins is moderate to high and many source rock sections have at least some potential for hydrocarbon generation. Some data for the Cumnock Formation indicate a considerably higher source rock potential than the basin average, with S1 + S2 data in the mid-20 mg HC/g sample range, and some hydrocarbons have been generated. This implies that the genetic potential for all of these strata may have been higher prior to the igneous activity. However, the intergranular porosity and permeability of the Triassic strata are low, which makes fractured reservoirs more attractive as drilling targets. In some places, gravity and magnetic surveys that are used to locate buried intrusive rock may identify local thermal sources that have facilitated gas generation. Alternatively, awareness of the distribution of large intrusive igneous bodies at depth may direct exploration into other areas, where thermal maturation is less than the limits of hydrocarbon destruction. Areas prospective for natural gas also contain large surficial clay resources and any gas discovered could be used as fuel for local industries that produce clay products (principally brick), as well as fuel for other local industries.

Families of miocene monterey crude oil, seep, and tarball samples, coastal California

USGS Publications Warehouse

Peters, K.E.; Hostettler, F.D.; Lorenson, T.D.; Rosenbauer, R.J.

2008-01-01

Biomarker and stable carbon isotope ratios were used to infer the age, lithology, organic matter input, and depositional environment of the source rocks for 388 samples of produced crude oil, seep oil, and tarballs to better assess their origins and distributions in coastal California. These samples were used to construct a chemometric (multivariate statistical) decision tree to classify 288 additional samples. The results identify three tribes of 13C-rich oil samples inferred to originate from thermally mature equivalents of the clayey-siliceous, carbonaceous marl and lower calcareous-siliceous members of the Monterey Formation at Naples Beach near Santa Barbara. An attempt to correlate these families to rock extracts from these members in the nearby COST (continental offshore stratigraphic test) (OCS-Cal 78-164) well failed, at least in part because the rocks are thermally immature. Geochemical similarities among the oil tribes and their widespread distribution support the prograding margin model or the banktop-slope-basin model instead of the ridge-and-basin model for the deposition of the Monterey Formation. Tribe 1 contains four oil families having geochemical traits of clay-rich marine shale source rock deposited under suboxic conditions with substantial higher plant input. Tribe 2 contains four oil families with traits intermediate between tribes 1 and 3, except for abundant 28,30-bisnorhopane, indicating suboxic to anoxic marine marl source rock with hemipelagic input. Tribe 3 contains five oil families with traits of distal marine carbonate source rock deposited under anoxic conditions with pelagic but little or no higher plant input. Tribes 1 and 2 occur mainly south of Point Conception in paleogeographic settings where deep burial of the Monterey source rock favored petroleum generation from all three members or their equivalents. In this area, oil from the clayey-siliceous and carbonaceous marl members (tribes 1 and 2) may overwhelm that from the lower calcareous-siliceous member (tribe 3) because the latter is thinner and less oil-prone than the overlying members. Tribe 3 occurs mainly north of Point Conception where shallow burial caused preferential generation from the underlying lower calcareous-siliceous member or another unit with similar characteristics. In a test of the decision tree, 10 tarball samples collected from beaches in Monterey and San Mateo counties in early 2007 were found to originate from natural seeps representing different organofacies of Monterey Formation source rock instead from one anthropogenic pollution event. The seeps apparently became more active because of increased storm activity. Copyright ?? 2008. The American Association of Petroleum Geologists. All rights reserved.

Source-rock geochemistry of the San Joaquin Basin Province, California: Chapter 11 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

USGS Publications Warehouse

Peters, Kenneth E.; Magoon, Leslie B.; Valin, Zenon C.; Lillis, Paul G.

2007-01-01

Source-rock thickness and organic richness are important input parameters required for numerical modeling of the geohistory of petroleum systems. Present-day depth and thickness maps for the upper Miocene Monterey Formation, Eocene Tumey formation of Atwill (1935), Eocene Kreyenhagen Formation, and Cretaceous-Paleocene Moreno Formation source rocks in the San Joaquin Basin were determined using formation tops data from 266 wells. Rock-Eval pyrolysis and total organic carbon data (Rock-Eval/TOC) were collected for 1,505 rock samples from these source rocks in 70 wells. Averages of these data for each well penetration were used to construct contour plots of original total organic carbon (TOCo) and original hydrogen index (HIo) in the source rock prior to thermal maturation resulting from burial. Sufficient data were available to construct plots of TOCo and HIo for all source-rock units except the Tumey formation of Atwill (1935). Thick, organic-rich, oil-prone shales of the upper Miocene Monterey Formation occur in the Tejon depocenter in the southern part of the basin with somewhat less favorable occurrence in the Southern Buttonwillow depocenter to the north. Shales of the upper Miocene Monterey Formation generated most of the petroleum in the San Joaquin Basin. Thick, organic-rich, oil-prone Kreyenhagen Formation source rock occurs in the Buttonwillow depocenters, but it is thin or absent in the Tejon depocenter. Moreno Formation source rock is absent from the Tejon and Southern Buttonwillow depocenters, but thick, organic-rich, oil-prone Moreno Formation source rock occurs northwest of the Northern Buttonwillow depocenter adjacent to the southern edge of Coalinga field.

Geological sources of fluoride and acceptable intake of fluoride in an endemic fluorosis area, southern Iran.

PubMed

Battaleb-Looie, Sedigheh; Moore, Farid; Jacks, Gunnar; Ketabdari, Mohammad Reza

2012-10-01

The present study is the first attempt to put forward possible source(s) of fluoride in the Dashtestan area, Bushehr Province, southern Iran. In response to reports on the high incidence of dental fluorosis, 35 surface and groundwater samples were collected and analysed for fluoride. The results indicate that dissolved fluoride in the study area is above the maximum permissible limit recommended by the World Health Organization (WHO). An additional 35 soil and rock samples were also collected and analysed for fluoride, and rock samples were subjected to petrographic investigations and X-ray diffraction. The results of these analyses show that the most likely source for fluoride in the groundwater is from clay minerals (chlorite) and micas (muscovite, sericite, and biotite) in the soils and rocks in the area. We also note that due to the high average temperatures all year round and excessive water consumption in the area, the optimum fluoride dose level should be lower than that recommended by the WHO.

Apollo Lunar Sample Integration into Google Moon: A New Approach to Digitization

NASA Technical Reports Server (NTRS)

Dawson, Melissa D.; Todd, nancy S.; Lofgren, Gary E.

2011-01-01

The Google Moon Apollo Lunar Sample Data Integration project is part of a larger, LASER-funded 4-year lunar rock photo restoration project by NASA s Acquisition and Curation Office [1]. The objective of this project is to enhance the Apollo mission data already available on Google Moon with information about the lunar samples collected during the Apollo missions. To this end, we have combined rock sample data from various sources, including Curation databases, mission documentation and lunar sample catalogs, with newly available digital photography of rock samples to create a user-friendly, interactive tool for learning about the Apollo Moon samples

Geochemistry of the Neoproterozoic metabasic rocks from the Negele area, southern Ethiopia: Tectonomagmatic implications

NASA Astrophysics Data System (ADS)

Yihunie, Tadesse; Adachi, Mamoru; Yamamoto, Koshi

2006-03-01

Neoproterozoic metabasic rocks along with metasediments and ultramafic rocks constitute the Kenticha and Bulbul lithotectonic domains in the Negele area. They occur as amphibolite and amphibole schist in the Kenticha, and amphibole schist and metabasalt in the Bulbul domains. These rocks are dominantly basaltic in composition and exhibit low-K tholeiitic characteristics. They are slightly enriched in large ion lithophile (LIL) and light rare earth (LRE) elements and depleted in high field strength (HFS) and heavy rare earth (HRE) elements. They exhibit chemical characteristics similar to back-arc basin and island-arc basalts, but include a few samples with slightly higher Y, Zr and Nb contents. Initial Sr isotopic ratios and ɛNd values for the Kenticha metabasic rocks range from 0.7048 to 0.7051 and from 4.7 to 9.6 whereas for the Bulbul metabasic rocks they range from 0.7032 to 0.7055 and from -0.1 to 5.5, respectively. The trace elements and Sr-Nd isotope compositions of samples from the Kenticha and Bulbul domains suggest similar, but isotopically heterogeneous magma sources. The magma is inferred to have derived from depleted source with a contribution from an enriched mantle source component.

Paleofacies of Eocene Lower Ngimbang Source Rocks in Cepu Area, East Java Basin based on Biomarkers and Carbon-13 Isotopes

NASA Astrophysics Data System (ADS)

Devi, Elok A.; Rachman, Faisal; Satyana, Awang H.; Fahrudin; Setyawan, Reddy

2018-02-01

The Eocene Lower Ngimbang carbonaceous shales are geochemically proven hydrocarbon source rocks in the East Java Basin. Sedimentary facies of source rock is important for the source evaluation that can be examined by using biomarkers and carbon-13 isotopes data. Furthermore, paleogeography of the source sedimentation can be reconstructed. The case study was conducted on rock samples of Lower Ngimbang from two exploration wells drilled in Cepu area, East Java Basin, Kujung-1 and Ngimbang-1 wells. The biomarker data include GC and GC-MS data of normal alkanes, isoprenoids, triterpanes, and steranes. Carbon-13 isotope data include saturate and aromatic fractions. Various crossplots of biomarker and carbon-13 isotope data of the Lower Ngimbang source samples from the two wells show that the source facies of Lower Ngimbang shales changed from transitional/deltaic setting at Kujung-1 well location to marginal marine setting at Ngimbang-1 well location. This reveals that the Eocene paleogeography of the Cepu area was composed of land area in the north and marine setting to the south. Biomarkers and carbon-13 isotopes are powerful data for reconstructing paleogeography and paleofacies. In the absence of fossils in some sedimentary facies, these geochemical data are good alternatives.

Source rock potential in Pakistan

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

Raza, H.A.

1991-03-01

Pakistan contains two sedimentary basins: Indus in the east and Balochistan in the west. The Indus basin has received sediments from precambrian until Recent, albeit with breaks. It has been producing hydrocarbons since 1914 from three main producing regions, namely, the Potwar, Sulaisman, and Kirthar. In the Potwar, oil has been discovered in Cambrian, Permian, Jurassic, and Tertiary rocks. Potential source rocks are identified in Infra-Cambrian, Permian, Paleocene, and Eocene successions, but Paleocene/Eocene Patala Formation seems to be the main source of most of the oil. In the Sulaiman, gas has been found in Cretaceous and Tertiary; condensate in Cretaceousmore » rocks. Potential source rocks are indicated in Cretaceous, Paleocene, and Eocene successions. The Sembar Formation of Early Cretaceous age appears to be the source of gas. In the Kirthar, oil and gas have been discovered in Cretaceous and gas has been discovered in paleocene and Eocene rocks. Potential source rocks are identified in Kirthar and Ghazij formations of Eocene age in the western part. However, in the easter oil- and gas-producing Badin platform area, Union Texas has recognized the Sembar Formation of Early Cretaceous age as the only source of Cretaceous oil and gas. The Balochistan basin is part of an Early Tertiary arc-trench system. The basin is inadequately explored, and there is no oil or gas discovery so far. However, potential source rocks have been identified in Eocene, Oligocene, Miocene, and Pliocene successions based on geochemical analysis of surface samples. Mud volcanoes are present.« less

Petrology of lunar rocks and implication to lunar evolution

NASA Technical Reports Server (NTRS)

Ridley, W. I.

1976-01-01

Recent advances in lunar petrology, based on studies of lunar rock samples available through the Apollo program, are reviewed. Samples of bedrock from both maria and terra have been collected where micrometeorite impact penetrated the regolith and brought bedrock to the surface, but no in situ cores have been taken. Lunar petrogenesis and lunar thermal history supported by studies of the rock sample are discussed and a tentative evolutionary scenario is constructed. Mare basalts, terra assemblages of breccias, soils, rocks, and regolith are subjected to elemental analysis, mineralogical analysis, trace content analysis, with studies of texture, ages and isotopic composition. Probable sources of mare basalts are indicated.

Extraction of Iodine from Source Rock and Oil for Radioiodine Dating Final Report CRADA No. TC-1550-98

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

Moran, J. E.; Summa, L.

This was a collaborative effort between the University of California, Lawrence Livermore National Laboratory (LLNL) and Exxon Production Research Company (EPR) to develop improved techniques for extracting, concentrating, and measuring iodine from large volumes of source rock and oil. The purpose of this project was to develop a technique for measuring total iodine extracted from rock, obtain isotopic ratios, and develop age models for samples provided by EPR.

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 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.

Geochemical Analysis of Parasequences within the Productive Middle Member of the Eagle Ford Formation at Lozier Canyon near Del Rio, Texas

NASA Astrophysics Data System (ADS)

Shane, Timothy E.

The middle member of the Eagle Ford formation is a heterogeneous, carbonate-shale unit that is a focus of unconventional oil and gas exploration in southern Texas. Exploration results have been mixed because of the apparent heterogeneity of the member. In this study, the extent of heterogeneities in the Eagle Ford on the "bedding-scale" were examined by evaluating changes in organic and inorganic geochemistry. Samples were collected vertically in outcrop covering four non-consecutive parasequences. These samples were analyzed using a Rock Eval 6 Analyzer(TM) to determine source rock generative potential and a Niton(TM) XRF to evaluate inorganic geochemistry to identify changes in paleoredox conditions, paleoproductivity, and clastic influx. From pyrolysis data, it is determined that Parasequence 1 potentially displays an increase in source rock potential, Parasequence 2 potentially displays a constant source rock potential, and Parasequences 3 and 4 potentially display overall decreases in source rock potential during deposition. From the inferred paleoredox conditions, paleoproductivity, and clastic influx, it is determined that Parasequence 1 experienced a potential increase in oxygen abundance, Parasequence 2 experienced a potential decrease in oxygen abundance, and Parasequences 3 and 4 potentially experienced increases in oxygen abundance during deposition. It is concluded that geochemical heterogeneities do exist on a bedding scale within the parasequences of the middle member of the Eagle Ford. Additional comprehensive sampling and analysis is recommended in the future in order to tie these data to subsurface data for economic application.

Melting behavior and phase relations of lunar samples. [Apollo 12 rock samples

NASA Technical Reports Server (NTRS)

Hays, J. F.

1975-01-01

Cooling rate studies of 12002 were conducted and the results interpreted in terms of the crystallization history of this rock and certain other picritic Apollo 12 samples. Calculations of liquid densities and viscosities during crystallization, crystal settling velocities, and heat loss by the parent rock body are discussed, as are petrographic studies of other Apollo 12 samples. The process of magmatic differentiation that must have accompanied the early melting and chemical fractionation of the moon's outer layers was investigated. The source of regions of both high- and low-titanium mare basalts were also studied.

A Model of the Chicxulub Impact Basin Based on Evaluation of Geophysical Data, Well Logs, and Drill Core Samples

NASA Technical Reports Server (NTRS)

Sharpton, Virgil L.; Marin, Luis E.; Carney, John D.; Lee, Scott; Ryder, Graham; Schuraytz, Benjamin C.; Sikora, Paul; Spudis, Paul D.

1996-01-01

Abundant evidence now shows that the buried Chicxulub structure in northern Yucatan, Mexico, is indeed the intensely sought-after source of the ejecta found world-wide at the Cretaceous-Tertiary (K/T) boundary. In addition to large-scale concentric patterns in gravity and magnetic data over the structure, recent analyses of drill-core samples reveal a lithological assemblage similar to that observed at other terrestrial craters. This assemblage comprises suevite breccias, ejecta deposit breccias (Bunte Breccia equivalents), fine-grained impact melt rocks, and melt-matrix breccias. All these impact-produced lithologies contain diagnostic evidence of shock metamorphism, including planar deformation features in quartz, feldspar, and zircons; diaplectic glasses of quartz and feldspar; and fused mineral melts and whole-rock melts. In addition, elevated concentrations of Ir, Re, and Os, in meteoritic relative proportions, have been detected in some melt-rock samples from the center of the structure. Isotopic analyses, magnetization of melt-rock samples, and local stratigraphic constraints identify this crater as the source of K/T boundary deposits.

High resolution study of petroleum source rock variation, Lower Cretaceous (Hauterivian and Barremian) of Mikkelsen Bay, North Slope, Alaska

USGS Publications Warehouse

Keller, Margaret A.; Macquaker, Joe H.S.; Lillis, Paul G.

2001-01-01

Open File Report 01-480 was designed as a large format poster for the Annual Meeting of the American Association of Petroleum Geologists and the Society for Sedimentary Geology in Denver Colorado in June 2001. It is reproduced here in digital format to make widely available some unique images of mudstones. The images include description, interpretation, and Rock-Eval data that resulted from a high-resolution study of petroleum source rock variation of the Lower Cretaceous succession of the Mobil-Phillips Mikkelsen Bay State #1 well on the North Slope of Alaska. Our mudstone samples with Rock-Eval data plus color images are significant because they come from one of the few continuously cored and complete intervals of the Lower Cretaceous succession on the North Slope. This succession, which is rarely preserved in outcrop and very rarely cored in the subsurface, is considered to include important petroleum source rocks that have not previously been described nor explained Another reason these images are unique is that the lithofacies variability within mudstone dominated successions is relatively poorly known in comparison with that observed in coarser clastic and carbonate successions. They are also among the first published scans of thin sections of mudstone, and are of excellent quality because the sections are well made, cut perpendicular to bedding, and unusually thin, 20 microns. For each of 15 samples, we show a thin section scan (cm scale) and an optical photomicrograph (mm scale) that illustrates the variability present. Several backscattered SEM images are also shown. Rock-Eval data for the samples can be compared with the textures and mineralogy present by correlating sample numbers and core depth.

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.

Image analysis for quantification of bacterial rock weathering.

PubMed

Puente, M Esther; Rodriguez-Jaramillo, M Carmen; Li, Ching Y; Bashan, Yoav

2006-02-01

A fast, quantitative image analysis technique was developed to assess potential rock weathering by bacteria. The technique is based on reduction in the surface area of rock particles and counting the relative increase in the number of small particles in ground rock slurries. This was done by recording changes in ground rock samples with an electronic image analyzing process. The slurries were previously amended with three carbon sources, ground to a uniform particle size and incubated with rock weathering bacteria for 28 days. The technique was developed and tested, using two rock-weathering bacteria Pseudomonas putida R-20 and Azospirillum brasilense Cd on marble, granite, apatite, quartz, limestone, and volcanic rock as substrates. The image analyzer processed large number of particles (10(7)-10(8) per sample), so that the weathering capacity of bacteria can be detected.

Metabasalts as sources of metals in orogenic gold deposits

NASA Astrophysics Data System (ADS)

Pitcairn, Iain K.; Craw, Dave; Teagle, Damon A. H.

2015-03-01

Although metabasaltic rocks have been suggested to be important source rocks for orogenic gold deposits, the mobility of Au and related elements (As, Sb, Se, and Hg) from these rocks during alteration and metamorphism is poorly constrained. We investigate the effects of increasing metamorphic grade on the concentrations of Au and related elements in a suite of metabasaltic rocks from the Otago and Alpine Schists, New Zealand. The metabasaltic rocks in the Otago and Alpine Schists are of MORB and WPB affinity and are interpreted to be fragments accreted from subducting oceanic crust. Gold concentrations are systematically lower in the higher metamorphic grade rocks. Average Au concentrations vary little between sub-greenschist (0.9 ± 0.5 ppb) and upper greenschist facies (1.0 ± 0.5 ppb), but decrease significantly in amphibolite facies samples (0.21 ± 0.07 ppb). The amount of Au depleted from metabasaltic rocks during metamorphism is on a similar scale to that removed from metasedimentary rocks in Otago. Arsenic concentrations increase with metamorphic grade with the metabasaltic rocks acting as a sink rather than a source of this element. The concentrations of Sb and Hg decrease between sub-greenschist and amphibolite facies but concentration in amphibolite facies rocks are similar to those in unaltered MORB protoliths and therefore unaltered oceanic crust cannot be a net source of Sb and Hg in a metamorphic environment. The concentrations of Au, As, Sb, and Hg in oceanic basalts that have become integrated into the metamorphic environment may be heavily influenced by the degree of seafloor alteration that occurred prior to metamorphism. We suggest that metasedimentary rocks are much more suitable source rocks for fluids and metals in orogenic gold deposits than metabasaltic rocks as they show mobility during metamorphism of all elements commonly enriched in this style of deposit.

Circum-Arctic petroleum systems identified using decision-tree chemometrics

USGS Publications Warehouse

Peters, K.E.; Ramos, L.S.; Zumberge, J.E.; Valin, Z.C.; Scotese, C.R.; Gautier, D.L.

2007-01-01

Source- and age-related biomarker and isotopic data were measured for more than 1000 crude oil samples from wells and seeps collected above approximately 55??N latitude. A unique, multitiered chemometric (multivariate statistical) decision tree was created that allowed automated classification of 31 genetically distinct circumArctic oil families based on a training set of 622 oil samples. The method, which we call decision-tree chemometrics, uses principal components analysis and multiple tiers of K-nearest neighbor and SIMCA (soft independent modeling of class analogy) models to classify and assign confidence limits for newly acquired oil samples and source rock extracts. Geochemical data for each oil sample were also used to infer the age, lithology, organic matter input, depositional environment, and identity of its source rock. These results demonstrate the value of large petroleum databases where all samples were analyzed using the same procedures and instrumentation. Copyright ?? 2007. The American Association of Petroleum Geologists. All rights reserved.

Organic geochemistry and petrology of oil source rocks, Carpathian Overthrust region, southeastern Poland - Implications for petroleum generation

USGS Publications Warehouse

Kruge, M.A.; Mastalerz, Maria; Solecki, A.; Stankiewicz, B.A.

1996-01-01

The organic mailer rich Oligocene Menilite black shales and mudstones are widely distributed in the Carpathian Overthrust region of southeastern Poland and have excellent hydrocarbon generation potential, according to TOC, Rock-Eval, and petrographic data. Extractable organic matter was characterized by an equable distribution of steranes by carbon number, by varying amounts of 28,30-dinor-hopane, 18??(H)-oleanane and by a distinctive group of C24 ring-A degraded triterpanes. The Menilite samples ranged in maturity from pre-generative to mid-oil window levels, with the most mature in the southeastern portion of the study area. Carpathian petroleum samples from Campanian Oligocene sandstone reservoirs were similar in biomarker composition to the Menilite rock extracts. Similarities in aliphatic and aromatic hydrocarbon distributions between petroleum asphaltene and source rock pyrolyzates provided further evidence genetically linking Menilite kerogens with Carpathian oils.

Hydrocarbon Reservoir Identification in Volcanic Zone by using Magnetotelluric and Geochemistry Information

NASA Astrophysics Data System (ADS)

Firda, S. I.; Permadi, A. N.; Supriyanto; Suwardi, B. N.

2018-03-01

The resistivity of Magnetotelluric (MT) data show the resistivity mapping in the volcanic reservoir zone and the geochemistry information for confirm the reservoir and source rock formation. In this research, we used 132 data points divided with two line at exploration area. We used several steps to make the resistivity mapping. There are time series correction, crosspower correction, then inversion of Magnetotelluric (MT) data. Line-2 and line-3 show anomaly geological condition with Gabon fault. The geology structure from the resistivity mapping show the fault and the geological formation with the geological rock data mapping distribution. The geochemistry information show the maturity of source rock formation. According to core sample analysis information, we get the visual porosity for reservoir rock formation in several geological structure. Based on that, we make the geological modelling where the potential reservoir and the source rock around our interest area.

Shale characterization in mass transport complex as a potential source rock: An example from onshore West Java Basin, Indonesia

NASA Astrophysics Data System (ADS)

Nugraha, A. M. S.; Widiarti, R.; Kusumah, E. P.

2017-12-01

This study describes a deep-water slump facies shale of the Early Miocene Jatiluhur/Cibulakan Formation to understand its potential as a source rock in an active tectonic region, the onshore West Java. The formation is equivalent with the Gumai Formation, which has been well-known as another prolific source rock besides the Oligocene Talang Akar Formation in North West Java Basin, Indonesia. The equivalent shale formation is expected to have same potential source rock towards the onshore of Central Java. The shale samples were taken onshore, 150 km away from the basin. The shale must be rich of organic matter, have good quality of kerogen, and thermally matured to be categorized as a potential source rock. Investigations from petrography, X-Ray diffractions (XRD), and backscattered electron show heterogeneous mineralogy in the shales. The mineralogy consists of clay minerals, minor quartz, muscovite, calcite, chlorite, clinopyroxene, and other weathered minerals. This composition makes the shale more brittle. Scanning Electron Microscope (SEM) analysis indicate secondary porosities and microstructures. Total Organic Carbon (TOC) shows 0.8-1.1 wt%, compared to the basinal shale 1.5-8 wt%. The shale properties from this outcropped formation indicate a good potential source rock that can be found in the subsurface area with better quality and maturity.

Natural radionuclides in the rocks of the Valle del Cervo Pluton in Piedmont.

PubMed

Sesana, Lucia; Fumagalli, Marco; Carnevale, Mauro; Polla, Giancarla; Facchini, Ugo; Colombo, Annita; Tunesi, Annalisa; De Capitani, Luisa; Rusconi, Rosella

2006-01-01

Monitoring of the gamma radiation in Valle del Cervo Pluton was performed by determining U and Th contents in the main rock types cropping out over the entire area and pertaining to the granitic complex, syenitic complex and monzonitic complex. In particular, syenitic rocks were largely used as building and ornamental materials (e.g. Sienite della Balma). All the samples are fresh and do not present joints or fractures filled with U minerals. In the crushed samples the activity of uranium varies from 346 to 764 Bq/kg. Concentration of thorium varies from 202 to 478 Bq/kg. For all the analysed rocks uranium activity is higher than thorium one. The lowest value of radioactive concentration is referred to rocks of the granitic complex. The most active rocks are syenites. The data confirm the high activities of Valle del Cervo rock types, strongly connected with high K content of the source magma (geochemical signature); on the contrary, the activity seems to be not related to the location of the samples.

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.

Occurrence and Distribution of Organic Wastewater Compounds in Rock Creek Park, Washington, D.C., 2007-08

USGS Publications Warehouse

Phelan, Daniel J.; Miller, Cherie V.

2010-01-01

The U.S. Geological Survey, and the National Park Service Police Aviation Group, conducted a high-resolution, low-altitude aerial thermal infrared survey of the Washington, D.C. section of Rock Creek Basin within the Park boundaries to identify specific locations where warm water was discharging from seeps or pipes to the creek. Twenty-three stream sites in Rock Creek Park were selected based on the thermal infrared images. Sites were sampled during the summers of 2007 and 2008 for the analysis of organic wastewater compounds to verify potential sources of sewage and other anthropogenic wastewater. Two sets of stormwater samples were collected, on June 27-28 and September 6, 2008, at the Rock Creek at Joyce Road water-quality station using an automated sampler that began sampling when a specified stage threshold value was exceeded. Passive-sampler devices that accumulate organic chemicals over the duration of deployment were placed in July 2008 at the five locations that had the greatest number of detections of organic wastewater compounds from the June 2007 base-flow sampling. During the 2007 base-flow synoptic sampling, there were ubiquitous low-level detections of dissolved organic wastewater indicator compounds such as DEET, caffeine, HHCB, and organophosphate flame retardants at more than half of the 23 sites sampled in Rock Creek Park. Concentrations of DEET and caffeine in the tributaries to Rock Creek were variable, but in the main stem of Rock Creek, the concentrations were constant throughout the length of the creek, which likely reflects a distributed source. Organophosphate flame retardants in the main stem of Rock Creek were detected at estimated concentrations of 0.2 micrograms per liter or less, and generally did not increase with distance downstream. Overall, concentrations of most wastewater indicators in whole-water samples in the Park were similar to the concentrations found at the upstream sampling station at the Maryland/District of Columbia boundary. Polycyclic aromatic hydrocarbons were the dominant organic compounds found in the stormwater samples at the Joyce Road station. Polycyclic aromatic hydrocarbons were consistently found in higher concentrations either in sediment or in whole-water samples than in the dissolved samples collected during base-flow conditions at the 23 synoptic sites, or in the Joyce Road station stormwater samples.

Geochemical evaluation of Niger Delta sedimentary organic rocks: a new insight

NASA Astrophysics Data System (ADS)

Akinlua, Akinsehinwa; Torto, Nelson

2011-09-01

A geochemical evaluation of Niger Delta organic matter was carried out using supercritical fluid extraction (SFE) sample preparation procedure. Comparison of geochemical significance of gas chromatographic data of rock extracts of SFE with those of Soxhlet extraction method from previous studies was made in order to establish the usefulness of SFE in geochemical exploration. The assessment of geochemical character of the rock samples from the comparison and interpretation of other geochemical parameters were used to give more insights into understanding the source rocks characteristics of onshore and shelf portions of the Niger Delta Basin. The results of the gas chromatographic (GC) analysis of the rock extracts across the lithostratigraphic units show that Pr/Ph, Pr/nC17, Pr/nC18, CPI and odd/even preference ranged from 0.07 to 12.39, 0.04 to 6.66, 0.05 to 13.80, 0.12 to 8.4 and 0.06 to 8.12, respectively. The Rock-Eval pyrolysis data and geochemical ratios and parameters calculated from the GC data showed that most of the samples are mature and have strong terrestrial provenance while a few samples have strong marine provenance. The few marine source rocks are located in the deeper depth horizon. Pr/Ph and standard geochemical plots indicate that most of samples were derived from organic matter deposited in less reducing conditions, i.e. more of oxidizing conditions while a few samples have predominantly influence of reducing conditions. The results of trace metal analysis of older samples from Agbada Formation also indicate marine and mixed organic matter input deposited in less reducing conditions. The results obtained in this study are comparable with those obtained from previous studies when Soxhlet extraction method was used and also indicated the presence of more than one petroleum systems in the Niger Delta.

RECONNAISSANCE FOR URANIUM IN ASPHALT-BEARING ROCKS IN THE WESTERN UNITED STATES

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

Hail, W.J. Jr.

1957-01-01

An appraisal of asphait-bearing rocks as potential sources of uranium was made during 1953 and 1954 in 45 areas in Calif., Utah, Wyo., Mont., N. Mex., Tex., Okla., and Mo. A total of 202 samples from these areas was analyzed for uranium. The oldest rocks sampled are Ordovician in age, and the youngest are Recent. Although none of the deposits are of value at this time as a source of U, some of the deposits may constitute a low-grade U resource, but recovery of the U will depend upon the primary use of the asphalt. Significant amounts of U lnmore » the ash of oil extracted from these rocks were found in samples from 7 of the 45 areas examined. These areas are Chalome Creek, McKittrick, Edna, and Los Alamos Calif.; Vernal, Utah; Sulphur, Okla.; and Ellis, Mo. The average U content in the ash of the extracted oil of samples from these 7 areas ranges from 0.028 to 0.376%. All except the Chalone Creek area contain large estimated reserves of asphalt-bearing rock, ranging from 15 million to almost 2 billion tons. The average U content of samples from 13 additiomal areas ranges from 0.020 to 0.06B% in the ash of the extracted oil. Many of these areas contain very large reserves of asphalt-bearing rocks. It is believed that most of the asphalt deposits are oil residues, and that the U was introduced during or after the late stages of oil movement and loss of the lighter oil fractions. (auth)« less

North Slope, Alaska: Source rock distribution, richness, thermal maturity, and petroleum charge

USGS Publications Warehouse

Peters, K.E.; Magoon, L.B.; Bird, K.J.; Valin, Z.C.; Keller, M.A.

2006-01-01

Four key marine petroleum source rock units were identified, characterized, and mapped in the subsurface to better understand the origin and distribution of petroleum on the North Slope of Alaska. These marine source rocks, from oldest to youngest, include four intervals: (1) Middle-Upper Triassic Shublik Formation, (2) basal condensed section in the Jurassic-Lower Cretaceous Kingak Shale, (3) Cretaceous pebble shale unit, and (4) Cretaceous Hue Shale. Well logs for more than 60 wells and total organic carbon (TOC) and Rock-Eval pyrolysis analyses for 1183 samples in 125 well penetrations of the source rocks were used to map the present-day thickness of each source rock and the quantity (TOC), quality (hydrogen index), and thermal maturity (Tmax) of the organic matter. Based on assumptions related to carbon mass balance and regional distributions of TOC, the present-day source rock quantity and quality maps were used to determine the extent of fractional conversion of the kerogen to petroleum and to map the original TOC (TOCo) and the original hydrogen index (HIo) prior to thermal maturation. The quantity and quality of oil-prone organic matter in Shublik Formation source rock generally exceeded that of the other units prior to thermal maturation (commonly TOCo > 4 wt.% and HIo > 600 mg hydrocarbon/g TOC), although all are likely sources for at least some petroleum on the North Slope. We used Rock-Eval and hydrous pyrolysis methods to calculate expulsion factors and petroleum charge for each of the four source rocks in the study area. Without attempting to identify the correct methods, we conclude that calculations based on Rock-Eval pyrolysis overestimate expulsion factors and petroleum charge because low pressure and rapid removal of thermally cracked products by the carrier gas retards cross-linking and pyrobitumen formation that is otherwise favored by natural burial maturation. Expulsion factors and petroleum charge based on hydrous pyrolysis may also be high compared to nature for a similar reason. Copyright ?? 2006. The American Association of Petroleum Geologists. All rights reserved.

Sm-Nd and Rb-Sr isotopic systematics of the Pea Ridge Fe-P deposit and related rocks, southeast Missouri

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

Marikos, M.A.; Barton, M.D.

1993-03-01

Pea ridge is a discordant Middle Proterozoic Fe-P deposit hosted in rhyolite tuffs and flows of the 1.4--1.5 Ga St. Francois terrane. Host rocks and the deposit are cut by basalt and aplite/pegmatite dikes. The deposit overlies a blind pluton which is partially surrounded by a trachytic ring complex. In the deposit, which is mined for Fe, early Qtz+Amph+Mag+Ap rock is cut by Mag+Ap+Qtz rock. Subsequently, portions of the deposit and host rocks were brecciated, oxidized and silicified to produce a complex suite of rocks enriched in Hem+Qtz+Ksp+Mu. Late breccia pipes/dikes cut the complex and were mineralized with Bar+Ksp+Flu+Chl+Cc+REE-phosphates. Sm/Ndmore » and Rb/Sr isotopic systematics have been studied to: (1) constrain source(s) of igneous rocks and deposit components, (2) refine ages of magmatism, mineralization, and later hydrothermal activity, (3) begin regional comparison of isotopic systematics in SE Missouri Fe deposits, and (4) complement ongoing Missouri DGLS/USGS studies. Fourteen combined Sm-Nd and Rb-Sr analyses were done on materials including two host rhyolites, two nearby trachytes, two gneiss samples representing plausible basement, two intramineral dikes, and six samples of mineralization.« less

Constraints on the magmatic evolution of the oceanic crust from plagiogranite intrusions in the Oman ophiolite

NASA Astrophysics Data System (ADS)

Haase, Karsten M.; Freund, Sarah; Beier, Christoph; Koepke, Jürgen; Erdmann, Martin; Hauff, Folkmar

2016-05-01

We present major and trace element as well as Sr, Nd, and Hf isotope data on a suite of 87 plutonic rock samples from 27 felsic crustal intrusions in seven blocks of the Oman ophiolite. The rock compositions of the sample suite including associated more mafic rocks range from 48 to 79 wt% SiO2, i.e. from gabbros to tonalites. The samples are grouped into a Ti-rich and relatively light rare earth element (LREE)-enriched P1 group [(Ce/Yb) N > 0.7] resembling the early V1 lavas, and a Ti-poor and LREE-depleted P2 group [(Ce/Yb) N < 0.7] resembling the late-stage V2 lavas. Based on the geochemical differences and in agreement with previous structural and petrographic models, we define phase 1 (P1) and phase 2 (P2) plutonic rocks. Felsic magmas in both groups formed by extensive fractional crystallization of olivine, clinopyroxene, plagioclase, apatite, and Ti-magnetite from mafic melts. The incompatible element compositions of P1 rocks overlap with those from mid-ocean ridges but have higher Ba/Nb and Th/Nb trending towards the P2 rock compositions and indicating an influence of a subducting slab. The P2 rocks formed from a more depleted mantle source but show a more pronounced slab signature. These rocks also occur in the southern blocks (with the exception of the Tayin block) of the Oman ophiolite implying that the entire ophiolite formed above a subducting slab. Initial Nd and Hf isotope compositions suggest an Indian-MORB-type mantle source for the Oman ophiolite magmas. Isotope compositions and high Th/Nb in some P2 rocks indicate mixing of a melt from subducted sediment into this mantle.

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.

Geochemistry of approximately 1.9 Ga sedimentary rocks from northeastern Labrador, Canada

NASA Technical Reports Server (NTRS)

Hayashi, K. I.; Fujisawa, H.; Holland, H. D.; Ohmoto, H.

1997-01-01

Fifty-eight rock chips from fifteen samples of sedimentary rocks from the Ramah Group (approximately 1.9 Ga) in northeastern Labrador, Canada, were analyzed for major and minor elements, including C and S, to elucidate weathering processes on the Earth's surface about 1.9 Ga ago. The samples come from the Rowsell Harbour, Reddick Bight, and Nullataktok Formations. Two rock series, graywackes-gray shales of the Rowsell Harbour, Reddick Bight and Nullataktok Formations, and black shales of the Nullataktok Formation, are distinguishable on the basis of lithology, mineralogy, and major and trace element chemistry. The black shales show lower concentrations than the graywackes-gray shales in TiO2 (0.3-0.7 wt% vs. 0.7-1.8 wt%), Al2O3 (9.5-20.1 wt% vs. 13.0-25.0 wt%), and sigma Fe (<1 wt% vs. 3.8-13.9 wt% as FeO). Contents of Zr, Th, U, Nb, Ce, Y, Rb, Y, Co, and Ni are also lower in the black shales. The source rocks for the Ramah Group sediments were probably Archean gneisses with compositions similar to those in Labrador and western Greenland. The major element chemistry of source rocks for the Ramah Group sedimentary rocks was estimated from the Al2O3/TiO2 ratios of the sedimentary rocks and the relationship between the major element contents (e.g., SiO2 wt%) and Al2O3/TiO2 ratios of the Archean gneisses. This approach is justified, because the Al/Ti ratios of shales generally retain their source rock values; however, the Zr/Al, Zr/Ti, and Cr/Ni ratios fractionate during the transport of sediments. The measured SiO2 contents of shales in the Ramah Group are generally higher than the estimated SiO2 contents of source rocks by approximately 5 wt%. This correction may also have to be applied when estimating average crustal compositions from shales. Two provenances were recognized for the Ramah Group sediments. Provenance I was comprised mostly of rocks of bimodal compositions, one with SiO2 contents approximately 45 wt% and the other approximately 65 wt%, and was the source for most sedimentary rocks of the Ramah Group, except for black shales of the Nullataktok Formation. The black shales were apparently derived from Provenance II that was comprised mostly of felsic rocks with SiO2 contents approximately 65 wt%. Comparing the compositions of the Ramah Group sedimentary rocks and their source rocks, we have recognized that several major elements, especially Ca and Mg, were lost almost entirely from the source rocks during weathering and sedimentation. Sodium and potassium were also leached almost entirely during the weathering of the source rocks. However, significant amounts of Na were added to the black shales and K to all the rock types during diagenesis and/or regional metamorphism. The intensity of weathering of source rocks for the Ramah Group sediments was much higher than that of typical Phanerozoic sediments, possibly because of a higher PCO2 in the Proterozoic atmosphere. Compared to the source rock values, the Fe3+/Ti ratios of many of the graywackes and gray shales of the Ramah Group are higher, the Fe2+/Ti ratios are lower, and the sigma Fe/Ti ratios are the same. Such characteristics of the Fe geochemistry indicate that these sedimentary rocks are comprised of soils formed by weathering of source rocks under an oxygen-rich atmosphere. The atmosphere about 1.9 Ga was, therefore, oxygen rich. Typical black shales of Phanerozoic age exhibit positive correlations between the organic C contents and the concentrations of S, U, and Mo, because these elements are enriched in oxygenated seawater and are removed from seawater by organic matter in sediments. However, such correlations are not found in the Ramah Group sediments. Black shales of the Ramah Group contain 1.7-2.8 wt% organic C, but are extremely depleted in sigma Fe (<1 wt% as FeO), S (<0.3 wt%), U (approximately l ppm), Mo (<5 ppm), Ni (<2 ppm), and Co (approximately 0 ppm). This lack of correlation, however, does not imply that the approximately 1.9 Ga atmosphere-ocean system was anoxic. Depletion of these elements from the Ramah Group sediments may have occurred during diagenesis.

Petroleum geochemistry of oil and gas from Barbados: Implications for distribution of Cretaceous source rocks and regional petroleum prospectivity

USGS Publications Warehouse

Hill, R.J.; Schenk, C.J.

2005-01-01

Petroleum produced from the Barbados accretionary prism (at Woodbourne Field on Barbados) is interpreted as generated from Cretaceous marine shale deposited under normal salinity and dysoxic conditions rather than from a Tertiary source rock as previously proposed. Barbados oils correlate with some oils from eastern Venezuela and Trinidad that are positively correlated to extracts from Upper Cretaceous La Luna-like source rocks. Three distinct groups of Barbados oils are recognized based on thermal maturity, suggesting petroleum generation occurred at multiple levels within the Barbados accretionary prism. Biodegradation is the most significant process affecting Barbados oils resulting in increased sulfur content and decreased API gravity. Barbados gases are interpreted as thermogenic, having been co-generated with oil, and show mixing with biogenic gas is limited. Gas biodegradation occurred in two samples collected from shallow reservoirs at the Woodbourne Field. The presence of Cretaceous source rocks within the Barbados accretionary prism suggests that greater petroleum potential exists regionally, and perhaps further southeast along the passive margin of South America. Likewise, confirmation of a Cretaceous source rock indicates petroleum potential exists within the Barbados accretionary prism in reservoirs that are deeper than those from Woodbourne Field.

Factors controlling the regional distribution of vanadium in ground water

USGS Publications Warehouse

Wright, Michael T.; Belitz, Kenneth

2010-01-01

Although the ingestion of vanadium (V) in drinking water may have possible adverse health effects, there have been relatively few studies of V in groundwater. Given the importance of groundwater as a source of drinking water in many areas of the world, this study examines the potential sources and geochemical processes that control the distribution of V in groundwater on a regional scale. Potential sources of V to groundwater include dissolution of V rich rocks, and waste streams from industrial processes. Geochemical processes such as adsorption/desorption, precipitation/dissolution, and chemical transformations control V concentrations in groundwater. Based on thermodynamic data and laboratory studies, V concentrations are expected to be highest in samples collected from oxic and alkaline groundwater. However, the extent to which thermodynamic data and laboratory results apply to the actual distribution of V in groundwater is not well understood. More than 8400 groundwater samples collected in California were used in this study. Of these samples, high (> or = 50 μg/L) and moderate (25 to 49 μg/L) V concentrations were most frequently detected in regions where both source rock and favorable geochemical conditions occurred. The distribution of V concentrations in groundwater samples suggests that significant sources of V are mafic and andesitic rock. Anthropogenic activities do not appear to be a significant contributor of V to groundwater in this study. High V concentrations in groundwater samples analyzed in this study were almost always associated with oxic and alkaline groundwater conditions, which is consistent with predictions based on thermodynamic data.

Distribution of organic carbon and petroleum source rock potential of Cretaceous and lower Tertiary carbonates, South Florida Basin: preliminary results

USGS Publications Warehouse

Palacas, James George

1978-01-01

Analyses of 134 core samples from the South Florida Basin show that the carbonates of Comanchean age are relatively richer in average organic carbon (0.41 percent) than those of Coahuilan age (0.28 percent), Gulfian age (0.18 percent) and Paleocene age (0.20 percent). They are also nearly twice as rich as the average world, wide carbonate (average 0.24 percent). The majority of carbonates have organic carbons less than 0.30 percent but the presence of many relatively organic rich beds composed of highly bituminous, argillaceous, highly stylolitic, and algal-bearing limestones and dolomites accounts for the higher percentage of organic carbon in some of the stratigraphic units. Carbonate rocks that contain greater than 0.4 percent organic carbon and that might be considered as possible petroleum sources were noted in almost each subdivision of the Coahuilan and Comanchean Series but particularly the units of Fredericksburg 'B', Trinity 'A', Trinity 'F', and Upper Sunniland. Possible source rocks have been ascribed by others to the Lower Sunniland, but lack of sufficient samples precluded any firm assessment in this initial report. In the shallower section of the basin, organic-rich carbonates containing as much as 3.2 percent organic carbon were observed in the lowermost part of the Gulfian Series and carbonate rocks with oil staining or 'dead' and 'live oil' were noted by others in the uppermost Gulfian and upper Cedar Keys Formation. It is questionable whether these shallower rocks are of sufficient thermal maturity to have generated commercial oil. The South Florida basin is still sparsely drilled and produces only from the Sunniland Limestone at an average depth of 11,500 feet (3500 m). Because the Sunniland contains good reservoir rocks and apparently adequate source rocks, and because the success rate of new oil field discoveries has increased in recent years, the chances of finding additional oil reserves in the Sunniland are promising. Furthermore, the presence of possible source rocks in many of the other stratigraphic units, in particular, the Fredericksburg, should give further impetus to exploring for other productive horizons.

Thermal Maturity Data Used by the U.S. Geological Survey for the U.S. Gulf Coast Region Oil and Gas Assessment

USGS Publications Warehouse

Dennen, Kristin O.; Warwick, Peter D.; McDade, Elizabeth Chinn

2010-01-01

The U.S. Geological Survey is currently assessing the oil and natural gas resources of the U.S. Gulf of Mexico region using a total petroleum system approach. An essential part of this geologically based method is evaluating the effectiveness of potential source rocks in the petroleum system. The purpose of this report is to make available to the public RockEval and vitrinite reflectance data from more than 1,900 samples of Mesozoic and Tertiary rock core and coal samples in the Gulf of Mexico area in a format that facilitates inclusion into a geographic information system. These data provide parameters by which the thermal maturity, type, and richness of potential sources of oil and gas in this region can be evaluated.

Petrologic variations in Apollo 16 surface soils

NASA Technical Reports Server (NTRS)

Houck, K. J.

1982-01-01

Source rock, maturation history and intrasite variation data are derived for the Apollo 16 regolith by comparing modal analyses of 15 surface soils with rake and rock sample data. Triangular source rock component plots show that Apollo 16 soils have similar source rocks that are well homogenized throughout the site. The site can be divided into three soil petrographic provinces. Central site soils are mature, well homogenized, and enriched in glass. They are probably the most typical Cayley Plains materials present. North Ray soils are immature to submature, containing North Ray ejecta. South Ray soils are mature, but contain small amounts of fresh impact melts and plagioclase, due perhaps to the breakdown of blocky South Ray ejecta. The different compositions and physical properties of North and South Ray ejecta support the hypothesis that the latter event excavated Cayley material, while the former excavated Descartes materials.

The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)

NASA Astrophysics Data System (ADS)

Ahadnejad, Vahid; Hirt, Ann Marie; Valizadeh, Mohammad-Vali; Bokani, Saeed Jabbari

2011-04-01

The ammonium (NH4+) contents of the Malayer area (Western Iran) have been determined by using the colorimetric method on 26 samples from igneous and metamorphic rocks. This is the first analysis of the ammonium contents of Iranian metamorphic and igneous rocks. The average ammonium content of metamorphic rocks decreases from low-grade to high-grade metamorphic rocks (in ppm): slate 580, phyllite 515, andalusite schist 242. In the case of igneous rocks, it decreases from felsic to mafic igneous types (in ppm): granites 39, monzonite 20, diorite 17, gabbro 10. Altered granitic rocks show enrichment in NH4+ (mean 61 ppm). The high concentration of ammonium in Malayer granites may indicate metasedimentary rocks as protoliths rather than meta-igneous rocks. These granitic rocks (S-types) have high K-bearing rock-forming minerals such as biotite, muscovite and K-feldspar which their potassium could substitute with ammonium. In addition, the high ammonium content of metasediments is probably due to inheritance of nitrogen from organic matter in the original sediments. The hydrothermally altered samples of granitic rocks show highly enrichment of ammonium suggesting external sources which intruded additional content by either interaction with metasedimentary country rocks or meteoritic solutions.

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.

Estimating carbon and nitrogen pools in a forest soil: Influence of soil bulk density methods and rock content

Treesearch

Martin F. Jurgensen; Deborah S. Page-Dumroese; Robert E. Brown; Joanne M. Tirocke; Chris A. Miller; James B. Pickens; Min Wang

2017-01-01

Soils with high rock content are common in many US forests, and contain large amounts of stored C. Accurate measurements of soil bulk density and rock content are critical for calculating and assessing changes in both C and nutrient pool size, but bulk density sampling methods have limitations and sources of variability. Therefore, we evaluated the use of small-...

Comparative Analysis of Fluoride Concentrations in Groundwaters in Northern and Southern Ghana: Implications for the Contaminant Sources

NASA Astrophysics Data System (ADS)

Sunkari, Emmanuel Daanoba; Zango, Musah Saeed; Korboe, Harriet Mateko

2018-04-01

Bongo and Sekyere South districts, both in the northern and southern parts of Ghana, respectively, have high populations living in rural areas and most of them use groundwater for drinking purposes. The groundwater in these areas is prone to contamination from natural and/or artificial sources. Therefore this study aims; (1) to present a comparative analysis of the fluoride concentration in groundwater samples from Bongo and Sekyere South districts and the associated groundwater-rock interaction that may be the cause for the varied fluoride concentrations, (2) to determine the leaching potential of fluoride from the host rocks as the possible mechanism for groundwater contamination. Sixty (60) groundwater samples from active pumping wells and twelve (12) rock samples from outcrops were collected from various communities in the two districts for fluoride concentration and mineralogical analysis. Based on the variations in fluoride concentration, fluoride spatial distribution maps were prepared using empirical Bayesian kriging interpolation method and analysed by means of hierarchical cluster analysis. The fluoride concentration in Bongo district varies between 1.71 and 4.0 mg/L, whereas that in Sekyere South district changes from 0.3 to 0.8 mg/L. From the mineralogical studies, biotite has the highest percentage in the Bongo district and has positive correlation with fluoride concentration in the analysed water samples than in the Sekyere South district. The elevated fluoride concentration in the Bongo district relative to the Sekyere South district is due to the dissolution of biotite in the groundwater and the sufficient groundwater-rock interaction since the water samples are mainly sourced from deeper boreholes. This high fluoride concentration has resulted in a plethora of reported cases of dental fluorosis and other health-related issues in Bongo.

Comparative Analysis of Fluoride Concentrations in Groundwaters in Northern and Southern Ghana: Implications for the Contaminant Sources

NASA Astrophysics Data System (ADS)

Sunkari, Emmanuel Daanoba; Zango, Musah Saeed; Korboe, Harriet Mateko

2018-05-01

Bongo and Sekyere South districts, both in the northern and southern parts of Ghana, respectively, have high populations living in rural areas and most of them use groundwater for drinking purposes. The groundwater in these areas is prone to contamination from natural and/or artificial sources. Therefore this study aims; (1) to present a comparative analysis of the fluoride concentration in groundwater samples from Bongo and Sekyere South districts and the associated groundwater-rock interaction that may be the cause for the varied fluoride concentrations, (2) to determine the leaching potential of fluoride from the host rocks as the possible mechanism for groundwater contamination. Sixty (60) groundwater samples from active pumping wells and twelve (12) rock samples from outcrops were collected from various communities in the two districts for fluoride concentration and mineralogical analysis. Based on the variations in fluoride concentration, fluoride spatial distribution maps were prepared using empirical Bayesian kriging interpolation method and analysed by means of hierarchical cluster analysis. The fluoride concentration in Bongo district varies between 1.71 and 4.0 mg/L, whereas that in Sekyere South district changes from 0.3 to 0.8 mg/L. From the mineralogical studies, biotite has the highest percentage in the Bongo district and has positive correlation with fluoride concentration in the analysed water samples than in the Sekyere South district. The elevated fluoride concentration in the Bongo district relative to the Sekyere South district is due to the dissolution of biotite in the groundwater and the sufficient groundwater-rock interaction since the water samples are mainly sourced from deeper boreholes. This high fluoride concentration has resulted in a plethora of reported cases of dental fluorosis and other health-related issues in Bongo.

Physical and chemical properties of submarine basaltic rocks from the submarine flanks of the Hawaiian Islands

USGS Publications Warehouse

Yokose, H.; Lipman, P.W.; Kanamatsu, T.

2005-01-01

To evaluate physical and chemical diversity in submarine basaltic rocks, approximately 280 deep submarine samples recovered by submersibles from the underwater flanks of the Hawaiian Islands were analyzed and compared. Based on observations from the submersibles and hand specimens, these samples were classified into three main occurrence types (lavas, coarse-grained volcaniclastic rocks, and fine-grained sediments), each with several subtypes. The whole-rock sulfur content and porosity in submarine basaltic rocks, recovered from depths greater than 2000 m, range from < 10 ppm and 2 vol.% to 2200 ppm and 47 vol.%, respectively. These wide variations cannot be due just to different ambient pressures at the collection depths, as inferred previously for submarine erupted lavas. The physical and chemical properties of the recovered samples, especially a combination of three whole-rock parameters (Fe-oxidation state, Sulfur content, and Porosity), are closely related to the occurrence type. The FSP triangular diagram is a valuable indicator of the source location of basaltic fragments deposited in deep submarine areas. This diagram can be applied to basaltic rocks such as clasts in debris-flow deposits, submarine-emplaced lava flows that may have crossed the shoreline, and slightly altered geological samples. ?? 2005 Elsevier B.V. All rights reserved.

Ultra-high sensitivity moment magnetometry of geological samples using magnetic microscopy

NASA Astrophysics Data System (ADS)

Lima, Eduardo A.; Weiss, Benjamin P.

2016-09-01

Useful paleomagnetic information is expected to be recorded by samples with moments up to three orders of magnitude below the detection limit of standard superconducting rock magnetometers. Such samples are now detectable using recently developed magnetic microscopes, which map the magnetic fields above room-temperature samples with unprecedented spatial resolutions and field sensitivities. However, realizing this potential requires the development of techniques for retrieving sample moments from magnetic microscopy data. With this goal, we developed a technique for uniquely obtaining the net magnetic moment of geological samples from magnetic microscopy maps of unresolved or nearly unresolved magnetization. This technique is particularly powerful for analyzing small, weakly magnetized samples such as meteoritic chondrules and terrestrial silicate crystals like zircons. We validated this technique by applying it to field maps generated from synthetic sources and also to field maps measured using a superconducting quantum interference device (SQUID) microscope above geological samples with moments down to 10-15 Am2. For the most magnetic rock samples, the net moments estimated from the SQUID microscope data are within error of independent moment measurements acquired using lower sensitivity standard rock magnetometers. In addition to its superior moment sensitivity, SQUID microscope net moment magnetometry also enables the identification and isolation of magnetic contamination and background sources, which is critical for improving accuracy in paleomagnetic studies of weakly magnetic samples.

The Chinese Cretaceous Continental Scientific Drilling Project in the Songliao Basin, NE China: Organic-rich source rock evaluation with geophysical logs from Borehole SK-2

NASA Astrophysics Data System (ADS)

Zhang, X.; Zou, C.

2017-12-01

The Cretaceous strata have been recognized as an important target of oil or gas exploration in the Songliao Basin, northeast China. The second borehole (SK-2) of the Chinese Cretaceous Continental Scientific Drilling Project in the Songliao Basin (CCSD-SK) is the first one to drill through the Cretaceous continental strata in the frame of ICDP. It was designed not only to solve multiple scientific problems (including the Cretaceous paleoenvironment and paleoclimate, as well as deep resources exploration of the Songliao Basin), but also to expect to achieve new breakthroughs in oil and gas exploration. Based on the project, various geophysical log data (including gamma, sonic, resistivity, density etc.) and core samples have been collected from Borehole SK-2. We do research on organic-rich source rocks estimation using various geophysical log data. Firstly, we comprehensively analyzed organic-rich source rocks' geophysical log response characteristics. Then, source rock's identification methods were constructed to identify organic-rich source rocks with geophysical logs. The main identification methods include cross-plot, multiple overlap and Decision Tree method. Finally, the technique and the CARBOLOG method were applied to evaluate total organic carbon (TOC) content from geophysical logs which provide continuous vertical profile estimations (Passey, 1990; Carpentier et al., 1991). The results show that source rocks are widely distributed in Borehole SK-2, over a large depth strata (985 5700m), including Nenjiang, Qingshankou, Denglouku, Yingcheng, Shahezi Formations. The organic-rich source rocks with higher TOC content occur in the Qingshankou (1647 1650m), Denglouku (2534 2887m) and Shahezi (3367 5697m) Formations. The highest TOC content in these formations can reach 10.31%, 6.58%, 12.79% respectively. The bed thickness of organic-rich source rocks in the these formations are totally up to 7.88m, 74.34m, 276.60m respectively. These organic-rich rocks in the Qingshankou, Denglouku and Shahezi Formations can be considered as excellent source rocks in the Songliao Basin, which are beneficial for oil or gas accumulation. This work was supported by the CCSD-SK of China Geological Survey (No. 12120113017600) and the National Natural Science Foundation Project (grant No.41274185).

HYDROCARBON SOURCE ROCK EVALUATION OF MIDDLE PROTEROZOIC SOLOR CHURCH FORMATION, NORTH AMERICAN MID-CONTINENT RIFT SYSTEM, RICE COUNTY, MINNESOTA.

USGS Publications Warehouse

Hatch, J.R.; Morey, G.B.

1985-01-01

Hydrocarbon source rock evaluation of the Middle Proterozoic Solor Church Formation (Keweenawan Supergroup) as sampled in the Lonsdale 65-1 well, Rice County, shows that: the rocks are organic matter lean; the organic matter is thermally post-mature, probably near the transition between the wet gas phase of catagenesis and metagenesis; and the rocks have minimal potential for producing additional hydrocarbons. The observed thermal maturity of the organic matter requires significantly greater burial depths, a higher geothermal gradient, or both. It is likely, that thermal maturation of the organic matter in the Solor Church took place relatively early, and that any hydrocarbons generated during this early phase were probably lost prior to deposition of the overlying formation.

40Ar/39Ar Data for White Mica, Biotite, and K-Feldspar Samples from Low-Grade Metamorphic Rocks in the Westminster Terrane and Adjacent Rocks, Maryland

USGS Publications Warehouse

Kunk, Michael J.; McAleer, Ryan J.

2008-01-01

This report contains reduced 40Ar/39Ar data of white mica and K-feldspar mineral separates and matrix of a whole rock phyllite, all from low-grade metamorphic rocks of the Westminster terrane and adjacent strata in central Maryland. This report presents these data in a preliminary form, but in more detail than can be accommodated in todays professional journals. Also included in this report is information on the location of the samples and a brief description of the samples. The data contained herein are not interpreted in a geological context, and care should be taken by readers unfamiliar with argon isotopic data in the use of these results; many of the individual apparent ages are not geologically meaningful. This report is primarily a detailed source document for subsequent publications that will integrate these data into a geological context.

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.

Source identification of soil mercury in the Spanish islands.

PubMed

Rodríguez Martín, José Antonio; Carbonell, Gregoria; Nanos, Nikos; Gutiérrez, Carmen

2013-02-01

This study spatially analysed the relation between mercury (Hg) content in soil and Hg in rock fragment for the purpose of assessing natural soil Hg contribution compared with Hg from human inputs. We present the Hg content of 318 soil and rock fragment samples from 11 islands distributed into two Spanish archipelagos (the volcanic Canary Islands [Canaries] and the Mediterranean Balearic [Balearic] islands). Assumedly both are located far enough away from continental Hg sources to be able to minimise the effects of diffuse pollution. Physical and chemical soil properties were also specified for the samples. Hg contents were significantly greater in the Balearic limestone soils (61 μg kg(-1)) than in the volcanic soils of the Canaries (33 μg kg(-1)). Hg levels were also greater in topsoil than in rocky fragments, especially on the Balearics. The soil-to-rock ratios varied between 1 and 30. Interestingly, the highest topsoil-to-rock Hg ratio (>16 ×) was found in the vicinity of a coal-fired power plant in Majorca, whereas no similar areas in the Canary archipelago were identified.

Composition and sources of atmospheric dusts in snow at 3200 meters in the St. Elias Range, southeastern Alaska, USA

USGS Publications Warehouse

Hinkley, T.K.

1994-01-01

Dusts in snow from the accumulation zone in the St. Elias Range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition. These dusts, with respect to their composition and to the moderate degree of variation that occurs through a depositional year, are similar those deposited in Greenland. The high portion of the St. Elias Range is isolated from dominance by any local dust source terranes, because of altitude and the extent of the surrounding glacierized and snow-covered region. In Greenland the altitude is typically lower, but local sources are even less likely to dominate the character of the dusts deposited into the ice record there. The similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial-period conditions are uniform and representative of a broad regional or even hemispheric background dust. The dusts in the snow were measured by means of a suite of major, minor, and trace rock-forming metals chosen to give information about rock types, their constituent minerals, degree of degradation (weathering), and energies of atmospheric uptake from source. The variations in amounts of rock dust through the year in the St. Elias Range snowpack have no time-stratigraphic correspondence to the also large variations in concentrations of other species that are not constituents of rock-derived dusts, such the anions chloride, sulfate, and nitrate; the highs and lows of the two types of materials are apparently completely independent. The structure revealed by the moderately fine-scale sampling of the present study (??? 10 increments/y) serves as a background for the interpretation of analysis of ice core samples, in which annual layers may be too compressed to permit analysis of sub-annual samples. ?? 1994.

Composition and sources of atmospheric dusts in snow at 3200 meters in the St. Elias Range, southeastern Alaska, USA

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

Hinkley, T.K.

1994-08-01

Dusts in snow from the accumulation zone in the St. Elias Range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition. These dusts, with respect to their composition and to the moderate degree of variation that occurs through a depositional year, are similar to those deposited in Greenland. The high portion of the St. Elias Range is isolated from dominance by any local dust source terranes, because of altitude and the extent of the surrounding glacierized and snow-covered region. In Greenland the altitude is typically lower, but local sources are even less likely tomore » dominate the character of the dusts deposited into the ice record there. The similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial-period conditions are uniform and representative of a broad regional or even hemispheric background dust. The dusts in the snow were measured by means of a suite of major, minor, and track rock-forming metals chosen to give information about rock types, their constituent minerals, degree of degradation (weathering), and energies of atmospheric uptake from source. The variations in amounts of rock dust through the year in the St. Elias Range snowpack have no time-stratigraphic correspondence to the also-large variations in concentrations of other species that are not constituents of rock-derived dusts, such the anions chloride, sulfate, and nitrate; the highs and lows of the two types of materials are apparently completely independent. The structure revealed by the moderately fine-scale sampling of the present study ([approximately]10 increments/y) serves as a background for the interpretation of analysis of ice core samples, in which annual layers may be too compressed to permit analysis of sub-annual samples.« less

Measurement of Thermal Properties of Rocks at Temperature up to 1,000°C with Transient Plane Source Techniques

NASA Astrophysics Data System (ADS)

Kim, S. K.; Lee, Y.

2017-12-01

A set of devices that can measure thermal properties of rocks over a temperature range from room temperature up to 1,000°C with transient plane source techniques (also known as a Hot Disk method) is introduced. It consists of a main control system (e.g., TPS 2500 S from Hot Disk), mica-insulated sensor, tubular furnace, N2 gas supplier, and pressure regulator. The TPS 2500 S is the core instrument designed for precise analysis of thermal transport properties including thermal conductivity, thermal diffusivity, and volumetric heat capacity. The mica-insulated sensor is composed of an insulated nickel double spiral, which is utilized for both transient heating and precise temperature reading; a mica insulator protects the sensor against mechanical and thermal damage at high temperatures. The tubular furnace can hold two rock core samples of 50-mm-diameter and 25-mm-height with increasing temperatures up to 1,000°C. N2 gas supplier and pressure regulator are used to keep the inside the furnace away from oxygen. Thermal properties of most rocks and minerals vary with increasing temperatures. Experimental measurements of thermal properties at high temperatures have been made mostly using laser flash, needle probe, and divided bar methods in the previous researches, and no previous measurements with the Hot Disk method have been reported yet. We report thermal conductivities, thermal diffusivities, and volumetric heat capacities determined by a transient plane heat source method for fused silica and mafic rock samples using the introduced transient plane source apparatus. The thermal properties of fused silica have been measured mainly over the temperature range from ambient temperature to 500°C. The results seem to agree moderately with the previously reported values by Birch and Clark (Am. J. Sci., 1940). We now check the possible causes of measurement errors in our measurements and prepare to measure thermal properties of the mafic rock samples at temperatures up to 1,000°C using the hot disk method.

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).

Age and origin of the Merrimack terrane, southeastern New England: A detrital zircon U-Pb geochronology study

NASA Astrophysics Data System (ADS)

Sorota, Kristin

Metasedimentary rocks of the Merrimack terrane (MT) originated as a thick cover sequence on Ganderia consisting of sandstones, calcareous sandstones, pelitic rocks and turbidites. In order to investigate the age, provenance and stratigraphic order of these rocks and correlations with adjoining terranes, detrital zircon suites from 7 formations across the MT along a NNE-trending transect from east-central Massachusetts to SE New Hampshire were analyzed by U-Pb LA-ICP-MS methods on 90-140 grains per sample. The youngest detrital zircons in the western units, the Worcester, Oakdale and Paxton Formations, are ca. 438 Ma while those in the Kittery, Eliot and Berwick Formations in the northeast are ca. 426 Ma. The Tower Hill Formation previously interpreted to form the easternmost unit of the MT in MA, has a distinctly different zircon distribution with its youngest zircon population in the Cambrian. All samples except for the Tower Hill Formation have detrital zircon age distributions with significant peaks in the mid-to late Ordovician, similar abundances of early Paleozoic and late Neoproterozoic zircons, significant input from ˜1.0 to ˜1.8 Ga sources and limited Archean grains. The similarities in zircon provenance suggest that all units across the terrane, except for the Tower Hill Formation, belong to a single sequence of rocks, with similar sources and with the units in the NE possibly being somewhat younger than those in east-central Massachusetts. The continuous zircon age distributions observed throughout the Mesoproterozoic and late Paleoproterozoic are consistent with an Amazonian source. All samples, except the Tower Hill Formation, show sedimentary input from both Ganderian and Laurentian sources and suggest that Laurentian input increases as the maximum depositional age decreases.

Compositions of Mars Rocks: SNC Meteorites, Differentiates, and Soils

NASA Technical Reports Server (NTRS)

Rutherford, M. J.; Minitti, M.; Weitz, C. M.

1999-01-01

The 13 samples from Mars identified in the terrestrial meteorite collections vary from dunite to pyroxenite to microgabbro or basalt. All of these rocks appear to have formed from primitive melts with similar major element compositional characteristics; i.e., FeO-rich and Al2O3-Poor melts relative to terrestrial basalt compositions. Although all of the SNC rocks can be derived by melting of the same Al-depleted mantle, contamination of SNC's by a Rb-enriched mantle or crustal source is required to explain the different REE characteristics of SNC rocks. Thus, there are indications of an old crustal rocktype on Mars, and this rock does not appear to have been sampled. This paper focuses primarily on the composition of the SNC basalts, however, and on the compositions of rocks which could be derived from SNC basaltic melt by magmatic processes. In particular, we consider the possible compositions which could be achieved through accumulation of early-formed crystals in the SNC primitive magma. Through a set of experiments we have determined (1) melt (magma) compositions which could be produced by melt evolution as crystals are removed from batches of this magma cooling at depth, and (2) which evolved (Si02enriched, MgO-depleted) rock compositions could be produced from the SNC magma, and how these compare with the Pathfinder andesite composition. Finally, we compare the SNC magma compositions to the Mars soil composition in order to determine whether any source other than SNC is required.

A gas sampling system for withdrawing humid gases from deep boreholes

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

Rousseau, J.P.; Thordarson, W.; Kurzmack, M.A.

A gas sampling system, designed to withdraw nearly vapor-saturated gases (93 to 100% relative humidity) from deep, unsaturated zone boreholes, was developed by the U.S. Geological Survey for use in the unsaturated zone borehole instrumentation and monitoring program at Yucca Mountain, Nye County, Nevada. This gas sampling system will be used to: (1) sample formation rock gases in support of the unsaturated zone hydrochemical characterization program; and (2) verify downhole, thermocouple psychrometer measurements of water potential in support of the unsaturated zone borehole instrumentation and monitoring program. Using this sampling system, nearly vapor-saturated formation rock-gases can be withdrawn from deepmore » boreholes without condensing water vapor in the sampling tubes, and fractionating heavy isotopes of oxygen, hydrogen, and carbon. The sampling system described in this paper uses a dry carrier-gas (nitrogen) to lower the dew point temperature of the formation rock-gas at its source. Mixing of the dry carrier gas with the source gas takes place inside a specially designed downhole instrument station apparatus (DISA). Nitrogen inflow is regulated in a manner that lowers the dew point temperature of the source gas to a temperature that is colder than the coldest temperature that the mixed gas will experience in moving from warmer, deeper depths, to colder, shallower depths near the land surface. A test of this gas sampling system was conducted in December, 1992, in a 12.2 meter deep borehole that was instrumented in October, 1991. The water potential calculated using this system reproduced in-situ measurements of water potential to within five percent of the average value, as recorded by two thermocouple psychrometers that had been in operation for over 12 months.« less

Geochemistry, palynology, and regional geology of worldclass Upper Devonian source rocks in the Madre de Dios basin, Bolivia

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

Peters, K.E.; Conrad, K.T.; Carpenter, D.G.

Recent exploration drilling indicates the existence of world-class source rock in the Madre de Dios basin, Bolivia. In the Pando-1 X and -2X wells, over 200 m of poorly bioturbated, organic-rich (TOC = 3-16 wt.%) prodelta to shelf mudstones in the Frasnian-Famennian Tomachi Formation contain oil-prone organic matter (hydrogen index = 400-600 mg HC/g TOC). Our calculated source prolificity indices for this interval in these wells (SPI = 15-18 tons of hydrocarbons per square meter of source rock) exceed that for the Upper Jurassic in Central Saudi Arabia. The Tomachi interval is lithologically equivalent to the Colpacucho Formation in themore » northern Altiplano, the Iquiri Formation in the Cordillera Oriental, and is coeval with other excellent source rocks in North America, Africa, and Eurasia. All of these rocks were deposited under conditions favorable for accumulation of organic matter, including a global highstand and high productivity. However, the Madre de Dios basin was situated at high latitude during the Late Devonian and some of the deposits are interpreted to be of glacial origin, indicating conditions not generally associated with organic-rich deposition. A biomarker and palynological study of Upper Devonian rocks in the Pando-1X well suggests deposition under conditions similar to certain modern fjords. High productivity resulted in preservation of abundant organic matter in the bottom sediments despite a cold, toxic water column. Low-sulfur crude oil produced from the Pando-1X well is geochemically similar to, but more mature than, extracts from associated organic-rich Tomachi samples, and was generated from deeper equivalents of these rocks.« less

New bulk and in situ isotopic and elemental geochemistry of shallow drill core from Atlantis Massif: insights into the sources and paths of fluids and clasts

NASA Astrophysics Data System (ADS)

Bilenker, L.; Weis, D.; Scoates, J. S.

2017-12-01

We present stable Fe and radiogenic isotope and complementary trace element data for samples from Atlantis Massif. This oceanic core complex is located at 30°N where the Atlantis Transform Fault intersects the Mid-Atlantic Ridge (MAR) and is associated with the Lost City Hydrothermal Field (LCHF). It is a unique place to investigate the abiotic and biotic geochemical processes that play a role in the alteration of both crustal and mantle seafloor rocks. The samples analyzed represent a shallow (<15 m) survey of five drill sites (IODP Expedition 357) within Atlantis Massif, varying in distance from the LCHF and MAR. Analyses were performed on a sample set spanning a wide range in degree of alteration and lithology. Bulk measurements involved dissolving whole rock powders, whereas in situ analyses were performed on digested microdrilled samples or by laser ablation. Bulk rock Fe isotope values (n = 34) are correlated with loss-on-ignition (LOI) by sample lithology and location relative to LCHF. Using LOI as a proxy for degree of alteration, this observation indicates that the Fe isotope systematics of seafloor crustal and mantle rocks preserve indicators of fluid flow and source. The Hf and Nd isotope compositions for various lithologies form all analyzed sites are homogeneous, indicating minimal alteration of these isotopic systems. Bulk Sr values provide insight into elemental exchange between seawater and the surface of Atlantis Massif and bulk Pb isotopes allow for fingerprinting of the source of basalt breccias through comparison with published Pb isotope values of MAR basalts. The new results cluster around the Pb, Hf, Nd isotopic composition of mid-ocean ridge basalt from 30.68°N and do not match samples north or south of that location. In situ Fe isotope data within three altered samples reflect varying degrees of hydrothermal and seawater interaction, where the Fe isotope ratios within each sample are likely correlated with extent of exchange or redox. Laser trace element and Pb isotope data in progress will allow us to investigate this further. This study contributes to our understanding of element mobility and mass transfer during chemical reactions within the seafloor, provides insight into the source of the lithological units and fluid flow, and allows for quantification of alteration processes.

Distribution and geological sources of selenium in environmental materials in Taoyuan County, Hunan Province, China.

PubMed

Ni, Runxiang; Luo, Kunli; Tian, Xinglei; Yan, Songgui; Zhong, Jitai; Liu, Maoqiu

2016-06-01

The selenium (Se) distribution and geological sources in Taoyuan County, China, were determined by using hydride generation atomic fluorescence spectrometry on rock, soil, and food crop samples collected from various geological regions within the county. The results show Se contents of 0.02-223.85, 0.18-7.05, and 0.006-5.374 mg/kg in the rock, soil, and food crops in Taoyuan County, respectively. The region showing the highest Se content is western Taoyuan County amid the Lower Cambrian and Ediacaran black rock series outcrop, which has banding distributed west to east. A relatively high-Se environment is found in the central and southern areas of Taoyuan County, where Quaternary Limnetic sedimentary facies and Neoproterozoic metamorphic volcanic rocks outcrop, respectively. A relatively low-Se environment includes the central and northern areas of Taoyuan County, where Middle and Upper Cambrian and Ordovician carbonate rocks and Cretaceous sandstones and conglomerates outcrop. These results indicate that Se distribution in Taoyuan County varies markedly and is controlled by the Se content of the bedrock. The Se-enriched Lower Cambrian and Ediacaran black rock series is the primary source of the seleniferous environment observed in Taoyuan County. Potential seleniferous environments are likely to be found near outcrops of the Lower Cambrian and Ediacaran black rock series in southern China.

Application of Multivariate Statistical Analysis to Biomarkers in Se-Turkey Crude Oils

NASA Astrophysics Data System (ADS)

Gürgey, K.; Canbolat, S.

2017-11-01

Twenty-four crude oil samples were collected from the 24 oil fields distributed in different districts of SE-Turkey. API and Sulphur content (%), Stable Carbon Isotope, Gas Chromatography (GC), and Gas Chromatography-Mass Spectrometry (GC-MS) data were used to construct a geochemical data matrix. The aim of this study is to examine the genetic grouping or correlations in the crude oil samples, hence the number of source rocks present in the SE-Turkey. To achieve these aims, two of the multivariate statistical analysis techniques (Principle Component Analysis [PCA] and Cluster Analysis were applied to data matrix of 24 samples and 8 source specific biomarker variables/parameters. The results showed that there are 3 genetically different oil groups: Batman-Nusaybin Oils, Adıyaman-Kozluk Oils and Diyarbakir Oils, in addition to a one mixed group. These groupings imply that at least, three different source rocks are present in South-Eastern (SE) Turkey. Grouping of the crude oil samples appears to be consistent with the geographic locations of the oils fields, subsurface stratigraphy as well as geology of the area.

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.

Lithologic characterization of active ITD aggregate sources and implications for aggregate quality.

DOT National Transportation Integrated Search

2014-03-01

Aggregate from 40 material sources across Idaho were sampled and the lithologies identified quantitatively. Aggregate compositions are compared with commercial AASHTO T 303 and ASTM C1293 results and the geologic map of Idaho to identify those rock t...

The thermal maturation degree of organic matter from source rocks revealed by wells logs including examples from Murzuk Basin, Libya

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

Negoita, V.; Gheorghe, A.

1995-08-01

The customary technique used to know the organic matter quantity per rock volume it as well as the organic matter maturation stage is based on geochemical analyses accomplished on a preselected number of samples and cuttings drawn from boreholes during the drilling period. But the same objectives can be approached without any extra cost using the continuous measurements of well logs recorded in each well from the ground surface to the total depth. During the diagenetic stage, the identification of potential source rocks out of which no hydrocarbon have been generated may be carried out using a well logging suitemore » including Gamma Ray Spectrometry, the Compensated Neutron/Litho Density combination and a Dual Induction/Sonic Log. During the catagenetic stage the onset of oil generation brings some important changes in the organic matter structure as well as in the fluid distribution throughout the pore space of source rocks. The replacement of electric conductive water by electric non-conductive hydrocarbons, together with water and oil being expelled from source rocks represent a process of different intensities dependent of time/temperature geohistory and kerogen type. The different generation and expulsion scenarios of hydrocarbons taking place during the catagenetic and metagenetic stages of source rocks are very well revealed by Induction and Laterolog investigations. Several crossplots relating vitrinite reflectance, total organic carbon and log-derived physical parameters are illustrated and discussed. The field applications are coming from Murzuk Basin, where Rompetrol of Libya is operating.« less

Origin of middle rare earth element enrichments in acid waters of a Canadian high Arctic lake.

NASA Astrophysics Data System (ADS)

Johannesson, Kevin H.; Zhou, Xiaoping

1999-01-01

-Middle rare earth element (MREE) enriched rock-normalized rare earth element (REE) patterns of a dilute acidic lake (Colour Lake) in the Canadian High Arctic, were investigated by quantifying whole-rock REE concentrations of rock samples collected from the catchment basin, as well as determining the acid leachable REE fraction of these rocks. An aliquot of each rock sample was leached with 1 N HNO 3 to examine the readily leachable REE fraction of each rock, and an additional aliquot was leached with a 0.04 M NH 2OH · HCl in 25% (v/v) CH 3COOH solution, designed specifically to reduce Fe-Mn oxides/oxyhydroxides. Rare earth elements associated with the leachates that reacted with clastic sedimentary rock samples containing petrographically identifiable Fe-Mn oxide/oxyhydroxide cements and/or minerals/amorphous phases, exhibited whole-rock-normalized REE patterns similar to the lake waters, whereas whole-rock-normalized leachates from mafic igneous rocks and other clastic sedimentary rocks from the catchment basin differed substantially from the lake waters. The whole-rock, leachates, and lake water REE data support acid leaching or dissolution of MREE enriched Fe-Mn oxides/oxyhydroxides contained and identified within some of the catchment basin sedimentary rocks as the likely source of the unique lake water REE patterns. Solution complexation modelling of the REEs in the inflow streams and lake waters indicate that free metal ions (e.g., Ln 3+, where Ln = any REE) and sulfate complexes (LnSO 4+) are the dominant forms of dissolved REEs. Consequently, solution complexation reactions involving the REEs during weathering, transport to the lake, or within the lake, cannot be invoked to explain the MREE enrichments observed in the lake waters.

Strontium and neodymium isotope systematics of target rocks and impactites from the El'gygytgyn impact structure: Linking impactites and target rocks

NASA Astrophysics Data System (ADS)

Wegner, Wencke; Koeberl, Christian

2016-12-01

The 3.6 Ma El'gygytgyn structure, located in northeastern Russia on the Chukotka Peninsula, is an 18 km diameter complex impact structure. The bedrock is formed by mostly high-silica volcanic rocks of the 87 Ma old Okhotsk-Chukotka Volcanic Belt (OCVB). Volcanic target rocks and impact glasses collected on the surface, as well as drill core samples of bedrock and impact breccias have been investigated by thermal ionization mass spectrometry (TIMS) to obtain new insights into the relationships between these lithologies in terms of Nd and Sr isotope systematics. Major and trace element data for impact glasses are added to compare with the composition of target rocks and drill core samples. Sr isotope data are useful tracers of alteration processes and Nd isotopes reveal characteristics of the magmatic sources of the target rocks, impact breccias, and impact glasses. There are three types of target rocks mapped on the surface: mafic volcanics, dacitic tuff and lava of the Koekvun' Formation, and dacitic to rhyolitic ignimbrite of the Pykarvaam Formation. The latter represents the main contributor to the impact rocks. The drill core is divided into a suevite and a bedrock section by the Sr isotope data, for which different postimpact alteration regimes have been detected. Impact glasses from the present-day surface did not suffer postimpact hydrothermal alteration and their data indicate a coherent alteration trend in terms of Sr isotopes with the target rocks from the surface. Surprisingly, the target rocks do not show isotopic coherence with the Central Chukotka segment of the OCVB or with the Berlozhya magmatic assemblage (BMA), a late Jurassic felsic volcanic suite that crops out in the eastern part of the central Chukotka segment of the OCVB. However, concordance for these rocks exists with the Okhotsk segment of the OCVB. This finding argues for variable source magmas having contributed to the build-up of the OCVB.

Petrologic evolution of Miocene-Pliocene mafic volcanism in the Kangal and Gürün basins (Sivas-Malatya), central east Anatolia: Evidence for Miocene anorogenic magmas contaminated by continental crust

NASA Astrophysics Data System (ADS)

Kocaarslan, Ayça; Ersoy, E. Yalçın

2018-06-01

This study discusses the geochemical features of the Early-Middle Miocene and Pliocene basaltic (SiO2 = 46-52; MgO = 6-10 wt%) to andesitic (SiO2 = 59; MgO = 4 wt%) rocks exposed in the Gürün and Kangal basins (Sivas, eastern part of central Anatolia), respectively. The basaltic rocks are characterized by alkaline to tholeiitic affinities, while the more evolved andesitic samples show calc-alkaline affinity. Trace element variations reveal that they can be evaluated in three sub-groups, each represented by different contents of trace elements for given Nb contents. Primary magmas of each groups were likely produced by different degrees of partial melting ( 1-2, 2-3, 7-10% respectively) from a common mantle source, subsequently underwent different degrees of fractionation and crustal contamination. Derivation from a common mantle source of the primitive magmas of each group is supported by similar Sr, Nd and Pb isotopic ratios. Increasing degrees of partial melting seem to be responsible for the alkaline to tholeiitic variation among the basaltic samples, while higher degrees of crustal contamination (AFC) resulted in calc-alkaline affinity of the more evolved samples. Most primitive Pliocene samples show intra-plate (anorogenic) geochemical features, while the more evolved Miocene calc-alkaline samples resemble geochemically subduction-related (orogenic) magmatic rocks. However, on the basis of detailed geochemical models, we propose that the calc-alkaline affinity among the Miocene samples can also be gained by crustal contamination of their primary magmas which were also anorogenic in character. If this is true, overall, the Miocene and Pliocene basaltic to andesitic rocks in the Gürün and Kangal basins appear to may have formed by variable degrees of partial melting of a common anorogenic mantle that had not been subject to subduction-related metasomatism. This is an alternative approach to the general view assuming the Early-Middle Miocene magmatic activity in the region was derived from subduction-modified mantle sources in response to subduction of the Arabian Plate under the Anatolian Plate. This hypothesis further implies that either delamination of the sub-continental lithosphere or slab break-off processes beneath the central to eastern Anatolia might took place well before the Miocene, thus allowing upwelling unaltered mantle to provide the source of the Miocene to Pliocene volcanic rocks.

Thermal maturity of type II kerogen from the New Albany Shale assessed by13C CP/MAS NMR

USGS Publications Warehouse

Werner-Zwanziger, U.; Lis, G.; Mastalerz, Maria; Schimmelmann, A.

2005-01-01

Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance. ?? 2004 Elsevier Inc. All rights reserved.

Re-Os isotopic evidence for an enriched-mantle source for the Noril'sk-type, ore-bearing intrusions, Siberia

USGS Publications Warehouse

Walker, R.J.; Morgan, J.W.; Horan, M.F.; Czamanske, G.K.; Krogstad, E.J.; Fedorenko, V.A.; Kunilov, V.E.

1994-01-01

Magmatic Cu-Ni sulfide ores and spatially associated ultramafic and mafic rocks from the Noril'sk I, Talnakh, and Kharaelakh intrusions are examined for Re-Os isotopic systematics. Neodymium and lead isotopic data also are reported for the ultramafic and mafic rocks. The Re-Os data for most samples indicate closed-system behavior since the ca. 250 Ma igneous crystallization age of the intrusions. There are small but significant differences in the initial osmium isotopic compositions of samples from the three intrusions. Ores from the Noril'sk I intrusion have ??Os values that vary from +0.4 to +8.8, but average +5.8. Ores from the Talnakh intrusion have ??Os values that range from +6.7 to +8.2, averaging +7.7. Ores from the Kharaelakh intrusion have ??Os values that range from +7.8 to +12.9, with an average value of +10.4. The osmium isotopic compositions of the ore samples from the Main Kharaelakh orebody exhibit minimal overlap with those for the Noril'sk I and Talnakh intrusions, indicating that these Kharaelakh ores were derived from a more radiogenic source of osmium than the other ores. Combined osmium and lead data for major orebodies in the three intrusions plot in three distinct fields, indicating derivation of osmium and lead from at least three isotopically distinct sources. Some of the variation in lead isotopic compositions may be the result of minor lower-crustal contamination. However, in contrast to most other isotopic and trace element data, Os-Pb variations are generally inconsistent with significant crustal contamination or interaction with the subcontinental lithosphere. Thus, the osmium and lead isotopic compositions of these intrusions probably reflect quite closely the compositions of their mantle source, and suggest that these two isotope systems were insensitive to lithospheric interaction. Ultramafic and mafic rocks have osmium and lead isotopic compositions that range only slightly beyond the compositions of the ores. These rocks also have relatively uniform ??{lunate}Nd values that range only from -0.8 to + 1.1. This limited variation in neodymium isotopic composition may reflect the characteristics of the mantle sources of the rocks, or it may indicate that somehow similar proportions of crust contaminated the parental melts. The osmium, lead, and neodymium isotopic data for these rocks most closely resemble the mantle sources of certain ocean island basalts (OIB), such as some Hawaiian basalts. Hence, these data are consistent with derivation of primary melts from a mantle source similar to that of some types of hotspot activity. The long-term Re/Os enrichment of this and similar mantle sources, relative to chondritic upper mantle, may reflect 1. (1) incorporation of recycled oceanic crust into the source more than 1 Ga ago, 2. (2) derivation from a mantle plume that originated at the outer core-lower mantle interface, or 3. (3) persistence of primordial stratification of rhenium and osmium in the mantle. ?? 1994.

Evaluation of stress and saturation effects on seismic velocity and electrical resistivity - laboratory testing of rock samples

NASA Astrophysics Data System (ADS)

Vilhelm, Jan; Jirků, Jaroslav; Slavík, Lubomír; Bárta, Jaroslav

2016-04-01

Repository, located in a deep geological formation, is today considered the most suitable solution for disposal of spent nuclear fuel and high-level waste. The geological formations, in combination with an engineered barrier system, should ensure isolation of the waste from the environment for thousands of years. For long-term monitoring of such underground excavations special monitoring systems are developed. In our research we developed and tested monitoring system based on repeated ultrasonic time of flight measurement and electrical resistivity tomography (ERT). As a test site Bedřichov gallery in the northern Bohemia was selected. This underground gallery in granitic rock was excavated using Tunnel Boring Machine (TBM). The seismic high-frequency measurements are performed by pulse-transmission technique directly on the rock wall using one seismic source and three receivers in the distances of 1, 2 and 3 m. The ERT measurement is performed also on the rock wall using 48 electrodes. The spacing between electrodes is 20 centimeters. An analysis of relation of seismic velocity and electrical resistivity on water saturation and stress state of the granitic rock is necessary for the interpretation of both seismic monitoring and ERT. Laboratory seismic and resistivity measurements were performed. One series of experiments was based on uniaxial loading of dry and saturated granitic samples. The relation between stress state and ultrasonic wave velocities was tested separately for dry and saturated rock samples. Other experiments were focused on the relation between electrical resistivity of the rock sample and its saturation level. Rock samples with different porosities were tested. Acknowledgments: This work was partially supported by the Technology Agency of the Czech Republic, project No. TA 0302408

U-Th-Pb systematics of some Apollo 17 lunar samples and implications for a lunar basin excavation chronology

NASA Technical Reports Server (NTRS)

Nunes, P. D.; Tatsumoto, M.; Unruh, D. M.

1974-01-01

U, Th, and Pb concentrations and lead isotopic compositions of selected Apollo 17 soil and rock samples are presented. Concordia treatments of U-Pb whole samples of Apollo 17 mare basalts and highland rocks probably reflect several early thermal events about 4.5 b.y. old more consistently than do U-Pb ages of samples collected at other lunar sites. We propose that all lunar U-Th-Pb data reflect a multistate U-Pb evolution history most easily understood as being related to a complex planetesimal bombardment history of the moon which apparently dominated lunar events from about 4.5 to about 3.9 b.y. ago. Semi-distinct events at about 4.0, about 4.2, and 4.4-4.5 b.y. are evident on whole-rock frequency versus Pb-207/Pb-206 age histograms. Each of these events may reflect multiple cratering episodes. For mare basalts, complete resetting of the source rock U-Pb systems owing to Pb loss relative to U was apparently often approached after a major planetesimal impact.

Material-balance assessment of the New Albany-Chesterian petroleum system of the Illinois basin

USGS Publications Warehouse

Lewan, M.D.; Henry, M.E.; Higley, D.K.; Pitman, Janet K.

2002-01-01

The New Albany-Chesterian petroleum system of the Illinois basin is a well-constrained system from which petroleum charges and losses were quantified through a material-balance assessment. This petroleum system has nearly 90,000 wells penetrating the Chesterian section, a single New Albany Shale source rock accounting for more than 99% of the produced oil, well-established stratigraphic and structural frameworks, and accessible source rock samples at various maturity levels. A hydrogen index (HI) map based on Rock-Eval analyses of source rock samples of New Albany Shale defines the pod of active source rock and extent of oil generation. Based on a buoyancy-drive model, the system was divided into seven secondary-migration catchments. Each catchment contains a part of the active pod of source rock from which it derives a petroleum charge, and this charge is confined to carrier beds and reservoirs within these catchments as accountable petroleum, petroleum losses, or undiscovered petroleum. A well-constrained catchment with no apparent erosional or leakage losses is used to determine an actual petroleum charge from accountable petroleum and residual migration losses. This actual petroleum charge is used to calibrate the other catchments in which erosional petroleum losses have occurred. Petroleum charges determined by laboratory pyrolysis are exaggerated relative to the actual petroleum charge. Rock-Eval charges are exaggerated by a factor of 4-14, and hydrouspyrolysis charges are exaggerated by a factor of 1.7. The actual petroleum charge provides a more meaningful material balance and more realistic estimates of petroleum losses and remaining undiscovered petroleum. The total petroleum charge determined for the New Albany-Chesterian system is 78 billion bbl, of which 11.4 billion bbl occur as a accountable in place petroleum, 9 billion bbl occur as residual migration losses, and 57.6 billion bbl occur as erosional losses. Of the erosional losses, 40 billion bbl were lost from two catchments that have highly faulted and extensively eroded sections. Anomalies in the relationship between erosional losses and degree of erosion suggest there is potential for undiscovered petroleum in one of the catchments. These results demonstrate that a material-balance assessment of migration catchments provides a useful means to evaluate and rank areas within a petroleum system. The article provides methodologies for obtaining more realistic petroleum charges and losses that can be applied to less data-rich petroleum systems.

Geochemical Analyses of Rock, Sediment, and Water from the Region In and Around the Tuba City Landfill, Tuba City, Arizona

USGS Publications Warehouse

Johnson, Raymond H.; Wirt, Laurie

2009-01-01

The Tuba City Landfill (TCL) started as an unregulated waste disposal site in the 1940s and was administratively closed in 1997. Since the TCL closure, radionuclides have been detected in the shallow ground water. In 2006, the Bureau of Indian Affairs (BIA) contracted with the U.S. Geological Survey (USGS) to better understand the source of radionuclides in the ground water at the TCL compared to the surrounding region. This report summarizes those data and presents interpretations that focus on the geochemistry in the rocks and water from the Tuba City region. The TCL is sited on Navajo Sandstone above the contact with the Kayenta Formation. These formations are not rich in uranium but generally are below average crustal abundance values for uranium. Uranium ores in the area were mined nearby in the Chinle Formation and processed at the Rare Metals mill (RMM). Regional samples of rock, sediment, leachates, and water were collected in and around the TCL site and analyzed for major and minor elements, 18O, 2H, 3H, 13C, 14C,34S, 87Sr, and 234U/238U, as appropriate. Results of whole rock and sediment samples, along with leachates, suggest the Chinle Formation is a major source of uranium and other trace elements in the area. Regional water samples indicate that some of the wells within the TCL site have geochemical signatures that are different from the regional springs and surface water. The geochemistry from these TCL wells is most similar to leachates from the Chinle Formation rocks and sediments. Isotope samples do not uniquely identify TCL-derived waters, but they do provide a useful indicator for shallow compared to deep ground-water flow paths and general rock/water interaction times. Information in this report provides a comparison between the geochemistry within the TCL and in the region as a whole.

Detrital zircon U-Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico

USGS Publications Warehouse

Gehrels, G.E.; Stewart, John H.

1998-01-01

One hundred and eighty two individual detrital zircon grains from Cambrian through Permian miogeoclinal strata, Ordovician eugeoclinal rocks, and Triassic post-orogenic sediments in northwestern Sonora have been analyzed. During Cambrian, Devonian, Permian, and Triassic time, most zircons accumulating along this part of the Cordilleran margin were shed from 1.40-1.45 and 1.62-1.78 Ga igneous rocks that are widespread in the southwestern United States and northwestern Mexico. Zircons with ages of approximately 1.11 Ga are common in Cambrian strata and were apparently shed from granite bodies near the sample site. The sources of 225-280 Ma zircons in our Triassic sample are more problematic, as few igneous rocks of these ages are recognized in northwestern Mexico. Such sources may be present but unrecognized, or the grains could have been derived from igneous rocks of the appropriate ages to the northwest in the Mojave Desert region, to the east in Chihuahua and Coahuila, or to the south in accreted(?) arc-type terranes. Because the zircon grains in our Cambrian and Devonian to Triassic samples could have accumulated in proximity to basement rocks near their present position or in the Death Valley region of southern California, our data do not support or refute the existence of the Mojave-Sonora megashear. Ordovician strata of both miogeoclinal and eugeoclinal affinity are dominated by >1.77 Ga detrital zircons, which are considerably older than most basement rocks in the region. Zircon grains in the miogeoclinal sample were apparently derived from the Peace River arch area of northwestern Canada and transported southward by longshore currents. The eugeoclinal grains may also have come from the Peace River arch region, with southward transport by either sedimentary or tectonic processes, or they may have been shed from off-shelf slivers of continents (perhaps Antarctica?) removed from the Cordilleran margin during Neoproterozoic rifting. It is also possible that the Ordovician eugeoclinal strata are far traveled and exotic to North America.

Hydrogeochemical Investigations of Historic Mining Districts, Central Western Slope of Colorado, Including Influence on Surface-Water Quality

USGS Publications Warehouse

Nash, J. Thomas

2002-01-01

This report describes reconnaissance hydrogeochemical investigations of 22 mining districts on the Western Slope of Colorado in the Gunnison and Uncompahgre National Forests and adjacent public lands administered by the Bureau of Land Management. Sources and fates of contaminants from historic mines, mine waste, and mill tailings are interpreted from chemical analyses for 190 samples of surface waters; 185 samples of mined rocks, mill tailings, and altered rocks; and passive leach analyses of 116 samples of those mineralized materials. Short reaches of several headwater streams show relatively low level effects of historic mining; the headwaters of the Uncompahgre River are highly contaminated by mines and unmined altered rocks in the Red Mountain district. There is encouraging evidence that natural processes attenuate mine-related contamination in most districts.

Geochemical constraints on the petrogenesis of the pyroclastic rocks in Abakaliki basin (Lower Benue Rift), Southeastern Nigeria

NASA Astrophysics Data System (ADS)

Chukwu, Anthony; Obiora, Smart C.

2018-05-01

The pyroclastic rocks in the Cretaceous Abakaliki basin occur mostly as oval-shaped bodies, consisting of lithic/lava and vitric fragments. They are commonly characterized by parallel and cross laminations, as well contain xenoliths of shale, mudstone and siltstones from the older Asu River Group of Albian age. The rocks are basic to ultrabasic in composition, comprising altered alkali basalts, altered tuffs, minor lapillistones and agglomerates. The mineral compositions are characterized mainly by laths of calcic plagioclase, pyroxene (altered), altered olivines and opaques. Calcite, zeolite and quartz represent the secondary mineral constituents. Geochemically, two groups of volcaniclastic rocks, are distinguished: alkaline and tholeiitic rocks, both represented by fresh and altered rock samples. The older alkali basalts occur within the core of the Abakaliki anticlinorium while the younger tholeiites occur towards the periphery. Though most of the rocks are moderate to highly altered [Loss on ignition (LOI, 3.43-22.07 wt. %)], the use of immobile trace element such as Nb, Zr, Y, Hf, Ti, Ta and REEs reflect asthenospheric mantle source compositions. The rocks are enriched in incompatible elements and REEs (∑REE = 87.98-281.0 ppm for alkaline and 69.45-287.99 ppm for tholeiites). The ratios of La/Ybn are higher in the alkaline rocks ranging from 7.69 to 31.55 compared to the tholeiitic rocks which range from 4.4 to 16.89 and indicating the presence of garnet-bearing lherzolite in the source mantle. The spidergrams and REEs patterns along with Zr/Nb, Ba/Nb, Rb/Nb ratios suggest that the rocks were generated by a mantle plume from partial melting of mixed enriched mantle sources (HIMU, EMI and EMII) similar to the rocks of the south Atlantic Ocean such as St. Helena (alkaline rocks) and Ascension rocks (tholeiitic rocks). The rocks were formed in a within-plate setting of the intra-continental rift type similar to other igneous rocks in the Benue Rift and are not related to any subduction event as previously suggested.

delta 15N and non-carbonate delta 13C values for two petroleum source rock reference materials and a marine sediment reference material

USGS Publications Warehouse

Dennen, Kristin O.; Johnson, Craig A.; Otter, Marshall L.; Silva, Steven R.; Wandless, Gregory A.

2006-01-01

Samples of United States Geological Survey (USGS) Certified Reference Materials USGS Devonian Ohio Shale (SDO-1), and USGS Eocene Green River Shale (SGR-1), and National Research Council Canada (NRCC) Certified Marine Sediment Reference Material (PACS-2), were sent for analysis to four separate analytical laboratories as blind controls for organic rich sedimentary rock samples being analyzed from the Red Dog mine area in Alaska. The samples were analyzed for stable isotopes of carbon (delta13Cncc) and nitrogen (delta15N), percent non-carbonate carbon (Wt % Cncc) and percent nitrogen (Wt % N). SDO-1, collected from the Huron Member of the Ohio Shale, near Morehead, Kentucky, and SGR-1, collected from the Mahogany zone of the Green River Formation are petroleum source rocks used as reference materials for chemical analyses of sedimentary rocks. PACS-2 is modern marine sediment collected from the Esquimalt, British Columbia harbor. The results presented in this study are, with the exceptions noted below, the first published for these reference materials. There are published information values for the elemental concentrations of 'organic' carbon (Wt % Corg measured range is 8.98 - 10.4) and nitrogen (Wt % Ntot 0.347 with SD 0.043) only for SDO-1. The suggested values presented here should be considered 'information values' as defined by the NRCC Institute for National Measurement Reference Materials and should be useful for the analysis of 13C, 15N, C and N in organic material in sedimentary rocks.

Geochemistry

NASA Technical Reports Server (NTRS)

Carr, M. H.; Toulmin, P., III

1976-01-01

The most effective strategy for the geochemical study of a planet is to proceed systematically with the mineralogical and chemical characterization of its materials in accordance with geologically determined priorities. It is insufficient merely to analyze chemically the surface rocks. To appreciate the meaning of a chemical analysis, some assessment must be made of the geologic history of the sample - what its source and mode of origin are and what processes have operated upon the sample to cause chemical fractionation. Determination of mineralogy, texture, lithology, and other properties of the rock that might be relevant to origin is, therefore, necessary.

Hydrocarbon source-rock evaluation - Solor Church Formation (middle Proterozoic, Keweenawan Supergroup), southeastern Minnesota

USGS Publications Warehouse

Hatch, J.R.; Morey, G.B.

1984-01-01

In the type section (Lonsdale 65-1 core, Rice County, Minnesota) the Solor Church Formation (Middle Proterozoic, Keweenawan Supergroup) consists primarily of reddish-brown mudstone and siltstone and pale reddish-brown sandstone. The sandstone and siltstone are texturally and mineralogically immature. Hydrocarbon source-rock evaluation of bluish-gray, greenish-gray and medium-dark-gray to grayish-black beds, which primarily occur in the lower 104 m (340 ft) of this core, shows: (1) the rocks have low organic carbon contents (<0.5 percent for 22 of 25 samples); (2) the organic matter is thermally very mature (Tmax = 494°C, sample 19) and is probably near the transition between the wet gas phase of catagenesis and metagenesis (dry gas zone); and (3) the rocks have minimal potential for producing additional hydrocarbons (genetic potential <0.30 mgHC/gm rock). Although no direct evidence exists from which to determine maximum depths of burial, the observed thermal maturity of the organic matter requires significantly greater depths of burial and(or) higher geothermal gradients. It is likely, at least on the St. Croix horst, that thermal alteration of the organic matter in the Solor Church took place relatively early, and that any hydrocarbons generated during this early thermal alteration were probably lost prior to deposition of the overlying Fond du Lac Formation (Middle Proterozoic, Keweenawan Supergroup).

Hydrocarbon source rock evaluation: Solor Church Formation. (Middle Proterozoic, Keweenawan Supergroup) southeastern Minnesota

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

Hatch, J.R.; Morey, G.B.

In the type section (Lonsdale 65-1 core, Rice County, Minnesota) the Solar Church Formation (Middle Proterozoic, Keweenawan Supergroup) consists primarily of reddish-brown mudstone and siltstone and pale reddish-brown sandstone. The sandstone and siltstone are texturally and mineralogically immature. Hydrocarbon source-rock evaluation of bluish-gray, greenish-gray and medium-dark-gray to grayish-black beds, which primarily occur in the lower 104 m (340 ft) of this core, shows: (1) the rocks have low organic carbon contents (<0.5% for 22 of 25 samples); (2) the organic matter is thermally very mature (T/sub max/ = 494/sup 0/C, sample 19) and is probably near the transition between themore » wet gas phase of catagenesis and metagenesis (dry gas zone); and (3) the rocks have minimal potential for producing additional hydrocarbons (genetic potential <0.30 mgHC/gm rock). Although no direct evidence exists from which to determine maximum depths of burial, the observed thermal maturity of the organic matter requires significantly greater depths of burial and(or) higher geothermal gradients. It is likely, at least on the St. Croix horst, that thermal alteration of the organic matter in the Solor Church took place relatively early, and that any hydrocarbons generated during this early thermal alteration were probably lost prior to deposition of the overlying Fond du Lac Formation (Middle Proterozoic, Keweenawan Supergroup). 5 figs., 2 tabs.« less

Palaeoenvironment and Its Control on the Formation of Miocene Marine Source Rocks in the Qiongdongnan Basin, Northern South China Sea

PubMed Central

Li, Wenhao; Zhang, Zhihuan; Wang, Weiming; Lu, Shuangfang; Li, Youchuan; Fu, Ning

2014-01-01

The main factors of the developmental environment of marine source rocks in continental margin basins have their specificality. This realization, in return, has led to the recognition that the developmental environment and pattern of marine source rocks, especially for the source rocks in continental margin basins, are still controversial or poorly understood. Through the analysis of the trace elements and maceral data, the developmental environment of Miocene marine source rocks in the Qiongdongnan Basin is reconstructed, and the developmental patterns of the Miocene marine source rocks are established. This paper attempts to reveal the hydrocarbon potential of the Miocene marine source rocks in different environment and speculate the quality of source rocks in bathyal region of the continental slope without exploratory well. Our results highlight the palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin of the northern South China Sea and speculate the hydrocarbon potential of the source rocks in the bathyal region. This study provides a window for better understanding the main factors influencing the marine source rocks in the continental margin basins, including productivity, preservation conditions, and the input of terrestrial organic matter. PMID:25401132

Aquifers survey in the context of source rocks exploitation: from baseline acquisition to long term monitoring

NASA Astrophysics Data System (ADS)

Garcia, Bruno; Rouchon, Virgile; Deflandre, Jean-Pierre

2017-04-01

Producing hydrocarbons from source rocks (like shales: a mix of clays, silts, carbonate and sandstone minerals containing matured organic matter, i.e. kerogen oil and gas, but also non-hydrocarbon various species of chemical elements including sometimes radioactive elements) requires to create permeability within the rock matrix by at least hydraulically fracturing the source rock. It corresponds to the production of hydrocarbon fuels that have not been naturally expelled from the pressurized matured source rock and that remain trapped in the porosity or/and kerogen porosity of the impermeable matrix. Azimuth and extent of developed fractures can be respectively determined and mapped by monitoring the associated induced microseismicity. This allows to have an idea of where and how far injected fluids penetrated the rock formation. In a geological context, aquifers are always present in the vicinity -or on fluid migration paths- of such shale formations: deep aquifers (near the shale formation) up to sub-surface and potable (surface) aquifers. Our purpose will be to track any unsuitable invasion or migration of chemicals specifies coming from matured shales of production fluids including both drilling and fracturing ones into aquifers. Our objective is to early detect and alarm of any anomaly to avoid any important environmental issue. The approach consists in deploying a specific sampling tool within a well to recover formation fluids and to run a panoply of appropriate laboratory tests to state on fluid characteristics. Of course for deep aquifers, such a characterization process may consider aquifer properties prior producing shale oil and gas, as they may contain naturally some chemical species present in the source rocks. One can also consider that a baseline acquisition could be justified in case of possible previous invasion of non-natural fluids in the formation under survey (due to any anthropogenic action at surface or in the underground). The paper aims at presenting the protocol and routine test we propose to make our early detection approach efficient for production of shale hydrocarbon fluids, in considering the source-rock reservoir itself, the aquifers, and also the chemical species present in the fluids that are used for hydraulic fracturing operations.

Sm-Nd isotopic systematics of the ancient Gneiss complex, southern Africa

NASA Technical Reports Server (NTRS)

Carlson, R. W.; Hunter, D. R.; Barker, F.

1983-01-01

In order to shed some new light on the question of the absolute and relative ages of the Ancient Gneiss Complex and Onverwacht Group, a Sm-Nd whole-rock and mineral isochron study of the AGC was begun. At this point, the whole-rock study of samples from the Bimodal Suite selected from those studied for their geochemical characteristics by Hunter et al., is completed. These results and their implications for the chronologic evolution of the Kaapvaal craton and the sources of these ancient rocks are discussed.

Permian arc-back-arc basin development along the Ailaoshan tectonic zone: Geochemical, isotopic and geochronological evidence from the Mojiang volcanic rocks, Southwest China

NASA Astrophysics Data System (ADS)

Fan, Weiming; Wang, Yuejun; Zhang, Aimei; Zhang, Feifei; Zhang, Yuzhi

2010-10-01

This paper presents a set of new SHRIMP zircon U-Pb geochronological, elemental and Sr-Nd-Pb isotopic data for the Wusu and Yaxuanqiao basaltic rocks (the Mojiang area) along the Ailaoshan tectonic zone. The Wusu basaltic sequence is dominated by SiO 2-poor, MgO- and TiO 2-rich basalts with a major mineral assemblage of plagioclase + clinopyroxene. These rocks gave a SHRIMP zircon U-Pb age of 287 ± 5 Ma (MSWD = 0.58). In contrast, the Yaxuanqiao basaltic sequence is predominantly composed of high-Al basaltic andesite, which gave a SHRIMP zircon U-Pb age of 265 ± 7 Ma (MSWD = 0.34). The analyzed samples for both sequences exhibit significant enrichment in LILEs and depletion in HFSEs with (Nb/La)n of 0.38-0.81, similar to arc-like volcanics. They have positive ɛNd(t) values (+ 3.52 to + 5.54). In comparison with MORB-derived magmatic rocks, the Wusu basalts are more enriched in LILEs and REEs, and the Yaxuanqiao samples are more enriched in LILEs but variably depleted in Ti, Y and HREE. The Wusu samples show high Pb isotopic ratios, similar to the Tethyan basalts, whereas the Yaxuanqiao samples plot in the field of the global pelagic sediments. The geochemical and Sr-Nd-Pb isotopic characteristics suggest that the Wusu basalts originated from a MORB-like source metasomatised by slab-derived fluids, while the Yaxuanqiao rocks have a fluid-modified MORB source with the input of subducted sediments. The geochemical affinity to both MORB- and arc-like sources, together with other geological observations, appears to support the development of a Permian arc-back-arc basin along the Ailaoshan-Song Ma tectonic zone in response to the northward subduction of the Paleotethys main Ocean. The final closure of the arc-back-arc basin took place in the uppermost Triassic due to the diachronous amalgamation between the Yangtze and Simao-Indochina Blocks.

Two Distinct Sets of Magma Sources in Cretaceous Rocks From Magnet Cove, Prairie Creek, and Other Igneous Centers of the Arkansas Alkaline Province, USA

NASA Astrophysics Data System (ADS)

Duke, G. I.; Carlson, R. W.; Eby, G. N.

2008-12-01

Two distinct sets of magma sources from the Arkansas alkaline province (~106-89 Ma) are revealed by Sr-Nd-Pb isotopic compositions of olivine lamproites vs. other alkalic rock types, including carbonatite, ijolite, lamprophyres, tephrite, malignite, jacupirangite, phonolite, trachyte, and latite. Isotopic compositions of diamond-bearing olivine lamproites from Prairie Creek and Dare Mine Knob point to Proterozoic lithosphere as an important source, and previous Re-Os isotopic data indicate derivation from subcontinental mantle lithosphere. Both sources were probably involved in lamproite generation. Magnet Cove carbonatites and other alkalic magmas were likely derived from an asthenospheric source. Lamproite samples are isotopically quite different from other rock types in Sr-Nd-Pb isotopic space. Although three lamproite samples from Prairie Creek have a large range of SiO2 contents (40-60 wt %), initial values of ɛNd (-10 to -13), 206Pb/204Pb (16.61-16.81), 207Pb/204Pb (15.34-15.36), and 208Pb/204Pb (36.57-36.76) are low and similar. Only 87Sr/86Sr(i) displays a wide range in the Prairie Creek lamproites (0.70627-0.70829). A fourth lamproite from Dare Mine Knob has the most negative ɛNd(i) of -19. Lamproite isotope values show a significant crustal component and isotopically overlap subalkalic rhyolites from the Black Hills (SD), which assimilated Proterozoic crust. Six samples of carbonatite, ijolite, and jacupirangite from Magnet Cove and Potash Sulphur Springs exhibit the most depleted Sr-Nd isotopic signatures of all samples. For these rock types, 87Sr/86Sr(i) is 0.70352 - 0.70396, and ɛNd(i) is +3.8 - +4.3. Eight other rock types have a narrow range of ɛNd(i) (+1.9 - +3.7), but a wide range of 87Sr/86Sr(i) (0.70424 - 0.70629). These 14 samples comprise a fairly tight cluster of Pb isotopic values: 206Pb/204Pb (18.22-19.23), 207Pb/204Pb (15.54-15.62), and 208Pb/204Pb (38.38-38.94), suggesting very little crustal assimilation. They are most similar to EM-2 (sub-group of OIB). Published ages of crustal amphibolite xenoliths from the Prairie Creek lamproite are Proterozoic (~1.32- 1.47 Ga), in keeping with isotopic evidence for crustal assimilation, including Tdm = 1.3-1.7 Ga. Published ages of lamproite (~106 Ma) indicate that these magmas intruded first, whereas carbonatites and other alkalic magmas were later (~102 to ~89 Ma). Asthenospheric upwelling first melted lithospheric mantle and crust, producing lamproitic magmas; asthenospheric magmas followed as swelling of the lithosphere ensued.

Numerical simulation and analysis for low-frequency rock physics measurements

NASA Astrophysics Data System (ADS)

Dong, Chunhui; Tang, Genyang; Wang, Shangxu; He, Yanxiao

2017-10-01

In recent years, several experimental methods have been introduced to measure the elastic parameters of rocks in the relatively low-frequency range, such as differential acoustic resonance spectroscopy (DARS) and stress-strain measurement. It is necessary to verify the validity and feasibility of the applied measurement method and to quantify the sources and levels of measurement error. Relying solely on the laboratory measurements, however, we cannot evaluate the complete wavefield variation in the apparatus. Numerical simulations of elastic wave propagation, on the other hand, are used to model the wavefield distribution and physical processes in the measurement systems, and to verify the measurement theory and analyze the measurement results. In this paper we provide a numerical simulation method to investigate the acoustic waveform response of the DARS system and the quasi-static responses of the stress-strain system, both of which use axisymmetric apparatus. We applied this method to parameterize the properties of the rock samples, the sample locations and the sensor (hydrophone and strain gauges) locations and simulate the measurement results, i.e. resonance frequencies and axial and radial strains on the sample surface, from the modeled wavefield following the physical experiments. Rock physical parameters were estimated by inversion or direct processing of these data, and showed a perfect match with the true values, thus verifying the validity of the experimental measurements. Error analysis was also conducted for the DARS system with 18 numerical samples, and the sources and levels of error are discussed. In particular, we propose an inversion method for estimating both density and compressibility of these samples. The modeled results also showed fairly good agreement with the real experiment results, justifying the effectiveness and feasibility of our modeling method.

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.

Uranium-Lead Zircon Ages and Sr, Nd, and Pb Isotope Geochemistry of Selected Plutonic Rocks from Western Idaho

USGS Publications Warehouse

Unruh, Daniel M.; Lund, Karen; Kuntz, Mel A.; Snee, Lawrence W.

2008-01-01

Across the Salmon River suture in western Idaho, where allochthonous Permian to Cretaceous oceanic rocks are juxtaposed against Proterozoic North American rocks, a wide variety of plutonic rocks are exposed. Available data indicate much variation in composition, source, and structural state of these plutons. The plutonic rocks were long described as the western border zone of the Cretaceous Idaho batholith but limited pre-existing age data indicate more complicated origins. Because the affinity and age of the plutonic rocks cannot be reliably determined from field relations, TIMS U-Pb dating in conjunction with Sr, Nd, and Pb isotopic studies of selected plutons across the suture in western Idaho were undertaken. The data indicate three general groups of plutons including (1) those that intruded the island arc terranes during the Triassic and Jurassic, those that intruded near the western edge of oceanic rocks along the suture in the Early Cretaceous, and the plutons of the Idaho batholith that intruded Proterozoic North American rocks in the Late Cretaceous. Plutons that intruded Proterozoic North American rocks commonly include xenocrystic zircons and in several cases, ages could not be determined. The least radiogenic Sr and most radiogenic Nd are found among the Blue Mountains superterrane island arc samples. Suture-zone plutons have isotopic characteristics that span the range between Idaho batholith and island arc samples but mostly follow island arc signatures. Plutons of the Idaho batholith have the most radiogenic initial Pb and Sr ratios and the least radiogenic Nd of the samples analyzed.

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.

Organic and clay mineral diagenesis in Neogene sediments of western Taiwan

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

Hsueh, C.M.

1985-01-01

Three deep wells (two in the northern region and one in the southern region) with completion depths of over 5000m have been selected and the rock samples thoroughly examined. The TOC data of most samples studied are less than 1%, which is the TOC of an average shale. The low TOC is unfavorable for the Neogene sediments in western Taiwan as good source rocks. The data of C,H elemental analysis and Rock-Eval pyrolysis imply that the quality of kerogen in the northern region inclines to type II wet-gas prone, and in the southern region inclines to type III dry-gas prone.more » The maturity parameters of bitumen ratio, vitrinite reflectance, Tmax of Rock-Eval pyrolysis, and TTI of Lopatin's method show that the threshold of the oil-generative zone (about 0.6% Ro) in the northern region is in middle Miocene (about 3000m) and in the southern region is in lower Pliocene (about 4500m). The result of clay mineral analysis reveals that the transformation of smectitic clays to ordered mixed-layered smectite-illite can be identified and correlated with 0.6% Ro vitrinite reflectance. The illite crystallinity values are in the range of incipient to weak metamorphism and decrease with burial depth implying that the source area of low-grade metamorphic rocks has been uplifted rapidly so that the erosion from the exposed source area where the metamorphic grade became higher and higher was sufficiently fast to prevent weathering of illite. The Neogene sediments studied would not be expected to generate substantial amounts of oil. However, it can be expected that the pre-Miocene sediments in the northern region and the pre-Pliocene sediments in the southern region should have generated substantial amounts of gas at deeper depths.« less

Oxidation state inherited from the magma source and implications for mineralization: Late Jurassic to Early Cretaceous granitoids, Central Lhasa subterrane, Tibet

NASA Astrophysics Data System (ADS)

Cao, MingJian; Qin, KeZhang; Li, GuangMing; Evans, Noreen J.; McInnes, Brent I. A.; Li, JinXiang; Zhao, JunXing

2018-03-01

Arc magmas are more oxidized than mid-ocean ridge basalts; however, there is continuing debate as to whether this higher oxidation state is inherited from the source magma or developed during late-stage magmatic differentiation processes. Well-constrained Late Jurassic to Early Cretaceous arc-related intermediate to felsic rocks derived from distinct magma sources provide us with a good opportunity to resolve this enigma. A series of granitoids from the western Central Lhasa subterrane were analyzed for whole-rock magnetic susceptibility, Fe2O3/FeO ratios, and trace elements in zircon. Compared to Late Jurassic samples (1.8 ± 2.0 × 10-4 emu g-1 oe-1, Fe3+/Fetotal = 0.32 ± 0.07, zircon Ce4+/Ce3+* = 15.0 ± 13.4), Early Cretaceous rocks show higher whole-rock magnetic susceptibility (5.8 ± 2.5 × 10-4 emu g-1 oe-1), Fe3+/Fetotal ratios (0.43 ± 0.04), and zircon Ce4+/Ce3+* values (23.9 ± 22.3). In addition, positive correlations among whole-rock magnetic susceptibility, Fe3+/Fetotal ratios, and zircon Ce4+/Ce3+* reveal a slight increase in oxidation state from fO2 = QFM to NNO in the Late Jurassic to fO2 = ˜NNO in the Early Cretaceous. Obvious linear correlation between oxidation indices (whole-rock magnetic susceptibility, zircon Ce4+/Ce3+*) and source signatures (zircon ɛHf(t), TDM C ages) indicates that the oxidation state was predominantly inherited from the source with only a minor contribution from magmatic differentiation. Thus, the sources for both the Late Jurassic and Early Cretaceous rocks were probably influenced by mantle wedge-derived magma, contributing to the increased fO2. Compared to ore-forming rocks at giant porphyry Cu deposits, the relatively low oxidation state (QFM to NNO) and negative ɛHf(t) (-16 to 0) of the studied granitoids implies relative infertility. However, this study demonstrates two potential fast and effective indices ( fO2 and ɛHf(t)) to evaluate the fertility of granitoids for porphyry-style mineralization. In an exploration context for the west Central Lhasa subterrane, features indicative of potential fertility might include more oxidized, positive ɛHf(t), young rocks (<130 Ma).

Diamondoid hydrocarbons as a molecular proxy for thermal maturity and oil cracking: Geochemical models from hydrous pyrolysis

USGS Publications Warehouse

Wei, Z.; Moldowan, J.M.; Zhang, S.; Hill, R.; Jarvie, D.M.; Wang, Hongfang; Song, F.; Fago, F.

2007-01-01

A series of isothermal hydrous pyrolysis experiments was performed on immature sedimentary rocks and peats of different lithology and organic source input to explore the generation of diamondoids during the thermal maturation of sediments. Oil generation curves indicate that peak oil yields occur between 340 and 360 ??C, followed by intense oil cracking in different samples. The biomarker maturity parameters appear to be insensitive to thermal maturation as most of the isomerization ratios of molecular biomarkers in the pyrolysates have reached their equilibrium values. Diamondoids are absent from immature peat extracts, but exist in immature sedimentary rocks in various amounts. This implies that they are not products of biosynthesis and that they may be generated during diagenesis, not just catagenesis and cracking. Most importantly, the concentrations of diamondoids are observed to increase with thermal stress, suggesting that they can be used as a molecular proxy for thermal maturity of source rocks and crude oils. Their abundance is most sensitive to thermal exposure above temperatures of 360-370 ??C (R0 = 1.3-1.5%) for the studied samples, which corresponds to the onset of intense cracking of other less stable components. Below these temperatures, diamondoids increase gradually due to competing processes of generation and dilution. Calibrations were developed between their concentrations and measured vitrinite reflectance through hydrous pyrolysis maturation of different types of rocks and peats. The geochemical models obtained from these methods may provide an alterative approach for determining thermal maturity of source rocks and crude oils, particularly in mature to highly mature Paleozoic carbonates. In addition, the extent of oil cracking was quantified using the concentrations of diamondoids in hydrous pyrolysates of rocks and peats, verifying that these hydrocarbons are valuable indicators of oil cracking in nature. ?? 2006 Elsevier Ltd. All rights reserved.

Rock-forming metals and Pb in modern Alaskan snow

USGS Publications Warehouse

Hinkley, Todd K.

1993-01-01

Metal concentrations in annual and subannual increments of snowpack from the accumulation zone of a south central Alaska glacier indicate that the deposition of Pb with and upon snow is decoupled from that of rock dusts. Rock dusts accumulate, apparently as dry deposition, on the topmost, exposed surfaces of snowpacks in spring and summer, whereas Pb does not. Pb concentration is elevated throughout the latest one third of an annual snowpack, whereas that of rock dusts is not. For whole-year snowpacks, there is a generally sympathetic relationship among concentration of Pb, concentration of rock dust, degree of dominance of rock dusts over ocean solutes, and ferromagnesian character of the rock dusts; however, the fractional abundance of Pb in whole year samples may decrease when rock dust masses become large and/or when rock dusts dominate most strongly over salts. The metal suite chosen to characterize rock dusts and to distinguish them from ocean solutes gives detailed information about rock type of dust source areas and about the nature of the degraded rock products that are taken up, transported, and deposited by the atmosphere. Rock dusts are present at concentrations of only about 300 nanograms (ng) of dust per gram of snow in the Alaskan snowpacks. Concentrations of Pb in the Alaska snow samples are moderate, ranging from 0.1 to 0.3 ng Pb/g snow. This contrasts with larger Pb concentrations of 0.4 to 0.9 ng Pb/g snow in whole-year snowpack samples from the Sierra Nevada, California; with similar to smaller concentrations from north and south Greenland of about 0.04 ng Pb/g snow or less, and about 0.2 ng Pb/g snow or less, respectively, and with much smaller concentrations from Antarctica, now believed to range from a minimum of about 0.001 to a maximum of 0.005 (or 0.01) ng Pb/g snow.

Nitrate release from waste rock dumps in the Elk Valley, British Columbia, Canada.

PubMed

Mahmood, Fazilatun N; Barbour, S Lee; Kennedy, C; Hendry, M Jim

2017-12-15

The origin, distribution and leaching of nitrate (NO 3 - ) from coal waste rock dumps in the Elk Valley, British Columbia, Canada were defined using chemical and NO 3 - isotope analyses (δ 15 N- and δ 18 O-NO 3 - ) of solids samples of pre- and post-blast waste rock and from thick (up to 180m) unsaturated waste rock dump profiles constructed between 1982 and 2012 as well as water samples collected from a rock drain located at the base of one dump and effluent from humidity cell (HC) and leach pad (LP) tests on waste rock. δ 15 N- and δ 18 O-NO 3 - values and NO 3 - concentrations of waste rock and rock drain waters confirmed the source of NO 3 - in the waste rock to be explosives and that limited to no denitrification occurs in the dump. The average mass of N released during blasting was estimated to be about 3-6% of the N in the explosives. NO 3 - concentrations in the fresh-blast waste rock and recently placed waste rock used for the HC and LP experiments were highly variable, ranging from below detection to 241mg/kg. The mean and median concentrations of these samples ranged from 10-30mg/kg. In this range of concentrations, the initial aqueous concentration of fresh-blasted waste rock could range from approximately 200-600mg NO 3 - -N/L. Flushing of NO 3 - from the HCs, LPs and a deep field profile was simulated using a scale dependent leaching efficiency (f) where f ranged from 5-15% for HCs, to 35-80% for the LPs, to 80-90% for the field profile. Our findings show aqueous phase NO 3 - from blasting residuals is present at highly variable initial concentrations in waste rock and the majority of this NO 3 - (>75%) should be flushed by recharging water during displacement of the first stored water volume. Copyright © 2017 Elsevier B.V. All rights reserved.

Isotopic composition of Pb and Th in interplinian volcanics from Somma-Vesuvius volcano, Italy

USGS Publications Warehouse

Cortini, M.; Ayuso, R.A.; de Vivo, B.; Holden, P.; Somma, R.

2004-01-01

We present a detailed isotopic study of volcanic rocks emitted from Somma-Vesuvius volcano during three periods of interplinian activity: "Protohistoric" (3550 y B.P. to 79 A.D.), "Ancient Historic" (79 to 472 A.D.) and "Medieval" (472 to 1631 A.D.). Pb isotopic compositions of two acid leached fractions and whole rock residues of 37 whole rock samples (determined by Somma et al., 2001) show that each of the three interplinian periods is distinguished by small, systematic, and unique uranogenic and thorogenic Pb isotopic trends. This key and novel feature is compatible with the notion that the Pb isotopic data reflect small-scale source heterogeneity operating over relatively short periods of time. From this representative group of samples, a selected set of nine whole rocks were analysed for Th isotopes. 232Th/238U ratios in the source can be obtained independently from Pb and from Th isotopes. Those obtained from Pb isotopes represent source ratios, time-integrated over the whole age of the Earth; they range from 3.9 to 4.1. 232Th/238U obtained from Th isotopes are those of the present source. They are lower, and cluster around 3.5; this difference probably indicates recent U enrichment of the present source. The behaviour of Pb, as inferred by its isotopic ratios, is quite distinct from that of Sr and Nd isotopes: Pb isotope variations are not correlated to Sr or Nd isotope variations. The isotopic contrast is compatible with the idea that the isotopes were decoupled during magmatic production, evolution, and ascent through the crust. Thus, the Pb isotopes do not reflect the effects of the same processes as in the case of the Sr and Nd isotopes, or, as we also favor, they do not necessarily reflect the same source contributions into the magmas. Moreover, the Pb isotopic evolution of the interplinian rocks chiefly reflects mixing, driven by processes that are superimposed on, and independent of, other source contributions that determine the isotopic compositions of Sr and Nd. We suggest that reactions between magmas and fluids transported Pb and U, but not Sr. These data show that isotope mixing in the mantle is active at different times and scales. ?? Springer-Verlag 2004.

The geochemistry of primitive volcanic rocks of the Ankaratra volcanic complex, and source enrichment processes in the genesis of the Cenozoic magmatism in Madagascar

NASA Astrophysics Data System (ADS)

Melluso, L.; Cucciniello, C.; le Roex, A. P.; Morra, V.

2016-07-01

The Ankaratra volcanic complex in central Madagascar consists of lava flows, domes, scoria cones, tuff rings and maars of Cenozoic age that are scattered over 3800 km2. The mafic rocks include olivine-leucite-nephelinites, basanites, alkali basalts and hawaiites, and tholeiitic basalts. Primitive samples have high Mg# (>60), high Cr and Ni concentrations; their mantle-normalized patterns peak at Nb and Ba, have troughs at K, and smoothly decrease towards the least incompatible elements. The Ankaratra mafic rocks show small variation in Sr-Nd-Pb isotopic compositions (e.g., 87Sr/86Sr = 0.70377-0.70446, 143Nd/144Nd = 0.51273-0.51280, 206Pb/204Pb = 18.25-18.87). These isotopic values differ markedly from those of Cenozoic mafic lavas of northern Madagascar and the Comoro archipelago, typical Indian Ocean MORB and oceanic basalt end-members. The patterns of olivine nephelinitic magmas can be obtained through 3-10% partial melting of a mantle source that was enriched by a Ca-rich alkaline melt, and that contained garnet, carbonates and phlogopite. The patterns of tholeiitic basalts can be obtained after 10-12% partial melting of a source enriched with lower amounts of the same alkaline melt, in the spinel- (and possibly amphibole-) facies mantle, hence in volumes where carbonate is not a factor. The significant isotopic change from the northernmost volcanic rocks of Madagascar and those in the central part of the island implicates a distinct source heterogeneity, and ultimately assess the role of the continental lithospheric mantle as source region. The source of at least some volcanic rocks of the still active Comoro archipelago may have suffered the same time-integrated geochemical and isotopic evolution as that of the northern Madagascar volcanic rocks.

Strontium and neodymium isotopic evidence for the heterogeneous nature and development of the mantle beneath Afar (Ethiopia)

NASA Astrophysics Data System (ADS)

Betton, P. J.; Civetta, L.

1984-11-01

Neodymium isotope and REE analyses of recent volcanic rocks and spinel lherzolite nodules from the Afar area are reported. The 143Nd/ 144Nd ratios of the volcanic rocks range from 0.51286 to 0.51304, similar to the range recorded from Iceland. However, the 87Sr/ 86Sr ratios display a distinctly greater range (0.70328-0.70410) than those reported from the primitive rocks of Iceland. Whole rock samples and mineral separates from the spinel lherzolite nodules exhibit uniform 143Nd/ 144Nd ratios (ca. 0.5129) but varied 87Sr/ 86Sr ratios in the range 0.70427-0.70528. The Sr sbnd Nd isotope variations suggest that the volcanic rocks may have been produced by mixing between two reservoirs with distinct isotopic compositions. Two possible magma reservoirs in this area are the source which produced the "MORB-type" volcanics in the Red Sea and Gulf of Aden and the anomalous source represented by the nodule suite. The isotopic composition of the volcanics is compatible with mixing between these two reservoirs. It is shown that the anomalous source with a high 87Sr/ 86Sr ratio cannot have been produced by simple processes of partial melting and mixing within normal mantle. Instead the high 87Sr/ 86Sr is equated with a fluid phase. A primitive cognate fluid, subducted seawater or altered oceanic lithosphere may have been responsible for the generation of the source with a high 87Sr/ 86Sr ratio.

The Sm-Nd history of KREEP. [in lunar rocks

NASA Technical Reports Server (NTRS)

Lugmair, G. W.; Carlson, R. W.

1978-01-01

Sm-Nd whole rock measurements on a variety of KREEP-rich samples from different landing sites are reported. Despite a variation of Nd and Sm concentrations of almost a factor of 3, the Sm-Nd ratios, as well as the Nd-143/Nd-144 values, show an extremely close grouping. No systematic differences between samples from different landing sites are resolved. These results are taken to be indicative of a moon-wide process having been responsible for the generation of the KREEP source reservoir, 4.36 plus or minus 0.06 AE ago, as estimated from model age calculation.

Apollo rocks, fines and soil cores

NASA Astrophysics Data System (ADS)

Allton, J.; Bevill, T.

Apollo rocks and soils not only established basic lunar properties and ground truth for global remote sensing, they also provided important lessons for planetary protection (Adv. Space Res ., 1998, v. 22, no. 3 pp. 373-382). The six Apollo missions returned 2196 samples weighing 381.7 kg, comprised of rocks, fines, soil cores and 2 gas samples. By examining which samples were allocated for scientific investigations, information was obtained on usefulness of sampling strategy, sampling devices and containers, sample types and diversity, and on size of sample needed by various disciplines. Diversity was increased by using rakes to gather small rocks on the Moon and by removing fragments >1 mm from soils by sieving in the laboratory. Breccias and soil cores are diverse internally. Per unit weight these samples were more often allocated for research. Apollo investigators became adept at wringing information from very small sample sizes. By pushing the analytical limits, the main concern was adequate size for representative sampling. Typical allocations for trace element analyses were 750 mg for rocks, 300 mg for fines and 70 mg for core subsamples. Age-dating and isotope systematics allocations were typically 1 g for rocks and fines, but only 10% of that amount for core depth subsamples. Historically, allocations for organics and microbiology were 4 g (10% for cores). Modern allocations for biomarker detection are 100mg. Other disciplines supported have been cosmogenic nuclides, rock and soil petrology, sedimentary volatiles, reflectance, magnetics, and biohazard studies . Highly applicable to future sample return missions was the Apollo experience with organic contamination, estimated to be from 1 to 5 ng/g sample for Apollo 11 (Simonheit &Flory, 1970; Apollo 11, 12 &13 Organic contamination Monitoring History, U.C. Berkeley; Burlingame et al., 1970, Apollo 11 LSC , pp. 1779-1792). Eleven sources of contaminants, of which 7 are applicable to robotic missions, were identified and reduced; thus, improving Apollo 12 samples to 0.1 ng/g. Apollo sample documentation preserves the parentage, orientation, and location, packaging, handling and environmental histories of each of the 90,000 subsamples currently curated. Active research on Apollo samples continues today, and because 80% by weight of the Apollo collection remains pristine, researchers have a reservoir of material to support studies well into the future.

Detailed description of oil shale organic and mineralogical heterogeneity via fourier transform infrared mircoscopy

USGS Publications Warehouse

Washburn, Kathryn E.; Birdwell, Justin E.; Foster, Michael; Gutierrez, Fernando

2015-01-01

Mineralogical and geochemical information on reservoir and source rocks is necessary to assess and produce from petroleum systems. The standard methods in the petroleum industry for obtaining these properties are bulk measurements on homogenized, generally crushed, and pulverized rock samples and can take from hours to days to perform. New methods using Fourier transform infrared (FTIR) spectroscopy have been developed to more rapidly obtain information on mineralogy and geochemistry. However, these methods are also typically performed on bulk, homogenized samples. We present a new approach to rock sample characterization incorporating multivariate analysis and FTIR microscopy to provide non-destructive, spatially resolved mineralogy and geochemistry on whole rock samples. We are able to predict bulk mineralogy and organic carbon content within the same margin of error as standard characterization techniques, including X-ray diffraction (XRD) and total organic carbon (TOC) analysis. Validation of the method was performed using two oil shale samples from the Green River Formation in the Piceance Basin with differing sedimentary structures. One sample represents laminated Green River oil shales, and the other is representative of oil shale breccia. The FTIR microscopy results on the oil shales agree with XRD and LECO TOC data from the homogenized samples but also give additional detail regarding sample heterogeneity by providing information on the distribution of mineral phases and organic content. While measurements for this study were performed on oil shales, the method could also be applied to other geological samples, such as other mudrocks, complex carbonates, and soils.

Application of uniaxial confining-core clamp with hydrous pyrolysis in petrophysical and geochemical studies of source rocks at various thermal maturities

USGS Publications Warehouse

Lewan, Michael D.; Birdwell, Justin E.; Baez, Luis; Beeney, Ken; Sonnenberg, Steve

2013-01-01

Understanding changes in petrophysical and geochemical parameters during source rock thermal maturation is a critical component in evaluating source-rock petroleum accumulations. Natural core data are preferred, but obtaining cores that represent the same facies of a source rock at different thermal maturities is seldom possible. An alternative approach is to induce thermal maturity changes by laboratory pyrolysis on aliquots of a source-rock sample of a given facies of interest. Hydrous pyrolysis is an effective way to induce thermal maturity on source-rock cores and provide expelled oils that are similar in composition to natural crude oils. However, net-volume increases during bitumen and oil generation result in expanded cores due to opening of bedding-plane partings. Although meaningful geochemical measurements on expanded, recovered cores are possible, the utility of the core for measuring petrophysical properties relevant to natural subsurface cores is not suitable. This problem created during hydrous pyrolysis is alleviated by using a stainless steel uniaxial confinement clamp on rock cores cut perpendicular to bedding fabric. The clamp prevents expansion just as overburden does during natural petroleum formation in the subsurface. As a result, intact cores can be recovered at various thermal maturities for the measurement of petrophysical properties as well as for geochemical analyses. This approach has been applied to 1.7-inch diameter cores taken perpendicular to the bedding fabric of a 2.3- to 2.4-inch thick slab of Mahogany oil shale from the Eocene Green River Formation. Cores were subjected to hydrous pyrolysis at 360 °C for 72 h, which represents near maximum oil generation. One core was heated unconfined and the other was heated in the uniaxial confinement clamp. The unconfined core developed open tensile fractures parallel to the bedding fabric that result in a 38 % vertical expansion of the core. These open fractures did not occur in the confined core, but short, discontinuous vertical fractures on the core periphery occurred as a result of lateral expansion.

Provenance analysis on detrital zircons from the back-arc Arivechi basin: Implications for the Upper Cretaceous tectonic evolution of northern Sonora and southern Arizona

NASA Astrophysics Data System (ADS)

Rodríguez-Castañeda, José Luis; Ortega-Rivera, Amabel; Roldán-Quintana, Jaime; Espinoza-Maldonado, Inocente Guadalupe

2018-07-01

In the Arivechi region of eastern Sonora, northwestern Mexico, mountainous exposures of Upper Cretaceous rocks that contain monoliths within coarse sedimentary debris are enigmatic, in a province of largely Late Cretaceous continental-margin arc rocks. The rocks sequence in the study area are grouped in two Upper Cretaceous units: the lower Cañada de Tarachi and the younger El Potrero Grande. Detrital zircons collected from three samples of the Cañada de Tarachi and El Potrero Grande units have been analyzed for U-Pb ages to constrain their provenance. These ages constrain the age of the exposed rocks and provide new insights into the geological evolution of eastern Sonora Cretaceous rocks. The detrital zircon age populations determined for the Cañada de Tarachi and El Potrero Grande units contain distinctive Precambrian, Paleozoic, and Mesozoic zircon ages that provide probable source areas which are discussed in detail constraining the tectonic evolution of the region. Comparison of these knew ages with published data suggests that the source terranes, that supplied zircons to the Arivechi basin, correlate with Proterozoic, Paleozoic and Mesozoic domains in southern California and Baja California, northern Sonora, southern Arizona and eastern Chihuahua. The provenance variation is vital to constrain the source of the Cretaceous rocks in eastern Sonora and support a better understanding of the Permo-Triassic Cordilleran Magmatic Arc in the southwestern North America.

Study of gamma spectrometry laboratory measurement in various sediment and vulcanic rocks

NASA Astrophysics Data System (ADS)

Nurhandoko, Bagus Endar B.; Kurniadi, Rizal; Rizka Asmara Hadi, Muhammad; Rizal Komara, Insan

2017-01-01

Gamma-ray spectroscopy is the quantitative study of the energy spectra of gamma-ray sources. This method is powerful to characterize some minerals, especially to differentiate rocks which contains among Potassium, Uranium, dan Thorium. Rock contains radioactive material which produce gamma rays in various energies and intensities. When these emissions are detected and analyzed with a spectroscopy system, a gamma-ray energy spectrum can be used as indicator for mineral content of rock. Some sediment and vulcanic rock have been collected from East Java Basin. Samples are ranging from Andesite vulcanics, Tuff, Shale, various vulcanic clay and Alluvial clay. We present some unique characteristics of gamma spectrometry in various sedimentar and vulcanic rocks of East Java Basins. Details contents of gamma ray spectra give enrichments to characterize sample of sediment and vulcanic in East Java. Weathered vulcanic clay has lower counting rate of gamma ray than alluvial deltaic clay counting rate. Therefore, gamma spectrometrometry can be used as tool for characterizing the enviroment of clay whether vulcanic or alluvial-deltaic. This phenomena indicates that gamma ray spectrometry can be as tool for characterizing the clay whether it tends to Smectite or Illite

Oil-source correlations between the Mississippian Heath Shales and the reservoired oils in the Pennsylvanian Tyler Sands, Montana

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

Cole, G.A.; Drozd, R.J.; Daniel, J.A.

The Mississippi Heath Formation exposed in Fergus County, central Montana, is comprised predominantly of nearshore, marine, black, calcareous shales and carbonates with minor anhydrite and coal beds. The black shales and limestones have been considered as sources for shale oil via Fischer Assay and pyrolysis analysis. These shales are potential source units for the oils reservoired in the overlying Pennsylvanian Tyler Formation sands located 50 mi (80 km) to the east of the Fergus County Heath sediment studied. Heath Formation rocks from core holes were selectively sampled in 2-ft increments and analyzed for their source rock characteristics. Analyses include percentmore » total organic carbon (%TOC), Rock-Eval pyrolysis, pyrolysis-gas chromatography, and characterization of the total soluble extracts using carbon isotopes and gas chromatography-mass Spectrometry. Results indicated that the Heath was an excellent potential source unit that contained oil-prone, organic-rich (maximum of 17.6% TOC), calcareous, black shale intervals. The Heath and Tyler formations also contained intervals dominated by gas-prone, organic-rich shales of terrestrial origin. Three oils from the Tyler Formation sands in Musselshell and Rosebud counties were characterized by similar methods as the extracts. The oils were normally mature, moderate API gravity, moderate sulfur, low asphaltene crudes. Oil to source correlations between the Heath shale extracts and the oils indicated the Heath was an excellent candidate source rock for the Tyler reservoired oils. Conclusions were based on excellent matches between the carbon isotopes of the oils and the kerogen-kerogen pyrolyzates, and from the biomarkers.« less

Evolving Mantle Sources in Postcollisional Early Permian-Triassic Magmatic Rocks in the Heart of Tianshan Orogen (Western China)

NASA Astrophysics Data System (ADS)

Tang, Gong-Jian; Cawood, Peter A.; Wyman, Derek A.; Wang, Qiang; Zhao, Zhen-Hua

2017-11-01

Magmatism postdating the initiation of continental collision provides insight into the late stage evolution of orogenic belts including the composition of the contemporaneous underlying subcontinental mantle. The Awulale Mountains, in the heart of the Tianshan Orogen, display three types of postcollisional mafic magmatic rocks. (1) A medium to high K calc-alkaline mafic volcanic suite (˜280 Ma), which display low La/Yb ratios (2.2-11.8) and a wide range of ɛNd(t) values from +1.9 to +7.4. This suite of rocks was derived from melting of depleted metasomatized asthenospheric mantle followed by upper crustal contamination. (2) Mafic shoshonitic basalts (˜272 Ma), characterized by high La/Yb ratios (14.4-20.5) and more enriched isotope compositions (ɛNd(t) = +0.2 - +0.8). These rocks are considered to have been generated by melting of lithospheric mantle enriched by melts from the Tarim continental crust that was subducted beneath the Tianshan during final collisional suturing. (3) Mafic dikes (˜240 Ma), with geochemical and isotope compositions similiar to the ˜280 Ma basaltic rocks. This succession of postcollision mafic rock types suggests there were two stages of magma generation involving the sampling of different mantle sources. The first stage, which occurred in the early Permian, involved a shift from depleted asthenospheric sources to enriched lithospheric mantle. It was most likely triggered by the subduction of Tarim continental crust and thickening of the Tianshan lithospheric mantle. During the second stage, in the middle Triassic, there was a reversion to more asthenospheric sources, related to postcollision lithospheric thinning.

Rhenium-osmium isotopes and highly siderophile elements in ultramafic rocks from the Eoarchean Saglek Block, northern Labrador, Canada: implications for Archean mantle evolution

NASA Astrophysics Data System (ADS)

Ishikawa, Akira; Suzuki, Katsuhiko; Collerson, Kenneth D.; Liu, Jingao; Pearson, D. Graham; Komiya, Tsuyoshi

2017-11-01

We determined highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) concentrations and 187Os/188Os ratios for ultramafic rocks distributed over the Eoarchean gneiss complex of the Saglek-Hebron area in northern Labrador, Canada in order to constrain to what extent variations in HSE abundances are recorded in Early Archean mantle that have well-resolved 182W isotope anomalies relative to the present-day mantle (∼+11 ppm: Liu et al., 2016). The samples analysed here have been previously classified into two suites: mantle-derived peridotites occurring as tectonically-emplaced slivers of lithospheric mantle, and metakomatiites comprising mostly pyroxenitic layers in supracrustal units dominated by amphibolites. Although previous Sm-Nd and Pb-Pb isotope studies provided whole-rock isochrons indicative of ∼3.8 Ga protolith formation for both suites, our whole-rock Re-Os isotope data on a similar set of samples yield considerably younger errorchrons with ages of 3612 ± 130 Ma (MSWD = 40) and 3096 ± 170 Ma (MSWD = 10.2) for the metakomatiite and lithospheric mantle suites, respectively. The respective initial 187Os/188Os = 0.10200 ± 18 for metakomatiites and 0.1041 ± 18 for lithospheric mantle rocks are within the range of chondrites. Re-depletion Os model ages for unradiogenic samples from the two suites are consistent with the respective Re-Os errorchrons (metakomatiite TRD = 3.4-3.6 Ga; lithospheric mantle TRD = 2.8-3.3 Ga). These observations suggest that the two ultramafic suites are not coeval. However, the estimated mantle sources for the two ultramafics suites are similar in terms of their broadly chondritic evolution of 187Os/188Os and their relative HSE patterns. In detail, both mantle sources show a small excess of Ru/Ir similar to that in modern primitive mantle, but a ∼20% deficit in absolute HSE abundances relative to that in modern primitive mantle (metakomatiite 74 ± 18% of PUM; lithospheric mantle 82 ± 10% of PUM), consistent with the ∼3.8 Ga Isua mantle source and Neoarchean komatiite sources around the world (∼70-86% of PUM). This demonstrates that the lower HSE abundances are not unique to the sources of komatiites, but rather might be a ubiquitous feature of Archean convecting mantle. This tentatively suggests that chondritic late accretion components boosted the convecting mantle HSE inventory after core separation in the Hadean, and that the Eoarchean to Neoarchean convecting mantle was depleted in its HSE content relative to that of today. Further investigation of Archean mantle-derived rocks is required to explore this hypothesis.

Isotopic evidence for closed-system anatexis at midcrustal levels: An example from the Acadian Appalachians of New England

NASA Astrophysics Data System (ADS)

Lathrop, Alison S.; Blum, Joel D.; Chamberlain, C. Page

1994-05-01

We have investigated the Sr and O isotope systematics of granitoid and metasedimentary samples from the Central Main Terrane (CMT) of New England. Granitoid samples were taken from interior and contact zones within the Acadian-aged (approximately 410 m.y.), synmetamorphic and syntectonic Kinsman Quartz Monzonite (KQM), which is a member of the New Hampshire Plutonic Series. Metasedimentary samples were taken from Silurian and Devonian formations hosting the KQM. Initial Sr isotope ratios (Sr(sub i) and delta O-18 values for the KQM range from 0.70799 to 0.71246 and 7.6% to 12.9%, respectively, and Sr(sub i) and delta O-18 values of the metasedimentary rocks range from 0.70770 to 0.75008 and 6.2% to 14.1%, respectively. We observe a linear and slightly positive correlation between Sr(sub i) and delta O-18 for interior KQM samples that can be duplicated by a mixing curve calculated for metasedimentary endmembers, whereas the Sr(sub i) and delta O-18 values of contact KQM samples cluster near the Sr(sub i) and delta O-18 values of the metasedimentary rocks with which they are in contact. Mixing calculations provide no evidence for a measurable primitive mantle component in either interior or contact KQM samples, and we conclude that the Sr-O isotopic composition of the KQM is most likely a reflection of isotopic heterogeneities inherited from a complex package of midcrustal metasedimentary source rocks. We propose that the KQM is the product of midcrustal partial melting that was initiated due to excess thermal energy from the decay of anomalously high concentrations of heat-producing elements in Silurian source rocks within the CMT. Because we see no isotopic evidence for a lower-crustal or mantle component in the KQM, we suggest that midcrustal anatexis may have occurred as a closed-system process, requiring no accompanying mantle-derived magma or above normal mantle heat flow.

Petrology of basalts from Loihi Seamount, Hawaii

NASA Astrophysics Data System (ADS)

Hawkins, James; Melchior, John

1983-12-01

Loihi Seamount is the southeasternmost active volcano of the Emperor-Hawaii linear volcanic chain. It comprises a spectrum of basalt compositional varieties including basanite, alkali basalt, transitional basalt and tholeiite. Samples from four dredge collections made on Scripps Institution of Oceanography Benthic Expedition in October 1982 are tholeiite. The samples include highly vesicular, olivine-rich basalt and dense glass-rich pillow fragments containing olivine and augite phenocrysts. Both quartz-normative and olivine-normative tholeiites are present. Minor and trace element data indicate relatively high abundances of low partition coefficient elements (e.g., Ti, K, P. Rb, Ba, Zr) and suggest that the samples were derived by relatively small to moderate extent of partial melting, of an undepleted mantle source. Olivine composition, MgO, Cr and Ni abundances, and Mg/(Mg+Fe), are typical of moderately fractionated to relatively unfractionated "primary" magmas. The variations in chemistry between samples cannot be adequately explained by low-pressure fractional crystallization but can be satisfied by minor variations in extent of melting if a homogeneous source is postulated. Alternatively, a heterogeneous source with variable abundances of certain trace elements, or mixing of liquids, may have been involved. Data for 3He/ 4He, presented in a separate paper, implies a mantle plume origin for the helium composition of the Loihi samples. There is little variation in the helium isotope ratio for samples having different compositions and textures. The helium data are not distinctive enough to unequivocally separate the magma sources for the tholeiitic rocks from the other rock types such as Loihi alkalic basalts and the whole source region for Loihi may have a nearly uniform helium compositions even though other element abundances may be variable. Complex petrologic processes including variable melting, fractional crystallization and magma mixing may have blurred original helium isotopic signatures.

Information Seeking Behavior of Geologists When Searching for Physical Samples

ERIC Educational Resources Information Center

Ramdeen, Sarah

2017-01-01

Information seeking is "a conscious effort to acquire information in response to a need or gap" in your knowledge (Case, 2007, p. 5). In the geosciences, physical samples such as cores, cuttings, fossils, and rocks are primary sources of information; they represent "the foundation of basic and applied geoscience research and…

Origin of radon concentration of Csalóka Spring in the Sopron Mountains (West Hungary).

PubMed

Freiler, Ágnes; Horváth, Ákos; Török, Kálmán; Földes, Tamás

2016-01-01

We examined the Csalóka Spring, which has the highest radon concentration in the Sopron Mountains (West Hungary) (, yearly average of 227 ± 10 Bq L(-1)). The main rock types here are gneiss and micaschist, formed from metamorphism of former granitic and clastic sedimentary rocks respectively. The aim of the study was to find a likely source of the high radon concentration in water. During two periods (2007-2008 and 2012-2013) water samples were taken from the Csalóka Spring to measure its radon concentration (from 153 ± 9 Bq L(-1) to 291 ± 15 Bq L(-1)). Soil and rock samples were taken within a 10-m radius of the spring from debrish and from a deformed gneiss outcrop 500 m away from the spring. The radium activity concentration of the samples (between 24.3 ± 2.9 Bq kg(-1) and 145 ± 6.0 Bq kg(-1)) was measured by gamma-spectroscopy, and the specific radon exhalation was determined using radon-chamber measurements (between 1.32 ± 0.5 Bq kg(-1) and 37.1 ± 2.2 Bq kg(-1)). Based on these results a model calculation was used to determine the maximum potential radon concentration, which the soil or the rock may provide into the water. We showed that the maximum potential radon concentration of these mylonitic gneissic rocks (cpot = 2020 Bq L(-1)) is about eight times higher than the measured radon concentration in the water. However the maximum potential radon concentration for soils are significantly lower (41.3 Bq L(-1)) Based on measurements of radon exhalation and porosity of rock and soil samples we concluded that the source material can be the gneiss rock around the spring rather than the soil there. We determined the average radon concentration and the time dependence of the radon concentration over these years in the spring water. We obtained a strong negative correlation (-0.94 in period of 2007-2008 and -0.91 in 2012-2013) between precipitation and radon concentration. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Influence of Lithology on the Formation of Reaction Infiltration Instabilities in Mantle Rocks

NASA Astrophysics Data System (ADS)

Pec, M.; Holtzman, B. K.; Zimmerman, M. E.; Kohlstedt, D. L.

2017-12-01

The formation of oceanic plates requires extraction of large volumes of melt from the mantle. Several lines of evidence suggest that melt extraction is rapid and, therefore, necessitates high-permeability pathways. Such pathways may form as a result of melt-rock reactions. We report the results of a series of Darcy-type experiments designed to study the development of channels due to melt-solid reactions in mantle lithologies. We sandwiched a partially molten rock between a melt source and a porous sink and annealed it at high pressure (P = 300 MPa) and high temperatures (T = 1200° or 1250°C) with a controlled pressure gradient (∂P/∂z = 0-100 MPa/mm). To study the influence of lithology on the channel formation, we synthesized partially molten rocks of harzburgitic (40:40:20 Ol - Opx - basalt), wehrlitic (40:40:20 Ol - Cpx - basalt) and lherzolitic (65:25:10 Ol - Opx - Cpx) composition. The melt source was a disk of alkali basalt. In all experiments, irrespective of the exact mineralogy, melt - undersaturated in silica - from the source dissolved pyroxene in the partially molten rock and precipitated olivine ( Fo82), thereby forming a dunite reaction layer at the interface between the source and the partially molten rock. In samples annealed under a small pressure gradient, the reaction layer was roughly planar. However, if the velocity of melt due to porous flow exceeded 0.1 µm/s, the reaction layer locally protruded into the partially molten rock forming finger-like, melt-rich channels in rocks of wehrlitic and harzburgitic composition. The lherzolitic rocks were generally impermeable to the melt except at highest-pressure gradients where a narrow fracture developed, forming a dyke which drained the melt reservoir. Three-dimensional reconstructions using micro-CT images revealed clear differences between the dyke (a narrow, through-going planar feature) and the channels formed by reactive infiltration (multiple sinuous finger-like features). Apparently, the fraction of soluble minerals together with the melt fraction in the partially molten rock control whether dykes or reactive channels develop. Our experiments demonstrate that melt-rock reactions can lead to channelization in mantle lithologies, and the observed lithological transformations broadly agree with those observed in nature

Petroleum systems of the San Joaquin Basin Province -- geochemical characteristics of gas types: Chapter 10 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

USGS Publications Warehouse

Lillis, Paul G.; Warden, Augusta; Claypool, George E.; Magoon, Leslie B.

2008-01-01

The San Joaquin Basin Province is a petroliferous basin filled with predominantly Late Cretaceous to Pliocene-aged sediments, with organic-rich marine rocks of Late Cretaceous, Eocene, and Miocene age providing the source of most of the oil and gas. Previous geochemical studies have focused on the origin of the oil in the province, but the origin of the natural gas has received little attention. To identify and characterize natural gas types in the San Joaquin Basin, 66 gas samples were analyzed and combined with analyses of 15 gas samples from previous studies. For the purpose of this resource assessment, each gas type was assigned to the most likely petroleum system. Three general gas types are identified on the basis of bulk and stable carbon isotopic composition—thermogenic dry (TD), thermogenic wet (TW) and biogenic (B). The thermogenic gas types are further subdivided on the basis of the δ13C values of methane and ethane and nitrogen content into TD-1, TD-2, TD-Mixed, TW-1, TW-2, and TW-Mixed. Gas types TD-1 and TD-Mixed, a mixture of biogenic and TD-1 gases, are produced from gas fields in the northern San Joaquin Basin. Type TD-1 gas most likely originated from the Late Cretaceous to Paleocene Moreno Formation, a gas-prone source rock. The biogenic component of the TD-Mixed gas existed in the trap prior to the influx of thermogenic gas. For the assessment, these gas types were assigned to the Winters- Domengine Total Petroleum System, but subsequent to the assessment were reclassified as part of the Moreno-Nortonville gas system. Dry thermogenic gas produced from oil fields in the southern San Joaquin Basin (TD-2 gas) most likely originated from the oil-prone source rock of Miocene age. These samples have low wetness values due to migration fractionation or biodegradation. The thermogenic wet gas types (TW-1, TW-2, TW-Mixed) are predominantly associated gas produced from oil fields in the southern and central San Joaquin Basin. Type TW-1 gas most likely originates from source rocks within the Eocene Kreyenhagen Formation or the Eocene Tumey formation of Atwill (1935). Type TW-2 gas most likely originates from the Miocene Monterey Formation and equivalents. TW-Mixed gas is likely a mixture of biogenic and wet thermogenic gas (TW-1 or TW-2) derived from source rocks mentioned above. The thermogenic wet gas types are included in the corresponding Eocene or Miocene total petroleum systems. Type B gas is a dry, nonassociated gas produced from the Pliocene San Joaquin Formation in the central and southern San Joaquin Basin. This gas type most likely originated from Pliocene marine source rocks as a product of methanogenesis, and defines the Neogene Nonassociated Gas Total Petroleum System.

Petrogenesis of metaultramafic rocks from the Quadrilátero Ferrífero and adjacent terrains, Minas Gerais, Brazil: Two events of ultramafic magmatism?

NASA Astrophysics Data System (ADS)

da Fonseca, Gabriela Magalhães; Jordt-Evangelista, Hanna; Queiroga, Gláucia Nascimento

2018-03-01

In the worldwide known Quadrilátero Ferrífero and the adjacent terrains, southeastern Brazil, many serpentinite and soapstone quarries, and some rare bodies of metaultramafic rocks that partially preserve minerals or textures from the original igneous protolith can be found. It is not known if the protoliths and the ages of the metaultramafic rocks found in the Quadrilátero Ferrífero (and its oriental basement) and Mineiro Belt regions are the same or if they represent distinct magmatic episodes. The petrogenetic investigation, specially concerning the REE contents, aimed to gather informations about the type of magmatism and the mantle source in order to compare the metaultramafic rocks of both regions. The interpretation of the data concerning petrography, mineral chemistry and geochemistry shows that the metaultramafic rocks are similar to komatiitic peridotites, with MgO contents > 22 wt % and TiO2 < 0.9 wt %. The plot of the REE for the lithotypes found in the Quadrilátero Ferrífero shows decrease in LREE possibly reflecting the depletion of the mantle source. On the other hand the samples from the Mineiro Belt are enriched in LREE suggesting a mantle source enriched in these elements. This enrichment may have been caused by mantle metassomatism that occurred during accretion of the Paleoproterozoic magmatic arc that generated the Mineiro belt. In this paper, we therefore suggest two periods of ultramafic magmatism. The first one found in the Archean basement of the Quadrilátero Ferrífero, with a depleted mantle source. The second occurred in the Paleoproterozoic basement of the Mineiro belt, having a metassomatized mantle as source.

Variability over time in the sources of South Portuguese Zone turbidites: evidence of denudation of different crustal blocks during the assembly of Pangaea

NASA Astrophysics Data System (ADS)

Pereira, M. F.; Ribeiro, C.; Vilallonga, F.; Chichorro, M.; Drost, K.; Silva, J. B.; Albardeiro, L.; Hofmann, M.; Linnemann, U.

2014-07-01

This study combines geochemical and geochronological data in order to decipher the provenance of Carboniferous turbidites from the South Portuguese Zone (SW Iberia). Major and trace elements of 25 samples of graywackes and mudstones from the Mértola (Visean), Mira (Serpukhovian), and Brejeira (Moscovian) Formations were analyzed, and 363 U-Pb ages were obtained on detrital zircons from five samples of graywackes from the Mira and Brejeira Formations using LA-ICPMS. The results indicate that turbiditic sedimentation during the Carboniferous was marked by variability in the sources, involving the denudation of different crustal blocks and a break in synorogenic volcanism. The Visean is characterized by the accumulation of immature turbidites (Mértola Formation and the base of the Mira Formation) inherited from a terrane with intermediate to mafic source rocks. These source rocks were probably formed in relation to Devonian magmatic arcs poorly influenced by sedimentary recycling, as indicated by the almost total absence of pre-Devonian zircons typical of the Gondwana and/or Laurussia basements. The presence of Carboniferous grains in Visean turbidites indicates that volcanism was active at this time. Later, Serpukhovian to Moscovian turbiditic sedimentation (Mira and Brejeira Formations) included sedimentary detritus derived from felsic mature source rocks situated far from active magmatism. The abundance of Precambrian and Paleozoic zircons reveals strong recycling of the Gondwana and/or Laurussia basements. A peri-Gondwanan provenance is indicated by zircon populations with Neoproterozoic (Cadomian-Avalonian and Pan-African zircon-forming events), Paleoproterozoic, and Archean ages. The presence of late Ordovician and Silurian detrital zircons in Brejeira turbidites, which have no correspondence in the Gondwana basement of SW Iberia, indicates Laurussia as their most probable source.

Studies on geological background and source of fluorine in drinking water in the North China Plate fluorosis areas

USGS Publications Warehouse

Luo, K.; Feng, F.; Li, H.; Chou, C.-L.; Feng, Z.; Yunshe, D.

2008-01-01

Endemic fluorosis in northern China is usually produced by high fluorine (F) content in drinking water. Thirty-one samples of drinking waters, mainly well waters and nearly 200 samples of rocks, loess, and coal were analyzed for F content using the combustion hydrolysis-fluoride-ion selective electrode (ISE) method. The geologic cross sections of two well-known fluorosis basins were studied. The solubility of F in different rock types collected from fluorosis areas was determined. Results showed that areas of endemic fluorosis in northern China are located in coal-bearing basins which are comprised of three stratagraphic portions. The lowest portion is Precambrian granitic rocks or Cambrian-Ordovician carbonates. The middle portion consists of Permo-Carboniferous or Jurassic coal-bearing sequences. The upper portion is 0-400 m Pleistocene loess. Flourine content in the Precambrian granite-gneiss contained (a) 1090-1460 ppm, in the Cambrian-Ordovician limestone and dolomite, (b) 52-133 ppm, in black shales and coal gob of Permo-Carboniferous coal-bearing strata, (c) 200-700 ppm, and (d) Pleistocene loess 454-542 ppm. The solubility of F in black shales of coal-bearing sequences was higher than in Precambrian granitic rocks, and both were more soluble than loess. F solubility from Precambrian granitic rocks was moderate, but Precambrian granitic rocks have high F content and thus contribute an appreciable amount of ion to the shallow groundwater (well water). Varying F content in shallow groundwater is controlled by geological conditions. The sources of F in the shallow groundwater from fluorosis areas in northern China are mainly derived from black shales of coal-bearing sequences and Precambrian granitic basement in the basins of northern China. ?? 2008 Taylor & Francis.

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

Preliminary biological sampling of GT3 and BT1 cores and the microbial community dynamics of existing subsurface wells

NASA Astrophysics Data System (ADS)

Kraus, E. A.; Stamps, B. W.; Rempfert, K. R.; Ellison, E. T.; Nothaft, D. B.; Boyd, E. S.; Templeton, A. S.; Spear, J. R.

2017-12-01

Subsurface microbial life is poorly understood but potentially very important to the search for life on other planets as well as increasing our understanding of Earth's geobiological processes. Fluids and rocks of actively serpentinizing subsurface environments are a recent target of biological study due to their apparent ubiquity across the solar system. Areas of serpentinization can contain high concentrations of molecular hydrogen, H2, that can serve as the dominant fuel source for subsurface microbiota. Working with the Oman Drilling Project, DNA and RNA were extracted from fluids of seven alkaline wells and two rock cores from drill sites GT3 and BT1 within the Samail ophiolite. DNA and cDNA (produced via reverse transcription from the recovered RNA) were sequenced using universal primers to identify microbial life across all three domains. Alkaline subsurface fluids support a microbial community that changes with pH and host-rock type. In peridotite with pH values of >11, wells NSHQ 14 and WAB 71 have high relative abundances of Meiothermus, Methanobacterium, the family Nitrospiraceae, and multiple types of the class Dehalococcoidia. While also hosted in peridotite but at pH 8.5, wells WAB 104 and 105 have a distinct, more diverse microbial community. This increased variance in community make-up is seen in wells that sit near/at the contact of gabbro and peridotite formations as well. Core results indicate both sampled rock types host a very low biomass environment subject to multiple sources of contamination during the drilling process. Suggestions for contaminant reduction, such as having core handlers wear nitrile gloves and flame-sterilizing the outer surfaces of core rounds for biological sampling, would have minimal impact to overall ODP coreflow and maximize the ability to better understand in situ microbiota in this low-biomass serpentinizing subsurface environment. While DNA extraction was successful with gram amounts of crushed rock, much can be done to improve yields and reduce contamination sources for Phase II drilling.

Evaluating Re-Os systematics in organic-rich sedimentary rocks in response to petroleum generation using hydrous pyrolysis experiments

USGS Publications Warehouse

Rooney, A.D.; Selby, D.; Lewan, M.D.; Lillis, P.G.; Houzay, J.-P.

2012-01-01

Successful application of the 187Re–187Os geochronometer has enabled the determination of accurate and precise depositional ages for organic-rich sedimentary rocks (ORS) as well as establishing timing constraints of petroleum generation. However, we do not fully understand the systematics and transfer behaviour of Re and Os between ORS and petroleum products (e.g., bitumen and oil). To more fully understand the behaviour of Re–Os systematics in both source rocks and petroleum products we apply hydrous pyrolysis to two immature hydrocarbon source rocks: the Permian Phosphoria Formation (TOC = 17.4%; Type II-S kerogen) and the Jurassic Staffin Formation (TOC = 2.5%; Type III kerogen). The laboratory-based hydrous pyrolysis experiments were carried out for 72 h at 250, 300, 325 and 350 °C. These experiments provided us with whole rock, extracted rock and bitumen and in some cases expelled oil and asphaltene for evaluation of Re–Os isotopic and elemental abundance. The data from these experiments demonstrate that the majority (>95%) of Re and Os are housed within extracted rock and that thermal maturation does not result in significant transfer of Re or Os from the extracted rock into organic phases. Based on existing thermodynamic data our findings suggest that organic chelating sites have a greater affinity for the quadravalent states of Re and Os than sulphides. Across the temperature range of the hydrous pyrolysis experiments both whole rock and extracted rock 187Re/188Os ratios show small variations (3.3% and 4.7%, for Staffin, respectively and 6.3% and 4.9% for Phosphoria, respectively). Similarly, the 187Os/188Os ratios show only minor variations for the Staffin and Phosphoria whole rock and extracted rock samples (0.6% and 1.4% and 1.3% and 2.2%). These isotopic data strongly suggest that crude oil generation through hydrous pyrolysis experiments does not disturb the Re–Os systematics in ORS as supported by various studies on natural systems. The elemental abundance data reveal limited transfer of Re and Os into the bitumen from a Type III kerogen in comparison to Type II-S kerogen (0.02% vs. 3.7%), suggesting that these metals are very tightly bound in Type III kerogen structure. The 187Os/188Os data from the pyrolysis generated Phosphoria bitumens display minor variation (4%) across the experimental temperatures, with values similar to that of the source rock. This indicates that the isotopic composition of the bitumen reflects the isotopic composition of the source rock at the time of petroleum generation. These data further support the premise that the Os isotopic composition of oils and bitumens can be used to fingerprint petroleum deposits to specific source rocks. Oil generated through the hydrous pyrolysis experiments does not contain appreciable quantities of Re or Os (~120 and ~3 ppt, respectively), in contrast to natural oils (2–50 ppb and 34–288 ppt for Re and Os, respectively), which may suggest that kinetic parameters are fundamental to the transfer of Re and Os from source rocks to oils. From this we hypothesise that, at the temperatures employed in hydrous pyrolysis, Re and Os are assimilated into the extracted rock as a result of cross-linking reactions.

Evaluating Re-Os systematics in organic-rich sedimentary rocks in response to petroleum generation using hydrous pyrolysis experiments

NASA Astrophysics Data System (ADS)

Rooney, Alan D.; Selby, David; Lewan, Michael D.; Lillis, Paul G.; Houzay, Jean-Pierre

2012-01-01

Successful application of the 187Re-187Os geochronometer has enabled the determination of accurate and precise depositional ages for organic-rich sedimentary rocks (ORS) as well as establishing timing constraints of petroleum generation. However, we do not fully understand the systematics and transfer behaviour of Re and Os between ORS and petroleum products (e.g., bitumen and oil). To more fully understand the behaviour of Re-Os systematics in both source rocks and petroleum products we apply hydrous pyrolysis to two immature hydrocarbon source rocks: the Permian Phosphoria Formation (TOC = 17.4%; Type II-S kerogen) and the Jurassic Staffin Formation (TOC = 2.5%; Type III kerogen). The laboratory-based hydrous pyrolysis experiments were carried out for 72 h at 250, 300, 325 and 350 °C. These experiments provided us with whole rock, extracted rock and bitumen and in some cases expelled oil and asphaltene for evaluation of Re-Os isotopic and elemental abundance. The data from these experiments demonstrate that the majority (>95%) of Re and Os are housed within extracted rock and that thermal maturation does not result in significant transfer of Re or Os from the extracted rock into organic phases. Based on existing thermodynamic data our findings suggest that organic chelating sites have a greater affinity for the quadravalent states of Re and Os than sulphides. Across the temperature range of the hydrous pyrolysis experiments both whole rock and extracted rock 187Re/188Os ratios show small variations (3.3% and 4.7%, for Staffin, respectively and 6.3% and 4.9% for Phosphoria, respectively). Similarly, the 187Os/188Os ratios show only minor variations for the Staffin and Phosphoria whole rock and extracted rock samples (0.6% and 1.4% and 1.3% and 2.2%). These isotopic data strongly suggest that crude oil generation through hydrous pyrolysis experiments does not disturb the Re-Os systematics in ORS as supported by various studies on natural systems. The elemental abundance data reveal limited transfer of Re and Os into the bitumen from a Type III kerogen in comparison to Type II-S kerogen (0.02% vs. 3.7%), suggesting that these metals are very tightly bound in Type III kerogen structure. The 187Os/188Os data from the pyrolysis generated Phosphoria bitumens display minor variation (4%) across the experimental temperatures, with values similar to that of the source rock. This indicates that the isotopic composition of the bitumen reflects the isotopic composition of the source rock at the time of petroleum generation. These data further support the premise that the Os isotopic composition of oils and bitumens can be used to fingerprint petroleum deposits to specific source rocks. Oil generated through the hydrous pyrolysis experiments does not contain appreciable quantities of Re or Os (∼120 and ∼3 ppt, respectively), in contrast to natural oils (2-50 ppb and 34-288 ppt for Re and Os, respectively), which may suggest that kinetic parameters are fundamental to the transfer of Re and Os from source rocks to oils. From this we hypothesise that, at the temperatures employed in hydrous pyrolysis, Re and Os are assimilated into the extracted rock as a result of cross-linking reactions.

Petrology and K-Ar ages of rift-related basaltic rocks, offshore northern Brazil, 3/sup 0/N

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

Fodor, R.V.; McKee, E.H.

1986-07-01

Tholeiitic basaltic rock in three cores from Petrobras drill site APS-21, 1960-2480 m depths, Amapa basin, offshore Brazil is compositionally similar to rift-related basaltic rock associated with the opening of both the North and South Atlantic Oceans (SiO/sub 2/ 52-54 wt %; K/sub 2/O 0.7-1.3%; TiO/sub 2/ 1.3-2%). Whole-rock K-Ar ages are 185.4, 183.2, and 126.5 m.y. If these represent crystallization ages, then the older samples correspond to North Atlantic tectonism (as represented by the Liberian dike system) and the younger correlates with South Atlantic rift-related magmatism (of which Serra Geral flood basalts are the best example). Trace- and REE-elementsmore » identify T-type mantle source-areas (La/Sm/sub (n)/ approx. 2; Zr/Nb 8-11) that feasibly were mixes of N-type and P-type components (metasomatized or veined upper mantle). These Amapa basin mafic rocks document the southernmost magmatism related to North Atlantic rifting, as well as early Mesozoic mantle source-areas and processes beneath Gondwanaland such as those identified with basalts in the South Atlantic basin.« less

Lead-isotopic, sulphur-isotopic, and trace-element studies of galena from the Silesian-Cracow Zn-Pb ores, polymetallic veins from the Gory Swietokrzyskie MTS, and the Myszkow porphyry copper deposit, Poland

USGS Publications Warehouse

Church, S.E.; Vaughn, R.B.; Gent, C.A.; Hopkins, R.T.

1996-01-01

Lead-isotopic data on galena samples collected from a paragenetically constrained suite of samples from the Silesian-Cracow ore district show no regional or paragenetically controlled lead-isotopic trends within the analytical reproducibility of the measurements. Furthermore, the new lead-isotopic data agree with previously reported lead-isotopic results (R. E. Zartman et al., 1979). Sulfur-isotopic analyses of ores from the Silesian-Cracow district as well as from vein ore from the Gory Swietokrzyskie Mts. and the Myszkow porphyry copper deposit, when coupled with trace-element data from the galena samples, clearly discriminate different hydrothermal ore-forming events. Lead-isotopic data from the Permian and Miocene evaporite deposits in Poland indicate that neither of these evaporite deposits were a source of metals for the Silesian-Cracow district ores. Furthermore, lead-isotopic data from these evaporite deposits and the shale residues from the Miocene halite samples indicate that the crustal evolution of lead in the central and western European platform in southern Poland followed normal crustal lead-isotopic growth, and that the isotopic composition of crustal lead had progressed beyond the lead-isotopic composition of lead in the Silesian-Cracow ores by Permian time. Thus, Mesozoic and Tertiary sedimentary flysch rocks can be eliminated as viable source rocks for the metals in the Silesian-Cracow Mississippi Valley-type (MVT) deposits. The uniformity of the isotopic composition of lead in the Silesian-Cracow ores, when coupled with the geologic evidence that mineralization must post-date Late Jurassic faulting (E. Gorecka, 1991), constrains the geochemical nature of the source region. The source of the metals is probably a well-mixed, multi-cycle molasse sequence of sedimentary rocks that contains little if any Precambrian metamorphic or granitic clasts (S. E. Church, R. B. Vaughn, 1992). If ore deposition was post Late Jurassic (about 150 m. y.) or later as indicated by the geologic evidence, the source rocks probably contained elevated concentrations of Zn and Pb (75-100 ppm), and relatively low concentrations of U and Th (2 and 8 ppm or less, respectively). The Carboniferous coal-bearing molasse rocks of the Upper Silesian Coal Basin are a prime candidate for such a source region. The presence of ammonia and acetate in the fluid inclusions (Viets et al., 1996a) also indicate that the Carboniferous coal-bearing molasse sequence in the Upper Silesian Coal Basin may have been a suitable pathway for the MVT ore fluids. The lead-isotopic homogeneity, when coupled with the sulfur-isotopic heterogeneity of the ores suggests that mixing of a single metal-bearing fluid with waters from separate aquifers containing variable sulfur-isotopic compositions in karsts in the Muschelkalk Formation of Middle Triassic age may have been responsible for the precipitation of the ores of the Silesian-Cracow district.

Nanoscale Compositional Relations in Lunar Rock Patina: Deciphering Sources for Patina Components on an Apollo 17 Station 6 Boulder

NASA Technical Reports Server (NTRS)

Christoffersen, R.; Noble, S. K.; Keller, L. P.

2014-01-01

Space weathering on the Moon and other airless bodies modifies the surfaces of regolith grains as well as the space-exposed surfaces of larger rocks and boulders. As space weathering witness plates, rocks and boulders are distinguished from regolith grains based on their ability to persist as physically intact substrates over longer time scales before being disaggregated by impact processes. Because lunar surfaces, including exposed rocks, quickly develop an optically thick layer of patina, it is important to understand the compositional relationship between patinas and their underlying rock substrates, particularly to support remote-sensing of rocky lunar terrains. Based on analytical TEM techniques, supported by focused ion beam (FIB) cross-sectioning, we have begun to systematize the multi-layer microstructural complexity of patinas on rock samples with a range of space exposure histories. Our on-going work has particularly focused on lunar rock 76015, both because it has a long (approx. 22 my) exposure history, and because its surface was exposed to patina development approximately 1 m off the regolith surface on a boulder in the Apollo 17 Station 6 boulder field. Potential sources for the 76015 patina therefore include impact-melted and vaporized material derived from the local rock substrate, as well as from the mix of large boulders and regolith in the Station 6 area. While similar, there are differences in the mineralogy and chemistry of the rocks and regolith at Station 6. We were interested to see if these, or other sources, could be distinguished in the average composition, as well as the compositional nanostratigraphy of the 76015 patina. To date we have acquired a total of 9 TEM FIB cross-sections from the 76015 patina, giving us reasonable confidence of being able to arrive at an integrated average for the patina major element composition based on analytical TEM methods.

Spatial Distribution of Stony Desertification and Key Influencing Factors on Different Sampling Scales in Small Karst Watersheds

PubMed Central

Zhang, Zhenming; Zhou, Yunchao; Wang, Shijie

2018-01-01

Karst areas are typical ecologically fragile areas, and stony desertification has become the most serious ecological and economic problems in these areas worldwide as well as a source of disasters and poverty. A reasonable sampling scale is of great importance for research on soil science in karst areas. In this paper, the spatial distribution of stony desertification characteristics and its influencing factors in karst areas are studied at different sampling scales using a grid sampling method based on geographic information system (GIS) technology and geo-statistics. The rock exposure obtained through sampling over a 150 m × 150 m grid in the Houzhai River Basin was utilized as the original data, and five grid scales (300 m × 300 m, 450 m × 450 m, 600 m × 600 m, 750 m × 750 m, and 900 m × 900 m) were used as the subsample sets. The results show that the rock exposure does not vary substantially from one sampling scale to another, while the average values of the five subsamples all fluctuate around the average value of the entire set. As the sampling scale increases, the maximum value and the average value of the rock exposure gradually decrease, and there is a gradual increase in the coefficient of variability. At the scale of 150 m × 150 m, the areas of minor stony desertification, medium stony desertification, and major stony desertification in the Houzhai River Basin are 7.81 km2, 4.50 km2, and 1.87 km2, respectively. The spatial variability of stony desertification at small scales is influenced by many factors, and the variability at medium scales is jointly influenced by gradient, rock content, and rock exposure. At large scales, the spatial variability of stony desertification is mainly influenced by soil thickness and rock content. PMID:29652811

Spatial Distribution of Stony Desertification and Key Influencing Factors on Different Sampling Scales in Small Karst Watersheds.

PubMed

Zhang, Zhenming; Zhou, Yunchao; Wang, Shijie; Huang, Xianfei

2018-04-13

Karst areas are typical ecologically fragile areas, and stony desertification has become the most serious ecological and economic problems in these areas worldwide as well as a source of disasters and poverty. A reasonable sampling scale is of great importance for research on soil science in karst areas. In this paper, the spatial distribution of stony desertification characteristics and its influencing factors in karst areas are studied at different sampling scales using a grid sampling method based on geographic information system (GIS) technology and geo-statistics. The rock exposure obtained through sampling over a 150 m × 150 m grid in the Houzhai River Basin was utilized as the original data, and five grid scales (300 m × 300 m, 450 m × 450 m, 600 m × 600 m, 750 m × 750 m, and 900 m × 900 m) were used as the subsample sets. The results show that the rock exposure does not vary substantially from one sampling scale to another, while the average values of the five subsamples all fluctuate around the average value of the entire set. As the sampling scale increases, the maximum value and the average value of the rock exposure gradually decrease, and there is a gradual increase in the coefficient of variability. At the scale of 150 m × 150 m, the areas of minor stony desertification, medium stony desertification, and major stony desertification in the Houzhai River Basin are 7.81 km², 4.50 km², and 1.87 km², respectively. The spatial variability of stony desertification at small scales is influenced by many factors, and the variability at medium scales is jointly influenced by gradient, rock content, and rock exposure. At large scales, the spatial variability of stony desertification is mainly influenced by soil thickness and rock content.

Evidence for methane in Martian meteorites

PubMed Central

Blamey, Nigel J. F.; Parnell, John; McMahon, Sean; Mark, Darren F.; Tomkinson, Tim; Lee, Martin; Shivak, Jared; Izawa, Matthew R. M.; Banerjee, Neil R.; Flemming, Roberta L.

2015-01-01

The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity. PMID:26079798

Evidence for methane in Martian meteorites.

PubMed

Blamey, Nigel J F; Parnell, John; McMahon, Sean; Mark, Darren F; Tomkinson, Tim; Lee, Martin; Shivak, Jared; Izawa, Matthew R M; Banerjee, Neil R; Flemming, Roberta L

2015-06-16

The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity.

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

Analysis of Shublik Formation rocks from Mt. Michelson quadrangle, Alaska

USGS Publications Warehouse

Detterman, Robert L.

1970-01-01

Analysis of 88 samples from the Shublik formation on Fire Creek, Mt. Michelson Quadrangle, Alaska, are presented in tabular form. The results include the determination of elements by semiquantitative spectrographic analysis, phosphate by X-ray fluorescence, carbon dioxide by acid decomposable carbonate, total carbon by induction furnace, carbonate carbon by conversion using the conversion factor of 0.2727 for amount of carbon in carbon dioxide, and organic carbon by difference. A seven- cycle semilogarithmic chart presents the data graphically and illustrates the range, mode, and mean for some of the elements. The chart shows, also, the approximate concentration of the same elements in rocks similar to the black shale and limestone of the Shublik Formation. Each sample represents 5 feet of section and is composed of rock chips taken at 1 - foot intervals. The samples are keyed into a stratigraphic column of the formation. Rocks of the Shublik Formation contain anomalously high concentrations of some of the elements. These same elements might be expected to be high in some of the petroleum from northern Alaska if the Shublik Formation is a source for this petroleum. Several of the stratigraphic intervals may represent, also, a low-grade phosphate deposit.

South-to-north pyroxenite-peridotite source variation correlated with an OIB-type to arc-type enrichment of magmas from the Payenia backarc of the Andean Southern Volcanic Zone (SVZ)

NASA Astrophysics Data System (ADS)

Brandt, Frederik Ejvang; Holm, Paul Martin; Søager, Nina

2017-01-01

New high-precision minor element analysis of the most magnesian olivine cores (Fo85-88) in fifteen high-MgO (Mg#66-74) alkali basalts or trachybasalts from the Quaternary backarc volcanic province, Payenia, of the Andean Southern Volcanic Zone in Argentina displays a clear north-to-south decrease in Mn/Feol. This is interpreted as the transition from mainly peridotite-derived melts in the north to mainly pyroxenite-derived melts in the south. The peridotite-pyroxenite source variation correlates with a transition of rock compositions from arc-type to OIB-type trace element signatures, where samples from the central part of the province are intermediate. The southernmost rocks have, e.g., relatively low La/Nb, Th/Nb and Th/La ratios as well as high Nb/U, Ce/Pb, Ba/Th and Eu/Eu* = 1.08. The northern samples are characterized by the opposite and have Eu/Eu* down to 0.86. Several incompatible trace element ratios in the rocks correlate with Mn/Feol and also reflect mixing of two geochemically distinct mantle sources. The peridotite melt end-member carries an arc signature that cannot solely be explained by fluid enrichment since these melts have relatively low Eu/Eu*, Ba/Th and high Th/La ratios, which suggest a component of upper continental crust (UCC) in the metasomatizing agent of the northern mantle. However, the addition to the mantle source of crustal materials or varying oxidation state cannot explain the variation in Mn and Mn/Fe of the melts and olivines along Payenia. Instead, the correlation between Mn/Feol and whole-rock (wr) trace element compositions is evidence of two-component mixing of melts derived from peridotite mantle source enriched by slab fluids and UCC melts and a pyroxenite mantle source with an EM1-type trace element signature. Very low Ca/Fe ratios ( 1.1) in the olivines of the peridotite melt component and lower calculated partition coefficients for Ca in olivine for these samples are suggested to be caused by higher H2O contents in the magmas derived from subduction zone enriched mantle. Well-correlated Mn/Fe ratios in the wr and primitive olivines demonstrate that the Mn/Fewr of these basalts that only fractionated olivine and chromite reflects the Mn/Fe of the primitive melts and can be used as a proxy for the amount of pyroxenite melt in the magmas. Using Mn/Fewr for a large dataset of primitive Payenia rocks, we show that decreasing Mn/Fewr is correlated with decreasing Mn and increasing Zn/Mn as expected for pyroxenite melts.

Nd, Sr and O isotopic study of the petrogenesis of two syntectonic members of the New Hampshire Plutonic Series

NASA Astrophysics Data System (ADS)

Lathrop, A. S.; Blum, Joel D.; Chamberlain, C. Page

1996-07-01

Nd, Sr and O isotope systematics were used to investigate the petrogenesis of two adjacent plutons of the Bethlehem Gneiss (BG) and the Kinsman Quartz Monzonite (KQM), exposed within the Central Maine Terrane (CMT) of New England. Both are Acadian-aged (≈413 Ma) synmetamorphic and syntectonic members of the New Hampshire Plutonic Series (NHPS). Potential source rocks analyzed for this study include Silurian and Devonian metasedimentary rocks of the CMT, and Ordovician metasedimentary rocks and granitic gneisses of the Bronson Hill Anticlinorium (BHA), which border the CMT to the west. The ɛSr(413), ɛNd(413) and δ18O values for the KQM range from 56.3 to 120.0, 2.8 to -6.4, and 7.6‰ to 12.9‰, respectively; values for the BG range from 7.4 to 144.7, 0.6 to -9.3, and 8.3‰ to 11.3‰, respectively; and values for possible source rocks range from 38.1 to 654.2, -10.7 to 5.4, and 6.2‰ to 14.1‰, respectively. Both the BG and KQM have extremely heterogeneous initial isotopic compositions consistent with mixing of multiple crustal source rocks, and neither contains a volumetrically significant (i.e., ≥10%) mantlederived component. Overlapping values of ɛNd(413), ɛSr(413) and δ18O values for both the BG and KQM samples resemble values for metasedimentary host rocks of the CMT and BHA. We observe no systematic correlations between ɛNd and ɛSr values for either the BG or the KQM. The ɛSr and δ18O values for the BG do not form any simple mixing trends, nor is there any direct correlation between the isotopic compositions of contact BG samples and their adjacent host rocks, in contrast to our observations for the KQM (Lathrop et al. 1994). We propose that the KQM and BG magmas were generated through anatexis of metasedimentary rocks from both the BHA and CMT in response to crystal thickening during the Acadian orogeny. Melting may have been initiated within CMT metasediments in response to high heat production in these mid-crustal rocks combined with crustal thickening, whereas melting of BHA rocks with normal crustal heat production, which were located at lower-crustal levels than CMT rocks, is likely to have been driven by crustal thickening alone. Following upward advection of mobile BHA magmas, BHA- and CMT-derived magmas may have mingled during complex Acadian deformation in the CMT, thus accounting for the isotopic similarities we observe between the BG and the KQM.

Cyclic Sediment Trading Between Channel and River Bed Sediments

NASA Astrophysics Data System (ADS)

Haddadchi, A.

2015-12-01

Much of the previous work on sediment tracing has focused on determining either the initial sources of the sediment (soils derive from a particular rock type) or the erosion processes generating the sediment. However, alluvial stores can be both a source and sink for sediment transported by streams. Here geochemical and fallout radionuclide tracing of river-bed and alluvial sediments are used to determine the role of secondary sources, sediment stores, as potential sources of sediment leaving Emu Creek catchment, southeastern Queensland, Australia. Activity concentrations of 137Cs on the river sediments are consistent with channel erosion being the dominant source at all sites sampled along the river. To characterise the deposition and remobilisation cycles in the catchment, a novel geochemical tracing approach was used. Successive pockets of alluvium were treated as discrete sink terms within geochemical mixing models and their source contributions compared with those of river bed sediments collected adjacent to each alluvial pocket. Three different size fractions were examined; silts and clays (<10 μm), silts (10-63 μm), and fine sands (63-212 μm). The contribution of the initial soil/rock type sources to river bed and alluvial sediments at each sampling site was identical for all three different size fractions, but varied along the stream. Combining these findings it is concluded that proximal alluvial stores dominated the supply of sediment to the river at each location, with this being particularly evident at the catchment outlet. Identical contribution of rock type sources to both river bed and alluvial pockets together with the dominant erosion being from channel banks indicates a high degree of 'trading' between the fluvial space and the alluvial space. Hence, management works aimed at primarily reducing the supply of sediments to the outlet of Emu Creek should focus on rehabilitation of channel banks in the lower catchment.

Proterozoic to Mesozoic evolution of North-West Africa and Peri-Gondwana microplates: Detrital zircon ages from Morocco and Canada

NASA Astrophysics Data System (ADS)

Marzoli, Andrea; Davies, Joshua H. F. L.; Youbi, Nasrrddine; Merle, Renaud; Dal Corso, Jacopo; Dunkley, Daniel J.; Fioretti, Anna Maria; Bellieni, Giuliano; Medina, Fida; Wotzlaw, Jörn-Frederik; McHone, Greg; Font, Eric; Bensalah, Mohamed Khalil

2017-05-01

The complex history of assemblage and disruption of continental plates surrounding the Atlantic Ocean is in part recorded by the distribution of detrital zircon ages entrained in continental sedimentary strata from Morocco (Central High Atlas and Argana basins) and Canada (Grand Manan Island, New Brunswick). Here we investigate detrital zircon from the latest Triassic (ca. 202 Ma) sedimentary strata directly underlying lava flows of the Central Atlantic magmatic province or interlayered within them. SHRIMP (Sensitive High-Resolution Ion MicroProbe) and LA-ICP-MS (Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry) U-Pb ages for zircon range from Paleozoic to Archean with a dominant Neoproterozoic peak, and significant amounts of ca. 2 Ga zircon. These ages suggest a prevailing West African (Gondwanan) provenance at all sampling sites. Notably, the Paleoproterozoic zircon population is particularly abundant in central Morocco, north of the High Atlas chain, suggesting the presence of Eburnean-aged rocks in this part of the country, which is consistent with recent geochronologic data from outcropping rocks. Minor amounts of late Mesoproterozoic and early Neoproterozoic zircon ages (ca. 1.1-0.9 Ga) in Moroccan samples are more difficult to interpret. A provenance from Avalonia or Amazonia, as proposed by previous studies is not supported by the age distributions observed here. An involvement of more distal source regions, possibly located in north-eastern Africa (Arabian Nubian Shield) would instead be possible. Paleozoic zircon ages are abundant in the Canadian sample, pointing to a significant contribution from Hercynian aged source rocks. Such a signal is nearly absent in the Moroccan samples, suggesting that zircon-bearing Hercynian granitic rocks of the Moroccan Meseta block were not yet outcropping at ca. 200 Ma. The only Moroccan samples that yield Paleozoic zircon ages are those interlayered within the CAMP lavas, suggesting an increased dismantling (i.e. uplift) of the Hercynian chain during emplacement of CAMP lava flows, combined with subsidence of the volcanic grabens.

Nitrate and selected pesticides in ground water of the Mid-Atlantic region

USGS Publications Warehouse

Ator, Scott W.; Ferrari, Matthew J.

1997-01-01

Data from more than 850 sites were compiled and analyzed to document the occurrence of nitrate and pesticides in ground water of the Mid-Atlantic region as part of the Mid-Atlantic Integrated Assessment program of the U.S. Environmental Protection Agency. Only those data collected by the U.S. Geological Survey as part of regional networks between October 1985 and September 1996 (inclusive) were used in the analyses, and the data were examined to ensure analytical results are not biased toward sites at the same location or sites sampled multiple times during this period. Regional data are available for most of the Mid-Atlantic region but large spatial gaps in available data do exist. Nitrate was detected in nearly three-quarters of the samples for which it was analyzed, commonly at levels that suggest anthropogenic sources. Ten percent of samples contained nitrate at concentrations exceeding the Federal Maximum Contaminant Level (MCL) of 10 milligrams per liter as nitrogen. Pesticide compounds (including atrazine, metolachlor, prometon, simazine, and desethylatrazine, an atrazine degradate) were detected in about half of the samples for which they were analyzed, but rarely at concentrations exceeding established MCL?s. The most commonly detected pesticide compounds were desethylatrazine and atrazine. The occurrence of nitrate and pesticides in ground water of the Mid-Atlantic region is related to land cover and rock type. Likely sources of nitrate and pesticides to ground water include agricultural and urban land-use practices; rock type affects the movement of these compounds into and through the ground-water system. Nitrate concentrations in the compiled data set are significantly higher in ground water in agricultural areas than in urban or forested areas, but concentrations in areas of row crops are statistically indistinguishable from those in areas of pastures. Detection frequencies of atrazine, desethylatrazine, and simazine are indistinguishable among urban areas, row crops, and pastures. Prometon was most commonly detected in ground water in urban areas. Ground-water samples from forested areas typically contained the lowest concentrations of nitrate and detection frequencies of pesticides. Concentrations of nitrate and detection frequencies of pesticides were significantly higher in samples from carbonate rocks than in those from any other rock type. Most areas of the Mid-Atlantic region that are underlain by carbonate rocks have been developed for agricultural or urban use and the solution channels that are typical of carbonate rocks allow for relatively rapid transport of surficial contaminants throughout the ground-water system. Nitrate concentrations in unconsolidated aquifers were among the lowest for all rock types, possibly because of denitrification in organic-rich subsoils and shallow sediments.

Detrital zircon U-Pb geochronology and whole-rock Nd-isotope constraints on sediment provenance in the Neoproterozoic Sergipano orogen, Brazil: From early passive margins to late foreland basins

NASA Astrophysics Data System (ADS)

Oliveira, E. P.; McNaughton, N. J.; Windley, B. F.; Carvalho, M. J.; Nascimento, R. S.

2015-11-01

SHRIMP U-Pb detrital zircon geochronology and depleted-mantle Nd-model ages of clastic rocks were combined to understand the sediment provenance in the Neoproterozoic Sergipano Belt. The Sergipano is the main orogenic belt between the Borborema province and the São Francisco Craton, eastern South America; it is divisible into several lithostratigraphic domains from North to South: Canindé, Poço Redondo-Marancó, Macururé, Vaza Barris, and Estância. Nd model ages (TDM) and detrital zircon U-Pb SHRIMP geochronology indicate that the protoliths of clastic metasedimentary rocks from the Marancó and Macururé domains were mostly derived from eroded late Mesoproterozoic to early Neoproterozoic rocks (1000-900 Ma), whereas detritus of similar rocks from the Canindé domain came from a younger source (ca. 700 Ma and 1000 Ma). Samples from the Vaza Barris domain show the greatest scatter of both TDM and zircon ages amongst all domains, but with important contributions from Proterozoic sources (690-1050 Ma and ca. 2100 Ma) and less from Archaean sources. The Estância domain samples have zircon population peaks at 570 Ma, 600 Ma, and 920-980 Ma, with a few older grains; one diamictite contains only ca. 2150 Ma zircon grains. Our preliminary results support a model in which sediments of the Marancó and Macururé domains were deposited on a continental margin of the ancient Borborema plate before its collision with the São Francisco Craton; the Canindé domain is likely to be an aborted Neoproterozoic rift assemblage within the southern part of the Borborema plate (Pernambuco-Alagoas massif). The basal units of the Vaza Barris and Estância domains have clast sources from the São Francisco Craton and are best interpreted as passive margin sediments. However, the uppermost units of the Estância and Vaza Barris domains come from foreland basins formed during collision of Borborema plate with the São Francisco Craton.

Estimating thermal maturity in the Eagle Ford Shale petroleum system using gas gravity data

USGS Publications Warehouse

Birdwell, Justin E.; Kinney, Scott A.

2017-01-01

Basin-wide datasets that provide information on the geochemical properties of petroleum systems, such as source rock quality, product composition, and thermal maturity, are often difficult to come by or assemble from publically available data. When published studies are available and include these kinds of properties, they generally have few sampling locations and limited numbers and types of analyses. Therefore, production-related data and engineering parameters can provide useful proxies for geochemical properties that are often widely available across a play and in some states are reported in publically available or commercial databases. Gas-oil ratios (GOR) can be calculated from instantaneous or cumulative production data and can be related to the source rock geochemical properties like kerogen type (Lewan and Henry, 1999) and thermal maturity (Tian et al., 2013; U.S. Energy Information Administration [EIA], 2014). Oil density or specific gravity (SG), often reported in American Petroleum Institute units (°API = 141.5 /SG – 131.5), can also provide information on source rock thermal maturity, particularly when combined with GOR values in unconventional petroleum systems (Nesheim, 2017).

Origins of cryptic variation in the Ediacaran-Fortunian rhyolitic ignimbrites of the Saldanha Bay Volcanic Complex, Western Cape, South Africa

NASA Astrophysics Data System (ADS)

Clemens, J. D.; Stevens, G.; Frei, D.; Joseph, C. S. A.

2017-12-01

The Saldanha eruption centre, on the West Coast of South Africa, consists of 542 Ma, intracaldera, S-type, rhyolite ignimbrites divided into the basal Saldanha Ignimbrite and the partly overlying Jacob's Bay Ignimbrite. Depleted-mantle Nd model ages suggest magma sources younger than the Early Mesoproterozoic, and located within the Neoproterozoic Malmesbury Group and Swartland complex metasedimentary and metavolcanic rocks that form the regional basement. The Sr isotope systematics suggest that the dominant source rocks were metavolcaniclastic rocks and metagreywackes, and that the magmas formed from separate batches extracted from the same heterogeneous source. No apparent magma mixing trends relate the Saldanha to the Jacob's Bay Ignimbrites, or either of these to the magmas that formed the Plankiesbaai or Tsaarsbank Ignimbrites in the neighbouring Postberg eruption centre. The magmas were extracted from their source rocks carrying small but significant proportions of peritectic and restitic accessory minerals. Variations in the content of this entrained crystal cargo were responsible for most of the chemical variations in the magmas. Although we cannot construct a cogent crystal fractionation model to relate these groups of magmas, at least some crystal fractionation occurred, as an overlay on the primary signal due to peritectic assemblage entrainment (PAE). Thus, the causes of the cryptic chemical variation among the ignimbrite magmas of the Saldanha centre are variable, but dominated by the compositions of the parent melts and PAE. The preservation of clear, source-inherited chemical signatures, in individual samples, calls into question the common interpretation of silicic calderas as having been formed in large magma reservoirs, with magma compositions shaped by magma mingling, mixing, and fractional crystallization. The Saldanha rocks suggest a more intimate connection between source and erupted magma, and perhaps indicate that silicic magmas are too viscous to be significantly modified by magma-chamber processes.

Reconnaissance for radioactive materials in the southern part of Brazil

USGS Publications Warehouse

Pierson, Charles T.; Haynes, Donald D.; Filho, Evaristo Ribeiro

1957-01-01

During 1954-1956 a reconnaissance for radioactive minerals was made with carborne, airborne and handborne scintillation equipment in the southern Brazilian states of Rio de Janeiro, Sao Paulo, Parana, Santa Catarina and Rio Grande do Sul. During the traverse covering more than 5,000 kilometers the authors checked the radioactivity of Precambrian igneous and metamorphic rocks, Paleozoic, Mesozoic and Cenozoic sedimentary rocks, and Mesozoic alkalic intrusive and basaltic extrusive rocks. The 22 samples collected contained from 0.003 to 0.029 percent equivalent uranium oxide and from 0.10 to 0.91 percent equivalent thorimn; two samples were taken from radioactive pegmati tes for mineralogic studies. None of the localities is at present a commercial source of uranium or thorium; however, additional work should be done near the alkalic stock at Lages in the State of Santa Catarina and at the Passo das Tropas fossil plant locality near Santa Maria in the state of Rio Grande do Sul. Near Lages highly altered alkalic rock from a dike contained 0.026 percent uranium oxide. At Passo das Tropas highly altered, limonite-impregnated sandstone from the Rio do Rasto group of sedimentary rocks contained 0.029 percent uranium oxide.

Water-quality data collected to determine the presence, source, and concentration of lead in the drinking water supply at Pipe Spring National Monument, northern Arizona

USGS Publications Warehouse

Macy, Jamie P.; Sharrow, David; Unema, Joel

2013-01-01

Pipe Spring National Monument in northern Arizona contains historically significant springs. The groundwater source of these springs is the same aquifer that presently is an important source of drinking water for the Pipe Spring National Monument facilities, the Kaibab Paiute Tribe, and the community of Moccasin. The Kaibab Paiute Tribe monitored lead concentrations from 2004 to 2009; some of the analytical results exceeded the U.S. Environmental Protection Agency action level for treatment technique for lead of 15 parts per billion. The National Park Service and the Kaibab Paiute Tribe were concerned that the local groundwater system that provides the domestic water supply might be contaminated with lead. Lead concentrations in water samples collected by the U.S. Geological Survey from three springs, five wells, two water storage tanks, and one faucet were less than the U.S. Environmental Protection Agency action level for treatment technique. Lead concentrations of rock samples representative of the rock units in which the local groundwater resides were less than 22 parts per million.

A program to calculate pulse transmission responses through transversely isotropic media

NASA Astrophysics Data System (ADS)

Li, Wei; Schmitt, Douglas R.; Zou, Changchun; Chen, Xiwei

2018-05-01

We provide a program (AOTI2D) to model responses of ultrasonic pulse transmission measurements through arbitrarily oriented transversely isotropic rocks. The program is built with the distributed point source method that treats the transducers as a series of point sources. The response of each point source is calculated according to the ray-tracing theory of elastic plane waves. The program could offer basic wave parameters including phase and group velocities, polarization, anisotropic reflection coefficients and directivity patterns, and model the wave fields, static wave beam, and the observed signals for pulse transmission measurements considering the material's elastic stiffnesses and orientations, sample dimensions, and the size and positions of the transmitters and the receivers. The program could be applied to exhibit the ultrasonic beam behaviors in anisotropic media, such as the skew and diffraction of ultrasonic beams, and analyze its effect on pulse transmission measurements. The program would be a useful tool to help design the experimental configuration and interpret the results of ultrasonic pulse transmission measurements through either isotropic or transversely isotropic rock samples.

Geochemistry of the Upper Triassic black mudstones in the Qiangtang Basin, Tibet: Implications for paleoenvironment, provenance, and tectonic setting

NASA Astrophysics Data System (ADS)

Wang, Zhongwei; Wang, Jian; Fu, Xiugen; Zhan, Wangzhong; Armstrong-Altrin, John S.; Yu, Fei; Feng, Xinglei; Song, Chunyan; Zeng, Shengqiang

2018-07-01

The Qiangtang Basin is the largest Mesozoic marine basin in the Tibetan Plateau. The Upper Triassic black mudstones are among the most significant hydrocarbon source rocks in this basin. Here, we present geochemical data for the Upper Triassic black mudstones to determine their paleoenvironment conditions, provenance, and tectonic setting. To achieve these, 30 black mudstones formed in various sedimentary environments were collected from the Zangxiahe, Zana, and Bagong formations. The results show that the total REE concentrations of mudstones from these formations range from 169 to 214 ppm, 204 to 220 ppm, and 141 to 194 ppm, respectively. All samples have chondrite-normalized REE patterns with enrichment of LREE, depletion of HREE and negative Eu and Ce anomalies. Specifically, mudstones from the Bagong Formation exhibit higher negative Eu anomalies and lower REE contents than those from the Zangxiahe and Zana formations. Mudstones from the Zangxiahe and Zana formations with low Sr/Ba and Sr/Cu ratios indicate the humid climate, whereas the high Sr/Ba and Sr/Cu ratios of rocks from the Bagong Formation suggest the arid climate. The low U/Th, (Cu + Mo)/Zn, V/Cr and Ni/Co ratios of rocks from the Zangxiahe, Zana, and Bagong formations are indicators of oxidized conditions. The bivariate diagrams (TiO2 vs. Al2O3, TiO2 vs. Zr, La/Th vs. Hf, and Co/Th vs. La/Sc) reveal that mudstones from the Zangxiahe and Zana formations were potentially derived from intermediate igneous rocks, whereas mudstones from the Bagong Formation were probably sourced from felsic igneous rocks. Their source rocks are mostly deposited in the collisional setting. REE of mudstones from the Zangxiahe, Zana, and Bagong formations were possibly originated from terrigenous detritus, with minor non-terrigenous contributions into the Zana samples. The REE contents of these mudstones are controlled mainly by terrigenous detrital minerals, rather than by the paleoclimate, paleoredox conditions, or organic matter. However, calcite minerals could dilute REE. Therefore, the REE contents of the Bagong Formation mudstones are significant lower than those of the Zangxiahe and Zana formations mudstones.

Lead (Pb) Isotope Baselines for Studies of Ancient Human Migration and Trade in the Maya Region.

PubMed

Sharpe, Ashley E; Kamenov, George D; Gilli, Adrian; Hodell, David A; Emery, Kitty F; Brenner, Mark; Krigbaum, John

2016-01-01

We examined the potential use of lead (Pb) isotopes to source archaeological materials from the Maya region of Mesoamerica. The main objectives were to determine if: 1) geologic terrains throughout the Maya area exhibit distinct lead isotope ratios (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb), and 2) a combination of lead and strontium ratios can enhance sourcing procedures in the Mesoamerica region. We analyzed 60 rock samples for lead isotope ratios and a representative subset of samples for lead, uranium, and thorium concentrations across the Maya region, including the Northern Lowlands of the Mexican Yucatan Peninsula, the Southern Lowlands of Guatemala and Belize, the Volcanic Highlands, the Belizean Maya Mountains, and the Metamorphic Province/Motagua Valley. Although there is some overlap within certain sub-regions, particularly the geologically diverse Metamorphic Province, lead isotopes can be used to distinguish between the Northern Lowlands, the Southern Lowlands, and the Volcanic Highlands. The distinct lead isotope ratios in the sub-regions are related to the geology of the Maya area, exhibiting a general trend in the lowlands of geologically younger rocks in the north to older rocks in the south, and Cenozoic volcanic rocks in the southern highlands. Combined with other sourcing techniques such as strontium (87Sr/86Sr) and oxygen (δ18O), a regional baseline for lead isotope ratios can contribute to the development of lead isoscapes in the Maya area, and may help to distinguish among geographic sub-regions at a finer scale than has been previously possible. These isotope baselines will provide archaeologists with an additional tool to track the origin and movement of ancient humans and artifacts across this important region.

Lead (Pb) Isotope Baselines for Studies of Ancient Human Migration and Trade in the Maya Region

PubMed Central

Kamenov, George D.; Gilli, Adrian; Hodell, David A.; Emery, Kitty F.; Brenner, Mark; Krigbaum, John

2016-01-01

We examined the potential use of lead (Pb) isotopes to source archaeological materials from the Maya region of Mesoamerica. The main objectives were to determine if: 1) geologic terrains throughout the Maya area exhibit distinct lead isotope ratios (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb), and 2) a combination of lead and strontium ratios can enhance sourcing procedures in the Mesoamerica region. We analyzed 60 rock samples for lead isotope ratios and a representative subset of samples for lead, uranium, and thorium concentrations across the Maya region, including the Northern Lowlands of the Mexican Yucatan Peninsula, the Southern Lowlands of Guatemala and Belize, the Volcanic Highlands, the Belizean Maya Mountains, and the Metamorphic Province/Motagua Valley. Although there is some overlap within certain sub-regions, particularly the geologically diverse Metamorphic Province, lead isotopes can be used to distinguish between the Northern Lowlands, the Southern Lowlands, and the Volcanic Highlands. The distinct lead isotope ratios in the sub-regions are related to the geology of the Maya area, exhibiting a general trend in the lowlands of geologically younger rocks in the north to older rocks in the south, and Cenozoic volcanic rocks in the southern highlands. Combined with other sourcing techniques such as strontium (87Sr/86Sr) and oxygen (δ18O), a regional baseline for lead isotope ratios can contribute to the development of lead isoscapes in the Maya area, and may help to distinguish among geographic sub-regions at a finer scale than has been previously possible. These isotope baselines will provide archaeologists with an additional tool to track the origin and movement of ancient humans and artifacts across this important region. PMID:27806065

Popping rocks from the Mid-Atlantic Ridge: Insights into mantle volatile concentrations and degassing dynamics

NASA Astrophysics Data System (ADS)

Jones, M.; Soule, S. A.; Kurz, M. D.; Wanless, V. D.; Le Roux, V.; Klein, F.; Mittelstaedt, E. L.; Curtice, J.

2016-12-01

During a 1985 cruise, the Mid-Atlantic Ridge (MAR) near 14°N yielded an unusually vesicular mid-ocean ridge (MOR) basalt that popped upon recovery from the seafloor due to the release of trapped volatiles. This `popping rock' has been inferred to be representative of primitive, undegassed magmas from the upper mantle due to its high volatile concentrations. Thus, the sample has been used to constrain CO2 flux from the MOR system, upper mantle volatile concentrations, and magma degassing dynamics. However, the lack of geologic context for the original popping rock raises questions about whether it truly reflects the volatile content of its mantle source. Here, we present results from a 2016 cruise to the MAR aimed at characterizing the geologic context of popping rocks and understanding their origins. The newly recovered samples display differences in volatile concentrations and vesicularities between popping and non-popping rocks. These differences may be related to geologic setting and eruption dynamics with potential implications for mantle volatile concentrations. Volatile concentrations in the outer quenched margin of new samples were measured by ion microprobe to elucidate degassing systematics, brine/magma interactions, and popping rock formation. The large variability in dissolved H2O (0.05-0.77 wt%) can be attributed to spatially variable brine contamination. Dissolved CO2 concentrations (153-356 ppm) are likely controlled by initial volatile concentrations and variable degrees of degassing. The subset of popping samples display low dissolved CO2 concentrations (161-178 ppm) and moderate dissolved H2O concentrations (.44-.50 wt%) and are at equilibrium with their eruption depth based on solubility calculations. X-ray microtomography reveals vesicularity in newly collected popping rocks exceeding 19%, making these samples the most highly vesicular recovered from the MAR. The total gas contents in the basaltic glasses are inferred from dissolved volatile concentrations and vesicularity. These calculations are aided by analysis of gas contents in vesicles by confocal Raman spectroscopy and vacuum crushing experiments. The preliminary results and seafloor observations allow an evaluation of the origins of popping rocks and their implications for mantle volatile concentrations.

Large-scale removal of lithosphere underneath the North China Craton in the Early Cretaceous: Geochemical constraints from volcanic lavas in the Bohai Bay Basin

NASA Astrophysics Data System (ADS)

Sun, Jing; Liu, Zheng; Zhang, Shuai; Li, Xiaoguang; Qi, Jiafu

2017-11-01

Cratons are generally considered as the most stable tectonic units on the Earth. Rare magmatism, seismic activity, and intracrustal ductile deformation occur in them. However, several cratons experienced entirely different fates, including the North China Craton (NCC), and were subsequently destroyed. Geodynamic mechanisms and timing of the cratonic destruction are strongly debated. In this paper, we investigate a suite of Mesozoic intermediate to felsic volcanic rocks which are collected from boreholes in the Liaohe Depression of the Bohai Bay Basin the eastern NCC. These volcanic rocks have Precambrian basement-like Sr-Nd isotopic characteristics, consistent with derivation from the lower continental crust underneath the NCC. The Late Jurassic ( 165 Ma) intermediate volcanic rocks don't exhibit markedly negative Eu anomalies, which require a source beyond the plagioclase stability field. And the low heavy rare earth elements (HREEs) contents of these samples indicate that their source has garnet as residue. The Early Cretaceous ( 122 Ma) felsic volcanic rocks are depleted in HREEs but with remarkable Eu anomalies, suggesting that their source have both garnet and plagioclase. The crust thicknesses, estimated from the geochemistry of the intermediate and felsic rocks, are ≥ 50 km at 165 Ma and 30-50 km at 122 Ma, respectively. The crustal thinning is attributed to lithospheric delamination beneath the NCC. Our results combined with previous studies imply that the large-scale lithospheric removal occurred in the Early Cretaceous, between 140 and 120 Ma.

Geochemistry and origins of mineralized waters in the Floridan aquifer system, northeastern Florida

USGS Publications Warehouse

Phelps, G.G.

2001-01-01

Increases in chloride concentration have been observed in water from numerous wells tapping the Floridan aquifer system in northeastern Florida. Although most increases have been in the eastern part of Duval County, Florida, no spatial pattern in elevated chloride concentrations is discernible. Possible sources of the mineralized water include modern seawater intrusion; unflushed Miocene-to-Pleistocene-age seawater or connate water in aquifer sediments; or mineralized water from deeper zones of the aquifer system or from formations beneath the Floridan aquifer system. The purpose of this study was to document the chemical and isotopic characteristics of water samples from various aquifer zones, and from geochemical and hydrogeologic data, to infer the source of the increased mineralization. Water samples were collected from 53 wells in northeastern Florida during 1997-1999. Wells tapped various zones of the aquifer including: the Fernandina permeable zone (FPZ), the upper zone of the Lower Floridan aquifer (UZLF), the Upper Floridan aquifer (UFA), and both the UFA and the UZLF. Water samples were analyzed for major ions and trace constituents and for isotopes of carbon, oxygen, hydrogen, sulfur, strontium, chlorine, and boron. Samples of rock from the aquifer were analyzed for isotopes of oxygen, carbon, and strontium. In general, water from various aquifer zones cannot be differentiated based on chemistry, except for water from FPZ wells. Major-ion concentrations vary as much within the upper zone of the Lower Floridan aquifer and the Upper Floridan aquifer as between these two zones. Simple models of mixing between fresh ground water and either modern seawater or water from the FPZ as a mineralized end member show that many water samples from the UZLF aquifer and the UFA are enriched in bicarbonate, calcium, magnesium, sulfate, fluoride, and silica and are depleted in sodium and potassium (as compared to concentrations predicted by simple mixing). Chemical mass-balance models of mixing and reactions between a hypothetical initial seawater and aquifer minerals cannot account for the observed water chemistry in a few wells, implying a source other than seawater, either ancient or modern, or the occurrence of other more complex rock-water reactions. Hydrogeologic and geochemical data from water and aquifer samples indicate that the most likely source of mineralized water in some wells yielding water with increasing chloride concentrations is water from the FPZ. In other wells, the flushing of Miocene-to-Pleistocene-age seawater can account for the observed chloride concentrations. The fact that most of the water samples collected are a mixture of less than one percent of mineralized water with more than 99 percent fresh or recharge water makes identifying the source of the mineralized water difficult. Differences in carbon-14 and sulfur-34 values probably reflect areal differences in aquifer mineralogy and distribution of organic carbon related to paleokarst features. Geochemical mass-balance models of seawater-rock interaction are unable to account for the chemical and isotopic composition of mineralized water from the FPZ, which implies another source of mineralized water, such as a brine, or the occurrence of more complex water-rock reactions.

Provenance from zircon U-Pb age distributions in crustally contaminated granitoids

NASA Astrophysics Data System (ADS)

Bahlburg, Heinrich; Berndt, Jasper

2016-05-01

The basement of sedimentary basins is often entirely covered by a potentially multi-stage basin fill and therefore removed from direct observation and sampling. Melts intruding through the basin stratigraphy at a subsequent stage in the geological evolution of a region may assimilate significant volumes of country rocks. This component may be preserved in the intrusive body either as xenoliths or it may be reflected only by the age spectrum of incorporated zircons. Here we present the case of an Ordovician calc-alkaline intrusive belt in NW Argentina named the "Faja Eruptiva de la Puna Oriental" (Faja Eruptiva), which in the course of intrusion sampled the unexposed and unknown basement of the Ordovician basin in this region, and parts of the basin stratigraphy. We present new LA-ICP-MS U-Pb ages on zircons from 9 granodiorites and granites of the Faja Eruptiva. The main part of the Faja Eruptiva intruded c. 445 Ma in the Late Ordovician. The zircon ages obtained from the intrusive rocks have a large spread between 2683.5 ± 21.6 and 440.0 ± 4.9 Ma and reflect the underlying crust and may be interpreted in several ways. The inherited zircons may have been derived from the oldest known unit in the region, the thick siliciclastic turbidite successions of the upper Neoproterozoic-lower Cambrian Puncoviscana Formation, which is inferred to represent the basement of the NW Argentina. The basement to the Puncoviscana Formation is not known. Alternatively, the inherited zircons may reflect the geochronological structure of the entire unexposed Early Paleozoic crust underlying this region of which the Puncoviscana Formation was only one component. This crust likely contained rocks pertaining to and detritus derived from earlier orogenic cycles of the southwestern Amazonia craton, including sources of Early Meso- and Paleoproterozoic age. Detritus derived, in turn, from the Faja Eruptiva intrusive belt reflects the origin of the granitoids as well as the inherited geochronological and isotope geochemical structure of either the basement and/or distant sources having supplied material to the basement rocks. If unrecognized, sediment formed from such granitoid sources may erroneously be used to infer the exposure of, and direct detrital contributions from, a variety of older source rocks in fact not directly involved in the studied source-sink system.

Questa baseline and premining ground-water quality investigation. 8. Lake-sediment geochemical record from 1960 to 2002, Eagle Rock and Fawn Lakes, Taos County, New Mexico

USGS Publications Warehouse

Church, S.E.; Fey, D.L.; Marot, M.E.

2005-01-01

Geochemical studies of lake sediment from Eagle Rock Lake and upper Fawn Lake were conducted to evaluate the effect of mining at the Molycorp Questa porphyry molybdenum deposit located immediately north of the Red River. Two cores were taken, one from each lake near the outlet where the sediment was thinnest, and they were sampled at 1-cm intervals to provide geochemical data at less than 1-year resolution. Samples from the core intervals were digested and analyzed for 34 elements using ICP-AES (inductively coupled plasma-atomic emission spectrometry). The activity of 137Cs has been used to establish the beginning of sedimentation in the two lakes. Correlation of the geochemistry of heavy-mineral suites in the cores from both Fawn and Eagle Rock Lakes has been used to develop a sedimentation model to date the intervals sampled. The core from upper Fawn Lake, located upstream of the deposit, provided an annual sedimentary record of the geochemical baseline for material being transported in the Red River, whereas the core from Eagle Rock Lake, located downstream of the deposit, provided an annual record of the effect of mining at the Questa mine on the sediment in the Red River. Abrupt changes in the concentrations of many lithophile and deposit-related metals occur in the middle of the Eagle Rock Lake core, which we correlate with the major flood-of-record recorded at the Questa gage at Eagle Rock Lake in 1979. Sediment from the Red River collected at low flow in 2002 is a poor match for the geochemical data from the sediment core in Eagle Rock Lake. The change in sediment geochemistry in Eagle Rock Lake in the post-1979 interval is dramatic and requires that a new source of sediment be identified that has substantially different geochemistry from that in the pre-1979 core interval. Loss of mill tailings from pipeline breaks are most likely responsible for some of the spikes in trace-element concentrations in the Eagle Rock Lake core. Enrichment of Al2O3, Cu, and Zn occurred as a result of chemical precipitation of these metals from ground water upstream in the Red River. Comparisons of the geochemistry of the post-1979 sediment core with both mine wastes and with premining sediment from the vicinity of the Questa mine indicate that both are possible sources for this new component of sediment. Existing data have not resolved this enigma.

ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

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

Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

2002-11-18

During the sixth quarter of this research project the research team developed a method and the experimental procedures for acquiring the data needed for ultrasonic tomography of rock core samples under triaxial stress conditions as outlined in Task 10. Traditional triaxial compression experiments, where compressional and shear wave velocities are measured, provide little or no information about the internal spatial distribution of mechanical damage within the sample. The velocities measured between platen-to-platen or sensor-to-sensor reflects an averaging of all the velocities occurring along that particular raypath across the boundaries of the rock. The research team is attempting to develop andmore » refine a laboratory equivalent of seismic tomography for use on rock samples deformed under triaxial stress conditions. Seismic tomography, utilized for example in crosswell tomography, allows an imaging of the velocities within a discrete zone within the rock. Ultrasonic or acoustic tomography is essentially the extension of that field technology applied to rock samples deforming in the laboratory at high pressures. This report outlines the technical steps and procedures for developing this technology for use on weak, soft chalk samples. Laboratory tests indicate that the chalk samples exhibit major changes in compressional and shear wave velocities during compaction. Since chalk is the rock type responsible for the severe subsidence and compaction in the North Sea it was selected for the first efforts at tomographic imaging of soft rocks. Field evidence from the North Sea suggests that compaction, which has resulted in over 30 feet of subsidence to date, is heterogeneously distributed within the reservoir. The research team will attempt to image this very process in chalk samples. The initial tomographic studies (Scott et al., 1994a,b; 1998) were accomplished on well cemented, competent rocks such as Berea sandstone. The extension of the technology to weaker samples is more difficult but potentially much more rewarding. The chalk, since it is a weak material, also attenuates wave propagation more than other rock types. Three different types of sensors were considered (and tested) for the tomographic imaging project: 600 KHz PZT, 1 MHz PZT, and PVDF film sensors. 600 KHz PZT crystals were selected because they generated a sufficiently high amplitude pulse to propagate across the damaged chalk. A number of different configurations were considered for placement of the acoustic arrays. It was decided after preliminary testing that the most optimum arrangement of the acoustic sensors was to place three arrays of sensors, with each array containing twenty sensors, around the sample. There would be two horizontal arrays to tomographically image two circular cross-sectional planes through the rock core sample. A third array would be vertically oriented to provide a vertical cross-sectional view of the sample. A total of 260 acoustic raypaths would be shot and acquired in the horizontal acoustic array to create each horizontal tomographic image. The sensors can be used as both acoustic sources or as acoustic each of the 10 pulsers to the 10 receivers.« less

Provenance analysis and detrital zircon geochronology on the onshore Makran accretionary wedge, SE Iran: implication for the geodynamic setting

NASA Astrophysics Data System (ADS)

Mohammadi, Ali; Burg, Jean-Pierre; Winkler, Wilfried; Ruh, Jonas

2014-05-01

The Makran, located in Southeast Iran and South Pakistan, is one of the largest accretionary wedges on Earth. In Iran it comprises turbiditic sediments ranging in age from Late Cretaceous to Holocene. We present a provenance analysis on sandstones, which is aimed at reconstructing the assemblages of source rocks and the tectonic setting from which the clastic material was derived. Sandstone samples collected from different units span the regional stratigraphy from Late Cretaceous to Miocene. Laser ablation ICP-MS resulted in ca 2800 new U-Pb ages of individual detrital zircons from 18 samples collected in onshore Makran. 101 detrital zircons from a Late Cretaceous fine grained sandstone range from 180 to 160 Ma (Middle Jurassic). 478 detrital zircons from mid- to late Eocene sandstones allow differentiating a NE and NW sector of the Makran Basin. Zircon grains in the NE basin belong to two populations peaking at 180 to 160 Ma (late Early to Middle Jurassic) and 50 to 40 Ma (Mid-Eocene), with the noticeable absence of Cretaceous grains. In the NW basin, detrital zircons are 120 to 40 Ma (late Early Cretaceous to Lutetian, Eocene). 587 detrital zircon grains from fine to medium grained Oligocene sandstones collected over the whole area also range from 120 to 40 Ma (late Early Cretaceous to Eocene, Lutetian). 1611 detrital zircons from early Miocene sandstones show again distinctly different ages in the eastern and western parts of the basin. They range from 120 to 40 Ma (late Early Cretaceous to Eocene) in the eastern and from 80 to 40 Ma (Late Cretaceous to Eocene) in the western basin. Hf isotopes analyses were performed on 120 zircon grains from 6 samples. Negative values (-2 to -15) in Middle Jurassic and late Early Cretaceous zircons indicate minor or no influence of mantle reservoirs which implies a rifting setting during crystallization of the zircons. Low negative to positive (-5 to +10) values in Late Cretaceous and Eocene zircons indicate mixed crustal and juvenile magma sources, which are common in continental arc environments. Point counts of 32 sandstone thin sections were performed following the Gazzi-Dikinson method. 300-400 points were counted in each thin section. The sandstones are feldspathic litharenites and litharenites. Feldspar is dominantly plagioclase (> 90%) with minor amounts of K-feldspar. Most of the quartz grains (75%) are mono-crystalline but poly-crystalline ones (maximum 25%) also occur. Rock fragments are represented by sedimentary, volcanic and metamorphic grains. Volcanic rock-fragments mostly are andesites and volcanic chert. Sedimentary lithic grains comprise mostly sandstone, siltstone, limestone and dolomite. Metamorphic lithic grains generally are low-grade schists and phyllites. In various compositional ternary diagrams, the sources of the sandstones plot in the transitional to dissected arc and recycled orogenic fields. We selected 26 samples for heavy mineral study. 200-300 grain were identified and counted in each sample. Heavy mineral suites show a highly variable composition including (1) a group of ultra-stable minerals (zircon, monazite, tourmaline, rutile, brookite, anatase and sphene) derived from a granitic continental crust sources, (2) metastable minerals delivered from variable metamorphic-grade source rocks (epidote group, garnet, staurolite, chloritoid, kyanite, andalusite, glaucophane), (3) chromian spinel from ultrabasic rocks, (4) common hornblende either supplied from metamorphic or basic igneous series, and (5) a local pyroxene-rich source in the pyroclastic sandstone formation overlying pillow lavas. Glaucophane (5-20%) occurs in several samples, which indicates high-pressure/low-temperature metamorphic rocks in the detrital source areas for Eocene and Miocene sandstones. Earlier work in the Pakistani Makran suggested that pre-Miocene sediments were supplied from the Himalaya, whereas Miocene to Recent deposits were reworked older sediments of the accretionary wedge. Our data do not support this conclusion. Instead, we identified rifting-related detrital sources from Middle Jurassic to late Early Cretaceous (175 - 100 Ma) and the establishment of a continental volcanic arc from Late Cretaceous to Eocene (80 to 40 Ma). In addition, paleocurrent directions in Makran sandstone show general sediment transport from North to South; Cr-spinel as well as high-P/low-T heavy minerals most likely have been derived from the blueschist-bearing Makran ophiolitic and igneous belt to the North.

Thermal conductivity determinations on solid rock - a comparison between a steady-state divided-bar apparatus and a commercial transient line-source device

USGS Publications Warehouse

Sass, J.H.; Stone, C.; Munroe, R.J.

1984-01-01

Two apparatuses were used to measure thermal conductivities on pairs of contiguous samples from 17 specimens of solid rock: the USGS divided-bar apparatus, a steadystate comparative method, and the Shotherm "Quick Thermal Meter" (QTM), which employs a transient strip heat source. Both devices were calibrated relative to fused silica. Both devices have a reproducibility of ??5% or better depending, to some extent, on the physical nature of the specimen being tested. For solid rocks, specimen preparation for the divided bar is much more tedious and expensive than for the QTM, which seems insensitive to minor surface roughness. The QTM does, however, require quite large specimens (30 mm ?? 60 mm ?? 100 mm as a minimum for rocks) with even larger specimens (50 mm ?? 100 mm ?? 100 mm) required for higher conductivity material (3.5 W m-1 K-1 and greater). Experimental times are comparable; however, the QTM is a self-contained unit that can be transported easily and set up quickly and requires no more space than a standard desk top. From a formal statistical comparison, it appears that, over a large range of conductivities (1.4 to ???5 W m-1 K-1) and rock types, the two instruments will yield the same value of thermal conductivity for isotropic rocks. ?? 1984.

Geochemical Database for Igneous Rocks of the Ancestral Cascades Arc - Southern Segment, California and Nevada

USGS Publications Warehouse

du Bray, Edward A.; John, David A.; Putirka, Keith; Cousens, Brian L.

2009-01-01

Volcanic rocks that form the southern segment of the Cascades magmatic arc are an important manifestation of Cenozoic subduction and associated magmatism in western North America. Until recently, these rocks had been little studied and no systematic compilation of existing composition data had been assembled. This report is a compilation of all available chemical data for igneous rocks that constitute the southern segment of the ancestral Cascades magmatic arc and complement a previously completed companion compilation that pertains to rocks that constitute the northern segment of the arc. Data for more than 2,000 samples from a diversity of sources were identified and incorporated in the database. The association between these igneous rocks and spatially and temporally associated mineral deposits is well established and suggests a probable genetic relationship. The ultimate goal of the related research is an evaluation of the time-space-compositional evolution of magmatism associated with the southern Cascades arc segment and identification of genetic associations between magmatism and mineral deposits in this region.

Selenium and Other Elements in Water and Adjacent Rock and Sediment of Toll Gate Creek, Aurora, Arapahoe County, Colorado, December 2003 through March 2004

USGS Publications Warehouse

Herring, J.R.; Walton-Day, Katherine

2007-01-01

Streamwater and solid samples (rock, unconsolidated sediment, stream sediment, and efflorescent material) in the Toll Gate Creek watershed, Colorado, were collected and analyzed for major and trace elements to determine trace-element concentrations and stream loads from December 2003 through March 2004, a period of seasonally low flow. Special emphasis was given to selenium (Se) concentrations because historic Se concentrations exceeded current (2004) stream standards. The goal of the project was to assess the distribution of Se concentration and loads in Toll Gate Creek and to determine the potential for rock and unconsolidated sediment in the basin to be sources of Se to the streamwater. Streamwater samples and discharge measurements were collected during December 2003 and March 2004 along Toll Gate Creek and its two primary tributaries - West Toll Gate Creek and East Toll Gate Creek. During both sampling periods, discharge ranged from 2.5 liters per second to 138 liters per second in the watershed. Discharge was greater in March 2004 than December 2003, but both periods represent low flow in Toll Gate Creek, and results of this study should not be extended to periods of higher flow. Discharge decreased moving downstream in East Toll Gate Creek but increased moving downstream along West Toll Gate Creek and the main stem of Toll Gate Creek, indicating that these two streams gain flow from ground water. Se concentrations in streamwater samples ranged from 7 to 70 micrograms per liter, were elevated in the upstream-most samples, and were greater than the State stream standard of 4.6 micrograms per liter. Se loads ranged from 6 grams per day to 250 grams per day, decreased in a downstream direction along East Toll Gate Creek, and increased in a downstream direction along West Toll Gate Creek and Toll Gate Creek. The largest Se-load increases occurred between two sampling locations on West Toll Gate Creek during both sampling periods and between the two sampling locations on the main stem of Toll Gate Creek during the December 2003 sampling. These load increases may indicate that sources of Se exist between these two locations; however, Se loading along West Toll Gate Creek and Toll Gate Creek primarily was characterized by gradual downstream increases in load. Linear regressions between Se load and discharge for both sampling periods had large, significant values of r2 (r2 > 0.96, p < 0.0001) because increases in Se load (per unit of flow increase) were generally constant. This relation is evidence for a constant addition of water having a relatively constant Se concentration over much of the length of Toll Gate Creek, a result which is consistent with a ground-water source for the Se loads. Rock outcroppings along the stream were highly weathered, and Se concentrations in rock and other solid samples ranged from below detection (1 part per million) to 25 parts per million. One sample of efflorescence (a surface encrustation produced by evaporation) had the greatest selenium concentration of all solid samples, was composed of thenardite (sodium sulfate), gypsum (calcium sulfate) and minor halite (sodium chloride), and released all of its Se during a 30-minute water-leaching procedure. Calculations indicate there was an insufficient amount of this material present throughout the watershed to account for the observed Se load in the stream. However, this material likely indicates zones of ground-water discharge that contain Se. This report did not identify an unequivocal source of Se in Toll Gate Creek. However, multiple lines of evidence indicate that ground-water discharge supplies Se to Toll Gate Creek: (1) the occurrence of elevated Se concentrations in the stream throughout the watershed and in the headwater regions, upstream from industrial sources; (2) the progressive increase in Se loads moving downstream, which indicates a continuous input of Se along the stream rather than input from point sources; (3) the occurr

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.

Mineralogical, chemical and K-Ar isotopic changes in Kreyenhagen Shale whole rocks and <2 μm clay fractions during natural burial and hydrous-pyrolysis experimental maturation

NASA Astrophysics Data System (ADS)

Clauer, N.; Lewan, M. D.; Dolan, M. P.; Chaudhuri, S.; Curtis, J. B.

2014-04-01

Progressive maturation of the Eocene Kreyenhagen Shale from the San Joaquin Basin of California was studied by combining mineralogical and chemical analyses with K-Ar dating of whole rocks and <2 μm clay fractions from naturally buried samples and laboratory induced maturation by hydrous pyrolysis of an immature outcrop sample. The K-Ar age decreases from 89.9 ± 3.9 and 72.4 ± 4.2 Ma for the outcrop whole rock and its <2 μm fraction, respectively, to 29.7 ± 1.5 and 21.0 ± 0.7 Ma for the equivalent materials buried to 5167 m. The natural maturation does not produce K-Ar ages in the historical sense, but rather K/Ar ratios of relative K and radiogenic 40Ar amounts resulting from a combined crystallization of authigenic and alteration of initial detrital K-bearing minerals of the rocks. The Al/K ratio of the naturally matured rocks is essentially constant for the entire depth sequence, indicating that there is no detectable variation in the crystallo-chemical organization of the K-bearing alumino-silicates with depth. No supply of K from outside of the rock volumes occurred, which indicates a closed-system behavior for it. Conversely, the content of the total organic carbon (TOC) content decreases significantly with burial, based on the progressive increasing Al/TOC ratio of the whole rocks. The initial varied mineralogy and chemistry of the rocks and their <2 μm fractions resulting from differences in detrital sources and depositional settings give scattered results that homogenize progressively during burial due to increased authigenesis, and concomitant increased alteration of the detrital material. Hydrous pyrolysis was intended to alleviate the problem of mineral and chemical variations in initially deposited rocks of naturally matured sequences. However, experiments on aliquots from thermally immature Kreyenhagen Shale outcrop sample did not mimic the results from naturally buried samples. Experiments conducted for 72 h at temperatures from 270 to 365 °C did not induce significant changes at temperatures above 310 °C in the mineralogical composition and K-Ar ages of the rock and <2 μm fraction. The K-Ar ages of the <2 μm fraction range from 72.4 ± 4.2 Ma in the outcrop sample to 62.4 ± 3.4 Ma in the sample heated the most at 365 °C for 216 h. This slight decrease in age outlines some loss of radiogenic 40Ar, together with losses of organic matter as oil, gas, and aqueous organic species. Large amounts of smectite layers in the illite-smectite mixed layers of the pyrolyzed outcrop <2 μm fraction remain during thermal experiments, especially above 310 °C. With no illitization detected above 310 °C, smectite appears to have inhibited rather than promoted generation of expelled oil from decomposition of bitumen. This hindrance is interpreted to result from bitumen impregnating the smectite interlayer sites and rock matrix. Bitumen remains in the <2 μm fraction despite leaching with H2O2. Its presence in the smectite interlayers is apparent by the inability of the clay fraction to fully expand or collapse once bitumen generation from the thermal decomposition of the kerogen is completed, and by almost invariable K-Ar ages confirming for the lack of any K supply and/or radiogenic 40Ar removal. This suggests that once bitumen impregnates the porosity of a progressively maturing source rock, the pore system is no longer wetted by water and smectite to illite conversion ceases. Experimental attempts to evaluate the smectite conversion to illite should preferentially use low-TOC rocks to avoid inhibition of the reaction by bitumen impregnation.

Geogenic Groundwater Contamination: A Case Study Of Canakkale - Western Turkey

NASA Astrophysics Data System (ADS)

Deniz, Ozan; Çalık, Ayten

2016-04-01

Study area is located NW of Turkey. Total area of the drainage basin is 465 square kilometers and mostly covered by volcanic rocks. Majority of these rocks have highly altered and lost their primary properties because of alteration processes. Especially argillic alteration is common. Tectonic movements and cooling fractures were created suitable circulation environment of groundwater in the rocks (secondary porosity). Alteration affects the composition of groundwater and some rock elements pass into groundwater during the movement of water in the cavities of rocks. High concentration of natural contaminants related to water-rock interaction in spring water has been studied in this research. Field measurements such as pH, electrical conductivity, temperature, oxidation-reduction potential and salinity carried out in 500 water points (spring, drilling, well and stream). 150 water samples taken from the water points and 50 rock samples taken from the source of springs has been investigated in point of major anion-cations, heavy metals and trace elements. Some components in the water such as pH (3.5-9.1), specific electrical conductivity (84-6400 microS/cm), aluminum (27-44902 ppb), iron (10-8048 ppb), manganese (0.13-8740 ppb), nickel (0.2-627 ppb), lead (0.1-42.5 ppb) and sulphate (10 to 1940 ppm) extremely high or low in the springs sourced from especially highly altered Miocene aged volcanic rocks. Some measured parameters highly above according to European Communities Drinking Water Regulations (2007) and TS266 (2015-Intended for Human Consumption Water Regulations of Turkey) drinking water standards. The most common element which is found in the groundwater is aluminum that is higher than to the drinking water standards (200 microg/L). The highest levels of the Al values measured in acidic waters with very low pH (3.4) emerging from altered volcanic rocks because of acid mine drainage in Obakoy district, north of the study area. The abundance of this element in some water sources is believed to be closely associated with the alteration of feldspar minerals in the andesite and basalts of the Middle Eocene Sahinli Formation. Various studies related to topic show that consumption of these water containing high aluminum, iron, manganese, nickel and lead for drinking purposes cause serious health problems (Alzheimer's, Parkinson's, physical and mental development disorders in children, various cancers, stomach - intestinal disorders and skin diseases). This situation limits the usable groundwater potential and causes potable water scarcity in the region. Consequently, while using of these groundwater resources in the region, taking several precautions are necessary and doing new water resource explorations are recommended. This study is supported by The Turkish Scientific and Technical Research Institute (Project number: 113Y577). Keywords: Geogenic groundwater contamination, Water-Rock Interaction, Canakkale

Ground-water quality in the carbonate-rock aquifer of the Great Basin, Nevada and Utah, 2003

USGS Publications Warehouse

Schaefer, Donald H.; Thiros, Susan A.; Rosen, Michael R.

2005-01-01

The carbonate-rock aquifer of the Great Basin is named for the thick sequence of Paleozoic limestone and dolomite with lesser amounts of shale, sandstone, and quartzite. It lies primarily in the eastern half of the Great Basin and includes areas of eastern Nevada and western Utah as well as the Death Valley area of California and small parts of Arizona and Idaho. The carbonate-rock aquifer is contained within the Basin and Range Principal Aquifer, one of 16 principal aquifers selected for study by the U.S. Geological Survey’s National Water- Quality Assessment Program.Water samples from 30 ground-water sites (20 in Nevada and 10 in Utah) were collected in the summer of 2003 and analyzed for major anions and cations, nutrients, trace elements, dissolved organic carbon, volatile organic compounds (VOCs), pesticides, radon, and microbiology. Water samples from selected sites also were analyzed for the isotopes oxygen-18, deuterium, and tritium to determine recharge sources and the occurrence of water recharged since the early 1950s.Primary drinking-water standards were exceeded for several inorganic constituents in 30 water samples from the carbonate-rock aquifer. The maximum contaminant level was exceeded for concentrations of dissolved antimony (6 μg/L) in one sample, arsenic (10 μg/L) in eleven samples, and thallium (2 μg/L) in one sample. Secondary drinking-water regulations were exceeded for several inorganic constituents in water samples: chloride (250 mg/L) in five samples, fluoride (2 mg/L) in two samples, iron (0.3 mg/L) in four samples, manganese (0.05 mg/L) in one sample, sulfate (250 mg/L) in three samples, and total dissolved solids (500 mg/L) in seven samples.Six different pesticides or metabolites were detected at very low concentrations in the 30 water samples. The lack of VOC detections in water sampled from most of the sites is evidence thatVOCs are not common in the carbonate-rock aquifer. Arsenic values for water range from 0.7 to 45.7 μg/L, with a median value of 9.6 μg/L. Factors affecting arsenic concentration in the carbonate-rock aquifer in addition to geothermal heating are its natural occurrence in the aquifer material and time of travel along the flow path.Most of the chemical analyses, especially for VOCs and nutrients, indicate little, if any, effect of overlying land-use patterns on ground-water quality. The water quality in recharge areas for the aquifer where human activities are more intense may be affected by urban and/or agricultural land uses as evidenced by pesticide detections. The proximity of the carbonate-rock aquifer at these sites to the land surface and the potential for local recharge to occur through the fractured rock likely results in the occurrence of these and other land-surface related contaminants in the ground water. Water from sites sampled near outcrops of carbonate-rock aquifer likely has a much shorter residence time resulting in a potential for detection of anthropogenic or land-surface related compounds. Sites located in discharge areas of the flow systems or wells that are completed at a great depth below the land surface generally show no effects of land-use activities on water quality. Flow times within the carbonate-rock aquifer, away from recharge areas, are on the order of thousands of years, so any contaminants introduced at the land surface that will not degrade along the flow path have not reached the sampled sites in these areas.

Chemical composition of rocks and soils at Taurus-Littrow

NASA Technical Reports Server (NTRS)

Rose, H. J., Jr.; Cuttitta, F.; Berman, S.; Brown, F. W.; Carron, M. K.; Christian, R. P.; Dwornik, E. J.; Greenland, L. P.

1974-01-01

Seventeen soils and seven rock samples were analyzed for major elements, minor elements, and trace elements. Unlike the soils at previous Apollo sites, which showed little difference in composition at each collection area, the soils at Taurus-Littrow vary widely. Three soil types are evident, representative of (1) the light mantle at the South Massif, (2) the dark mantle in the valley, and (3) the surface material at the North Massif. The dark-mantle soils are chemically similar to those at Tranquillitatis. Basalt samples from the dark mantle are chemically similar although they range from fine to coarse grained. It is suggested that they originated from the same source but crystallized at varying depths from the surface.

Osmium Isotopic Evolution of the Mantle Sources of Precambrian Ultramafic Rocks

NASA Astrophysics Data System (ADS)

Gangopadhyay, A.; Walker, R. J.

2006-12-01

The Os isotopic composition of the modern mantle, as recorded collectively by ocean island basalts, mid- oceanic ridge basalts (MORB) and abyssal peridotites, is evidently highly heterogeneous (γ Os(I) ranging from <-10 to >+25). One important question, therefore, is how and when the Earth's mantle developed such large-scale Os isotopic heterogeneities. Previous Os isotopic studies of ancient ultramafic systems, including komatiites and picrites, have shown that the Os isotopic heterogeneity of the terrestrial mantle can be traced as far back as the late-Archean (~ 2.7-2.8 Ga). This observation is based on the initial Os isotopic ratios obtained for the mantle sources of some of the ancient ultramafic rocks determined through analyses of numerous Os-rich whole-rock and/or mineral samples. In some cases, the closed-system behavior of these ancient ultramafic rocks was demonstrated via the generation of isochrons of precise ages, consistent with those obtained from other radiogenic isotopic systems. Thus, a compilation of the published initial ^{187}Os/^{188}Os ratios reported for the mantle sources of komatiitic and picritic rocks is now possible that covers a large range of geologic time spanning from the Mesozoic (ca. 89 Ma Gorgona komatiites) to the Mid-Archean (e.g., ca. 3.3 Ga Commondale komatiites), which provides a comprehensive picture of the Os isotopic evolution of their mantle sources through geologic time. Several Precambrian komatiite/picrite systems are characterized by suprachondritic initial ^{187}Os/^{188}Os ratios (e.g., Belingwe, Kostomuksha, Pechenga). Such long-term enrichments in ^{187}Os of the mantle sources for these rocks may be explained via recycling of old mafic oceanic crust or incorporation of putative suprachondritic outer core materials entrained into their mantle sources. The relative importance of the two processes for some modern mantle-derived systems (e.g., Hawaiian picrites) is an issue of substantial debate. Importantly, however, the high-precision initial Os isotopic compositions of the majority of ultramafic systems show strikingly uniform initial ^{187}Os/^{188}Os ratios, consistent with their derivation from sources that had Os isotopic evolution trajectory very similar to that of carbonaceous chondrites. In addition, the Os isotopic evolution trajectories of the mantle sources for most komatiites show resolvably lower average Re/Os than that estimated for the Primitive Upper Mantle (PUM), yet significantly higher than that obtained in some estimates for the modern convecting upper mantle, as determined via analyses of abyssal peridotites. One possibility is that most of the komatiites sample mantle sources that are unique relative to the sources of abyssal peridotites and MORB. Previous arguments that komatiites originate via large extents of partial melting of relatively deep upper mantle, or even lower mantle materials could, therefore, implicate a source that is different from the convecting upper mantle. If so, this source is remarkably uniform in its long-term Re/Os, and it shows moderate depletion in Re relative to the PUM. Alternatively, if the komatiites are generated within the convective upper mantle through relatively large extents of partial melting, they may provide a better estimate of the Os isotopic composition of the convective upper mantle than that obtained via analyses of MORB, abyssal peridotites and ophiolites.

Petromagnetic Properties In The Naica Mining District, Chihuahua, Mexico: Searching For Source of Mineralization

NASA Astrophysics Data System (ADS)

Alva, L.; Gogichaishvili, A.; Urrutia, J.

Ore mineral and host lithologies have been sampled with 89 oriented samples from 14 sites in the Naica District, northern Mexico. Magnetic parameters permit to charac- terise samples: saturation magnetization, density, low- high-temperature magnetic sus- ceptibility, remanence intensity, Koenigsberger ratio, Curie temperature and hystere- sis parameters. Rock magnetic properties are controlled by variations in titanomag- netite content and hydrothermal alteration. Post-mineralization hydrothermal alter- ation seems the major event that affected the minerals and magnetic properties. Curie temperatures are characteristic of titanomagnetites or titanomaghemites. Hysteresis parameters indicate that most samples have pseudo-single domain (PSD) magnetic grains. Alternating filed (AF) demagnetization and isothermal remanence (IRM) ac- quisition both indicate that natural and laboratory remanences are carried by MD-PSD spinels in the host rocks. The trend of NRM intensity vs susceptibility suggests that the carrier of remanent and induced magnetization is the same in all cases (spinels). The Koenigsberger ratio range from 0.05 to 34.04, indicating the presence of MD and PSD magnetic grains. Constraints on the geometry of the intrusive source body devel- oped in the model of the magnetic anomaly are obtained by quantifying the relative contributions of induced and remanent magnetization components.

Predicting Risk from Radon in Source Waters from Water Quality Parameters

EPA Science Inventory

Overall, 47 groundwater samples were collected from 45 small community water systems (CWSs) and analyzed for radon and other water quality constituents. In general, groundwater from unconsolidated deposits and sedimentary rocks had lower average radon levels (ranging from 223 to...

Correlation of Rock Spectra with Quantitative Morphologic Indices: Evidence for a Single Rock Type at the Mars Pathfinder Landing Site

NASA Technical Reports Server (NTRS)

Yingst, R. A.; Biedermann, K. L.; Pierre, N. M.; Haldemann, A. F. C.; Johnson, J. R.

2005-01-01

The Mars Pathfinder (MPF) landing site was predicted to contain a broad sampling of rock types varying in mineralogical, physical, mechanical and geochemical characteristics. Although rocks have been divided into several spectral categories based on Imager for Mars Pathfinder (IMP) visible/near-infrared data, efforts in isolating and classifying spectral units among MPF rocks and soils have met with varying degrees of success, as many factors influencing spectral signatures cannot be quantified to a sufficient level to be removed. It has not been fully determined which spectral categories stem from intrinsic mineralogical differences between rocks or rock surfaces, and which result from factors such as physical or chemical weathering. This has made isolation of unique rock mineralogies difficult. Morphology, like composition, is a characteristic tied to the intrinsic properties and geologic and weathering history of rocks. Rock morphologies can be assessed quantitatively and compared with spectral data, to identify and classify rock types at the MPF landing site. They can also isolate actual rock spectra from spectral types that are surficial in origin, as compositions associated with mantling dust or chemical coatings would presumably not influence rock morphology during weathering events. We previously reported on an initial classification of rocks using the quantitative morphologic indices of size, roundness, sphericity and elongation. Here, we compare this database of rock characteristics with associated rock surface spectra to improve our ability to discriminate between spectra associated with rock types and those from other sources.

Evolution of the Mazatzal province and the timing of the Mazatzal orogeny: Insights from U-Pb geochronology and geochemistry of igneous and metasedimentary rocks in southern New Mexico

USGS Publications Warehouse

Amato, J.M.; Boullion, A.O.; Serna, A.M.; Sanders, A.E.; Farmer, G.L.; Gehrels, G.E.; Wooden, J.L.

2008-01-01

New U-Pb zircon ages, geochemistry, and Nd isotopic data are presented from three localities in the Paleoproterozoic Mazatzal province of southern New Mexico, United States. These data help in understanding the source regions and tectonic setting of magmatism from 1680 to 1620 Ma, the timing of the Mazatzal orogeny, the nature of postorogenic maginatism, Proterozoic plate tectonics, and provide a link between Mazatzal subblocks in Arizona and northern New Mexico. The data indicate a period from 1680 to 1650 Ma in which juvenile felsic granitoids were formed, and a later event between 1646 and 1633 Ma, when these rocks were deformed together with sedimentary rocks. No evidence of pre-1680 Ma rocks or inherited zircons was observed. The igneous rocks have ENd(t) from -1.2 to +4.3 with most between +2 and +4, suggesting a mantle source or derivation from similar-aged crust. Nd isotope and trace element concentrations are consistent with models for typical are magmatism. Detrital zircon ages from metasedimentary rocks indicate that sedimentation occurred until at least 1646 Ma. Both local and Yavapai province sources contributed to the detritus. All of the samples older than ca. 1650 Ma are deformed, whereas undeformed porphyroblasts were found in the contact aureole of a previously dated 1633 Ma gabbro. Regionally, the Mlazatzal orogeny occurred mainly between 1654 and 1643 Ma, during final accretion of a series of island arcs and intervening basins that may have amalgamated offshore. Rhyolite magmatism in the southern Mazatzal province was coeval with gabbro intrusions at 1633 Ma and this bimodal magmatism may have been related to extensional processes following arc accretion. ?? 2007 Geological Society of America.

Fate and transport of heavy metals and radioelements in groundwater aquifers of Al-Qunfudhah and Wadi Haliy quadrangles, southwest of Saudi Arabia

NASA Astrophysics Data System (ADS)

Bajabaa, S. A.; Abd El-Naby, H.; Dawood, Y.

2009-12-01

The fate and transport of heavy metals and radioelements in groundwater aquifers in five wadis located in the Al Qunfudhah and Wadi Haliy quadrangles were investigated. These wadis are an important source of water to the Red Sea coastal plain. Copper, zinc and other base-metals mineralization occur at eastern parts of these quadrangles that dominates the water catchments area of these wadis. Water, rock and soil samples were collected from all wadis and they were analyzed for major, trace elements, heavy metals and stable isotopes. The chemical and isotopic results showed active water/rock interaction. The preliminary investigation of the data analyses showed some samples with high heavy metals and uranium contents. Generally, the uranium and heavy metal contents are higher in samples collected from the upstream area of each wadi where the crystalline rocks are exposed and direct contact with the runoff. The uranium contents were as high as 120 ppb in some water samples. These elevated values are mainly due to two factors water rock interaction and concentration through evaporation. It was also observed to have elevated heavy metal contents near mining activates, which suggests that these mining activates are playing an important role in mobilizing the heavy elements and in turn affecting the water quality in these wadis.

No evidence of extraterrestrial noble metal and helium anomalies at Marinoan glacial termination

NASA Astrophysics Data System (ADS)

Peucker-Ehrenbrink, Bernhard; Waters, Christine A.; Kurz, Mark D.; Hoffman, Paul F.

2016-03-01

High concentrations of extraterrestrial iridium have been reported in terminal Sturtian and Marinoan glacial marine sediments and are used to argue for long (likely 3-12 Myr) durations of these Cryogenian glaciations. Reanalysis of the Marinoan sedimentary rocks used in the original study, supplemented by sedimentary rocks from additional terminal Marinoan sections, however, does not confirm the initial report. New platinum group element concentrations, and 187Os/188Os and 3He/4He signatures are consistent with crustal origin and minimal extraterrestrial contributions. The discrepancy is likely caused by different sample masses used in the two studies, with this study being based on much larger samples that better capture the stochastic distribution of extraterrestrial particles in marine sediments. Strong enrichment of redox-sensitive elements, particularly rhenium, up-section in the basal postglacial cap carbonates, may indicate a return to more fully oxygenated seawater in the aftermath of the Marinoan snowball earth. Sections dominated by hydrogenous osmium indicate increasing submarine hydrothermal sources and/or continental inputs that are increasingly dominated by young mantle-derived rocks after deglaciation. Sedimentation rate estimates for the basal cap carbonates yield surprisingly slow rates of a few centimeters per thousand years. This study highlights the importance of using sedimentary rock samples that represent sufficiently large area-time products to properly sample extraterrestrial particles representatively, and demonstrates the value of using multiple tracers of extraterrestrial matter.

MADISON ROADLESS AREA, MONTANA.

USGS Publications Warehouse

Simons, Frank S.; Lambeth, Robert H.

1984-01-01

A mineral-resource survey of the Madison Roadless Area in the Madison Range of southwestern Montana was made. The Madison Roadless Area has demonstrated resources of about 93,000 tons of sillimanite rock at the Placer Creek deposit and of about 83,000 tons of asbestos rock at the Karst deposit. The roadless area also has areas of substantiated phosphate resource potential; much of the phosphate is in thin deeply buried beds. An area near the south edge of the roadless area has a probable resource potential for copper and silver. The concentration of uranium-rich stream-sediment samples in the southwest part of the roadless area suggests that a further attempt to identify the source rocks might be justified.

Lithological Influences on Occurrence of High-Fluoride Waters in The Central Kenya Rift

NASA Astrophysics Data System (ADS)

Olaka, L. A.; Musolff, A.; Mulch, A.; Olago, D.; Odada, E. O.

2013-12-01

Within the East African rift, groundwater recharge results from the complex interplay of geology, land cover, geomorphology, climate and on going volcano-tectonic processes across a broad range of spatial and temporal scales. The interrelationships between these factors create complex patterns of water availability, reliability and quality. The hydrochemical evolution of the waters is further complex due to the different climatic regimes and geothermal processes going on in this area. High fluoridic waters within the rift have been reported by few studies, while dental fluorosis is high among the inhabitants of the rift. The natural sources of fluoride in waters can be from weathering of fluorine bearing minerals in rocks, volcanic or fumarolic activities. Fluoride concentration in water depends on a number of factors including pH, temperature, time of water-rock formation contact and geochemical processes. Knowledge of the sources and dispersion of fluoride in both surface and groundwaters within the central Kenya rift and seasonal variations between wet and dry seasons is still poor. The Central Kenya rift is marked by active tectonics, volcanic activity and fumarolic activity, the rocks are majorly volcanics: rhyolites, tuffs, basalts, phonolites, ashes and agglomerates some are highly fractured. Major NW-SE faults bound the rift escarpment while the rift floor is marked by N-S striking faults We combine petrographic, hydrochemistry and structural information to determine the sources and enrichment pathways of high fluoridic waters within the Naivasha catchment. A total of 120 water samples for both the dry season (January-February2012) and after wet season (June-July 2013) from springs, rivers, lakes, hand dug wells, fumaroles and boreholes within the Naivasha catchment are collected and analysed for fluoride, physicochemical parameters and stable isotopes (δ2 H, δ18 O) in order to determine the origin and evolution of the waters. Additionally, 30 soil and rock samples were also collected and analysed for fluoride, and rock samples were subjected to petrographic investigations and X-ray diffraction. The fluoride levels in surface and groundwater for the dry season range from 0.019 - 50.14 mg/L, on average above the WHO permissible limit. The high fluoride occurs both in the lake and groundwater. Preliminary petrographic studies show considerable fluoride in micas. The study is on-going and plans to present the relative abundances of fluoride in the lithology as the sources and the fluoride enrichment pathways of the groundwater within the Central Kenya rift.

Hydrocarbon potential evaluation of the source rocks from the Abu Gabra Formation in the Sufyan Sag, Muglad Basin, Sudan

NASA Astrophysics Data System (ADS)

Qiao, Jinqi; Liu, Luofu; An, Fuli; Xiao, Fei; Wang, Ying; Wu, Kangjun; Zhao, Yuanyuan

2016-06-01

The Sufyan Sag is one of the low-exploration areas in the Muglad Basin (Sudan), and hydrocarbon potential evaluation of source rocks is the basis for its further exploration. The Abu Gabra Formation consisting of three members (AG3, AG2 and AG1 from bottom to top) was thought to be the main source rock formation, but detailed studies on its petroleum geology and geochemical characteristics are still insufficient. Through systematic analysis on distribution, organic matter abundance, organic matter type, organic matter maturity and characteristics of hydrocarbon generation and expulsion of the source rocks from the Abu Gabra Formation, the main source rock members were determined and the petroleum resource extent was estimated in the study area. The results show that dark mudstones are the thickest in the AG2 member while the thinnest in the AG1 member, and the thickness of the AG3 dark mudstone is not small either. The AG3 member have developed good-excellent source rock mainly with Type I kerogen. In the Southern Sub-sag, the AG3 source rock began to generate hydrocarbons in the middle period of Bentiu. In the early period of Darfur, it reached the hydrocarbon generation and expulsion peak. It is in late mature stage currently. The AG2 member developed good-excellent source rock mainly with Types II1 and I kerogen, and has lower organic matter abundance than the AG3 member. In the Southern Sub-sag, the AG2 source rock began to generate hydrocarbons in the late period of Bentiu. In the late period of Darfur, it reached the peak of hydrocarbon generation and its expulsion. It is in middle mature stage currently. The AG1 member developed fair-good source rock mainly with Types II and III kerogen. Throughout the geological evolution history, the AG1 source rock has no effective hydrocarbon generation or expulsion processes. Combined with basin modeling results, we have concluded that the AG3 and AG2 members are the main source rock layers and the Southern Sub-sag is the main source kitchen in the study area. The AG3 and AG2 source rocks have supplied 58.1% and 41.9% of the total hydrocarbon generation, respectively, and 54.9% and 45.1% of the total hydrocarbon expulsion, respectively. Their hydrocarbon expulsion efficiency ratios are 71.0% and 62.3%, respectively. The Southern Sub-sag has supplied more than 90% of the total amounts of hydrocarbon generation and its expulsion.

Hydrocarbon source potential and maturation in eocene New Zealand vitrinite-rich coals: Insights from traditional coal analyses, and Rock-Eval and biomarker studies

USGS Publications Warehouse

Newman, J.; Price, L.C.; Johnston, J.H.

1997-01-01

The results of traditional methods of coal characterisation (proximate, specific energy, and ultimate analyses) for 28 Eocene coal samples from the West Coast of New Zealand correspond well with biomarker ratios and Rock-Eval analyses. Isorank variations in vitrinite fluorescence and reflectance recorded for these samples are closely related to their volatile-matter content, and therefore indicate that the original vitrinite chemistry is a key controlling factor. By contrast, the mineral-matter content and the proportion of coal macerals present appear to have had only a minor influence on the coal samples' properties. Our analyses indicate that a number of triterpane biomarker ratios show peak maturities by high volatile bituminous A rank; apparent maturities are then reversed and decline at the higher medium volatile bituminous rank. The Rock-Eval S1 +S2 yield also maximizes by high volatile bituminous A rank, and then declines; however, this decline is retarded in samples with the most hydrogen-rich (perhydrous) vitrinites. These Rock-Eval and biomarker trends, as well as trends in traditional coal analyses, are used to define the rank at which expulsion of gas and oil occurs from the majority of the coals. This expulsion commences at high volatile A bituminous rank, and persists up to the threshold of medium volatile bituminous rank (c. 1.1% Ro ran. or 1.2% Ro max in this sample set), where marked hydrocarbon expulsion from perhydrous vitrinites begins to take place.

MX Siting Investigation. Geotechnical Evaluation. Detailed Aggregate Resources Study. Pahroc Study Area, Nevada.

DTIC Science & Technology

1981-06-05

source is a fairly limited outcrop of calcareous sandstone classified as dolomite rock (Do). Class RBIb Sources: Pour basin-fill sources within the study...Paleozoic rocks consist of limestone, dolomite , and quartzite with interbedded sandstone and shale. These units are generally exposed along the northern...categories simplify discussion and presentation without altering the conclusions of the study. 2.2.1 Rock Units Dolomite rocks (Do) and carbonate rocks

Genetic aspects of barite mineralization related to rocks of the teschenite association in the Silesian Unit, Outer Western Carpathians, Czech Republic

NASA Astrophysics Data System (ADS)

Jirásek, Jakub; Dolníček, Zdeněk; Matýsek, Dalibor; Urubek, Tomáš

2017-04-01

Barite is a relatively uncommon phase in vein and amygdule mineralizations hosted by igneous rocks of the teschenite association in the Silesian Unit (Western Carpathians). In macroscopically observable sizes, it has been reported from 10 sites situated only in the Czech part of the Silesian Unit. Microscopic barite produced by the hydrothermal alteration of rock matrix and also by the supergene processes is more abundant. We examined four samples of barite by mineralogical and geochemical methods. Electron microprobe analyses proved pure barites with up to 0.038 apfu Sr and without remarkable internal zonation. Fluid inclusion and sulphur isotope data suggests that multiple sources of fluid components have been involved during barite crystallization. Barite contains primary and secondary aqueous all-liquid (L) or less frequent two-phase (L+V) aqueous fluid inclusions with variable salinity (0.4-2.9 wt. % NaCl eq.) and homogenization temperatures between 77 and 152 °C. The higher-salinity fluid endmember was probably Cretaceous seawater and the lower-salinity one was probably diagenetic water derived from surrounding flysch sediments during compaction and thermal alteration of clay minerals. The δ34S values of barite samples range between -1.0 ‰ and +16.4 ‰ CDT suggesting participation of two sources of sulphate, one with a near-zero δ34S values probably derived from wall rocks and another with high δ34S values being most probably sulphate from the Cretaceous seawater. All results underline the role of externally derived fluids during post-magmatic alteration of bodies of rock of the teschenite association.

Factors affecting occurrence and distribution of selected contaminants in ground water from selected areas in the Piedmont Aquifer System, Eastern United States, 1993-2003

USGS Publications Warehouse

Lindsey, Bruce D.; Falls, W. Fred; Ferrari, Matthew J.; Zimmerman, Tammy M.; Harned, Douglas A.; Sadorf, Eric M.; Chapman, Melinda J.

2006-01-01

Results of ground-water sampling from 255 wells and 19 springs in 11 studies done by the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program within the Piedmont Aquifer System (PAS) were analyzed to determine the factors affecting occurrence and distribution of selected contaminants. The contaminants, which were selected on the basis of potential human-health effects, included nitrate, pesticides, volatile organic compounds (VOCs), and radon.The PAS was subdivided on the basis of the general rock type of the aquifers into three areas for the study—crystalline, carbonate, and siliciclastic. The 11 studies were designed to areally represent an individual aquifer rock type and overall are representative of the PAS in their distribution; 7 studies are in the crystalline-rock aquifers, 3 studies are in the siliciclasticrock aquifers, and 1 study is in the carbonate-rock aquifers. Four of the studies were focused on land use, 1 in an agricultural area and 3 in urban areas. The remaining studies had wells representing a range of land-use types.Analysis of results of nitrate sampling indicated that in 8 of the 10 areas where nitrate concentrations were measured, median concentrations of nitrate were below 3 mg/L (milligrams per liter); 2 of the 10 areas had statistically significant higher median concentrations when compared to the other 8 areas. The agricultural land-use study in the carbonate-rock aquifer in the Lower Susquehanna River Basin had the highest median nitrate concentration (11 mg/L), and 60 percent of the wells sampled exceeded the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level (MCL) of 10 mg/L. The major aquifer study in the crystalline-rock aquifer of the Lower Susquehanna River Basin Study Unit had the second-highest median nitrate concentration. Nitrate concentrations were positively correlated to the percentage of agricultural land use around the well, the total input of nitrogen from all sources, dissolved oxygen concentration, lithology, depth to water, and soil-matrix characteristics. A linear regression model was used to determine that increases in the percentage of agricultural land use, the input of nitrogen from all sources, and dissolved oxygen were the most significant variables affecting increased concentration of nitrate. A logistic regression model was used to determine that those same factors were the most significant variables affecting whether or not the nitrate concentration would exceed 4 mg/L.Of the analysis of samples from 253 wells and 19 springs for 47 pesticides, no sample had a pesticide concentration that exceeded any USEPA MCL. The most frequently detected pesticide was desethyl atrazine, a degradation product of atrazine; the detection frequency was 47 percent. Other frequently detected pesticides included atrazine, metolachlor, simazine, alachlor, prometon, and dieldrin. Detection frequency was affected by the analytical reporting limits; the frequency of detection was somewhat lower when all pesticides were censored to the highest common detection limit. Source factors such as agricultural land use (for agricultural herbicides), urban land use (for insecticides), and the application rate were found to have positive statistical correlations with pesticide concentration. Transport factors such as depth to water and percentage of well-drained soils, sand, or silt typically were positively correlated with higher pesticide concentrations.Sampling for VOCs was conducted in 187 wells and 19 springs that were sampled for 59 VOCs. There were 137 detections of VOCs above the common censoring limit of 0.2 µg/L. The most frequently detected VOCs were chloroform, a trihalomethane, and methyl-tert butyl ether (MTBE), a fuel oxygenate. Seventy-nine wells had at least one VOC detected. The detections were related to land use and well depth. Kendall’s tau correlations indicated a significant positive correlation between chloroform concentration and urban land use, leaking underground storage tanks, population density, and well depth. MTBE concentrations also were positively correlated to urban land use, leaking underground storage tanks, population density, and well depth.Radon was sampled at 205 sites. The subdivisions used for analysis of other contaminants were not adequate for analysis of radon because radon varies on the basis of variations in mineralogy that are not reflected by the general lithologic categories used for the rest of the studies. Concentrations of radon were highest in areas where the crystalline-rock aquifers had felsic mineralogy, and the lowest concentrations of radon were in areas where the crystalline-rocks aquifer had mafic mineralogy. Water from wells in siliciclastic-rock aquifers had concentrations of radon lower than that in the felsic crystalline-rock aquifers. More than 90 percent of the wells sampled for radon exceeded the proposed MCL of 300 pCi/L (picoCuries per liter); however, only 13 percent of those wells had concentrations in water that exceeded the alternative maximum contaminant level (AMCL), a higher level that can be used by municipalities addressing other sources of radon exposure.Overall, concentrations of constituents were related to land-use factors for nitrate, pesticides, VOCs, and to aquifer lithology for radon. None of the 47 pesticides or 59 VOCs analyzed exceeded the MCLs where those constituents were sampled. Concentrations exceeded the MCL for nitrate in 11 percent of the wells sampled. Nearly 91 percent of the wells sampled exceeded the proposed MCL for radon. Additional sampling in selected areas would improve overall understanding of the PAS and increase the possibility of creating predictive models of ground-water quality in this area.

Lower Paleozoic Through Archean Detrital Zircon Ages From Metasedimentary Rocks of the Nome Group, Seward Peninsula, Alaska

NASA Astrophysics Data System (ADS)

Amato, J. M.; Miller, E. L.; Gehrels, G.

2003-12-01

Metamorphic rocks of Seward Peninsula have been divided into two groups based on their metamorphic grade and history: The Nome Group and the Kigluaik Group. Although it is sometime been assumed that the higher structural position of the Nome Group versus the Kigluaik Group indicates the Kigluaik Group is older, this relationship and the age of the protoliths of these rocks has never been well-established. The Nome Group includes (delete the) lower grade blueschist and greenschist facies rocks which are widespread across the Seward Peninsula (delete) Rock types include pelitic schist, more mafic chlorite-white mica-albite schist, marble, quartzite, and metabasite. An early metamorphic event (pre-120 Ma) occurred at high pressure and relatively low temperature, and is everywhere overprinted by younger deformation and greenschist facies Rare eclogite facies assemblages are preserved in metabasites, and garnet-glaucophane in some of the pelitic schists. The Kigluaik Group includes upper greenschist to granulite facies rocks that are exposed in the core of a gneiss dome. They record a younger event (~91 Ma) that occurred at higher temperatures and resulted in partial thermal overprinting of the Nome Group and upper greenschist to granulite facies assemblages forming in the Kigluaik Group. The Kigluaik Group and equivalent rocks in the Bendeleben and Darby Mountains represent at least in part similar protoliths to many of the units in the Nome Group (Till and Dumoulin, 1994). The boundary between the rocks of the Nome Group and those clearly affected by the second metamorphic event is placed arbitrarily at the "Biotite-in" isograd along the flanks of the gneiss dome. In order to assess the protolith ages and source rock ages for these units, detrital zircon ages were obtained from three samples from the Nome Group, with Kigluaik Group ages forthcoming. LA-MC-ICPMS U/Pb isotope analysis was used for dating. Two samples were collected from the western Kigluaik Mountains near Eldorado Creek and one further south along the Feather River. Each sample yielded 90-105 analyses and all uncertainties are 1 sigma. Chlorite schist MC-74 has a range of ages from the two youngest grains at 484 +/- 18 Ma and 510 +/- 7 Ma to 2984 +/- 2 Ma. Chlorite schist LMC-30 has a youngest grain at 521 +/- 2 Ma and an oldest grain of 2027 +/- 12. Quartz-mica schist LMC-58 also has a youngest grain at 521 +/- 2 Ma and an oldest grain of 2655 +/- 7 Ma. All three therefore have lower Paleozoic zircons, suggesting Lower Cambrian or younger depositional ages. Combining the data from all three rocks results in peaks on a cumulative probability plot at (in descending order of importance): 600 Ma, 683 Ma, 1593 Ma, 522 Ma, and 2985 Ma, with several smaller peaks between 774-1540 Ma and 1685-1960 Ma. Published ages from Nome Group orthogneisses are 680 Ma, suggesting the samples so far analyzed are likely in part sourced from local basement rocks that were eroded to provide ~680 Ma detrital zircons to sedimentary protoliths of part of the Nome Group.

The cretaceous source rocks in the Zagros Foothills of Iran: An example of a large size intracratonic basin

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

Bordenave, M.L.; Huc, A.Y.

1993-02-01

The Zagros orogenic belt of Iran is one of the world most prolific petroleum producing area. However, most of the oil production is originated from a relatively small area, the 60,000 km[sup 2] wide Dezful Embayment which contains approximately 12% of the proven oil global reserves. The distribution of the oil and gas fields results from the area extent of six identified source rock layers, their thermal history and reservoir, cap rock and trap availability. In this paper, the emphasis is three of the layers of Cretaceous sources rocks. The Garau facies was deposited during the Neocomian to Albian intervalmore » over Lurestan, Northeast Khuzestan and extends over the extreme northeast part of Fars, the Kazhdumi source rock which deposited over the Dezful Embayment, and eventually the Senonian Gurpi Formation which has marginal source rock characteristics in limited areas of Khuzestan and Northern Fars. The deposition environment of these source rock layers corresponds to semipermanent depressions, included in an overall shallow water intracratonic basin communicating with the South Tethys Ocean. These depressions became anoxic when climatic oceanographical and geological conditions were adequate, i.e., humid climate, high stand water, influxes of fine grained clastics and the existence of sills separating the depression from the open sea. Distribution maps of these source rock layers resulting from extensive field work and well control are also given. The maturation history of source rocks is reconstructed from a set of isopachs. It was found that the main contributor to the oil reserves is the Kazhdumi source rock which is associated with excellent calcareous reservoirs.« less

Lead in the Getchell-Turquoise ridge Carlin-type gold deposits from the perspective of potential igneous and sedimentary rock sources in Northern Nevada: Implications for fluid and metal sources

USGS Publications Warehouse

Tosdal, R.M.; Cline, J.S.; Fanning, C.M.; Wooden, J.L.

2003-01-01

Lead isotope compositions of bulk mineral samples (fluorite, orpiment, and realgar) determined using conventional techniques and of ore-stage arsenian pyrite using the Sensitive High Resolution Ion-Microprobe (SHRIMP) in the Getchell and Turquoise Ridge Carlin-type gold deposits (Osgood Mountains) require contribution from two different Pb sources. One Pb source dominates the ore stage. It has a limited Pb isotope range characterized by 208Pb/206Pb values of 2.000 to 2.005 and 207Pb/206Pb values of 0.8031 to 0.8075, as recorded by 10-??m-diameter spot SHRIMP analyses of ore-stage arsenian pyrite. These values approximately correspond to 206Pb/204Pb of 19.3 to 19.6, 207Pb/204Pb of 15.65 to 15.75, and 208Pb/204Pb of 39.2 to 39.5. This Pb source is isotopically similar to that in average Neoproterozoic and Cambrian elastic rocks but not to any potential magmatic sources. Whether those clastic rocks provided Pb to the ore fluid cannot be unequivocally proven because their Pb isotope compositions over the same range as in ore-stage arsenian pyrite are similar to those of Ordovician to Devonian siliciclastic and calcareous rocks. The Pb source in the calcareous rocks most likely is largely detrital minerals, since that detritus was derived from the same sources as the detritus in the Neoproterozoic and Cambrian clastic rocks. The second Pb source is characterized by a large range of 206Pb/204Pb values (18-34) with a limited range of 208Pb/204Pb values (38.1-39.5), indicating low but variable Th/U and high and variable U/Pb values. The second Pb source dominates late and postore-stage minerals but is also found in preore sulfide minerals. These Pb isotope characteristics typify Ordovician to Devonian siliciclastic and calcareous rocks around the Carlin trend in northeast Nevada. Petrologically similar rocks host the Getchell and Turquoise Ridge deposits. Lead from the second source was either contributed from the host sedimentary rock sequences or brought into the hydrothermal system by oxidized ground water as the system collapsed. Late ore- and postore-stage sulfide minerals (pyrite, orpiment, and stibnite) from the Betze-Post and Meikle deposits in the Carlin trend and from the Jerritt Canyon mining district have Pb isotope characteristics similar to those determined in Getchell and Turquoise Ridge. This observation suggests that the Pb isotope compositions of their ore fluids may be similar to those at Getchell and Turquoise Ridge. Two models can explain the Pb isotope compositions of the ore-stage arsenian pyrite versus the late ore or postore sulfide minerals. In either model, Pb from the Ordovician to Devonian siliciclastic and calcareous rock source enters the hydrothermal system late in the ore stage but not to any extent during the main stage of ore deposition. In one model, ore-stage Pb was derived from a source with Pb isotope compositions similar to those of the Neoproterozoic and Cambrian clastic sequence, transported as part of the ore fluid and then deposited in the ore-stage arsenian pyrite and fluorite. The second model is based on the observation that the Pb isotope characteristics of the ore-stage minerals also are found in some Ordovician to Devonian calcareous and siliciclastic rocks. Hence, ore-stage Pb could have been derived locally and simply concentrated during the ore stage. Critical to the second model is the removal of all high 206Pb/204Pb (>20) material during alteration. It Also requires the retention of only the low 206Pb/204Pb component of the Ordovician to Devonian sedimentary rocks. This critical step is possible only if the high 206Pb/204Pb values are contained in readily dissolvable mineral phases, whereas the low 206Pb/204Pb values are found only in refractory minerals that released Pb during a final alteration stage just prior deposition of auriferous arsenian pyrite. Distinguishing between Pb transported with the ore fluid or inherited from the site of mineral deposition is not straightforward

Alaskan North Slope petroleum systems

USGS Publications Warehouse

Magoon, L.B.; Lillis, P.G.; Bird, K.J.; Lampe, C.; Peters, K.E.

2003-01-01

Six North Slope petroleum systems are identified, described, and mapped using oil-to-oil and oil-to-source rock correlations, pods of active source rock, and overburden rock packages. To map these systems, we assumed that: a) petroleum source rocks contain 3.2 wt. % organic carbon (TOC); b) immature oil-prone source rocks have hydrogen indices (HI) >300 (mg HC/gm TOC); c) the top and bottom of the petroleum (oil plus gas) window occur at vitrinite reflectance values of 0.6 and 1.0% Ro, respectively; and d) most hydrocarbons are expelled within the petroleum window. The six petroleum systems we have identified and mapped are: a) a southern system involving the Kuna-Lisburne source rock unit that was active during the Late Jurassic and Early Cretaceous; b) two western systems involving source rock in the Kingak-Blankenship, and GRZ-lower Torok source rock units that were active during the Albian; and c) three eastern systems involving the Shublik-Otuk, Hue Shale and Canning source rock units that were active during the Cenozoic. The GRZ-lower Torok in the west is correlative with the Hue Shale to the east. Four overburden rock packages controlled the time of expulsion and gross geometry of migration paths: a) a southern package of Early Cretaceous and older rocks structurally-thickened by early Brooks Range thrusting; b) a western package of Early Cretaceous rocks that filled the western part of the foreland basin; c) an eastern package of Late Cretaceous and Paleogene rocks that filled the eastern part of the foreland basin; and d) an offshore deltaic package of Neogene rocks deposited by the Colville, Canning, and Mackenzie rivers. This petroleum system poster is part of a series of Northern Alaska posters on modeling. The poster in this session by Saltus and Bird present gridded maps for the greater Northern Alaskan onshore and offshore that are used in the 3D modeling poster by Lampe and others. Posters on source rock units are by Keller and Bird as well as Peters and others. Sandstone and shale compaction properties used in sedimentary basin modeling are covered in a poster by Rowan and others. The results of this modeling exercise will be used in our next Northern Alaska oil and gas resource assessment.

Measurements of I-129 in meteorites and lunar rock by tandem accelerator mass spectrometry

NASA Technical Reports Server (NTRS)

Nizhiizumi, K.; Arnold, J. R.; Elmore, D.; Gove, H. E.; Honda, M.

1983-01-01

Precise measurements of the half-life of I-129 in three different meteorites and one lunar surface rock are reported. The meteorite source of I-129 was produced by cosmic ray secondary neutron reactions on Te, while the source in lunar materials in spallation on barium and rare earth elements. The Abee, Allende, and Dhajala meteorites were examined, together with the lunar rock 14310. Details of the process used to extract the iodine are provided. The Abee and Allende samples exhibited a production of 0.5 atom/min per gm of Te from the (n,2n) reaction and 0.05 atom/min/gm for the (n,gamma) reaction. The I-129 is concluded to be a viable tool for long-lived cosmogenic nuclide studies. Further work to extend the data to include the constancy of the cosmic ray flux, the meteorite bombardment history, and the cosmic exposure age dating by means of the I-129 and Xe-129 method is indicated.

In search of a Silurian Total Petroleum System in the Appalachian Basin of New York, Ohio, Pennsylvania, and West Virginia

USGS Publications Warehouse

Ryder, Robert T.; Swezey, Christopher S.; Trippi, Michael H.; Lentz, Erika E.; Avary, K. Lee; Harper, John A.; Kappel, William M.; Rea, Ronald G.

2007-01-01

This report provides an evaluation of the source rock potential of Silurian strata in the U.S. portion of the northern Appalachian Basin, using new TOC and RockEval data. The study area consists of all or parts of New York, Ohio, Pennsylvania, and West Virginia. The stratigraphic intervals that were sampled for this study are as follows: 1) the Lower Silurian Cabot Head Shale, Rochester Shale, and Rose Hill Formation; 2) the Lower and Upper Silurian McKenzie Limestone, Lockport Dolomite, and Eramosa Member of the Lockport Group; and 3) the Upper Silurian Wills Creek Formation, Tonoloway Limestone, Salina Group, and Bass Islands Dolomite. These Silurian stratigraphic intervals were chosen because they are cited in previous publications as potential source rocks, they are easily identified and relatively continuous across the basin, and they contain beds of dark gray to black shale and (or) black argillaceous limestone and dolomite.

Correlated compositional and mineralogical investigations at the Chang'e-3 landing site.

PubMed

Ling, Zongcheng; Jolliff, Bradley L; Wang, Alian; Li, Chunlai; Liu, Jianzhong; Zhang, Jiang; Li, Bo; Sun, Lingzhi; Chen, Jian; Xiao, Long; Liu, Jianjun; Ren, Xin; Peng, Wenxi; Wang, Huanyu; Cui, Xingzhu; He, Zhiping; Wang, Jianyu

2015-12-22

The chemical compositions of relatively young mare lava flows have implications for the late volcanism on the Moon. Here we report the composition of soil along the rim of a 450-m diameter fresh crater at the Chang'e-3 (CE-3) landing site, investigated by the Yutu rover with in situ APXS (Active Particle-induced X-ray Spectrometer) and VNIS (Visible and Near-infrared Imaging Spectrometer) measurements. Results indicate that this region's composition differs from other mare sample-return sites and is a new type of mare basalt not previously sampled, but consistent with remote sensing. The CE-3 regolith derived from olivine-normative basaltic rocks with high FeO/(FeO+MgO). Deconvolution of the VNIS data indicates abundant high-Ca ferropyroxene (augite and pigeonite) plus Fe-rich olivine. We infer from the regolith composition that the basaltic source rocks formed during late-stage magma-ocean differentiation when dense ferropyroxene-ilmenite cumulates sank and mixed with deeper, relatively ferroan olivine and orthopyroxene in a hybridized mantle source.

Assessment of the U-Th-Pb system in two Archean metabasalts - Deciphering the complex histories of sulfides and silicates using acid leaching methods

NASA Astrophysics Data System (ADS)

Smith, Patrick E.; Farquhar, Ronald M.; Tatsumoto, Mitsunobo

1989-08-01

A detailed U-Th-Pb isotopic study of two Archean basalts from two greenstone belts in the eastern Wawa Subprovince of the Canadian shield was carried out on samples that were either dissolved at once or leached in either 1N HNO3, 2N HCl, or 6N HCl. The abundances and isotopic compositions from these samples suggest that variable disturbances had occurred in both rock systems, which can be attributed to Pb mobility, particularly in the form of sulphide addition at various times, and, in one case, by recent Pb loss. The Pb isotopic compositions of the sulphides record late events which affected the greenstone terrains. The results also indicate that the sulphides and silicate rocks could have originated from a common source. The isotopic compositions of the basalt suggest that, in the Archean, both depleted and enriched mantle sources existed beneath the Wawa Subprovince.

Decarboxylation of Carbon Compounds as a Potential Source for CO2 and CO Observed by SAM at Yellowknife Bay, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Eigenbrode, J. L.; Bower, H.; Archer, P. Jr.

2014-01-01

Martian carbon was detected in the Sheepbed mudtsone at Yellowknife Bay, Gale Crater, Mars by the Sample Analysis at Mars (SAM) instrument onboard Curiosity, the rover of the Mars Science Laboratory missio]. The carbon was detected as CO2 thermally evolved from drilled and sieved rock powder that was delivered to SAM as a <150-micron-particle- size fraction. Most of the CO2 observed in the Cumberland (CB) drill hole evolved between 150deg and 350deg C. In the John Klein (JK) drill hole, the CO2 evolved up to 500deg C. Hypotheses for the source of the the CO2 include the breakdown of carbonate minerals reacting with HCl released from oxychlorine compounds, combustion of organic matter by O2 thermally evolved from the same oxychlorine minerals, and the decarboxylation of organic molecules indigenous to the martian rock sample. Here we explore the potential for the decarboxylation hypothesis.

Organic geochemistry of sediments of deep Gulf of Mexico basin

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

Fang, J.; Sassen, R.; Nunn, J.

1989-09-01

An analysis of 716 core samples from DSDP (Deep Sea Drilling Project) Leg 96 in the Mississippi submarine fan and the Orca and Pigmy basins in the Louisiana continental slope was done using a Rock-Eval pyrolysis unit with TOC (total organic carbon) module. The analysis allows computation of the hydrogen index (HI), TOC, and kerogen type, and assessment of the oil-generative capacity of the sediments in the Louisiana continental slope. No samples are obviously oil prone. TOC content ranges from 0.12 to 2.29%, with an overall average of 0.82%. HI values are generally less than 150 mg HC/g TOC. T{submore » max} (temperature of the maximum of the S{sub 2} peak) values (425{degree}C average) show the sediments are immature throughout the study area. Hydrocarbon-generative potential of the sediments ranges from 492 to 1,107 ppm, with an average of 854 ppm. Because of organic lean, thermally immature, and gas-prone terrestrial organic matter, there is little reason to assume that the sediments from the Mississippi fan can provide oil source rock for the Gulf Coast basin, and that sediments of anoxic basins in the Louisiana continental slope are analogs to the past environments where source rocks for crude oil have been deposited.« less

Oil/source rock correlations in the Polish Flysch Carpathians and Mesozoic basement and organic facies of the Oligocene Menilite Shales: Insights from hydrous pyrolysis experiments

USGS Publications Warehouse

Curtis, John B.; Kotarba, M.J.; Lewan, M.D.; Wieclaw, D.

2004-01-01

The Oligocene Menilite Shales in the study area in the Polish Flysch Carpathians are organic-rich and contain varying mixtures of Type-II, Type-IIS and Type-III kerogen. The kerogens are thermally immature to marginally mature based on atomic H/C ratios and Rock-Eval data. This study defined three organic facies, i.e., sedimentary strata with differing hydrocarbon-generation potentials due to varying types and concentrations of organic matter. These facies correspond to the Silesian Unit and the eastern and western portions of the Skole Unit. Analysis of oils generated by hydrous pyrolysis of outcrop samples of Menilite Shales demonstrates that natural crude oils reservoired in the flysch sediments appear to have been generated from the Menilite Shales. Natural oils reservoired in the Mesozoic basement of the Carpathian Foredeep appear to be predominantly derived and migrated from Menilite Shales, with a minor contribution from at least one other source rock most probably within Middle Jurassic strata. Definition of organic facies may have been influenced by the heterogeneous distribution of suitable Menilite Shales outcrops and producing wells, and subsequent sample selection during the analytical phases of the study. ?? 2004 Elsevier Ltd. All rights reserved.

Petrophysical Rock Typing of Unconventional Shale Plays: A Case Study for the Niobrara Formation of the Denver-Julesburg (DJ) Basin

NASA Astrophysics Data System (ADS)

Kamruzzaman, A.; Prasad, M.

2015-12-01

The hydrocarbon-rich mudstone rock layers of the Niobrara Formation were deposited in the shallow marine environment and have evolved as overmature oil- or gas-prone source and reservoir rocks. The hydrocarbon production from its low-porosity, nano-darcy permeability and interbedded chalk-marl reservoir intervals is very challenging. The post-diagenetic processes have altered the mineralogy and pore structure of its sourcing and producing rock units. A rock typing analysis in this play can help understand the reservoir heterogeneity significantly. In this study, a petrophysical rock typing workflow is presented for the Niobrara Formation by integrating experimental rock properties with geologic lithofacies classification, well log data and core study.Various Niobrara lithofacies are classified by evaluating geologic depositional history, sequence stratigraphy, mineralogy, pore structure, organic content, core texture, acoustic properties, and well log data. The experimental rock measurements are conducted on the core samples recovered from a vertical well from the Wattenberg Field of the Denver-Julesburg (DJ) Basin. Selected lithofacies are used to identify distinct petrofacies through the empirical analysis of the experimental data-set. The grouped petrofacies are observed to have unique mineralogical properties, pore characteristics, and organic contents and are labelled as discrete Niobrara rock types in the study area.Micro-textural image analysis (FESEM) is performed to qualitatively examine the pore size distribution, pore types and mineral composition in the matrix to confirm the classified rock units. The principal component analysis and the cluster analysis are carried out to establish the certainty of the selected rock types. Finally, the net-to-pay thicknesses of these rock units are compared with the cumulative production data from the field to further validate the chosen rock types.For unconventional shale plays, the rock typing information can be used to locate hydrocarbon sweetspots, facilitate the placement of the horizontal section of the wells along the sweetspots, and can augment engineers' abilities on suitable well placement considerations. It can also help enhancing the effectiveness of the hydraulic fracture stimulation and completion operation.

Geologically Controlled Isotope-Time Patterns Reveal Early Differentiation and Crust Formation Processes

NASA Astrophysics Data System (ADS)

Bennett, V. C.; Nutman, A. P.

2014-12-01

The mechanisms of continental crust production and evolution in the early Earth remain controversial, as are questions of the relative roles of early differentiation versus subsequent tectonic procssing in creating Earth's chemical signatures. Here we present geologic observations integrated with whole rock major, trace element and Sm-Nd isotopic signatures and combined with U-Pb and Lu-Hf isotopic compositions of zircon populations from the same rocks, from the most extensive early rock record comprising the 3.9 Ga to 3.6 Ga terranes of southwest Greenland. These data reveal repeated patterns of formation of juvenile TTG crust and associated mafic and ultramafic rocks in convergent margin settings followed by formation of more evolved granites [1]. Our new zircon Lu-Hf data from rare 3.6-3.7 Ga tonalites within the Itsaq Gneiss Complex, obtained from single component, non-migmatitic gneisses with simple zircon populations, limited within sample Hf isotopic variability and accurate U-Pb ages, now document extraction of juvenile tonalites from a near chondritic mantle source between 3.9 Ga and 3.6 Ga. The more evolved, granitic rocks in each area show slightly negative initial ɛHf in accord with crustal reworking of the older (3.8-3.9 Ga) gniesses. There is no evidence for Hadean material in the sources of the granitoids. The Hf isotope-time patterns are consistent with juvenile crust production from a mantle source that experienced only modest amounts of prior crustal extraction. They are distinct from those predicted by reprocessing of an enriched Hadean mafic crust, as has been proposed for this region [2] and for the source of the Hadean Jack Hills zircons [3]. The well-documented, time decreasing, positive 142Nd anomalies [e.g., 4] from these rocks are further evidence of crustal derivation from a convecting mantle source, rather than reworking of an enriched mafic lithosphere. The 143Nd isotopic -time patterns are more complex, reflecting the interplay between early Sm/Nd fractionation processes as required by the 142Nd data, juvenile crustal growth and in some cases geologic disturbance of the whole rock Sm-Nd system. [1] Nutman, et al, (2013) Amer. Jour. Sci. 313, 877-911. [2] Naeraa et al.. (2012) Nature 485, 627-631. [3] Kemp et al., (2010) EPSL 296, 45-56. [4] Bennett et al., (20070 Science 318, 1907.

Erosional history of the Appalachians as recordeed in detrital zircon fission-track ages and lithic detritus in Atlantic Coastal Plain sediments

USGS Publications Warehouse

Naeser, C.W.; Naeser, N.D.; Edwards, Lucy E.; Weems, Robert E.; Southworth, C. Scott; Newell, Wayne L.

2016-01-01

Comparison of fission-track (FT) ages of detrital zircons recovered from Atlantic Coastal Plain sediments to FT ages of zircons from bedrock in source terranes in the Appalachians provides a key to understanding the provenance of the sediments and, in turn, the erosional and depositional history of the Atlantic passive margin.In Appalachian source terranes, the oldest zircon fission-track (ZFT) ages from bedrock in the western Appalachians (defined for this paper as the Appalachian Plateau, Valley and Ridge, and far western Blue Ridge) are notably older than the oldest ages from bedrock in the eastern Appalachians (Piedmont and main part of the Blue Ridge). The age difference is seen both in ZFT sample ages and in individual zircon grain ages and reflects differences in the thermotectonic history of the rocks. In the east, ZFT data indicate that the rocks cooled from temperatures high enough to partially or totally reset ZFT ages during the Paleozoic and (or) Mesozoic. The majority of the rocks are interpreted to have cooled through the ZFT closure temperature (∼235 °C) at various times during the late Paleozoic Alleghanian orogeny. In contrast, most of the rocks sampled in the western Appalachians have never been heated to temperatures high enough to totally reset their ZFT ages. Reflecting their contrasting thermotectonic histories, nearly 80 percent of the sampled western rocks yield one or more zircon grains with very old FT ages, in excess of 800 Ma; zircon grains yielding FT ages this old have not been found in rocks in the Piedmont and main part of the Blue Ridge. The ZFT data suggest that the asymmetry of zircon ages of exposed bedrock in the eastern and western Appalachians was in evidence by no later than the Early Cretaceous and probably by the Late Triassic.Detrital zircon suites from sands collected in the Atlantic Coastal Plain provide a record of detritus eroded from source terranes in the Appalachians during the Mesozoic and Cenozoic. In Virginia and Maryland, sands of Early Cretaceous through late early Oligocene age do not yield any old zircons comparable in age to the old zircons found in bedrock in the western Appalachians. Very old zircons yielding FT ages >800 Ma are only encountered in Coastal Plain sands of middle early Miocene and younger age.Miocene and younger fluvial-deltaic deposits associated with the major mid-Atlantic Coastal Plain rivers that now head in the western Appalachians (the Hudson, Delaware, Susquehanna, Potomac, James, and Roanoke) contain abundant clasts of fossiliferous chert and quartzite and other distinctive rock types derived from Paleozoic rocks of the western Appalachians. These distinctive clasts have not been reported in older Coastal Plain sediments.The ZFT and lithic detritus data indicate that the drainage divide for one or more east-flowing mid-Atlantic rivers migrated west into the western Appalachians, and the river(s) began transporting western Appalachian detritus to the Atlantic Coastal Plain, sometime between the late early Oligocene and middle early Miocene. By no later than late middle Miocene most if not all of the major rivers that now head west of the Blue Ridge were transporting western Appalachian detritus to the Coastal Plain. Prior to the drainage divide migrating into the western Appalachians, the ZFT data are consistent with the dominant source of Atlantic Coastal Plain sediments being detritus from the Piedmont and main part of the Blue Ridge, with possible input from distant volcanic sources.The ZFT data suggest that the rapid increase in the rate of siliciclastic sediment accumulation in middle Atlantic margin offshore basins that peaked in the middle Miocene and produced almost 30 percent of the total volume of post-rift siliciclastic sediments in the offshore basins began in the early Miocene when Atlantic river(s) gained access to the relatively easily eroded Paleozoic sedimentary rocks of the western Appalachians.

Goechemical and Hydrogeochemical Properties of Cappadocia Geothermal Province

NASA Astrophysics Data System (ADS)

Furkan Sener, Mehmet; Sener, Mehmet; Uysal, Tonguc

2016-04-01

In order to determine the geothermal resource potential of Niǧde, Nevşehir and Aksaray provinces in Central Anatolian Volcanic Province (CAVP), geothermal fluids, surface water, and alteration rock samples from the Cappadocia volcanic zone in Turkey were investigated for their geochemical and stable isotopic characteristics in light of published geological and tectonic studies. Accordingly, the Cappadocia Geothermal Province (CGP) has two different geothermal systems located along tectonic zones including five active and two potential geothermal fields, which are located between Tuzgölü Fault Zone and Keçiboyduran-Melendiz Fault and north of Keçiboyduran-Melendiz Fault. Based on water chemistry and isotope compositions, samples from the first area are characterized by Ca-Mg-HCO3 ve Ca-HCO3 type mineral poor waters and Ca-Na-SO4 and Ca-Mg-SO4 type for the cold waters and the hot waters, respectively, whereas hot waters from the second area are Na-Cl-HCO3 and Ca-Na-HCO3 type mineral poor waters. According to δ18O and δ2H isotope studies, the geothermal waters are fed from meteoric waters. Results of silica geothermometer indicate that the reservoir temperature of Dertalan, Melendiz Mount, Keçiboyduran Mount, Hasan Mount (Keçikalesi), Ziga, Acıgöl, and Derinkuyu geothermal waters are 150-173 oC, 88-117 oC, 91-120 oC, 94-122 oC, 131-156 oC, 157-179 oC; 152-174 oC and 102-130 oC, respectively. The REE composition of geothermal fluids, surface water, and mineral precipitates indicate that temperature has a strong effect on REE fractionation of the sampled fluids. Eu- and Ce- anomalies (Eu/Eu*, Ce/Ce*) are visible in several samples, which are related to the inheritance from the host reservoir rocks and redox-controlled fractionation of these elements during water-rock interactions. REE and Yttrium geochemistry results of altered rock samples and water samples, which were taken from same locations exhibited quite similar features in each system. Hence, it was conclude that the same hydrothermal fluid in geothermal system was reached to the surface and interacted with the surface rocks. Our conceptual geothermal model for Cappadocia Geothermal Province based on our geochemical and hydrogeochemical data in combination with geological and geophysical information suggest that the geothermal resources in this region are controlled by primary (active fault) and secondary (buried fault) tectonic belts. Further, our geochemical data indicate the Paleozoic-Mesozoic marble and gneiss being the reservoir rocks. Geogradient and impending heat fluxes to the surface with a possible crustal thinning, which was developed after regional tectonic activities during the Late Pliocene-Quaternary period, constitutes the heat sources. In addition, our study suggest that the Quaternary tuff and ignimbrites of Cappadocia Volcanics represent the seal rock of the geothermal system. In conclusion this study provide evidence for a significant geothermal potential in the Cappadocia region with well-defined seal rocks. However, further studies are needed to resolve the geothermal fluid source problem. Keywords: Cappadocia, geothermal systems, geochemistry, rare earth elements, hydrogeochemistry, hydrothermal alteration.

Lead isotopes tracing the life cycle of a catchment: From source rock via weathering to human impact

NASA Astrophysics Data System (ADS)

Negrel, P. J.; Petelet-Giraud, E.; Guerrot, C.; Millot, R.

2015-12-01

Chemical weathering of rocks involves consumption of CO2, a greenhouse gas with a strong influence on climate. Among rocks exposed to weathering, basalt plays a major role in the carbon cycle as it is more easily weathered than other crystalline silicate rocks. This means that basalt weathering acts as a major atmospheric CO2 sink. The present study investigated the lead isotopes in rock, soil and sediment for constraining the life cycle of a catchment, covering source rocks, erosion processes and products, and anthropogenic activities. For this, we investigated the Allanche river drainage basin in the Massif Central, the largest volcanic areas in France, that offers opportunities for selected geochemical studies since it drains a single type of virtually unpolluted volcanic rock, with agricultural activity increasing downstream. Soil and sediment are derived exclusively from basalt weathering, and their chemistry, coupled to isotope tracing, should shed light on the behavior of chemical species during weathering from parental bedrock. Bedrock samples of the basin, compared to regional bedrock of the volcanic province, resulted from a complex history and multiple mantle reservoir sources and mixing. Regarding soils and sediments, comparison of Pb and Zr normalized to mobile K shows a linear evolution of weathering processes, whereby lead enrichment from atmospheric deposition is the other major contributor. Lead-isotope ratios showed that most of the lead budget in sediment and soil results from bedrock weathering with an influence of past mining and mineral processing of ores in the Massif Central, and deposition of lead-rich particles from gasoline combustion, but no lead input from agricultural activity. A classic box model was used to investigate the dynamics of sediment transfer at the catchment scale, the lead behavior in the continuum bedrock-soil-sediment and the historical evolution of anthropogenic aerosol emissions.

High-frequency rock temperature data from hyper-arid desert environments in the Atacama and the Antarctic Dry Valleys and implications for rock weathering

NASA Astrophysics Data System (ADS)

McKay, Christopher P.; Molaro, Jamie L.; Marinova, Margarita M.

2009-09-01

In desert environments with low water and salt contents, rapid thermal variations may be an important source of rock weathering. We have obtained temperature measurements of the surface of rocks in hyper-arid hot and cold desert environments at a rate of 1/s over several days. The values of temperature change over 1-second intervals were similar in hot and cold deserts despite a 30 °C difference in absolute rock surface temperature. The average percentage of the time dT/dt > 2 °C/min was ~ 8 ± 3%, > 4 °C/min was 1 ± 0.9%, and > 8 °C/min was 0.02 ± 0.03%. The maximum change over a 1-second interval was ~ 10 °C/min. When sampled to simulate data taken over intervals longer than 1 s, we found a reduction in time spent above the 2 °C/min temperature gradient threshold. For 1-minute samples, the time spent above any given threshold was about two orders of magnitude lower than the corresponding value for 1-second sampling. We suggest that a rough measure of efficacy of weathering as a function of frequency is the product of the percentage of time spent above a given threshold value multiplied by the damping depth for the corresponding frequency. This product has a broad maximum for periods between 3 and 10 s.

Analytical performance of a versatile laboratory microscopic X-ray fluorescence system for metal uptake studies on argillaceous rocks

NASA Astrophysics Data System (ADS)

Gergely, Felicián; Osán, János; Szabó, B. Katalin; Török, Szabina

2016-02-01

Laboratory-scale microscopic X-ray fluorescence (micro-XRF) plays an increasingly important role in various fields where multielemental investigations of samples are indispensable. In case of geological samples, the reasonable detection limits (LOD) and spatial resolutions are necessary to identify the trace element content in microcrystalline level. The present study focuses on the analytical performance of a versatile laboratory-scale micro-XRF system with various options of X-ray sources and detectors to find the optimal experimental configuration in terms of sensitivities and LOD for selected elements in loaded petrographic thin sections. The method was tested for sorption studies involving thin sections prepared from cores of Boda Claystone Formation, which is a potential site for a high-level radioactive waste repository. Loaded ions in the sorption measurements were Cs(I) and Ni(II) chemically representing fission and corrosion products. Based on the collected elemental maps, the correlation between the elements representative of main rock components and the selected loaded ion was studied. For the elements of interest, Cs(I) and Ni(II) low-power iMOXS source with polycapillary and silicon drift detector was found to be the best configuration to reach the optimal LOD values. Laboratory micro-XRF was excellent to identify the responsible key minerals for the uptake of Cs(I). In case of nickel, careful corrections were needed because of the relatively high Ca content of the rock samples. The results were compared to synchrotron radiation micro-XRF.

Characterization and obtainment of phosphate rock concentrates of Turmequé, Boyacá

NASA Astrophysics Data System (ADS)

Zanguña, S. Quijano; Lozano Gómez, L. F.; Pineda Triana, Y.

2017-12-01

The work focuses on the use and exploitation of the mineral concentrates from phosphate rock (PR) coming from mines with a low percentage of phosphorus. The procedure was based on the collection of a source of phosphate rock from the department of Boyacá (municipality of Turmequé), using a randomized design with three replications. The samples were initially milled and sifted using meshes between 140 and 200 US standard, homogenizing them and improving the process of solubility of the phosphorus in the soil. We conduced Z-potential tests, which show that by performing a prior wash on the mineral and maintaining certain concentrations and pH defined, better results are achieved in terms of the buoyancy of the particles in the flotation process. The results obtained from the microflotation tests; both direct and inverse, and the results of chemical composition, with X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD), before and after the microflotation process, were carried out to obtain of commercial laws grade phosphate rock concentrate, confirm that the protocol used increases by 9% the value of total phosphorus in the collected sample. These concentrates from phosphate rock, could be used in the future for the attainment of simple superphosphate (SSP), with the help of sulphuric acid and ammonium thiosulphate mixtures.

Mineralogy and geochemistry of the Lower Cretaceous siliciclastic rocks of the Morita Formation, Sierra San José section, Sonora, Mexico

NASA Astrophysics Data System (ADS)

Madhavaraju, J.; Pacheco-Olivas, S. A.; González-León, Carlos M.; Espinoza-Maldonado, Inocente G.; Sanchez-Medrano, P. A.; Villanueva-Amadoz, U.; Monreal, Rogelio; Pi-Puig, T.; Ramírez-Montoya, Erik; Grijalva-Noriega, Francisco J.

2017-07-01

Clay mineralogy and geochemical studies were carried out on sandstone and shale samples collected from the Sierra San José section of the Morita Formation to infer the paleoclimate and paleoweathering conditions that prevailed in the source region during the deposition of these sediments. The clay mineral assemblages (fraction < 2 μm) of the Sierra San José section are composed of chlorite and illite. The abundance of illite and chlorite in the studied samples suggest that the physical weathering conditions were dominant over chemical weathering. Additionally, the illite and chlorite assemblages reflect arid or semi-arid climatic conditions in the source regions. K2O/Al2O3 ratio of shales vary between 0.15 and 0.26, which lie in the range of values for clay minerals, particularly illite composition. Likewise, sandstones vary between 0.06 and 0.13, suggesting that the clay minerals are mostly kaolinte and illite types. On the chondrite-normalized diagrams, sandstone and shale samples show enriched light rare earth elements (LREE), flat heavy rare earth elements (HREE) patterns and negative Eu anomalies. The CIA and PIA values and A-CN-K plot of shales indicate low to moderate degree of weathering in the source regions. However, the sandstones have moderate to high values of CIA and PIA suggesting a moderate to intense weathering in the source regions. The SiO2/Al2O3 ratios, bivariate and ternary plots, discriminant function diagram and elemental ratios indicate the felsic source rocks for sandstone and shale of the Morita Formation.

Natural Offshore Oil Seepage and Related Tarball Accumulation on the California Coastline - Santa Barbara Channel and the Southern Santa Maria Basin: Source Identification and Inventory

USGS Publications Warehouse

Lorenson, T.D.; Hostettler, Frances D.; Rosenbauer, Robert J.; Peters, Kenneth E.; Dougherty, Jennifer A.; Kvenvolden, Keith A.; Gutmacher, Christina E.; Wong, Florence L.; Normark, William R.

2009-01-01

Oil spillage from natural sources is very common in the waters of southern California. Active oil extraction and shipping is occurring concurrently within the region and it is of great interest to resource managers to be able to distinguish between natural seepage and anthropogenic oil spillage. The major goal of this study was to establish the geologic setting, sources, and ultimate dispersal of natural oil seeps in the offshore southern Santa Maria Basin and Santa Barbara Basins. Our surveys focused on likely areas of hydrocarbon seepage that are known to occur between Point Arguello and Ventura, California. Our approach was to 1) document the locations and geochemically fingerprint natural seep oils or tar; 2) geochemically fingerprint coastal tar residues and potential tar sources in this region, both onshore and offshore; 3) establish chemical correlations between offshore active seeps and coastal residues thus linking seep sources to oil residues; 4) measure the rate of natural seepage of individual seeps and attempt to assess regional natural oil and gas seepage rates; and 5) interpret the petroleum system history for the natural seeps. To document the location of sub-sea oil seeps, we first looked into previous studies within and near our survey area. We measured the concentration of methane gas in the water column in areas of reported seepage and found numerous gas plumes and measured high concentrations of methane in the water column. The result of this work showed that the seeps were widely distributed between Point Conception east to the vicinity of Coal Oil Point, and that they by in large occur within the 3-mile limit of California State waters. Subsequent cruises used sidescan and high resolution seismic to map the seafloor, from just south of Point Arguello, east to near Gaviota, California. The results of the methane survey guided the exploration of the area west of Point Conception east to Gaviota using a combination of seismic instruments. The seafloor was mapped by sidescan sonar, and numerous lines of high -resolution seismic surveys were conducted over areas of interest. Biomarker and stable carbon isotope ratios were used to infer the age, lithology, organic matter input, and depositional environment of the source rocks for 388 samples of produced crude oil, seep oil, and tarballs mainly from coastal California. These samples were used to construct a chemometric fingerprint (multivariate statistics) decision tree to classify 288 additional samples, including tarballs of unknown origin collected from Monterey and San Mateo County beaches after a storm in early 2007. A subset of 9 of 23 active offshore platform oils and one inactive platform oil representing a few oil reservoirs from the western Santa Barbara Channel were used in this analysis, and thus this model is not comprehensive and the findings are not conclusive. The platform oils included in this study are from west to east: Irene, Hildago, Harvest, Hermosa, Heritage, Harmony, Hondo, Holly, Platform A, and Hilda (now removed). The results identify three 'tribes' of 13C-rich oil samples inferred to originate from thermally mature equivalents of the clayey-siliceous, carbonaceous marl, and lower calcareous-siliceous members of the Monterey Formation. Tribe 1 contains four oil families having geochemical traits of clay-rich marine shale source rock deposited under suboxic conditions with substantial higher-plant input. Tribe 2 contains four oil families with intermediate traits, except for abundant 28,30-bisnorhopane, indicating suboxic to anoxic marine marl source rock with hemipelagic input. Tribe 3 contains five oil families with traits of distal marine carbonate source rock deposited under anoxic conditions with pelagic but little or no higher-plant input. Tribes 1 and 2 occur mainly south of Point Conception in paleogeographic settings where deep burial of the Monterey Formation source rock favored generation from all thre

Petrography and geochemistry of Jurassic sandstones from the Jhuran Formation of Jara dome, Kachchh basin, India: Implications for provenance and tectonic setting

NASA Astrophysics Data System (ADS)

Periasamy, V.; Venkateshwarlu, M.

2017-06-01

Sandstones of Jhuran Formation from Jara dome, western Kachchh, Gujarat, India were studied for major, trace and rare earth element (REE) geochemistry to deduce their paleo-weathering, tectonic setting, source rock characteristics and provenance. Petrographic analysis shows that sandstones are having quartz grains with minor amount of K-feldspar and lithic fragments in the modal ratio of Q 89:F 7:L 4. On the basis of geochemical results, sandstones are classified into arkose, sub-litharenite, wacke and quartz arenite. The corrected CIA values indicate that the weathering at source region was moderate to intense. The distribution of major and REE elements in the samples normalized to upper continental crust (UCC) and chondrite values indicate similar pattern of UCC. The tectonic discrimination diagram based on the elemental concentrations and elemental ratios of Fe2O3 + MgO vs. TiO2, SiO2 vs. log(K2O/Na2O), Sc/Cr vs. La/Y, Th-Sc-Zr/10, La-Th-Sc plots Jhuran Formation samples in continental rift and collision settings. The plots of Ni against TiO2, La/Sc vs. Th/Co and V-Ni-Th ∗10 reveals that the sediments of Jhuran Formation were derived from felsic rock sources. Additionally, the diagram of (Gd/Yb) N against Eu/Eu ∗ suggest the post-Archean provenance as source possibly Nagar Parkar complex for the studied samples.

Tracking hydrothermal alteration and mineralization in rock-forming and accessory minerals from the Lyon Mountain Granite and related iron oxide apatite (IOA) ores from the Adirondack Mountains, New York State

NASA Astrophysics Data System (ADS)

Buchanan, A.; Hanchar, J. M.; Steele-MacInnis, M. J.; Crowley, J. L.; Valley, P. M.; Fisher, C. M.; Fedo, C.; Piccoli, P. M.; Fournelle, J.

2012-12-01

The Lyon Mountain granite (LMG) is located in the northeastern Adirondack Mountains in New York State and hosts several low-titanium iron oxide apatite (IOA) ore deposits. The ores are predominately hosted by perthite bearing granite, which has been extensively altered to albite and microcline granite by Na and K metasomatism. This alteration results in several distinct groups of rocks that are dominated by either K or Na addition and a group composed of mixed Na and K addition. The different groups of altered perthite also lie on a trend suggestive of addition of Fe to each, consistent with a secondary mineralization origin. Previous work showed that the host rocks of the IOA ores have zircon with ~1150 Ma cores and 1060-1050 Ma rims and whole grains. This study aims to further constrain the timing of LMG emplacement, subsequent hydrothermal alteration, and Fe mineralization through geochemical analysis of the major, minor, and accessory phases and geochronology of accessory phases. SIMS analyses of zircon from several of the IOA ores reveal at least two periods of growth after LMG magmatism, at 1039 +/- 4.4 Ma and 1016 +/- 7 Ma to 1000 +/- 9 Ma. In situ EMPA and LA-ICPMS trace element analyses of the zircon rims and cores reveal that in two samples the zircon rims are enriched in rare earth elements (REE) compared to their cores, potentially pointing to a hydrothermal origin. Apatite has unusually high REE and Y concentrations (some total REE2O3 > 20 wt. % oxide and up to 8 wt. % oxide Y2O3), as does titanite, which allowed for the in situ analysis of Sm-Nd in apatite and titanite by LA-MC-ICP-MS. Initial Nd isotopic composition of both ore and host rock apatite and host rock titanite are consistent with published Adirondack initial Nd whole rock data, suggesting a local source for REE in these ores. EMPA and LA-ICPMS trace-element analyses of the major rock-forming minerals indicate that the feldspar have undergone Na-metasomatism and are depleted in REEs, perhaps signifying the "local source" and the mechanism of the REE enrichment in the LMG apatite in the IOA ores and host rocks. In contrast, the minor- and trace-element compositions of the other major rock-forming minerals (e.g., clinopyroxene and fayalite) as well as the zircon, and fluorite in the LMG have average igneous granitic trace- and minor-element compositions. To better understand the timing and origin of these post ~1050 Ma events, U-Pb ID-TIMS dating of apatite and titanite, and in situ LA-MC-ICPMS Sm-Nd analysis were done on the ore and host rock samples. Apatite dates range from 1050 to 850 Ma and titanite dates range from ~1015 to 970 Ma. There is significant age variation within samples and within grains. Titanite does not have sufficient spread for accurate Sm-Nd isochron dating and two ore-apatite samples have homogenous initial Nd isotopic and Sm-Nd elemental ratios, precluding calculation of Sm-Nd dates. A third ore sample shows a large spread in Sm-Nd and yields a Sm-Nd isochron date of ~850 Ma, in close agreement with U-Pb apatite dates. The Sm-Nd isochron and U-Pb apatite dates may reflect cooling recorded in these minerals or a younger hydrothermal mineralization event.

Identification of sulfur sources and isotopic equilibria in submarine hot-springs using multiple sulfur isotopes

NASA Astrophysics Data System (ADS)

McDermott, Jill M.; Ono, Shuhei; Tivey, Margaret K.; Seewald, Jeffrey S.; Shanks, Wayne C.; Solow, Andrew R.

2015-07-01

Multiple sulfur isotopes were measured in metal sulfide deposits, elemental sulfur, and aqueous hydrogen sulfide to constrain sulfur sources and the isotopic systematics of precipitation in seafloor hydrothermal vents. Areas studied include the Eastern Manus Basin and Lau Basin back-arc spreading centers and the unsedimented basalt-hosted Southern East Pacific Rise (SEPR) and sediment-hosted Guaymas Basin mid-ocean ridge spreading centers. Chalcopyrite and dissolved hydrogen sulfide (H2S) δ34S values range from -5.5‰ to +5.6‰ in Manus Basin samples, +2.4‰ to +6.1‰ in Lau Basin samples, and +3.7‰ to +5.7‰ in SEPR samples. Values of δ34S for cubic cubanite and H2S range from -1.4‰ to +4.7‰ in Guaymas Basin samples. Multiple sulfur isotope systematics in fluid-mineral pairs from the SEPR and Lau Basin show that crustal host rock and thermochemical reduction of seawater-derived dissolved sulfate (SO4) are the primary sources of sulfur in mid-ocean ridge and some back-arc systems. At PACMANUS and SuSu Knolls hydrothermal systems in the Eastern Manus Basin, a significant contribution of sulfur is derived from disproportionation of magmatic sulfur dioxide (SO2), while the remaining sulfur is derived from crustal host rocks and SO4 reduction. At the sedimented Guaymas Basin hydrothermal system, sulfur sources include crustal host rock, reduced seawater SO4, and biogenic sulfide. Vent fluid flow through fresher, less-mature sediment supplies an increased quantity of reactant organic compounds that may reduce 34S-enriched SO4, while fluid interaction with more highly-altered sediments results in H2S characterized by a small, but isotopically-significant input of 34S-depleted biogenic sulfides. Near-zero Δ33S values in all samples implicate the abiotic processes of SO4 reduction and leaching of host rock as the major contributors to sulfur content at a high temperature unsedimented mid-ocean ridge and at a back-arc system. Δ33S values indicate that SO2 disproportionation is an additional process that contributes sulfur to a different back-arc system and to acid spring-type hydrothermal fluid circulation. At the sedimented Guaymus Basin, near-zero Δ33S values are also observed, despite negative δ34S values that indicate inputs of biogenic pyrite for some samples. In contrast with previous studies reporting isotope disequilibrium between H2S and chalcopyrite, the δ34S values of chalcopyrite sampled from the inner 1-2 mm of a chimney wall are within ±1‰ of δ34S values for H2S in the paired vent fluid, suggesting equilibrium fluid-mineral sulfur isotope exchange at 300-400 °C. Isotopic equilibrium between hydrothermal fluid H2S and precipitating chalcopyrite implies that sulfur isotopes in the chalcopyrite lining across a chimney wall may accurately record past hydrothermal activity.

Modelling of the petroleum formation in the Mahakam sediments (Indonesia): Organic geochemical controls of the results

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

Brosse, E.; Burris, J.; Ouidin, J.L.

1990-06-01

Since the Miocene, the delta of the Mahakam River has accumulated thousands of meters of sediments in the eastern part of the Kutei Basin (Kalimantan, Indonesia). Source-rock candidates are the coals of the deltaic plain and several types of shales, mainly the delta front/prodelta area. Organic matter basically derives from higher plants, but each source facies presents important intrinsic variations of petroleum potential. These variations are overprinted by subsequent maturation trends. Geochemical and petrographical data are integrated on the general framework provided by a new synthetic interpretation of the sedimentary sequences, relying upon the concepts of seismic stratigraphy. From coremore » samples at a given level of maturation, the variations of several organic parameters are discussed in relation to the depositional paleoenvironment and to the possible precursors. 1D and 2D numerical routines are used to reconstruct the maturation history of source rocks. These tools are based upon a kinetic modeling of kerogen cracking. Model outputs are compared with observed maturation trends. The understanding of the initial organic facies distribution provides precise constraints in the selection of a homogenous samples set for this comparison purpose.« less

Spectral variations in rocks and soils containing ferric iron hydroxide and(or) sulfate minerals as seen by AVIRIS and laboratory spectroscopy

USGS Publications Warehouse

Rockwell, Barnaby W.

2004-01-01

Analysis of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data covering the Big Rock Candy Mountain area of the Marysvale volcanic field, west-central Utah, identified abundant rocks and soils bearing jarosite, goethite, and chlorite associated with volcanic rocks altered to propylitic grade during the Miocene (2321 Ma). Propylitically-altered rocks rich in pyrite associated with the relict feeder zones of convecting, shallow hydrothermal systems are currently undergoing supergene oxidation to natrojarosite, kaolinite, and gypsum. Goethite coatings are forming at the expense of jarosite where most pyrite has been consumed through oxidation in alluvium derived from pyrite-bearing zones. Spectral variations in the goethite-bearing rocks that resemble variations found in reference library samples of goethites of varying grain size were observed in the AVIRIS data. Rocks outside of the feeder zones have relatively low pyrite content and are characterized by chlorite, epidote, and calcite, with local copper-bearing quartz-calcite veins. Iron-bearing minerals in these rocks are weathering directly to goethite. Laboratory spectral analyses were applied to samples of iron-bearing rock outcrops and alluvium collected from the area to determine the accuracy of the AVIRIS-based mineral identification. The accuracy of the iron mineral identification results obtained by analysis of the AVIRIS data was confirmed. In general, the AVIRIS analysis results were accurate in identifying medium-grained goethite, coarse-grained goethite, medium- to coarse-grained goethite with trace jarosite, and mixtures of goethite and jarosite. However, rock fragments from alluvial areas identified as thin coatings of goethite with the AVIRIS data were found to consist mainly of medium- to coarse-grained goethite based on spectral characteristics in the visible and near-infrared. To determine if goethite abundance contributed to the spectral variations observed in goethite-bearing rocks with AVIRIS data, a laboratory experiment was performed in which spectra were acquired of a goethite-bearing rock while progressively decreasing the areal abundance of the rock with respect to a background of white, fine-grained quartz sand. This experiment found that, with decreasing material abundance, the crystal field absorption feature of goethite near 1.0 micron decreases in depth and narrows more from the long wavelength side of the feature than from the short wavelength side, as is the case in goethite reference spectra as grain size decreases from coarse to fine. In the Marysvale study area, goethite-bearing alluvium downgradient from source outcrops tends to be identified as finer-grained or thin coatings of goethite due to the minerals presence in lesser abundance. The goethite-bearing alluvium is a closer match to reference spectra of thin coatings of goethite even though the actual grain size of the contained goethite fragments is medium to coarse grained, the same on average as that from the source outcrops. Coarser-grained goethite most likely will be correctly identified in areas of greater goethite abundance proximal to jarosite-bearing source rock where the surface is relatively free of goethite-free soil components and vegetation that corrupt the goethite spectral response. When analysis of imaging spectroscopy data is performed using reference spectra of iron minerals of varying grain sizes and mixed compositions, the results are useful not only for purposes of mineral identification, but also for distinguishing goethite-bearing outcrop from alluvial surfaces with similar mineralogy, providing valuable information for geologic, geomorphologic, mineral exploration, and environmental assessment studies.

Occurrence of phosphorus, other nutrients, and triazine herbicides in water from the Hillsdale Lake basin, Northeast Kansas, May 1994 through May 1995

USGS Publications Warehouse

Putnam, J.E.

1997-01-01

An investigation of the occurrence of phosporus, other nutrients, and triazine herbicides in water samples from the Hillsdale Lake Basin in northeast Kansas was conducted from May 1994 through May 1995. Point-source and nonpoint-source contributions of these water-quality constituents were estimated by conducting synoptic sampling at 48 sites in the basin during five periods of low- flow conditions. Samples were collected for the determination of nutrients, including total phosphorus as phosphorus, dissolved orthophosphate as phosphorus, total nitrite plus nitrate as nitrogen, and total ammonia plus organic nitrogen as nitrogen, and for selected triazine herbicides. On the basis of criteria developed by the Kansas Department of Health and Environment, the Hillsdale Water-Quality Protection Project established a goal to maintain water quality in the tributaries of the Hillsdale Lake Basin at a mean annual low-flow total phosphorus concentration of 0.05 mg/L (milligrams per liter). The mean low- flow total phosphorus concentration of water samples collected in the Big Bull Creek (which includes drainage from Martin Creek), Rock Creek, Little Bull Creek, Wade Branch, and Smith Branch subbasins during low-flow conditions ranged from 0.05 to 4.9 mg/L during this study. Of the 44 sites sampled during low flow, 95 percent had low-flow total phosphorus concentrations larger than the 0.05-mg/L criterion. Discharges from wastewater- treatment plants located in Big Bull Creek and Martin Creek subbasins and the Little Bull Creek subbasin affected nutrient concentrations. Nutrient concentrations in water samples collected from the subbasins not affected by point-source discharges generally were smaller than those in the Big Bull Creek and Little Bull Creek subbasins. Estimated annual low-flow phosphorus loads computed at sampling sites located at the outlet of the subbasins show that the Big Bull Creeksubbasin, which includes drainage from the Martin Creek subbasin, had the largest estimate annual low-flow load, 2,740 kg/yr (kilograms per year).Rock Creek, Little Bull Creek, Wade Branch, and Smith Branch subbasins contributed less annual low-flow phosphorus load, 175, 161, 234, and 22kg/yr, respectively. With the exception of the Smith Branch subbasin, the largest triazine herbicide concentrations occurred in water samples collectedduring May 1994 and May 1995. During May 1994, 10 of 17 sampling sites in the Big Bull Creek and Martin Creek subbasins, 5 of 6 sites in theRock Creek subbasin, and 4 of 10 sites in the Little Bull Creek subbasin had triazine herbicide concentrations in water larger than the U.S.Environmental Protection Agency's Maximum Contaminant Level (MCL), which is an annual mean 3.0 ug/L (micrograms per liter) for atrazine indrinking water. During May 1995, 7 of 19 sites in the Big Bull Creek and Martin Creek subbasins, 5 of 6 sites in the Rock Creek subbasin, 1 of 12 sites in the Little Bull Creek subbasin, and 2 of 4 sites in the Wade Branch subbasin had samples with trazine herbicide concentrations larger than the MCL.Water samples collected in the Rock Creek subbasins had the largest mean triazine herbicide concentrations during May 1994 and May 1995, 6.4 and 4.5 ug/L, respectively.

Potential for formation of disinfection by-products from storage of chlorinated surface water in the Basalt aquifer near Fallon, Nevada

USGS Publications Warehouse

Fram, Miranda S.; Maurer, Douglas K.; Lico, Michael S.

2005-01-01

Increased pumpage from a basalt aquifer near Fallon, Nevada, has caused its water levels to decline and has induced changes in the quality of water pumped from the basalt. The aquifer is the sole source of water for municipal supply to the city of Fallon, the Naval Air Station Fallon, and the Fallon Paiute-Shoshone Tribe. These changes may be mitigated by storage of surface water in the basalt for subsequent use. Because chlorination of the surface water may be required for storage, the U.S. Geological Survey, in cooperation with the Fallon Paiute-Shoshone Tribe, made laboratory tests using laboratory carbon-organic-free water, surface-water, ground-water, and basaltic-rock samples to determine the potential for formation of disinfection by-products. Experiments with water samples only (no rock and no chlorine) indicated no change in dissolved-organic-carbon (DOC) concentrations over a 20-day reaction period; whereas, all experiments using rock, water, and no chlorine indicated an increase in DOC concentrations. The greatest increase in DOC concentrations for all three water samples occurred in experiments with the rock samples from outcrops on Rattlesnake Hill. Experiments with water only and chlorine yielded a total trihalomethane (THM) concentration of 97.4 ?g/L for the ground-water sample and 347 ?g/L for the surface-water sample. Experiments with mixtures of water, rocks, and chlorine indicated that reactions with the rock consumed chlorine and released significant amounts of organic carbon from the rock, increasing the DOC concentration in the water. The organic carbon in the rocks likely is associated with the secondary clay minerals that line vesicles and fractures in the rocks. THM concentrations were greatest, from 335 to 909 ?g/L, for surface water equilibrated with rock samples from Rattlesnake Hill. However, the concentration of chlorine required to produce these high THM concentrations ranged from 18 to 84 mg/L. The results of the experiments suggest that the amount of organic carbon released from the rocks during successive cycles of recharge, storage, and recovery of chlorinated surface water may be relatively small. The chlorine demand of the rocks is so large that all of the free chlorine in the entire volume of recharged water likely would be consumed by only a very small volume of the aquifer surrounding an injection well, or beneath an infiltration bed. The majority of the volume of the aquifer filled by the stored water likely would never come in contact with free chlorine, and the increases in concentration of DOC observed in these experiments likely would occur in a very small volume of the stored water. For this reason, increases in concentration of THMs for the entire volume of water stored also likely would be considerably less than those measured in these experiments. To test this hypothesis, additional laboratory experiments using varying levels of chlorination, varying lengths of reaction periods, and repeated cycles of chlorination would be useful. A field experiment made at a small scale in an isolated part of the basalt aquifer would aid in the design of an operational system.

Thermal maturity patterns (conodont color alteration index and vitrinite reflectance) in Upper Ordovician and Devonian rocks of the Appalachian basin: a major revision of USGS Map I-917-E using new subsurface collections: Chapter F.1 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

USGS Publications Warehouse

Repetski, John E.; Ryder, Robert T.; Weary, David J.; Harris, Anita G.; Trippi, Michael H.; Ruppert, Leslie F.; Ryder, Robert T.

2014-01-01

The conodont color alteration index (CAI) introduced by Epstein and others (1977) and Harris and others (1978) is an important criterion for estimating the thermal maturity of Ordovician to Mississippian rocks in the Appalachian basin. Consequently, the CAI isograd maps of Harris and others (1978) are commonly used by geologists to characterize the thermal and burial history of the Appalachian basin and to better understand the origin and distribution of oil and gas resources in the basin. The main objectives of this report are to present revised CAI isograd maps for Ordovician and Devonian rocks in the Appalachian basin and to interpret the geologic and petroleum resource implications of these maps. The CAI isograd maps presented herein complement, and in some areas replace, the CAI-based isograd maps of Harris and others (1978) for the Appalachian basin. The CAI data presented in this report were derived almost entirely from subsurface samples, whereas the CAI data used by Harris and others (1978) were derived almost entirely from outcrop samples. Because of the different sampling methods, there is little geographic overlap of the two data sets. The new data set is mostly from the Allegheny Plateau structural province and most of the data set of Harris and others (1978) is from the Valley and Ridge structural province, east of the Allegheny structural front (fig. 1). Vitrinite reflectance, based on dispersed vitrinite in Devonian black shale, is another important parameter for estimating the thermal maturity in pre-Pennsylvanian-age rocks of the Appalachian basin (Streib, 1981; Cole and others, 1987; Gerlach and Cercone, 1993; Rimmer and others, 1993; Curtis and Faure, 1997). This chapter also presents a revised percent vitrinite reflectance (%R0) isograd map based on dispersed vitrinite recovered from selected Devonian black shales. The Devonian black shales used for the vitrinite studies reported herein also were analyzed by RockEval pyrolysis and total organic carbon (TOC) content in weight percent. Although the RockEval and TOC data are included in this chapter (table 1), they are not shown on the maps. The revised CAI isograd and percent vitrinite reflectance isograd maps cover all or parts of Kentucky, New York, Ohio, Pennsylvania, Virginia, and West Virginia (fig. 1), and the following three stratigraphic intervals: Upper Ordovician carbonate rocks, Lower and Middle Devonian carbonate rocks, and Middle and Upper Devonian black shales. These stratigraphic intervals were chosen for the following reasons: (1) they represent target reservoirs for much of the oil and gas exploration in the Appalachian basin; (2) they are stratigraphically near probable source rocks for most of the oil and gas; (3) they include geologic formations that are nearly continuous across the basin; (4) they contain abundant carbonate grainstone-packstone intervals, which give a reasonable to good probability of recovery of conodont elements from small samples of drill cuttings; and (5) the Middle and Upper Devonian black shale contains large amounts of organic matter for RockEval, TOC, and dispersed vitrinite analyses. Thermal maturity patterns of the Upper Ordovician Trenton Limestone are of particular interest here, because they closely approximate the thermal maturity patterns in the overlying Upper Ordovician Utica Shale, which is the probable source rock for oil and gas in the Upper Cambrian Rose Run Sandstone (sandstone), Upper Cambrian and Lower Ordovician Knox Group (Dolomite), Lower and Middle Ordovician Beekmantown Group (dolomite or Dolomite), Upper Ordovician Trenton and Black River Limestones, and Lower Silurian Clinton/Medina sandstone (Cole and others, 1987; Jenden and others, 1993; Laughrey and Baldassare, 1998; Ryder and others, 1998; Ryder and Zagorski, 2003). The thermal maturity patterns of the Lower Devonian Helderberg Limestone (Group), Middle Devonian Onondaga Limestone, and Middle Devonian Marcellus Shale-Upper Devonian Rhine street Shale Member-Upper Devonian Ohio Shale are of interest, because they closely approximate the thermal maturity patterns in the Marcellus Shale, Upper Devonian Rhinestreet Shale Member, and Upper Devonian Huron Member of the Ohio Shale, which are the most important source rocks for oil and gas in the Appalachian basin (de Witt and Milici, 1989; Klemme and Ulmishek, 1991). The Marcellus, Rhinestreet, and Huron units are black-shale source rocks for oil and (or) gas in the Lower Devonian Oriskany Sandstone, the Upper Devonian sandstones, the Middle and Upper Devonian black shales, and the Upper Devonian-Lower Mississippian(?) Berea Sandstone (Patchen and others, 1992; Roen and Kepferle, 1993; Laughrey and Baldassare, 1998).

Howardites - Samples of the regolith of the eucrite parent-body: Petrology of Frankfort, Pavlovka, Yurtuk, Malvern, and ALHA 77302

NASA Technical Reports Server (NTRS)

Labotka, T. C.; Papike, J. J.

1980-01-01

Modal petrographic methods have been applied to the meteorites Frankfort, Pavlovka, Yurtuk, Malvern, and ALHA 77302, to determine some of the characteristics of the regolith of the eucrite parent body. Lithic clasts in the meteorites fall into three major groups: pyroxene + plagioclase rocks, orthopyroxenites, and fused-soil clasts. Lithic clasts make up a small proportion of the soil; mineral clasts from orthopyroxenites dominate the coarse-grained fraction; and the fine-grained fraction contains minerals from both orthopyroxenites and plagioclase + pyroxene rocks. The eucrite regolith appears to have the following characteristics: the source rocks are friable, the soils are immature, comminution is the major soil-forming process, and the soil is well mixed.

Zircon Hf-O isotopic constraints on the origin of Late Mesozoic felsic volcanic rocks from the Great Xing'an Range, NE China

NASA Astrophysics Data System (ADS)

Gong, Mingyue; Tian, Wei; Fu, Bin; Wang, Shuangyue; Dong, Jinlong

2018-05-01

The voluminous Late Mesozoic magmatism was related to extensive re-melting of juvenile materials that were added to the Central East Asia continent in Phanerozoic time. The most favoured magma generation mechanism of Late Mesozoic magmas is partial melting of underplated lower crust that had radiogenic Hf-Nd isotopic characteristics, but this mechanism faces difficulties when interpreting other isotopic data. The tectonic environment controlling the generation of the Late Mesozoic felsic magmas is also in dispute. In this study, we obtained new U-Pb ages, and geochemical and isotopic data of representative Jurassic (154.4 ± 1.5 Ma) and Cretaceous (140.2 ± 1.5 Ma) felsic volcanic samples. The Jurassic sample has inherited zircon cores of Permian age, with depleted mantle-like εHf(t) of +7.4 - +8.5, which is in contrast with those of the magmatic zircons (εHf(t) = +2.4 ± 0.7). Whereas the inherited cores and the magmatic zircons have identical mantle-like δ18O composition ranges (4.25-5.29‰ and 4.69-5.54‰, respectively). These Hf-O isotopic characteristics suggest a mixed source of enriched mantle materials rather than ancient crustal components and a depleted mantle source represented by the inherited Permian zircon core. This mechanism is manifested by the eruption of Jurassic alkaline basalts originated from an enriched mantle source. The Cretaceous sample has high εHf(t) of +7.0 - +10.5, suggesting re-melting of a mafic magma derived from a depleted mantle-source. However, the sub-mantle zircon δ18O values (3.70-4.58‰) suggest the depleted mantle-derived mafic source rocks had experienced high temperature hydrothermal alteration at upper crustal level. Therefore, the Cretaceous felsic magma, if not all, could be generated by re-melting of down-dropped supracrustal volcanic rocks that experienced high temperature oxygen isotope alteration. The two processes, enriched mantle-contribution and supracrustal juvenile material re-melting, are new generation mechanisms of the Late Mesozoic magmas from Central East Asia. Rift settings may have controlled these processes throughout crustal and mantle levels.

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).

REE Distribution in Cultivated and No Cultivated Soils in Two Viticultural Areas of Central Chile: Mineralogical, Pedological and Anthropic Influences

NASA Astrophysics Data System (ADS)

Castillo, P.; Townley, B.; Aburto, F.

2017-12-01

Within the scope of a Corfo-Innova Project (I+D Wines of Chile-University of Chile) we have recognized remarkable REE patterns in soils of two vineyards located in traditional vinicultural areas: Casablanca and Santa Cruz. Both vineyards have granitic parent rock, with similar petrographic features and REE patterns. We studied REE distribution on twelve cultivated soil profiles at each vineyard, where a full mineralogical, geochemical and pedogenic sampling and characterization was performed. To establish the effect of management no cultivated soil profiles were included from each vineyard location. REE in soil samples were measured by ICP-MS using two digestion methods: lithium metaborate/tetraborate fusion to obtain REE contents in total soil and MMI® partial extraction technique for REE contents on bioavailable phases.Soils display similar signatures of REEs respect to the rock source at both vineyards, but showing relative enrichments in soils of Casablanca and depletion in soils of Santa Cruz. Bioavailable phase data indicates a relative depletion of LREEs compared to HREEs and different anomalies for Ce (positive vs negative) in different areas of the same vineyard. Similar patterns of soils and parent rock suggest that REEs are adequate tracers of lithological source. Enrichments and/or depletions of REE patterns in soils respect to the rock source and Ce anomalies, evidence differential pedogenetic processes occurring at each sampled site. Results of bioavailable phase are coherent with the immobilization and fractionation of LREEs by stable minerals within soils as clays and Fe oxides. Mineralogical results in soil thin sections of Casablanca evidence the occurrence of Ti phases as sphene, ilmenite and rutile, which probably control the relative REE enrichment, since these minerals are considered more stable under pedogenic conditions.Finally, cultivated soils show a depleted but analogous pattern of REE regarding to no cultivated soil, indicating the REEs loss due to agricultural land use. Our preliminary hypothesis is the existence of organometallic complexes that retain REEs in natural soils, which are degraded with vinicultural management. However other factors as differential weathering rates of minerals, clays mineralogy and fractionation of REE by plants must be considered.

Monitoring Fluid Flow in Fractured Carbonate Rocks Using Seismic Measurements

NASA Astrophysics Data System (ADS)

Li, W.; Pyrak-Nolte, L. J.

2008-12-01

The physical properties of carbonate rock are strongly influenced by the rock fabric which depends on the depositional environment, diagenetic and tectonic processes. The most common form of heterogeneity is layering caused by a variation in porosity among layers and within layers. The variation in porosity among layers leads to anisotropic behavior in the hydraulic, mechanical and seismic properties of carbonate rocks. We present the results of a laboratory study to examine the effect of fabric-controlled layering on fluid flow and seismic wave propagation through intact and fractured carbonate rock. Experiments were performed on cubic samples of Austin Chalk Cordova Cream. Samples AC1, AC5 and AC6 are cubic samples that measure 100 mm on edge. The samples were sealed and contained three inlet and three outlet ports for fluid invasion experiments. Two orthogonal seismic arrays were used to record both compressional and shear wave transmission through intact and fractured samples. The arrays used piezoelectric contact transducers with a central frequency 1.0 MHz. Between the two arrays, sixteen sources and sixteen receivers were used. Seismic measurements were made on the samples as a function of stress and during fluid saturation. The location of the invading fluid front as a function of time was monitored by using the peak-to-peak amplitude of the transmitted signals. The front was assumed to be between a source-receiver pair when the signal amplitude decreased by 50% over the initial value. The hydraulic gradient was parallel and perpendicular to the layers for AC5 and AC6, respectively. Sample AC1 was fractured and flow ports were established on the edges of the fracture plane. The weakly directed fabric controlled the rate at which fluid flowed through the samples. From the seismic data on AC6, the fluid first spread vertically along a layer before flowing across the layers. For AC6, it took the fluid two and half hours to flow between the inlet and the outlet across the layers. However, for AC5, the water flowed quickly along the layers and crossed the entire sample in one and a half hours. From the seismic data on fractured sample AC1, the water initially took more than 15 hours to transverse the sample though portions of the fracture were invaded after two hours. No water was produced at the outlet over a 15 hour period. Upon inspection, chemical precipitation was observed along the fracture plane and fracture- matrix interaction controlled the saturation of the matrix. Seismic monitoring of the fluid-front during saturation indicates that fine bedding affects the hydraulic properties of the sample while geochemical interactions in fractures affect fracture-matrix communication. Acknowledgments: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DEFG02-97ER14785 08) and by Exxon Mobil Upstream Research Company.

TRAY MOUNTAIN ROADLESS AREA, GEORGIA.

USGS Publications Warehouse

Nelson, Arthur E.; Chatman, Mark L.

1984-01-01

A mineral survey indicates that the Tray Mountain Roadless Area, Georgia has little promise for the occurrence of metallic mineral resources. Rocks underlying the Tray Mountain Roadless Area are suitable for crushed rock or aggregate; however, other sources for these materials are available closer to present markets. There is a possibility for the occurrence of hydrocarbon resources underlying the area at great depth, but no hydrocarbon potential was identified. Detailed studies are needed to establish the presence or absence and mineral-resource potential of olivine, nickel, cobalt, and chrome in the two mafic-ultramafic bodies in the Hayesville thrust sheet. The cause of the lead anomaly in pan concentrate samples taken from the southwest part of the roadless area has not been established; the mineral residence and source of the anomaly remain to be determined.

Modal petrology of six soils from Apollo 16 double drive tube core 64002

NASA Technical Reports Server (NTRS)

Houck, K. J.

1982-01-01

Petrographic data form six size fractions for six samples of Apollo 16 drive tube section 64002 show source rocks similar to those of core 60009. Analysis of modal data from the 64002 core show that the upper three and lowest core soils are mature and have similar maturation histories, while the two middle soils are submature and have histories that are similar to each other but unlike those from the aforementioned soils. In all of these soils, mixing has dominated over reworking, and appears to involve two mature soils distinguished by differing source rocks and an immature, plagioclase-rich soil which is correlated with larger clasts of chalky, friable breccia. These breccias and the plagioclase-rich soil are tentatively associated with the Descartes Formation.

Hydrocarbons in recent sediment of the Monterey Bay National Marine Sanctuary

USGS Publications Warehouse

Kvenvolden, K.A.; Hostettler, F.D.; Rosenbauer, R.W.; Lorenson, T.D.; Castle, W.T.; Sugarman, S.

2002-01-01

A complex mixture of hydrocarbons is present in the recent sediment of the Monterey Bay National Marine Sanctuary. Eighteen samples from the continental shelf between San Francisco and Monterey contain aliphatic and aromatic hydrocarbons showing biological contributions from both marine and terrigenous sources, with the terrigenous indicators more pronounced near Monterey. Of particular interest, however, is a low-level background of petroleum-related compounds, including 28,30-bisnorhopane and 18??+??(H)-oleanane, which are characteristic of many crude oils from the Monterey Formation of California. Thus, the sediments are overprinted by a regional chemical signature which may be derived from eroded Monterey Formation rocks and from onshore and offshore seeps releasing petroleum from Monterey Formation source rocks. ?? 2002 Elsevier Science B.V. All rights reserved.

Mössbauer spectroscopic study of the test well (DND) located in Jaisalmer Basin of Rajasthan, India

NASA Astrophysics Data System (ADS)

Ganwani, Girish; Meena, Samay Singh; Ram, Sahi; Bhatia, Beena; Tripathi, R. P.

2018-05-01

The Jaisalmer basin represents mainly the westerly dipping flank of Indus shelf. The palynological and geochemical studies have predicted good quality of hydrocarbons in this basin. The cretaceous and Jurassic sediments are believed to contain source rock in this basin. In present preliminary study, Mössbauer spectroscopic investigation has been done on sedimentary samples collected from different depths of upper cretaceous sedimentary sequence of well DND-1 drilled in Jaisalmer basin. The iron is found mainly in carbonate and clay. The relatively small presence of Fe2+ in comparison to Fe3+ in clay is an indication of poor reducing environment in sediments, which can be attributed to poor maturity of source rocks in upper cretaceous sediments of this basin.

Planning for the Collection and Analysis of Samples of Martian Granular Materials Potentially to be Returned by Mars Sample Return

NASA Astrophysics Data System (ADS)

Carrier, B. L.; Beaty, D. W.

2017-12-01

NASA's Mars 2020 rover is scheduled to land on Mars in 2021 and will be equipped with a sampling system capable of collecting rock cores, as well as a specialized drill bit for collecting unconsolidated granular material. A key mission objective is to collect a set of samples that have enough scientific merit to justify returning to Earth. In the case of granular materials, we would like to catalyze community discussion on what we would do with these samples if they arrived in our laboratories, as input to decision-making related to sampling the regolith. Numerous scientific objectives have been identified which could be achieved or significantly advanced via the analysis of martian rocks, "regolith," and gas samples. The term "regolith" has more than one definition, including one that is general and one that is much more specific. For the purpose of this analysis we use the term "granular materials" to encompass the most general meaning and restrict "regolith" to a subset of that. Our working taxonomy includes the following: 1) globally sourced airfall dust (dust); 2) saltation-sized particles (sand); 3) locally sourced decomposed rock (regolith); 4) crater ejecta (ejecta); and, 5) other. Analysis of martian granular materials could serve to advance our understanding areas including habitability and astrobiology, surface-atmosphere interactions, chemistry, mineralogy, geology and environmental processes. Results of these analyses would also provide input into planning for future human exploration of Mars, elucidating possible health and mechanical hazards caused by the martian surface material, as well as providing valuable information regarding available resources for ISRU and civil engineering purposes. Results would also be relevant to matters of planetary protection and ground-truthing orbital observations. We will present a preliminary analysis of the following, in order to generate community discussion and feedback on all issues relating to: What are the specific reasons (and their priorities) for collecting samples of granular materials? How do those reasons translate to sampling priorities? In what condition would these samples be expected to be received? What is our best projection of the approach by which these samples would be divided, prepared, and analyzed to achieve our objectives?

Central Antarctic provenance of Permian sandstones in Dronning Maud Land and the Karoo Basin: Integration of U Pb and TDM ages and host-rock affinity from detrital zircons

NASA Astrophysics Data System (ADS)

Veevers, J. J.; Saeed, A.

2007-12-01

In conjugate SE Africa and Antarctica, Early Permian sandstones of the Swartrant Formation of the Ellisras Basin, Vryheid Formation of the Karoo Basin, and Amelang Plateau Formation of Dronning Maud Land (DML) were deposited after Gondwanan glaciation on a westward paleoslope. We analysed detrital zircons for U-Pb ages by a laser ablation microprobe-inductively coupled plasma mass spectrometer (LAM-ICPMS) and attached age significance only to clusters of three or more overlapping analyses. We analysed Hf-isotope compositions by a multi-collector spectrometer (LAM-MC-ICPMS) and trace elements by electron microprobe (EMP) and ICPMS. These analyses indicate the rock type and source (whether crustal or juvenile mantle) of the host magma, and a "crustal" model age ( TDMC). The integrated analysis gives a more distinctive, and more easily interpreted, picture of crustal evolution in the provenance area than age data alone. Zircons from the Ellisras Basin are aged 2700-2540 Ma with minor populations about 2815 Ma and 2040 Ma, which correspond with the ages of the upslope parts of the proximal Kaapvaal Craton and Limpopo Belt. Mafic rock is the dominant host rock, and it reflects the Archean granite-greenstone terrane of the Kaapvaal Craton. The three Karoo Basin samples and the two DML samples have zircons with these common properties: (1) 1160-880 Ma, host magma mafic granitoid (< 65% SiO 2) derived from juvenile depleted mantle sources ( ɛHf positive) at 1.65 Ga and 1.35 Ga, with TDMC of 2.0-0.9 Ga; (2) 760 to 480 Ma, host magma granitoid and low-heavy rare earth element rock (?alkaline rock-carbonatite), derived from mixed crustal and juvenile depleted mantle sources ( ɛHf positive and negative) at 1.50 Ga and 1.35 Ga, with TDMC of 2.0-0.9 Ga. Together with similar detrital zircons in Triassic sandstone of SE Australia, these properties reflect those in upslope central Antarctica, indicating a provenance of ˜ 1000 Ma (Grenville) cratons embedded in 700-500 Ma (Pan-Gondwanaland) fold belts. Detrital zircons in Cambrian sediments of the Ellsworth-Whitmore Mountains block and Cambrian metasediments of the Welch Mountains with comparable properties suggest that the central Antarctic provenance operated also in the ˜ 500 Ma Cambrian.

Geochemistry and provenance of some detrital heavy minerals of alluvial sediments from Neagra Şarului River, Eastern Carpathians, Romania

NASA Astrophysics Data System (ADS)

Ciortescu, Catalina; Iancu, Ovidiu Gabriel; Bulgariu, Dumitru; Popa, Ciprian

2014-05-01

The present work focuses on the analyses of a selection of heavy mineral assemblages sampled from the Neagra Şarului River's alluvia, in order to determine their provenance and distribution, using their geochemical and physical characteristics. The study focused on a mountain river of about 30 km long, located in the north-western part of the Eastern Carpathians, an important tributary of the Bistria River. The bedrocks in the river drainage basin are constituted mainly by igneous rocks from Călimani Volcanic Complex in the west, and secondarily by a small area of low to medium grade metamorphic rocks, part of Crystalline-Mesozoic Zone, in the east. In order to trace the source of each individual mineral species, we prepared our samples via field separation and subsequent laboratory sieving using 8 different size fractions. An electromagnetic separator (Frantz Isodynamic) was used to separate and classify each heavy minerals species, depending on their magnetic susceptibility. Thus prepared, more than 500 grains per samples (from the 0.5-1 mm size fraction) were mounted on thin sections and analyzed using a Cambridge Microscan M9 with EDS system. These analyses served for mineral identification and relative abundance determination. The classification of the minerals and the nature of their inclusions are derived from the major element compositions computed from SEM-EDX analysis. We also used a stereo microscope in order to determine complementary properties of the grains, such as: color, degree of roundness and degree of alteration. In order of abundance, the main heavy minerals are magnetite, hematite, pyroxene, pyrite, manganese oxides, garnet, apatite, titanium oxides (ilmenite, titanite and rutile/anatase), chlorite, olivine, epidote, biotite and rhodochrosite. A particularity of the studied area is the presence of an altered magnetite caused first by the hydrothermal alteration and strong weathering of the source rocks and second by the river's acid water. Manganese oxides are present only in grain fractions greater than 0.25 mm due to higher susceptibility to weathering and dissolution of the Mn aggregates in the river bed. Despite low distribution of the metamorphic units in the river's studied basin, the garnets almandine (Alm 13-88%) and spessartine (Sps 0.5-87%), specific to the medium grade metamorphic rocks, have a relative high frequency. In this study, heavy mineral assemblages generally reflect the composition of primary (augite, almandine) and accessory minerals present in source rocks. The last ones are both primary (apatite) and secondary, which are mainly derived from hydrothermal deposition (e. g. pyrite) and from supergene alterations (e. g. manganese, iron oxides/ hydroxides, and other altered product of magnetite). Therefore, the mineral analyses were not limited to only tracking the source of each mineral species, but they also revealed the characteristics of their parent rocks.

Methane clumped isotopes in the Songliao Basin (China): New insights into abiotic vs. biotic hydrocarbon formation

NASA Astrophysics Data System (ADS)

Shuai, Yanhua; Etiope, Giuseppe; Zhang, Shuichang; Douglas, Peter M. J.; Huang, Ling; Eiler, John M.

2018-01-01

Abiotic hydrocarbon gas, typically generated in serpentinized ultramafic rocks and crystalline shields, has important implications for the deep biosphere, petroleum systems, the carbon cycle and astrobiology. Distinguishing abiotic gas (produced by chemical reactions like Sabatier synthesis) from biotic gas (produced from degradation of organic matter or microbial activity) is sometimes challenging because their isotopic and molecular composition may overlap. Abiotic gas has been recognized in numerous locations on the Earth, although there are no confirmed instances where it is the dominant source of commercially valuable quantities in reservoir rocks. The deep hydrocarbon reservoirs of the Xujiaweizi Depression in the Songliao Basin (China) have been considered to host significant amounts of abiotic methane. Here we report methane clumped-isotope values (Δ18) and the isotopic composition of C1-C3 alkanes, CO2 and helium of five gas samples collected from those Xujiaweizi deep reservoirs. Some geochemical features of these samples resemble previously suggested identifiers of abiotic gas (13C-enriched CH4; decrease in 13C/12C ratio with increasing carbon number for the C1-C4 alkanes; abundant, apparently non-biogenic CO2; and mantle-derived helium). However, combining these constraints with new measurements of the clumped-isotope composition of methane and careful consideration of the geological context, suggests that the Xujiaweizi depression gas is dominantly, if not exclusively, thermogenic and derived from over-mature source rocks, i.e., from catagenesis of buried organic matter at high temperatures. Methane formation temperatures suggested by clumped-isotopes (167-213 °C) are lower than magmatic gas generation processes and consistent with the maturity of local source rocks. Also, there are no geological conditions (e.g., serpentinized ultramafic rocks) that may lead to high production of H2 and thus abiotic production of CH4 via CO2 reduction. We propose that the Songliao gas is representative of an atypical type of thermogenic gas that can be mistaken for abiotic gas. Such gases may be encountered more frequently in future exploration of deep or over-mature petroleum systems.

The upper limit of maturity of natural gas generation and its implication for the Yacheng formation in the Qiongdongnan Basin, China

NASA Astrophysics Data System (ADS)

Su, Long; Zheng, Jianjing; Chen, Guojun; Zhang, Gongcheng; Guo, Jianming; Xu, Yongchang

2012-08-01

Vitrinite reflectance (VR, Ro%) measurements from residual kerogen of pyrolysis experiments were performed on immature Maoming Oil Shale substituted the samples for the gas-prone source rocks of Yacheng formation of the Qiongdongnan Basin in the South China Sea. The work was focused on determination an upper limit of maturity for gas generation (ULMGG) or "the deadline of natural gas generation". Ro values at given temperatures increase with increasing temperature and prolonged heating time, but ΔRo-value, given a definition of the difference of all values for VR related to higher temperature and adjacent lower temperature in open-system non-isothermal experiment at the heating rate of 20 °C/min, is better than VR. And representative examples are presented in this paper. It indicates that the range of natural gas generation for Ro in the main gas generation period is from 0.96% to 2.74%, in which ΔRo is in concordance with the stage for the onset and end of the main gas generation period corresponding to 0.02% up to 0.30% and from 0.30% up to 0.80%, respectively. After the main gas generation period of 0.96-2.74%, the evolution of VR approach to the ULMGG of the whole rock for type II kerogen. It is equal to 4.38% of VR, where the gas generation rates change little with the increase of maturation, ΔRo is the maximum of 0.83% corresponding to VR of 4.38%Ro, and the source rock does not nearly occur in the end process of hydrocarbon gas generation while Ro is over 4.38%. It shows that it is the same the ULMGG from the whole rock for type II kerogen as the method with both comparison and kinetics. By comparing to both the conclusions of pyrolysis experiments and the data of VR from the source rock of Yacheng formation on a series of selected eight wells in the shallow-water continental shelf area, it indicate that the most hydrocarbon source rock is still far from reaching ULMGG from the whole rock for type II kerogen. The source rock of Yacheng formation in the local areas of the deepwater continental slope basin have still preferable natural gas generative potential, especially in the local along the central depression belt (namely the Ledong, Lingshui, Songnan and Baodao sags from southwest to northeast) from the depocenter to both the margin and its adjacent areas. It help to evaluate the resource potential for oil and gas of the hydrocarbon source rock in the deepwater continental slope of the Qiongdongnan Basin or other basins with lower exploration in the northern of the South China Sea and to reduce the risk in exploration.

Can cathodoluminescence of feldspar be used as provenance indicator?

NASA Astrophysics Data System (ADS)

Scholonek, Christiane; Augustsson, Carita

2016-05-01

We have studied feldspar from crystalline rocks for its textural and spectral cathodoluminescence (CL) characteristics with the aim to reveal their provenance potential. We analyzed ca. 60 rock samples of plutonic, volcanic, metamorphic, and pegmatitic origin from different continents and of 16 Ma to 2 Ga age for their feldspar CL textures and ca. 1200 feldspar crystals from these rocks for their CL color spectra. Among the analyzed rocks, igneous feldspar is most commonly zoned, whereby oscillatory zoning can be confirmed to be typical for volcanic plagioclase. The volcanic plagioclase also less commonly contains twin lamellae that are visible in CL light than crystals from other rock types. Alkali feldspar, particularly from igneous and pegmatitic rocks, was noted to be most affected by alteration features, visible as dark spots, lines and irregular areas. The size of all textural features of up to ca. 150 μm, in combination with possible alteration in both the source area and the sedimentary system, makes the CL textures of feldspar possible to use for qualitative provenance research only. We observed alkali feldspar mostly to luminesce in a bluish color and sometimes in red, and plagioclase in green to yellow. The corresponding CL spectra are dominated by three apparent intensity peaks at 440-520 nm (mainly blue), 540-620 nm (mainly green) and 680-740 nm (red to infrared). A dominance of the peak in the green wavelength interval over the blue one for plagioclase makes CL particularly useful for the differentiation of plagioclase from alkali feldspar. An apparent peak position in red to infrared at < 710 nm for plagioclase mainly is present in mafic rocks. Present-day coastal sand from Peru containing feldspar with the red to infrared peak position mainly exceeding 725 nm for northern Peruvian sand and a larger variety for sand from southern Peru illustrates a discriminative effect of different source areas. We conclude that the provenance application particularly can reveal first-cycle input from mafic rocks and source variations for detritus from arid areas that has been affected by little feldspar alteration.

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

Paleocene Turbidite Deposition in the Central American Seaway (NW Costa Rica): Geochemical Analysis and Provenance of Detrital Spinel and Clinopyroxene

NASA Astrophysics Data System (ADS)

Giblin, A. C.

2015-12-01

The Central American Land Bridge is the crucial connection between North and South America, and the Miocene closure of the Panama seaway led to a change in global oceanic circulation patterns. Modern Costa Rica is part of the island arc that formed over the western Caribbean subduction zone, and the Santa Elena peninsula is on the northwest coast of Costa Rica next to the Sandino forearc basin. This study focuses on the origin and provenance of the Paleocene deep-water Rivas and Descartes turbidites that crop out on the northern part of the Santa Elena peninsula in northwestern Costa Rica. Understanding the sedimentary fill of the Sandino Basin that contributed to the closing of the seaway may lead to a better understanding of the Late Cretaceous-Paleogene arcs. Provenance studies of the Santa Elena Peninsula turbidite sandstone bodies constrain the history of the paleogeography and tectonics of the region. Petrographic analyses of rock thin sections constrain source areas; geochemical analysis of individual detrital heavy minerals from rock samples give indications of sediment sources and tectonic setting during deposition. This study is a provenance analysis based on (i) semi-quantitative energy-dispersive spectrometry analysis of heavy minerals, (ii) quantitative wavelength-dispersive spectrometry for major elements of detrital clinopyroxene and spinel grains, (iii) trace element analysis through laser ablation of single detrital clinopyroxene grains, and (iv) comparative analysis of the different potential source rocks to clearly identify the most likely sediment sources. The detrital spinel and clinopyroxene are possibly sourced from: mantle ophiolites, mid-ocean ridge gabbros, or volcanic arc tholeiitic basalts or calc-alkaline andesites. Spinel and clinopyroxne geochemistry suggests a possible peridotitic source, linked to mantle rocks that are now covered by Tertiary volcanics or have completely eroded. The character of the crustal minerals indicates sources from mid-ocean ridge gabbros, and island arc tholeiites and andesites. This suggests that during the early history of the gateway uplift and seaway closure, sediment sources were dominated first by older ophiolites and gabbroic sources, then by volcanic inputs from the arc.

Fluorine, fluorite, and fluorspar in central Colorado

USGS Publications Warehouse

Wallace, Alan R.

2010-01-01

Fluorine (F) is a widespread element that was deposited in a variety of rocks, minerals, and geologic environments in central Colorado. It occurs as a trace element, as a major component of the mineral fluorite (CaFs), and as a major economic source of fluorine in fluorspar deposits, which are massive concentrations of fluorite. This study has compiled available geochemical analyses of rocks, both unmineralized and mineralized, to determine the distribution of fluorine in specific age-lithologic categories, ranging from 1.8-giga-annum (Ga) metamorphic rocks to modern soils, throughout central Colorado. It also draws upon field studies of fluorine-rich mineral deposits, including fluorspar deposits, to decipher the nearly two-billion-year-long geologic history of fluorine in the study area, with implications for mineral-resource evaluations and exploration. The resulting compilation provides an important inventory of the naturally occurring levels and sources of fluorine that ultimately weather, erode, and become part of surface waters that are used for domestic water supplies in densely populated areas along the Colorado Front Range. Most commonly, fluorine is a trace element in virtually all rocks in the region. In the 3,798 unmineralized rocks that were analyzed for fluorine in the study area, the average fluorine content was 1,550 parts per million (ppm). The median was 640 ppm, nearly identical to the average crustal abundance of 650 ppm, and some high-fluorine rocks in the Pikes Peak area skewed the average to a value much greater than the median. Most unmineralized age-lithologic rock suites, including Proterozoic metamorphic rocks, 1.7- and 1.4-Ga granitic batholiths, Cambrian igneous rocks, Phanerozoic sedimentary rocks, and Laramide and Tertiary igneous rocks, had median fluorine values of 400 to 740 ppm fluorine. In all suites, however, a small number of analyzed samples contained more than 1 percent (10,000 ppm) fluorine. The 1.1-Ga plutonic rocks related to the Pikes Peak batholith had a mean fluorine content of 1,700 ppm, and primary magmatic fluorite and fluorite-bearing pegmatites are common throughout that igneous mass. Fluorine was deposited in many types of economic mineral deposits in central Colorado, and it currently is a significant trace element in some thermal springs. In the fluorspar deposits, fluorine contents were as high as 37 percent. Some fluorine-rich porphyry systems, such as Jamestown, had fluorine values that ranged from 200 ppm to nearly 37 percent fluorine, and veins in other deposits contained hydrothermal fluorite, although it was not ubiquitous. For the 495 samples from non-fluorspar mining districts (and excluding Jamestown), however, the median fluorine content was 990 ppm. This is above the crustal average but still relatively modest compared to the fluorspar deposits, and it indicates that the majority of the mineralizing systems in central Colorado did not deposit large amounts of fluorine. Nevertheless, the fluorine- and fluorite-rich mineral deposits could be used as guides for the evaluation and discovery of related but concealed porphyry and epithermal base- and precious-metal deposits. The Cenozoic geologic history of central Colorado included multiple periods during which fluorine-bearing rocks and mineral deposits were exposed, weathered, and eroded. This protracted history has released fluorine into soils and regoliths, and modern rainfall and snowmelt interact with these substrates to add fluorine to the hydrosphere. This study did not evaluate the fluorine contents of water or make any predictions about what areas might be major sources for dissolved fluorine. However, the abundant data that are available on fluorine in surface water and ground water can be coupled with the results of this study to provide additional insight into natural sources of fluorine in domestic drinking water.

The feasibility of TEA CO2 laser-induced plasma for spectrochemical analysis of geological samples in simulated Martian conditions

NASA Astrophysics Data System (ADS)

Savovic, Jelena; Stoiljkovic, Milovan; Kuzmanovic, Miroslav; Momcilovic, Milos; Ciganovic, Jovan; Rankovic, Dragan; Zivkovic, Sanja; Trtica, Milan

2016-04-01

The present work studies the possibility of using pulsed Transversely Excited Atmospheric (TEA) carbon dioxide laser as an energy source for laser-induced breakdown spectroscopy (LIBS) analysis of rocks under simulated Martian atmospheric conditions. Irradiation of a basaltic rock sample with the laser intensity of 56 MW cm- 2, in carbon-dioxide gas at a pressure of 9 mbar, created target plasma with favorable conditions for excitation of all elements usually found in geological samples. Detection limits of minor constituents (Ba, Cr, Cu, Mn, Ni, Sr, V, and Zr) were in the 3 ppm-30 ppm range depending on the element. The precision varied between 5% and 25% for concentration levels of 1% to 10 ppm, respectively. Generally, the proposed relatively simple TEA CO2 laser-LIBS system provides good sensitivity for geological studies under reduced CO2 pressure.

Oil and gas geochemistry and petroleum systems of the Fort Worth Basin

USGS Publications Warehouse

Hill, R.J.; Jarvie, D.M.; Zumberge, J.; Henry, M.; Pollastro, R.M.

2007-01-01

Detailed biomarker and light hydrocarbon geochemistry confirm that the marine Mississippian Barnett Shale is the primary source rock for petroleum in the Fort Worth Basin, north-central Texas, although contributions from other sources are possible. Biomarker data indicate that the main oil-generating Barnett Shale facies is marine and was deposited under dysoxic, strong upwelling, normal salinity conditions. The analysis of two outcrop samples and cuttings from seven wells indicates variability in the Barnett Shale organic facies and a possibility of other oil subfamilies being present. Light hydrocarbon analyses reveal significant terrigenous-sourced condensate input to some reservoirs, resulting in terrigenous and mixed marine-terrigenous light hydrocarbon signatures for many oils. The light hydrocarbon data suggest a secondary, condensate-generating source facies containing terrigenous or mixed terrigenous-marine organic matter. This indication of a secondary source rock that is not revealed by biomarker analysis emphasizes the importance of integrating biomarker and light hydrocarbon data to define petroleum source rocks. Gases in the Fort Worth Basin are thermogenic in origin and appear to be cogenerated with oil from the Barnett Shale, although some gas may also originate by oil cracking. Isotope data indicate minor contribution of biogenic gas. Except for reservoirs in the Pennsylvanian Bend Group, which contain gases spanning the complete range of observed maturities, the gases appear to be stratigraphically segregated, younger reservoirs contain less mature gas, and older reservoirs contain more mature gas. We cannot rule out the possibility that other source units within the Fort Worth Basin, such as the Smithwick Shale, are locally important petroleum sources. Copyright ?? 2007. The American Association of Petroleum Geologists. All rights reserved.

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.

Determination of chemical composition of soils and rocks at the MER landing sites Gusev crater and Meridiani Planum using the APXS

NASA Astrophysics Data System (ADS)

Brueckner, J.

2004-05-01

The new Alpha Particle X-Ray Spectrometer (APXS) is a small, light-weight instrument to obtain x-ray spectra from Martian surface samples. The sensor head contains a high-resolution x-ray detector that is surrounded by a circle of radioactive Cm-244 sources. Alpha and x-ray radiation emitted by the sources is used to induce x-ray excitation in the sample. Elements from sodium to zinc (increasing by atomic weight) are detected and their concentrations determined. The APXS is mounted on each Instrument Deployment Device (IDD) of the two Mars Exploration Rovers (MER) Spirit and Opportunity. Rover Spirit landed in the large Gusev crater that seems to have been altered by water activities in the past based on evidence of orbital images. Rover Opportunity landed in a very small crater of the Meridiani Planum, where the mineral hematite that points to water-related processes is expected to be found. Inside the little crater, a light-colored outcrop is exposed that shows widespread fine layering. The first APXS high-resolution x-ray spectrum of a Gusev soil indicated many similarities to the composition of the Mars Pathfinder (MPF) and Viking soils. However, differences are also noticeable: Low-Z elements are somewhat higher compared to MPF soils, while high-Z elements are depleted, notably Ti. Potassium in the soils reflects the K concentration of the local rocks at the different landing sites pointing toward a local contribution to the soil's composition. The Rock Abrasion Tool was used to grind the first rock on Mars at Gusev: Adirondack's undisturbed and ground surface was measured by the APXS. The composition of its fresh surface is different from the MPF soilfree rock, noticeably in Mg and Al, and clearly exhibits a basaltic nature related to the composition of basaltic shergottites. The first rock at the Meridiani crater outcrop (dubbed Robert-E) exhibited a very high sulfur concentration, more than a factor of 15 compared to rock Adirondack, indicating it is doubtful that this outcrop is from igneous activity. Camera based observations of the layering of rock Robert-E and its chemical composition are pointing to a sedimentary process where sulfate played a significant role in the cementation of the outcrop.

Evidence for Seismogenic Hydrogen Gas, a Potential Microbial Energy Source on Earth and Mars.

PubMed

McMahon, Sean; Parnell, John; Blamey, Nigel J F

2016-09-01

The oxidation of molecular hydrogen (H2) is thought to be a major source of metabolic energy for life in the deep subsurface on Earth, and it could likewise support any extant biosphere on Mars, where stable habitable environments are probably limited to the subsurface. Faulting and fracturing may stimulate the supply of H2 from several sources. We report the H2 content of fluids present in terrestrial rocks formed by brittle fracturing on fault planes (pseudotachylites and cataclasites), along with protolith control samples. The fluids are dominated by water and include H2 at abundances sufficient to support hydrogenotrophic microorganisms, with strong H2 enrichments in the pseudotachylites compared to the controls. Weaker and less consistent H2 enrichments are observed in the cataclasites, which represent less intense seismic friction than the pseudotachylites. The enrichments agree quantitatively with previous experimental measurements of frictionally driven H2 formation during rock fracturing. We find that conservative estimates of current martian global seismicity predict episodic H2 generation by Marsquakes in quantities useful to hydrogenotrophs over a range of scales and recurrence times. On both Earth and Mars, secondary release of H2 may also accompany the breakdown of ancient fault rocks, which are particularly abundant in the pervasively fractured martian crust. This study strengthens the case for the astrobiological investigation of ancient martian fracture systems. Deep biosphere-Faults-Fault rocks-Seismic activity-Hydrogen-Mars. Astrobiology 16, 690-702.

Geology and hydrocarbon potential of the Hartford-Deerfield Basin, Connecticut and Massachusetts

USGS Publications Warehouse

Coleman, James

2016-01-01

The Hartford-Deerfield basin, a Late Triassic to Early Jurassic rift basin located in central Connecticut and Massachusetts, is the northernmost basin of the onshore Mesozoic rift basins in the eastern United States. The presence of asphaltic petroleum in outcrops indicates that at least one active petroleum system has existed within the basin. However, to-date oil and gas wells have not been drilled in the basin to test any type of petroleum trap. There are good to excellent quality source rocks (up to 3.8% present day total organic carbon) within the Jurassic East Berlin and Portland formations. While these source rock intervals are fairly extensive and at peak oil to peak gas stages of maturity, individual source rock beds are relatively thin (typically less than 1 m) based solely on outcrop observations. Potential reservoir rocks within the Hartford-Deerfield basin are arkosic conglomerates, pebbly sandstones, and finer grained sandstones, shales, siltstones, and fractured igneous rocks of the Triassic New Haven and Jurassic East Berlin and Portland formations (and possibly other units). Sandstone porosity data from 75 samples range from less than 1% to 21%, with a mean of 5%. Permeability is equally low, except around joints, fractures, and faults. Seals are likely to be unfractured intra-formational shales and tight igneous bodies. Maturation, generation, and expulsion likely occurred during the late synrift period (Early Jurassic) accentuated by an increase in local geothermal gradient, igneous intrusions, and hydrothermal fluid circulation. Migration pathways were likely along syn- and postrift faults and fracture zones. Petroleum resources, if present, are probably unconventional (continuous) accumulations as conventionally accumulated petroleum is likely not present in significant volumes.

Variation of rock-forming metals in sub-annual increments of modern Greenland snow

USGS Publications Warehouse

Hinkley, T.K.

1992-01-01

Modern snowpack from central south Greenland was sampled in sub-seasonal increments and analysed for a suite of major, minor and trace rock-forming metals (K, Rb, Cs, Ca, Sr, Ba). There is a sharp seasonal concentration maximum for all six metals that comes in summer, later than mid-June. Metal concentrations in all other parts of the year's snowpack are up to 10 or more times smaller. The concentration maximum is preceded by low values in autumn-winter, very low values in early-mid-spring, and moderate-to-high values in late spring early summer; this pattern is seen consistently in three separate time stratigraphic intervals representing the same seasonal periods, spanning the time interval 1981-1984. The absolute concentration values of the snow strata representing the low-concentration portion of the year, autumn-winter-spring, may vary substantially from year to year, by a factor of two, or more. The finding that all rock-forming metals are at a sharp concentration maximum in late summer contrasts with the interpretations of several other studies in high-latitude northern regions. Those studies have reported a broad maximum of continental dust-associated metals in late winter and spring. However samples of the other studies have mostly come from regions farther to the north, and the analyses have emphasized industrial pollutant metals rather than the matched rock-forming suite of the present study. The metals measured were chosen to give information about the origin and identity of the rock and soil dusts, and sea salts, present as impurities in the snow. Metal ratios indicate that the dusts in the snowpacks are of continental origin and from ferromagnesian rocks. Source rock types for dusts in central south Greenland snow contrast with the felsic rock dusts of the Sierra Nevada, CA, annual snowpacks, and with the very felsic rock dusts in large south central Alaskan mountain glaciers. Samples in which masses of sea salt are much larger than those of rock dusts may be identified by small changes in metal ratios caused by moderate increases of K and Ca from marine sources, nearly unaccompanied by the minor and trace metals Rb, Cs and Ba, that are very rare in the oceans. A sampling frequency, such as that of the present study, that divides a year's accumulation into 8-10 subsamples is sufficient to reveal details of the time pattern of variation in proportions and concentrations of metals that give information about atmospheric deposition of important types of earth materials.Modern snowpack from central south Greenland was sampled in sub-seasonal increments and analyzed for a suite of major, minor and trace rock-forming metals (K, Rb, Cs, Ca, Sr, Ba). There is a sharp seasonal concentration maximum for all six metals that comes in summer, later than mid-June. Metal concentrations in all other parts of the year's snowpack are up to 10 or more times smaller. The concentration maximum is preceded by low values in autumn-winter, very low values in early-mid-spring, and moderate-to-high values in late spring-early summer; this pattern is seen consistently in three separate time stratigraphic intervals representing the same seasonal periods, spanning the time interval 1981-1984. The absolute concentration values of the snow strata representing the low-concentration portion of the year, autumn-winter-spring, may vary substantially from year to year, by a factor of two, or more. The finding that all rock-forming metals are at a sharp concentration maximum in late summer contrasts with the interpretations of several other studies in high-latitude northern regions. Those studies have reported a broad maximum of continental dust-associated metals in late winter and spring. However, samples of the other studies have mostly come from regions farther to the north, and the analyses have emphasized industrial pollutant metals rather than the matched rock-forming suite of the present study. The metals measured were chosen to give informati

Lower Cody Shale (Niobrara equivalent) in the Bighorn Basin, Wyoming and Montana: thickness, distribution, and source rock potential

USGS Publications Warehouse

Finn, Thomas M.

2014-01-01

The lower shaly member of the Cody Shale in the Bighorn Basin, Wyoming and Montana is Coniacian to Santonian in age and is equivalent to the upper part of the Carlile Shale and basal part of the Niobrara Formation in the Powder River Basin to the east. The lower Cody ranges in thickness from 700 to 1,200 feet and underlies much of the central part of the basin. It is composed of gray to black shale, calcareous shale, bentonite, and minor amounts of siltstone and sandstone. Sixty-six samples, collected from well cuttings, from the lower Cody Shale were analyzed using Rock-Eval and total organic carbon analysis to determine the source rock potential. Total organic carbon content averages 2.28 weight percent for the Carlile equivalent interval and reaches a maximum of nearly 5 weight percent. The Niobrara equivalent interval averages about 1.5 weight percent and reaches a maximum of over 3 weight percent, indicating that both intervals are good to excellent source rocks. S2 values from pyrolysis analysis also indicate that both intervals have a good to excellent source rock potential. Plots of hydrogen index versus oxygen index, hydrogen index versus Tmax, and S2/S3 ratios indicate that organic matter contains both Type II and Type III kerogen capable of generating oil and gas. Maps showing the distribution of kerogen types and organic richness for the lower shaly member of the Cody Shale show that it is more organic-rich and more oil-prone in the eastern and southeastern parts of the basin. Thermal maturity based on vitrinite reflectance (Ro) ranges from 0.60–0.80 percent Ro around the margins of the basin, increasing to greater than 2.0 percent Ro in the deepest part of the basin, indicates that the lower Cody is mature to overmature with respect to hydrocarbon generation.

Marine and nonmarine gas-bearing rocks in Upper Cretaceous Blackhawk and Neslen Formations, eastern Uinta Basin, Utah: sedimentology, diagenesis, and source rock potential

USGS Publications Warehouse

Pitman, Janet K.; Franczyk, K.J.; Anders, D.E.

1987-01-01

Thermogenic gas was generated from interbedded humic-rich source rocks. The geometry and distribution of hydrocarbon source and reservoir rocks are controlled by depositional environment. The rate of hydrocarbon generation decreased from the late Miocene to the present, owing to widespread cooling that occurred in response to regional uplift and erosion associated with the development of the Colorado Plateau. -from Authors

Organic geochemistry of sediments of the Deep Gulf of Mexico Basin

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

Sassen, R.; Fang Jiasong

1990-05-01

Analysis of 716 core samples cored at DSDP (Deep Sea Drilling Project) Leg 96 in the Mississippi submarine fan and the Orca and Pigmy basins in the Louisiana continental slope using a Rock-Eval pyrolysis unit with a TOC (total organic carbon) module allows computations of hydrogen index (HI), total organic carbon, kerogen type, and oil generative capacity assessment. No samples are obviously oil prone. TOC content ranges from 0.12 to 2.29%, with an overall average of 9.82%. HI values are generally less than 150 mg HC/g TOC. T{sub max} (maximum temperature of S{sub 2}) values (average = 425{degree}C) show themore » sediments are thermally immature through-out the study area. Hydrocarbon generative potential of the sediments ranges from 492 to 1,107 ppm, with an average of 854 ppm. Higher PI (Production index) values, ranging from 0.12 to 0.32 and averaging 0.15, suggest the presence of hydrocarbon seepage. Because of organically lean, thermally immature, and gas-prone terrestrial kerogen, there is little reason to assume that the sediments of the Mississippi fan can provide oil source rock for the Gulf of Mexico Basin, or that sediments of anoxic basins in the Louisiana continental slope are analogs to past environments where source rocks for crude oil have been deposited.« less

Geochemistry of Archean shales from the Pilbara Supergroup, Western Australia

NASA Astrophysics Data System (ADS)

McLennan, Scott M.; Taylor, S. R.; Eriksson, K. A.

1983-07-01

Archean clastic sedimentary rocks are well exposed in the Pilbara Block of Western Australia. Shales from turbidites in the Gorge Creek Group ( ca. 3.4 Ae) and shales from the Whim Creek Group ( ca. 2.7 Ae) have been examined. The Gorge Creek Group samples, characterized by muscovite-quartzchlorite mineralogy, are enriched in incompatible elements (K, Th, U, LREE) by factors of about two, when compared to younger Archean shales from the Yilgarn Block. Alkali and alkaline earth elements are depleted in a systematic fashion, according to size, when compared with an estimate of Archean upper crust abundances. This depletion is less notable in the Whim Creek Group. Such a pattern indicates the source of these rocks underwent a rather severe episode of weathering. The Gorge Creek Group also has fairly high B content (85 ± 29 ppm) which may indicate normal marine conditions during deposition. Rare earth element (REE) patterns for the Pilbara samples are characterized by light REE enrichment ( La N/Yb N ≥ 7.5 ) and no or very slight Eu depletion ( Eu/Eu ∗ = 0.82 - 0.99 ). A source comprised of about 80% felsic igneous rocks without large negative Eu-anomalies (felsic volcanics, tonalites, trondhjemites) and 20% mafic-ultramafic volcanics is indicated by the trace element data. Very high abundances of Cr and Ni cannot be explained by any reasonable provenance model and a secondary enrichment process is called for.

X-Ray Diffraction on Mars: Scientific Discoveries Made by the CheMin Instrument

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Blake, D. F.; Ming, D. W.; Bristow, T. F.

2017-01-01

The Mars Science Laboratory Curiosity landed in Gale crater in August 2012 with the goal to identify and characterize habitable environments on Mars. Curiosity has been studying a series of sedimentary rocks primarily deposited in fluviolacustrine environments approximately 3.5 Ga. Minerals in the rocks and soils on Mars can help place further constraints on these ancient aqueous environments, including pH, salinity, and relative duration of liquid water. The Chemistry and Mineralogy (CheMin) X-ray diffraction and X-ray fluorescence instrument on Curiosity uses a Co X-ray source and charge-coupled device detector in transmission geometry to collect 2D Debye-Scherrer ring patterns of the less than 150 micron size fraction of drilled rock powders or scooped sediments. With an angular range of approximately 2.52deg 20 and a 20 resolution of approximately 0.3deg, mineral abundances can be quantified with a detection limit of approximately 1-2 wt. %. CheMin has returned quantitative mineral abundances from 16 mudstone, sandstone, and aeolian sand samples so far. The mineralogy of these samples is incredibly diverse, suggesting a variety of depositional and diagenetic environments and different source regions for the sediments. Results from CheMin have been essential for reconstructing the geologic history of Gale crater and addressing the question of habitability on ancient Mars.

A non-zircon Hf isotope record in Archean black shales from the Pilbara craton confirms changing crustal dynamics ca. 3 Ga ago.

PubMed

Nebel-Jacobsen, Yona; Nebel, Oliver; Wille, Martin; Cawood, Peter A

2018-01-17

Plate tectonics and associated subduction are unique to the Earth. Studies of Archean rocks show significant changes in composition and structural style around 3.0 to 2.5 Ga that are related to changing tectonic regime, possibly associated with the onset of subduction. Whole rock Hf isotope systematics of black shales from the Australian Pilbara craton, selected to exclude detrital zircon components, are employed to evaluate the evolution of the Archean crust. This approach avoids limitations of Hf-in-zircon analyses, which only provide input from rocks of sufficient Zr-concentration, and therefore usually represent domains that already underwent a degree of differentiation. In this study, we demonstrate the applicability of this method through analysis of shales that range in age from 3.5 to 2.8 Ga, and serve as representatives of their crustal sources through time. Their Hf isotopic compositions show a trend from strongly positive εHf initial values for the oldest samples, to strongly negative values for the younger samples, indicating a shift from juvenile to differentiated material. These results confirm a significant change in the character of the source region of the black shales by 3 Ga, consistent with models invoking a change in global dynamics from crustal growth towards crustal reworking around this time.

GEOCHEMICAL INVESTIGATIONS OF CO₂-BRINE-ROCK INTERACTIONS OF THE KNOX GROUP IN THE ILLINOIS BASIN

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

Yoksoulian, Lois; Berger, Peter; Freiburg, Jared

Increased output of greenhouse gases, particularly carbon dioxide (CO₂), into the atmosphere from anthropogenic sources is of great concern. A potential technology to reduce CO₂ emissions is geologic carbon sequestration. This technology is currently being evaluated in the United States and throughout the world. The geology of the Illinois Basin exhibits outstanding potential as a carbon sequestration target, as demonstrated by the ongoing Illinois Basin – Decatur Project that is using the Mt. Simon Sandstone reservoir and Eau Claire Shale seal system to store and contain 1 million tonnes of CO₂. The Knox Group-Maquoketa Shale reservoir and seal system, locatedmore » stratigraphically above the Mt. Simon Sandstone-Eau Claire Shale reservoir and seal system, has little economic value as a resource for fossil fuels or as a potable water source, making it ideal as a potential carbon sequestration target. In order for a reservoir-seal system to be effective, it must be able to contain the injected CO₂ without the potential for the release of harmful contaminants liberated by the reaction between CO₂-formation fluids and reservoir and seal rocks. This study examines portions of the Knox Group (Potosi Dolomite, Gunter Sandstone, New Richmond Sandstone) and St. Peter Sandstone, and Maquoketa Shale from various locations around the Illinois Basin. A total of 14 rock and fluid samples were exposed to simulated sequestration conditions (9101–9860 kPa [1320–1430 psi] and 32°–42°C [90°– 108°F]) for varying amounts of time (6 hours to 4 months). Knox Group reservoir rocks exhibited dissolution of dolomite in the presence of CO₂ as indicated by petrographic examination, X-ray diffraction analysis, and fluid chemistry analysis. These reactions equilibrated rapidly, and geochemical modeling confirmed that these reactions reached equilibrium within the time frames of the experiments. Pre-reaction sample mineralogy and postreaction fluid geochemistry from this study suggests only limited potential for the release of United States Environmental Protection Agency regulated inorganic contaminants into potable water sources. Short-term core flood experiments further verify that the carbonate reactions occurring in Knox Group reservoir samples reach equilibrium rapidly. The core flood experiments also lend insight to pressure changes that may occur during CO₂ injection. The Maquoketa Shale experiments reveal that this rock is initially chemically reactive when in contact with CO₂ and brine. However, due to the conservative nature of silicate and clay reaction kinetics and the rapid equilibration of carbonate reactions that occur in the shale, these reactions would not present a significant risk to the competency of the shale as an effective seal rock.« less

Laboratory Investigation of the Effect of Water-Saturation on Seismic Wave Dispersion in Carbonates

NASA Astrophysics Data System (ADS)

Li, W.; Pyrak-Nolte, L. J.

2009-12-01

In subsurface rock, fluid content changes with time through natural causes or because of human interactions, such as extraction or sequestration of fluids. The ability to monitor, seismically, fluid migration in the subsurface requires an understanding of the effects that the degree of saturation and spatial distribution of fluids have on wave propagation in rock. In this study, we find that the seismic dispersion of a dry carbonate rock can be masked by saturating the sample. We used a laboratory mini-seismic array to monitor fluid invasion and withdrawal in a carbonate rock with fabric-controlled layering. Experiments were performed on prismatic samples of Austin Chalk measuring 50mm x 50mm x 100mm. The epoxy-sealed samples contained an inlet and an outlet port to enable fluid invasion/withdrawal along the long axis of the sample. Water was infused and withdrawn from the sample at a rate of 1ml/hr. The mini-seismic array consisted of a set of 12 piezoelectric contact transducers, each with a central frequency 1.0 MHz. Three compressional wave source-receiver pairs and three shear wave source-receiver pairs were used to probe along the length of the sample prior to invasion and during invasion and withdrawal of water from the sample. A pressure transducer was used to record the fluid pressure simultaneously with the full transmitted wave forms every 15-30 minutes. A wavelet analysis determined the effect of fluid invasion on velocity dispersion. We observed that the compressional wave dispersion was more sensitive to changes in saturation than the shear wave dispersion. When the sample was unsaturated, the high frequency components of the compressional wave (1.2MHz to 2MHz) had lower velocities (~ 2750m/s) than the low frequency components, which decrease monotonically from 2890 m/s for 0.2MHz to 1.2 MHz. As water infused the sample, the dispersion weakened. When the sample as fully saturated, the compressional wave velocity was frequency independent. The functional form of the dependence of the shear wave velocity on frequency is relatively constant with fluid saturation, but the magnitude of the velocity decreased (~35 m/s) with increasing saturation. From theoretical calculations, the shear modulus increased during water invasion and was independent of frequency. However, the changes in the Young’s modulus with water invasion depended on the frequency of observation. When 46.5ml was infused into the sample, the Young’s modulus interpreted from the high-frequency components (wavelength from 1.43mm to 2.4mm) increased 70%, while the modulus from the low-frequency components (wavelengths vary from 1.4cm to 3.4mm) increased between 20% and 55%. Interpreting seismic data to determine fluid saturation in rock with fabric-controlled layering requires an understanding of the seismic dispersion properties of the rock in addition to the ability of fluids on alter or mask the dispersion. Acknowledgments: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DEFG02-97ER14785 08), by Exxon Mobil Upstream Research Company and the GeoMathematical Imaging Group at Purdue University.

Fluid-rock interactions during UHP metamorphism: A review of the Dabie-Sulu orogen, east-central China

NASA Astrophysics Data System (ADS)

Zhang, Z. M.; Shen, K.; Liou, J. G.; Dong, X.; Wang, W.; Yu, F.; Liu, F.

2011-08-01

Comprehensive review on the characteristics of petrology, oxygen isotope, fluid inclusion and nominally anhydrous minerals (NAMs) for many Dabie-Sulu ultrahigh-pressure (UHP) metamorphic rocks including drill-hole core samples reveals that fluid has played important and multiple roles during complicated fluid-rock interactions attending the subduction and exhumation of supracrustal rocks. We have identified several distinct stages of fluid-rock interactions as follows: (1) The Neoproterozoic supercrustal protoliths of UHP rocks experienced variable degrees of hydration through interactions with cold meteoric water with extremely low oxygen isotope compositions during Neoproterozoic Snow-ball Earth time. (2) A series of dehydration reactions took place during Triassic subduction of the Yangtze plate beneath the Sino-Korean plate; the released fluid entered mainly into volatile-bearing high-pressure (HP) and UHP minerals, such as phengite, zoisite-epidote, talc, lawsonite and magnesite, as well as into UHP NAMs, such as garnet, omphacite and rutile. (3) Silicate-rich supercritical fluid (hydrous melt) existed during the UHP metamorphism at mantle depths >100 km which mobilized many normally fluid-immobile elements and caused unusual element fractionation. (4) The fluid exsolved from the NAMs during the early exhumation of the Dabie-Sulu terrane was the main source for HP hydrate retrogression and generation of HP veins. (5) Local amphibolite-facies retrogression at crustal depths took place by infiltration of aqueous fluid of various salinities possibly derived from an external source. (6) The greenschist-facies overprinting and low-pressure (LP) quartz veins were generated by fluid flow along ductile shear zones and brittle faults during late-stage uplift of the UHP terrane.

Geochemical and Isotopic Evidences of the Magmatic Sources in the Eastern Sector of the Trans-Mexican Volcanic Belt: Xihuingo-Chichicuautla Volcanic Field

NASA Astrophysics Data System (ADS)

Valadez, S.; Martinez-serrano, R.; Juarez-Lopez, K.; Solis-Pichardo, G.; Perez-Arvizu, O.

2011-12-01

The study of magmatism in the Trans-Mexican Volcanic Belt (TMVB) has great importance due to several features such as its obliquity with respect to the Middle American Trench and its petrological and geochemical variability, which are not common in most typical volcanic arcs. Although several papers have contributed significantly to the understanding of most important magmatic processes in this province, there are still several questions such as the characterization of magmatic sources. In the present work, we provide new stratigraphic, petrographic, geochemical and Sr, Nd and Pb isotopic data as well as some K-Ar age determinations from the Xihuingo-Chichicuautla volcanic field (XCVF), located at the eastern part of the TMVB, with the aim to identify the magmatic sources that produced the main volcanic rocks. The volcanic structures in the XCVF are divided in two main groups according to the petrographic and geochemical compositions: 1) dacitic domes, andesitic lava flows and some dacitic-rhyolitic ignimbrites and 2) scoria cones, shield volcanoes and associated lava flows of basalt to basaltic-andesite composition. Distribution of most volcanic structures is probably controlled by NE-SW fault and fractures system. This fault system was studied by other authors who established that volcanic activity started ca. 13.5 Ma ago, followed by a volcanic hiatus of ca. 10 Ma, and the late volcanic activity began ca. 3 to 1 Ma. In this work we dated 2 rock samples by K-Ar method, which yielded ages of 402 and 871 Ka, which correspond to the most recent volcanic activity in this study area. The volcanic rocks of the XCVF display compositions from basalts to rhyolites but in general all rocks show trace element patterns typical of magmatic arcs. However, we can identify two main magmatic sources: a depleted magmatic source represented by dacitic-andesitic rocks which present a LILE enrichment with respect to HFSE indicating that a magmatic source was modified by fluids derived from the subduction processes. These magmas probably suffered fractional crystallization and minor assimilation in the continental crust. Sr, Nd isotopic compositions for this first group display the most radiogenic values (87Sr/86Sr from 0.7046 to 0.7047 and ɛNd from 2.2 to 2.8). The second source for the basaltic-andesite and basalt could be associated with an enriched mantle. These rocks present a minor LILE enrichment with respect to HSFE, and Sr and Nd isotopic values less radiogenic than the felsic rocks of the first group (87Sr/86Sr from 0.7040 to 0.7045 and ɛNd from 3.1 to 4.8). According to these evidences we can establish that the magmas emplaced in the study area were produced from a heterogeneous mantle source with complex magmatic processes combined with different interaction degrees between the magmas and continental crust.

Overview of the potential and identified petroleum source rocks of the Appalachian basin, eastern United States: Chapter G.13 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

USGS Publications Warehouse

Coleman, James L.; Ryder, Robert T.; Milici, Robert C.; Brown, Stephen; Ruppert, Leslie F.; Ryder, Robert T.

2014-01-01

The Appalachian basin is the oldest and longest producing commercially viable petroleum-producing basin in the United States. Source rocks for reservoirs within the basin are located throughout the entire stratigraphic succession and extend geographically over much of the foreland basin and fold-and-thrust belt that make up the Appalachian basin. Major source rock intervals occur in Ordovician, Devonian, and Pennsylvanian strata with minor source rock intervals present in Cambrian, Silurian, and Mississippian strata.

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.

Characterization of Geologic Structures and Host Rock Properties Relevant to the Hydrogeology of the Standard Mine in Elk Basin, Gunnison County, Colorado

USGS Publications Warehouse

Caine, Jonathan S.; Manning, Andrew H.; Berger, Byron R.; Kremer, Yannick; Guzman, Mario A.; Eberl, Dennis D.; Schuller, Kathryn

2010-01-01

The Standard Mine Superfund Site is a source of mine drainage and associated heavy metal contamination of surface and groundwaters. The site contains Tertiary polymetallic quartz veins and fault zones that host precious and base metal sulfide mineralization common in Colorado. To assist the U.S. Environmental Protection Agency in its effort to remediate mine-related contamination, we characterized geologic structures, host rocks, and their potential hydraulic properties to better understand the sources of contaminants and the local hydrogeology. Real time kinematic and handheld global positioning systems were used to locate and map precisely the geometry of the surface traces of structures and mine-related features, such as portals. New reconnaissance geologic mapping, field and x-ray diffraction mineralogy, rock sample collection, thin-section analysis, and elemental geochemical analysis were completed to characterize hydrothermal alteration, mineralization, and subsequent leaching of metallic phases. Surface and subsurface observations, fault vein and fracture network characterization, borehole geophysical logging, and mercury injection capillary entry pressure data were used to document potential controls on the hydrologic system.

The Birth of a Cratonic Core: Petrologic Evolution of the Hadean-Eoarchean Acasta Gneiss Complex

NASA Astrophysics Data System (ADS)

Reimink, J. R.; Chacko, T.; Davies, J.; Pearson, D. G.; Stern, R. A.; Heaman, L. M.; Carlson, R.; Shirey, S. B.

2016-12-01

Granitoid magmatism within the 4.02-3.6 Ga Acasta Gneiss Complex records distinct whole-rock compositional changes during the building the Slave Craton. Previously1,2 we suggested that these signatures implied petrologic changes from initiation of evolved crust formation in an Iceland-like setting to partial melting of hydrated mafic crust at increasing depth through time, culminating in relatively voluminous magmatism at 3.6 Ga. Increasing La/Yb in these rocks suggest increasing depth of melting (and increasing residual garnet content) with time, ending in emplacement of rocks comparable to other Archean TTG suites3, with both high pressure (high La/Yb) and low pressure (low La/Yb) rocks represented at 3.6 Ga. Data from rocks with variable La/Yb that crystallized 3.6 Ga allow us to evaluate potential mechanisms for formation of rocks of this age such as subduction/accretion or intracrustal melting/delamination. Despite major and trace element compositional and age variability, zircon oxygen isotope compositions from a wide variety of rocks are extremely consistent (+6.0-6.5 ‰ from 3.9-2.9 Ga), implying a similar source, one that had been altered by surface waters1. Potential source rocks include the upper portion of oceanic crust, which contains a large portion of mafic crust that had been altered at low temperatures (e.g., 4). Paired whole rock and zircon radiogenic isotopic data are especially sensitive to the extent of pre-existing felsic material in the region, as well as the longevity of primary, basaltic rocks prior to their reworking into more evolved crust. New paired zircon Hf and whole rock Nd isotope data collected from these samples show variably unradiogenic signatures and allow an exploration of similarities and disparities between crust formation in the Acasta Gneiss Complex and other Paleoarchean-Mesoarchean crustal blocks. [1] Reimink et al., 2016. Precambrian Research 281, 453-472. [2] Reimink et al., 2014 Nature Geoscience 7, 529-533. [3] Moyen and Martin, 2012 Lithos 148, 312-348. [4] Eiler, J.M., 2001 Reviews in Mineralogy and Geochemistry 43, 319-364.

Determining quantity and quality of retained oil in mature marly chalk and marlstone of the Cretaceous Niobrara Formation by low-temperature hydrous pyrolysis

USGS Publications Warehouse

Lewan, Michael; Sonnenfeld, Mark D.

2017-01-01

Low-temperature hydrous pyrolysis (LTHP) at 300°C (572°F) for 24 h released retained oils from 12- to 20-meshsize samples of mature Niobrara marly chalk and marlstone cores. The released oil accumulated on the water surface of the reactor, and is compositionally similar to oil produced from the same well. The quantities of oil released from the marly chalk and marlstone by LTHP are respectively 3.4 and 1.6 times greater than those determined by tight rock analyses (TRA) on aliquots of the same samples. Gas chromatograms indicated this difference is a result of TRA oils losing more volatiles and volatilizing less heavy hydrocarbons during collection than LTHP oils. Characterization of the rocks before and after LTPH by programmable open-system pyrolysis (HAWK) indicate that under LTHP conditions no significant oil is generated and only preexisting retained oil is released. Although LTHP appears to provide better predictions of quantity and quality of retained oil in a mature source rock, it is not expected to replace the more time and sample-size efficacy of TRA. However, LTHP can be applied to composited samples from key intervals or lithologies originally recognized by TRA. Additional studies on duration, temperature, and sample size used in LTHP may further optimize its utility.

Distribution and variation of the inorganic fraction of Devonian to Bashkirian black shales in the north-western part of the Dniepr-Donets Basin, Ukraine

NASA Astrophysics Data System (ADS)

Wegerer, Eva; Sachsenhofer, Reinhard; Misch, David; Aust, Nicolai

2016-04-01

Mineralogical data of 112 core samples from 12 wells are used to investigate lateral and vertical variations in the lithofacies of Devonian to Bashkirian black shales in the north-western part of the Dniepr-Donets-Basin. Sulphur and carbonate contents as well as organic geochemical parameters, including TOC and Hydrogen Index have been determined on the same sample set within the frame of an earlier study (Sachsenhofer et al. 2010). This allows the correlation of inorganic and organic composition of the black shales. Aims of the study are to distinguish between detrital and authigenic minerals, to relate the lithofacies of the black shales with the tectono-stratigraphic sequences of the Dniepr-Donets Basin, to contribute to the reconstruction of the depositional environment and to relate diagenetic processes with the thermal history of the basin. Mineral compositions were determined primarily using XRD-measurements applying several measurement procedures, e.g. chemical and temperature treatment, and specific standards. Major differences exist in the mineralogical composition of the black shales. For example, clay mineral contents range from less than 20 to more than 80 Vol%. Kaolinite contents are significantly higher in rocks with a Tournaisian or Early Visean age than in any other stratigraphic unit. This is also true for two Lower Visean coal samples from the shallow north-westernmost part of the basin. Chlorite contents reach maxima in uppermost Visean and overlying rocks. Quartz contents are often high in Upper Visean rocks and reach maxima in Bashkirian units. Feldspar-rich rocks are observed in Devonian sediments from the north-western part of the study area and may reflect the proximity to a sediment source. Carbonate contents are typically low, but reach very high values in some Tournaisian, Lower Visean and Serpukhovian samples. Pyrite contents reach maxima along the basin axis in Tournaisian and Visean rocks reflecting anoxic conditions. Mixed layer minerals are dominated by illite. Their presence in samples from depth exceeding 5 km reflects the low thermal overprint of Paleozoic rocks in the north-western Dniepr-Donets-Basin.

Implications of Eocene-age Philippine Sea and forearc basalts for initiation and early history of the Izu-Bonin-Mariana arc

NASA Astrophysics Data System (ADS)

Yogodzinski, Gene M.; Bizimis, Michael; Hickey-Vargas, Rosemary; McCarthy, Anders; Hocking, Benjamin D.; Savov, Ivan P.; Ishizuka, Osamu; Arculus, Richard

2018-05-01

Whole-rock isotope ratio (Hf, Nd, Pb, Sr) and trace element data for basement rocks at ocean drilling Sites U1438, 1201 and 447 immediately west of the KPR (Kyushu-Palau Ridge) are compared to those of FAB (forearc basalts) previously interpreted to be the initial products of IBM subduction volcanism. West-of-KPR basement basalts (drill sites U1438, 1201, 447) and FAB occupy the same Hf-Nd and Pb-Pb isotopic space and share distinctive source characteristics with εHf mostly > 16.5 and up to εHf = 19.8, which is more radiogenic than most Indian mid-ocean ridge basalts (MORB). Lead isotopic ratios are depleted, with 206Pb/204Pb = 17.8-18.8 accompanying relatively high 208Pb/204Pb, indicating an Indian-MORB source unlike that of West Philippine Basin plume basalts. Some Sr isotopes show affects of seawater alteration, but samples with 87Sr/86Sr < 0.7034 and εNd > 8.0 appear to preserve magmatic compositions and also indicate a common source for west-of-KPR basement and FAB. Trace element ratios resistant to seawater alteration (La/Yb, Lu/Hf, Zr/Nb, Sm/Nd) in west-of-KPR basement are generally more depleted than normal MORB and so also appear similar to FAB. At Site U1438, only andesite sills intruding sedimentary rocks overlying the basement have subduction-influenced geochemical characteristics (εNd ∼ 6.6, εHf ∼ 13.8, La/Yb > 2.5, Nd/Hf ∼ 9). The key characteristic that unites drill site basement rocks west of KPR and FAB is the nature of their source, which is more depleted in lithophile trace elements than average MORB but with Hf, Nd, and Pb isotope ratios that are common in MORB. The lithophile element-depleted nature of FAB has been linked to initiation of IBM subduction in the Eocene, but Sm-Nd model ages and errorchron relationships in Site U1438 basement indicate that the depleted character of the rocks is a regional characteristic that was produced well prior to the time of subduction initiation and persists today in the source of modern IBM arc volcanic rocks with Sm/Nd > 0.34 and εNd ∼ 9.0.

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.

A-type granites from the Guéra Massif, Central Chad: Petrology, geochemistry, geochronology, and petrogenesis.

NASA Astrophysics Data System (ADS)

Pham, Ngoc Ha T.; Shellnutt, J. Gregory; Yeh, Meng-Wan; Lee, Tung-Yi

2017-04-01

The poorly studied Saharan Metacraton of North-Central Africa is located between the Arabian-Nubian Shield in the east, the Tuareg Shield in the west and the Central African Orogenic Belt in the south. The Saharan Metacraton is composed of Neoproterozoic juvenile crust and the relics of pre-Neoproterozoic components reactivated during the Pan-African Orogeny. The Republic of Chad, constrained within the Saharan Metacraton, comprises a Phanerozoic cover overlying Precambrian basement outcroppings in four distinct massifs: the Mayo Kebbi, Tibesti, Ouaddaï, and the Guéra. The Guéra massif is the least studied of the four massifs but it likely preserves structures that were formed during the collision between Congo Craton and Saharan Metacraton. The Guéra Massif is composed of mostly granitic rocks. The granitoids have petrologic features that are consistent with A-type granite, such as micrographic intergrowth of sodic and potassic feldspar, the presence of sodic- and iron-rich amphibole, and iron-rich biotite. Compositionally, the granitic rocks of the Guéra Massif have high silica (SiO2 ≥ 68.9 wt.%) content and are metaluminous to marginally peraluminous. The rocks are classified as ferroan calc-alkalic to alkali-calcic with moderately high to very high Fe* ratios. The first zircon U/Pb geochronology of the silicic rocks from the Guéra Massif yielded three main age groups: 590 Ma, 570 Ma, 560 Ma, while a single gabbro yielded an intermediate age ( 580 Ma). A weakly foliated biotite granite yielded two populations, in which the emplacement age is interpreted to be 590 ± 10 Ma, whereas the younger age (550 ± 11 Ma) is considered to be a deformation age. Furthermore, inherited Meso- to Paleoproterozoic zircons are found in this sample. The geochemical and geochronology data indicate that there is a temporal evolution in the composition of rocks with the old, high Mg# granitoids shifting to young, low Mg# granitoids. This reveals that the A-type granites in the Guéra Massif were probably derived by the repeated melting of a single source region, from an initial fertile source to a less fertile source at distinct intervals. Finally, the oldest inherited zircons indicate that the Guéra Massif is either built upon Paleoproterozoic continental crust or that pre-Neoproterozoic rocks were the source of the silicic Ediacaran rocks.

Stratigraphic variations in the biomarker distribution of the Moreno Formation: Their correlation with San Joaquin basin oils

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

Bac, M.G.; Schulein, B.J.

1990-05-01

Variability in the biomarker compositions of petroleums is typically employed in the recognition and distinction of contributions from different source rocks. We demonstrate that the fluctuations in the biomarker distributions of different intervals within a single source rock sequence appear to account for specific compositional differences in a suite of oils from the San Joaquin basin California. Rock-Eval pyrolysis studies of a 100-m-thick immature, laminated, marine shale sequence within the Upper Cretaceous lo lower Paleocene portion of the Moreno Formation reveals TOC (total organic carbon) contents consistently around 2% and moderate hydrogen indices (i.e., 175-300 mg HC/g org. C) characteristicsmore » suggestive of a uniform depositional sequence with source rock potential. Analyses of the extractable aliphatic hydrocarbons of cored samples taken at approximately 10-m intervals from the sequence reveal significant variability in biomarker distributions. Such differences are exemplified by the triterpenoids (as seen in m/z 191 chromatograms from GC-MS and GC-MS/MS analyses) where the dominant component fluctuates from a 17{alpha}(h),21{beta}(H)-30-norhopane to 28,30-l8{alpha}(H)-bisnorhopane to 20S and 20R danunar-13(17)-enes. Some components are dominant in one interval, but are not detected in others, suggesting discrete stratigraphic variations in the biomarker characteristics of the Moreno. Similar discrepancies in biomarker distributions are evident in the aliphatic hydrocarbons of the suite of oils. The three petroleums reservoired in the San Carlos sandstone member of the Lodo Formation which directly overlies the Moreno, reflect biomarker contributions from a Moreno source, including compound distributions, and the occurrence of both alkanes (e.g., 28.30-bisnorhopane) and alkenes (e.g.. danunarenes and diasterenes).« less

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.

Oil gravity distribution in the diatomite at South Belridge Field, Kern County, CA: Implications for oil sourcing and migration

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

Hill, D.W.; Sande, J.J.; Doe, P.H.

1995-04-01

Understanding oil gravity distribution in the Belridge Diatomite has led to economic infill development and specific enhanced recovery methods for targeted oil properties. To date more than 100 wells have provided samples used to determining vertical and areal distribution of oil gravity in the field. Detailed geochemical analyses were also conducted on many of the oil samples to establish different oil types, relative maturities, and to identify transformed oils. The geochemical analysis also helped identify source rock expulsion temperatures and depositional environments. The data suggests that the Belridge diatomite has been charged by a single hydrocarbon source rock type andmore » was generated over a relatively wide range of temperatures. Map and statistical data support two distinct oil segregation processes occurring post expulsion. Normal gravity segregation within depositional cycles of diatomite have caused lightest oils to migrate to the crests of individual cycle structures. Some data suggests a loss of the light end oils in the uppermost cycles to the Tulare Formation above, or through early biodegradation. Structural rotation post early oil expulsion has also left older, heavier oils concentrated on the east flank of the structure. With the addition of other samples from the south central San Joaquin area, we have been able to tie the Belridge diatomite hydrocarbon charge into a regional framework. We have also enhanced our ability to predict oil gravity and well primary recovery by unraveling some key components of the diatomite oil source and migration history.« less

Correlated compositional and mineralogical investigations at the Chang′e-3 landing site

PubMed Central

Ling, Zongcheng; Jolliff, Bradley L.; Wang, Alian; Li, Chunlai; Liu, Jianzhong; Zhang, Jiang; Li, Bo; Sun, Lingzhi; Chen, Jian; Xiao, Long; Liu, Jianjun; Ren, Xin; Peng, Wenxi; Wang, Huanyu; Cui, Xingzhu; He, Zhiping; Wang, Jianyu

2015-01-01

The chemical compositions of relatively young mare lava flows have implications for the late volcanism on the Moon. Here we report the composition of soil along the rim of a 450-m diameter fresh crater at the Chang′e-3 (CE-3) landing site, investigated by the Yutu rover with in situ APXS (Active Particle-induced X-ray Spectrometer) and VNIS (Visible and Near-infrared Imaging Spectrometer) measurements. Results indicate that this region's composition differs from other mare sample-return sites and is a new type of mare basalt not previously sampled, but consistent with remote sensing. The CE-3 regolith derived from olivine-normative basaltic rocks with high FeO/(FeO+MgO). Deconvolution of the VNIS data indicates abundant high-Ca ferropyroxene (augite and pigeonite) plus Fe-rich olivine. We infer from the regolith composition that the basaltic source rocks formed during late-stage magma-ocean differentiation when dense ferropyroxene-ilmenite cumulates sank and mixed with deeper, relatively ferroan olivine and orthopyroxene in a hybridized mantle source. PMID:26694712

Rafting rocks reveal marine biological dispersal: A case study using clasts from beach-cast macroalgal holdfasts

NASA Astrophysics Data System (ADS)

Garden, Christopher J.; Craw, Dave; Waters, Jonathan M.; Smith, Abigail

2011-12-01

Tracking and quantifying biological dispersal presents a major challenge in marine systems. Most existing methods for measuring dispersal are limited by poor resolution and/or high cost. Here we use geological data to quantify the frequency of long-distance dispersal in detached bull-kelp (Phaeophyceae: Durvillaea) in southern New Zealand. Geological resolution in this region is enhanced by the presence of a number of distinct and readily-identifiable geological terranes. We sampled 13,815 beach-cast bull-kelp plants across 130 km of coastline. Rocks were found attached to 2639 of the rafted plants, and were assigned to specific geological terranes (source regions) to quantify dispersal frequencies and distances. Although the majority of kelp-associated rock specimens were found to be locally-derived, a substantial number (4%) showed clear geological evidence of long-distance dispersal, several having travelled over 200 km from their original source regions. The proportion of local versus foreign clasts varied considerably between regions. While short-range dispersal clearly predominates, long-distance travel of detached bull-kelp plants is shown to be a common and ongoing process that has potential to connect isolated coastal populations. Geological analyses represent a cost-effective and powerful method for assigning large numbers of drifted macroalgae to their original source regions.

Sedimentary provenance of Maastrichtian oil shales, Central Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Fathy, Douaa; Wagreich, Michael; Mohamed, Ramadan S.; Zaki, Rafat

2017-04-01

Maastrichtian oil shales are distributed within the Central Eastern Desert in Egypt. In this study elemental geochemical data have been applied to investigate the probable provenance of the sedimentary detrital material of the Maastrichtian oil shale beds within the Duwi and the Dakhla formations. The Maastrichtian oil shales are characterized by the enrichment in Ca, P, Mo, Ni, Zn, U, Cr and Sr versus post-Archean Australian shales (PAAS). The chondrite-normalized patterns of the Maastrichtian oil shale samples are showing LREE enrichment, HREE depletion, slightly negative Eu anomaly, no obvious Ce anomaly and typical shale-like PAAS-normalized patterns. The total REE well correlated with Si, Al, Fe, K and Ti, suggesting that the REE of the Maastrichtian oil shales are derived from terrigenous source. Chemical weathering indices such as Chemical Index of Alteration (CIA), Chemical Proxy of Alteration (CPA) and Plagioclase Index of Alteration (PIA) indicate moderate to strong chemical weathering. We suggest that the Maastrichtian oil shale is mainly derived from first cycle rocks especially intermediate rocks without any significant inputs from recycled or mature sources. The proposed data illustrated the impact of the parent material composition on evolution of oil shale chemistry. Furthermore, the paleo-tectonic setting of the detrital source rocks for the Maastrichtian oil shale is probably related to Proterozoic continental island arcs

New geochemical data from the Nigerian sector of the Chad basin: implications on hydrocarbon prospectivity

NASA Astrophysics Data System (ADS)

Obaje, N. G.; Wehner, H.; Hamza, H.; Scheeder, G.

2004-04-01

Organic geochemical studies have been carried out to assess the qualities of source rocks penetrated by four wells (Kemar-1, Murshe-1, Tuma-1 and Ziye-1) in the Nigerian sector of the Chad basin. The Chad basin is a large intracratonic basin in Central West Africa. Commercial hydrocarbon accumulations have been discovered in some sectors of the basin outside the Nigerian border in a structurally related contiguous basin. Fair to poor quality source rocks are inherent in the sequences penetrated by the studied wells. About 80% of all samples have their total organic carbon (TOC) contents more than 0.5 wt.%, the minimum limit for hydrocarbon generation. Juxtaposition of the hydrogen indices against the TOC and Tmax indicates that the source rocks are entirely gas-prone. However, biomarker chromatograms and extract vs. TOC plots indicate the presence of oil shows in Ziye-1 well at a depth of 1210 m. Although generated hydrocarbons (wherever they have accumulated) would be overwhelmingly gaseous, gas is the energy of the future. The gas resources of this part of Nigeria's inland basins can be economically exploited through policies that will increase the tempo of gas-utilization projects and the construction of a national grid of gas pipelines with nodal points of input and output.

Risk Assessment of Heavy Metals in Abandoned Mine Lands as Signifcant Contamination Problem in Romania

NASA Astrophysics Data System (ADS)

Horvath, E.; Jordan, G.; Fugedi, U.; Bartha, A.; Kuti, L.; Heltai, G.; Kalmar, J.; Waldmann, I.; Napradean, I.; Damian, G.

2009-04-01

INTRODUCTION Wide-spread environmental contamination associated with historic mining in Europe has triggered social responses to improve related environmental legislation, the environmental assessment and management methods for the mining industry. Pollution by acid mine drainage (AMD) from ore and coal mining is the outstanding and most important source of mining-induced environmental pollution. Younger et al. (2002) estimates that watercourses polluted by coal mine drainage could be in the order of 2,000 to 3,000 km, and 1,000 to 1,500 km polluted by metal mine discharges for the EU 15 Member States (Younger et al. 2002). Significance of contamination risk posed by mining is also highlighted by mine accidents such as those in Baia Mare, Romania in 2002 and in Aznalcollar, Spain in 1999 (Jordan and D'Alessandro 2004). The new EU Mine Waste Directive (Directive 2006/21/EC) requires the risk-based inventory of abandoned mines in the EU. The cost-effective implementation of the inventory is especially demanding in countries with extensive historic mining and great number of abandoned mine sites, like Romania. The problem is further complicated in areas with trans-boundary effects. The objective of this investigation to carry out the risk-based contamination assessment of a mine site with possible trans-boundary effects in Romania. Assessment follows the source-pathway-receptor chain with a special attention to heavy metal leaching from waste dumps as sources and to transport modelling along surface water pathways. STUDY AREA In this paper the Baiut mine catchment located in the Gutai Mts., Romania, close to the Hungarian border is studied. The polymetallic deposites in the Tertiary Inner-Carpathian Volcanic Arc are exposed by a series of abandoned Zn and Pb mines first operated in the 14th century. Elevation in the high relief catchment ranges from 449m to 1044m. Geology is characterised by andesites hosting the ore deposits and paleogene sediments dominating at the lower topographic elevations. Several mine adits, waste rock dumps are located along the main stream and a large tailings dump is found next to village Baiut just above the receiving floodplain. Predominant land cover is coniferous and mixed forests with agricultural lands on the downstream floodplain. METHODS Six samples at vaious depths were collected from the two major waste rock dumps in the headwater area, and the large tailings dump was also sampled for heavy metal source characterisation. 11 stream sediment samples were collected along the main surface water contamination transport pathway, and a further 11 soil samples were collected in 2 boreholes in the receptor floodplain in October 2008. Besides background stream sediment samples, samples from the exposed rock formations were also collected in order to capture natural background geochemistry in the studied mineralised area. The collected waste rock, stream sediment, soil and rock samples are analysed for total chemical composition (major elements and heavy metals) by ICP-MS spectroscopy, and XRD is used for the determination of mineralogical composition. Rock sample mineralogy is further investigated in thin-sections by petrological microscopy. According to EU legislation expectations, a special emphasis is taken on the determination of metal mobility from the waste rock dumps and various leaching tests are performed and compared including US EPA, USGS and ISO methods. A simple cathcment-based distributed sediment transport model (Jordan et al, 2005; Jordan et al. 2005, 2008) is used to decribe the pathways and quantities of particle-bound contamination. RESULTS AND CONCLUSIONS Results show that (1) sediments are an efficient means for the preliminary inventory of mine contamination as a preparation for the more detailed hydrological sampling and assessment, and (2) the risk-based contamination assessment of mining sites often located in diverse geological, hydrological and landcover environment requires careful and successive sampling design and a tiered assessment approach. Leaching tests are shown cost-efficient and informative methods for source (hazard) characterisation. REFERENCES Directive 2006/21/EC the European Parliament and of the Council on the management of waste from extractive industries and amending Directive 2004/35/EC. Commission of the European Communities, Brussels. Jordan G. and D'Alessandro M. (eds) (2004) Mining, Mining Waste and Related Environmental Issues: Problems and Solutions in the Central and Eastern European Candidate Countries. Joint Research Centre of the European Commission, Ispra. LB-NA-20868-EN-C. Jordan G., van Rompaey A., Szilassi P., Csillag G., Mannaerts C. and Woldai T. (2005) Historical land use changes and their impact on sediment fluxes in the Balaton basin (Hungary). Agriculture, Ecosystems and Environment, 108, 119-133. Jordan G., van Rompaey A., Somody A., Fügedi U., Bats M. and Farsang A. (2008) Spatial Modelling of Contamination in a Catchment Area Impacted by Mining: a Case Study for the Recsk Copper Mines, Hungary. Journal of Land Contamination and Reclamation (in press). Younger P.L., Banwart S.A., Hedin R.S. (2002) Mine water. Hydrology, pollution, remediation. Kluwer Academic Publishers, Dodrecht.

The relationship of angiosperms and oleanane in petroleum through geologic time

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

Moldowan, J.M.; Dahl, J.E.; Huizinga, B.J.

1993-02-01

The biological marker oleanane has been suggested as an indicator of angiosperm (flowering plant) input into source rocks and their derived oils. Parallels should therefore be evident between the angiosperm fossil record and oleanane occurrence and abundance. A global selection of more than 50 core samples from marine rocks of different ages and from different locations was quantitatively analyzed for oleanane to determine its abundance over geologic time relative to the bacterial marker hopane. Oleanane was recognized using Metastable Reaction Monitoring (MRM) GC-MS. A parallel was observed between the oleanane/hopane ratio and angiosperm diversity in the fossil record through time.more » The first fossil evidence of angiosperms is during the Early Cretaceous with radiation during the Late Cretaceous and Tertiary. Occurrences of oleanane are confirmed throughout the Cretaceous system. Early-to-middle Cretaceous (Berriasian-Cenomanian) occurrences are sporadic and oleanan/hopane ratios are less than 0.07. Late Cretaceous (Turonian-Maastrichtian) oleanane/hopane ratios range up to 0.15 with higher ratios in many Tertiary samples. It appears that oleanane/hopane ratios of oils can restrict the age of their unavailable or unknown source rocks. High ratios indicate Tertiary age and lower ratios can indicate Cretaceous or Tertiary age, depending on depositional environment. While these data do not rule out pre-Cretaceous oleanane, preliminary data show that oleanane/hopane ratios for Jurassic and older rock extracts are typically below our detection limits (<0.03). While oleanane precursors are abundant in angiosperms, they also occur, rarely, in other modern plant groups. We identified oleanane in low abundances in three Early Cretaceous fossil benettitialeans, an extinct plant group (Late Triassic to Late Cretaceous) thought to be related to angiosperms. These findings suggest that oleanane could be present in low abundance in some pre-Cretaceous rocks and oils.« less

Episodic growth of a Late Cretaceous and Paleogene intrusive complex of pegmatitic leucogranite, Ruby Mountains core complex, Nevada, USA

USGS Publications Warehouse

Howard, Keith A.; Wooden, J.L.; Barnes, C.G.; Premo, W.R.; Snoke, A.W.; Lee, S.-Y.

2011-01-01

Gneissic pegmatitic leucogranite forms a dominant component (>600 km3) of the midcrustal infrastructure of the Ruby Mountains–East Humboldt Range core complex (Nevada, USA), and was assembled and modified episodically into a batholithic volume by myriad small intrusions from ca. 92 to 29 Ma. This injection complex consists of deformed sheets and other bodies emplaced syntectonically into a stratigraphic framework of marble, calc-silicate rocks, quartzite, schist, and other granitoids. Bodies of pegmatitic granite coalesce around host-rock remnants, which preserve relict or ghost stratigraphy, thrusts, and fold nappes. Intrusion inflated but did not disrupt the host-rock structure. The pegmatitic granite increases proportionally downward from structurally high positions to the bottoms of 1-km-deep canyons where it constitutes 95%–100% of the rock. Zircon and monazite dated by U-Pb (sensitive high-resolution ion microprobe, SHRIMP) for this rock type cluster diffusely at ages near 92, 82(?), 69, 38, and 29 Ma, and indicate successive or rejuvenated igneous crystallization multiple times over long periods of the Late Cretaceous and the Paleogene. Initial partial melting of unexposed pelites may have generated granite forerunners, which were remobilized several times in partial melting events. Sources for the pegmatitic granite differed isotopically from sources of similar-aged interleaved equigranular granites. Dominant Late Cretaceous and fewer Paleogene ages recorded from some pegmatitic granite samples, and Paleogene-only ages from the two structurally deepest samples, together with varying zircon trace element contents, suggest several disparate ages of final emplacement or remobilization of various small bodies. Folded sills that merge with dikes that cut the same folds suggest that there may have been in situ partial remobilization. The pegmatitic granite intrusions represent prolonged and recurrent generation, assembly, and partial melting modification of a batholithic volume even while the regional tectonic environment varied dramatically from contractile thickening to extension and mafic underplating.

The Mapping X-ray Fluorescence Spectrometer (MapX)

NASA Astrophysics Data System (ADS)

Sarrazin, P.; Blake, D. F.; Marchis, F.; Bristow, T.; Thompson, K.

2017-12-01

Many planetary surface processes leave traces of their actions as features in the size range 10s to 100s of microns. The Mapping X-ray Fluorescence Spectrometer (MapX) will provide elemental imaging at 100 micron spatial resolution, yielding elemental chemistry at a scale where many relict physical, chemical, or biological features can be imaged and interpreted in ancient rocks on planetary bodies and planetesimals. MapX is an arm-based instrument positioned on a rock or regolith with touch sensors. During an analysis, an X-ray source (tube or radioisotope) bombards the sample with X-rays or alpha-particles / gamma-rays, resulting in sample X-ray Fluorescence (XRF). X-rays emitted in the direction of an X-ray sensitive CCD imager pass through a 1:1 focusing lens (X-ray micro-pore Optic (MPO)) that projects a spatially resolved image of the X-rays onto the CCD. The CCD is operated in single photon counting mode so that the energies and positions of individual X-ray photons are recorded. In a single analysis, several thousand frames are both stored and processed in real-time. Higher level data products include single-element maps with a lateral spatial resolution of 100 microns and quantitative XRF spectra from ground- or instrument- selected Regions of Interest (ROI). XRF spectra from ROI are compared with known rock and mineral compositions to extrapolate the data to rock types and putative mineralogies. When applied to airless bodies and implemented with an appropriate radioisotope source for alpha-particle excitation, MapX will be able to analyze biogenic elements C, N, O, P, S, in addition to the cations of the rock-forming elements >Na, accessible with either X-ray or gamma-ray excitation. The MapX concept has been demonstrated with a series of lab-based prototypes and is currently under refinement and TRL maturation.

Petrological and geochemical compositions of beach sands of the Barton and Weaver peninsulas of King George Island, West Antarctica: implications for provenance and deglacial history

NASA Astrophysics Data System (ADS)

Lee, Y. I.; Lim, H. S.; Choi, T.

2017-12-01

We studied the provenance of beach sediments of the Baton and Weaver peninsulas of King George Island, the South Shetland Islands of West Antarctica. The studied beach sand sediments of the both peninsulas are predominantly composed of volcanic-rock fragment, followed by altered grain and plutonic rock fragment in that order. In rock fragments, the volcanic rock fragments are about four times more than the plutonic rock fragments. The median quartz-feldspar-rock fragment (Q-F-R) ratios of the beach sands of the Weaver and Barton peninsulas are Q3.4-F5.5-R99.1 and Q0.5-F2.7-R96.8, respectively. These beach sands may have been originated from basaltic andesite-andesite distributed in the ice-free areas of the Barton and Weaver peninsulas and granodiorite of the Barton Peninsula. According to the geochemistry of the beach sand sediments of the two peninsulas, most of the sand samples are interpreted as originating from intermediate rocks that have experienced little chemical weathering. Taking together the modal composition and geochemical composition of the beach sand samples, the tectonic setting of the source area is interpreted as a magmatic arc setting. This interpretation is consistent with geology of the ice-free areas of the Barton and Weaver peninsulas and the tectonic setting of King George Island. However, the sand samples of the Barton Peninsula southern beach and the Weaver Peninsula beach were not derived from basement rocks currently exposed in the ice-free areas of the corresponding peninsula, but were formerly glaciomarine sediments derived from erosion of ice-covered subglacial basement rocks and transported to the submerged glacier grounding line prior to deglaciation. Sand sediments derived from wave erosion of basement rocks of paleoshoreline might have been mixed with these glaciomarine sediments. King George Island became uplifted due to deglaciation 6,000 years ago. The studied beach sediments might have been reworked after the uplift of the King George Island to the present level. Accordingly, the studied beach sand sediments of the Barton and Weaver peninsulas are interpreted to be a palimpsest deposit comprising a mixture of originally glaciomarine sediments accumulated in the shallow fjord post the Last Glacial Maximum and some detritus supplied to the beaches since deglaciation.

Relationships between data from Rock-Eval pyrolysis and proximate, ultimate, petrographic, and physical analyses of 142 diverse U.S. coal samples

USGS Publications Warehouse

Bostick, N.H.; Daws, T.A.

1994-01-01

Basic research on coal and oil shale led to automated pyrolysis analysis of petroleum source rocks; most widely used is the Rock-Eval equipment. In order to interpret Rock-Eval analyses in relation to traditional coal data, we analyzed 142 commercial coals with diverse rank, age, maceral and sulfur contents, for most regions of the United States. We compared the Rock-Eval data with traditional industrial coal data, including volatile matter, calorific value, hydrogen and oxygen content, free swelling index, and vitrinite reflectance. We found: (1) there is a close relationship between Tmax and vitrinite reflectance in the ranges 420-590??C Tmax and 0.4-3%Romax of most coals. (2) A close relationship between Tmax and volatile matter (%VM) extends through the entire sample range, including low-rank samples with 35-70% VM, a range where %VM is not considered to be a useful rank parameter. (3) TOC of medium- and high-rank coals is seriously under-measured by Rock-Eval; TOC of low-rank coals (less than 0.8%Romax) is close to "dry basis" carbon from ultimate analysis. (4) The direct relationships between oxygen index (OI) and %O and between hydrogen index (HI) and %H are clear, though only broadly defined. However, there is virtually no band of concentrated data points on the HI versus OI pseudo-Van Krevelen diagram comparable to the "development line" on the H/C versus O/C diagram. (5) There are systematic relationships between Rock-Eval and industrial coal parameters such as calorific value and FSI, but much standardization would be needed before Rock-Eval could find a place in the coal industry. Tests with blends of coal and quartz sand and with various loads of coal alone showed that the amount of organic matter in the Rock-Eval load greatly influences results. Total load in the crucible, if largely inert, plays a small role, however. Increasing absolute or relative coal content causes under-evaluation of Rock-Eval TOC and over-rating of hydrogen. Blends of several coals yielded hydrogen and oxygen indexes related proportionally to the properties of the individual coals, but Tmax is not raised by addition of high-rank coal until over 40% is added. ?? 1994.

Natural and anthropogenic factors affecting the groundwater quality in Serbia.

PubMed

Devic, Gordana; Djordjevic, Dragana; Sakan, Sanja

2014-01-15

Various chemometric techniques were used to analyze the quality of groundwater data sets. Seventeen water quality parameters: the cations Na, K, Ca, Mg, the anions Cl, SO4, NO3, HCO3 and nine trace elements Pb, As, Mn, Ni, Cu, Cd, Fe, Zn and Cr were measured at 66 different key sampling sites in ten representative areas (low land-Northern Autonomous Province of Serbia, Vojvodina and central Serbia) for the summer period of 2009. HCA grouped the sample sites into four clusters based on the similarities of the characteristics of the groundwater quality. DA showed two parameters, HCO3 and Zn, affording more than 90% correct assignments in the spatial analysis of four/three different regions in Serbia. Factor analysis was applied on the log-transformed data sets and allowed the identification of a reduced number of factors with hydrochemical meaning. The results showed severe pollution with Mn, As, NO3, Ni, Pb whereby anthropogenic origin of these contaminants was indicated. The pollution comes from both scattered point sources (industrial and urban effluent) and diffuse source agricultural activity. These samples may not be suitable for human consumption; the water quality belongs to class III/IV (contaminated). The Fe anomalies (7.1mg/L) in the water from the Vetrnica site can be attributed to natural sources, such as the dissolution of rock masses and rock fragments. The serious groundwater contamination with As (25.7-137.8 μg/L) in the area of Banat (Northern Autonomous Province of Serbia, Vojvodina) and a sample No. 9 at the Great Morava River requires urgent attention. © 2013.

U-Pb ages and Hf isotope compositions of zircons in plutonic rocks from the central Famatinian arc, Argentina

NASA Astrophysics Data System (ADS)

Otamendi, Juan E.; Ducea, Mihai N.; Cristofolini, Eber A.; Tibaldi, Alina M.; Camilletti, Giuliano C.; Bergantz, George W.

2017-07-01

The Famatinian arc formed around the South Iapetus rim during the Ordovician, when oceanic lithosphere subducted beneath the West Gondwana margin. We present combined in situ U-Th-Pb and Lu-Hf isotope analyses for zircon to gain insights into the origin and evolution of Famatinian magmatism. Zircon crystals sampled from four intermediate and silicic plutonic rocks confirm previous observations showing that voluminous magmatism took place during a relatively short pulse between the Early and Middle Ordovician (472-465 Ma). The entire zircon population for the four plutonic rocks yields coherent εHf negative values and spreads over several ranges of initial εHf(t) units (-0.3 to -8.0). The range of εHf units in detrital zircons of Famatinian metasedimentary rocks reflects a prolonged history of the cratonic sources during the Proterozoic to the earliest Phanerozoic. Typical tonalites and granodiorites that contain zircons with evolved Hf isotopic compositions formed upon incorporating (meta)sedimentary materials into calc-alkaline metaluminous magmas. The evolved Hf isotope ratios of zircons in the subduction related plutonic rocks strongly reflect the Hf isotopic character of the metasedimentary contaminant, even though the linked differentiation and growth of the Famatinian arc crust was driven by ascending and evolving mantle magmas. Geochronology and Hf isotope systematics in plutonic zircons allow us understanding the petrogenesis of igneous series and the provenance of magma sources. However, these data could be inadequate for computing model ages and supporting models of crustal evolution.

Maastrichtian sedimentation and palaeoenvironments of the Saratov Volga region

NASA Astrophysics Data System (ADS)

Iakovishina, Elena; Blinova, Irina; Kopaevich, Ludmila; Vishnevskaya, Valentina; Bordunov, Sergey

2016-04-01

The Saratov Volga region was a shallow-marine epicontinental basin North-Eastern shelf zone of the Tethys Ocean in the Maastrichtian. The basis for the modeling conditions of sedimentation was the detection mineral composition of rocks, as well as the contents of various chemical elements in rocks in three reference sections: Lower Bannovka, quarries "Bolshevik" and "Kommunar". Rocks of quarries "Bolshevik" and "Kommunar" characterized by quartz-calcite mineral association. The main rock-forming mineral is calcite, small amounts in rocks contain quartz. Other mineral composition characterized section Lower Bannovka. At the base of the section in the rock marked the presence of the opal. The source of silica are radiolarians. Favorable conditions for the existence of which is cold deep water enriched with SiO2. Above the section marked authigenic glauconite, which are confined to zones of skip in sedimentation.Further up begins to dominate the accumulation of calcite with rich bentic foraminifera. Clay minerals in rocks of the section Lower Bannovka presented montmorillonite and illite. The relationship of chemical elements and their alkali modules allow to detail the conditions of sedimentation. The ratio of Fe/Mn in them varies from 44 to 5729. Higher values are characteristic of glauconite sandstones. Up the section marked decrease in the Ti/Zr, indicating that the increase in the distance from the source area to the place of deposition. The similarity values of the ratio Ti/Zr samples indicates a community source area. Sedimentation Model revealed the impact of the PreUral strait connecting Tethys and Paleoarktic. Through the Strait of deep cold water saturated with SiO2, penetrated into the of the Saratov Volga region, were accumulated clay. The closing of the PreUral Strait changed the conditions of sedimentation, the associated fall in sea levels due to global cooling reflected in the crisis of radiolarians, increase in the number of glauconite. Subsequent warming and warm-water transgression caused dominance of carbonates. The work was supported by grants 15-05-04990, 15-05-04700 Russian Foundation for Basic Research and IGCP project 609.

Geochemistry of shale and sedimentary pyrite as a proxy for gold fertility in the Selwyn basin area, Yukon

NASA Astrophysics Data System (ADS)

Sack, Patrick J.; Large, Ross R.; Gregory, Daniel D.

2018-01-01

Selwyn basin area strata contain sedimentary pyrite with Au above background levels when analyzed by laser ablation-inductively coupled mass spectrometry. Hyland Group rocks contain framboidal pyrite contents of 670 ppb Au, 1223 ppm As, and 5.3 ppm Te; the mean of all types of sedimentary pyrite in the Hyland Group is 391 ppb Au, 1489 ppm As, and 3.8 ppm Te. These levels are similar to sedimentary pyrite in host lithologies from major orogenic gold districts in New Zealand and Australia. Comparison of whole rock and pyrite data show that rocks deposited in continental slope settings with significant terrigenous input contain pyrite that is consistently enriched in Au, As, Te, Co, and Cu. Although data are limited, whole rock samples of stratigraphic units containing Au-rich pyrite also contain high Au, indicating that most of the Au is within sedimentary pyrite. Based on geologic characteristics and comparison of pyrite chemistry data with whole rock chemistry, Selwyn basin area strata have the necessary ingredients to form orogenic gold deposits: Au-enriched source rocks, metamorphic conditions permissive of forming a metamorphic ore fluid, and abundant structural preparation for channeling fluids and depositing ore.

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, A.; Sproule, R. A.; Walker, R. J.; Lesher, C.

2004-12-01

Re-Os concentrations and isotopic compositions have been examined in one komatiite unit and one komatiitic basalt unit at Dundonald Beach, which is part of the spatially-extensive 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 was lost due to shallow degassing during eruption and/or hydrothermal leaching during or immediately after the lava emplacement. Second, the Re-Os isotope systematics of the rocks with 187Re/188Os ratios >1 were reset at ˜2.5 Ga, most likely due to a regional metamorphic event. Finally, there is evidence for relatively recent gain and loss of Re. The variations in Os concentrations in the Dundonald komatiites yield a relative bulk distribution coefficient for Os (DOs solid/liquid) of 2-4, consistent with those obtained for stratigraphically-equivalent komatiites in the nearby Alexo area and in Munro Township. This suggests that Os was moderately compatible during crystal-liquid fractionation of the magma parental to the Kidd-Munro komatiitic rocks. Furthermore, 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 (\\gammaOs = 0.0 ± 0.6). 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. Our Os isotope results for the Dundonald komatiitic rocks, combined with those in the Alexo and Pyke Hill areas suggest that the mantle source region for the Kidd- Munro volcanic assemblage had evolved along a long-term chondritic Os isotopic trajectory until their eruption at ˜2.7 Ga. 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 ˜2.7 Ga mantle source for the Kidd-Munro komatiites contrasts with the typical large-scale Os isotopic heterogeneity in the mantle sources for komatiites from the Gorgona Island, present-day ocean island basalts or arc-related lavas. This suggests a significantly more homogeneous mantle source in the Archean compared to the presentday mantle.

Thermal conductivity anisotropy of metasedimentary and igneous rocks

NASA Astrophysics Data System (ADS)

Davis, Michael G.; Chapman, David S.; van Wagoner, Thomas M.; Armstrong, Phillip A.

2007-05-01

Thermal conductivity anisotropy was determined for three sets of metasedimentary and igneous rocks from central Utah, USA. Most conductivity measurements were made in transient mode with a half-space, line source instrument oriented in two orthogonal directions on a flat face cut perpendicular to bedding. One orientation of the probe yields thermal conductivity parallel to bedding (kpar) directly, the other orientation of the probe measures a product of conductivities parallel and perpendicular to bedding from which the perpendicular conductivity (kperp) is calculated. Some direct measurements of kpar and kperp were made on oriented cylindrical discs using a conventional divided bar device in steady state mode. Anisotropy is defined as kpar/kperp. Precambrian argillites from Big Cottonwood Canyon have anisotropy values from 0.8 to 2.1 with corresponding conductivity perpendicular to bedding of 2.0 to 6.2 W m-1 K-1. Anisotropy values for Price Canyon sedimentary samples are less than 1.2 with a mean of 1.04 although thermal conductivity perpendicular to bedding for the samples varied from 1.3 to 5.0 W m-1 K-1. The granitic rocks were found to be essentially isotropic with thermal conductivity perpendicular to bedding having a range of 2.2 to 3.2 W m-1 K-1 and a mean of 2.68 W m-1 K-1. The results confirm the observation by Deming [1994] that anisotropy is negligible for rocks having kperp greater than 4.0 W m-1 K-1 and generally increases for low conductivity metamorphic and clay-rich rocks. There is little evidence, however, for his suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2.5 for low thermal conductivity rocks.

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.

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.

Mantle contribution and tectonic transition in the Aqishan-Yamansu Belt, Eastern Tianshan, NW China: Insights from geochronology and geochemistry of Early Carboniferous to Early Permian felsic intrusions

NASA Astrophysics Data System (ADS)

Du, Long; Long, Xiaoping; Yuan, Chao; Zhang, Yunying; Huang, Zongying; Wang, Xinyu; Yang, Yueheng

2018-04-01

Late Paleozoic is a key period for the accretion and collision of the southern Central Asian Orogenic Belt (CAOB). Here, we present new zircon U-Pb ages, whole-rock geochemistry and Sr-Nd isotopic compositions for four Late Paleozoic felsic plutons in Eastern Tianshan (or Tienshan in some literatures) in order to constrain the tectonic evolution of the southern CAOB. The granodioritic pluton and its dioritic enclaves were synchronously formed in the Early Carboniferous (336 ± 3 Ma and 335 ± 2 Ma, respectively). These rocks are depleted in Nb, Ta and Ti, and enriched in Rb, Ba, Th and U related to the primitive mantle, which show typical features of arc rocks. They both have similar Sr-Nd isotopic ratios to those granitic rocks from the eastern Central Tianshan Block and have the latest Mesoproterozoic two stage Nd model ages (TDM2) (1111-1195 Ma for the granodioritic pluton and 1104-1108 Ma for the enclaves, respectively), indicating that their source magmas may have been derived from the Mesoproterozoic crust. The albitophyric pluton was also emplaced in the Early Carboniferous (333 ± 3 Ma). Rocks of this pluton have similar εNd(t) values (-0.69 to -0.37) and TDM2 ages (1135-1161 Ma) to those of the granodioritic rocks, suggest similar crustal source for both types of rocks. In contrast, the K-feldspar granitic and monzonitic plutons were emplaced in the Early Permian (292 ± 3 Ma and 281 ± 2 Ma, respectively). Samples of the K-feldspar granitic pluton have high K2O + Na2O, FeO/MgO, Ga/Al, HFSE (e.g., Zr and Hf) and low CaO, Sr and Ba, exhibiting characteristics of A2-type granites, which probably emplaced in a post-collisional extension environment. They have higher εNd(t) values (+2.77 to +3.27) and more juvenile TDM2 ages (799-841 Ma) than the Early Carboniferous plutons, suggesting that they were derived from relatively younger crustal sources. The monzonitic granites are metaluminous to weakly peraluminous with A/CNK ranging from 0.93 to 1.05, and have very low P2O5, indicating characteristics of I-type granites. They also have positive εNd(t) values (+2.22 to +2.34) and juvenile TDM2 ages (868-878 Ma), suggesting this pluton was also produced by partial melting of relatively young crustal source. Based on an isotopic mixing simulation, significant mantle contributions were added to the magma source of both the Early Carboniferous and the Early Permian felsic rocks. The mantle contribution changes from 60% in the Early Carboniferous to 75% in the Early Permian. The remarkably increasing of mantle materials in the magma source of the felsic rocks in the Aqishan-Yamansu belt was most likely induced by the tectonic transition from an Early Carboniferous continental arc to an Early Permian post-collisional extension environment.

Magnetic properties, acid neutralization capacity, and net acid production of rocks in the Animas River Watershed Silverton, Colorado

USGS Publications Warehouse

McCafferty, Anne E.; Yager, Douglas B.; Horton, Radley M.; Diehl, Sharon F.

2006-01-01

Federal land managers along with local stakeholders in the Upper Animas River watershed near Silverton, Colorado are actively designing and implementing mine waste remediation projects to mitigate the effects of acid mine drainage from several abandoned hard rock metal mines and mills. Local source rocks with high acid neutralization capacity (ANC) within the watershed are of interest to land managers for use in these remediation projects. A suite of representative samples was collected from propylitic to weakly sericitic-altered volcanic and plutonic rocks exposed in outcrops throughout the watershed. Acid-base accounting laboratory methods coupled with mineralogic and geochemical characterization provide insight into lithologies that have a range of ANC and net acid production (NAP). Petrophysical lab determinations of magnetic susceptibility converted to estimates for percent magnetite show correlation with the environmental properties of ANC and NAP for many of the lithologies. A goal of our study is to interpret watershed-scale airborne magnetic data for regional mapping of rocks that have varying degrees of ANC and NAP. Results of our preliminary work are presented here.

Rock property measurements and analysis of selected igneous, sedimentary, and metamorphic rocks from worldwide localities

USGS Publications Warehouse

Johnson, Gordon R.

1983-01-01

Dry bulk density and grain density measurements were made on 182 samples of igneous, sedimentary, and metamorphic rocks from various world-wide localities. Total porosity values and both water-accessible and helium-accessible porosities were calculated from the density data. Magnetic susceptibility measurements were made on the solid samples and permeability and streaming potentials were concurrently measured on most samples. Dry bulk densities obtained using two methods of volume determination, namely direct measurement and Archlmedes principle, were nearly equivalent for most samples. Grain densities obtained on powdered samples were typically greater than grain densities obtained on solid samples, but differences were usually small. Sedimentary rocks had the highest percentage of occluded porosity per rock volume whereas metamorphic rocks had the highest percentage of occluded porosity per total porosity. There was no apparent direct relationship between permeability and streaming potential for most samples, although there were indications of such a relationship in the rock group consisting of granites, aplites, and syenites. Most rock types or groups of similar rock types of low permeability had, when averaged, comparable levels of streaming potential per unit of permeability. Three calcite samples had negative streaming potentials.

Studies of Minerals, Organic and Biogenic Materials through Time-Resolved Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Nyugen, Trac; Elsayed-Ali, hani

2009-01-01

A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized including marble, which contain CaCO3. Analysis of the results reveals the short (approx.10-13 s) lifetime of the Raman process, and shows that Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. Moreover, it was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due the presence of very strong short-lived fluorescence.

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.

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.

Relation of arsenic, iron, and manganese in ground water to aquifer type, bedrock lithogeochemistry, and land use in the New England coastal basins

USGS Publications Warehouse

Ayotte, Joseph D.; Nielsen, Martha G.; Robinson, Gilpin R.; Moore, Richard B.

1999-01-01

In a study of arsenic concentrations in public-supply wells in the New England Coastal Basins, concentrations at or above 0.005 mg/L (milligrams per liter) were detected in more samples of water from wells completed in bedrock (25 percent of all samples) than in water from wells completed in stratified drift (7.5 percent of all samples). Iron and manganese were detected (at concentrations of 0.05 and 0.03 mg/L, respectively) at approximately the same frequency in water from wells in both types of aquifers. Concentrations of arsenic in public-supply wells drilled in bedrock (in the National Water-Quality Assessment Program New England Coastal Basins study unit) vary with the bedrock lithology. Broad groups of lithogeochemical units generalized from bedrock lithologic units shown on state geologic maps were used in the statistical analyses. Concentrations of arsenic in water from public-supply wells in metasedimentary bedrock units that contain slightly to moderately calcareous and calcsilicate rocks (lithogeochemical group Mc) were significantly higher than the concentrations in five other groups of bedrock units in the study unit. Arsenic was detected, at or above 0.005 mg/L, in water from 44 percent of the wells in the lithogeochemical group M c and in water from less than 28 percent of wells in the five other groups. Additionally, arsenic concentrations in ground water were the lowest in the metasedimentary rocks that are characterized as variably sulfidic (group Ms ). Generally, concentrations of arsenic were low in water from bedrock wells in the felsic igneous rocks (group If ) though locally some bedrock wells in granitic rocks are known to have ground water with high arsenic concentrations, especially in New Hampshire. The concentrations of arsenic in ground water also correlate with land-use data; significantly higher concentrations are found in areas identified as agricultural land use than in undeveloped areas. There is, however, more agricultural land in areas overlying the metasedimentary rocks of lithogeochemical groups Mc and the minimally-deformed clastic sediments of group Mmd than in areas overlying other lithogeochemical groups. This correlation complicates the interpretation of sources of arsenic to ground water in bedrock. A test of this association revealed that relations between arsenic concentrations and the metasedimentary rocks of group Mc are not weakened when data associated with agricultural land use is removed; the reverse is true, however, if the data associated with the group Mc are removed from the analysis. The occurrence and variability of arsenic in water from bedrock supply wells could be related to several factors. These include (1) the distribution and chemical form of arsenic in soils and rocks that are part of the ground-water-flow system, (2) the characteristics that influence the solubility and transport of arsenic in ground water, (3) the differing degrees of vulnerability of ground-water supplies to surface contamination, and (4) the spatial associations between land use, geology, and ground-water-flow patterns. Strong relations between agricultural land use and the metasedimentary rocks of group Mc complicate the interpretation of arsenic source to water in these bedrock aquifers. This is due in part to the past use of arsenical pesticides; additionally, few whole-rock geochemical data are available for the rock types in the lithogeochemical groups of aquifers that contain ground water with elevated concentrations of arsenic. Without such data, identifying specific bedrock types as arsenic sources is not possible. In southern Maine and south-central New Hampshire, and in northern Massachusetts, the few available whole-rock analyses suggest, at least for these local areas, a connection between known bedrock chemistry and ground-water arsenic levels. Although the lithogeochemical group and land-use category variables individually describe much of the variance in the concentrations of

The post-collisional late Variscan ferroan granites of southern Sardinia (Italy): Inferences for inhomogeneity of lower crust

NASA Astrophysics Data System (ADS)

Conte, Aida Maria; Cuccuru, Stefano; D'Antonio, Massimo; Naitza, Stefano; Oggiano, Giacomo; Secchi, Francesco; Casini, Leonardo; Cifelli, Francesca

2017-12-01

The post-collisional late Variscan magmatism of Sardinia-Corsica batholith attained a peak at about 290 Ma. In southern Sardinia, in the frontal part of the Variscan orogenic wedge, this magmatism is represented by three suites of granitoids, here defined as GS1, GS2 and GS3. GS1, GS2 and GS3 are slightly peraluminous and F-bearing granitoids; GS1 and GS3 granites show in addition a ferroan character, whereas GS2 rocks range from magnesian to ferroan, from granodiorites to leucogranites. From magnetic susceptibility data, GS1 and GS2 belong to the ilmenite series, whereas GS3 is a slightly oxidized rock-suite plotting on the ilmenite/magnetite series boundary. Each rock-suite shows distinctive characters, in terms of petrography, petrochemistry, rock associations, as well as metallogenic signature of the related fluids. The distinction among rock-suite types is made on the basis of both mafic and characteristic accessory minerals. Siderophyllitic dark mica as the only mafic phase, and accessory xenotime (Y) characterize the GS1 rocks; GS2 mineral associations include biotite ± hornblende + allanite + magnetite; GS3 rocks show an association of hastingsite + annite + allanite + magnetite. Chemical variations in the studied samples suggest different magmatic evolution of independent magmas. Pb, Sr and Nd isotopic data constrain the origin of magmas to lower crustal sources. Chemical composition of rocks and dark micas meet those of liquids experimentally obtained by low degrees of partial melting of different meta-igneous deep crustal sources, felsic for GS1 rock-types and more mafic for GS3 rock-types. GS1 intrusions show granophile-type (Sn-W-Mo) metallogenic signatures, very low magnetic susceptibility, and Nd model ages (referred to the Depleted Mantle - TDM) of 2.3 Ga, coherent with a possible derivation from an old (early Proterozoic-Neoarchean), reduced and weathered basement, tectonically buried under Variscan covers. A definite deep crustal inhomogeneity is mirrored by GS3 granites, whose compositional and isotopic features indicate a younger (Nd model age: 1.6 Ga) tonalitic amphibolite source. Overall, the peculiarities of the studied granitoids suggest further compositional differences in the deep crust between southern and northern portion of the Sardinia-Corsica Variscan transect. Late Variscan lithospheric delamination appears as the most reliable mechanism that may have determined the high thermal regime that triggered partial melting of the crust. The close field association, at 290 Ma, of tholeiitic dike swarms and ferroan granitoids, supports this inference.

40Ar/39Ar age-spectrum data for hornblende, biotite, white mica, and K-feldspar samples from metamorphic rocks in the Great Smoky Mountains of North Carolina and Tennessee

USGS Publications Warehouse

Kunk, Michael J.; McAleer, Ryan J.

2011-01-01

This report contains reduced 40Ar/39Ar data of hornblende, biotite, white mica and (or) sericite, and potassium-feldspar mineral separates and phyllite groundmass samples from metamorphic rocks of the Great Smoky Mountains in North Carolina and Tennessee. Included in this report are information on the location of the samples and a brief description of the samples. The data contained herein are not interpreted in a geological context, and care should be taken by users unfamiliar with argon isotopic data in the use of these results. No geological meaning is implied for any of the apparent ages presented below, and many of the individual apparent ages are not geologically meaningful. This report is primarily a detailed source document for subsequent publications that will integrate these data into a geological context. All the samples in this report were collected in and around the Great Smoky Mountain National Park in western North Carolina and eastern Tennessee.

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.

Petrographic and geochemical analyisis for determination of provenance of the Slovenj Gradec Miocene Basin fill (Western Central Paratethys)

NASA Astrophysics Data System (ADS)

Ivančič, Kristina; Trajanova, Mirka; Skaberne, Dragomir; Šmuc, Andrej

2017-04-01

The Slovenj Gradec Basin (SGB) is located in northern Slovenia between eastern margin of the Northern Karavanke and the western Pohorje Mts. Structurally, it belongs to Eastern Alps. It is filled with Miocene clastic sediments. Modal composition of sandstones was determined on thin sections by point-counter and presented with the QFL and QmFLt diagrams. Their geochemical composition was determined by classical method and by Inductively Coupled Plasma-Mass Spectrometry. Based on petrography, sedimentary fill of the SGB consists mostly of lithic grains and quartz, derived from metamorphic and carbonate rocks. Locally, fragments of granitoids occur. Binder consists of carbonate, subordinately quartz cement, and carbonate matrix. Recycled orogen (lithic and transitional recycled) provenance of the grains was determined. Geochemical composition shows that: - Sandstones from the SGB belong to the fields of shale, wacke, litharenite, arkose and subarkose (Pettijohn, 1972). - In the ternary diagram of weathering trends (cf. Nesbitt & Young 1984), the samples group near the CaO+Na2OAl2O3 conjunctive. Calculated minimum CIA (Fedo et al., 1995) is 40.06, indicating that the source rocks were not subjected to considerable weathering. - According to discriminant function (cf. Roser & Korsch, 1988) all samples from SGB originate from quartzose sedimentary rocks. - For determination of tectonic setting of source rocks (Verma & Armstrong-Altrin, 2013) the studied samples plot in the field of collision zone. - In the multidimensional discriminant function diagram for the discrimination of active and passive margin after Verma and Armstrong (2016), the samples plot into the field of passive margin. The data indicate that source rocks of the SGB sedimentary fill were derived from Eastern Alps and Southern Alps. It is suggested that SGB was detached from the Styrian and Mura-Zala Basins in the course of the Pohorje Mts. oblique transpressive uplift during the late Miocene to Pliocene (Trajanova, 2013). Consequently, the area of the wider SGB was still an integral part of the Central Paratethys until late Miocene. References Fedo, C.M., Nesbitt, H.W. & Young, G.M., 1995. Unravelling the effects of potassium metasomatism in sedimentary rocks and paleosols, with implications for paleoweathering conditions and provenance. Geology, 23(10), pp.921-924. Nesbitt, H. W., & Young, G. M., 1984. Prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations. Geochimica et Cosmochimica Acta, 48 (7), 1523-1534. Pettijohn, F.J., Potter, P.E., Siever, R., 1972. Sand and Sandstone, second ed., Springer, New York, heidelberg, Berlin 618, pp. Roser, B.P. & Korsch, R.J., 1988. Provenance signatures of sandstone-mudstonen suites determined using discriminant function of major-element data. Chemical Geology, 67(1-2), pp.119-139. Trajanova, M. 2013: Starost pohorskega magmatizma; nov pogled na nastanek pohorskega tektonskega bloka (Age of the Pohorje Mountains magmatism; new view on the origin of the Pohorje tectonic block). PhD thesis. 183 pp., Ljubljana. Verma, S.P. & Armstrong-Altrin, J.S., 2013. New multi-dimensional diagrams for tectonic discrimination of siliciclastic sediments and their application to Precambrian basins. Chemical Geology, 355, pp.117-133. Verma, S. P., & Armstrong-Altrin, J. S. (2016). Geochemical discrimination of siliciclastic sediments from active and passive margin settings. Sedimentary Geology, 332, 1-12.

Catalytic properties of volcanic rocks in the synthesis of hydrocarbons from carbon monoxide and hydrogen

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

Taran, Yu.A.; Novak, F.I.; Antoshchuk, I.A.

1981-10-01

Results obtained from studying the catalytic properties of effusive rocks of various chemical compositions, extracted from lava flows of several Kamchatka volcanos, in the process of synthesis from carbon monoxide and hydrogen, are presented. It was evident that samples of volcanic rock display catalytic properties in the process of synthesis from CO and H/sub 2/ in which liquid and gaseous hydrocarbons and an insignificant amount of oxygen-containing compounds are formed as products of the reactions. At a synthesis temperature of 350/sup 0/C the catalytic activity of the samples is characterized by the conversion of CO at a level of 70more » to 80%, and H/sub 2/ at 50 to 60%. The yield of oil, gasoline, and natural gas reached 40, 11, and 3 ml/m/sup 3/, respectively. The light synthetic products were presented based on saturated hydrocarbons of an aliphatic series with significant contents of olefins and insignificant quantities of alcohols and carbonyl compounds. The composition of gaseous products is characterized by significant unsaturation (approx. 33%) and a high content of butane-butylenic fractions (to approx. 55%). The data obtained showed that volcanic rocks were able to catalyze the synthesis of hydrocarbons from CO and H/sub 2/. The sources of the catalytic properties of the rocks shown are evidently iron compounds, and the remaining ingredients of the rocks are able to fulfill the role of structural or chemical promoters influencing the properties of the catalysts and the composition of the reaction products formed. 2 tables. (DP)« less

Test and Delivery of the Chemin Mineralogical Instrument for Mars Science Laboratory

NASA Technical Reports Server (NTRS)

Blake, D. F.; Vaniman, D.; Anderson, R.; Bish, D.; Chipera, S.; Chemtob, S.; Crisp, J.; DesMarais, D. J.; Downs, R.; Feldman, S.;

The Mapping X-Ray Fluorescence Spectrometer (MAPX)

NASA Technical Reports Server (NTRS)

Blake, David; Sarrazin, Philippe; Bristow, Thomas; Downs, Robert; Gailhanou, Marc; Marchis, Franck; Ming, Douglas; Morris, Richard; Sole, Vincente Armando; Thompson, Kathleen;

Source rock contributions to the Lower Cretaceous heavy oil accumulations in Alberta: a basin modeling study

USGS Publications Warehouse

Berbesi, Luiyin Alejandro; di Primio, Rolando; Anka, Zahie; Horsfield, Brian; Higley, Debra K.

2012-01-01

The origin of the immense oil sand deposits in Lower Cretaceous reservoirs of the Western Canada sedimentary basin is still a matter of debate, specifically with respect to the original in-place volumes and contributing source rocks. In this study, the contributions from the main source rocks were addressed using a three-dimensional petroleum system model calibrated to well data. A sensitivity analysis of source rock definition was performed in the case of the two main contributors, which are the Lower Jurassic Gordondale Member of the Fernie Group and the Upper Devonian–Lower Mississippian Exshaw Formation. This sensitivity analysis included variations of assigned total organic carbon and hydrogen index for both source intervals, and in the case of the Exshaw Formation, variations of thickness in areas beneath the Rocky Mountains were also considered. All of the modeled source rocks reached the early or main oil generation stages by 60 Ma, before the onset of the Laramide orogeny. Reconstructed oil accumulations were initially modest because of limited trapping efficiency. This was improved by defining lateral stratigraphic seals within the carrier system. An additional sealing effect by biodegraded oil may have hindered the migration of petroleum in the northern areas, but not to the east of Athabasca. In the latter case, the main trapping controls are dominantly stratigraphic and structural. Our model, based on available data, identifies the Gordondale source rock as the contributor of more than 54% of the oil in the Athabasca and Peace River accumulations, followed by minor amounts from Exshaw (15%) and other Devonian to Lower Jurassic source rocks. The proposed strong contribution of petroleum from the Exshaw Formation source rock to the Athabasca oil sands is only reproduced by assuming 25 m (82 ft) of mature Exshaw in the kitchen areas, with original total organic carbon of 9% or more.

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.

Initiation and Activation of Faults in Dry and Wet Rock by Fluid Injection

NASA Astrophysics Data System (ADS)

Stanchits, S.; Mayr, S.; Shapiro, S. A.; Dresen, G.

2008-12-01

We studied fracturing of rock samples induced by water injection in axial compression tests on cylindrical specimens of Flechtingen sandstone and Aue granite of 50 mm diameter and 105-125 mm length. Samples were intact solid rock cylinders and cylinders with central boreholes of 5 mm diameter and 52 mm length or through-boreholes of 2.5 mm diameter. To monitor acoustic emissions (AE) and ultrasonic velocities, twelve P-wave and six polarized S-wave sensors were glued to the cylindrical surface of the rock. Full waveforms were stored in a 12 channel transient recording system (PROEKEL, Germany). Polarity of AE first motion was used to discriminate source types associated with tensile, shear and pore-collapse cracking. To monitor strain, two pairs of orthogonally oriented strain-gages were glued onto the specimen surface. Samples were deformed in two consecutive loading steps: 1) Initial triaxial loading was performed at 20-50 MPa confining pressure on dry (under vacuum) or fully saturated samples until the yield point was reached. 2) In a second stage distilled water was injected into the samples with pore pressure increasing up to 20 MPa. For saturated samples the pore pressure was increased in steps and in periodic pulses. Injection of water into dry porous sandstone resulted in propagation of an AE hypocenter cloud closely linked to propagation of the water front. Position of the migrating water front was estimated from ultrasonic velocity measurements and measurements of the injected water volume. Propagation rate of AE-induced cloud parallel to bedding was higher than perpendicular to bedding, possibly related to permeability anisotropy. Nucleation of a brittle shear fault occurred at a critical pore pressure level with a nucleation patch located at the central borehole. Micro-structural analysis of fractured samples shows excellent agreement between location of AE hypocenters and macroscopic faults.

Spatial variation of radon and helium in soil gas vis-à-vis geology of area, NW Himalayas, India

NASA Astrophysics Data System (ADS)

Mahajan, S.; Bajwa, B.; Kumar, A.; Singh, S.; Walia, V.; Yang, T. F.

2009-12-01

In an effort to quantify the geological/lithological control on radon, helium soil gas potential and appraise the use of soil gas technique as a geological mapping tool, soil gas measurements were made, in some parts of Himachal Himalayas of NW Himalayan range, using soil gas grab sampling technique. More than 360 soil gas samples were collected from four different geological/lithologic rock units of the area under consideration. The collected soil gas samples were analyzed for radon and helium using RTM-2100 (SARAD) and Helium leak detector (ALCATEL) respectively. The observed values were then correlated with the geology/lithology of the study area. The study area is broadly divided into four different units on the basis of geology/lithology i.e. (A) Upper Shiwaliks (B) Middle & Lower Shiwaliks (C) Lesser Himalayan rocks (D) Higher Himalayan rocks. Significant differences in the soil gas concentrations among the geologic units were observed, where Lesser Himalayan rocks showing maximum concentrations of both radon (254 KBq/m3) and helium (5.46 ppm). Lesser Himalayan zone lies mainly between two major thrusts MBT and MCT running along the Himalayan trend, which still are tectonically active. It can be concluded from the present study that soil gases (radon and helium) can be used as a productive tool for geological mapping. These findings may have very important connation for health risk assessment of the area, since it has been shown that radon soil gas found in soils overlying basement rocks are the main source for indoor radon concentrations. Radioactive isotopes attach rapidly to atmospheric aerosols and can enter into a human body thus constitute significant hazard to human health.

The Kingak shale of northern Alaska-regional variations in organic geochemical properties and petroleum source rock quality

USGS Publications Warehouse

Magoon, L.B.; Claypool, G.E.

1984-01-01

The Kingak Shale, a thick widespread rock unit in northern Alaska that ranges in age from Early Jurassic through Early Cretaceous, has adequate to good oil source rock potential. This lenticular-shaped rock unit is as much as 1200 m thick near the Jurassic shelf edge, where its present-day burial depth is about 5000 m. Kingak sediment, transported in a southerly direction, was deposited on the then marine continental shelf. The rock unit is predominantly dark gray Shale with some interbeds of thick sandstone and siltstone. The thermal maturity of organic matter in the Kingak Shale ranges from immature (2.0%R0) in the Colville basin toward the south. Its organic carbon and hydrogen contents are highest in the eastern part of northern Alaska south of and around the Kuparuk and Prudhoe Bay oil fields. Carbon isotope data of oils and rock extracts indicate that the Kingak Shale is a source of some North Slope oil, but is probably not the major source. ?? 1984.

Timing and petroleum sources for the Lower Cretaceous Mannville Group oil sands of northern Alberta based on 4-D modeling

USGS Publications Warehouse

Higley, D.K.; Lewan, M.D.; Roberts, L.N.R.; Henry, M.

2009-01-01

The Lower Cretaceous Mannville Group oil sands of northern Alberta have an estimated 270.3 billion m3 (BCM) (1700 billion bbl) of in-place heavy oil and tar. Our study area includes oil sand accumulations and downdip areas that partially extend into the deformation zone in western Alberta. The oil sands are composed of highly biodegraded oil and tar, collectively referred to as bitumen, whose source remains controversial. This is addressed in our study with a four-dimensional (4-D) petroleum system model. The modeled primary trap for generated and migrated oil is subtle structures. A probable seal for the oil sands was a gradual updip removal of the lighter hydrocarbon fractions as migrated oil was progressively biodegraded. This is hypothetical because the modeling software did not include seals resulting from the biodegradation of oil. Although the 4-D model shows that source rocks ranging from the Devonian-Mississippian Exshaw Formation to the Lower Cretaceous Mannville Group coals and Ostracode-zone-contributed oil to Mannville Group reservoirs, source rocks in the Jurassic Fernie Group (Gordondale Member and Poker Chip A shale) were the initial and major contributors. Kinetics associated with the type IIS kerogen in Fernie Group source rocks resulted in the early generation and expulsion of oil, as early as 85 Ma and prior to the generation from the type II kerogen of deeper and older source rocks. The modeled 50% peak transformation to oil was reached about 75 Ma for the Gordondale Member and Poker Chip A shale near the west margin of the study area, and prior to onset about 65 Ma from other source rocks. This early petroleum generation from the Fernie Group source rocks resulted in large volumes of generated oil, and prior to the Laramide uplift and onset of erosion (???58 Ma), which curtailed oil generation from all source rocks. Oil generation from all source rocks ended by 40 Ma. Although the modeled study area did not include possible western contributions of generated oil to the oil sands, the amount generated by the Jurassic source rocks within the study area was 475 BCM (2990 billion bbl). Copyright ?? 2009. The American Association of Petroleum Geologists. All rights reserved.

Multi-criteria correlation of tephra deposits to source centres applied in the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Hopkins, Jenni L.; Wilson, Colin J. N.; Millet, Marc-Alban; Leonard, Graham S.; Timm, Christian; McGee, Lucy E.; Smith, Ian E. M.; Smith, Euan G. C.

2017-07-01

Linking tephras back to their source centre(s) in volcanic fields is crucial not only to reconstruct the eruptive history of the volcanic field but also to understand tephra dispersal patterns and thus the potential hazards posed by a future eruption. Here we present a multi-disciplinary approach to correlate distal basaltic tephra deposits from the Auckland Volcanic Field (AVF) to their source centres using proximal whole-rock geochemical signatures. In order to achieve these correlations, major and trace element tephra-derived glass compositions are compared with published and newly obtained whole-rock geochemical data for the entire field. The results show that incompatible trace element ratios (e.g. (Gd/Yb)N, (La/Yb)N, (Zr/Yb)N) vary widely across the AVF (e.g. (La/Yb)N = 5 to 40) but show a more restricted range within samples from a single volcanic centre (e.g. (La/Yb)N = 5 to 10). These ratios are also the least affected by fractional crystallisation and are therefore the most appropriate geochemical tools for correlation between tephra and whole-rock samples. However, findings for the AVF suggest that each volcanic centre does not have a unique geochemical signature in the field as a whole, thus preventing unambiguous correlation of tephras to source centre using geochemistry alone. A number of additional criteria are therefore combined to further constrain the source centres of the distal tephras including age, eruption scale, and location (of centres, and sites where tephra were sampled). The combination of tephrostratigraphy, 40Ar/39Ar dating and morphostratigraphic constraints allow, for the first time, the relative and absolute ordering of 48 of 53 volcanic centres of the Auckland Volcanic Field to be resolved. Eruption frequencies are shown to vary between 0.13 and 1.5 eruptions/kyr and repose periods between individual eruptions vary from <0.1 to 13 kyr, with 23 of the 48 centres shown to have pre-eruptive repose periods of <1000 years. No spatial evolutionary trends are noted, although a relationship between short repose periods and closely spaced eruption locations is identified for a number of centres. In addition, no temporal-geochemical trends are noted, but a relationship between geochemical signature and eruption volume is highlighted.

Detailed Aggregate Resources Study, Dry Lake Valley, Nevada.

DTIC Science & Technology

1981-05-29

LOCAL SAND SOURCES IGENERALLY CYLINDERS. DRYING SHRINKAGE I COLLECTED WITHIN A FEW MILES OF CORRESPONDING LEDGE-ROCK SOURCES) SUPPLIED FINE MENS...COMPRESSIVE AND TENSILE STh LEDGE-ROCK SOURCES SUPPLIED COARSE AGGREGATES; LOCAL SAND SOURCES IGENERALLY CYLINDERS. DRYING SHRINKAGE COLLECTED WITHIN A FEW

Effect of ultramafic intrusions and associated mineralized rocks on the aqueous geochemistry of the Tangle Lakes Area, Alaska: Chapter C in Studies by the U.S. Geological Survey in Alaska, 2011

USGS Publications Warehouse

Wang, Bronwen; Gough, Larry P.; Wanty, Richard B.; Lee, Gregory K.; Vohden, James; O’Neill, J. Michael; Kerin, L. Jack

2013-01-01

Stream water was collected at 30 sites within the Tangle Lakes area of the Delta mineral belt in Alaska. Sampling focused on streams near the ultramafic rocks of the Fish Lake intrusive complex south of Eureka Creek and the Tangle Complex area east of Fourteen Mile Lake, as well as on those within the deformed metasedimentary, metavolcanic, and intrusive rocks of the Specimen Creek drainage and drainages east of Eureka Glacier. Major, minor, and trace elements were analyzed in aqueous samples for this reconnaissance aqueous geochemistry effort. The lithologic differences within the study area are reflected in the major-ion chemistry of the water. The dominant major cation in streams draining mafic and ultramafic rocks is Mg2+; abundant Mg and low Ca in these streams reflect the abundance of Mg-rich minerals in these intrusions. Nickel and Cu are detected in 84 percent and 87 percent of the filtered samples, respectively. Nickel and Cu concentrations ranged from Ni <0.4 to 10.1 micrograms per liter (mg/L), with a median of 4.2 mg/L, and Cu <0.5 to 27 mg/L, with a median of 1.2 mg/L. Trace-element concentrations in water are generally low relative to U.S. Environmental Protection Agency freshwater aquatic-life criteria; however, Cu concentrations exceed the hardness-based criteria for both chronic and acute exposure at some sites. The entire rare earth element (REE) suite is found in samples from the Specimen Creek sites MH5, MH4, and MH6 and, with the exception of Tb and Tm, at site MH14. These samples were all collected within drainages containing or downstream from Tertiary gabbro, diabase, and metagabbro (Trgb) exposures. Chondrite and source rock fractionation profiles for the aqueous samples were light rare earth element depleted, with negative Ce and Eu anomalies, indicating fractionation of the REE during weathering. Fractionation patterns indicate that the REE are primarily in the dissolved, as opposed to colloidal, phase.

A field instrument for quantitative determination of beryllium by activation analysis

USGS Publications Warehouse

Vaughn, William W.; Wilson, E.E.; Ohm, J.M.

1960-01-01

A low-cost instrument has been developed for quantitative determinations of beryllium in the field by activation analysis. The instrument makes use of the gamma-neutron reaction between gammas emitted by an artificially radioactive source (Sb124) and beryllium as it occurs in nature. The instrument and power source are mounted in a panel-type vehicle. Samples are prepared by hand-crushing the rock to approximately ?-inch mesh size and smaller. Sample volumes are kept constant by means of a standard measuring cup. Instrument calibration, made by using standards of known BeO content, indicates the analyses are reproducible and accurate to within ? 0.25 percent BeO in the range from 1 to 20 percent BeO with a sample counting time of 5 minutes. Sensitivity of the instrument maybe increased somewhat by increasing the source size, the sample size, or by enlarging the cross-sectional area of the neutron-sensitive phosphor normal to the neutron flux.

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).

Contrasting sources of Late Paleozoic rhyolite magma in the Polish Lowlands: evidence from U-Pb ages and Hf and O isotope composition in zircon

NASA Astrophysics Data System (ADS)

Słodczyk, Elżbieta; Pietranik, Anna; Glynn, Sarah; Wiedenbeck, Michael; Breitkreuz, Christoph; Dhuime, Bruno

2018-02-01

The Polish Lowlands, located southwest of the Teisseyre-Tornquist Zone, within Trans-European Suture Zone, were affected by bimodal, but dominantly rhyolitic, magmatism during the Late Paleozoic. Thanks to the inherited zircon they contain, these rhyolitic rocks provide a direct source of information about the pre-Permian rocks underlying the Polish Lowland. This paper presents zircon U-Pb geochronology and Hf and O isotopic results from five drill core samples representing four rhyolites and one granite. Based on the ratio of inherited vs. autocrystic zircon, the rhyolites can be divided into two groups: northern rhyolites, where autocrystic zircon is more abundant and southern rhyolites, where inherited zircon dominates. We suggest that the magma sources and the processes responsible for generating high silica magmas differ between the northern and southern rhyolites. Isotopically distinct sources were available during formation of northern rhyolites, as the Hf and O isotopes in magmatic zircon differ between the two analysed localities of northern rhyolites. A mixing between magmas formed from Baltica-derived mudstone-siltstone sediments and Avalonian basement or mantle can explain the diversity between the zircon compositions from the northern localities Daszewo and Wysoka Kamieńska. Conversely, the southern rhyolites from our two localities contain zircon with similar compositions, and these units can be further correlated with results from the North East German Basin, suggesting uniform source rocks over this larger region. Based on the ages of inherited zircon and the isotopic composition of magmatic ones, we suggest that the dominant source of the southern rhyolites is Variscan foreland sediments mixed with Baltica/Avalonia-derived sediments.

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.

Sources Sought for Innovative Scientific Instrumentation for Scientific Lunar Rovers

NASA Technical Reports Server (NTRS)

Meyer, C.

1993-01-01

Lunar rovers should be designed as integrated scientific measurement systems that address scientific goals as their main objective. Scientific goals for lunar rovers are presented. Teleoperated robotic field geologists will allow the science team to make discoveries using a wide range of sensory data collected by electronic 'eyes' and sophisticated scientific instrumentation. rovers need to operate in geologically interesting terrain (rock outcrops) and to identify and closely examine interesting rock samples. Enough flight-ready instruments are available to fly on the first mission, but additional instrument development based on emerging technology is desirable. Various instruments that need to be developed for later missions are described.

Three-dimensional seismic tomography from P wave and S wave microearthquake travel times and rock physics characterization of the Campi Flegrei Caldera

NASA Astrophysics Data System (ADS)

Vanorio, T.; Virieux, J.; Capuano, P.; Russo, G.

2005-03-01

The Campi Flegrei (CF) Caldera experiences dramatic ground deformations unsurpassed anywhere in the world. The source responsible for this phenomenon is still debated. With the aim of exploring the structure of the caldera as well as the role of hydrothermal fluids on velocity changes, a multidisciplinary approach dealing with three-dimensional delay time tomography and rock physics characterization has been followed. Selected seismic data were modeled by using a tomographic method based on an accurate finite difference travel time computation which simultaneously inverts P wave and S wave first-arrival times for both velocity model parameters and hypocenter locations. The retrieved P wave and S wave velocity images as well as the deduced Vp/Vs images were interpreted by using experimental measurements of rock physical properties on CF samples to take into account steam/water phase transition mechanisms affecting P wave and S wave velocities. Also, modeling of petrophysical properties for site-relevant rocks constrains the role of overpressured fluids on velocity. A flat and low Vp/Vs anomaly lies at 4 km depth under the city of Pozzuoli. Earthquakes are located at the top of this anomaly. This anomaly implies the presence of fractured overpressured gas-bearing formations and excludes the presence of melted rocks. At shallow depth, a high Vp/Vs anomaly located at 1 km suggests the presence of rocks containing fluids in the liquid phase. Finally, maps of the Vp*Vs product show a high Vp*Vs horseshoe-shaped anomaly located at 2 km depth. It is consistent with gravity data and well data and might constitute the on-land remainder of the caldera rim, detected below sea level by tomography using active source seismic data.

Characterization and provenance of the building stones from Pompeii's archaeological site (southern Italy)

NASA Astrophysics Data System (ADS)

Balassone, G.; Kastenmeier, P.; di Maio, G.; Mormone, A.; Joachimski, M.

2009-04-01

Pompeii is one of the most famous and complex areas of archaeological investigation in the world and with a uniquely favorable state of preservation. Even if many studies have been devoted in time to many archaeological aspects of this ancient city, large-scale and detailed studies aimed at characterizing mineralogy, petrography and isotope geochemistry of the building stones are still lacking. The scope of the present research is to fill this gap, pointing to the definition of the provenance of the stony materials used for ancient constructions of the city of Pompeii and to the possible trade routes. This work is part of a large-scale survey carried out by the Deutsches Archäologisches Institut of Berlin, with the purposes of reconstructing the sources of raw materials of various archaeological sites of the Sarno Plain (e.g. Longola-Poggiomarino settlement, Nuceria, Stabiae, etc.) and consequently also the paleo-environments of this area during the Olocene (Seiler, 2006, 2008; Kastemeier and Seiler, 2007). We sampled all the litotypes with different macroscopic characteristics from various buildings according to location, age (time span VI century B.C. - I century A.D.) and utilization; the architectural buildings considered for this study are mainly represented public and religious buildings, houses and funerary monuments. As possible source areas, representative litotypes have been sampled from ancient pits and outcrops surrounding Pompeii as well. A set of 80 samples have been sampled by means of micro-drillings for mineralogical, petrographic and geochemical analyses, comprising optical microscopy, X-ray diffraction, inductively coupled plasma mass, X-ray fluorescence and C-O isotope geochemistry. Minero-petrographic and XRD studies of Pompeii rock samples have shown that at least ten different litologies occur as building stones, belonging to basaltic to tephritic lavas, pyroclasts (tuffs, scoriae, etc.) and sedimentary rocks (limestone, travertines). Preliminary results on source localities indicate a local provenance for a set of volcanic rock samples, whereas the possible source areas of the sedimentary litotypes seem to be more complex. New minero-petrographic data of samples from surrounding outcrops are presented and compared to the related Pompeii building stones. References Seiler F. (2006) - Current research projects. In: Aktuelle Forchungsprojeckte, Deutsches Archäologisches Institut Zentrale, 34-35. Seiler F. (2008) - Rekonstruktion der antiken Kulturlandschaften des Sarno-Beckens. Ein multidisziplinäres Kooperationsprojekt mit Partnern aus Naturwissenschaften und Altertumswissenschaften in Deutschland, Italien und England. In: P. G. Guzzo - M. P. Guidobaldi (Eds), Nuove ricerche archeologiche nell'area vesuviana (scavi 2003-2006). Convegno Internazionale, Roma 1-3 febbraio, 485-490. Kastenmeier P., Seiler F. (2007) - La ricostruzione dei paleo-paesaggi nella piana del Sarno. Quaderni Autorità di Bacino del Sarno. Studi, documentazione e ricerca, 1, 24-26.

Development of a Neutron Diffraction Based Experiemental Capability for Investigating Hydraulic Fracturing for EGS-like Conditions

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

Polsky, Yarom; Anovitz, Lawrence; An, Ke

2013-01-01

Hydraulic fracturing to enhance formation permeability is an established practice in the Oil & Gas (O&G) industry and is expected to be an enabler for EGS. However, it is rarely employed in conventional geothermal systems and there are significant questions regarding the translation of practice from O&G to both conventional geothermal and EGS applications. Lithological differences(sedimentary versus crystalline rocks, significantly greater formation temperatures and different desired fracture characteristics are among a number of factors that are likely to result in a gap of understanding of how to manage hydraulic fracturing practice for geothermal. Whereas the O&G community has had bothmore » the capital and the opportunity to develop its understanding of hydraulic fracturing operations empirically in the field as well through extensive R&D efforts, field testing opportunities for EGS are likely to be minimal due to the high expense of hydraulic fracturing field trials. A significant portion of the knowledge needed to guide the management of geothermal/EGS hydraulic fracturing operations will therefore likely have to come from experimental efforts and simulation. This paper describes ongoing efforts at Oak Ridge National Laboratory (ORNL) to develop an experimental capability to map the internal stresses/strains in core samples subjected to triaxial stress states and temperatures representative of EGS-like conditions using neutron diffraction based strain mapping techniques. This capability is being developed at ORNL\\'s Spallation Neutron Source, the world\\'s most powerful pulsed neutron source and is still in a proof of concept phase. A specialized pressure cell has been developed that permits independent radial and axial fluid pressurization of core samples, with axial flow through capability and a temperature rating up to 300 degrees C. This cell will ultimately be used to hydraulically pressurize EGS-representative core samples to conditions of imminent fracture and map the associated internal strain states of the sample. This will hopefully enable a more precise mapping of the rock material failure envelope, facilitate a more refined understanding of the mechanism of hydraulically induced rock fracture, particularly in crystalline rocks, and serve as a platform for validating and improving fracture simulation codes. The elements of the research program and preliminary strain mapping results of a Sierra White granite sample subjected only to compressive loading will be discussed in this paper.« less

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.

Origin and modal petrography of Luna 24 soils

NASA Technical Reports Server (NTRS)

Basu, A.; Mckay, D. S.; Fruland, R. M.

1978-01-01

Petrographic modal analyses of polished grain mounts of fractions in the 20 to 250 micron size range from Luna 24 soil samples are presented and used to infer the nature and relative contributions of source rocks. It is found that more than 90% of the identifiable rock fragments are mare basalts, with about 11% of the soil consisting of the crystalline form. Soil breccias, which make up nearly 10% of the soil, are found to be immature. Electron probe analysis of glass particles reveals principle clusters conforming to anorthosite, anorthositic gabbro and mare basalts. More than half of the soil is composed of monomineralic particles, with pyroxene as the most abundant mineral. It is concluded that 85% of the regolith is derived from local mare basalts and gabbros and about 10% is derived from early cumulates of local mare basalt magma. Highland sources are considered to contribute not more than 3% of the regolith.

Clastic metasediments of the Early Proterozoic Broken Hill Group, New South Wales, Australia: Geochemistry, provenance, and metallogenic significance

USGS Publications Warehouse

Slack, J.F.; Stevens, B.P.J.

1994-01-01

Whole-rock analyses of samples of pelite, psammite, and psammopelite from the Early Proterozoic Broken Hill Group (Willyama Supergroup) in the Broken Hill Block, New South Wales, Australia, reveal distinctive geochemical signatures. Major-element data show high Al2O3 and K2O, low MgO and Na2O, and relatively high Fe2O3T MgO ratios, compared to average Early Proterozoic clastic metasediments. High field strength elements (HFSE) are especially abundant, including Nb (most 15-27 ppm), Ta (most 1.0-2.2 ppm), Th (17-36 ppm), Hf (4-15 ppm), and Zr (most 170-400 ppm); Y (33-74 ppm) is also high. Concentrations of ferromagnesian elements are generally low (Sc = < 20 ppm, Ni = ??? 62 ppm, Co = <26 ppm; Cr = most < 100 ppm). Data for rare earth elements (REEs) show high abundances of light REEs (LaCN = 116-250 ?? chondrite; LaCN = 437 in one sample), high LaCN YbCN ratios (5.6-13.9), and large negative Eu anomalies ( Eu Eu* = 0.32-0.57). The geochemical data indicate derivation of the metasedimentary rocks of the Broken Hill Group by the erosion mainly of felsic igneous (or meta-igneous) rocks. High concentrations of HFSE, Y, and REEs in the metasediments suggest a provenance dominanted by anorogenic granites and(or) rhyolites, including those with A-type chemistry. Likely sources of the metasediments were the rhyolitic to rhyodacitic protoliths of local quartz + feldspar ?? biotite ?? garnet gneisses (e.g., Potosi-type gneiss) that occur within the lower part of the Willyama Supergroup, or chemically similar basement rocks in the region; alternative sources may have included Early Proterozoic anorogenic granites and(or) rhyolites in the Mount Isa and(or) Pine Creek Blocks of northern Australia, or in the Gawler craton of South Australia. Metallogenic considerations suggest that the metasediments of the Broken Hill Block formed enriched source rocks during the generation of pegmatite-hosted deposits and concentrations of La, Ce, Nb, Ta, Th, and Sn in the region. Li, Be, B, W, and U in pegmatite minerals of the district may have been acquired during granulite-facies metamorphism of the local metasediments. ?? 1994.

Pb-isotopic systematics of lunar highland rocks (>3.9 Ga): Constraints on early lunar evolution

USGS Publications Warehouse

Premo, W.R.; Tatsumoto, M.; Misawa, K.; Nakamuka, N.; Kita, N.I.

1999-01-01

The present lead (Pb)-isotopic database of over 200 analyses from nearly 90 samples of non-mare basalt, lunar highland rocks (>3.9 Ga) delineate at least three isotopically distinct signatures that in some combination can be interpreted to characterize the systematics of the entire database. Two are fairly new sets of lunar data and are typical of Pb data from other solar-system objects, describing nearly linear arrays slightly above the 'geochron' values, with 207Pb/206Pb values 500). Although the age and origin of this exotic Pb is not well constrained, it is interpreted to be related to the entrapment of incompatible-element-rich (U, Th) melts within the lunar upper mantle and crust between 4.36 and 4.46 Ga (urKREEP residuum?). The latest discovered Pb signature is found only in lunar meteorites and is characterized by relatively low source ?? values between 10 and 50 at 3.9 Ga. The fact that most lunar crustal rocks (>3.9 Ga) exhibit high 207Pb/206Pb values requires that they were derived from, mixed with, or contaminated by Pb produced from early-formed, high-?? sources. The ubiquity of these U-Pb characteristics in the sample collection is probably an artifact of Apollo and Luna sampling sites, all located on the near side of the Moon, which was deeply excavated during the basin-forming event(s). However, the newest Pb-isotopic data support the idea that the Moon originally had a ?? value of ~8 to 35, slightly elevated from Earth values, and that progressive U-Pb fractionations occurred within the Moon during later stages of differentiation between 4.36 and 4.46 Ga.

Split Hopkinson resonant bar test for sonic-frequency acoustic velocity and attenuation measurements of small, isotropic geological samples.

PubMed

Nakagawa, Seiji

2011-04-01

Mechanical properties (seismic velocities and attenuation) of geological materials are often frequency dependent, which necessitates measurements of the properties at frequencies relevant to a problem at hand. Conventional acoustic resonant bar tests allow measuring seismic properties of rocks and sediments at sonic frequencies (several kilohertz) that are close to the frequencies employed for geophysical exploration of oil and gas resources. However, the tests require a long, slender sample, which is often difficult to obtain from the deep subsurface or from weak and fractured geological formations. In this paper, an alternative measurement technique to conventional resonant bar tests is presented. This technique uses only a small, jacketed rock or sediment core sample mediating a pair of long, metal extension bars with attached seismic source and receiver-the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the length and mass added to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The experiment can be conducted under elevated confining pressures up to tens of MPa and temperatures above 100 [ordinal indicator, masculine]C, and concurrently with x-ray CT imaging. The described split Hopkinson resonant bar test is applied in two steps. First, extension and torsion-mode resonance frequencies and attenuation of the entire system are measured. Next, numerical inversions for the complex Young's and shear moduli of the sample are performed. One particularly important step is the correction of the inverted Young's moduli for the effect of sample-rod interfaces. Examples of the application are given for homogeneous, isotropic polymer samples, and a natural rock sample. © 2011 American Institute of Physics

Quantification of metal loads by tracer injection and synoptic sampling in Daisy Creek and the Stillwater River, Park County, Montana, August 1999

USGS Publications Warehouse

Nimick, David A.; Cleasby, Thomas E.

2001-01-01

A metal-loading study using tracer-injection and synoptic-sampling methods was conducted in Daisy Creek and a short reach of the Stillwater River during baseflow in August 1999 to quantify the metal inputs from acid rock drainage in the New World Mining District near Yellowstone National Park and to examine the downstream transport of these metals into the Stillwater River. Loads were calculated for many mainstem and inflow sites by combining streamflow determined using the tracer-injection method with concentrations of major ions and metals that were determined in synoptic water-quality samples. Water quality and aquatic habitat in Daisy Creek have been affected adversely by drainage derived from waste rock and adit discharge at the McLaren Mine as well as from natural weathering of pyrite-rich mineralized rock that comprises and surrounds the ore zones. However, the specific sources and transport pathways are not well understood. Knowledge of the main sources and transport pathways of metals and acid can aid resource managers in planning and conducting effective and cost-efficient remediation activities. The metals cadmium, copper, lead, and zinc occur at concentrations that are sufficiently elevated to be potentially lethal to aquatic life in Daisy Creek and to pose a toxicity risk in part of the Stillwater River. Copper is of most concern in Daisy Creek because it occurs at higher concentrations than the other metals. Acidic surface inflows had dissolved concentrations as high as 20.6 micrograms per liter (?g/L) cadmium, 26,900 ?g/L copper, 76.4 ?g/L lead, and 3,000 ?g/L zinc. These inflows resulted in maximum dissolved concentrations in Daisy Creek of 5.8 ?g/L cadmium, 5,790 ?g/L copper, 3.8 ?g/L lead, and 848 ?g/L zinc. Significant copper loading to Daisy Creek occurred only in the upper half of the stream. Sources included subsurface inflow and right-bank (mined side) surface inflows. Copper loads in left-bank (unmined side) surface inflows were negligible. Most (71 percent) of the total copper loading in the study reach occurred along a 341-foot reach near the stream?s headwaters. About 53 percent of the total copper load was contributed by five surface inflows that drain a manganese bog and the southern part of the McLaren Mine. Copper loading from subsurface inflow was substantial, contributing 46 percent of the total dissolved copper load to Daisy Creek. More than half of this subsurface copper loading occurred downstream from the reaches that received significant surface loading. Flow through the shallow subsurface appears to be the main copper-transport pathway from the McLaren Mine and surrounding altered and mineralized bedrock to Daisy Creek during base-flow conditions. Little is known about the source of acid and copper in this subsurface flow. However, possible sources include the mineralized rocks of Fisher Mountain upgradient of the McLaren Mine area, the surficial waste rock at the mine, and the underlying pyritic bedrock.

Detrital rutile geochemistry and thermometry from the Dabie orogen: Implications for source-sediment links in a UHPM terrane

NASA Astrophysics Data System (ADS)

Liu, Lei; Xiao, Yilin; Wörner, G.; Kronz, A.; Simon, K.; Hou, Zhenhui

2014-08-01

This study explores the potential of detrital rutile geochemistry and thermometry as a provenance tracer in rocks from the Central Dabie ultrahigh-pressure metamorphic (UHPM) zone in east-central China that formed during Triassic continental collision. Trace element data of 176 detrital rutile grains selected from local river sediments and 91 rutile grains from distinct bedrocks in the Shuanghe and Bixiling areas, obtained by both electron microprobe (EMP) and in situ LA-ICP-MS analyses, suggest that geochemical compositions and thermometry of detrital rutiles are comparable to those from their potential source rocks. After certification of the Cr-Nb discrimination method for the Central Dabie UHPM zone, we show that 29% of the detrital rutiles in the Shuanghe area were derived from metamafic sources whereas in the Bixiling area that it is up to 76%. Furthermore, the proportion of distinct types of detrital rutiles combined with modal abundances of rutile in metapelites and metamafic bedrocks can be used to estimate the proportion of different source lithologies. Based on this method the proportion of mafic source rocks was estimated to ∼10% at Shuanghe and >60% at Bixiling, respectively, which is consistent with the proportions of eclogite (the major rutile-bearing metamafic rock) distribution in the field. Therefore, the investigation of detrital rutiles is a potential way to evaluate the proportion of metamafic rocks and even to prospect for metamafic bodies in UHPM terranes. Zr-in-rutile temperatures were calculated at different pressures and compared with temperatures derived from rock-in rutiles and garnet-clinopyroxene Fe-Mg thermometers. Temperatures calculated for detrital rutiles range from 606 °C to 707 °C and 566 °C to 752 °C in Shuanghe and Bixiling, respectively, at P = 3 GPa with an average temperatures of ca. 630 °C for both areas. These temperature averages and ranges are similar to those calculated for rutiles from surrounding source rocks. Combined with comparable Zr distribution characteristics between detrital and source rock rutiles, demonstrating a close source-sediment link for rutiles from clastic and rock in UHPM terranes. Thus rutiles can be accurate tracers of source rock lithologies in sedimentary provenance studies even at a small regional scale. In Bixiling, Nb/Ta ratios of metamafic and metapelitic detrital rutiles fall between 11.0 to 27.3 and 7.7 to 20.5, respectively. In contrast, in Shuanghe, these ratios are highly variable, ranging from 10.9 to 71.0 and 7.6 to 87.1, respectively. When ignoring four outlier compositions with extremely high Nb/Ta in Shuanghe, a distinct clustering of Nb/Ta ratios in rutiles is shown: metapelitic detrital rutiles have Nb/Ta of 7-40 vs. metamafic detrital rutiles with Nb/Ta = 11-25. The Nb/Ta characteristics in detrital rutiles from both areas may reflect the degree of fluid-rock interaction during metamorphism and/or different source lithologies. Therefore, the trace element compositions in detrital rutiles can accurately trace the lithology, proportion and fluid-rock interaction of different source rocks.

Did the Kiruna iron ores form as a result of a metasomatic or igneous process? New U-Pb and Nd data for the iron oxide apatite ores and their host rocks in the Norrbotten region of northern Sweden

NASA Astrophysics Data System (ADS)

Westhues, A.; Hanchar, J. M.; Whitehouse, M. J.; Fisher, C. M.

2012-12-01

A number of iron deposits near Kiruna in the Norrbotten region of northern Sweden are of the iron oxide apatite (IOA) type of deposits; also referred to as Kiruna-type deposits. They are commonly considered a subgroup or end-member of iron oxide copper gold (IOCG) deposits, containing no economic grades of copper or gold. Both IOCG and IOA deposits are characterized by abundant low-Ti Fe oxides, an enrichment in REE, and intense sodium and potassium wall-rock alteration adjacent to the ores. Deposits of these types are of a great economic importance, not only for iron, but also for other elements such as rare earth elements (REE) or uranium. Kiruna, the type locality of the IOA type of mineral deposits, is the focus of this study. Despite a century-long mining history and 2500 Mt of iron ore produced in the region to date (with grades of 30 to 70 wt.% Fe), the genesis of these deposits is poorly understood: theories of a magmatic vs. a hydrothermal or metasomatic origin have been debated, and the timing of mineralization of the ores in the Norbotten region has never been directly dated. The results anticipated from this study will provide a better understanding of the nature of the IOA type of mineral deposits and their relation to IOCG deposits such as Olympic Dam in Australia. An array of geochemical methods is used in order to gain insights on the emplacement history of the host rocks, their subsequent alteration, and the ore genesis of these deposits. This includes in situ U/Pb geochronology of zircon, monazite, and titanite to constrain the timing between host rock emplacement, alteration and mineralization. Isotopic data from whole rocks and in situ at mineral scale will provide constraints on the involvement of hydrothermal fluids and their possible sources, as well as on the sources of Fe, U, and the REE. Newly obtained Sm-Nd isotopic data points to distinct source differences between host rocks, ore and alteration related samples. Preliminary in situ U-Pb dating of zircon from both host rock and ore samples confirms a previously documented event around 1880 - 1900 Ma in the Norrbotten region. However, U-Pb in monazite from an ore sample suggests a further event at ca. 1650 Ma, a period of known activity in Fennoscandia. Further investigation and more U-Pb data are needed to confirm those dates and how the iron mineralization is related to those two events. The combination of U-Th-Pb ages, tracer isotopes and trace element abundances at mineral scale (e.g., Lu-Hf in zircon, and Sm-Nd in monazite, apatite, titanite), along with the O isotopic composition of zircon, will be used to decipher whether the Kiruna iron ore deposits are of metasomatic or igneous origin. Overall, the study also intends to develop a predictive model for exploration of similar iron oxide apatite deposits worldwide.

Molecular marker and stable carbon isotope analyses of carbonaceous Ambassador uranium ores of Mulga Rock in Western Australia

NASA Astrophysics Data System (ADS)

Jaraula, C.; Schwark, L.; Moreau, X.; Grice, K.; Bagas, L.

2013-12-01

Mulga Rock is a multi-element deposit containing uranium hosted by Eocene peats and lignites deposited in inset valleys incised into Permian rocks of the Gunbarrel Basin and Precambrian rocks of the Yilgarn Craton and Albany-Fraser Orogen. Uranium readily adsorbs onto minerals or phytoclasts to form organo-uranyl complexes. This is important in pre-concentrating uranium in this relatively young ore deposit with rare uraninite [UO2] and coffinite [U(SiO4)1-x(OH)4x], more commonly amorphous and sub-micron uranium-bearing particulates. Organic geochemical and compound-specific stable carbon isotope analyses were conducted to identify possible associations of molecular markers with uranium accumulation and to recognize effect(s) of ionizing radiation on molecular markers. Samples were collected from the Ambassador deposit containing low (<200 ppm) to high (>2000 ppm) uranium concentrations. The bulk rock C/N ratios of 82 to 153, Rock-Eval pyrolysis yields of 316 to 577 mg hydrocarbon/g TOC (Hydrogen Index, HI) and 70 to 102 mg CO2/g TOC (Oxygen Index, OI) are consistent with a terrigenous and predominantly vascular plant OM source deposited in a complex shallow water system, ranging from lacustrine to deltaic, swampy wetland and even shallow lake settings as proposed by previous workers. Organic solvent extracts were separated into saturated hydrocarbon, aromatic hydrocarbon, ketone, and a combined free fatty acid and alcohol fraction. The molecular profiles appear to vary with uranium concentration. In samples with relatively low uranium concentrations, long-chain n-alkanes, alcohols and fatty acids derived from epicuticular plant waxes dominate. The n-alkane distributions (C27 to C31) reveal an odd/even preference (Carbon Preference Index, CPI=1.5) indicative of extant lipids. Average δ13C of -27 to -29 ‰ for long-chain n-alkanes is consistent with a predominant C3 plant source. Samples with relatively higher uranium concentrations contain mostly intermediate-length n-alkanes, ketones, alcohols, and fatty acids (C20 to C24) with no preferential distribution (CPI~1). Intermediate length n-alkanes have modest carbon isotope enrichment compared to long-chain n-alkanes. These shorter-chain hydrocarbons are interpreted to represent alteration products. The diversity and relative abundance of ketones in highly mineralised Mulga Rock peats and lignites are not consistent with aerobic and diagenetic degradation of terrigenous OM in oxic environments. Moreover, molecular changes cannot be associated with thermal breakdown due to the low maturity of the deposits. It is possible that the association of high uranium concentrations and potential radiolysis resulted in the oxidation of alcohol functional groups into aldehydes and ketones and breakdown of highly aliphatic macromolecules (i.e. spores, pollen, cuticles, and algal cysts). These phytoclasts are usually considered to be recalcitrant as they evolved to withstand chemical and physical degradation. Previous petrographic analyses show that spores, pollen and wood fragments are preferentially enriched in uranium. Their molecular compositions are feasible sources of short- to intermediate-length n-alkanes that dominate the mineralised peats and lignites.

A comparison of the rates of hydrocarbon generation from Lodgepole, False Bakken, and Bakken formation petroleum source rocks, Williston Basin, USA

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

Jarvie, D.M.; Elsinger, R.J.; Inden, R.F.

1996-06-01

Recent successes in the Lodgepole Waulsortian Mound play have resulted in the reevaluation of the Williston Basin petroleum systems. It has been postulated that hydrocarbons were generated from organic-rich Bakken Formation source rocks in the Williston Basin. However, Canadian geoscientists have indicated that the Lodgepole Formation is responsible for oil entrapped in Lodgepole Formation and other Madison traps in portions of the Canadian Williston Basin. Furthermore, geoscientists in the U.S. have recently shown oils from mid-Madison conventional reservoirs in the U.S. Williston Basin were not derived from Bakken Formation source rocks. Kinetic data showing the rate of hydrocarbon formation frommore » petroleum source rocks were measured on source rocks from the Lodgepole, False Bakken, and Bakken Formations. These results show a wide range of values in the rate of hydrocarbon generation. Oil prone facies within the Lodgepole Formation tend to generate hydrocarbons earlier than the oil prone facies in the Bakken Formation and mixed oil/gas prone and gas prone facies in the Lodgepole Formation. A comparison of these source rocks using a geological model of hydrocarbon generation reveals differences in the timing of generation and the required level of maturity to generate significant amounts of hydrocarbons.« less

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.

Tracing groundwater with low-level detections of halogenated VOCs in a fractured carbonate-rock aquifer, Leetown Science Center, West Virginia, USA

USGS Publications Warehouse

Plummer, Niel; Sibrell, Philip L.; Casile, Gerolamo C.; Busenberg, Eurybiades; Hunt, Andrew G.; Schlosser, Peter

2013-01-01

Measurements of low-level concentrations of halogenated volatile organic compounds (VOCs) and estimates of groundwater age interpreted from 3H/3He and SF6 data have led to an improved understanding of groundwater flow, water sources, and transit times in a karstic, fractured, carbonate-rock aquifer at the Leetown Science Center (LSC), West Virginia. The sum of the concentrations of a set of 16 predominant halogenated VOCs (TDVOC) determined by gas chromatography with electron-capture detector (GC–ECD) exceeded that possible for air–water equilibrium in 34 of the 47 samples (median TDVOC of 24,800 pg kg−1), indicating that nearly all the water sampled in the vicinity of the LSC has been affected by addition of halogenated VOCs from non-atmospheric source(s). Leakage from a landfill that was closed and sealed nearly 20 a prior to sampling was recognized and traced to areas east of the LSC using low-level detection of tetrachloroethene (PCE), methyl chloride (MeCl), methyl chloroform (MC), dichlorodifluoromethane (CFC-12), and cis-1,2-dichloroethene (cis-1,2-DCE). Chloroform (CHLF) was the predominant VOC in water from domestic wells surrounding the LSC, and was elevated in groundwater in and near the Fish Health Laboratory at the LSC, where a leak of chlorinated water occurred prior to 2006. The low-level concentrations of halogenated VOCs did not exceed human or aquatic-life health criteria, and were useful in providing an awareness of the intrinsic susceptibility of the fractured karstic groundwater system at the LSC to non-atmospheric anthropogenic inputs. The 3H/3He groundwater ages of spring discharge from the carbonate rocks showed transient behavior, with ages averaging about 2 a in 2004 following a wet climatic period (2003–2004), and ages in the range of 4–7 a in periods of more average precipitation (2008–2009). The SF6 and CFC-12 data indicate older water (model ages of 10s of years or more) in the low-permeability shale of the Martinsburg Formation located to the west of the LSC. A two-a record of specific conductance, water temperature, and discharge recorded at 30-min intervals demonstrated an approximately 3-month lag in discharge at Gray Spring. The low groundwater ages of waters from the carbonate rocks support rapid advective transport of contaminants from the LSC vicinity, yet the nearly ubiquitous occurrence of low-level concentrations of halogenated VOCs at the LSC suggests the presence of long-term persistent sources, such as seepage from the closed and sealed landfill, infiltration of VOCs that may persist locally in the epikarst, exchange with low-permeability zones in fractured rock, and upward leakage of older water that may contain elevated concentrations of halogenated VOCs from earlier land use activities.

Typhoon impacts on chemical weathering source provenance of a High Standing Island watershed, Taiwan

NASA Astrophysics Data System (ADS)

Meyer, Kevin J.; Carey, Anne E.; You, Chen-Feng

2017-10-01

Chemical weathering source provenance changes associated with Typhoon Mindulle (2004) were identified for the Choshui River Watershed in west-central Taiwan using radiogenic Sr isotope (87Sr/86Sr) and major ion chemistry analysis of water samples collected before, during, and following the storm event. Storm water sampling over 72 h was conducted in 3 h intervals, allowing for novel insight into weathering regime changes in response to intense rainfall events. Chemical weathering sources were determined to be bulk silicate and disseminated carbonate minerals at the surface and silicate contributions from deep thermal waters. Loss on ignition analysis of collected rock samples indicate disseminated carbonate can compose over 25% by weight of surface mineralogy, but typically makes up ∼2-3% of watershed rock. 87Sr/86Sr and major element molar ratios indicate that Typhoon Mindulle caused a weathering regime switch from normal flow incorporating a deep thermal signature to that of a system dominated by surface weathering. The data suggest release of silicate solute rich soil pore waters during storm events, creating a greater relative contribution of silicate weathering to the solute load during periods of increased precipitation and runoff. Partial depletion of this soil solute reservoir and possible erosion enhanced carbonate weathering lead to increased importance of carbonates to the weathering regime as the storm continues. Major ion data indicate that complex mica weathering (muscovite, biotite, illite, chlorite) may represent an important silicate weathering pathway in the watershed. Deep thermal waters represent an important contribution to river solutes during normal non-storm flow conditions. Sulfuric acid sourced from pyrite weathering is likely a major weathering agent in the Choshui River watershed.

Oils and hydrocarbon source rocks of the Baltic syneclise

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

Kanev, S.; Margulis, L.; Bojesen-Koefoed, J.A.

Prolific source rock horizons of varying thickness, having considerable areal extent, occur over the Baltic syneclise. These source sediments are rich and have excellent petroleum generation potential. Their state of thermal maturity varies form immature in the northeastern part of the syneclise to peak generation maturity in the southwestern part of the region-the main kitchen area. These maturity variations are manifest in petroleum composition in the region. Hence, mature oils occur in the Polish and Kaliningrad areas, immature oils in small accumulations in Latvian and central Lithuanian onshore areas, and intermediate oils in areas between these extremes. The oil accumulationsmore » probably result from pooling of petroleum generated from a number of different source rocks at varying levels of thermal maturity. Hence, no single source for petroleum occurrences in the Baltic syneclise may be identified. The paper describes the baltic syneclise, source rocks, thermal maturity and oils and extracts.« less

Early Precambrian mantle derived rocks in the southern Prince Charles Mountains, East Antarctica: age and isotopic constraints

USGS Publications Warehouse

Mikhalsky, E.V.; Henjes-Kunst, F.; Roland, N.W.

2007-01-01

Mafic and ultramafic rocks occurring as lenses, boudins, and tectonic slabs within metamorphic units in the southern Mawson Escarpment display mantle characteristics of either a highly enriched, or highly depleted nature. Fractionation of these mantle rocks from their sources may be as old as Eoarchaean (ca 3850 Ma) while their tectonic emplacement probably occurred prior to 2550 Ma (U-Pb SHRIMP data). These results provide for the first time evidence for Archaean suturing within East Antarctica. Similar upper mantle sources are likely present in the northern Mawson Escarpment. A younger age limit of these rocks is 2200 Ma, as indicated by presumably metamorphic zircon ages while their magmatic age may be constrained by single zircon dates at 2450-2250 Ma. The area of the northern Mawson Escarpment is most likely of ensimatic origin and includes mafic rocks which were derived from distinct mantle source(s) during Palaeoproterozoic time.

Geochemical Characteristics of Aquifer system in Taichung Area, Central Taiwan

NASA Astrophysics Data System (ADS)

Tsai, Jui-Fen; Chen, Cheng-Hong; Liu, Tsung-Kwei

2016-04-01

For understanding the relationship between water bodies and host rocks and getting more information for groundwater in Taichung area, Central Taiwan, we systematically analyzed the stable isotopes (hydrogen and oxygen), helium isotopes and radon concentrations of dissolved gases from 54 groundwater, 39 river and 4 rain samples collected from Taichung Basin in wet and dry seasons of the year 2015. In the δ18O vs. δD plot, all samples present a linear trend similar to local meteoric water, indicating a meteoric origin. However, river samples are relative lighter than rain samples, it appears that the rivers are mainly recharged from precipitation of high-elevation areas with a lighter isotopic composition. Because the seasonal isotopic variation of river samples is significant, we calculated relative contribution of precipitation by seasons using the mass balance equation. Results show that the precipitation in the rainy season is the major source of groundwater. The helium isotopic ratio in dissolved gases of most groundwater samples are close to 1 RA (RA = 3He/4He ratio of air), except the sample from Wu-Feng well that exhibits 0.3 RA. This sample also has an older C-14 age (˜27000 yrs.) than others (<200 yrs.), implying that the dissolved helium is likely affected by radiogenic 4He of surrounding rocks. The average concentration of radon for groundwater in the northern section of Taichung Basin is 20.3 Bq/L, which is higher than that of the southern section (14.5 Bq/L). Variations of radon concentrations in the two sections may be related to the different drainage systems (Paleo-Dajia River vs. Wu River), in which sediments from Paleo-Dajia River may contain higher uranium concentrations. On the other hand, water in rivers usually contains undetectable radon (<0.37 Bq/L) because it rapidly escapes to the atmosphere. However, river samples from the central part of basin have radon concentrations ranging between 1 and 3 Bq/L, reflecting that the sampling sites are in the vicinity of points of groundwater inflow. This study illustrates the utility of hydrogen and oxygen isotopes to trace the groundwater source and determine the seasonal contribution ratios of precipitation to groundwater recharge, and demonstrates the advantage of using dissolved gas to investigate the groundwater-host rocks interaction. Key words: Central Taiwan, groundwater, dissolved gas, helium isotope, hydrogen and oxygen isotopes, water radon

Thermal Conductivity Anisotropy of Metasedimentary and Igneous Rocks

NASA Astrophysics Data System (ADS)

Davis, M. G.; Chapman, D. S.; van Wagoner, T. M.; Armstrong, P. A.

2005-12-01

Thermal conductivity anisotropy was determined for two sets of rocks: a series of sandstones, mudstones, and limey shales of Cretaceous age from Price Canyon, Utah, and metasedimentary argillites and quartzites of Precambrian age from the Big Cottonwood Formation in north central Utah. Additional anisotropy measurements were made on granitic rocks from two Tertiary plutons in Little Cottonwood Canyon, north central Utah. Most conductivity measurements were made in transient mode with a half-space, line-source instrument oriented in two orthogonal directions on a flat face cut perpendicular to bedding. One orientation of the probe yields thermal conductivity parallel to bedding (kmax) directly, the other orientation of the probe measures a product of conductivities parallel and perpendicular to bedding from which the perpendicular conductivity (kperp) is calculated. Some direct measurements of kmax and kperp were made on oriented cylindrical discs using a conventional divided bar device in steady-state mode. Anisotropy is defined as kmax/kperp. The Precambrian argillites from Big Cottonwood Canyon have anisotropy values from 0.8 to 2.1 with corresponding conductivity perpendicular to bedding of 2.0 to 6.2 W m-1 K-1. Anisotropy values for the Price Canyon samples are less than 1.2 with a mean of 1.04 although thermal conductivity perpendicular to bedding for the samples varied from 1.3 to 5.0 W m-1 K-1. The granitic rocks were found to be essentially isotropic with thermal conductivity perpendicular to bedding having a range of 2.2 to 3.2 W m-1 K-1 and a mean of 2.68 W m-1 K-1. The results confirm the observation by Deming (1994) that anisotropy is negligible for rocks having kperp greater than 4.0 W m-1 K-1 and generally increases for low conductivity metamorphic and clay-rich rocks. There is little evidence, however, for his suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2.5 for low thermal conductivity rocks.

Characterization of potential sources of magnetic anomalies within the crust in a tectonically active region: Amphibolites and migmatites from Potrillo Maar, New Mexico

NASA Technical Reports Server (NTRS)

Spear, F. S.; Padovanni, E.

1985-01-01

The purpose was to characterize the oxide mineralogy and petrology of samples collected from Potrillo Maar, New Mexico with the goal of explaining the magnetic anamoly that is observed over this region from remote sensing. Potrillo Maar is a diatreme that has brought rocks from all depths in the crust to the surface almost instantaneously. The samples are therefore thought to be representative of the crust as it exists today below this portion of the Rio Grande Rift. It is generally believed that oxide minerals (magnetite, hematite, etc.) are responsible for the magnetic signature of the crust. The samples from Portillo Maar therefore offer a unique opportunity to examine the magnetic mineralogy of the entire crust. The results indicate that the magnetic anamoly observed over Rio Grande Rift may be consequence of the tectonic activity that caused mylonitization of the rocks and allowed the infiltration of oxidizing fluids.

Changes in porosity and organic matter phase distribution monitored by NMR relaxometry following hydrous pyrolysis under uniaxial confinement

USGS Publications Warehouse

Washburn, Kathryn E.; Birdwell, Justin E.; Lewan, Michael D.; Miller, Michael; Baez, Luis; Beeney, Ken; Sonnenberg, Steve

2013-01-01

Artificial maturation methods are used to induce changes in source rock thermal maturity without the uncertainties that arise when comparing natural samples from a particular basin that often represent different levels of maturation and different lithofacies. A novel uniaxial confinement clamp was used on Woodford Shale cores in hydrous pyrolysis experiments to limit sample expansion by simulating the effect of overburden present during thermal maturation in natural systems. These samples were then subjected to X-ray computed tomography (X-CT) imaging and low-field nuclear magnetic resonance (LF-NMR) relaxometry measurements. LF-NMR relaxometry is a noninvasive technique commonly used to measure porosity and pore-size distributions in fluid-filled porous media, but may also measure hydrogen present in hydrogen-bearing organic solids. Standard T1 and T2 relaxation distributions were determined and two dimensional T1-T2 correlation measurements were performed on the Woodford Shale cores. The T1-T2 correlations facilitate resolution of organic phases in the system. The changes observed in NMR-relaxation times correspond to bitumen and lighter hydrocarbon production that occur as source rock organic matter matures. The LF-NMR porosities of the core samples at maximum oil generation are significantly higher than porosities measured by other methods. This discrepancy likely arises from the measurement of highly viscous organic constituents in addition to fluid-filled porosity. An unconfined sample showed shorter relaxation times and lower porosity. This difference is attributed to the lack of fractures observed in the unconfined sample by X-CT.

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.

Metamorphism of brecciated ANT rocks - Anorthositic troctolite 72559 and norite 78527. [Anorthositic-Noritic-Troctolitic

NASA Technical Reports Server (NTRS)

Nehru, C. E.; Warner, R. D.; Keil, K.; Taylor, G. J.

1978-01-01

Rake samples 72559 and 78527 are annealed rocks of ANT-suite mineralogy and bulk composition. The rocks were presumably derived from ancient lunar highland ANT rocks of cumulate origin. Sample 72559 is polymict and its precursors were anorthositic-troctolitic in composition. Sample 78527 is monomict and of noritic derivation. The precursors were brecciated due to impact processes; 72559 shows evidence of some impact melting. The samples were thermally metamorphosed forming rocks with granoblastic matrix textures. Coexisting matrix pyroxenes indicate equilibration temperatures of 950-1000 C for both rocks. Accessory opaque oxide minerals in the rocks show rather wide compositional variations. These probably primarily reflect compositional ranges inherited from the precursor/s with little integranular equilibration among them during metamorphism.

Geochemistry of Archean metasedimentary rocks of the Aravalli craton, NW India: Implications for provenance, paleoweathering and supercontinent reconstruction

NASA Astrophysics Data System (ADS)

Ahmad, Iftikhar; Mondal, M. E. A.; Satyanarayanan, M.

2016-08-01

Basement complex of the Aravalli craton (NW India) known as the Banded Gneissic Complex (BGC) is classified into two domains viz. Archean BGC-I and Proterozoic BGC-II. We present first comprehensive geochemical study of the Archean metasedimentary rocks occurring within the BGC-I. These rocks occur associated with intrusive amphibolites in a linear belt within the basement gneisses. The association is only concentrated on the western margin of the BGC-I. The samples are highly mature (MSm) to very immature (MSi), along with highly variable geochemistry. Their major (SiO2/Al2O3, Na2O/K2O and Al2O3/TiO2) and trace (Th/Sc, Cr/Th, Th/Co, La/Sc, Zr/Sc) element ratios, and rare earth element (REE) patterns are consistent with derivation of detritus from the basement gneisses and its mafic enclaves, with major contribution from the former. Variable mixing between the two end members and closed system recycling (cannibalism) resulted in the compositional heterogeneity. Chemical index of alteration (CIA) of the samples indicate low to moderate weathering of the source terrain in a sub-tropical environment. In A-CN-K ternary diagram, some samples deceptively appear to have undergone post-depositional K-metasomatism. Nevertheless, their petrography and geochemistry (low K2O and Rb) preclude the post-depositional alteration. We propose non-preferential leaching of elements during cannibalism as the cause of the deceptive K-metasomatism as well as enigmatic low CIA values of some highly mature samples. The Archean metasedimentary rocks were deposited on stable basement gneisses, making the BGC-I a plausible participant in the Archean Ur supercontinent.

Effects of fluid-rock interactions on faulting within active fault zones - evidence from fault rock samples retrieved from international drilling projects

NASA Astrophysics Data System (ADS)

Janssen, C.; Wirth, R.; Kienast, M.; Yabe, Y.; Sulem, J.; Dresen, G. H.

2015-12-01

Chemical and mechanical effects of fluids influence the fault mechanical behavior. We analyzed fresh fault rocks from several scientific drilling projects to study the effects of fluids on fault strength. For example, in drill core samples on a rupture plane of an Mw 2.2 earthquake in a deep gold mine in South Africa the main shock occurred on a preexisting plane of weakness that was formed by fluid-rock interaction (magnesiohornblende was intensively altered to chlinochlore). The plane acted as conduit for hydrothermal fluids at some time in the past. The chemical influence of fluids on mineralogical alteration and geomechanical processes in fault core samples from SAFOD (San Andreas Fault Observatory at Depth) is visible in pronounced dissolution-precipitation processes (stylolites, solution seams) as well as in the formation of new phases. Detrital quartz and feldspar grains are partially dissolved and replaced by authigenic illite-smectite (I-S) mixed-layer clay minerals. Transmission Electron Microscopy (TEM) imaging of these grains reveals that the alteration processes and healing were initiated within pores and small intra-grain fissures. Newly formed phyllosilicates growing into open pore spaces likely reduced the fluid permeability. The mechanical influence of fluids is indicated by TEM observations, which document open pores that formed in-situ in the gouge material during or after deformation. Pores were possibly filled with formation water and/or hydrothermal fluids suggesting elevated fluid pressure preventing pore collapse. Fluid-driven healing of fractures in samples from SAFOD and the DGLab Gulf of Corinth project is visible in cementation. Cathodoluminescence microscopy (CL) reveals different generations of calcite veins. Differences in CL-colors suggest repeated infiltration of fluids with different chemical composition from varying sources (formation and meteoric water).

Evidence for Seismogenic Hydrogen Gas, a Potential Microbial Energy Source on Earth and Mars

NASA Astrophysics Data System (ADS)

McMahon, Sean; Parnell, John; Blamey, Nigel J. F.

2016-09-01

The oxidation of molecular hydrogen (H2) is thought to be a major source of metabolic energy for life in the deep subsurface on Earth, and it could likewise support any extant biosphere on Mars, where stable habitable environments are probably limited to the subsurface. Faulting and fracturing may stimulate the supply of H2 from several sources. We report the H2 content of fluids present in terrestrial rocks formed by brittle fracturing on fault planes (pseudotachylites and cataclasites), along with protolith control samples. The fluids are dominated by water and include H2 at abundances sufficient to support hydrogenotrophic microorganisms, with strong H2 enrichments in the pseudotachylites compared to the controls. Weaker and less consistent H2 enrichments are observed in the cataclasites, which represent less intense seismic friction than the pseudotachylites. The enrichments agree quantitatively with previous experimental measurements of frictionally driven H2 formation during rock fracturing. We find that conservative estimates of current martian global seismicity predict episodic H2 generation by Marsquakes in quantities useful to hydrogenotrophs over a range of scales and recurrence times. On both Earth and Mars, secondary release of H2 may also accompany the breakdown of ancient fault rocks, which are particularly abundant in the pervasively fractured martian crust. This study strengthens the case for the astrobiological investigation of ancient martian fracture systems.

Provenance and geochemical behavior of fluorine in the soils of an endemic fluorosis belt, central Iran

NASA Astrophysics Data System (ADS)

Dehbandi, Reza; Moore, Farid; Keshavarzi, Behnam

2017-05-01

The concentration of fluorine, major, trace and rare earth elements (REEs) were used to estimate the probable sources and provenance of fluorine in the soils of an endemic fluorosis belt in central Iran. Total fluorine (TF) in soils varied from 146 to 406 mg/kg with a mean of 277.5 mg/kg. Calculated enrichment factor (EF) and single factor pollution index (SFPI) revealed that the majority of soil samples were moderately contaminated by fluorine. The very strong positive correlation of TF with weathering indices and soil's fine sized fractions indicated that chemical weathering and alteration of parent rocks/soils are the main controlling factors of fluorine behavior in soils. Fluorine affinity to immobile transition trace elements and REEs suggested the role of heavy minerals as the potential F host phases. Modal mineralogy along with SEM-EDX analysis indicated that apatite, fluorapophyllite, epidote, biotite, muscovite and chlorite, as well as, clay minerals are the main F-bearing minerals in the studied soils. Discriminant, bivariate and ternary diagrams of elemental compositions displayed similar geochemical signature of soils to intermediate-acidic rocks and local shales. Based on the weathering indices, soils were immature and showed a non-steady state weathering trend from upper continental crust (UCC), acidic and intermediate igneous source rocks towards shale composition possibly due to mixing of moderately weathered and un-weathered sources of different primary compositions.

Local structuring factors of invertebrate communities in ephemeral freshwater rock pools and the influence of more permanent water bodies in the region

USGS Publications Warehouse

Jocque, M.; Graham, T.; Brendonck, L.

2007-01-01

We used three isolated clusters of small ephemeral rock pools on a sandstone flat in Utah to test the importance of local structuring processes on aquatic invertebrate communities. In the three clusters we characterized all ephemeral rock pools (total: 27) for their morphometry, and monitored their water quality, hydrology and community assemblage during a full hydrocycle. In each cluster we also sampled a set of more permanent interconnected freshwater systems positioned in a wash, draining the water from each cluster of rock pools. This design allowed additional testing for the potential role of more permanent water bodies in the region as source populations for the active dispersers and the effect on the community structure in the rock pools. Species richness and community composition in the rock pools correlated with level of permanence and the ammonia concentration. The length of the rock pool inundation cycle shaped community structure, most probably by inhibiting colonization by some taxa (e.g. tadpoles and insect larvae) through developmental constraints. The gradient in ammonia concentrations probably reflects differences in primary production. The more permanent water bodies in each wash differed both environmentally and in community composition from the connected set of rock pools. A limited set of active dispersers was observed in the rock pools. Our findings indicate that aquatic invertebrate communities in the ephemeral rock pools are mainly structured through habitat permanence, possibly linked with biotic interactions and primary production. ?? 2007 Springer Science+Business Media B.V.

Extended 3{beta}-alkyl steranes and 3-alkyl triaromatic steroids in crude oils and rock extracts

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

Dahl, J.; Moldowan, J.M.; Summons, R.E.

1995-09-01

In oils and Precambian- to Miocene-age source rocks from varying depositional environments, we have conclusively identified several novel 3-alkyl sterane and triaromatic steroid series, including (1) 3{beta}-n-pentyl steranes, (2) 3{beta}-isopentyl steranes, (3) 3{beta}-n-hexyl steranes, (4) 3{beta}-n-hepatyl steranes, (5) 3,4-dimethyl steranes, (6) 3{beta}-butyl,4-methyl steranes, (7) triaromatic 3-n-pentyl steroids, and (8) triaromatic 3-isopentyl steroids. We have also tentatively identified additional homologs with 3-alkyl substituents as large as C{sub 11}. The relative abundances of these compounds vary substantially between samples, as indicated by (1) the ratio of 3{beta}-n-pentyl steranes to 3{beta}-isopentyl steranes and (2) the ratio of 3-n-pentyl triaromatic steroids to 3-isopentyl triaromaticmore » steroids. These data suggest possible utility for these parameters as tools for oil-source rock correlations and reconstruction of depositional environments. Although no 3-alkyl steroid natural products are currently known, several lines of evidence suggest that 3{beta}-alkyl steroids result from bacterial side-chain additions to diagenetic {delta}{sup 2}-sterenes.« less

The Dissolved Ca Isotope Composition of Himalayan-Tibetan Waters

NASA Astrophysics Data System (ADS)

Tipper, E. T.; Galy, A.; Bickle, M. J.

2004-12-01

Determining the relative proportions of carbonate versus silicate weathering in the Himalaya is important for understanding the long-term atmospheric CO2 budget and the marine Sr isotope record. 87Sr/86Sr is not a straightforward proxy of carbonate to silicate weathering in the Himalaya and up to 50% of the dissolved Ca may be removed by the precipitation of secondary calcite. Ca isotopes have the potential to constrain the relative inputs of carbonates to silicates and incongruent dissolution processes in the weathering environment. Ca is the major cation carried by rivers. Thirty four Himalayan rock and water samples from the Nepal Himalaya and Tibet have been analysed for 44/42Ca and 43/42Ca on a Nu-Instruments Multiple Collector -ICP-MS. Unlike the 44/40Ca ratio the 44/42Ca is not susceptible to excess 40Ca production from the decay of K. All samples lie on a single mass fractionation line. There is a total range of 0.4 \\permil variation in \\delta44Ca with values from 0.63 \\permil - 0.21 \\permil relative to the SRM915a standard. This is comparable to that already reported with \\delta44/40Ca for small catchments and global rivers. Small first order catchments from each of the main lithotectonic units of the Himalaya have been analysed to examine the effect of lithology on dissolved Ca isotopic composition. In agreement with previous studies elsewhere there is little correlation between source rock and dissolved composition for small rivers spanning a range of source rock from limestone to various silicates and covering a vegetation range from temperate semi-desert to jungle. \\delta44Ca is not correlated with 87Sr/86Sr or Na/Ca ratios confirming that source rock composition is not the dominant control on the observed range in \\delta44Ca. A time-series has been examined for the Marsyandi River, central Nepal. In spite of significant systematic variations in major element chemistry including Ca concentration and 87Sr/86Sr the variations in \\delta44Ca are limited to 0.16 \\permil. Either there is only a single isotopic source of Ca or the \\delta44Ca is controlled by incongruent dissolution processes. The most important incongruent process to affect the Ca budget is the precipitation of pedogenic carbonate. Such incongruent processes should be detectable in the Ca-isotope budget.

Lithofacies control in detrital zircon provenance studies: Insights from the Cretaceous Methow basin, southern Canadian Cordillera

USGS Publications Warehouse

DeGraaff-Surpless, K.; Mahoney, J.B.; Wooden, J.L.; McWilliams, M.O.

2003-01-01

High-frequency sampling for detrital zircon analysis can provide a detailed record of fine-scale basin evolution by revealing the temporal and spatial variability of detrital zircon ages within clastic sedimentary successions. This investigation employed detailed sampling of two sedimentary successions in the Methow/Methow-Tyaughton basin of the southern Canadian Cordillera to characterize the heterogeneity of detrital zircon signatures within single lithofacies and assess the applicability of detrital zircon analysis in distinguishing fine-scale provenance changes not apparent in lithologic analysis of the strata. The Methow/Methow-Tyaughton basin contains two distinct stratigraphic sequences of middle Albian to Santonian clastic sedimentary rocks: submarine-fan deposits of the Harts Pass Formation/Jackass Mountain Group and fluvial deposits of the Winthrop Formation. Although both stratigraphic sequences displayed consistent ranges in detrital zircon ages on a broad scale, detailed sampling within each succession revealed heterogeneity in the detrital zircon age distributions that was systematic and predictable in the turbidite succession but unpredictable in the fluvial succession. These results suggest that a high-density sampling approach permits interpretation of finescale changes within a lithologically uniform turbiditic sedimentary succession, but heterogeneity within fluvial systems may be too large and unpredictable to permit accurate fine-scale characterization of the evolution of source regions. The robust composite detrital zircon age signature developed for these two successions permits comparison of the Methow/Methow-Tyaughton basin age signature with known plutonic source-rock ages from major plutonic belts throughout the Cretaceous North American margin. The Methow/Methow-Tyaughton basin detrital zircon age signature matches best with source regions in the southern Canadian Cordillera, requiring that the basin developed in close proximity to the southern Canadian Cordillera and providing evidence against large-scale dextral translation of the Methow terrane.

The geochemistry and petrogenesis of an ophiolitic sequence from Pindos, Greece

NASA Astrophysics Data System (ADS)

Capedri, S.; Venturelli, G.; Bocchi, G.; Dostal, J.; Garuti, G.; Rossi, A.

1980-06-01

The ophiolites of Northern Pindos have been studied in a section close to the village of Perivoli (Grevena District). The section comprises cumulus rocks ranging from ultramafics to gabbros, overlain by dolerites (non-cumulus microgabbro) capped by thick frequently pillowed lava flows. The sequence is cut by basaltic dykes. While the cumulus rocks and the dolerites are mostly fresh, the lavas and dykes are strongly transformed. Major and trace element (Ni, Cr, Sc, Y, Zr, Nb, Sr, Ba, Zn, Cu, V, Li) data are presented for selected samples from the sequence. For some elements, the volcanic/subvolcanic rocks (flows, dykes, dolerites) exhibit wide chemical characteristics which are considered to mainly reflect variations within the parent magmas. Some lavas appear to be closely comparable with the present-day ocean-floor basalts, while other flows and most of the dykes are strongly depleted in some “incompatible” elements and are similar to some rocks from immature island arcs. The dolerites have transitional chemical features. The Pindos lavas differ from Western Mediterranean ophiolites in that the former have lower Ti,P,Zr,Y, higher Fe tot. and normally higher Ti/Zr ratio. The volcanic/subvolcanic rocks from Pindos have been derived from separate magmas. Some lavas were possibly produced by variable partial melting of an already depleted mantle source, while the lavas exhibiting ocean-floor affinity were probably generated by partial melting of a less depleted source. The wide chemical variations of the Pindos lavas cannot be easily explained by an ocean-ridge system. An “island arc-marginal basin system” could better account for the observed chemical features.

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.

Identifying Provenance of Archaean Basal Conglomerates: An Evidence from Sigegudda and Bababudan Conglomerate Quartzites, India

NASA Astrophysics Data System (ADS)

Mitra, A.; Dey, S.

2017-12-01

Geochemical characteristics of clastic sedimentary rocks deposited and later preserved in ancient supracrustal sequences of Archaean terrain are competent representation of their source rocks in provenance. These rocks usually sample a wide geographic area and bear signature of subsequently destroyed and dismembered terrains. In this study the quartz pebble conglomerate-quartz sandstone association of Sigegudda and Bababudan belt of western Dharwar craton (WDC), Southern India have been studied to understand the nature of their provenance. Both Sigegudda and Bababudan belt represent younger (2.8-2.6 Ga) greenstone sequences of WDC. They start with a prominent band of conglomerate-quartzite lying over Palaeo to Meso Archaean Peninsular Gneiss (3.35-3.29 Ga) with older Sargur greentone (3.35-3.28 Ga) enclaves along an unconformity. Here, we present a comprehensive provenance (mainly source rock characterization) study of major and trace element composition of low to moderately metamorphosed basal siliciclastics of the younger greenstone sequences of WDC. Chemically they are enriched in Th, U, HFSE (Hf, Nb, Zr) and depleted in Sc, Co, Cr and Eu content with elevated La/Sc and Th/Sc values depicting a differentiated felsic source. This is further supported by fractionated LREE (10.64 - 14.66), significant negative Eu anomaly (0.67 - 0.55) and nearly flat HREE indicating granitoid rocks as source. In La-Th-Cr/100 and La-Th-Sc triangular diagram, quartz arenite field overlap with the Peninsular Gneiss and plotted far away from the mafic-ultramafics of Sargur. The chemical index of alteration (CIA) values of arenites of Sigegudda (71) and Bababudan (75), Peninsular Gneisses (avg-50) and Sargur group (avg-30) implies their derivation from the underlying gneisses associated with a prolonged weathering. The presence of a thick conglomerate-quartz sandstone association with differently sized quartz in their framework and matrix, depicts the development of a stable craton in WDC during the Mesoarchaean. The geochemical results of conglomerate - quartzites along with their supported petrography strongly recommend the Peninsular gneiss as their provenance with prolonged erosion and sediment recycling.

Small scale inhomogeneity in the mantle source of the Cape Verde hotspot is probably related to plume complexity: implications from Sr, Nd and high precision Pb isotopes and geochemistry

NASA Astrophysics Data System (ADS)

Holm, P. M.; Sørensen, R. V.

2009-04-01

The volcanic rocks of one of the major islands of the Cape Verde hotspot have been investigated in order to test mantle plume models. From the centre of the Cape Verde Rise an array of islands trend west, the northern HIMU-type Cape Verde Islands. Of these, São Nicolau (SN) is the easternmost and Santo Antão the westernmost. Sixty samples of primitive (MgO = 9-14 wt%) basanitic composition from SN that represent the four volcanic stages of the 9 - 0.1 Ma evolution of the island have been analysed for Sr, Nd and high precision Pb isotopic composition. Pb ranges to a less radiogenic composition than on SA [1] and has lower 8/4 than the rocks of the southern EM1-type Cape Verde islands. Most SN lavas have a young HIMU character with negative 7/4. The most radiogenic Pb at SN is less thorogenic than Pb at SA. Temporal variation is also evident: An intermediate age group of samples have particularly low La/Nb = 0.4 - 0.5 and the least LREE-enrichment for SN. The youngest group of rocks has the lowest Zr/Nb = 2.5 - 3.0 and the most unradiogenic Sr and radiogenic Nd in the archipelago. At least four of the mantle source components for the SN magmas are different from any found in the SA magmas. High precision Pb data allow identification of parallel trends for northern SN and the southern island Santiago, which therefore must have unrelated source components. For the northern Cape Verde islands source compositions vary from E to W as well as with time. This cannot be explained by stationary enriched lithosphere components. The derivation of melts from a complex plume source is modelled. [1] Holm P.M., Wilson J.R., Christensen B.P., Hansen S.L., Hein K.M., Mortensen A.K., Pedersen R., Plesner S., and Runge M.K. (2006) JPetrol 47, 145-189.

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.

Geochemistry of Archean Mafic Amphibolites from the Amsaga Area, West African Craton, Mauritania: Occurrence of Archean oceanic plateau

NASA Astrophysics Data System (ADS)

El Atrassi, Fatima; Debaille, Vinciane; Mattielli, Nadine; Berger, Julien

2015-04-01

While Archean terrains are mainly composed of a TTG (Tonalite-trondhjemite-granodiorite) suite, more mafic lithologies such as amphibolites are also a typical component of those ancient terrains. Although mafic rocks represent only ~10% of the Archean cratons, they may provide key evidence of the role and nature of basaltic magmatism in the formation of the Archean crust as well as the evolution of the Archean mantle. This study focuses on the Archean crust from the West African craton in Mauritania (Amsaga area). The Amsaga Archean crust mainly consists of TTG and thrust-imbricated slices of mafic volcanic rocks, which have been affected by polymetamorphic events from the amphibolite to granulite facies. We report the results of a combined petrologic, Sm-Nd isotopic, major element and rare earth element (REE) study of the Archean amphibolites in the West African craton. This study was conducted in order to characterize these rocks, to constrain the time of their formation and to evaluate their tectonic setting and their possible mantle source. Our petrological observations show that these amphibolites have fine to medium granoblastic and nematoblastic textures. They are dominated by amphibolite-facies mineral assemblages (mainly amphibole and plagioclase), but garnet and clinopyroxene occur in a few samples. These amphibolites have tholeiitic basalt composition. On a primitive mantle-normalized diagram, they display fairly flat patterns without negative anomalies for either Eu or Nb-Ta. We have shown using Sm-Nd whole rock isotopic data that these amphibolites formed at 3.3 ±0.075 Ga. They have positive ɛNdi values (+5.2 ± 1.6). These samples show isotopically juvenile features, which rule out the possibility of significant contamination of the protolith magmas by ancient continental crust. Based on these geochemical data we propose that the tholeiitic basalts were formed in an oceanic plateau tectonic setting from a mantle plume source and that they have a depleted mantle source. It is the first time that such a signature is observed in the Archean part of the West African craton, and would suggest a widespread bimodal distribution of trace elements signature in all Archean basalts.

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.

Geology, thermal maturation, and source rock geochemistry in a volcanic covered basin: San Juan sag, south-central Colorado

USGS Publications Warehouse

Gries, R.R.; Clayton, J.L.; Leonard, C.

1997-01-01

The San Juan sag, concealed by the vast San Juan volcanic field of south-central Colorado, has only recently benefited from oil and gas wildcat drilling and evaluations. Sound geochemical analyses and maturation modeling are essential elements for successful exploration and development. Oil has been produced in minor quantities from an Oligocene sill in the Mancos Shale within the sag, and major oil and gas production occurs from stratigraphically equivalent rocks in the San Juan basin to the south-west and in the Denver basin to the northeast. The objectives of this study were to identify potential source rocks, assess thermal maturity, and determine hydrocarbon-source bed relationships. Source rocks are present in the San Juan sag in the upper and lower Mancos Shale (including the Niobrara Member), which consists of about 666 m (2184 ft) of marine shale with from 0.5 to 3.1 wt. % organic carbon. Pyrolysis yields (S1 + S2 = 2000-6000 ppm) and solvent extraction yields (1000-4000 ppm) indicate that some intervals within the Mancos Shale are good potential source rocks for oil, containing type II organic matter, according to Rock-Eval pyrolysis assay. Oils produced from the San Juan sag and adjacent part of the San Juan basin are geochemically similar to rock extracts obtained from these potential source rock intervals. Based on reconstruction of the geologic history of the basin integrated with models of organic maturation, we conclude that most of the source rock maturation occurred in the Oligocene and Miocene. Little to no maturation took place during Laramide subsidence of the basin, when the Animas and Blanco Basin formations were deposited. The timing of maturation is unlike that of most Laramide basins in the Rocky Mountain region, where maturation occurred as a result of Paleocene and Eocene basin fill. The present geothermal gradient in the San Juan sag is slightly higher (average 3.5??C/100 m; 1.9??F/100 ft) than the regional average for southern Rocky Mountain basins; however, although the sag contains intrusives and a volcanic cover, the gradient is significantly lower than that reported for parts of the adjacent San Juan basin (4.7??C/100 m; 2.6??F/100 ft). Burial depth appears to be a more important controlling factor in the thermal history of the source rocks than local variations in the geothermal gradient due to volcanic activity. Interestingly, the thick overburden of volcanic rocks appears to have provided the necessary burial depth for maturation.

Coal-rock interface detector

NASA Technical Reports Server (NTRS)

Rose, S. D.; Crouch, C. E.; Jones, E. W. (Inventor)

1979-01-01

A coal-rock interface detector is presented which employs a radioactive source and radiation sensor. The source and sensor are separately and independently suspended and positioned against a mine surface of hydraulic pistons, which are biased from an air cushioned source of pressurized hydraulic fluid.

Major Element Analysis of the Target Rocks at Meteor Crater, Arizona

NASA Technical Reports Server (NTRS)

See, Thomas H.; Hoerz, Friedrich; Mittlefehldt, David W.; Varley, Laura; Mertzman, Stan; Roddy, David

2002-01-01

We collected approximately 400 rock chips in continuous vertical profile at Meteor Crater, Arizona, representing, from bottom to top, the Coconino, Toroweap, Kaibab, and Moenkopi Formations to support ongoing compositional analyses of the impact melts and their stratigraphic source depth(s) and other studies at Meteor Crater that depend on the composition of the target rocks. These rock chips were subsequently pooled into 23 samples for compositional analysis by XRF (x ray fluorescence) methods, each sample reflecting a specific stratigraphic "subsection" approximately 5-10 in thick. We determined the modal abundance of quartz, dolomite, and calcite for the entire Kaibab Formation at vertical resolutions of 1-2 meters. The Coconino Formation composes the lower half of the crater cavity. It is an exceptionally pure sandstone. The Toroweap is only two inches thick and compositionally similar to Coconino, therefore, it is not a good compositional marker horizon. The Kaibab Formation is approximately 80 in thick. XRD (x ray diffraction) studies show that the Kaibab Formation is dominated by dolomite and quartz, albeit in highly variable proportions; calcite is a minor phase at best. The Kaibab at Meteor Crater is therefore a sandy dolomite rather than a limestone, consistent with pronounced facies changes in the Permian of SE Arizona over short vertical and horizontal distances. The Moenkopi forms the 12 in thick cap rock and has the highest Al2O3 and FeO concentrations of all target rocks. With several examples, we illustrate how this systematic compositional and modal characterization of the target ideologies may contribute to an understanding of Meteor Crater, such as the depth of its melt zone, and to impact cratering in general, such as the liberation of CO2 from shocked carbonates.

Environmental consequences of shale gas exploitation and the crucial role of rock microfracturing

NASA Astrophysics Data System (ADS)

Renard, Francois

2015-04-01

The growing exploitation of unconventional gas and oil resources has dramatically changed the international market of hydrocarbons in the past ten years. However, several environmental concerns have also been identified such as the increased microseismicity, the leakage of gas into freshwater aquifers, and the enhanced water-rock interactions inducing the release of heavy metals and other toxic elements in the produced water. In all these processes, fluids are transported into a network of fracture, ranging from nanoscale microcracks at the interface between minerals and the kerogen of the source rock, to well-developed fractures at the meter scale. Characterizing the fracture network and the mechanisms of its formation remains a crucial goal. A major difficulty when analyzing fractures from core samples drilled at depth is that some of them are produced by the coring process, while some other are produced naturally at depth by the coupling between geochemical and mechanical forces. Here, I present new results of high resolution synchrotron 3D X-ray microtomography imaging of shale samples, at different resolutions, to characterize their microfractures and their mechanisms of formation. The heterogeneities of rock microstructure are also imaged, as they create local stress concentrations where cracks may nucleate or along which they propagate. The main results are that microcracks form preferentially along kerogen-mineral interfaces and propagate along initial heterogeneities according to the local stress direction, connecting to increase the total volume of fractured rock. Their lifetime is also an important parameter because they may seal by fluid circulation, fluid-rock interactions, and precipitation of a cement. Understanding the multi-scale processes of fracture network development in shales and the coupling with fluid circulation represents a key challenge for future research directions.

Trace-metal sources and their release from mine wastes: examples from humidity cell tests of hardrock mine waste and from Warrior Basin coal

USGS Publications Warehouse

Diehl, S.F.; Smith, Kathleen S.; Desborough, G.A.; White, W.W.; Lapakko, K.A.; Goldhaber, Martin B.; Fey, David L.

2003-01-01

To assess the potential impact of metal and acid contamination from mine-waste piles, it is important to identify the mineralogic source of trace metals and their mode of occurrence. Microscopic analysis of mine-waste samples from both hard-rock and coalmine waste samples demonstrate a microstructural control, as well as mineralogic control, on the source and release of trace metals into local water systems. The samples discussed herein show multiple periods of sulfide mineralization with varying concentrations of trace metals. In the first case study, two proprietary hard-rock mine-waste samples exposed to a series of humidity cell tests (which simulate intense chemical weathering conditions) generated acid and released trace metals. Some trace elements of interest were: arsenic (45-120 ppm), copper (60-320 ppm), and zinc (30-2,500 ppm). Untested and humidity cell-exposed samples were studied by X-ray diffraction, scanning electron microscope with energy dispersive X-ray (SEM/EDX), and electron microprobe analysis. Studies of one sample set revealed arsenic-bearing pyrite in early iron- and magnesium-rich carbonate-filled microveins, and iron-, copper-, arsenic-, antimony-bearing sulfides in later crosscutting silica-filled microveins. Post humidity cell tests indicated that the carbonate minerals were removed by leaching in the humidity cells, exposing pyrite to oxidative conditions. However, sulfides in the silica-filled veins were more protected. Therefore, the trace metals contained in the sulfides within the silica-filled microveins may be released to the surface and (or) ground water system more slowly over a greater time period. In the second case study, trace metal-rich pyrite-bearing coals from the Warrior Basin, Alabama were analyzed. Arsenic-bearing pyrite was observed in a late-stage pyrite phase in microfaults and microveins that crosscut earlier arsenic.

Extracting real-crack properties from non-linear elastic behaviour of rocks: abundance of cracks with dominating normal compliance and rocks with negative Poisson ratios

NASA Astrophysics Data System (ADS)

Zaitsev, Vladimir Y.; Radostin, Andrey V.; Pasternak, Elena; Dyskin, Arcady

2017-09-01

Results of examination of experimental data on non-linear elasticity of rocks using experimentally determined pressure dependences of P- and S-wave velocities from various literature sources are presented. Overall, over 90 rock samples are considered. Interpretation of the data is performed using an effective-medium description in which cracks are considered as compliant defects with explicitly introduced shear and normal compliances without specifying a particular crack model with an a priori given ratio of the compliances. Comparison with the experimental data indicated abundance (˜ 80 %) of cracks with the normal-to-shear compliance ratios that significantly exceed the values typical of conventionally used crack models (such as penny-shaped cuts or thin ellipsoidal cracks). Correspondingly, rocks with such cracks demonstrate a strongly decreased Poisson ratio including a significant (˜ 45 %) portion of rocks exhibiting negative Poisson ratios at lower pressures, for which the concentration of not yet closed cracks is maximal. The obtained results indicate the necessity for further development of crack models to account for the revealed numerous examples of cracks with strong domination of normal compliance. Discovering such a significant number of naturally auxetic rocks is in contrast to the conventional viewpoint that occurrence of a negative Poisson ratio is an exotic fact that is mostly discussed for artificial structures.

Geochemical prospecting for copper and nickel in the Wulgai and Tor Tangi areas southeast of Hindubagh, Quetta Division, Pakistan

USGS Publications Warehouse

Stanin, S. Anthony; Wahid, M.A.; Khan, Shamsher

1975-01-01

Showings of magnetite, copper, and possible nickel mineralization in the Hindubagh chromite mining district are near Wulgai and Tor Tangi. Several hundred samples of clastic material from dry streambeds in these areas were sieved for the minus-80-mesh fraction and analyzed for copper using 2, 2'-biquinoline and for nickel using alpha-furildioxime. The copper threshold is 75 ppm, and the nickel threshold is 400 ppm. A geochemical map has been prepared that shows nine areas of anomalously high copper and six areas of high nickel. The nickel anomalies may represent secondary dispersion patterns derived from the erosion of nickeliferous ultramafic rocks of the Hindubagh intrusive complex. Copper showings in and near four of the anomalous copper areas indicate that detailed geological investigation and detailed geochemical sampling of rocks, soil, and unconsolidated clastic material are required to determine the source of the anomalies.

South Atlantic sag basins: new petroleum system components

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

Henry, S.G.; Mello, M.R.

Newly discovered pre-salt source rocks, reservoirs and seals need to be included as components to the petroleum systems of both sides of the South Atlantic. These new components lie between the pre-salt rift strata and the Aptian salt layers, forming large, post-rift, thermal subsidence sag basins. These are differentiated from the older rift basins by the lack of syn-rift faulting and a reflector geometry that is parallel to the base salt regional unconformity rather than to the Precambrian basement. These basins are observed in deep water regions overlying areas where both the mantle and the crust have been involved inmore » the extension. This mantle involvement creates post-rift subsiding depocenters in which deposition is continuous while proximal rift-phase troughs with little or no mantle involvement are bypassed and failed to accumulate potential source rocks during anoxic times. These features have been recognized in both West African Kwanza Basin and in the East Brasil Rift systems. The pre-salt source rocks that are in the West African sag basins were deposited in lacustrine brackish to saline water environment and are geochemically distinct from the older, syn-rift fresh to brackish water lakes, as well as from younger, post-salt marine anoxic environments of the drift phase. Geochemical analyses of the source rocks and their oils have shown a developing source rock system evolving from isolated deep rift lakes to shallow saline lakes, and culminating with the infill of the sag basin by large saline lakes to a marginally marine restricted gulf. Sag basin source rocks may be important in the South Atlantic petroleum system by charging deep-water prospects where syn-rift source rocks are overmature and the post-salt sequences are immature.« less

Seismic velocity uncertainties and their effect on geothermal predictions: A case study

NASA Astrophysics Data System (ADS)

Rabbel, Wolfgang; Köhn, Daniel; Bahadur Motra, Hem; Niederau, Jan; Thorwart, Martin; Wuttke, Frank; Descramble Working Group

2017-04-01

Geothermal exploration relies in large parts on geophysical subsurface models derived from seismic reflection profiling. These models are the framework of hydro-geothermal modeling, which further requires estimating thermal and hydraulic parameters to be attributed to the seismic strata. All petrophysical and structural properties involved in this process can be determined only with limited accuracy and thus impose uncertainties onto the resulting model predictions of temperature-depth profiles and hydraulic flow, too. In the present study we analyze sources and effects of uncertainties of the seismic velocity field, which translate directly into depth uncertainties of the hydraulically and thermally relevant horizons. Geological sources of these uncertainties are subsurface heterogeneity and seismic anisotropy, methodical sources are limitations in spread length and physical resolution. We demonstrate these effects using data of the EU-Horizon 2020 project DESCRAMBLE investigating a shallow super-critical geothermal reservoir in the Larderello area. The study is based on 2D- and 3D seismic reflection data and laboratory measurements on representative rock samples under simulated in-situ conditions. The rock samples consistently show P-wave anisotropy values of 10-20% order of magnitude. However, the uncertainty of layer depths induced by anisotropy is likely to be lower depending on the accuracy, with which the spatial orientation of bedding planes can be determined from the seismic reflection images.

New data supporting a Sm-146,147-Nd-142,143 formation interval for the lunar mantle

NASA Technical Reports Server (NTRS)

Nyquist, L. E.; Wiesmann, H.; Bansal, B. M.; Shih, C.-Y.

1994-01-01

Very small variations in Nd-142 abundance in SNC meteorites lunar basalts, and a terrestrial supracrustal rock, have been attributed to the decay of 103 Ma Sm-146 initially present in basalt source regions in varying abundances as a result of planetary differentiation. We previously interpreted variations in Nd-142 abundances in two Apollo 17 high-Ti basalts, three Apollo 12 low-Ti basalts, and two KREEP basalts as defining an isochron giving a formation interval of approximately 94 Ma for the lunar mantle. Here we report new data for a third Apollo 17 high-Ti basalt, two Apollo 15 low-Ti basalts, the VLT basaltic lunar meteorite A881757 (formerly Asuka 31), basalt-like KREEP impact melt rocks 14310 and 14078, and three terrestrial rock standards. Those lunar samples which were not exposed to large lunar surface thermal neutron fluences yield a revised mantle formation interval of 237 +/- 64 Ma.

Magnetic and gravity gradiometry framework for Mesoproterozoic iron oxide-apatite and iron oxide-copper-gold deposits, southeast Missouri, USA

USGS Publications Warehouse

McCafferty, Anne E.; Phillips, Jeffrey; Driscoll, Rhonda L.

2016-01-01

High-resolution airborne magnetic and gravity gradiometry data provide the geophysical framework for evaluating the exploration potential of hidden iron oxide deposits in Mesoproterozoic basement rocks of southeast Missouri. The data are used to calculate mineral prospectivity for iron oxide-apatite (IOA) ± rare earth element (REE) and iron oxide-copper-gold (IOCG) deposits. Results delineate the geophysical footprints of all known iron oxide deposits and reveal several previously unrecognized prospective areas. The airborne data are also inverted to three-dimensional density and magnetic susceptibility models over four concealed deposits at Pea Ridge (IOA ± REE), Boss (IOCG), Kratz Spring (IOA), and Bourbon (IOCG). The Pea Ridge susceptibility model shows a magnetic source that is vertically extensive and traceable to a depth of greater than 2 km. A smaller density source, located within the shallow Precambrian basement, is partly coincident with the magnetic source at Pea Ridge. In contrast, the Boss models show a large (625-m-wide), vertically extensive, and coincident dense and magnetic stock with shallower adjacent lobes that extend more than 2,600 m across the shallow Precambrian paleosurface. The Kratz Spring deposit appears to be a smaller volume of iron oxides and is characterized by lower density and less magnetic rock compared to the other iron deposits. A prospective area identified south of the Kratz Spring deposit shows the largest volume of coincident dense and nonmagnetic rock in the subsurface, and is interpreted as prospective for a hematite-dominant lithology that extends from the top of the Precambrian to depths exceeding 2 km. The Bourbon deposit displays a large bowl-shaped volume of coincident high density and high-magnetic susceptibility rock, and a geometry that suggests the iron mineralization is vertically restricted to the upper parts of the Precambrian basement. In order to underpin the evaluation of the prospectivity and three-dimensional models, an extensive statistical summary of density and apparent magnetic susceptibility measurements is presented that includes data on several hundred samples taken from the deposits, altered wall rocks, and unaltered country rocks.

Sea Level and Paleoenvironment Control on Late Ordovician Source Rocks, Hudson Bay Basin, Canada

NASA Astrophysics Data System (ADS)

Zhang, S.; Hefter, J.

2009-05-01

Hudson Bay Basin is one of the largest Paleozoic sedimentary basins in North America, with Southampton Island on its north margin. The lower part of the basin succession comprises approximately 180 to 300 m of Upper Ordovician strata including Bad Cache Rapids and Churchill River groups and Red Head Rapids Formation. These units mainly comprise carbonate rocks consisting of alternating fossiliferous limestone, evaporitic and reefal dolostone, and minor shale. Shale units containing extremely high TOC, and interpreted to have potential as petroleum source rocks, were found at three levels in the lower Red Head Rapids Formation on Southampton Island, and were also recognized in exploration wells from the Hudson Bay offshore area. A study of conodonts from 390 conodont-bearing samples from continuous cores and well cuttings from six exploration wells in the Hudson Bay Lowlands and offshore area (Comeault Province No. 1, Kaskattama Province No. 1, Pen Island No. 1, Walrus A-71, Polar Bear C-11 and Narwhal South O-58), and about 250 conodont-bearing samples collected from outcrops on Southampton Island allows recognition of three conodont zones in the Upper Ordovician sequence, namely (in ascendant sequence) Belodina confluens, Amorphognathus ordovicicus, and Rhipidognathus symmetricus zones. The three conodont zones suggest a cycle of sea level changes of rising, reaching the highest level, and then falling during the Late Ordovician. Three intervals of petroleum potential source rock are within the Rhipidognathus symmetricus Zone in Red Head Rapids Formation, and formed in a restricted anoxic and hypersaline condition during a period of sea level falling. This is supported by the following data: 1) The conodont Rhipidognathus symmetricus represents the shallowest Late Ordovician conodont biofacies and very shallow subtidal to intertidal and hypersaline condition. This species has the greatest richness within the three oil shale intervals to compare other parts of Red Head Rapids Formation. 2) Type I kerogen is normally formed in quiet, oxygen-deficient, shallow water environment. Rock-Eval6 data from 40 samples of the three oil shale intervals, collected from outcrops on Southampton Island, demonstrate that the proportion of Type I kerogen gradually increases in the mixed Type I-Type II kerogen from the lower to upper oil shale intervals. 3) Pristane/phytane ratio can be used as a paleoenvironment indicator. The low ratios in the three oil shale intervals range from 0.5 to 0.9 and indicate anoxic and hypersaline conditions. In addition, the presence of isorenieratene derivatives from green phototrophic sulfur bacteria (Chlorobiaceae), with highest relative concentrations in the lower oil shale intervals, points to anoxia reaching into the photic zone of the water column.

Kaersutite-bearing xenoliths and megacrysts in volcanic rocks from the Funk Seamount in the souhtwest Indian Ocean

NASA Technical Reports Server (NTRS)

Reid, Arch M.; Le Roex, Anton P.

1988-01-01

The petrography, mineral chemistry, and whole-rock compositions of volcanic rocks dredged from the Funk Seamount, located 60 km NW of Marion Island in the southwestern Indian Ocean, are presented together with the mineral chemistry of their inclusions. On the basis of these characteristics, the possible relationships between the Funk Seamount's volcanic rocks and the megacrysts and xenoliths in these rocks are discussed. It is argued that the Funk Seamount lavas derive from a similar mantle source region as that of the Marion Island and Prince Edward Island hotspot lavas. The geochemical signature of these lavas implies derivation from a source that is enriched (e.g., in Ti, K, P, and Nb) over the depleted mantle source regions for the adjacent mid-ocean ridge basalts.

Documentation of Apollo 15 samples

NASA Technical Reports Server (NTRS)

Sutton, R. L.; Hait, M. H.; Larson, K. B.; Swann, G. A.; Reed, V. S.; Schaber, G. G.

1972-01-01

A catalog is presented of the documentation of Apollo 15 samples using photographs and verbal descriptions returned from the lunar surface. Almost all of the Apollo 15 samples were correlated with lunar surface photographs, descriptions, and traverse locations. Where possible, the lunar orientations of rock samples were reconstructed in the lunar receiving laboratory, using a collimated light source to reproduce illumination and shadow characteristics of the same samples shown in lunar photographs. In several cases, samples were not recognized in lunar surface photographs, and their approximate locations are known only by association with numbered sample bags used during their collection. Tables, photographs, and maps included in this report are designed to aid in the understanding of the lunar setting of the Apollo 15 samples.

Geochemistry characterization, biomarker and determination of correlation, maturity of petroleum from Bangko-Rohil and Duri Bengkalis, Riau

NASA Astrophysics Data System (ADS)

Tamboesai, Emrizal Mahidin

2017-11-01

Petroleum is the main source of the energy for industry, transportation. Thedemand for crude oil in Indonesia is much higher than its production which leads to current energy crisis. One of solutions for this crisis is to conduct correlation study, which determines the genetic relationship at each oil well. This study is aimed to provide the indication of the genetic relationship (source matter, source rock and the origins) of Bangko and Duri crude oil. The saturated fraction was analyzed using Gas Chromatography (GC). On the basis of the abundance of hydrocarbon aliphatic, the crude oils samples have small ratio value, which is 0,38-0,50 forPr/n-C17 and 0,16-0,18Ph/n-C18. This values indicated that the samples were originated from higher vascular plants (terrestrial). The samples derived from lacustrine environments (lake) have ratio valueof Pr/Ph (2,50-2,90). The calculation from Star diagram have showed that the oil samples in area MB-07, MB-076 dan MB-172 of Bangko with the oil sample in Duri (MD-01) are negatively correlated. The negative correlation indicated that the oil samples have different the genetic relationship source matter and different in enhance oil recovery.

Chlorine Abundances in Martian Meteorites

NASA Technical Reports Server (NTRS)

Bogard, D.D.; Garrison, D.H.; Park, J.

2009-01-01

Chlorine measurements made in martian surface rocks by robotic spacecraft typically give Chlorine (Cl) abundances of approximately 0.1-0.8%. In contrast, Cl abundances in martian meteorites appear lower, although data is limited, and martian nakhlites were also subjected to Cl contamination by Mars surface brines. Chlorine abundances reported by one lab for whole rock (WR) samples of Shergotty, ALH77005, and EET79001 range 108-14 ppm, whereas Cl in nakhlites range 73-1900 ppm. Measurements of Cl in various martian weathering phases of nakhlites varied 0.04-4.7% and reveal significant concentration of Cl by martian brines Martian meteorites contain much lower Chlorine than those measured in martian surface rocks and give further confirmation that Cl in these surface rocks was introduced by brines and weathering. It has been argued that Cl is twice as effective as water in lowering the melting point and promoting melting at shallower martian depths, and that significant Cl in the shergottite source region would negate any need for significant water. However, this conclusion was based on experiments that utilized Cl concentrations more analogous to martian surface rocks than to shergottite meteorites, and may not be applicable to shergottites.

Petrography of isotopically-dated clasts in the Kapoeta howardite and petrologic constraints on the evolution of its parent body

NASA Technical Reports Server (NTRS)

Dymek, R. F.; Albee, A. L.; Chodos, A. A.; Wasserburg, G. J.

1976-01-01

Results are presented for petrographic and electron microprobe studies of the isotopically dated A, B, C, and rho basaltic rock fragments separated from the howardite Kapoeta. Other lithic clasts and numerous mineral fragments in thin sections of Kapoeta are investigated in order to outline the range in lithology and chemistry of the source materials from which the Kapoeta meteorite is derived. The data obtained are compared to those from other meteorite and lunar samples, with particular reference to the observational consequences for the evolution of the Kapoeta parent body. A major conclusion is that there is no clearcut evidence for young magmatism on the Kapoeta parent body. The observations preclude the interpretation that the Kapoeta is a simple mixture of eucrites and diogenites. In contrast to the moon, a source of anorthositic rocks does not appear to have been present on the Kapoeta parent body which involved chiefly pyroxene. The FeO-MnO relationships suggest that the source of the materials in the Kapoeta parent planet are fundamentally related.

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.

Use of spatial statistics and isotopic tracers to measure the influence of arsenical pesticide use on stream sediment chemistry in New England, USA

USGS Publications Warehouse

Robinson, G.R.; Ayuso, R.A.

2004-01-01

Arsenical pesticides and herbicides, principally Pb arsenate, Ca arsenate, and Na arsenate with lesser use of other metal-As pesticides, were widely applied on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Agricultural census data for this time period is used to define an agricultural index that identifies areas that are inferred to have used arsenical pesticides extensively. Factor analysis on metal concentrations in 1597 stream sediment samples collected throughout New England, grouped by agricultural-index categories, indicate a positive association of areas with stream sediment sample populations that contain higher As and Pb concentrations than samples from the region as a whole with sample site settings having high agricultural-index values. Population statistics for As and Pb concentrations and factor scores for an As-Pb factor all increase systematically and significantly with increasing agricultural-index intensity in the region, as tested by Kruskal-Wallis analysis. Lead isotope compositions for 16 stream sediments from a range of agricultural-index settings generally overlap the observed variation in rock sulfides and their weathering products; however, sediments collected from high agricultural-index settings have slightly more radiogenic Pb compositions, consistent with an industrial Pb contribution to these samples. Although weathering products from rocks are likely to be the dominant source of As and metals to most of the stream sediment samples collected in the region, the widespread use of arsenical pesticides and herbicides in New England during the early 1900-1960s appears to be a significant anthropogenic source of As and metals to many sediments in agricultural areas in the region and has raised background levels of As in some regions. Elevated concentrations of As in stream sediments are of concern for two reasons. Stream sediments with elevated As concentrations delineate areas with elevated background concentrations of As from both natural rock and anthropogenic sources that may contribute As to groundwater systems used for drinking water supplies. Conversion of agricultural land contaminated with arsenical pesticide residues to residential development may increase the likelihood that humans will be exposed to As. In addition, many stream sediment sites have As concentrations that exceed sediment quality guidelines established for freshwater ecosystems. Thirteen percent of the New England sediment sample sites exceed 9.79 mg/kg As, the threshold effects concentration (TEC), below which harmful effects are unlikely to be observed. Arsenic concentrations exceed 33 mg/kg, the probable effects concentration (PEC), above which harmful effects on sediment-dwelling organisms are expected to occur frequently, at 1.25% of the sediment sample sites. The sample sites that exceed the PEC value occur predominately in agricultural areas that used arsenical pesticides.

Effects of source rocks, soil features and climate on natural gamma radioactivity in the Crati valley (Calabria, Southern Italy).

PubMed

Guagliardi, Ilaria; Rovella, Natalia; Apollaro, Carmine; Bloise, Andrea; De Rosa, Rosanna; Scarciglia, Fabio; Buttafuoco, Gabriele

2016-05-01

The study, which represents an innovative scientific strategy to approach the study of natural radioactivity in terms of spatial and temporal variability, was aimed to characterize the background levels of natural radionuclides in soil and rock in the urban and peri-urban soil of a southern Italy area; to quantify their variations due to radionuclide bearing minerals and soil properties, taking into account nature and extent of seasonality influence. Its main novelty is taking into account the effect of climate in controlling natural gamma radioactivity as well as analysing soil radioactivity in terms of soil properties and pedogenetic processes. In different bedrocks and soils, activities of natural radionuclides ((238)U, (232)Th (4) K) and total radioactivity were measured at 181 locations by means of scintillation γ-ray spectrometry. In addition, selected rocks samples were collected and analysed, using a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS) and an X-Ray Powder Diffraction (XRPD), to assess the main sources of radionuclides. The natural-gamma background is intimately related to differing petrologic features of crystalline source rocks and to peculiar pedogenetic features and processes. The radioactivity survey was conducted during two different seasons with marked changes in the main climatic characteristics, namely dry summer and moist winter, to evaluate possible effects of seasonal climatic variations and soil properties on radioactivity measurements. Seasonal variations of radionuclides activities show their peak values in summer. The activities of (238)U, (232)Th and (4) K exhibit a positive correlation with the air temperature and are negatively correlated with precipitations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Genesis of the post-caldera eastern Upper Basin Member rhyolites, Yellowstone, WY: from volcanic stratigraphy, geochemistry, and radiogenic isotope modeling

NASA Astrophysics Data System (ADS)

Pritchard, Chad J.; Larson, Peter B.

2012-08-01

An array of samples from the eastern Upper Basin Member of the Plateau Rhyolite (EUBM) in the Yellowstone Plateau, Wyoming, were collected and analyzed to evaluate styles of deposition, geochemical variation, and plausible sources for low δ18O rhyolites. Similar depositional styles and geochemistry suggest that the Tuff of Sulphur Creek and Tuff of Uncle Tom's Trail were both deposited from pyroclastic density currents and are most likely part of the same unit. The middle unit of the EUBM, the Canyon flow, may be composed of multiple flows based on a wide range of Pb isotopic ratios (e.g., 206Pb/204Pb ranges from 17.54 to 17.86). The youngest EUBM, the Dunraven Road flow, appears to be a ring fracture dome and contains isotopic ratios and sparse phenocrysts that are similar to extra-caldera rhyolites of the younger Roaring Mountain Member. Petrologic textures, more radiogenic 87Sr/86Sr in plagioclase phenocrysts (0.7134-0.7185) than groundmass and whole-rock ratios (0.7099-0.7161), and δ18O depletions on the order of 5‰ found in the Tuff of Sulphur Creek and Canyon flow indicate at least a two-stage petrogenesis involving an initial source rock formed by assimilation and fractional crystallization processes, which cooled and was hydrothermally altered. The source rock was then lowered to melting depth by caldera collapse and remelted and erupted. The presence of a low δ18O extra-caldera rhyolite indicates that country rock may have been hydrothermally altered at depth and then assimilated to form the Dunraven Road flow.

Geology, geochronology, and geochemistry of basaltic flows of the Cat Hills, Cat Mesa, Wind Mesa, Cerro Verde, and Mesita Negra, central New Mexico

USGS Publications Warehouse

Maldonado, F.; Budahn, J.R.; Peters, L.; Unruh, D.M.

2006-01-01

The geochronology, geochemistry, and isotopic compositions of basaltic flows erupted from the Cat Hills, Cat Mesa, Wind Mesa, Cerro Verde, and Mesita Negra volcanic centres in central New Mexico indicate that each of these lavas had unique origins and that the predominant mantle involved in their production was an ocean-island basalt type. The basalts from Cat Hills (0.11 Ma) and Cat Mesa (3.0 Ma) are similar in major and trace element composition, but differences in MgO contents and Pb isotopic values are attributed to a small involvement of a lower crustal component in the genesis of the Cat Mesa rocks. The Cerro Verde rock is comparable in age (0.32 Ma) to the Cat Hills lavas, but it is more radiogenic in Sr and Nd, has higher MgO contents, and has a lower La/Yb ratio. This composition is explained by the melting of an enriched mantle source, but the involvement of another crustal component cannot be disregarded. The Wind Mesa rock is characterized by similar age (4.01 Ma) and MgO contents, but it has enriched rare-earth element contents compared with the Cat Mesa samples. These are attributed to a difference in the degree of partial melting of the Cat Mesa source. The Mesita Negra rock (8.11 Ma) has distinctive geochemical and isotopic compositions that suggest a different enriched mantle and that large amounts of a crustal component were involved in generating this magma. These data imply a temporal shift in magma source regions and crustal involvement, and have been previously proposed for Rio Grande rift lavas. ?? 2006 NRC Canada.

Geochemistry of sandstones from the Pliocene Gabir Formation, north Marsa Alam, Red Sea, Egypt: Implication for provenance, weathering and tectonic setting

NASA Astrophysics Data System (ADS)

Zaid, Samir M.

2015-02-01

Petrographic, major and trace element compositions of sandstones from the Pliocene Gabir Formation, Central Eastern Desert, Egypt have been investigated to determine their provenance, intensity of paleo-weathering of the source rocks and their depositional tectonic setting. Gabir Formation is composed mainly of sandstones alternating with limestone and shale beds. The Gabir sandstone is yellowish gray to yellowish brown color, calcareous and fossiliferous. The composition of this formation refers to shallow warm agitated marine conditions. Texturally, Gabir sandstones are immature, poorly sorted and grain supported. Abundance of feldspars indicates rapid deposition of sediments from a nearby source rocks. Their average modal composition (Q71.35F16.6L12.05), classifies them as sublitharenite and arkose with subordinate litharenite and subarkose, which is also supported by geochemical study. Chemical analyses revealed that sandstones have high SiO2, K2O > Na2O, and low Fe2O3 values, which are consistent with the modal data. Also, sandstone samples are enriched in most trace elements such as Ba, Sr, Ni, Cr and Zr and depleted in U and Th. The petrography and geochemistry suggest that Gabir sandstones were deposited in an active continental margin basin. They were mainly derived from granitic and low grade metamorphic sources. The CIA values (41.69-74.84) of the Gabir sandstones indicate low to moderate degree of chemical weathering, which may reflect cold and/or arid climate conditions in the source area. The source rocks are probably identified to be Proterozoic granites, metagabbros and metavolcanics, which must have been exposed during rifting, initiated during Oligocene and continued till post Miocene.

Characterisation of heavy metal-bearing phases in stream sediments of the Meža River Valley, Slovenia, by means of SEM/EDS analysis

NASA Astrophysics Data System (ADS)

Miler, M.; Gosar, M.

2010-02-01

Stream sediment reflects the rock structure of the catchment area, its geochemical characteristics and possible recent contamination upstream of the sampling point and thus, it is most frequently used in geochemical researches of heavy metal pollution. Stream sediment samples were collected along the Meža River and its tributaries and the Drava River, located in the NNE part of Slovenia. Previous geochemical studies have shown that these sediments are heavily polluted with heavy metals as a consequence of past mining of Pb-Zn ore and steelworks activities. Conventional geochemical analyses (ICP-MS, AAS, etc.) provided limited information on mineralogy, morphology and sources of heavy metal-bearing phases therefore SEM/EDS was utilized. Several problems were confronted with during EDS analysis, which are related to identification and quantification of light elements, identification of elements due to peak overlaps and quantification of spectra from unpolished samples. These problems were successfully dealt with. SEM/EDS enabled successful identification of heavy metal-bearing phases in stream sediments. Ore mineral phases, such as cerussite, sphalerite, smithsonite and galena, different heavy metal-bearing Fe-alloys, Fe-oxides and spherical particles and common rock-forming and accessory mineral phases, such as barite, rutile, ilmenite, zircon and monazite, were identified using solely SEM/EDS. These results were used for subsequent geochemical interpretation and source apportionment of heavy metals, according to associations of different heavy metal-bearing phases. Heavy metal-bearing phases were arranged by their source and genesis into three groups, denoted as geogenic/technogenic, technogenic and geogenic.

Review of samples of sediment, tailings, and waters adjacent to the Cactus Queen gold mine, Kern County, California

USGS Publications Warehouse

Rytuba, James J.; Kim, Christopher S.; Goldstein, Daniel N.

2011-01-01

The Cactus Queen Mine is located in the western Mojave Desert in Kern County, California. The Cactus Queen gold-silver (Au-Ag) deposit is similar to other Au-Ag deposits hosted in Miocene volcanic rocks that consist of silicic domes and associated flows, pyroclastic rocks, and subvolcanic intrusions. The volcanic rocks were emplaced onto a basement of Mesozoic silicic intrusive rocks. A part of the Cactus Queen Mine is located on Federal land managed by the U.S. Bureau of Land Management (BLM). Staff from the BLM initially sampled the mine area and documented elevated concentrations of arsenic (As) in tailings and sediment. BLM then requested that the U.S. Geological Survey (USGS), in collaboration with Chapman University, measure and characterize As and other geochemical constituents in sediment, tailings, and waters on the part of the mine on Federal lands. This report is made in response to the request by the BLM, the lead agency mandated to conduct a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) - Removal Site Investigation (RSI). The RSI applies to the potential removal of As-contaminated mine waste from the Cactus Queen Mine as a means of reducing As release and exposure to humans and biota. This report summarizes data obtained from field sampling of sediments, mine tailings, and surface waters at the Cactus Queen Mine on January 27, 2008. Our results provide a preliminary assessment of the sources of As and associated chemical constituents that could potentially impact humans and biota.

The new Athena alpha particle X-ray spectrometer for the Mars Exploration Rovers

NASA Astrophysics Data System (ADS)

Rieder, R.; Gellert, R.; Brückner, J.; Klingelhöfer, G.; Dreibus, G.; Yen, A.; Squyres, S. W.

2003-11-01

The new alpha particle X-ray spectrometer (APXS) is part of the Athena payload of the two Mars Exploration Rovers (MER). The APXS sensor head is attached to the turret of the instrument deployment device (IDD) of the rover. The APXS is a very light-weight instrument for determining the major and minor elemental composition of Martian soils, rocks, and other geological materials at the MER landing sites. The sensor head has simply to be docked by the IDD on the surface of the selected sample. X-ray radiation, excited by alpha particles and X rays of the radioactive sources, is recorded by a high-resolution X-ray detector. The X-ray spectra show elements starting from sodium up to yttrium, depending on their concentrations. The backscattered alpha spectra, measured by a ring of detectors, provide additional data on carbon and oxygen. By means of a proper calibration, the elemental concentrations are derived. Together with data from the two other Athena instruments mounted on the IDD, the samples under investigation can be fully characterized. Key APXS objectives are the determination of the chemistry of crustal rocks and soils and the examination of water-related deposits, sediments, or evaporates. Using the rock abrasion tool attached to the IDD, issues of weathering can be addressed by measuring natural and abraded surfaces of rocks.

Organic petrology and geochemistry of Eocene Suzak bituminous marl, north-central Afghanistan: Depositional environment and source rock potential

USGS Publications Warehouse

Hackley, Paul C.; Sanfilipo, John

2016-01-01

Organic geochemistry and petrology of Eocene Suzak bituminous marl outcrop samples from Madr village in north-central Afghanistan were characterized via an integrated analytical approach to evaluate depositional environment and source rock potential. Multiple proxies suggest the organic-rich (TOC ∼6 wt.%) bituminous marls are ‘immature’ for oil generation (e.g., vitrinite Ro < 0.4%, Tmax < 425 °C, PI ≤ 0.05, C29 ααα S/S + R ≤ 0.12, C29 ββS/ββS+ααR ≤ 0.10, others), yet oil seeps are present at outcrop and live oil and abundant solid bitumen were observed via optical microscopy. Whole rock sulfur content is ∼2.3 wt.% whereas sulfur content is ∼5.0–5.6 wt.% in whole rock extracts with high polar components, consistent with extraction from S-rich Type IIs organic matter which could generate hydrocarbons at low thermal maturity. Low Fe-sulfide mineral abundance and comparison of Pr/Ph ratios between saturate and whole extracts suggest limited Fe concentration resulted in sulfurization of organic matter during early diagenesis. From these observations, we infer that a Type IIs kerogen in ‘immature’ bituminous marl at Madr could be generating high sulfur viscous oil which is seeping from outcrop. However, oil-seep samples were not collected for correlation studies. Aluminum-normalized trace element concentrations indicate enrichment of redox sensitive trace elements Mo, U and V and suggest anoxic-euxinic conditions during sediment deposition. The bulk of organic matter observed via optical microscopy is strongly fluorescent amorphous bituminite grading to lamalginite, possibly representing microbial mat facies. Short chain n-alkanes peak at C14–C16 (n-C17/n-C29 > 1) indicating organic input from marine algae and/or bacterial biomass, and sterane/hopane ratios are low (0.12–0.14). Monoaromatic steroids are dominated by C28clearly indicating a marine setting. High gammacerane index values (∼0.9) are consistent with anoxia stratification and may indicate intermittent saline-hypersaline conditions. Stable C isotope ratios also suggest a marine depositional scenario for the Suzak samples, consistent with the presence of marine foraminifera including abundant planktic globigerinida(?) and rare benthic discocyclina(?) and nummulites(?). Biomarker 2α-methylhopane for photosynthetic cyanobacteria implies shallow photic zone deposition of Madr marls and 3β-methylhopane indicates presence of methanotrophic archaea in the microbial consortium. The data presented herein are consistent with deposition of Suzak bituminous marls in shallow stratified waters of a restricted marine basin associated with the southeastern incipient or proto-Paratethys. Geochemical proxies from Suzak rock extracts (S content, high polar content, C isotopes, normal (αααR) C27–29 steranes, and C29/C30 and C26/C25 hopane ratios) are similar to extant data from Paleogene oils produced to the north in the Afghan-Tajik Basin. This observation may indicate laterally equivalent strata are effective source rocks as suggested by previous workers; however, further work is needed to strengthen oil-source correlations.

Qualitative and quantitative analysis of Dibenzofuran, Alkyldibenzofurans, and Benzo[b]naphthofurans in crude oils and source rock extracts

USGS Publications Warehouse

Meijun Li,; Ellis, Geoffrey S.

2015-01-01

Dibenzofuran (DBF), its alkylated homologues, and benzo[b]naphthofurans (BNFs) are common oxygen-heterocyclic aromatic compounds in crude oils and source rock extracts. A series of positional isomers of alkyldibenzofuran and benzo[b]naphthofuran were identified in mass chromatograms by comparison with internal standards and standard retention indices. The response factors of dibenzofuran in relation to internal standards were obtained by gas chromatography-mass spectrometry analyses of a set of mixed solutions with different concentration ratios. Perdeuterated dibenzofuran and dibenzothiophene are optimal internal standards for quantitative analyses of furan compounds in crude oils and source rock extracts. The average concentration of the total DBFs in oils derived from siliciclastic lacustrine rock extracts from the Beibuwan Basin, South China Sea, was 518 μg/g, which is about 5 times that observed in the oils from carbonate source rocks in the Tarim Basin, Northwest China. The BNFs occur ubiquitously in source rock extracts and related oils of various origins. The results of this work suggest that the relative abundance of benzo[b]naphthofuran isomers, that is, the benzo[b]naphtho[2,1-d]furan/{benzo[b]naphtho[2,1-d]furan + benzo[b]naphtho[1,2-d]furan} ratio, may be a potential molecular geochemical parameter to indicate oil migration pathways and distances.

FNF Construction Inc. Window Rock Airport Project: Coverage Under General Air Quality Permit for New or Modified Minor Source Cement Batch Plants in Indian Country

EPA Pesticide Factsheets

Approved Request for Coverage under General Air Quality Permit for New or Modified Minor Source Cement Batch Plants in Indian Country for FNF Construction Inc. Window Rock Airport Soil Cement Mixing Plant Project, Beacon Road, Window Rock, Arizona 86515.

Investigation of the relationship between radon anomalıes in deep water resources near Akşehir fault zone and the radial distances of the sources to an earthquake center

NASA Astrophysics Data System (ADS)

Gümüş, Ayla; Yalım, Hüseyin Ali

2018-02-01

Radon emanation occurs all the rocks and earth containing uranium element. Anomalies in radon concentrations before earthquakes are observed in fault lines, geothermal sources, uranium deposits, volcanic movements. The aim of this study is to investigate the relationship between the radon anomalies in water resources and the radial distances of the sources to the earthquake center. For this purpose, radon concentrations of 9 different deep water sources near Akşehir fault line were determined by taking samples with monthly periods for two years. The relationship between the radon anomalies and the radial distances of the sources to the earthquake center was obtained for the sources.

Re-Os systematics of early proterozoic ferropicrites, Pechenga Complex, northwestern Russia: Evidence for ancient 187Os-enriched plumes

NASA Astrophysics Data System (ADS)

Walker, Richard J.; Morgan, John W.; Hanski, Eero J.; Smolkin, Valery F.

1997-08-01

The Re-Os isotopic systematics of various ferropicritic flows and sills of the Pechenga Complex, Russia, have been examined. During crystallization about 1.98 Ga ago, many of these bodies became highly differentiated. In addition, some of the larger igneous units are associated with major NiCu ore deposits. The melts that produced these rocks have been termed ferropicritic because of their high FeO and MgO contents. They are also enriched in light rare earth elements (LREEs), TiO 2, Zr, and many other incompatible trace elements. Previous studies have concluded that the ferropicrites were most likely derived from an Fe-rich mantle plume that had a complex history of long-term LREE depletion (initial ɛNd = + 1.4), but that also experienced a LREE enrichment event within 200 Ma of the generation of the rocks. Whole rock samples believed to be most representative of primary melt compositions indicate that initial melt concentrations of rhenium and osmium were approximately 1.1 ppb and 0.5 ppb, respectively. The high primary melt concentrations presumably made the osmium contained in the melts relatively immune to the effects of crustal contamination. Nonetheless, all ore-bearing intrusions examined show osmium isotopic evidence for crustal contamination. For example, the initial γOs for some primary magmatic sulfides from the Pilgujärvi intrusion average +46. Other ore-bearing intrusions, such as the Kammikivi sill, appear to have been similarly contaminated by crustal osmium during the injection of magma, with initial yo, values as high as +251. The seemingly high levels of crustal osmium may be attributed to the rapidly diminishing concentrations of osmium in the melts as the larger bodies differentiated, combined with localized in situ assimilation of the metasedimentary rocks that comprise the country rocks. The Re-Os systematics of some whole rock samples of both mineralized and sulfide-poor intrusions were affected by post-magmatic events, especially the greenschist grade metamorphism that impacted the rocks between about 1.7 and 1.8 Ga ago. The metamorphic effects are reflected in the recrystallization of many of the primary sulfides. As a consequence of this open-system behavior in many whole rock samples, the primary igneous Re-Os systematics of these rocks are best examined via analysis of magmatic phases such as chromite, olivine, clinopyroxene, and primary sulfides. Chromite and ilmenite+sulfide separates from two sulfide-poor lava flows, the Lammas and Keskitunturi, have characteristically low 187Re/ 188Os ( < l), and because of the limited age correction, precisely define the initial γOs of these systems to be +6.0±0.7. Because of the identical initial compositions of the two, spatially distinct lava flows, and the fact that these flows were extruded onto only slightly older volcanic rocks, we conclude that the +6.0 value reflects the composition of the mantle source and not minor crustal contamination. Although 187Os-enriched, plume-derived systems are common during the Phanerozoic, this is the earliest known evidence for the existence of long-term, Re-enriched mantle reservoirs. The most commonly invoked model to explain 187Os enrichments in Phanerozoic systems, oceanic crustal recycling, in this instance requires that very large proportions of oceanic crust were recycled into the mantle source and that the event was likely very ancient. Other options, such as core-mantle interaction and a stratified mantle, are also discussed.

Understanding Sulfur Systematics in Large Igneous Provinces Using Sulfur Isotopes

NASA Astrophysics Data System (ADS)

Novikova, S.; Edmonds, M.; Turchyn, A. V.; Maclennan, J.; Svensen, H.; Frost, D. J.; Yallup, C.

2013-12-01

The eruption of the Siberian Traps coincided with perhaps the greatest environmental catastrophe in Earth's history, at the Permo-Triassic boundary. The source and magnitude of the volatile emissions, including sulfur, associated with the eruption remain poorly understood yet were critical in forcing environmental change. Two of the primary questions are how much sulfur gases were emitted during the eruptions and from where they were sourced. Primary melts carry dissolved sulfur from the mantle. Magmas ponding in sills and ascending through dykes may also assimilate sulfur from country rocks, as well as heat the country rocks and generate fluids through contact metamorphism. If the magmas interacted thermally, for prolonged periods, with sulfur-rich country rocks then it is probable that the sulfur budget of these eruptions might have been augmented considerably. This is exactly what we have shown recently for a basaltic sill emplaced in oil shale that fed eruptions of the British Tertiary Province, where surrounding sediments showed extensive desulfurization (Yallup et al. Geoch. Cosmochim. Acta, online, 2013). In the current study sulfur isotopes and trace element abundances are used to discriminate sulfur sources and to model magmatic processes for a suite of Siberian Traps sill and lava samples. Our bulk rock and pyrite geochemical analyses illustrate clearly their high abundance of 34S over 32S. The high 34S/32S has been noted previously and linked to assimilation of sulfur from sediments but may alternatively be inherited from the mantle plume source. With the aim of investigating the sulfur isotopic signature in the melt prior to devolatilization, we use secondary ion mass spectrometry (SIMS), for which a specific set of glass standards was synthesised. In order to understand how sulfur isotopes fractionate during degassing we have also conducted a parallel study of well-characterized tephras from Kilauea Volcano, where sulfur degassing behavior is well known.

[Fluoride in drinking water in Cuba and its association with geological and geographical variables].

PubMed

Luna, Liliam Cuéllar; Melián, Maricel García

2003-11-01

To determine the association between different concentrations of the fluoride ion in drinking water and some geological and geographical variables in Cuba, by using a geographic information system. From November 1998 to October 1999 we studied the fluoride concentration in the sources of drinking water for 753 Cuban localities that had at least 1 000 inhabitants. For the information analysis we utilized the MapInfo Professional version 5.5 geographic information system, using the overlaying method. The study variables were the concentration of the fluoride ion in the water sources, the geological characteristics of the area, the alignments (geological characteristics that were found together), the types of water sources, and whether an area was a plain or mountainous. The results were grouped by locality and municipality. In 83.1% of the localities, the water samples were collected from wells and springs, and the remaining 16.9% came from dams and rivers. Of the 753 localities studied, 675 of them (89.6%) had low or medium fluoride concentrations (under 0.7 mg/L). The eastern region of the country was the one most affected by high fluoride concentrations in the waters, followed by the central region of the country. The majority of the localities with high natural fluoride concentrations were in areas located on Cretaceous volcanic arc rocks. The presence of fluoride in the drinking waters was related to the alignments with the earth's crust, in rock complexes of volcanic-sedimentary origin and of intrusive origin and also in carbonate rocks. However, the highest fluoride concentrations generally coincided with rock complexes of volcanic-sedimentary origin and of intrusive origin. All the localities with high fluoride concentrations in the water were associated with wells. The fluoride concentration is low or medium in the drinking water sources for 89.6% of the Cuban localities with at least 1 000 inhabitants. Geological and geographical characteristics can help identify areas with optimal or high concentrations of the fluoride ion in the drinking water.

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 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.

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.

Age and speciation of iodine in groundwater and mudstones of the Horonobe area, Hokkaido, Japan: Implications for the origin and migration of iodine during basin evolution

NASA Astrophysics Data System (ADS)

Togo, Yoko S.; Takahashi, Yoshio; Amano, Yuki; Matsuzaki, Hiroyuki; Suzuki, Yohey; Terada, Yasuko; Muramatsu, Yasuyuki; Ito, Kazumasa; Iwatsuki, Teruki

2016-10-01

This paper reports the concentration, speciation and isotope ratio (129I/127I) of iodine from both groundwater and host rocks in the Horonobe area, northern Hokkaido, Japan, to clarify the origin and migration of iodine in sedimentary rocks. Cretaceous to Quaternary sedimentary rocks deposited nearly horizontally in Tenpoku Basin and in the Horonobe area were uplifted above sea level during active tectonics to form folds and faults in the Quaternary. Samples were collected from the Pliocene Koetoi and late Miocene Wakkanai formations (Fms), which include diatomaceous and siliceous mudstones. The iodine concentration in groundwater, up to 270 μmol/L, is significantly higher than that of seawater, with the iodine enrichment factor relative to seawater reaching 800-1500. The iodine concentration in the rocks decreases from the Koetoi to Wakkanai Fms, suggesting that iodine was released into the water from the rocks of deeper formations. The iodine concentration in the rocks is sufficiently high for forming iodine-rich groundwater as found in this area. X-ray absorption near edge structure (XANES) analysis shows that iodine exists as organic iodine and iodide (I-) in host rocks, whereas it exists mainly as I- in groundwater. The isotope ratio is nearly constant for iodine in the groundwater, at [0.11-0.23] × 10-12, and it is higher for iodine in rocks, at [0.29-1.1] × 10-12, giving iodine ages of 42-60 Ma and 7-38 Ma, respectively. Some iodine in groundwater must have originated from Paleogene and even late Cretaceous Fms, which are also considered as possible sources of oil and gas, in view of the old iodine ages of the groundwater. The iodine ages of the rocks are older than the depositional ages, implying that the rocks adsorbed some iodine from groundwater, which was sourced from greater depths. The iodine concentration in groundwater decreases with decreasing chlorine concentration due to mixing of iodine-rich connate water and meteoric water. A likely scenario is that iodine-rich brine formed during the long-term basin evolution from the Cretaceous to Quaternary and that this brine was diluted by mixing with meteoric water during uplifting and denudation of the area.

40 CFR 436.180 - Applicability; description of the phosphate rock subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... phosphate rock subcategory. 436.180 Section 436.180 Protection of Environment ENVIRONMENTAL PROTECTION... SOURCE CATEGORY Phosphate Rock Subcategory § 436.180 Applicability; description of the phosphate rock... bearing rock, ore or earth for the phosphate content. [43 FR 9809, Mar. 10, 1978] ...

40 CFR 436.180 - Applicability; description of the phosphate rock subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... phosphate rock subcategory. 436.180 Section 436.180 Protection of Environment ENVIRONMENTAL PROTECTION... SOURCE CATEGORY Phosphate Rock Subcategory § 436.180 Applicability; description of the phosphate rock... bearing rock, ore or earth for the phosphate content. [43 FR 9809, Mar. 10, 1978] ...

40 CFR 436.180 - Applicability; description of the phosphate rock subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... phosphate rock subcategory. 436.180 Section 436.180 Protection of Environment ENVIRONMENTAL PROTECTION... SOURCE CATEGORY Phosphate Rock Subcategory § 436.180 Applicability; description of the phosphate rock... bearing rock, ore or earth for the phosphate content. [43 FR 9809, Mar. 10, 1978] ...

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.

In Situ Production of Chlorine-36 in the Eastern Snake River Plain Aquifer, Idaho: Implications for Describing Ground-Water Contamination Near a Nuclear Facility

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

L. D. Cecil; L. L. Knobel; J. R. Green

2000-06-01

The purpose of this report is to describe the calculated contribution to ground water of natural, in situ produced 36Cl in the eastern Snake River Plain aquifer and to compare these concentrations in ground water with measured concentrations near a nuclear facility in southeastern Idaho. The scope focused on isotopic and chemical analyses and associated 36Cl in situ production calculations on 25 whole-rock samples from 6 major water-bearing rock types present in the eastern Snake River Plain. The rock types investigated were basalt, rhyolite, limestone, dolomite, shale, and quartzite. Determining the contribution of in situ production to 36Cl inventories inmore » ground water facilitated the identification of the source for this radionuclide in environmental samples. On the basis of calculations reported here, in situ production of 36Cl was determined to be insignificant compared to concentrations measured in ground water near buried and injected nuclear waste at the INEEL. Maximum estimated 36Cl concentrations in ground water from in situ production are on the same order of magnitude as natural concentrations in meteoric water.« less

Geochemical Evolution of Groundwater in the Medicine Lodge Creek Drainage Basin with Implications for the Eastern Snake River Plain Aquifer, Eastern Idaho

NASA Astrophysics Data System (ADS)

Ginsbach, M. L.; Rattray, G. W.; McCurry, M. O.; Welhan, J. A.

2012-12-01

The eastern Snake River Plain aquifer (ESRPA) is an unconfined, continuous aquifer located in a northeast-trending structural basin filled with basaltic lava flows and sedimentary interbeds in eastern Idaho. The ESPRA is not an inert transport system, as it acts as both a sink and source for solutes found in the water. More than 90% of the water recharged naturally to the ESRPA is from the surrounding mountain drainage basins. Consequently, in order to understand the natural geochemistry of water within the ESRPA, the chemistry of the groundwater from the mountain drainage basins must be characterized and the processes that control the chemistry need to be understood. The U.S. Geological Survey, in cooperation with the U.S. Department of Energy and Idaho State University, has been studying these mountain drainage basins to help understand the movement of waste solutes in the ESRPA at the Idaho National Laboratory (INL) in eastern Idaho. This study focuses on the Medicine Lodge Creek drainage basin, which originates in the Beaverhead Mountains, extends onto the eastern Snake River Plain, and contributes recharge to the ESRPA beneath the INL as underflow along the northeastern INL boundary. Water and rock samples taken from the Medicine Lodge Creek drainage basin were analyzed to better understand water/rock interactions occurring in this system and to define the groundwater geochemistry of this drainage basin. Water samples were collected at 10 locations in the drainage basin during June 2012: 6 groundwater wells used for agricultural irrigation or domestic use and 4 springs. These water samples were analyzed for major ions, nutrients, trace metals, isotopes, and dissolved gasses. Samples of rock representative of the basalt, rhyolite, and sediments that occur within the drainage basin also were collected. These samples were analyzed using x-ray diffraction and petrographic study to determine the mineralogical constituents of the rock and the presence and composition of alteration products. The lithologic variability in this area leads to differing water-rock interactions occurring in different parts of the drainage basin. Anthropogenic influences also affect the water; at the far downgradient end of the drainage basin, increased levels of chloride and sulfate in the groundwater suggest an increased influence of irrigation recharge. Results from both water and rock analyses are combined in geochemical modeling software to determine plausible reactions that occur in groundwater collected at the sampling sites.

Hydrocarbon gases associated with permafrost in the Mackenzie Delta, Northwest Territories, Canada

USGS Publications Warehouse

Collett, T.S.; Dallimore, S.R.

1999-01-01

Molecular and isotopic analyses of core gas samples from 3 permafrost research core holes (92GSCTAGLU, 92GSCKUMAK, 92GSCUNIPKAT; sample core depths ranging from 0.36 to 413.82 m) in the Mackenzie Delta of the Northwest Territories of Canada reveal the presence of hydrocarbon gases from both microbial and thermogenic sources. Analyses of most headspace and blended gas samples from the ice-bonded permafrost portion of the core holes yielded C1/(C2 + C3) hydrocarbon gas ratios and CH4-C isotopic compositions (??13C CH4) indicative of microbially sourced CH4 gas. However, near the base of ice-bonded permafrost and into the underlying non-frozen stratigraphic section, an increase in ethane (C2) concentrations, decreases in C1/(C2 + C3) hydrocarbon gas ratios, and CH4-C isotopic (??13C CH4) data indicate the presence of hydrocarbon gases derived from a thermogenic source. The thermogenic gas below permafrost in the Mackenzie Delta likely migrated from deeper hydrocarbon accumulations and/or directly from thermally mature hydrocarbon source rocks.

Pb-Pb systematics of lunar rocks: differentiation, magmatic and impact history of the Moon

NASA Astrophysics Data System (ADS)

Nemchin, A.; Martin, W.; Norman, M. D.; Snape, J.; Bellucci, J. J.; Grange, M.

2016-12-01

Two independent decay chains in U-Pb system allow the determination of both ages and initial isotope compositions by analyzing only Pb in the samples. A typical Pb analysis represents a mixture of radiogenic Pb produced from the in situ U decay, initial Pb and laboratory contamination. Utilizing the ability of ion probes to analyse 10-30 micrometer-sized spots in the samples while avoiding fractures and other imperfections that commonly host contamination, permits extraction of pure lunar Pb compositions from the three component mixtures. This results in both accurate and precise ages of the rocks and their initial compositions. Lunar Mare and KREEP basalts postdating the major lunar bombardment are likely to represent such three component mixtures and are therefore appropriate for this approach, also giving an opportunity to investigate Pb evolution in their sources. A source evolution model constrained using available data indicates a major differentiation on the Moon at 4376±18 Ma and very radiogenic lunar mantle at this time. This age is likely to reflect the mean time of KREEP formation during the last stage of Magma Ocean differentiation. Rocks older than about 3.9 Ga are more complex than basalts and may include an extra Pb component, if modified by impacts. An example of this is presented by Pb-Pb data obtained for the anorthosite sample 62236, where the age of the rock is determined as 4367±29 Ma from analyses of CPx lamellae inside the large Opx grains: however large plagioclase crystals do not contain Pb in quantities sufficient for ion probe analysis, precluding determination of the initial Pb composition of the sample. Most of Pb is found in the brecciated parts of the anorthosite between the large grains. The composition of this Pb is similar to the initial Pb of 3909±17 Ma Apollo 16 breccia 66095, suggesting that is was injected into the anorthosite during a 3.9 Ga impact. Similar ca 3.9 Ga ages were determined for 1-2 millimeter size feldspathic clasts from several Apollo 14 breccias, where they are likely to date Pb homogenization during the Imbrium impact. Combined with U-Pb data obtained previously using U-bearing minerals such as zircon and phosphates, the new Pb-Pb data sets open an opportunity for a detailed chronological and isotopic investigation of lunar differentiation, magmatic evolution and impact history.

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.

Detrital Zircon Signature of Proterozoic Metasedimentary Rocks of the Pearya Terrane, Northern Ellesmere Island: Implications for Terrane Stratigraphy and Circum-Arctic Terrane Correlations

NASA Astrophysics Data System (ADS)

Malone, S. J.; McClelland, W.

2012-12-01

The Pearya Terrane, currently recognized as the only exotic terrane in the Canadian Arctic margin, includes early Tonian metaigneous rocks and a sequence of sedimentary rocks ranging from Proterozoic shallow marine to Silurian arc-accretionary units. Succession II (Trettin, 1987) of the Pearya Terrane represents variably metamorphosed metasedimentary rocks of presumed Neoproterozoic to early Ordocician age. These units are structurally juxtaposed with earliest Neoproterozoic orthogneiss of Succession I and the overlaying sedimentary rocks of the Paleozoic section. Detrital zircon age spectra from seven samples of Neoproterozoic meta-sedimentary rocks define three groups on the basis of dominant age peaks and the age of the youngest peaks. Group I, representing three quartzite samples, contains young zircon age peaks at c. 1050 Ma with numerous c. 1100 Ma to 1800 Ma peaks. Detrital zircon spectra from Group I correlate closely with data from the latest Mesoproterozoic Brennevinsfjorden Group of Northeastern Svalbard, suggesting that the base of Succession II may be older than the Succession I orthogneiss, and that the contact between them is tectonic. Group II is defined by a dominant c. 970 Ma age peak that overlaps with ages determined for basement orthogneiss units and indicates that local sedimentary sources, possibly relating to Tonian igneous activity, dominated. Group III displays a similar pattern of c. 1000 Ma to 1800 Ma age peaks to Group I, but contains a small population of c. 600 Ma to 700 Ma grains that are likely sourced from elements of the Timanide orogen and/or the Arctic Alaska-Chukotka (AAC) microplate. The ubiquitous Mesoproterozoic ages suggest extensive sediment input from the Grenville-Svegonorwegian domains of Laurentia and Baltica, either directly or by sediment recycling. This is consistent with detrital zircon datasets from other North Atlantic-Arctic Caledonide terranes, reinforcing stratigraphic links between the Pearya Terrane, Svalbard, and the Caledonides of Norway and Greenland. In addition, the Succession II dataset provides a Neoproterozoic background for terranes originating in the northern Caledonides. Similar detrital zircon age peaks appear in Paleozoic sediments of AAC and the Alexander Terrane. The Pearya Terrane represents a critical link between the Arctic Caledonides and terranes translated into the Panthalassic realm during the Paleozoic.

The role of acoustic emission in the study of rock fracture

USGS Publications Warehouse

Lockner, D.

1993-01-01

The development of faults and shear fracture systems over a broad range of temperature and pressure and for a variety of rock types involves the growth and interaction of microcracks. Acoustic emission (AE), which is produced by rapid microcrack growth, is a ubiquitous phenomenon associated with brittle fracture and has provided a wealth of information regarding the failure process in rock. This paper reviews the successes and limitations of AE studies as applied to the fracture process in rock with emphasis on our ability to predict rock failure. Application of laboratory AE studies to larger scale problems related to the understanding of earthquake processes is also discussed. In this context, laboratory studies can be divided into the following categories. 1) Simple counting of the number of AE events prior to sample failure shows a correlation between AE rate and inelastic strain rate. Additional sorting of events by amplitude has shown that AE events obey the power law frequency-magnitude relation observed for earthquakes. These cumulative event count techniques are being used in conjunction with damage mechanics models to determine how damage accumulates during loading and to predict failure. 2) A second area of research involves the location of hypocenters of AE source events. This technique requires precise arrival time data of AE signals recorded over an array of sensors that are essentially a miniature seismic net. Analysis of the spatial and temporal variation of event hypocenters has improved our understanding of the progression of microcrack growth and clustering leading to rock failure. Recently, fracture nucleation and growth have been studied under conditions of quasi-static fault propagation by controlling stress to maintain constant AE rate. 3) A third area of study involves the analysis of full waveform data as recorded at receiver sites. One aspect of this research has been to determine fault plane solutions of AE source events from first motion data. These studies show that in addition to pure tensile and double couple events, a significant number of more complex event types occur in the period leading to fault nucleation. 4) P and S wave velocities (including spatial variations) and attenuation have been obtained by artificially generating acoustic pulses which are modified during passage through the sample. ?? 1993.

Non-zero Δ33S preserved in rocks from the Basal Ultramafic Sequence indicate crustal contamination in the most primitive magma of the Rustenburg Layered Suite (Bushveld Complex, South Africa)

NASA Astrophysics Data System (ADS)

Magalhaes, N.; Wilson, A.; Penniston-Dorland, S.; Farquhar, J.

2017-12-01

The sulfur isotope composition of the Rustenburg Layered Suite (RLS) of the Bushveld Complex is different than expected from a magma sourced from the mantle (Δ33S=0), as measurements indicate the presence of an Archean surface-derived sulfur component. The Basal Ultramafic Sequence (BUS) is thought to be the most primitive magma of the RLS, as it is the lowest in the stratigraphy, has the highest Mg# (>0.92) for primary phases (olivine and orthopyroxene), and is in direct contact with the Magaliesberg quartzite of the Pretoria Group.We have measured the composition of sulfides in rocks from the Lower Zone, Marginal Zone, and the BUS, which were sampled in a 2300m drill core from the Clapham area, in the eastern Bushveld Complex. While the rocks of the Lower Zone have a relatively homogeneous non-zero Δ33S of 0.065‰, comparable to previous findings, there is an abrupt increase in the value of Δ33S (up to +0.301‰) in the Marginal Zone, which may be consistent with the observation in hand sample of assimilation of country rocks. The BUS also shows a surface-derived signal (average of 0.040‰), which is the lowest measured for any zone of the RLS.The non-zero Δ33S found in the Basal Ultramafic Sequence is evidence of the contamination of the magma with surface-derived material. In the upper parts of the intrusion, the Δ33S signature relates to whole-rock Sr and Nd isotopes, and their relationship suggests multiple sources of contamination. However, the relationship between sulfur and in-situ strontium isotope compositions (plagioclase) in this section of the RLS is not as clear as it is further up in the stratigraphy. This might reflect small-scale processes during the magmatic chamber stage, different compositions of local wall rock compared to deeper contaminants, or the presence of decoupled behavior between the isotope systems.These differences in the sulfur isotope composition between the different stratigraphic layers have been preserved regardless of any late magmatic processes that may have occurred, which further supports that the sulfur isotope composition of the RLS was not fully homogenized at a later stage by fluid migration.

Contrasting styles of sedimentation and deformation in the Chugach Terrane accretionary complex, south-central Alaska

NASA Astrophysics Data System (ADS)

Amato, J. M.; Pavlis, T. L.; Worthman, C.; Kochelek, E.; Day, E. M.; Clift, P. D.; Hecker, J.

2011-12-01

In southeast Alaska the Chugach terrane represents an accretionary complex associated with several arcs active at 200-65 Ma. This lithostratigraphic unit consists of blueschists with Early Jurassic metamorphic ages and uncertain depositional ages; the Jurassic-Cretaceous McHugh Complex; and the Late Cretaceous Valdez Group. Detrital zircon ages from densely sampled transects reveals patterns in the assembly of the complex. Blueschists are almost totally barren of zircon, suggesting protoliths derived from mafic-intermediate volcanic protoliths far from a continental source. There is an age gap between the blueschists and the McHugh complex interpreted to be caused by an episode of tectonic erosion. The McHugh Complex is two separate units that are lithologically and geochronologically distinct. The older McHugh is a melange is dominated by stratally disrupted volcanic rocks, chert, and argillite. The oldest McHugh rocks have maximum depositional ages (MDA) of 177-150 Ma at Seldovia and 157-145 Ma at Turnagain Arm; the lack of older rocks at Turnagain Arm suggests removal of structural section by faulting. The MDAs of the older McHugh rocks do not decrease progressively away from the arc. There is a 45 m.y. gap in MDA between the older McHugh and the Late Cretaceous McHugh rocks. The younger McHugh rocks are dominated by volcanogenic sandstone and coarse conglomerate and MDA decreases from 100 Ma near the boundary with the older McHugh mesomelange to 85 Ma near the Valdez Group. The Valdez Group consists of coherently bedded turbidites with a MDA range of 85-60 Ma that decreases progressively outboard of the arc source. A sample from the Orca Group of the Prince William terrane is lithologically similar to the Valdez Group and there is no gap in MDA between Valdez and Orca Groups. 55 Ma dikes cut the McHugh and Valdez Groups in the western Chugach and Kenai Mountains. The oldest units of the Chugach terrane are the most deformed, with deformation and metamorphism becoming progressively less intense. The older part of the McHugh Complex was likely also subducted deeper than younger units but not beyond greenschist facies. Another period of tectonic erosion was initiated by ridge subduction at ~120 Ma, followed by continuous accretion the younger McHugh complex, the Valdez Group, and continued <60 Ma in the Orca Group.

A longitudinal assessment of the aquatic macroinvertebrate community in the channelized lower Missouri River

USGS Publications Warehouse

Poulton, Barry C.; Wildhaber, Mark L.; Charbonneau, Collette S.; Fairchild, James F.; Mueller, Brad G.; Schmitt, Christopher J.

2003-01-01

We conducted an aquatic macroinvertebrate assessment in the channelized reach of the lower Missouri River, and used statistical analysis of individual metrics and multimetric scores to identify community response patterns and evaluate relative biological condition. We examined longitudinal site differences that are potentially associated with water qualityrelated factors originating from the Kansas City metropolitan area, using data from coarse rock substrate in flowing water habitats (outside river bends), and depositional mud substratein slack water habitats (dike fields). Three sites above rivermile (RM) 369 in Kansas City (Nebraska City, RM = 560; St. Joseph, RM = 530; Parkville, RM = 377) and three below (Lexington, RM = 319; Glasgow, RM = 228; Hermann, RM = 94) were sampled with rock basket artificial substrates, a qualitative kicknet method, and the Petite Ponar. We also compared the performance of the methods used. A total of 132 aquatic macroinvertebrate taxa were collected from the lower Missouri River; one third of these taxa belonged to the sensitiveEPOT insect orders (Ephemeroptera, Plecoptera, Odonata, and Trichoptera). Rock baskets had the highest mean efficiency (34.1%) of the methods, and the largest number of taxa was collected by Ponar (n = 69) and kicknet (n = 69) methods. Seven of the 15 metrics calculated from rock basket data, and five ofthe nine metrics calculated from Ponar data showed highly significant differences (ANOVA, P < 0.001) at one or more sitesbelow Kansas City. We observed a substantial reduction in net-spinning Trichoptera in rock habitats below Kansas City (Lexington), an increase in relative dominance of Oligochaeta in depositional habitats at the next site downstream (Glasgow), and lower relative condition scores in rock habitat at Lexingtonand depositional habitat at Glasgow. Collectively, these data indicate that some urban-related impacts on the aquatic macroinvertebrate community are occurring. Our results suggest that the methods and assessment framework we used in this studycould be successfully applied on a larger scale with concurrentwater and sediment chemistry to validate metrics, establish impairment levels, and develop a specific macroinvertebrate community index for the lower Missouri River. We recommend accomplishing this with longitudinal multi-habitat sampling at a larger number of sites related to all potential sources of impairment, including major tributaries, urban areas, and point sources.

Reservoir Condition Pore-scale Imaging of Multiple Fluid Phases Using X-ray Microtomography

PubMed Central

Andrew, Matthew; Bijeljic, Branko; Blunt, Martin

2015-01-01

X-ray microtomography was used to image, at a resolution of 6.6 µm, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space of a carbonate rock at pressures and temperatures representative of typical formations used for CO2 storage. Chemical equilibrium between the CO2, brine and rock phases was maintained using a high pressure high temperature reactor, replicating conditions far away from the injection site. Fluid flow was controlled using high pressure high temperature syringe pumps. To maintain representative in-situ conditions within the micro-CT scanner a carbon fiber high pressure micro-CT coreholder was used. Diffusive CO2 exchange across the confining sleeve from the pore-space of the rock to the confining fluid was prevented by surrounding the core with a triple wrap of aluminum foil. Reconstructed brine contrast was modeled using a polychromatic x-ray source, and brine composition was chosen to maximize the three phase contrast between the two fluids and the rock. Flexible flow lines were used to reduce forces on the sample during image acquisition, potentially causing unwanted sample motion, a major shortcoming in previous techniques. An internal thermocouple, placed directly adjacent to the rock core, coupled with an external flexible heating wrap and a PID controller was used to maintain a constant temperature within the flow cell. Substantial amounts of CO2 were trapped, with a residual saturation of 0.203 ± 0.013, and the sizes of larger volume ganglia obey power law distributions, consistent with percolation theory. PMID:25741751

Association of Sub-continental and Asthenosphere related Volcanism in NW Iran,Implication forMantle thermal perturbation induced by slab break off and collision event

NASA Astrophysics Data System (ADS)

Jahangiri, A.

2017-12-01

Cenozoic magmatic rocks occur extensively in the north of the Zagros suture zone and constitute a significant component of the continental crust in this segment of the Alpine-Himalayan orogenic belt. They range in age from Eocene to quaternary. Miocene to Plio-Quaternary volcanism with post-collisional related significant is covered vast areas in NW Iran. These volcanic rocks can be divided into three different sub-groups on the basis of their mineralogy, geochemistry and magma sources including: 1. alkaline leucite-bearing mafic rocks, which are characterized with high ratios of K2O/Na2O, high content LILE and low HFS elements like Ti, Nb and Ta. They are display fractionated REE patterns and based on different discrimination diagrams show similarity with subduction related magmas. 2- Olivine basalt to trachy-basaltic samples which shows similarity to within plate basalts with high content of TiO2, Nb, Ta and fractionated REE pattern. However, compared with a global average of OIB, they are display slightly higher LIL elements and lower HFS elements concentrations, features that resemble to the arc magmas and suggest that the source of the magmas may have been contaminated by slab-derived fluids. These rocks have simple mineralogical composition with plagioclase, clinopyroxene and olivine. 3- Dominant dacitic volcanic rocks with adakitic geochemical characteristics such as highly fractionate REE pattern and high Sr/Y ratio. Generation of adakitic magmas can be related to increased temperatures in the subduction zone due to mantle upwelling and slab tearing. Subsequent asthenospheric upwelling could be caused direct melting of sub-continental mantle to produce the alkaline magmas, with high contents of K2O, MgO and volatile rich phase's potassic magmas that led to crystallization of leucite, phlogopite, apatite and olivine in studied samples. Rupture of the continental lithosphere by strike-slip-related transtensional deformation might have caused decompression partial melting of the asthenospheric mantle and generating alkali basalts. Continental lithosphere rupturing is occurred subsequent to slab breakoff/delamination and sub-continental mantle thermal perturbation processes following closure of Neo-Tethys and collision of Arabian plate with microplate of Iran.

Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments

NASA Astrophysics Data System (ADS)

Martín-Hernández, F.; Dekkers, M. J.; Bominaar-Silkens, I. M. A.; Maan, J. C.

2008-07-01

Here we report on the sources of magnetic anisotropy in pyrrhotite, an iron sulphide present in many rocks as an important carrier of the Natural Remanent Magnetization. While the magnetic hysteresis parameters of pyrrhotite are well known, the existing database concerning its anisotropy behaviour is patchy and ambiguous. Therefore, a collection of 11 seemingly single crystals of natural pyrrhotite was scrutinized. Before embarking on the anisotropy determinations the set of single crystals was extensively characterized rock magnetically by measuring Curie temperatures, hysteresis loops, IRM acquisition curves, and FORC diagrams (the latter three all at room temperature). First the variation of the low-field susceptibility as function of applied field and grain size was evaluated for fields ranging from 1 to 450 A m-1. Existing grain size dependent data and the present larger crystals show a logarithmic grain size dependence. This enables estimating the grain size for unimodal pyrrhotite distributions in rocks. Measured trends are better fitted with an exponential function than with a Rayleigh Law style function. Based on the rock magnetic characterization and the behaviour of the anisotropy of magnetic susceptibility six samples (of the original 11) were selected for the high-field anisotropy determinations within the basal plane. Those data were acquired with a torque cantilever-type magnetometer. As expected, most single crystals showed a pure 6-θ curve within their basal plane because of the easy axis configuration. In some crystals, however, lower harmonic terms overlapped the 6-θ term. This may be the dominant source of the observed variation in magnetic anisotropy properties. Torque data of three of the six samples were of sufficient quality to allow evaluation of K1. Re-evaluation of existing torque data and including the present newly derived determinations, yields for the anisotropy constant of pyrrhotite within the basal plane K1: (2.7 +/- 0.2) 104 Jm-3. This is over an order of magnitude more precise than the sparse existing K1 data; only the value reported by Mikami and co-authors in 1959 agrees with the new determination. With this firmly established K1 value meaningful anisotropy models are now possible for pyrrhotite-bearing rocks.

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.

Geochemistry, Nd-Pb Isotopes, and Pb-Pb Ages of the Mesoproterozoic Pea Ridge Iron Oxide-Apatite–Rare Earth Element Deposit, Southeast Missouri

USGS Publications Warehouse

Ayuso, Robert A.; Slack, John F.; Day, Warren C.; McCafferty, Anne E.

2016-01-01

Iron oxide-apatite and iron oxide-copper-gold deposits occur within ~1.48 to 1.47 Ga volcanic rocks of the St. Francois Mountains terrane near a regional boundary separating crustal blocks having contrasting depleted-mantle Sm-Nd model ages (TDM). Major and trace element analyses and Nd and Pb isotope data were obtained to characterize the Pea Ridge deposit, improve identification of exploration targets, and better understand the regional distribution of mineralization with respect to crustal blocks. The Pea Ridge deposit is spatially associated with felsic volcanic rocks and plutons. Mafic to intermediate-composition rocks are volumetrically minor. Data for major element variations are commonly scattered and strongly suggest element mobility. Ratios of relatively immobile elements indicate that the felsic rocks are evolved subalkaline dacite and rhyolite; the mafic rocks are basalt to basaltic andesite. Granites and rhyolites display geochemical features typical of rocks produced by subduction. Rare earth element (REE) variations for the rhyolites are diagnostic of rocks affected by hydrothermal alteration and associated REE mineralization. The magnetite-rich rocks and REE-rich breccias show similar REE and mantle-normalized trace element patterns.Nd isotope compositions (age corrected) show that: (1) host rhyolites have ɛNd from 3.44 to 4.25 and TDM from 1.51 to 1.59 Ga; (2) magnetite ore and specular hematite rocks display ɛNd from 3.04 to 4.21 and TDM from 1.6 to 1.51 Ga, and ɛNd from 2.23 to 2.81, respectively; (3) REE-rich breccias have ɛNd from 3.04 to 4.11 and TDM from 1.6 to 1.51 Ga; and (4) mafic to intermediate-composition rocks range in ɛNd from 2.35 to 3.66 and in TDM from 1.66 to 1.56. The ɛNd values of the magnetite and specular hematite samples show that the REE mineralization is magmatic; no evidence exists for major overprinting by younger, crustal meteoric fluids, or by externally derived Nd. Host rocks, breccias, and magnetite ore shared a common origin from a similar source.Lead isotope ratios are diverse: (1) host rhyolite has 206Pb/204Pb from 24.261 to 50.091; (2) Pea Ridge and regional galenas have 206Pb/204Pb from 16.030 to 33.548; (3) REE-rich breccia, magnetite ore, and specular hematite rock are more radiogenic than galena; (4) REE-rich breccias have high 206Pb/204Pb (38.122–1277.61) compared to host rhyolites; and (5) REE-rich breccias are more radiogenic than magnetite ore and specular-hematite rock, having 206Pb/204Pb up to 230.65. Radiogenic 207Pb/206Pb age estimates suggest the following: (1) rhyolitic host rocks have ages of ~1.50 Ga, (2) magnetite ore is ~1.44 Ga, and (3) REE-rich breccias are ~1.48 Ga. These estimates are broadly consistent and genetically link the host rhyolite, REE-rich breccia, and magnetite ore as being contemporaneous.Alteration style and mineralogical or textural distinctions among the magnetite-rich rocks and REE-rich breccias do not correlate with different isotopic sources. In our model, magmatic fluids leached metals from the coeval felsic rocks (rhyolites), which provided the metal source reflected in the compositions of the REE-rich breccias and mineralized rocks. This model allows for the likelihood of contributions from other genetically related felsic and intermediate to more mafic rocks stored deeper in the crust. The deposit thus records an origin as a magmatic-hydrothermal system that was not affected by Nd and Pb remobilization processes, particularly if these processes also triggered mixing with externally sourced metal-bearing fluids. The Pea Ridge deposit was part of a single, widespread, homogeneous mixing system that produced a uniform isotopic composition, thus representing an excellent example of an igneous-dominated system that generated coeval magmatism and REE mineralization. Geochemical features suggest that components in the Pea Ridge deposit originated from sources in an orogenic margin. Basaltic magmatism produced by mantle decompression melting provided heat for extracting melts from the middle or lower crust. Continual addition of mafic magmas to the base of the subcontinental lithosphere, in a back-arc setting, remelted calc-alkaline rocks enriched in metals that were stored in the crust.The St. Francois Mountains terrane is adjacent to the regional TDM line (defined at a value of 1.55 Ga) that separates ~1600 Ma basement to the west, from younger basements to the east. Data for Pea Ridge straddle the TDM values proposed for the line. The Sm-Nd isotope system has been closed since formation of the deposit and the original igneous signatures have not been affected by cycles of alteration or superimposed mineralizing events. No evidence exists for externally derived Nd or Sm. The source region for metals within the Pea Ridge deposit had a moderate compositional variation and the REE-rich breccias and mineralized rocks are generally isotopically homogeneous. The Pea Ridge deposit thus constitutes a distinctive isotopic target for use as a model in identifying other mineralized systems that may share the same metal source in the St. Francois Mountains terrane and elsewhere in the eastern Granite-Rhyolite province.

Sudbury Breccia and suevite as glacial indicators transported 800 km to Kentland Astrobleme, Indiana

NASA Technical Reports Server (NTRS)

Mchone, John F.; Dietz, Robert S.; Peredery, Walter V.

1992-01-01

A glacial erratic whose place of origin is known by direct comparison with bedrock is known as an indicator. In 1971, while visiting the known astrobleme at Kentland, Indiana, Peredery recognized and sampled in the overlying glacial drift deposits a distinctive boulder of Sudbury suevite (black member, Onaping Formation) that normally occurs within the Sudbury Basin as an impact fall-back or wash-in deposit. The rock was sampled (but later mislaid) from a farmer's cairn next to a cleared field. Informal reports of this discovery prompted the other authors to recently reconnoiter the Kentland locality in an attempt to relocate the original boulder. Several breccia blocks were sampled but laboratory examination proved most of these probably to be diamictites from the Precambrian Gowganda Formation, which outcrops extensively in the southern Ontario. However, one sample was confirmed as typical Sudbury Breccia, which outcrops in the country rock surrounding the Sudbury Basin. Thus two glacial indicators were transported by Pleistocene continental glaciers about 820 km over a tightly proscribed path and, curiously, from one astrobleme to another. Brecciated boulders in the Illinois/Indiana till plain are usually ascribed to the Gowganda or Mississagi formations in Ontario. But impact-generated rocks need not be confused. The carbonaceous matrix of the suevite, for example, was sufficiently distinctive to assign it to the upper portion of the black Onaping. The unique and restricted source area of these indicators provide an accurate and reliable control for estimating Pleistocene ice movement.

Investigating the Sources and Timing of Projectiles Striking the Lunar Surface

NASA Technical Reports Server (NTRS)

Joy, K. H.; Kring, D. A.; Zolensky, M. E.; McKay, D. S.; Ross, D. K.

2011-01-01

The lunar surface is exposed to bombardment by asteroids, comets, and debris from them. Surviving fragments of those projectiles in the lunar regolith provide a direct measure of the sources of exogenous material delivered to the Moon. Con-straining the temporal flux of their delivery will directly address key questions about the bombardment history of the inner Solar System. Regolith breccias, which are consolidated samples of the lunar regolith, were closed to further impact processing at the time they were assembled into rocks [1]. They are, therefore, time capsules of impact bombardment at different times through lunar history. Here we investigate the impact archive preserved in the Apollo 16 regolith breccias and compare this record to evidence of projectile species in other lunar samples.

Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California

USGS Publications Warehouse

Bateman, P.C.; Dodge, F.C.W.; Kistler, R.W.

1991-01-01

Measurement of the magnetic susceptibility of more than 6000 samples of granitic rock from the Mariposa 1?? by 2?? quadrangle, which crosses the central part of the Sierra Nevada batholith between 37?? and 38??N latitude, shows that magnetic susceptibility values are above 10-2 SI units in the east and central parts of the batholith and drop abruptly to less than 10-3 SI units in the western foothills. In a narrow transitional zone, intermediate values (10-3 to 10-2) prevail. Magnetic susceptibility appears to decrease slightly westward within the zones of both high and low values. Magnetic susceptibility in plutonic rocks is chiefly a function of the abundance of magnetite, which depends, in turn, on the total iron content of the rocks and their oxidation ratio. Correlations of magnetic susceptibility with initial 87Sr/86Sr suggest that oxidation ratios have been inherited from the source regions for the magmas from which the rocks crystallized. Reduction of Fe3+ to Fe2+ by organic carbon or other reducing substances may also have affected magnetic susceptibility. -from Authors

Coeval Ar-40/Ar-39 ages of 65.0 million years ago from Chicxulub crater melt rock and Cretaceous-Tertiary boundary tektites

NASA Technical Reports Server (NTRS)

Swisher, Carl C., III; Grajales-Nishimura, Jose M.; Montanari, Alessandro; Margolis, Stanley V.; Claeys, Philippe; Alvarez, Walter; Renne, Paul; Cedillo-Pardo, Esteban; Maurrasse, Florentin J.-M. R.; Curtis, Garniss H.

1992-01-01

Ar-40/Ar-39 dating of drill-core samples of a glassy melt rock recovered from beneath a massive impact breccia contained with the 180-kilometer subsurface Chicxulub crater yields well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from Ar-40/Ar-39 ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The Ar-40/Ar-39 ages, in conjunction with geochemical and petrological similarities, strengthen the suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.

Provenance and tectonic setting of the Neoproterozoic clastic rocks hosting the Banana Zone Cu-Ag mineralisation, northwest Botswana

NASA Astrophysics Data System (ADS)

Kelepile, Tebogo; Bineli Betsi, Thierry; Franchi, Fulvio; Shemang, Elisha; Suh, Cheo Emmanuel

2017-05-01

Petrographic and geochemical data were combined in order to decipher the petrogenesis of the Neoproterozoic sedimentary succession associated with the Banana Zone Cu-Ag mineralisation (northwest Botswana), in the Kalahari Copperbelt. The investigated Neoproterozoic sedimentary succession is composed of two formations including the Ngwako Pan and the D'kar Formations. The Ngwako Pan Formation is made up of continental siliciclastic sediments, mainly sandstones interbedded with siltstones and mudstones, whereas the D'kar Formation is comprised of shallow marine laminated siltstones, sandstones and mudstones, with subordinate limestone. Copper-Ag mineralisation is essentially confined at the base of the D'kar Formation, which bears reduced organic components, likely to have controlled Cu-Ag precipitation. Sandstones of both the Ngwako Pan and the D'kar Formations are arkoses and subarkoses, composed of quartz (Q), feldspars (F) and lithic fragments (L). Moreover, geochemically the sandstones are considered as potassic and classified as arkoses. On the other hand, mudrocks of the D'kar Formation are finely laminated and are dominated by muscovite, sericite, chlorite and quartz. The modified chemical index of weathering (CIW‧) values indicated an intense chemical weathering of the source rock. The dominance of detrital quartz and feldspar grains coupled with Al2O3/TiO2 ratios (average 29.67 and 24.52 for Ngwako Pan and D'kar Formations, respectively) and Ni and Cr depletion in the sandstones, suggest a dominant felsic source. However, high concentrations of Ni and Cr and a low Al2O3/TiO2 ratio (<20) in the mudrocks of the D'kar Formation indicate a mixed source. Provenance of the investigated sandstones and mudrocks samples is further supported by the REE patterns, the size of Eu anomaly as well as La/Co, Th/Co, Th/Cr and Cr/Th ratios, which show a felsic source for the sandstones of both the Ngwako Pan and D'kar Formations and an intermediate source for the mudrocks of the D'kar Formation. Detrital modes (QFL diagrams) and geochemical characteristics of the sandstones of both the Ngwako Pan and D'kar Formations indicate that the detritus were probably supplied from a heavily weathered felsic continental block and deposited in a continental rift setting (passive margin) in a humid environment. The source rocks might have been the Palaeoproterozoic basement rocks (granitoids and granitic gneiss) and the Mesoproterozoic Kgwebe volcanic rocks exposed north of the study area.

Petrography and geochemistry of clastic sedimentary rocks as evidences for provenance of the Lower Cambrian Lalun Formation, Posht-e-badam block, Central Iran

NASA Astrophysics Data System (ADS)

Etemad-Saeed, N.; Hosseini-Barzi, M.; Armstrong-Altrin, John S.

2011-09-01

Petrography and geochemistry (major, trace and rare earth elements) of clastic rocks from the Lower Cambrian Lalun Formation, in the Posht-e-badam block, Central Iran, have been investigated to understand their provenance. Petrographical analysis suggests that the Lalun conglomerates are dominantly with chert clasts derived from a proximal source, probably chert bearing Precambrian Formations. Similarly, purple sandstones are classified as litharenite (chertarenite) and white sandstones as quartzarenite types. The detrital modes of purple and white sandstones indicate that they were derived from recycled orogen (uplifted shoulders of rift) and stable cratonic source. Most major and trace element contents of purple sandstones are generally similar to upper continental crust (UCC) values. However, white sandstones are depleted in major and trace elements (except SiO 2, Zr and Co) relative to UCC, which is mainly due to the presence of quartz and absence of other Al-bearing minerals. Shale samples have considerably lower content in most of the major and trace elements concentration than purple sandstones, which is possibly due to intense weathering and recycling. Modal composition (e.g., quartz, feldspar, lithic fragments) and geochemical indices (Th/Sc, La/Sc, Co/Th, Cr/Th, Cr/V and V/Ni ratios) of sandstones, and shales (La/Sc and La/Cr ratios) indicate that they were derived from felsic source rocks and deposited in a passive continental margin. The chondrite-normalized rare earth element (REE) patterns of the studied samples are characterized by LREE enrichment, negative Eu anomaly and flat HREE similar to an old upper continental crust composed chiefly of felsic components in the source area. The study of paleoweathering conditions based on modal composition, chemical index of alteration (CIA), plagioclase index of alteration (PIA) and A-CN-K (Al 2O 3 - CaO + Na 2O - K 2O) relationships indicate that probably chemical weathering in the source area and recycling processes have been more important in shale and white sandstones relative to purple sandstones. The results of this study suggest that the main source for the Lalun Formation was likely located in uplifted shoulders of a rifted basin (probably a pull-apart basin) in its post-rift stage (Pan-African basement of the Posht-e-badam block).

Chemistry of surface water at a volcanic summit area, Norikura, central Japan: multivariate statistical approach.

PubMed

Anazaw, K; Ohmori, L H

2001-11-01

Many hydrochemical studies on chemical formation of shallow ground water have been reported as results of water-rock interaction, and contamination of paleo-brine or human activities, whereas the preliminary formation of precipitation source in the recharged region has not been established yet. The purpose of this research work is to clarify the geochemical process of water formation from a water source unpolluted by seawater or human activity. Norikura volcano, located in western part of central Japan provided a suitable source for this research purpose, and hence chemical compositions of water samples from the summit and the mountainside area of Norikura volcano were determined. Most samples in the summit area showed very low electrical conductivity, and lower than 12 microS/cm. On the basis of the chemical compositions, principal component analysis (PCA) and factor analysis (FA), such as kinds of multivariate statistical techniques were used to extract geochemical factors affecting hydrochemical process. As a result, three factors were extracted. The first factor showed high loading on K+, Ca2+, SO2 and SiO2, and this factor was interpreted due to influence of the chemical interaction between acidic precipitated water and rocks. The second factor showed high loading on Na+ and Cl-, and it was assumed to be an influence of seawater salt. The third factor showed loading on NO3-, and it was interpreted to be caused by biochemical effect of vegetation. The proportionate contributions of these factors to the evolution of water chemical composition were found to be 45%, 20%, and 10% for factors 1, 2 and 3, respectively. The same exploration at the mountainside of Norikura volcano revealed that the chemical variances of the non-geothermal water samples were highly influenced by water-rock interactions. The silicate dissolution showed 45% contribution for all chemical variances, while the adsorption of Ca2+ and Mg2+ by precipitation or ion exchange showed 20% contribution. The seawater salt influence or biochemical effect was statistically negligible in this area. The clear differentiation of geochemical process on water formation was found between the summit area and the mountainside area.

Mercury isotope constraints on the source for sediment-hosted lead-zinc deposits in the Changdu area, southwestern China

NASA Astrophysics Data System (ADS)

Xu, Chunxia; Yin, Runsheng; Peng, Jiantang; Hurley, James P.; Lepak, Ryan F.; Gao, Jianfeng; Feng, Xinbin; Hu, Ruizhong; Bi, Xianwu

2018-03-01

The Lanuoma and Cuona sediment-hosted Pb-Zn deposits hosted by Upper Triassic limestone and sandstone, respectively, are located in the Changdu area, SW China. Mercury concentrations and Hg isotopic compositions from sulfide minerals and potential source rocks (e.g., the host sedimentary rocks and the metamorphic basement) were investigated to constrain metal sources and mineralization processes. In both deposits, sulfide minerals have higher mercury (Hg) concentrations (0.35 to 1185 ppm) than the metamorphic basement rocks (0.05 to 0.15 ppm) and sedimentary rocks (0.02 to 0.08 ppm). Large variations of mass-dependent fractionation (3.3‰ in δ202Hg) and mass-independent fractionation (0.3‰ in Δ199Hg) of Hg isotopes were observed. Sulfide minerals have Hg isotope signatures that are similar to the hydrothermal altered rocks around the deposit, and similar to the metamorphic basement, but different from barren sedimentary rocks. The variation of Δ199Hg suggests that Hg in sulfides was mainly derived from the underlying metamorphic basement. Mercury isotopes could be a geochemical tracer in understanding metal sources in hydrothermal ore deposits.

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.

HIMU-type Mid-Ocean Ridge Basalts Incorporate a Primitive Component

NASA Astrophysics Data System (ADS)

Tucker, J.; Mukhopadhyay, S.; Schilling, J. E.

2011-12-01

Samples from 5°N to 7°S along the MAR axis span a range of compositions from depleted MORB (La/SmN ~0.5, 206Pb/204Pb ~18) to very enriched MORB (La/SmN ~3, 206Pb/204Pb ~20). The measured 206Pb/204Pb in the enriched samples are among the highest measured MORB values and are thought to represent a HIMU type mantle (high μ where μ is the U/Pb ratio). Therefore, the enriched samples provide a unique opportunity to characterize the heavy noble gas composition of the HIMU mantle. If HIMU mantle is related to recycled crust, then the noble gas measurements can also provide insights into recycling of atmospheric noble gases back into the mantle. Additionally, the depleted equatorial samples provide an opportunity to characterize the Ar and Xe composition of the N-MORB source for comparison to the 14°N E-MORB popping rock. Finally, the large variations in lithophile isotopes over a geographically short distance affords the opportunity to study the nature of coupling between the noble gases and lithophile tracers, and understand the origin of the heterogeneities in the MORB source. Stepwise crushing and rare gas analysis (He, Ne, Ar, Xe) was undertaken for both enriched and depleted samples. Many of the crushing steps yielded 20Ne/22Ne > 12, and good correlations between Ne, Ar, and Xe isotopes allow for mantle source compositions of Ar and Xe to be determined by extrapolating the measured values to a mantle 20Ne/22Ne of 12.5. The highest measured values of Ar and Xe in a depleted N-MORB are comparable to measured values of the E-MORB popping rock (40Ar/36Ar ~28,000, 129Xe/130Xe ~7.7). When extrapolated to a mantle 20Ne/22Ne of 12.5, the depleted MORB sample indicates a 40Ar/36Ar of ~43,000 (higher than popping rock) and 129Xe/130Xe of ~7.8. Enriched MORB samples from this suite, thought to represent the HIMU mantle, have the same He and Ne characteristics as HIMU basalts from the Cook and Austral Islands; more radiogenic He than MORBs is accompanied by less nucleogenic Ne than MORBs. Additionally, the enriched MORB samples also constrain the HIMU mantle 40Ar/36Ar to ~20,000 and 129Xe/130Xe ~7.3-7.5, significantly lower than the depleted MORBs. Like the HIMU basalts from the Cook and Austral Islands, a less degassed reservoir than the MORB source must be invoked to explain the He and Ne systematics in the HIMU-type MORBs. If HIMU represents recycled crust, then it must have entrained or been entrained by a less degassed mantle from the deep interior. This less degassed reservoir would also explain the good correspondence between low 21Ne/22Ne, low 40Ar/36Ar and low 129Xe/130Xe in the HIMU-type samples. While we cannot rule out recycling of atmospheric noble gases to explain the low 40Ar/36Ar and 129Xe/130Xe, involvement of a source less degassed in He and Ne would also be accompanied by a less degassed Ar and Xe isotopic signature. Therefore the simplest explanation of the covariation between the noble gases and lithophile isotopes involves a mixture of a less processed and hence more primitive component, a degassed recycled component, and depleted MORB mantle beneath the equatorial Mid-Atlantic Ridge.

Strain localization and fabric development in polycrystalline anorthite + melt by water diffusion in an axial deformation experiment

NASA Astrophysics Data System (ADS)

Fukuda, Jun-ichi; Muto, Jun; Nagahama, Hiroyuki

2018-01-01

We performed two axial deformation experiments on synthetic polycrystalline anorthite samples with a grain size of 3 μm and 5 vol% Si-Al-rich glass at 900 °C, a confining pressure of 1.0 GPa, and a strain rate of 10-4.8 s-1. One sample was deformed as-is (dry); in the other sample, two half-cut samples (two cores) with 0.15 wt% water at the boundary were put together in the apparatus. The mechanical data for both samples were essentially identical with a yield strength of 700 MPa and strain weakening of 500 MPa by 20% strain. The dry sample appears to have been deformed by distributed fracturing. Meanwhile, the water-added sample shows plastic strain localization in addition to fracturing and reaction products composed of zoisite grains and SiO2 materials along the boundary between the two sample cores. Infrared spectra of the water-added sample showed dominant water bands of zoisite. The maximum water content was 1500 wt ppm H2O at the two-core boundary, which is the same as the added amount. The water contents gradually decreased from the boundaries to the sample interior, and the gradient fitted well with the solution of the one-dimensional diffusion equation. The determined diffusion coefficient was 7.4 × 10-13 m2/s, which agrees with previous data for the grain boundary diffusion of water. The anorthite grains in the water-added sample showed no crystallographic preferred orientation. Textural observations and water diffusion indicate that water promotes the plastic deformation of polycrystalline anorthite by grain-size-sensitive creep as well as simultaneous reactions. We calculated the strain rate evolution controlled by water diffusion in feldspar aggregates surrounded by a water source. We assumed water diffusion in a dry rock mass with variable sizes. Diffused water weakens a rock mass with time under compressive stress. The calculated strain rate decreased from 10-10 to 10-15 s-1 with an increase in the rock mass size to which water is supplied from < 1 m to 1 km and an increase in the time of water diffusion from < 1 to 10,000 years. This indicates a decrease in the strain rate in a rock mass with increasing deformation via water diffusion.

Organic geochemical study of domanik deposits, Tatarstan Republic.

NASA Astrophysics Data System (ADS)

Nosova, F. F.; Pronin, N. V.

2010-05-01

High-bituminous argillo-siliceous carbonate deposits of domanik formation (DF) occurring within pale depressions and down warps in the east of the Russian platform are treated by many investigators as a main source of oil and gas in the Volga-Ural province. In this study a special attention was turned to organic-rich rocks DF witch outcrop in the central part (Uratminskaya area 792, 806 boreholes) and in the west part (Sviyagskaya, 423) of the Tatarstan Republic. The aim of the present paper is to characterize the organic matter: origin, depositional environments, thermal maturity and biodegradation-weathering effects. Nowadays the most informative geochemical parameters are some biomarkers which qualitatively and are quantitatively defined from distributions of n-alkanes and branched alkanes. Biomarkers - it's original fingerprints of biomass of organic matter, that reflect molecular hydrocarbonic structure. The bulk, molecular composition of oil is initially a function of the type and maturity of the source rock from which it has been expelled, while the source rock type reflects both the nature of precursor organisms and the conditions of its deposition. Methodology used in this study included sampling, bitumen extraction, liquid-column chromatography and gas chromatography/mass spectrometry analyses. The bitumen was fractionated by column chromatography on silica gel. Non-aromatic or alifatics, aromatics and polar compounds were obtained. Alifatic were analysed by gas chromatography/mass spectrometry Percin Elmer. The hydrocarbons present in the sediments of DF and have a carbon numbers ranging from 12 through 38. The samples contain variably inputs from both terrigenous and non-terrigenous (probably marine algal) organic matter as evident in bimodal GC fingerprints of some samples. Pristane and phytane, also, occur in very high concentration in sample extracts. The relatively low Pr/Ph ratios, CPI and OEP<1 imply that the domanik organic matter was deposited in reducing environments. Mass chromatograms show the distribution of regular steranes, iso-steranes, lower molecular weight C21 and C22 steranes (pregnanes) (m/z 217) and triterpanes (m/z 191). The biomarkers distribution of the domanic samples generally suggests a major marine phytoplankton contribution relative to terrigenous land plant source input. The marine affinity is evident from the relatively abundant C27 steranes, which are biomarkers for marine algal contribution to organic matter and low C29 sterane contens. In this present study, samples are dominated by 5α, 14α, 17α (H)-20R and 5β, 14α, 17α (H)-20R steranes (biological configuration). The ratios of 20S/(20S+20R) for αααC29 steranes and ββ/(αα + ββ) for 5α-C29 steranes in the samples, are 0.21 to 0.55 and to 0.12 to 0.50, respectively. The thermal maturity level, assessed by values of several biomarker parameters has been estimated to be within end of diagenesis/eginning of catagenesis and correspond to theoretical vitrinite values (R0) in the range 0.57-0.65%.

Comparison of natural gases accumulated in Oligocene strata with hydrous pyrolysis gases from Menilite Shales of the Polish Outer Carpathians

USGS Publications Warehouse

Kotarba, M.J.; Curtis, John B.; Lewan, M.D.

2009-01-01

This study examined the molecular and isotopic compositions of gases generated from different kerogen types (i.e., Types I/II, II, IIS and III) in Menilite Shales by sequential hydrous pyrolysis experiments. The experiments were designed to simulate gas generation from source rocks at pre-oil-cracking thermal maturities. Initially, rock samples were heated in the presence of liquid water at 330 ??C for 72 h to simulate early gas generation dominated by the overall reaction of kerogen decomposition to bitumen. Generated gas and oil were quantitatively collected at the completion of the experiments and the reactor with its rock and water was resealed and heated at 355 ??C for 72 h. This condition simulates late petroleum generation in which the dominant overall reaction is bitumen decomposition to oil. This final heating equates to a cumulative thermal maturity of 1.6% Rr, which represents pre-oil-cracking conditions. In addition to the generated gases from these two experiments being characterized individually, they are also summed to characterize a cumulative gas product. These results are compared with natural gases produced from sandstone reservoirs within or directly overlying the Menilite Shales. The experimentally generated gases show no molecular compositions that are distinct for the different kerogen types, but on a total organic carbon (TOC) basis, oil prone kerogens (i.e., Types I/II, II and IIS) generate more hydrocarbon gas than gas prone Type III kerogen. Although the proportionality of methane to ethane in the experimental gases is lower than that observed in the natural gases, the proportionality of ethane to propane and i-butane to n-butane are similar to those observed for the natural gases. ??13C values of the experimentally generated methane, ethane and propane show distinctions among the kerogen types. This distinction is related to the ??13C of the original kerogen, with 13C enriched kerogen generating more 13C enriched hydrocarbon gases than kerogen less enriched in 13C. The typically assumed linear trend for ??13C of methane, ethane and propane versus their reciprocal carbon number for a single sourced natural gas is not observed in the experimental gases. Instead, the so-called "dogleg" trend, exemplified by relatively 13C depleted methane and enriched propane as compared to ethane, is observed for all the kerogen types and at both experimental conditions. Three of the natural gases from the same thrust unit had similar "dogleg" trends indicative of Menilite source rocks with Type III kerogen. These natural gases also contained varying amounts of a microbial gas component that was approximated using the ????13C for methane and propane determined from the experiments. These approximations gave microbial methane components that ranged from 13-84%. The high input of microbial gas was reflected in the higher gas:oil ratios for Outer Carpathian production (115-1568 Nm3/t) compared with those determined from the experiments (65-302 Nm3/t). Two natural gas samples in the far western part of the study area had more linear trends that suggest a different organic facies of the Menilite Shales or a completely different source. This situation emphasizes the importance of conducting hydrous pyrolysis on samples representing the complete stratigraphic and lateral extent of potential source rocks in determining specific genetic gas correlations. ?? 2009 Elsevier Ltd.

Stable isotopic evidence for anaerobic maintained sulphate discharge in a polythermal glacier

NASA Astrophysics Data System (ADS)

Ansari, A. H.

2016-03-01

To understand the sources and sinks of sulphate and associated biogeochemical processes in a High Arctic environment, late winter snowpacks, the summer melt-waters and rock samples were collected and analysed for major ions and stable isotope tracers (δ18O, δ34S). The SO42bar/Clbar ratio reveal that more than 87% of sulphate (frequently > 95%) of total sulphate carried by the subglacial runoff and proglacial streams was derived from non-snowpack sources. The proximity of non-snowpack sulphate δ34S (∼8-19‰) to the δ34S of the major rocks in the vicinity (∼-6 to +18‰) suggest that the non-snowpack sulphate was principally derived from rock weathering. Furthermore, Ca2++Mg2+/SO42ˉ molar shows that sulphate acquisition in the meltwaters was controlled by two major processes: 1) coupled-sulphide carbonate weathering (molar ratio ∼ 2) and, 2) re-dissolution of secondary salts (molar ratio ∼ 1). The δ34S-SO4 = +19.4‰ > δ34S-S of rock, accompanied by increased sulphate concentration also indicates an input from re-dissolution of secondary salts. Overall, δ18O composition of these non-snowpack sulphate (-11.9 to -2.2‰) mostly stayed below the threshold δ18O value (-6.7 to -3.3‰) for minimum O2 condition, suggesting that certain proportion of sulphate was regularly supplied from anaerobic sulphide oxidation.

An integrated zircon geochronological and geochemical investigation into the Miocene plutonic evolution of the Cyclades, Aegean Sea, Greece: part 2—geochemistry

NASA Astrophysics Data System (ADS)

Bolhar, Robert; Ring, Uwe; Kemp, Anthony I. S.; Whitehouse, Martin J.; Weaver, Steve D.; Woodhead, Jon D.; Uysal, I. Tonguc; Turnbull, Rose

2012-12-01

Zircons from 14 compositionally variable granitic rocks were examined in detail using CL image-guided micro-analysis to unravel the complex magmatic history above the southward retreating Hellenic subduction zone system in the Aegean Sea. Previously published U-Pb ages document an episodic crystallisation history from 17 to 11 Ma, with peraluminous (S-type) granitic rocks systematically older than closely associated metaluminous (I-type) granitic rocks. Zircon O- and Hf isotopic data, combined with trace element compositions, are highly variable within and between individual samples, indicative of open-system behaviour involving mantle-derived melts and evolved supracrustal sources. Pronounced compositional and thermal fluctuations highlight the role of magma mixing and mingling, in accord with field observations, and incremental emplacement of distinct melt batches coupled with variable degrees of crustal assimilation. In the course of partial fusion, more fertile supracrustal sources dominated in the earlier stages of Aegean Miocene magmatism, consistent with systematically older crystallisation ages of peraluminous granitic rocks. Differences between zircon saturation and crystallisation temperatures (deduced from zircon Ti concentrations), along with multimodal crystallisation age spectra for individual plutons, highlight the complex and highly variable physico-compositional and thermal evolution of silicic magma systems. The transfer of heat and juvenile melts from the mantle varied probably in response to episodic rollback of the subducting lithospheric slab, as suggested by punctuated crystallisation age spectra within and among individual granitic plutons.

Neoproterozoic rift basins and their control on the development of hydrocarbon source rocks in the Tarim Basin, NW China

NASA Astrophysics Data System (ADS)

Zhu, Guang-You; Ren, Rong; Chen, Fei-Ran; Li, Ting-Ting; Chen, Yong-Quan

2017-12-01

The Proterozoic is demonstrated to be an important period for global petroleum systems. Few exploration breakthroughs, however, have been obtained on the system in the Tarim Basin, NW China. Outcrop, drilling, and seismic data are integrated in this paper to focus on the Neoproterozoic rift basins and related hydrocarbon source rocks in the Tarim Basin. The basin consists of Cryogenian to Ediacaran rifts showing a distribution of N-S differentiation. Compared to the Cryogenian basins, those of the Ediacaran are characterized by deposits in small thickness and wide distribution. Thus, the rifts have a typical dual structure, namely the Cryogenian rifting and Ediacaran depression phases that reveal distinct structural and sedimentary characteristics. The Cryogenian rifting basins are dominated by a series of grabens or half grabens, which have a wedge-shaped rapid filling structure. The basins evolved into Ediacaran depression when the rifting and magmatic activities diminished, and extensive overlapping sedimentation occurred. The distributions of the source rocks are controlled by the Neoproterozoic rifts as follows. The present outcrops lie mostly at the margins of the Cryogenian rifting basins where the rapid deposition dominates and the argillaceous rocks have low total organic carbon (TOC) contents; however, the source rocks with high TOC contents should develop in the center of the basins. The Ediacaran source rocks formed in deep water environment of the stable depressions evolving from the previous rifting basins, and are thus more widespread in the Tarim Basin. The confirmation of the Cryogenian to Ediacaran source rocks would open up a new field for the deep hydrocarbon exploration in the Tarim Basin.

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.

Hydrogeochemical and isotopic studies of groundwater in the middle voltaian aquifers of the Gushegu district of the Northern region

NASA Astrophysics Data System (ADS)

Salifu, Musah; Yidana, Sandow Mark; Anim-Gyampo, Maxwell; Appenteng, Michael; Saka, David; Aidoo, Felix; Gampson, Enoch; Sarfo, Mark

2017-06-01

This work is to establish the hydrochemistry and origin of groundwater in some parts of the Gushegu district of the Northern Region of Ghana. Hydrochemical data from 19 groundwater and 7 rock samples have been used to evaluate water quality, water types, and sources of various ions as well as origin of the groundwater. The study results show that the quality of groundwater from the area is generally not good due to their fluoride (F-), bicarbonate (HCO3 -) and electrical conductivity (EC) concentrations. The F- contents of the groundwater have values as high as 1.97 mg/L, with 53 % of the groundwater having concentrations of F- exceeding the WHO recommended allowable limits. These high F- values have the potential of causing serious health problems such as kidney failure, dental and skeletal fluorosis, reproductive problem and reduction in intelligent quotient of consumers. A plot of Gibbs diagram reveals that rock weathering and precipitation are the major hydrogeochemical processes regulating the water chemistry of the study area. Petrographic thin-section analyses of rock samples identify minerals present to be muscovite, plagioclase feldspars, quartz, sericite and iron oxide. Stable isotope (18O and 2H) composition of the waters reveals that most of the groundwater is likely to be recharged from local precipitation, indicating their meteoric origin. Some samples, however, showed considerable evaporation.

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.

Provenance of sands from the confluence of the Amazon and Madeira rivers based on detrital heavy minerals and luminescence of quartz and feldspar

NASA Astrophysics Data System (ADS)

do Nascimento, Daniel R.; Sawakuchi, André O.; Guedes, Carlos C. F.; Giannini, Paulo C. F.; Grohmann, Carlos H.; Ferreira, Manuela P.

2015-03-01

Source-to-sink systems are poorly known in tropical rivers. For the Amazonian rivers, the majority of the provenance studies remain focused on the suspended load, implying a poor understanding of the processes governing production and distribution of sands. In this study, we perform heavy mineral and optically stimulated luminescence (OSL) analysis to cover the entire spectrum (heavy and light minerals fraction) of 29 sand samples of the Lower Madeira river region (Amazon and Madeira rivers), of which the main goal was to find provenance indicators specific to these rivers. Despite the tropical humid climate, the sands of the Amazon and Lower Madeira rivers are rich in unstable heavy minerals as augite, hypersthene, green hornblende and andalusite. The Madeira river is highlighted by its higher content of andalusite, with source attributed to the Amazon Craton (medium-to-high grade metamorphic rocks), while the Amazon river, upstream of the Madeira river mouth, has a signature of augite and hypersthene, that suggests an Andean provenance (volcanic rocks). Sands from the Madeira river can be tracked in the Amazon river by the increasing concentration in andalusite. OSL analysis of the light minerals fraction was used as an index of feldspar concentration and sedimentary history of quartz grains. Lower feldspar concentration and quartz grains with longer sedimentary history (higher OSL sensitivity) also point to a major contribution of cratonic sources for the sands in the Madeira river. While the sands from the Lower Madeira would be mainly supplied by cratonic rocks, previous work recognised that suspended sediments (silt and clay) are derived from Andean rocks. Therefore, we interpret a decoupling between the sources of sand and mud (silt and clay) under transport in the Madeira river. Andean sands (rich in augite and hypersthene) would be trapped in the foreland zones of the Beni and Mamoré tributaries. In the Amazon river sands, the low OSL sensitivity of the quartz, higher content of feldspar and unstable heavy mineral assemblage dominated by augite and hypersthene suggest both a fast transport from Andean sources with fine sediment bypass over foreland areas.

Zirconium and hafnium in the southeastern Atlantic States

USGS Publications Warehouse

Mertie, J.B.

1958-01-01

The principal source of zirconium and hafnium is zircon, though a minor source is baddeleyite, mined only in Brazil. Zircon is an accessory mineral in igneous, metamorphic, and sedimentary rocks, but rarely occurs in hardrock in minable quantities. The principal sources of zircon are therefore alluvial deposits, which are mined in many countries of five continents. The principal commercial deposits in the United States are in Florida, though others exist elsewhere in the southeastern Coastal Plain. The evidence indicates that conditions for the accumulation of workable deposits of heavy minerals were more favorable during the interglacial stages of the Pleistocene epoch than during Recent time. Therefore detrital ores of large volume and high tenor are more likely to be found in the terrace deposits than along the present beaches. Other concentrations of heavy minerals, however, are possible at favored sites close to the Fall Line where the Tuscaloosa formation rests upon the crystalline rocks of the Piedmont province. A score of heavy and semiheavy minerals occur in the detrital deposits of Florida, but the principal salable minerals are ilmenite, leucoxene, rutile, and zircon, though monazite and staurolite are saved at some mining plants. Commercial deposits of heavy minerals are generally required to have a tenor of 4 percent, though ores with a lower tenor can be mined at a profit if the content of monazite is notably high. The percentages of zircon in the concentrates ranges from 10 to 16 percent, and in eastern Florida from 13 to 15 percent. Thus the tenor in zircon of the ore-bearing sands ranges from 0.4 to 0.6 percent. The content of hafnium in zircon is immaterial for many uses, but for some purposes very high or very low tenors in hafnium are required. Alluvial zircon cannot be separated into such varieties, which, if needed, must be obtained from sources in bedrock. It thus becomes necessary to determine the Hf : Zr ratios in zircon from many kinds of bedrock.Granitic rocks are the principal sources of zircon, though not the best sources of zircon with a high tenor in hafnium. A general study by the Geological Survey of the granitic rocks of the Southeastern Atlantic States has been in progress for 10 years, and hundreds of samples of granitic accessory minerals have been acquired. Thirty samples of zircon from these collections were selected for spectrographic and X-ray determinations of their tenors in hafnium. Nine other samples of alluvial zircon were included, of which three are from Florida and six from foreign countries. No domestic zircon was discovered with very high or very low tenors in hafnium.The volume of zircon in the southeastern Coastal Plain is enormous, but most of it is not recoverable. The minable reserves of heavy minerals, however, are very large, and from these it is estimated conservatively that 10 million short tons of zircon can be obtained. The corresponding amounts of zirconium and hafnium, using the mean Hf:Zr ratio of the deposits in Florida, are 4,868,000 and 112,000 tons, respectively. These reserves could be delivered, if needed, at the rate of 100,000 tons a year.

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.

Alteration mineralogy and geochemistry as an exploration tool for detecting basement heat sources in sedimentary basins

NASA Astrophysics Data System (ADS)

Uysal, Tonguc; Gasparon, Massimo; van Zyl, Jacobus; Wyborn, Doone

2010-05-01

The Cooper Basin located in South Australia and Queensland hosts some of the hottest granites in the world at economic drilling depths (240°C at 3.5 km). Investigating the mechanism of heat-producing element enrichment in the Cooper Basin granite is crucial for understanding hot-dry rock geothermal systems and developing exploration strategies. Trace element (by ICP-MS) and stable isotope geochemistry of whole rock granite samples and hydrothermal phyllosilicate alteration minerals separated from the granite and overlying sandstones and mudstones of the Cooper Basin were examined in detail. Granite core samples from relatively shallow depths in Moomba 1 and Big Lake 1 are strongly altered with pervasive sericite (illite) and quartz precipitation, probably associated with intense micro-fracturing and veining. The intensity of hydrothermal alteration is less in deeper samples from Mcleod 1, Jolokia and Habanero 1. Highly altered granites from former holes are substantially enriched in lithophile elements, particularly in Cs, Rb, Be, Th, U and rare earth elements (REE) relative to the upper continental crust (UCC). U and Th contents with concentrations of up to 30 and 144 ppm, respectively, are 10 and 13 times higher than those of the UCC. Comparison of the trace element composition of the same samples dissolved by open beaker acid digestion and high-pressure acid bomb digestion (to dissolve zircon) shows that zircon is not the main repository of U and Th in the Cooper Basin granite. Instead, we propose that the enrichment of heat-producing elements was promoted by a regional hydrothermal event leading to the precipitation of U and Th- bearing minerals such as illite, K-feldspar and thorite. Crystallinity index (illite crystallinity) of the sericite indicates hydrothermal temperatures ranging from 250°C (in Moomba 1 and Big Lake 1) to 350°C (in McLeod 1 and Jolokia 1). In the overlying sedimentary rocks, crystallinity of authigenic illites translates to lower crystallisation temperatures (150-200°C). Normalised REE patterns of the mostly altered granite samples show a strong negative Ce anomaly, signifying oxidation of trivalent Ce to less soluble tetravalent Ce. Oxygen and hydrogen isotope compositions of illites from the granites and sedimentary rocks are very similar, with d18O = -1.8 per mill to +2.7 per mill; δD = -99 per mill to -121 per mill for granites and d18O = +2.3 per mill to +9.7 per mill, dD = -78 per mill to -119 per mill for sedimentary rocks. The calculated oxygen and hydrogen isotope compositions of fluids in equilibrium with the illites are depleted in 18O and deuterium, comparable to those of waters reported for most high-latitude sedimentary basins. Hence, stable isotope data of alteration minerals in the granite and the overlying sedimentary rocks suggest the operation of a hydrothermal system involving high latitude meteoric waters during extensional tectonism in the Cooper Basin region. Investigation of alteration mineralogy and geochemistry of relatively shallow sedimentary sections (generally intersected in previously drilled petroleum holes) represents a potentially strong tool to evaluate the presence of a geothermal heat source in the basement of sedimentary basins.

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.

Reservoir and Source Rock Identification Based on Geologycal, Geophysics and Petrophysics Analysis Study Case: South Sumatra Basin

NASA Astrophysics Data System (ADS)

Anggit Maulana, Hiska; Haris, Abdul

2018-05-01

Reservoir and source rock Identification has been performed to deliniate the reservoir distribution of Talangakar Formation South Sumatra Basin. This study is based on integrated geophysical, geological and petrophysical data. The aims of study to determine the characteristics of the reservoir and source rock, to differentiate reservoir and source rock in same Talangakar formation, to find out the distribution of net pay reservoir and source rock layers. The method of geophysical included seismic data interpretation using time and depth structures map, post-stack inversion, interval velocity, geological interpretations included the analysis of structures and faults, and petrophysical processing is interpret data log wells that penetrating Talangakar formation containing hydrocarbons (oil and gas). Based on seismic interpretation perform subsurface mapping on Layer A and Layer I to determine the development of structures in the Regional Research. Based on the geological interpretation, trapping in the form of regional research is anticline structure on southwest-northeast trending and bounded by normal faults on the southwest-southeast regional research structure. Based on petrophysical analysis, the main reservoir in the field of research, is a layer 1,375 m of depth and a thickness 2 to 8.3 meters.

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.

Publications - GMC 209 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 209 Publication Details Title: Source rock potential and geochemical characterization of OCS Y Reference DGSI, Inc., 1993, Source rock potential and geochemical characterization of OCS Y-0943-1 (Aurora

Biomarker chemistry and flux quantification methods for natural petroleum seeps and produced oils, offshore southern California

USGS Publications Warehouse

Lorenson, T.D.; Leifer, Ira; Wong, Florence L.; Rosenbauer, Robert J.; Campbell, Pamela L.; Lam, Angela; Hostettler, Frances D.; Greinert, Jens; Finlayson, David P.; Bradley, Eliza S.; Luyendyk, Bruce P.

2011-01-01

Sustained, natural oil seepage from the seafloor is common off southern California, and is of great interest to resource managers, who are tasked with distinguishing natural from anthropogenic oil sources. The major purpose of this study was to build upon the work previously funded by the Bureau of Ocean Energy Management (BOEM) and the U.S. Geological Survey (USGS) that has refined the oil-fingerprinting process to enable differentiation of the highly similar Monterey Formation oils from Outer Continental Shelf (OCS) production and adjacent natural seeps. In these initial studies, biomarker and stable carbon isotope ratios were used to infer the age, lithology, organic-matter input, and depositional environment of the source rocks for 388 samples of produced crude oil, seep oil, and tarballs mainly from coastal California. The analysis resulted in a predictive model of oil source families that could be applied to samples of unknown origin.

[Source apportionment of soil heavy metals in Jiapigou goldmine based on the UNMIX model].

PubMed

Ai, Jian-chao; Wang, Ning; Yang, Jing

2014-09-01

The paper determines 16 kinds of metal elements' concentration in soil samples which collected in Jipigou goldmine upper the Songhua River. The UNMIX Model which was recommended by US EPA to get the source apportionment results was applied in this study, Cd, Hg, Pb and Ag concentration contour maps were generated by using Kriging interpolation method to verify the results. The main conclusions of this study are: (1)the concentrations of Cd, Hg, Pb and Ag exceeded Jilin Province soil background values and enriched obviously in soil samples; (2)using the UNMIX Model resolved four pollution sources: source 1 represents human activities of transportation, ore mining and garbage, and the source 1's contribution is 39. 1% ; Source 2 represents the contribution of the weathering of rocks and biological effects, and the source 2's contribution is 13. 87% ; Source 3 is a comprehensive source of soil parent material and chemical fertilizer, and the source 3's contribution is 23. 93% ; Source 4 represents iron ore mining and transportation sources, and the source 4's contribution is 22. 89%. (3)the UNMIX Model results are in accordance with the survey of local land-use types, human activities and Cd, Hg and Pb content distributions.

Aquifer susceptibility in Virginia, 1998-2000

USGS Publications Warehouse

Nelms, David L.; Harlow, George E.; Plummer, Niel; Busenberg, Eurybiades

2003-01-01

The U.S. Geological Survey (USGS), in cooperation with the Virginia Department of Health, sampled water from 171 wells and springs across the Commonwealth of Virginia between 1998 and 2000 as part of the Virginia Aquifer Susceptibility study. Most of the sites sampled are public water supplies that are part of the comprehensive Source Water Assessment Program for the Commonwealth. The fundamental premise of the study was that the identification of young waters (less than 50 years) by multiple environmental tracers could be used as a guide for classifying aquifers in terms of susceptibility to contamination from near-surface sources. Environmental tracers, including chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), tritium (3H), and tritium/helium-3 (3H/3He), and carbon isotopes (14C and d13C) were used to determine the age of water discharging from wells and springs. Concentrations of CFCs greater than 5 picograms per kilogram and 3H concentrations greater than 0.6 tritium unit were used as thresholds to indicate that parts of the aquifer sampled have a component of young water and are, therefore, susceptible to near-surface contamination. Concentrations of CFCs exceeded the susceptibility threshold in 22 percent of the wells and in one spring sampled in the Coastal Plain regional aquifer systems. About 74 percent of the samples from wells with the top of the first water zone less than 100 feet below land surface exceeded the threshold values, and water supplies developed in the upper 100 feet of the Coastal Plain are considered to be susceptible to contamination from near-surface sources. The maximum depth to the top of the screened interval for wells that contained CFCs was less than 150 feet. Wells completed in the deep confined aquifers in the Coastal Plain generally contain water older than 1,000 years, as indicated by carbon-14 dating, and are not considered to be susceptible to contamination under natural conditions. All of the water samples from wells and springs in the fractured-rock terrains (the Appalachian Plateaus, Valley and Ridge, Blue Ridge, and Piedmont regional aquifer systems) contained concentrations of CFCs and 3H greater than one or both of the thresholds. Because all of the water samples exceeded at least one of the threshold values, young water is present throughout most of these regional aquifer systems; therefore, water supplies developed in these systems are susceptible to contamination from near-surface sources. No relation between well depth and presence of CFCs is evident from samples in the fractured-rock terrains. More than 95 percent of the samples for which the dating methods were applicable contained waters with apparent ages less than 35 years. About 5 percent of these samples, most of which were from the Blue Ridge and Piedmont regional aquifer systems, contained young waters with apparent ages of less than 5 years. Most of the samples from the Valley and Ridge Carbonate, Blue Ridge, and Piedmont regional aquifer systems had young water fractions of more than 50 percent, whereas samples from the Coastal Plain Shallow and Appalachian Plateaus regional aquifer systems contained less than 40 percent young waters. Concentrations of CFCs in excess of air-water equilibrium, which can indicate that nonatmospheric sources (such as sewage effluent) have introduced CFCs into the ground-water system, were measured in 6 and 48 percent of the water samples from the Coastal Plain and fractured-rock regional aquifer systems, respectively. The nitrate (NO3) concentrations greater than the USGS detection level of 0.05 milligrams per liter generally increase as the apparent age of the young water fraction decreases, with the highest NO3 concentrations for samples in which one or more of the CFCs are above modern atmospheric mixing ratios (commonly referred to as 'contaminated' for ground-water dating purposes). Most of the samples in which NO3 was detected w

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.

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.

WEST AND EAST PALISADES ROADLESS AREAS, IDAHO AND WYOMING.

USGS Publications Warehouse

Oriel, Steven S.; Benham, John R.

1984-01-01

Studies of the West and East Palisades Roadless Areas, which lie within the Idaho-Wyoming thrust belt, document structures, reservoir formations, source beds, and thermal maturities comparable to those in producing oil and gas field farther south in the belt. Therefore, the areas are highly favorable for the occurrence of oil and gas. Phosphate beds of appropriate grade within the roadless areas are thinner and less accessible than those being mined from higher thrust sheets to the southwest; however, they contain 98 million tons of inferred phosphate rock resources in areas of substantiated phosphate resource potential. Sparsely distributed thin coal seams occur in the roadless areas. Although moderately pure limestone is present, it is available from other sources closer to markets. Geochemical anomalies from stream-sediment and rock samples for silver, copper, molydenum, and lead occur in the roadless areas but they offer little promise for the occurrence of metallic mineral resources. A possible geothermal resource is unproven, despite thermal phenomena at nearby sites.

Review of samples of tailings, soils and stream sediment adjacent to and downstream from the Ruth Mine, Inyo County, California

USGS Publications Warehouse

Rytuba, James J.; Kim, Christopher S.; Goldstein, Daniel N.

2011-01-01

The Ruth Mine and mill are located in the western Mojave Desert in Inyo County, California (fig. 1). The mill processed gold-silver (Au-Ag) ores mined from the Ruth Au-Ag deposit, which is adjacent to the mill site. The Ruth Au-Ag deposit is hosted in Mesozoic intrusive rocks and is similar to other Au-Ag deposits in the western Mojave Desert that are associated with Miocene volcanic centers that formed on a basement of Mesozoic granitic rocks (Bateman, 1907; Gardner, 1954; Rytuba, 1996). The volcanic rocks consist of silicic domes and associated flows, pyroclastic rocks, and subvolcanic intrusions (fig. 2) that were emplaced into Mesozoic silicic intrusive rocks (Troxel and Morton, 1962). The Ruth Mine is on Federal land managed by the U.S. Bureau of Land Management (BLM). Tailings from the mine have been eroded and transported downstream into Homewood Canyon and then into Searles Valley (figs. 3, 4, 5, and 6). The BLM provided recreational facilities at the mine site for day-use hikers and restored and maintained the original mine buildings in collaboration with local citizen groups for use by visitors (fig. 7). The BLM requested that the U.S. Geological Survey (USGS), in collaboration with Chapman University, measure arsenic (As) and other geochemical constituents in soils and tailings at the mine site and in stream sediments downstream from the mine in Homewood Canyon and in Searles Valley (fig. 3). The request was made because initial sampling of the site by BLM staff indicated high concentrations of As in tailings and soils adjacent to the Ruth Mine. This report summarizes data obtained from field sampling of mine tailings and soils adjacent to the Ruth Mine and stream sediments downstream from the mine on June 7, 2009. Our results permit a preliminary assessment of the sources of As and associated chemical constituents that could potentially impact humans and biota.

High soil and groundwater arsenic levels induce high body arsenic loads, health risk and potential anemia for inhabitants of northeastern Iran.

PubMed

Taheri, Masumeh; Mehrzad, Jalil; Mahmudy Gharaie, Mohamad Hosein; Afshari, Reza; Dadsetan, Ahmad; Hami, Shakiba

2016-04-01

Arsenic bioavailability in rock, soil and water resources is notoriously hazardous. Geogenic arsenic enters the body and adversely affects many biochemical processes in animals and humans, posing risk to public health. Chelpu is located in NE Iran, where realgar, orpiment and pyrite mineralization is the source of arsenic in the macroenvironment. Using cluster random sampling strategy eight rocks, 23 soils, 12 drinking water resources, 36 human urine and hair samples and 15 adult sheep urine and wool samples in several large-scale herds in the area were randomly taken for quantification of arsenic in rock/soil/water, wool/hair/urine. Arsenic levels in rock/soil/water and wool/hair/urine were measured using inductively coupled plasma spectroscopy and atomic absorption spectrophotometry, respectively. While arsenic levels in rocks, soils and water resources hazardously ranged 9.40-25,873.3 mg kg(-1), 7.10-1448.80 mg kg(-1) and 12-606 μg L(-1), respectively, arsenic concentrations in humans' hair and urine and sheep's wool and urine varied from 0.37-1.37 μg g(-1) and 9-271.4 μg L(-1) and 0.3-3.11 μg g(-1) and 29.1-1015 μg L(-1), respectively. Local sheep and human were widely sick and slightly anemic. Hematological examination of the inhabitants revealed that geogenic arsenic could harm blood cells, potentially resulting in many other hematoimmunological disorders including cancer. The findings warn widespread exposure of animals and human in this agroecologically and geopolitically important region (i.e., its proximity with Afghanistan, Pakistan and Turkmenistan) and give a clue on how arsenic could induce infectious and non-infectious diseases in highly exposed human/animals.

Sr-Nd-Pb isotope systematics of the Permian volcanic rocks in the northern margin of the Alxa Block (the Shalazhashan Belt) and comparisons with the nearby regions: Implications for a Permian rift setting?

NASA Astrophysics Data System (ADS)

Shi, Guanzhong; Wang, Hua; Liu, Entao; Huang, Chuanyan; Zhao, Jianxin; Song, Guangzeng; Liang, Chao

2018-04-01

The petrogenesis of the Permian magmatic rocks in the Shalazhashan Belt is helpful for us to understand the tectonic evolution of the Central Asian Orogenic Belt (CAOB) in the northern margin of the Alxa Block. The Permian volcanic rocks in the Shalazhashan Belt include basalts, trachyandesites and trachydacites. Our study shows that two basalt samples have negative εNd(t) values (-5.4 to -1.5) and higher radiogenic Pb values, which are relevant to the ancient subcontinental lithospheric mantle. One basalt sample has positive εNd(t) value (+10) representing mafic juvenile crust and is derived from depleted asthenosphere. The trachyandesites are dated at 284 ± 3 Ma with εNd(t) = +2.7 to +8.0; ISr = 0.7052 to 0.7057, and they are generated by different degrees of mixing between mafic magmas and crustal melts. The trachydacites have high εNd(t) values and slightly higher ISr contents, suggesting the derivation from juvenile sources with crustal contamination. The isotopic comparisons of the Permian magmatic rocks of the Shalazhashan Belt, the Nuru-Langshan Belt (representing the northern margin of the Alxa Block), the Solonker Belt (Mandula area) and the northern margin of the North China Craton (Bayan Obo area) indicate that the radiogenic isotopic compositions have an increasingly evolved trend from the south (the northern margins of the Alxa Block and the North China Craton) to the north (the Shalazhashan Belt and the Solonker Belt). Three end-member components are involved to generate the Permian magmatic rocks: the ancient subcontinental lithospheric mantle, the mafic juvenile crust or newly underplated mafic rocks that were originated from depleted asthenosphere, and the ancient crust. The rocks correlative with the mafic juvenile crust or newly underplated mafic rocks are predominantly distributed along the Shalazhashan Belt and the Solonker Belt, and the rocks derived from ancient, enriched subcontinental lithospheric mantle are mainly distributed along the northern margins of the Alxa Block and the North China Craton. The magmatic rock types, isotopic features and their temporal, spatial distributions suggest an extensional regime probably related to rifting.

Lithium and boron in late-orogenic granites - Isotopic fingerprints for the source of crustal melts?

NASA Astrophysics Data System (ADS)

Romer, Rolf L.; Meixner, Anette; Förster, Hans-Jürgen

2014-04-01

Geochemically diverse late- and post-Variscan granites of the Erzgebirge-Vogtland, the Saxon Granulite Massif, and Thuringia (Germany) formed by anatectic melting of Palaeozoic sedimentary successions and associated mafic to felsic volcanic rocks. The compositional diversity of the least evolved of these granites is largely inherited from the protoliths. We present Li and B-isotopic data of these granites and compare them with the isotopic composition of their protoliths, to investigate whether (i) there exist systematic differences in the Li and B-isotopic composition among different granite types and (ii) Li and B-isotopic compositions provide information on the granite sources complementary to information from the isotopic composition of Sr, Nd, and Pb and the trace-element signatures. Low-F biotite and two-mica granite types have flat upper continental crust (UCC)-normalized trace-element pattern with variable enrichments in Li, Rb, Cs, Sn, and W and depletions in Sr, Ba, and Eu. These signatures are least pronounced for the Niederbobritzsch biotite granite, which has the largest contribution of mafic material, and most pronounced for the two-mica granites. The granites show a relatively narrow range of δ7Li values (-3.0 to -0.5) and a broad range of δ11B values (-13.4 to +20.1). The δ11B values are lower in rocks with distinctly higher contents of Li, Rb, Cs, and Sn. The high δ11B of the Niederbobritzsch granite may be explained by the melting of former altered oceanic crust in its source. Relative to UCC, intermediate-F to high-F low-P granites show strong depletions in Sr, Ba, Eu as well as Zr and Hf, strong enrichments in Li, Rb, and Cs as well as Nb, Sn, Ta, and W, and REE pattern with stronger enrichments for HREE than for LREE. These granites show narrow ranges of δ7Li (-2.0 to +1.6) and δ11B values (-14.7 to -9.1), reflecting the smaller variability of the Li and B-isotopic composition in their source lithologies. The anomalously high δ7Li value (14.7) of one granite sample (Burgberg), which is similar to δ7Li values of its wall rocks (up to 14.5), may indicate late-magmatic fluid-rock interaction with external, wall rock-derived fluids. Because of the small compositional range of most source lithologies, the Li and B-isotopic variation in the granites is also small indicating that the isotopic composition of Li and B does not represent a particularly sensitive source tracer, with the exception of source lithologies characterized by extreme δ7Li or δ11B values.

The Mesoarchean Tiejiashan-Gongchangling potassic granite in the Anshan-Benxi area, North China Craton: Origin by recycling of Paleo- to Eoarchean crust from U-Pb-Nd-Hf-O isotopic studies

NASA Astrophysics Data System (ADS)

Dong, Chunyan; Wan, Yusheng; Xie, Hangqiang; Nutman, Allen P.; Xie, Shiwen; Liu, Shoujie; Ma, Mingzhu; Liu, Dunyi

2017-10-01

Mesoarchean and older potassic granites are important indicators of recycling of ancient continental crust early in Earth's history. This study of integrated whole rock and zircon geochemistry and geochronology reports the age and identification of the source materials of the > 200 km2 Mesoarchean Tiejiashan-Gongchangling granite in the Anshan-Benxi area, North China Craton, the largest pre-Neoarchean granite domain in the craton. SHRIMP U-Pb zircon dating on 15 samples indicates the magmatic crystallization of the granites between 2.95 and 3.0 Ga and reveals a superimposed tectonothermal event at 2.91 Ga. The granites are characterized by high SiO2 and K2O, low CaO, FeOt, MgO and TiO2 with peraluminuous features. They show large variations in (La/Yb)n and strong negative Eu and Ba anomalies and Nb, P and Ti depletions. Whole rock Nd and magmatic zircon Hf isotopic compositions show large variations, but with most having εNd(t) and εHf(t) values < 0, with tDM(Nd) and tDM(Hf) values varying from 3.3 to 3.9 Ga and 3.3 to 4.0 Ga, respectively. Magmatic zircons without very strong lead loss (discordance ≤ 20%) have δ18O values of + 3.14 to + 8.39. 3.3-3.7 Ga xenocrystic zircons occur in some samples. The granite formed as a result of recycling of Paleo- to Eoarchean continental material in an intracontinental environment, with little if any contribution from Mesoarchean mantle sources. The sources could be predominantly unaltered ancient gneisses, together with yet to be identified Paleo- to Eoarchean materials affected by early low temperature alteration (weathered rocks or clastic sediment).

Chemistry and origin of Miocene and Eocene oils and tars in the onshore and offshore Santa Cruz Basins, California

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

Kornacki, A.S.; McNeil, R.I.

1996-12-31

The Santa Cruz (La Honda) Basin is a small {open_quote}slice{close_quote} of the San Joaquin Basin that has been displaced c. 300 km to the northwest by the San Andreas Fault. The poorly-explored offshore area that now lies within the Monterey Bay NMS includes portions of the Outer Santa Cruz and Bodega basins. A modest amount (c. 1.3 MM bbl) of variable-quality oil has been produced from Eocene and Pliocene pay zones in the La Honda Field. Much smaller amounts of light oil ({ge}40{degrees} API) have been produced from three other fields (Oil Creek; Moody Gulch; Half Moon Bay). Large tarmore » deposits also outcrop near the city of Santa Cruz. Proven source rocks in this basin include the Eocene Twobar Shale and three Miocene units: the Lambert Shale, Monterey Formation, and the Santa Cruz Mudstone. A high-gravity oil sample from the Oil Creek Field contains isotopically-light carbon ({delta}{sup 13}C = - 28.2 per mil) and has a relatively high pristane/phytane ratio. This oil was generated at high temperature (c. 140{degrees}C) by pre-Miocene source rocks (probably the Twobar Shale). The presence of isotopically-heavy carbon in all other oil and tar samples demonstrates they were generated by Miocene source rocks. But the C{sub 7} oil-generation temperatures, sulfur content, vanadium/nickel ratios, and biomarker chemistry of these Miocene oils are significantly different than in Monterey oils from the prolific Santa Maria Basin (SMB). The sulfur content (8.0 wt%) and V-Ni chemistry of tarry petroleum recovered in the P-036-1 well (Outer Santa Cruz Basin) resembles the chemistry of very heavy (<15{degrees}API) oils generated by phosphatic Monterey shales in the SMB.« less

Chemistry and origin of Miocene and Eocene oils and tars in the onshore and offshore Santa Cruz Basins, California

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

Kornacki, A.S.; McNeil, R.I.

1996-01-01

The Santa Cruz (La Honda) Basin is a small [open quote]slice[close quote] of the San Joaquin Basin that has been displaced c. 300 km to the northwest by the San Andreas Fault. The poorly-explored offshore area that now lies within the Monterey Bay NMS includes portions of the Outer Santa Cruz and Bodega basins. A modest amount (c. 1.3 MM bbl) of variable-quality oil has been produced from Eocene and Pliocene pay zones in the La Honda Field. Much smaller amounts of light oil ([ge]40[degrees] API) have been produced from three other fields (Oil Creek; Moody Gulch; Half Moon Bay).more » Large tar deposits also outcrop near the city of Santa Cruz. Proven source rocks in this basin include the Eocene Twobar Shale and three Miocene units: the Lambert Shale, Monterey Formation, and the Santa Cruz Mudstone. A high-gravity oil sample from the Oil Creek Field contains isotopically-light carbon ([delta][sup 13]C = - 28.2 per mil) and has a relatively high pristane/phytane ratio. This oil was generated at high temperature (c. 140[degrees]C) by pre-Miocene source rocks (probably the Twobar Shale). The presence of isotopically-heavy carbon in all other oil and tar samples demonstrates they were generated by Miocene source rocks. But the C[sub 7] oil-generation temperatures, sulfur content, vanadium/nickel ratios, and biomarker chemistry of these Miocene oils are significantly different than in Monterey oils from the prolific Santa Maria Basin (SMB). The sulfur content (8.0 wt%) and V-Ni chemistry of tarry petroleum recovered in the P-036-1 well (Outer Santa Cruz Basin) resembles the chemistry of very heavy (<15[degrees]API) oils generated by phosphatic Monterey shales in the SMB.« less

VNIR reflectance spectroscopy of natural carbonate rocks: implication for remote sensing identification of fault damage zones

NASA Astrophysics Data System (ADS)

Traforti, Anna; Mari, Giovanna; Carli, Cristian; Demurtas, Matteo; Massironi, Matteo; Di Toro, Giulio

2017-04-01

Reflectance spectroscopy in the visible and near-infrared (VNIR) is a common technique used to study the mineral composition of Solar System bodies from remote sensed and in-situ robotic exploration. In the VNIR spectral range, both crystal field and vibrational overtone absorptions can be present with spectral characteristics (i.e. albedo, slopes, absorption band with different positions and depths) that vary depending on composition and texture (e.g. grain size, roughness) of the sensed materials. The characterization of the spectral variability related to the rock texture, especially in terms of grain size (i.e., both the size of rock components and the size of particulates), commonly allows to obtain a wide range of information about the different geological processes modifying the planetary surfaces. This work is aimed at characterizing how the grain size reduction associated to fault zone development produces reflectance variations in rock and mineral spectral signatures. To achieve this goal we present VNIR reflectance analysis of a set of fifteen rock samples collected at increasing distances from the fault core of the Vado di Corno fault zone (Campo Imperatore Fault System - Italian Central Apennines). The selected samples had similar content of calcite and dolomite but different grain size (X-Ray Powder Diffraction, optical and scanning electron microscopes analysis). Consequently, differences in the spectral signature of the fault rocks should not be ascribed to mineralogical composition. For each sample, bidirectional reflectance spectra were acquired with a Field-Pro Spectrometer mounted on a goniometer, on crushed rock slabs reduced to grain size <800, <200, <63, <10 μm and on intact fault zone rock slabs. The spectra were acquired on dry samples, at room temperature and normal atmospheric pressure. The source used was a Tungsten Halogen lamp with an illuminated spot area of ca. 0.5 cm2and incidence and emission angles of 30˚ and 0˚ respectively. The spectral analysis of the crushed and intact rock slabs in the VNIR spectral range revealed that in both cases, with increasing grain size: (i) the reflectance decreases (ii) VNIR spectrum slopes (i.e. calculated between wavelengths of 0.425 - 0.605 μm and 2.205 - 2.33 μm, respectively) and (iii) carbonate main absorption band depth (i.e. vibrational absorption band at wavelength of ˜2.3 μm) increase. In conclusion, grain size variations resulting from the fault zone evolution (e.g., cumulated slip or development of thick damage zones) produce reflectance variations in rocks and mineral spectral signatures. The remote sensing analysis in the VNIR spectral range can be applied to identify the spatial distribution and extent of fault core and damage zone domains for industrial and seismic hazard applications. Moreover, the spectral characterization of carbonate-built rocks can be of great interest for the surface investigation of inner planets (e.g. Earth and Mars) and outer bodies (e.g. Galilean icy satellites). On these surfaces, carbonate minerals at different grain sizes are common and usually related to water and carbon distribution, with direct implications for potential life outside Earth (e.g. Mars).

Subcritical water extraction of organic matter from sedimentary rocks.

PubMed

Luong, Duy; Sephton, Mark A; Watson, Jonathan S

2015-06-16

Subcritical water extraction of organic matter containing sedimentary rocks at 300°C and 1500 psi produces extracts comparable to conventional solvent extraction. Subcritical water extraction of previously solvent extracted samples confirms that high molecular weight organic matter (kerogen) degradation is not occurring and that only low molecular weight organic matter (free compounds) are being accessed in analogy to solvent extraction procedures. The sedimentary rocks chosen for extraction span the classic geochemical organic matter types. A type I organic matter-containing sedimentary rock produces n-alkanes and isoprenoidal hydrocarbons at 300°C and 1500 psi that indicate an algal source for the organic matter. Extraction of a rock containing type II organic matter at the same temperature and pressure produces aliphatic hydrocarbons but also aromatic compounds reflecting the increased contributions from terrestrial organic matter in this sample. A type III organic matter-containing sample produces a range of non-polar and polar compounds including polycyclic aromatic hydrocarbons and oxygenated aromatic compounds at 300°C and 1500 psi reflecting a dominantly terrestrial origin for the organic materials. Although extraction at 300°C and 1500 psi produces extracts that are comparable to solvent extraction, lower temperature steps display differences related to organic solubility. The type I organic matter produces no products below 300°C and 1500 psi, reflecting its dominantly aliphatic character, while type II and type III organic matter contribute some polar components to the lower temperature steps, reflecting the chemical heterogeneity of their organic inventory. The separation of polar and non-polar organic compounds by using different temperatures provides the potential for selective extraction that may obviate the need for subsequent preparative chromatography steps. Our results indicate that subcritical water extraction can act as a suitable replacement for conventional solvent extraction of sedimentary rocks, but can also be used for any organic matter containing mineral matrix, including soils and recent sediments, and has the added benefit of tailored extraction for analytes of specific polarities. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Quantification of mine-drainage inflows to Little Cottonwood Creek, Utah, using a tracer-injection and synoptic-sampling study

USGS Publications Warehouse

Kimball, B.; Runkel, R.; Gerner, L.

2001-01-01

Historic mining in Little Cottonwood Canyon in Utah has left behind many mine drainage tunnels that discharge water to Little Cottonwood Creek. To quantify the major sources of mine drainage to the stream, synoptic sampling was conducted during a tracer injection under low flow conditions (September 1998). There were distinct increases in discharge downstream from mine drainage and major tributary inflows that represented the total surface and subsurface contributions. The chemistry of stream water determined from synoptic sampling was controlled by the weathering of carbonate rocks and mine drainage inflows. Buffering by carbonate rocks maintained a high pH throughout the study reach. Most of the metal loading was from four surface-water inflows and three subsurface inflows. The main subsurface inflow was from a mine pool in the Wasatch Tunnel. Natural attenuation of all the metals resulted in the formation of colloidal solids, sorption of some metals, and accumulation onto the streambed. The deposition on the streambed could contribute to chronic toxicity for aquatic organisms. Information from the study will help to make decisions about environmental restoration.

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.

Lithium isotopes in large rivers reveal the cannibalistic nature of modern continental weathering and erosion

NASA Astrophysics Data System (ADS)

Dellinger, Mathieu; Gaillardet, Jérôme; Bouchez, Julien; Calmels, Damien; Galy, Valier; Hilton, Robert G.; Louvat, Pascale; France-Lanord, Christian

2014-09-01

The erosion of major mountain ranges is thought to be largely cannibalistic, recycling sediments that were deposited in the ocean or on the continents prior to mountain uplift. Despite this recognition, it has not yet been possible to quantify the amount of recycled material that is presently transported by rivers to the ocean. Here, we have analyzed the Li content and isotope composition (δLi7) of suspended sediments sampled along river depth profiles and bed sands in three of the largest Earth's river systems (Amazon, Mackenzie and Ganga-Brahmaputra rivers). The δLi7 values of river-sediments transported by these rivers range from +5.3 to -3.6‰ and decrease with sediment grain size. We interpret these variations as reflecting a mixture of unweathered rock fragments (preferentially transported at depth in the coarse fraction) and present-day weathering products (preferentially transported at the surface in the finest fraction). Only the finest surface sediments contain the complementary reservoir of Li solubilized by water-rock interactions within the watersheds. Li isotopes also show that river bed sands can be interpreted as a mixture between unweathered fragments of igneous and sedimentary rocks. A mass budget approach, based on Li isotopes, Li/Al and Na/Al ratios, solved by an inverse method allows us to estimate that, for the large rivers analyzed here, the part of solid weathering products formed by present-day weathering reactions and transported to the ocean do not exceed 35%. Li isotopes also show that the sediments transported by the Amazon, Mackenzie and Ganga-Brahmaputra river systems are mostly sourced from sedimentary rocks (>60%) rather than igneous rocks. This study shows that Li isotopes in the river particulate load are a good proxy for quantifying both the erosional rock sources and the fingerprint of present-day weathering processes. Overall, Li isotopes in river sediments confirm the cannibalistic nature of erosion and weathering.

Whole rock and discrete pyrite geochemistry as complementary tracers of ancient ocean chemistry: An example from the Neoproterozoic Doushantuo Formation, China

NASA Astrophysics Data System (ADS)

Gregory, Daniel D.; Lyons, Timothy W.; Large, Ross R.; Jiang, Ganqing; Stepanov, Aleksandr S.; Diamond, Charles W.; Figueroa, Maria C.; Olin, Paul

2017-11-01

The trace element content of pyrite is a recently developed proxy for metal abundance in paleo-oceans. Previous studies have shown that the results broadly match those of whole rock studies through geologic time. However, no detailed study has evaluated the more traditional proxies for ocean chemistry for comparison to pyrite trace element data from the same samples. In this study we compare pyrite trace element data from 14 samples from the Wuhe section of the Ediacaran-age Doushantuo Formation, south China, measured by laser ablation inductively coupled plasma mass spectrometry with new and existing whole rock trace element concentrations; total organic carbon; Fe mineral speciation; S isotope ratios; and pyrite textural relationships. This approach allows for comparison of data for individual trace elements within the broader environmental context defined by the other chemical parameters. The results for discrete pyrite analyses show that several chalcophile and siderophile elements (Ag, Sb, Se, Pb, Cd, Te, Bi, Mo, Ni, and Au) vary among the samples with patterns that mirror those of the independent whole rock data. A comparison with existing databases for sedimentary and hydrothermal pyrite allows us to discriminate between signatures of changing ocean conditions and those of known hydrothermal sources. In the case of the Wuhe samples, the observed patterns for trace element variation point to primary marine controls rather than higher temperature processes. Specifically, our new data are consistent with previous arguments for pulses of redox sensitive trace elements interpreted to be due to marine oxygenation against a backdrop of mostly O2-poor conditions in the Ediacaran ocean-with important implications for the availability of bioessential elements. The agreement between the pyrite and whole rock data supports the use of trace element content of pyrite as a tracer of ocean chemistry in ways that complement existing approaches, while also opening additional windows of opportunity. For example, unlike the potential vulnerability of whole rock data to secondary alteration, the pyrite record may survive greenschist facies metamorphism. Furthermore, early-formed pyrite can be identified through textural relationships as a proxy of primary marine chemistry even in the presence of hydrothermal overprints on whole rock chemistry via secondary fluids. Finally, pyrite analyses may allow for the possibility of more quantitative interpretations of the ancient ocean once the elemental partitioning between the mineral and host fluids are better constrained. Collectively, these advances can greatly increase the number of basins that may be investigated for early ocean chemistry, especially those of Precambrian age.

A four-dimensional petroleum systems model for the San Joaquin Basin Province, California: Chapter 12 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

USGS Publications Warehouse

Peters, Kenneth E.; Magoon, Leslie B.; Lampe, Carolyn; Scheirer, Allegra Hosford; Lillis, Paul G.; Gautier, Donald L.

2008-01-01

A calibrated numerical model depicts the geometry and three-dimensional (3-D) evolution of petroleum systems through time (4-D) in a 249 x 309 km (155 x 192 mi) area covering all of the San Joaquin Basin Province of California. Model input includes 3-D structural and stratigraphic data for key horizons and maps of unit thickness, lithology, paleobathymetry, heat flow, original total organic carbon, and original Rock-Eval pyrolysis hydrogen index for each source rock. The four principal petroleum source rocks in the basin are the Miocene Antelope shale of Graham and Williams (1985; hereafter referred to as Antelope shale), the Eocene Kreyenhagen Formation, the Eocene Tumey formation of Atwill (1935; hereafter referred to as Tumey formation), and the Cretaceous to Paleocene Moreno Formation. Due to limited Rock-Eval/total organic carbon data, the Tumey formation was modeled using constant values of original total organic carbon and original hydrogen index. Maps of original total organic carbon and original hydrogen index were created for the other three source rocks. The Antelope shale was modeled using Type IIS kerogen kinetics, whereas Type II kinetics were used for the other source rocks. Four-dimensional modeling and geologic field evidence indicate that maximum burial of the three principal Cenozoic source rocks occurred in latest Pliocene to Holocene time. For example, a 1-D extraction of burial history from the 4-D model in the Tejon depocenter shows that the bottom of the Antelope shale source rock began expulsion (10 percent transformation ratio) about 4.6 Ma and reached peak expulsion (50 percent transformation ratio) about 3.6 Ma. Except on the west flank of the basin, where steep dips in outcrop and seismic data indicate substantial uplift, little or no section has been eroded. Most petroleum migration occurred during late Cenozoic time in distinct stratigraphic intervals along east-west pathways from pods of active petroleum source rock in the Tejon and Buttonwillow depocenters to updip sandstone reservoirs. Satisfactory runs of the model required about 18 hours of computation time for each simulation using parallel processing on a Linux-based cluster.

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.

Publications - GMC 54 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

DGGS GMC 54 Publication Details Title: Source rock evaluation/TAI for ARCO Itkillik River Unit #1 information. Bibliographic Reference Texaco, Inc., [n.d.], Source rock evaluation/TAI for ARCO Itkillik River

Publications - GMC 249 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 249 Publication Details Title: Source rock geochemical and visual kerogen data from cuttings Reference Unknown, 1995, Source rock geochemical and visual kerogen data from cuttings (2,520-8,837') of the

Degree of Phosphorus Saturation and Soil Phosphorus Thresholds in an Ultisol Amended with Triple Superphosphate and Phosphate Rocks

PubMed Central

Gikonyo, E. W.; Zaharah, A. R.; Hanafi, M. M.; Anuar, A. R.

2011-01-01

Soil phosphorus (P) release capability could be assessed through the degree of P saturation (DPS). Our main objective was to determine DPS and, hence, P threshold DPS values of an Ultisol treated with triple superphosphate (TSP), Gafsa phosphate rocks (GPR), or Christmas Island phosphate rocks (CIPR), plus or minus manure. P release was determined by the iron oxide—impregnated paper strip (strip P), while DPS was determined from ammonium oxalate—extractable aluminum (Al), iron (Fe), and P. Soils were sampled from a closed incubation study involving soils treated with TSP, GPR, and CIPR at 0–400 mg P kg-1, and a field study where soils were fertilized with the same P sources at 100–300 kg P ha-1 plus or minus manure. The DPS was significantly influenced by P source x P rate, P source x manure (incubated soils), and by P source x P rate x time (field-sampled soils). Incubated soil results indicated that both initial P and total strip P were related to DPS by exponential functions: initial strip P = 1.38exp0.18DPS, R2 = 0.82** and total strip P = 8.01exp0.13DPS, R2 = 0.65**. Initial strip P was linearly related to total P; total P = 2.45, initial P + 8.41, R2 = 0.85**. The threshold DPS value established was about 22% (incubated soil). Field soils had lower DPS values <12% and strip P was related to initial DPS and average DPS in exponential functions: strip P = 2.6exp0.44DPS, R2 = 0.77** and strip P = 1.1DPS2 — 2.4DPS + 6.2, R2 = 0.58**, respectively. The threshold values were both at ≈8% and P release was 11–14 mg P kg-1. Results are evident that DPS can be used to predict P release, but the threshold values are environmentally sensitive; hence, recommendations should be based on field trials. PMID:21805012

Degree of phosphorus saturation and soil phosphorus thresholds in an ultisol amended with triple superphosphate and phosphate rocks.

PubMed

Gikonyo, E W; Zaharah, A R; Hanafi, M M; Anuar, A R

2011-07-28

Soil phosphorus (P) release capability could be assessed through the degree of P saturation (DPS). Our main objective was to determine DPS and, hence, P threshold DPS values of an Ultisol treated with triple superphosphate (TSP), Gafsa phosphate rocks (GPR), or Christmas Island phosphate rocks (CIPR), plus or minus manure. P release was determined by the iron oxide-impregnated paper strip (strip P), while DPS was determined from ammonium oxalate-extractable aluminum (Al), iron (Fe), and P. Soils were sampled from a closed incubation study involving soils treated with TSP, GPR, and CIPR at 0-400 mg P kg-1, and a field study where soils were fertilized with the same P sources at 100-300 kg P ha-1 plus or minus manure. The DPS was significantly influenced by P source x P rate, P source x manure (incubated soils), and by P source x P rate x time (field-sampled soils). Incubated soil results indicated that both initial P and total strip P were related to DPS by exponential functions: initial strip P = 1.38exp0.18DPS, R2 = 0.82** and total strip P = 8.01exp0.13DPS, R2 = 0.65**. Initial strip P was linearly related to total P; total P = 2.45, initial P + 8.41, R2 = 0.85**. The threshold DPS value established was about 22% (incubated soil). Field soils had lower DPS values <12% and strip P was related to initial DPS and average DPS in exponential functions: strip P = 2.6exp0.44DPS, R2 = 0.77** and strip P = 1.1DPS2 ¨C 2.4DPS + 6.2, R2 = 0.58**, respectively. The threshold values were both approximately equal to 8% and P release was 11-14 mg P kg-1. Results are evident that DPS can be used to predict P release, but the threshold values are environmentally sensitive; hence, recommendations should be based on field trials.

The effect of weathering in the Buyukmelen River basin on the geochemistry of suspended and bed sediments and the hyrogeochemical characteristics of river water, Duzce, Turkey

NASA Astrophysics Data System (ADS)

Pehlivan, Rustem

2010-07-01

The Buyukmelen River is expected to be a water source that can supply the drinking water needs of Istanbul until 2040. The drinking and utility water needs of Istanbul are to transport water from the Buyukmelen River to Istanbul via pipeline and pump it into the Alibeykoy and Omerli reservoirs when their water levels drop. The Buyukmelen River is located in the province of Duzce in 170 km east of Istanbul and its water basin is approximately 2250 km 2. The Buyukmelen River flows muddy in the rainy season and into the Black Sea. The chemical compositions of natural waters alter due to interaction with geological formations, physical and chemical weathering of various rocks and the effects of mining and agricultural production. A research was conducted at the Buyukmelen River basin to determine the effects of hydrological processes. Therefore, the samples of rocks, soil, stream water, suspended and bed sediment were collected from the Buyukmelen River basin. Geochemical and water chemistry analyses of samples were performed at ALS Chemex laboratories, Canada. The bed sediments contain quartz, calcite, plagioclase, amphibole and clay minerals. The clay minerals in the suspended and bed sediment samples are kaolinite, smectite and illite. The water samples collected from the Aksu, Kucukmelen, Asarsu and Ugursuyu streams and the Buyukmelen River in winter (December 2005) and summer (June 2006) periods are rich in Ca and HCO 3 ions. The ions most abundant in rainfall sample are HCO 3 and Na. The ion compositions of surface waters have increased due to the weathering of limestone, agglomerate and volcanic sandstones, light acidic rainfall, semi-arid Black Sea climate in the Buyukmelen basin. The suspended sediment amount of the Buyukmelen River in the rainy season (December 2005) is 174 mg/l. According to the water contamination regulation of Turkey, the Buyukmelen Rivers belongs to quality class 4 based on Al ion and to quality class 3 based on Fe ion in winter period, and to quality class 2 based on Mn concentration in summer period. Chemical index of alteration (CIA) indices observed in the suspended and bed sediments (average of 55) suggest that their source area underwent moderate degrees of chemical weathering processes. According to Upper Continental Crust (UCC) values, the suspended sediment was rich in elements such as Fe 2O 3, CaO, MgO, MnO, TiO 2, P 2O 5, V, Cr, Co, Cu, Zn, As, Cd, Sb, Hg and Pb. The element concentrations of the suspended sediments were related to size fractionation, mainly of clay content. The mentioned enrichment was contributed by agglomerate, basalt, volcanic sandstone and graywacke from rocks in the study area. Source of ions such as Al, Fe, Mn, Ba, Cr, Co, Cu, Ni, Ti and Hg and major in the Buyukmelen River is interaction with rocks such as the agglomerate, basalt, andesite, volcanic sandstone and graywacke. As suggested by Singh et al. (2005), before weathering of some rocks in the Buyukmelen River basin, it was determined that they were graywacke and literanite based on the geochemistry of the suspended and bed sediments.

Mudstone Mineralogy from Curiosity CheMin, 2013 to 2016

NASA Image and Video Library

2016-12-13

This series of pie charts shows similarities and differences in the mineral compositions of mudstones at 10 sites where NASA's Curiosity Mars rover collected rock-powder samples and analyzed them with the rover's Chemistry and Mineralogy (CheMin) instrument. The charts are arrayed in chronological order, with an indication of relative elevation as the rover first sampled two sites on the floor of Gale Crater in 2013 and later began climbing the crater's central mound, Mount Sharp. The pie chart farthest to the right and uphill shows composition at the "Sebina" target, sampled in October 2016. Five non-mudstone rock targets that the rover drilled and analyzed within this time frame are not included. The mineralogical variations in these mudstones may be due to differences in any or all of these factors: the source materials deposited by water that entered lakes, the processes of sedimentation and rock forming, and how the rocks were later altered. One trend that stands out is that the mineral jarosite -- shown in purple -- was more prominent in the "Pahrump Hills" area of lower Mount Sharp than at sites examined either earlier or later. Jarosite is an indicator of acidic water. Mudstone layers uphill from Pahrump Hills have barely detectable amounts of jarosite, indicating a shift away from acidic conditions in these overlying -- thus younger -- layers. Clay minerals, shown as green, declined in abundance at sites midway through this series, then came back as the rover climbed higher. Each drilled-and-analyzed target is identified with a two-letter abbreviation: JK for "John Klein," CB for "Cumberland." CH for "Confidence Hills," MJ for "Mojave," TP for "Telegraph Peak," BK for "Buckskin," OD for "Oudam," MB for "Marimba," QL for "Quela," and SB for Sebina. http://photojournal.jpl.nasa.gov/catalog/PIA21146

Diamond exploration and regional prospectivity of Western Australia

NASA Astrophysics Data System (ADS)

Hutchison, Mark T.

2018-06-01

Pre-1.6 Ga rocks comprise around 45% of the onshore area of Western Australia (WA), constituting the West Australian Craton (WAC) (including the Archean Yilgarn and Pilbara Cratons) and the western part of the North Australian Craton (NAC). These areas provide the conditions suitable for diamond formation at depth, and numerous diamondiferous lamproite and kimberlite fields are known. As emplacement ages span close to 2500 Ma, there are significant opportunities for diamond-affinity rocks being present near-surface in much of the State, including amongst Phanerozoic rocks. WA's size, terrain, infrastructure and climate, mean that many areas remain underexplored. However, continuous diamond exploration since the 1970s has resulted in abundant data. In order to advance future exploration, a comprehensive database of results of diamond exploration sampling (Geological Survey of Western Australia 2018) has been assessed. The Yilgarn and Pilbara Cratons have spinel indicators almost exclusively dominated by chromite (>90% of grains), whereas (Mg,Fe,Ti)-bearing Al-chromites account for more of the indicator spinels in the NAC, up to 50% of grains at the Northern Territory (NT) border. Increasing dominance of Al in chromites is interpreted as a sign of weathering or a shallower source than Al-depleted Mg-chromites. Garnet compositions across the State also correlate with geological subdivisions, with lherzolitic garnets showing more prospective compositions (Ca-depleted) in WAC samples compared to the NAC. WAC samples also show a much broader scatter into strongly diamond-prospective G10 and G10D compositions. Ilmenites from the NAC show Mg-enriched compositions (consistent with kimberlites), over and above those present in NT data. However, ilmenites from the WAC again show the most diamond-prospective trends. Numerous indicator mineral concentrations throughout the State have unknown sources. Due in part to the presence of diamondiferous lamproites, it is cautioned that some accepted indicator mineral criteria do not apply in parts of WA. For example Ca-depleted garnets, Mg-depleted ilmenites and Cr-depleted and Al-absent clinopyroxenes are all sometimes associated with strongly diamondiferous localities. Quantitative prospectivity analysis has also been carried out based on the extent and results of sampling, age of surface rocks relative to ages of diamond-prospective rocks, and the underlying mantle structure. Results show that locations within the NAC and with proximity to WA's diamond mines score well. However, results point to parts of the WAC being more prospective, consistent with mineral chemical data. Most notable are the Hamersley Basin, Eastern Goldfields Superterrane and the Goodin Inlier of the Yilgarn Craton. Despite prolific diamond exploration, WA is considerably underexplored and the ageing Argyle mine and recent closure of operations at Ellendale warrant a re-evaluation of diamond potential. Results of mineral chemistry and prospectivity analysis make a compelling case for renewed exploration.

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.

Permeability of intact and fractured rocks in Krafla geothermal reservoir, Iceland

NASA Astrophysics Data System (ADS)

Eggertsson, Gudjon; Lavallée, Yan; Markusson, Sigurdur

2016-04-01

The magmatic-hydrothermal system at Krafla Volcano, North-East Iceland, has been the source of an important geothermal fluids, exploited by Landsvirkjun National Power since 1977 to generate electricity (~60 MW). In the last decade, the energy was extracted from fluids of moderate temperature (200-300°C), but in order to satisfy the demand for sustainable, environmentally-safe energy, Landsvirkjun is aiming to source fluids in the super high-enthalpy hydrothermal system (400°-600°C and <220 bar). In relation to this, IDDP-1 was drilled in 2009. Drilling was terminated at a depth of 2100m when the drill string penetrated rhyolite magma. The rock around this rhyolite magma body shows great potential for production, as its temperatures are very high and it is located at shallow depth. Here, we present the results of mechanical and permeability tests carried out on the main lithologies forming the geothermal reservoir rock. During a field survey in fall 2015, and through information gathered from previous drilling exercises, five main rock types were identified and sampled to carry out this study: that is, basalts (10% to 60% porosity), hyaloclastites (35% to 45% porosity), obsidians (0,25% to 5% porosity), ignimbrites (13% to 18% porosity), and intrusive felsites and microgabbros (10% to 16% porosity). The only rock type not found in outcrops on the surface is the felsite and microgabbros which are thought to be directly above the rhyolite magma (~80m thick). The reason they can be found on the surface is that during the Mývatns-fires, an explosion creating the Víti crater and scattered these rocks around the area. For all these lithologies, the porosity was determined using helium pycnometry. On-going permeability measurements are made using a classic hydrostatic cell. To simulate the stress conditions extant in the hydrothermal field, we performed permeability measurements at a range of confining pressure (1 to 100 MPa), using a pore pressure differential of 0.5 - 1.5 MPa (at an average pore pressure of 1.25 MPa). We present the results of permeability-porosity relationships for each rock as a function of confining pressure and discuss the permeability of the fluid reservoir as a function of effective pressure (i.e., = confining pressure - pore pressure) to constrain fluid flow during different pressurisation events. Complementary Brazilian tests were also performed to induce a fracture in the samples and the permeability of these fractured rocks will be measured to describe the role of macrofractures in controlling fluid flow. Permeability measurements at high temperature (up to ~500 C) will be performed on selected rocks. The aim of these experiments will be to discover the relative role of the various lithologies on the permeability of the reservoir, which will inform us how to improve the geothermal productivity of the proposed deep well through thermo-mechanical stimulations.

Chapter 5: Geologic Assessment of Undiscovered Petroleum Resources in the Waltman Shale Total Petroleum System,Wind River Basin Province, Wyoming

USGS Publications Warehouse

Roberts, Steve B.; Roberts, Laura N.R.; Cook, Troy

2007-01-01

The Waltman Shale Total Petroleum System encompasses about 3,400 square miles in the Wind River Basin Province, Wyoming, and includes accumulations of oil and associated gas that were generated and expelled from oil-prone, lacustrine shale source rocks in the Waltman Shale Member of the Paleocene Fort Union Formation. Much of the petroleum migrated and accumulated in marginal lacustrine (deltaic) and fluvial sandstone reservoirs in the Shotgun Member of the Fort Union, which overlies and intertongues with the Waltman Shale Member. Additional petroleum accumulations derived from Waltman source rocks are present in fluvial deposits in the Eocene Wind River Formation overlying the Shotgun Member, and also might be present within fan-delta deposits included in the Waltman Shale Member, and in fluvial sandstone reservoirs in the uppermost part of the lower member of the Fort Union Formation immediately underlying the Waltman. To date, cumulative production from 53 wells producing Waltman-sourced petroleum exceeds 2.8 million barrels of oil and 5.8 billion cubic feet of gas. Productive horizons range from about 1,770 feet to 5,800 feet in depth, and average about 3,400 to 3,500 feet in depth. Formations in the Waltman Shale Total Petroleum System (Fort Union and Wind River Formations) reflect synorogenic deposition closely related to Laramide structural development of the Wind River Basin. In much of the basin, the Fort Union Formation is divided into three members (ascending order): the lower unnamed member, the Waltman Shale Member, and the Shotgun Member. These members record the transition from deposition in dominantly fluvial, floodplain, and mire environments in the early Paleocene (lower member) to a depositional setting characterized by substantial lacustrine development (Waltman Shale Member) and contemporaneous fluvial, and marginal lacustrine (deltaic) deposition (Shotgun Member) during the middle and late Paleocene. Waltman Shale Member source rocks have total organic carbon values ranging from 0.93 to 6.21 weight percent, averaging about 2.71 weight percent. The hydrocarbon generative potential of the source rocks typically exceeds 2.5 milligrams of hydrocarbon per gram of rock and numerous samples had generative potentials exceeding 6.0 milligrams of hydrocarbon per gram of rock. Waltman source rocks are oil prone, and contain a mix of Type-II and Type-III kerogen, indicating organic input from a mix of algal and terrestrial plant matter, or a mix of algal and reworked or recycled material. Thermal maturity at the base of the Waltman Shale Member ranges from a vitrinite reflectance value of less than 0.60 percent along the south basin margin to projected values exceeding 1.10 percent in the deep basin west of Madden anticline. Burial history reconstructions for three wells in the northern part of the Wind River Basin indicate that the Waltman Shale Member was well within the oil window (Ro equal to or greater than 0.65 percent) by the time of maximum burial about 15 million years ago; maximum burial depths exceeded 10,000 feet. Onset of oil generation calculated for the base of the Waltman Shale member took place from about 49 million years ago to about 20 million years ago. Peak oil generation occurred from about 31 million years ago to 26 million years ago in the deep basin west of Madden anticline. Two assessment units were defined in the Waltman Shale Total Petroleum System: the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit (50350301) and the Waltman Fractured Shale Continuous Oil Assessment Unit (50350361). The conventional assessment unit primarily relates to the potential for undiscovered petroleum accumulations that are derived from source rocks in the Waltman Shale Member and trapped within sandstone reservoirs in the Shotgun Member (Fort Union Formation) and in the lower part of the overlying Wind River Formation. The potential for Waltman-sourced oil accumulations in fan-delta depos

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.

Characterization of anthropogenic and natural sources of acid rock drainage at the Cinnamon Gulch abandoned mine land inventory site, Summit County, Colorado

USGS Publications Warehouse

Bird, D.A.

2003-01-01

Colorado's Cinnamon Gulch releases acid rock drainage (ARD) from anthropogenic and natural sources. In 2001, the total discharge from Cinnamon Gulch was measured at 1.02 cfs (29 L/s) at base flow and 4.3 cfs (122 L/s) at high flow (spring runoff). At base flow, natural sources account for 98% of the discharge from the watershed, and about 96% of the chemical loading. At high flow, natural sources contribute 96% of discharge and 92 to 95% of chemical loading. The pH is acidic throughout the Cinnamon Gulch watershed, ranging from 2.9 to 5.4. At baseflow, nearly all of the trace metals analyzed in the 18 samples exceeded state hardness-dependent water quality standards for aquatic life. Maximum dissolved concentrations of selected constituents included 16 mg/ L aluminum, 15 mg/L manganese, 40 mg/L iron, 2 mg/L copper, 560 ??g/L lead, 8.4 mg/L zinc, and 300 mg/L sulfate. Average dissolved concentrations of selected metals at baseflow were 5.5 mg/L aluminum, 5.5 mg/L manganese, 14 ??g/L cadmium, 260 ??g/L copper, 82 ??g/L lead, and 2.8 mg/L zinc.

Asymmetric Early Crust-Building Magmatism on the Lunar Nearside Due to KREEP-Induced Melting Point Depression

NASA Technical Reports Server (NTRS)

Elardo, S. M.; Shearer, C. K.; McCuddin, F. M.

2018-01-01

The lunar magnesian-suite, or Mg-suite, is a series of ancient plutonic rocks from the lunar crust with ages and compositions indicating that they represent crust-building magmatism occurring immediately after the end of magma ocean crystallization. Samples of the Mg-suite were found at every Apollo landing site except 11 and ubiquitously have geochemical characteristics indicating the involvement of KREEP in their petrogenesis. This observation has led to the suggestion that the presence of the KREEP reservoir under the lunar nearside was responsible for this episode of crust building. The lack of any readily identifiable Mg-suite rocks in meteoritic regolith breccias sourced from outside the Procellarum KREEP Terrane (PKT) seemingly supports this interpretation.

Ubiquitous tar balls with a California-source signature on the shorelines of Prince William Sound, Alaska

USGS Publications Warehouse

Kvenvolden, K.A.; Hostettler, F.D.; Carlson, P.R.; Rapp, J.B.; Threlkeld, C.N.; Warden, A.

1995-01-01

Although the shorelines of Prince William Sound still bear traces of the 1989 Exxon Valdez oil spill, most of the flattened tar balls that can be found today on these shorelines are not residues of Exxon Valdez oil. Instead, the carbon-isotopic and hydrocarbon-biomarker signatures of 61 tar ball samples, collected from shorelines throughout the northern and western parts of the sound, are all remarkably similar and have characteristics consistent with those of oil products that originated from the Monterey Formation source rocks of California. The carbon-isotopic compositions of the tar balls are all closely grouped (??13CPDB = -23.7 ?? 0.2???), within the range found in crude oils from those rocks, but are distinct from isotopic compositions of 28 samples of residues from the Exxon Valdez oil spill (??13CPDB = -29.4 ?? 0.1???). Likewise, values for selected biomarker ratios in the tar balls are all similar but distinct from values of residues from the 1989 oil spill. Carbon-isotopic and biomarker signatures generally relate the tar balls to oil products used in Alaska before ???1970 for construction and pavements. How these tar balls with such similar geochemical characteristics became so widely dispersed throughout the northern and western parts of the sound is not known with certainty, but the great 1964 Alaska earthquake was undoubtedly an important trigger, causing spills from ruptured storage facilities of California-sourced asphalt and fuel oil into Prince William Sound.

Quantification of Organic richness through wireline logs: a case study of Roseneath shale formation, Cooper basin, Australia

NASA Astrophysics Data System (ADS)

Ahmad, Maqsood; Iqbal, Omer; Kadir, Askury Abd

2017-10-01

The late Carboniferous-Middle Triassic, intracratonic Cooper basin in northeastern South Australia and southwestern Queensland is Australia's foremost onshore hydrocarbon producing region. The basin compromises Permian carbonaceous shale like lacustrine Roseneath and Murteree shale formation which is acting as source and reservoir rock. The source rock can be distinguished from non-source intervals by lower density, higher transit time, higher gamma ray values, higher porosity and resistivity with increasing organic content. In current dissertation we have attempted to compare the different empirical approaches based on density relation and Δ LogR method through three overlays of sonic/resistivity, neutron/resistivity and density/resistivity to quantify Total organic content (TOC) of Permian lacustrine Roseneath shale formation using open hole wireline log data (DEN, GR, CNL, LLD) of Encounter 1 well. The TOC calculated from fourteen density relations at depth interval between 3174.5-3369 meters is averaged 0.56% while TOC from sonic/resistivity, neutron/resistivity and density/resistivity yielded an average value of 3.84%, 3.68%, 4.40%. The TOC from average of three overlay method is yielded to 3.98%. According to geochemical report in PIRSA the Roseneath shale formation has TOC from 1 - 5 wt %.There is unpromising correlations observed for calculated TOC from fourteen density relations and measured TOC on samples. The TOC from average value of three overlays using Δ LogR method showed good correlation with measured TOC on samples.

Sr-Nd-Hf Isotopic Analysis of <10 mg Dust Samples: Implications for Ice Core Dust Source Fingerprinting

NASA Astrophysics Data System (ADS)

Újvári, Gábor; Wegner, Wencke; Klötzli, Urs; Horschinegg, Monika; Hippler, Dorothee

2018-01-01

Combined Sr-Nd-Hf isotopic data of two reference materials (AGV-1/BCR2) and 50, 10, and 5 mg aliquots of carbonate-free fine grain (<10 μm) separates of three loess samples (Central Europe/NUS, China/BEI, USA/JUD) are presented. Good agreement between measured and reference Sr-Nd-Hf isotopic compositions (ICs) demonstrate that robust isotopic ratios can be obtained from 5 to 10 mg size rock samples using the ion exchange/mass spectrometry techniques applied. While 87Sr/86Sr ratios of dust aluminosilicate fractions are affected by even small changes in pretreatments, Nd isotopic ratios are found to be insensitive to acid leaching, grain-size or weathering effects. However, the Nd isotopic tracer is sometimes inconclusive in dust source fingerprinting (BEI and NUS both close to ɛNd(0) -10). Hafnium isotopic values (<10 μm fractions) are homogenous for NUS, while highly variable for BEI. This heterogeneity and vertical arrays of Hf isotopic data suggest zircon depletion effects toward the clay fractions (<2 μm). Monte Carlo simulations demonstrate that the Hf IC of the dust <10 μm fraction is influenced by both the abundance of zircons present and maturity of crustal rocks supplying this heavy mineral, while the <2 μm fraction is almost unaffected. Thus, ɛHf(0) variations in the clay fraction are largely controlled by the Hf IC of clays/heavy minerals having high Lu/Hf and radiogenic 176Hf/177Hf IC. Future work should be focused on Hf IC of both the <10 and <2 μm fractions of dust from potential source areas to gain more insight into the origin of last glacial dust in Greenland ice cores.

The Leeb Hardness Test for Rock: An Updated Methodology and UCS Correlation

NASA Astrophysics Data System (ADS)

Corkum, A. G.; Asiri, Y.; El Naggar, H.; Kinakin, D.

2018-03-01

The Leeb hardness test (LHT with test value of L D ) is a rebound hardness test, originally developed for metals, that has been correlated with the Unconfined Compressive Strength (test value of σ c ) of rock by several authors. The tests can be carried out rapidly, conveniently and nondestructively on core and block samples or on rock outcrops. This makes the relatively small LHT device convenient for field tests. The present study compiles test data from literature sources and presents new laboratory testing carried out by the authors to develop a substantially expanded database with wide-ranging rock types. In addition, the number of impacts that should be averaged to comprise a "test result" was revisited along with the issue of test specimen size. Correlation for L D and σ c for various rock types is provided along with recommended testing methodology. The accuracy of correlated σ c estimates was assessed and reasonable correlations were observed between L D and σ c . The study findings show that LHT can be useful particularly for field estimation of σ c and offers a significant improvement over the conventional field estimation methods outlined by the ISRM (e.g., hammer blows). This test is rapid and simple, with relatively low equipment costs, and provides a reasonably accurate estimate of σ c .

Modified method for estimating petroleum source-rock potential using wireline logs, with application to the Kingak Shale, Alaska North Slope

USGS Publications Warehouse

Rouse, William A.; Houseknecht, David W.

2016-02-11

In 2012, the U.S. Geological Survey completed an assessment of undiscovered, technically recoverable oil and gas resources in three source rocks of the Alaska North Slope, including the lower part of the Jurassic to Lower Cretaceous Kingak Shale. In order to identify organic shale potential in the absence of a robust geochemical dataset from the lower Kingak Shale, we introduce two quantitative parameters, $\\Delta DT_\\bar{x}$ and $\\Delta DT_z$, estimated from wireline logs from exploration wells and based in part on the commonly used delta-log resistivity ($\\Delta \\text{ }log\\text{ }R$) technique. Calculation of $\\Delta DT_\\bar{x}$ and $\\Delta DT_z$ is intended to produce objective parameters that may be proportional to the quality and volume, respectively, of potential source rocks penetrated by a well and can be used as mapping parameters to convey the spatial distribution of source-rock potential. Both the $\\Delta DT_\\bar{x}$ and $\\Delta DT_z$ mapping parameters show increased source-rock potential from north to south across the North Slope, with the largest values at the toe of clinoforms in the lower Kingak Shale. Because thermal maturity is not considered in the calculation of $\\Delta DT_\\bar{x}$ or $\\Delta DT_z$, total organic carbon values for individual wells cannot be calculated on the basis of $\\Delta DT_\\bar{x}$ or $\\Delta DT_z$ alone. Therefore, the $\\Delta DT_\\bar{x}$ and $\\Delta DT_z$ mapping parameters should be viewed as first-step reconnaissance tools for identifying source-rock potential.

The significance of the Medicine Hat Block (southern Alberta, northern Montana) in the assembly of Laurentia: New interpretations from recent single grain zircon geochronological and geochemical data

NASA Astrophysics Data System (ADS)

LaDouceur, B. O.; Gifford, J.; Malone, S.; Davis, B.

2017-12-01

Keywords: Medicine Hat Block, Zircon, U/Pb ages, Hf isotopes, Laurentia The Medicine Hat Block (MHB) is one of the core cratonic elements that amalgamated in the Paleoproterozoic to form Laurentia. However, unlike many of the other cratons, the role of the MHB in the formation of Laurentia is poorly constrained. Virtually all of the MHB is concealed by Proterozoic and younger supracrustal sequences, limiting the data collected from this craton. The primary source of samples from the MHB comes from two sources: 1) xenoliths of variably metamorphoses gneisses, amphibolites, and meta-plutonic rocks collected from Eocene volcanic rock, and 2) similar lithologies recovered from boreholes that penetrate to the MHB basement. Multigrain zircon TIMS analyses yielded U/Pb ages ranging from 1.70 Ga to 3.26 Ga. Recent zircon single-grain LA-ICPMS U-Pb ages revealed a slightly older range of Archean ages, 2.63 Ga to 3.27 Ga, and two samples yielding Paleoproterozoic ages at 1.78 and 1.82 Ga. Whole-rock Sm/Nd data indicated that the samples formed from crustal sources, with model ages ranging between 1.80 Ga to 3.48 Ga. In-situ zircon Hf isotopic results revealed that Archean-aged zircon are generally suprachondritic, with eHf(t) values between 8.3 and -8.7. In contrast, the Paleoproterozoic grains yielded negative eHf(t) values ranging from -6.8 to -21.2, suggestive of a reworked Archean crustal component in their genesis. In particular, the Sweetgrass Hill xenolith suite is characterized solely by Paleoproterozoic ages, with evolved eHf(t) suggesting that any older U-Pb ages were reset by granulite facies metamorphism and zircon recrystallization. The combined U-Pb and Hf isotopic data from these samples helps illuminate the character of the MHB and its relationships to the Wyoming and Hearne cratons, as well as the Great Falls Tectonic Zone (GFTZ). The ages overlap between cratonic elements; however, the abundance of positive eHf(t) values of the 2.8 Ga ages suggests that the MHB is distinct from the Wyoming Craton, and that the GFTZ must indeed be a collisional zone as proposed by others. The Paleoproterozoic ages observed in the granulite xenolith samples supports this distinctness as well, and also supports proposed models of a Paleoproterozoic underplating event observed in other xenoliths and in seismic sections.

Volcanostratigraphy, petrography and petrochemistry of Late Cretaceous volcanic rocks from the Görele area (Giresun, NE Turkey)

NASA Astrophysics Data System (ADS)

Oguz, Simge; Aydin, Faruk; Baser, Rasim

2015-04-01

In this study, we have reported for lithological, petrographical and geochemical features of late Cretaceous volcanic rocks from the Çanakçı and the Karabörk areas in the south-eastern part of Görele (Giresun, NE Turkey) in order to investigate their origin and magmatic evolution. Based on the previous ages and recent volcano-stratigraphic studies, the late Cretaceous time in the study area is characterized by an intensive volcanic activity that occurred in two different periods. The first period of the late Cretaceous volcanism (Cenomanian-Santonian; 100-85 My), conformably overlain by Upper Jurassic-Lower Cretaceous massive carbonates (Berdiga Formation), is represented by bimodal units consisting of mainly mafic rock series (basaltic-andesitic lavas and hyaloclastites, dikes and sills) in the lower part (Çatak Formation), and felsic rock series (dacitic lavas and hyaloclastites, crystal- and pyrite-bearing tuffs) in the upper part (Kızılkaya Formation). The second period of the late Cretaceous volcanism (Santonian-Late Campanian; 85-75 Ma) is also represented by bimodal character and again begins with mafic rock suites (basaltic-basaltic andesitic lavas and hyaloclastites) in the lower part (Çağlayan Formation), and grades upward into felsic rock suites (biotite-bearing rhyolitic lavas, ignimbrites and hyaloclastites) through the upper part (Tirebolu Formation). These bimodal units are intercalated with volcanic conglomerates-sandstones, claystones, marl and red pelagic limestones throughout the volcanic sequence, and the felsic rock series have a special important due to hosting of volcanogenic massive sulfide deposits in the region. All volcano-sedimentary units are covered by Tonya Formation (Late Campanian-Paleocene) containing calciturbidites, biomicrites and clayey limestones. The mafic rocks in the two volcanic periods generally include basalt, basaltic andesite and minor andesite, whereas felsic volcanics of the first period mainly consists of dacite but those of the second period have biotite-bearing rhyolite. The basalts and basaltic andesites exhibit subaphyric to porphyritic texture with phenocrysts of calcic plagioclase and augite in a fine-grained to microcrystalline groundmass, consisting of plag+cpx+mag. Andesite samples display a porphyritic texture with phenocrysts of calcic to sodic plagioclase and augite in a hyalopilitic matrix of plag+cpx±amph+mag. Zircon and magnetite are common accessory minerals, whereas chlorite, epidote and calcite are typical alteration products. On the other hand, the dacitic and rhyolitic rocks commonly show a porphyritic texture with predominant feldspar, quartz and some biotite phenocrysts. The microgranular to felsophyric groundmass is mainly composed of aphanitic plagioclase, K-feldspar and quartz. Accessory minerals include zircon, apatite and magnetite. Typical alteration minerals include late-formed sericite, albite and clay minerals. Late Cretaceous mafic and felsic volcanic rocks have a largely sub-alkaline character with typical arc geochemical signatures. N-MORB-normalised multi-element patterns show that all rock samples are enriched in LILEs (e.g. Rb, Ba, Th) but depleted in Nb and Ti. The chondrite-normalized REE patterns are concave shapes with low to medium enrichment, suggesting a common mantle source for the studied bimodal rock series. All geochemical data reflecting typical characteristics of subduction-related magmas are commonly attributed to a depleted mantle source, which has been previously enriched by fluids or sediments. Acknowledgments This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK, grant 112Y365)

Geology, mineralization, and hydrothermal alteration and relationships to acidic and metal-bearing surface waters in the Palmetto Gulch area, southwestern Colorado

USGS Publications Warehouse

Bove, Dana J.; Kurtz, Jeffrey P.; Wright, Winfield G.

2002-01-01

The Palmetto Gulch area is affected by low pH and metal-bearing drainage from abandoned mines, and perhaps, from natural weathering around vein zones. To investigate these anthropogenic and potential natural sources of acidity and metals, we mapped the geology, veins, and hydrothermally altered areas; conducted mine dump leachate studies; and collected reconnaissance water quality data. Several small abandoned mines are present in the Palmetto Gulch area that produced small amounts of relatively high-grade silver ore from fault-controlled polymetallic vein deposits. These veins are hosted in lavas, breccias, and related volcaniclastic sediments that ponded within the 28 Ma San Juan-Uncompahgre caldera complex. These rock units generally have conformable contacts and have shallow dips to the northwest. Lava flows of pyroxene andesite, which host the Roy-Pray mine, are massive near their base and typically grade upward into tightly jointed rock with 2-15 cm joint spacing. In general, most hydrothermally altered rock within the Palmetto Gulch area is restricted to envelopes surrounding the mineralized veins and faults. Composite zones of vein-related alteration vary from about 50 to 80 m wide along the high ridgelines and narrow to less than 10 to 15 m beneath an elevation of about 5,462 m. Where unaffected by surficial oxidation, these altered zones contain as much as 7 to 10 volume percent finely-disseminated pyrite. The majority of rocks in the area were affected by regional and vein-related propylitic alteration. These greenish-colored rocks have alteration products consisting of chlorite, illite, and calcite; and feldspars are typically weakly altered. Most of these rocks have detectable amounts of calcite, while as much as 11 percent by weight was detected in samples collected during this study. The Palmetto Gulch area is affected by low pH and metal-bearing drainage from abandoned mines, and perhaps, from natural weathering around vein zones. To investigate these anthropogenic and potential natural sources of acidity and metals, we mapped the geology, veins, and hydrothermally altered areas; conducted mine dump leachate studies; and collected reconnaissance water quality data. Several small abandoned mines are present in the Palmetto Gulch area that produced small amounts of relatively high-grade silver ore from fault-controlled polymetallic vein deposits. These veins are hosted in lavas, breccias, and related volcaniclastic sediments that ponded within the 28 Ma San Juan-Uncompahgre caldera complex. These rock units generally have conformable contacts and have shallow dips to the northwest. Lava flows of pyroxene andesite, which host the Roy-Pray mine, are massive near their base and typically grade upward into tightly jointed rock with 2-15 cm joint spacing. In general, most hydrothermally altered rock within the Palmetto Gulch area is restricted to envelopes surrounding the mineralized veins and faults. Composite zones of vein-related alteration vary from about 50 to 80 m wide along the high ridgelines and narrow to less than 10 to 15 m beneath an elevation of about 5,462 m. Where unaffected by surficial oxidation, these altered zones contain as much as 7 to 10 volume percent finely-disseminated pyrite. The majority of rocks in the area were affected by regional and vein-related propylitic alteration. These greenish-colored rocks have alteration products consisting of chlorite, illite, and calcite; and feldspars are typically weakly altered. Most of these rocks have detectable amounts of calcite, while as much as 11 percent by weight was detected in samples collected during this study.

Earthquake source properties from instrumented laboratory stick-slip

USGS Publications Warehouse

Kilgore, Brian D.; McGarr, Arthur F.; Beeler, Nicholas M.; Lockner, David A.; Thomas, Marion Y.; Mitchell, Thomas M.; Bhat, Harsha S.

2017-01-01

Stick-slip experiments were performed to determine the influence of the testing apparatus on source properties, develop methods to relate stick-slip to natural earthquakes and examine the hypothesis of McGarr [2012] that the product of stiffness, k, and slip duration, Δt, is scale-independent and the same order as for earthquakes. The experiments use the double-direct shear geometry, Sierra White granite at 2 MPa normal stress and a remote slip rate of 0.2 µm/sec. To determine apparatus effects, disc springs were added to the loading column to vary k. Duration, slip, slip rate, and stress drop decrease with increasing k, consistent with a spring-block slider model. However, neither for the data nor model is kΔt constant; this results from varying stiffness at fixed scale.In contrast, additional analysis of laboratory stick-slip studies from a range of standard testing apparatuses is consistent with McGarr's hypothesis. kΔt is scale-independent, similar to that of earthquakes, equivalent to the ratio of static stress drop to average slip velocity, and similar to the ratio of shear modulus to wavespeed of rock. These properties result from conducting experiments over a range of sample sizes, using rock samples with the same elastic properties as the Earth, and scale-independent design practices.

Geochemistry of groundwater in the Beaver and Camas Creek drainage basins, eastern Idaho

USGS Publications Warehouse

Rattray, Gordon W.; Ginsbach, Michael L.

2014-01-01

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, is studying the fate and transport of waste solutes in the eastern Snake River Plain (ESRP) aquifer at the Idaho National Laboratory (INL) in eastern Idaho. This effort requires an understanding of the natural and anthropogenic geochemistry of groundwater at the INL and of the important physical and chemical processes controlling the geochemistry. In this study, the USGS applied geochemical modeling to investigate the geochemistry of groundwater in the Beaver and Camas Creek drainage basins, which provide groundwater recharge to the ESRP aquifer underlying the northeastern part of the INL. Data used in this study include petrology and mineralogy from 2 sediment and 3 rock samples, and water-quality analyses from 4 surface-water and 18 groundwater samples. The mineralogy of the sediment and rock samples was analyzed with X-ray diffraction, and the mineralogy and petrology of the rock samples were examined in thin sections. The water samples were analyzed for field parameters, major ions, silica, nutrients, dissolved organic carbon, trace elements, tritium, and the stable isotope ratios of hydrogen, oxygen, carbon, sulfur, and nitrogen. Groundwater geochemistry was influenced by reactions with rocks of the geologic terranes—carbonate rocks, rhyolite, basalt, evaporite deposits, and sediment comprised of all of these rocks. Agricultural practices near and south of Dubois and application of road anti-icing liquids on U.S. Interstate Highway 15 were likely sources of nitrate, chloride, calcium, and magnesium to groundwater. Groundwater geochemistry was successfully modeled in the alluvial aquifer in Camas Meadows and the ESRP fractured basalt aquifer using the geochemical modeling code PHREEQC. The primary geochemical processes appear to be precipitation or dissolution of calcite and dissolution of silicate minerals. Dissolution of evaporite minerals, associated with Pleistocene Lake Terreton, is an important contributor of solutes in the Mud Lake-Dubois area. Oxidation-reduction reactions are important influences on the chemistry of groundwater at Camas Meadows and the Camas National Wildlife Refuge. In addition, mixing of different groundwaters or surface water with groundwater appears to be an important physical process influencing groundwater geochemistry in much of the study area, and evaporation may be an important physical process influencing the groundwater geochemistry of the Camas National Wildlife Refuge. The mass-balance modeling results from this study provide an explanation of the natural geochemistry of groundwater in the ESRP aquifer northeast of the INL, and thus provide a starting point for evaluating the natural and anthropogenic geochemistry of groundwater at the INL.

Petroleum systems of the Southeast Tertiary basins and Marbella area, Southeast Mexico

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

Fuentes, F.

1996-08-01

This study was done in an area where insufficient organic-rich rocks were available for a reliable oil-source rock correlation. However, oil-rock correlations, molecular characteristics of key horizons, paleofacies maps, maturation and potential migration pathways suggest the Tithonian as a major source rock. Moreover, there is good evidence of high quality source rocks in Oxfordian, Kimmeridgian, Middle-Upper Cretaceous and Paleogene (mainly in the Eocene). Plays were identified in Upper Jurassic oolitic sequences, Early-Middle Cretaceus carbonate platform rocks and breccias, Late Cretaceous basinal fracture carbonates, Paleogene carbonates and breccias, Early-Middle Miocene mounds and submarine fans and isolated carbonate platform sediments and Miocene-Recentmore » turbidites. Seal rocks are shaly carbonates and anhydrites from Tithonian, basinal carbonates and anhydrites from Middle-Upper Cretaceous, basinal carbonates and marls from Upper Cretaceous and Paleogene shales, and bathyal shales from Early Miocene-Recent. The first phase of oil migration from upper Jurassic-Early Cretaceous source rocks occurred in the Early-Middle Cretaceous. In the Upper Cretaceous the Chortis block collided with Chiapas, and as a result mild folding and some hydrocarbons were emplaced to the structural highs. The main phase of structuration and folding of the Sierra de Chiapas started in the Miocene, resulting in well-defined structural traps. Finally, in Plio-Pleistocene the Chortis block was separated, the major compressional period finished and the southern portion of Sierra de Chiapas was raised isostatically. As a result of major subsidence, salt withdrawal and increased burial depth, conditions were created for the generation of liquid hydrocarbons from the Paleogene shales.« less

Extended HFSE systematics of Apollo samples - wrenching further Secrets from the Lunar Mantle

NASA Astrophysics Data System (ADS)

Thiemens, M. M.; Sprung, P.; Munker, C.

2016-12-01

As Earth's intimate companion, the Moon provides a close extraterrestrial view on planetary differentiation. In turn, investigating chemical and isotopic compositions of lunar rocks for traces of a putative crystallizing Lunar Magma Ocean (LMO) provides a better understanding of the evolution and differentiation of infant planetary bodies.We expand on high-precision extended High Field Strength Element (HFSE) observations of Münker [1]. In detail, we investigate if the HFSE systematics of low- and high- Ti basalts, KREEPy basalts and breccias, soils, and ferroan anorthosites (FAN) are consistent with their formation from the LMO (FAN, KREEP) or mantle sources comprising mixtures of primary LMO products [2] (mare basalts). Of particular interest is the recently discovered dependence of HFSE partitioning on the Ti-concentration of co-existing melts [3] and that of W partitioning on oxygen fugacity [3,4].Our data form a positively correlated array in Zr/Hf vs. Nb/Ta space, similar to previous high-precision [1] but unlike lower-precision data. The HFSE systematics of different rock types from the Apollo missions mostly form distinct groups. High-Ti and some Apollo 12 low-Ti mare basalts form the lower end of the array, KREEPy samples its upper end. Low Zr/Nb in most high-Ti mare basalts and the globally highest Hf/W confirm involvement of Ti-rich-oxide-bearing cumulates in high-Ti formation [e.g., 1,2]. No global lunar trends exist for Hf/W vs. Zr/Nb. Overall, the composition of KREEPy samples agrees reasonably well with model KREEP-compositions assuming a LMO below IW-1 [1,4].Clearly distinct groupings observed for the various rock types and the lack of a global trend in Hf/W vs. Zr/Nb calls for melting of distinct ultramafic sources [1]. The HFSE systematics of Apollo rocks tend to support a LMO scenario, setting the stage for more detailed petrogenetic modeling. Initial modeling suggests that the lunar mantle must possess residual metal to reconcile the HFSE systematics of Apollo rocks within an LMO-scenario, providing an alternative explanation for the very low abundances of HSE in the lunar crust [5].[1] Münker, C. (2010) GCA 74, 7340-7361. [2] Snyder et al. (1992) GCA 56, 3809-3823. [3] Leitzke et al. (in press) Chem. Geol. [4] Fonseca et al. (2014) EPSL 404, 1-13. [5] Day & Walker (2015) EPSL 423, 114-124

Location-Related Differences in Weathering Behaviors and Populations of Culturable Rock-Weathering Bacteria Along a Hillside of a Rock Mountain.

PubMed

Wang, Qi; Wang, Rongrong; He, Linyan; Sheng, Xiafang

2017-05-01

Bacteria play important roles in rock weathering, elemental cycling, and soil formation. However, little is known about the weathering potential and population of bacteria inhabiting surfaces of rocks. In this study, we isolated bacteria from the top, middle, and bottom rock samples along a hillside of a rock (trachyte) mountain as well as adjacent soils and characterized rock-weathering behaviors and populations of the bacteria. Per gram of rock or surface soil, 10 6 -10 7 colony forming units were obtained and total 192 bacteria were isolated. Laboratory rock dissolution experiments indicated that the proportions of the highly effective Fe (ranging from 67 to 92 %), Al (ranging from 40 to 48 %), and Cu (ranging from 54 to 81 %) solubilizers were significantly higher in the top rock and soil samples, while the proportion of the highly effective Si (56 %) solubilizers was significantly higher in the middle rock samples. Furthermore, 78, 96, and 6 % of bacteria from the top rocks, soils, and middle rocks, respectively, significantly acidified the culture medium (pH < 4.0) in the rock dissolution process. Most rock-weathering bacteria (79 %) from the rocks were different to those from the soils and most of them (species level) have not been previously reported. Furthermore, location-specific rock-weathering bacterial populations were found and Bacillus species were the most (66 %) frequently isolated rock-weathering bacteria in the rocks based on cultivation methods. Notably, the top rocks and soils had the highest and lowest diversity of rock-weathering bacterial populations, respectively. The results suggested location-related differences in element (Si, Al, Fe, and Cu) releasing effectiveness and communities of rock-weathering bacteria along the hillside of the rock mountain.

[Spectral characteristics and implications of quartz from Heliao lead-zinc polymetallic ore district in the south of Qinzhou-Hangzhou joint belt].

PubMed

Lü, Wen-Chao; Yang, Zhi-Jun; Zhou, Yong-Zhang; Li, Hong-Zhong; Zeng, Xiang-Qing; Chen, Qing; Liang, Jin; Zeng, Chang-Yu

2013-05-01

The XRD, FTIR and Raman spectrum were employed to study the characters of quartz from three types of rock samples, which are mineralized rock sample, near ore body rock sample and far away from ore body rock sample in Heliao lead-zinc polymetallic ore district. The research shows that the quartz in the mineralized rock and far away from ore body rock is pure, while the quartz in near ore body rock contains a small amount of impurities. But such small amounts of impurities did not cause apparent change in the quartz lattice parameters. From far away from ore body rock-->near ore body rock-->mineralized rock, the crystallinity and order degree of quartz are higher and higher. And the quartz in the mineralized rock has a trend to change into low symmetry quartz. It's a unique to mineralized rock that the quartz's absorption peak at 1 050 cm(-1) was split into two strongest ones. It can be used as the signs of whether exists mineralization. The cause for the quartz microstructure changes may be related to the activities of late mineralized hydrothermal fluids. Late hydrothermal influence was very weak to the quartz far away from ore body rock. And through the impact of the multi-stage hydrothermal effect, the quartz in mineralized rock may be purified by recrystallization and structural adjustment. However the quartz in near ore body rock didn't have enough hydrothermal influence, so it's not pure. Genealogy research technology is a useful technique for in-depth exploration of study area mineralization process and metallogenic regularity.

Geophysical well-log analysis of fractured crystalline rocks at East Bull Lake, Ontario, Canada

USGS Publications Warehouse

Paillet, Frederick L.; Hess, A.E.

1986-01-01

Various conventional geophysical borehole measurements were made in conjunction with measurements using a recently designed, low-frequency, acoustic-waveform probe and slow velocity flowmeter for characterization of a fractured mafic intrusion in southern Ontario, Canada. Conventional geophysical measurements included temperature, caliper, gamma, acoustic, single-point resistance, and acoustic televiewer logs. Hole stability problems prevented the use of neutron and gamma-gamma logs, because these logs require that a radioactive source be lowered into the borehole. Measurements were made in three boreholes as much as 850 m deep and penetrating a few tens of meters into granitic basement. All rocks within the mafic intrusion were characterized by minimal gamma radiation and acoustic velocities of about 6.9 km/sec. The uniformity of the acoustic velocities and the character of acoustic-waveform logs made with a conventional high-frequency logging source correlated with the density of fractures evident on televiewer logs. Sample intervals of high-frequency waveform logs were transformed into interpretations of effective fracture opening using a recent model for acoustic attenuation in fractured rocks. The new low-frequency sparker source did not perform as expected at depths below 250 m because of previously unsuspected problems with source firing under large hydrostatic heads. A new heat-pulse, slow velocity flowmeter was used to delineate in detail the flow regime indicated in a general way by temperature logs. The flowmeter measurements indicated that water was entering 2 of the boreholes at numerous fractures above a depth of 200 m, with flow in at least 2 of the boreholes exiting through large isolated fractures below a depth of 400 m. (Author 's abstract)

Rb-Sr, K-Ar, and stable isotope evidence for the ages and sources of fluid components of gold-bearing quartz veins in the northern Sierra Nevada foothills metamorphic belt, California

USGS Publications Warehouse

Böhlke, John Karl; Kistler, R. W.

1986-01-01

Gold-bearing quartz veins occur in and near major fault zones in deformed oceanic and island-arc rocks west of the main outcrop of the Sierra Nevada composite batholith. Veins typically occupy minor reverse faults that crosscut blueschist to amphibolite-grade metamorphic rocks whose metamorphic ages range from early Paleozoic to Jurassic. Vein micas and carbonate-quartz-mica assemblages that formed by hydrothermal metasomatism of ultramafic wall rocks in the Alleghany, Grass Valley, Washington, and Mother Lode districts yield concordant K-Ar and Rb-Sr ages. The dated veins are significantly younger than prograde metamorphism, penetrative deformation, and accretion of their host rocks to the continental margin. New and previously published mineralization ages from 13 localities in the Sierra foothills range from about 140 to 110 m.y. ago, with mean and median between 120 and 115 m.y. The age relations suggest that mineralizing fluids were set in motion by deep magmatic activity related to the resumption of east-dipping subduction along the western margin of North America following the Late Jurassic Nevadan collision event.CO 2 -bearing fluids responsible for metasomatism and much of the vein mica, carbonate, albite, and quartz deposition in several northern mines were isotopically heavy (delta 18 O [asymp] 8-14ppm; delta D between about -10 and -50ppm) and do not resemble seawater, magmatic, or meteoric waters. Metasomatic and vein-filling mica, dolomite, magnesite, and quartz in altered ultramafic rocks generally formed from fluids with similar Sr and O isotope ratios at a given locality. Consistent quartz-mica delta 18 O fractionations (delta 18 O (sub Q-M) = 4.5-4.9ppm) from various localities imply uniform equilibration temperatures, probably between 300 degrees and 350 degrees C. On a local (mine) scale, fluids responsible for both carbonate alteration of mafic and ultramafic wall rocks and albitic alteration of felsic and pelitic rocks had similar Sr isotope ratios.Samples from three veins in the central Alleghany district fit a 115.7 + or - 3-m.y. Rb-Sr isochron with a ( 87 Sr/ 86 Sr) i value of approximately 0.7119. Inferred 87 Sr/ 86 Sr ratios of metasomatic fluids from mines in different parts of the foothills region vary considerably (0.704-0.718), suggesting that Sr was derived from sources ranging from "western assemblage" Mesozoic ophiolitic or arc volcanic rocks to early Paleozoic continent-derived clastic rocks of the Shoo Fly Complex. Systematic geographic variations in both Sr and O isotopes can be rationalized by assuming extensive fluid interaction with rocks similar to the ones that are exposed within a few kilometers of the veins, but the ultimate sources of the fluids, and of Au and other constituents, may be independent of these. Isotopically lighter (meteoric?) fluids deposited some late quartz overgrowths and occupied secondary fluid inclusions in earlier vein quartz.

Effect of Particle Shape on Mechanical Behaviors of Rocks: A Numerical Study Using Clumped Particle Model

PubMed Central

Rong, Guan; Liu, Guang; Zhou, Chuang-bing

2013-01-01

Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied. PMID:23997677

Effect of particle shape on mechanical behaviors of rocks: a numerical study using clumped particle model.

PubMed

Rong, Guan; Liu, Guang; Hou, Di; Zhou, Chuang-Bing

2013-01-01

Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied.

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.

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).

Iron-oxide Magnetic, Morphologic, and Compositional Tracers of Sediment Provenance and Ice Sheet Extent in the ANDRILL AND-1B Drill Core, Ross Sea, Antarctica (Invited)

NASA Astrophysics Data System (ADS)

Brachfeld, S. A.; Pinzon, J.; Darley, J. S.; Sagnotti, L.; Kuhn, G.; Florindo, F.; Wilson, G. S.; Ohneiser, C.; Monien, D.; Joseph, L. H.

2013-12-01

The first drilling season of the Antarctic Drilling Program (ANDRILL) recovered a 13.57 million year Miocene through Pleistocene record of paleoclimate change (core AND-1B) within the Ross Sea. The magnetic mineral assemblage records the varying contributions of biological productivity, changing sediment sources, the emergence of volcanic centers, and post-depositional diagenesis. Characterization of bedrock samples from the McMurdo Volcanic Group (MVG) and Transantarctic Mountain (TAM) lithologic units allows us to construct fingerprints for the major source rocks bordering the Ross Sea, and identify their signatures within the AND-1B sediment. Key parameters that can be traced from source rock to sediment for the MVG-derived sediment include a 100-200 C order-disorder transition, titanomaghemite grains with homogenous textures but with substantial Al and Mg content, Fe-spinels with substantial Al, Cr, Mg, and Ti content, and titanomagnetite host grains with 1-3 swarms of ilmenite lamellae (both with variable amounts of oxidation). Distinctive signatures in TAM lithologies include low S-ratios in Koettlitz Group gneisses and Fe-sulfides with magnetite intergrowths in Byrd Glacier basement samples. The Cambrian Granite Harbor Intrusive Complex is characterized by coarse, homogeneous Mn-bearing ilmenite and nearly pure magnetite. The Jurassic dolerites and basalts of the Ferrar Group contain pseudo single domain to stable single domain-sized Fe-oxides with low-Ti content and homogeneous textures. Cu-Fe sulfides are also present in the Ferrar Group. Diamictites in the Pliocene-Pleistocene section of the AND-1B drill core contains Fe-oxide assemblages with MVG-type rock magnetic and textural characteristics, while the Miocene diamictites contain TAM-type signatures. These observations can be explained by increased ice flow from the west during the Miocene and/or the absence of MVG volcanic centers, which had not yet reached a significant size. During the Pliocene and Pleistocene, ice flow was from the south, entraining sediment from MVG volcanic centers south of the drill site. This work demonstrates the utility of using the combination of rock magnetic and electron microscopy signatures of Fe-oxides and Fe-sulfides to serve as provenance tracers in both ice proximal and distal sedimentary units, aiding in the study of ice sheet dynamics, and the identification of ice rafted debris sources and dispersal patterns in the Ross Sea sector of Antarctica.

Isotopic and trace element variations in the Ruby Batholith, Alaska, and the nature of the deep crust beneath the Ruby and Angayucham Terranes

USGS Publications Warehouse

Arth, Joseph G.; Zmuda, Clara C.; Foley, Nora K.; Criss, Robert E.; Patton, W.W.; Miller, T.P.

1989-01-01

Thirty-six samples from plutons of the Ruby batholith of central Alaska were collected and analyzed for 22 trace elements, and many were analyzed for the isotopic compositions of Sr, Nd, O, and Pb in order to delimit the processes that produced the diversity of granodioritic to granitic compositions, to deduce the nature of the source of magmas at about 110 Ma, and to characterize the deep crust beneath the Ruby and Angayucham terranes. Plutons of the batholith show a substantial range in initial 87Sr/86Sr (SIR) of 0.7055–0.7235 and a general decrease from southwest to northeast. Initial 143Nd/144Nd (NIR) have a range of 0.51150–0.51232 and generally increase from southwest to northeast. The δ18O values for most whole rocks have a range of +8.4 to +11.8 and an average of +10.3‰. Rb, Cs, U, and Th show large ranges of concentration, generally increase as SiO2 increases, and are higher in southwest than in northeast plutons. Sr, Ba, Zr, Hf, Ta, Sc, Cr, Co, and Zr show large ranges of concentration and generally decrease as SiO2 increases. Rare earth elements (REE) show fractionated patterns and negative Eu anomalies. REE concentrations and anomalies are larger in the southwest than in the northeast plutons. Uniformity of SIR and NIR in Sithylemenkat and Jim River plutons suggests a strong role for fractional crystallization or melting of uniform magma sources at depth. Isotopic variability in Melozitna, Ray Mountains, Hot Springs, and Kanuti plutons suggests complex magmatic processes such as magma mixing and assimilation, probably combined with fractional crystallization, or melting of a complex source at depth. The large variations in SIR and NIR in the batholith require a variation in source materials at depth. The southwestern plutons probably had dominantly siliceous sources composed of metamorphosed Proterozoic and Paleozoic upper crustal rocks. The northeastern plutons probably had Paleozoic sources that were mixtures of siliceous and intermediate to mafic crustal rocks. The inferred sources could well have been the higher-metamorphic-grade lithologic equivalents of the exposed Proterozoic(?) to Paleozoic schists, orthogneisses, and metavolcanic rocks of Ruby terrane, the silicic portions of which are quite radiogenic. The deeper crustal sources that gave rise to most of the batholithic magmas are inferred to be similar under both the Ruby metamorphic terrane and the Angayucham ophiolitic terrane.

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.

Cooperative investigation of precision and accuracy: In chemical analysis of silicate rocks

USGS Publications Warehouse

Schlecht, W.G.

1951-01-01

This is the preliminary report of the first extensive program ever organized to study the analysis of igneous rocks, a study sponsored by the United States Geological Survey, the Massachusetts Institute of Technology, and the Geophysical Laboratory of the Carnegie Institution of Washington. Large samples of two typical igneous rocks, a granite and a diabase, were carefully prepared and divided. Small samples (about 70 grams) of each were sent to 25 rock-analysis laboratories throughout the world; analyses of one or both samples were reported by 34 analysts in these laboratories. The results, which showed rather large discrepancies, are presented in histograms. The great discordance in results reflects the present unsatisfactory state of rock analysis. It is hoped that the ultimate establishment of standard samples and procedures will contribute to the improvement of quality of analyses. The two rock samples have also been thoroughly studied spectrographically and petrographically. Detailed reports of all the studies will be published.

Changes in bacteria recoverable from subsurface volcanic rock samples during storage at 4{degrees}C

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

Haldeman, D.L.; Amy, P.S.; White, D.C.

1994-08-01

The abundance of viable microorganisms recovered from deep subsurface volcanic rock samples increased after rock perturbation and storage for 1 week at 4{degrees}C, while the diversity and evenness of recoverable heterotrophic bacterial communities generally decreased. One sample of each morphologically distinct colony type, recovered both before and after storage of U12n rock samples, was purified and characterized by fatty acid methyl ester (MIDI) and API rapid NFT strips. As determined by MIDI cluster analysis, the composition of the recoverable microbial communities changed with storage of rock samples; some groups of organisms were recovered only before, only after, or at bothmore » sample times. In general, the isolates recovered only after storage of rock samples had a greater ability to utilize the carbohydrates included in API test strips and had faster generation times than isolates recovered only on initial plating. The nutritional versatility and faster growth rates of organisms recovered in higher proportions after sample storage provide evidence that some microbial community changes may be due to the proliferation of a few bacterial types. However, because some new genera are recovered only after storage, the possibility also exists that dormant bacterial types are resuscitated during sample perturbation and storage. 30 refs., 1 fig., 5 tabs.« less

40 CFR 60.401 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock Plants § 60.401 Definitions. (a) Phosphate rock plant means any plant which produces or prepares phosphate rock product by any or..., calcining, and grinding. (b) Phosphate rock feed means all material entering the process unit, including...

40 CFR 60.401 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock Plants § 60.401 Definitions. (a) Phosphate rock plant means any plant which produces or prepares phosphate rock product by any or..., calcining, and grinding. (b) Phosphate rock feed means all material entering the process unit, including...

40 CFR 60.401 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock Plants § 60.401 Definitions. (a) Phosphate rock plant means any plant which produces or prepares phosphate rock product by any or..., calcining, and grinding. (b) Phosphate rock feed means all material entering the process unit, including...