Characterization and modes of occurrence of elements in feed coal and coal combustion products from a power plant utilizing low-sulfur coal from the Powder River Basin, Wyoming

USGS Publications Warehouse

Brownfield, Michael E.; Cathcart, James D.; Affolter, Ronald H.; Brownfield, Isabelle K.; Rice, Cynthia A.; O'Connor, Joseph T.; Zielinski, Robert A.; Bullock, John H.; Hower, James C.; Meeker, Gregory P.

2005-01-01

The U.S. Geological Survey and the University of Kentucky Center for Applied Energy Research are collaborating with an Indiana utility company to determine the physical and chemical properties of feed coal and coal combustion products from a coal-fired power plant. The Indiana power plant utilizes a low-sulfur (0.23 to 0.47 weight percent S) and lowash (4.9 to 6.3 weight percent ash) subbituminous coal from the Wyodak-Anderson coal zone in the Tongue River Member of the Paleocene Fort Union Formation, Powder River Basin, Wyoming. Based on scanning electron microscope and X-ray diffraction analyses of feed coal samples, two mineral suites were identified: (1) a primary or detrital suite consisting of quartz (including beta-form grains), biotite, feldspar, and minor zircon; and (2) a secondary authigenic mineral suite containing alumino-phosphates (crandallite and gorceixite), kaolinite, carbonates (calcite and dolomite), quartz, anatase, barite, and pyrite. The primary mineral suite is interpreted, in part, to be of volcanic origin, whereas the authigenic mineral suite is interpreted, in part, to be the result of the alteration of the volcanic minerals. The mineral suites have contributed to the higher amounts of barium, calcium, magnesium, phosphorus, sodium, strontium, and titanium in the Powder River Basin feed coals in comparison to eastern coals. X-ray diffraction analysis indicates that (1) fly ash is mostly aluminate glass, perovskite, lime, gehlenite, quartz, and phosphates with minor amounts of periclase, anhydrite, hematite, and spinel group minerals; and (2) bottom ash is predominantly quartz, plagioclase (albite and anorthite), pyroxene (augite and fassaite), rhodonite, and akermanite, and spinel group minerals. Microprobe and scanning electron microscope analyses of fly ash samples revealed quartz, zircon, and monazite, euhedral laths of corundum with merrillite, hematite, dendritic spinels/ferrites, wollastonite, and periclase. The abundant calcium and magnesium mineral phases in the fly ash are attributed to the presence of carbonate, clay, and phosphate minerals in the feed coal and their alteration to new phases during combustion. The amorphous diffraction-scattering maxima or glass 'hump' appears to reflect differences in chemical composition of fly ash and bottom ash glasses. In Wyodak-Anderson fly and bottom ashes, the center point of scattering maxima is due to calcium and magnesium content, whereas the glass 'hump' of eastern fly ash reflects variation in aluminum content. The calcium- and magnesium-rich and alumino-phosphate mineral phases in the coal combustion products can be attributed to volcanic minerals deposited in peat-forming mires. Dissolution and alteration of these detrital volcanic minerals occurred either in the peat-forming stage or during coalification and diagenesis, resulting in the authigenic mineral suite. The presence of free lime (CaO) in fly ash produced from Wyodak-Anderson coal acts as a self-contained 'scrubber' for SO3, where CaO + SO3 form anhydrite either during combustion or in the upper parts of the boiler. Considering the high lime content in the fly ash and the resulting hydration reactions after its contact with water, there is little evidence that major amounts of leachable metals are mobilized in the disposal or utilization of this fly ash.

Role of Organic Acids in Bioformation of Kaolinite: Results of Laboratory Experiments

NASA Astrophysics Data System (ADS)

Bontognali, T. R. R.; Vasconcelos, C.; McKenzie, J. A.

2012-04-01

Clay minerals and other solid silica phases have a broad distribution in the geological record and greatly affect fundamental physicochemical properties of sedimentary rocks, including porosity. An increasing number of studies suggests that microbial activity and microbially produced organic acids might play an important role in authigenic clay mineral formation, at low temperatures and under neutral pH conditions. In particular, early laboratory experiments (Linares and Huertas, 1971) reported the precipitation of kaolinite in solutions of SiO2 and Al2O3 with different molar ratios SiO2/Al2O3, together with fulvic acid (a non-characterized mixture of many different acids containing carboxyl and phenolate groups) that was extracted from peat soil. Despite many attempts, these experiments could not be reproduced until recently. Fiore et al. (2011) hypothesized that the non-sterile fulvic acid might have contained microbes that participated in the formation of kaolinite. Using solutions saturated with Si and Al and containing oxalate and/or mixed microbial culture extracted from peat-moss soil, they performed incubation experiments, which produced kaolinite exclusively in solutions containing oxalate and microbes. We proposed to test the role of specific organic acids for kaolinite formation, conducting laboratory experiments at 25˚C, with solutions of sodium silicate, aluminum chloride and various organic compounds (i.e. EDTA, citric acid, succinic acid and oxalic acid). Specific organic acids may stabilize aluminum in octahedral coordination positions, which is crucial for the initial nucleation step. In our experiments, a poorly crystalline mineral that is possibly a kaolinite precursor formed exclusively in the presence of succinic acid. In experiments with other organic compounds, no incorporation of Al was observed, and amorphous silica was the only precipitated phase. In natural environments, succinic acid is produced by a large variety of microbes as an intermediate product of the tricarboxylic acid cycle. Our results demonstrate, for the first time, that the formation of a specific clay mineral (proto-kaolinite) occurs in the presence of a specific organic compound (succinic acid). This implies that microbial species capable of excreting succinate among their EPS may promote authigenic kaolinite formation at low temperature and neutral pH. This biological degradation process might play a crucial role for the formation of authigenic kaolinite, which is a widespread clay mineral in sedimentary environments. Fiore, S., Dumontet, S., Huertas, F.J., and Pasquale, V., 2011. Bacteria-induced crystallization of kaolinite. Applied Clay Science, 53:566-571. Linares, J., and Huertas, F., 1971. Kaolinite: Synthesis at room temperature. Science 171: 896-897.

SEM/STEM observations of magnetite in carbonates of eastern North America: Evidence for chemical remagnettzation during the Alleghenian Orogeny

NASA Astrophysics Data System (ADS)

Suk, Dongwoo; Van der Voo, Rob; Peacor, Donald R.

Early to middle Paleozoic carbonates of eastern North America have been pervasively remagnetized. In order to determine the process of remagnetization, scanning and scanning transmission electron microscopy have been used to characterize magnetite in thin sections and in concentrated separates. Samples included Ordovician Knox carbonates from east Tennessee, Ordovician Trenton limestone and Devonian Onondaga and Helderberg limestones from New York, and Ordovician Trenton carbonates from Michigan. Inclusions of authigenic minerals within magnetite grains, lack of cations other than iron, and a variety of textural relations all imply that the magnetite is authigenic. These data are consistent with estimates that paleotemperatures never exceeded values that would reset magnetic directions. The remagnetization is thus a chemical remanent magnetization (CRM) rather than viscous remanent magnetization (VRM). As the timing of remagnetization corresponds to the Alleghenian orogeny, the observed relations imply stress-induced crystallization of magnetite that was mediated by fluids, consistent with but not requiring fluid flow on a regional basis.

Methane seep carbonates yield clumped isotope signatures out of equilibrium with formation temperatures

DOE PAGES

Loyd, S. J.; Sample, J.; Tripati, R. E.; ...

2016-07-22

Here, methane cold seep systems typically exhibit extensive buildups of authigenic carbonate minerals, resulting from local increases in alkalinity driven by methane oxidation. Here, we demonstrate that modern seep authigenic carbonates exhibit anomalously low clumped isotope values (Δ47), as much as ~0.2‰ lower than expected values. In modern seeps, this range of disequilibrium translates into apparent temperatures that are always warmer than ambient temperatures, by up to 50 °C. We examine various mechanisms that may induce disequilibrium behaviour in modern seep carbonates, and suggest that the observed values result from several factors including kinetic isotopic effects during methane oxidation, mixingmore » of inorganic carbon pools, pH effects and rapid precipitation. Ancient seep carbonates studied here also exhibit potential disequilibrium signals. Ultimately, these findings indicate the predominance of disequilibrium clumped isotope behaviour in modern cold seep carbonates that must be considered when characterizing environmental conditions in both modern and ancient cold seep settings.« less

Authigenic magnetite formation from goethite and hematite and chemical remanent magnetization acquisition

NASA Astrophysics Data System (ADS)

Till, J. L.; Nowaczyk, N.

2018-06-01

The iron oxyhydroxide goethite is unstable at elevated temperatures and can transform to magnetite under reducing conditions. In this study, various heating experiments were conducted to simulate Fe-mineral transformations during pyrogenic or burial diagenesis alteration in the presence of organic matter. Thermomagnetic measurements, capsule heating experiments and thermochemical remanence acquisition measurements were performed to determine the effect of organic carbon additions on samples containing synthetic microcrystalline goethite, microcrystalline hematite or nanocrystalline goethite. Changes in magnetic properties with heating were monitored to characterize the magnetic behaviour of secondary magnetite and hematite formed during the experiments. Authigenic magnetite formed in all samples containing organic C, while goethite heated without organic C altered to poorly crystalline pseudomorphic hematite. The concentration of organic matter was found to have little influence on the rate or extent of reaction or on the characteristics of the secondary phases. Authigenic magnetite formed from microcrystalline goethite and hematite dominantly behaves as interacting single-domain particles, while nanophase goethite alters to a mixture of small single-domain and superparamagnetic magnetite. Authigenic magnetite and hematite both acquire a stable thermochemical remanence on heating to temperatures between 350 and 600 °C, although the remanence intensity acquired below 500 °C is much weaker than that at higher temperatures. Reductive transformation of fine-grained goethite or hematite is therefore a potential pathway for the production of authigenic magnetite and the generation of stable chemical remanence that may be responsible for remagnetization in organic-matter-bearing sedimentary rocks.

Livers, guts and gills: mapping the decay profiles of soft tissues to understand authigenic mineral replacement.

NASA Astrophysics Data System (ADS)

Clements, Thomas; Purnell, Mark; Gabbott, Sarah

2016-04-01

The hard mineralised parts of organisms such as shells, teeth and bones dominate the fossil record. There are, however, sites around the world where soft-tissues are preserved often through rapid replacement of original tissue by rapidly-precipitating authigenic minerals. These exceptionally well-preserved soft-bodied fossils are much more informative about the anatomy, physiology, ecology and behaviour of ancient organisms as well as providing a more inclusive picture of ecosystems and evolution throughout geological time. However, despite the wealth of information that soft-bodied fossils can provide they must first be correctly interpreted as the processes of both decay and preservation act to modify the carcass from its in vivo condition. Decay leads to alteration of the appearance and topology of anatomy, and ultimately to loss. Preservation is selective with some anatomical features being more likely to be captured than others. These problems are especially germane to the interpretation of deep-time and/or enigmatic fossils where no modern analogue exist for comparative anatomical analysis. It is therefore of vital importance to understand the processes carcasses undergo during the fossilisation process, , in order to interpret the anatomical remains of fossils and thus extract true evolutionary presence or absence of anatomy from absence due to taphonomic biases. We have designed a series of novel experiments to investigate, in real time, how decay processes affect the fossilisation potential of soft-tissues - especially of internal anatomy. Our data allow us to unravel both the timing and sequence of anatomical decay of different organs. At the same time through measuring Eh and pH in selected organs we can predict when anatomical features will fall in to the window of authigenic mineralization and thus potentially become preserved. We can also place constraints on which minerals will operate to capture tissues. Our findings are applied to the fossil record allowing greater accuracy in reading the record of exceptionally preserved organisms.

Induced and catalysed mineral precipitation in the deep biosphere

NASA Astrophysics Data System (ADS)

Meister, Patrick

2017-04-01

Authigenic and early diagenetic minerals provide archives of past (bio)geochemical processes. In particular, isotopic signatures preserved in the diagenetic phases have been shown to document drastic changes of subsurface microbial activity (the deep biosphere) over geological time periods (Contreras et al., 2013; Meister, 2015). Geochemical and isotopic signatures in authigenic minerals may also document surface conditions and past climate. Nevertheless, such use of authigenic mineral phases as (bio)geochemical archives is often hampered by the insufficient understanding of mineral precipitation mechanisms. Accordingly the time, place and rate of mineral precipitation are often not well constrained. Also, element partitioning and isotopic fractionation may be modified as a result of the precipitation mechanism. Early diagenetic dolomite and quartz from drilled sequences in the Pacific were compared with adjacent porewater compositions and isotope signatures to gain fundamental insight into the factors controlling mineral precipitation. The formation of dolomite in carbonate-free organic carbon-rich ocean margin sediments (e.g. Peru Margin; Ocean Drilling Program, ODP, Site 1229; Meister et al., 2007) relies on the alkalinity-increase driven by anaerobic oxidation of methane and, perhaps, by alteration of clay minerals. In contrast, quartz is often significantly oversaturated in marine porewaters as the dissolved silica concentration is buffered by more soluble opal-A. For example, quartz does not form throughout a 400 metre thick sedimentary sequence in the Eastern Equatorial Pacific (ODP Site 1226; Meister et al., 2014) because it is kinetically inhibited. This behaviour can be explained by Ostwald's step rule, which suggests that the metastable phase forms faster. However, hard-lithified quartz readily forms where silica concentration drops sharply below opal-saturation. This violation of Ostwald's step rule must be driven by an auxiliary process, such as the adsorption of silica to freshly precipitated iron oxides along a deep iron oxidation front. In conclusion, two different modes of precipitation can be observed in modern sub-seafloor porewater systems. Dolomite precipitation is thermodynamically controlled through microbially induced supersaturation. Quartz formation is controlled through an auxiliary process that helps it to overcome a kinetic barrier. These observations exemplify the importance to distinguish between kinetic and thermodynamic effects on mineral formation under Earth surface conditions. To evaluate geochemical signatures, these modes of precipitation need to be taken into account. Contreras et al. (2013) Proc. Natl. Acad. Sci., doi/10.1073/pnas.1305981110 Meister, et al. (2007) Sedimentology 54, 1007-1032. Meister, et al. (2014) Geochim. Cosmochim. Acta 137, 188-207. Meister, P. (2015) Terra Nova, Focus Article, 00, 1-9.

Rare earth elements in Hamersley BIF minerals

NASA Astrophysics Data System (ADS)

Alibert, Chantal

2016-07-01

Minerals from the Hamersley banded iron formation, Western Australia, were analyzed for Y and rare earth elements (YREEs) by laser ablation ICP-MS to investigate diagenetic pathways, from precursor phases to BIF minerals. One group of apatites carries the seawater REE signature, giving evidence that P and REEs, thoroughly scavenged from the water column by Si-ferrihydrite particles, were released upon microbial Fe3+ reductive dissolution of Si-ferrihydrite in pore-water and finally sequestered mainly in authigenic apatite. The absence of fractionation between apatite and seawater suggests that REE were first incorporated into an amorphous calcium phosphate as fully hydrated cations, i.e. as outer-sphere complexes. The iron oxides and carbonates carry only a small fraction of the whole-rock REE budget. Their REE patterns are distinctly enriched in Yb and show some M-type tetrad effect consistent with experimental Kd(REE) between solid and saline solution with low carbonate ion concentrations. It is deduced that hematite formed at an incipient stage of Fe2+-catalyzed dissolution of Si-ferrihydrite, via a dissolution-reprecipitation pathway. The REE pattern of greenalite, found as sub-micron particles in quartz in a chert-siderite sample, is consistent with its authigenic origin by precipitation in pore-water after dissolution of a small amount of Si-ferrihydrite. Magnetite carries very low YREEs (ppb-level), has an homogeneous pattern distinctly enriched in the mid-REEs compared to hematite, and includes a late population depleted in light-REEs, Ba and As. Magnetite forming aggregates and massive laminae is tentatively interpreted as reflecting some fluid-aided hematite-magnetite re-equilibration or transformation at low-grade metamorphic temperatures.

Deep aquifer as driver for mineral authigenesis in Gulf of Alaska sediments (IODP Expedition 341, Site U1417)

NASA Astrophysics Data System (ADS)

Zindorf, Mark; März, Christian; Wagner, Thomas; Strauss, Harald; Gulick, Sean P. S.; Jaeger, John M.; LeVay, Leah J.

2016-04-01

Bacterial sulphate reduction plays a key role in authigenic mineral formation in marine sediments. Usually, decomposition of organic matter follows a sequence of microbial metabolic pathways, where microbial sulphate reduction leads to sulphate depletion deeper in the sediment. When sulphate is consumed completely from the pore waters, methanogenesis commences. The contact of sulphate- and methane-containing pore waters is a well-defined biogeochemical boundary (the sulphate-methane transition zone, SMTZ). Here authigenic pyrite, barite and carbonates form. Pyrite formation is directly driven by bacterial sulphate reduction since pyrite precipitates from produced hydrogen sulphide. Barite and carbonate formation are secondary effects resulting from changes of the chemical milieu due to microbial activity. However, this mineral authigenesis is ultimately linked to abiotic processes that determine the living conditions for microorganisms. At IODP Site U1417 in the Gulf of Alaska, a remarkable diagenetic pattern has been observed: Between sulphate depletion and methane enrichment, a ~250 m wide gap exists. Consequently, no SMTZ can be found under present conditions, but enrichments of pyrite indicate that such zones have existed in the past. Solid layers consisting of authigenic carbonate-cemented sand were partly recovered right above the methane production zone, likely preventing continued upward methane diffusion. At the bottom of the sediment succession, the lower boundary of the methanogenic zone is constrained by sulphate-rich pore waters that appear to originate from a deeper source. Here, a well-established SMTZ exists, but in reversed order (sulphate diffusing up, methane diffusing down). Sulphur isotopes of pyrite reveal that sulphate reduction here does not occur under closed system conditions. This indicates that a deep aquifer is actively recharging the deep sulphate pool. Similar deep SMTZs have been found at other sites, yet mostly in geologically active environments such as ridge flanks or above subduction zones. Therefore Site U1417, in a relatively inactive intraplate environment, represents a so far under-sampled geochemical setting. Calculated accumulation times for authigenic minerals in the deep SMTZ are on the same order of magnitude as the onset of subduction-related bending of the Pacific Plate, suggesting that both processes are linked. Plate bending could create fractures in the overlying sediments allowing seawater to penetrate and recharge a deep aquifer. Our study provides insights into a newly discovered geological process suitable for delivering sulphate-rich water deep into the sediments and installing diagenetically active environments where microbial activity would otherwise be very limited.

On the origin of mixed-layered clay minerals from the San Andreas Fault at 2.5-3 km vertical depth (SAFOD drillhole at Parkfield, California)

NASA Astrophysics Data System (ADS)

Schleicher, A. M.; Warr, L. N.; van der Pluijm, B. A.

2009-02-01

A detailed mineralogical study is presented of the matrix of mudrocks sampled from spot coring at three key locations along the San Andreas Fault Observatory at depth (SAFOD) drill hole. The characteristics of authigenic illite-smectite (I-S) and chlorite-smectite (C-S) mixed-layer mineral clays indicate a deep diagenetic origin. A randomly ordered I-S mineral with ca. 20-25% smectite layers is one of the dominant authigenic clay species across the San Andreas Fault zone (sampled at 3,066 and 3,436 m measured depths/MD), whereas an authigenic illite with ca. 2-5% smectite layers is the dominant phase beneath the fault (sampled at 3,992 m MD). The most smectite-rich mixed-layered assemblage with the highest water content occurs in the actively deforming creep zone at ca. 3,300-3,353 m (true vertical depth of ca. 2.7 km), with I-S (70:30) and C-S (50:50). The matrix of all mudrock samples show extensive quartz and feldspar (both plagioclase and K-feldspar) dissolution associated with the crystallization of pore-filling clay minerals. However, the effect of rock deformation in the matrix appears only minor, with weak flattening fabrics defined largely by kinked and fractured mica grains. Adopting available kinetic models for the crystallization of I-S in burial sedimentary environments and the current borehole depths and thermal structure, the conditions and timing of I-S growth can be evaluated. Assuming a typical K+ concentration of 100-200 ppm for sedimentary brines, a present-day geothermal gradient of 35°C/km and a borehole temperature of ca. 112°C for the sampled depths, most of the I-S minerals can be predicted to have formed over the last 4-11 Ma and are probably still in equilibrium with circulating fluids. The exception to this simple burial pattern is the occurrence of the mixed layered phases with higher smectite content than predicted by the burial model. These minerals, which characterize the actively creeping section of the fault and local thin film clay coating on polished brittle slip surfaces, can be explained by the influence of either cooler fluids circulating along this segment of the fault or the flow of K+-depleted brines.

Scanning electron microscopy of clays and clay minerals

USGS Publications Warehouse

Bohor, B.F.; Hughes, R.E.

1971-01-01

The scanning electron microscope (SEM) proves to be ideally suited for studying the configuration, texture, and fabric of clay samples. Growth mechanics of crystalline units—interpenetration and interlocking of crystallites, crystal habits, twinning, helical growth, and topotaxis—also are uniquely revealed by the SEM.Authigenic kaolins make up the bulk of the examples because their larger crystallite size, better crystallinity, and open texture make them more suited to examination by the SEM than most other clay mineral types.

Neodymium and strontium isotopic dating of diagenesis and low-grade metamorphism of argillaceous sediments

NASA Astrophysics Data System (ADS)

Schaltegger, Urs; Stille, Peter; Rais, Naoual; Piqué, Alain; Clauer, Norbert

1994-03-01

The behaviour of the Rb-Sr and Sm-Nd isotopic systems with increasing degree of Hercynian metamorphic overprint was studied along a transect in Cambrian shales of northwestern Morocco. Clay fractions of < 0.2 to 2-6 μm size from five samples were investigated, representing a range from nonmetamorphic to epizonal metamorphic conditions. The samples were washed in cold l N HC1 prior to digestion to separate soluble/exchangeable Rb, Sr, Sm, and Nd from amounts of these elements fixed in the crystallographic sites of the minerals and to analyze both components separately. The results reveal that the Rb-Sr isotopic system is dominated by Sr hosted by clay mineral phases (both detrital and authigenic illite and chlorite) and carbonate-hosted soluble Sr. Isotopic homogenization of Sr occurred during Hercynian metamorphism, yielding ages between 309 and 349 Ma. The Sm-Nd isotopic system, on the other hand, is dominated by cogenetic apatite and Fe oxide/ hydroxide, both having high contents of leachable REEs. The leachates yield a Sm-Nd isochron age of 523 ± 72 Ma, indicating diagenetic equilibrium between apatite and Fe-oxide/hydroxide. Fine-grained clay fractions of < 0.2 μm size plot onto this reference line, suggesting isotopic equilibrium with the leachates. Size fractions > 0.2 μm show inheritance of a detrital Nd component. The study demonstrates that the diagenesis of the investigated argillaceous sediments can be dated by the Sm-Nd chronometer in authigenic cement phases. The isotopic system of these minerals (apatite, Fe hydroxide/oxide) was homogenized during authigenic mineral growth in a sediment that was flushed by diagenetic fluids and had abundant primary or secondary interconnected pore space. The Hercynian metamorphic overprint caused partial isotopic rehomogenization of the adsorbed and clay-hosted portion of the Sr as well as of the carbonate-hosted Sr. The Sm-Nd system in the cement phases survived this metamorphism. This results in decoupling of the two isotopic systems and allows the dating of diagenesis on the one hand (Sm-Nd) and metamorphism on the other hand (Rb-Sr).

Evidence for Biogenic Iron in Ediacaran Limestones of the Yenisei Ridge Vorogovka Series (South-Western Framing of the Siberian Craton).

NASA Astrophysics Data System (ADS)

Vinogradov, E.; Kosareva, L.; Metelkin, D. V.; Vishnevskaya, I.

2017-12-01

The composition and origin of magnetic minerals are used for reconstructing paleogeography and changes in paleoenvironments. Ediacaran limestones of the Vorogovka Series were studied in the Yenisei Ridge. Rock magnetism of the upper part of the Vorogovka Series completely depends on terrigenous admixture of iron. Non-carbonate residue consists of quartz, plagioclase, muscovite, Fe-Mg chlorite, smectite and pyrite. A prominent positive correlation is observed between the Fe content (1550…9350 ppm) and the amount of insoluble residue. Magnetization of the lower part of Vorogovka Series is due to authigenic iron. There are several indirect indications of the presence of magnetotactic bacteria and seaweed remains in these limestones. While Fe content is high (1200…8330 ppm), Fe-hydroxides, pyrite and other minerals indicating secondary transformations were not detected. Thus, iron was included in the carbonate material during sedimentation. There is no correlation between iron content and the amount of insoluble residue, which indicates that iron could not have been taken from terrigenous admixture. Study of the dependence of magnetic susceptibility from temperature in inert atmosphere (argon) revealed magnetic minerals with demagnetization temperatures of 320°C and 580°C. The former may correspond to greigite (Curie Temperature 307°C) or hexagonal pyrrhotine (325°C). The latter indicates magnetite (Curie Temperature 586°C) which may be authigenic or newly formed during the experiment. Both magnetite and greigite, are major biogenic minerals produced by magnetotactic bacteria. The main environment of modern magnetotactic bacteria is microaerophilic habitat. Therefore, their abundant presence in the Ediacaran sediments is quite natural. All of these are preliminary conclusions until bacteria can be visualized by electron microscopy, which is an ongoing. The work was supported by the Ministry of Education and Science of Russia 5.2324.2017/4.6 and the RFBR 15-05-01428.

Trace element geochemistry and mineralogy of coal from Samaleswari open cast coal block (S-OCB), Eastern India

NASA Astrophysics Data System (ADS)

Saha, Debasree; Chatterjee, Debashis; Chakravarty, Sanchita; Mazumder, Madhurina

2018-04-01

Coal samples of Samaleswari open cast coal block (S-OCB) are high ash (Aad, mean value 35.43%) and low sulphur content (St, on dry basis, mean value 0.91% < 1%) in quality. The stratigraphic variation of volatile matter and fixed carbon (dry ash-free) reflect a progress of coal metamorphism with depth that accordance to the coal rank variation from lignite to high volatile bituminous in the studied borehole. The younger coal seams have greater detrital minerals (quartz, illite, rutile) influence whereas older coal seams have greater authigenic mineral (kaolinite, dolomite, siderite, apatite) contribution that are possibly due to subsidence and sediment transportation. In S-OCB coal trace elements affinities in-between mineral and organic fraction are identified with statistical hierarchical cluster analysis. The work is further supported by the use of chemical fractionation experiment that reveals the multi mode of occurrence of several environmentally concern and interested trace elements (Sb, As, Be, Cd, Cr, Co, Cu, Pb, Mn, Ni, Zn). Among the analysed trace elements Co, Mn and Zn have major silicate association along with significant carbonate/oxide/monosulfide association. Whereas As, Cd, Cu, Pb and Ni have dominant pyritic association with notable silicate and carbonate/oxide/monosulfide association. The rest three elements (Sb, Be, Cr) have principally organic association with minor silicate and carbonate/oxide/monosulfide association. The stratigraphic variation of organo-mineral matrix content and detrital-authigenic mineral ratio are primarily related to coal rank. Geochemical character of coal also reflects a light towards proper utilisation of S-OCB coal from technical and environmental view point.

Metal Transport, Heavy Metal Speciation and Microbial Fixation Through Fluvial Subenvironments, Lower Coeur D'Alene River Valley, Idaho

NASA Astrophysics Data System (ADS)

Hooper, R. L.; Mahoney, J. B.

2001-12-01

The lower Coeur d'Alene River Valley of northern Idaho is the site of extensive lead and zinc contamination resulting from both direct riverine tailings disposal and flood remobilization of contaminated sediments derived from the Coeur d'Alene mining district upstream. Variations in the hydrologic regime, redox conditions, porosity/permeability, organic content and microbial activity results in complicated metal transport pathways. Documentation of these pathways is a prerequisite to effective remediation, and requires accurate analysis of lateral and vertical variations. An analytical approach combining sequential extraction, electron microscopy, and microanalysis provides a comprehensive assessment of particulate speciation in this complex hydrologic system. Rigorously controlled sample preparation and a new sequential extraction protocol provide unprecedented insight into the role of metal sequestration in fluvial subenvironments. Four subenvironments were investigated: bedload, overbank (levee), marsh, and lacustrine. Periodic floods remobilize primary ore minerals and secondary minerals from upstream tailings (primarily oxyhydroxides, sulfides and carbonates). The bedload in the lower valley is a reducing environment and acts as a sink for detrital carbonates and sulfides moving downstream. In addition, authigenic/biogenic Fe, Pb and Zn sulfides and phosphates are common in bedload sediments near the sediment/water interface. Flood redistribution of oxide, sulfide and carbonate phases results in periodic contaminant recharge generating a complex system of metal dissolution, mobilization, migration and precipitation. In levee environments, authigenic sulfides from flood scouring are quickly oxidized resulting in development of oxide coated grain surfaces. Stability of detrital minerals on the levee is variable depending on sediment permeability, grain size and mineralogy resulting in a complex stratigraphy of oxide zones mottled with zones dominated by detrital and authigenic carbonate and sulfide phases. Marshes subjected to periodic subaerial exposure/flooding are even more complex and dominated by authigenic and biogenic mineralization. Lacustrine environments are dominated by nanocrystalline inorganic and biogenic sulfide minerals in the upper third of the contaminated sediment column with increasing amounts of silt sized detrital sulfides (especially sphalerite) closer to the premining surface. In pH-neutral subenvironments within the wetlands and lateral lakes of the lower Coeur d'Alene River Valley, microbial fixation plays a critical role in sequestering metals. Complex metal oxyhydroxide phases provided via flood recharge to river edge, marsh and lacustrine environments rapidly dissolve upon encountering anoxic conditions. Microbial activity is extremely effective in removing heavy metals from the water column, producing a nanocrystalline biofilm substrate characterized by ZnS (sphalerite) and non-stoichiometric PbS, FeS, and mixed metal sulfides. These solid phases are inherently unstable, and the sequestered metals become readily available through changes in redox or pH conditions, particularly dam-controlled annual fluctuations in base level, or during removal by bottom-feeding aquatic water fowl. The recognition of the inherent complexity and instability of microbially produced sulfidic material in a pH-neutral environment has important implications for remediation efforts utilizing wetland filtration methods.

Authigenic potassium feldspar: a tracer for the timing of palaeofluid flow in carbonate rocks, Northern Calcareous Alps, Austria

USGS Publications Warehouse

Spotl, C.; Kunk, Michael J.; Ramseyer, K.; Longstaffe, F.J.

1998-01-01

This paper is included in the Special Publication entitled 'Dating and duration of fluid flow and fluid-rock interaction', edited by J. Parnell. Feldspar is a common authigenic constituent in Permian carbonate rocks which occur as tectonically isolated blocks within the evaporitic Haselgebirge melange in the Northern Calcareous Alps (NCA). Coexisting with pyrite, anhydrite, (saddle) dolomite, magnesite, fluorite and calcite, K-feldspar and minor albite record an event of regionally extensive interaction of hot brines with carbonate rocks. Detailed petrographic, crystallographic and geochemical studies reveal a variability in crystal size and shape, Al-Si ordering, elemental and stable isotopic compositions of the K-feldspar, which is only partially consistent with the traditional view of authigenic feldspar as a well-ordered, compositionally pure mineral. 40Ar-39Ar step- heating measurements of authigenic potassium feldspar from several localities yield two age populations, an older one of 145-154 Ma, and a younger one of c.90-97 Ma. Most age spectra reflect cooling through the argon retention temperature interval, which was rapid in some localities (as indicated by plateau ages) and slower in others. Rb-Sr isotope data are more difficult to interpret, because in many K-feldspar samples they are controlled largely by Sr-bearing inclusions. The Jurassic 40Ar-39Ar dates are interpreted as minimum ages of feldspar growth and hence imply that fluid-rock interaction is likely to be simultaneous with or to slightly predate melange formation. Deformation associated with the closure and subduction of the Meliata-Hallstatt ocean south of the NCA during the Upper Jurassic is regarded as the principal geodynamic driving force for both enhanced fluid circulation and melange formation. Some localities were reheated beyond the argon retention temperature for microcline during mid-Cretaceous nappe stacking of the NCA, thus obliterating the older signal.

Methane seepage intensities traced by biomarker patterns in authigenic carbonates from the South China Sea

NASA Astrophysics Data System (ADS)

Guan, H.; Feng, D.

2015-12-01

Authigenic carbonate rocks from an active seep (Site F) at 1120 m water depth of the South China Sea (SCS) were studied using mineralogical and lipid biomarker analyses. Carbonate mineral compositions, in specific samples, were predominantly aragonite, high-Mg calcite (HMC), or a mixture of both. Abundant 13C-depleted lipid biomarkers (various isoprenoids) diagnostic for archaea provide evidence that anaerobic oxidation of methane (AOM) mediated by anaerobic methane oxidizing archaea (ANME) and their bacterial partners is the major process leading to formation of the carbonates. Nearly a pure suite of AOM biomarkers was preserved in aragonitic carbonate in which predominant consortia were most likely ANME-2/Desulfosarcina & Desulfococcus (DSS) assemblages and a mixture of ANME-2/DSS and ANME-1/DSS consortia in the mixed mineral sample, the predominant consortia are in good accordance with the point that the relative higher methane seepage intensity favors the precipitation of aragonite over HMC. In contrast, the completely different biomarker patterns in HMC sample were mainly composed terrestrial organic matter and marine Thaumarchaea, which most likely originally within sediments accompanied with high organic matter input and low methane supply. This environment is known to be favored for archaea of ANME-1 and precipitation of HMC. High concentrations of 13C-depleted hopanoids, including diplopterol, hopanoic acids and hopanols were observed in the aragonite sample that may be sourced by the intermittent presence of oxic conditions in an overall anoxic condition, which was possibly induced by changing seepage intensities.

Reconstruction of paleoenvironment recorded in the Ediacaran Lantain black shales

NASA Astrophysics Data System (ADS)

Liu, Y. H.; Lee, D. C.; You, C. F.; Zhou, C.

2016-12-01

The Ediacaran period (635-542 Ma) was a critical time in the history of life and Earth, during which profound changes in complex megascopic life and probably ocean oxygenation occurred. A growing evidence demonstrates that the Early Ediacaran ocean was not simply a largely anoxic basin as previous thought. Pulsed oxidation or a multilayered water column had been proposed to explain the presence of Lantain macrofossils. To verify these models, in-situ isotopic analysis becomes critical in identifying the isotopic signatures of authigenic minerals, and to avoid mixing in the signals from detrital and diagenetic phases. In this study, samples from Lantain Member II, a 40 m thick black shale unit containing macrofossils and overlaying the cap carbonate, were analyzed, including one sample from the lower part of Member II and six samples from upper part of Member II. Abundant xenotimes were overgrown on the detrital zircon grains during early diagenesis in all the samples. This authigenic phosphate mineral provides the best constraint of depositional age. In addition, framboidal pyrites and microbial mats are alternatively present on the top of Member II, where layered barites are found in one sample, supporting the model of frequent changes of redox conditions. Preliminary results show that the depositional age of barite-bearing black shale is > 520 Ma. In this study, we will combine the in-situ U-Pb xenotime dating and sulfur isotopes in barite and pyrite to discuss the evolution of redox conditions in the Ediacaran ocean.

Environmental controls on sulfur isotopic composition of sulfide minerals in seep carbonates from the South China Sea

NASA Astrophysics Data System (ADS)

Gong, S.; Li, N.; Liang, Q.; Chen, D.; Feng, D.

2017-12-01

Authigenic carbonates and pyrite associated with sulfate-driven anaerobic oxidation of methane (AOM) at methane seeps provide archives to explore the biogeochemical processes involved and seepage dynamics over time. The wide range and extremely high δ34Spy value of authigenic sulfide has been used to trace the AOM-related processes. However, the detail mechanism for this is unknown. We proposed the δ34Spy characteristics result from high sulfate reduction rate and its competition with sulfate supply rate. To test this hypothesis, we investigated Mo content, Sr/Ca and Mg/Ca ratios, pyrite content, and its sulfur isotopic compositions in methane-derived carbonates from Site F and Haima in northern South China Sea. Calcite and aragonite were distinguished through the Sr/Ca and Mg/Ca ratios. The data show that aragonites are always associated with relatively low δ34Spy values compared to calcites. The Mo content and pyrite have good linear correlations in both aragonites and calcites, and aragonites have more positive slope than calcites. This indicates that there is more Mo available from seawater during the aragonite precipitation. The data suggest that the low δ34Spy values are formed at higher supply rate of sulfate under relatively open system, and high δ34Spy values result from a deep sulfate methane transition zone where dissolve sulfate near to complete exhausted via AOM. The combination of a detailed elemental study of authigenic carbonate with sulfur isotopes of sulfide minerals in carbonates are promising tools for reconstructing the dynamics of seep intensities in modern and, potentially, geological record.

The Geologic Signature of Anaerobic Oxidation of Methane (Invited)

NASA Astrophysics Data System (ADS)

Ussler, W.; Paull, C. K.

2010-12-01

Anaerobic oxidation of methane (AOM) is an enormous sink in anoxic marine sediments for methane produced in situ or ascending through the sediment column towards the seafloor. Existing estimates indicate that between 75 and 382 Tg of sedimentary methane are oxidized each year before reaching the sediment-water interface making AOM a diagenetic process of global significance. This methane is derived from a variety of sources including microbial production, thermocatalytic cracking of complex organic matter, decomposing gas hydrates, and possibly abiogenic processes. Stables isotopes of membrane lipid biomarkers and authigenic carbonates associated with zones of AOM, fluorescence in situ hybridization, and anaerobic methane incubations have substantiated the role Archaea and sulfate-reducing bacteria have in driving AOM. The products of AOM are dissolved inorganic carbon (predominantly HCO3-) and bisulfide (HS-). Stable isotope measurements of authigenic carbonates associated with zones of AOM are consistent with the diagenetic carbon being primarily methane derived. These methane-derived carbonates occur in a variety of forms including sedimentary nodules and thin lenses within and below zones of contemporary AOM; outcrops of slabs, ledges, and jagged authigenic carbonates exhumed on the seafloor; and authigenic carbonate mounds associated with near-subsurface methane gas accumulations. Examples of exhumed authigenic carbonates include rugged outcrops along the Guaymas Transform in the Gulf of California, extensive slabs and ledges in the Eel River Basin, and mounds in various stages of development near Bullseye Vent, off Vancouver Island and in the Santa Monica Basin. It is clear from basic microbial biogeochemistry and the occurrences of massive authigenic carbonate which span a large range in size that DIC produced by AOM is preserved as authigenic carbonate within the seafloor and not on the seafloor. These exhumed authigenic carbonate provide a glimpse of how authigenic carbonates may be appear in the geologic record. Based on the stochiometry of the AOM reaction [CH4 + SO4= → HCO3- + HS-], HCO3- and HS- should occur in a 1:1 molar ratio in sediment pore water. Methane-derived carbonates are common in methane-rich sediments and methane venting areas, however the corresponding amount of HS- precipitated as iron monosulfides (FeS) is not. The prediction, based on their molecular weights and densities, is that the volume ratio of authigenic carbonate to FeS should be 2:1. However, in anoxic Black Sea sediments, where a high degree of preservation would be expected, the authigenic carbonate to FeS ratio is ~50:1. Massive accumulations of FeS associated with authigenic carbonates have not been observed. There are a number of fates for the HS- produced by AOM: (1) HS- is oxidized in situ adding sulfate back to the pore water pool; (2) HS- selectively diffuses (relative to HCO3-) towards the seafloor and is oxidized in the benthic water column; or (3) FeS precipitates, but is oxidized when authigenic carbonates are exhumed leaving a vuggy texture. None of these explanations are entirely satisfactory for the early diagenetic loss of HS- from sediments, but strongly suggest that massive accumulations of FeS derived from AOM will not be found in the geologic record.

The influence of authigenic clay formation on the mineralogy and stable isotopic record of lacustrine carbonates

NASA Astrophysics Data System (ADS)

Bristow, Thomas F.; Kennedy, Martin J.; Morrison, Keith D.; Mrofka, David D.

2012-08-01

The mineralogical, compositional and stable isotopic variability of lacustrine carbonates are frequently used as proxies for ancient paleoenvironmental change in continental settings, under the assumption that precipitated carbonates reflect conditions and chemistry of ancient lake waters. In some saline and alkaline lake systems, however, authigenic clay minerals, forming at or near the sediment water interface, are a major sedimentary component. Often these clays are rich in Mg, influencing the geochemical budget of lake waters, and are therefore expected to influence the properties of contemporaneous authigenic carbonate precipitates (which may also contain Mg). This paper documents evidence for a systematic feedback between clay mineral and carbonate authigenesis through multiple precessionally driven, m-scale sedimentary cycles in lacustrine oil-shale deposits of the Eocene Green River Formation from the Uinta Basin (NE Utah). In the studied section, authigenic, Mg-rich, trioctahedral smectite content varies cyclically between 9 and 39 wt.%. The highest concentrations occur in oil-shales and calcareous mudstones deposited during high lake level intervals that favored sedimentary condensation, lengthening the time available for clay diagenesis and reducing dilution by other siliciclastic phases. An inverse relation between dolomite percentage of carbonate and trioctahedral smectite abundance suggests the Mg uptake during clay authigenesis provides a first order control on carbonate mineralogy that better explains carbonate mineralogical trends than the possible alternative controls of (1) variable Mg/Ca ratios in lake water and (2) degree of microbial activity in sediments. We also observe that cyclical change in carbonate mineralogy, believed to be induced by clay authigenesis, also causes isotopic covariation between δ13CPDB and δ18OPDB of bulk sediments because of differences in the equilibrium fractionation factors of dolomite and calcite (˜2‰ and ˜2.6%, respectively). This provides an alternative mechanism for the common pattern of isotopic covariation, which is typically attributed to the effect of simultaneous changes in water balance and biological activity on the carbon and oxygen isotopic composition of lake waters. These findings may help improve paleoenvironmental reconstructions based on lacustrine carbonate records by adding to the factors known to influence the mineralogical, compositional and stable isotopic signals recorded by lacustrine carbonates.

From Black Hole to Hydrate Hole: Gas hydrates, authigenic carbonates and vent biota as indicators of fluid migration at pockmark sites of the Northern Congo Fan

NASA Astrophysics Data System (ADS)

Kasten, S.; Schneider, R.; Spiess, V.; Cruise Participants Of M56b

2003-04-01

A recent high-resolution seismic, echosounder and video survey combined with detailed geological and geochemical sampling of pockmark sites on the Northern Congo Fan was carried out with RV Meteor in November/December 2002 in the frame of the project "CONGO" (BMBF/BEO "Geotechnologien"). These investigations revealed the extensive occurrence of surface and sub-surface gas hydrates as well as characteristic features of fluid venting such as clams (Calyptogena), tube worms (Pogonophera) and huge amounts of authigenic carbonates. In a first approach the patchyness in the occurrence of these features was mapped in relation to pockmark structure and seismic reflectors. Detailed sampling of three pockmarks by gravity corer showed that gas hydrates are present at and close to the sediment surface and often occur as several distinct layers and/or veins intercalated with hemipelagic muds. The depth of the upper boundary of these hydrate-bearing sediments increases from the center towards the edge of the pockmark structures. Pore water concentration profiles of sulfate and methane document the process of anaerobic methane oxidation above the hydrate-bearing layers. For those cores which contained several gas hydrate layers preliminary pore water profiles suggest the occurrence of more than one zone of anaerobic methane oxidation. Authigenic carbonates are found in high abundance, irregularly distributed within the pockmarks close to the sediment surface. These carbonates occur in a wide variety with respect to size, shape, structure and mineralogy. Their formation is associated with high amounts of bicarbonate released by the process of anaerobic methane oxidation. In the gravity cores authigenic carbonates are always present above hydrate-bearing sections. However, the quantities and characteristics of these authigenic minerals in relation to venting and microbial activity as well as to gas hydrate dissociation are not clear yet. Unraveling this relationship will be a major target of further investigation. By means of detailed studies of the sedimentary solid-phase, authigenic carbonates, clam layers and molecular biomarkers we will also try to reconstruct the history of venting and the dynamics of gas hydrate formation and decomposition in the Northern Congo fan area.

Petrologic and isotopic data from the Cretaceous (Campanian) Blackhawk Formation and Star Point Sandstone (Mesaverde Group), Wasatch Plateau, Utah

USGS Publications Warehouse

Fishman, Neil S.; Turner, Christine E.; Peterson, Fred

2013-01-01

The presence of discrete minerals associated with coal—whether (1) detrital or authigenic constituents of the coals or in thin mudstone or siltstone units interbedded with coals, or (2) authigenic phases that formed along cleats—might influence its utilization as an energy resource. The build-up of sintered ash deposits on the surfaces of heat exchangers in coal-fired power plants, due to the alteration of minerals during combustion of the coal, can seriously affect the functioning of the boiler and enhance corrosion of combustion equipment. In particular, the presence of sodium in coals has been considered a key factor in the fouling of boilers; however, other elements (such as calcium or magnesium) and the amount of discrete minerals burned with coal can also play a significant role in the inefficiency of and damage to boilers. Previous studies of the quality of coals in the Cretaceous (Campanian) Blackhawk Formation of the Wasatch Plateau, Utah, revealed that the sodium content of the coals varied across the region. To better understand the origin and distribution of sodium in these coals, petrologic studies were undertaken within a sedimentological framework to evaluate the timing and geochemical constraints on the emplacement of sodium-bearing minerals, particularly analcime, which previously had been identified in coals in the Blackhawk Formation. Further, the study was broadened to include not just coals in the Blackhawk Formation from various localities across the Wasatch Plateau, but also sandstones interbedded with the coals as well as sandstones in the underlying Star Point Sandstone. The alteration history of the sandstones in both formations was considered a key component of this study because it records the nature and timing of fluids passing through them and the associated precipitation of sodium-bearing minerals; thus, the alteration history could place constraints on the distribution and timing of sodium mineralization in the interbedded or overlying Blackhawk coals. Although some preliminary results were previously presented at scientific meetings, the petrologic and geochemical data have not been fully compiled and reported. The purpose of this report is to present the methods of data acquisition and the results of petrologic and isotopic analyses on coal and sandstone samples from the Blackhawk Formation as well as sandstones of the underlying Star Point Sandstone.

Mineralogical Characterization of the Miocene Olcese Formation, Southern San Joaquin Valley, California

NASA Astrophysics Data System (ADS)

Lopez, K. A.; Baron, D.; Guo, J.; Woolford, J. M.

2016-12-01

The early to middle Miocene Olcese Formation in the southern San Joaquin Valley of California consists of shallow marine shelf sands in its lower and upper parts, and non-marine, frequently pumiceous sands in its middle part, and varies in thickness up to 1800 ft. There is little known as to the origin, nature, quantity, and distribution of clay minerals throughout the formation. This study examined 95 sidewall core samples from three wells, as well as 388 cutting samples from four wells and 12 samples from 3 outcrops. Well samples were from depths between 1,800 and 4,000 ft. Qualitative and quantitative mineralogy including clay minerals of the sidewall samples and selected cutting samples was determined by powder X-ray diffraction (XRD). XRD analyses were supplemented by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and petrographic microscopy of selected samples. The main minerals of bulk samples include composite clay, quartz, potassium feldspar/plagioclase, calcite, and clinoptilolite. Content of composite clay varies between 17% and 51%. The clay-size fraction is predominantly composed of smectite, illite, kaolinite and chlorite with smectite being the most abundant. Smectite and clinoptilolite may be the alteration products of deeper burial of volcanic materials. The formation permeability could be significantly lowered by these authigenic minerals.

Stable silicon isotope signatures of marine pore waters - Biogenic opal dissolution versus authigenic clay mineral formation

NASA Astrophysics Data System (ADS)

Ehlert, Claudia; Doering, Kristin; Wallmann, Klaus; Scholz, Florian; Sommer, Stefan; Grasse, Patricia; Geilert, Sonja; Frank, Martin

2016-10-01

Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment-water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm-2 yr-1. The fractionation factor between the precipitates and the pore waters is estimated at -2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.

Diagenetic effects on magnetic minerals in a Holocene lacustrine sediment core from Huguangyan maar lake, southeast China

NASA Astrophysics Data System (ADS)

Wu, Xudong; Wang, Yong; Bian, Liu; Shen, Ji

2016-09-01

Post-depositional reductive diagenesis usually results in partial or entire cleansing of the pristine palaeomagnetic signal, therefore, its intensity is important to be assessed for sediments that are in the purpose of retrieving palaeomagnetic information. Grain size, rock magnetic and geochemical studies on the entire core, along with scanning electron microscope observations and X-ray diffraction analyses for representative samples were carried out on a Holocene sediment core retrieved from the deep water part of Huguangyan maar lake (HGY), southeast China. The pristine magnetic mineral assemblage of the studied core is domianted by superparamagnetic (SP) and stable single domain titanomagnetite, and high coercivity minerals are not detectable. Based on down-core variations of the average grain size (MZ), total organic carbon (TOC), detrital elements (Al, Ti, Fe and Mn) and the concentration and mineralogy of magnetic minerals, the studied core could be divided into three subsections. The uppermost subsection is the least affected by diagenesis, with detrital titanomagnetite as the dominant magnetic mineral. This is owing to low TOC contents, but high detrital input generated by weak Asian summer monsoon intensity during the late Holocene. The intermediate subsection shows down-core progressively enhanced dissolution of detrital titanomagnetite, and concomitant formation of authigenic pyrite and siderite, which indicates down-core progressively enhanced diagenesis generated by down-core progressive increasing TOC content, but decreasing detrital input as the result of down-core progressively strengthened Asian summer monsoon intensity. The pristine magnetic mineral assemblage has been profoundly modified in the lowermost subsection. At certain positions of the lowermost subsection, detrital titanomagnetite has been even completely dissolved via diagenesis, giving place to authigenic pyrite and siderite. High TOC content, but low detrital input generated from strong Asian summer monsoon intensity during the early Holocene are accountable for intensive diagenesis in the lowermost subsection. Complete erasing of detrital magnetic input signal at certain positions of the lowermost subsection, and considerable formation of authigenic siderite indicate that palaeomagnetic records of the studied core have been significantly compromised. The studied core has relatively higher TOC content, lower detrital matter content, calmer sedimentary environments, and less DO available at its water-sediment interface than the cores retrieved at relatively shallower water depths, which all contribute to its relatively stronger diagenesis. Progressive thickening of the upper two subsections with increasing water depth is owing to progressive increase in sedimentation rate with increasing water depth, which is the key factor in determining the thickness of each diagenetic subsection of cores from HGY. It would be better that lake sediments for palaeomagnetic investigations collected at a water depth shallower than the depth of its thermocline.

Microscale Biosignatures and Abiotic Mineral Authigenesis in Little Hot Creek, California

PubMed Central

Kraus, Emily A.; Beeler, Scott R.; Mors, R. Agustin; Floyd, James G.; Stamps, Blake W.; Nunn, Heather S.; Stevenson, Bradley S.; Johnson, Hope A.; Shapiro, Russell S.; Loyd, Sean J.; Spear, John R.; Corsetti, Frank A.

2018-01-01

Hot spring environments can create physical and chemical gradients favorable for unique microbial life. They can also include authigenic mineral precipitates that may preserve signs of biological activity on Earth and possibly other planets. The abiogenic or biogenic origins of such precipitates can be difficult to discern, therefore a better understanding of mineral formation processes is critical for the accurate interpretation of biosignatures from hot springs. Little Hot Creek (LHC) is a hot spring complex located in the Long Valley Caldera, California, that contains mineral precipitates composed of a carbonate base (largely submerged) topped by amorphous silica (largely emergent). The precipitates occur in close association with microbial mats and biofilms. Geological, geochemical, and microbiological data are consistent with mineral formation via degassing and evaporation rather than direct microbial involvement. However, the microfabric of the silica portion is stromatolitic in nature (i.e., wavy and finely laminated), suggesting that abiogenic mineralization has the potential to preserve textural biosignatures. Although geochemical and petrographic evidence suggests the calcite base was precipitated via abiogenic processes, endolithic microbial communities modified the structure of the calcite crystals, producing a textural biosignature. Our results reveal that even when mineral precipitation is largely abiogenic, the potential to preserve biosignatures in hot spring settings is high. The features found in the LHC structures may provide insight into the biogenicity of ancient Earth and extraterrestrial rocks.

Eocene volcanism and the origin of horizon A

USGS Publications Warehouse

Gibson, T.G.; Towe, K.M.

1971-01-01

A series of closely time-equivalent deposits that correlate with seismic reflector horizon A exists along the coast of eastern North America. These sediments of Late-Early to Early-Middle Eocene age contain an authigenic mineral suite indicative of the alteration of volcanic glass. A volcanic origin for these siliceous deposits onshore is consistent with a volcanic origin for the cherts of horizon A offshore.

Authigenic minerals related to carbon and sulfur biogeochemical cycling from deep-sea active methane seeps offshore South-West Africa

NASA Astrophysics Data System (ADS)

Pierre, C.; Blanc-Valleron, M.; Demange, J.; Boudouma, O.; Pape, T.; Himmler, T.; Fekete, N.; Spiess, V.

2011-12-01

The South-West African continental margin is well known for occurrences of active methane-rich fluid seeps that are associated with seafloor pockmarks in a broad range of water depths, from the shelf to the deep basins. High gas flares in the water column, luxurious oases of benthic fauna, gas hydrate accumulations and diagenetic carbonate crusts have been observed at these seeps. During the M76/3a expedition of R/V METEOR (summer 2008) gravity cores recovered abundant authigenic carbonate concretions from five pockmarks of the South-West African margin including previously studied sites (Hydrate Hole, Worm Hole, Regab Pockmark) and two sites (Deep Hole, Baboon Cluster) newly discovered during the cruise. Carbonate concretions were mostly associated to sediments settled by seep-associated benthic macrofauna and bearing shallow gas hydrates. We present new results of the comprehensive analysis of the mineralogy and isotope geochemistry of the diagenetic carbonates sampled in the five pockmarks. The mineralogy of authigenic carbonates is dominated by magnesian calcite and aragonite, associated occasionally with dolomite. The oxygen and carbon isotopic compositions of authigenic carbonates (+2.4 < δ18O % V-PDB < +6.2 ; -61.0 < δ13C % V-PDB < -40.1) indicate that microbial anaerobic oxidation of methane (AOM) was the main process controling carbonate precipitation within sub-seafloor sediments deposited from the glacial-time up to the present. The frequent occurrence of diagenetic gypsum crystals within the sediments demonstrates that bio-irrigation with oxygenated bottom water by the burrowing activity of benthic fauna caused the secondary oxidation of reduced sulfur (hydrogen sulfide and pyrite) that was produced by sulfate reducting bacteria as a by-product of AOM; during the sulfide oxidation process, the released acidity induced the partial dissolution of carbonates. Our results demonstrate also the strong link that existed between the carbon and sulfur cycles in cold seep systems where the anoxic-oxic boundary may move within the sediment due to variations in the strength of the methane flux.

The Atmospheric Supply of Terrestrial Authigenic Phosphate Minerals to Open Marine Sediments

NASA Astrophysics Data System (ADS)

Flaum, J. A.; Jacobson, A. D.; Sageman, B. B.

2007-12-01

Authigenic P-bearing minerals (Pauth), such as carbonate fluorapatite, form within shallow marine sediments as biological processes degrade organic matter and release associated phosphate to the dissolved pool during early diagenesis. Thus, Pauth is commonly used as a proxy for productivity in modern and ancient marine depositional environments. To help refine this proxy and further improve understanding of the marine P cycle, we investigated if dust deposition could supply terrestrially derived Pauth and other P-bearing phases to modern marine sediments. We used the SEDEX sequential extraction procedure to quantify the occurrence of P in ten samples of loess from the Chinese Loess Plateau, a major source of dust to the North Pacific Ocean (NPO). On average, 40% of the total P within Chinese Loess occurs as Pauth, 33% as detrital apatite (Pdet), 17% in organic matter (Porg), and 10% bound to Fe-Al oxides (Pox). Using eolian dust and total P accumulation rates reported for core LL44-GC3 taken from the central NPO, we find that ~86% of the total P accumulation within the central NPO could originate from the atmospheric deposition of Pauth and Pdet. Hence, productivity estimates based upon total P accumulation for this site are likely lower than previously estimated. Our findings suggest that marine productivity studies predicated on the measurement of Pauth need to quantify the fraction of Pauth supplied from terrestrial sources. This may be even more significant along continental margins where rivers can supply sediments with high concentrations of Pauth minerals.

Comparison of authigenic carbonates formation at mud volcanoes and pockmarks in the Portuguese Margin vs. at the Yinazao serpentinite mud volcano in the Marianas forearc

NASA Astrophysics Data System (ADS)

Magalhaes, V. H.; Freitas, M.; Azevedo, M. R.; Pinheiro, L. M.; Salgueiro, E.; Abrantes, F. F. G.

2017-12-01

On the Portuguese passive continental margin, active and past seepage processes form mud volcanoes and pockmarks at the seafloor. Often associated with these structures are extensive methane-derived authigenic carbonates that form from deep-sourced methane-rich fluids that ascend from deep to the upper sedimentary column and often discharge at the seafloor. These carbonates form within the sediments and are either dominated by dolomite and high-Mg calcites, when formed under a restricted seawater circulation environment, anoxic and low sulphate conditions; or by aragonite and calcite when formed close to or at the seafloor in a high sulphate system. The δ13C values (-56.2‰ VPDB) found on the carbonate-cemented material clearly indicates methane as the major carbon source. On the Yinazao serpentinite mud volcano at an active, non-accretionary, convergent margin, sediment samples from IODP Sites U1491 and U1492 (Exp. 366) contain authigenic minerals such as aragonite, calcite, brucite, gypsum among others. Authigenic aragonite occurs predominantly within the top meters of the cores where both oxidation and seawater circulation in the sedimentary column are higher. In this system, initial results indicate that the major carbon source is most probably not methane but seawater related. This work discusses and compares the major carbon sources in both systems: sedimentary mud volcanoes and pockmarks of a passive margin vs. a serpentinite mud volcano of an active, non-accretionary, convergent margin. We acknowledge the support from the PES project - Pockmarks and fluid seepage in the Estremadura Spur: implications for regional geology, biology, and petroleum systems (PTDC/GEOFIQ/5162/2014) financed by the Portuguese Foundation for Science and Technology (FCT).

Rock magnetic and geochemical evidence for authigenic magnetite formation via iron reduction in coal-bearing sediments offshore Shimokita Peninsula, Japan (IODP Site C0020)

NASA Astrophysics Data System (ADS)

Phillips, Stephen C.; Johnson, Joel E.; Clyde, William C.; Setera, Jacob B.; Maxbauer, Daniel P.; Severmann, Silke; Riedinger, Natascha

2017-06-01

Sediments recovered at Integrated Ocean Drilling Program (IODP) Site C0020, in a fore-arc basin offshore Shimokita Peninsula, Japan, include numerous coal beds (0.3-7 m thick) that are associated with a transition from a terrestrial to marine depositional environment. Within the primary coal-bearing unit (˜2 km depth below seafloor) there are sharp increases in magnetic susceptibility in close proximity to the coal beds, superimposed on a background of consistently low magnetic susceptibility throughout the remainder of the recovered stratigraphic sequence. We investigate the source of the magnetic susceptibility variability and characterize the dominant magnetic assemblage throughout the entire cored record, using isothermal remanent magnetization (IRM), thermal demagnetization, anhysteretic remanent magnetization (ARM), iron speciation, and iron isotopes. Magnetic mineral assemblages in all samples are dominated by very low-coercivity minerals with unblocking temperatures between 350 and 580°C that are interpreted to be magnetite. Samples with lower unblocking temperatures (300-400°C), higher ARM, higher-frequency dependence, and isotopically heavy δ56Fe across a range of lithologies in the coal-bearing unit (between 1925 and 1995 mbsf) indicate the presence of fine-grained authigenic magnetite. We suggest that iron-reducing bacteria facilitated the production of fine-grained magnetite within the coal-bearing unit during burial and interaction with pore waters. The coal/peat acted as a source of electron donors during burial, mediated by humic acids, to supply iron-reducing bacteria in the surrounding siliciclastic sediments. These results indicate that coal-bearing sediments may play an important role in iron cycling in subsiding peat environments and if buried deeply through time, within the subsequent deep biosphere.

Geochemistry of phosphatic-shales and associated authigenic minerals of the Miocene Monterey Formation: Implications for paragenetic evolution

NASA Astrophysics Data System (ADS)

Sandoval, A.; Loyd, S. J.

2016-12-01

The Monterey Formation is a petroleum source and reservoir rock in California that was deposited in several basins during the tectonically-active Middle Miocene. The middle carbonaceous marl member of the Monterey Formation contains intervals of phosphatic-shales that are rhythmically cemented by dolomite as layers and concretions. Diagenetic minerals can form as the result of organic matter remineralization facilitated by microbes utilizing oxygen, nitrate, iron (III), sulfate and fermentation products as electron acceptors. Precipitation of phosphate and carbonate minerals tends to occur in suboxic-anoxic sediments, generally experiencing sulfate reduction, where degradation of organic matter yields alkalinity, sulfide and phosphate ions. Here, we present sulfur and carbon geochemical data in order to better characterize the conditions that led to the precipitation of phosphorous-rich minerals (e.g., carbonate-fluorapatite (CFA)) and dolomite that occur in close stratigraphic proximity. These data include concentration of CFA-associated sulfate, carbonate associated sulfate (CAS) and the respective δ°S values. The concentration of inorganic/organic carbon and associated δC values have been determined for CFA, dolomite and the host-shale, in order to further characterize the diagenetic environment of precipitation. These data indicate that authigenesis occurred in pore waters influenced by multiple microbial reactions, including respiration and methanogenesis reactions, and ultimately highlight the complexity of the Monterey diagenetic environment.

Microstructures imply cataclasis and authigenic mineral formation control geomechanical properties of New Zealand's Alpine Fault

NASA Astrophysics Data System (ADS)

Schuck, B.; Janssen, C.; Schleicher, A. M.; Toy, V. G.; Dresen, G.

2018-05-01

The Alpine Fault is capable of generating large (MW > 8) earthquakes and is the main geohazard on South Island, NZ, and late in its 250-291-year seismic cycle. To minimize its hazard potential, it is indispensable to identify and understand the processes influencing the geomechanical behavior and strength-evolution of the fault. High-resolution microstructural, mineralogical and geochemical analyses of the Alpine Fault's core demonstrate wall rock fragmentation, assisted by mineral dissolution, and cementation resulting in the formation of a fine-grained principal slip zone (PSZ). A complex network of anastomosing and mutually cross-cutting calcite veins implies that faulting occurred during episodes of dilation, slip and sealing. Fluid-assisted dilatancy leads to a significant volume increase accommodated by vein formation in the fault core. Undeformed euhedral chlorite crystals and calcite veins that have cut footwall gravels demonstrate that these processes occurred very close to the Earth's surface. Microstructural evidence indicates that cataclastic processes dominate the deformation and we suggest that powder lubrication and grain rolling, particularly influenced by abundant nanoparticles, play a key role in the fault core's velocity-weakening behavior rather than frictional sliding. This is further supported by the absence of smectite, which is reasonable given recently measured geothermal gradients of more than 120 °C km-1 and the impermeable nature of the PSZ, which both limit the growth of this phase and restrict its stability to shallow depths. Our observations demonstrate that high-temperature fluids can influence authigenic mineral formation and thus control the fault's geomechanical behavior and the cyclic evolution of its strength.

Trace element and isotope geochemistry of Cretaceous-Tertiary boundary sediments: identification of extra-terrestrial and volcanic components

NASA Technical Reports Server (NTRS)

Margolis, S. V.; Doehne, E. F.

1988-01-01

Trace element and stable isotope analyses were performed on a series of sediment samples crossing the Cretaceous-Tertiary (K-T) boundary from critical sections at Aumaya and Sopelano, Spain. The aim is to possibly distinguish extraterrestrial vs. volcanic or authigenic concentration of platinum group and other elements in K-T boundary transitional sediments. These sediments also have been shown to contain evidence for step-wise extinction of several groups of marine invertebrates, associated with negative oxygen and carbon isotope excursions occurring during the last million years of the Cretaceous. These isotope excursions have been interpreted to indicate major changes in ocean thermal regime, circulation, and ecosystems that may be related to multiple events during latest Cretaceous time. Results to date on the petrographic and geochemical analyses of the Late Cretaceous and Early Paleocene sediments indicate that diagenesis has obviously affected the trace element geochemistry and stable isotope compositions at Zumaya. Mineralogical and geochemical analysis of K-T boundary sediments at Zumaya suggest that a substantial fraction of anomalous trace elements in the boundary marl are present in specific mineral phases. Platinum and nickel grains perhaps represent the first direct evidence of siderophile-rich minerals at the boundary. The presence of spinels and Ni-rich particles as inclusions in aluminosilicate spherules from Zumaya suggests an original, non-diagenetic origin for the spherules. Similar spherules from southern Spain (Caravaca), show a strong marine authigenic overprint. This research represents a new approach in trying to directly identify the sedimentary mineral components that are responsible for the trace element concentrations associated with the K-T boundary.

Features structure of iron-bearing strata’s of the Bakchar deposit, Western Siberia

NASA Astrophysics Data System (ADS)

Asochakova, E. M.

2017-12-01

The ore-bearing strata’s of Bakchar deposit have complicated structural-textural heterogeneity and variable mineral composition. This deposit is one of the most promising areas of localization of sedimentary iron ore. The ore-bearing strata’s are composed mainly of sandstones (sometimes with ferruginous pebbles, less often conglomerates), siltstones and clays. The ironstones are classified according to their lithology and geochemistry into three types: goethite-hydrogoethitic oolitic, glauconite-chloritic and transitional (intermediate) type iron ores. The mineral composition includes many different minerals: terrigenous, authigenic and clayey. Ironstones are characterized by elevated concentrations of many rare and valuable metals present in them as trace elements, additionally alloying (Mn, V, Cr, Ti, Zr, Mo, etc.) and harmful impurities (S, As, Cu, Pb, Zn, P). There are prerequisites for the influence of numerous factors, such as prolonged transgression of the sea, swamping of paleo-river deltas, the appearance of a tectonic fracture zone associated with active bottom tectonics and unloading of catagenetic waters, regression and natural ore enrichment due to the re-washing of slightly-iron rocks. These factors are reflected in the structure of the ore-bearing strata in which rhythmic cycles of ore sedimentation with successive changes in them are distinguished by an association of different mineral composition.

Lower Carboniferous Siderites: A Product of Bottom Seeps and Bacterial Metanogenesis (Subpolar Urals)

NASA Astrophysics Data System (ADS)

Antoshkina, A. I.; Ryabinkina, N. N.

2018-02-01

Complex modern micro- and spectroscopic methods for study of siderite concretions in the Lower Carboniferous terrigenous strata on the Kozhym River (Subpolar Urals) have shown that its formation was caused by destruction of clay minerals due to the activity of bacterial communities. The abundance of these bacteria was caused by gas-fluid seeps and bacterial methanogenesis processes in bottom deposits. In basins with normal marine fauna, this led to local desalination, hydrogen sulfide contamination, mass collapse of primary organisms, and the development of element-specific bacteria. The occurrence of these bacteria caused the formation of specific authigenic mineralization in the concretion of sideritic bacteriolites: the framboidal pyrite, sphalerite, galenite, barite, sulfoselenides, and tellurides.

Mineral precipitation and dissolution at two slag-disposal sites in northwestern Indiana, USA

USGS Publications Warehouse

Bayless, E.R.; Schulz, M.S.

2003-01-01

Slag is a ubiquitous byproduct of the iron- and steel-refining industries. In northwestern Indiana and northeastern Illinois, slag has been deposited over more than 52 km2 of land surface. Despite the widespread use of slag for fill and construction purposes, little is known about its chemical effects on the environment. Two slagdisposal sites were examined in northwestern Indiana where slag was deposited over the native glacial deposits. At a third site, where slag was not present, background conditions were defined. Samples were collected from cores and drill cuttings and described with scanning electron microscopy and electron microprobe analysis. Ground-water samples were collected and used to assess thermodynamic equilibria between authigenic minerals and existing conditions. Differences in the mineralogy at background and slag-affected sites were apparent. Calcite, dolomite, gypsum, iron oxides, and clay minerals were abundant in native sediments immediately beneath the slag. Mineral features indicated that these minerals precipitated rapidly from slag drainage and co-precipitated minor amounts of non-calcium metals and trace elements. Quartz fragments immediately beneath the slag showed extensive pitting that was not apparent in sediments from the background site, indicating chemical weathering by the hyperalkaline slag drainage. The environmental impacts of slag-related mineral precipitation include disruption of natural ground-water flow patterns and bed-sediment armoring in adjacent surface-water systems. Dissolution of native quartz by the hyperalkaline drainage may cause instability in structures situated over slag fill or in roadways comprised of slag aggregates.

The Phosphates of Pleistocene-Holocene Sediments of the Eastern Gallery of Denisova Cave

NASA Astrophysics Data System (ADS)

Shunkov, M. V.; Kulik, N. A.; Kozlikin, M. B.; Sokol, E. V.; Miroshnichenko, L. V.; Ulianov, V. A.

2018-01-01

Authigenic phosphate mineralization was first studied on the territory of Russia on the basis of the Holocene and Pleistocene deposits of Denisova Cave. The formation of phosphates in the eastern gallery is related to biodegradation of the horizons of guano of insectivorous bats, which inhabited the cave in the absence man. The results confirmed the archaeological record of the Holocene and the upper part of Pleistocene sequences of the eastern gallery.

Constraining the Texture and Composition of Pore-Filling Cements at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Siebach, K. L.; Grotzinger, J. P.; McLennan, S. M.; Hurowitz, J. A.; Ming, D. W.; Vaniman, D. T.; Rampe, E. B.; Blaney, D. L.; Kah, L. C.

2015-01-01

The Mars Science Laboratory (MSL) rover Curiosity has encountered a wide variety of sedimentary rocks deposited in fluvio-lacuestrine sequences at the base of Gale Crater. The presence of sedimentary rocks requires that initial sediments underwent diagenesis and were lithified. Lithification involves sediment compaction, cementation, and re-crystallization (or authigenic) processes. Analysis of the texture and composition of the cement can reveal the environmental conditions when the cements were deposited, enabling better understanding of early environments present within Gale Crater. The first step in lithification is sediment compaction. The Gale crater sediments do not show evidence for extensive compaction prior to cementation; the Sheepbed mudstone in Yellowknife Bay (YKB) has preserved void spaces ("hollow nodules"), indicating that sediments were cemented around the hollow prior to compaction, and conglomerates show imbrication, indicating minimal grain reorganization prior to lithification. Furthermore, assuming the maximum burial depth of these sediments is equivalent to the depth of Gale Crater, the sediments were never under more than 1 kb of pressure, and assuming a 15 C/km thermal gradient in the late Noachian, the maximum temperature of diagenesis would have been approximately 75 C. This is comparable to shallow burial diagenetic conditions on Earth. The cementation and recrystallization components of lithification are closely intertwined. Cementation describes the precipitation of minerals between grains from pore fluids, and recrystallization (or authigenesis) is when the original sedimentary mineral grains are altered into secondary minerals. The presence of authigenic smectites and magnetite in the YKB formation suggests that some recrystallization has taken place. The relatively high percentage of XRD-amorphous material (25-40%) detected by CheMin suggests that this recrystallization may be limited in scope, and therefore may not contribute significantly to the cementing material. However, relatively persistent amorphous components could exist in the Martian environment (e.g. amorphous MgSO4), so recrystallization, including loss of crystallinity, cannot yet be excluded as a method of cementation. In order to describe the rock cementation, both the rock textures and their composition must be considered. Here, we attempt to summarize the current understanding of the textural and compositional aspects of the cement across the rocks analyzed by Curiosity to this point.

Magnetite Authigenesis and the Ancient Martian Atmosphere

NASA Astrophysics Data System (ADS)

Tosca, N. J.; Ahmed, I. A.; Ashpitel, A.; Hurowitz, J.

2017-12-01

Although the Curiosity rover has documented lacustrine sediments at Gale Crater, how liquid water became physically stable is unknown. The early Martian atmosphere is thought to have been dominated by CO2 [1], but the Curiosity rover has provided only ambiguous detections of carbonate minerals at abundances significantly less than 1 wt. % [2, 3], and climate models indicate that in the absence of additional components, multi-bar CO2 atmospheres could not have maintained surface temperatures above freezing. To constrain the composition of the ancient Martian atmosphere, we experimentally investigated the nucleation and growth kinetics of authigenic Fe(II)-minerals in Gale Crater mudstones. Experiments show that as basaltic waters experience pH increases above 8.0, a series of anoxic mineral transformations generates magnetite in days. Electrochemical and dissolved gas analyses show that one stage of this process, the conversion of Fe(OH)2 to green rust, generates H2(g). Experiments including dissolved CO2 show that, despite magnetite formation, Fe(II)-carbonate does not nucleate until significant supersaturation is reached, at PCO2 levels far above previous estimates. Our experimental observations imply that Gale Crater lakes could have been in contact with a CO2-rich atmosphere. In addition, geochemical calculations show that groundwater infiltration into lacustrine sediments triggered magnetite and H2(g) generation at Gale Crater (instead of Fe(II)-carbonate cementation). Groundwater infiltration is consistent with data from the Sheepbed member mudstones, and deep-water mudstones of the Murray formation, both of which contain abundant authigenic magnetite [2, 4]. Low temperature H2 production may have provided a globally significant but transient feedback for stabilizing liquid water on early Mars. Data collected to date by the Curiosity rover are consistent with both estimated timescales and climatic shifts associated with H2-induced warming. Low temperature H2 production also implies that a wide range of biologically relevant chemical reactions may have been operative on the early Martian surface. [1] J. Pollack, et al. (1987) Icarus 71, 203-24. [2] D. Vaniman et al., (2014) Science 343, 8. [3] D. Ming, et al., (2014) Science 343, 1245267. [4] J. Hurowitz, et al. (2017) Science 356, 922.

Characterizing phosphorus speciation of Chesapeake Bay sediments using chemical extraction, 31P NMR, and X-ray absorption fine structure spectroscopy.

PubMed

Li, Wei; Joshi, Sunendra R; Hou, Guangjin; Burdige, David J; Sparks, Donald L; Jaisi, Deb P

2015-01-06

Nutrient contamination has been one of the lingering issues in the Chesapeake Bay because the bay restoration is complicated by temporally and seasonally variable nutrient sources and complex interaction between imported and regenerated nutrients. Differential reactivity of sedimentary phosphorus (P) pools in response to imposed biogeochemical conditions can record past sediment history and therefore a detailed sediment P speciation may provide information on P cycling particularly the stability of a P pool and the formation of one pool at the expense of another. This study examined sediment P speciation from three sites in the Chesapeake Bay: (i) a North site in the upstream bay, (ii) a middle site in the central bay dominated by seasonally hypoxic bottom water, and (iii) a South site at the bay-ocean boundary using a combination of sequential P extraction (SEDEX) and spectroscopic techniques, including (31)P NMR, P X-ray absorption near edge structure spectroscopy (XANES), and Fe extended X-ray absorption fine structure (EXAFS). Results from sequential P extraction reveal that sediment P is composed predominantly of ferric Fe-bound P and authigenic P, which was further confirmed by solid-state (31)P NMR, XANES, and EXAFS analyses. Additionally, solution (31)P NMR results show that the sediments from the middle site contain high amounts of organic P such as monoesters and diesters, compared to the other two sites, but that these compounds rapidly decrease with sediment depth indicating remineralized P could have precipitated as authigenic P. Fe EXAFS enabled to identify the changes in Fe mineral composition and P sinks in response to imposed redox condition in the middle site sediments. The presence of lepidocrocite, vermiculite, and Fe smectite in the middle site sediments indicates that some ferric Fe minerals can still be present along with pyrite and vivianite, and that ferric Fe-bound P pool can be a major P sink in anoxic sediments. These results provide improved insights into sediment P dynamics, particularly the rapid remineralization of organic P and the stability of Fe minerals and the ferric Fe-bound P pool in anoxic sediments in the Chesapeake Bay.

Inter-layered clay stacks in Jurassic shales

NASA Technical Reports Server (NTRS)

Pye, K.; Krinsley, D. H.

1983-01-01

Scanning electron microscopy in the backscattered electron mode is used together with energy-dispersive X-ray microanalysis to show that Lower Jurassic shales from the North Sea Basin contain large numbers of clay mineral stacks up to 150 microns in size. Polished shale sections are examined to determine the size, shape orientation, textural relationships, and internal compositional variations of the clays. Preliminary evidence that the clay stacks are authigenic, and may have formed at shallow burial depths during early diagenesis, is presented.

Diagenetic contrast of sandstones in hydrocarbon prospective Mesozoic rift basins (Ethiopia, UK, USA)

NASA Astrophysics Data System (ADS)

Wolela, A.

2014-11-01

Diagenetic studied in hydrocarbon-prospective Mesozoic rift basins were carried out in the Blue Nile Basin (Ethiopia), Ulster Basin (United Kingdom) and Hartford Basin (United States of America). Alluvial fan, single and amalgamated multistorey meandering and braided river, deep and shallow perennial lake, shallow ephemeral lake, aeolian and playa mud-flat are the prominent depositional environments. The studied sandstones exhibit red bed diagenesis. Source area geology, depositional environments, pore-water chemistry and circulation, tectonic setting and burial history controlled the diagenetic evolution. The diagenetic minerals include: facies-related minerals (calcrete and dolocrete), grain-coating clay minerals and/or hematite, quartz and feldspar overgrowths, carbonate cements, hematite, kaolinite, illite-smectite, smectite, illite, chlorite, actinolite, laumontite, pyrite and apatite. Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment and burial history of the basins. Variation in infiltrated clays, carbonate cements and clay minerals observed in the studied sandstones. The alluvial fan and fluviatile sandstones are dominated by kaolinite, illite calcite and ferroan calcite, whereas the playa and lacustrine sandstones are dominated by illite-smectite, smectite-chlorite, smectite, chlorite, dolomite ferroan dolomite and ankerite. Albite, pyrite and apatite are predominantly precipitated in lacustrine sandstones. Basaltic eruption in the basins modified mechanically infiltrated clays to authigenic clays. In all the studied sandstones, secondary porosity predominates over primary porosity. The oil emplacement inhabited clay authigenesis and generation of secondary porosity, whereas authigenesis of quartz, pyrite and apatite continued after oil emplacement.

Dolomitization of felsic volcaniclastic rocks in continental strata: A study from the Lower Cretaceous of the A'nan Sag in Er'lian Basin, China

NASA Astrophysics Data System (ADS)

Zhu, Shifa; Yue, Hui; Zhu, Xiaomin; Sun, Shuyang; Wei, Wei; Liu, Xin; Jia, Ye

2017-05-01

Dolomitization of fine-grained volcaniclastic rocks is common in the Lower Cretaceous of the A'nan Sag in the Er'lian Basin of China. Analysis of core samples shows that the organic-rich volcaniclastic rocks are mainly composed of reworked felsic volcanic materials and terrigenous clay minerals. The fine-grained volcaniclastic rocks can be divided into four types: volcaniclastic rocks without carbonatization, volcaniclastic rocks with ferroan dolomites, dolomitized and calcified volcaniclastic rocks, and calcified volcaniclastic rocks. The parent rocks of the volcaniclastic rocks have high silicon and potassium contents and low iron and magnesium contents, and are probably felsic magma of the calc-alkaline series. The average values of δ13CPDB of the carbonate minerals are about 3.13‰; the average values of δ18OPDB are about - 16.74‰. The compositions of C and O isotopes are probably influenced by bacterial methanogenesis. Iron, magnesium, and calcium are probably derived from illitization of terrigenous smectite. A model for dolomitization of felsic volcaniclastic rock is proposed, including three stages: 1) mixed sedimentation and bacterial methanogenesis (< 75 °C); 2) transformation of clay minerals (> 70 °C) and dolomitization (75 to 97 °C); and 3) dissolution. Late dissolution of authigenic carbonate minerals, creating abundant secondary pores, is significant for hydrocarbon accumulation.

Quantification of the "global" authigenic carbonate δ13C value and implications for carbon cycling

NASA Astrophysics Data System (ADS)

Loyd, S. J.

2017-12-01

Relationships among early Earth ocean chemistry, atmospheric chemistry and the evolution/radiation of life have been inferred from carbon isotope compositions (δ13C) of marine carbonates. Under steady-state conditions, the isotope compositions of marine carbonates reflect both the amount and δ13C of carbon entering and leaving the oceans. Recently the traditional "two-output" (marine carbonate and organic matter) mass-balance equation has been modified to include a third, authigenic carbonate output term. However, the formation mechanisms of authigenic carbonates remain poorly understood, particularly from a global prospective. The utility of the new mass-balance approach will be limited until authigenic carbonates are better characterized (e.g., through δ13C analyses). Authigenic carbonates form largely as a result of 1) the respiratory degradation of organic matter (e.g., sulfate reduction), 2) the oxidation of methane and 3) the production of methane. These major reaction pathways can produce authigenic carbonates with highly variable δ13C compositions (δ13Cac). Spatiotemporal variation in the extent and prevalence of different pathways therefore exert a first order control on "global" δ13Cac. Here, values are compiled from new and existing data sets and a modern, global δ13Cac is calculated. When calculated as an average of all data or an averaged mean of individual sites, this value is very similar to normal marine sedimentary organic matter. This finding suggests that marine sediments behave largely as closed systems in the context of organic matter degradation and carbonate authigenesis. In addition, the lack of significant difference between authigenic and organic δ13C implies that these two mass-balance output terms can be considered collectively in more recent time intervals. It may be appropriate to separate these two terms when characterizing more ancient settings when redox characteristics promoted more reducing organic matter degradation pathways.

Origin and diagenesis of clay minerals in relation to sandstone paragenesis: An example in eolian dune reservoirs and associated rocks, Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming

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

Pollastro, R.M.; Schenk, C.J.

Eolian dune sandstones are the principal reservoir rocks in the Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming. These sandstones formed as shorelines retreated and dunes migrated across siliciclastic sabkhas. Sandstones are mainly quartzarenites; on average, clay minerals constitute about 5 wt.% the whole rock. Although present in minor amounts, clay minerals play an important role in the diagenetic evolution of these sandstones. Allogenic clay minerals are present in shaly rock fragments and laminae. Early infiltration of clays into porous sabkha sands commonly form characteristic menisei or bridges between framework grains or, when more extensive, form coatingsmore » or rims on grain surfaces. Authigenic clays include nearly pure smectite, mixed-layer illite/smectite (I/S), and late diagenetic illite and corrensite; these clay minerals are present as pore-lining cements. In addition to the deposition and neoformation of clay minerals throughout sandstone paragenesis, the conversion of smectite to illite occurred as temperatures increased with progressive burial. A temperature of 103C is calculated at a present depth of 3,200 m using a geothermal gradient of 30C/km and a mean annual surface temperature of 7C. After correction for uplift and erosion (250 m), the maximum calculated temperature for the conversion of all random I/S to ordered I/S is 100C. This calculated temperature is in excellent agreement with temperatures of 100-110C implied from I/S geothermometry.« less

Diagenetic history of the Surma Group sandstones (Miocene) in the Surma Basin, Bangladesh

NASA Astrophysics Data System (ADS)

Rahman, M. Julleh Jalalur; McCann, Tom

2012-02-01

This study examines the various diagenetic controls of the Miocene Surma Group sandstones encountered in petroleum exploration wells from the Surma Basin, which is situated in the northeastern part of the Bengal Basin, Bangladesh. The principal diagenetic minerals/cements in the Surma Group sandstones are Fe-carbonates (with Fe-calcite dominating), quartz overgrowths and authigenic clays (predominantly chlorite, illite-smectite and minor kaolin). The isotopic composition of the carbonate cement revealed a narrow range of δ 18O values (-10.3‰ to -12.4‰) and a wide range of δ 13C value (+1.4‰ to -23.1‰). The δ 13C VPDB and δ 18O VPDB values of the carbonate cements reveal that carbon was most likely derived from the thermal maturation of organic matter during burial, as well as from the dissolution of isolated carbonate clasts and precipitated from mixed marine-meteoric pore waters. The relationship between the intergranular volume (IGV) versus cement volume indicates that compaction played a more significant role than cementation in destroying the primary porosity. However, cementation also played a major role in drastically reducing porosity and permeability in sandstones with poikilotopic, pore-filling blocky cements formed in early to intermediate and deep burial areas. In addition to Fe-carbonate cements, various clay minerals including illite-smectite and chlorite occur as pore-filling and pore-lining authigenic phases. Significant secondary porosity has been generated at depths from 2500 m to 4728 m. The best reservoir rocks found at depths of 2500-3300 m are well sorted, relatively coarse grained; more loosely packed and better rounded sandstones having good porosities (20-30%) and high permeabilities (12-6000 mD). These good quality reservoir rocks are, however, not uniformly distributed and can be considered to be compartmentalized as a result of interbedding with sandstone layers of low to moderate porosities, low permeabilities owing to poor sorting and extensive compaction and cementation.

Investigating Rare Earth Element Systematics in the Marcellus Shale

NASA Astrophysics Data System (ADS)

Yang, J.; Torres, M. E.; Kim, J. H.; Verba, C.

2014-12-01

The lanthanide series of elements (the 14 rare earth elements, REEs) have similar chemical properties and respond to different chemical and physical processes in the natural environment by developing unique patterns in their concentration distribution when normalized to an average shale REE content. The interpretation of the REE content in a gas-bearing black shale deposited in a marine environment must therefore take into account the paleoredox conditions of deposition as well as any diagenetic remobilization and authigenic mineral formation. We analyzed 15 samples from a core of the Marcellus Shale (Whipkey ST1, Greene Co., PA) for REEs, TOC, gas-producing potential, trace metal content, and carbon isotopes of organic matter in order to determine the REE systematics of a black shale currently undergoing shale gas development. We also conducted a series of sequential leaching experiments targeting the phosphatic fractions in order to evaluate the dominant host phase of REEs in a black shale. Knowledge of the REE system in the Marcellus black shale will allow us to evaluate potential REE release and behavior during hydraulic fracturing operations. Total REE content of the Whipkey ST1 core ranged from 65-185 μg/g and we observed three distinct REE shale-normalized patterns: middle-REE enrichment (MREE/MREE* ~2) with heavy-REE enrichment (HREE/LREE ~1.8-2), flat patterns, and a linear enrichment towards the heavy-REE (HREE/LREE ~1.5-2.5). The MREE enrichment occurred in the high carbonate samples of the Stafford Member overlying the Marcellus Formation. The HREE enrichment occurred in the Union Springs Member of the Marcellus Formation, corresponding to a high TOC peak (TOC ~4.6-6.2 wt%) and moderate carbonate levels (CaCO3 ~4-53 wt%). Results from the sequential leaching experiments suggest that the dominant host of the REEs is the organic fraction of the black shale and that the detrital and authigenic fractions have characteristic MREE enrichments. We present our conclusions on the impact of depositional setting and diagenetic remobilization and authigenic mineral formation on the REE system in the Marcellus Shale.

Diagenetic Mineralogy at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Vaniman, David; Blake, David; Bristow, Thomas F.; Chipera, Steve; Gellert, Ralf; Ming, Douglas; Morris, Richard; Rampe, E. B.; Rapin, William

2015-01-01

Three years into exploration of sediments in Gale crater on Mars, the Mars Science Laboratory rover Curiosity has provided data on several modes and episodes of diagenetic mineral formation. Curiosity determines mineralogy principally by X-ray diffraction (XRD), but with supporting data from thermal-release profiles of volatiles, bulk chemistry, passive spectroscopy, and laser-induced breakdown spectra of targeted spots. Mudstones at Yellowknife Bay, within the landing ellipse, contain approximately 20% phyllosilicate that we interpret as authigenic smectite formed by basalt weathering in relatively dilute water, with associated formation of authigenic magnetite as in experiments by Tosca and Hurowitz [Goldschmidt 2014]. Varied interlayer spacing of the smectite, collapsed at approximately 10 A or expanded at approximately 13.2 A, is evidence of localized diagenesis that may include partial intercalation of metal-hydroxyl groups in the approximately 13.2 A material. Subsequent sampling of stratigraphically higher Windjana sandstone revealed sediment with multiple sources, possible concentration of detrital magnetite, and minimal abundance of diagenetic minerals. Most recent sampling has been of lower strata at Mount Sharp, where diagenesis is widespread and varied. Here XRD shows that hematite first becomes abundant and products of diagenesis include jarosite and cristobalite. In addition, bulk chemistry identifies Mg-sulfate concretions that may be amorphous or crystalline. Throughout Curiosity's traverse, later diagenetic fractures (and rarer nodules) of mm to dm scale are common and surprisingly constant and simple in Ca-sulfate composition. Other sulfates (Mg,Fe) appear to be absent in this later diagenetic cycle, and circumneutral solutions are indicated. Equally surprising is the rarity of gypsum and common occurrence of bassanite and anhydrite. Bassanite, rare on Earth, plays a major role at this location on Mars. Dehydration of gypsum to bassanite in the dry atmosphere of Mars has been proposed but considered unlikely based on lab studies of dehydration kinetics in powdered samples. Dehydration is even less likely for bulk vein samples, as lab data show dehydration rates one to two orders of magnitude slower in bulk samples than in powders. On Mars, exposure ages of 100 Ma or more may be a significant factor in dehydration of hydrous phases.

Advances in authigenic silicate geochemistry: Evidence for Precessional Control of Pleistocene Lake Salinity at Olduvai Gorge, Tanzania

NASA Astrophysics Data System (ADS)

Deocampo, D.; Simpson, A. J.; Cuadros, J.; Beverly, E.; Ashley, G. M.; Delaney, J. S.; Longstaffe, F. J.

2017-12-01

Magnesium enrichment of authigenic clays is an indicator of elevated salinity in hydrologically closed lake basins. Studies at Olduvai Gorge over the last four decades have shown that chemically-precipitated clay minerals form a substantial portion of the sedimentary succession, in some intervals even dominating the sediment. Outcrops of lacustrine mud in two localities near the depocenter were examined using a new geochronological framework based on Ar/Ar dating of volcaniclastic sanidine (Deino, 2012). Olduvai's clay mineralogy is dominated by 2:1 clays, including smectite, illite, and interstratified illite-smectite. Previous work has shown that clay alteration includes octahedral Mg-enrichment, Fe-reduction, K-fixation, and low-temperature illitization. Here we show that long term environmental conditions in Paleolake Olduvai indicated by sub-micron clay geochemistry were generally saline and alkaline between 1.78 and 1.92 Ma, but 6 episodes of freshened paleolake water are indicated by intervals of lower Mg content. Five of these freshening episodes occurred at peak climatic precession. The sub-micron clay geochemistry agrees with infrared spectroscopy and whole-rock geochemical compositions, and the same stratigraphic variation is observed at both localities, separated laterally by 330m. Preliminary analyses show that the <0.1µm clay mineral δ18Oclay suggest a δ18OH2O range of about -4 to +3‰ (SMOW) through this stratigraphic interval. No significant correlation is found with elemental composition, but lighter isotopic values are associated stratigraphically with geochemically defined freshening events. This suggests that isotopic and elemental equilibrium may not be reached at the same time, or that diagenetic events may have differentially altered the isotopic record. The environmental changes recorded in the Olduvai sediments occurred at a time when zonal Walker circulation increasingly affected global climate, new stone technologies emerged, and the genus Homo spread beyond Africa. Unraveling the details of mineralogical records such as those at Olduvai will be important in characterizing details of continental Quaternary environmental change, particularly in stratigraphic intervals where biotic proxies are unavailable.

The Peru Margin as an Authigenic Mineral Factory, Evidence From Surface Sediments and Oceanography

NASA Astrophysics Data System (ADS)

Dean, W. E.; Arthur, M. A.

2004-12-01

Characteristics of sediments deposited within an intense oxygen-minimum zone (OMZ) on the Peru continental margin were mapped by submersible, and studied in samples collected in deck-deployed box cores and submersible push cores on two east-west transects over water depths of 75 to 1000 m at 12 degrees and 13.5 degrees S. On the basis of sampling of the top 1-2 cm of available cores, three main belts of sediments were identified in each transect with increasing depth: 1) organic-carbon (OC)-rich muds; 2) authigenic phosphatic mineral crusts; and 3) glaucony facies. These facies patterns are primarily controlled by redox conditions and strength of bottom currents. OC-rich sediments on the 12-degree transect were mainly located on the outer shelf and upper slope (150-350 m), but they occurred in much shallower water (ca. 100 m) on the 13.5-degree transect. The organic matter is almost entirely marine, resulting from very high primary productivity. The OC concentrations are highest (up to 18%) in sediments where intermediate water masses with low dissolved oxygen concentrations (less than 5 micromoles/kg) impinge on the slope at water depths between 75 and 450 m. The region between 175 and 350 m depth is characterized by bedforms stabilized by bacterial mats, extensive authigenic mineral crusts, and (or) thick organic flocs. Currents as high as 30 cm/sec were measured over that depth interval. Current-resuspension of surficial organic matter, activity of organisms, and transport to and from more oxygenated zones contribute to greater oxidation and poorer preservation of organic matter than occur under oxygen-deficient conditions. Phosphate-rich sediments occurred at depths of about 300 to 550 m on both transects. Nodular crusts cemented by carbonate-fluorapatite (CFA; phosphorite) or dolomite form within the OMZ. The crusts start by cementation of sediment near the sediment-water interface forming stiff but friable phosphatizes claystone "protocrusts". The protocrusts evolve into dense, dark phosphorite crusts, cemented breccias, and pavements. The degree of phosphatization and thickness of the phosphorite crusts depends on rates of sediment supply and strength and frequency of currents that re-expose crusts on the seafloor. Glaucony-rich surficial sediments, relatively undiluted by other components, mainly were found in deeper water on the 13.5 degree transect (750 m to at least 1067 m). These sediments consist almost entirely of sand-size glaucony pellets (aggregates of clay minerals with pelletoid shapes). These widespread glaucony sands possibly formed in situ and were then concentrated and reworked by strong currents that winnowed away the fine-grained matrix. Overall, sedimentation rate must be slow in order for the glaucony minerals to remain in contact with seawater, which is the source of cations during growth. The close association of glaucony and phosphorite indicates that there is a delicate balance between slightly oxidizing and slightly reducing conditions at the base of the OMZ- slightly reducing to mobilize iron and phosphate, and slightly oxidizing to form glaucony.

Deep sea authigenic clays as a sink for seawater Mg through the Cenozoic

NASA Astrophysics Data System (ADS)

Dunlea, A. G.; Murray, R. W.; Ramos, D. S.; Higgins, J. A.

2016-12-01

The most enigmatic sink of many elements in the global ocean is the formation of authigenic aluminosilicates. Pelagic clays cover 40% of the seafloor and "reverse weathering" type reactions within this lithology have the potential to be a large sink of seawater Mg and affect carbon cycling in the ocean. We use pelagic clays from Integrated Ocean Drilling Program Expedition 329 Site U1366 in the South Pacific Gyre to track authigenic aluminosilicates with two complementary methods: (1) Mg isotopic analyses, and (2) bulk sediment geochemistry with provenance modeling. Mg isotopic analyses of the bulk, unleached clay samples reveal isotopic values significantly heavier than average continental crust (δ26Mg = -0.1 to -0.3%o) indicating significant authigenic uptake. The bulk sediment geochemistry (i.e., major, trace, rare earth element concentrations) and multivariate statistical models of provenance determine the mass fraction of six different sediment sources that mixed to create the sediments: Fe/Mn-oxyhydroxides, apatite, excess Si, dust, and two altered volcanic ashes. A significant correlation between the mass fraction of one of the specific altered ash end-member and the δ26Mg signature allows us to characterize and track the abundance of the authigenic aluminosilicate component downcore. Trends in the provenance models suggest that the elements that compose the authigenic aluminosilicates may originate from volcanic ash, biogenic Si, and/or hydrothermal plume deposits. We examine variations in the spatial and temporal contributions of each of these sources and assess how these variations may have affected the amount of Mg authigenically consumed by deep sea authigenic clays through the Cenozoic. If the authigenic aluminosilicates are created by "reverse weathering" reactions, their formation also has important implications for carbon cycling in the global ocean.

Micro- and Nanostructures of SAFOD Core Samples - First Results

NASA Astrophysics Data System (ADS)

Janssen, C.; Wirth, R.; Rybacki, E.; Naumann, R.; Kemnitz, H.; Wenk, H.; Dresen, G. H.

2009-12-01

Microstructures and chemical composition of ultra-cataclastic rocks from the San Andreas Fault drill hole (SAFOD) were examined using TEM, SEM and XRD analyses. The ultra-cataclasites are mainly composed of quartz, clay minerals (illite/smectite, chlorite), feldspar (plagioclase) and calcite with grain sizes between 200 nm and 500 μm. In particular we found: (1) amorphous materials, identified by transmission electron microscopy. Chemical analyses suggest that all amorphous material was formed by comminution (crush-origin) of fragments rather than by melting (melt-origin) and that the observed amorphous phases may act as hydrodynamic lubricating layers that reduce friction in the San Andreas Fault. (2) Pressure solution seams and localized precipitation of hydrous mixed-layered clay minerals suggest intensive dissolution-precipitation processes. These may lead to a thin film covering slip surfaces. (3) Authigenic clay minerals forming a flocculated fabric. (4) The fine-grained (< 1μm) gouge matrix contains clasts (feldspar, quartz) and is frequently cut by fault-related veins. The veins are filled with calcite or quartz. Observed micorstructures in the fine-grained matrix suggest comminution and sliding of the nanoscale grains. Open pore spaces up to 2.25 μm3 have been formed during and after deformation within the gouge matrix. These were possibly filled with hydrothermal fluids at elevated pore fluid pressure preventing closure. (5) Detrital quartz and feldspar grains are partly dissolved and replaced by authigenic illite-smectite (I-S) mixed-layer clay minerals. TEM imaging of these grains reveal that initial alteration processes started within pores and small fissures of grains. The crystallographic-preferred orientation of illite and I/S grains is rather weak with a maximum m.r.d. (multiples of random orientation) of 2.3. (6) Some older fault-related vein-calcites show evidence for intense intracrystalline plasticity (deformation twins and dislocation creep). Dislocation densities in calcite grains indicate a local maximum stress of about 40 MPa. The younger fault-related vein-calcite generation with elongated to fibrous habit suggests slow opening by aseismic slip. These crystals are not fractured or twinned (or only less); indicating that healing processes (cementation) outlasted deformation.

Opposing authigenic controls on the isotopic signature of dissolved iron in hydrothermal plumes

NASA Astrophysics Data System (ADS)

Lough, A. J. M.; Klar, J. K.; Homoky, W. B.; Comer-Warner, S. A.; Milton, J. A.; Connelly, D. P.; James, R. H.; Mills, R. A.

2017-04-01

Iron is a scarce but essential micronutrient in the oceans that limits primary productivity in many regions of the surface ocean. The mechanisms and rates of Fe supply to the ocean interior are still poorly understood and quantified. Iron isotope ratios of different Fe pools can potentially be used to trace sources and sinks of the global Fe biogeochemical cycle if these boundary fluxes have distinct signatures. Seafloor hydrothermal vents emit metal rich fluids from mid-ocean ridges into the deep ocean. Iron isotope ratios have the potential to be used to trace the input of hydrothermal dissolved iron to the oceans if the local controls on the fractionation of Fe isotopes during plume dispersal in the deep ocean are understood. In this study we assess the behaviour of Fe isotopes in a Southern Ocean hydrothermal plume using a sampling program of Total Dissolvable Fe (TDFe), and dissolved Fe (dFe). We demonstrate that δ56Fe values of dFe (δ56dFe) within the hydrothermal plume change dramatically during early plume dispersal, ranging from -2.39 ± 0.05‰ to -0.13 ± 0.06‰ (2 SD). The isotopic composition of TDFe (δ56TDFe) was consistently heavier than dFe values, ranging from -0.31 ± 0.03‰ to 0.78 ± 0.05‰, consistent with Fe oxyhydroxide precipitation as the plume samples age. The dFe present in the hydrothermal plume includes stabilised dFe species with potential to be transported to the deep ocean. We estimate that stable dFe exported from the plume will have a δ56Fe of -0.28 ± 0.17‰. Further, we show that the proportion of authigenic iron-sulfide and iron-oxyhydroxide minerals precipitating in the buoyant plume exert opposing controls on the resultant isotope composition of dissolved Fe passed into the neutrally buoyant plume. We show that such controls yield variable dissolved Fe isotope signatures under the authigenic conditions reported from modern vent sites elsewhere, and so ought to be considered during iron isotope reconstructions of past hydrothermalism from ocean sediment records.

Chemical composition and geologic history of saline waters in Aux Vases and Cypress Formations, Illinois Basin

USGS Publications Warehouse

Demir, I.; Seyler, B.

1999-01-01

Seventy-six samples of formation waters were collected from oil wells producing from the Aux Vases or Cypress Formations in the Illinois Basin. Forty core samples of the reservoir rocks were also collected from the two formations. Analyses of the samples indicated that the total dissolved solids content (TDS) of the waters ranged from 43,300 to 151,400 mg/L, far exceeding the 35,400 mg/mL of TDS found in typical seawater. Cl-Br relations suggested that high salinities in the Aux Vases and Cypress formation waters resulted from the evaporation of original seawater and subsequent mixing of the evaporated seawater with concentrated halite solutions. Mixing with the halite solutions increased Na and Cl concentrations and diluted the concentration of other ions in the formation waters. The elemental concentrations were influenced further by diagenetic reactions with silicate and carbonate minerals. Diagenetic signatures revealed by fluid chemistry and rock mineralogy delineated the water-rock interactions that took place in the Aux Vases and Cypress sandstones. Dissolution of K-feldspar released K into the solution, leading to the formation of authigenic illite and mixed-layered illite/smectite. Some Mg was removed from the solution by the formation of authigenic chlorite and dolomite. Dolomitization, calcite recrystallization, and contribution from clay minerals raised Sr levels significantly in the formation waters. The trend of increasing TDS of the saline formation waters with depth can be explained with density stratification. But, it is difficult to explain the combination of the increasing TDS and increasing Ca/Na ratio with depth without invoking the controversial 'ion filtration' mechanism.

Experimental alteration of artificial and natural impact melt rock from the Chesapeake Bay impact structure

USGS Publications Warehouse

Declercq, J.; Dypvik, H.; Aagaard, Per; Jahren, J.; Ferrell, R.E.; Horton, J. Wright

2009-01-01

The alteration or transformation of impact melt rock to clay minerals, particularly smectite, has been recognized in several impact structures (e.g., Ries, Chicxulub, Mj??lnir). We studied the experimental alteration of two natural impact melt rocks from suevite clasts that were recovered from drill cores into the Chesapeake Bay impact structure and two synthetic glasses. These experiments were conducted at hydrothermal temperature (265 ??C) in order to reproduce conditions found in meltbearing deposits in the first thousand years after deposition. The experimental results were compared to geochemical modeling (PHREEQC) of the same alteration and to original mineral assemblages in the natural melt rock samples. In the alteration experiments, clay minerals formed on the surfaces of the melt particles and as fine-grained suspended material. Authigenic expanding clay minerals (saponite and Ca-smectite) and vermiculite/chlorite (clinochlore) were identified in addition to analcime. Ferripyrophyllite was formed in three of four experiments. Comparable minerals were predicted in the PHREEQC modeling. A comparison between the phases formed in our experiments and those in the cores suggests that the natural alteration occurred under hydrothermal conditions similar to those reproduced in the experiment. ?? 2009 The Geological Society of America.

Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

NASA Astrophysics Data System (ADS)

Audry, S.; Pokrovsky, O. S.; Shirokova, L. S.; Kirpotin, S. N.; Dupré, B.

2011-11-01

This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m-2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions was suggested. This shift was likely promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

NASA Astrophysics Data System (ADS)

Audry, S.; Pokrovsky, O. S.; Shirokova, L. S.; Kirpotin, S. N.; Dupré, B.

2011-08-01

This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m-2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways was evidenced from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions. This shift was promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

Age of Sulfate Methane Transition Zone Determined by Modelling Barium Sulfate Growth

NASA Astrophysics Data System (ADS)

Lin, S.; Wang, W. C.; Lien, K. L.; Liu, C. C.; Fan, L. F.

2017-12-01

Methane seep to the sediment/water interface could initiate anaerobic methane oxidation (AOM) with subsequent build up of chemosynthetic community, carbonate, pyrite and a number of other authigenic mineral formation. Determination the duration, sequence and time of methane seeps are keys to understand how methane seep to the environment and degree of alteration to the vicinity area. However, limited method existed in defining time of methane seep since there are some known problems involving typical dating methods, i.e. old carbon on C14 of fossil test or authigenic carbonate, thorium from surrounding matrix on U/Th authigenic carbonate dating. In this study, we have employed barium determination method (Dickens, 2001) to model timing of methane seep at two locations in the South China Sea. Our objective is to compare timing of the barium accumulation near the sulfate methane transition zone (SMTZ) on these two different locations and to seek if a similar mechanism driving the methane seep at two locations far apart. Dissolved barium, total sediment barium and aluminum were measured as well as pore water sulfate, and sediment pyrite concentrations. Time for the barium sulfate accumulation is calculated by: T = C/F, C= ∫ I x p x (1-Ø) Our results show that SMTZ is stabilized at each site for a duration of about 4000-5000 years. AOM process have been active at both sites at about the same time. In conjunction, pyrite also accumulated at a depth near the SMTZ as a result of methane oxidation. This result show that AOM could stay at the SMTZ for a relatively long period of time, on a scale of thousands of years.

Effects of seasonal anoxia on the distribution of phosphorus fractions in the surface sediments of southeastern Arabian Sea shelf

NASA Astrophysics Data System (ADS)

Sudheesh, V.; Movitha, M.; Hatha, A. A. Mohamed; Renjith, K. R.; Resmi, P.; Rahiman, Mujeeb; Nair, S. M.

2017-11-01

The seasonal upwelling along the southeastern Arabian Sea (SEAS) brings cold, nutrient-rich low oxygen subsurface water to the continental shelf. The subsurface oxygen deficiency due to upwelling is severe in some years, the intensity of which could profoundly influence the nutrient cycling along the SEAS. Herein, we studied the effect of seasonal anoxia on fractionation of phosphorus during the peak upwelling period of August 2013. Abundance of five fractions of phosphorus (P), namely exchangeable or loosely sorbed P (Pads), iron-bound P (PFe), authigenic P (Paut), detrital apatite plus other inorganic P (Pdet) and organic P (Porg), in surface sediments of SEAS shelf has been studied using a sequential extraction procedure (SEDEX) to examine their distributions and sources. Total P (TP) concentrations ranged from 209 to 1081 μg g-1 with an average of 508 ± 256 μg g-1. Among the five P fractions, the authigenic P was the dominant species, representing about 60% of TP. The relative abundance of P fractions was in the order: Paut>Pdet>Porg>PFe> Pads. Multivariate analyses revealed that the P fractions were primarily associated with the organic constituents and fine sediments. The hypoxic bottom condition associated with summer monsoon upwelling significantly reduced the concentrations of PFe, Pads and Porg in the surface sediments. The enhanced release of organic bound and iron oxides bound P under low oxygen condition was evident from the enhanced C/P and N/P ratios and lower C/N ratio in the sediments. The intense biomineralization of organic matter and reduction of Fe-Mn oxides due to the periodic anoxia resulted in the transformations of their associated P fractions and enhanced accumulation as authigenic calcium phosphate mineral.

Beneath it all: bedrock geology of the Catskill Mountains and implications of its weathering.

PubMed

Ver Straeten, Charles A

2013-09-01

The Devonian-age bedrock of the Catskill Mountains has been the focus of many studies. This paper reviews the character and composition of the rocks of the Catskills, and examines weathering (rock decay) processes and their implications in the Catskills. Rocks of the Catskills and closest foothills consist of siliciclastic rocks (sandstones, mudrocks, conglomerates) with minimal, locally dispersed carbonate rocks. The former are dominated by quartz, metamorphic and sedimentary rock fragments, and clay minerals. Other minor sediment components include cements, authigenic and heavy minerals, and fossil organic matter. Physical, chemical, and biological weathering of the Catskill bedrock since uplift of the Appalachian region, combined with glaciation, have dissected a plateau of nearly horizontally layered rocks into a series of ridges, valleys, and peaks. The varied weathering processes, in conjunction with many factors (natural and anthropogenic), fragment the rocks, forming sediment and releasing various elements and compounds. These may have positive, neutral, or negative implications for the region's soils, waters, ecology, and human usage. A new generation of studies and analyses of the Catskill bedrock is needed to help answer a broad set of questions and problems across various fields of interest. © 2013 New York Academy of Sciences.

Raman spectroscopic and microthermometric studies of authigenic quartz (the Pepper Mts., Central Poland) as an indicator of fluids circulation

NASA Astrophysics Data System (ADS)

Naglik, Beata; Toboła, Tomasz; Natkaniec-Nowak, Lucyna; Luptáková, Jarmila; Milovská, Stanislava

2017-02-01

Differently colored authigenic quartz crystals were found as the druses compound within mudstone heteroliths from the Pepper Mts. Shale Formation (Cambrian unit of the Holy Cross Mts., Central Poland). The genesis of this mineral was established on the basis of fluid inclusion study. Raman microspectroscopy was the key instrumental technique to identify the nature of the compounds trapped in the fluid inclusions. Methane (2917 cm- 1) or water vapor (broad band 2500-3000 cm- 1) occur within two-phased primary inclusion assemblages, while nitrogen (2329 cm- 1) associated with methane and trace amount of carbon dioxide (1285, 1388 cm- 1) occur within secondary fluid inclusion assemblage. Temperatures of homogenization of primary fluid inclusions was obtained on the basis of heating experiments and ranged from 171° to 266 °C. These values are much higher than expected for the diagenetic system without metamorphic changes what may imply hydrothermal origin of quartz crystals. The source of fluids is uncertain as in the Holy Cross Mts. there was no volcanic activity to the end of Late Devonian. However, fluids originated in metamorphic basin could use deep faults as the migration paths.

Landed XRD/XRF analysis of prime targets in the search for past or present Martian life.

PubMed

Vaniman, D; Bish, D; Blake, D; Elliott, S T; Sarrazin, P; Collins, S A; Chipera, S

1998-12-25

Mars landers seeking evidence for past or present life will be guided by information from orbital mapping and from previous surface exploration. Several target options have been proposed, including sites that may harbor extant life and sites most likely to preserve evidence of past life These sites have specific mineralogic characteristics. Extant life might be gathered around the sinters and associated mineral deposits of rare active fumaroles, or held within brine pockets and inclusions in a few evaporite-mineral deposits. Possibilities for fossilization include deltaic and lake-bottom sediments of once-flooded craters, sinters formed by ancient hot-spring deposits, and the carbonate deposits associated with some evaporite systems. However, the highly varied mineralogy of fossil occurrences on Earth leads to the inference that Mars, an equally complex planet, could host a broad variety of potential fossilizing deposits. The abundance of volcanic systems on Mars and evidence for close associations between volcanism and water release suggest possibilities of organism entrapment and mineralization in volcaniclastic deposits, as found in some instances on Earth. Thus the targets being considered for exploration include a wide variety of unique deposits that would be characterized by silica or various nonsilicate minerals. Beyond these "special" deposits and in the most general case, an ability to distinguish mineralized from uncemented volcanic detritus may be the key to success in finding possible fossil-bearing authigenic mineralogies. A prototype miniaturized X ray diffraction/X ray fluorescence (XRD/XRF) instrument has been evaluated with silica, carbonate, and sulfate minerals and with a basalt, to examine the capabilities of this tool in mineralogic and petrologic exploration for exobiological goals. This instrument. CHEMIN (chemical and mineralogical analyzer), is based on an innovative low-power X ray tube, transmission geometry, and CCD collection and discrimination of diffracted and fluoresced X rays. The ability to accumulate and integrate the entire circumference of each complete Debye diffraction ring compensates for poor powder preparations, as might be produced by robotic sampling systems. With CHEMIN, a wide range of minerals can be uniquely identified. Using Rietveld analysis of the XRD results, mineral quantification is also possible. Expanded capabilities in phase analysis and constrained data solutions using quantitative XRD and XRF are within reach.

Deglacial variability of Antarctic Intermediate Water penetration into the North Atlantic from authigenic neodymium isotope ratios

NASA Astrophysics Data System (ADS)

Xie, Ruifang C.; Marcantonio, Franco; Schmidt, Matthew W.

2012-09-01

Understanding intermediate water circulation across the last deglacial is critical in assessing the role of oceanic heat transport associated with Atlantic Meridional Overturning Circulation variability across abrupt climate events. However, the links between intermediate water circulation and abrupt climate events such as the Younger Dryas (YD) and Heinrich Event 1 (H1) are still poorly constrained. Here, we reconstruct changes in Antarctic Intermediate Water (AAIW) circulation in the subtropical North Atlantic over the past 25 kyr by measuring authigenic neodymium isotope ratios in sediments from two sites in the Florida Straits. Our authigenic Nd isotope records suggest that there was little to no penetration of AAIW into the subtropical North Atlantic during the YD and H1. Variations in the northward penetration of AAIW into the Florida Straits documented in our authigenic Nd isotope record are synchronous with multiple climatic archives, including the Greenland ice core δ18O record, the Cariaco Basin atmosphere Δ14C reconstruction, the Bermuda Rise sedimentary Pa/Th record, and nutrient and stable isotope data from the tropical North Atlantic. The synchroneity of our Nd records with multiple climatic archives suggests a tight connection between AAIW variability and high-latitude North Atlantic climate change.

Orbital evidence for clay and acidic sulfate assemblages on Mars based on mineralogical analogs from Rio Tinto, Spain

NASA Astrophysics Data System (ADS)

Kaplan, Hannah H.; Milliken, Ralph E.; Fernández-Remolar, David; Amils, Ricardo; Robertson, Kevin; Knoll, Andrew H.

2016-09-01

Outcrops of hydrated minerals are widespread across the surface of Mars, with clay minerals and sulfates being commonly identified phases. Orbitally-based reflectance spectra are often used to classify these hydrated components in terms of a single mineralogy, although most surfaces likely contain multiple minerals that have the potential to record local geochemical conditions and processes. Reflectance spectra for previously identified deposits in Ius and Melas Chasma within the Valles Marineris, Mars, exhibit an enigmatic feature with two distinct absorptions between 2.2 and 2.3 μm. This spectral 'doublet' feature is proposed to result from a mixture of hydrated minerals, although the identity of the minerals has remained ambiguous. Here we demonstrate that similar spectral doublet features are observed in airborne, field, and laboratory reflectance spectra of rock and sediment samples from Rio Tinto, Spain. Combined visible-near infrared reflectance spectra and X-ray diffraction measurements of these samples reveal that the doublet feature arises from a mixture of Al-phyllosilicate (illite or muscovite) and jarosite. Analyses of orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) shows that the martian spectral equivalents are also consistent with mixtures of Al-phyllosilicates and jarosite, where the Al-phyllosilicate may also include kaolinite and/or halloysite. A case study for a region within Ius Chasma demonstrates that the relative proportions of the Al-phyllosilicate(s) and jarosite vary within one stratigraphic unit as well as between stratigraphic units. The former observation suggests that the jarosite may be a diagenetic (authigenic) product and thus indicative of local pH and redox conditions, whereas the latter observation may be consistent with variations in sediment flux and/or fluid chemistry during sediment deposition.

The Missing Silica Sink: Revisiting the Marine Sedimentary Si Cycle Using Cosmogenic 32Si

NASA Astrophysics Data System (ADS)

Rahman, S.; Aller, R. C.; Cochran, J. K.

2017-10-01

Burial of biogenic silica (bSitotal) in high sedimentation rate continental margins remains highly uncertain. Cosmogenic 32Si (t1/2 140 years) can be used to trace the fates of bSitotal postdeposition, including as opal (bSiopal) and diagenetically altered opal (bSialtered), the latter dominantly authigenic clay (bSiclay). To determine the magnitude and form of bSitotal storage in coastal sediments, conventional operational leaches targeting bSiopal and bSialtered (including bSiclay) were modified for large-scale samples necessary for measurement of 32Si. The 32Si activity was used to estimate total biogenic silica burial (bSitotal = bSiopal + bSialtered) in several depositional settings: Gulf of Papua, Gulf of Mexico, Long Island Sound, and in the previously studied Amazon-Guianas deltaic system. In subtropical and temperate regions, 32Si was detected in both traditional biogenic silica leaches (bSiopal) and residual authigenic clays. Traditional bSiopal and modified operational leaches designed to target the most reactive authigenic silicates ( bSialtered) consistently underestimate authigenic clay formation (bSiclay) and thus the magnitude of bSitotal burial in temperate coastal zones and subtropical deltas by 2-4-fold. In tropical deltas, 32Si activities in the residual fraction after removal of bSiopal demonstrate rapid and almost complete alteration of initial bSiopal to new forms, most likely bSiclay. Globally, 4.5-4.9 Tmol/yr Si may be trapped in marine nearshore deposits as rapidly formed clay (bSiclay), 100% of the "missing silica sink" in the marine silica budget.

Microbe-Mineral Interactions Along Biogeochemical Gradients in Bahamian Stromatolites: Key to Lithification and Preservation

NASA Astrophysics Data System (ADS)

Andres, M. S.; Sumner, D. Y.; Visscher, P. T.; Swart, P. K.; Reid, R. P.

2005-12-01

Understanding on how modern stromatolites form and lithify is critical to properly interpreting the origins of ancient stromatolites and the early evolution of life. Lithification in Bahamian stromatolites is tied to specific, 20-60-micron thick horizons characterized by laterally continuous sheets of microcrystalline carbonate (aragonite). Microbial processes associated with these horizons are 1) photosynthetic production by cyanobacteria and 2) heterotrophic respiration by bacteria as well as the production of extrapolymeric substances (EPS). The aim of this study is to better understand the coupling of microstructure and microbial processes. The competing influences of photosynthetic CO2 uptake, sulfate reduction, and degradation of Ca-binding EPS influence both carbonate saturation states and the isotopic composition of dissolved inorganic carbon (DIC). In Bahamian stromatolites, photosynthesis and sulfate reduction are associated with specific microbial mat types creating distinctive chemical gradients that can be preserved in authigenic carbonate. Aragonite that precipitated within stromatolites is > 1 per mill depleted in 13C relative to aragonite precipitated in equilibrium with local seawater. These data suggest that more aragonite precipitates when and where respiration, rather than photosynthesis, influences local DIC, which is consistent with sulfate reduction promoting carbonate precipitation and calcium release during decay of exopolymeric substances. Biogeochemical gradients vary on a temporal and spatial scale as indicated by in-situ pH measurements across a the living mat. Highest pH correlates to maximum photosynthesis signal in the early afternoon while the lowest pH to that of maximum respiration just before sunrise. Corresponding carbon isotope analysis of authigenic carbonate precipitate will determine when microscale biological activity is captured in the mineral phase and potentially preserved.

Mixed biogenic and hydrothermal quartz in Permian lacustrine shale of Santanghu Basin, NW China: implications for penecontemporaneous transformation of silica minerals

NASA Astrophysics Data System (ADS)

Jiao, Xin; Liu, Yiqun; Yang, Wan; Zhou, Dingwu; Wang, Shuangshuang; Jin, Mengqi; Sun, Bin; Fan, Tingting

2018-01-01

The cycling of various isomorphs of authigenic silica minerals is a complex and long-term process. A special type of composite quartz (Qc) grains in tuffaceous shale of Permian Lucaogou Formation in the sediment-starved volcanically and hydrothermally active intracontinental lacustrine Santanghu rift basin (NW China) is studied in detail to demonstrate such processes. Samples from one well in the central basin were subject to petrographic, elemental chemical, and fluid inclusion analyses. About 200 Qc-bearing laminae are 0.1-2 mm and mainly 1 mm thick and intercalated within tuffaceous shale laminae. The Qc grains occur as framework grains and are dispersed in igneous feldspar-dominated matrix, suggesting episodic accumulation. The Qc grains are bedding-parallel, uniform in size (100 s µm), elongate, and radial in crystal pattern, suggesting a biogenic origin. Qc grains are composed of a core of anhedral microcrystalline quartz and an outer part of subhedral mega-quartz grains, whose edges are composed of small euhedral quartz crystals, indicating multiple episodic processes of recrystallization and overgrowth. Abundance of Al and Ti in quartz crystals and estimated temperature from fluid inclusions in Qc grains indicate that processes are related to hydrothermal fluids. Finally, the Qc grains are interpreted as original silica precipitation in microorganism (algae?) cysts, which were reworked by bottom currents and altered by hydrothermal fluids to recrystalize and overgrow during penecontemporaneous shallow burial. It is postulated that episodic volcanic and hydrothermal activities had changed lake water chemistry, temperature, and nutrient supply, resulting in variations in microorganic productivities and silica cycling. The transformation of authigenic silica from amorphous to well crystallized had occurred in a short time span during shallow burial.

Oligocene lacustrine tuff facies, Abu Treifeya, Cairo-Suez Road, Egypt

NASA Astrophysics Data System (ADS)

Abdel-Motelib, Ali; Kabesh, Mona; El Manawi, Abdel Hamid; Said, Amir

2015-02-01

Field investigations in the Abu Treifeya area, Cairo-Suez District, revealed the presence of Oligocene lacustrine volcaniclastic deposits of lacustrine sequences associated with an Oligocene rift regime. The present study represents a new record of lacustrine zeolite deposits associated with saponite clay minerals contained within reworked clastic vitric tuffs. The different lithofacies associations of these clastic sequences are identified and described: volcaniclastic sedimentary facies represent episodic volcaniclastic reworking, redistribution and redeposition in a lacustrine environment and these deposits are subdivided into proximal and medial facies. Zeolite and smectite minerals are mainly found as authigenic crystals formed in vugs or crusts due to the reaction of volcanic glasses with saline-alkaline water or as alteration products of feldspars. The presence of abundant smectite (saponite) may be attributed to a warm climate, with alternating humid and dry conditions characterised by the existence of kaolinite. Reddish iron-rich paleosols record periods of non-deposition intercalated with the volcaniclastic tuff sequence.

Applicability of anaerobic nitrate-dependent Fe(II) oxidation to microbial enhanced oil recovery (MEOR).

PubMed

Zhu, Hongbo; Carlson, Han K; Coates, John D

2013-08-06

Microbial processes that produce solid-phase minerals could be judiciously applied to modify rock porosity with subsequent alteration and improvement of floodwater sweep in petroleum reservoirs. However, there has been little investigation of the application of this to enhanced oil recovery (EOR). Here, we investigate a unique approach of altering reservoir petrology through the biogenesis of authigenic rock minerals. This process is mediated by anaerobic chemolithotrophic nitrate-dependent Fe(II)-oxidizing microorganisms that precipitate iron minerals from the metabolism of soluble ferrous iron (Fe(2+)) coupled to the reduction of nitrate. This mineral biogenesis can result in pore restriction and reduced pore throat diameter. Advantageously and unlike biomass plugs, these biominerals are not susceptible to pressure or thermal degradation. Furthermore, they do not require continual substrate addition for maintenance. Our studies demonstrate that the biogenesis of insoluble iron minerals in packed-bed columns results in effective hydrology alteration and homogenization of heterogeneous flowpaths upon stimulated microbial Fe(2+) biooxidation. We also demonstrate almost 100% improvement in oil recovery from hydrocarbon-saturated packed-bed columns as a result of this metabolism. These studies represent a novel departure from traditional microbial EOR approaches and indicate the potential for nitrate-dependent Fe(2+) biooxidation to improve volumetric sweep efficiency and enhance both the quality and quantity of oil recovered.

Methane-derived authigenic carbonates along the North Anatolian fault system in the Sea of Marmara (Turkey)

NASA Astrophysics Data System (ADS)

Crémière, Antoine; Pierre, Catherine; Blanc-Valleron, Marie-Madeleine; Zitter, Tiphaine; Çağatay, M. Namik; Henry, Pierre

2012-08-01

The Marnaut cruise (May-June 2007) investigated the submerged part of the North Anatolian fault system, an active tectonic area in the Sea of Marmara. Already known and new fluid venting sites along the fault system were visited by submersible diving. Cold seeps present a considerable diversity of geochemical background associated with occurrences of authigenic carbonate crusts outcropping at the seafloor. Buried carbonate concretions were also recovered by coring within the sediments of the Tekirdağ Basin and of the Western-High ridge that separates the Tekirdağ and Central Basins. Interestingly, numerous of these early diagenetic carbonates were found within the transitional sediments from lacustrine to marine environment deposited after the late glacial maximum. The authigenic carbonates are mainly composed of aragonite, Mg-calcite and minor amounts of dolomite, and are often associated with pyrite and barite. The carbon isotopic compositions of carbonates present a wide range of values from -50.6‰ to +14.2‰ V-PDB indicating different diagenetic settings and complex mixtures of dissolved inorganic carbon from different sources. The low δ13C values of the seafloor crusts and of most buried concretions indicate that the carbon source was a mixture of microbial and thermogenic methane and possibly other hydrocarbons that were oxidized by anaerobic microbial processes. The positive δ13C values of a few buried concretions from the Western-High ridge reflect the mineralization of heavy CO2, which is thought to represent the residual by-product of oil biodegradation in a subsurface petroleum reservoir that migrated up with brines. Most of the oxygen isotopic compositions of seafloor carbonates are close to the isotopic equilibrium with the present-day bottom water conditions but a few values as low as -1.9‰ V-PDB indicate precipitation from brackish waters. In buried carbonate concretions, δ18O values as high as +4.9‰ V-PDB reflect the contribution of water enriched in 18O. The results support the hypothesis that after the late glacial/Holocene transition, precipitation of authigenic carbonates, now buried within the sediments of the Western-High mound structures, was promoted due to enhancement of anaerobic oxidation of methane, possibly from massive methane release by gas hydrate dissociation, and by sulfate rich Mediterranean water incursion.

New insights to the formation of modern dolomite in a terrestrial low-temperature environment

NASA Astrophysics Data System (ADS)

Zünterl, Andrea; Baldermann, Andre; Boch, Ronny; Dietzel, Martin

2017-04-01

Although dolomite [CaMg(CO3)2] is a rock-forming mineral in ancient carbonate platforms, its occurrence in modern-marine carbonate-depositing settings and in particular in terrestrial, low-temperature environments is scarce - an enigma that is referred to as the "dolomite problem". At present, it is generally accepted that microbial activity, bacterially-mediated sulfate reduction, high aqueous Mg/Ca ratios and anoxic conditions favour the nucleation and crystal growth of dolomite; albeit the precise reaction paths causing the formation of dolomite at low temperatures remain questionable. Here, we present a novel study about the environmental controls and reaction mechanisms leading to the formation of authigenic Mg-Ca carbonates in (active) fault zones of the Erzberg (Styria, Austria) - Europe's largest iron ore opencast mine. Our petrographic and mineralogical results revealed the presence of ˜2-20 cm thick laminated successions of embedded needle-shaped, radiating aragonite and blocky low-Mg calcite (a repetitive sequence also-called "erzbergite") and subsequently deposited (Ca-rich) non-stoichiometric dolomite, which is clogging former voids and unconsolidated sediment in the heavily deteriorated fault zone. First U-Th age determinations of the respective aragonite layers indicate its formation at ˜19,000-13,000 years BP, also suggesting a "young" age of the sedimentary dolomite. Based on the combination of X-ray diffraction and electron microprobe analyses we identified two types of matrix-replacing dolomite: type 1 dolomite is nearly stoichiometric (˜51 mol% CaCO3) and shows a high degree of cation ordering (0.4-0.6), whereas type 2 dolomite is characterized by Ca-excess (˜55 mol% CaCO3) and a low degree of ordering (<0.3). Both types of dolomite grow on the extent of matrix minerals, such as detrital low-Mg calcite, ankerite, siderite, quartz, goethite, chlorite and illitic clay minerals, implying a low-temperature origin of the Ca-excess dolomite and its formation through replacement of CaCO3 precursor phases at high aqueous Mg/Ca ratios of the mineralizing (meteroric) fluids. Further analysis of the δ18O, δ13C, δ26Mg and clumped isotopic (Δ47) signatures of the authigenic Ca-Mg carbonates will give new insights to the physicochemical conditions and reaction paths causing dolomitization in such an exotic, terrestrial environment.

Early Jurassic clay authigenesis in the Central Appalachian Valley and Ridge province; infiltration of surface-derived fluids during Pangean rifting

NASA Astrophysics Data System (ADS)

Lynch, E. A.; van der Pluijm, B.; Vennemann, T. W.

2017-12-01

The eastern margin of North America has a protracted and intricate tectonic history. The terminal collision of Gondwana and Laurentia in the late Paleozoic formed the Appalachian mountain belt, a trans-continental orogen that persisted for almost 100 million years until Mesozoic break-up of the supercontinent Pangea. A host of studies have targeted the evolution and migration of fluids through Appalachian crust in an effort to understand how fluid promotes mass and heat redistribution, and mediates crustal deformation, particularly during the assembly of Pangea. Folded clay units from the Central Appalachian Valley and Ridge province were sampled for stable and radiogenic isotope analysis. Separation of samples into different grain-size fractions characterizes detrital (host) and authigenic (neomineralized) clays. Stable H-isotope compositions reveal a systematic pattern with varying proportions of illite polytypes—the finer, younger fraction is D-depleted compared to the coarser, primarily detrital fraction. For each individual location, the H-isotopic composition of the fluid from which the authigenic population was grown is calculated. δDVSMOW of these fluids has a range from -77 to -52 ± 2 ‰, consistent with a surface-derived fluid source. The notably negative values for several samples indicates a meteoric composition of moderate to high elevation origin, suggesting that they are not connate waters, but instead preserve infiltration of fluids due to fracture-induced permeability. Key to this interpretation is 40Ar/39Ar-dating of a subset of these samples that reveals a post-orogenic age for authigenic clay mineralization in the Early Jurassic ( 180 Ma). These ages are evidence that surface fluid infiltration was unrelated to the Appalachian orogeny, but coeval with (upper) crustal extension from the initial break-up of Pangea and the emplacement of the Central Atlantic Magmatic Province.

Mineralogy of Sediments on a Cold and Icy Early Mars

NASA Astrophysics Data System (ADS)

Rampe, E. B.; Horgan, B. H. N.; Smith, R.; Scudder, N.; Rutledge, A. M.; Bamber, E.; Morris, R. V.

2017-12-01

The water-related minerals discovered in ancient martian terrains suggest liquid water was abundant on the surface and/or near subsurface during Mars' early history. The debate remains, however, whether these minerals are indicative of a warm and wet or cold and icy climate. To characterize mineral assemblages of cold and icy mafic terrains, we analyzed pro- and supraglacial rocks and sediments from the Collier and Diller glacial valleys in Three Sisters, Oregon. We identified primary and secondary phases using X-ray diffraction (XRD), scanning and transmission electron microscopies with energy dispersive spectroscopy (SEM, TEM, EDS), and visible/short-wave-infrared (VSWIR) and thermal-infrared (TIR) spectroscopies. Samples from both glacial valleys are dominated by primary igneous minerals (i.e., plagioclase and pyroxene). Sediments in the Collier glacial valley contain minor to trace amounts of phyllosilicates and zeolites, but these phases are likely detrital and sourced from hydrothermally altered units on North Sister. We find that the authigenic phases in cold and icy mafic terrains are poorly crystalline and/or amorphous. TEM-EDS analyses of the <2 um size fraction of glacial flour shows the presence of many different nanophase materials, including iron oxides, devitrified volcanic glass, and Fe-Si-Al (e.g., proto-clay) phases. A variety of primary and secondary amorphous materials (e.g., volcanic glass, leached glass, allophane) have been suggested from orbital IR data from Mars, and the CheMin XRD on the Curiosity rover has identified X-ray amorphous materials in all rocks and soils measured to date. The compositions of the Gale Crater amorphous components cannot be explained by primary volcanic glass alone and likely include secondary silicates, iron oxides, and sulfates. We suggest that the prevalence of amorphous materials on the martian surface and the variety of amorphous components may be a signature of a cold and icy climate on Early Mars.

Authigenic molybdenum formation in marine sediments: A link to pore water sulfide in the Santa Barbara Basin

USGS Publications Warehouse

Zheng, Yen; Anderson, Robert F.; VanGeen, A.; Kuwabara, J.

2000-01-01

Pore water and sediment Mo concentrations were measured in a suite of multicores collected at four sites along the northeastern flank of the Santa Barbara Basin to examine the connection between authigenic Mo formation and pore water sulfide concentration. Only at the deepest site (580 m), where pore water sulfide concentrations rise to >0.1 ??M right below the sediment water interface, was there active authigenic Mo formation. At shallower sites (550,430, and 340 m), where pore water sulfide concentrations were consistently <0.05 ??M, Mo precipitation was not occuring at the time of sampling. A sulfide concentration of ???0.1 ??M appears to be a threshold for the onset of Mo-Fe-S co-precipitation. A second threshold sulfide concentration of ???100 ??M is required for Mo precipitation without Fe, possibly as Mo-S or as particle-bound Mo. Mass budgets for Mo were constructed by combining pore water and sediment results for Mo with analyses of sediment trap material from Santa Barbara Basin as well as sediment accumulation rates derived from 210Pb. The calculations show that most of the authigenic Mo in the sediment at the deepest site is supplied by diffusion from overlying bottom waters. There is, however, a non-lithogenic particulate Mo associated with sinking particles that contributes ???15% to the total authigenic Mo accumulation. Analysis of sediment trap samples and supernant brine solutions indicates the presence of non-lithogenic particulate Mo, a large fraction of which is easily remobilized and, perhaps, associated with Mn-oxides. Our observations show that even with the very high flux of organic carbon reaching the sediment of Santa Barbara Basin, active formation of sedimentary authigenic Mo requires a bottom water oxygen concentration below 3 ??M. However, small but measurable rates of authigenic Mo accumulation were observed at sites where bottom water oxygen ranged between 5 and 23 ??M, indicating that the formation of authigenic Mo occured in the recent past, but not at the time of sampling. Copyright ?? 2000 Elsevier Science Ltd.

Ion-probe U–Pb dating of authigenic and detrital opal from Neogene-Quaternary alluvium

USGS Publications Warehouse

Neymark, Leonid; Paces, James B.

2013-01-01

Knowing depositional ages of alluvial fans is essential for many tectonic, paleoclimatic, and geomorphic studies in arid environments. The use of U–Pb dating on secondary silica to establish the age of Neogene-Quaternary clastic sediments was tested on samples of authigenic and detrital opal and chalcedony from depths of ∼25 to 53 m in boreholes at Midway Valley, Nevada. Dating of authigenic opal present as rinds on rock clasts and in calcite/silica cements establishes minimum ages of alluvium deposition; dating of detrital opal or chalcedony derived from the source volcanic rocks gives the maximum age of sediment deposition.Materials analyzed included 12 samples of authigenic opal, one sample of fracture-coating opal from bedrock, one sample of detrital opal, and two samples of detrital chalcedony. Uranium–lead isotope data were obtained by both thermal ionization mass spectrometry and ion-microprobe. Uranium concentrations ranged from tens to hundreds of μg/g. Relatively large U/Pb allowed calculation of 206Pb/238U ages that ranged from 1.64±0.36 (2σ) to 6.16±0.50 Ma for authigenic opal and from 8.34±0.28 to 11.2±1.3 Ma for detrital opal/chalcedony. Three samples with the most radiogenic Pb isotope compositions also allowed calculation of 207Pb/235U ages, which were concordant with 206Pb/238U ages from the same samples.These results indicate that basin development at Midway Valley was initiated between about 8 and 6 Ma, and that the basin was filled at long-term average deposition rates of less than 1 cm/ka. Because alluvium in Midway Valley was derived from adjacent highlands at Yucca Mountain, the low rates of deposition determined in this study may imply a slow rate of erosion of Yucca Mountain. Volcanic strata underlying the basin are offset by a number of buried faults to a greater degree than the relatively smooth-sloping bedrock/alluvium contact. These geologic relations indicate that movement on most faults ceased prior to erosional planation and burial. Therefore, ages of the authigenic opal from basal alluvium indicate that the last movement on buried faults was older than about 6 Ma.

Geothermal studies in oil field districts of North China

NASA Astrophysics Data System (ADS)

Wang, Ji-An; Wang, Ji-Yang; Yan, Shu-Zhen; Lu, Xiu-Wen

In North China, Tertiary sediments give the main oil-genetic series. The mean value of terrestrial heat flow density has been considered to be 60 - 65 mW/m2, and the geothermal gradient in Tertiary sediments usually ranges from 30 to 40° C/km in the region studied. Supposing that the onset of oil generation lies at about 90° C, the upper limit of the depth of oil-generation is at about 2000 to 2500 m depth. Recent paleogeothermal studies using vitrinite reflectance, clay and authigenic minerals, as well as other methods showed that in Eocene the geothermal gradient has been higher than at present. Some results were obtained and discussed.

Corrosion of copper and authigenic sulfide mineral growth in hydrothermal bentonite experiments

NASA Astrophysics Data System (ADS)

Caporuscio, F. A.; Palaich, S. E. M.; Cheshire, M. C.; Jové Colón, C. F.

2017-03-01

The focus of this experimental work is to characterize interaction of bentonite with possible used-fuel waste container materials. Experiments were performed up to 300 °C at 150-160 bars for five to six weeks. Bentonite was saturated with a 1900 ppm K-Ca-Na-Cl-bearing water with Cu-foils. Copper rapidly degrades into chalcocite (CuS2) and minor covellite (CuS) in the presence of H2S. Chalcocite growth and corrosion pit depths were measured for four different experimental runs yielding corrosion rates between 8.8 and 116 μm/yr depending on duration of experiment, brine composition, and clay type (bentonite vs. Opalinus Clay). Results of this research show that although pit-corrosion is demonstrated on Cu substrates, experiments show that the reactions that ensue, and the formation of minerals that develop, are extraordinarily slow. This supports the use of Cu in nuclide-containment systems as a possible engineered barrier system material.

Corrosion of copper and authigenic sulfide mineral growth in hydrothermal bentonite experiments

DOE PAGES

Caporuscio, F. A.; Palaich, Sarah E. M.; Cheshire, M. C.; ...

2016-12-29

The focus of this experimental paper is to characterize interaction of bentonite with possible used-fuel waste container materials. Experiments were performed up to 300 °C at 150–160 bars for five to six weeks. Bentonite was saturated with a 1900 ppm K-Ca-Na-Cl-bearing water with Cu-foils. Copper rapidly degrades into chalcocite (CuS 2) and minor covellite (CuS) in the presence of H 2S. Chalcocite growth and corrosion pit depths were measured for four different experimental runs yielding corrosion rates between 8.8 and 116 μm/yr depending on duration of experiment, brine composition, and clay type (bentonite vs. Opalinus Clay). Results of this researchmore » show that although pit-corrosion is demonstrated on Cu substrates, experiments show that the reactions that ensue, and the formation of minerals that develop, are extraordinarily slow. Finally, this supports the use of Cu in nuclide-containment systems as a possible engineered barrier system material.« less

Nanomineralogy as a new dimension in understanding elusive geochemical processes in soils: The case of low-solubility-index elements

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

Schindler, Michael; Hochella, Michael F.

2016-05-20

Nanomineralogy is a new dimension in understanding chemical processes in soils. These processes are revealed at the nanoscale within the structures and compositions of phases that heretofore were not even known to exist in the soils in which they are found. The discovery and understanding of soil chemistry in this way is best accessible via a combination of focused ion beam technology (for sample preparation) and high resolution, analytical transmission electron microscopy (for phase identification). We have used this scientific framework and these techniques to decipher past and present chemical processes in a soil in Sudbury, Ontario, Canada that hasmore » been impacted by both smelter contamination (acidification) and subsequent remediation within the past century. In this study, we use these methods to investigate mobilization and sequestration of the relatively immobile elements Al, Ti and Zr. In a micrometer-thick alteration layer on an albite grain, a first generation of clay minerals represents weathering of the underlying mineral prior to the acidification of the soils. Complex assemblages of Ti- and Zr-bearing nanophases occur on the surfaces of Fe-(hydr)oxide crystals and are the result of the dissolution of silicates and oxides and the mobilization of Ti- and Zr-bearing colloids under acidic conditions. These phases include anatase (TiO2), kleberite (Fe3+Ti6O11(OH)5) Ti4O7, baddelyite (ZrO2), a structural analogue to kelyshite (NaZr[Si2O6(OH)]) and authigenic zircon (ZrSiO4). Subsequent remediation of the acidic soils has resulted in the sequestration of Al and in the neoformation of the clay minerals kaolinite, smectite and illite. These complex mineral assemblages form a porous layer that controls the interaction of the underlying mineral with the environment.« less

Spatial and temporal variation of Cenozoic surface elevation in the Great Basin and Sierra Nevada

USGS Publications Warehouse

Horton, T.W.; Sjostrom, D.J.; Abruzzese, M.J.; Poage, M.A.; Waldbauer, J.R.; Hren, M.; Wooden, J.; Chamberlain, C.P.

2004-01-01

The surface uplift of mountain belts caused by tectonism plays an important role in determining the long-term climate evolution of the Earth. However, the general lack of information on the paleotopography of mountain belts limits our ability to identify the links and feedbacks between topography, tectonics, and climate change on geologic time-scales. Here, we present a ??18O and ??D record of authigenic minerals for the northern Great Basin that captures the timing and magnitude of regional surface uplift and subsidence events in the western United States during the Cenozoic. Authigenic calcite, smectite, and chert ??18O values suggest the northern Great Basin region experienced ???2km of surface uplift between the middle Eocene and early Oligocene followed by ???1 to 2km of surface subsidence in the southern Great Basin and/or Sierra Nevada since the middle Miocene. These data when combined with previously published work show that the surface uplift history varied in both space and time. Surface uplift migrated from north to south with high elevations in southern British Columbia and northeastern Washington in the middle Eocene and development of surface uplift in north and central Nevada in the Oligocene. This pattern of north to south surface uplift is similar to the timing of magmatism in the western Cordillera, a result that supports tectonic models linking magamtism with removal of mantle lithosphere and/or a subducting slab.

Lithologic Control on Secondary Clay Mineral Formation in the Valles Caldera, New Mexico

NASA Astrophysics Data System (ADS)

Caylor, E.; Rasmussen, C.; Dhakal, P.

2015-12-01

Understanding the transformation of rock to soil is central to landscape evolution and ecosystem function. The objective of this study was to examine controls on secondary mineral formation in a forested catchment in the Catalina-Jemez CZO. We hypothesized landscape position controls the type of secondary minerals formed in that well-drained hillslopes favor Si-poor secondary phases such as kaolinite, whereas poorly drained portions of the landscape that collect solutes from surrounding areas favor formation of Si-rich secondary phases such as smectite. The study focused on a catchment in Valles Caldera in northern New Mexico where soils are derived from a mix of rhyolitic volcanic material, vegetation includes a mixed conifer forest, and climate is characterized by a mean annual precipitation of ~800 mm yr-1 and mean annual temperature of 4.5°C. Soils were collected at the soil-saprolite boundary from three landscape positions, classified as well drained hillslope, poorly drained convergent area, and poorly drained hill slope. Clay fractions were isolated and analyzed using a combination of quantitative and qualitative x-ray diffraction (XRD) analyses and thermal analysis. Quantitative XRD of random powder mounts indicated the presence of both primary phases such as quartz, and alkali and plagioclase feldspars, and secondary phases that include illite, Fe-oxyhydroxides including both goethite and hematite, kaolinite, and smectite. The clay fractions were dominated by smectite ranging from 36-42%, illite ranging from 21-35%, and kaolinite ranging from 1-8%. Qualitative XRD of oriented mounts confirmed the presence of smectite in all samples, with varying degrees of interlayering and interstratification. In contrast to our hypothesis, results indicated that secondary mineral assemblage was not strongly controlled by landscape position, but rather varied with underlying variation in lithology. The catchment is underlain by a combination of porphorytic rhyolite and hydrothermally altered rhyolitic tuff, with an intrusion of Paleozoic sandstone. Smectite content was generally greater in areas underlain by the tuff and likely represent a combination of both diagenic smectite formed by hydrothermal alteration of volcanic glass and authigenic smectites formed in the soils via chemical weathering.

Interactions between microbial iron reduction and metal geochemistry: effect of redox cycling on transition metal speciation in iron bearing sediments.

PubMed

Cooper, D Craig; Picardal, Flynn F; Coby, Aaron J

2006-03-15

Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respectto Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a -3x increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by approximately 12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest that in situ redox cycling may serve as an effective method for

Identification of remagnetization processes in Paleozoic sedimentary rocks of the northeast Rhenish Massif in Germany by K-Ar dating and REE tracing of authigenic illite and Fe oxides

NASA Astrophysics Data System (ADS)

Zwing, A.; Clauer, N.; Liewig, N.; Bachtadse, V.

2009-06-01

This study combines mineralogical, chemical (rare earth elemental (REE)) and isotopic (K-Ar) data of clay minerals as well as chemical compositions (major and REE) of Fe oxide leachates from remagnetized Palaeozoic sedimentary rocks from NE Rhenish Massif in Germany, for which the causes of remagnetization are not yet clear. The dominant carrier of the syntectonic, pervasive Carboniferous magnetization is magnetite. The Middle Devonian clastic rocks record an illitization event at 348 ± 7 Ma probably connected to a major magmatic event in the Mid-German Crystalline Rise, whereas a second illitization episode at 324 ± 3 Ma is coeval to the northward migrating deformation through the Rhenish Massif, being only detected in Upper Devonian and Lower Carboniferous rocks. The age of that younger illitization is not significantly different from that of the remagnetization, which, however, is not restricted to the upper part of the orogenic belt, but affects also the Middle Devonian strata. The REE patterns of the Fe-enriched leachates support two mineralization episodes with varied oxidation-reduction conditions outlined by varied Eu and Ce anomalies. This is not compatible with a unique, pervasive migration of orogenic fluids on a regional scale to explain the remagnetization in the studied region. While clay diagenesis and remagnetization are time-equivalent in Upper Devonian and Lower Carboniferous rocks, they are not so in Middle Devonian rocks. Transformation of smectite into illite cannot, therefore, account for the growth of associated authigenic magnetite, which must have been triggered by a different process. Since remagnetization and deformation ages are similar, the mechanism could relate to local physical conditions such as pressure solution and changing pore fluid pressure due to tectonic stress as well as to chemical conditions such as changing composition of the pore fluids.

Authigenic carbonate precipitation at the end-Guadalupian (Middle Permian) in China: Implications for the carbon cycle in ancient anoxic oceans

NASA Astrophysics Data System (ADS)

Saitoh, Masafumi; Ueno, Yuichiro; Isozaki, Yukio; Shibuya, Takazo; Yao, Jianxin; Ji, Zhansheng; Shozugawa, Katsumi; Matsuo, Motoyuki; Yoshida, Naohiro

2015-12-01

Carbonate precipitation is a major process in the global carbon cycle. It was recently proposed that authigenic carbonate (carbonate precipitated in situ at the sediment-water interface and/or within the sediment) played a major role in the carbon cycle throughout Earth's history. The carbon isotopic composition of authigenic carbonates in ancient oceans have been assumed to be significantly lower than that of dissolved inorganic carbon (DIC) in seawater, as is observed in the modern oceans. However, the δ13Ccarb values of authigenic carbonates in the past has not been analyzed in detail. Here, we report authigenic carbonates in the uppermost Guadalupian (Middle Permian) rocks at Chaotian, Sichuan, South China. Monocrystalline calcite crystals <20 mm long are common in the black mudstone/chert sequence that was deposited on a relatively deep anoxic slope/basin along the continental margin. Textures of the crystals indicate in situ precipitation on the seafloor and/or within the sediments. The calcite precipitation corresponds stratigraphically with denitrification and sulfate reduction in the anoxic deep-water mass, as indicated by previously reported nitrogen and sulfur isotope records, respectively. Relatively high δ13Ccarb values of the authigenic carbonates (largely -1 ‰) compared with those of organic matter in the rocks (ca. -26 ‰) suggest that the main carbon source of the carbonates was DIC in the water column. The calcite crystals precipitated in an open system with respect to carbonate, possibly near the sediment-water interface rather than deep within the sediments. The δ13Ccarb values of the carbonates were close to the δ13CDIC value of seawater due to mixing of 13C-depleted remineralized organic carbon (that was released into the water column by the water-mass anaerobic respiration) with the large DIC pool in the oceans. Our results imply that δ13Ccarb values of authigenic carbonates in the anoxic oceans might have been systematically different from the values in the oxic oceans in Earth's history, controlled by the depth of the redoxcline in the water column and sediments. If our model is correct, authigenic carbonates with relatively high δ13Ccarb values in the ancient anoxic oceans may have had a less substantial influence on the bulk δ13Ccarb values in geologic records than has been previously suggested.

The Eocene-Oligocene sedimentary record in the Chesapeake Bay impact structure: Implications for climate and sea-level changes on the western Atlantic margin

USGS Publications Warehouse

Schulte, P.; Wade, B.S.; Kontny, A.; ,

2009-01-01

A multidisciplinary investigation of the Eocene-Oligocene transition in the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville core from the Chesapeake Bay impact basin was conducted in order to document environmental changes and sequence stratigraphic setting. Planktonic foraminifera and calcareous nannofossil biostratigraphy indicate that the Eyreville core includes an expanded upper Eocene (Biozones E15 to E16 and NP19/20 to NP21, respectively) and a condensed Oligocene-Miocene (NP24-NN1) sedimentary sequence. The Eocene-Oligocene contact corresponds to a =3-Ma-long hiatus. Eocene- Oligocene sedimentation is dominated by great diversity and varying amounts of detrital and authigenic minerals. Four sedimentary intervals are identified by lithology and mineral content: (1) A 30-m-thick, smectite- and illite-rich interval directly overlies the Exmore Formation, suggesting long-term reworking of impact debris within the Chesapeake Bay impact structure. (2) Subsequently, an increase in kaolinite content suggests erosion from soils developed during late Eocene warm and humid climate in agreement with data derived from other Atlantic sites. However, the kaolinite increase may also be explained by change to a predominant sediment input from outside the Chesapeake Bay impact structure caused by progradation of more proximal facies belts during the highstand systems tract of the late Eocene sequence E10.Spectral analysis based on gamma-ray and magnetic susceptibility logs suggests infl uence of 1.2 Ma low-amplitude oscillation of the obliquity period during the late Eocene. (3) During the latest Eocene (Biozones NP21 and E16), several lithological contacts (clay to clayey silt) occur concomitant with a prominent change in the mineralogical composition with illite as a major component: This lithological change starts close to the Biozone NP19/20-NP21 boundary and may correspond to sequence boundary E10-E11 as observed in other northwest Atlantic margin sections. It could result from a shift to more distal depositional environments and condensed sedimentation during maximum fl ooding, rather than refl ecting a climatic change in the hinterland. The distinct 1% increase of the oxygen isotopes may correspond to the short-term latest Eocene "precursor isotope event." (4) The abrupt increase of sediment grainsize, carbonate content, and abundance of authigenic minerals (glauconite) across the major unconformity that separates Eocene from Oligocene sediments in the Eyreville core refl ects deposition in shallower settings associated with erosion, winnowing, and reworking. Sediments within the central crater were affected by the rapid eustatic sea-level changes associated with the greenhouse-icehouse transition, as well as by an abrupt major uplift event and possibly enhanced current activity on the northwestern Atlantic margin. ?? 2009 The Geological Society of America.

Chemical openness and potential for misinterpretation of the solute environment of coastal sabkhat

USGS Publications Warehouse

Wood, W.W.; Sanford, W.E.; Frape, S.K.

2005-01-01

Sabkha deposits in the geologic record are commonly used to interpret the environmental conditions of deposition. Implicit in this use is the assumption that the solute system is chemically closed, that is, the authigenic minerals represent the composition of the fluids in their environment of origin. Thermodynamic and mass-balance calculations based on measurements of water and solute flux of contemporary Abu Dhabi coastal sabkha system, however, demonstrate that the system is open for sodium and chloride, where nearly half of the input is lost, but closed for sulfur, where nearly 100% is retained. Sulfur and chloride isotopes were consistent with this observation. If these sabkha deposits were preserved in the geologic record, they would suggest a solute environment rich in sulfate and poor in chloride; yet the reverse is true. In most coastal-sabkha environments, capillary forces bring solutes and water to the surface, where the water evaporates and halite, carnallite, sylvite, and other soluble minerals are precipitated. Retrograde minerals, such as anhydrite, calcite, dolomite, and gypsum, however, precipitate and accumulate in the capillary zone beneath the surface of the coastal sabkha. Because they possess relatively low solubility and are below the surface, these retrograde minerals are protected from dissolution and physical erosion occurring from infrequent but intense rainfall events. Thus, they are more likely to be preserved in the geological record than highly soluble minerals formed on the surface. ?? 2004 Elsevier B.V. All rights reserved.

XRD-based 40Ar/39Ar age correction for fine-grained illite, with application to folded carbonates in the Monterrey Salient (northern Mexico)

NASA Astrophysics Data System (ADS)

Fitz-Díaz, Elisa; Hall, Chris M.; van der Pluijm, Ben A.

2016-05-01

Due to their minute size, 40Ar/39Ar analysis of illite faces significant analytical challenges, including mineral characterization and, especially, effects of grain size and crystallography on 39Ar recoil. Quantifying the effects of 39Ar recoil requires the use of sample vacuum encapsulation during irradiation, which permits the measurement of the fraction of recoiled 39Ar as well as the 39Ar and 40Ar∗ retained within illite crystals that are released during step heating. Total-Gas Ages (TGA) are calculated by using both recoiled and retained argon, which is functionally equivalent to K-Ar ages, while Retention Ages (RA) only involve retained Ar in the crystal. Natural applications have shown that TGA fits stratigraphic constraints of geological processes when the average illite crystallite thickness (ICT) is smaller than 10 nm, and that RA matches these constraints for ICTs larger than 50 nm. We propose a new age correction method that takes into account the average ICT and corresponding recoiled 39Ar for a sample, with X-ray Corrected Ages (XCA) lying between Total-Gas and Retention Ages depending on ICT. This correction is particularly useful in samples containing authigenic illite formed in the anchizone, with typical ICT values between 10 and 50 nm. In three samples containing authigenic illite from Cretaceous carbonates in the Monterrey Salient in northern Mexico, there is a range in TGAs among the different size-fractions of 46-49, 36-43 and 40-52 Ma, while RAs range from 54-64, 47-52 and 53-54 Ma, respectively. XCA calculations produce tighter age ranges for these samples of 52.5-56, 45.5-48.5 and 49-52.5 Ma, respectively. In an apparent age vs ICT or %2M 1illite plot, authigenic illite grains show a slope that is in general slightly positive for TGA, slightly negative for RA, but close to zero for XCA, with thinner crystallites showing more dispersion than thicker ones. In order to test if dispersion is due to a different formation history or the result of retention capability, degassing spectra were modeled for site XCA averages and overall XCA average. Modeling shows that local site age average best match the measured spectra, instead of a global average age, indicating that illite growth reflects local deformation, and is not the result of regional metamorphism. Modeling also shows that Ar-degassing spectra are very sensitive to grain size, such that age interpretation based on Ar-plateaus is meaningless for most fine-grained clays.

Determining the Sensitivity of the Hf-Nd Proxy to Glacial Weathering

NASA Astrophysics Data System (ADS)

Namsinh, A.; Scher, H.; Piotrowski, A. M.

2017-12-01

The history of polar ice sheets through the Cenozoic is incompletely known. Estimates of the onset of northern hemisphere glaciation range from the Pliocene to mid-Eocene and precursor Antarctic glaciations are believed to have commenced in the middle Eocene. Uncertainty surrounding the history of ice sheets has resulted in debates about the sensitivity of ice sheets to changes in atmospheric CO2 through the Cenozoic. Geochemical proxies for continental weathering — particularly those that are sensitive to mechanical breakdown of the upper continental crust by ice sheets — could improve the fidelity of paleoclimate reconstructions of ice sheet history. Coupled hafnium (Hf) and neodymium (Nd) isotopes in seawater and authigenic sediment phases show a strong correlation with mechanical weathering rates, however the proxy has not been systematically tested on Pleistocene time scales. We measured the Hf and Nd isotope ratios of authigenic and detrital phases of sediment cores from 1150 m to 4045 m depth on the Rockall Plateau in the NE Atlantic Ocean. Our study is limited to the LGM, deglaciation and Holocene intervals. The authigenic fraction was extracted from bulk sediments by leaching with dilute hydroxylamine hydrochloride and EDTA to prevent readsorption of Hf. A stronger leach solution was then used to isolate the terrigenous detrital fraction. The fidelity of the seawater signal obtained by leaching is assessed by comparison of leachate eNd values to previously published eNd values from uncleaned forams from the same depth intervals. Initial tests with Holocene and deglacial samples verify that leachate eNd values are statistically indistinguishable from uncleaned forams. Shale-normalized REE patterns for leachates reveal negative Ce anomalies and a MREE enrichment typical of Fe-Mn oxydydroxide phases. Coupled Hf-Nd isotopes from authigenic leachates from our initial tests fall along the Seawater Array when plotted on a Hf-Nd isotope diagram, confirming that a primary seawater Hf isotope signal can also be extracted from authigenic leachates. Further isotopic analysis of these cores, including the LGM intervals, will reveal if changes in weathering style through the deglaciation resulted in decoupling of Hf and Nd isotopes, which may be expressed as a deviation from the Seawater Array.

Authigenic Carbonate Formation on the Peru Margin; New Insights from IODP Site 1230

NASA Astrophysics Data System (ADS)

Abdullajintakam, S.; Naehr, T. H.

2015-12-01

Fluid seepage of reduced organic compounds such as methane impacts the geology and biology of the seabed by inducing complex, microbially mediated biogeochemical processes. Authigenic carbonates serve as one of the few permanent records of these of dynamic biogeochemical interactions that involve methanogenesis, methanotrophy, sulfate reduction and carbonate precipitation. Meister et al. (2007) investigated deep-sea dolomite formation at Sites 1227-1229 on the Peru margin, where dolomite precipitation occurs in association with organic carbon-rich continental margin sediments. Geochemical and petrographic studies indicated episodic dolomite precipitation at a dynamic sulfate methane transition zone (SMTZ). Variations in δ13C values of these dolomites between +15‰ and -15‰ were attributed to non-steady state conditions as a result of the upward and downward migration of the SMTZ. Our study aims to better understand the biogeochemical processes associated with authigenic carbonate precipitation in this dynamic deep-sea setting. We focused our efforts on IODP Site 1230, which is a gas-hydrate-bearing site that shows sulphate consumption within the uppermost 10 m below the seafloor as well as high methane production. Using a multi proxy approach, we combined X-ray diffraction, stable isotope geochemistry, and trace metal analysis of authigenic carbonates to elucidate conditions for authigenic carbonate formation. Results from Site 1230 are compared to Sites 1227 and 1229, which lacks gas hydrates and is characterized by high pore water sulfate and low methane concentrations. This study contributes to a more comprehensive understanding of authigenic carbonate formation and associated biogeochemical processes in continental margin sediments. Meister, P., Mckenzie, J. A., Vasconcelos, C., Bernasconi, S., Frank, M., Gutjhar, M. and SCHRAG, D. P. (2007), Dolomite formation in the dynamic deep biosphere: results from the Peru Margin. Sedimentology, 54: 1007-1032.

Changes in deep-sea carbonate-hosted microbial communities associated with high and low methane flux

NASA Astrophysics Data System (ADS)

Case, D. H.; Steele, J. A.; Chadwick, G.; Mendoza, G. F.; Levin, L. A.; Orphan, V. J.

2012-12-01

Methane seeps on continental shelves are rich in authigenic carbonates built of methane-derived carbon. These authigenic carbonates are home to micro- and macroscopic communities whose compositions are thus far poorly constrained but are known to broadly depend on local methane flux. The formation of authigenic carbonates is itself a result of microbial metabolic activity, as associations of anaerobic methane oxidizing archaea (ANME) and sulfate reducing bacteria (SRB) in the sediment subsurface increase both dissolved inorganic carbon (DIC) and alkalinity in pore waters. This 1:1 increase in DIC and alkalinity promotes the precipitation of authigenic carbonates. In this study, we performed in situ manipulations to test the response of micro- and macrofaunal communities to a change in methane flux. Methane-derived authigenic carbonates from two locations at Hydrate Ridge, OR, USA (depth range 595-604 mbsl), were transplanted from "active" cold seep sites (high methane flux) to "inactive" background sites (low methane flux), and vise versa, for one year. Community diversity surveys using T-RFLP and 16S rRNA clone libraries revealed how both bacterial and archaeal assemblages respond to this change in local environment, specifically demonstrating reproducible shifts in different ANME groups (ANME-1 vs. ANME-2). Animal assemblage composition also shifted during transplantation; gastropod representation increased (relative to control rocks) when substrates were moved from inactive to active sites and polychaete, crustacean and echinoderm representation increased when substrates were moved from active to inactive sites. Combined with organic and inorganic carbon δ13C measurements and mineralogy, this unique in situ experiment demonstrates that authigenic carbonates are viable habitats, hosting microbial and macrofaunal communities capable of responding to changes in external environment over relatively short time periods.

Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky

USGS Publications Warehouse

Hower, J.C.; Ruppert, L.F.; Eble, C.F.

1999-01-01

The Fire Clay coal bed in the Central Appalachian basin region contains a laterally-persistent tonstein that is found in the coal throughout most of its areal extent. The tonstein contains an array of minerals, including sanidine, ??-quartz, anatase and euhedral zircon, thhat constitutes strong evidence for a volcanic origin of the parting. For this study, five samples of the tonstein and four sets of coal samples underlying the tonstein were collected from five sites in eastern Kentucky. Inductively coupled plasma-mass spectroscopy (ICP-MS) analysis of the tonstein and underlying coal collected from four sites in eastern Kentucky show that although Zr concentrations are high in the tonstein (570-1820 ppm on a coal-ash basis (cab)), they are highest in the coal directly underlying the tonstein (2870-4540 ppm (cab)). A similar enrichment pattern is observed in the concentration of Y plus the sum of the rare earth elements (Y + ??REE): total Y + ??REE concentrations in the five tonstein samples range from 511 to 565 ppm (cab). However, Y + ??REE contents are highest in the coals directly underlying the tonsteins: values range from 1965 to 4198 ppm (cab). Scanning electron microscopy of samples from coal which directly underlies two of the tonstein samples show that REE-rich phosphate, tentatively identified as monazite, commonly infills cracks in clays and cells in clarain and vitrain. Zircon is rare and commonly subhedral. On the basis of coal chemistry and grain morphology, we suggest that volcanic components in the tonstein were leached by ground water. The leachate, rich in Y and REE precipitated as authigenic mineral phases in the underlying coal.The Fire Clay coal bed in the Central Appalachian basin region contains a laterally-persistent tonstein that is found in the coal throughout most of its areal extent. The tonstein contains an array of minerals, including sanidine, ??-quartz, anatase and euhedral zircon, that constitutes strong evidence for a volcanic origin of the parting. For this study, five samples of the tonstein and four sets of coal samples underlying the tonstein were collected from five sites in eastern Kentucky. Inductively coupled plasma-mass spectroscopy (ICP-MS) analysis of the tonstein and underlying coal collected from four sites in eastern Kentucky show that although Zr concentrations are high in the tonstein (570-1820 ppm on a coal-ash basis (cab)), they are highest in the coal directly underlying the tonstein (2870-4540 ppm (cab)). A similar enrichment pattern is observed in the concentration of Y plus the sum of the rare earth elements (Y+???REE): total Y+???REE concentrations in the five tonstein samples range from 511 to 565 ppm (cab). However, Y+???REE contents are highest in the coals directly underlying the tonsteins: values range from 1965 to 4198 ppm (cab). Scanning electron microscopy of samples from coal which directly underlies two of the tonstein samples show that REE-rich phosphate, tentatively identified as monazite, commonly infills cracks in clays and cells in clarain and vitrain. Zircon is rare and commonly subhedral. On the basis of coal chemistry and grain morphology, we suggest that volcanic components in the tonstein were leached by ground water. The leachate, rich in Y and REE precipitated as authigenic mineral phases in the underlying coal.

Characteristics of gas hydrate-bearing sediments of the northern South China Sea: insight into past hydrate episodic dissociations and intensities of seepage

NASA Astrophysics Data System (ADS)

Chen, F.; Su, X.; Zhou, Y.; Zhang, G.; Zhuang, C.; Lu, H.

2016-12-01

In 2013 the second China's major gas hydrate expedition, GMGS2, cored and recovered abundant gas hydrates at five sites, which were located in the South China Sea.Site GMGS08 (95m long) contained two gas hydrate intervals and five authigenic carbonate intervals. We analyzed carbon and oxygen isotopes of authigenic carbonates and foraminifera shells in sediments recovered at this site, in order to understanding of features of hydrate-bearing sediments and timing of gas hydrate dissociation and methane seepage at this site. An age of younger than 0.27 Ma was estimated for the 95 m sedimentary sequences at Site GMGS08. A detailed age model was further established by employing of U/Th and AMS14C dating of authigenic carbonates and seep bivalve fragments. These carbonates are featured by 13C-depleted (with a range from -38.9‰ to 56.7‰ δ13C) and positive δ18O (from 2.94‰ to 5.66‰ δ18O) values. A further analysis indicated the formation of carbonates were correlated to methane seepages derived from gas hydrate dissociation. Subsequently, these five authigenic carbonates intervals were seen as five hydrate episodic dissociation events since last 0.27Ma at this site. The most significant event during the period of 0.11 Ma to 0.13 Ma were account for the formation of thick authigenic carbonate (with the lowest -56.8‰ δ13C value) platform on paleo-seafloor at this site. The upmost authigenic carbonates interval is just overlying on the top of the upper gas hydrate occurrence zone, and it represents the latest methane seepage event with an age of 26ka to 36ka. Well correlated to these five events, it existed five intervals with strongly 13C-depleted carbon (-15.85‰ PDB) of foraminifera shells both from benthic and planktonic. The anomalous δ13C depletion records of planktonic G. ruber shells should be caused by formation of secondary authigenic carbonates on the shells, which were derived from the anaerobic oxidation of methane (AOM). The analyses on carbonate samples indicated varied intensity of methane flux in each event. The most intensive methane venting flux occurred during the event of 0.11 Ma to 0.13 Ma, which is correlated to a warm and relative high sea level period of MIS stage 5. These records obtained at Site GMGS08 implied much complicated causes for formation of authigenic carbonates and gas hydrate episodic dissociation.

A urolith of biogenic dolomite - another clue in the dolomite mystery

NASA Astrophysics Data System (ADS)

Mansfield, Charles F.

1980-06-01

A male Dalmatian, Canis familiaris, produced uroliths of almost pure dolomite, 3-8 mm across, in his urinary bladder in less than 8 months at 38°C and about 1 atm. The X-ray diffractogram identified the predominant mineral as dolomite, and the sharp (01.5) peak showed it is ordered dolomite, not the disordered form, protodolomite. Geochemically and biologically plausible causes include (1) renal, respiratory, or metabolic alkalosis, (2) infection by urease-producing (urea-splitting) fungi or bacteria and (3) infection by uric acid-fermenting bacteria. Hematological, bacteriological, urological and geochemical considerations most strongly implicate infection by either anaerobic, urease-producing bacteria or anaerobic, uric acid-fermenting bacteria. The physical and chemical conditions of this urinary system more closely approximate modern and inferred ancient carbonate depositional settings than most previous laboratory experiments, especially in terms of temperature, pressure, total salinity and, possibly, biota. The presence of urease-producing and/or uric acid-fermenting bacteria in urea- and/or acid-containing sediment, such as fecal pellets and algal mats, could promote formation of authigenic dolomite or other carbonates.

Soft-Bodied Fossils Are Not Simply Rotten Carcasses - Toward a Holistic Understanding of Exceptional Fossil Preservation: Exceptional Fossil Preservation Is Complex and Involves the Interplay of Numerous Biological and Geological Processes.

PubMed

Parry, Luke A; Smithwick, Fiann; Nordén, Klara K; Saitta, Evan T; Lozano-Fernandez, Jesus; Tanner, Alastair R; Caron, Jean-Bernard; Edgecombe, Gregory D; Briggs, Derek E G; Vinther, Jakob

2018-01-01

Exceptionally preserved fossils are the product of complex interplays of biological and geological processes including burial, autolysis and microbial decay, authigenic mineralization, diagenesis, metamorphism, and finally weathering and exhumation. Determining which tissues are preserved and how biases affect their preservation pathways is important for interpreting fossils in phylogenetic, ecological, and evolutionary frameworks. Although laboratory decay experiments reveal important aspects of fossilization, applying the results directly to the interpretation of exceptionally preserved fossils may overlook the impact of other key processes that remove or preserve morphological information. Investigations of fossils preserving non-biomineralized tissues suggest that certain structures that are decay resistant (e.g., the notochord) are rarely preserved (even where carbonaceous components survive), and decay-prone structures (e.g., nervous systems) can fossilize, albeit rarely. As we review here, decay resistance is an imperfect indicator of fossilization potential, and a suite of biological and geological processes account for the features preserved in exceptional fossils. © 2017 The Authors. BioEssays Published by WILEY Periodicals, Inc.

Authigenic carbonates from newly discovered active cold seeps on the northwestern slope of the South China Sea: Constraints on fluid sources, formation environments, and seepage dynamics

NASA Astrophysics Data System (ADS)

Liang, Qianyong; Hu, Yu; Feng, Dong; Peckmann, Jörn; Chen, Linying; Yang, Shengxiong; Liang, Jinqiang; Tao, Jun; Chen, Duofu

2017-06-01

Authigenic carbonates recovered from two newly discovered active cold seeps on the northwestern slope of the South China Sea have been studied using petrography, mineralogy, stable carbon and oxygen isotopic, as well as trace element compositions, together with AMS 14C ages of shells of seep-dwelling bivalves to unravel fluid sources, formation conditions, and seepage dynamics. The two seeps (ROV1 and ROV2), referred to as 'Haima seeps' herein, are approximately 7 kilometers apart, and are typified by abundant carbonate rocks represented bycrusts and nodules. Aragonite and high-Mg calcite are the main carbonate minerals. Based on low δ13Ccarbonate values ranging from -43.0‰ to -27.5‰ (V-PDB) methane is apparently the predominant carbon source of seep carbonates. The corresponding δ18O values, varying from 2.5‰ to 5.8‰ (V-PDB), mostly are higher than calculated values representing precipitation in equilibrium with seawater (2.5‰ to 3.8‰), which probably reflects past destabilization of locally abundant gas hydrates. In addition, we found that carbonates with bivalve shells are generally aragonite-dominated, and bear no barium enrichment but uranium enrichments, reflecting shallow formation depths close to the seafloor. In contrast, carbonate crusts without bivalve shells and nodules contain more calcite, and are characterized by major molybdenum enrichment and different degrees of barium enrichment, agreeing with precipitation at greater depth under strictly anoxic conditions. AMS 14C ages suggest that a major episode of carbonate precipitation occurred between 6.1 ka and 5.1 ka BP at the Haima seeps, followed by a possibly subordinate episode from approximately 3.9 ka to 2.9 ka BP. The common occurrence of dead bivalves at both sites indicates that chemosynthesis-based communities flourished to a greater extent in the past, probably reflecting a decline of seepage activity in recent times. Overall, these results confirm that authigenic carbonates from gas hydrate-bearing areas can provide insight into long-term seepage dynamics and the genesis and fate of marine gas hydrate reservoirs.

Sediment Sources, Depositional Environment, and Diagenetic Alteration of the Marcellus Shale, Appalachian Basin, USA: Nd, Sr, Li and U Isotopic Constraints

NASA Astrophysics Data System (ADS)

Phan, T. T.; Capo, R. C.; Gardiner, J. B.; Stewart, B. W.

2017-12-01

The organic-rich Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, is a major target of natural gas exploration. Constraints on local and regional sediment sources, depositional environments, and post-depositional processes are essential for understanding the evolution of the basin. In this study, multiple proxies, including trace metals, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U and Li isotopes were applied to bulk rocks and authigenic fractions of the Marcellus Shale and adjacent limestone/sandstone units from two locations separated by 400 km. The range of ɛNd values (-7.8 to -6.4 at 390 Ma) is consistent with a clastic sedimentary component derived from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt. The Sm-Nd isotope system and bulk REE distributions appear to have been minimally affected by post-depositional processes, while the Rb-Sr isotope system shows evidence of limited post-depositional redistribution. While REE are primarily associated with silicate minerals (80-95%), REE patterns of sequentially extracted fractions reflect post-depositional alteration at the intergranular scale. Although the chemical index of alteration (CIA = 54 to 60) suggests the sediment source was not heavily weathered, Li isotope data are consistent with progressively increasing weathering of the source region during Marcellus Shale deposition. δ238U values in bulk shale and reduced phases (oxidizable fraction) are higher than those of modern seawater and upper crust. The isotopically heavy U accumulated in these authigenic phases can be explained by the precipitation of insoluble U in anoxic/euxinic bottom water. Unlike carbonate cement within the shale, the similarity between δ238U values and REE patterns of the limestone units and those of modern seawater indicates that the limestone formed under open ocean (oxic) conditions.

Formation of carbonate concretions in deep-sea sediment below the CCD and above an active gas hydrate system

NASA Astrophysics Data System (ADS)

Dicus, C. M.; Snyder, G. T.; Dickens, G. R.

2004-12-01

Site 1230 of the Ocean Drilling Program targeted the chemistry and microbiology of an active deep-water gas hydrate system in the Peru Trench. The site is noteworthy because, at nearly 6000 m water depth, it lies well below the carbonate compensation depth and the sediments comprise mostly terrigenous clays and biogenic silica. Shipboard work at this site delineated a prominent sulfate-methane transition (SMT) at 8-10 m below seafloor (mbsf) as well as some carbonate horizons. In this study, we present calcium and strontium data for pore waters and sediments at this site, including across the SMT. Concentration profiles show that dissolved Ca2+ diffuses downward from the seafloor toward the SMT, where a sharp inflection indicates consumption of Ca2+ into an authigenic phase. Dissolved Sr2+, on the other hand, diffuses upward from depth toward the SMT. Again, however, a prominent inflection suggests removal of Sr2+ to sediment. The inferences from pore water profiles are borne out by sediment chemistry. Large peaks in the calcium and strontium content of sediment mark the SMT. The calcium and strontium fronts reach ˜2700 and ˜5 mmol/kg, respectively, at 9 mbsf, which are much greater than average background values of ˜10 and ˜1 mmol/kg. These authigenic fronts are primarily composed of carbonate minerals, as determined by acetic acid extractions and x-ray diffraction. Because the calcium and strontium fronts coincide with both the SMT and changes in dissolved chemistry, it is proposed that the carbonates are currently forming as follows: methane rising from the underlying gas hydrate system reacts with dissolved sulfate through anaerobic oxidation of methane which releases HCO3- and alkalinity and causes carbonate precipitation. The overall process has been observed elsewhere; the Peru Trench is interesting, however, because the process leads to carbonate in sediments otherwise devoid of carbonate.

Unmixing Magnetic Hysteresis Loops

NASA Astrophysics Data System (ADS)

Heslop, D.; Roberts, A. P.

2012-04-01

Magnetic hysteresis loops provide important information in rock and environmental magnetic studies. Natural samples often contain an assemblage of magnetic particles composed of components with different origins. Each component potentially carries important environmental information. Hysteresis loops, however, provide information concerning the bulk magnetic assemblage, which makes it difficult to isolate the specific contributions from different sources. For complex mineral assemblages an unmixing strategy with which to separate hysteresis loops into their component parts is therefore essential. Previous methods to unmix hysteresis data have aimed at separating individual loops into their constituent parts using libraries of type-curves thought to correspond to specific mineral types. We demonstrate an alternative approach, which rather than decomposing a single loop into monomineralic contributions, examines a collection of loops to determine their constituent source materials. These source materials may themselves be mineral mixtures, but they provide a genetically meaningful decomposition of a magnetic assemblage in terms of the processes that controlled its formation. We show how an empirically derived hysteresis mixing space can be created, without resorting to type-curves, based on the co-variation within a collection of measured loops. Physically realistic end-members, which respect the expected behaviour and symmetries of hysteresis loops, can then be extracted from the mixing space. These end-members allow the measured loops to be described as a combination of invariant parts that are assumed to represent the different sources in the mixing model. Particular attention is paid to model selection and estimating the complexity of the mixing model, specifically, how many end-members should be included. We demonstrate application of this approach using lake sediments from Butte Valley, northern California. Our method successfully separates the hysteresis loops into sources with a variety of terrigenous and authigenic origins.

Quantification of octacalcium phosphate, authigenic apatite and detrital apatite in coastal sediments using differential dissolution and standard addition

NASA Astrophysics Data System (ADS)

Oxmann, J. F.; Schwendenmann, L.

2014-06-01

Knowledge of calcium phosphate (Ca-P) solubility is crucial for understanding temporal and spatial variations of phosphorus (P) concentrations in water bodies and sedimentary reservoirs. In situ relationships between liquid- and solid-phase levels cannot be fully explained by dissolved analytes alone and need to be verified by determining particular sediment P species. Lack of quantification methods for these species limits the knowledge of the P cycle. To address this issue, we (i) optimized a specifically developed conversion-extraction (CONVEX) method for P species quantification using standard additions, and (ii) simultaneously determined solubilities of Ca-P standards by measuring their pH-dependent contents in the sediment matrix. Ca-P minerals including various carbonate fluorapatite (CFAP) specimens from different localities, fluorapatite (FAP), fish bone apatite, synthetic hydroxylapatite (HAP) and octacalcium phosphate (OCP) were characterized by XRD, Raman, FTIR and elemental analysis. Sediment samples were incubated with and without these reference minerals and then sequentially extracted to quantify Ca-P species by their differential dissolution at pH values between 3 and 8. The quantification of solid-phase phosphates at varying pH revealed solubilities in the following order: OCP > HAP > CFAP (4.5% CO3) > CFAP (3.4% CO3) > CFAP (2.2% CO3) > FAP. Thus, CFAP was less soluble in sediment than HAP, and CFAP solubility increased with carbonate content. Unspiked sediment analyses together with standard addition analyses indicated consistent differential dissolution of natural sediment species vs. added reference species and therefore verified the applicability of the CONVEX method in separately determining the most prevalent Ca-P minerals. We found surprisingly high OCP contents in the coastal sediments analyzed, which supports the hypothesis of apatite formation by an OCP precursor mechanism.

Quantification of octacalcium phosphate, authigenic apatite and detrital apatite in coastal sediments using differential dissolution and standard addition

NASA Astrophysics Data System (ADS)

Oxmann, J. F.; Schwendenmann, L.

2014-01-01

Knowledge of calcium phosphate (Ca-P) solubility is crucial for understanding temporal and spatial variations of phosphorus (P) concentrations in water bodies and sedimentary reservoirs. In-situ relationships between liquid and solid-phase levels cannot be fully explained by dissolved analytes alone and need to be verified by determination of particular sediment P species. Lack of quantification methods for these species limits the knowledge of the P cycle. To address this issue, we (i) optimized a specifically developed conversion-extraction (CONVEX) method for P species quantification using standard additions; and (ii) simultaneously determined solubilities of Ca-P standards by measuring their pH-dependent contents in the sediment matrix. Ca-P minerals including various carbonate fluorapatite (CFAP) specimens from different localities, fluorapatite (FAP), fish bone apatite, synthetic hydroxylapatite (HAP) and octacalcium phosphate (OCP) were characterized by XRD, Raman, FTIR and elemental analysis. Sediment samples were incubated with and without these reference minerals and then sequentially extracted to quantify Ca-P species by their differential dissolution at pH values between 3 and 8. The quantification of solid-phase phosphates at varying pH revealed solubilities in the following order: OCP > HAP > CFAP (4.5% CO3) > CFAP (3.4% CO3) > CFAP (2.2% CO3) > FAP. Thus, CFAP was less soluble in sediment than HAP, and CFAP solubility increased with carbonate content. Unspiked sediment analyses together with standard addition analyses indicated consistent differential dissolution of natural sediment species vs. added reference species and therefore verified the applicability of the CONVEX method in separately determining the most prevalent Ca-P minerals. We found surprisingly high OCP contents in the analyzed coastal sediments which supports the hypothesis of apatite formation by an OCP precursor.

Ferrimagnetic Iron Sulfide Formation and Methane Venting Across the Paleocene-Eocene Thermal Maximum in Shallow Marine Sediments, Ancient West Siberian Sea

NASA Astrophysics Data System (ADS)

Rudmin, Maxim; Roberts, Andrew P.; Horng, Chorng-Shern; Mazurov, Aleksey; Savinova, Olesya; Ruban, Aleksey; Kashapov, Roman; Veklich, Maxim

2018-01-01

Authigenesis of ferrimagnetic iron sulfide minerals (greigite and monoclinic pyrrhotite) occurred across the Paleocene-Eocene Thermal Maximum (PETM) within the Bakchar oolitic ironstone in southeastern Western Siberia. Co-occurrence of these minerals is associated with diagenetic environments that support anaerobic oxidation of methane, which has been validated by methane fluid inclusion analysis in the studied sediments. In modern settings, such ferrimagnetic iron sulfide formation is linked to upward methane diffusion in the presence of minor dissolved sulfide ions. The PETM was the most extreme Cenozoic global warming event and massive methane mobilization has been proposed as a major contributor to the globally observed warming and carbon isotope excursion associated with the PETM. The studied sediments provide rare direct evidence for methane mobilization during the PETM. Magnetic iron sulfide formation associated with methanogenesis in the studied sediments can be explained by enhanced local carbon burial across the PETM. While there is no strong evidence to link local methane venting with more widespread methane mobilization and global warming, the magnetic, petrographic, and geochemical approach used here is applicable to identifying authigenic minerals that provide telltale signatures of methane mobility that can be used to assess methane formation and mobilization through the PETM and other hyperthermal climatic events.

Mineralogical compositions of fault rocks from surface ruptures of Wenchuan earthquake and implication of mineral transformation during the seismic cycle along Yingxiu-Beichuan fault, Sichuan Province, China

NASA Astrophysics Data System (ADS)

Dang, Jiaxiang; Zhou, Yongsheng; He, Changrong; Ma, Shengli

2018-06-01

There are two co-seismic bedrock surface ruptures from the Mw 7.9 Wenchuan earthquake in the northern and central parts of the Beichuan-Yingxiu fault, Sichuan Province, southwest China. In this study, we report on the macrostructure of the fault rocks and results from X-ray powder diffraction analysis of minerals from rocks in the fault zone. The most recent fault gouge (the gouge produced by the most recent co-seismic fault movement) in all the studied outcrops is dark or grayish-black, totally unconsolidated and ultrafine-grained. Older fault gouges in the same outcrops are grayish or yellowish and weakly consolidated. X-ray powder diffraction analysis results show that mineral assemblages in both the old fault gouge and the new fault gouge are more complicated than the mineral assemblages in the bedrock as the fault gouge is rich in clay minerals. The fault gouge inherited its major rock-forming minerals from the parent rocks, but the clay minerals in the fault gouge were generated in the fault zone and are therefore authigenic and synkinematic. In profiles across the fault, clay mineral abundances increase as one traverses from the bedrock to the breccia to the old gouge and from the old gouge to the new gouge. Quartz and illite are found in all collected gouge samples. The dominant clay minerals in the new fault gouge are illite and smectite along the northern part of the surface rupture and illite/smectite mixed-layer clay in the middle part of the rupture. Illite/smectite mixed-layer clay found in the middle part of the rupture indicates that fault slip was accompanied by K-rich fluid circulation. The existence of siderite, anhydrite, and barite in the northern part of the rupture suggests that fault slip at this locality was accompanied by acidic fluids containing ions of Fe, Ca, and Ba.

Thorium-derived dust fluxes to the tropical Pacific Ocean, 58 Ma

NASA Astrophysics Data System (ADS)

Woodard, Stella C.; Thomas, Deborah J.; Marcantonio, Franco

2012-06-01

Eolian dust in pelagic deep sea sediments can be used to reconstruct ancient wind patterns and paleoenvironmental response to climate change. Traditional methods to determine dust accumulation involve isolating the non-dissolvable aluminosilicate minerals from deep sea sediments through a series of chemical leaches, but cannot differentiate between minerals from eolian, authigenic and volcanogenic sources. Other geochemical proxies, such as sedimentary 232Th and crustal 4He content, have been used to construct high-resolution records of atmospheric dust fluxes to the deep sea during the Quaternary. Here we use sedimentary Th content as a proxy for terrigenous material (eolian dust) in ˜58 Myr-old sediments from the Shatsky Rise (ODP Site 1209) and compare our results with previous dust estimates generated using the traditional chemical extraction method and sedimentary 4Hecrustal concentrations. We find excellent agreement between Th-based dust estimates and those generated using the traditional method. In addition our results show a correlation between sedimentary Th and 4Hecrustal content, which suggests a source older than present day Asian loess supplied dust to the central subtropical Pacific Ocean during the early Paleogene.

Relationships between sedimentation, depositional environments, and coal quality: upper Potomac coalfield, West Virginia and Maryland

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

Jake, T.R.

1987-09-01

Evaluations were made of sedimentation patterns and depositional environments from approximately 450 core logs and 225 surface exposures in the Upper Potomac coalfield. The relationships between the clastic depositional facies and the distribution and quality of the Bakerstown and upper Freeport coals were also investigated. Data from 61 Bakerstown and 35 upper Freeport coal samples from selected cores indicate a change from uniform coal quality to highly variable coal quality when moving from related interchannel and bay-fill facies to channel, channel-fill, levee, and crevasse-splay facies. Areas of uniform coal quality range from 20-26% ash and 55-62% fixed carbon (weight percent,more » dry basis), whereas areas of highly variable coal quality range from 26-54% ash and 33-55% fixed carbon. The channel and related facies represent areas where increased fresh water was introduced into the topogenous swamp system, causing increased microbial degradation and the concentration of authigenic minerals within the peat material. These conditions, combined with the introduction of detrital minerals, resulted in areas of lower quality coal.« less

Occurrence and origin of minerals in a chamosite-bearing coal of Late Permian age, Zhaotong, Yunnan, China

USGS Publications Warehouse

Dai, S.; Chou, C.-L.

2007-01-01

The minerals found in the no.5 coal (Late Permian) from the Zhaotong Coalfield, Yunnan Province, southwestern China, have been examined and found to consist mainly of kaolinite, pyrite, chamosite, quartz, and calcite, with trace amounts of illite and mixed-layer illite-smectite. The proportion of chamosite in clay minerals ranges from 32 to 56 wt%, with an average of 46 wt%. Chamosite is distributed not only in collodetrinite, but also occurs as cell fillings in fusinite, semifusinite, and telinite. The high content and mode of occurrence of chamosite in this mine indicate its formation by interaction of kaolinite with Fe-Mg-rich fluids during early diagenesis. Except for a minor amount of terfigenous quartz, most quartz is of authigenic origin and formed from kaolinite desilication. The calcite content of the no. 5 coal is 1.4-6.3% (with an average of 3%) and is distributed in collodetrinite and as cell fillings of coal-forming plants. Calcite originated from seawater invasion during peat accumulation. Pyrite occurs in several ways: as massive, framboidal, isolated enhedral/ anhedral, and euhedral forms. In addition, the presence of a large amount of pyritized red algae provides strong evidence of seawater invasion during peat accumulation. The red algae may have played an important role in the enrichment of sulfur in the coal. The characteristic assemblage of minerals in this mine resulted from a unique basinal environment in which the mineral matter was derived from a basaltic source region, volcanic activity, and seawater transgression during coal formation.

Formation of the Shelf-edge Cretaceous-Tertiary contact off the southeastern U.S. Coast

USGS Publications Warehouse

Poppe, L.J.; Hathaway, J.C.; Hall, R.E.; Commeau, R.F.

1986-01-01

Submarine erosion, associated with changes in position of the proto-Gulf Stream, was the dominant mechanism controlling the formation of the Cretaceous-Tertiary unconformity in AMCOR borehole 6004. Paleontologic evidence indicates that this unconformity, which is marked by a gravelly-sand enriched in glauconitic and phosphoritic concretions, represents a hiatus of about 7 m.y. Both Cretaceous and Paleocene sediments contain middle-outer neritic foraminiferal assemblages that become more diverse with distance from the contact. Of the elemental abundances measured, Al, Ba, Co, Fe, Ga, K, Mg/Ca, Mo, Ni, P, Sr/Ca, V, Y, and Zn show a strong positive correlation with proximity to the contact, probably as a result of the concentration of authigenic and heavy minerals present as lag sediments on the erosion surface. ?? 1986.

Syn- and post-sedimentary controls on clay mineral assemblages in a tectonically active basin, Andean Argentinean foreland

NASA Astrophysics Data System (ADS)

Do Campo, Margarita; Nieto, Fernando; del Papa, Cecilia; Hongn, Fernando

2014-07-01

In the northern part of the Calchaquí Valley (NW Argentina), Palaeogene Andean foreland sediments are represented by a 1400-metre-thick continental succession (QLC: Quebrada de Los Colorados Formation) consisting of claystones, siltstones, sandstones, and conglomerates representing sedimentation in fluvial-alluvial plains and alluvial fan settings. To understand the main syn- and postsedimentary variables controlling the clay mineral assemblages of this succession, we have studied the fine-grained clastic sediments by X-ray diffraction and electron microscopy, along with a detailed sedimentary facies analysis, for two representative sections. In the northern section, the whole succession was sampled and analysed by XRD, whereas in the second section, a control point 15 km to the south, only the basal levels were analysed. The XRD study revealed a strong contrast in clay mineral assemblages between these two sections as well as with sections in the central Calchaquí Valley studied previously. In the northernmost part of the study area, a complete evolution from smectite at the top to R3 illite/smectite mixed-layers plus authigenic kaolinite at the bottom, through R1-type mixed-layers in between, has been recognized, indicating the attainment of late diagenesis. In contrast, the clay mineral assemblages of equivalent foreland sediments cropping out only 15 km to the south contain abundant smectite and micas, subordinate kaolinite and chlorite, and no I/S mixed-layers to the bottom of the sequence. Early diagenetic conditions were also inferred in a previous study for equivalent sediments of the QLC Formation cropping out to the south, in the central Calchaquí Valley, as smectite occurs in basal strata. Burial depths of approximately 3000 m were estimated for the QLC Formation in the central and northern Calchaquí Valley; in addition, an intermediate to slightly low geothermal gradient can be considered likely for both areas as foreland basins are regarded as hypothermal basins. Consequently, the attainment of late diagenesis in the northernmost study area cannot be explained by significant differences in burial depth nor in geothermal gradient in relation to the section 15 km to the south nor with the central Calchaquí Valley. The formation of R3 mixed-layer I/S and authigenic kaolinite in the northern study area was most likely controlled by the circulation of hot, deep fluids along the reverse faults that bounded the Calchaquí valley. These faults were active during the Cenozoic, as evidenced by the syndepositional deformation features preserved in the studied sediments. Stress could also have been a driving force in burial diagenesis at the R3 mixed-layer I/S stage in these young continental sediments.

Development and Application of a Paleomagnetic/Geochemical Method for Constraining the Timing of Burial Diagenetic Events

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

Elmore, Richard D.; Engel, Michael H.

2006-01-05

Studies of diagenesis caused by fluid migration or other events are commonly hindered by a lack of temporal control. Our results to date demonstrate that a paleomagnetic/geochemical approach can be used to date fluid migration as well as burial diagenetic events. Our principal working hypothesis is that burial diagenetic processes (e.g., maturation of organic-rich sediments and clay diagenesis) and the migration of fluids can trigger the authigenesis of magnetic mineral phases. The ages of these events can be constrained by comparing chemical remanent magnetizations (CRMs) to independently established Apparent Polar Wander Paths. Whilst geochemical (e.g. stable isotope and organic analyses)more » and petrographic studies provide important clues for establishing these relationships, the ultimate test of this hypothesis requires the application of independent dating methods to verify the paleomagnetic ages. Towards this end, we have used K-Ar dating of illitization as an alternative method for constraining the ages of magnetic mineral phases in our field areas. We have made significant progress toward understanding the origin and timing of chemical remagnetization related to burial diagenetic processes. For example, a recently completed field study documents a relationship between remagnetization and the maturation of organic matter (Blumstein et al., 2004). We have tested the hypothesized connection between clay diagenesis and remagnetization by conducting K-Ar dating of authigenic illites in units in Scotland and Montana with CRMs (e.g., Elliott et al., 2006a; Elliott et al., 2006b). We have also developed a fluid related model for alteration and remagnetization of Appalachian red beds that involves reduction and mobilization of iron phases by hydrocarbons and precipitation of authigenic hematite as a result of the introduction of meteoric fluid recharge (Cox et al., 2005). In addition, our recent studies of fluid-related CRMs along faults in Scotland provide information on the timing and origin of fluid flow events along the Moine and Great Glen faults (Parnell et al., 2004; Blumstein et al., 2005; Elmore et al., 2006).« less

Stable carbon, nitrogen and sulfur isotopes in non-carbonate fractions of cold-seep carbonates

NASA Astrophysics Data System (ADS)

Feng, Dong; Peng, Yongbo; Peckmann, Jörn; Roberts, Harry; Chen, Duofu

2017-04-01

Sulfate-driven anaerobic oxidation of methane (AOM) supports chemosynthesis-based communities and limits the release of methane from marine sediments. This process promotes the formation of carbonates close to the seafloor along continental margins. The geochemical characteristics of the carbonate minerals of these rocks are increasingly understood, questions remain about the geochemical characteristics of the non-carbonate fractions. Here, we report stable carbon, nitrogen and sulfur isotope patterns in non-carbonate fractions of seep carbonates. The authigenic carbonates were collected from three modern seep provinces (Black Sea, Gulf of Mexico, and South China Sea) and three ancient seep deposits (Marmorito, northern Italy, Miocene; SR4 deposit of the Lincoln Creek Formation and Whiskey Creek, western Washington, USA, Eocene to Oligocene). The δ13C values of non-carbonate fractions range from ˜-25‰ to -80‰ VPDB. These values indicate that fossil methane mixed with varying amounts of pelagic organic matter is the dominant source of carbon in these fractions. The relatively small offset between the δ34S signatures of the non-carbonate fractions and the respective sulfide minerals suggests that locally produced hydrogen sulfide is the main source of sulfur in seep environments. The δ15N values of the non-carbonate fractions are generally lower than the corresponding values of deep-sea sediments, suggesting that organic nitrogen is mostly of a local origin. This study reveals the potential of using δ13C, δ15N, δ34S values to discern seep and non-seep deposits. In cases where δ13Ccarbonate values are only moderately low due to mixing processes and lipid biomarkers have been erased in the course of burial, it is difficult to trace back AOM owing to the lack of other records. This problem is even more pronounced when authigenic carbonate is not available in ancient seep environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support of the deep-sea dives. Funding was provided by the NSF of China (Grants: 41422602 and 41373085) and the "Hundred Talents Program" of CAS.

Palaeoredox indicators from the organic-rich Messinian early post-evaporitic deposits of the Apennines (Central Italy)

NASA Astrophysics Data System (ADS)

Sampalmieri, G.; Iadanza, A.; Cipollari, P.; Cosentino, D.; Lo Mastro, S.

2009-04-01

Bottom redox conditions in marine and lacustrine ancient basins are often inferred by the occurrence of peculiar sedimentological structures and microfaunal assemblages. The co-occurrence, in such environments, of authigenic uranium, framboidal pyrite, barite and Fe-Mn nodules and encrustations, provides a good constraint for palaeo reconstructions. Authigenic uranium is a common constituent of hydrocarbon source rocks: it forms at the sediment-water interface under oxygen-deficient conditions and accumulates together with organic matter (OM). Its precipitation is triggered by the reduction of the soluble U6+ion in seawater to insoluble U4+. With respect to black shales, uranium content has even been used to estimate the TOC. Also authigenic pyrite forms under anoxic conditions and replaces organic matter: 1) the increase in pyrite content and in organic matter are directly correlated; 2) the size distribution of framboidal pyrite (consistent with sulphate-reducing bacterial activity) is considered a measure of redox conditions within the sediment. Barite is an authigenic mineral related to Corg content, since its organic precipitation is triggered by sulphate-reduction processes occurring in decaying OM-bearing microenvironments. Finally, also Fe-Mn oxyhydroxide are typical indicators of redox conditions. About 6 My ago the Mediterranean Sea underwent a giant event of concentration referred to as Messinian Salinity Crisis, which can be roughly subdivided into an evaporitic and a post evaporitic phase. The post evaporitic phase (p-ev; 5.61-5.33 Ma) developed in a context of humid conditions and can be further distinguished into two steps: p-ev1 (early post evaporitic phase) and p-ev2 (late post evaporitic phase). Previous works focused on pev2, which is interpreted to represent the establishment of brackish water conditions (Lago-Mare biofacies). In other respects, the palaeoenvironment of p-ev1 deposits, mostly represented by resedimented evaporitic deposits or barren laminated sediments, hasn't been thoroughly clarified yet. The aim of the present study, dealing with messinian p-ev1 deposits from Marche and Maiella successions, is to provide more details in the definition of the environment developed during the early post-evaporitic phase. Since the lamination and the absence of benthic fauna suggest the occurrence of anoxic conditions, the following indirect proxies for the detection of organic matter have been investigated: 1) sedimentary fabric and microfacies; 2) framboidal pyrite size distribution; 3) natural radioactivity (authigenic uranium values, Th/U ratios). Natural radioactivity has been achieved through gamma spectrometry, with field and laboratory specific techniques. In the Maccarone section (Marche region), p-ev1 deposits are constituted by: barren greyish shales; laminated black shales interbedded with calcitic and ankeritic horizons; thin intercalations of sandstones. Organic-matter and framboidal pyrite commonly occur. Size analysis of framboids populations yielded a mean diameter of 4÷8 m, typical of disaerobic facies. Microfacies analysis yielded also the presence of crystals aggregates of barite, up to 50 m in size, and of isolated detrital (silicilastic) crystals. Without considering γ-ray values of the volcaniclastic layer (52-65 Cps) occurring within the p-ev1 interval, black shales horizons revealed the maximum natural radioactivity (NRD of about 50 Cps) recorded inthe studied section. Lower γ-activity characterizes the calcitic layers (i.e. "Colombacci") and the ankerites. Field NRD spectra acquired on different lithologies, showed variable contributions of 238U, 232Th and 40K. Both the blue-greyish shales and the black shales are characterized by total NRD related to the three main radioelements: 40K is associated to abundant 238U content (Thppm/Uppm 1). The 238U content is primarily referable to processes of organic matter enrichment (authigenic uranium) and secondarily to the input of detrital grains. In contrast, 40K and 232Th are entirely ascribed to the clastic fraction. P-ev1 deposits from Maiella section consist of thinly-laminated grey-brownish pelites, enclosing carbonatic lenses and interrupted horizons. The pelitic fraction contains Fe-Mn-Ni encrustated micronodules. The carbonate portion is made up of locally brecciated calcitic limestones, associated with calcitic concretions and discontinuous laminae. Traces of organic matter and bitumen have been observed in thin section. Framboidal pyrite occurs both as single element and as aggregate, reaching dimensions up to about 10 m. Barite and celestite occur as well. NRD measurements yielded high values of radioactivity both in carbonates (20-63 Cps) and in terrigenous sediments (21-70 Cps). Limestones NRD-spectra showed a 238U-dominant (5 ppm in content) radioactivity. 238U is totally referable to an authigenic origin, since the γ-activity of limestones is devoid of contributions from 40K and 232Th (proxies for the detritic fraction). In the latest Messinian frame, authigenic uranium, barite, ankerite, Fe-Mn oxyhydroxide and framboidal pyrite indicate strongly palaeoredox conditions (from disaerobic to fully anoxic). In particular, with respect to NRD data, this peculiar environment is confirmed by the Th/U ratio, mostly

An application of synchrotron based x-ray tomography in palaeontology: Investigating small, three-dimensional, exceptionally preserved fossil arthropods

NASA Astrophysics Data System (ADS)

Braiden, A. K.; Orr, P. J.; Tafforeau, P.; Kearns, S. L.

2009-04-01

The fossil record is biased towards biomineralised elements (for example bones, shells and teeth) that usually retain their original three-dimensional shape. Non-biomineralised arthropods, often comprising only exoskeletal tissues such as cuticle, are comparatively rare and are usually preserved in two-dimensions (including examples inside early diagenetic concretions). Rarer still are exceptionally preserved fossils that contain replicated soft tissues; although tissues that are replicated during the initial stages of decay are usually three- dimensional and often preserved in detail, the fossil as a whole is almost invariably two dimensional. Fossil shrimp recovered from Upper Triassic (Rhaetian) unconsolidated clays at Frome, Somerset, England represent a low diversity, three-dimensionally preserved fauna, in which certain labile tissues and organs are routinely preserved in three dimensions in life position. Initial SEM analysis of exposed, internal structures in unprepared specimens confirmed the presence of musculature (replicated in calcium phosphate) and a clay infilled gut. Due to the rarity of the material, and small size of the specimens (maximum length 12mm), non-destructive synchrotron radiation, x-ray microtomography was used to determine the extent, and fidelity, of preservation of the internal anatomy. Medium resolution (voxel size of 5.3μm) and high resolution (voxel size 0.7μm) imaging was carried out on selected specimens. This confirmed high fidelity replication of the following: limited volumes of abdominal, and more rarely, cephalothoracic musculature; the hepatopancreas; gonads and, in rare cases, blood vessels and antennal glands. Notably, these are all preserved in situ enveloped by structureless, fine-grained, authigenic carbonate. This carbonate precipitated inside the cuticle, but only at the periphery of the carcass and after, or during, the initial stages of decay; it infills voids created by the initial shrinkage of abdominal musculature (possibly due to dehydration) but not those created by its subsequent decay. The digestive tract is infilled with ingested clay material. X-ray microtomographic imaging also revealed the presence of pyrite as framboids and polyhedra. The spatial distribution of framboidal pyrite, and tissue replicating calcium phosphate, indicates their precipitation is likely to be related to the original composition of the biological tissues. For example, although the pyrite framboids do not replicate tissues, they are found in association with the hepatopancreas. It is probably not coincidental that iron is especially abundant in this area in vivo. Notably, subtle differences in greyscale tone in the x-ray images are shown to correspond to authigenic phases of different composition. When calibrated against phases for which accurate compositions can be determined using other criteria (e.g. SEM-EDX), it is possible to identify the presence of particular authigenic mineral phases in such fossils.

Neocrystallization, fabrics and age of clay minerals from an exposure of the Moab Fault, Utah

USGS Publications Warehouse

Solum, J.G.; van der Pluijm, B.A.; Peacor, D.R.

2005-01-01

Pronounced changes in clay mineral assemblages are preserved along the Moab Fault (Utah). Gouge is enriched up to ???40% in 1Md illite relative to protolith, whereas altered protolith in the damage zone is enriched ???40% in illite-smectite relative to gouge and up to ???50% relative to protolith. These mineralogical changes indicate that clay gouge is formed not solely through mechanical incorporation of protolith, but also through fault-related authigenesis. The timing of mineralization is determined using 40Ar/39Ar dating of size fractions of fault rocks with varying detrital and authigenic clay content. We applied Ar dating of illite-smectite samples, as well as a newer approach that uses illite polytypes. Our analysis yields overlapping, early Paleocene ages for neoformed (1Md) gouge illite (63??2 Ma) and illite-smectite in the damage zone (60??2 Ma), which are compatible with results elsewhere. These ages represent the latest period of major fault motion, and demonstrate that the fault fabrics are not the result of recent alteration. The clay fabrics in fault rocks are poorly developed, indicating that fluids were not confined to the fault zone by preferentially oriented clays; rather we propose that fluids in the illite-rich gouge were isolated by adjacent lower permeability, illite-smectite-bearing rocks in the damage zone. ?? 2005 Elsevier Ltd. All rights reserved.

Depositional and diagenetic processes of Qa Khanna playa, North Jordan basaltic plateau, Jordan

NASA Astrophysics Data System (ADS)

Howari, F. M.; Banat, K. M.; Abu-Salha, Y. A.

2010-09-01

The present study explored mineral occurrences and sediment characteristics of playas from northern Jordan and explained depositional and diagenetic processes as reflected from bulk chemistry and sedimentary structures. Mudcracks of different sizes and shape patterns, laminations, intersediment vesicles, and bioturbation pipes are the main sedimentary structures. Plagioclase, olivine, orthopyroxene, nepheline and other opaque minerals are all of detrital origin, and are derived from the basaltic bedrocks surrounding the studied playa. Evaporites are very rare; they are represented only by trace amounts of gypsum. The identified clay minerals in the clay fraction of the studied sediments, arranged according to their decreasing abundances are palygorskite, illite, kaolinite, smectite and chlorite. The elemental abundances were tied to clay, CaCO 3 and nearby igneous rocks. The type of clay minerals, the high pH values of the studied sediments, and the considerable incorporation of Mg and K in palygorskite and illite respectively, may strongly reflect a high evaporative and alkaline environment under arid to semi-arid conditions in an ephemeral lake of the Qa Khanna. Concentrations and distributions of both major and trace elements are essentially controlled by the clay mineralogy and the calcium carbonate content; Ca is mainly incorporated in the CaCO 3, which is either generated authigenically or by aeolian deposition. Fe and K are incorporated and fixed by illite under an evaporative and alkaline environment. Mg is incorporated in palygorskite while Mn is adsorbed on various clay minerals. Sr substitutes for Ca in the aeolian CaCO 3 and its presence in the studied sediments is independent of the prevailing conditions during the playa evolution. Rb substitutes for K in illite under the prevailing chemical conditions in the studied playa.

Diagenetic controls on reservoir heterogeneity in St. Peter Sandstone, deep Michigan basin

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

Barnes, D.A.; Turmelle, T.M.; Adam, R.

1989-03-01

The St. Peter Sandstone is a highly productive gas and condensate reservoir throughout the central part of the Michigan basin. Production occurs in several intervals: a laterally continuous zone at the top of the formation typified in the Woodville, Falmouth, and Rose City fields and less continuous intervals lower in the formation typified in the Ruwe Gulf zone of the Reed City field. Porosity is not limited to hydrocarbon productive zones, however. Diagenesis has dramatically modified primary mineralogy and textures in the formation. Dominant diagenetic components are quartz, dolomite, and clay authigenic cements, extensive chemical compaction, and pervasive mineral leaching.more » Their model for sandstone diagenesis is consistent throughout the basin. Variation in the significance of these diagenetic components is strongly templated by stratigraphically predictable facies variations within the St. Peter Sandstone.« less

APPLICATIONS OF CATHODOLUMINESCENCE OF QUARTZ AND FELDSPAR TO SEDIMENTARY PETROLOGY.

USGS Publications Warehouse

Ruppert, Leslie F.

1987-01-01

Cathodoluminescence (CL), the emission of visible light during electron bombardment, was first used in sandstone petrology in the mid-1960's. CL techniques are especially useful for determining the origin and source of quartz and feldspar, two of the most common constituents in clastic rocks. CL properties of both minerals are dependent on their temperature of crystallization, duration of cooling, and/or history of deformation. Detrital quartz and feldspar are typically derived from igneous and metamorphic sources and luminesce in the visible range whereas authigenic quartz and feldspar form at low temperatures and do not luminesce. Quantification of luminescent and non-luminescent quartz and feldspar with the scanning electron microscope, electron microprobe, or a commercial CL device can allow for the determination of origin, diagenesis, and source of clastic rocks when used in conjunction with field and other petrographic analyses.

The impact of sedimentary coatings on the diagenetic Nd flux

NASA Astrophysics Data System (ADS)

Abbott, April N.; Haley, Brian A.; McManus, James

2016-09-01

Because ocean circulation impacts global heat transport, understanding the relationship between deep ocean circulation and climate is important for predicting the ocean's role in climate change. A common approach to reconstruct ocean circulation patterns employs the neodymium isotope compositions of authigenic phases recovered from marine sediments. In this approach, mild chemical extractions of these phases is thought to yield information regarding the εNd of the bottom waters that are in contact with the underlying sediment package. However, recent pore fluid studies present evidence for neodymium cycling within the upper portions of the marine sediment package that drives a significant benthic flux of neodymium to the ocean. This internal sedimentary cycling has the potential to obfuscate any relationship between the neodymium signature recovered from the authigenic coating and the overlying neodymium signature of the seawater. For this manuscript, we present sedimentary leach results from three sites on the Oregon margin in the northeast Pacific Ocean. Our goal is to examine the potential mechanisms controlling the exchange of Nd between the sedimentary package and the overlying water column, as well as the relationship between the εNd composition of authigenic sedimentary coatings and that of the pore fluid. In our comparison of the neodymium concentrations and isotope compositions from the total sediment, sediment leachates, and pore fluid we find that the leachable components account for about half of the total solid-phase Nd, therefore representing a significant reservoir of reactive Nd within the sediment package. Based on these and other data, we propose that sediment diagenesis determines the εNd of the pore fluid, which in turn controls the εNd of the bottom water. Consistent with this notion, despite having 1 to 2 orders of magnitude greater Nd concentration than the bottom water, the pore fluid is still <0.001% of the total Nd reservoir in the upper sediment column. Therefore, the pore fluid reservoir is too small to maintain a unique signature, and instead must be controlled by the larger reservoir of Nd in the reactive coatings. In addition, to achieve mass balance, we find it necessary to invoke a cryptic radiogenic (εNd of +10) trace mineral source of neodymium within the upper sediment column at our sites. When present, this cryptic trace metal results in more radiogenic pore fluid.

Anomalous concentrations of zinc and copper in highmoor peat bog, southeast coast of Lake Baikal

NASA Astrophysics Data System (ADS)

Bobrov, V. A.; Bogush, A. A.; Leonova, G. A.; Krasnobaev, V. A.; Anoshin, G. N.

2011-08-01

When examining the peat deposit discovered in Vydrinaya bog, South Baikal region, the authors encountered anomalous Zn and Cu concentrations for highmoors being up to 600-500 ppm on a dry matter basis in the Early Holocene beds (360-440 cm) formed 11 000-8500 years ago. It has been demonstrated that Zn and Cu are present inside the plant cells of peat moss in the form of authigenic sulfide minerals of micron size. Apart from Zn and Cu, native Ag particles (5-7 um) have been encountered in the peat of the Vydrinaya bog at a depth of 390-410 cm; these particles formed inside the organic matter of the plasma membrane of peat moss containing Ca, Al, S, and Cu. This study suggests probable patterns of the formation of zinc sulfides, copper sulfides, and native silver in peat moss. The results obtained indicate that biogenic mineral formation plays a significant role in this system, which is a very important argument in the discussion on the ore genesis, in which physicochemical processes are normally favored, while the role of living matter is quite frequently disregarded.

Mineralogy and sedimentology of the Miocene Göcenoluk borate deposit, Kırka district, western Anatolia, Turkey

NASA Astrophysics Data System (ADS)

García-Veigas, Javier; Helvacı, Cahit

2013-05-01

The Miocene boratiferous district of Kırka, in western Anatolia (Turkey), is the most important Na-borate (borax) resource in the world. Two separate deposits in the Kırka district are located near the villages of Sarıkaya and Göcenoluk (Eskişehir Province). Borax is intensively exploited in open-pit mines in the Sarıkaya deposit while only small quarries of colemanite are known in the Göcenoluk deposit. Recent exploratory drilling in the Göcenoluk area intersected a thick succession of dolostones, tuffs and three borate-bearing units (Lower, Intermediate and Upper Borate Units). In them, the most abundant borate mineral is ulexite (Ca-Na-borate) passing at depth to probertite. Borax (Na-borate) is only present in the Intermediate Borate Unit. Minor amounts of colemanite (Ca-borate) and hydroboracite (Ca-Mg-borate) occur at the base, and/or top, of each mineralized unit. Pyroclastic layers within the borate units show intense alteration by alkaline, boron-bearing waters and formation of diagenetic clay minerals (smectites), zeolites (analcime) and borosilicates (searlesite). The Göcenoluk succession is interpreted as a shallow, ephemeral, alkaline lake deposit in which carbonates formed as stromatolites and travertines. Borate precipitation in the Göcenoluk area took place interstitially within muddy and carbonate sediments in a lateral progression from marginal Ca-borates towards Na-Ca-borates and rarely to Na-borates in the center of the lake. Authigenic silicate mineral distribution shows parallel changes toward the center of the lake that reflect increasing pH gradient.

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.

Formation of Authigenic Sulfates in Cold Dry Glaciers: Terrestrial and Planetary Implications of Sublimites

NASA Astrophysics Data System (ADS)

Massé, M.; Rondeau, B.; Ginot, P.; Schmitt, B.; Bourgeois, O.; Mitri, G.

2015-12-01

Salts are common on planetary surfaces, and sulfates have been widely observed on Earth, Mars (Gendrin et al., 2005) and on some of Jupiter's and Saturn's icy moons like Europa (Dalton et al., 2007). These minerals can form under a wide range of conditions, and the determination of sulfate formation processes can provide key elements for deciphering past planetary surface conditions. Most terrestrial sulfates form as evaporites in warm environments with high water/rock ratios, but these conditions are rarely encountered on other planets. Here we describe the formation of cryogenic sulfates in an extreme cold and dry environment: the Guanaco glacier located in the Chilean Andes (Fig.1a, Rabatel et al., 2011). Field analyses reveal that it is a cold-based glacier, its surface temperature remains below 0°C throughout the year, and ablation occurs mostly by sublimation. Ablation creates ice cliffs punctuated of pluricentimetric whitish, tapered crystals embedded in the ice (Fig.1b, c). By Raman and chemistry, they proved to be gypsum, covered by micrometric crystals of jarosite, halotrichite and native sulfur. The euhedral morphology of these soft minerals indicates that they are neoformed and have not been transported in the ice. This is supported by the absence of gypsum crystals in ice cores drilled through the glacier. We infer that the crystallization thus occurred at the glacier surface during ice sublimation and does not involve liquid water. To distinguish this original salt formation process from the more common evaporites, we name these minerals "sublimites". Though this formation process is uncommon and generates minor quantities of sulfates on Earth, it may be dominant on other bodies in the Solar System where sublimation is effective. Examples of planetary sublimites may include gypsum on the North Polar Cap of Mars (Massé et al., 2012), and other sulfates on icy moons where sublimation has been observed (Howard et al., 2008).

The origin and implications of clay minerals from Yellowknife Bay, Gale crater, Mars†

PubMed Central

Bristow, Thomas F.; Bish, David L.; Vaniman, David T.; Morris, Richard V.; Blake, David F.; Grotzinger, John P.; Rampe, Elizabeth B.; Crisp, Joy A.; Achilles, Cherie N.; Ming, Doug W.; Ehlmann, Bethany L.; King, Penelope L.; Bridges, John C.; Eigenbrode, Jennifer L.; Sumner, Dawn Y.; Chipera, Steve J.; Moorokian, John Michael; Treiman, Allan H.; Morrison, Shaunna M.; Downs, Robert T.; Farmer, Jack D.; Marais, David Des; Sarrazin, Philippe; Floyd, Melissa M.; Mischna, Michael A.; McAdam, Amy C.

2016-01-01

The Mars Science Laboratory (MSL) rover Curiosity has documented a section of fluvio-lacustrine strata at Yellowknife Bay (YKB), an embayment on the floor of Gale crater, approximately 500 m east of the Bradbury landing site. X-ray diffraction (XRD) data and evolved gas analysis (EGA) data from the CheMin and SAM instruments show that two powdered mudstone samples (named John Klein and Cumberland) drilled from the Sheepbed member of this succession contain up to ~20 wt% clay minerals. A trioctahedral smectite, likely a ferrian saponite, is the only clay mineral phase detected in these samples. Smectites of the two samples exhibit different 001 spacing under the low partial pressures of H2O inside the CheMin instrument (relative humidity <1%). Smectite interlayers in John Klein collapsed sometime between clay mineral formation and the time of analysis to a basal spacing of 10 Å, but largely remain open in the Cumberland sample with a basal spacing of ~13.2 Å. Partial intercalation of Cumberland smectites by metal-hydroxyl groups, a common process in certain pedogenic and lacustrine settings on Earth, is our favored explanation for these differences. The relatively low abundances of olivine and enriched levels of magnetite in the Sheepbed mudstone, when compared with regional basalt compositions derived from orbital data, suggest that clay minerals formed with magnetite in situ via aqueous alteration of olivine. Mass-balance calculations are permissive of such a reaction. Moreover, the Sheepbed mudstone mineral assemblage is consistent with minimal inputs of detrital clay minerals from the crater walls and rim. Early diagenetic fabrics suggest clay mineral formation prior to lithification. Thermodynamic modeling indicates that the production of authigenic magnetite and saponite at surficial temperatures requires a moderate supply of oxidants, allowing circum-neutral pH. The kinetics of olivine alteration suggest the presence of fluids for thousands to hundreds of thousands of years. Mineralogical evidence of the persistence of benign aqueous conditions at YKB for extended periods indicates a potentially habitable environment where life could establish itself. Mediated oxidation of Fe2+ in olivine to Fe3+ in magnetite, and perhaps in smectites provided a potential energy source for organisms. PMID:28798492

The origin and implications of clay minerals from Yellowknife Bay, Gale crater, Mars.

PubMed

Bristow, Thomas F; Bish, David L; Vaniman, David T; Morris, Richard V; Blake, David F; Grotzinger, John P; Rampe, Elizabeth B; Crisp, Joy A; Achilles, Cherie N; Ming, Doug W; Ehlmann, Bethany L; King, Penelope L; Bridges, John C; Eigenbrode, Jennifer L; Sumner, Dawn Y; Chipera, Steve J; Moorokian, John Michael; Treiman, Allan H; Morrison, Shaunna M; Downs, Robert T; Farmer, Jack D; Marais, David Des; Sarrazin, Philippe; Floyd, Melissa M; Mischna, Michael A; McAdam, Amy C

2015-04-01

The Mars Science Laboratory (MSL) rover Curiosity has documented a section of fluvio-lacustrine strata at Yellowknife Bay (YKB), an embayment on the floor of Gale crater, approximately 500 m east of the Bradbury landing site. X-ray diffraction (XRD) data and evolved gas analysis (EGA) data from the CheMin and SAM instruments show that two powdered mudstone samples (named John Klein and Cumberland) drilled from the Sheepbed member of this succession contain up to ~20 wt% clay minerals. A trioctahedral smectite, likely a ferrian saponite, is the only clay mineral phase detected in these samples. Smectites of the two samples exhibit different 001 spacing under the low partial pressures of H 2 O inside the CheMin instrument (relative humidity <1%). Smectite interlayers in John Klein collapsed sometime between clay mineral formation and the time of analysis to a basal spacing of 10 Å, but largely remain open in the Cumberland sample with a basal spacing of ~13.2 Å. Partial intercalation of Cumberland smectites by metal-hydroxyl groups, a common process in certain pedogenic and lacustrine settings on Earth, is our favored explanation for these differences. The relatively low abundances of olivine and enriched levels of magnetite in the Sheepbed mudstone, when compared with regional basalt compositions derived from orbital data, suggest that clay minerals formed with magnetite in situ via aqueous alteration of olivine. Mass-balance calculations are permissive of such a reaction. Moreover, the Sheepbed mudstone mineral assemblage is consistent with minimal inputs of detrital clay minerals from the crater walls and rim. Early diagenetic fabrics suggest clay mineral formation prior to lithification. Thermodynamic modeling indicates that the production of authigenic magnetite and saponite at surficial temperatures requires a moderate supply of oxidants, allowing circum-neutral pH. The kinetics of olivine alteration suggest the presence of fluids for thousands to hundreds of thousands of years. Mineralogical evidence of the persistence of benign aqueous conditions at YKB for extended periods indicates a potentially habitable environment where life could establish itself. Mediated oxidation of Fe 2+ in olivine to Fe 3+ in magnetite, and perhaps in smectites provided a potential energy source for organisms.

Organic matter diagenesis as the key to a unifying theory for the genesis of tabular uranium-vanadium deposits in the Morrison Formation, Colorado Plateau

USGS Publications Warehouse

Hansley, P.L.; Spirakis, C.S.

1992-01-01

Interstitial, epigenetic amorphous organic matter is intimately associated with uranium in the Grants uranium region and is considered essential to genetic models for these deposits. In contrast, uranium minerals are intimately associated with authigenic vanadium chlorite and vanadium oxides in amorphous organic matter-poor ores of the Slick Rock and Henry Mountains mining districts and therefore, in some genetic models amorphous organic matter is not considered crucial to the formation of these deposits. Differences in organic matter content can be explained by recognizing that amorphous organic matter-poor deposits have been subjected to more advanced stages of diagenesis than amorphous organic matter-rich deposits. Evidence that amorphous organic matter was involved in the genesis of organic matter-poor, as well as organic matter-rich, deposits is described. -from Authors

The spatial distribution of major and trace elements in the surface sediments from the northeastern Beibu Gulf, South China Sea

NASA Astrophysics Data System (ADS)

Ge, Q.; Xue, Z. G.

2017-12-01

Major and trace elements contents and grain size were analyzed for surface sediments retrieved from the northeastern Beibu (Tonkin) Gulf. The study area was divided into four zones: Zone I locates in the northeastern coastal area of the gulf, which received large amount of the fluvial materials from local rivers; Zone II locates in the center of the study area, where surface sediments is from multiple sources; Zone III locates in the Qiongzhou Strait, which is dominated by material from the Pearl River and Hainan Island; Zone IV locates in the southwest of the study area, and the sediments mainly originated from the Red River. Statistical analyses of sediment geochemical characteristics reveal that grain size is the leading factor for elementary distribution, which is also influenced by hydrodynamics, mineral composition of terrigenous sediments, anthropogenic activity, and authigenic components.

REY-Th-U Solute Dynamics in the Critical Zone: Combined Influence of Chemical Weathering, Atmospheric Deposit Leaching, and Vegetation Cycling (Mule Hole Watershed, South India)

NASA Astrophysics Data System (ADS)

Braun, Jean-Jacques; Riotte, Jean; Battacharya, Shrema; Violette, Aurélie; Prunier, Jonathan; Bouvier, Vincent; Candaudap, Frédéric; Maréchal, Jean-Christophe; Ruiz, Laurent; Panda, Smruthi Rekha; Subramanian, S.

2017-12-01

The source and proportion of REY, Th, and U exported by groundwater and by the ephemeral stream along with the elemental proportions passing through vegetation have been assessed in the subhumid tropical forested CZO of Mule Hole, Southern India. The study relies on a pluriannual hydrogeochemical monitoring combined with a hydrological model. The significant difference between the soil input (SI) and output (SO) solute fluxes (mmol/km2/yr) of LREE (SI-SO = 13,250-1,500), HREE (1,930-235), Th (64-12), and U (63-25) indicates a strong uptake by roots carried by canopy and forest floor processes. The contribution of atmospheric dust leaching can reach about 60% of LREE and 80% of HREE. At the watershed scale, the U solute flux exported by groundwater (180 mmol/km2/yr) mainly originates from the breakdown of primary U-bearing accessory minerals and dominates by a factor of 25 the stream flux. The precipitation of authigenic U-bearing phases and adsorption onto Fe-oxides and oxyhydroxides play a significant role for limiting the U mobility. In the groundwater, the plagioclase chemical weathering is efficiently traced by the positive Eu-anomaly. The very low (REY) to nil (Th) contents are explained by the precipitation of authigenic phases. In the stream flow, dominated by the overland flow (87% of the yearly stream flow), the solute exports (in mmol/km2/yr) of REY (1,080 for LREE and 160 for HREE) and of Th (14) dominate those by groundwater. Their mobility is enhanced by chelation with organic ligands produced by forest floor and canopy processes.

Understanding Potassium Isotope Fractionation During Authigenic Clay Formation in Pore-fluid Systems: Implications for the δ41K of Seawater

NASA Astrophysics Data System (ADS)

Santiago Ramos, D. P.; Higgins, J. A.

2015-12-01

Improvements in analytical precision on the latest generation multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS) have revealed a ~2‰ range in the ratios of stable potassium isotopes (41K/39K) in terrestrial materials (Morgan et al., in prep). Preliminary measurements of δ41K values indicate that seawater and silicate rocks are isotopically distinct reservoirs, with seawater having a δ41K value that is ~0.5‰ heavier than the silicate average (-0.5‰; Morgan et al., in prep). The heavy δ41K character of seawater might be related to 1) an isotopically enriched input flux (rivers and high-temperature hydrothermal reactions); or 2) a 41K-depleted sink associated with authigenic clay formation during low-temperature alteration of volcanic rocks. Here we present measurements of the δ41K values of pore-fluids from ODP site 1052 in order to constrain potassium isotope fractionation during secondary clay formation. We find that δ41K values and K concentrations both decline systematically with depth. Results from 1-D diffusion-advection-reaction modeling of potassium concentrations and isotopic compositions indicate that fractionation of K isotopes during diffusion (Bourg et al., 2010) can explain all of the change in δ41K values of the pore-fluid with depth. Although the size of the K sink at site 1052 is a trivial fraction of the global K sink in clay minerals, our results suggest that diffusive fractionation of K isotopes in shallow pore-fluids may be, in part, responsible for the elevated δ41K value of seawater.

The Effect of Authigenic Phyllosilicate Growth on the Mechanical Behaviour of Upper Crustal Faults

NASA Astrophysics Data System (ADS)

Evans, S.; Holdsworth, R.; Imber, J.; Marco, S.; Weinberger, R.; De Paola, N.

2014-12-01

Deformation at shallow crustal depths is dominated by brittle processes, but it is increasingly recognised that diffusive mass transfer (DMT) processes and "ductile" folding also play a significant role in fault zone development. We present data from exhumed sections (<5 km depth) of the southern Dead Sea Fault System, Israel, an active continental transform fault that has accumulated 105 km of sinistral displacement since the Miocene. The faults juxtapose various wall rock lithologies (crystalline basement, carbonate and clastic cover), but the studied sections all have phyllosilicate-rich fault cores. Damage zones show a range of deformation mechanisms including pulverisation, pressure-solution and cataclasis. Our results show that fault cores comprise three distinct types of fault gouge (alongside coarser-grained cataclasite): cataclastic gouge that is mineralogically similar to wall rock compositions; authigenic gouge that is dominated by Mg-rich smectite not present in adjacent formations; and mechanically entrained, folded shale gouge that is almost identical in mineralogy to a local shale protolith. Microstructural observations suggest authigenic gouge is the result of DMT processes, following an earlier phase of gouge formation through microfracturing and cataclasis. The low abundance of carbonate within fault cores suggests its dissolution is a contributing factor in authigenic smectite precipitation. Such mineralogical transformations may lead to significant changes in the frictional properties of fault zones, from materials of relatively high frictional strength (quartz, feldspars, dolomite, where μ = 0.6 - 0.85) to those with much lower frictional strengths, such as smectite (where μ can be as low as 0.15). We demonstrate how the physical properties of faults may evolve over time when conditions allow precipitation of weak-phases in addition to brittle deformation, which may facilitate ingress of fluid into fault cores and enhance phyllosilicate development. The presence of both pulverisation textures and microfolds suggests interaction of these deformation styles may lead to changes in overall fault behaviour, from velocity-weakening and seismogenic where brittle processes dominate, to velocity-strengthening and aseismic when sufficient weak material has accumulated.

Uranium-series dated authigenic carbonates and Acheulian sites in southern Egypt

NASA Technical Reports Server (NTRS)

Szabo, B. J.; Mchugh, W. P.; Schaber, G. G.; Breed, C. S.; Haynes, C. V., Jr.

1989-01-01

Field investigations of aggraded paleovalleys, which were identified in southern Egypt using SIR, are discussed. Acheulian artifacts were found in authigenic carbonate deposites along the edges of the paleovalleys. Uranium series dating of 25 carbonate samples shows that widespread carbonate deposition in the area occurred about 45, 141, and 212 thousand years ago. Analysis of the carbonate suggests that the deposition may be related to late Pleistocene humid climates that facilitated human settlement in the region.

Distribution, microfabric, and geochemical characteristics of siliceous rocks in central orogenic belt, China: implications for a hydrothermal sedimentation model.

PubMed

Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch

2014-01-01

Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian--Ordovician, and Carboniferous--Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08-95.30%), Ba (42.45-503.0 ppm), and ΣREE (3.28-19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb) N, and (La/Ce) N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics.

Distribution, Microfabric, and Geochemical Characteristics of Siliceous Rocks in Central Orogenic Belt, China: Implications for a Hydrothermal Sedimentation Model

PubMed Central

Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch.

2014-01-01

Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian—Ordovician, and Carboniferous—Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08–95.30%), Ba (42.45–503.0 ppm), and ΣREE (3.28–19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb)N, and (La/Ce)N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics. PMID:25140349

Magnetic Mineralogy as Indicator of dry Conditions in Lacustrine Sediments From Santa María del Oro, Nayarit, Central Mexico

NASA Astrophysics Data System (ADS)

Ortega, B.; Vazquez, G.; Rodriguez, A.

2007-05-01

Combined magnetic and geochemical analysis were conducted on laminated sediments from Santa Maria del Oro, a crater lake in Nayarit (Mexico), to build up a model of paleoenvironmental conditions for the late Holocene. The occurrence of a severe drought at the end of the archeological Classic period (100 - 900 AD) has been documented in sites of central Mexico (Zirahuen lake and Lerma basin), the Gulf of Mexico coast (Los Tuxtlas) and the Yucatan peninsula. The effects of this climatic event are considered to have stressed the social and political situation in the Yucatan area and other sites in Mesoamerica, and resulted in the "collapse" of the Maya civilization. Santa Maria del Oro sediments between ca. 600 - 1140 AD are characterized by repeated sequences of ocher silt laminae with high inorganic carbon content, authigenic siderite, and low concentration of SD magnetic minerals, followed upward by an increase of concentrations of fine grained SD and SP ferrimagnetic minerals in brown silt laminae. This sequence is considered to represent dissolution-precipitation cycles of magnetic minerals in low erosion, concentrated waters and anoxic water-sediment interface environments. Dissolution of magnetite occurs in reductive conditions, which are considered as warmer and dryer periods. Above the ocher silt, precipitation of fine grained magnetite occurs when conditions change to oxic environments. Ostracode C and O isotopy document a negative precipitation/evaporation balance during this time period.

Diagenetic mineralization in Pennsylvanian coals from Indiana, USA: 13C/12C and 18O/16O implications for cleat origin and coalbed methane generation

USGS Publications Warehouse

Solano-Acosta, W.; Schimmelmann, A.; Mastalerz, Maria; Arango, I.

2008-01-01

Cleats and fractures in southwestern Indiana coal seams are often filled with authigenic kaolinite and/or calcite. Carbon- and oxygen-stable isotope ratios of kaolinite, calcite, and coalbed CO2 were evaluated in combination with measured values and published estimates of ??18O of coalbed paleowaters that had been present at the time of mineralization. ??18Omineral and ??18Owater values jointly constrain the paleotemperature of mineralization. The isotopic evidence and the thermal and tectonic history of this part of the Illinois Basin led to the conclusion that maximum burial and heat-sterilization of coal seams approximately 272??Ma ago was followed by advective heat redistribution and concurrent precipitation of kaolinite in cleats at a burial depth of < 1600??m at ??? 78 ?? 5????C. Post-Paleozoic uplift, the development of a second generation of cleats, and subsequent precipitation of calcite occurred at shallower burial depth between ??? 500 to ??? 1300??m at a lower temperature of 43 ?? 6????C. The available paleowater in coalbeds was likely ocean water and/or tropical meteoric water with a ??18Owater ??? - 1.25??? versus VSMOW. Inoculation of coalbeds with methanogenic CO2-reducing microbes occurred at an even later time, because modern microbially influenced 13C-enriched coalbed CO2 (i.e., the isotopically fractionated residue of microbial CO2 reduction) is out of isotopic equilibrium with 13C-depleted calcite in cleats. ?? 2007 Elsevier B.V. All rights reserved.

Authigenic chlorite as a controlling factor in the exploration of Turonian/Coniacian turbidites in the Santos Basin

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

Porsche, E.; Lopes de Freitas, E.

1996-08-01

Upper Turonian/Coniacian and Campanian turbidites are major targets for petroleum exploration in the Santos Basin, southeastern Brazil. They occur between 140 and 1000 m of present water depth, are buried at about 4500 m, and reach thickness of up to 60 m. The main reservoir facies is composed of unstratified, fine to very fine grained, poorly sorted sandstones, which framework is compositionally immature, including a high proportion of feldspars and volcanic rock fragments. Early coating of grains by authigenic chlorite inhibited pressure solution and quartz cementation in the reservoir. This diagenetic characteristic allowed important preservation of primary porosity (>20%) inmore » the reservoir; nevertheless its permeability never exceeds 30 ml. The study of sedimentary facies and related depositional processes has been conducted to predict the distribution of petroleum-bearing turbidites throughout the Santos Basin; this comprises a major challenge for the petroleum exploration in this important Brazilian exploration frontier.« less

Reconstruction of deglacial Antarctic Intermediate Water variations in the subtropical North Atlantic

NASA Astrophysics Data System (ADS)

Xie, R. C.; Marcantonio, F.; Schmidt, M. W.

2012-12-01

Understanding intermediate water circulation across the last deglaciation is critical in assessing the role of oceanic heat transport associated with Atlantic Meridional Overturning Circulation (AMOC) variability across abrupt climate events. Abrupt changes in the northward flow of Antarctic Intermediate Water (AAIW) associated with AMOC reduction during the Younger Dryas (YD) and Heinrich Event 1 (H1) have been hypothesized, suggesting a potential connection between the Southern Ocean and high-latitude North Atlantic climate change. However, controversy persists as to whether the northward flow of AAIW is stronger or weaker during these abrupt cold events. One school maintains that there is an increase in the northward penetration of AAIW associated with weaker AMOC during both the YD and H1 cold events (e.g., [1-2]). However, each of these previous studies analyzed sediment cores retrieved from depths deeper than the modern depth range of AAIW (500-1100 m in the tropical and subtropical North Atlantic). Another school comes to the opposite conclusion, namely that there is a weakening of AAIW at least during one of the deglacial events (e.g., [3-4]). Here, we reconstruct deglacial AAIW variations using authigenic Nd isotope ratios from sediment recovered from core VM12-107 (11.33°N, 66.63°W; 1079 m) in the Southern Caribbean Sea. VM12-107 lies at the boundary between modern AAIW and modern upper NADW and thus is ideal for investigating the shoaling/deepening of the competing water masses as well as the variations of AAIW across abrupt climate events during the last deglaciation. We measured authigenic Nd isotope compositions in three different fractions in core VM12-107: the Fe-Mn oxyhydroxide leachate of the bulk sediment, the uncleaned planktonic foraminifera (mixed species), and fish debris wherever possible. Preliminary authigenic Nd isotope results from the Fe-Mn leachate show little variability in the ɛNd values, ranging from -9.6 to -10.6, during the last deglaciation. No discernable long-term trend is suggested. The small variation in authigenic ɛNd values may suggest little change in the northward penetration of AAIW at our study site during the last deglaciation. On the other hand, shoaling of the glacial analogue of NADW (i.e., Glacial North Atlantic Intermediate Water), with a more radiogenic ɛNd signature during the YD and H1, can also explain our authigenic ɛNd record from the Fe-Mn leachates. Comparing our authigenic Nd isotope record with those recently published from the Florida Straits [4] and those from the Tobago Basin [1], we propose that sediment cores retrieved from depths below the modern AAIW depth range are not suitable in tracing deglacial AAIW variability. Because the Nd isotope record from authigenic Fe-Mn leachate fraction can be biased by excess leaching of the detrital fraction of the sediment, ɛNd values from uncleaned planktonic foraminifera (mixed species) and fish debris will be presented to test the Nd isotope record from authigenic Fe-Mn leachates. [1] Pahnke et al. (2008) Nature Geoscience 1, 870-874 [2] Thornalley et al. (2011) Science 331(6014), 202-205; [3] Came et al. (2008) Paleoceanography 23, PA1217; [4] Xie et al. (in press) Paleoceanography, doi:10.1029/2012PA002337

Geological Characteristics of Active Methane Expulsion In Accretionary Prism Kaoping Slope Off SW Taiwan

NASA Astrophysics Data System (ADS)

Huang, C.; Chien, C.; Yang, T. F.; Lin, S.

2005-12-01

The Kaoping Slope off SW Taiwan represents the syn-collision accretionary prism characterized by active NW-trending folding - thrusting structures and high sedimentation rate favoring the formation of gas hydrate. For an assessment of gas hydrate potential in the Kaoping Slope off SW Taiwan, sedimentology, paleontology and geochemistry in box cores and piston cores were studied. BSRs are commonly found in seismic profiles in 400-600 m below seafloor of water depth 2500-1000 m. Active expulsions of methane were found along active thrust faults where sulfate/methane interface could be as shallow as 30 cm and the methane concentration of dissolved gases in bottom water and in pore-space of drilled core samples could be three-four order higher than the normal marine environments. Occurrences of authigenic carbonate and elongated pyrite tubes are correlated with shallow SMI depth and high methane content in bottom water and pore-space of sediment cores. Authigenic carbonates were found in seafloor surface and in 20-25 meters below seafloor. The authigenic carbonate nodules are characterized by irregular shape, whitish color, no visible microfossil, containing native sulfur, pyrites, gypsum, small open spaces, and very depleted carbon isotope (-54 ~ -43 per mil PDB). Tiny native sulfur and gypsum crystals were commonly found either on surface of foraminiferal tests and elongated pyrite tubes or in the authigenic carbonate nodules. Morphological measurements of elongated pyrite tubes show that they could represent pseudomorphs after three types of Pogonophora tube worm. Foraminifers are commonly filled by rhomboidal pyrites or cemented by pyrite crystals. Normal marine benthic foraminifers predominated by calcareous tests of slope fauna are associated with authigenic carbonate nodules in the study area, suggesting no major geochemistry effect on distribution of benthic foraminifers. Integrating sedimentology, paleontology and geochemistry characters, there could be high potential to have gas hydrate in the accretionary prism off SW Taiwan.

Post-impact alteration of the Manson impact structure

NASA Technical Reports Server (NTRS)

Crossey, L. J.; Mccarville, P.

1993-01-01

Core materials from the Manson impact site (Manson, Iowa) are examined in order to evaluate post-impact alteration processes. Diagenetic interpretation of post-impact events is based on petrologic, mineralogic, and geochemical investigation of core materials including the following: target strata, disturbed and disrupted strata, ejecta, breccias, microbreccias, and impact melt. The diagenetic study utilizes research cores obtained by the continental scientific drilling project (CSDP) at the Manson structure, as well as core and cuttings of related materials. Samples include impactites (breccias, microbreccias, and melt material), crater fill material (sedimentary clast breccias), disturbed and disrupted target rocks, and reference target material (Amoco Eisheid No. 1 materials). The study of multiple cores will permit development of a regional picture of post-impact thermal history. The specific objectives are as follows: (1) provide a detailed description of authigenic and alteration mineralogy from diverse lithologies encountered in research drill cores at the Manson impact structure, and (2) identify and relate significant post-impact mineral alteration to post-impact thermal regime (extent and duration). Results will provide mineralogical and geochemical constraints on models for post-impact processes including the following: infilling of the crater depression; cooling and hydrothermal alteration of melt rocks; and subsequent long-term, low-temperature alteration of target rocks, breccias, and melt rocks. Preliminary petrologic and x-ray diffraction examination of fracture linings and void fillings from research core M1 indicate the presence of quartz, chlorite, mixed-layer clays, gypsum/anhydrite, calcite, and minor pyrite.

Isotopic studies of authigenic sulfides, silicates and carbonates, and calcite and pyrite veinlets in the Creede Formation, San Juan Mountains, Southwest Colorado

USGS Publications Warehouse

Bethke, Philip M.; Rye, Robert O.; Finkelstein, David B.

2000-01-01

Sulfur isotope analysis of authigenic pyrite in the Creede Formation documents its precipitation by the reaction between iron in the volcaniclastic sediments and H2S formed through bacteriogenic reduction of sulfate added to the lake during and immediately following repeated volcanic eruptions during sedimentation. Pyrite veinlets in the underlying Snowshoe Mountain Tuff were formed by the percolation of H2S-bearing pore waters into fractures in the tuff. Conventional analyses of bulk samples of authigenic pyrite range from -20.4% to 34.5% essentially equivalent to the range of -30% to 40% determined using SHRIMP microprobe techniques. Conventional analyses of bulk samples of pyrite from veinlets in the Snowshow Mountain Tiff range from -3.5% to 17.6% much more limited than the ranges of -23% to 111% and -15.6% to 67.0% determined by SHRIMP and laser ablation microbeam techniques, respectively. The extreme range of δ34S for the veinlets is interpreted to be the result of continued fractionation of the already 34S-depleted pore water. Oxygen isotope analysis of authigenic smectite, kaolinite, and K-feldspar together with fluid-inclusion temperatures and oxygen isotope analysis of calcite coexisting with kaolinite indicate that the smectites formed early during burial diagenesis, in accord with petrographic observations. The 40Ar/39Ar dating of K-feldspar, concorfance of K-feldspar, kaolinite, and calcite δ18O values, and fluid-inclusion temperatures in calcite, indicate that the sediments at core hole CCM-1 were subjected to a hydrothermal event at 17.6 Ma. The minerals formed oxygen-shifted meteoric waters with δ18O values of ~-9% Smecities at CCM-1 at least partially exchanged with these waters. Carbon and oxygen isotope analysis of authigenic calcites in the Creede Formation show that they formed over a wide range of temperatures from fluids having a wide range of isotopic composition, presumably over an extended period time. Some of the cements apparently formed very late from unexchanged meteoric water. Concretions and possibly some cements at CCM-1 appear to have exchanged with the 17.6 Ma oxygen-shifted hydrothermal fluids. Such exchange is consistent with evidence that lacustrine carbonates at CCM-1 exchanged with low 18O waters, whereas those at CCM-2 underwent little, if any, exchange. The δ13C-δ18O values for calcite veinlets in the Creede Formation are similar to those for authegenic calcites. Fluid-inclusion temperatures and δ18O indicate that some were deposited during the 17.6 Ma hydrothermal event and others from unexchanged meteoric water at a later date. The isotope studies confirm that part of the model of Rye et al., proposing that the barites in the southern end of the Creede Mining District were formed by mixing of the Creede hydrotermal system with Lake Creede pore of lake waters. The silicate and carbonate isotope data indicate that the pores of the Creede Formation were occupied by at least three isotopically distinct water since the time of deposition. The original pore fluids were probably shifted to lower δ18O values during burial diagensis as a result of the hydrolysis of the volcanic glass to for smectites and other hydrous silicates. During or prior to a 17.6 Ma hydrothermal event in the vicinity of CCM-1, the Creede Formation was flushed with oxygen-shifted meteoric water, possibly related to the breaching of the east side of the caldera wall sometime between 20 and 22 Ma. Later, the Creede Formation was again flushed, this time with unexchanged meteoric water with δD-δ18O values of present-day waters, possibly during the incision of the Rio Grande drainage during uplifting of the southern Rocky Mountains beginning about 5 Ma.

Cleats and their relation to geologic lineaments and coalbed methane potential in Pennsylvanian coals in Indiana

USGS Publications Warehouse

Solano-Acosta, W.; Mastalerz, Maria; Schimmelmann, A.

2007-01-01

Cleats and fractures in Pennsylvanian coals in southwestern Indiana were described, statistically analyzed, and subsequently interpreted in terms of their origin, relation to geologic lineaments, and significance for coal permeability and coalbed gas generation and storage. These cleats can be interpreted as the result of superimposed endogenic and exogenic processes. Endogenic processes are associated with coalification (i.e., matrix dehydration and shrinkage), while exogenic processes are mainly associated with larger-scale phenomena, such as tectonic stress. At least two distinct generations of cleats were identified on the basis of field reconnaissance and microscopic study: a first generation of cleats that developed early on during coalification and a second generation that cuts through the previous one at an angle that mimics the orientation of the present-day stress field. The observed parallelism between early-formed cleats and mapped lineaments suggests a well-established tectonic control during early cleat formation. Authigenic minerals filling early cleats represent the vestiges of once open hydrologic regimes. The second generation of cleats is characterized by less prominent features (i.e., smaller apertures) with a much less pronounced occurrence of authigenic mineralization. Our findings suggest a multistage development of cleats that resulted from tectonic stress regimes that changed orientation during coalification and basin evolution. The coals studied are characterized by a macrocleat distribution similar to that of well-developed coalbed methane basins (e.g., Black Warrior Basin, Alabama). Scatter plots and regression analyses of meso- and microcleats reveal a power-law distribution between spacing and cleat aperture. The same distribution was observed for fractures at microscopic scale. Our observations suggest that microcleats enhance permeability by providing additional paths for migration of gas out of the coal matrix, in addition to providing access for methanogenic bacteria. The abundance, distribution, and orientation of cleats control coal fabric and are crucial features in all stages of coalbed gas operations (i.e., exploration and production). Understanding coal fabric is important for coal gas exploration as it may be related to groundwater migration and the occurrence of methanogenic bacteria, prerequisite to biogenic gas accumulations. Likewise, the distribution of cleats in coal also determines pathways for migration and accumulation of thermogenic gas generated during coalification. ?? 2007 Elsevier B.V. All rights reserved.

Authigenic carbon entombed in methane-soaked sediments from the northeastern transform margin of the Guaymas Basin, Gulf of California

NASA Astrophysics Data System (ADS)

Paull, Charles K.; Ussler, William; Peltzer, Edward T.; Brewer, Peter G.; Keaten, Rendy; Mitts, Patrick J.; Nealon, Jeffrey W.; Greinert, Jens; Herguera, Juan-Carlos; Elena Perez, M.

2007-06-01

Extensive ROV-based sampling and exploration of the seafloor was conducted along an eroded transform-parallel fault scarp on the northeastern side of the Guaymas Basin in the Gulf of California to observe the nature of fluids venting from the seafloor, measure the record left by methane-venting on the carbonates from this area, and determine the association with gas hydrate. One gas vent vigorous enough to generate a water-column gas plume traceable for over 800 m above the seafloor was found to emanate from a ˜10-cm-wide orifice on the eroded scarp face. Sediment temperature measurements and topography on a sub-bottom reflector recorded in a transform-parallel seismic reflection profile identified a subsurface thermal anomaly beneath the gas vent. Active chemosynthetic biological communities (CBCs) and extensive authigenic carbonates that coalesce into distinct chemoherm structures were encountered elsewhere along the eroded transform-parallel scarp. The carbon isotopic composition of methane bubbles flowing vigorously from the gas vent (-53.6±0.8‰ PDB) is comparable to methane found in sediment cores taken within the CBCs distributed along the scarp (-51.9±8.1‰ PDB). However, the δ13C value of the CO 2 in the vent gas (+12.4±1.1‰ PDB) is very distinct from those for dissolved inorganic carbon (DIC) (-35.8‰ to -2.9‰ PDB) found elsewhere along the scarp, including underneath CBCs. The δ13C values of the carbonate-rich sediments and rocks exposed on the seafloor today also span an unusually large range (-40.9‰ to +12.9‰ PDB) and suggest two distinct populations of authigenic carbonate materials were sampled. Unconsolidated sediments and some carbonate rocks, which have lithologic evidence for near-seafloor formation, have negative δ13C values, while carbonate rocks that clearly formed in the subsurface have positive δ13C values (up to +23.0‰) close to that measured for CO 2 in the vent gas. There appears to be two carbon sources for the authigenic carbonates: (1) deeply-sourced, isotopically heavy CO 2 (˜+12‰); and (2) isotopically light DIC derived from local anaerobic oxidation of methane at the sulfate-methane interface in the shallow subsurface. Addition of isotopically light methane-derived carbon at the seafloor may completely mask the isotopically heavy CO 2 signature (+12.4‰) in the underlying sediments. Thus, the authigenic carbonates may have formed from the same methane- and carbon dioxide-bearing fluid, but under different migration and alteration conditions, depending on how it migrated through the sediment column.

Hydrothermal Rock-Fluid Interactions in 15-year-old Submarine Basaltic Tuff at Surtsey Volcano, Iceland

NASA Astrophysics Data System (ADS)

Jackson, M. D.; Couper, S.; Li, Y.; Stan, C. V.; Tamura, N.; Stefansson, A.; Moore, J. G.; Wenk, H. R.

2016-12-01

Basaltic tephra at Surtsey volcano, produced by 1963-1967 eruptions in the offshore SE Icelandic rift zone, record the complex interplay of factors that determine rates of palagonitization and crystallization of authigenic minerals in seafloor basalts worldwide. We investigate how formation of nanocrystalline clay mineral in fresh sideromelane glass influenced crystallization of mineral cements in submarine tuff from a 181 m core drilled in 1979. Synchrotron-based microdiffraction and microfluorescence maps (2x5 µm X-ray beam spot size) at beamline 12.3.2, Advanced Light Source, SEM-EDS compositional analyses, and fluid geochemical models compare processes in lapilli-sized glass fragments, vitric cementing matrix, and fine ash accretions. In lapilli at 137.9 m (100°C), nanocrystalline clay mineral in gel-palagonite has asymetric 14.9-12.6 Å (001) reflections, with Fe and Ti enrichment relative to Si, Al and Ca, compared with adjacent sideromelane. Neighboring fibro-palagonite has symmetric (001) and greater Fe and Ti enrichment. Al-tobermorite, a rare calcium-silicate-hydrate, crystallized in nearby vesicles. The 11.30-11.49 Å (002) interlayer and Ca/(Si+Al) ratio of 0.9-1.0 record release of Si, Al, and Ca in a chemical system relatively isolated from submarine hydrothermal fluid flow. In vitric matrix relatively open to fluid flow, however, phillipsite zeolite cement predominates. Al-tobermorite formed at 88.45 m (130°C) and 102.6 m (140°C), but is associated with fibro-palagonite and analcite, reflecting more rapid palagonitization, and changing cation solubility and pH at higher temperature. Tubular palagonite microstructures show nanocrystalline clay mineral with (001) preferred orientations that wrap around relict microchannels, produced perhaps through biogenic activity. Nanocrystalline clay mineral d-spacings suggest similarities with nontronite, but zeolite in palagonite diffraction patterns and 6-9 wt% MgO suggest a polycrystalline composite with smectite mineral precursor(s). Fifteen years after eruption, Al-tobermorite-zeolite assemblages varied with porosity, pH, and reactive rock mass/liquid volume ratio in submillimeter-scale hydrothermal environments. This initial phase of alteration is rarely preserved in older palagonitized rift zone basalts.

Magnetic Mineral diagenesis in changing water environments in the Black Sea since ˜41.6 ka

NASA Astrophysics Data System (ADS)

Liu, Jiabo; Nowaczyk, Norbert; Frank, Ute; Arz, Helge

2017-04-01

Magnetic mineral diagenesis plays a key role in the global iron cycle. To understand the authigenic magnetic mineral formation by diagenesis is also fundamentally important for the interpretation of environmental magnetic as well as paleomagnetic signals. Core MSM33-55-1, recovered from the SW Black Sea, was subjected to rock-magnetic and SEM studies. The results demonstrate that four different magnetic mineral assemblages associated to specific water conditions can be observed. Between ˜41.6 ka and ˜19 ka, magnetite and greigite are alternatively in dominance in the sediment. Due to low organic matter input during the late MIS 3 and the last glacial maximum (LGM), oxygenated bottom water in the Black Sea was favourable for preserving detrital magnetite. Greigite in this interval have irregular shapes and assemble in spots, which were formed in a micro environment with limited sulfate availability. Between ˜19 ka and ˜16.5 ka, black layers were deposited as a result of organic matter accumulation induced by productivity blooming and riverine discharge soaring after the LGM. Hence less oxygenated bottom water conditions developed, and more fine grained greigite was formed. After melt-water pulse (MWP) events (˜16.5 ka), both primary productivity and the sea level were continuously rising until ˜8.3 ka, leading to the depletion of oxygen in bottom water. In addition to greigite, pyrite was also formed and gradually in dominance as approaching the Holocene. The influx of salt water masses from the Mediterranean Sea after ˜8.3 ka contributed to the establishment of the anoxic Black Sea, which resulted in the formation of ubiquitous frambiods of pyrite. Additionally, bacterial magnetic minerals are likely present in the sediment younger than ˜8.3 ka as indicated by rock magnetic results. In this paper, four different magnetic mineral assemblages, reflecting gradual changes from an oxic to an anoix Black Sea, were identified, yielding insights into the relation between magnetic minerals diagenesis and bottom water conditions.

Arsenic Incorporation Into Authigenic Pyrite, Bengal Basin Sediment, Bangladesh

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

Lowers, H.A.; Breit, G.N.; Foster, A.L.

2007-07-10

Sediment from two deep boreholes ({approx}400 m) approximately 90 km apart in southern Bangladesh was analyzed by X-ray absorption spectroscopy (XAS), total chemical analyses, chemical extractions, and electron probe microanalysis to establish the importance of authigenic pyrite as a sink for arsenic in the Bengal Basin. Authigenic framboidal and massive pyrite (median values 1500 and 3200 ppm As, respectively), is the principal arsenic residence in sediment from both boreholes. Although pyrite is dominant, ferric oxyhydroxides and secondary iron phases contain a large fraction of the sediment-bound arsenic between approximately 20 and 100 m, which is the depth range of wellsmore » containing the greatest amount of dissolved arsenic. The lack of pyrite in this interval is attributed to rapid sediment deposition and a low sulfur flux from riverine and atmospheric sources. The ability of deeper aquifers (>150 m) to produce ground water with low dissolved arsenic in southern Bangladesh reflects adequate sulfur supplies and sufficient time to redistribute the arsenic into pyrite during diagenesis.« less

Arsenic incorporation into authigenic pyrite, Bengal Basin sediment, Bangladesh

USGS Publications Warehouse

Lowers, H.A.; Breit, G.N.; Foster, A.L.; Whitney, J.; Yount, J.; Uddin, Md. N.; Muneem, Ad. A.

2007-01-01

Sediment from two deep boreholes (???400 m) approximately 90 km apart in southern Bangladesh was analyzed by X-ray absorption spectroscopy (XAS), total chemical analyses, chemical extractions, and electron probe microanalysis to establish the importance of authigenic pyrite as a sink for arsenic in the Bengal Basin. Authigenic framboidal and massive pyrite (median values 1500 and 3200 ppm As, respectively), is the principal arsenic residence in sediment from both boreholes. Although pyrite is dominant, ferric oxyhydroxides and secondary iron phases contain a large fraction of the sediment-bound arsenic between approximately 20 and 100 m, which is the depth range of wells containing the greatest amount of dissolved arsenic. The lack of pyrite in this interval is attributed to rapid sediment deposition and a low sulfur flux from riverine and atmospheric sources. The ability of deeper aquifers (>150 m) to produce ground water with low dissolved arsenic in southern Bangladesh reflects adequate sulfur supplies and sufficient time to redistribute the arsenic into pyrite during diagenesis.

National Uranium Resource Evaluation: Marfa Quadrangle, Texas

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

Henry, C D; Duex, T W; Wilbert, W P

1982-09-01

The uranium favorability of the Marfa 1/sup 0/ by 2/sup 0/ Quadrangle, Texas, was evaluated in accordance with criteria established for the National Uranium Resource Evaluation. Surface and subsurface studies, to a 1500 m (5000 ft) depth, and chemical, petrologic, hydrogeochemical, and airborne radiometric data were employed. The entire quadrangle is in the Basin and Range Province and is characterized by Tertiary silicic volcanic rocks overlying mainly Cretaceous carbonate rocks and sandstones. Strand-plain sandstones of the Upper Cretaceous San Carlos Formation and El Picacho Formation possess many favorable characteristics and are tentatively judged as favorable for sandstone-type deposits. The Tertiarymore » Buckshot Ignimbrite contains uranium mineralization at the Mammoth Mine. This deposit may be an example of the hydroauthigenic class; alternatively, it may have formed by reduction of uranium-bearing ground water produced during diagenesis of tuffaceous sediments of the Vieja Group. Although the presence of the deposit indicates favorability, the uncertainty in the process that formed the mineralization makes delineation of a favorable environment or area difficult. The Allen intrusions are favorable for authigenic deposits. Basin fill in several bolsons possesses characteristics that suggest favorability but which are classified as unevaluated because of insufficient data. All Precambrian, Paleozoic, other Mesozoic, and other Cenozoic environments are unfavorable.« less

Authigenic carbonate formation at hydrocarbon seeps in continental margin sediments: A comparative study

USGS Publications Warehouse

Naehr, T.H.; Eichhubl, P.; Orphan, V.J.; Hovland, M.; Paull, C.K.; Ussler, W.; Lorenson, T.D.; Greene, H. Gary

2007-01-01

Authigenic carbonates from five continental margin locations, the Eel River Basin, Monterey Bay, Santa Barbara Basin, the Sea of Okhotsk, and the North Sea, exhibit a wide range of mineralogical and stable isotopic compositions. These precipitates include aragonite, low- and high-Mg calcite, and dolomite. The carbon isotopic composition of carbonates varies widely, ranging from -60??? to +26???, indicating complex carbon sources that include 13C-depleted microbial and thermogenic methane and residual, 13C-enriched, bicarbonate. A similarly large variability of ??18O values (-5.5??? to +8.9???) demonstrates the geochemical complexity of these sites, with some samples pointing toward an 18O-enriched oxygen source possibly related to advection of 18O-enriched formation water or to the decomposition of gas hydrate. Samples depleted in 18O are consistent with formation deeper in the sediment or mixing of pore fluids with meteoric water during carbonate precipitation. A wide range of isotopic and mineralogical variation in authigenic carbonate composition within individual study areas but common trends across multiple geographic areas suggest that these parameters alone are not indicative for certain tectonic or geochemical settings. Rather, the observed variations probably reflect local controls on the flux of carbon and other reduced ions, such as faults, fluid conduits, the presence or absence of gas hydrate in the sediment, and the temporal evolution of the local carbon reservoir. Areas with seafloor carbonates that indicate formation at greater depth below the sediment-water interface must have undergone uplift and erosion in the past or are still being uplifted. Consequently, the occurrence of carbonate slabs on the seafloor in areas of active hydrocarbon seepage is commonly an indicator of exhumation following carbonate precipitation in the shallow subsurface. Therefore, careful petrographic and geochemical analyses are critical components necessary for the correct interpretation of processes related to hydrocarbon seepage in continental margin environments and elsewhere. ?? 2007 Elsevier Ltd. All rights reserved.

A new estimate of detrital redox-sensitive metal concentrations and variability in fluxes to marine sediments

NASA Astrophysics Data System (ADS)

Cole, Devon B.; Zhang, Shuang; Planavsky, Noah J.

2017-10-01

The enrichment and depletion of redox sensitive trace metals in marine sediments have been used extensively as paleoredox proxies. The trace metals in shale are comprised of both detrital (transported or particulate) and authigenic (precipitated, redox-driven) constituents, potentially complicating the use of this suite of proxies. Untangling the influence of these components is vital for the interpretation of enrichments, depletions, and isotopic signals of iron (Fe), chromium (Cr), uranium (U), and vanadium (V) observed in the rock record. Traditionally, a single crustal average is used as a cutoff for detrital input, and concentrations above or below this value are interpreted as redox derived authigenic enrichment or depletion, while authigenic isotopic signals are frequently corrected for an assumed detrital contribution. Building from an extensive study of soils across the continental United States - which upon transport will become marine sediments - and their elemental concentrations, we find large deviations from accepted crustal averages in redox-sensitive metals (Fe, Cr, U, V) compared to typical detrital tracers (Al, Ti, Sc, Th) and provide new estimates for detrital contributions to the ocean. The variability in these elemental ratios is present over large areas, comparable to the catchment-size of major rivers around the globe. This heterogeneity in detrital flux highlights the need for a reevaluation of how the detrital contribution is assessed in trace metal studies, and the use of confidence intervals rather than single average values, especially in local studies or in the case of small authigenic enrichments.

Mineralogy of Fluvio-Lacustrine Sediments Investigated by Curiosity during the Prime Mission: Implications for Diagenesis

NASA Astrophysics Data System (ADS)

Rampe, E. B.; Morris, R. V.; Bish, D. L.; Vaniman, D. T.; Bristow, T.; Chipera, S.; Blake, D. F.; Ming, D. W.; Farmer, J.; Morrison, S. M.; Treiman, A. H.; Achilles, C.; Crisp, J.; Des Marais, D. J.; Downs, R. T.; Morookian, J. M.; Sarrazin, P.; Spanovich, N.; Yen, A.

2014-12-01

The Mars Science Laboratory rover Curiosity investigated sedimentary rocks that were deposited in a diversity of fluvio-lacustrine settings. The entire science payload was employed to characterize the mineralogy and chemistry of the Sheepbed mudstone at Yellowknife Bay and the Windjana sandstone at the Kimberley. Data from the CheMin instrument, a transmission X-ray diffractometer, were used to determine the quantitative mineralogy of both samples. The Sheepbed mudstone contains detrital basaltic minerals, calcium sulfates, iron oxides or hydroxides, iron sulfides, trioctahedral smectite, and amorphous material. The mineral assemblage and chemical data from APXS suggest that the trioctahedral smectite and magnetite formed authigenically as a result of alteration of olivine. The apparent lack of higher-grade phyllosilicates (e.g., illite and chlorite) and the presence of anhydrite indicate diagenesis at ~50-80 ºC. The mineralogy of the Windjana sandstone is different than the Sheepbed mudstone. Windjana contains significant abundances of K-feldspar, low- and high-Ca pyroxenes, magnetite, phyllosilicates, and amorphous material. At least two distinct phyllosilicate phases exist: a 10 Å phase and a component that is expanded with a peak at ~11.8 Å. The identity of the expanded phase is currently unknown, but could be a smectite with interlayer H2O, and the 10 Å phase could be illite or collapsed smectite. Further work is necessary to characterize the phyllosilicates, but the presence of illite could suggest that Windjana experienced burial diagenesis. Candidates for the cementing agents include fine-grained phyllosilicates, Fe-oxides, and/or amorphous material. Interpretations of CheMin data from the Windjana sandstone are ongoing at the time of writing, but we will present an estimate of the composition of the amorphous material from mass balance calculations using the APXS bulk chemistry and quantitative mineralogy from CheMin.

Some chemical aspects of diagenetic carbonates from the Miocene of Sitakund, Bangladesh

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

Akhter, S.H.; Chowdhury, S.Q.; Kandaker, N.I.

1990-05-01

A preliminary chemical and petrological study was done of the Miocene limestone and its comparison with surrounding and overlying marine shales. The material for these studies was obtained from the Miocene Surma sediments exposed in Sitakund region, Cluttagong, Bangladesh. These limestones occur in a predominantly marine shale sequence and show an apparent angular structural relationship with respect to the host marine shales. Three types of carbonates are recognized: banded limestone, dark laminated limestone, and argillaceous limestone. These are devoid of any skeletal remains and often show recrystallization phenomena. Carbonate mineral phases included calcite, aragonite, dolomite, and more rarely magnesite andmore » ankerite. Noncarbonate fraction shows quartz, although very fine grained, is intricately intergrown, indicating that it is at least recrystallized, if not authigenic. Petrographic study of these carbonates show a great variability in terms of texture and composition and suggest a complex multistep and presumably continuous diagenesis. Relatively high REE (rare earth elements) abundances in these carbonates are most likely due to diagenesis and incorporation of mobile REE from local detrital phases into diagenetic carbonates. The anomalously low abundances of cerium in all the carbonates indicates a predominantly marine source for the REE. Recrystallization of carbonate resulted in the extensive exchange of Sr and O between carbonate and diagenetic fluid, the latter being low in REE/Ca ratios. Associated marine shales have quite dissimilar trace-element signatures. This may reflect uncommon crustal sources of REE for the carbonates and clastics. The enrichment of Ni and Zn in marine shales are related to the proximality of local bedrock source areas and clay minerals in the marine sediments.« less

Mineralogy of Fluvio-Lacustrine Sediments Investigated by Curiosity During the Prime Mission: Implications for Diagenesis

NASA Technical Reports Server (NTRS)

Rampe, Elizabeth B.; Morris, R. V.; Bish, D. L.; Vaniman, D. T.; Bristow, T. F.; Chipera, S. J.; Blake, D. F.; Ming, D. W.; Farmer, J. D.; Morrison, S. M.;

Use of Dialysis Multi-level Samplers to Examine Microbial Processes in a Shallow Alluvial Aquifer of the Rio Grande, New Mexico

NASA Astrophysics Data System (ADS)

Crossey, L. J.; Vinson, D. S.; Block, S. E.; Dahm, C. N.; Spilde, M.; Pershall, A. D.

2001-12-01

The riparian zone of the Rio Grande near Belen, New Mexico, hosts a shallow sand-dominated aquifer with discharge - recharge events occurring on time scales ranging from hours to months. Using a multi-level sampler with dialysis cells (DMLS), we have sampled the upper 1.5 m of the water table at 10 cm vertical resolution. The DMLS system provides a passive means of water sampling at high resolution and with minimal disturbance to the environment being studied. Water samples have been analyzed for major ion chemistry as well as redox-sensitive parameters (iron, manganese, dissolved oxygen, sulfur, organic carbon, and redox potential). Depth-related trends emerge through the DMLS approach that are not evident from traditional well sampling methods. Vertical hydrochemical profiles reveal substantial seasonal variability, as well as changes related to major infiltration events during monsoon rains. In conjunction with continuously recorded water table data, we can assess redox-related biogeochemical and microbiological processes in terms of groundwater-surface water interaction. In addition, we have examined mineral products and bacterial growths within the dialysis cells. Cells with membrane pore size of 10†m serve as microcosms to investigate solid products that would be difficult to isolate from the natural sediments. Over a period of several weeks, sufficient microbial/mineral growth occurs. These samples have been imaged with scanning electron microscopy and chemically inspected by energy-dispersive X-ray spectroscopy. Notable products include iron sulfides; iron and manganese oxides (crystalline and amorphous); and tentatively authigenic phosphates, some containing rare earth elements. DMLS is a useful tool for coupling high-resolution chemical investigation of groundwater with examination of microbial activity in this shallow aquifer. The approach may have applications in other environments where good vertical resolution is needed.

Geothermal alteration of basaltic core from the Snake River Plain, Idaho

NASA Astrophysics Data System (ADS)

Sant, Christopher J.

The Snake River Plain is located in the southern part of the state of Idaho. The eastern plain, on which this study focuses, is a trail of volcanics from the Yellowstone hotspot. Three exploratory geothermal wells were drilled on the Snake River Plain. This project analyzes basaltic core from the first well at Kimama, north of Burley, Idaho. The objectives of this project are to establish zones of geothermal alteration and analyze the potential for geothermal power production using sub-aquifer resources on the axial volcanic zone of the Snake River Plain. Thirty samples from 1,912 m of core were sampled and analyzed for clay content and composition using X-ray diffraction. Observations from core samples and geophysical logs are also used to establish alteration zones. Mineralogical data, geophysical log data and physical characteristics of the core suggest that the base of the Snake River Plain aquifer at the axial zone is located 960 m below the surface, much deeper than previously suspected. Swelling smectite clay clogs pore spaces and reduces porosity and permeability to create a natural base to the aquifer. Increased temperatures favor the formation of smectite clay and other secondary minerals to the bottom of the hole. Below 960 m the core shows signs of alteration including color change, formation of clay, and filling of other secondary minerals in vesicles and fractured zones of the core. The smectite clay observed is Fe-rich clay that is authigenic in some places. Geothermal power generation may be feasible using a low temperature hot water geothermal system if thermal fluids can be attained near the bottom of the Kimama well.

Insights into methane dynamics from analysis of authigenic carbonates and chemosynthetic mussels at newly-discovered Atlantic Margin seeps

USGS Publications Warehouse

Prouty, Nancy G.; Sahy, Diana; Ruppel, Carolyn D.; Roark, E. Brendan; Condon, Dan; Brooke, Sandra; Ross, Steve W.; Demopoulos, Amanda W.J.

2016-01-01

The recent discovery of active methane venting along the US northern and mid-Atlantic margin represents a new source of global methane not previously accounted for in carbon budgets from this region. However, uncertainty remains as to the origin and history of methane seepage along this tectonically inactive passive margin. Here we present the first isotopic analyses of authigenic carbonates and methanotrophic deep-sea mussels, Bathymodiolus   sp., and the first direct constraints on the timing of past methane emission, based on samples collected at the upper slope Baltimore Canyon (∼385 m water depth) and deepwater Norfolk (∼1600 m) seep fields within the area of newly-discovered venting. The authigenic carbonates at both sites were dominated by aragonite, with an average  signature of −47‰, a value consistent with microbially driven anaerobic oxidation of methane-rich fluids occurring at or near the sediment–water interface. Authigenic carbonate U and Sr isotope data further support the inference of carbonate precipitation from seawater-derived fluids rather than from formation fluids from deep aquifers. Carbonate stable and radiocarbon ( and ) isotope values from living Bathymodiolus   sp. specimens are lighter than those of seawater dissolved inorganic carbon, highlighting the influence of fossil carbon from methane on carbonate precipitation. U–Th dates on authigenic carbonates suggest seepage at Baltimore Canyon between 14.7±0.6 ka to 15.7±1.6 ka, and at the Norfolk seep field between 1.0±0.7 ka to 3.3±1.3 ka, providing constraint on the longevity of methane efflux at these sites. The age of the brecciated authigenic carbonates and the occurrence of pockmarks at the Baltimore Canyon upper slope could suggest a link between sediment delivery during Pleistocene sea-level lowstand, accumulation of pore fluid overpressure from sediment compaction, and release of overpressure through subsequent venting. Calculations show that the Baltimore Canyon site probably has not been within the gas hydrate stability zone (GHSZ) in the past 20 ka, meaning that in-situ release of methane from dissociating gas hydrate cannot be sustaining the seep. We cannot rule out updip migration of methane from dissociation of gas hydrate that occurs farther down the slope as a source of the venting at Baltimore Canyon, but consider that the history of rapid sediment accumulation and overpressure may play a more important role in methane emissions at this site.

238U-Series in Fe Oxy/Hydroxides by LA-MC-ICP-MS, New Insights Into Weathering Geochronology

NASA Astrophysics Data System (ADS)

Bernal, J.; McCulloch, M.; Eggins, S.; Grun, R.; Eggleton, R.

2003-12-01

The establishment of a geochronological framework for weathering processes is essential for an understanding of the evolution of the regolith and its dynamics. However, there are few robust answers regarding the absolute age of weathering and its rates. Nowadays, 40Ar/39Ar analysis of Mn-Oxides (cryptomelane) and K-bearing secondary sulphates have provided one of the few generally reliable chronometers (e.g. 1), but is restricted to high-K secondary phases. This work presents a different approach to obtain geochronological information from weathering minerals, namely measurement of 238U-series disequilibria in authigenic Fe oxy/hydroxides. These may be potentially useful recorders of weathering processes as they commonly occur as weathering products and have high affinity towards dissolved uranyl complexes. Furthermore, U-Th fractionation during weathering has been extensively reported [2], effectively resetting the U/230Th geochronometer. LA-MC-ICP-MS facilitates in situ measurement of 238U-series disequilibria in authigenic microcrystalline iron oxy/hydroxides (precipitated between cracks and veins in partially and heavily weathered chlorite-muscovite schist) and pisoliths (ferruginous concretions). Contrary to previous studies [e.g. 3], in situ measurement of 238U-nuclides enables selective analysis or iron oxy/hydroxides phases, minimizes contributions from allogenic phases and, reduces the need of mathematical corrections to obtain the activity ratios for the authigenic phase [4, 5]. The results suggest that supergene iron oxy/hydroxides are good recorders of weathering processes; they precipitate during the early stages of weathering, reflect the U-isotopic composition of the groundwater, appear to act as closed-systems in weathering conservative environments, and behave in a predictable fashion when subjected to intense weathering and leaching conditions. The 230Th-ages of the iron oxy/hydroxides indicate that the timing and intensity of weathering appears to be largely controlled by global climatic changes, suggesting that weathering rates have not been constant during the last 300 ka in Northern Australia. References: 1 P.M. Vasconcelos. Annual Review in Earth and Planetary Sciences 27(1), 183-229, (1999) 2 M. Ivanovich and R.S. Harmon, Uranium-series disequilibrium : applications to earth, marine, and environmental science, xxxiv, 910 pp., Oxford University Press, Oxford, (1992) 3 S.A. Short, R.T. Lowson, J. Ellis and D.M. Price. Geochimica et Cosmochimica Acta 53, 1379-1389, (1989) 4 K.R. Ludwig and D.M. Titterington. Geochimica et Cosmochimica Acta 58(22), 5031-5042, (1994) 5 Luo, S. and T. L. Ku. Geochimica et Cosmochimica Acta 55(2): 555-564. (1991)

Interstitial Water Geochemistry and Low Temperature Alteration in Volcaniclastic Sediments from the Amami Sankaku Basin at IODP Site U1438 (Expedition 351)

NASA Astrophysics Data System (ADS)

Loudin, L. C.; Yogodzinski, G. M.; Sena, C.; van der Land, C.; Zhang, Z.; Marsaglia, K. M.; Meffre, S.

2014-12-01

Interstitial water (IW) geochemistry provides insight into the diagenetic transformation of sediment to rock by component dissolution/alteration and precipitation of new mineral phases as pore-filling cements, as well as providing insight into ion exchange reactions with secondary minerals. At Site U1438, 67 IW samples were collected within a ~950 m section of volcaniclastic sediments. These were analyzed for pH as well as major and trace elements. The corresponding host sediments were mineralogically characterized by XRD and petrographic observations. Three alteration zones are inferred: 1) the upper alteration zone (~0-300 mbsf) characterized by maximum IW concentrations of Si (790.1 μM), Sr (138.5 μM) and Mn (279.5 μM), consistent with volcanic glass and siliceous microfossil dissolution, enhanced reduction of Mn oxides, and carbonate recrystallization. Maximum concentrations in Li and B coupled with the lowest pH (6.7) imply that Li and B are released into the IW due to silicate dissolution and clay desorption. 2) At intermediate depths (~300 to ~550 mbsf) Mg, K, Sr, Si, Mn, Li, and B are at concentration minima, possibly due to growth of authigenic minerals. B and Li minimum concentrations occur at high pH (~9) suggesting that these elements are preferentially removed from high pH waters during the precipitation of clay mineral and zeolite cements in primary and secondary (dissolution) pores. The mineralogy of these phases is confirmed by XRD data, and their pore-filling nature is seen in thin sections of the coarser lithologies. 3) The deep alteration zone (>~550m) is characterized by an increase in B, Li, Sr and Ca. At ~650 mbsf, Ca becomes the dominant cation in solution consistent with either mineral interaction with the IW, or diffusive input from underlying igneous basement (~1400 mbsf).

Foundation Considerations in Siting of Nuclear Facilities in Karst Terrains and Other Areas Susceptible to Ground Collapse.

DTIC Science & Technology

1981-05-01

Page Time of occurrence .... ............. ... 159 Effect of precipitation .. ........ ... 159 Types of overburden strata .. ......... ... 159...fill the void space between allochems and/or terrigenous grains; usually orthochems are precipitated authigene- tically or during early diagenesis. (d...m Chemical deposits These include the familiar stalagmites, stalactites, "cave flowers," and tufa, which have been chemically precipitated by

Authigenic kaolinite and associated pyrite in chalk of the Cretaceous Niobrara Formation, Eastern Colorado.

USGS Publications Warehouse

Pollastro, R.M.

1981-01-01

Cores from the Smoky Hill Chalk Member of the Cretaceous Niobrara Formation have several zones containing authigenic kaolinite as spherical, moldic, polycrystalline aggregates that occur within single or multichambered foraminiferal tests and are commonly associated with framboidal pyrite. Such kaolinite is inferred to result from volcanic ash deposited during chalk sedimentation. Shortly after burial, a colloidal aluminous gel or solution formed from the unstable ash and moved into organic-rich foraminiferal tests, where sulfate-reducing bacteria created a favorable microenvironment for the simultaneous crystallization of kaolinite and pyrite. -Author

Late Archean mineralised cyanobacterial mats and their modern analogs

NASA Astrophysics Data System (ADS)

Kazmierczak, J.; Altermann, W.; Kremer, B.; Kempe, S.; Eriksson, P. G.

2008-09-01

Abstract Reported are findings of Neoarchean benthic colonial coccoid cyanobacteria preserved as abundant remnants of mineralized capsules and sheaths visible in SEM images as characteristic patterns after etching highly polished carbonate rock platelets. The samples described herein were collected from the Nauga Formation at Prieska (Kaapvaal craton, South Africa). The stratigraphic position of the sampling horizon (Fig. 1) is bracketed by single zircon ages from intercalated tuffs, of 2588±6 Ma and 2549±7Ma [1]. The cyanobacteria-bearing samples are located within sedimentary sequence which begins with Peritidal Member displaying increasingly transgressive character, passing upward into the Chert Member and followed by the Proto-BIF Member and by the Naute Shale Member of the Nauga Formation successively. All three latter members were deposited below the fair weather wave base. As in our previous report [2], the samples are taken from lenses of massive micritic flat pebble conglomerate occurring in otherwise finely laminated siliceous shales intercalating with thin bedded platy limestone. This part of the Nauga Formation is about 30 m thick. The calcareous, cyanobacteria-bearing flat pebble conglomerate and thin intercalations of fine-grained detrital limestones embedded in the clayey sapropel-rich deposits are interpreted as carbonate sediments winnowed during stormy weather from the nearby located peritidal carbonate platform. The mass occurrence and exceptional preservation of mineralised cyanobacterial remains in the micritic carbonate (Mg-calcite) of the redeposited flat pebbles can be explained by their sudden burial in deeper, probably anoxic clay- and sapropel-rich sediments. When examined with standard petrographic optical microscopic technique, the micritic carbonates show rather obscure structure (Fig. 2a), whereas under the SEM, polished and slightly etched platelets of the same samples reveal surprisingly well preserved patterns (Fig. 2b,c) reminiscent of common sheaths (glycocalix), typical for coccoidal colonial (pseudoparenchymatous) entophysalidacean or pleurocapsalean cyanobacteria (Fig. 2d-f). The remains of the coccoid sheaths and capsules are visible as a system of rimmed subglobular or irregularly polygonal pits separated from adjacent pits by 2-3 μm thick walls. Microprobe analyses show that the interiors of the pits are composed of almost pure calcium carbonate whereas the rims and walls of calcium carbonate with high admixture of silicates (mostly Al-Fe clay-like silicates) and dolomite. High magnification images of rims and walls confirm the microprobe data indicating authigenic character of the minerals forming both the carbonate infilling the pits interiors (CaCO3) and their rims and walls (CaCO3 + Al-Fe silicates + dolomite). EPSC Abstracts, Vol. 3, EPSC2008-A-00493, 2008 European Planetary Science Congress, Author(s) 2008 It seems that carbonates were the first mineral phase filling the spaces remained after the plasmolysis of the cyanobacterial cell contents, whereas the formation of silicates within the exopolysaccharides forming the bulk of the sheaths and capsules was a later diagenetic process. Microprobe analyses of mineralised modern coccoid cyanobacterial mats forming tower-like structures in the highly alkaline Lake Van, Turkey [3,4] display a set of elements indicative for the presence of authigenic carbonate and silicate minerals which are almost identical with that occurring in the studied Neoarchean samples. Also the optical and SEM images of polished and etched platelets of permineralised Lake Van microbialites are strikingly similar (Fig. 2d-f). Similarly as in modern cyanobacterial and other microbial mats, the process of early post mortem mineralisation, in the case of the Nauga Formation, was most probably associated with the action of heterotrophic bacteria upon the dead cyanobacterial biomass. Heterotrophic bacteria occupying EPS layers of living and dead cyanobacterial cells have the ability to bind various ions and may serve as nucleation centres for a variety of minerals [5, 6]. These, often amorphous precursor mineral phases can be transformed, during later diagenesis, into authigenic carbonates, feldspar and phyllosilicates, as observed in the case of both Nauga Formation and Lake Van cyanobacterial sheaths and capsules. The early massive appearance of benthic coccoid cyanobacteria, as evidenced by the mineralised mats in the Neoarchean Nauga Formation, and their ability to produce fine-grained limestones, confirms the significant role of these micro organisms in the formation of vast deposits of marine micritic limestones, as suggested also for younger geologic ages [7, 8]. References [1] Altermann, W. and Nelson, D. R. (1998) Sed. Geol. 120, 225-256. [2] Kazmierczak, J. and Altermann, W. (2002) Science 298, 2351. [3] Kempe, S. et al. (1991) Nature 394, 605-608. [4] Kazmierczak, J. and Altermann, W. (2002) 16th Intern. Sed. Congr. Abstract Vol., 191. [5] Douglas, S. and Beveridge, T. J. (1998) FEMS Microbiol. Ecol. 26, 79-88. [6] Barker, W. W. and Banfield, J. F. (1998) Geomicrobiol. J. 15, 223-244. [7] Kazmierczak, J. et al. (1996) Acta Palaeont. Polonica 41, 319-338. [8] Altermann, W. et al. (2006) Geobiology 4, 147- 166.

Characterization of diagenetic siderites formed in recent and ancient ferruginous sediments of Lake Towuti, Indonesia.

NASA Astrophysics Data System (ADS)

Vuillemin, Aurele; Kallmeyer, Jens; Wagner, Dirk; Kemnitz, Helga; Wirth, Richard; Luecke, Andreas; Mayr, Christoph

2016-04-01

Authigenic minerals in lacustrine settings can be formed in the water column and within the sediment, abiotically and/or triggered by biological activity. Such minerals have been used as paleosalinity and paleoproductivity proxies, reflecting trophic state, and/or early diagenetic conditions. They have also been considered as potential biosignatures of past and present microbial activity. Here we present a study from Lake Towuti, a deep tectonic basin in Sulawesi, Indonesia. Its geographic position makes it a prime location to record paleoclimatic changes in the tropical Western Pacific warm pool in its sedimentary sequence. The ultramafic rocks and surrounding lateritic soils in the catchment area supply considerable amounts of iron and other metals to the lake. These elements further restrain primary productivity along with the development of specific microbial metabolic pathways involved in early diagenesis. Lake Towuti is stratified with anoxic conditions below 130 m, allowing metal reduction processes to take place in the hypolimnion. The extreme scarcity of sulphate and nitrate/nitrite make Lake Towuti's bottom waters a modern analogue for the Archaean Ocean. It was therefore chosen as a drilling target by the International Continental Drilling Program (ICDP). In May to July 2015, the Towuti Drilling Project recovered a total >1000 m of sediment core from three drilling sites, including a 114 m long core drilled with a contamination tracer dedicated to geomicrobiological studies. Heavy mineral fractions were extracted from core catcher samples and siderite crystals (FeCO3) were selected from different depths. Characterization of their habitus was achieved via SEM and TEM imaging. Preliminary results show that siderites grow from amorphous into nanocrystalline phases and form twinned aggregates developing into mosaic monocrystals with depth. Gradual filling of vugs and microporosity were observed along with inclusions of magnetite nanocrystals. Work in progress includes parallel δ13C measurements on bulk organic matter (OM) surrounding the minerals and on the siderites themselves to trace organic to inorganic carbon transfer associated with microbial respiration of OM and infer possible relationships to methane oxidation processes. Analysis of δ56Fe compositions will complement this dataset to highlight the role of dissimilatory Fe (III) reduction in siderite formation. We hypothesize that sedimentary siderite is formed by precipitation from pore water due to saturation resulting from microbial OM and iron respiration processes. A similar approach will be applied to vivianite crystals (Fe3(PO4)3ṡ8H2O) that were found concomitantly with siderite in sedimentary horizons intercalated with tephra layers.

Magnetic properties of the remagnetized Middle-Ordovician limestones of the Ponón Trehué Formation (San Rafael Block, central-western Argentina): Insights into the Permian widespread Sanrafaelic overprint

NASA Astrophysics Data System (ADS)

Fazzito, Sabrina Y.; Rapalini, Augusto E.

2016-10-01

The widespread Sanrafaelic remagnetization reset most of the early Cambrian to mid-Ordovician carbonate platform of the Argentine Precordillera and the calcareous units of the San Rafael Block. We conducted a detailed rock-magnetic study on the Middle-Ordovician limestones of the Ponón Trehué Formation at both limbs of a tight anticline exposed in the San Rafael Block (Mendoza province, central-western Argentina) that are carriers of a syntectonic magnetization of Permian age. We found that the magnetic overprint in the Ponón Trehué Formation is carried by both pyrrhotite and magnetite, with goethite and subordinate haematite likely related to weathering. Hysteresis parameters, frequency dependence of magnetic susceptibility, Cisowski and modified Lowrie-Fuller tests suggest the presence of ultrafine particles of chemical origin. Demagnetization of natural remanent magnetization and of three-axis isothermal remanence confirm pyrrhotite and magnetite as important contributors to the remanence. Both minerals carry the same magnetic syntectonic component suggesting a coeval or nearly coeval remanence acquisition and therefore mineral formation. This and the results of the magnetic fabric analyses indicate an authigenic origin of the magnetic minerals during folding associated with the Sanrafaelic tectonic phase (ca. 280 Ma). Although the chemically active (oxidizing?) fluids expelled from the orogen as it developed in the early Permian is a viable explanation for the Sanrafaelic remagnetization, the role of the nearly coeval magmatism in Precordillera and the San Rafael Block remains to be properly evaluated.

Simultaneous influence of indigenous microorganism along with abiotic factors controlling arsenic mobilization in Brahmaputra floodplain, India

NASA Astrophysics Data System (ADS)

Sathe, Sandip S.; Mahanta, Chandan; Mishra, Pushpanjali

2018-06-01

In the dynamic cycling of oxic and anoxic aqueous alluvial aquifer environments, varying Arsenic (As) concentrations are controlled by both abiotic and biotic factors. Studies have shown a significant form of toxic As (III) being released through the reductive dissolution of iron-oxy/hydroxide minerals and microbial reduction mechanisms, which leads to a serious health concern. The present study was performed in order to assess the abiotic and biotic factors influencing As release into the alluvial aquifer groundwater in Brahmaputra floodplain, India. The groundwater chemistry, characterization of the sediments, isolation, identification and characterization of prominent As releasing indigenous bacterium were conducted. The measured solid and liquid phases of total As concentration were ranged between 0.02 and 17.2 mg kg-1 and 8 to 353 μg L-1, respectively. The morphology and mineralogy showed the presence of detrital and authigenic mineral assemblages whereas primary and secondary As bearing Realgar and Claudetite minerals were identified, respectively. Furthermore, significant non-labile As fraction was found associated with the amorphous oxides of Fe, Mn and Al. The observed groundwater chemistry and sediment color, deduced a sub-oxic reducing aquifer conditions in As-contaminated regions. In addition, 16S rDNA sequencing results of the isolated bacterium showed the prominent Pseudomonas aeruginosa responsible for the mobilization of As, reducing condition, biomineralization and causing grey color to the sediments at the shallower and deeper aquifers in the study area. These findings suggest that microbial metabolic activities are equally responsible in iron-oxy/hydroxide reductive dissolution, controlling As mobilization in dynamic fluvial flood plains.

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

NASA Astrophysics Data System (ADS)

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

2009-12-01

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

Authigenic 10Be/9Be ratio signatures of the cosmogenic nuclide production linked to geomagnetic dipole moment variation since the Brunhes/Matuyama boundary.

PubMed

Simon, Quentin; Thouveny, Nicolas; Bourlès, Didier L; Valet, Jean-Pierre; Bassinot, Franck; Ménabréaz, Lucie; Guillou, Valéry; Choy, Sandrine; Beaufort, Luc

2016-11-01

Geomagnetic dipole moment variations associated with polarity reversals and excursions are expressed by large changes of the cosmogenic nuclide beryllium-10 ( 10 Be) production rates. Authigenic 10 Be/ 9 Be ratios (proxy of atmospheric 10 Be production) from oceanic cores therefore complete the classical information derived from relative paleointensity (RPI) records. This study presents new authigenic 10 Be/ 9 Be ratio results obtained from cores MD05-2920 and MD05-2930 collected in the west equatorial Pacific Ocean. Be ratios from cores MD05-2920, MD05-2930 and MD90-0961 have been stacked and averaged. Variations of the authigenic 10 Be/ 9 Be ratio are analyzed and compared with the geomagnetic dipole low series reported from global RPI stacks. The largest 10 Be overproduction episodes are related to dipole field collapses (below a threshold of 2 × 10 22  Am 2 ) associated with the Brunhes/Matuyama reversal, the Laschamp (41 ka) excursion, and the Iceland Basin event (190 ka). Other significant 10 Be production peaks are correlated to geomagnetic excursions reported in literature. The record was then calibrated by using absolute dipole moment values drawn from the Geomagia and Pint paleointensity value databases. The 10 Be-derived geomagnetic dipole moment record, independent from sedimentary paleomagnetic data, covers the Brunhes-Matuyama transition and the whole Brunhes Chron. It provides new and complementary data on the amplitude and timing of millennial-scale geomagnetic dipole moment variations and particularly on dipole moment collapses triggering polarity instabilities.

Interpreting benthic oxygen levels in mudrocks: A new approach

NASA Astrophysics Data System (ADS)

Wignall, Paul B.; Myers, Keith J.

1988-05-01

Quantified paleoecology and gamma-ray spectrometry have been applied in the analysis of the Kimmeridge Clay, a highly organic-rich British Jurassic mudrock. Decreasing benthic oxygen trends are reflected in decreasing species richness and dominance-diversity values. Similarly, the degree of fragmentation of the benthos reflects the benthic energy levels and covaries with benthic oxygen. The calculation of authigenic uranium values from data gathered by gamma-ray spectrometry shows enrichment in more oxygen-deficient environments. The good correlation between the independently derived paleoecological and authigenic U data indicates the importance of these techniques in environmental analysis of marine petroleum source rocks.

Sequence-stratigraphic controls on sandstone diagenesis: An example from the Williams Fork formation, Piceance Basin, Colorado

NASA Astrophysics Data System (ADS)

Aboktef, Adel

This study documents the distribution of diagenetic alterations in Williams Fork fluvial sandstones, assess sequence stratigraphic controls on diagenetic features, and addresses diagenetic impacts on porosity. Petrographic point counts of 220 thin sections from six wells forms the database. The near absence of potassium feldspar and volcanic rock fragments in the lower Williams Fork interval and increasing plagioclase content upward represent changes in sediment provenance rather than stratigraphic variability in diagenesis. The lower Williams Fork sands are from sedimentary sources whereas middle and upper Williams Fork sands include input from magmatic arcs and basement uplifts. Compaction, early and late cementation, dissolution, and replacement by calcite or clay minerals combined to alter Williams Fork sandstones. Infiltration of clays occurred prior to any burial. Chlorite, quartz, non-ferroan calcite, compaction and dissolution features, and kaolinite formed during eo-diagenesis at <70°C. More quartz, compaction and dissolution features, plus albite, illite, mixed-layer illite/smectite, ferroan calcite, and dolomite formed in the meso-diagenetic realm (>70°C). Four of these features show spatial variability with respect to systems tracts. Infiltrated clays are concentrated in lowstand systems tracts (LST) and highstand systems tracts (HST) because accommodation space rose slow or fell during deposition of those sands, which led to prolonged sand body exposure on floodplain and ample opportunities for downward percolation of mud during flood events. Concentration of pseudomatrix (mud intraclasts) in HST and LST deposits resulted from floodplain erosion when base-level fell with decreasing accommodation space. Authigenic chlorite formed in the HST and transgressive systems tracts (TST) of the upper half of the Williams Fork Formation because volcanic clasts are abundant in that interval. Quartz overgrowths are more likely to exceed 7% in TST deposits for reasons that are unknown. High total clay content (infiltrated, grain coatings, pseudomatrix) does inhibit quartz overgrowths in all systems tracts. Williams Fork sandstones form low-permeability tight-gas reservoirs. Primary porosity was almost entirely destroyed by compaction and cementation. Reservoir rock resulted from one of two pathways. Eogenetic authigenic chlorite and/or calcite inhibited quartz cementation, minimized compaction and protected some primary porosity. Alternately, dissolution of framework grains or cements created secondary porosity. The later pathway tends to be the more dominant.

Early diagenesis and trace element accumulation in North American Arctic margin sediments

NASA Astrophysics Data System (ADS)

Kuzyk, Zou Zou A.; Gobeil, Charles; Goñi, Miguel A.; Macdonald, Robie W.

2017-04-01

Concentrations of redox-sensitive elements (S, Mn, Mo, U, Cd, Re) were analyzed in a set of 27 sediment cores collected along the North American Arctic margin (NAAM) from the North Bering Sea to Davis Strait via the Canadian Archipelago. Sedimentary distributions and accumulation rates of the elements were used to evaluate early diagenesis in sediments along this section and to estimate the importance of this margin as a sink for key elements in the polar and global oceans. Distributions of Mn, total S and reduced inorganic S demonstrated that diagenetic conditions and thus sedimentary carbon turnover in the NAAM is organized regionally: undetectable or very thin layers (<0.5 cm) of surface Mn enrichment occurred in the Bering-Chukchi shelves; thin layers (1-5 cm) of surface Mn enrichment occurred in Barrow Canyon and Lancaster Sound; and thick layers (5-20 cm) of surface Mn enrichment occurred in the Beaufort Shelf, Canadian Archipelago, and Davis Strait. Inventories of authigenic S below the Mn-rich layer decreased about fivefold from Bering-Chukchi shelf and Barrow Canyon to Lancaster Sound and more than ten-fold from Bering-Chukchi shelf to Beaufort Shelf, Canadian Archipelago and Davis Strait. The Mn, total S and reduced inorganic S distributions imply strong organic carbon (OC) flux and metabolism in the Bering-Chukchi shelves, lower aerobic OC metabolism in Barrow Canyon and Lancaster Sound, and deep O2 penetration and much lower OC metabolism in the Beaufort Shelf, Canadian Archipelago, and Davis Strait. Accumulation rates of authigenic S, Mo, Cd, Re, and U displayed marked spatial variability along the NAAM reflecting the range in sedimentary redox conditions. Strong relationships between the accumulation rates and vertical carbon flux, estimated from regional primary production values and water depth at the coring sites, indicate that the primary driver in the regional patterns is the supply of labile carbon to the seabed. Thus, high primary production combined with a shallow water column (average 64 m) leads to high rates of authigenic trace element accumulation in sediments from the Bering-Chukchi shelves. High to moderate primary production combined with deep water (average 610 m) leads to moderate rates of authigenic trace element accumulation in sediments from Lancaster Sound. Low to very low primary production combined with moderate water depths (average 380 m) leads to low rates of authigenic trace element accumulation in sediments in the Beaufort Shelf, Davis Strait and Canadian Archipelago. Authigenic Mo accumulation rates show a significant relationship with vascular plant input to the sediments, implying that terrestrial organic matter contributes significantly to metabolism in Arctic margin sediments. Our results suggest that the broad and shallow shelf of the Chukchi Sea, which has high productivity sustained by imported nutrients, contributes disproportionately to global biogeochemical cycles.

Authigenic Uranium in Eastern Equatorial Pacific Sediments

NASA Astrophysics Data System (ADS)

Marcantonio, F.; Lyle, M. W.; Loveley, M. R.; Ibrahim, R.

2014-12-01

Authigenic U concentrations have been used as an indicator of redox state in marine sediments. Soluble U(VI) in porewaters is reduced to insoluble U(IV) under suboxic conditions setting up a diffusion gradient through which U in bottom waters is supplied to reducing sediments. Researchers have used sedimentary redox enrichment of U as a tool to identify past redox changes, which may be caused by changes in organic carbon rain rates and/or bottom water oxygen levels. Differentiating between these two explanations is important, as the former is tied to the use of authigenic U as a paleoproductivity proxy. We examined sediments from 4 sediment cores retrieved from two different localities in the Panama Basin in the eastern equatorial Pacific. Two cores were retrieved from the northern Panama basin at the Cocos Ridge, (4JC at 5° 44.7'N 85° 45.5' W, 1730 m depth; 8JC at 6° 14.0'N 86° 2.6' W, 1993 m depth), and two were retrieved from the south at the Carnegie Ridge, (11JC at 0° 41.6'S 85° 20.0' W, 2452 m depth; 17JC at 0° 10.8'S 85° 52.0' W, 2846 m depth). Using 230Th systematics and seismic profiling at each of the sites, we've identified significant sediment winnowing (4JC and 11JC) and focusing (8JC and 17JC). At all sites, we believe that changes in age-model-derived sand (i.e., >63µm) mass accumulation rates (MAR) best represent changes in rain rates. Glacial rain rates are higher than those in the Holocene by a factor of 2-3 at both sites. Peak Mn levels (>1%), the brown-to-green color transition (which likely represents the oxic/post-oxic boundary), and peak U concentrations all appear in the same order with increasing depth down core. At the Carnegie sites, where MARs are greater than those at the Cocos sites, increases in authigenic U (up to 4 ppm) occur during the mid- to late Holocene at depths of 10-15 cm. At the Cocos sites, increases in authigenic U (up to 12 ppm) occur lower in the sediment column (25-30 cm) during the late glacial. The decrease in sediment MAR (and, likely, productivity) between the last glacial and the Holocene has most likely driven the syndiagenetic enrichment of U at these sites by diffusion of bottom water U to slightly beyond the oxic/post-oxic boundary. Hence, changing bottom water oxygen levels are not a requirement to explain authigenic U concentrations in eastern equatorial Pacific sediments.

The Archean Nickel Famine Revisited.

PubMed

Konhauser, Kurt O; Robbins, Leslie J; Pecoits, Ernesto; Peacock, Caroline; Kappler, Andreas; Lalonde, Stefan V

2015-10-01

Iron formations (IF) preserve a history of Precambrian oceanic elemental abundance that can be exploited to examine nutrient limitations on early biological productivity. However, in order for IF to be employed as paleomarine proxies, lumped-process distribution coefficients for the element of interest must be experimentally determined or assumed. This necessitates consideration of bulk ocean chemistry and which authigenic ferric iron minerals controlled the sorption reactions. It also requires an assessment of metal mobilization reactions that might have occurred in the water column during particle descent and during post-depositional burial. Here, we summarize recent developments pertaining to the interpretation and fidelity of the IF record in reconstructions of oceanic trace element evolution. Using an updated compilation, we reexamine and validate temporal trends previously reported for the nickel content in IF (see Konhauser et al., 2009 ). Finally, we reevaluate the consequences of methanogen Ni starvation in the context of evolving views of the Archean ocean-climate system and how the Ni famine may have ultimately facilitated the rise in atmospheric oxygen.

Mineralogy and provenance of clays in miarolitic cavities of the Pikes Peak Batholith, Colorado

USGS Publications Warehouse

Kile, D.E.

2005-01-01

Clay samples from 105 cavities within miarolitic granitic pegmatites throughout the Pikes Peak batholith, in Colorado, were analyzed by powder X-ray diffraction (XRD). Smectite (beidellite), illite, and kaolinite were found within the cavities. Calculation of crystallite-thickness distribution (CTD), mean thickness of the crystallites, and variance in crystallite thickness, as deduced from XRD patterns, allowed a determination of provenance and mode of formation for illite and smectite. Authigenic miarolitic-cavity illite and smectite show lognormal CTDs and larger mean thicknesses of crystallites than do their soil-derived counterparts; non-lognormal illite in a cavity results from mixing of cavity and soil illite. Analysis of mean thickness and thickness variance shows that crystal growth of illite is initiated by a nucleation event of short duration, followed by surface-controlled kinetics. Crystallization of the miarolitic cavity clays is presumed to occur by neoformation from hydrothermal fluids. The assessment of provenance allows a determination of regional and local distributions of clay minerals in miarolitic cavities within the Pikes Peak batholith.

Mineralogy and Isotopic Records of Carbonate and Silicate Cementation of the Siliciclastic Sediments of the New Jersey Shelf (IODP Expedition 313)

NASA Astrophysics Data System (ADS)

Pierre, C.; Blanc-Valleron, M. M.; Lofi, J.

2016-12-01

The New Jersey continental shelf extends up to 150 km away from the shoreline. During IODP Expedition 313 the siliciclastic deposits of late Eocene to late Pleistocene age were drilled down to 631 mbsf, 669 mbsf and 700 mbsf at the three sites 27A, 28A, 29A respectively, in very shallow water depth (33.5 to 36 m). Pore water salinities display multilayered fresh-salty-brine units 10 to 170 m thick, where freshwater is preferentially stored in fine-grained sediments (van Geldern et al 2013 ; Lofi et al 2013). The sharp boundaries of these buried aquifers are often marked by hardly cemented layers a few centimeters thick. The mineralogy and SEM observations of these layers show two phases of cementation by authigenic minerals : (1) the early carbonate cement is made of Fe-dolomite, ankerite and occasionally calcite, frequently associated with pyrite (2) the late silicate cement (silica, K-Fe-rich clay minerals, zeolites) fills in the residual porosity. The isotopic compositions of the carbonate cements vary in wide ranges : -2.4 < δ18O‰ VPDB < +2.8 ; -15.1< δ13C ‰ VPDB <+15.6. The δ18O values indicate carbonate precipitation with pore waters more or less depleted in 18O of the buried aquifers. The δ13C values of carbonate are related to organic matter diagenesis providing 13C-depleted DIC during bacterial sulphate reduction (with pyrite as a by-product of the reaction) and 13C-rich DIC during methanogenesis. The diagenetic cementation processes included chemical weathering of reactive silicate minerals by the CO2-rich pore waters issued from organic matter diagenesis that released bicarbonate, cations and dissolved silica, which were further precipitated as carbonate and silicate cements. The temperature estimated (18 ± 4°C) for the precipitation of carbonate indicates that cementation occurred at moderate burial depths, i.e. probably very soon after deposition. Lofi J et al 2013. Geosphere, 9, 4, 1009-1024 Van Geldern R et al 2013. Geosphere, 9, 1, 96-112

Authigenic 10Be/9Be ratio signatures of the cosmogenic nuclide production linked to geomagnetic dipole moment variation since the Brunhes/Matuyama boundary

PubMed Central

Thouveny, Nicolas; Bourlès, Didier L.; Valet, Jean‐Pierre; Bassinot, Franck; Ménabréaz, Lucie; Guillou, Valéry; Choy, Sandrine; Beaufort, Luc

2016-01-01

Abstract Geomagnetic dipole moment variations associated with polarity reversals and excursions are expressed by large changes of the cosmogenic nuclide beryllium‐10 (10Be) production rates. Authigenic 10Be/9Be ratios (proxy of atmospheric 10Be production) from oceanic cores therefore complete the classical information derived from relative paleointensity (RPI) records. This study presents new authigenic 10Be/9Be ratio results obtained from cores MD05‐2920 and MD05‐2930 collected in the west equatorial Pacific Ocean. Be ratios from cores MD05‐2920, MD05‐2930 and MD90‐0961 have been stacked and averaged. Variations of the authigenic 10Be/9Be ratio are analyzed and compared with the geomagnetic dipole low series reported from global RPI stacks. The largest 10Be overproduction episodes are related to dipole field collapses (below a threshold of 2 × 1022 Am2) associated with the Brunhes/Matuyama reversal, the Laschamp (41 ka) excursion, and the Iceland Basin event (190 ka). Other significant 10Be production peaks are correlated to geomagnetic excursions reported in literature. The record was then calibrated by using absolute dipole moment values drawn from the Geomagia and Pint paleointensity value databases. The 10Be‐derived geomagnetic dipole moment record, independent from sedimentary paleomagnetic data, covers the Brunhes‐Matuyama transition and the whole Brunhes Chron. It provides new and complementary data on the amplitude and timing of millennial‐scale geomagnetic dipole moment variations and particularly on dipole moment collapses triggering polarity instabilities. PMID:28163989

A comparative study of authigenic carbonates from mussel and tubeworm environments: Implications for discriminating the effects of tubeworms

NASA Astrophysics Data System (ADS)

Feng, Dong; Cordes, Erik E.; Roberts, Harry H.; Fisher, Charles R.

2013-05-01

The Gulf of Mexico hydrocarbon seeps are often populated by dense mussel beds and tubeworm aggregations, as well as exposed authigenic carbonate outcrops. Previous studies suggest the activity of mussels and tubeworms could influence the sediment geochemistry of their habitats, resulting in variations in the stable carbon isotopes of the associated carbonates. However, this conclusion was based on the analyses of samples from a single site. To better understand whether there are consistent differences in the geochemical environments of mussels and tubeworms, mineralogical and stable isotopic compositions of authigenic carbonates from mussel and tubeworm environments from four seep sites were analyzed. The studied sites span a depth range of 1200 m to 2800 m on the northern Gulf of Mexico continental slope. We found that carbonate samples from tubeworm environments were more prone to contain aragonite whereas carbonates from mussel environments were more likely to have calcite. This finding supports the hypothesis that vestimentiferans release sulfate across their roots into the pore waters of the surrounding sediments, a process that could generate a locally sulfate-enriched environment that favors the precipitation of aragonite instead of calcite. Moreover, the δ13C values of tubeworm carbonates are generally lighter than that of mussel carbonates from the same site, which is consistent with the fact that tubeworms are fueling extra subsurface methane oxidation through the release of sulfate into the sediment. Such a process, consequently, enriches the subsurface dissolved inorganic carbon pool with light carbon derived from the seeping hydrocarbons. Taken together, our data suggest that tubeworms could produce a carbon isotope shift that is sufficient to influence the sediment geochemistry of their immediate area, and that this impact is reflected in the associated authigenic carbonates.

Speciation of phosphorus in the continental shelf sediments in the Eastern Arabian Sea

NASA Astrophysics Data System (ADS)

Acharya, Shiba Shankar; Panigrahi, Mruganka Kumar; Kurian, John; Gupta, Anil Kumar; Tripathy, Subhasish

2016-03-01

The distributions of various forms of phosphorus (P) and their relation with sediment geochemistry in two core sediments near Karwar and Mangalore offshore have been studied through the modified SEDEX procedure (Ruttenberg et al., 2009) and bulk chemical analysis. The present study provides the first quantitative analysis of complete phosphorus speciation in the core sediments of the Eastern Arabian shelf. The chemical index of alteration (CIA), chemical Index of Weathering (CIW) and Al-Ti-Zr ternary diagram suggest low to moderate source area weathering of granodioritic to tonalitic source rock composition, despite the intense orographic rainfall in the source area. Due to the presence of same source rock and identical oxic depositional environment, the studied sediments show the same range of variation of total phosphorus (24 to 83 μmol/g) with a down-depth depleting trend. Organic bound P and detrital P are the two major chemical forms followed by iron-bound P, exchangeable/loosely bound P and authigenic P. The authigenic P content in the sediments near Mangalore coast varies linearly with calcium (r=0.88) unlike that of Karwar coast. The different reactive-phosphorus pools exhibit identical depleting trend with depth. This indicates that the phosphorus released from the organic matter and Fe bound fractions are prevented from precipitating as authigenic phosphates in the deeper parts of the sediment column. The low concentration of total P, dominance of detrital non-reactive fraction of P and inhibition of formation of authigenic phosphate result in the absence of active phosphatization in the Eastern Arabian Shelf in the studied region. High sedimentation rate (35-58 cm/kyr) and absence of winnowing effect appear to be the dominant factor controlling the P-speciation in the studied sediments.

The role microbial sulfate reduction in the direct mediation of sedimentary authigenic carbonate precipitation

NASA Astrophysics Data System (ADS)

Turchyn, A. V.; Walker, K.; Sun, X.

2016-12-01

The majority of modern deep marine sediments are bathed in water that is undersaturated with respect to calcium carbonate. However, within marine sediments changing chemical conditions, driven largely by the microbial oxidation of organic carbon in the absence of oxygen, lead to supersaturated conditions and drive calcium carbonate precipitation. This sedimentary calcium carbonate is often called `authigenic carbonate', and is found in the form of cements and disseminated crystals within the marine sedimentary pile. As this precipitation of this calcium carbonate is microbially mediated, identifying authigenic carbonate within the geological record and understanding what information its geochemical and/or isotopic signature may hold is key for understanding its importance and what information it may contain past life. However, the modern controls on authigenic carbonate precipitation remain enigmatic because the myriad of microbially mediated reactions occurring within sediments both directly and indirectly impact the proton balance. In this submission we present data from 25 ocean sediment cores spanning the globe where we explore the deviation from the stoichiometrically predicted relationships among alkalinity, calcium and sulfate concentrations. In theory for every mol of organic carbon reduced by sulfate, two mol of alkalinity is produced, and to precipitate subsurface calcium carbonate one mol of calcium is used to consume two mol of alkalinity. We use this data with a model to explore changes in carbonate saturation state with depth below the seafloor. Alkalinity changes in the subsurface are poorly correlated with changes in calcium concentrations, however calcium concentrations are directly and tightly coupled to changes in sulfate concentrations in all studied sites. This suggests a direct role for sulfate reducing bacteria in the precipitation of subsurface carbonate cements.

Cold-seep-driven carbonate deposits at the Central American forearc: contrasting evolution and timing in escarpment and mound settings

NASA Astrophysics Data System (ADS)

Liebetrau, V.; Augustin, N.; Kutterolf, S.; Schmidt, M.; Eisenhauer, A.; Garbe-Schönberg, D.; Weinrebe, W.

2014-10-01

Continuous surface cores of cold-seep carbonates were recovered offshore Pacific Nicaragua and Costa Rica from 800 to 1,500-m water depths (Meteor 66/3) in order to decipher their evolution and methane enriched fluid emanation in contrasting geological settings. Cores from the mounds Iguana, Perezoso, Baula V and from the Jaco Scarp escarpment were used for a multi-method approach. For both settings aragonite was revealed as dominant authigenic carbonate phase in vein fillings and matrix cementation, followed by Mg-calcite as second most abundant. This common precipitation process of CaCO3 polymorphs could be ascribed as indirectly driven by chemical changes of the advecting pore water due to anaerobic oxidation of methane. A more direct influence of seep-related microbial activity on the authigenic mineral assemblage in both settings is probably reflected by the observed minor amounts of dolomite and a dolomite-like CaMg carbonate (MgCO3 ~ 42 %). δ13C data of Jaco Scarp samples are significantly lower (-43 to -56 ‰ PDB) than for mound samples (-22 to -36 ‰ PDB), indicating differences in fluid composition and origin. Noteworthy, δ18O values of Scarp samples correlate most closely with the ocean signature at their time of formation. Documenting the archive potential, a high resolution case study of a mound core implies at least 40 changes in fluid supply within a time interval of approximately 14 ky. As most striking difference, the age data indicate a late-stage downward-progressing cementation front for all three mound cap structures (approx. 2-5 cm/ky), but a significantly faster upward carbonate buildup in the bulging sediments on top of the scarp environment (approx. 120 cm/ky). The latter data set leads to the hypothesis of chemoherm carbonate emplacement in accord with reported sedimentation rates until decompression of the advective fluid system, probably caused by the Jaco Scarp landslide and dating this to approximately 13,000 years ago.

Authigenic apatite and octacalcium phosphate formation due to adsorption-precipitation switching across estuarine salinity gradients

NASA Astrophysics Data System (ADS)

Oxmann, J. F.; Schwendenmann, L.

2015-02-01

Mechanisms governing phosphorus (P) speciation in coastal sediments remain largely unknown due to the diversity of coastal environments and poor analytical specificity for P phases. We investigated P speciation across salinity gradients comprising diverse ecosystems in a P-enriched estuary. To determine P load effects on P speciation we compared the high P site with a low P site. Octacalcium phosphate (OCP), authigenic apatite (carbonate fluorapatite, CFAP) and detrital apatite (fluorapatite) were quantitated in addition to Al/Fe-bound P (Al/Fe-P) and Ca-bound P (Ca-P). Gradients in sediment pH strongly affected P fractions across ecosystems and independent of the site-specific total P status. We found a pronounced switch from adsorbed Al/Fe-P to mineral Ca-P with decreasing acidity from land to sea. This switch occurred at near-neutral sediment pH and has possibly been enhanced by redox-driven phosphate desorption from iron oxyhydroxides. The seaward decline in Al/Fe-P was counterbalanced by the precipitation of Ca-P. Correspondingly, two location-dependent accumulation mechanisms occurred at the high P site due to the switch, leading to elevated Al/Fe-P at pH < 6.6 (landward; adsorption) and elevated Ca-P at pH > 6.6 (seaward; precipitation). Enhanced Ca-P precipitation by increased P loads was also evident from disproportional accumulation of metastable Ca-P (Ca-Pmeta) at the high P site. Here, sediments contained on average 6-fold higher Ca-Pmeta levels compared with the low P site, although these sediments contained only 2-fold more total Ca-P than the low P sediments. Phosphorus species distributions indicated that these elevated Ca-Pmeta levels resulted from transformation of fertilizer-derived Al/Fe-P to OCP and CFAP in nearshore areas. Formation of CFAP as well as its precursor, OCP, results in P retention in coastal zones and can thus lead to substantial inorganic P accumulation in response to anthropogenic P input.

Natural CO 2 accumulations in the western Williston Basin: A mineralogical analog for CO 2 injection at the Weyburn site

DOE PAGES

Ryerson, F. J.; Lake, John; Whittaker, Steven; ...

2013-01-17

The Devonian carbonates of the Duperow Formation on the western flank of the Williston Basin in southwest Saskatchewan contain natural accumulations of CO 2, and may have done so for as long as 50 million years. These carbonate sediments are characterized by a succession of carbonate cycles capped by anhydrite-rich evaporites that are thought to act as seals to fluid migration. The Weyburn CO 2 injection site lies 400 km to the east in a series of Mississippian carbonates that were deposited in a similar depositional environment. That long-term isolation of natural CO 2 can be accomplished within carbonate stratamore » has motivated the investigation of the Duperow rocks as a potential natural analog for storage of anthropogenic CO 2 in carbonate lithologies. For the Duperow strata to represent a legitimate analog for Midale injection and storage, the similarity in lithofacies, whole rock compositions, mineral compositions and porosity with the Midale Beds must be established. Here we compare lithofacies, whole rock compositions, mineralogy and mineral compositions from both locales. The major mineral phases at both locales are calcite, dolomite and anhydrite. In addition, accessory pyrite, fluorite, quartz and celestine (strontium sulfate) are also observed. Dawsonite, a potential CO 2-trapping mineral, is not observed within the CO 2-bearing horizons of the Duperow Formation, however. The distribution of porosity in the Midale Vuggy units is similar to that of the Duperow Formation, but the Marly units of the Midale have significantly higher porosity. The Duperow Formation is topped by the Dinesmore evaporite that is rich in anhydrite, and often contains authigenic K-feldspar. The chemistry of dolomite and calcite from the two localities also overlaps. Silicate minerals are in low abundance (<3%) within the analyzed Duperow samples, with quartz and K-feldspar the only silicates observed petrographically or in X-ray diffraction patterns. The Midale Beds contain significantly higher silica/silicate concentrations (Durocher et al., 2003), but the paucity of mono- and divalent cations that can be derived from dissolution of these silicate minerals likely precludes significant carbonate mineral formation. Therefore physical and solution trapping are likely to be the primary CO 2 trapping mechanisms at both sites.« less

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

NASA Astrophysics Data System (ADS)

Aquilina, Alfred; Homoky, William B.; Hawkes, Jeffrey A.; Lyons, Timothy W.; Mills, Rachel A.

2014-07-01

Short sediment cores were collected from ∼1100 m water depth at the top of Hook Ridge, a submarine volcanic edifice in the Central Basin of the Bransfield Strait, Antarctica, to assess Fe and Mn supply to the water column. Low-temperature hydrothermal fluids advect through these sediments and, in places, subsurface H2S is present at high enough concentrations to support abundant Sclerolinum sp., an infaunal tubeworm that hosts symbiotic thiotrophic bacteria. The water column is fully oxic, and oxygen penetration depths at all sites are 2-5 cmbsf. Pore water Fe and Mn content is high within the subsurface ferruginous zone (max. 565 μmol Fe L-1, >3-7 cmbsf)-14-18 times higher than values measured at a nearby, background site of equivalent water depth. Diffusion and advection of pore waters supply significant Fe and Mn to the surface sediment. Sequential extraction of the sediment demonstrates that there is a significant enrichment in a suite of reactive, authigenic Fe minerals in the upper 0-5 cm of sediment at one site characterised by weathered crusts at the seafloor. At a site with only minor authigenic mineral surface enrichment we infer that leakage of pore water Fe and Mn from the sediment leads to enriched total dissolvable Fe and Mn in bottom waters. An Eh sensor mounted on a towed package mapped a distinct Eh signature above this coring site which is dispersed over several km at the depth of Hook Ridge. We hypothesise that the main mechanism for Fe and Mn efflux from the sediment is breach of the surface oxic layer by the abundant Sclerolinum sp., along with episodic enhancements by physical mixing and resuspension of sediment in this dynamic volcanic environment. We propose that Hook Ridge sediments are an important source of Fe and Mn to the deep waters of the Central Basin in the Bransfield Strait, where concentrations are sustained by the benthic flux, and Fe is stabilised in the water column as either colloidal phases or ligand-bound dissolved species. Entrainment of this water mass into the Drake Passage and thereby the Antarctic Circumpolar Current could provide a significant metal source to this HNLC region of the Southern Ocean if mixing and upwelling occurs before removal of this metal pool to underlying sediments. Sediment-covered volcanic ridges are common within rifted margins and may play a previously overlooked role in the global Fe cycle.

Linking microbial assemblages to paleoenvironmental conditions from the Holocene and Last Glacial Maximum times in Laguna Potrok Aike sediments, Argentina

NASA Astrophysics Data System (ADS)

Vuillemin, Aurele; Ariztegui, Daniel; Leavitt, Peter R.; Bunting, Lynda

2014-05-01

Laguna Potrok Aike is a closed basin located in the southern hemisphere's mid-latitudes (52°S) where paleoenvironmental conditions were recorded as temporal sedimentary sequences resulting from variations in the regional hydrological regime and geology of the catchment. The interpretation of the limnogeological multiproxy record developed during the ICDP-PASADO project allowed the identification of contrasting time windows associated with the fluctuations of Southern Westerly Winds. In the framework of this project, a 100-m-long core was also dedicated to a detailed geomicrobiological study which aimed at a thorough investigation of the lacustrine subsurface biosphere. Indeed, aquatic sediments do not only record past climatic conditions, but also provide a wide range of ecological niches for microbes. In this context, the influence of environmental features upon microbial development and survival remained still unexplored for the deep lacustrine realm. Therefore, we investigated living microbes throughout the sedimentary sequence using in situ ATP assays and DAPI cell count. These results, compiled with pore water analysis, SEM microscopy of authigenic concretions and methane and fatty acid biogeochemistry, provided evidence for a sustained microbial activity in deep sediments and pinpointed the substantial role of microbial processes in modifying initial organic and mineral fractions. Finally, because the genetic material associated with microorganisms can be preserved in sediments over millennia, we extracted environmental DNA from Laguna Potrok Aike sediments and established 16S rRNA bacterial and archaeal clone libraries to better define the use of DNA-based techniques in reconstructing past environments. We focused on two sedimentary horizons both displaying in situ microbial activity, respectively corresponding to the Holocene and Last Glacial Maximum periods. Sequences recovered from the productive Holocene record revealed a microbial community adapted to subsaline conditions producing methane with a high potential of organic matter degradation. In contrast, sediments rich in volcanic detritus from the Last Glacial Maximum showed a substantial presence of lithotrophic microorganisms and sulphate-reducing bacteria mediating authigenic minerals. Together, these features suggested that microbial communities developed in response to climatic control of lake and catchment productivity at the time of sediment deposition. Prevailing climatic conditions exerted a hierarchical control on the microbial composition of lake sediments by regulating the influx of organic and inorganic material to the lake basin, which in turn determined water column chemistry, production and sedimentation of particulate material, resulting in the different niches sheltering these microbial assemblages. Moreover, it demonstrated that environmental DNA can constitute sedimentary archives of phylogenetic diversity and diagenetic processes over tens of millennia.

Phosphate mineral formation in Lake Baikal sediments and implications for paleoclimate

NASA Astrophysics Data System (ADS)

Fagel, N.; Alleman, L. Y.; André, L.; Cloots, R.; Hatert, F.; Juvigné, E.; Renson, V.

2003-04-01

The more than 20 million years old Lake Baikal sedimentary record provides a good climate archive. While most paleoclimate reconstructions are mainly based on biotic proxies, we tested in this study other minerogenic tracers. In particular, it was suggested that the formation of authigenic and/or diagenetic phosphate minerals in Baïkal sediments underlines transitions from glacial to interglacial periods (Deike et al., 1997). The phosphate mineral formation previously evidenced (Müller et al., 2002) may be sensitive to suspended sediment concentrations: glacial periods are characterised by high detrital discharge, interglacial intervals are marked by low detrital supply but high biogenic sedimentation. Phosphate minerals were observed in Baïkal sediments from recent to 65 kyr BP. Their abundance was related to the sedimentation rate, the phosphate enrichment layers being particularly common on low sedimentation site, i.e., the Academician Ridge. Major and trace elements have been analysed by ICP-AES and ICP-MS on four cores drilled on topographic hills, in the southern basin (Posolsky bank, CON01-604), in the central part (Academician Ridge, VER98-1-3 and VER98-1-14) and in the northern basin (Continent Ridge, CON01-603). The geochemical signature is consistent with the occurrence of Mn-Fe-phosphate minerals. For instance P2O5 reaches up to 3% wt. relative to a mean value of 0.3 in the background sediment, MnO2 presents an enrichment factor up to 6. There is no associated enrichment in any of the trace elements measured at the same levels. In the sediments, those P-Mn-Fe rich levels are related either to sparse millimetric dark concretions or to a layer (or a group of layers) defined by an alignment of numerous concretions but there is no so-called crusts. The concretions, isolated by >63 mm sieving, present a lamellar morphology. They are identified as Fe-phosphate phases with a variable proportion of Mn. The powder diffraction diagram is consistent with vivianite, a mineral that has been previously characterized in lacustrine sediments worldwide, including Baïkal. However, its precise formation process is not yet fully understood. Dean et al. (2002) emphasize that the occurrence of phosphate minerals in Elk lake (USA) is indicative of the paleo-productivity of the water-column. For Deike et al. (2002), phosphate crusts mainly accumulate under slow sedimentation conditions. We discuss the paleo-environmental implications of the occurrence of phosphate minerals in sediments. By studying the distribution of the phosphate concretions in sedimentary columns characterised under different sedimentary conditions, we would like to point up the implications of phosphate minerals for paleoclimate reconstruction. Dean et al., 2002. A 1500-year record of climatic and environmental change in Elk Lake, Cearwater County, Minnesota II : Geochemistry , mineralogy, and stable isotopes. J. Paleolimn. 27, 301-319. Müller et al., 2002. P, As, Sb, Mo, and other elements in sedimentary Fe/Mn layers of Lake Baïkal, Environmental Science and Technology, 36, 411-420. Deike et al., 1997. Formation of ferric iron crusts in quaternnary sediments of Lake Baikal, Russia and implications for paleoclimate. Marine Geology 139, 21-46.

Reactive silica fractions in coastal lagoon sediments from the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Krause, Jeffrey W.; Darrow, Elizabeth S.; Pickering, Rebecca A.; Carmichael, Ruth H.; Larson, Ashley M.; Basaldua, Jose L.

2017-12-01

Continental-margin sediments account for 50% of the oceanic biogenic silica burial despite covering < 10% of its area. In Mississippi Sound, a coastal lagoon in the northern Gulf of Mexico (nGoM), we measured sediment biogenic silica at sites removed from major freshwater discharge sources using the traditional method and a method that has been modified for deltaic systems to quantify other reactive silica pools, specifically those involved in the process of reverse weathering. The magnitude of authigenically-altered biogenic silica during our study was significant and represented, on average, 33% of the total sediment biogenic silica among core depths and sites. Additionally, there was a significant relationship between the degree to which the biogenic silica pool was authigenically altered and the source of the sediment organic matter, with lower modification in sediments corresponding with higher terrestrial organic matter. We observed no positive correlation between the magnitude of authigenic modification and sediment clay content. Thus, our findings suggest that these processes may occur within a variety of sediment compositions and add to a growing body of evidence suggesting that reverse weathering of silica in coastal systems is a significant pathway in the global silica budget.

AUthigenic feldspar as an indicator of paleo-rock/water interactions in Permian carbonates of the Northern Calcareous Alps, Austria

USGS Publications Warehouse

Spotl, C.; Kralik, M.; Kunk, Michael J.

1996-01-01

Dolostones interbedded with Upper Permian evaporites at the base of the Northern Calcareous Alps contain abundant authigenic K-feldspar. Two petrographically, structurally, and isotopically distinct generations of K-feldspar can be distinguished: crystals composed of an inclusion-rich core and a clear rim, and optically unzoned, transparent crystals. Both feldspar types have essentially identical K-feldspar end-member compositions with ??? 99.5 mole % Or component. Low oxygen isotope ratios (+16.1??? to +18.1??? SMOW) suggest precipitation from 18O-enriched, saline fluids at temperatures in excess of ??? 140??C. 40Ar/39Ar plateau-age spectra of five samples range from 145 ?? 1 to 144 ?? 1 Ma (Early Berriasian) and suggest that both types of feldspar were formed within an interval that did not exceed ??? 2 m.y. Rb/Sr model ages range from 152 to 140 Ma, assuming that the burial diagenetic regime was buffered with respect to strontium by the associated marine Permian evaporites. Authigenic K-feldspar records two distinct events of hot brine flow, most likely triggered by tectonic movements (detachment) and by an increase in the subsurface temperature in response to thrust loading.

Extraction of seawater-derived neodymium from different phases of deep sea sediments by selective leaching

NASA Astrophysics Data System (ADS)

Blaser, P.; Lippold, J. A.; Frank, N.; Gutjahr, M.; Böhm, E.

2014-12-01

In order to deduce reliable information about the interaction of the oceans with the climate system as a whole in the past, the reconstruction of water mass circulation is crucial. The analysis of seawater-derived neodymium isotopes (143Nd/144Nd, expressed as ɛNd) in marine sediments provides a unique proxy for deep water provenance in particular in the Atlantic [1]. The ɛNd signature and thus the mixing proportion of the local bottom water masses is archived in authigenic phases in the sediment. Obtaining seawater ɛNd from authigenic accretions bound to foraminiferal tests has lately become the preferred since most reliable method [2]. Attempts have also been made to extract the Nd-rich authigenic metal fraction by leaching it off the bulk sediment and thereby use this proxy with less effort, in the highest possible resolution and in sediments where foraminifera are not sufficiently present. However, often other sedimentary components are also leached in the process and contaminate the extracted Nd [3,4]. In this project several core-top and older sediments across the Atlantic have been leached in ten consecutive steps with either dilute buffered acetic acid or an acid-reductive solution. The leachates were analysed on their elemental and Nd isotope compositions, as well as rare earth element (REE) distributions. By graduating the total leaching procedure into smaller stages the results display which processes take place in the course of sediment leaching in the laboratory and which components of the sediment are most reactive. Thus, they help to better evaluate the quality of sediment leaches for ɛNd analysis. Clearly, organic calcite acts as a fast reacting buffer and at the point where its amount is sufficiently reduced the leaching of other components commences and the Nd concentration peaks. Corruption of the extracted ɛNd signal by non-authigenic sources in many cases occured early in the leaching sequence, indicating that only very cautious leaching can reliably extract an authigenic ɛNd signal from diverse sedimentary environments. References: [1] Crocket, K. C. et al. (2011), Geology 39, 515-518 [2] Tachikawa, K. et al. (2014), Quat. Sci. Rev. 88, 1-13 [3] Elmore, A. C. et al. (2011), G³ Vol. 12/9 [4] Wilson, D. J. et al. (2013), GCA 109, 197-221

Millennial Variability of Eastern Equatorial Bottom Water Oxygenation and Atmospheric CO2 over the past 100 kyr

NASA Astrophysics Data System (ADS)

Marcantonio, F.; Loveley, M.; Wisler, M.; Hostak, R.; Hertzberg, J. E.; Schmidt, M. W.; Lyle, M. W.

2017-12-01

Storage of respired carbon in the deep ocean may play a significant role in lowering atmospheric CO2 concentrations by about 80 ppm during the last glacial maximum compared to pre-industrial times. The cause of this sequestration and the subsequent release of the deep respired carbon pool at the last termination remains elusive. Within the last glacial period, on millennial timescales, the relationship between the CO2 cycle and any waxing and waning of a deep respired pool also remains unclear. To further our understanding of the millennial variability in the storage of a deep-ocean respired carbon pool during the last glacial, we measure authigenic uranium and 230Th-derived non-lithogenic barium fluxes (xsBa flux) in two high-sedimentation-rate cores from the Panama Basin of the Eastern Equatorial Pacific (EEP) (8JC, 6° 14.0' N, 86° 02.6' W; 1993 m water depth; 17JC 00° 10.8' S, 85° 52.0' W; 2846 m water depth). Sediment authigenic U concentrations are controlled by the redox state of sediments which, in turn, is a function of the rain of organic material from the surface ocean and the oxygen content of bottom waters. At both 8JC and 17JC, the mismatch between xsBa fluxes, a proxy for the reconstruction of oceanic productivity, and authigenic uranium concentrations suggests that the primary control of the latter values is changes in bottom water oxygenation. Peak authigenic uranium concentrations occur during glacial periods MIS 2, 3, and 4, respectively, and are two to three times higher than those during interglacial periods, MIS 1 and 5. EEP bottom waters were likely suboxic during times of the last glacial period when atmospheric CO2 concentrations were at their lowest concentrations. In addition, the pattern of increased deep-water oxygenation during times of higher CO2 during the last glacial is similar to that reported in a study of authigenic U in sediments from the Antarctic Zone of the Southern Ocean (Jaccard et al., 2016). We suggest that a respired carbon pool existed within a large swath of the abyssal Southern and Pacific Oceans throughout the entire last glacial cycle, and that this respired carbon was periodically released through increased ventilation of deep ocean waters. Jaccard et al. (2016) Nature 530, 207-210.

The geochemistry of redox sensitive trace metals in sediments

NASA Astrophysics Data System (ADS)

Morford, Jennifer L.; Emerson, Steven

1999-06-01

We analyzed the redox sensitive elements V, Mo, U, Re and Cd in surface sediments from the Northwest African margin, the U.S. Northwest margin and the Arabian Sea to determine their response under a range of redox conditions. Where oxygen penetrates 1 cm or less into the sediments, Mo and V diffuse to the overlying water as Mn is reduced and remobilized. Authigenic enrichments of U, Re and Cd are evident under these redox conditions. With the onset of sulfate reduction, all of the metals accumulate authigenically with Re being by far the most enriched. General trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes: oxic, reducing where oxygen penetrates ≤1 cm, and anoxic conditions. Using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations, we calculate the area of sediments below 1000 m water depth in which oxygen penetration is ≤1 cm to be 4% of the ocean floor. We conclude that sediments where oxygen penetrates ≤1 cm release Mn, V and Mo to seawater at rates of 140%-260%, 60%-150% and 5%-10% of their respective riverine fluxes, using the authigenic metal concentrations and accumulation rates from this work and other literature. These sediments are sinks for Re, Cd and U, with burial fluxes of 70%-140%, 30%-80% and 20%-40%, respectively, of their dissolved riverine inputs. We modeled the sensitivity of the response of seawater Re, Cd and V concentrations to changes in the area of reducing sediments where oxygen penetrates ≤1 cm. Our analysis suggests a negligible change in seawater Re concentration, whereas seawater concentrations of Cd and V could have decreased and increased, respectively, by 5%-10% over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10%-20% if the area increased by a factor of 3. The concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of Cd/Ca and V/Ca ratios observed in foraminifera shells over the last 40 kyr. This implies that the area of reducing sediments in the ocean deeper than 1000 m (4%) has not been greater than twice the present value in the recent past.

Similarity of nannobacterial lifeforms in cultures, in the human body, in minerals

NASA Astrophysics Data System (ADS)

Folk, R.

Nearly a dozen labs world-wide have succeeded in culturing minute organisms in the 50-200 nm size range, so the characterization of nannobacteria as some form of "life" is no longer arguable. Within the human body, they are found in blood, kidney stones, dental plaque, arterial disease and cataracts as shown by the Kajander group in Finland, and by our work with Mayo Clinic (e.g. Folk et al., 2001 GSA abs.). Nannobacteria can be concentrated in waters from hot springs, lakes, rivers and the sea. Their charged cell walls attract ions thus triggering precipitation of such varied authigenic minerals as aragonite, calcite, dolomite and siderite; sulfur, pyrite, chalcocite, chalcopyrite; phosphates; chalcedony quartz; and smectite, illite, kaolinite, chlorite and palygorskite clay. So it should be no surprise that on Mars, with reactive FeMg minerals, subsurface (and once surface) water, and internal heat, nannobacteria would be able to thrive both in vein-fill carbonates (McKay et al, 1996) and on the altered surfaces of unstable pyroxenes (Folk and Taylor, in press Met. &Plan. S i., 2002). Striking identities of sizes, shapes, and colonial affinitiesc are found between Martian nannobacteria and those in clays from Sicily and elsewhere (Folk and Lynch, 1997 SPIE). Extraterrestrial forms range from spheroids and ovoids of 30-80 nm, to worm- and caterpillar-shaped objects (40 X 150 nm) and chains of 40 nm beads. Even in the Allende carbonaceous chondrite, groups of 40- 150 nm bodies resembly earthly Streptococcus and Staphylococcus are found (Folk and Lynch 1998 SPIE). The highly-matured nature of the kerogen-like carbon in Allende demonstrates that it is not the result of earthly contamination; furthermore Allende contains clay minerals which demand the former presence of some water, a requirement for biology.The only objection to the claimed discovery of extraterrestrial life in the form of nannobacteria is the Old Testament view that God created life only on Earth and nowhere else.

Variations in sedimentological properties in Lake Challa, East Africa: Understanding the source to sink processes

NASA Astrophysics Data System (ADS)

Meyer, Inka; Eloy, Jonas; Verschuren, Dirk; De Batist, Marc

2016-04-01

The clastic mineral fraction of lacustrine sediments has been proven to provide valuable information about sedimentation dynamics within a lake, and it can be used to define distinct terrestrial source areas and transport mechanisms from source to sink. Down-core variation in the properties of the clastic mineral fraction yields indications for changes in terrestrial sediment sources over time. However, in order to use terrestrial proxies in palaeo-environmental reconstruction, we have to understand and quantify the modern conditions of sediment provenance and deposition at the study site. In this study we present data on grain-size distribution, mineralogy and particle shape of the clastic mineral component of lacustrine sediments from Lake Challa, a small freshwater lake of volcanic origin, located on the eastern slope of Mt. Kilimanjaro. Situated close to the equator, it contains a uniquely long and continuous sediment sequence allowing the study of inter-hemispheric climate dynamics. The finely laminated profundal sediments of Lake Challa are characterized by a fine-grained texture and are mainly composed of organic matter, biogenic silica and authigenic carbonate, with a relatively minor component of detrital mineral that can either originate from erosion of the steep volcanic crater walls or was mobilized by wind from unvegetated areas of the surrounding scrub savannah landscape. In order to distinguish between these two sources of terrestrial sediment input (i.e., local run-off versus distant aeolian) into Lake Challa, and to map out differences in sediment properties, samples were investigated from profundal surface sediments and short cores, as well as on-shore soils from several locations around the lake and from beyond the crater catchment. Variation in grain-size distribution and mineralogy can be linked to distinct terrestrial sources, whereas the shape of single particles gives additional information about transport dynamics. In future, the results from this study will be applied to the down-core record of Lake Challa to reconstruct climate-driven changes in terrigenous sediment input over time.

Dolomite Formation within Microbial Mats in the Sabkha of Abu Dhabi (UAE) and Associated Microsedimentary Structures

NASA Astrophysics Data System (ADS)

Bontognali, T. R.; Vasconcelos, C.; McKenzie, J. A.

2008-12-01

The link between microbial activity and dolomite formation has been evaluated in the coastal sabkha of Abu Dhabi (UAE). This modern dolomite-forming environment is frequently cited as the type analogue for the interpretation of many ancient evaporitic sequences. The investigation of sabkha sediments along a transect from intertidal to supratidal zones revealed a close association between microbial mats and dolomite. Authigenic dolomite occurs within surface and buried microbial mats, which are comprised of exopolymeric substances (EPS). Dolomite forms as a direct consequence of mineral nucleation and growth within microbially produced EPS. The cation-binding effect of the EPS molecules influences the composition of the precipitate. The early stage of this process is characterized by the complexation of an amorphous Mg-Si precipitate, which promotes dolomite development. Mineral formation within EPS appears to be enhanced by evaporation with consequent supersaturation of the pore waters with respect to dolomite. Partial EPS degradation during diagenesis may also provide an additional source of cations. However, the specific mineral-template property of EPS, rather than an increase in cation concentrations, is the key factor for dolomite formation in the studied area of the sabkha. Indeed, within the modern microbial mat located at the surface, dolomite precipitates from pore waters whose composition is very close to seawater. In the supratidal zone, pore water analysis and stable isotope values did not reveal any linkage between dolomite formation and microbial excretion and/or consumption of metabolites along the sediment profiles. This is in contrast with current models, in which dolomite formation is mainly linked to microbial increase of pH and alkalinity or consumption of dissolved SO4 in pore-waters. The EPS of the microbial mats is characterized by an alveolar microfabric, which can be mineralized during early diagenesis, preserving fossil imprints of the original biofilm. Recognition of this biostructure, combined with the atypical Mg-Si phase, may be used to interpret ancient microbial dolomite throughout the geological record.

Reconstructing fluid-flow events in Lower-Triassic sandstones of the eastern Paris Basin by elemental tracing and isotopic dating of nanometric illite crystals

NASA Astrophysics Data System (ADS)

Blaise, Thomas; Clauer, Norbert; Cathelineau, Michel; Boiron, Marie-Christine; Techer, Isabelle; Boulvais, Philippe

2016-03-01

Lower- to Middle-Triassic sandstones from eastern Paris Basin were buried to a maximum depth of 2500 m at a paleo-temperature of about 100 °C. They contain extensive amounts of authigenic platy and filamentous illite particles similar to those reported in reservoirs generally buried at 3000 to -5000 m and subjected to temperatures of 120 to -150 °C. To evaluate this unexpected occurrence, such sandstones were collected from drill cores between 1825 and 2000 m depth, and nanometric-sized sub-fractions were separated. The illite crystals were identified by XRD, observed by SEM and TEM, analyzed for their major, trace, rare-earth elements and oxygen isotope compositions, and dated by K-Ar and Rb-Sr. Illite particles display varied growth features in the rock pore-space and on authigenic quartz and adularia that they postdate. TEM-EDS crystal-chemical in situ data show that the illite lath/fiber and platelet morphologies correspond at least to two populations with varied interlayer charges: between 0.7 and 0.9 for the former and between 0.8 and 1.0 for the latter, the Fe/Fe + Mg ratio being higher in the platelets. Except for the deeper conglomerate, the PAAS-normalized REE patterns of the illite crystals are bell-shaped, enriched in middle REEs. Ca-carbonates and Ca-phosphates were detected together with illite in the separates. These soluble components yield 87Sr/86Sr ratios that are not strictly in chemical equilibrium with the illite crystals, suggesting successive fluids flows with different chemical compositions. The K-Ar data of finer <0.05 μm illite separates confirm two crystallization events at 179.4 ± 4.5 and 149.4 ± 2.5 Ma during the Early and Late Jurassic. The slightly coarser fractions contain also earlier crystallized or detrital K-bearing minerals characterized by lower δ18O values. The δ18O of the finest authigenic illite separates tends to decrease slightly with depth, from 18.2 (±0.2) to 16.3 (±0.2)‰, suggesting different but contemporaneous crystallization conditions deeper in the section. The illite platelets and filaments crystallized in changing physical-chemical crystallization conditions induced by fluids flows through the host-rock pore system. These flow events were probably driven by repetitive rifting episodes of the North Atlantic Ocean, although located several hundreds kilometers away from eastern Paris Basin, and/or by fracturing events in the nearby basement of the Vosges Massif. Complex relationships between geodynamical events, thermal anomalies, and advective fluids confirm that remote tectonic activities can impact quiescent basins, even if located far from tectono-thermal activities, by discrete and long-distance fluid flows.

Water column particulate matter: A key contributor to phosphorus regeneration in a coastal eutrophic environment, the Chesapeake Bay: Particulate phosphorus in the Chesapeake Bay

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

Li, Jiying; Reardon, Patrick; McKinley, James P.

Particulate phosphorus (PP) in the water column is an essential component of phosphorus (P) cycling in aquatic ecosystems yet its composition and transformations remain largely uncharacterized. To understand the roles of suspended particulates on regeneration of inorganic P (Pi) into the water column as well as sequestration into more stable mineral precipitates, we studied seasonal variation in both organic and inorganic P speciation in suspended particles in three sites in the Chesapeake Bay using sequential P extraction, 1D (31P) and 2D (1H-31P) nuclear magnetic resonance (NMR) spectroscopies, and electron microprobe analyses (EMPA). Remineralization efficiency of particulate P average 8% andmore » 56% in shallow and deep sites respectively, suggesting the importance of PP remineralization is in resupplying water column Pi. Strong temporal and spatial variability of organic P composition, distributions, and remineralization efficiency were observed relating to water column parameters such as temperature and redox conditions: concentration of orthophosphate monoesters and diesters, and diester-to-monoester (D/M) ratios decreased with depth. Both esters and the D/M ratios were lower in the hypoxic July and September. In contrast, pyrophosphate and orthophosphate increased with depth, and polyphosphates was high in the anoxic water column. Sequential extraction and EMPA analyses of the suspended particles suggest presence of Ca-bound phosphate in the water column. We hypothesize authigenic precipitation of carbonate fluorapatite and/or its precursor mineral(s) in Pi rich water column, supported by our thermodynamic calculations. Our results, overall, reveal the important role suspended particles play in P remineralization and P sequestration in the Chesapeake Bay water column, provide important implications on P bioavailability and P sinks in similar eutrophic coastal environments.« less

A Perspective on Diagenetic Geometries and Patterns of Iron Oxide Cement and Coloration: Understanding Challenges and Complexities

NASA Astrophysics Data System (ADS)

Chan, M. A.; Wang, Y.

2015-12-01

Diagenetic records of fluid flow are underutilized proxies of water and environmental conditions in sedimentary rocks on Earth as well as Mars. The terrestrial iron-oxide records can be highly varied from faint wisps of coloration, to heavily cemented masses and layers. Other than vein cements, concretionary forms are some of the most prominent, yet enigmatic records. Concretions can have various mineral cement compositions with sizes that can span three orders of magnitude from mm, to cm, and m scales, in remarkably consistent, common spheroidal forms. Concretion geometries and banding may indicate directions and timings of fluid flow and precipitation, but deciphering the origins can be difficult with limited analytical tools. Definite complexities are the possibilities of: 1) overprinted events in an open system; 2) the role of organics in the nucleation and precipitation of authigenic minerals; and 3) multiple fluids, pathways, or processes that may produce similar-looking end products. In near-surface environments, likely any water since the Proterozoic has contained microbial life, and thus it seems highly probable that microbes play a significant role in the precipitation of diagenetic minerals due to the interactions of the biosphere and geosphere. However, recognition of ancient biosignatures that may have poor preservation potential remains a challenge. Iron oxides are particularly common, valuable indicators of near-surface iron cycling and are recognizable because the visual coloration. Our recent studies in Jurassic sandstones indicate preserved records of fingering at the interface of two immiscible fluids. The integration of geochemical self-organization models and field data provides new insights to understanding diagenetic fluid compositions, their relative densities, and flow direction flux and movement. These studies can have valuable implications and applications for understanding past fluid flow history, and reservoir characterization for CO2, hydrocarbon, and water.

Inorganic geochemistry of domed peat in Indonesia and its implication for the origin of mineral matter in coal

USGS Publications Warehouse

Neuzil, Sandra G.; Supardi,; Cecil, C. Blaine; Kane, Jean S.; Soedjono, Kadar

1993-01-01

The inorganic geochemistry of three domed ombrogenous peat deposits in Riau and West Kalimantan provinces, Indonesia, was investigated as a possible modern analogue for certain types of low-ash, low-sulfur coal. Mineral matter entering the deposits is apparently limited to small amounts from the allogenic sources of dryfall, rainfall, and diffusion from substrate pore water. In the low-ash peat in the interior of the deposits, a large portion of the mineral matter is authigenic and has been mobilized and stabilized by hydrological, chemical, and biological processes and conditions.Ash yield and sulfur content are low through most of the peat deposits and average 1.1% and 0.14%, respectively, on a moisture-free basis. Ash and sulfur contents only exceed 5% and 0.3%, respectively, near the base of the deposits, with maximum concentrations of 19.9% ash and 0.56% sulfur. Peat water in all three deposits has a low pH, about 4 units, and low dissolved cation concentration, averaging 14 ppm. Near the base, in the geographic interior of each peat deposit, pH is about two units higher and dissolved cation concentration averages 110 ppm. Relative concentrations of the inorganic constituents vary, resulting in chemical facies in the peat. In general, Si, Al, and Fe are the abundant inorganic constituents, although Mg, Ca, and Na dominate in the middle horizon in the geographic interior of coastal peat deposits.The composition of the three deposits reported in this paper indicates that domed ombrogenous peat deposits will result in low ash and sulfur coal, probably less than 10% ash and 1% sulfur, even if marine rocks are laterally and vertically adjacent to the coal.

Mineral-microorganism interactions in Acid Mine Drainage environments: preliminary results

NASA Astrophysics Data System (ADS)

Carbone, Cristina; Zotti, Mirca; Pozzolini, Marina; Giovine, Marco; Di Piazza, Simone; Mariotti, Mauro; Lucchetti, Gabriella

2014-05-01

Minerals play a key role in controlling the mobility and distribution of metals and metalloids of environmental concern in supergenic environments. These are involved in a variety of processes, spanning the alteration of primary minerals to the formation of secondary authigenic phases and can represent a source or a trap for Potentially Ecotoxic Elements (PTEs). Soil, sediments, and waters heavily polluted with PTEs through AMD processes are a reservoir of a unusual bacteria and fungi well adapted to these toxic environments. Classical studies of biotic weathering have mainly focused on water-mineral interaction and on the ability of microorganism to influence the soil solution chemical composition. In this work, we analyzed two different representative ochreous and greenish-blue AMD colloidal precipitates in order to i) characterize the biota population present in these colloidal minerals and ii) verify the bioaccumulation of PTEs into the fungi and the potential impact of bacteria in the geochemistry of the system. The samples are composed by nanocrystalline goethite which contains high amounts of Fe, Cu, Zn, Pb, and Ni and woodwardite that is characterized by Cu, Zn, Ni, Y, and Ce. These precipitates were examined in order to evaluate the presence of fungal strains and to extract bacteria DNA. The preliminary results of fungi characterization show an interesting and selected mycobiota able to survive under unfavourable environmental conditions. A significant number of fungal strains was isolated in pure culture. Most of them belong to the genus Mucor and Penicillium. It is worth noting the presence of Trametes versicolor, a macrofungal lignicolous species already known for heavy metal biosorption capability from aqueous solution (Gülay et al 2003). The same colloidal precipitates have been processed to extract bacteria DNA, using a specific procedure developed for DNA extraction from sediments. The results gave a good yield of nucleic acids and the positive PCR amplification of 16S rDNA accomplished the first step for future metagenomic analysis. Gülay B., Sema B., M. Yakup A.. 2003 Biosorption of heavy metal ions on immobilized white-rot fungus Trametes versicolor. Journal of Hazardous Materials B101 (2003) 285-300

Septate-tubular textures in 2.0-Ga pillow lavas from the Pechenga Greenstone Belt: a nano-spectroscopic approach to investigate their biogenicity.

PubMed

Fliegel, D; Wirth, R; Simonetti, A; Furnes, H; Staudigel, H; Hanski, E; Muehlenbachs, K

2010-12-01

Pillow lava rims and interpillow hyaloclastites from the upper part of the Pechenga Greenstone Belt, Kola Peninsula, N-Russia contain rare tubular textures 15-20 μm in diameter and up to several hundred μm long in prehnite-pumpellyite to lower greenschist facies meta-volcanic glass. The textures are septate with regular compartments 5-20 μm across and exhibit branching, stopping and no intersecting features. Synchrotron micro-energy dispersive X-ray was used to image elemental distributions; scanning transmission X-ray microscopy, Fe L-edge and C K-edge were used to identify iron and carbon speciation at interfaces between the tubular textures and the host rock. In situ U-Pb radiometric dating by LA-MC-ICP-MS (laser ablation multicollector inductively coupled plasma mass spectrometry) of titanite from pillow lavas yielded a metamorphic age of 1790 ± 89 Ma. Focused ion-beam milling combined with transmission electron microscopy was used to analyze the textures in three dimensions. Electron diffraction showed that the textures are mineralized by orientated pumpellyite. On the margins of the tubes, an interface between mica or chlorite and the pumpellyite shows evidence of dissolution reactions where the pumpellyite is replaced by mica/chlorite. A thin poorly crystalline Fe-phase, probably precipitated out of solution, occurs at the interface between pumpellyite and mica/chlorite. This sequence of phases leads to the hypothesis that the tubes were initially hollow, compartmentalized structures in volcanic glass that were mineralized by pumpellyite during low-grade metamorphism. Later, a Fe-bearing fluid mineralized the compartments between the pumpellyite and lastly the pumpellyite was partially dissolved and replaced by chlorite during greenschist metamorphism. The most plausible origin for a septate-tubular texture is a progressive etching of the host matrix by several generations of microbes and subsequently these tubes were filled by authigenic mineral precipitates. This preserves the textures in the rock record over geological time. The micro textures reported here thus represent a pumpellyite-mineralized trace fossil that records a Paleoproterozoic sub-seafloor biosphere. © 2010 Blackwell Publishing Ltd.

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.

Comparison of the Wymark CO2 Reservoir with the Midale Beds at the Weyburn CO2 Injection Project

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

Ryerson, F; Johnson, J

2010-11-22

The Devonian carbonates of the Duperow Formation on the western flank of the Williston Basin in southwest Saskatchewan contain natural accumulations of CO{sub 2}, and may have done so for as long as 50 m.y. in the views of some investigations. These carbonate sediments are characterized by a succession of carbonate cycles capped by anhydrite-rich evaporites that are thought to act as seals to fluid migration. The Weyburn CO{sub 2} injection site lies 400 km to the east in a series of Mississippian carbonates that were deposited in a similar depositional environment. That natural CO{sub 2} can be stored long-termmore » within carbonate strata has motivated the investigation of the Duperow rocks as a potential natural analogue to storage of anthropogenic CO{sub 2} that may ultimately provide additional confidence for CO{sub 2} sequestration in carbonate lithologies. For the Duperow strata to represent a legitimate analog for Midale injection and storage, the similarity in lithofacies, whole rock compositions, mineral compositions and porosity with the Midale Beds must be established. Previous workers have demonstrated the similarity of the lithofacies at both sites. Here we compare the whole rock compositions, mineralogy and mineral compositions. The major mineral phases at both locales are calcite, dolomite and anhydrite. In addition, accessory pyrite, fluorite and celestine are also observed. The distribution of porosity in the Midale Vuggy units is virtually identical to that of the Duperow Formation, but the Marly units of the Midale have significantly higher porosity. The Duperow Formation is topped by the Dinesmore evaporite that is particularly rich in anhydrite, and often contains authigenic K-feldspar. The chemistry of dolomite and calcite from the two localities also overlaps. Silicate minerals are in low abundance within the analyzed Duperow samples, < 3 wt% on a normative basis, with quartz the only phase identifiable in x-ray diffraction patterns. The Midale Beds contain significantly higher silica/silicate concentrations, but the silicate minerals observed, K-feldspar and quartz, are unlikely to participate in carbonate mineral precipitation due to the absence of alkaline earths. Hence, physical and solution trapping are likely to be the primary trapping mechanisms at both sites. Given the similarity of mineral constituents, whole rock and mineral chemistry, reactive transport models developed for the Weyburn site should also be applicable to the Duperow lithologies.« less

Mobility of authigenic rhenium, silver, and selenium during postdepositional oxidation in marine sediments

USGS Publications Warehouse

Crusius, John; Thomson, John

2003-01-01

Sedimentary records of redox-sensitive trace elements hold significant potential as indicators of paleoceanographic environmental conditions. Records of Re can reveal the intensity of past reducing conditions in sediments at the time of deposition, whereas records of Ag may record the magnitude of past diatom fluxes to the seafloor. Confidence in paleoenvironmental reconstruction from records of either metal, however, requires it to have experienced negligible redistribution since deposition. This study examines diagenetic rearrangements of Re and Ag that occur in response to exposure to bottom-water O2 in environments of low sedimentation rate, including Madeira Abyssal Plain turbidites and eastern Mediterranean basin sapropels. Authigenic Re was remobilized quantitatively by oxidation but poorly retained by the underlying sediments. All records are consistent with previous work demonstrating that only a limited reimmobilization of Re occurs preferentially in Corg-rich, reducing sediments. Silver was also mobilized quantitatively by oxidation, but it was subsequently immobilized more efficiently in all cases as sharp peaks immediately into anoxic conditions below active oxidation fronts, and these peaks remain immobile in anoxic conditions during long-term burial. Comparison of Ag, S, and Se records from various cores suggests that Ag is likely to have been immobilized as a selenide, a mechanism previously proposed for Hg in similar situations (Mercone et al., 1999). Coexisting narrow peaks of Ag and Hg with Se offer a means of assessing whether oxidative burndown has ever occurred at the top of Corg- and sulfide-rich sedimentary units. Although these results suggest that caution must be used when inferring paleoenvironmental information from records of Ag and Re in cores with low sediment accumulation rates (<5 cm ka−1), they should not affect the promise that authigenic Ag and Re records hold for paleoenvironmental reconstruction in sediments with higher accumulation rates and where anoxic conditions have been maintained continuously.

Regional patterns of labile organic carbon flux in North American Arctic Margin (NAAM) as reflected by redox sensitive-elements distributions in sediments

NASA Astrophysics Data System (ADS)

Gobeil, C.; Kuzyk, Z. Z. A.; Goni, M. A.; Macdonald, R. W.

2016-02-01

Concentrations of elements (S, Mn, Mo, U, Cd, Re) providing insights on organic C metabolized through oxidative processes at the sea floor were measured in 27 sediment cores collected along a section extending from the North Bering Sea to Davis Strait via the Canadian Archipelago. Sedimentary distributions and accumulation rates of these elements were used to i) document the relative importance of aerobic versus anaerobic degradation of organic C in NAAM sediments, ii) infer variations in water column carbon flux and iii) estimate the importance of this margin as a sink for key elements in the Arctic and global ocean. Distributions of Mn, total S and reduced inorganic S demonstrated that most sediments along the NAAM had relatively thick (>1 cm) surface oxic layers, underlain by sediments with weakly reducing conditions and limited sulphate reduction. Strongly reducing conditions accompanied by substantial sedimentary pyrite burial occurred only in certain subregions, including the Bering-Chukchi Shelves, shallow portions of Barrow Canyon. Estimated accumulation rates of authigenic S, Mo, Cd and U, and total Re displayed marked spatial variability that was related to sedimentary redox conditions induced by the supply of labile C to the seabed, as shown by significant relationships between the accumulation rates and vertical C flux, estimated from regional primary production values and water depth at the coring sites. High primary production combined with shallow water columns drive elevated rates of authigenic trace element accumulation in sediments from the Bering-Chukchi Shelves whereas low production combined with moderately deep conditions drive low rates of accumulation in sediments in the Beaufort Shelf, Davis Strait and Canadian Archipelago. Using the average authigenic trace element accumulation rates in sediments from the various regions, we submit that the shelves along the NAAM margin are important sinks in global marine biogeochemical budgets.

Gypsum crystals observed in experimental and natural sea ice

NASA Astrophysics Data System (ADS)

Geilfus, N.-X.; Galley, R. J.; Cooper, M.; Halden, N.; Hare, A.; Wang, F.; Søgaard, D. H.; Rysgaard, S.

2013-12-01

gypsum has been predicted to precipitate in sea ice, it has never been observed. Here we provide the first report on gypsum precipitation in both experimental and natural sea ice. Crystals were identified by X-ray diffraction analysis. Based on their apparent distinguishing characteristics, the gypsum crystals were identified as being authigenic. The FREeZing CHEMistry (FREZCHEM) model results support our observations of both gypsum and ikaite precipitation at typical in situ sea ice temperatures and confirms the "Gitterman pathway" where gypsum is predicted to precipitate. The occurrence of authigenic gypsum in sea ice during its formation represents a new observation of precipitate formation and potential marine deposition in polar seas.

Distribution and origin of authigenic smectite clays in Cape Roberts Project Core 3, Victoria Land Basin, Antarctica

USGS Publications Warehouse

Priestas, A.W.; Wise, S.W.

2007-01-01

Of some 800 m of lower Oligocene marine sediments cored continuously from the seafloor in the Victoria Land Basin of Antarctica at Cape Roberts Site CRP-3, the lower 500 m exhibit authigenic smectite clay coats on shallow-water sandstone grains. A scanning electron microscope/EDS study of 46 fracture sections confirms that the distribution of the clay coats through the unit is not uniform or evenly distributed, but rather varies with depth, original porosity, and the kinds and abundance of source materials. Our results suggest that smectite emplacement resulted from in-situ, low-temperature burial diagenesis rather than hydrothermal or fault-focused thermobaric fluids.

Developing alternative resources of rare earth elements in Europe - EURARE and the red mud challenge

NASA Astrophysics Data System (ADS)

Deady, Eimear; Mouchos, Evangelos; Goodenough, Kathryn; Wall, Frances; Williamson, Ben

2015-04-01

Rare earth elements (REE) are considered to be highly "critical" by the European Commission [1], owing to the concentration of global supply [2] and their use in a wide range of emerging technologies (e.g. smart phones, electric cars and wind turbines). The main source of REE is the mineral bastnäsite, which is primarily extracted from carbonatites. Alternative resources of REE have been identified in a variety of other environments such as alluvial placers, bauxites and ore tailings. The EURARE project (www.eurare.eu), funded by the European Commission, aims to improve understanding of potential REE resources in Europe with the overall objective of establishing the basis for a European REE industry. As a part of this project, alternative sources of rare earth elements in Europe are being considered. REE have been identified as being particularly enriched in karst-bauxites and hence in the red muds generated as a waste product from the processing of these bauxites to alumina through the Bayer process [3]. Karst-bauxites are widely distributed with deposits known across the Mediterranean and with intermittent exploitation occurring over many decades. REE become concentrated in the bauxite deposits by the bauxitisation process and are retained due to the geochemical barrier created by the limestone bedrock below. This can result in several processes, including the crystallisation of authigenic REE-bearing minerals, the accumulation of residual phases and the adsorption of ions onto clays and other mineral surfaces [4]. Red muds produced from alumina processing represent a potentially important concentration of REE as it has been demonstrated that the REE pass through the alumina extraction process into the waste, and the total REE concentrations are typically enriched by a factor of two compared with the original bauxite ore [5]. Bauxites and red muds from the Parnassus Ghiona region of Greece [6] and the Seydişehir-Akseki region of Turkey have been assessed as part of this study. Red muds from these deposits contain on average 900 ppm REE compared with typical values of <100 ppm to ~500 ppm REE in the bauxites. Extraction of REE from red muds has been shown to be feasible [5,7] although it is challenging due to the heterogeneous spatial distribution of REE in the primary bauxite deposits [8], an unclear understanding of the mobility of REE in red mud tailings ponds, and the need for development of appropriate processing methods. However, the resource potential of red muds in Europe is significant with approximately 3.5 Mt of bauxite ore extracted in 2012 [2], resulting in approximately 1.4 Mt of red mud from the production of alumina. In addition a large volume of stockpiled red muds exists from historical processing of bauxites, the total of which is not well constrained. Understanding the REE potential of both bauxites and red muds is integral to an assessment of European REE resources. References [1] European Commission, "Report on critical raw materials for the EU. Report of the Ad hoc Working Group on defining critical raw materials". May 2014. [2] T. Brown, N. Idoine, E. Raycraft, R. Shaw, E. Deady, J. Rippingale, T. Bide, C. Wrighton, J. Rodley, "World Mineral Production 2008-12" British Geological Survey, Keyworth, Nottingham, 2014. [3] Z. Maksimović and G. Pantó, "Authigenic rare earth minerals in karst-bauxites and karstic nickel deposits". In: A.P. Jones, F. Wall and C.T. Williams, Rare earth minerals, chemistry, origin and ore deposits, Chapter 10, pp. 257-279, 1996. [4] G. Bárdossy, "Karst Bauxites, Bauxite Deposits on Carbonate Rocks". Elsevier, 444pp, 1982. [5] M. Ochsenkühn-Petropoulou, T. Lyberopoulou, and G. Parissakis, "Direct determination of lanthanides, yttium and scandium in bauxites and red mud from alumina production", Analytica Chimica Acta, vol. 296, no. 3, pp. 305-313, October 1994. [6] É. Deady, E. Mouchos, K. Goodenough, B. Williamson and F. Wall. "Rare Earth Elements in Karst-Bauxites: a Novel Untapped European Resource?" ERES 1st European Rare Earth Resources conference, Milos, Greece, (5-6/09/2014). [7] A. Wagh and W. Pinnock, "Occurrence of scandium and rare earth elements in Jamaican bauxite waste", Economic Geology, vol. 82, no. 3, pp. 757-761, May 1987. [8] G. Mongelli, "Ce-anomalies in the textural components of Upper Cretaceous karst bauxites from the Apulian carbonate platform (southern Italy)", Chemical Geology, vol. 140, no. 1, pp. 69-79, June 1997. Additional resources: www.eurare.eu; www.redmud.org.

Oceanographic controls on sedimentary and geochemical facies on the Peru outer shelf and upper slope

USGS Publications Warehouse

Arthur, Michael A.; Dean, Walter E.

2013-01-01

Concentrations and characteristics of organic matter in surface sediments deposited under an intense oxygen-minimum zone (OMZ) on the Peru margin were mapped and studied in samples from deck-deployed box cores and push cores acquired by submersible on two east-west transects spanning depths of 75 to 1,000 meters (m) at 12°S and 13.5°S. On the basis of sampling and analyses of the top 1–2 centimeters (cm) of available cores, three main belts of sediments were identified on each transect with increasing depth: (1) muds rich in organic carbon (OC); (2) authigenic phosphatic mineral crusts and pavements; and (3) glaucony facies.Sediments rich in OC on the 12°S transect were mainly located on the outer shelf and upper slope (150–350 m), but they occurred in much shallower water (approximately 100 m) on the 13.5°S transect. The organic matter is almost entirely marine as confirmed by Rock-Eval pyrolysis and isotopic composition of OC. Concentrations of OC are highest (up to 18 percent) in sediments within the OMZ where dissolved oxygen (DO) concentrations are <5 micromoles per kilogram (μM). Even at these low concentrations of DO, however, the surface sediments from within the OMZ are dominantly unlaminated. Concentrations of DO may have the dominant effect on organic matter characteristics, but reworking of fine-grained sediment and organic matter by strong bottom currents with velocities as high as 30 centimeters per second (cm/s) on the slope between 150 and 300 m and redeposition on the seafloor in areas of lower energy and higher DO concentration also exert important controls on OC concentration and degree of oxidation in this region.Phosphate-rich sediments and crusts occurred at depths of about 300 to 550 m on both transects. Nodular crusts of sediment cemented by carbonate-fluorapatite (CFA; phosphorite) or dolomite form within the OMZ. These phosphorite crusts evolve through cementation from light olive-green, stiff but friable, phosphatized claystone “protocrusts” through dense, dark phosphorite crusts, cemented breccias, and pavements. The degree of phosphatization and thickness of the crusts depend on the rates of sediment supply and on the strength and frequency of currents that re-expose crusts on the seafloor. Phosphorite crusts and pavements on the Peru margin can only become buried and incorporated into the geologic record once bottom currents slacken sufficiently to allow fine-grained sediment to accumulate.Glaucony-rich surface sediments, relatively undiluted by other components, were found mainly in deeper water on the 13.5°S transect (750 m to at least 1,067 m). These sediments consist almost entirely of sand-size glaucony pellets. These widespread glaucony sands formed in place and were then concentrated and reworked by strong currents that winnowed away the fine-grained matrix. Although the glaucony occurs in sand-size pellets, the pellets are made up of aggregates of authigenic, platy, micaceous clay minerals. Glaucony is predominantly a potassium (K), sodium (Na), iron (Fe), magnesium (Mg) aluminosilicate with an approximate formula of (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2. The glaucony on the 13.5°S transect forms by alteration of one or more original “framework” minerals (carbonate and [or] aluminosilicates) to form pellital aggregates of Fe-, K-, and Mg-rich clay minerals. Because Fe, K, and Mg are derived from seawater, sedimentation rates must be extremely slow in order for the original framework minerals to remain in contact with seawater. The close association of glaucony and phosphorite indicates a delicate balance between the slightly oxidizing conditions at the base of the OMZ that form glaucony and the slightly reducing conditions that mobilize iron and phosphate to form phosphorite.

Carbonate and silicate cementation of siliciclastic sediments of the New Jersey shelf (IODP Expedition 313): relation with organic matter diagenesis and submarine groundwater discharge

NASA Astrophysics Data System (ADS)

Pierre, Catherine; Blanc-Valleron, Marie-Madeleine; Boudouma, Omar; Lofi, Johanna

2017-12-01

The New Jersey continental shelf extends 150 km off the shoreline. During IODP Expedition 313, siliciclastic deposits of late Eocene to late Pleistocene age were drilled down to 631, 669 and 755 m below seafloor at sites 27A, 28A and 29A respectively in very shallow waters (33.5 to 36 m depth). Pore water salinities display multilayered brackish-salty-brine units 10 to 170 m thick, where low-salinity water is preferentially stored in fine-grained sediments. The sharp boundaries of these buried aquifers are often marked by cemented layers a few centimetres thick. The mineralogy and scanning electron microscope observations of these layers show two phases of cementation by authigenic minerals: (1) the early carbonate cement is frequently associated with pyrite, and (2) the late silicate cement infills the residual porosity. The isotopic compositions of the carbonate cements vary widely: -2.4 < δ18O ‰ VPDB < +2.8; -15.1 < δ13C ‰ VPDB < +15.6. The δ18O values indicate that the carbonate cements precipitated with pore waters comprising variable mixtures of seawater and 18O-depleted fresh water originating from submarine groundwater discharge. The δ13C values of the carbonate cements are related to organic matter diagenesis, providing 13C-depleted dissolved inorganic carbon during bacterial sulphate reduction and anaerobic oxidation of methane, and 13C-rich dissolved inorganic carbon during methanogenesis. The diagenetic cementation processes included chemical weathering of reactive silicate minerals by the CO2-rich pore waters issued from organic matter diagenesis that released bicarbonate, cations and dissolved silica, which were further precipitated as carbonate and silicate cements. The estimated range of temperature (18±4 °C) during carbonate precipitation is consistent with carbonate cementation at moderate burial depths; however, silicate cementation occurred later during diagenesis at deeper burial depths.

Geochemical and multi-isotopic (87Sr/86Sr, 143Nd/144Nd, 238U/235U) perspectives of sediment sources, depositional conditions, and diagenesis of the Marcellus Shale, Appalachian Basin, USA

NASA Astrophysics Data System (ADS)

Phan, Thai T.; Gardiner, James B.; Capo, Rosemary C.; Stewart, Brian W.

2018-02-01

We investigate sediment sources, depositional conditions and diagenetic processes affecting the Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, a major target of natural gas exploration. Multiple proxies, including trace metal contents, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U isotopes were applied to whole rock digestions and sequentially extracted fractions of the Marcellus shale and adjacent units from two locations in the Appalachian Basin. The narrow range of εNd values (from -7.8 to -6.4 at 390 Ma) is consistent with derivation of the clastic sedimentary component of the Marcellus Shale from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt, and indicate minimal post-depositional alteration of the Sm-Nd system. While silicate minerals host >80% of the REE in the shale, data from sequentially extracted fractions reflect post-depositional modifications at the mineralogical scale, which is not observed in whole rock REE patterns. Limestone units thought to have formed under open ocean (oxic) conditions have δ238U values and REE patterns consistent with modern seawater. The δ238U values in whole rock shale and authigenic phases are greater than those of modern seawater and the upper crust. The δ238U values of reduced phases (the oxidizable fraction consisting of organics and sulfide minerals) are ∼0.6‰ greater than that of modern seawater. Bulk shale and carbonate cement extracted from the shale have similar δ238U values, and are greater than δ238U values of adjacent limestone units. We suggest these trends are due to the accumulation of chemically and, more likely, biologically reduced U from anoxic to euxinic bottom water as well as the influence of diagenetic reactions between pore fluids and surrounding sediment and organic matter during diagenesis and catagenesis.

Influence of depositional environment on diagenesis in St. Peter sandstone, Michigan basin

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

Lundgren, C.E. Jr.; Barnes, D.A.

1989-03-01

The Middle Ordovician St. Peter Sandstone in the Michigan basin was deposited in marine peritidal to storm-dominated, outer shelf depositional environments that evolved in a regionally significant transgressive pattern. The formation is bounded by carbonate and shaly clastic strata of the Prairie du Chien Group below and is transitional to condensed sequence clastics and carbonates of the Glenwood Formation above. Sedimentologic and petrographic analysis of conventional core from 25 wells suggests that reservoir quality in the formation is strongly dependent on a complex diagenetic history, especially the nature and subsequent dissolution of intergranular carbonate in the sandstone. Petrographic evidence indicatesmore » that porosity in the formation formed by dissolution of precursor dolomite of various origins and, locally, the formation of pore-filling authigenic clay (chlorite-illite). Authigenic clay is the incongruent dissolution product of dolomite, detrital K-feldspar, and, possibly, muscovite and results in diminished reservoir quality where abundant in the St. Peter Sandstone. Authigenic clay is volumetrically more significant in the upper portions of the formation and is associated with higher concentrations of detrital K-feldspar. Depositional facies controlled the distribution and types of intergranular carbonate (now dolomite) and detrital K-feldspar in the St. Peter Sandstone and hence reservoir quality; both components were more significant in storm-shelf sandstone facies.« less

Do Leached Authigenic Fractions Reflect the Neodymium Seawater Composition?

NASA Astrophysics Data System (ADS)

Pimbert, A.; Gourlan, A. T.; Chauvel, C.

2016-12-01

Leaching of marine sediment is often used to recover past Nd seawater composition and reconstruct past ocean circulation. It is assumed to reliably extract REE from the authigenic fraction of sediment [1]. However, while most studies assume that the recovered signal is that of past seawater, very few report complete isotopic and trace element data that clearly demonstrate it is the case. We present new ɛNd values and REE contents measured on leachates of sediments from two Cretaceous marine sections deposited at shallow water depth (Taghazoute in Morocco) and at greater depth in the Atlantic (DSDP Site 367). REE patterns of leachates vary according to lithology: bell-shaped patterns or positive Ce anomalies for organic-poor samples and seawater-like patterns (negative Ce anomaly, low Nd/Yb ratio) for black shales. ɛNd values also vary: between -5.6 and -9.6 at Taghazoute and between -10 and -8.1 at Site 367. Interestingly, ɛNd values correlate with Ce anomalies for Taghazoute black shales. Samples with the largest Ce negative anomalies have the highest ɛNd while samples with no Ce anomalies have much lower ɛNd. This suggests the presence in the leached material of detritus mixed up with the authigenic fraction for sediments deposited in shallow environment. This confirms the findings made by Huck et al. [2] for fish teeth in a similar environment. In such environment, recovering the pristine seawater signal requires (a) the acquisition of both Nd isotopes and trace element contents, and (b) selection of the only Nd isotopic compositions associated to clear seawater trace element characteristics. For sediments deposited in open-ocean setting (Site 367), no detrital contamination affects leached fractions. The REE patterns vary depending on the nature of authigenic fraction but ɛNd remains constant. Here, ɛNd values can be used to discuss oceanic reconstructions. [1] Martin et al. (2010), Chem. Geol, 269, 414-431. [2] Huck et al. (2016), G3, 17, 679-698.

Biogeochemical Controls on Authigenic Carbonate Formation at the Chapopote "Asphalt Volcano", Bay of Campeche

NASA Astrophysics Data System (ADS)

Naehr, T. H.; Bohrmann, G.; Birgel, D.; MacDonald, I. R.

2007-12-01

Unusual hydrocarbon seep features, so-called "asphalt volcanoes" were explored in the Bay of Campeche, southern Gulf of Mexico, in the spring of 2006. Guided by data from satellite imagery that showed evidence for persistent oil seeps in the region, we investigated lava-like flows of solidified asphalt along the rim of a dissected salt dome at a water depth of about 3000 m. Fresh asphalt contains copious thermogenic gas and gas hydrate. Slabs of authigenic carbonate form surface crusts with layers of oil pooled beneath. Sediments are anoxic with H2S concentrations of 8 to 13 mM. Gas hydrate forms layers and mounds in the surface sediments. Alkalinity profiles show values from 29 to 35 mM, indicating oxidation of hydrocarbons by reduction of seawater sulfate. Molecular and isotopic compositions of gas hydrate and sediment headspace indicate moderately mature, thermogenic gas. Oily sediment extracts and asphalt pieces are composed of a degraded mixture of hydrocarbons with a peak at n-C30 and a few resolved C29 to C32 hopanes. Authigenic carbonate crusts from Chapopote are porous, aragonite-cemented mudstones. Peloidal textures are common, as are bivalve shells and at least two generations of aragonite-cemented intraclasts. The carbon isotopic composition of the authigenic aragonite cements varies between -28.6 ‰ and -17.9 ‰ (PDB), indicating a contribution of carbon from non-methane liquid hydrocarbons to the total pool of dissolved CO2. δ18O values of the carbonates range from +3.2 ‰ to +4.5 ‰ (PDB), suggesting aragonite formation under near-equilibrium conditions in the shallow subsurface. Molecular fossils extracted from one carbonate sample contain abundant 13C-depleted archeal lipids, derived from anaerobic methanotrophs, suggesting that organisms mediating the anaerobic oxidation of methane are closely associated with carbonate authigenesis at the Chapopote asphalt seep site.

Paired measurements of K and Mg isotopes and clay authigenesis in marine sediments

NASA Astrophysics Data System (ADS)

Santiago Ramos, D. P.; Dunlea, A. G.; Higgins, J. A.

2016-12-01

Despite its importance as a major sink for seawater K and Mg, estimates of clay authigenesis in marine sediments remain poorly constrained. Previous work on Mg isotope fractionation during clay formation has revealed a preferential uptake of 26Mg, yielding authigenic clay products with potentially distinct δ26Mg compared to the detrital component. In a similar manner, we aim to quantify the K isotope fractionation during authigenic clay formation and to use paired δ26Mg and δ41K measurements as proxies for the identification and quantification of authigenic clays in shallow and deep marine sedimentary systems. To better understand the behavior of paired Mg and K isotopes during authigenic clay formation in marine sediments, we measured δ26Mg and δ41K values of pore-fluids and sediments from ODP/IODP sites 1052, U1395, U1403 and U1366. We find that while pore-fluid K concentrations at sites 1052, U1395 and U1403 all decline with depth, δ41K profiles differ significantly. These differences might be a result of a complex interplay between clay authigenesis, sedimentation rate, and fractionation of K isotopes during diffusion. Results from 1-D diffusion-advection-reaction models suggest that, in contrast to Mg, diffusion may play an important role in determining the overall K isotope fractionation during clay authigenesis in sites with low-sedimentation rates. Sites with high sedimentation rates may act as close systems where diffusion is negligible. In such cases, K uptake can be modeled as a Rayleigh distillation process and K isotope fractionation can be estimated. Measurements of δ26Mg and δ41K of pore-fluids from site U1395 and bulk sediments from U1366 suggest that paired measurements of these isotopic systems in siliciclastic marine sediments can provide new insights into rates of marine clay authigenesis, a globally important but understudied component of many geochemical cycles.

Determining the speciation of Zn in soils around the sediment ponds of chemical plants by XRD and XAFS spectroscopy and sequential extraction.

PubMed

Minkina, Tatiana; Nevidomskaya, Dina; Bauer, Tatiana; Shuvaeva, Victoria; Soldatov, Alexander; Mandzhieva, Saglara; Zubavichus, Yan; Trigub, Alexander

2018-09-01

For a correct assessment of risk of polluted soil, it is crucial to establish the speciation and mobility of the contaminants. The aim of this study was to investigate the speciation and transformation of Zn in strongly technogenically transformed contaminated Spolic Technosols for a long time in territory of sludge collectors by combining analytical techniques and synchrotron techniques. Sequential fractionation of Zn compounds in studied soils revealed increasing metal mobility. Phyllosilicates and Fe and Mn hydroxides were the main stabilizers of Zn mobility. A high degree of transformation was identified for the composition of the mineral phase in Spolic Technosols by X-ray powder diffraction. Technogenic phases (Zn-containing authigenic minerals) were revealed in Spolic Technosols samples through the analysis of their Zn K-edge EXAFS and XANES spectra. In one of the samples Zn local environment was formed by predominantly oxygen atoms, and in the other one mixed ZnS and ZnO bonding was found. Zn speciation in the studied technogenically transformed soils was due to the composition of pollutants contaminating the floodplain landscapes for a long time, and, second, this is the combination of physicochemical properties controlling the buffer properties of investigated soils. X-ray spectroscopic and X-ray powder diffraction analyses combined with sequential extraction assays is an effective tool to check the affinity of the soil components for heavy metal cations. Copyright © 2018 Elsevier B.V. All rights reserved.

Authigenic carbonates from active methane seeps offshore southwest Africa

NASA Astrophysics Data System (ADS)

Pierre, Catherine; Blanc-Valleron, Marie-Madeleine; Demange, Jérôme; Boudouma, Omar; Foucher, Jean-Paul; Pape, Thomas; Himmler, Tobias; Fekete, Noemi; Spiess, Volkhard

2012-12-01

The southwest African continental margin is well known for occurrences of active methane-rich fluid seeps associated with seafloor pockmarks at water depths ranging broadly from the shelf to the deep basins, as well as with high gas flares in the water column, gas hydrate accumulations, diagenetic carbonate crusts and highly diverse benthic faunal communities. During the M76/3a expedition of R/V METEOR in 2008, gravity cores recovered abundant authigenic carbonate concretions from three known pockmark sites—Hydrate Hole, Worm Hole, the Regab pockmark—and two sites newly discovered during that cruise, the so-called Deep Hole and Baboon Cluster. The carbonate concretions were commonly associated with seep-benthic macrofauna and occurred within sediments bearing shallow gas hydrates. This study presents selected results from a comprehensive analysis of the mineralogy and isotope geochemistry of diagenetic carbonates sampled at these five pockmark sites. The oxygen isotope stratigraphy obtained from three cores of 2-5 m length indicates a maximum age of about 60,000-80,000 years for these sediments. The authigenic carbonates comprise mostly magnesian calcite and aragonite, associated occasionally with dolomite. Their very low carbon isotopic compositions (-61.0 < δ13C ‰ V-PDB < -40.1) suggest anaerobic oxidation of methane (AOM) as the main process controlling carbonate precipitation. The oxygen isotopic signatures (+2.4 < δ18O ‰ V-PDB < +6.2) lie within the range in equilibrium under present-day/interglacial to glacial conditions of bottom seawater; alternatively, the most positive δ18O values might reflect the contribution of 18O-rich water from gas hydrate decomposition. The frequent occurrence of diagenetic gypsum crystals suggests that reduced sulphur (hydrogen sulphide, pyrite) from sub-seafloor sediments has been oxidized by oxygenated bottom water. The acidity released during this process can potentially induce the dissolution of carbonate, thereby providing enough Ca2+ ions for pore solutions to reach gypsum saturation; this is thought to be promoted by the bio-irrigation and burrowing activity of benthic fauna. The δ18O-δ13C patterns identified in the authigenic carbonates are interpreted to reflect variations in the rate of AOM during the last glacial-interglacial cycle, in turn controlled by variably strong methane fluxes through the pockmarks. These results complement the conclusions of Kasten et al. in this special issue, based on authigenic barite trends at the Hydrate Hole and Worm Hole pockmarks which were interpreted to reflect spatiotemporal variations in AOM related to subsurface gas hydrate formation-decomposition.

Apportioning carbon sources of authigenic carbonate of extremely 13C-depleted foraminifera from the western North Pacific sediments: Implication from the coupled 13C and 14C isotopic mass balance approach

NASA Astrophysics Data System (ADS)

Uchida, M.; Ohkushi, K.; Ahagon, N.; Kimoto, K.; Inagaki, F.; Shibata, Y.

2005-12-01

Recently, Uchida et al. (G-cubed, 2004) and Ohkushi et al. (G-cubed, 2005) interprete /delta 13C variations of planktonic and benthic foraminifera found in Last Glacial sediments in off Shimokita Peninsula and Tokachi as evidence for periodic releases of methane, arising from the dissociation of methane hydrate, and its subsequent oxidation in bottom- and/or surface-water environments. According to recent observations of anomalous bottom-simulating reflections, northwest Pacific marginal sediments around Japan main islands bear large abundances of methane hydrate. In this study, analyzed piston cores (42° 21.42' N, 144° 13.36' E) at a water depth 1066-m was retrieved from the off Tokachi continental slope in the Oyashio current region, where recently is found to bear immense amounts of methane hydrate. The piston core covered past 22 ka with high-resolution. Here we showed that carbon isotope signals indicated that planktonic and benthic foraminifera in several glacial sediment layers in the core were highly depleted in13 C; both the planktonic and benthic foraminiferal /delta 13C values ranged from about -10/permil to -2/permil. Most foraminiferal tests in these horizons were brown as a result of postdepositional alteration. Foraminiferal oxygen isotopes fluctuated abnormally in the glacial sediment layers, showing small (about 0.5/permil) positive shifts relative to normal glacial values. We attributed the positive shifts to authigenic carbonate formation in the foraminiferal tests. In order to decipher the relation between foraminifera carbon isotopic signal and methane release from the seafloor, we have apportioned carbon sources (methane from methane hydrate or not) of foraminiferal carbon isotopic anomalies using dual mass balance isotopic model (14C/ 12C and 13C/ 12C). It has been suggested that sulfate-dependent anaerobic methane oxidation (AOM) dominates carbon oxidation and attendant authigenic carbonate precipitation to foraminifera. To this assumption, we have quantified the relative contributions of dissolved carbon dioxide (/SigmaCO/_2) from oxidation of methane in anomaly foraminifera. At the layer of 17,840 years cal. age with planktonic foraminifera of dual isotopic data (/delta 13C: -8.1/permil and /Delta 14C: -847/permil) , relative contribution of carbon from authigenic carbonate was 17 percent of total carbonate and its /delta 13C was -48.1/permil, suggesting indirect records of enhanced incorporation of 13C-depleted CO2 formed by anaerobic methane oxidation process that use 12C-enriched methane as their main source of carbon. Moreover, biomarker and phylogenetic compositions were investigated in the light of the past activity of methanotrophic bacteria in the oxic-anoxic interface in the overlying water column and/or surface sediment. Mg/Ca ratios were also analyzed to evaluate foraminiferal 13C depleted carbonate precipitation in comparison with authigenic carbonate produced in the cold seep environment. In the conference, we discuss about what mechanism contribute to authigenic carbon precipitation in terms with carbon source with 13C-depleted foraminifera.

Arsenic concentrations in Baltic Sea sediments close to chemical munitions dumpsites

NASA Astrophysics Data System (ADS)

Bełdowski, Jacek; Szubska, Marta; Emelyanov, Emelyan; Garnaga, Galina; Drzewińska, Anna; Bełdowska, Magdalena; Vanninen, Paula; Östin, Anders; Fabisiak, Jacek

2016-06-01

In addition to natural sources and land-originated pollution, the Baltic Sea has another anthropogenic source of arsenic in bottom sediments-arsenic-based Chemical Warfare Agents (CWA). To examine the potential usage of arsenic contents results for monitoring the leakage from chemical weapons, sediment samples were collected from officially reported and potential chemical weapon dumpsites located in the Baltic Sea, and total and inorganic arsenic concentrations were analyzed. Results showed an elevated arsenic content in dumpsite areas compared to reference areas. Correlations of arsenic with other metals and organic matter were studied to elucidate any unusual behavior of arsenic in the dumpsites. In the area of the Bornholm Deep, such behavior was observed for inorganic arsenic. It appears that in close vicinity of dumped munitions, the inorganic arsenic concentration of sediments is not correlated with either organic matter content or authigenic minerals formation, as is commonly observed elsewhere. Investigations on CWA concentrations, performed within the CHEMSEA (Chemical Munition Search and Assesment) project, allowed us to compare the results of arsenic concentrations with the occurrence of arsenic-containing CWA.

Coupled Reactive Transport Modeling of CO2 Injection in Mt. Simon Sandstone Formation, Midwest USA

NASA Astrophysics Data System (ADS)

Liu, F.; Lu, P.; Zhu, C.; Xiao, Y.

2009-12-01

CO2 sequestration in deep geological formations is one of the promising options for CO2 emission reduction. While several large scale CO2 injections in saline aquifers have shown to be successful for the short-term, there is still a lack of fundamental understanding on key issues such as CO2 storage capacity, injectivity, and security over multiple spatial and temporal scales that need to be addressed. To advance these understandings, we applied multi-phase coupled reactive mass transport modeling to investigate the fate of injected CO2 and reservoir responses to the injection into Mt. Simon Formation. We developed both 1-D and 2-D reactive transport models in a radial region of 10,000 m surrounding a CO2 injection well to represent the Mt. Simon sandstone formation, which is a major regional deep saline reservoir in the Midwest, USA. Supercritical CO2 is injected into the formation for 100 years, and the modeling continues till 10,000 years to monitor both short-term and long-term behavior of injected CO2 and the associated rock-fluid interactions. CO2 co-injection with H2S and SO2 is also simulated to represent the flue gases from coal gasification and combustion in the Illinois Basin. The injection of CO2 results in acidified zones (pH ~3 and 5) adjacent to the wellbore, causing progressive water-rock interactions in the surrounding region. In accordance with the extensive dissolution of authigenic K-feldspar, sequential precipitations of secondary carbonates and clay minerals are predicted in this zone. The vertical profiles of CO2 show fingering pattern from the top of the reservoir to the bottom due to the density variation of CO2-impregnated brine, which facilitate convection induced mixing and solubility trapping. Most of the injected CO2 remains within a radial distance of 2500 m at the end of 10,000 years and is sequestered and immobilized by solubility and residual trapping. Mineral trapping via secondary carbonates, including calcite, magnesite, ankerite and dawsonite, is predicted, but only constituting a minor component as compared to other trapping mechanisms. The mineral alteration induced by CO2 injection results in changes in porosity/permeability due to these complex mineral dissolution and precipitation reactions. Increases in porosity (from 15% to 16.2%) occur in the low-pH zones due to the acidic dissolution of minerals. However, within the carbonate mineral trapping zone, porosity reduction occurs. Co-injection of H2S causes relatively limited modification from the CO2 alone case while significantly higher water-rock reactivity is associated with the SO2 co-injection. Although co-injection of CO2 with H2S and SO2 could potentially reduce separation and injection cost, it may lead to some uncertainty and risks and therefore require further investigation.

Uranium-series dated authigenic carbonates and acheulian sites in southern Egypt

USGS Publications Warehouse

Szabo, B. J.; McHugh, W.P.; Schaber, G.G.; Haynes, C.V.; Breed, C.S.

1989-01-01

Field investigations in southern Egypt have yielded Acheulian artifacts in situ in authigenic carbonate deposits (CaCO3-cemented alluvium) along the edges of nowaggraded paleovalleys (Wadi Arid and Wadi Safsaf). Uranium-series dating of 25 carbonate samples from various localities as far apart as 70 kilometers indicates that widespread carbonate deposition occurred about 45, 141 and 212 ka (thousand years ago). Most of the carbonate appears to have been precipitated from groundwater, which suggests that these three episodes of deposition may be related to late Pleistocene humid climates that facilitated human settlement in this now hyperarid region. Carbonate cements from sediments containing Acheulian artifacts provide a minimum age of 212 ka for early occupation of the paleovalleys.

Multi-isotope (C - O - S - H - B - Mg - Ca - Ba) and trace element variations along a vertical pore water profile across a brackish-fresh water transition, Baltic Sea

NASA Astrophysics Data System (ADS)

Böttcher, Michael E.; Lapham, Laura; Gussone, Nikolaus; Struck, Ulrich; Buhl, Dieter; Immenhauser, Adrian; Moeller, Kirsten; Pretet, Chloé; Nägler, Thomas F.; Dellwig, Olaf; Schnetger, Bernhard; Huckriede, Hermann; Halas, Stan; Samankassou, Elias

2013-04-01

The Holocene Baltic Sea has been switched several times between fresh water and brackish water modes. Modern linear sedimentation rates, based on 210-Pb, 137-Cs, and Hg dating of surface sediments, are between 0.1 and 0.2 mm per year. The change in paleo-environmental conditions caused downcore gradients in the concentrations of dissolved species from modern brackish waters towards fresh paleo-pore waters, interrupted by the brief brackish Yoldia stage. These strong physico-chemical changes had consequences for e.g., microbial activity and further physical and chemical water-solid interactions associated with multiple stable isotope fractionation processes, and, in turn, have strong implications for isotope and trace element partitioning upon early diagenetic mineral (trans)formations. In this communication, we present the results from the first integrated multi-isotope and trace element investigation conducted in this type of salinity-gradient system. It is found that concentrations of conservative elements (e.g., Na, Cl) decrease with depth due to diffusion of ions from brackish waters into underlying fresh waters. This is associated with pronounced depletions in H-2 and O-18 of pore water with depth. Covariations of both isotope systems are close to the meteoric water line as defined by modern Baltic Sea surface waters. A downward increase and decrease of Ca and Mg concentrations, respectively, is associated with decreasing Ca-44 and Mg-26 isotope values. B-11 isotope values decrease in the limnic part of the sediments, too. On the other hand, an increase in Ba concentrations with depth is associated with an increase in Ba-137/134 isotope values. Microbial sulfate reduction and organic matter oxidation lead to an increase in DIC, but a decrease in sulfate concentrations and in C-13 contents of DIC with depth. Suess (1981) was probably the first to propose, that desorption of Ca and Ba from glacial sediments due to downward diffusing ions may be responsible for a downcore increase in pore water concentrations of earth alkaline ions and the formation of authigenic barites. Coupled S-34 and O-18 isotope signals in authigenic barites suggest that they were formed in pre-Yoldia sediments from pore waters strongly depleted in O-18 (as low as -20 per mil vs. VSMOW). In the present communication, we will discuss possible impacts of diagenetic processes on multi-isotope signals in pore waters and authigenic phases. A combination of mixing between brackish and fresh water, ion exchange, precipitation/dissolution, and transport reactions is considered to explain most of the observed isotope variations along the vertical pore water profile. This work was supported by the Leibniz IOW, BONUS+ program, the Universities of Bern, Geneva, Bochum, Münster, and Oldenburg, and the Natural Museum of History, Berlin.

Microbially induced iron precipitation associated with a neutrophilic spring at Borra Caves, Vishakhapatnam, India.

PubMed

Baskar, Sushmitha; Baskar, Ramanathan; Thorseth, Ingunn H; Ovreås, Lise; Pedersen, Rolf B

2012-04-01

The present investigation uncovers various pieces of evidence for the possible biologically induced mineralization in iron mats associated with a pH-neutral spring in the Borra caves, Vishakhapatnam, India. Electron microscopy [scanning electron microscopy (SEM) and transmission electron microscopy (TEM)] demonstrated large numbers of (i) hollow tubes (diameter ∼1 μm) resembling sheaths of the iron-oxidizing bacteria Leptothrix, (ii) thin (diameter <1 μm) solid fibers of uncertain origin, (iii) nanoscale subspherical to irregularly shaped particles encrusting tubes and fibers, and (iv) aggregates of broken and partially disintegrated sheaths, fibers, and particles embedded in extracellular polymeric substances (EPS) occasionally including microbial cells. X-ray microanalyses by energy dispersive spectroscopy (EDS) revealed that the mat accumulated largely Fe but also smaller amounts of Si and traces of P and Ca. Particles rich in Si and Al (possibly kaolinite) and Ca (carbonate) were also observed. High-resolution TEM/EDS of unstained ultrathin sections suggests that microbial sheaths were highly mineralized by amorphous to cryptocrystalline Fe-rich phases and less frequently by other fine-grained and fibrous authigenic claylike minerals. Total number of microorganisms in the iron mats was 5.8×10(5) cells, g sed(-1) (wet weight). Analysis of the 16S rRNA gene diversity revealed microorganisms assigned to eight different phyla [Proteobacteria (62%), Chloroflexi (8%), Bacteroidetes (7%), Planctomycetes (1%), Actinobacteria (5%), Acidobacteria (6%), Nitrospira (1%), Firmicutes (5%)]. Within the Proteobacteria, Betaproteobacteria was the predominant class, which accounted for 28% of the sequences. Within this class some obvious similarities between the obtained sequences and sequences from other cave systems could be seen, especially sequences affiliated with Leptothrix, Siderooxidans, Crenothrix, Comamonadaceae, Dechloromonas, and many uncultured Betaproteobacteria. Four (4%) of the sequences could not be assigned to phylum level but were affiliating with the candidate division TM7 (2%), candidate division OP11 (1%), and candidate division WWE3 (1%). The results allow us to infer a possible relationship of microbial sheaths, EPS, and the iron precipitates to microbial community diversity in the Borra cave springs. Understanding biogenic iron oxides in caves has important astrobiological applications as it provides a potential tool for the detection of extraterrestrial life.

Origin of the Mariano Lake uranium deposit, McKinley County, New Mexico

USGS Publications Warehouse

Fishman, Neil S.; Reynolds, Richard L.

1982-01-01

The Mariano Lake uranium deposit, hosted by the Brushy Basin Member of the Jurassic Morrison Formation, occurs in the trough of an east-west trending syncline at the western end of the Smith Lake-Mariano Lake group of uranium deposits near Crownpoint, New Mexico. The orebody, which contains abundant amorphous organic material, is situated on the reduced side of a regional reduction-oxidation (redox) interface. The presence of amorphous organic material suggests the orebody may represent a tabular (primary) deposit, whereas the close proximity of the orebody to the redox interface is suggestive that uranium was secondarily redistributed by oxidative processes from pre-existing tabular orebodies. Uranium contents correlate positively with both organic carbon and vanadium contents. Petrographic evidence and scanning electron microscope-energy dispersive analyses point to uranium residence in the epigentically introduced amorphous organic material, which coats detrital grains and fills voids. Uranium mineralization was preceded by the following diagenetic alterations: precipitation of pyrite (d34S values ranging from-11.0 to-38.2 per mil); precipitation of mixed-layer smectite-illite clays; partial dissolution of some of the detrital feldspar population; and precipitation of quartz and adularia overgrowths. Alterations associated with uranium mineralization include emplacement of amorphous organic material (possibly uranium bearing); destruction of detrital iron-titanium oxide grains; coprecipitation of chlorite and microcrystalline quartz, and precipitation of pyrite and marcasite (d34S values for these sulfides ranging from -29.4 to -41.6 per mil). After mineralization, calcite, dolomite, barite, and kaolinite precipitated, and authigenic iron disulfides were replaced by ferric oxides and hydroxides. Geochemical data (primarily the positive correlation of uranium content to both organic carbon and vanadium contents) and petrographic observations (epigentically introduced amorphous organic matter and uranium residence in this organic matter) indicate that the Mariano Lake orebody is a tabular-type uranium deposit. Oxidative processes have not noticeably redistributed and reconcentrated primary uranium in the immediate vicinity of the deposit nor have they greatly modified geochemical characteristics in the ore. Preservation of the Mariano Lake deposit may not only be related to its position along the synclinal trough, where oxidative destruction of the orebody has been inhibited by stagnation of oxidizing ground waters by the structure, but also due to the deflection of ground waters (resulting from low orebody porosity) around the orebody.

Cyclic sedimentation, synsedimentary volcanism, microfabrics, and fracture intensity in the Austin Chalk, Texas

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

Hovorka, S.D.

1992-01-01

Pelagic depositional environments of the Austin Chalk (Coniacian-Santonian) were influenced by sea-level variation, planktonic productivity, and allochthonous detrital input. Subtle differences in chalk facies influence fracture intensity, therefore imposing stratigraphic variability on hydrologic properties of the Austin Chalk. Variations in fracture intensity may affect ground-water flow through the Superconducting Super Collider (SSC) site south of Dallas in the same way that they influence hydrocarbon production in South Texas. The lower Austin Chalk was deposited during transgression. Glauconitic sandstone is overlain by cyclic chalk containing chalk-filled channels. Meter-thick chalk/marl cycles have frequencies in the Milankovitch spectrum. Marl accumulated during episodes ofmore » decreased planktonic productivity. Maximum flooding is indicated by organic-rich marls in the upper part of the Lower Austin Chalk. Shallowing during deposition of the middle and upper Austin Chalk is indicated by increasing abundance of winnowed lag deposits and firm grounds, resulting in increased faunal diversity. Authigenic clay, a product of alteration of volcanic ash codeposited with the chalk and marl, increases ductility in the middle Austin Chalk. The stratigraphic distribution of authigenic clay corresponds to disseminated biotite, quartz, and feldspar phenocrysts in most samples of the middle Austing Chalk. Authigenic clay decreases porosity, influences porosity-permeability relationships, and provides a regionally traceable low SP log response that correlates with low fracture intensity.« less

On morphology of methane-derived authigenic carbonates

NASA Astrophysics Data System (ADS)

Logvina, E.; Matveeva, T.

2009-04-01

Studies of methane-derived carbonates revealed a great variety their morphological types. Although the processes of these carbonates formation is not clearly understood, it has been suggested that in general bacterially mediated processes of hydrocarbon oxidation, coupled with sulphate reduction, produce unusually high levels of alkalinity and dissolved inorganic carbon in the pore fluids that is partitioned between the precipitating carbonate and CO2 rich plumes which emanate into the water column (Aharon, 1994). These carbonates consist by three main CaCO3 polymorphs - calcite, aragonite and dolomite. Carbonates with different petrography cemented from these polymorphs can be classified according to their specific locality mode of formation and biogenic or non-biogenic origin (Greinert et al., 2002). There are classifications for the authigenic carbonates which are based on petrography, morphology, or based on age and origin. In this work we will consider the petrographical and morphological differences of authigenic carbonates. The large structures vary from 10 to 200 m size, named as chemoherm carbonates. Usually they cemented by pure aragonite with minor Mg-calcite admixture. These chemoherms rise up to 50 m above the seafloor. The structures are irregular in shape and have numerous pores and open pathways resulting from plumbing system of fluid expulsion. This type of authigenic carbonates was observed in the NE Black Sea (Michaelis et al., 2002), at the Hydrate Ridge area (Greinert et al., 2001), at Aleutian accretionary margin (Greinert et al., 2002). Diagenetic carbonates - carbonate cemented sediments both growing at the seafloor or within the sediment framework and showing a large variety of shapes (chimneys, crusts, concretions est.), with grey to dark-grey color. Petrographically the carbonate cement represents by Mg-calcite, protodolomite and dolomite. The diagenetic carbonates occur widely in the fluid venting areas. In particular, diagenetic carbonate chimneys were observed in the NE Atlantic, in the Gulf of Cadiz (Diaz del Rio et al., 2003), offshore Morocco (Magalhães et al., 2002), at northern Kattegat (Jensen et al., 1992), in the Pobitite Kamani area, in north-eastern Bulgaria (Botz et al., 1993). Clathrites (gas hydrate carbonates) are formed at the seawater/sediment interface or within the sediment in close contact with gas hydrates and bacterial mats. This type of the authigenic carbonates in direct contact with gas hydrates were identified and described by G. Bohrmann at Hydrate Ridge in 1998. According to (Bohrmann et al., 1998), they characterize by carbonate-cemented breccia composed of angular clasts cementing by Mg-calcite and aragonite. The brecciated structure causes by gas hydrate formation processes. A pure aragonite layers which form in elongated pores formerly occupied by gas hydrate are typical. This pseudomorphism resembles gas hydrate bubble structures. As a whole, clathrites are associated with bacterial mats on the seafloor next to gas hydrates and within the gas hydrate pore structure. References: G. Bohrmann, J. Greinert, E. Suess and M. Torres. Authigenic carbonates from the Cascadia subduction zone and their relation to gas hydrate stability: Geology, 1998, v. 26, pp. 647-650. J. Greinert, G. Bohrmann, and E. Suess. Gas hydrate-associated carbonates and methane-venting at Hydrate Ridge: Classification, distribution, and origin of authigenic lithologies, in Paull, C. and Dillon W.P. ed., Natural gas hydrates: Occurrence, distribution, and detection: Geophysical Monograph 124: 87-98, American Geophysical Union, 2001, pp. 99-113. J. Greinert, G. Bohrmann, and M. Elvert Stromatolitic fabric of authigenic carbonate crusts in 4850 m water depth, Aleutian accretionary margin: Result of anaerobic methane oxidation by Archaea at cold seeps. International Journal of Earth Sciences, 2002, 91, pp. 698-711. P. Aharon. Carbon and oxygen isotope tracers of submarine hydrocarbon emissions: Northern Gulf of Mexico. Israel Journal of earth Sciences, 1994, 43, pp. 157-164. P. Jensen, I. Aagaard, R. A. Burke Jr et al. "Bubbling reefs" in the Kattegat: submarine landscapes of carbonate-cemented rocks support a diverse ecosystem at methane seeps, Mar. Ecol. Prog. Ser., 1992, 83, pp. 103-112. R.W. Botz, V. Georgiev, P. Stoffers, et al. Stable isotope study of carbonate-cemented rocks from the Pobitite Kamani area, north-eastern Bulgaria. Geologische Rundschau, 1993, 82, pp. 663- 666. V. Diaz del Rio, L. Somoza, J. Martinez-Frias, et al. Vast field of hydrocarbon-derived carbonate chimneys related to the accretionary wedge/olistostrome of the Gulf of Cadiz. Marine Geology, 2003, 195, pp.177-200. V. Magalhães, C. Vasconcelos, L. Gaspar et al. Methane related aythigenic carbonates, chimneys and crusts from the Gulf of Cadiz, Geophysical Research Abstracts, 2002, Vol. 5, 12842. W. Michaelis, R. Seifert, K. Nauhaus, T. et al. Microbial Reefs in the Black Sea Fueled by Anaerobic Oxidation of Methane. Science, 2002, 297, pp. 1013-1015.

Formation of Mg-aluminosilicates During Early Diagenesis of Carbonate Sediments in the Volcanic Crater Lake of Dziani Dzaha (Mayotte - Indian Ocean)

NASA Astrophysics Data System (ADS)

Milesi, V. P.; Jezequel, D.; Debure, M.; Marty, N.; Guyot, F. J.; Claret, F.; Virgone, A.; Gaucher, E.; Ader, M.

2017-12-01

Authigenic clays are increasingly reported in ancient carbonate rocks, but their origin remains poorly understood, strongly limiting paleoenvironmental interpretations. To tackle this issue, the carbonate sediments of the volcanic crater lake Dziani Dzaha are studied and reactive transport modeling is performed to assess the processes originating carbonate sediments associated with Mg-rich silicates during early diagenesis. The Dziani Dzaha is characterized by CO2-rich gases bubbling in three different locations, a high primary productivity leading to organic carbon contents of up to 30wt.% in the sediment, an alkalinity of 0.26 molal in the water column and pH values of 9 to 9.5. Characterization of bulk samples and clay fraction (<2µm) from the first meter of sediment with X-ray powder diffraction and X-ray fluorescence spectrometry indicates aragonite and hydromagnesite in surface sediment. The contents of hydromagnesite and organic matter decrease at depth while saponite, a Mg- and Al-rich trioctahedral smectite, accumulates to reach up to 25wt.% of mineral phases. Concurrently, chemical analyses of pore waters show a decrease of pH values from 9 to 8.3. Modeling of these diagenetic evolutions is performed with the reactive transport code Crunchflow, taking into account the sediment burial. High pH values combined with the alteration of alkaline feldspars and clinopyroxenes from the volcanic catchment allow supersaturation of lake waters relative to aragonite, hydromagnesite and saponite. Kinetic limitations in the formation of saponite explain its accumulation at depth. Production of CO2 associated with organic matter mineralization accounts for the pH decrease of pore waters, which induces hydromagnesite destabilisation leaving behind a saponite-aragonite mineral assemblage. The main driving force for the observed sequence is the intense primary productivity partly fueled by inputs of CO2-rich volcanic gases, which generates high pH, promoting the formation of saponite, aragonite and hydromagnesite, which precipitates at first before being destabilized at depth due to organic matter mineralization. The observed carbon cycle, influenced by volcanic gases, may thus play a key role in the development of carbonate rocks associated with Mg-silicates.

Radiocarbon-based carbon source quantification of anomalous isotopic foraminifera in last glacial sediments in the western North Pacific

NASA Astrophysics Data System (ADS)

Uchida, Masao; Ohkushi, Ken'ichi; Kimoto, Katsunori; Inagaki, Fumio; Ishimura, Toyoho; Tsunogai, Urumu; Tuzino, Taqumi; Shibata, Yasuyuki

2008-04-01

A previous study interpreted extremely 13C-depleted excursions of planktonic and benthic foraminifera in last glacial sediments (17,500 to 25,400 cal years B.P.) of the core retrieved from off Shimokita Peninsula and off Hokkaido, Japan, as evidence for periodic releases of methane, arising from the dissociation of methane hydrate. To better understand the formation process of the 13C-depleted excursions, we conducted high-resolution natural radiocarbon measurements and biogeochemical analyses. We found highly depleted 13C excursions ranging from -10.2‰ to -1.6‰ and -6.8‰ to -1.6‰ in planktonic and benthic foraminifera, respectively. Most of the foraminiferal tests in these horizons were brown, most likely as a result of postdepositional alteration, reflecting the formation of authigenic carbonate on the surface of tests. These alterations were also supported by high levels of Mg-calcite and the acid-leaching test for anomalous foraminifera. To evaluate the carbon sources in the altered foraminifera tests, we quantified the relative contributions of 14C-free methane-derived carbon sources to the formation of authigenic carbonates in foraminifera with depleted 13C excursions using a coupled mass balance isotopic model (14C/C and 13C/12C). The radiocarbon ages of both planktonic and benthic 13C-depleted foraminifera were approximately 600 to 2000 years older than those of normal tests from nearby horizons. The relative contributions of authigenic carbonates derived from the methane oxidizing process reached to ˜22 wt% for planktonic foraminifera and ˜15 wt% for benthic foraminifera. The δ13C values of methane calculated from the mass balance model were between -29‰ and -68‰ for planktonic foraminifera and between -40‰ and -108‰ for benthic foraminifera, consistent with δ13C values reported for thermogenic and abiogenic methane in global methane hydrate reservoirs. These data consistently suggest that methane-related drastic environmental change occurred in the horizons that included δ13C anomalies. This study provides important information for interpreting geological records of the methane hydrate instability associated with climate.

Authigenic 10Be/9Be Ratio Signatures of the Cosmogenic Nuclide Production Linked to Geomagnetic Dipole Moment Variation During and Since the Brunhes/Matuyama Boundary

NASA Astrophysics Data System (ADS)

Simon, Q.; Thouveny, N.; Bourles, D. L.; Ménabréaz, L.; Valet, J. P.; Valery, G.; Choy, S.

2015-12-01

The atmospheric production rate of cosmogenic nuclides is linked to the geomagnetic dipole moment (GDM) by a non-linear inverse relationship. Large amplitude GDM variations associated with reversals and excursions can potentially be reconstructed using time variation of the cosmogenic beryllium-10 (10Be) production recorded in ocean sediments. Downcore profiles of authigenic 10Be/9Be ratios (proxy of atmospheric 10Be production) in oceanic cores provide independent and additional records of the evolution of the geomagnetic intensity and complete previous information derived from relative paleointensity (RPI). Here are presented new authigenic 10Be/9Be results obtained from cores MD05-2920 and from the top of core MD05-2930 collected in the West Equatorial Pacific Ocean. Completing data of Ménabréaz et al. (2012, 2014), these results provide the first continuous 10Be production rate sedimentary record covering the last 800 ka. Along these cores, authigenic 10Be/9Be ratio peaks are recorded - within methodological errors - at the stratigraphic level of RPI lows. High-resolution chronologies (δ18O-derived) lead to interpret these peaks as successive global 10Be overproduction events triggered by geomagnetic dipole lows present in the PISO-1500 and Sint-2000 stacks. The largest amplitude 10Be production enhancement is synchronous to the very large decrease of the dipole field associated with the last polarity reversal (772 ka). It is consistent in shape and duration with the peak recorded in core MD90-0961 from the Maldive area (Indian Ocean) (Valet et al. 2014). Two significant 10Be production enhancements are coeval with the Laschamp (41 ka) and Icelandic basin (190 ka) excursions, while 10Be production peaks of lower amplitude correlate to other recognized excursions such as the Blake (120 ka), Pringle-Falls (215 ka), Portuguese Margin (290 ka), Big Lost (540 ka) among others. This study provides new data on the amplitude and timing of dipole field variations, helping to understand the difference between paleosecular variation, excursions, aborted reversals and reversals regimes.

Th-U-total Pb Geochronology of Authigenic Monazite Near the top of the Sturtian-Marinoan Interglacial, Adelaide Rift Complex, South Australia

NASA Astrophysics Data System (ADS)

Mahan, K. H.; Wernicke, B. P.; Jercinovic, M. J.

2007-12-01

The Adelaide Rift Complex in South Australia contains the type sections for Sturtian and Marinoan glacial deposits. The litho- and chemostratigraphy of these deposits play a central role in evaluating global Neoproterozoic ice age hypotheses ("snowball Earth") and Rodinia supercontinent reconstructions, but precise ages on igneous units do not yet exist. We report preliminary results of in situ Th-U-total Pb electron microprobe dating of monazite in sandstones within the Holowilena Ironstone ("older" Sturtian glacial at Enorama Creek) and at the top of the Enorama Shale (youngest pre-Marinoan, interglacial clastics at Elatina Creek). Several distinct populations are recognized. First, rounded cores with high Th, U, and Y + HREE abundances are interpreted as igneous or metamorphic detrital grains and yield ca. 1590 Ma, ca. 1280-1300 Ma, and ca. 1040 Ma dates related to well-known orogenic events in surrounding cratonic regions. A second group also occurs as "cores" but contains significantly lower U and Y + HREE, characteristics that may be indicative of an authigenic origin. Some rounded domains may represent "recycled" authigenic grains and yield dates of ca. 880 Ma and ca. 760 Ma. However, a subset observed in the Enorama sample occurs as very small (~2 x 10 microns), euhedral lathes that are unlikely to have survived a detrital history and yield a date of 680 +/-23 Ma. The youngest population forms very low Th and U, inclusion-rich overgrowths with ca. 500 Ma dates (Delamerian Orogeny) that probably grew hydrothermally. The recognition of "recycled" authigenic monazite further emphasizes the detail in textural and petrological documentation that is required for accurate geochronological interpretations. The date of 680 +/-23 Ma (1) provides an estimate for the age of the base of the Trezona carbon isotopic anomaly just beneath the Marinoan glacial deposits, (2) provides an absolute minimum age constraint on the underlying Sturtian glacial deposits, and (3) is confirming of proposed correlations between type Marinoan deposits and precisely dated glacial deposits in Namibia and China.

A refined genetic model for the Laisvall and Vassbo Mississippi Valley-type sandstone-hosted deposits, Sweden: constraints from paragenetic studies, organic geochemistry, and S, C, N, and Sr isotope data

NASA Astrophysics Data System (ADS)

Saintilan, Nicolas J.; Spangenberg, Jorge E.; Samankassou, Elias; Kouzmanov, Kalin; Chiaradia, Massimo; Stephens, Michael B.; Fontboté, Lluís

2016-06-01

The current study has aimed to refine the previously proposed two-fluid mixing model for the Laisvall (sphalerite Rb-Sr age of 467 ± 5 Ma) and Vassbo Mississippi Valley-type deposits hosted in Ediacaran to Cambrian sandstone, Sweden. Premineralization cements include authigenic monazite, fluorapatite, and anatase in the Upper Sandstone at Laisvall, reflecting anoxic conditions during sandstone burial influenced by the euxinic character of the overlying carbonaceous middle Cambrian to Lower Ordovician Alum Shale Formation ( δ 13Corg = -33.0 to -29.5 ‰, δ 15Norg = 1.5 to 3.3 ‰, 0.33 to 3.03 wt% C, 0.02 to 0.08 wt% N). The available porosity for epigenetic mineralization, including that produced by subsequent partial dissolution of pre-Pb-Zn sulfide calcite and barite cements, was much higher in calcite- and barite-cemented sandstone paleoaquifers (29 % by QEMSCAN mapping) than in those mainly cemented by quartz (8 %). A major change in the Laisvall plumbing system is recognized by the transition from barite cementation to Pb-Zn sulfide precipitation in sandstone. Ba-bearing, reduced, and neutral fluids had a long premineralization residence time (highly radiogenic 87S/86Sr ratios of 0.718 to 0.723) in basement structures. As a result of an early Caledonian arc-continent collision and the development of a foreland basin, fluids migrated toward the craton and expelled Ba-bearing fluids from their host structures into overlying sandstone where they deposited barite upon mixing with a sulfate pool ( δ 34Sbarite = 14 to 33 ‰). Subsequently, slightly acidic brines initially residing in pre-Ediacaran rift sediments in the foredeep of the early Caledonian foreland basin migrated through the same plumbing system and acquired metals on the way. The bulk of Pb-Zn mineralization formed at temperatures between 120 and 180 °C by mixing of these brines with a pool of H2S ( δ 34S = 24 to 29 ‰) produced via thermochemical sulfate reduction (TSR) with oxidation of hydrocarbons in sandstone. Other minor H2S sources are identified. Upward migration and fluctuation of the hydrocarbon-water interface in sandstone below shale aquicludes and the formation of H2S along this interface explain the shape of the orebodies that splay out like smoke from a chimney and the conspicuous alternating layers of galena and sphalerite. Intimate intergrowth of bitumen with sphalerite suggests that subordinate amounts of H2S might have been produced by TSR during Pb-Zn mineralization. Gas chromatograms of the saturated hydrocarbon fraction from organic-rich shale and from both mineralized and barren sandstone samples indicate that hydrocarbons migrated from source rocks in the overlying Alum Shale Formation buried in the foredeep into sandstone, where they accumulated in favorable traps in the forebulge setting.

Occurrence of Tourmaline in Metasedimentary Rocks of the Isua Supracrustal Belt, Greenland: Implications for Ribose Stabilization in Hadean Marine Sediments.

PubMed

Mishima, Shinpei; Ohtomo, Yoko; Kakegawa, Takeshi

2016-06-01

Abiotic formation of RNA was important for the emergence of terrestrial life, but the acknowledged difficulties of generating and stabilizing ribose have often raised questions regarding how the first RNA might have formed. Previous researchers have proposed that borate could have stabilized ribose; however, the availability of borate on the early Earth has been the subject of intense debate. In order to examine whether borate was available on the early Earth, this study examined metasedimentary rocks from the Isua Supracrustal Belt. Garnet, biotite, and quartz comprise the major constituents of the examined rocks. Field relationships and the chemical compositions of the examined rocks suggest sedimentary origin. The present study found that garnet crystals contain a number of inclusions of tourmaline (a type of borosilicate mineral). All tourmaline crystals are Fe-rich and categorized as schorl. Both garnet and tourmaline often contain graphite inclusions and this close association of tourmaline with garnet and graphite has not been recognized previously. Garnet-biotite and graphite geothermometers suggest that the tourmaline in garnet experienced peak metamorphic conditions (~500 °C and 5 kbar). The mineralogical characteristics of the tourmaline and the whole rock composition indicate that the tourmaline formed authigenically in the sediment during diagenesis and/or early metamorphism. Clay minerals in modern sediments have the capability to adsorb and concentrate borate, which could lead to boron enrichment during diagenesis, followed by tourmaline formation under metamorphic conditions. Clay minerals, deposited on the early Archean seafloor, were the precursors of the garnet and biotite in the examined samples. The studied tourmaline crystals were most likely formed in the same way as modern tourmaline in marine sediments. Therefore, boron enrichment by clays must have been possible even during the early Archean. Thus, similar enrichment could have been possible during the Hadean, providing a stabilization agent for ribose.

Greigite as a marker of paleo sulphate methane transition zone (SMTZ) in cold seep environment of Krishna-Godavari (KG) Basin, Bay of Bengal, India.

NASA Astrophysics Data System (ADS)

B, F. K.; Dewangan, P.; Usapkar, A.; Mazumdar, A.; Kocherla, M.; Tammisetti, R.; Khalap, S. T.; Satelkar, N. P.; Mehrtens, T.; Rosenauer, A.

2014-12-01

Rockmagnetic results and electron microscopic observations on a sediment core retrieved from a proven cold seep environment of Krishna-Godavari (KG) Basin revealed an anomalously magnetically enhanced zone (17 - 23 mbsf) below the present-day SMTZ in the KG offshore basin. This zone is characterized by higher SIRM / k, kARM / SIRM and kfd % values indicating the presence of fine grained superparamagnetic (SP) sized ferrimagnetic iron sulphides minerals such as greigite formed due to anaerobic oxidation of methane (AOM). Identification of such mineral phases and understanding the mechanism of their formation and preservation is of vital importance which could provide better understanding of the geochemical processes on the paleo - SMTZ. Magnetic concentrates extracted from this zone were characterised by transmission electron microscopy and energy dispersive X- ray spectrometry. We observed two possible occurrences of magnetic phases within this sediment depths 17 - 23 mbsf. (a) authigenically formed SP sized ferrimagnetic inclusions of magnetite, pyrite and greigite within matrix of host siliceous grain, (b) poorly crystallized fine-grained magnetite with ill defined grain boundary possibily formed extracellulary by magnetotactic bacterias through biologically-induced mineralization. High methane fluxes as observed in this basin provides suitable environment for the formation of greigite in the vicinity of SMTZ. We hypothesize that due to availability of residual iron and low supply of hydrogen sulphide caused by downwards diffusion lead to preservation of greigite. The occurence of greigite as inclusion within the host silicate matrix might explain its preservation in this zone in spite of intense pyritization. The greigite would otherwise be converted to stable-form pyrite. It is challenging to explain the origin of biologically produced magnetite within 17 - 23 mbsf as it is expected to dissolve in this zone due to intense pyritization.

Deposition modes in the paleo-lake Colônia (São Paulo, SE / Brazil): detrital input and bio-geochemical processes

NASA Astrophysics Data System (ADS)

Roeser, Patricia; Ledru, Marie-Pierre; Thouveny, Nicolas; Tachikawa, Kazuyo; Rostek, Frauke; Garcia, Marta; Struck, Ulrich; Sawakuchi, André; Favier, Charly; Bard, Edouard

2017-04-01

Colônia, a geomorphological circular structure in southeast Brazil, probably originated from an meteor impact with still unknown age. The structure, situated 40 km south of the center of the mega city São Paulo, has ca. 3.6 km in diameter and a surrounding rim elevated by ca. 120 meters. At present, the inner part of the structure contains a swampy alluvial plain. Sediment columns recovered in September 2014 have shown that below a circa 8 meter thick peat deposit, sediments are lacustrine and characterized by light-gray bands (cm scale). According to a preliminary age-depth model, based on radiocarbon ages, luminescence ages and paleomagnetism, the transition between lake to peat deposition seems to relate to climate boundary conditions from glacial towards interglacial conditions. In the lacustrine fine-grained sediments, the banded gray layers have distinct grain size, as macroscopically observed from mica grains/plates. Correlated to high-resolution geochemical data, lighter colored bands hold increased amounts of K and Si [XRF counts], originating from detrital input from the basin, e.g. flood events during tropical storms. Potassium is mainly contained in the crystalline structure of muscovite, whereas silica is additionally contained in kaolinite and quartz, thereby completing the minerals that make out the major mineral assemblage found in the sediments. Pyrite is found as an accessory mineral with average concentrations between 1 and 2%, peaking at 5% up to 10% in covariance to Fe/Ti [XRF count ratio]. Overall a covariance pattern, with or without phase lag, between pyrite, ∂13C (of TOC) and the concentrations of the biomarker hopane is observed in the lacustrine sediments. These relationships likely originate from stratification conditions in the paleo-lake, such that a more stable stratification eventually led to anoxic lake bottom conditions, favoring authigenic/microbial pyrite precipitation, better preservation of organic matter and affecting gas exchange between the water and the atmosphere.

Phosphate rock formation and marine phosphorus geochemistry: the deep time perspective.

PubMed

Filippelli, Gabriel M

2011-08-01

The role that phosphorite formation, the ultimate source rock for fertilizer phosphate reserves, plays in the marine phosphorus (P) cycle has long been debated. A shift has occurred from early models that evoked strikingly different oceanic P cycling during times of widespread phosphorite deposition to current thinking that phosphorite deposits may be lucky survivors of a series of inter-related tectonic, geochemical, sedimentological, and oceanic conditions. This paradigm shift has been facilitated by an awareness of the widespread nature of phosphogenesis-the formation of authigenic P-bearing minerals in marine sediments that contributes to phosphorite formation. This process occurs not just in continental margin sediments, but in deep sea oozes as well, and helps to clarify the driving forces behind phosphorite formation and links to marine P geochemistry. Two processes come into play to make phosphorite deposits: chemical dynamism and physical dynamism. Chemical dynamism involves the diagenetic release and subsequent concentration of P-bearing minerals particularly in horizons, controlled by a number of sedimentological and biogeochemical factors. Physical dynamism involves the reworking and sedimentary capping of P-rich sediments, which can either concentrate the relatively heavy and insoluble disseminated P-bearing minerals or provide an episodic change in sedimentology to concentrate chemically mobilized P. Both processes can result from along-margin current dynamics and/or sea level variations. Interestingly, net P accumulation rates are highest (i.e., the P removal pump is most efficient) when phosphorites are not forming. Both physical and chemical pathways involve processes not dominant in deep sea environments and in fact not often coincide in space and time even on continental margins, contributing to the rarity of high-quality phosphorite deposits and the limitation of phosphate rock reserves. This limitation is becoming critical, as the human demand for P far outstrips the geologic replacement for P and few prospects exist for new discoveries of phosphate rock. Copyright © 2011 Elsevier Ltd. All rights reserved.

Interlaboratory comparison of mineral constituents in a sample from the Herrin (No. 6) coal bed from Illinois

USGS Publications Warehouse

Finkelman, Robert B.; Fiene, F.L.; Miller, R.N.; Simon, F.O.

1984-01-01

Approximately 20 kg of the Herrin (No. 6) coal was collected from a strip mine in St. Clair County, Ill. A 10-kg portion was ground to -60 mesh, homogenized, and riffled into 128 splits of 70-80 g each. Homogeneity of these splits was confirmed by moisture, ash, and sulfur analyses of six randomly selected splits. Results of these analyses were within the ASTM (American Society for Testing and Materials) guidelines for interlaboratory precision. Splits of the Herrin (No. 6) coal were then transmitted to more than 30 laboratories for analysis. Low-temperature plasma oxidation was used to isolate inorganic matter for quantitative chemical and mineralogical analysis. Despite a wide variation in ashing conditions, only minor variations in ash yields were obtained; these variations were attributed to differences in operating temperature and moisture content. Mineralogical analyses of low-temperature ash (LTA) concentrates prepared by five different laboratories indicated variations within the limits of analytical error. The mean values, in weight percent, for the major minerals are as follows: calcite, 9; quartz, 20; pyrite, 23; kaolinite, 14; and illite+mixed-layer clays, 31. Normative mineralogical calculations and Fourier transform infrared analysis (FTIR) yielded results similar to those obtained from X-ray diffraction (XRD). Choosing appropriate mineral standards was found to be critical for the proper use of analytical techniques such as XRD and FTIR. Good interlaboratory agreement was obtained for most major, minor, and trace elements despite differences in analytical procedures and in the type of sample analyzed (coal, high-temperature ash, or LTA). Discrepancies between analyses for zinc, strontium, manganese, and iron may be attributed to sampling inhomogeneity problems. Mossbauer spectroscopy showed that approximately 44 percent of the pyritic sulfur was lost through weathering in the first year after preparation of the interlaboratory sample. Szomolnokite and possibly coquimbite and jarosite were also identified. Scanning electron microscopy studies indicated ubiquitous pyrite framboids and, less commonly, euhedral crystals, skeletal grains, irregularly shaped particles, and vein fillings. Minor accessory minerals such as rare-earth phosphates and possibly silicates, zircon, barium sulfate, titanium oxide, and sphalerite were also found. The textural evidence indicates that the minerals in the banded material are detrital whereas the minerals occurring as vein and pore fillings are authigenic. Magnetic measurements indicate that coal crushed in a steel pulverizer is contaminated by small quantities of abrasion fragments from the crusher, which seriously affect the measured magnetic properties of the coal.

Microbial and diagenetic steps leading to the mineralisation of Great Salt Lake microbialites

NASA Astrophysics Data System (ADS)

Pace, Aurélie; Bourillot, Raphaël; Bouton, Anthony; Vennin, Emmanuelle; Galaup, Serge; Bundeleva, Irina; Patrier, Patricia; Dupraz, Christophe; Thomazo, Christophe; Sansjofre, Pierre; Yokoyama, Yusuke; Franceschi, Michel; Anguy, Yannick; Pigot, Léa; Virgone, Aurélien; Visscher, Pieter T.

2016-08-01

Microbialites are widespread in modern and fossil hypersaline environments, where they provide a unique sedimentary archive. Authigenic mineral precipitation in modern microbialites results from a complex interplay between microbial metabolisms, organic matrices and environmental parameters. Here, we combined mineralogical and microscopic analyses with measurements of metabolic activity in order to characterise the mineralisation of microbial mats forming microbialites in the Great Salt Lake (Utah, USA). Our results show that the mineralisation process takes place in three steps progressing along geochemical gradients produced through microbial activity. First, a poorly crystallized Mg-Si phase precipitates on alveolar extracellular organic matrix due to a rise of the pH in the zone of active oxygenic photosynthesis. Second, aragonite patches nucleate in close proximity to sulfate reduction hotspots, as a result of the degradation of cyanobacteria and extracellular organic matrix mediated by, among others, sulfate reducing bacteria. A final step consists of partial replacement of aragonite by dolomite, possibly in neutral to slightly acidic porewater. This might occur due to dissolution-precipitation reactions when the most recalcitrant part of the organic matrix is degraded. The mineralisation pathways proposed here provide pivotal insight for the interpretation of microbial processes in past hypersaline environments.

Eolian deposition cycles since AD 500 in Playa San Bartolo lunette dune, Sonora, Mexico: Paleoclimatic implications

NASA Astrophysics Data System (ADS)

Ortega, Beatriz; Schaaf, Peter; Murray, Andrew; Caballero, Margarita; Lozano, Socorro; Ramirez, Angel

2013-12-01

Records of past climatic changes in desert environments are scarce due to the poor preservation of biological proxies. To overcome this lack we consider the paleoenvironmental significance and age of a lunette dune at the eastern rim of Playa San Bartolo (PSB) in the Sonoran Desert (Mexico). Thermoluminescence and optical stimulated luminescence (TL and OSL) provide the chronology of lunette dune development. Mineralogical, geochemical (major, trace and REE element concentrations) and rock magnetic analyses allow for the assessment of sediment provenance and changes in the composition of the PSB dune over time. The upper 6 m of dune accumulation occurred over the past 1.5 ka, largely during AD 500-1200, a period that correlates with the Medieval climatic anomaly (AD 300-1300). Variability in composition of dune sediments is attributed to changes in sediment sources. Sand sized deposits are mainly eroded from granitoids from nearby outcrops. Sandy silt deposits, rich in evaporative minerals, resulted after the flooding of PSB, later deflation and accumulation of both detritic and authigenic components in the dune. These findings suggest that main dune accretion occurred during regionally extended drought conditions, disrupted by sporadic heavy rainfall.

Compositional changes of surface sediments and variability of manganese nodules in the Peru Basin

NASA Astrophysics Data System (ADS)

Marchig, Vesna; von Stackelberg, Ulrich; Hufnagel, Heinz; Durn, Goran

Two types of manganese nodules were observed in the Peru Basin: large botryoidal nodules in basins and small ellipsoidal nodules on slope positions. The sediment in areas with large botryoidal nodules contains a thinner and weaker oxidation zone than the sediment under small ellipsoidal nodules, indicating that diagenetic processes in the sediment, which supply manganese nodules with metals for their growth, are stronger in sediments on which large botryoidal nodules grow. Organic matter, which activates remobilization of metals, occurs mostly in the form of refractory lipidic compounds in the inner capsule of radiolaria. This material needs bacterial degradation to act as a reducing agent. Easily oxidizable organic components could not be found in the sediments. Other changes in sediment composition do not have a link to manganese nodule growth. Biogenous components (radiolarians, organogenic barite and apatite) increase towards the equatorial high-productivity zone. Authigenous clay minerals (nontronite as well as montmorillonite with high Fe +3 incorporation on positions of ochtaedral Al) increase with distance from the continent. The assessment of environmental impacts will have to take into account the regional differences in sediment composition and the small-scale variability of manganese nodules.

Asphalt Volcanism and Chemosynthetic Life in the Campeche Knolls, Gulf of Mexico

NASA Astrophysics Data System (ADS)

MacDonald, I. R.; Bohrmann, G.; Escobar, E.; Abegg, F.; Blanchon, P.; Blinova, V.; Brückmann, W.; Drews, M.; Eisenhauer, A.; Han, X.; Heeschen, K.; Meier, F.; Mortera, C.; Naehr, T.; Orcutt, B.; Bernard, B.; Brooks, J.; de Faragó, M.

2004-05-01

In the Campeche Knolls, in the southern Gulf of Mexico, lava-like flows of solidified asphalt cover more than 1 square kilometer of the rim of a dissected salt dome at a depth of 3000 meters below sea level. Chemosynthetic tubeworms and bivalves colonize the sea floor near the asphalt, which chilled and contracted after discharge. The site also includes oil seeps, gas hydrate deposits, locally anoxic sediments, and slabs of authigenic carbonate. Asphalt volcanism creates a habitat for chemosynthetic life that may be widespread at great depth in the Gulf of Mexico.

Geochemical constraints on the temperature and timing of carbonate formation and lithification in the Nankai Trough, NanTroSEIZE transect

NASA Astrophysics Data System (ADS)

Sample, James C.; Torres, Marta E.; Fisher, Andrew; Hong, Wei-Li; Destrigneville, Christine; Defliese, William F.; Tripati, Aradhna E.

2017-02-01

Information about diagenetic processes and temperatures during burial of sediments entering the subduction zone is important for understanding changes in physical properties and seismic behavior during deformation. The geochemistry of authigenic carbonates from accretionary prisms can serve as proxies for conditions during carbonate cementation and resultant lithification. We report results from the Nankai accretionary prism recovered from Integrated Ocean Drilling Program (IODP) sites C0011 and C0012 and we document continued cementation of deep sediment sections prior to subduction. Elemental and isotope data provide evidence for complex mixing of different isotopic reservoirs in pore waters contributing to carbonate chemical signatures. Carbon stable isotope values exhibit a broad range (δ13CV-PDB = +0.1‰ to -22.5‰) that corresponds to different stages of cement formation during burial. Carbonate formation temperatures from carbonate-clumped isotope geochemistry range from 16 °C to 63 °C at Site C0011 and 8.7 °C to 68 °C at Site C0012. The correspondence between the clumped-isotope temperatures and extrapolations of measured in situ temperatures indicate the carbonate is continuing to form at present. Calculated water isotopic compositions are in some cases enriched in 18O relative to measured interstitial waters suggesting a component of inherited seawater or input from clay-bound water. Low oxygen isotope values and the observed Ba/Ca ratios are also consistent with carbonate cementation at depth. Strontium isotopes of interstitial waters (87Sr/86Sr of 0.7059-0.7069) and carbonates (87Sr/86Sr of 0.70715-0.70891) support formation of carbonates from a mixture of strontium reservoirs including current interstitial waters and relic seawater contemporaneous with deposition. Collectively our data reflect mixed sources of dissolved inorganic carbon and cations that include authigenic phases driven by organic carbon and volcanic alteration reactions. Physical properties of input sediments continue to undergo modification by carbonate cementation at present. Due to ongoing recrystallization, temperatures from carbonate-clumped isotopes reflect the modern geothermal gradient and may serve as useful measures of geothermal gradients in other siliciclastic basins where carbonate cementation occurs. We conclude that clumped-isotope signatures in authigenic carbonates from accretionary prisms are important proxies for the timing and conditions of cementation in active margins. Our results highlight the importance of using multi-proxy approaches to elucidate the history of carbonate cementation, particularly to establish carbonate precipitation at depth and its potential impact on the physical and mechanical properties of the sediment prior to subduction.

The origin of collapse features appearing in a migrating parabolic dune along the southern coast of Lake Michigan

NASA Astrophysics Data System (ADS)

Argyilan, Erin P.; Avis, Peter G.; Krekeler, Mark P. S.; Morris, Charles C.

2015-12-01

Dune decomposition chimneys are collapse features formed when migrating dunes encroach on a forest and buried trees subsequently decay, leaving a temporarily stable open hole. The recent appearance of holes on the stoss slope of Mount Baldy at the Indiana Dunes National Lakeshore provided an opportunity for study of such features. Mount Baldy is a large parabolic dune that is rapidly migrating onshore over a late Holocene landscape with stabilized relict parabolic dunes that supported oak (Quercus spp.) trees visible on the 1939 aerial photo. Individual holes were mapped to locations on the dune surface that would directly overlie the arm of a buried relict parabolic dune. Analyses of buried trees and surrounding sediment indicated that saprotrophic wood decay fungi continue to actively decompose trees after burial and biomineralization of a calcium-carbonate-rich cement occurs at the contact between organic material and sands. Scanning electron microscopy of the cement showed neoformed authigenic minerals and organic structures consistent in morphology with fungal hyphae. We propose that, within the dune, portions of the decayed trees progressively collapse and infill, and open holes are temporarily stabilized by the calcium-carbonate-rich cement. Further, holes can exist undetected at the surface, covered by a thin veneer of sand. Migrating dune systems are observed in many coastal and inland areas. Ongoing work must address the relative contributions of individual environmental factors on the formation of dune decomposition chimneys, including the biomineralization of cement, sand mineralogy, rate of dune movement, tree species, climate, and the composition of fungal communities.

Bacterially mediated removal of phosphorus and cycling of nitrate and sulfate in the waste stream of a "zero-discharge" recirculating mariculture system.

PubMed

Krom, M D; Ben David, A; Ingall, E D; Benning, L G; Clerici, S; Bottrell, S; Davies, C; Potts, N J; Mortimer, R J G; van Rijn, J

2014-06-01

Simultaneous removal of nitrogen and phosphorus by microbial biofilters has been used in a variety of water treatment systems including treatment systems in aquaculture. In this study, phosphorus, nitrate and sulfate cycling in the anaerobic loop of a zero-discharge, recirculating mariculture system was investigated using detailed geochemical measurements in the sludge layer of the digestion basin. High concentrations of nitrate and sulfate, circulating in the overlying water (∼15 mM), were removed by microbial respiration in the sludge resulting in a sulfide accumulation of up to 3 mM. Modelling of the observed S and O isotopic ratios in the surface sludge suggested that, with time, major respiration processes shifted from heterotrophic nitrate and sulfate reduction to autotrophic nitrate reduction. The much higher inorganic P content of the sludge relative to the fish feces is attributed to conversion of organic P to authigenic apatite. This conclusion is supported by: (a) X-ray diffraction analyses, which pointed to an accumulation of a calcium phosphate mineral phase that was different from P phases found in the feces, (b) the calculation that the pore waters of the sludge were highly oversaturated with respect to hydroxyapatite (saturation index = 4.87) and (c) there was a decrease in phosphate (and in the Ca/Na molar ratio) in the pore waters simultaneous with an increase in ammonia showing there had to be an additional P removal process at the same time as the heterotrophic breakdown of organic matter. Copyright © 2014 Elsevier Ltd. All rights reserved.

New insights into the mineralogy of the Atlantis II Deep metalliferous sediments, Red Sea

NASA Astrophysics Data System (ADS)

Laurila, Tea E.; Hannington, Mark D.; Leybourne, Matthew; Petersen, Sven; Devey, Colin W.; Garbe-Schönberg, Dieter

2015-12-01

The Atlantis II Deep of the Red Sea hosts the largest known hydrothermal ore deposit on the ocean floor and the only modern analog of brine pool-type metal deposition. The deposit consists mainly of chemical-clastic sediments with input from basin-scale hydrothermal and detrital sources. A characteristic feature is the millimeter-scale layering of the sediments, which bears a strong resemblance to banded iron formation (BIF). Quantitative assessment of the mineralogy based on relogging of archived cores, detailed petrography, and sequential leaching experiments shows that Fe-(oxy)hydroxides, hydrothermal carbonates, sulfides, and authigenic clays are the main "ore" minerals. Mn-oxides were mainly deposited when the brine pool was more oxidized than it is today, but detailed logging shows that Fe-deposition and Mn-deposition also alternated at the scale of individual laminae, reflecting short-term fluctuations in the Lower Brine. Previous studies underestimated the importance of nonsulfide metal-bearing components, which formed by metal adsorption onto poorly crystalline Si-Fe-OOH particles. During diagenesis, the crystallinity of all phases increased, and the fine layering of the sediment was enhanced. Within a few meters of burial (corresponding to a few thousand years of deposition), biogenic (Ca)-carbonate was dissolved, manganosiderite formed, and metals originally in poorly crystalline phases or in pore water were incorporated into diagenetic sulfides, clays, and Fe-oxides. Permeable layers with abundant radiolarian tests were the focus for late-stage hydrothermal alteration and replacement, including deposition of amorphous silica and enrichment in elements such as Ba and Au.

Type Region of the Ione Formation (Eocene), Central California: Stratigraphy, Paleogeography, and Relation to Auriferous Gravels

USGS Publications Warehouse

Creely, Scott; Force, Eric R.

2007-01-01

The middle Eocene Ione Formation extends over 200 miles (320 km) along the western edge of the Sierra Nevada. Our study was concentrated in the type region, 30 miles (48 km) along strike. There a bedrock ridge forms the seaward western side of the Ione depositional tract, defining a subbasin margin. The eastern limit of the type Ione is locally defined by high-angle faults. Ione sediments were spread over Upper Mesozoic metamorphic and plutonic bedrock, fed by gold-bearing streams dissecting the western slope of the ancestral Sierra Nevada. By middle Eocene time, a tropical or subtropical climate prevailed, leading to deep chemical weathering (including laterization) and a distinctively mature mineral assemblage was fed to and generated within Ione deposits. The Ione is noted for its abundant kaolinitic clay, some of it coarsely crystalline; the clay is present as both detrital grains and authigenic cement. Quartz is abundant, mostly as angular grains. Heavy mineral fractions are dominated by altered ilmenite and zircon. Distribution of feldspar is irregular, both stratigraphically and areally. Non-marine facies are most voluminous, and include conglomerates, especially at the base and along the eastern margins of the formation where they pass into Sierran auriferous gravels. Clays, grading into lignites, and gritty sands are also common facies. Both braided and meandering fluvial facies have been recognized. Shallow marine waters flooded the basin probably twice. Tongues of sediment exhibiting a variety of estuarine to marine indicators are underlain and overlain by fluvial deposits. Marine body fossils are found at only a few localities, but burrows identified as Ophiomorpha and cf. Thalassinoides are abundant in many places. Other clues to marginal marine deposition are the occurrence of glauconite in one bed, typical relations of lagoonal to beach (locally heavy-mineral-rich) lithofacies, closed-basin three-dimensional morphology of basinal facies, and high sulfur content of some marginal coals. The Ione has been said to be deltaic; however the two transgressional-regressional cycles we propose imply that only the regressional parts were deltaic. At other times, much of the type Ione would better be termed an intertidal estuary. Because the lower marine sequence was deposited against a paleobasin margin on the west, deltaic morphology was constrained, but apparently progradation was from north to south despite drainage into the basin from the east. Relations to the south are unclear due to the Stockton arch. The eastern margin of the type-Ione basin, and to some extent even its marine facies, are poorly constrained. A surface on Sierran bedrock to the east may have been stripped of some Ione basinal facies, leaving only coeval entrenched fluvial channel deposits.

Regional fluid migration in the Illinois basin: evidence from in situ oxygen isotope analysis of authigenic K-feldspar and quartz from the Mount Simon Sandstone

USGS Publications Warehouse

Chen, Zhensheng; Riciputi, Lee R.; Mora, Claudia I.; Fishman, Neil S.

2001-01-01

Oxygen isotope compositions of widespread, authigenic K-feldspar and quartz overgrowths and cements in the Upper Cambrian Mount Simon Sandstone were measured by ion microprobe in 11 samples distributed across the Illinois basin and its periphery. Average K-feldspar δ18O values increase systematically from +14‰ ± 1‰ in the southernmost and deepest samples in Illinois to +24‰ ± 2‰ in the northernmost outcrop sample in Wisconsin. A similar trend was observed for quartz overgrowths (22‰ ± 2‰ to 28‰ ± 2‰). Constant homogenization temperatures (100–130 °C) of fluid inclusions associated with quartz overgrowths throughout the basin suggest that the geographic trend in oxygen isotope compositions is a result of diagenetic modification of a south to north migrating basinal fluid.

Changes in biogenic and detrital fluxes across the last two glacial terminations at the Shatsky Rise

NASA Astrophysics Data System (ADS)

Bradtmiller, L. I.; Kinsley, C. W.; McGee, D.; Ford, H. L.; Perala-Dewey, J.; Zhang, Y.

2017-12-01

The Shatsky Rise is located within strong gradients in SST and biological productivity between the subtropical and subarctic Pacific gyres. The region is highly sensitive to changes in atmospheric and oceanic circulation on glacial-interglacial timescales, which affect the delivery of Fe-bearing dust and other major nutrients, respectively. Here we use a range of proxies in an attempt to determine the effects of changes in westerly winds and gyre boundaries on dust delivery and biological productivity. We present 230Th-normalized fluxes of opal, Corg, CaCO3, and detrital material at ODP Site 1208 over the last two glacial terminations, extending to 145ka. Opal, Corg, and carbonate are products of surface biological productivity, while most detrital material at this site arrives in the form of windborne East Asian dust. In addition, we calculate the concentration of authigenic U as an indicator of relative oxygenation of the sediment water interface. We observe elevated opal and dust fluxes during the last two glacial maxima, and a decrease in both components during deglaciations. Authigenic U shows distinct peaks at the onset of both terminations. The peak at the penultimate deglaciation is also associated with a large peak in opal flux, while the peak in authigenic U during the last termination does not appear to be associated with any large changes in biogenic fluxes. We compare our records with other data from the subtropical-subarctic transition zone, and suggest that our data are consistent with northward shift of the mean position of the westerly jet and subarctic front during deglaciations.

Controls on the barium isotope compositions of marine sediments

NASA Astrophysics Data System (ADS)

Bridgestock, Luke; Hsieh, Yu-Te; Porcelli, Donald; Homoky, William B.; Bryan, Allison; Henderson, Gideon M.

2018-01-01

The accumulation of barium (Ba) in marine sediments is considered to be a robust proxy for export production, although this application can be limited by uncertainty in BaSO4 preservation and sediment mass accumulation rates. The Ba isotope compositions of marine sediments could potentially record insights into past changes in the marine Ba cycle, which should be insensitive to these limitations, enabling more robust interpretation of sedimentary Ba as a proxy. To investigate the controls on the Ba isotope compositions of marine sediments and their potential for paleo-oceanographic applications, we present the first Ba isotope compositions results for sediments, as well as overlying seawater depth profiles collected in the South Atlantic. Variations in Ba isotope compositions of the sediments predominantly reflect changes in the relative contributions of detrital and authigenic Ba sources, with open-ocean sediments constraining the isotope composition of authigenic Ba to be δ 138/134Ba ≈ + 0.1 ‰. This value is consistent with the average isotope composition inferred for sinking particulate Ba using simple mass balance models of Ba in the overlying water column and is hypothesized to reflect the removal of Ba from the upper water column with an associated isotopic fractionation of Δ diss-part 138/134Ba ≈ + 0.4 to +0.5. Perturbations to upper ocean Ba cycling, due to changes in export production and the supply of Ba via upwelling, should therefore be recorded by the isotope compositions of sedimentary authigenic Ba. Such insights will help to improve the reliable application of Ba accumulation rates in marine sediments as a proxy for past changes in export production.

Spotted Lake: Mineralogical Clues for the Formation of Authigenic Sulfates in Ancient Lakes on Mars

NASA Astrophysics Data System (ADS)

Cannon, K. M.; Fenwick, L. A.; Peterson, R. C.

2012-03-01

Spotted Lake in British Columbia has some of the highest sulfate concentrations in the world, and serves as a valuable analog for studying evaporation and freezing crystallization processes in martian paleolakes.

The impact of transport processes on rare earth element patterns in marine authigenic and biogenic phosphates

NASA Astrophysics Data System (ADS)

Auer, Gerald; Reuter, Markus; Hauzenberger, Christoph A.; Piller, Werner E.

2017-04-01

Rare earth elements (REEs) are commonly used proxies to reconstruct water chemistry and oxygen saturation during the formation of authigenic and biogenic phosphates in marine environments. In the modern ocean REEs exhibit a distinct pattern with enrichment of heavy REEs and strong depletion in cerium (Ce). The wide range of REE enrichment patterns found in ancient marine phosphates lead to the proposition that water chemistry has been very different in the Earth's past. However, both early and late diagenesis are known to affect REE signatures in phosphates altering primary marine signals. Herein we present a dataset of REE signatures in 38 grain specific LA-ICP-MS measurements of isolated phosphate and carbonate grains in three discrete rock samples. The phosphates mainly consist of authigenic phosphates and phosphatized microfossils that formed in a microbially mediated micro-milieu. In addition, isolated biogenic and reworked phosphatic grains are also present. The phosphates are emplaced in bioclastic grain- to packstones deposited on a carbonate ramp setting in the central Mediterranean Sea during the middle Miocene Monterey event. The results reveal markedly different REE patterns (normalized to the Post Archean Australian Shale standard) in terms of total enrichment and pattern shape. Analyses of REE diagenesis proxies show that diagenetic alteration affected the samples only to a minor degree. Grain shape and REE patterns together indicate that authigenic, biogenic and reworked phosphates have distinct REE patterns irrespective of the sample. Our study shows that while REE patterns in phosphates do reflect water chemistry during authigenesis, they are often already heavily altered during reworking, a process, which can occur in geologically negligible timespans. REE patterns are therefore more likely to reflect complex enrichment processes after their formation. Similarities in the REE patterns of reworked and biogenic phosphate further suggest that the frequently observed hat-shaped pattern in biogenic phosphates can result from increased middle REE (Neodymium to Holmium) scavenging during taphonomic processes prior to final deposition. Cluster analysis coupled with sedimentological and previously published geochemical data (bulk carbon isotope and X-ray fluorescence spectrometry) allowed the characterization of REE patterns of phosphates in terms of their formation conditions and depositional history, such as the distinction of phosphates formed in situ from reworked and transported phosphate grains.

Long-lasting Microbial Methane Release at the Aquitaine Shelf Break (Bay of Biscay): Relation with the (Plio)-Pleistocene Sedimentary Progradation of the Continental Margin

NASA Astrophysics Data System (ADS)

Dupré, S.; Michel, G.; Pierre, C.; Ruffine, L.; Scalabrin, C.; Ehrhold, A.; Loubrieu, B.; Gautier, E.; Baltzer, A.; Imbert, P.; Battani, A.; Deville, E.; Dupont, P.; Thomas, Y.; Théréau, E.

2017-12-01

The recent identification of acoustic and visual gas release in the water column at the Aquitaine Shelf (140 and 220 m water depths) led to the discovery of a 200 km2 fluid system at the seafloor with 3000 bubbling sites associated with microbial methane (Dupré et al 2014; Ruffine et al. 2017). The moderate methane fluxes (measured in situ, on average 200 mLn/min per bubbling site) contribute to the formation of small-scale sub-circular authigenic carbonate mounds (with reliefs < 1 m in height) (Pierre et al. 2017). The emitted gases have neither a genetic link with thermogenic hydrocarbons from the Parentis Basin beneath, nor are issued from gas hydrate dissociation, but originate from microbial CO2 reduction. Based on estimated thickness and growth rate of authigenic carbonates, this system has lasted for at least several tens to possibly hundreds of kyears with a volume of escaping methane reaching 3.1012 Ln per 10 kyr. Seismic evidences for gas-charged layers and fossil authigenic carbonates point to organic matter source levels within the sedimentary deposits of the Late Pleistocene progradation system. The Aquitaine Shelf fluid system highlights the edge of continental shelves as preferential areas for bio-geological processes. The GAZCOGNE project is co-funded by TOTAL and IFREMER as part of the PAMELA (Passive Margin Exploration Laboratories) scientific project. References Dupré S, Berger L, Le Bouffant N, Scalabrin C, Bourillet J-F (2014) Fluid emissions at the Aquitaine Shelf (Bay of Biscay, France): a biogenic origin or the expression of hydrocarbon leakage? Cont. Shelf Res. 88:24-33 Pierre C, Demange J, Blanc-Valleron M-M, Dupré S (2017) Authigenic carbonate mounds from active methane seeps on the southern Aquitaine Shelf (Bay of Biscay, France): Evidence for anaerobic oxidation of biogenic methane and submarine groundwater discharge during formation. Cont. Shelf Res. 133:13-25 Ruffine L, Donval J-P, Croguennec C, Bignon L, Birot D, Battani A, Bayon G, Caprais J-C, Lantéri N, Levaché D, Dupré S (2017) Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes. Geofluids 2017:13

Strong influence of the littoral zone on sedimentary lipid biomarkers in a meromictic lake.

PubMed

Bovee, R J; Pearson, A

2014-11-01

Planktonic sulfur bacteria growing in zones of photic zone euxinia (PZE) are important primary producers in stratified, sulfur-rich environments. The potential for export and burial of microbial biomass from anoxic photic zones remains relatively understudied, despite being of fundamental importance to interpreting the geologic record of bulk total organic carbon (TOC) and individual lipid biomarkers. Here we report the relative concentrations and carbon isotope ratios of lipid biomarkers from the water column and sediments of meromictic Mahoney Lake. The data show that organic matter in the central basin sediments is indistinguishable from material at the lake shoreline in both its lipid and carbon isotopic compositions. However, this material is not consistent with either the lipid profile or carbon isotope composition of biomass obtained directly from the region of PZE. Due to the strong density stratification and the intensive carbon and sulfur recycling pathways in the water column, there appears to be minimal direct export of the sulfur-oxidizing planktonic community to depth. The results instead suggest that basinal sediments are sourced via the littoral environment, a system that integrates an indigenous shoreline microbial community, the degraded remains of laterally rafted biomass from the PZE community, and detrital remains of terrigenous higher plants. Material from the lake margins appears to travel downslope, traverse the strong density gradient, and become deposited in the deep basin; its final composition may be largely heterotrophic in origin. This suggests an important role for clastic and/or authigenic minerals in aiding the burial of terrigenous and mat-derived organic matter in euxinic systems. Downslope or mineral-aided transport of anoxygenic, photoautotrophic microbial mats may have been a significant sedimentation process in early Earth history. © 2014 John Wiley & Sons Ltd.

Kuwaiti dolocrete: petrology, geochemistry and groundwater origin

NASA Astrophysics Data System (ADS)

El-Sayed, M. I.; Fairchild, I. J.; Spiro, B.

1991-09-01

Near-surface sediments in southern Kuwait show extensive development of duricrusts. The host materials are siliciclastic sandstones of the post-Eocene Kuwait Group. Inland, the duricrusts are dominantly pedogenic calcrete (with some silcrete and gypcrete), whereas within 10-20 km of the coast, dolomite is the dominant duricrust mineral. Both these dolocretes and the inland calcretes display a similar maturation sequence in which carbonate-rich nodules develop and coalesce, carbonate progressively replacing and displacing detrital grains. The dolomite of the dolocretes forms mosaics of crystals typically 10-70 μm in size, varying from simple rhombs to spherulites. An intermediate morphology, named artichoke dolomite from its appearance in SEM, is particularly abundant. Authigenic palygorskite is associated with the dolomite. Dissolution of cores or zones within dolomite crystals has occurred. Calcite is present as sparry crystals (always post-dating dolomite) and is the expected precipitate from present-day soil and groundwaters. Chemical analyses of dolomite show highly negative values of δ13C (- to - 10.7‰ PDB) and δ18O varying from + 0.6 to + 3.3‰ PDB. The oxygen isotope values are interpreted as reflecting evaporation of a marine-based fluid. Manganese values of around 1000 ppm show that this fluid was reducing. Strontium data show variability reflecting mineral-fluid reactions. The general absence of metastable carbonates and presence of zoning in dolomite crystals suggests that meteoric dilution of seawater also occurred. Given that the duricrusts lack biogenic features, the light carbon isotope values are taken to indicate oxidation of seeping hydrocarbons. The dolocretes are interpreted as groundwater precipitates near the water table of a brackish water body formed at a time of higher relative sea level than today.

Influence of the spatial distribution of cementation on the permeability and mechanical attributes of sedimentary and fault rocks

NASA Astrophysics Data System (ADS)

Mozley, P.; Yoon, H.; Williams, R. T.; Goodwin, L. B.

2015-12-01

The spatial distribution of pore-filling authigenic minerals (cements) is highly variable and controlled in large part by the mineralogy of the cements and host sediment grains. Two end-member distributions of cements that commonly occur in sedimentary material are: (1) concretionary, in which precipitation occurred in specific zones throughout the sediment, with intervening areas largely uncemented; and (2) grain-rimming, in which precipitation occurred on grain-surfaces relatively uniformly throughout the rock. Concretions form in rocks in which sediment grains have a different composition from the cement, whereas rim cements form in those that have the same composition. Both the mechanical attributes and permeability of a given volume of rock are affected to a much greater extent by grain rimming cements, which have a significant impact on properties at even low abundances. Concretionary cements have little impact on bulk properties until relatively large volumes have precipitated (~80% cemented) and concretions begin to link up. Precipitation of cement in fault zones also impacts both mechanical and hydrologic properties. Cementation will stiffen and strengthen unlithified sediment, thereby controlling the locus of fracturing in protolith or damage zones. Where fracture networks form in fault damage zones, they are initially high permeability elements. However, progressive cementation greatly diminishes fracture permeability, resulting in cyclical permeability variation linked to fault slip. To quantitatively describe the interactions of groundwater flow, permeability, and patterns and abundance of cements, we use pore-scale modeling of coupled fluid flow, reactive transport, and heterogeneous mineral-surface reactions. By exploring the effects of varying distributions of porosity and mineralogy, which impact patterns of cementation, we provide mechanistic explanations of the interactions of coupled processes under various flow and chemistry conditions.

Upper Cretaceous (Campanian) phosphorites in Jordan: implications for the formation of a south Tethyan phosphorite giant

NASA Astrophysics Data System (ADS)

Pufahl, Peir K.; Grimm, Kurt A.; Abed, Abdulkader M.; Sadaqah, Rushdi M. Y.

2003-10-01

A record of sedimentary, authigenic, and biological processes are preserved within the Upper Cretaceous (Campanian) Alhisa Phosphorite Formation (AP) in central and northern Jordan. The AP formed near the eastern extremity of the south Tethyan Phosphorite Province (STPP), a carbonate-dominated Upper Cretaceous to Eocene "phosphorite giant" that extends from Colombia, North Africa to the Middle East. Multidisciplinary research of the AP and associated cherts, chalks, and oyster buildups indicate that phosphatic strata formed on a highly productive, storm-dominated, east-west trending epeiric platform along the south Tethyan margin. The onset of phosphogenesis and the accumulation of economic phosphorite coincided with a rise in relative sea level that onlapped peritidal carbonates of the Ajlun Group. Pristine phosphates are associated with well-developed micrite concretionary horizons and contain abundant non-keeled spiral planktic foraminifera and a low diversity benthic assemblage of Buliminacean foraminifera, suggesting that pristine phosphates are a condensed facies and phosphogenesis was stimulated by the effects of a highly productive surface ocean and the suboxic diagenesis of sedimentary organic matter. The bulk sediment composition and absence of Fe-bearing authigenic phases such as glauconite, pyrite (including pyrite molds), siderite, and goethite within pristine phosphates suggests that deposition and authigenesis occurred under conditions of detrital starvation and that "iron-pumping" played a minimal role in phosphogenesis. Authigenic precipitation of phosphate occurred in a broad array of sedimentary environments—herein termed a "phosphorite nursery"—that spanned the entire platform. This is a non-uniformitarian phenomenon reflecting precipitation of sedimentary apatite across a wide depositional spectrum in a variety of depositional settings, wherever the conditions were suitable for phosphogenesis. Sedimentologic data indicate that pristine phosphates were concentrated into phosphatic grainstones through storm wave winnowing, and storm-generated, shelf-parallel geostrophic currents. Economic phosphorites formed through the amalgamation of storm-induced event beds. Stratigraphic packaging of phosphatic strata indicates that temporal variations in storm frequency were a prerequisite for the formation of economic phosphorite. Syndepositional phosphogenesis, reworking, and amalgamation to form phosphorites contrasts sharply with the principles of "Baturin Cycling". A transgressive systems tract coupled with high surface productivity created detritally starved settings favourable for phosphogenesis; storm reworking of pristine phosphate facies produced granular phosphorite; and amalgamation of storm-generated granular event beds formed economic phosphorite in a single systems tract.

Microbially Mediated Glass Alteration in the Geological Record: Textural clues for Microbial Functions.

NASA Astrophysics Data System (ADS)

Staudigel, H.; Furnes, H.; McLoughlin, N.; Banerjee, N.

2007-12-01

Fe and Mn oxidizing microbes interact with their environment through the microbially mediated formation of Fe/Mn oxides and through the corrosion textures they may leave behind in the solids they colonize and from which they extract nutrients. Understanding the geo-biology of Fe and Mn oxidation may focus on the study of the microbes themselves, the mineral products, its biocorrosion features and the relationships between these types of observations. We have reviewed our own data on glass bio-corrosion and in particular the wider literature on microbial mineral tunneling to develop a two stage biocorrosion model for volcanic glass that offers feedback for our understanding of the mechanisms and the dynamics of microbial dissolution. Traces of microbially mediated dissolution of volcanic glass are commonly observed in volcanic glass found in submarine volcanoes on the seafloor, and in uplifted submarine volcanoes of almost any geological age back to the origin of life. Two main bioalteration textures care observed, granular and tubular. Based on a comparison of these features in particular with tunneling by ectomycorrhizal fungi, we propose two distinct types of biocorrosion that affects glass: (1) Granular alteration textures, made up of colonies of microbe-sized, near spherical mineral - filled cavities that form irregular clusters ranging to a tens of micron thick bands at the glas surfaces. These granular textures are interpreted as the result of microbial colonization. accompanied by dissolution of the glass in their contact surface, deposition of authigenic minerals and the formation of a biofilm, that eventually seals the glass from easy access by seawater for hydration, or from microbes accessing Fe (II) in the glass. (2) The most spectacular bioalteration feature, repesented by the formation of tubes cannot be easily formed by the former mechanism because near spherical, individual microbes are likely not to produce the directionality that is required to produce the near linear or sometimes coiled tubes. Instead, we envision the activity of hyphae-like organelles or filaments, that may radiate out from a host body located in direct contact with circulating water, possibly penetrating a biofilm and entering/drilling into the fresh glass. Such microdrilling is well described in soils, where hyphae can slowly drill into silicates, in a process that takes about 1000 years to become visible as tunnels.

Timing of Hydrocarbon Fluid Emplacement in Sandstone Reservoirs in Neogene in Huizhou Sag, Southern China Sea, by Authigenic Illite 40Ar- 39Ar Laser Stepwise Heating

NASA Astrophysics Data System (ADS)

Hesheng, Shi; Junzhang, Zhu; Huaning, Qiu; yu, Shu; Jianyao, Wu; Zulie, Long

Timing of oil or gas emplacements is a new subject in isotopic geochronology and petroleum geology. Hamilton et al. expounded the principle of the illite K-Ar age: Illite is often the last or one of the latest mineral cements to form prior to hydrocarbon accumulation. Since the displacement of formation water by hydrocarbons will cause silicate diagenesis to cease, K-Ar ages for illite will constrain the timing of this event, and also constrain the maximum age of formation of the trap structure. In this study, the possibility of authigenic illites 40Ar- 39Ar dating has been investigated. The illite samples were separated from the Tertiary sandstones in three rich oil reservoir belts within the Huizhou sag by cleaning, fracturing by cycled cooling-heating, soxhlet-extraction with solvents of benzene and methanol and separating with centrifugal machine. If oil is present in the separated samples, ionized organic fragments with m/e ratios of 36 to 40 covering the argon isotopes will be yielded by the ion source of a mass spectrometer, resulting in wrong argon isotopic analyses and wrong 40Ar- 39Ar ages. The preliminary experiments of illite by heating did show the presence of ionized organic fragments with m/e ratios of 36 to 44. In order to clean up the organic gases completely and obtain reliable analysis results, a special purification apparatus has been established by Qiu et al. and proved valid by the sequent illite analyses. All the illite samples by 40Ar- 39Ar IR-laser stepwise heating yield stair-up age spectra in lower laser steps and plateaux in higher laser steps. The youngest apparent ages corresponding to the beginning steps are reasonable to be interpreted for the hydrocarbon accumulation ages. The weighted mean ages of the illites from the Zhuhai and Zhujiang Formations are (12.1 ± 1.1) Ma and (9.9 ± 1.2) Ma, respectively. Therefore, the critical emplacement of petroleum accumulation in Zhujiang Formation in Huizhou sag took place in ca 10 Ma. Late fault activity strengthened the entrance of hydrocarbon fluids into the oil systems based on the data of the studies of the fault evolvement history, petroleum system combinations, and homogeneous temperatures of fluid inclusions.

Illite authigenesis during faulting and fluid flow - a microstructural study of fault rocks

NASA Astrophysics Data System (ADS)

Scheiber, Thomas; Viola, Giulio; van der Lelij, Roelant; Margreth, Annina

2017-04-01

Authigenic illite can form synkinematically during slip events along brittle faults. In addition it can also crystallize as a result of fluid flow and associated mineral alteration processes in hydrothermal environments. K-Ar dating of illite-bearing fault rocks has recently become a common tool to constrain the timing of fault activity. However, to fully interpret the derived age spectra in terms of deformation ages, a careful investigation of the fault deformation history and architecture at the outcrop-scale, ideally followed by a detailed mineralogical analysis of the illite-forming processes at the micro-scale, are indispensable. Here we integrate this methodological approach by presenting microstructural observations from the host rock immediately adjacent to dated fault gouges from two sites located in the Rolvsnes granodiorite (Bømlo, western Norway). This granodiorite experienced multiple episodes of brittle faulting and fluid-induced alteration, starting in the Mid Ordovician (Scheiber et al., 2016). Fault gouges are predominantly associated with normal faults accommodating mainly E-W extension. K-Ar dating of illites separated from representative fault gouges constrains deformation and alteration due to fluid ingress from the Permian to the Cretaceous, with a cluster of ages for the finest (<0.1 µm) fraction in the early to middle Jurassic. At site one, high-resolution thin section structural mapping reveals a complex deformation history characterized by several coexisting types of calcite veins and seven different generations of cataclasite, two of which contain a significant amount of authigenic and undoubtedly deformation-related illite. At site two, fluid ingress along and adjoining the fault core induced pervasive alteration of the host granodiorite. Quartz is crosscut by calcite veinlets whereas plagioclase, K-feldspar and biotite are almost completely replaced by the main alteration products kaolin, quartz and illite. Illite-bearing micro-domains were physically separated by means of microsawing and drilling devices. K-Ar and XRD data from these separates are compared with bulk K-Ar and XRD data from the adjacent fault gouges, which may help to further unravel complex histories archived in multiply activated brittle fault zones. Scheiber, T., Viola, G., Wilkinson, C.M., Ganerød, M., Skår, Ø., and D. Gasser (2016): Direct 40Ar/39Ar dating of Late-Ordovician and Silurian brittle faulting in the southwestern Norwegian Caledonides. Terra Nova 28, 374-382.

Microstructures Indicate Large Influence of Temperature and Fluid Pressure on the Reactivation of the Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Schuck, B.; Janssen, C.; Schleicher, A.; Toy, V.; Dresen, G.

2017-12-01

The transpressional Alpine Fault within New Zealand's South Island is the major structure that accommodates relative motion between the Pacific and the Australian Plates. It has been intensively studied, because it is late in its 291-year seismic cycle (Cochran et al., 2017; doi: 10.1016/j.epsl.2017.02.026), is likely to generate large (i.e. MW > 8) earthquakes, thus presents the biggest seismic hazard in the region. However, because it is severely misoriented in the present-day stress field for reactivation (Boese et al., 2013; doi: 10.1016/j.epsl.2013.06.030), supra-lithostatic fluid-pressures are required for rupture nucleation. We have analyzed microstructures (SEM and TEM), geochemistry (ICP-OES) and mineralogy (XRD) of outcrop samples of the fault core to investigate the influence of fluids on the geomechanical behavior of the fault. Fluid-related alteration is pervasive within 20 m of the principal slip zone (PSZ) (Sutherland et al., 2012; doi: 10.1130/G33614.1), which is an incohesive, cemented and repeatedly reworked fault gouge mostly consisting of a fine-grained matrix composed of comminuted detrital quartz and feldspar as well as authigenic chlorite and calcite. Authigenic phases seal the PSZ for interseismic cross-fault fluid flow and enable fluid pressure to build-up. Notable, smectite, previously considered to significantly influence propagation of Alpine Fault ruptures, is not present in these samples. Undeformed, euhedral chlorite grains suggest that the processes leading to fault sealing are not only active at greater depths but also close to the surface. The absence of smectite and the presence of undeformed chlorite at very shallow depths can be attributed to the fault's high geothermal gradient of > 120 °C km-1 (Sutherland et al., 2012; doi:10.1038/nature22355), which gives temperature conditions unfavorable for smectite to be stable and fostering chlorite growth. A pervasive network of anastomosing calcite veins in the fault core, depicting mutual cross-cutting relations, attests for episodic fluid flow and mineralization within the PSZ. We interpret these as microstructural evidence for transient fault core permeability resulting from rupture nucleation due to supra-lithostatic fluid pressures following during fault-valve behavior.

Repeated Storage of Respired Carbon in the Equatorial Pacific Ocean Over the Last Three Glacial Cycles

NASA Astrophysics Data System (ADS)

Jacobel, A. W.; McManus, J. F.; Anderson, R. F.; Winckler, G.

2017-12-01

As the largest reservoir of carbon actively exchanging with the atmosphere on glacial-interglacial timescales, the deep ocean has been implicated as the likely location of carbon dioxide sequestration during Pleistocene glaciations. Despite strong theoretical underpinnings for this expectation, it has been challenging to identify unequivocal evidence for respired carbon storage in the paleoceanographic record. Data on the rate of ocean ventilation derived from paired planktonic-benthic foraminifera radiocarbon ages conflict across the equatorial Pacific, and different proxy reconstructions contradict one another about the depth and origin of the watermass containing the respired carbon. Because any change in the storage of respiratory carbon must be accompanied by corresponding changes in dissolved oxygen concentrations, proxy data reflecting bottom water oxygenation are of value in addressing these apparent inconsistencies. We present new records of the redox sensitive metal uranium from the central equatorial Pacific to qualitatively identify intervals associated with respiratory carbon storage over the past 350 kyr. Our data reveal periods of deep ocean authigenic uranium deposition in association with each of the last three glacial maxima. Equatorial Pacific export productivity data show intervals with abundant authigenic uranium are not associated with local productivity increases, indicating episodic precipitation of authigenic uranium does not directly reflect increases in situ microbial respiration, but rather occurs in response to basin-wide decreases in deep water oxygen concentrations. We combine our new data with previously published results to propose a picture of glacial carbon storage and equatorial Pacific watermass structure that is internally consistent. We conclude that respired carbon storage in the Pacific was a persistent feature of Pleistocene glaciations.

Uranium-234 anomalies in authigenic uranium as a new oxygenation proxy in the Southern Ocean

NASA Astrophysics Data System (ADS)

Hayes, C. T.; Severmann, S.; Anderson, A.

2016-12-01

Authigenic uranium (aU) is a sensitive indicator for suboxic conditions in marine pore waters that has been used to reconstruct past oxygenation conditions or organic matter export. aU suffers, however, from possible post-depositional remobilization or "burn-down" when the depth of the oxygenation front in the sediments undergoes rapid changes. In terms of isotope composition, the 234U/238U activity ratio, or δ234U in per mil notation, of authigenic U will reflect the isotope ratio in seawater (147‰) which has been relatively stable (within 15‰) for at least one ocean residence time of U (about 400 kyr). The δ234U ratio in bulk marine sediments should then reflect the mixture of the seawater ratio and the ratio of detrital U (0‰ or somewhat negative). In careful analysis of bulk δ234U over a peak in aU from Southern Ocean core ODP-1094, I found ratios higher than seawater (up to 250‰), not explainable by isotope mixing of known sources. I propose a new diagenetic effect in which a partial reoxidation of an aU emplacement can cause 234U that has been alpha-recoiled from in-situ 238U decay to diffuse into the aU emplacement. This means that with aU records that may be slightly altered by reoxidation, careful tracking of δ234U will allow proper identification of the depth/size of the original aU emplacement. Therefore, δ234U of aU is a more robust redox tracer than elemental proxies alone. In this presentation, I will recount the evidence for this assertion and lay out future research targets.

Methane-derived authigenic carbonates from the northern Gulf of Mexico - MD02 Cruise

USGS Publications Warehouse

Chen, Y.; Matsumoto, R.; Paull, C.K.; Ussler, W.; Lorenson, T.; Hart, P.; Winters, W.

2007-01-01

Authigenic carbonates were sampled in piston cores collected from both the Tunica Mound and the Mississippi Canyon area on the continental slope of the northern Gulf of Mexico during a Marion Dufresne cruise in July 2002. The carbonates are present as hardgrounds, porous crusts, concretions or nodules and shell fragments with or without carbonate cements. Carbonates occurred at gas venting sites which are likely to overlie gas hydrates bearing sediments. Electron microprobe, X-ray diffraction (XRD) and thinsection investigations show that these carbonates are high-Mg calcite (6-21??mol% MgCO3), with significant presence of framboidal pyrite. All carbonates are depleted in 13C (??13C = - 61.9 to - 31.5??? PDB) indicating that the carbon is derived mainly from anaerobic methane oxidation (AMO). Age estimates based on 14C dating of shell fragments and on regional sedimentation rates indicate that these authigenic carbonates formed within the last 1000??yr in the Mississippi Canyon and within 5500??yr at the Tunica Mound. The oxygen isotopic composition of carbonates ranges from + 3.4 to + 5.9??? PDB. Oxygen isotopic compositions and Mg2+ contents of carbonates, and present in-situ temperatures of bottom seawater/sediments, show that some of these carbonates, especially from a core associated with underlying massive gas hydrates precipitated in or near equilibrium with bottom-water. On the other hand, those carbonates more enriched in 18O are interpreted to have precipitated from 18O-rich fluids which are thought to have been derived from the dissociation of gas hydrates. The dissociation of gas hydrates in the northern Gulf of Mexico within the last 5500??yr may be caused by nearby salt movement and related brines. ?? 2007 Elsevier B.V. All rights reserved.

The Role of Authigenic Volcanic Ash in Marine Sediment

NASA Astrophysics Data System (ADS)

Scudder, R.; McKinley, C. C.; Thomas, D. J.; Murray, R. W.

2016-12-01

Marine sediments are a fundamental archive of the history of weathering and erosion, biological productivity, volcanic activity, patterns of deep-water formation and circulation, and a multitude of other earth, ocean, and atmosphere processes. In particular, the record and consequences of volcanic eruptions have long fascinated humanity. Volcanic ash layers are often visually stunning, and can have thicknesses of 10s of cm or more. While the ash layer records are of great importance by themselves, we are missing a key piece of information-that of the very fined grained size fractions. Dispersed ash is the very fine grained-component that has either been mixed into the bulk sediment by bioturbation, or is deposited from subaqueous eruptions, erosion of terrestrial deposits, general input during time periods of elevated global volcanism, or other mechanisms, plays an important role in the marine sediment. The presence of dispersed ash in the marine record has previously been relatively over-looked as it is difficult to identify petrographically due to its commonly extremely fine grain size and/or alteration to authigenic clay. The dispersed ash, either altered or unaltered, is extremely difficult to differentiate from detrital/terrigenous/authigenic clay, as they are all "aluminosilicates". Here we apply a combined geochemical, isotopic, and statistical technique that enables us to resolve volcanic from detrital terrigenous inputs at DSDP/ODP/IODP sites from both the Brazil Margin and the Northwest Pacific Oceans. Incorporating the combined geochemical/statistical techniques with radiogenic isotope records allows us to address paleoceanographic questions in addition to studies of the effect of sediment fluxes on carbon cycling, the relationship between volcanic ash and biological productivity of the open ocean and nutrient availability for subseafloor microbial life.

MOLYBDENUM ENRICHMENT AS AN INDICATOR OF HYPOXIC WATER CONDITION

EPA Science Inventory

Most programs examining the extent of low dissolved oxygen (DO) conditions in marine systems require in-situ sensors to be deployed during periods of low DO. This limits the ability to monitor hypoxia over larger spatial and/or temporal scales. Determination of authigenic molybde...

Iron and Sulfur Species and Sulfur Isotopic Compositions of Authigenic Pyrite in Gas Hydrate-Bearing Sediments from Hydrate Ridge, Cascadia Margin (ODP Leg 204): A Proposal of Conceptual Models to Indicate the Non-Steady State Depositional and Diagenetic Processes

NASA Astrophysics Data System (ADS)

Liu, C.; Jiang, S. Y.; Su, X.

2017-12-01

Two accretionary sediment sequences from Sites 1245 and 1252 recovered during Ocean Drilling Program (ODP) Leg 204 at Hydrate Ridge, Cascadia Margin were investigated to explore the non-steady state depositional and diagenetic history. Five iron species and three sulfur species were chemically extracted, and their concentrations and the sulfur isotopic compositions of pyrite were determined. After the mineral recognitions of these species and detailed comparative analyses, the aerobic history of bottom seawater has been determined. The formation of pyrite is thought to be controlled by the limited production of hydrogen sulfide relative to the supply of reactive iron. Also, the intrusion of oxygen by bioturbation would oxidize the reduced sulfur species and further suppress pyritization. To explain the geochemical relationship between pyrite and siderite and the sulfur isotope characteristics of pyrite, we propose seven conceptual models based on the variations in depositional rate and methane flux, and the models succeed in explaining the geochemical results and are validated by the observed non-steady state events. These models may contribute to the reconstruction of the non-steady state processes in other research areas in the future.

Uranium accumulation in modern and ancient Fe-oxide sediments: Examples from the Ashadze-2 hydrothermal sulfide field (Mid-Atlantic Ridge) and Yubileynoe massive sulfide deposit (South Urals, Russia)

NASA Astrophysics Data System (ADS)

Ayupova, N. R.; Melekestseva, I. Yu.; Maslennikov, V. V.; Tseluyko, A. S.; Blinov, I. A.; Beltenev, V. E.

2018-05-01

Fe-oxyhydroxide sediments (gossans) from the Ashadze-2 hydrothermal sulfide field (Mid-Atlantic Ridge) and hematite-carbonate-quartz rocks (gossanites) from the Yubileynoe Cu-Zn VHMS deposit (South Urals) are characterized by anomalously high U contents (up to 352 ppm and 73 ppm, respectively). In gossans from the Ashadze-2 hydrothermal sulfide field, rare isometric anhedral uraninite grains (up to 2 μm) with outer P- and Ca-rich rims, and numerous smaller (<1 μm) grains, occur in Fe-oxyhydroxides and sepiolite, associated with pyrite, isocubanite, chalcopyrite, galena, atacamite and halite. In gossanites from the Yubileynoe deposit, numerous uraninite particles (<3 μm) are associated with apatite, V-rich Mg-chlorite, micro-nodules of pyrite, Se-bearing galena, hessite and acanthite in a hematite-carbonate-quartz matrix. Small (1-3 μm) round grains of uraninite, which locally coalesce to large grains up to 10 μm in size, are associated with authigenic chalcopyrite. The similar diagenetic processes of U accumulation in modern and ancient Fe-oxyhydroxide sediments were the result of U fixation from seawater during the oxidation of sulfide minerals. Uraninite in gossanites was mainly deposited from diagenetic pore fluids, which circulated in the sulfide-hyaloclast-carbonate sediments.

The chemical composition of tertiary Indian coal ash and its combustion behaviour - a statistical approach: Part 2

NASA Astrophysics Data System (ADS)

Sharma, Arpita; Saikia, Ananya; Khare, Puja; Dutta, D. K.; Baruah, B. P.

2014-08-01

In Part 1 of the present investigation, 37 representative Eocene coal samples of Meghalaya, India were analyzed and their physico-chemical characteristics and the major oxides and minerals present in ash samples were studied for assessing the genesis of these coals. Various statistical tools were also applied to study their genesis. The datasets from Part 1 used in this investigation (Part 2) show the contribution of major oxides towards ash fusion temperatures (AFTs). The regression analysis of high temperature ash (HTA) composition and initial deformation temperature (IDT) show a definite increasing or decreasing trend, which has been used to determine the predictive indices for slagging, fouling, and abrasion propensities during combustion practices. The increase or decrease of IDT is influenced by the increase of Fe2O3, Al2O3, SiO2, and CaO, respectively. Detrital-authigenic index (DAI) calculated from the ash composition and its relation with AFT indicates Sialoferric nature of these coals. The correlation analysis, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA) were used to study the possible fouling, slagging, and abrasion potentials in boilers during the coal combustion processes. A positive relationship between slagging and heating values of the coal has been found in this study.

Early-diagenetic processes in marine mangrove sediments from Guadeloupe, French West Indies

NASA Astrophysics Data System (ADS)

Crémière, Antoine; Sebilo, Mathieu; Strauss, Harald; Gros, Olivier; Laverman, Anniet M.

2014-05-01

Sediment and pore-water geochemistry were investigated in two short sediment cores from the Manche-à-eau lagoon (Guadeloupe, French Caribbean island) surrounded by mangroves trees. These sediments present high total organic carbon content, ranging between 10 to 18 % wt, mainly originating from mangrove litter fall. Oxygen is depleted in the first few millimetres of the sediment indicating active organic carbon degradation. Seawater sulphate is entirely consumed within the first 20 cm of the sediments and total organic carbon content decreases with depth pointing out that early-diagenetic degradation of organic matter occurs with sulphate reduction. Sulphide produced as the results of sulphate reduction partly reacts with detrital iron-bearing minerals and precipitates as pyrite which is consistent with high amounts of sulphur in the sediments (4-5 % wt). The sulphur isotopic composition (δ34S) of both dissolved sulphate and sulphide in pore-water increases with depth displaying a large apparent isotopic fractionation (Δ34S) between both species of 65-80o as a result of bacterial sulphate reduction. Scanning electron microscopy investigation reveals that a part of the carbonate alkalinity produced either by organic matter oxidation or anaerobic methane oxidation leads to authigenic carbonates precipitation. These results provide straightforward evidence that carbon and sulphur biogeochemical cycles are intimately governed by sedimentary microbial activity.

A Mesoproterozoic iron formation

NASA Astrophysics Data System (ADS)

Canfield, Donald E.; Zhang, Shuichang; Wang, Huajian; Wang, Xiaomei; Zhao, Wenzhi; Su, Jin; Bjerrum, Christian J.; Haxen, Emma R.; Hammarlund, Emma U.

2018-04-01

We describe a 1,400 million-year old (Ma) iron formation (IF) from the Xiamaling Formation of the North China Craton. We estimate this IF to have contained at least 520 gigatons of authigenic Fe, comparable in size to many IFs of the Paleoproterozoic Era (2,500–1,600 Ma). Therefore, substantial IFs formed in the time window between 1,800 and 800 Ma, where they are generally believed to have been absent. The Xiamaling IF is of exceptionally low thermal maturity, allowing the preservation of organic biomarkers and an unprecedented view of iron-cycle dynamics during IF emplacement. We identify tetramethyl aryl isoprenoid (TMAI) biomarkers linked to anoxygenic photosynthetic bacteria and thus phototrophic Fe oxidation. Although we cannot rule out other pathways of Fe oxidation, iron and organic matter likely deposited to the sediment in a ratio similar to that expected for anoxygenic photosynthesis. Fe reduction was likely a dominant and efficient pathway of organic matter mineralization, as indicated by organic matter maturation by Rock Eval pyrolysis combined with carbon isotope analyses: Indeed, Fe reduction was seemingly as efficient as oxic respiration. Overall, this Mesoproterozoic-aged IF shows many similarities to Archean-aged (>2,500 Ma) banded IFs (BIFs), but with an exceptional state of preservation, allowing an unprecedented exploration of Fe-cycle dynamics in IF deposition.

The source and significance of argon isotopes in fluid inclusions from areas of mineralization

NASA Astrophysics Data System (ADS)

Kelley, S.; Turner, G.; Butterfield, A. W.; Shepherd, T. J.

1986-09-01

Argon isotopes in fluid inclusions in quartz veins associated with granite-hosted tungsten mineralization in the southwest and north of England have been investigated in detail by the 40Ar- 39Ar technique. The natural argon is present as a number of discrete components which can be identified through correlations with 39Ar, 38Ar and 37Ar induced by neutron bombardment of potassium, chlorine and calcium. The potassium-correlated component arises principally from in situ decay of potassium in solid phases in the inclusions. In the case of the Hemerdon tungsten deposit of southwest England the phases responsible are small (≈ 25 μm) captive authigenic micas which are shown to have been deposited from a fluid 268 ± 20 Ma ago, shortly after the emplacement of the host granite. The chlorine-correlated component is present in the brines which constitute the fluid phase of the inclusions. The argon in these hydrothermal fluids is made up in part of "parentless" or "excess" 40Ar leached from surrounding crustal rocks, and in part of dissolved ancient atmospheric argon. Absolute concentrations of both atmospheric and excess components in the brine can be estimated from ( 40ArCl ) ratios and independent determinations of the salinity of the inclusions. The absolute concentrations of the atmospheric argon are close to those found in modern meteoric water, while those of the excess component can be interpreted in terms of the degree of interaction betwen the circulating fluids and country rock. A calcium-correlated component, with a much higher ratio of excess to atmospheric argon than that in the brine, was found to be a dominant phase in one sample from the Hemerdon deposit, indicating the presence of a solid phase (probably a CaSO 4 daughter mineral). Inclusions of this composition represent fluids which have had a more prolonged interaction- with crustal rocks. The results obtained from this study provide a systematization and a framework for future multi-component argon studies of fluid inclusions, together with an indication of the wide range of information which can be inferred.

Discriminating sediment archives and sedimentary processes in the arid endorheic Ejina Basin, NW China using a robust geochemical approach

NASA Astrophysics Data System (ADS)

Yu, Kaifeng; Hartmann, Kai; Nottebaum, Veit; Stauch, Georg; Lu, Huayu; Zeeden, Christian; Yi, Shuangwen; Wünnemann, Bernd; Lehmkuhl, Frank

2016-04-01

Geochemical characteristics have been intensively used to assign sediment properties to paleoclimate and provenance. Nonetheless, in particular concerning the arid context, bulk geochemistry of different sediment archives and corresponding process interpretations are hitherto elusive. The Ejina Basin, with its suite of different sediment archives, is known as one of the main sources for the loess accumulation on the Chinese Loess Plateau. In order to understand mechanisms along this supra-regional sediment cascade, it is crucial to decipher the archive characteristics and formation processes. To address these issues, five profiles in different geomorphological contexts were selected. Analyses of X-ray fluorescence and diffraction, grain size, optically stimulated luminescence and radiocarbon dating were performed. Robust factor analysis was applied to reduce the attribute space to the process space of sedimentation history. Five sediment archives from three lithologic units exhibit geochemical characteristics as follows: (i) aeolian sands have high contents of Zr and Hf, whereas only Hf can be regarded as a valuable indicator to discriminate the coarse sand proportion; (ii) sandy loess has high Ca and Sr contents which both exhibit broad correlations with the medium to coarse silt proportions; (iii) lacustrine clays have high contents of felsic, ferromagnesian and mica source elements e.g., K, Fe, Ti, V, and Ni; (iv) fluvial sands have high contents of Mg, Cl and Na which may be enriched in evaporite minerals; (v) alluvial gravels have high contents of Cr which may originate from nearby Cr-rich bedrock. Temporal variations can be illustrated by four robust factors: weathering intensity, silicate-bearing mineral abundance, saline/alkaline magnitude and quasi-constant aeolian input. In summary, the bulk-composition of the late Quaternary sediments in this arid context is governed by the nature of the source terrain, weak chemical weathering, authigenic minerals, aeolian sand input, whereas pedogenesis and diagenesis exert only limited influences. Hence, this study demonstrates a practical geochemical strategy supplemented by grain size and mineralogical data, to discriminate sediment archives and thereafter enhance our ability to offer more intriguing information about the sedimentary processes in the arid central Asia.

Mineralogical and compositional characteristics of Late Permian coals from an area of high lung cancer rate in Xuan Wei, Yunnan, China: Occurrence and origin of quartz and chamosite

USGS Publications Warehouse

Dai, S.; Tian, L.; Chou, C.-L.; Zhou, Y.; Zhang, M.; Zhao, L.; Wang, Jingyuan; Yang, Z.; Cao, H.; Ren, D.

2008-01-01

Some townships in Xuan Wei County, Yunnan Province, have one of the highest lung cancer mortality rates in China and the epidemic disease in the area has generally been attributed to the polycyclic aromatic hydrocarbons (PAHs) released from domestic coal burning. However, the cancer-causing culprit is not settled as Tian [Tian, L., 2005. Coal Combustion Emissions and Lung Cancer in Xuan Wei, China. Ph.D. thesis, University of California, Berkeley.] found nanometer quartz in these coals, soot emissions, and lung cancer tissues. We have conducted mineralogical and geochemical studies of the coals from Xuan Wei for the purpose of shedding light on the minerals which may be related to the epidemic lung cancer. In this paper, abundances, modes of occurrence, and origins of minerals and elements in the coals from two mines in Xuan Wei have been studied using optical microscope, low-temperature ashing, X-ray diffraction analysis, scanning electron microscope equipped with energy-dispersive X-ray spectrometer, and inductively-coupled plasma mass spectrometry. The minerals in the coals are mainly composed of quartz, chamosite, kaolinite, and calcite. The particle size of quartz is rather small, mostly less than 20????m and it is of authigenic origin. Chamosite occurs mainly as cell-fillings. The occurrence of quartz and chamosite indicates that they were derived from the hydrothermal fluids. Epigenetic calcite is derived from calcic fluids. Kaolinite is derived mainly from sediment source region of Kangdian Oldland to the west of coal basin. The composition of Xuan Wei coal is high in SiO2, Fe2O3, TiO2, CaO, MnO, V, Co, Ni, Cu, and Zn. The high SiO2 content is attributed to quartz, and the Fe2O3 content to chamosite. The high Mn and low Mg contents in the coal indicate the inputs of hydrothermal fluids. CaO occurs mainly in epigenetic calcite. Elements Ti, Co, Ni, Cu, Zn, and rare earth elements were derived from the basaltic rocks at sediment source region. ?? 2008 Elsevier B.V. All rights reserved.

Mineral abundances at the final four curiosity study sites and implications for their formation

NASA Astrophysics Data System (ADS)

Poulet, F.; Carter, J.; Bishop, J. L.; Loizeau, D.; Murchie, S. M.

2014-03-01

A component of the landing site selection process for the Mars Science Laboratory (MSL) involved the presence of phyllosilicates as the main astrobiological targets. Gale crater was selected as the MSL landing site from among 4 down selected study sites (Gale, Eberswalde and Holden craters, Mawrth Vallis) that addressed the primary scientific goal of assessing the past habitability of Mars. A key constraint on the formation process of these phyllosilicate-bearing deposits is in the precise mineralogical composition. We present a reassessment of the mineralogy of the sites combined with a determination of the modal mineralogy of the major phyllosilicate-bearing deposits of the four final study sites from the modeling of near-infrared spectra using a radiative transfer model. The largest abundance of phyllosilicates (30-70%) is found in Mawrth Vallis, the lowest one in Eberswalde (<25%). Except for Mawrth Vallis, the anhydrous phases (plagioclase, pyroxenes and martian dust) are the dominant phases, suggesting formation conditions with a lower alteration grade and/or a post-formation mixing with anhydrous phases. The composition of Holden layered deposits (mixture of saponite and micas with a total abundance in the range of 25-45%) suggests transport and deposition of altered basalts of the Noachian crust without major chemical transformation. For Eberswalde, the modal mineralogy is also consistent with detrital clays, but the presence of opaline silica indicates that an authigenic formation occurred during the deposition. The overall composition including approximately 20-30% smectite detected by MSL in the rocks of Yellow-knife Bay area interpreted to be material deposited on the floor of Gale crater by channels (http://www.nasa.gov/mission_pages/msl/news/msl20130312.html).

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago.

PubMed

Bunch, Ted E; Hermes, Robert E; Moore, Andrew M T; Kennett, Douglas J; Weaver, James C; Wittke, James H; DeCarli, Paul S; Bischoff, James L; Hillman, Gordon C; Howard, George A; Kimbel, David R; Kletetschka, Gunther; Lipo, Carl P; Sakai, Sachiko; Revay, Zsolt; West, Allen; Firestone, Richard B; Kennett, James P

2012-07-10

It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica- and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum, mullite, and suessite (Fe(3)Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO(2) glass, or lechatelierite, with flow textures (or schlieren) that form at > 2,200 °C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.

Sedimentary condensation and authigenesis

NASA Astrophysics Data System (ADS)

Föllmi, Karl

2016-04-01

Most marine authigenic minerals form in sediments, which are subjected to condensation. Condensation processes lead to the formation of well individualized, extremely thin (< 1m) beds, which were accumulated during extremely long time periods (> 100ky), and which experienced authigenesis and the precipitation of glaucony, verdine, phosphate, iron and manganese oxyhydroxides, iron sulfide, carbonate and/or silica. They usually show complex internal stratigraphies, which result from an interplay of sediment accumulation, halts in sedimentation, sediment winnowing, erosion, reworking and bypass. They may include amalgamated faunas of different origin and age. Hardgrounds may be part of condensed beds and may embody strongly condensed beds by themselves. Sedimentary condensation is the result of a hydrodynamically active depositional regime, in which sediment accumulation, winnowing, erosion, reworking and bypass are processes, which alternate as a function of changes in the location and intensity of currents, and/or as the result of episodic high-energy events engendered by storms and gravity flow. Sedimentary condensation has been and still is a widespread phenomenon in past and present-day oceans. The present-day distribution of glaucony and verdine-rich sediments on shelves and upper slopes, phosphate-rich sediments and phosphorite on outer shelves and upper slopes, ferromanganese crusts on slopes, seamounts and submarine plateaus, and ferromanganese nodules on abyssal seafloors is a good indication of the importance of condensation processes today. In the past, we may add the occurrence of oolitic ironstone, carbonate hardgrounds, and eventually also silica layers in banded iron formations as indicators of the importance of condensation processes. Besides their economic value, condensed sediments are useful both as a carrier of geochemical proxies of paleoceanographic and paleoenvironmental change, as well as the product of episodes of paleoceanographic and paleoenvironmental change themselves.

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

USGS Publications Warehouse

Bunch, Ted E.; Hermes, Robert E.; Moore, Andrew M.T.; Kennett, Douglas J.; Weaver, James C.; Wittke, James H.; DeCarli, Paul S.; Bischoff, James L.; Hillman, Gordon C.; Howard, George A.; Kimbel, David R.; Kletetschka, Gunther; Lipo, Carl P.; Sakai, Sachiko; Revay, Zsolt; West, Allen; Firestone, Richard B.; Kennett, James P.

2012-01-01

It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica-and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum, mullite, and suessite (Fe3,/sup>Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO2 glass, or lechatelierite, with flow textures (or schlieren) that form at > 2,200 °C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.

Rise and fall of bat population induced from immobile elements and fossil helminth eggs of bat guano deposits, Korea

NASA Astrophysics Data System (ADS)

Jun, Chang-Pyo; Lee, Seong-Joo

2014-05-01

Bat guano samples were collected from three carbonate caves located along the eastern coast of Korean Peninsula: Gossi Cave (40 cm high and 200 cm wide dome), Baegryong Cave (50 cm high and 100 cm wide dome), and Seongryu Cave (20 cm high platform). The guano deposits are rich in organic materials including undigested insect fragments, together with authigenic minerals and imported clastic sediments. The guano profiles were calculated to have been deposited 1) from 3097 to 4200 BP yrs in Gossi guano, 2) from 3650 to 7150 BP yrs in Baegryong guano, and 3) from 150 to 6000 BP yrs in Seongryu guano. Among the immobile elements identified, three immobile elements including Al2O3, SiO2, and TiO2 were detected from all the bat guano profiles. Distributional pattern of these elements throughout each guano profile also shows a close similarity. Such immobile elements are those of clastic sediments blown into the caves as dust. The amount of such immobile elements is closely related with deposition rate of the bat guano; low concentration of those elements implies rapid deposition rate while high concentration represents slow deposition rate of bat guano profiles. Basically, deposition rate of bat guano is controlled by the population density of bat lived in the cave. The amount of immobile elements of the Gossi Cave, for example, tends to increase toward top layer with a sudden decrease at the middle-upper layer (4,000 BP yr). It is, thus be concluded that bat population experienced fluctuation showing an decrease from 6150 to 4150 BP yr and sudden increase at 4000 BP yr, followed by constant decrease to 3150 BP yr. Fossil parasite eggs were also found from the guano deposits, and the number of parasite eggs show similar trend to that of immobile elements.

Field Validation of Molybdenum Accumulation as an Indicator of Hypoxic Water Conditions

EPA Science Inventory

Laboratory experiments have shown that the accumulation rate of authigenic molybdenum (Mo) in marine sediments may serve as a quantitative surrogate for direct measurement of hypoxic conditions in overlying waters: Mo accumulation in the top 1 cm of sediment is linearly related t...

Laboratory Determination of Molybdenum Accumulation Rates as a Measure of Hypoxic Conditions

EPA Science Inventory

Redox sensitive metals, such as molybdenum (Mo), are enriched in reducing sediments due to authigenic fixation in anoxic interstitial waters of sediments. This study tested whether the process of fixation and accumulation of Mo in sediments could provide a geochemical indicator o...

Change in the Nd isotopic composition of the bottom water and detrital sediments on the Bering Slope over the last 500 kyrs with implications for the formation of the North Pacific Intermediate Water

NASA Astrophysics Data System (ADS)

Jang, K.; Huh, Y.; Han, Y.

2015-12-01

The Bering Sea is a potential location for the formation of the North Pacific Intermediate/Deep Water (NPIW/NPDW) and may play an important role in the global heat distribution. We reconstructed the neodymium isotopic ratio (ɛNd) of authigenic Fe-Mn oxide coatings and detrital sediments on the Bering Slope (IODP Expedition 323 site U1345; water depth 1008 m) over the last 500 kyrs. The ɛNd is a quasi-conservative water mass tracer. We compared three different leaching techniques to assure that authigenic signals are captured without contamination from terrigenous sources: (1) leaching (3 hours) with 0.02 M hydroxylamine hydrochloride (HH) in 25% buffered acetic acid after decarbonation; sediment/solution (v/v) > 10, (2) leaching (1 hour) with 0.02 M HH in 25% buffered acetic acid without decarbonation; sediment/solution ~ 1, and (3) leaching (1 hour) with 0.005 M HH in 1.5% buffered acetic acid-0.003 M Na-EDTA without decarbonation; sediment/solution > 40. The low Al concentrations and less radiogenic ɛNdvalues indicated that method (2) is the most appropriate leaching process. The average ɛNd of the authigenic fraction over the last 500 kyrs is -3.3 ± 0.9 (1σ, n=38), with large temporal fluctuations. The ɛNd of authigenic and detrital fractions are well correlated (r2 ~ 0.66), suggesting that the bottom water composition in the Bering Sea was governed by terrigenous inflow from surrounding areas. Radiogenic ɛNd peaks (up to -1.9) seem to be influenced by radiogenic water inflow from the the Kamchatka or Aluetian arcs. The high bulk density and low b* values imply higher terrigenous versus biological contribution and enhanced sea ice formation. Subsequent brine formation would have triggered sinking of radiogenic surface water, forming the NPIW. On the other hand, non-radiogenic ɛNd troughs (down to -5.3) are observed at times of low bulk density and high b* values. We presume higher biological productivity which is supported by the high opal content at these intervals (Kanematsu et al., 2013). Sea level rise and boundary exchange with terrigenous sediment derived from N. America is a likely mechanism. This work was supported by the Basic Science Research Program through the NRF funded by Ministry of Science, ICT and Future Planning (No. 2014 0498836)

Sulfur and oxygen isotopes in barite deposits of the western Brooks Range, Alaska, and implications for the origin of the Red Dog massive sulfide deposits

USGS Publications Warehouse

Johnson, C.A.; Kelley, K.D.; Leach, D.L.

2004-01-01

Sulfur and oxygen isotope analyses have been obtained for barite samples from the giant stratiform sulfide barite deposits at Red Dog in the western Brooks Range of Alaska, from stratiform barite deposits elsewhere in the Red Dog district, and from stratiform and vein and breccia barite occurrences in the central Brooks Range. Twelve of the 15 deposits studied lie within middle to Upper Mississippian black shale and chert units. The data reveal two different patterns on ?? 34S versus ??18O plots. The first, which is best illustrated by the barite deposit at Anarraaq, shows linear trends with slopes that vary with barite texture. For most samples, ??34S and ??18O values are both higher than the values characteristic of Mississippian marine sulfate. The second pattern, which is evident at the Red Dog deposits, shows no correlation between ??34S and ??18. In most samples, ??18O is below the value for Mississippian marine sulfate. Comparisons with sulfate in modern marine environments suggest a possible model for the mineralizing process. Anarraaq-type barite formed at sea-floor vents where ascending fluids carrying barium and methane encountered sulfate-bearing pore waters or bottom waters. Barite deposition was accompanied by the reduction of sulfate to H2S by means of microbially mediated anaerobic methane oxidation. Red Dog-type barite was formed in a manner similar to Anarraaq-type barite but was over-printed by a massive sulfide-forming event. Red Dog sulfides precipitated where metal-bearing hydrothermal fluids encountered pore waters that had been charged with H2S by anaerobic methane oxidation. Textural and isotopic evidence indicates that the sulfide bodies grew by consuming the available H2S and then by reductively dissolving barite. Dissolution of barite caused barium to be released to higher stratigraphic levels where it was reprecipitated on encountering sulfate. Isotopic evidence is pre sented for a link between methane venting and barite formation and raises the possibility that the coexistence of barite and sulfide at Red Dog, and the occurrence elsewhere in the district of barite-only and sulfide-only deposits, can be explained by a spectrum of vent types in the Mississippian basin analogous to the spectrum that is observed today along the modern continental margins. Authigenic barite formed at some but not all methane seeps, perhaps owing to differences in the barium content of vent fluids, differences in the relative proportion of aqueous fluid and gas emanating from vents, or differences in sulfate availability in local bottom waters. Some barite-forming seeps were later replaced by sulfides (Red Dog deposits) whereas others were not (e.g., Anarraaq barite horizon, Gull Creek, Moil). At sulfide occurrences where there is little evidence of preexisting barite (e.g., Anarraaq, Wulik, Suds), methane venting is indicated by fossils suggestive of chemosynthetic fauna. Mammiform sedimentary structures that are widespread in black chert at the top of the Kuna Formation may represent seeps that supported neither authigenic mineral formation nor chemosynthetic megafauna. ?? 2004 by Economic Geology.

Topographic and depositional signature of old anthropic lakes in northern part of the Moldavian Plateau (NE Romania)

NASA Astrophysics Data System (ADS)

Ciprian Margarint, Mihai; Niculita, Mihai; Nemeth, Alexandra; Cristea, Ionut

2017-04-01

The role of humans and theirs social activities in reshaping earth surface is obvious in many places of the world. Anthropic fingerprints on Earth's surface morphology are recognizable by theirs topographic and depositional signatures that can cause considerable changes in geomorphological organization of the landscape, with direct consequences on Earth surface processes. Anthropic dams and their associated sediments represent recent archives that record environmental changes. They can provide substantial data to reconstruct general models in geomorphic evolution of hydrologic catchments and the identification of extreme meteorological events and sediment fluxes. Also, geochemical tracers provide us relevant indicators about climatic patterns and local condition of sedimentation processes. Until quite recently, the identification and counting the old lakes have been carried out mostly by studying different old maps and less by analyzing their fingerprints on the Earth surface. Considered a real revolution in geomorphology, the high-resolution LiDAR data allow us nowadays a more precise recognition of minor landforms, their extent and cross-relationships, as well as to discover surface features that have escaped the attention before. Furthermore, by using Electrical Resistivity Tomography techniques, the 3D extension of the sediments can be revealed. Anthropic lakes are one of the most particular hydrological anthropic features of the landscape in the northern part of the Moldavian Plateau (Eastern Carpathian lowland). The need for water supply, have forced the inhabitants to build dams of various sizes along the entire river network. Over the time, many dams were abandoned, while others have been relocated with an impressive dynamic at historical time scale. For more than 3000 sq km we have carried out an accurate inventory of abandoned dams using LIDAR imagery. Taking into consideration the last appearance of the lakes on the old maps, they were classified: pre-1895, 1895-1940, 1940-2000 and present active. In this research we have analyzed 2 small old lakes (pre-1895) and theirs sedimentary archives. Using LIDAR high resolution DEM and ERT scans we have reconstruct the maximum extension of the lake and the deepening of the sediments. The sediments consist of clay and plant remains with some light-coloured horizons. Bioturbation is abundant in the wall of horizontal tunnels with diameter between 3 and 5 cm. Thin sections were prepared from some samples, opaque, octahedral minerals being visible around the size of 10 μm. Their colour in reflected light was bluishgrey which suggests that these could be magnetite grains instead of pyrite. Authigenic magnetite is abundant in lake sediments, close to the oxic-anoxic transition zone, where the sediment is not sulphidic. It is commonly precipitated as a result of bacterial activity, however these minerals usually don't exceed the size of 100 nm therefore the authigenic origin of the magnetite in our samples is not proven yet. The study of this sedimentary archives, we believe that needs to be extended in order to have an image of the hydrological and climatological evolution of the study area in the last 500 years.

Methanogenic calcite, 13C-depleted bivalve shells, and gas hydrate from a mud volcano offshore southern California

USGS Publications Warehouse

Hein, J.R.; Normark, W.R.; McIntyre, B.R.; Lorenson, T.D.; Powell, C.L.

2006-01-01

Methane and hydrogen sulfide vent from a cold seep above a shallowly buried methane hydrate in a mud volcano located 24 km offshore southern California in?? 800 m of water. Bivalves, authigenic calcite, and methane hydrate were recovered in a 2.1 m piston core. Aragonite shells of two bivalve species are unusually depleted in 13C (to -91??? ??13C), the most 13C-depleted shells of marine macrofauna yet discovered. Carbon isotopes for both living and dead specimens indicate that they used, in part, carbon derived from anaerobically oxidized methane to construct their shells. The ??13C values are highly variable, but most are within the range -12??? to -91???. This variability may be diagnostic for identifying cold-seep-hydrate systems in the geologic record. Authigenic calcite is abundant in the cores down to ???1.5 m subbottom, the top of the methane hydrate. The calcite is depleted in 13C (??13C = -46??? to -58???), indicating that carbon produced by anaerobically oxidized methane is the main source of the calcite. Methane sources include a geologic hydrocarbon reservoir from Miocene source rocks, and biogenic and thermogenic degradation of organic matter in basin sediments. Oxygen isotopes indicate that most calcite formed out of isotopic equilibrium with ambient bottom water, under the influence of gas hydrate dissociation and strong methane flux. High metal content in the mud volcano sediment indicates leaching of basement rocks by fluid circulating along an underlying fault, which also allows for a high flux of fossil methane. ?? 2006 Geological Society of America.

The Point Lookout Sandstone: a tale of two cores, or petrology, diagenesis, and reservoir properties of Point Lookout Sandstone, Southern Ute Indian Reservation, San Juan Basin, Colorado

USGS Publications Warehouse

Keighin, C.W.; Zech, R.S.; Dunbar, R.W.

1993-01-01

The Point Lookout sandstones are quartz-rich, fine to very-fine grained, and contain moderately variable quantities of potassium feldspar (2 to 20 modal percent) and lithic fragments (9 to 20 modal percent). Locally, sandstone is tightly cemented by carbonate cement; clays are not important as cementing agents, although they significantly reduce permeability of some samples. Pores are small; many are intergranular micropores between crystals of authigenic clay. Depositional environments are highly variable and range from lower shoreface to coastal plain and include minor deltaic environments. The best reservoir characteristics are generally in the upper shoreface sandstones. -from Authors

Field Validation of Molybdenum Accumulation in Sediments as an Indication of Hypoxic Water Conditions

EPA Science Inventory

Accumulation of authigenic molybdenum (Mo) in marine sediments has often been used as qualitative indicator of periods of hypoxic bottom water, but rarely, if ever, used quantitatively. Laboratory experiments have shown that the accumulation rate of Mo may serve as a quantitative...

Photosynthetic Microbial Mats are Exemplary Sources of Diverse Biosignatures (Invited)

NASA Astrophysics Data System (ADS)

Des Marais, D. J.; Jahnke, L. L.

2013-12-01

Marine cyanobacterial microbial mats are widespread, compact, self-contained ecosystems that create diverse biosignatures and have an ancient fossil record. Within the mats, oxygenic photosynthesis provides organic substrates and O2 to the community. Both the absorption and scattering of light change the intensity and spectral composition of incident radiation as it penetrates a mat. Some phototrophs utilize infrared light near the base of the photic zone. A mat's upper layers can become highly reduced and sulfidic at night. Counteracting gradients of O2 and sulfide shape the chemical environment and provide daily-contrasting microenvironments separated on a scale of a few mm. Radiation hazards (UV, etc.), O2 and sulfide toxicity elicit motility and other physiological responses. This combination of benefits and hazards of light, O2 and sulfide promotes the allocation of various essential mat processes between light and dark periods and to various depths in the mat. Associated nonphotosynthetic communities, including anaerobes, strongly influence many of the ecosystem's overall characteristics, and their processes affect any biosignatures that enter the fossil record. A biosignature is an object, substance and/or pattern whose origin specifically requires a biological agent. The value of a biosignature depends not only on the probability of life creating it, but also on the improbability of nonbiological processes producing it. Microbial mats create biosignatures that identify particular groups of organisms and also reveal attributes of the mat ecosystem. For example, branched hydrocarbons and pigments can be diagnostic of cyanobacteria and other phototrophic bacteria, and isoprenoids can indicate particular groups of archea. Assemblages of lipid biosignatures change with depth due to changes in microbial populations and diagenetic transformations of organic matter. The 13C/12C values of organic matter and carbonates reflect isotopic discrimination by particular microorganisms as well as networks of C flow within mats; thus they offer insights about community structure. For example, relative 13C/12C values of individual lipid biosignatures can indicate trophic relationships between key groups of microorganisms. Mat microenvironments can affect the stability of authigenic minerals and alter the chemical compositions and crystal forms of carbonate, sulfate and metal oxide minerals. Interactions between low molecular weight organic compounds and sulfides in mat pore waters can produce alkyl sulfide gases. Processes associated with these physically coherent biofilms can trap and bind detrital grains, enhance mineral precipitation or dissolution, and stabilize sediment surfaces. Accordingly mats can create distinctive sedimentary fabrics and structures. Stromatolites are the most ancient, widespread examples of such fabrics and structures. Thus photosynthetic microbial mats create diverse biosignatures that, when preserved in the geologic record, can help to identify the former presence of key populations of microorganisms and reveal key processes that occurred within ancient mats as well as the interactions between those ecosystems and their environment.

Authigenic carbonates from methane seeps of the Congo deep-sea fan

NASA Astrophysics Data System (ADS)

Pierre, Catherine; Fouquet, Yves

2007-06-01

Submersible investigations with the ROV Victor 6000 of some pockmark structures on the seafloor of the Congo deep-sea fan have shown that they are active venting sites of methane-rich fluids, associated with abundant fauna and carbonate crusts. Moreover, methane hydrates have been observed both outcropping and deep in the sediments in the centre of the “Regab” giant pockmark. Authigenic carbonates, mostly calcite sometimes mixed with aragonite, are cementing the sedimentary matrix components and fauna; diatoms are abundant but only as moulds, indicating that biogenic silica dissolution occurred in situ synchronous with carbonate precipitation. The occurrence of diagenetic barite and pyrite in some carbonate crusts demonstrates that they can be formed either within the sulphate/methane transition zone or deeper in sulphate-depleted sediments. The oxygen isotopic compositions of the diagenetic carbonates (3.17 6.01‰ V-PDB) indicate that precipitation occurred with bottom seawater mixed with a variable contribution of water from gas hydrate decomposition. The very low carbon isotopic compositions of the diagenetic carbonates (-57.1 to -27.75‰ V-PDB) demonstrate that carbon derives mostly from the microbial oxidation of methane.

Mesozoic clay diagenesis in the Appalachian Plateau

NASA Astrophysics Data System (ADS)

Boles, A.; Mulch, A.; van der Pluijm, B.

2017-12-01

Integrated investigation of authigenic clays in the Appalachian Plateau of the northeastern US Midcontinent using X-ray goniometry, Rietveld-method based illite polytype analysis, and 40Ar/39Ar geochronology yields novel insights about the structural diagenetic history of the North American sedimentary cover sequence. Texture analysis by High Resolution X-ray Texture Goniometry records the presence of a bedding-parallel diagenetic fabric, corresponding to a burial depth of 2-5 km. New development of polytype modeling using BGMN®, a quantitative X-ray powder diffraction forward modeling and whole-pattern matching program matches mineralic characteristic of illite at those depths and reduces uncertainty estimates in age analysis. Based on dating size fractions, the diagenetic age is constrained to 225-250 Ma (Triassic) by four authigenic illite samples, reflecting protracted, regional diagenesis in the area. Preliminary H isotopic analysis points to a surface-derived diagenetic fluid with δD values ranging from -48 to -72‰ (in the range of predicted Pangea meteoric fluid), with a dependence on proximity to the Appalachian Mountains that may reflect a rain shadow effect.

Uranium Stable Isotopes: A Proxy For Productivity Or Ocean Oxygenation?

NASA Astrophysics Data System (ADS)

Severmann, S.

2015-12-01

Uranium elemental abundances in sediments have traditionally been used to reconstruct primary productivity and carbon flux in the ocean. 238U/235U isotope compositions, in contrast, are currently understood to reflect the extent of bottom water anoxia in the ocean. A review of our current understanding of authigenic U enrichment mechanism into reducing sediments suggests that a revision of this interpretation is warranted. Specifically, the current interpretation of U isotope effects in suboxic vs. anoxic deposits has not taken into account the well-documented linear relationship with organic C burial rates. Although organic C rain rates (i.e., surface productivity) and bottom water oxygenation are clearly related, distinction between these two environmental controls is conceptually important as it relates to the mechanism of enhanced C burial and ultimately the strength of the biological pump. Here we will review new and existing data to test the hypothesis that the isotope composition of authigenic U in reducing sediments are best described by their relationship with parameters related to organic carbon delivery and burial, rather than bottom water oxygen concentration.

Controlling weathering and erosion intensity on the southern slope of the Central Himalaya by the Indian summer monsoon during the last glacial

NASA Astrophysics Data System (ADS)

Kuwahara, Yoshihiro; Masudome, Yukiko; Paudel, Mukunda Raj; Fujii, Rie; Hayashi, Tatsuya; Mampuku, Mami; Sakai, Harutaka

2010-03-01

This paper reports the results of clay mineral analysis (the amount of clay fraction, clay mineral assemblages, illite crystallinity) of samples collected from a drilled core (Rabibhawan (RB) core) located in the west-central part of the Kathmandu Basin on the southern slope of the Central Himalaya. The amount of clay fraction in the core sediments between 12 m and 45 m depth (corresponding to ca. 17-76 ka), which belong to the Kalimati Formation, is variable and shows three clay-poor zones (19-31 ka, 44-51 ka, and 66-75 ka). The variations correspond with those of illite crystallinity index (Lanson index (LI) and modified Lanson index (MLI)) and kaolinite/illite ratio as well as the fossil pollen and diatom records reported by previous workers. These data reveal the following transformations occurring during the weathering process in this area: micas(mainlymuscovite)→illite(→illite-smectitemixedlayermineral(R=1))→kaolinite The sedimentation rate (~ 50 cm/kyr) of clay-poor zones that correspond to dry climate intervals is only half that of clay-rich zones (~ 120 cm/kyr) that correspond to wet climate intervals, indicating weakened chemical weathering and erosion and low suspended discharge during dry climate intervals. The clay-poor zones commonly show unique laminite beds with very fine, authigenic calcite, which was probably precipitated under calm and high calcite concentration conditions caused by low precipitation and run-off. The variations between dry and wet conditions in this area as deduced from clay minerals appear to follow the Indian Summer Monsoon Index (ISMI) (30°N-30°S, 1 July) and northern hemisphere summer insolation (NHSI) signals (30°N) at 1 July, especially during the dry climate zones, whereas the wet maxima of the wet climate zones somewhat deviate from the strongest NHSI. On the other hand, the dry-wet records lead markedly the SPECMAP stack (by about 5000 years). These results suggest that the Indian summer monsoon precipitation was strongly controlled by the NHSI or summer insolation difference between the Himalayan-Tibetan Plateau and the subtropical Indian Ocean, showing a major fluctuation on the 23,000 years precessional cycle, and that it was not driven by changes in high-latitude ice volume, although the records of clay mineral indices during the wet intervals leave a question that other factors, in addition to insolation forcing, may play important roles in weathering, erosion, and sedimentation processes.

The campi flegrei (Italy) geothermal system: A fluid inclusion study of the mofete and San Vito fields

USGS Publications Warehouse

de, Vivo B.; Belkin, H.E.; Barbieri, M.; Chelini, W.; Lattanzi, P.; Lima, A.; Tolomeo, L.

1989-01-01

A fluid inclusion study of core from the Mofete 1, Mofete 2, Mofete 5, San Vito 1, and San Vito 3 geothermal wells (Campi Flegrei, Campania, Italy) indicates that the hydrothermal minerals were precipitated from aqueous fluids (??CO2) that were moderately saline (3-4 wt.% NaCl equiv.) to hypersaline (> 26 wt.% NaCl equiv.) and at least in part, boiling. Three types of primary fluid inclusions were found in authigenic K-feldspar, quartz, calcite, and epidote: (A) two-phase [liquid (L) + vapor (V)], liquid-rich inclusions with a range of salinity; (B) two-phase (L + V), vaporrich inclusions with low salinity; and (C) three-phase [L + V + crystals (NaCL)], liquid-rich inclusions with hypersalinity. Results of microthermometric and crushing studies are reported for twenty drill core samples taken from the lower portions of the five vertical wells. Data presented for selected core samples reveal a general decrease in porosity and increase in bulk density with increasing depth and temperature. Hydrothermal minerals commonly fill fractures and pore-spaces and define a zonation pattern, similar in all five wells studied, in response to increasing depth (pressure) and temperature. A greenschist facies assemblage, defined by albite + actinolite, gives way to an amphibolite facies, defined by plagioclase (andesine) + hornblende, in the San Vito 1 well at about 380??C. The fluid inclusion salinity values mimic the saline and hypersaline fluids found by drilling. Fluid inclusion V/L homogenization temperatures increase with depth and generally correspond to the extrapolated down-hole temperatures. However, fluid inclusion data for Mofete 5 and mineral assemblage data for San Vito 3, indicate fossil, higher-temperature regimes. A limited 87Sr/86Sr study of leachate (carbonate) and the leached cores shows that for most samples (except San Vito 3) the carbonate deposition has been from slightly 87Sr-enriched fluids and that Sr isotopic exchange has been incomplete. However, San Vito 3 cores show an approach to fluid/rock Sr equilibrium with a fluid similar to modern ocean water in 87Sr/86Sr ratio. The Campi Flegrei volcanic system has evolved undersaturated products, mostly trachyte, and defines a large (??? 12 km) caldera. The hydrothermal system developed in this location can be used as an analog for fossil systems in similar trachytic environments. The potential for ore mineralization is expressed by the recognition, from fluid inclusion and drilling data, of ore-forming environments such as boiling and brine stratification. ?? 1989.

Naturally weathered feldspar surfaces in the Navajo Sandstone aquifer, Black Mesa, Arizona: Electron microscopic characterization

NASA Astrophysics Data System (ADS)

Zhu, Chen; Veblen, David R.; Blum, Alex E.; Chipera, Stephen J.

2006-09-01

Naturally weathered feldspar surfaces in the Jurassic Navajo Sandstone at Black Mesa, Arizona, was characterized with high-resolution transmission and analytical electron microscope (HRTEM-AEM) and field emission gun scanning electron microscope (FEG-SEM). Here, we report the first HRTEM observation of a 10-nm thick amorphous layer on naturally weathered K-feldspar in currently slightly alkaline groundwater. The amorphous layer is probably deficient in K and enriched in Si. In addition to the amorphous layer, the feldspar surfaces are also partially coated with tightly adhered kaolin platelets. Outside of the kaolin coatings, feldspar grains are covered with a continuous 3-5 μm thick layer of authigenic smectite, which also coats quartz and other sediment grains. Authigenic K-feldspar overgrowth and etch pits were also found on feldspar grains. These characteristics of the aged feldspar surfaces accentuate the differences in reactivity between the freshly ground feldspar powders used in laboratory experiments and feldspar grains in natural systems, and may partially contribute to the commonly observed apparent laboratory-field dissolution rate discrepancy. At Black Mesa, feldspars in the Navajo Sandstone are dissolving at ˜10 5 times slower than laboratory rate at comparable temperature and pH under far from equilibrium condition. The tightly adhered kaolin platelets reduce the feldspar reactive surface area, and the authigenic K-feldspar overgrowth reduces the feldspar reactivity. However, the continuous smectite coating layer does not appear to constitute a diffusion barrier. The exact role of the amorphous layer on feldspar dissolution kinetics depends on the origin of the layer (leached layer versus re-precipitated silica), which is uncertain at present. However, the nanometer thin layer can be detected only with HRTEM, and thus our study raises the possibility of its wide occurrence in geological systems. Rate laws and proposed mechanisms should consider the possibility of this amorphous layer on feldspar surface.

Anhydrite pseudomorphs and the origin of stratiform Cu-Co ores in the Katangan Copperbelt (Democratic Republic of Congo)

NASA Astrophysics Data System (ADS)

Muchez, Ph.; Vanderhaeghen, P.; El Desouky, H.; Schneider, J.; Boyce, A.; Dewaele, S.; Cailteux, J.

2008-07-01

The stratiform Cu-Co ore mineralisation in the Katangan Copperbelt consists of dispersed sulphides and sulphides in nodules and lenses, which are often pseudomorphs after evaporites. Two types of pseudomorphs can be distinguished in the nodules and lenses. In type 1 examples, dolomite precipitated first and was subsequently replaced by Cu-Co sulphides and authigenic quartz, whereas in type 2 examples, authigenic quartz and Cu-Co sulphides precipitated prior to dolomite and are coarse-grained. The sulphur isotopic composition of the copper-cobalt sulphides in the type 1 pseudomorphs is between -10.3 and 3.1‰ relative to the Vienna Canyon Diablo Troilite, indicating that the sulphide component was derived from bacterial sulphate reduction (BSR). The generation of {text{HCO}}_3^ - during this process caused the precipitation and replacement of anhydrite by dolomite. A second product of BSR is the generation of H2S, resulting in the precipitation of Cu-Co sulphides from the mineralising fluids. Initial sulphide precipitation occurred along the rim of the pseudomorphs and continued towards the core. Precipitation of authigenic quartz was most likely induced by a pH decrease during sulphide precipitation. Fluid inclusion data from quartz indicate the presence of a high-salinity (8-18 eq. wt.% NaCl) fluid, possibly derived from evaporated seawater which migrated through the deep subsurface. 87Sr/86Sr ratios of dolomite in type 1 nodules range between 0.71012 and 0.73576, significantly more radiogenic than the strontium isotopic composition of Neoproterozoic marine carbonates (87Sr/86Sr = 0.7056-0.7087). This suggests intense interaction with siliciclastic sedimentary rocks and/or the granitic basement. The low carbon isotopic composition of the dolomite in the pseudomorphs (-7.02 and -9.93‰ relative to the Vienna Pee Dee Belemnite, V-PDB) compared to the host rock dolomite (-4.90 and +1.31‰ V-PDB) resulted from the oxidation of organic matter during BSR.

The Role of Authigenic (pigment) Hematite in Controlling the Remanence, Rock Magnetic, and Magnetic Fabric Properties of Red Beds--If You Have Seen One Red Bed, You Certainly Have Not Seen Them All!

NASA Astrophysics Data System (ADS)

Geissman, J. W.

2014-12-01

Discussion continues on the relative role of authigenic (pigment) fine-grained hematite, relative to detrital, considerably coarser specular hematite (specularite) as a carrier of geologically meaningful remanence, as a determinant of rock magnetic properties, and as a contributor to magnetic fabrics in red beds. For one, many workers commonly assume that the laboratory unblocking temperature spectra (Tlub) of a red bed dominated by authigenic pigment does not reach the maximum Tlub as approximated by the Neel temperature (~948 K) because of the ultra fine grain size of the pigment. This issue was discussed as recently as the IRM Santa Fe meeting in late June, 2014. Many laboratories routinely utilize chemical demagnetization in concert with progressive thermal demagnetization to attempt to assess the relative role of pigment vs. detrital hematite. However, the utility of chemical demagnetization has been long challenged. In studying the anisotropy of magnetic susceptibility and remanence in red beds, recent work has considered separating the contributions of both types of hematite to the fabric signal. Three different red bed "types" (siltstones of the Triassic Chugwater Group, Gros Ventre Range, Wyoming; mudrocks of lowermost Triassic Quartermaster Formation, west Texas; and siltstones to medium sandstones of Upper Cretaceous age, northwest Vietnam) are used to evaluate the effects of varying contributions by pigment hematite to remanence, rock magnetic, and magnetic fabric properties. All rocks are well-characterized petrographically, so that the modal abundance of detrital oxides is known. The Chugwater siltstones are notable because of a relatively low Tlub spectra (below about 620o C), with no evidence of a low coercivity cubic phase. Rock magnetic and magnetic fabric properties are monitored as a function of progressive chemical demagnetization to further elucidate the role of hematite pigment in rocks that have contributed much to the paleomagnetic record of Earth.

Ion microprobe analysis of {sup 18}O/{sup 16}O in authigenic and detrital quartz in the St. Peter Sandstone, Michigan Basin and Wisconsin Arch, USA: Contrasting diagenetic histories

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

Graham, C.M.; Valley, J.W.; Winter, B.L.

1996-12-01

The oxygen isotopic compositions of authigenic quartz cements in sandstones provide a monitor of the temperatures, compositions, and origins of pore-occluding fluids during diagenesis, but quartz overgrowths are too fine-grained to be amenable to conventional isotopic analysis. We have used a Cameca ims-4f ion microprobe to determine oxygen isotopic variations in authigenic and detrital quartz in four samples of the Ordovician St. Peter Sandstone from the Michigan Basin and Wisconsin Arch, midwestern USA. Ion microprobe isotopic analyses have been successfully accomplished with an internal precision of {+-}1{per_thousand} (1{sigma}) and a spatial resolution of 20-30 {mu}m at low mass resolution usingmore » a high voltage offset technique. Repeated analyses of the quartz standard demonstrate a reproducibility of close to {+-}1{per_thousand} (1 sd) in good agreement with that expected from counting statistics. Conventional and ion microprobe analyses are mutually consistent, supporting the accuracy of the ion microprobe analyses. Within-sample isotopic variations of up to 13{per_thousand} and micro-scale isotopic variations of at least 4{per_thousand} over a distance of 100 {mu}m have been measured within quartz overgrowths in a sandstone from the Wisconsin Arch. Overgrowths are uniformly higher in {delta}{sup 18}O than detrital grains, and gradients of up to 25% exist across a few microns. {sup 18}O-enriched quartz overgrowths in sandstones from the Wisconsin Arch show complex CL zonation and reflect one of two possible processes: (1) low-temperature quartz precipitation during mixing of meteoric waters with upwelling basinal fluids; (2) higher temperature quartz precipitation during episodic gravity-driven upwelling of warm basinal fluids (of comparable isotopic composition to Michigan Basin fluids) from the Illinois Basin, related to evolution of Mississippi Valley type Pb-Zn ore-forming fluids. 59 refs., 7 figs., 4 tabs.« less

Naturally weathered feldspar surfaces in the Navajo Sandstone aquifer, Black Mesa, Arizona: Electron microscopic characterization

USGS Publications Warehouse

Zhu, Chen; Veblen, D.R.; Blum, A.E.; Chipera, S.J.

2006-01-01

Naturally weathered feldspar surfaces in the Jurassic Navajo Sandstone at Black Mesa, Arizona, was characterized with high-resolution transmission and analytical electron microscope (HRTEM-AEM) and field emission gun scanning electron microscope (FEG-SEM). Here, we report the first HRTEM observation of a 10-nm thick amorphous layer on naturally weathered K-feldspar in currently slightly alkaline groundwater. The amorphous layer is probably deficient in K and enriched in Si. In addition to the amorphous layer, the feldspar surfaces are also partially coated with tightly adhered kaolin platelets. Outside of the kaolin coatings, feldspar grains are covered with a continuous 3-5 ??m thick layer of authigenic smectite, which also coats quartz and other sediment grains. Authigenic K-feldspar overgrowth and etch pits were also found on feldspar grains. These characteristics of the aged feldspar surfaces accentuate the differences in reactivity between the freshly ground feldspar powders used in laboratory experiments and feldspar grains in natural systems, and may partially contribute to the commonly observed apparent laboratory-field dissolution rate discrepancy. At Black Mesa, feldspars in the Navajo Sandstone are dissolving at ???105 times slower than laboratory rate at comparable temperature and pH under far from equilibrium condition. The tightly adhered kaolin platelets reduce the feldspar reactive surface area, and the authigenic K-feldspar overgrowth reduces the feldspar reactivity. However, the continuous smectite coating layer does not appear to constitute a diffusion barrier. The exact role of the amorphous layer on feldspar dissolution kinetics depends on the origin of the layer (leached layer versus re-precipitated silica), which is uncertain at present. However, the nanometer thin layer can be detected only with HRTEM, and thus our study raises the possibility of its wide occurrence in geological systems. Rate laws and proposed mechanisms should consider the possibility of this amorphous layer on feldspar surface. ?? 2006 Elsevier Inc. All rights reserved.

Authigenic Carbonate Fans from Lower Jurassic Marine Shales (Alberta, Canada)

NASA Astrophysics Data System (ADS)

Martindale, R. C.; Them, T. R., II; Gill, B. C.; Knoll, A. H.

2016-12-01

Authigenic aragonite seafloor fans are a common occurrence in Archean and Paleoproterozoic carbonates, as well as Neoproterozoic cap carbonates. Similar carbonate fans are rare in Phanerozoic strata, with the exception of two mass extinction events; during the Permo-Triassic and Triassic-Jurassic boundaries, carbonate fans formed at the sediment-water interface and within the sediment, respectively. These crystal fans have been linked to carbon cycle perturbations at the end of the Permian and Triassic periods driven by rapid flood volcanism. The Early Jurassic Toarcian Ocean Anoxic Event (T-OAE) is also correlated with the emplacement of a large igneous province, but biological consequences were more modest. We have identified broadly comparable fibrous calcite layers (2-10 cm thick) in Pliensbachian-Toarcian cores from Alberta, Canada. This work focuses on the geochemical and petrographic description of these fans and surrounding sediment in the context of the T-OAE. At the macroscale, carbonates exhibit a fan-like (occasionally cone-in-cone) structure and displace the sediment around them as they grew. At the microscale, the carbonate crystals (pseudomorphs of aragonite) often initiate on condensed horizons or shells. Although they grow in multiple directions (growth within the sediment), the predominant crystal growth direction is towards the sediment-water interface. Resedimentation of broken fans is evidence that crystal growth was penecontemporaneous with sedimentation. The carbon isotope composition of the fans (transects up bladed crystals) and elemental abundances within the layers support shallow subsurface, microbially mediated growth. The resemblance of these Early Jurassic fibrous calcite layers to those found at the end-Triassic and their paucity in the Phanerozoic record suggest that analogous processes occurred at both events. Nevertheless, the Pliensbachian-Toarcian carbonate fans occur at multiple horizons and while some are within the T-OAE, others are significantly above and below the event. The formation of these authigenic layers cannot be driven exclusively by the geochemical and paleoenvironmental changes during the T-OAE. Therefore, a new model of formation for the Early Jurassic carbonate fans is required.

Depositional environment of the downdip Queen City (Eocene) Sandstone, Mestena Grande Field Area, Jim Hogg and Duval Counties, Texas

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

McCormack, J.

1994-09-01

The downdip Queen City sandstone interval in the Mestena Grande field area of the south Texas Gulf Coast basin comprises two sandstone depositional units, referred to in this paper as A Lobe and B Lobe. A total of 583 ft (179 m) of conventional core from 11 wells containing predominantly B Lobe deposits were examined macroscopically. The A Lobe is a thin (6-34 ft; 1.8-10.4 m) fine- to very fine-grained, mostly bioturbated, well-sorted sandstone. The B Lobe is composed of fine to very fine, well-sorted sandstone interbedded with siltstone and mudstone. The trace fossil assemblage of the B Lobe indicatesmore » that sediments were deposited in the cruziana ichnofacies. Trace fossils and authigenic minerals also suggest oxygen stratification during deposition. B Lobe contains five subunits, each up to 13.5 ft (4 m) net sand thickness. These units were deposited as part of a highstands systems tract during the early Lutetian Stage (lower middle Eocene). B Lobe is a primarily aggradational unit composed of storm-generated sandstone and heterolithic deposits of the lower shoreface to inner shelf environment. A Lobe is a coarsening upward unit and represents progradation of the shoreface during late highstand systems tract development. An interlobal mudstone, which separates the units, marks the transition from early to late highstand systems tract development.« less

Marine phosphorites as potential resources for heavy rare earth elements and yttrium

USGS Publications Warehouse

Hein, James; Koschinsky, Andrea; Mikesell, Mariah; Mizell, Kira; Glenn, Craig R.; Wood, Ray

2016-01-01

Marine phosphorites are known to concentrate rare earth elements and yttrium (REY) during early diagenetic formation. Much of the REY data available are decades old and incomplete, and there has not been a systematic study of REY distributions in marine phosphorite deposits that formed over a range of oceanic environments. Consequently, we initiated this study to determine if marine phosphorite deposits found in the global ocean host REY concentrations of high enough grade to be of economic interest. This paper addresses continental-margin (CM) and open-ocean seamount phosphorites. All 75 samples analyzed are composed predominantly of carbonate fluorapatite and minor detrital and authigenic minerals. CM phosphorites have low total REY contents (mean 161 ppm) and high heavy REY (HREY) complements (mean 49%), while seamount phosphorites have 4–6 times higher individual REY contents (except for Ce, which is subequal; mean ΣREY 727 ppm), and very high HREY complements (mean 60%). The predominant causes of higher concentrations and larger HREY complements in seamount phosphorites compared to CM phosphorites are age, changes in seawater REY concentrations over time, water depth of formation, changes in pH and complexing ligands, and differences in organic carbon content in the depositional environments. Potential ore deposits with high HREY complements, like the marine phosphorites analyzed here, could help supply the HREY needed for high-tech and green-tech applications without creating an oversupply of the LREY.

Magnetic hysteresis parameters and Day plot analysis to characterize diagenetic alteration in gas hydrate-bearing sediments

NASA Astrophysics Data System (ADS)

Enkin, Randolph J.; Baker, Judith; Nourgaliev, Danis; Iassonov, Pavel; Hamilton, Tark S.

2007-06-01

The J meter coercivity spectrometer is a machine capable of rapid and simple measurement of magnetic hysteresis, isothermal remanence acquisition and magnetic viscosity of rocks and sediments. The J meter was used to study a suite of samples collected from strata in the gas hydrate-bearing JAPEX/JNOC/GSC Mallik 5L-38 well (69.5°N, 134.6°W) in the Mackenzie Delta of the northwestern Canadian Arctic. The Day plot of magnetic hysteresis ratios for these samples is exotic in that the points do not plot along a hyperbola as is usually observed. Rather, they plot as a scatter which is shown to contour into vertical slices using coercivity field (HC) or saturation magnetization (JS), and horizontal slices using the relative quantity of superparamagnetism (JSPM/JS). Optical microscopy reveals that the magnetic minerals are detrital magnetite and authigenic greigite. Greigite is dominant in sands which in situ had >70% gas hydrate saturation and in silts in which gas hydrate growth was blocked by insufficient porosity. We infer that the silts were the accumulation sites for solutes which had been excluded from the pore waters in neighboring coarser-grained sediments during the course of gas hydrate formation. Consequently, we conclude that magnetic properties are related to gas hydrate-related processes, and as such, may have potential as a method of remote sensing for gas hydrate deposits.

Reconstructing Carotenoid-Based and Structural Coloration in Fossil Skin.

PubMed

McNamara, Maria E; Orr, Patrick J; Kearns, Stuart L; Alcalá, Luis; Anadón, Pere; Peñalver, Enrique

2016-04-25

Evidence of original coloration in fossils provides insights into the visual communication strategies used by ancient animals and the functional evolution of coloration over time [1-7]. Hitherto, all reconstructions of the colors of reptile integument and the plumage of fossil birds and feathered dinosaurs have been of melanin-based coloration [1-6]. Extant animals also use other mechanisms for producing color [8], but these have not been identified in fossils. Here we report the first examples of carotenoid-based coloration in the fossil record, and of structural coloration in fossil integument. The fossil skin, from a 10 million-year-old colubrid snake from the Late Miocene Libros Lagerstätte (Teruel, Spain) [9, 10], preserves dermal pigment cells (chromatophores)-xanthophores, iridophores, and melanophores-in calcium phosphate. Comparison with chromatophore abundance and position in extant reptiles [11-15] indicates that the fossil snake was pale-colored in ventral regions; dorsal and lateral regions were green with brown-black and yellow-green transverse blotches. Such coloration most likely functioned in substrate matching and intraspecific signaling. Skin replicated in authigenic minerals is not uncommon in exceptionally preserved fossils [16, 17], and dermal pigment cells generate coloration in numerous reptile, amphibian, and fish taxa today [18]. Our discovery thus represents a new means by which to reconstruct the original coloration of exceptionally preserved fossil vertebrates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hexagonal platelet-like magnetite as a biosignature of thermophilic iron-reducing bacteria and its applications to the exploration of the modern deep, hot biosphere and the emergence of iron-reducing bacteria in early precambrian oceans.

PubMed

Li, Yi-Liang

2012-12-01

Dissimilatory iron-reducing bacteria are able to enzymatically reduce ferric iron and couple to the oxidation of organic carbon. This mechanism induces the mineralization of fine magnetite crystals characterized by a wide distribution in size and irregular morphologies that are indistinguishable from authigenic magnetite. Thermoanaerobacter are thermophilic iron-reducing bacteria that predominantly inhabit terrestrial hot springs or deep crusts and have the capacity to transform amorphous ferric iron into magnetite with a size up to 120 nm. In this study, I first characterize the formation of hexagonal platelet-like magnetite of a few hundred nanometers in cultures of Thermoanaerobacter spp. strain TOR39. Biogenic magnetite with such large crystal sizes and unique morphology has never been observed in abiotic or biotic processes and thus can be considered as a potential biosignature for thermophilic iron-reducing bacteria. The unique crystallographic features and strong ferrimagnetic properties of these crystals allow easy and rapid screening for the previous presence of iron-reducing bacteria in deep terrestrial crustal samples that are unsuitable for biological detection methods and, also, the search for biogenic magnetite in banded iron formations that deposited only in the first 2 billion years of Earth with evidence of life.

Biotic and abiotic pathways of phosphorus cycling in minerals and sediments: insights from oxygen isotopes in phosphate

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

Jaisi, Deb P.; Kukkadapu, Ravi K.; Stout, Lisa M.

2011-07-06

A key question to address in the development of oxygen isotope ratios in phosphate (18Op) as a tracer of biogeochemical cycling of phosphorus in ancient and modern environments is the nature of isotopic signatures associated with uptake and cycling of mineral-bound phosphate by microorganisms. Here we present experimental results aimed at understanding the biotic and abiotic pathway of P cycling during biological uptake of phosphate sorbed to ferrihydrite and the selective uptake of specific sedimentary phosphate phases by Escherichia coli, Vibrio fischeri and Marinobacter aquaeolei. Results indicate that a significant fraction of ferrihydrite-bound phosphate is biologically available. The fraction ofmore » phosphate taken up by E. coli attained an equilibrium isotopic composition in a short time (<50 hrs) due to efficient O-isotope exchange between phosphate and water (biotic pathway). The difference in isotopic composition between newly equilibrated aqueous and residual sorbed phosphate promoted the exchange of intact phosphate radicals (abiotic pathway) so that this difference gradually became negligible. In sediment containing different P phases, E. coli and V. fischeri ‘extracted’ loosely sorbed phosphate first while M. aquaeolei preferred iron-oxide bound phosphate. Each bacterium imprinted a biotic isotopic signature on each P phase that it took up and cycled. For example, the 18Op value of the sorbed phosphate phase shifted gradually towards equilibrium isotopic composition and the value of Fe oxide-bound phosphate showed slight changes at first, but when new iron oxides were formed, co-precipitated/occluded phosphate retained 18O values of aqueous phosphate at that time. Concentrations and isotopic compositions of authigenic and detrital phosphates did not change, suggesting that these phosphate phases were not utilized by bacteria. These findings support burgeoning applications of 18Op as a tracer of phosphorus cycling in sediments, soils and aquatic environments and as an indicator of paleo- environmental conditions.« less

Nuclear Repository steel canister: experimental corrosion rates

NASA Astrophysics Data System (ADS)

Caporuscio, F.; Norskog, K.

2017-12-01

The U.S. Spent Fuel & Waste Science & Technology campaign evaluates various generic geological repositories for the disposal of spent nuclear fuel. This experimental work analyzed and characterized the canister corrosion and steel interface mineralogy of bentonite-based EBS 304 stainless steel (SS), 316 SS, and low-carbon steel coupons in brine at higher heat loads and pressures. Experiments contrasted EBS with and without an argillite wall rock. Unprocessed bentonite from Colony, Wyoming simulated the clay buffer and Opalinus Clay represented the wall rock. Redox conditions were buffered at the magnetite-iron oxygen fugacity univariant curve. A K-Na-Ca-Cl-based brine was chosen to replicate generic granitic groundwater compositions, while Opalinous Clay groundwater was used in the wall rock series of experiments. Most experiments were run at 150 bar and 300°C for 4 to 6 weeks and one was held at elevated conditions for 6 months. The two major experimental mixtures were 1) brine-bentonite clay- steel, and 2) brine-bentonite clay-Opalinus Clay-steel. Both systems were equilibrated at a high liquid/clay ratio. Mineralogy and aqueous geochemistry of each experiment were evaluated to monitor the reactions that took place. In total 4291 measurements were obtained: 2500 measured steel corrosion depths and 1791 were of phyllosilicate mineral reactions/growths at the interface. The low carbon steel corrosion mechanism was via pit corrosion, while 304 SS and 316 SS were by general corrosion. The low carbon steel corrosion rate (1.95 μm/day) was most rapid. The 304 SS corrosion rate (0.37 μm/day) was slightly accelerated versus the 316 SS corrosion rate (0.26 μm/day). Note that the six month 316 SS experiment shows inhibited corrosion rates (0.07 μm/day). This may be in part due to mantling by the Fe-saponite/chlorite authigenic minerals. All phyllosilicate growth rates at the interface exhibit similar growth rate patterns to the steels (i.e. LCS>304>316> 316 six month).

Sedimentation across the central California oxygen minimum zone: an alternative coastal upwelling sequence.

USGS Publications Warehouse

Vercoutere, T.L.; Mullins, H.T.; McDougall, K.; Thompson, J.B.

1987-01-01

Distribution, abundance, and diversity of terrigenous, authigenous, and biogenous material provide evidence of the effect of bottom currents and oxygen minimum zone (OMZ) on continental slope sedimentation offshore central California. Three major OMZ facies are identified, along the upper and lower edges of OMZ and one at its core.-from Authors

A combined chemical, isotopic and microstructural study of pyrite from roll-front uranium deposits, Lake Eyre Basin, South Australia

NASA Astrophysics Data System (ADS)

Ingham, Edwina S.; Cook, Nigel J.; Cliff, John; Ciobanu, Cristiana L.; Huddleston, Adam

2014-01-01

The common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at Pepegoona, Pepegoona West and Pannikan, Lake Eyre Basin, South Australia. Combined chemical, isotopic and microstructural analysis of pyrite indicates variation in fluid composition, sulfur source and precipitation conditions during a protracted mineralization event. The results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low-temperature hydrothermal systems. In-situ micrometer-scale sulfur isotope analyses of pyrite demonstrated broad-scale isotopic heterogeneity (δ34S = -43.9 to +32.4‰VCDT), indicative of complex, multi-faceted pyrite evolution, and sulfur derived from more than a single source. Preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation. Authigenic pyrite underwent prolonged evolution and recrystallization, evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra. Secondary hydrothermal pyrite commonly displays hyper-enrichment of several trace elements (Mn, Co, Ni, As, Se, Mo, Sb, W and Tl) in ore-bearing horizons. Hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types. Irregular variation in δ34S, coupled with oscillatory trace element zonation in secondary pyrite, is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization. A late-stage oxidizing fluid may have mobilized selenium from pre-existing pyrite. Subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re-crystallization and precipitation of selenium as native selenium. These results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at Beverley North. Insights into depositional conditions and sources of both sulfide and uranium mineralization and an improved understanding of pyrite geochemistry can also underpin an effective vector for uranium exploration at Beverley North and other sedimentary systems of the Lake Eyre Basin, as well as in comparable geological environments elsewhere. Average intensity of 32S signal in counts per second × 108.Drift corrected 34S/32S prior to IMF calibration.Two-sigma propagated uncertainty on individual measurements.

Co-diagenesis of iron and phosphorus in hydrothermal sediments from the southern East Pacific Rise: Implications for the evaluation of paleoseawater phosphate concentrations

NASA Astrophysics Data System (ADS)

Poulton, Simon W.; Canfield, Donald E.

2006-12-01

We present a detailed study of the co-diagenesis of Fe and P in hydrothermal plume fallout sediments from ˜19°S on the southern East Pacific Rise. Three distal sediment cores from 340-1130 km from the ridge crest, collected during DSDP Leg 92, were analysed for solid phase Fe and P associations using sequential chemical extraction techniques. The sediments at all sites are enriched in hydrothermal Fe (oxyhydr)oxides, but during diagenesis a large proportion of the primary ferrihydrite precipitates are transformed to the more stable mineral form of goethite and to a lesser extent to clay minerals, resulting in the release to solution of scavenged P. However, a significant proportion of this P is retained within the sediment, by incorporation into secondary goethite, by precipitation as authigenic apatite, and by readsorption to Fe (oxyhydr)oxides. Molar P/Fe ratios for these sediments are significantly lower than those measured in plume particles from more northern localities along the southern East Pacific Rise, and show a distinct downcore decrease to a depth of ˜12 m. Molar P/Fe ratios are then relatively constant to a depth of ˜35 m. The Fe and P speciation data indicate that diagenetic modification of the sediments is largely complete by a depth of 2.5 m, and thus depth trends in molar P/Fe ratios can not solely be explained by losses of P from the sediment by diffusion to the overlying water column during early diagenesis. Instead, these sediments are likely recording changes in dissolved P concentrations off the SEPR, possibly as a result of redistribution of nutrients in response to changes in oceanic circulation over the last 10 million years. Furthermore, the relatively low molar P/Fe ratios observed throughout these sediments are not necessarily solely due to losses of scavenged P by diffusion to the overlying water column during diagenesis, but may also reflect post-depositional oxidation of pyrite originating from the volatile-rich vents of the southern East Pacific Rise. This study suggests that the molar P/Fe ratio of oxic Fe-rich sediments may serve as a proxy of relative changes in paleoseawater phosphate concentrations, particularly if Fe sulfide minerals are not an important component during transport and deposition.

Mineral dissolution in the Cape Cod aquifer, Massachusetts, USA: I . Reaction stoichiometry and impact of accessory feldspar and glauconite on strontium isotopes, solute concentrations, and REY distribution

USGS Publications Warehouse

Bau, Michael; Alexander, Brian; Chesley, John T.; Dulski, Peter; Brantley, Susan L.

2004-01-01

To compare relative reaction rates of mineral dissolution in a mineralogically simple groundwater aquifer, we studied the controls on solute concentrations, Sr isotopes, and rare earth element and yttrium (REY) systematics in the Cape Cod aquifer. This aquifer comprises mostly carbonate-free Pleistocene sediments that are about 90% quartz with minor K-feldspar, plagioclase, glauconite, and Fe-oxides. Silica concentrations and pH in the groundwater increase systematically with increasing depth, while Sr isotopic ratios decrease. No clear relationship between 87Sr/86Sr and Sr concentration is observed. At all depths, the 87Sr/86Sr ratio of the groundwater is considerably lower than the Sr isotopic ratio of the bulk sediment or its K-feldspar component, but similar to that of a plagioclase-rich accessory separate obtained from the sediment. The Si-87Sr/86Sr-depth relationships are consistent with dissolution of accessory plagioclase. In addition, solutes such as Sr, Ca, and particularly K show concentration spikes superimposed on their respective general trends. The K-Sr-87Sr/86Sr systematics suggests that accessory glauconite is another major solute source to Cape Cod groundwater. Although the authigenic glauconite in the Cape Cod sediment is rich in Rb, it is low in in-grown radiogenic 87Sr because of its young Pleistocene age. The low 87Sr/86Sr ratios are consistent with equilibration of glauconite with seawater. The impact of glauconite is inferred to vary due to its variable abundance in the sediments. In the Cape Cod groundwater, the variation of REY concentrations with sampling depth resembles that of K and Rb, but differs from that of Ca and Sr. Shale-normalized REY patterns are light REY depleted, show negative Ce anomalies and super-chondritic Y/Ho ratios, but no Eu anomalies. REY input from feldspar, therefore, is insignificant compared to input from a K-Rb-bearing phase, inferred to be glauconite. These results emphasize that interpretation of groundwater chemistry, even in relatively simple aquifers, may be complicated by solute contributions from “exotic” accessory minerals such as glauconite. To detect such peculiarities, groundwater studies should combine the study of elemental concentration and isotopic composition of several solutes that show different geochemical behavior.

Bacterial methane oxidation in sea-floor gas hydrate: Significance to life in extreme environments

NASA Astrophysics Data System (ADS)

Sassen, Roger; MacDonald, Ian R.; Guinasso, Norman L., Jr.; Joye, Samantha; Requejo, Adolfo G.; Sweet, Stephen T.; Alcalá-Herrera, Javier; Defreitas, Debra A.; Schink, David R.

1998-09-01

Samples of thermogenic hydrocarbon gases, from vents and gas hydrate mounds within a sea-floor chemosynthetic community on the Gulf of Mexico continental slope at about 540 m depth, were collected by research submersible. Our study area is characterized by low water temperature (mean =7 °C), high pressure (about 5400 kPa), and abundant structure II gas hydrate. Bacterial oxidation of hydrate-bound methane (CH4) is indicated by three isotopic properties of gas hydrate samples. Relative to the vent gas from which the gas hydrate formed, (1) methane-bound methane is enriched in 13C by as much as 3.8‰ PDB (Peedee belemnite), (2) hydrate-bound methane is enriched in deuterium (D) by as much as 37‰ SMOW (standard mean ocean water), and (3) hydrate-bound carbon dioxide (CO2) is depleted in 13C by as much as 22.4‰ PDB. Hydrate-associated authigenic carbonate rock is also depleted in 13C. Bacterial oxidation of methane is a driving force in chemosynthetic communities, and in the concomitant precipitation of authigenic carbonate rock that modifies sea-floor geology. Bacterial oxidation of hydrate-bound methane expands the potential boundaries of life in extreme environments.

Ikaite pseudomorphs in the Zaire deep-sea fan: An intermediate between calcite and porous calcite

NASA Astrophysics Data System (ADS)

Jansen, J. H. F.; Woensdregt, C. F.; Kooistra, M. J.; van der Gaast, S. J.

1987-03-01

Translucent brown aggregates of calcium-carbonate crystals have been found in cores from the Zaire deep-sea fan (west equatorial Africa). The aggregates are well preserved but very friable. Upon storage they become yellowish white and cloudy and release water. Chemical, mineralogical (XRD), petrographical, crystal-morphological, and stable-isotope data demonstrate that the crystals have passed through three phases: (1) an authigenic carbonate phase, probably calcium carbonate, which is represented by the external habit of the present crystals; (2) a translucent brown ikaite phase (CaCO3·6H2O), unstable at temperatures above 5 °C; and (3) a phase consisting of calcite microcrystals that are poorly cemented and form a porous mass within the crystal form of the morphologically unchanged first phase. The transformation from the first phase into ikaite was probably a kinetic replacement. The transformation from ikaite into the third phase occurred because of storage at room temperature. The presence of ikaite is indicative of a low-temperature, anaerobic, organic-carbon-rich marine environment. Ikaite is probably the precursor of a great number of porous calcite pseudomorphs, and possibly also of many marine authigenic microcrystalline carbonate nodules.

Organic petrology and geochemistry of mudrocks from the lacustrine Lucaogou Formation, Santanghu Basin, northwest China: Application to lake basin evolution

USGS Publications Warehouse

Hackley, Paul C.; Fishman, Neil; Wu, Tao; Baugher, Gregory

2016-01-01

Exploration for tight oil in the frontier Santanghu Basin of northwest China has resulted in recent commercial discoveries sourced from the lacustrine Upper Permian Lucaogou Formation, already considered a “world class source rock” in the Junggar Basin to the west. Here we apply an integrated analytical program to carbonate-dominated mudrocks from the Lucaogou Formation in Santanghu Basin to document the nature of organic matter (OM) in the context of an evolving lake system. The organic-rich samples (TOC 2.8–11.4 wt%; n = 10) were widely spaced from an ~ 200 m cored section, interpreted from textural and mineralogical evidence to document transition from a lower under-filled to an overlying balanced-filled lake. Organic matter is dominated by moderate to strongly fluorescent amorphous material with Type I geochemical signature (HI values 510–755; n = 10) occurring in a continuum from lamellar stringers, 10–20 μm thick, some ≥ 1 mm in length (possible microbial mat; preserved only in lower under-filled section) to finely-disseminated amorphous groundmass intimately intermixed with mineral matrix. Biomarkers for methanotrophs and photosynthetic cyanobacteria indicate a complex microbial consortium. A unicellular prasinophyte green alga(?), similar to Tasmanites in marine rocks, is present as discrete flattened discs 50–100 μm in diameter. Type III OM including vitrinite (some fluorescent) and inertinite also is abundant. Solid bitumen, indicating local kerogen conversion, fills voids and occurs throughout the cored section. Vitrinite reflectance values are 0.47–0.58%, consistent with strong OM fluorescence but may be “suppressed”. Other proxies, e.g., biomarker parameters, indicate the Lucaogou Formation is in the early oil window at this location. On average, slightly more amorphous OM and telalginite are present in the lower section, consistent with a shallow, stratified, saline environment with low sediment dilution. More inertinite is present in the upper section, indicating greater terrestrial influx and consistent with higher quartz and plagioclase content (dominantly authigenic chalcedony and albite). Laminated mudstones in the upper section indicate anoxia prevented bioturbation from benthic grazing, also indicating stratified water column conditions. A decrease upsection in authigenic dolomite with reciprocal increase of ankerite/siderite is consistent with decreasing salinity, as is an overall decrease in gammacerane index values. These observations suggest evolution from a shallow, stratified evaporative (saline) setting to a deeper, stratified freshwater basin with higher water input during Lucaogou deposition. The evolution from an under-filled to balance-filled lake in Santanghu Basin is similar to Lucaogou deposition in Junggar Basin, suggesting similar tectonic and climatic controls. Paleoclimate interpretations from other researchers in this area suggested an evolution from semi-arid to humid conditions during the Roadian; we interpret that the evolution from an under-filled to balanced-filled lake seen in our data is in response to climate change, and may represent increased groundwater delivery to the Santanghu Basin.

Paleoaltimetry of the Oiyug Basin, southern Tibet using clumped-isotope paleothermometry

NASA Astrophysics Data System (ADS)

Abbot, M. I.; Rowley, D. B.; Currie, B. S.; Colman, A. S.; He, B.; Olack, G.

2013-12-01

We present new paleoelevation estimates of the Oiyug Basin of the southern Tibetan Plateau during the mid-Miocene to Pliocene using carbonate Δ47 clumped isotope and conventional δ18O paleoaltimetry. Δ47 reflects the statistical overabundance of 13C-18O bonds in multiply-substituted isotopologues of CO2 generated from phosphoric acid digestion of carbonate minerals (Eiler, 2007). Paleoelevation estimates inform geodynamic models of the earth's surface response to climate, tectonics, and erosion at high elevations (Clark, 2007). Commonly applied techniques for reconstructing paleoelevation histories are based on paleobotany (paleoenthalpy derived from floral physiognomy, e.g. Spicer et al., 2003) the oxygen isotope record of meteoric and pedogenic minerals (e.g. Chamberlain and Poage, 2000), and compound specific δD of organic matter (Polissar et al. 2009). The carbonate clumped isotope paleothermometer provides independent constraints on both the temperature and isotopic composition of ancient surface waters (Ghosh et al., 2006a), making it a potentially powerful paleoaltimeter (Ghosh et al., 2006b, Quade et al., 2007) when the original isotopic signature is preserved. A burial history reconstructed from lipid-δD measurements in the Oiyug Basin suggests that these carbonates have not been buried, and give us high confidence that the carbonates are unaltered and retain their primary isotopic signature. This study tests the use of multiply substituted CO2 isotopologues as a paleoaltimeter for the Tibetan Plateau. We will obtain independent paleoelevation estimates from Δ47 temperatures to test our hypothesis that the Oiyug Basin has remained high (~5300-4600 meters) for the past 15 million years. Chamberlain, C.P., and M. A. Poage, 2000, Reconstructing the paleotopography of mountain belts from the isotopic composition of authigenic minerals, Geology, 28, 115-118. Eiler, J.M., 2007, 'Clumped-isotope' geochemistry-The study of naturally occurring multiply substituted isotopologues, Earth Planetary Sci. Lett., 262, 309-327. Ghosh, P., J. Adkins, H. Affek, B. Balta, W. Guo, E. Schauble, D. Schrag, and J. Eiler, 2006a, 13C-18O bonds in carbonate minerals: A new kind of paleothermometer, Geochim. Cosmochim. Acta, 70, 1439-1456. Ghosh, P., C. Garzione, and J.M. Eiler, 2006b, Rapid uplift of the Altiplano revealed through 13C-18O bonds in paleosol carbonates, Science, 311, 511-515. Polissar, P. J., K.H. Freeman, D.B. Rowley, F.A. Mcinerney, and B.S. Currie, 2009, Paleoaltimetry of the Tibetan Plateau from D/H ratios of lipid biomarkers. Earth and Planetary Science Letters, 287, 64-67. Quade, J.,C. Garzione, and J. Eiler, 2007, Paleoelevation reconstruction using pedogenic carbonates, Rev. Mineral. Geochem., 66, 53-87. Spicer, R.A., Harris, N.B.W., Widdowson, M., Herman, A.B., Guo, S., Valdes, P.J., Wolfe, J.A., and Kelley, S.P., 2003, Constant elevation of southern Tibet over the past 15 million years: Nature, v. 421, p. 622-624.

Mineralogy and diagenesis of low-permeability sandstones of Late Cretaceous age, Piceance Creek Basin, northwestern Colorado

USGS Publications Warehouse

Hansley, Paula L.; Johnson, Ronald C.

1980-01-01

This report presents preliminary results of a mineralogic and diagenetic study of some low-permeability sandstones from measured surface sections and cores obtained from drill holes in the Piceance Creek Basin of northwestern Colorado. A documentation of the mineralogy and diagenetic history will aid in the exploration for natural gas and in the development of recovery technology in these low-permability sandstones. These sandstones are in the nonmarine upper part of the Mesaverde Formation (or Group) of Late Cretaceous age and are separated from overlying lower Tertiary rocks by a major regional unconformity. Attention is focused on the sandstone units of the Ohio Creek Member, which directly underlies the unconformity; however, comparisons between the mineralogy of the Ohio Creek strata and that of the underlying sandstone units are made whenever possible. The Ohio Creek is a member of the Hunter Canyon Formation (Mesaverde Group) in the southwestern part of the basin, and the Mesaverde Formation in the southern and central parts of the basin. The detrital mineralogy is fairly constant throughout all of these nonrnarine Cretaceous sandstone units; however, in the southeastern part of the basin, there is an increase in percentage of feldspar, quartzite, and igneous rock fragments in sandstones of the Ohio Creek Member directly underlying the unconformity. In the southwestern part of the basin, sandstones of the Ohio Creek Member are very weathered and are almost-entirely comprised of quartz, chert, and kaolinite. A complex diagenetic history, partly related to the overlying unconformity, appears to be responsible for transforming these sandstones into potential gas reservoirs. The general diagenetic sequence for the entire Upper Cretaceous interval studied is interpreted to be (early to late): early(?) calcite cement, chlorite, quartz overgrowths, calcite cement, secondary porosity, analcime (surface only), kaolinite and illite, and late carbonate cements. Authigenic high-iron chlorite, which occurs on grain rims and in pore throats, is primarily responsible for the low-permeability of the subsurface sandstones of the Ohio Creek Member in the center of the basin. Kaolinite is the most abundant pore-filling authigenic clay in these sandstones, from the southwestern part of the basin and is responsible for their distinctive white-weathering color in outcrop. In the sandstones below the Ohio Creek Member, however, chlorite and kaolinite occur locally, and authigenic calcite and illite are more abundant. The occurrence and distribution of secondary porosity is one of the most important aspects of the diagenetic history of these sandstones. It is present as moldic intra- and intergranular porosity, as well as microporosity among authigenic clay pariicles. Although present locally in most sandstone units, secondary porosity is particularly common in the uppermost sandstone units and is interpreted to have formed primarily asa result ofweathering during the time represented by the Cretaceous-Tertiary unconformity.

Influences of petrographic parameters on technological properties of greywackes used for crushed stone production

NASA Astrophysics Data System (ADS)

Prikryl, Richard; Cermak, Martin; Krutilova, Katerina

2014-05-01

This study focuses on the influence of petrographic parameters on technological properties of greywackes. These sedimentary rocks make about 27 % of crushed stone market in the Czech Republic. Mainly in Moravia (eastern part of the Czech Republic), greywackes represent almost exclusive high quality aggregate. The behaviour of greywackes varies, however, from quarry to quarry. In this study, we have selected the most important deposits that cover major lithological variation of local greywackes. Studied greywackes were analysed for their petrographic parameters quantitatively (using image analysis of thin sections). The pore space characteristics were determined by using fluorescent dye - epoxy resin impregnated specimens. The studied rocks are composed of subangular and angular quartz grains, lithoclasts (stable rocks: quartzites, and unstable rocks: phylites, metaphylites, siltstones, slates, greywackes, and less frequently acid eruptive rocks), feldspars (orthoclas, microcline, plagioclase), and detrital micas. Detrital and authigenic chlorite has been found as well. The matrix which represents the largest volume of rock-forming components contains a mixture of sericite, chlorite, clay minerals, cements, and clasts in aleuropelitic size. Based on the microscopic examination, all studied rock types were classified as greywacke with fine- to medium-grained massive rock fabric. Only specimen from Bělkovice has shown partly layered structure. Alteration of feldspars and unstable rock fragments represents common feature. Diagenetic features included pressure dissolution of quartz clasts and formation of siliceous and/or calcite cements. Based on the experimental study of technological performance of studied greywackes and its correlation to petrographic features, the average size of clasts and volume of matrix make the driving factors affecting the LA values. The LA values decrease with the increasing of volume of matrix (R = 0.61) and with decreasing average grain size (R = 0.44). The degree of sorting influences LA values as well; more graded greywackes tend to show higher LA values. Regarding PSV, its values increase with increasing volume of quartz clasts.

A Multiproxy Approach to Unraveling Climate and Human Demography in the Peruvian Altiplano from a 5000 year Lake Sediment Core

NASA Astrophysics Data System (ADS)

Vaught-Mijares, R. M.; Hillman, A. L.; Abbott, M. B.; Werne, J. P.; Arkush, E.

2017-12-01

Drought and flood events are thought to have shaped the ways in which Andean societies have adapted to life in the Titicaca Basin region, particularly with regard to land use practices and settlement patterns. This study examines a small lake in the region, Laguna Orurillo. Water isotopes suggest that the lake primarily loses water through evaporation, making it hydrologically sensitive. In 2015, a 3.4 m overlapping sediment record was collected and inspected for evidence of shallow water facies and erosional unconformities to reconstruct paleohydrology. Sediment core chronology was established using 7 AMS radiocarbon dates and 210Pb dating and indicates that the core spans 5000 years. Additional sediment core measurements include magnetic susceptibility, bulk density, organic/carbonate content, and XRD. Results show a pronounced change in sediment composition from brittle, angular salt deposits to massive calcareous silt and clay around 5000 years BP. Multiple transitions from clay to sand show potential lake level depressions at 1540, 2090, and 2230, yr BP that are supported by a drastic increase in carbonate composition from 2760-1600 yr BP. Additional shallow-water periods may be reflected in the presence of rip-up clasts from 4000 to 3000 yr BP. These early interpretations align well with existing hydrologic records from Lake Titicaca. In order to develop a more detailed climate and land use record, isotope analyses of authigenic carbonate minerals using δ13C and δ18O and leaf waxes using δD are being developed. Ultimately, this record will be linked with records from nearby Lagunas Arapa and Umayo. Additional proxies for human population such as fecal 5β-stanols and proximal anthropologic surveys will be synthesized to contribute to a regional understanding of Holocene climate variability and human demography in the Peruvian Altiplano.

Authigenic Nd isotope record of North Pacific Intermediate Water formation and boundary exchange on the Bering Slope

NASA Astrophysics Data System (ADS)

Jang, Kwangchul; Huh, Youngsook; Han, Yeongcheol

2017-01-01

The Bering Sea is a potential location for the formation of the North Pacific Intermediate Water (NPIW), which drives the global ocean circulation as a counterpart to the North Atlantic Deep Water (NADW). To evaluate the NPIW-NADW seesaw hypothesis, we reconstructed the long-term variation of the bottom water Nd isotopic composition at site U1345 on the Bering Slope by extracting authigenic Fe-Mn oxyhydroxide from bulk sediments. We examined six different extractions in order to ensure that authentic seawater composition is recovered. For Bering Slope sediments whose typical carbonate content is less than 5% (average 2%), the most reliable results are obtained if the decarbonation step is omitted and a low reagent-to-sediment ratio is adopted. The reconstructed authigenic εNd record for the last 520 kyr exhibits large temporal variations depending on whether the NPIW formation or the boundary exchange process is dominant. Periods of radiogenic εNd can be attributed to NPIW formation triggered by brine rejection, as evidenced by the difference in δ18O of benthic foraminifera between sites (Δδ18Obf), high % sea-ice related diatoms, and low abundance of Bulimina aff. Exilis (low-oxygen deep fauna). Diminished supply of unradiogenic Nd from boundary exchange seems to intensify these radiogenic peaks. On the other hand, the unradiogenic εNd intervals can be attributed to stagnant bottom water conditions, as can be deduced from the Δδ18Obf values, low % sea-ice related diatoms, abundant B. aff. Exilis, and laminations. When there is no NPIW formation, the continental margin sediments are exposed to boundary exchange for a longer period of time, leading to release of unradiogenic Nd. The mid-MIS 6 and mid-MIS 5 are exceptions in that NPIW formation occurred yet the εNd compositions are unradiogenic. NPIW formation and cold climate (closed Bering Strait) are not always correlated. Comparison against εNd records of the South Atlantic suggests only an ambiguous NPIW-NADW seesaw for the last 200 kyr.

Authigenic oxide Neodymium Isotopic composition as a proxy of seawater: applying multivariate statistical analyses.

NASA Astrophysics Data System (ADS)

McKinley, C. C.; Scudder, R.; Thomas, D. J.

2016-12-01

The Neodymium Isotopic composition (Nd IC) of oxide coatings has been applied as a tracer of water mass composition and used to address fundamental questions about past ocean conditions. The leached authigenic oxide coating from marine sediment is widely assumed to reflect the dissolved trace metal composition of the bottom water interacting with sediment at the seafloor. However, recent studies have shown that readily reducible sediment components, in addition to trace metal fluxes from the pore water, are incorporated into the bottom water, influencing the trace metal composition of leached oxide coatings. This challenges the prevailing application of the authigenic oxide Nd IC as a proxy of seawater composition. Therefore, it is important to identify the component end-members that create sediments of different lithology and determine if, or how they might contribute to the Nd IC of oxide coatings. To investigate lithologic influence on the results of sequential leaching, we selected two sites with complete bulk sediment statistical characterization. Site U1370 in the South Pacific Gyre, is predominantly composed of Rhyolite ( 60%) and has a distinguishable ( 10%) Fe-Mn Oxyhydroxide component (Dunlea et al., 2015). Site 1149 near the Izu-Bonin-Arc is predominantly composed of dispersed ash ( 20-50%) and eolian dust from Asia ( 50-80%) (Scudder et al., 2014). We perform a two-step leaching procedure: a 14 mL of 0.02 M hydroxylamine hydrochloride (HH) in 20% acetic acid buffered to a pH 4 for one hour, targeting metals bound to Fe- and Mn- oxides fractions, and a second HH leach for 12 hours, designed to remove any remaining oxides from the residual component. We analyze all three resulting fractions for a large suite of major, trace and rare earth elements, a sub-set of the samples are also analyzed for Nd IC. We use multivariate statistical analyses of the resulting geochemical data to identify how each component of the sediment partitions across the sequential extractions. Here we present results comparing the two sites, and examine how the composition of the sediment impacts the resulting Nd IC.

Gas hydrate decomposition recorded by authigenic barite at pockmark sites of the northern Congo Fan

NASA Astrophysics Data System (ADS)

Kasten, Sabine; Nöthen, Kerstin; Hensen, Christian; Spieß, Volkhard; Blumenberg, Martin; Schneider, Ralph R.

2012-12-01

The geochemical cycling of barium was investigated in sediments of pockmarks of the northern Congo Fan, characterized by surface and subsurface gas hydrates, chemosynthetic fauna, and authigenic carbonates. Two gravity cores retrieved from the so-called Hydrate Hole and Worm Hole pockmarks were examined using high-resolution pore-water and solid-phase analyses. The results indicate that, although gas hydrates in the study area are stable with respect to pressure and temperature, they are and have been subject to dissolution due to methane-undersaturated pore waters. The process significantly driving dissolution is the anaerobic oxidation of methane (AOM) above the shallowest hydrate-bearing sediment layer. It is suggested that episodic seep events temporarily increase the upward flux of methane, and induce hydrate formation close to the sediment surface. AOM establishes at a sediment depth where the upward flux of methane from the uppermost hydrate layer counterbalances the downward flux of seawater sulfate. After seepage ceases, AOM continues to consume methane at the sulfate/methane transition (SMT) above the hydrates, thereby driving the progressive dissolution of the hydrates "from above". As a result the SMT migrates downward, leaving behind enrichments of authigenic barite and carbonates that typically precipitate at this biogeochemical reaction front. Calculation of the time needed to produce the observed solid-phase barium enrichments above the present-day depths of the SMT served to track the net downward migration of the SMT and to estimate the total time of hydrate dissolution in the recovered sediments. Methane fluxes were higher, and the SMT was located closer to the sediment surface in the past at both sites. Active seepage and hydrate formation are inferred to have occurred only a few thousands of years ago at the Hydrate Hole site. By contrast, AOM-driven hydrate dissolution as a consequence of an overall net decrease in upward methane flux seems to have persisted for a considerably longer time at the Worm Hole site, amounting to a few tens of thousands of years.

Meteoric 10Be/9Be ratios in marine sedimentary records: Deciphering the mixing between their marine and terrestrial sources and influence of costal trace metal fluxes

NASA Astrophysics Data System (ADS)

Wittmann, H.; von Blanckenburg, F.; Mohtadi, M.; Christl, M.; Bernhardt, A.

2017-12-01

Meteoric 10Be to stable 9Be ratios combine a cosmogenic nuclide produced in the atmosphere at a rate known from reconstructions of magnetic field strength with a stable isotope that records the present and past continental weathering and erosion flux. In seawater, the 10Be/9Be ratio provides important information on metal release from bottom sediments, called boundary exchange, and the oceanic mixing of reactive trace metals due to the inherently different sources of the two isotopes. When measured in the authigenic phase of marine sediments, the 10Be/9Be ratio allows deriving the feedbacks between erosion, weathering, and climate in the geologic past. At an ocean margin site 37°S offshore Chile, we use the 10Be/9Be ratio to trace changes in terrestrial particulate composition due to exchange with seawater. We analyzed the reactive (sequentially extracted) phase of marine surface sediments along a coast-perpendicular transect, and compared to samples from their riverine source. We find evidence for growth of authigenic rims through co-precipitation, not via reversible adsorption, that incorporate an open ocean 10Be/9Be signature from a deep water source only 30 km from the coast, thereby overprinting terrestrial riverine 10Be/9Be signatures. We show that the measured 10Be/9Be ratios in marine sediments comprise a mixture between seawater-derived and riverine-sourced phases. As 10Be/9Be ratios increase due to exchange with seawater, particulate-bound Fe concentrations increase, which we attribute to release of Fe-rich pore waters during boundary exchange in the sediment. The implications for the use of 10Be/9Be in sedimentary records for paleo-denudation flux reconstructions are that in coast-proximal sites that are neither affected by deeper water nor by narrow boundary currents, the authigenic record will be a direct recorder of terrigenous denudation of the adjacent river catchments. Hence archive location and past oceanic circulation have to be accounted for when reconstructing continental erosion and weathering, and only at open ocean sites that are fully reset by seawater global signals can be reconstructed.

The importance of XRD analysis in provenance and palaeoenvironmental studies of the Piedras de Afilar Formation, Neoproterozoic of Uruguay

NASA Astrophysics Data System (ADS)

Pamoukaghlian, K.; Poiré, D. G.; Gaucher, C.; Uriz, N.; Cingolani, C.; Frigeiro, P.

2009-04-01

The Piedras de Afilar Formation crops out in the southeast part of Uruguay, forming part of the Tandilia Terrane (sensu Bossi et al. 2005). Pamoukaghlian et al. (2006) and Gaucher et al. (2008) have published δ13C, δ18O and U/Pb SHRIMP results, which indicate a Neoproterozoic age for this formation. The palaeoenvironment has been defined as a shallow marine platform based on the presence of interference ripples, hummocky and mega-hummocky cross-stratification. X-ray diffraction (XRD) analyses help to better constrain the palaeoenvironment: the presence of chlorite/smectite found in black shales, suggest a reducing environment, and abundant illite indicates a cold to temperate climate. Provenance studies have been undertaken that utilise a combination of detailed palaeocurrent measurements, petrographic descriptions, XRD analyses, and geochemical isotopic analyses, including U/Pb SHRIMP determinations. Mineral compositional diagrams for sandstones suggest a stable cratonic provenance. Palaeocurrents are mainly from the NNE, indicating a provenance from the cratonic areas of the Tandilia Terrane. The illite crystal index indicates diagenetic to low-metamorphic conditions for the sequence; this is important to confirm that the identified minerals are authigenic. Clay minerals identified by XRD analysis of sandstones from the siliciclastic member are illite (80 - 90%), kaolinite (5 - 10%), and chlorite (5 - 10%). This is consistent with a provenance from the cratonic areas (quartz-feldspar dominated rock types). Isotopic analyses have been undertaken to provide better constraints on the tectonic setting. U/Pb SHRIMP ages for the youngest zircons are 990 Ma (Gaucher et al. 2008), and the basal granite (Granito de la Paz) is 2056 ± 11 Ma (Hartmann et al. 2001), suggesting a provenance from the Archaean basement for the Piedras de Afilar Formation, like its counterparts in the Rio de la Plata Craton. References Bossi, J., Piñeyro, D., Cingolani, C. (2005). El límite norte del Terreno Piedra Alta (Uruguay). Importancia de la faja milonítica sinestral de Colonia. Actas XVI Congreso Argentino de Geología, de La Plata. Gaucher, C., Poiré, D.G., Finney, S.C., Valencia, V.a., Blanco, G., Pamoukaghlian, K., Gómez Peral, L. (2008). Detrital zircón ages of Neoproterozoic sedimentary successions in Uruguay and Argentina: Insights into the geological evolution of the Rio de la Plata Craton. Precambrian Research. Hartmann, L.A., Campal, N., Santos, J.O., Mc. Neughton, N.J., Schipilov, A., Lafon, J.M. (2001). Archean crust in the Rio de la Plata Craton, Uruguay - SHRIMP U-Pb zircon reconnaissance geochronology. Journal of South American Earth Science, 14, 557-570. Pamoukaghlian, K., Gaucher, C., Bossi, J., Sial, N., Poire, D.G. (2006). First C and O isotopic data for the Piedras de Afilar Formation, Tandilia Terrane, Uruguay: their bearing on correlation and age. Fifth South American Symposium on Isotope Geology, Punta del Este.

Paragenesis and reservoir quality within a shallow combination trap: Central West Virginia

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

Bell, D.A.; Siegrist, H.G. Jr.; Buurman, J.D.

1993-12-01

Sandstone character and reservoir quality of the Lower Mississippian Pocono Big Injun sandstone were examined in Granny Creek-Stockly field, Clay County, West Virginia. Sixty-three samples from 6 wells were analyzed using transmitted light, x-ray diffraction, and scanning electron microscopy techniques. The Pocono Big Injun formation is divided into four [open quotes]sands[close quotes] (Injun 1 through 4) based on composition and hydrocarbon productivity. The Injun 1 sand is a fine-grained, carbonate-cemented litharenite below the oil-producing zone. The oil-productive Injun 2 and 3 sands are well sorted, fine-grained litharenites which contain more authigenic and allogenic clay minerals than adjacent sands. These sandsmore » have produced more than 3.4 million bbl of oil from the Granny Creek part of the field since 1925. The Injun 4 sand is generally a coarse-grained sublitharenite with marginal gas production limited to the uppermost section of the sand. The paragenetic sequence consists of (1) minor quartz overgrowths, (2) illite and chlorite grain coatings, (3) quartz overgrowths, (4) early carbonate, (5) kaolinite, (6) calcite, (7) dolomite, and (8) pyrite. Porosity and permeability were not preserved once paragenesis progressed past the kaolinite stage. Porosity and permeability are variably preserved when steps in the paragenetic sequence are absent within the Pocono Group. Where any porosity is identified within the Pocono sandstones, primary porosity is dominant. However, secondary porosity and microporosity in clay-rich intervals are also important.« less

Impact of silica diagenesis on the porosity of fine-grained strata: An analysis of Cenozoic mudstones from the North Sea

NASA Astrophysics Data System (ADS)

Wrona, Thilo; Taylor, Kevin G.; Jackson, Christopher A.-L.; Huuse, Mads; Najorka, Jens; Pan, Indranil

2017-04-01

Silica diagenesis has the potential to drastically change the physical and fluid flow properties of its host strata and therefore plays a key role in the development of sedimentary basins. The specific processes involved in silica diagenesis are, however, still poorly explained by existing models. This knowledge gap is addressed by investigating the effect of silica diagenesis on the porosity of Cenozoic mudstones of the North Viking Graben, northern North Sea through a multiple linear regression analysis. First, we identify and quantify the mineralogy of these rocks by scanning electron microscopy and X-ray diffraction, respectively. Mineral contents and host rock porosity data inferred from wireline data of two exploration wells are then analyzed by multiple linear regressions. This robust statistical analysis reveals that biogenic opal-A is a significant control and authigenic opal-CT is a minor influence on the porosity of these rocks. These results suggest that the initial porosity of siliceous mudstones increases with biogenic opal-A production during deposition and that the porosity reduction during opal-A/CT transformation results from opal-A dissolution. These findings advance our understanding of compaction, dewatering, and lithification of siliceous sediments and rocks. Moreover, this study provides a recipe for the derivation of the key controls (e.g., composition) on a rock property (e.g., porosity) that can be applied to a variety of problems in rock physics.

Filamentous microbial fossil from low-grade metamorphosed basalt in northern Chichibu belt, central Shikoku, Japan

NASA Astrophysics Data System (ADS)

Sakakibara, M.; Sugawara, H.; Tsuji, T.; Ikehara, M.

2014-05-01

The past two decades have seen the reporting of microbial fossils within ancient oceanic basalts that could be identical to microbes within modern basalts. Here, we present new petrographic, mineralogical, and stable isotopic data for metabasalts containing filamentous structures in a Jurassic accretionary complex within the northern Chichibu Belt of the Yanadani area of central Shikoku, Japan. Mineralized filaments within these rocks are present in interstitial domains filled with calcite, pumpellyite, or quartz, and consist of iron oxide, phengite, and pumpellyite. δ13CPDB values for filament-bearing calcite within these metabasalts vary from -2.49‰ to 0.67‰. A biogenic origin for these filamentous structures is indicated by (1) the geological context of the Yanadani metabasalt, (2) the morphology of the filaments, (3) the carbon isotope composition of carbonates that host the filaments, and (4) the timing of formation of these filaments relative to the timing of low-grade metamorphism in a subduction zone. The putative microorganisms that formed these filaments thrived between eruption (Late Paleozoic) and accretion (Early Jurassic) of the basalt. The data presented here indicate that cryptoendolithic life was present within water-filled vesicles in pre-Jurassic intraplate basalts. The mineralogy of the filaments reflects the low-grade metamorphic recrystallization of authigenic microbial clays similar to those formed by the encrustation of prokaryotes in modern iron-rich environments. These findings suggest that a previously unusual niche for life is present within intraplate volcanic rocks in accretionary complexes.

75 FR 69617 - Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-15

... 1219-AB64 Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust... hearings on the proposed rule addressing Lowering Miners' Exposure to Respirable Coal Mine Dust, Including... miners' exposure to respirable coal mine dust by revising the Agency's existing standards on miners...

The system controlling the composition of clastic sediments

USGS Publications Warehouse

Johnsson, Mark J.

1993-01-01

The composition of clastic sediments and rocks is controlled by a complex suite of parameters operating during pedogenesis, erosion, transport, deposition, and burial. The principal first-order parameters include source rock composition, modification by chemical weathering, mechanical disaggregation and abrasion, authigenic inputs, hydrodynamic sorting, and diagenesis. Each of these first-order parameters is influenced to varying degrees by such factors as the tectonic settings of the source region, transportational system and depositional environment, climate, vegetation, relief, slope, and the nature and energy of transportational and depositional systems. These factors are not independent; rather a complicated web of interrelationships and feedback mechanisms causes many factors to be modulated by others. Accordingly, processes controlling the composition of clastic sediments are best viewed as constituting a system, and in evaluating compositional information the dynamics of the system must be considered as whole.

Grain Refinement by Authigenic Inoculation Inherited from the Medium-Range Order Structure of Ni-Cr-W Superalloy

NASA Astrophysics Data System (ADS)

Gao, Zhongtang; Hu, Rui; Guo, Wei; Zhang, Chuanwei

2018-04-01

The combination of liquidus casting and thermal control solidification furnace was applied to obtain a fine-grained ingot. A rapid quenching method and x-ray diffraction measurement were used to investigate the effect of authigenic inoculation on grain refinement. The structure factor S(Q) of liquid Ni-Cr-W superalloy at 1400 °C (Liquidus temperature) and bright-field image of the microstructures quenched from 1400 °C have been measured by the high-temperature x-ray diffractometer and the transmission electron microscopy (TEM), respectively. The results show that a pre-peak exists on a S(Q) curve at the liquidus temperature. The clusters of atom in rapidly quenched microstructures obtained by isothermal heat treatment at 1400 °C were studied using TEM. Meanwhile, the effect of isothermal different temperatures on rapidly quenched microstructures was studied. The results also show that there are only the globular, equiaxed grains distributed in the solidification structure. These particles are inherited from the medium-range order structure, which is beneficial for grain refinement. The normalized work-hardening rate-strain curve indicates the work-hardening rate of fine grain is higher than that of conventional grain at the same temperature and the same deformation.

A rapid procedure for the determination of thorium, uranium, cadmium and molybdenum in small sediment samples by inductively coupled plasma-mass spectrometry: Application in Chesapeake Bay

USGS Publications Warehouse

Zheng, Yen; Weinman, B.; Cronin, T.; Fleisher, M.Q.; Anderson, Robert F.

2003-01-01

This paper describes a rapid procedure that allows precise analysis of Mo, Cd, U and Th in sediment samples as small as 10 mg by using a novel approach that utilizes a "pseudo" isotope dilution for Th and conventional isotope dilution for Mo, Cd and U by ICP-MS. Long-term reproducibility of the method is between 2.5 and 5% with an advantage of rapid analysis on a single digestion of sediment sample and the potential of adding other elements of interest if so desired. Application of this method to two piston cores collected near the mouth of the Patuxent River in Chesapeake Bay showed that the accumulation of authigenic Mo and Cd varied in response to the changing bottom water redox conditions, with anoxia showing consistent oscillations throughout both pre-industrial and industrial times. Accumulation of authigenic U shows consistent oscillations as well, without any apparent increase in productivity related to anoxic trends. Degrees of Mo and Cd enrichment also inversely correlate to halophilic microfaunal assemblages already established as paleoclimate proxies within the bay indicating that bottom water anoxia is driven in part by the amount of freshwater discharge that the area receives. ?? 2002 Elsevier Science Ltd. All rights reserved.

Grain Refinement by Authigenic Inoculation Inherited from the Medium-Range Order Structure of Ni-Cr-W Superalloy

NASA Astrophysics Data System (ADS)

Gao, Zhongtang; Hu, Rui; Guo, Wei; Zhang, Chuanwei

2018-05-01

The combination of liquidus casting and thermal control solidification furnace was applied to obtain a fine-grained ingot. A rapid quenching method and x-ray diffraction measurement were used to investigate the effect of authigenic inoculation on grain refinement. The structure factor S( Q) of liquid Ni -Cr-W superalloy at 1400 °C (Liquidus temperature) and bright-field image of the microstructures quenched from 1400 °C have been measured by the high-temperature x-ray diffractometer and the transmission electron microscopy (TEM), respectively. The results show that a pre-peak exists on a S( Q) curve at the liquidus temperature. The clusters of atom in rapidly quenched microstructures obtained by isothermal heat treatment at 1400 °C were studied using TEM. Meanwhile, the effect of isothermal different temperatures on rapidly quenched microstructures was studied. The results also show that there are only the globular, equiaxed grains distributed in the solidification structure. These particles are inherited from the medium-range order structure, which is beneficial for grain refinement. The normalized work-hardening rate-strain curve indicates the work-hardening rate of fine grain is higher than that of conventional grain at the same temperature and the same deformation.

Authigenic carbonate precipitates from the NE Black Sea: a mineralogical, geochemical, and lipid biomarker study

NASA Astrophysics Data System (ADS)

Bahr, A.; Pape, T.; Bohrmann, G.; Mazzini, A.; Haeckel, M.; Reitz, A.; Ivanov, M.

2009-04-01

Carbonate precipitates recovered from 2,000 m water depth at the Dolgovskoy Mound (Shatsky Ridge, north eastern Black Sea) were studied using mineralogical, geochemical and lipid biomarker analyses. The carbonates differ in shape from simple pavements to cavernous structures with thick microbial mats attached to their lower side and within cavities. Low δ13C values measured on carbonates (-41 to -32‰ V-PDB) and extracted lipid biomarkers indicate that anaerobic oxidation of methane (AOM) played a crucial role in precipitating these carbonates. The internal structure of the carbonates is dominated by finely laminated coccolith ooze and homogeneous clay layers, both cemented by micritic high-magnesium calcite (HMC), and pure, botryoidal, yellowish low-magnesium calcite (LMC) grown in direct contact to microbial mats. δ18O measurements suggest that the authigenic HMC precipitated in equilibrium with the Black Sea bottom water while the yellowish LMC rims have been growing in slightly 18O-depleted interstitial water. Although precipitated under significantly different environmental conditions, especially with respect to methane availability, all analysed carbonate samples show lipid patterns that are typical for ANME-1 dominated AOM consortia, in the case of the HMC samples with significant contributions of allochthonous components of marine and terrestrial origin, reflecting the hemipelagic nature of the primary sediment.

Organic Matter Remineralization Predominates Phosphorus Cycling in the Mid-Bay Sediments in the Chesapeake Bay

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

Sunendra, Joshi R.; Kukkadapu, Ravi K.; Burdige, David J.

2015-05-19

The Chesapeake Bay, the largest and most productive estuary in the US, suffers from varying degrees of water quality issues fueled by both point and non–point source nutrient sources. Restoration of the bay is complicated by the multitude of nutrient sources, their variable inputs and hydrological conditions, and complex interacting factors including climate forcing. These complexities not only restrict formulation of effective restoration plans but also open up debates on accountability issues with nutrient loading. A detailed understanding of sediment phosphorus (P) dynamics enables one to identify the exchange of dissolved constituents across the sediment- water interface and aid tomore » better constrain mechanisms and processes controlling the coupling between the sediments and the overlying waters. Here we used phosphate oxygen isotope ratios (δ18Op) in concert with sediment chemistry, XRD, and Mössbauer spectroscopy on the sediment retrieved from an organic rich, sulfidic site in the meso-haline portion of the mid-bay to identify sources and pathway of sedimentary P cycling and to infer potential feedback effect on bottom water hypoxia and surface water eutrophication. Isotope data indicate that the regeneration of inorganic P from organic matter degradation (remineralization) is the predominant, if not sole, pathway for authigenic P precipitation in the mid-bay sediments. We interpret that the excess inorganic P generated by remineralization should have overwhelmed any bottom-water and/or pore-water P derived from other sources or biogeochemical processes and exceeded saturation with respect to authigenic P precipitation. It is the first research that identifies the predominance of remineralization pathway against remobilization (coupled Fe-P cycling) pathway in the Chesapeake Bay. Therefore, these results are expected to have significant implications for the current understanding of P cycling and benthic-pelagic coupling in the bay, particularly on the source and pathway of P that sustains hypoxia and supports phytoplankton growth in the surface water.« less

Carbon, oxygen and strontium isotopic constraints on fluid sources, temperatures and biogeochemical processes during the formation of seep carbonates - Secchia River site, Northern Apennines

NASA Astrophysics Data System (ADS)

Viola, Irene; Capozzi, Rossella; Bernasconi, Stefano M.; Rickli, Jörg

2017-07-01

Understanding authigenic seep carbonate formation provides clues for hydrocarbon exploration and insights into contributions to gas budgets of marine environments and the atmosphere. Seep carbonates discovered in the outcropping succession along the Secchia riverbanks (near Modena, Italy) belong to the Argille Azzurre Formation of Early Pleistocene age deposited in an upper shelf environment overlying the Miocene foredeep successions, which include hydrocarbon fields. The fluid migration from the hydrocarbon fields, up to the surface, is presently active on land and started in the marine succession during the Late Miocene. Authigenic globular carbonate concretions and carbonate chimneys are interspersed along the strata throughout the section. A comprehensive geochemical characterisation of the carbonates has been carried out to understand the processes leading to their formation. The carbonate concretions are the record of past hydrocarbon vents linked to the Miocene petroleum system of the Northern Apennines. The samples are composed of > 50% microcrystalline dolomite. The δ13C signatures identify two groups in the samples according to different type of formation processes. Globular concretions have positive values that suggest an influence of CO2 associated to secondary methanogenesis due to microbial degradation of higher hydrocarbons. The analysed chimney, with negative δ13C values, is interpreted as former conduit where carbonate precipitation is promoted by Anaerobic Oxidation of Methane coupled with Sulfate Reduction. The δ18O range, coupled with 87/86Sr signatures, indicate that the contribution of deep connate water from the Miocene reservoirs is up to 23% during the formation of the globular concretions. The connate water occurrence is also documented by higher ambient temperatures. The different isotope signatures in seep carbonates result from the relative contribution of the recognised gas and water components, linked to different plumbing systems and fluid supply from a well-defined hydrocarbon field. The seep carbonate characteristics have enlightened variations in biogeochemical processes, which can be rarely quantified in ancient and present-day marine environments.

Provenance, diagenesis, tectonic setting and reservoir quality of the sandstones of the Kareem Formation, Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

Zaid, Samir M.

2013-09-01

The Middle Miocene Kareem sandstones are important oil reservoirs in the southwestern part of the Gulf of Suez basin, Egypt. However, their diagenesis and provenance and their impact on reservoir quality, are virtually unknown. Samples from the Zeit Bay Oil Field, and the East Zeit Oil Field represent the Lower Kareem (Rahmi Member) and the Upper Kareem (Shagar Member), were studied using a combination of petrographic, mineralogical and geochemical techniques. The Lower Rahmi sandstones have an average framework composition of Q95F3.4R1.6, and 90% of the quartz grains are monocrystalline. By contrast, the Upper Shagar sandstones are only slightly less quartzose with an average framework composition of Q76F21R3 and 82% of the quartz grains are monocrystalline. The Kareem sandstones are mostly quartzarenite with subordinate subarkose and arkose. Petrographical and geochemical data of sandstones indicate that they were derived from granitic and metamorphic terrains as the main source rock with a subordinate quartzose recycled sedimentary rocks and deposited in a passive continental margin of a syn rift basin. The sandstones of the Kareem Formation show upward decrease in maturity. Petrographic study revealed that dolomite is the dominant cement and generally occurs as fine to medium rhombs pore occluding phase and locally as a grain replacive phase. Authigenic quartz occurs as small euhedral crystals, locally as large pyramidal crystals in the primary pores. Authigenic anhydrites typically occur as poikilotopic rhombs or elongate laths infilling pores but also as vein filling cement. The kaolinite is a by-product of feldspar leaching in the presence of acidic fluid produced during the maturation of organic matter in the adjacent Miocene rocks. Diagenetic features include compaction; dolomite, silica and anhydrite cementation with minor iron-oxide, illite, kaolinite and pyrite cements; dissolution of feldspars, rock fragments. Silica dissolution, grain replacement and carbonate dissolution greatly enhance the petrophysical properties of many sandstone samples.

K-Ar age constrains on chemically weathered granitic basement rocks (saprolites) in Scandinavia

NASA Astrophysics Data System (ADS)

Margreth, Annina; Fredin, Ola; Viola, Giulio; Knies, Jochen; Sørlie, Ronald; Lie, Jan-Erik; Margrethe Grandal, Else; Zwingmann, Horst; Vogt, Christoph

2017-04-01

Remnants of in-situ weathered bedrock, saprolite, are found in several locations in Scandinavia. Saprolites contain important information about past climate conditions and landscape evolution, although their age and genesis are commonly difficult to constrain. It is generally thought that clay-poor, coarse-grained (arêne) saprolites, mostly occurring as thin regolith blankets or in larger outcrops, formed in temperate climate during the Cenozoic, whereas clay-rich (argillic) saprolites, commonly restricted to small, fracture-bounded outcrops, formed in (sub-)tropical climate during the Mesozoic. Recent methodological and conceptual advances in K-Ar dating of illite-bearing fault rocks have been applied to date clay-rich saprolites. To test the K-Ar dating technique for saprolites, we first selected an offshore site in the Viking Graben of the North Sea, where weathered and fractured granitic basement highs have been drilled during petroleum exploration, and an abandoned kaolin mine in Southern Sweden. Both targets provide independent age control through the presence of overlying Mesozoic sedimentary rocks. Clay-rich saprolites occurring in fractured basement rocks were additionally sampled in a joint valley landscape on the southwestern coast of Norway, which can be regarded as the possible onland correlative to the offshore basement high. In order to offer a sound interpretation of the obtained K-Ar ages, the mineralogical and chemical composition of the saprolites requires a thorough characterization. Scanning electron microscopy of thin sections, integrated by XRD and XRF analysis, reveals the progressive transformation of primary granitic rock minerals into secondary clay minerals. The authigenesis of illite is particularly important to understand, since it is the only K-bearing clay mineral that can be dated by the K-Ar method. K-feldspars and mica are the common primary K-bearing minerals, from which illite can be formed. While progressive leaching of interlayer potassium is observed in micas without significant modification of the mineral structure, K-feldspars are gradually dissolved with concomitant precipitation of illite, smectite and kaolinite. Individual illite minerals are difficult to identify, but low-K contents in smectite point to small amounts of illite-interlayers. This finding is supported by XRD patterns (powder analyses on clay size fractions) that lack a clear 10 Å peak indicating the presence of illite/mica, but show a prominent and slight asymmetric 14 Å peak representing smectite with potential low (<10 %) illite-interlayer content. In agreement with previous models of diminishing contamination of protolithic K-bearing phases in the finest grain size fractions, K-Ar ages invariably decrease with grain size suggesting that the finest grain-size is predominantly composed of authigenic, syn-weathering illite, whose age can thus be used to constrain the timing of saprolitization. The obtained Late Permian to Late Triassic ages i) are in accordance with independent age constraints supporting previous hypotheses of intense chemical weathering during the Mesozoic and ii) correlate with similar K-Ar ages obtained from nearby brittle faults suggesting a genetic relationship between weathering and brittle deformation. The combined investigation and K-Ar dating of illite-bearing fractured and weathered bedrock provides new insights into the tectonic and climatic evolution of the Scandinavian landscape prior to the major, and often obliterating, Quaternary glaciations.

Rocks and Minerals.

ERIC Educational Resources Information Center

Naturescope, 1987

1987-01-01

Provides background information on rocks and minerals, including the unique characteristics of each. Teaching activities on rock-hunting and identification, mineral configurations, mystery minerals, and growing crystals are provided. Reproducible worksheets are included for two of the activities. (TW)

The Sanrafaelic remagnetization revisited: Magnetic properties and magnetofabrics of Cambrian-Ordovician carbonates of the Eastern Precordillera of San Juan, Argentina

NASA Astrophysics Data System (ADS)

Fazzito, Sabrina Y.; Rapalini, Augusto E.; Poiré, Daniel G.

2017-11-01

Systematic rock-magnetic and magnetofabric studies were carried out on samples from twenty-three palaeomagnetic sites distributed on the La Laja, Zonda, La Flecha, La Silla and San Juan Formations, which constitute a thick middle Cambrian to early Ordovician carbonate sequence exposed in the Eastern Precordillera of Argentina. Previous palaeomagnetic studies on these rocks showed that this succession is characterized by a recent full overprint in the lower levels and a post-tectonic Permian remagnetization associated to the widespread Sanrafaelic event in the upper part. Our investigation revealed that the fluctuations of the magnetic properties are stratigraphically (lithologically) controlled. Anisotropy of magnetic and anhysteretic susceptibility measurements defined consistent fabrics along the entire section that switch progressively from "inverse", at the bottom, to "normal", at the top, with "intermediate" fabrics occurring mainly at medium levels. Degree of dolomitization significantly affects many rock-magnetic parameters, but appears unrelated to the presence of the Permian remagnetization, which is determined to reside in magnetite despite the complex magnetic mineralogy shown by the studied carbonates. Hysteresis cycles of rocks affected by the Sanrafaelic remagnetization are governed by ferromagnetic fractions showing a clear difference respect to those not affected and characterized by the dominance of paramagnetic or diamagnetic signals. The magnetic fabrics and mineralogical characterization rule out a thermoviscous origin and suggest a chemical remagnetization originated in the authigenic formation of magnetite for the Sanrafaelic overprint. X-ray diffraction analyses indicate that clay minerals are virtually absent in the whole succession with no traces of illite in any sample, discarding burial diagenesis of clay minerals for the origin of the remagnetization. Lack of late Palaeozoic magmatic rocks near the study area difficults correlation of this event with hydrothermal brines as well as casts serious doubts on any effect produced by an assumed geothermal anomaly associated with the Permo-Triassic Choiyoi magmatic province. The original model of remagnetization associated to chemically active fluids expelled from the San Rafael Orogen towards the foreland still holds as a viable mechanism.

Decoupling of paramagnetic and ferrimagnetic AMS development during the experimental chemical compaction of illite shale powder

NASA Astrophysics Data System (ADS)

Bruijn, Rolf H. C.; Almqvist, Bjarne S. G.; Hirt, Ann M.; Benson, Philip M.

2013-03-01

Inclination shallowing of detrital remanent magnetization in sedimentary strata has solely been constrained for the mechanical processes associated with mud deposition and shallow compaction of clay-rich sediment, even though a significant part of mud diagenesis involves chemical compaction. Here we report, for the first time, on the laboratory simulation of magnetic assemblage development in a chemically compacting illite shale powder of natural origin. The experimental procedure comprised three compaction stages that, when combined, simulate the diagenesis and low-grade metamorphism of illite mud. First, the full extent of load-sensitive mechanical compaction is simulated by room temperature dry axial compression. Subsequently, temperature controlled chemical compaction is initiated by exposing the sample in two stages to amphibolite or granulite facies conditions (temperature is 490 to 750°C and confining pressure is 170 or 300 MPa) both in the absence (confining pressure only) and presence of a deformation stress field (axial compression or confined torsion). Thermodynamic equilibrium in the last two compaction stages was not reached, but illite and mica dehydroxylation initiated, thus providing a wet environment. Magnetic properties were characterized by magnetic susceptibility and its anisotropy (AMS) in both high- and low-applied field. Acquisition of isothermal remanent magnetization (IRM), stepwise three-component thermal de-magnetization of IRM and first-order reversal curves were used to characterize the remanence-bearing minerals. During the chemical compaction experiments ferrimagnetic iron-sulphides formed after reduction of magnetite and detrital pyrite in a low sulphur fugacity environment. The degree of low-field AMS is unaffected by porosity reduction from 15 to ˜1 per cent, regardless of operating conditions and compaction history. High-field paramagnetic AMS increases with compaction for all employed stress regimes and conditions, and is attributed to illite transformation to iron-bearing mica. AMS of authigenic iron-sulphide minerals remained constant during compaction indicating an independence of ferrimagnetic fabric development to chemical compaction in illite shale powder. The decoupling of paramagnetic and ferrimagnetic AMS development during chemical compaction of pelite contrasts with findings from mechanical compaction studies.

In-situ observation of the transformation of amorphous calcium phosphate to crystalline hydroxyapatite

NASA Astrophysics Data System (ADS)

Stammeier, Jessica; Hippler, Dorothee; Mavromatis, Vasileios; Sacher, Stephan; Dietzel, Martin

2016-04-01

Amorphous calcium phosphate (Ca3(PO4)2*nH2O; ACP) is often a precursor phase of the mineral (hydroxy-) apatite (Ca5(PO4)3(OH)) that can be formed in natural settings during both authigenic and biogenic mineral formation. Particularly, in the biomineralization process of fish tissue, ACP has shown to be an important transient phase. In solution ACP rapidly transforms into the crystalline phase. The transformation rate highly depends on the physico-chemical conditions of the solution: Ca & P availability, pH and temperature. In natural settings Ca can be provided by different sources: from (1) seawater, (2) porewater, or (3) diagenetically-altered carbonates, whereas local supersaturation of P can be induced by microbial activity. In this study, we performed phosphate precipitation experiments in order to monitor the transformation process of the ACP to crystalline hydroxyapatite (HAP) using in-situ Raman spectroscopy. During the experiments the temperature was kept constant at 20.0 ± 0.01 ° C and pH at 9 ± 0.1. 50 ml of 0.3 CaCl 2H2O was titrated at a rate of 5 ml/min to an equal volume of 0.2 M Na2HPO4. The pH was kept constant by titration of 1 M NaOH. During the experiment samples were taken from the solution and instantly filtered. The obtained solid samples were lyophilized and analyzed with XRD, ATR and SEM. The respective solution samples were analyzed using ion chromatography and ICP OES, coupling the spectroscopic data with detailed solution chemistry data. We observed transformation of ACP to HAP to occur within 14 hours, illustrated in a clear peak shift in Raman spectra from 950 cm-1 to 960 cm-1. The obtained results are discussed in the aspects of distribution of major elements during the formation of phosphates and/or the diagenetic alteration of carbonates to phosphates in geologic settings. Financial support by DFG-FG 736 and NAWI Graz is kindly acknowledged.

New Insights into an Old Cycle: The Marine Phosphorus Cycle and the Formation of Critical Phosphate Rock Resources (Invited)

NASA Astrophysics Data System (ADS)

Filippelli, G. M.

2010-12-01

The cycling and geochemistry of phosphorus (P) in the marine environment is a critical component of biological productivity and of resource availability: P control the long-term carbon cycle via its role as a limiting nutrient, and the burial and concentration of P within marine sediments dictates the quality and availability of P as a fertilizer component from a resources standpoint. Given the projections of severe P fertilizer limitation over the next several centuries, understanding the controls on P geochemistry and concentration into a minable resource is critical in sustaining global populations. Several critical aspects of the marine P cycle have been uncovered over the past few decades which have clarified our understanding of P burial and concentration. First, the initial authigenic process of P mineralization within marine sediments, termed phosphogenesis, seems to occur regardless of marine setting. Phosphogenesis results from the release of P into sedimentary pore waters from organic and oxide-bound fractions, and the subsequent supersaturation with respect to carbonate fluorapatite. In sediment-starved basins with significant upwelling-driven productivity, the supply of P into sedimentary pore waters can be so high that visibly apparent layers of carbonate fluorapatite can be formed. Even in such environments, however, the mineral P content is too low to be of economic value unless it has undergone concentration via sediment reworking, a common occurrence in some dynamic continental margin environments. Thus, a combination of phosphogenesis in a high productivity setting plus sediment starvation plus condensation via reworking are necessary to produce phosphorites, sedimentary rocks with high P contents which are ideal as fertilizer-grade P resources. Given these special marine conditions, phosphorites are largely distributed along ancient marine environments (with the exception of the nearly-depleted atoll guano reserves). The largest currently-identified minable reservoirs of ore-grade P are found in the United States, in China, and in Morocco. Numerous less-economic sedimentary deposits exist, but these deposits are more dilute and represent former marine settings without the trifecta of productivity, geochemistry and sedimentology that makes phosphorites economically viable.

Cryptic Carbonate Alteration in Orogenic Sedimentary Basins: Saving the Signal

NASA Astrophysics Data System (ADS)

Ingalls, M.; Rowley, D. B.; Colman, A. S.; Currie, B.; Snell, K. E.

2017-12-01

The clumped isotope thermometer (T(Δ47)) is arguably one of the most important tools introduced to the fields of paleoclimatology and tectonics in the past decade. However, we measure clumped isotope abundances in natural materials collected from sedimentary basins, many of which have experienced complex thermal and fluid interaction histories. Throughout the history of an authigenic mineral—from precipitation to exhumation—there are multiple opportunities to overprint isotopic signatures and obscure the essential fingerprint of primary environmental conditions. Therefore, we must critically assess the presence or absence of textural and isotopic alteration after original mineral formation. We investigate Paleocene shallow marine carbonates from the Xigaze forearc (S. Tibet) that yield demonstrably non-marine δ18Oc values (-12 to -21‰ VPDB), significant cm-scale variation in clumped isotope values (0.456 to 0.721‰, or 80 to 20°C), and have experienced temperatures >150°C for longer than 10 My based on ages of partial resetting of zircon He. δ18Oc values require complete oxygen isotopic exchange during fluid-buffered diagenesis, but display little visible evidence of recrystallization. Further, within the constraints of the Xigaze forearc time-temperature history, we explain the intrasample Δ47 variation by a combination of the two known mechanisms of Δ47 alteration: (1) water-rock recrystallization and (2) solid-state reordering. The definitively altered marine carbonates pass the same optical screening tests for secondary mineralization traditionally used when employing δ18Oc or Δ47 as proxies for ancient Earth conditions, suggesting that alteration occurred on a spatial scale irresolvable by standard techniques. Therefore, higher spatial resolution detection of carbonate alteration is required to prevent incorrect or incomplete interpretation of carbonate isotopic values. We employ a suite of isotopic (δ18O, δ13C, Δ47, U/Pb), geochemical (EBSD), and optical (cathodoluminescence) techniques to identify evidence and episodes of micro-recrystallization. Our ability to screen for cryptic alteration and place isotopic alteration events within the constraints of a rock's diagenetic history is critical for the future use of the carbonate proxy record in geological applications.

Textural and isotopic evidence for Ca-Mg carbonate pedogenesis

NASA Astrophysics Data System (ADS)

Diaz-Hernandez, J. L.; Sánchez-Navas, A.; Delgado, A.; Yepes, J.; Garcia-Casco, A.

2018-02-01

Models for evaluating the terrestrial carbon cycle must take into account not only soil organic carbon, represented by a mixture of plant and animal remains, but also soil inorganic carbon, contained in minerals, mainly in calcite and dolomite. Thick soil caliches derived from weathering of mafic and ultramafic rocks must be considered as sinks for carbon storage in soils. The formation of calcite and dolomite from pedogenic alteration of volcanic tephras under an aridic moisture regime is studied in an unusually thick 3-m soil profile on Gran Canaria island (Canary Islands, Spain). The biological activity of the pedogenic environment (soil respiration) releases CO2 incorporated as dissolved inorganic carbon (DIC) in waters. It drives the formation of low-magnesian calcite and calcian dolomite over basaltic substrates, with a δ13C negative signature (-8 to -6‰ vs. V-PDB). Precipitation of authigenic carbonates in the soil is accompanied by the formation of Mg-rich clay minerals and quartz after the weathering of basalts. Mineralogical, textural, compositional, and isotopic variations throughout the soil profile studied indicate that dolomite formed at greater depths and earlier than the calcite. The isotopic signatures of the surficial calcite and deeper dolomite crusts are primary and resulted from the dissolution-precipitation cycles that led to the formation of both types of caliches under different physicochemical conditions. Dolomite formed within a clay-rich matrix through diffusive transport of reactants. It is precipitated from water with more negative δ18O values (-1.5 to -3.5‰ vs. V-SMOW) in the subsoil compared to those of water in equilibrium with surficial calcite. Thus, calcite precipitated after dolomite, and directly from percolating solutions in equilibrium with vadose water enriched in δ18O (-0.5 to +1.5‰) due to the evaporation processes. The accumulation of inorganic carbon reaches 586.1 kg m-2 in the soil studied, which means that the carbon sequestration capacity of mafic rocks must be taken into account for certain terrestrial settings. Dolomite together with calcite should be assessed when quantifying carbon stored in arid-semiarid soils as a result of the natural weathering processes.

Organic matter control on the distribution of arsenic in lake sediments impacted by ~65years of gold ore processing in subarctic Canada.

PubMed

Galloway, Jennifer M; Swindles, Graeme T; Jamieson, Heather E; Palmer, Michael; Parsons, Michael B; Sanei, Hamed; Macumber, Andrew L; Timothy Patterson, R; Falck, Hendrik

2018-05-01

Climate change is profoundly affecting seasonality, biological productivity, and hydrology in high northern latitudes. In sensitive subarctic environments exploitation of mineral resources led to contamination and it is not known how cumulative effects of resource extraction and climate warming will impact ecosystems. Gold mines near Yellowknife, Northwest Territories, subarctic Canada, operated from 1938 to 2004 and released >20,000t of arsenic trioxide (As 2 O 3 ) to the environment through stack emissions. This release resulted in elevated arsenic concentrations in lake surface waters and sediments relative to Canadian drinking water standards and guidelines for the protection of aquatic life. A meta-analytical approach is used to better understand controls on As distribution in lake sediments within a 30-km radius of historic mineral processing activities. Arsenic concentrations in the near-surface sediments range from 5mg·kg -1 to over 10,000mg·kg -1 (median 81mg·kg -1 ; n=105). Distance and direction from the historic roaster stack are significantly (p<0.05) related to sedimentary As concentration, with highest As concentrations in sediments within 11km and lakes located downwind. Synchrotron-based μXRF and μXRD confirm the persistence of As 2 O 3 in near surface sediments of two lakes. Labile organic matter (S1) is significantly (p<0.05) related to As and S concentrations in sediments and this relationship is greatest in lakes within 11km from the mine. These relations are interpreted to reflect labile organic matter acting as a substrate for microbial growth and mediation of authigenic precipitation of As-sulphides in lakes close to the historic mine where As concentrations are highest. Continued climate warming is expected to lead to increased biological productivity and changes in organic geochemistry of lake sediments that are likely to play an important role in the mobility and fate of As in aquatic ecosystems. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of mining and related activities on the sediment trace element geochemistry of Lake Coeur D'Alene, Idaho, USA. Part I: Surface sediments

USGS Publications Warehouse

Horowitz, Arthur J.; Elrick, Kent A.; Cook, Robert B.

1993-01-01

During the summer of 1989 surface sediment samples were collected in Lake Coeur d'Alene, the Coeur d'Alene River and the St Joe River, Idaho, at a density of approximately one sample per square kilometre. Additional samples were collected from the banks of the South Fork of the Coeur d'Alene and the Coeur d'Alene Rivers in 1991. All the samples were collected to determine trace element concentrations, partitioning and distribution patterns, and to relate them to mining, mining related and discharge operations that have occurred in the Coeur d'Alene district since the 1880s, some of which are ongoing.Most of the surface sediments in Lake Coeur d'Alene north of Conkling Point and Carey Bay are substantially enriched in Ag, As, Cu, Cd, Hg, Pb, Sb and Zn relative to unaffected sediments in the southern portion of the lake near the St Joe River. All the trace element enriched sediments are extremely fine grained (mean grain sizes « 63 μm). Most of the enriched trace elements, based on both the chemical analyses of separated heavy and light mineral fractions and a two step sequential extraction procedure, are associated with an operationally defined Fe oxide phase; much smaller percentages are associated either with operationally defined organics/sulphides or refractory phases.The presence, concentration and distribution of the Fe oxides and heavy minerals indicates that a substantial portion of the enriched trace elements are probably coming from the Coeur d'Alene River, which is serving as a point source. Within the lake, this relatively simple point source pattern is complicated by a combination of (1) the formation of trace element rich authigenic Fe oxides that appear to have reprecipitated from material solubilized from anoxic bed sediments and (2) physical remobilization by currents and wind driven waves. The processes that have caused the trace element enrichment in the surface sediments of Lake Coeur d'Alene are likely to continue for the foreseeable future.

Diagenetic Iron Cycling in Ancient Alkaline Saline Lacustrine Sedimentary Rocks: A Case Study on the Jurassic Brushy Basin Member of the Morrison Formation, Colorado Plateau, USA

NASA Astrophysics Data System (ADS)

Potter-McIntyre, S. L.; Chan, M. A.; McPherson, B. J. O. L.

2014-12-01

The upper part of the Brushy Basin Member in the Four Corners region of the U.S. was deposited in an ephemeral alkaline saline lake system with copious input of volcanic ash. The variegated shale formation provides a setting for the study of early diagenetic iron cycling that records the action of alkaline saline fluid chemistries reacting with volcaniclastic sediments in the presence of microbes. A bull's-eye pattern of authigenic minerals with increasing alteration towards the basinal center similar to modern alkaline saline lakes provides evidence for an extreme paleoenvironmental interpretation. The purpose of this research is to document specific factors, such as reactive sediments, microbial influences, and grain size that affect concretion formation and iron cycling in an ancient extreme environment. Three broad diagenetic facies are interpreted by color and associated bioturbation features: red, green and intermediate. Diagenetic facies reflect meter-scale paleotopography: red facies represent shallow water to subaerial, oxidizing conditions; green facies reflect saturated conditions and reducing pore water chemistry shortly after deposition, and intermediate facies represent a combination of the previous two conditions. Evidence of biotic influence is abundant and trace fossils exhibit patterns associated with the diagenetic facies. Red diagenetic facies typically contain burrows and root traces and green diagenetic facies exhibit restricted biotic diversity typically limited to algal molds (vugs). Microbial fossils are well-preserved and are in close proximity to specific iron mineral textures suggesting biotic influence on the crystal morphology. Three categories of concretions are characterized based on mineralogy: carbonate, iron (oxyhydr)oxide and phosphate concretions. Concretion mineralogy and size vary within an outcrop and even within a stratigraphic horizon such that more than one main category is typically present in an outcrop. Variation in concretion mineralogy and morphology within the Brushy Basin Member suggests that alkaline saline fluid chemistries in concert with microbial interaction created diagenetic microenvironments within a larger lake system to influence iron cycling and these reactions can be spatially variable even on 10s of cm scales.

Survival of the fittest: phosphorus burial in the sulfidic deep Black Sea

NASA Astrophysics Data System (ADS)

Kraal, Peter; Dijkstra, Nikki; Behrends, Thilo; Slomp, Caroline

2016-04-01

The Black Sea is characterized by permanently anoxic and sulfidic deep waters. Studies of the mechanisms of P burial in such a setting can be used to improve our understanding of P cycling in modern coastal systems undergoing eutrophication and ancient oceans during periods of anoxia in Earth's past. Here, we present phosphorus and iron (Fe) pools as determined in surface sediments along a transect from oxic shallow waters to sulfidic deep waters in the northwestern Black Sea, using a combination of bulk chemical analyses and micro-scale X-ray fluorescence (μXRF) and X-ray absorption spectroscopy (μXAS). We show that under oxic bottom water conditions, ferric iron oxides (Fe(III)ox) in surficial sediment efficiently scavenge dissolved phosphate from pore waters. Under these conditions, Fe(III)ox-bound P constitutes the main P pool at the sediment surface, but rapidly declines with depth in the sediment due to anoxic diagenesis. The transition from shallow (oxic) to deep (sulfidic) waters along the depth transect is reflected in a slight increase in the fraction of organic P. We also show evidence for authigenic calcium phosphate formation under sulfidic conditions at relatively low dissolved PO4 concentrations. Furthermore, we provide spectroscopic evidence for the presence of Fe(II)-Mn(II)-Mg-P minerals in sediments of the sulfidic deep basin. We hypothesize that these minerals are formed as a result of input of Fe(III)ox-P from shallower waters and subsequent transformation in either the water column or sediment. This finding suggests an unexpected strength of Fe-P shuttling from the shelf to the deep basin. While the presence of Fe-P species in such a highly sulfidic environment is remarkable, further analysis suggests that this P pool may not be quantitatively significant. In fact, our results indicate that some of the P that is interpreted as Fe-bound P based on chemical extraction may in fact be Ca-associated PO4 consisting of a combination of fish debris and adsorbed P.

Depositionally controlled recycling of iron and sulfur in marine sediments and its isotopic consequences

NASA Astrophysics Data System (ADS)

Riedinger, N.; Formolo, M.; Arnold, G. L.; Vossmeyer, A.; Henkel, S.; Sawicka, J.; Kasten, S.; Lyons, T. W.

2011-12-01

The continental margin off Uruguay and Argentina is characterized by highly dynamic depositional conditions. This variable depositional regime significantly impacts the biogeochemical cycles of iron and sulfur. Mass deposit related redeposition of reduced minerals can lead to the reoxidation of these phases and thus to an overprint of their geochemical primary signatures. Due to rapid burial these oxidized phases are still present in deeper subsurface sediments. To study the effects of sediment relocation on the sulfur and iron inventory we collected shallow and deep subsurface sediment samples via multicorer and gravity cores, respectively, in the western Argentine Basin during the RV Meteor Expedition M78/3 in May-July 2009. The samples were retrieved from shelf, slope and deep basin sites. The concentration and sulfur isotope composition of acid volatile sulfur (AVS), chromium reducible sulfur (CRS), elemental sulfur and total organic sulfur were determined. Furthermore, sequential iron extraction techniques were applied assess the distribution of iron oxide phases within the sediment. The investigated sediments are dominated by terrigenous inputs, with high amounts of reactive ferric iron minerals and only low concentrations of calcium carbonate. Total organic carbon concentrations show strong variation in the shallow subsurface sediments ranging between approximately 0.7 and 6.4 wt% for different sites. These concentrations do not correlate with water depths. Pore water accumulations of hydrogen sulfide are restricted to an interval at the sulfate-methane transition (SMT) zone a few meters below the sediment surface. In these deeper subsurface sediments pyrite is precipitated in this zone of hydrogen sulfide excess, whereas the accumulation of authigenic AVS and elemental sulfur (up to 2000 ppm) occurs at the upper and lower boundary of the sulfidic zone due the reaction of iron oxides with limited amounts of sulfide. Furthermore, our preliminary results indicate that there is a link between modern deposition in the shallow subsurface sediments and the long-term signals being buried and preserved in the deep subsurface layers. The data show that the burial of elemental sulfur into deep subsurface sediments can fuel the deep biosphere and has consequences for isotopic overprints tied, for example, to oxidation and disproportionation processes in the deeper sediments.

A geochronological 40Ar/39Ar and 87Rb/81Sr study of K-Mn oxides from the weathering sequence of Azul, Brazil

NASA Astrophysics Data System (ADS)

Ruffet, G.; Innocent, C.; Michard, A.; Féraud, G.; Beauvais, A.; Nahon, D.; Hamelin, B.

1996-06-01

KMn oxides of hollandite group minerals such as cryptomelane (K 1-2(Mn 3+, Mn 4+) 8O 16nH 2O) are often precipitated authigenically in weathering profiles. The presence of structural K allows these minerals to be dated by the KAr and 40Ar/ 39Ar methods, making it possible to study the progression of oxidation fronts during weathering processes. Within the context of a recent 40Ar/ 39Ar study of cryptomelane from the Azul Mn deposit in the Carajàs region (Amazônia, Brazil), Vasconcelos et al. (1994) defined three age clusters (65-69, 51-56, and 40-43 Ma) and proposed that they correspond to the episodic precipitation of the three generations of Mn oxide that have been identified in the deposit (Beauvais et al., 1987). We performed a laser probe 40Ar/ 39Ar and 87Rb/ 87Sr study on new samples from the same Mn deposit. Our 40Ar/ 39Ar data confirm that cryptomelane is a suitable mineral for 40Ar/ 39Ar dating, although in some cases we clearly identify the existence of 39Ar recoil effects. Although the corresponding age spectra are generally strongly disturbed, our results also confirm that the earliest cryptomelane generation is of Upper Cretaceous-Paleocene age. We obtained good plateau ages from veins and concretions of the second cryptomelane generation. Some of these results allow definition of a well-constrained age cluster at 46.7-48.1 Ma not observed by Vasconcelos et al. (1994). A petrographic study confirms that none of the samples analyzed in the present study contained material associated with the third generation of cryptomelane. We propose that these new results support the idea of a more or less continuous crystallization of KMn oxides, mainly constrained by local factors, rather than the model advanced by Vasconcelos et al. (1994), which suggests that each cryptomelane generation corresponds to distinct weathering events related to global climatic changes. 87Sr/ 86Sr data show large variations, clearly inherited from the 2.1 Ga parent rock of the Mn protore. The Rb/Sr results demonstrate that minimum fractionation occurs during cryptomelane crystallization, except for the latest generation, which is depleted in Sr. This precludes use of the Rb/Sr radiochronometer for dating secondary Mn oxides in laterites.

76 FR 2617 - Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-14

... 1219-AB64 Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust... comment period on the proposed rule addressing Lowering Miners' Exposure to Respirable Coal Mine Dust...), MSHA published a proposed rule, Lowering Miners' Exposure to Respirable Coal Mine Dust, Including...

A critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for Late Cretaceous global correlation

NASA Astrophysics Data System (ADS)

Wendler, Ines

2013-11-01

Climate variability is driven by a complex interplay of global-scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter-regional correlation, which in most cases cannot be obtained with biostratigraphic methods alone. Chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high-resolution correlation over large distances, but complications arise from a multitude of possible influences from local differences in biological, diagenetic and physico-chemical factors on individual δ13C records that can mask the global signal. To better assess the global versus local contribution in a δ13C record it is necessary to compare numerous isotopic records on a global scale. As a contribution to this objective, this paper reviews bulk sediment δ13Ccarb records from the Late Cretaceous in order to identify differences and similarities in secular δ13C trends that help establish a global reference δ13C record for this period. The study presents a global-scale comparison of twenty δ13C records from sections representing various palaeo-latitudes in both hemispheres and different oceanic settings from the Boreal, Tethys, Western Interior, Indian Ocean and Pacific Ocean, and with various diagenetic overprinting. The isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute δ13C values and variation in amplitude between the sites. These differences reflect the varying local influences e.g. from depositional settings, bottom water age and diagenetic history, whereas the concordant patterns in δ13C shifts might represent δ13C fluctuations in the global seawater dissolved inorganic carbon. The latter is modulated by variations in organic matter burial relative to re-mineralization, in the global-scale formation of authigenic carbonate, and in partitioning of carbon between organic carbon and carbonate sinks. These variations are mainly controlled by changes in climate and eustasy. Additionally, some globally synchronous shifts in the bulk δ13Ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment. Formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and, thus, can be globally synchronized by fluctuations in eustasy, atmospheric and oceanic oxygen levels or in large-scale oceanic circulation. Because the influence of early diagenetic cements on the bulk δ13Ccarb signal can, but need not be synchronized, chemostratigraphy should not be used as a stand-alone method for trans-continental correlation, and especially minor isotopic shifts have to be interpreted with utmost care. Nevertheless, the observed consistency of the δ13C correlations confirms global scale applicability of bulk sediment δ13C chemostratigraphy for the Late Cretaceous, including sediments that underwent lithification and burial diagenesis such as the sediments from the Himalayan and Alpine sections. Limitations arise from increased uncertainties (1) in sediments with very low carbonate content, (2) from larger δ13C variability in sediments from very shallow marine environments, (3) from unrecognized hiatuses or strong changes in sedimentation rates, and (4) in sections with short stratigraphic coverage or with few biostratigraphic marker horizons.

Mineral facilities of Africa and the Middle East

USGS Publications Warehouse

Eros, J.M.; Candelario-Quintana, Luissette

2006-01-01

This map displays over 1,500 mineral facilities in Africa and the Middle East. The mineral facilities include mines, plants, mills, or refineries of aluminum, cement, coal, copper, diamond, gold, iron and steel, nickel, platinum-group metals, salt, and silver, among others. The data used in this poster were compiled from multiple sources, including the 2004 USGS Minerals Yearbook (Africa and Middle East volume), Minerals Statistics and Information from the USGS Web site (http://minerals.usgs.gov/minerals/), and data collected by USGS minerals information country specialists. Data reflect the most recent published table of industry structure for each country. Other sources include statistical publications of individual countries, annual reports and press releases of operating companies, and trade journals. Due to the sensitivity of some energy commodity data, the quality of these data should be evaluated on a country-by-country basis. Additional information and explanation is available from the country specialists. See Table 1 for general information about each mineral facility site including country, location and facility name, facility type, latitude, longitude, mineral commodity, mining method, main operating company, status, capacity, and units.

Mineral Facilities of Latin America and Canada

USGS Publications Warehouse

Bernstein, Rachel; Eros, Mike; Quintana-Velazquez, Meliany

2006-01-01

This data set consists of records for over 900 mineral facilities in Latin America and Canada. The mineral facilities include mines, plants, smelters, or refineries of aluminum, cement, coal, copper, diamond, gold, iron and steel, nickel, platinum-group metals, salt, and silver, among others. Records include attributes such as commodity, country, location, company name, facility type and capacity if applicable, and generalized coordinates. The data were compiled from multiple sources, including the 2003 and 2004 USGS Minerals Yearbooks (Latin America and Candada volume), data to be published in the 2005 Minerals Yearbook Latin America and Canada Volume, minerals statistics and information from the USGS minerals information Web site (minerals.usgs.gov/minerals), and data collected by USGS minerals information country specialists. Data reflect the most recent published table of industry structure for each country. Other sources include statistical publications of individual countries, annual reports and press releases of operating companies,and trade journals. Due to the sensitivity of some energy commodity data, the quality of these data should be evaluated on a country-by-country basis. Additional information and explanation is available from the country specialists.

A Non-Steady-State Condition in Sediments at the Gashydrate Stability Boundary off West Spitsbergen: Evidence for Gashydrate Dissociation or Just Dynamic Methane Transport?

NASA Astrophysics Data System (ADS)

Treude, T.; Krause, S.; Bertics, V. J.; Steinle, L.; Niemann, H.; Liebetrau, V.; Feseker, T.; Burwicz, E.; Krastel, S.; Berndt, C.

2014-12-01

In 2008, a large area with several hundred methane plumes was discovered along the West Spitsbergen continental margin at water depths between 150 and 400 m (Westbrook et al. 2009, GRL 36, doi:10.1029/2009GL039191). Many of the observed plumes were located at the boundary of gas hydrate stability (~400 m water depth). It was speculated that the methane escape at this depth was correlated with gas hydrate destabilization caused by recent increases in water temperatures recorded in this region. In a later study, geochemical analyses of authigenic carbonates and modeling of heat flow data combined with seasonal changes in water temperature demonstrated that the methane seeps were active already prior to industrial warming but that the gas hydrate system nevertheless reacts very sensitive to even seasonal temperature changes (Berndt et al. 2014, Science 343: 284-287). Here, we report about a methane seep site at the gas hydrate stability boundary (394 m water depth) that features unusual geochemical profiles indicative for non-steady state conditions. Sediment was recovered with a gravity corer (core length 210 cm) and samples were analyzed to study porewater geochemistry, methane concentration, authigenic carbonates, and microbial activity. Porewater profiles revealed two zones of sulfate-methane transition at 50 and 200 cm sediment depth. The twin zones were confirmed by a double peaking in sulfide, total alkalinity, anaerobic oxidation of methane, and sulfate reduction. δ18O values sharply increased from around -2.8 ‰ between 0 and 126 cm to -1.2 ‰ below 126 cm sediment depth. While U/Th isotope measurements of authigenic seep carbonates that were collected from different depths of the core illustrated that methane seepage must be occurring at this site since at least 3000 years, the biogeochemical profiles suggest that methane flux must have been altered recently. By applying a multi-phase reaction-transport model using known initial parameters from the study site (e.g. water depth, temperature profile, salinity, and sediment surface concentrations of CH4, SO4, DIC, and POC) were able to show that the observed twin sulfate-methane transition zones are an ephemeral phenomenon occurring during increase of methane production in the sediment, which can be introduced by, e.g., gas hydrate dissociation.

Toward detection of supernova event near the earth based on high-resolution analysis of cosmogenic nuclide 10Be in marine sediments

NASA Astrophysics Data System (ADS)

Takiguchi, S.; Suganuma, Y.; Kataoka, R.; Yamaguchi, K. E.

2017-12-01

Cosmic rays react with substances in the Earth's atmosphere and form cosmogenic nuclides. The flux would abruptly increase with nearby supernova or terrestrial magnetic events such as reversal or excursion of terrestrial magnetism. The Earth must have been exposed to cosmic ray radiation for as long as 10 Ma, if any, by nearby supernova activities (Kataoka et al., 2014). Increased and prolonged activity of cosmic rays would affect Earth's climate through forming greenhouse gases and biosphere through damaging DNA. Therefore, interests have been growing as to whether and how past supernova events have ever left any fingerprints on them. However, detection of nearby supernova is still under debate (e.g., Knie et al., 2004) To detect long-term record of past supernova activities, we utilize cosmogenic nuclide 10Be because of its short residence time (1-2yr) in the atmosphere, simple transport process, and adequate half-life (1.36 kyr) which is nearly equivalent to the duration of present-day deep water circulation. Sediment samples collected from the equatorial western Pacific (706-825 kyr in age) were finely powdered and decomposed by mixed acids (HNO3, HF, and HClO4). Authigenic phase was also separated from bulk powders by leaching with a weak acid. Because quantitative separation of Be from samples is essential toward high-quality 10Be analysis, both Be-bearing fractions were applied to optimized anion exchange chromatography for Be separation, and Be abundance was measured by atomic absorption spectrometry. The 10Be abundance (10Be/9Be ratios) were measured by accelerator mass spectrometry. The authigenic phase showed temporal curve that is similar to that of bulk samples (Suganuma et al., 2012), reflecting the influence of relative paleo-intensity and utility of authigenic method. Increased data set in terms of sampling interval (density) and total age range would allow us to judge whether it could detect past supernova activities and how it appears when compared to the recent results of Wallner et al. (2016) using Fe isotopes. If past supernova activities are not detected, we then establish standard temporal curve, with higher resolution, of relative paleo-intensity of terrestrial magnetism and construct global ionization map as a function of terrestrial magnetism.

Review of selected global mineral industries in 2011 and an outlook to 2017

USGS Publications Warehouse

Menzie, W. David; Soto-Viruet, Yadira; Bermúdez-Lugo, Omayra; Mobbs, Philip M.; Perez, Alberto Alexander; Taib, Mowafa; Wacaster, Susan; ,

2013-01-01

This report reviews the world production of selected mineral commodities in 2011 and includes output projections (based on planned capacity expansions) through 2017. It also includes brief discussions of several issues that are of importance to the mineral sector, including the world economy, the availability of strategic minerals, significant company mergers and acquisitions in 2011, exploration investment made during the year, and the moves towards resource nationalization and expropriation of mineral assets by national Governments.

Sediment focusing creates 100-ka cycles in interplanetary dust accumulation on the Ontong Java Plateau

NASA Astrophysics Data System (ADS)

Higgins, Sean M.; Anderson, Robert F.; Marcantonio, Franco; Schlosser, Peter; Stute, Martin

2002-10-01

The accumulation of extraterrestrial 3He, a tracer for interplanetary dust particles (IDPs), in sediments from the Ontong Java Plateau (OJP; western equatorial Pacific Ocean) has been shown previously to exhibit a regular cyclicity during the late Pleistocene, with a period of ∼100 ka. Those results have been interpreted to reflect periodic variability in the global accretion of IDPs that, in turn, has been linked to changes in the inclination of Earth's orbit with respect to the invariable plane of the solar system. Here we show that the accumulation in OJP sediments of authigenic 230Th, produced by radioactive decay of 234U in seawater, exhibits a 100-ka cyclicity similar in phase and amplitude to that evident in the 3He record. We interpret the similar patterns of 230Th and 3He accumulation to reflect a common origin within the ocean-climate system. Comparing spatial and temporal patterns of sediment accumulation against regional patterns of biological productivity and against the well-established pattern of CaCO3 dissolution in the deep Pacific Ocean leads to the further conclusion that a common 100-ka cycle in accumulation of biogenic, authigenic and extraterrestrial constituents in OJP sediments reflects the influence of climate-related changes in sediment focusing, rather than changes in the rate of production or supply of sedimentary constituents.

Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

NASA Astrophysics Data System (ADS)

Pourmand, Ali; Marcantonio, Franco; Schulz, Hartmut

2004-04-01

High-resolution (one to two samples/ka) radionuclide proxy records from core 93KL in the northeastern Arabian Sea provide evidence for millennial climate variability over the past 110 ka. We interpret 230Th-normalized 232Th fluxes as a proxy for eolian input, and authigenic uranium concentrations as a proxy for past productivity. We attribute orbital and suborbital variations in both proxies to changes in the intensity of the southwest Indian Ocean monsoon. The highest 230Th-normalized 232Th fluxes occur at times that are consistent with the timing of the Younger Dryas, Heinrich events 1-7 and cold Dansgaard-Oeschger stadial events recorded in the GISP2 ice core. Such high dust fluxes may be due to a weakened southwest monsoon in conjunction with strengthened northwesterlies from the Arabian Peninsula and Mesopotamia. Authigenic uranium concentrations, on the other hand, are highest during warm Dansgaard-Oeschger interstadials when the southwest monsoon is intensified relative to the northwesterly winds. Our results also indicate that on orbital timescales maximum average eolian fluxes coincide with the timing of marine isotopic stage (MIS) 2 and 4, while minimum fluxes occur during MIS 1, 3 and 5. Although the forcing mechanism(s) controlling suborbital variabilities in monsoonal intensity is still debated, our findings suggest an atmospheric teleconnection between the low-latitude southwest monsoon and North Atlantic climate.

Release of Methane from Bering Sea Sediments During the Last Glacial Period

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

Mea Cook; Lloyd Keigwin

2007-11-30

Several lines of evidence suggest that during times of elevated methane flux the sulfate-methane transition zone (SMTZ) was positioned near the sediment-water interface. We studied two cores (from 700 m and 1457 m water depth) from the Umnak Plateau region. Anomalously low d13C and high d18O in benthic and planktonic foraminifera in these cores are the consequence of diagenetic overgrowths of authigenic carbonates. There are multiple layers of authigenic-carbonate-rich sediment in these cores, and the stable isotope compositions of the carbonates are consistent with those formed during anaerobic oxidation of methane (AOM). The carbonate-rich layers are associated with biomarkers producedmore » by methane-oxidizing archaea, archaeol and glyceryl dibiphytanyl glyceryl tetraether (GDGT). The d13C of the archaeol and certain GDGTs are isotopically depleted. These carbonate- and AOM-biomarker-rich layers were emplaced in the SMTZ during episodes when there was a high flux of methane or methane-rich fluids upward in the sediment column. The sediment methane in the Umnak Plateau region appears to have been very dynamic during the glacial period, and interacted with the ocean-atmosphere system at millennial time scales. The upper-most carbonate-rich layers are in radiocarbon-dated sediment deposited during interstitials 2 and 3, 28-20 ka, and may be associated with the climate warming during this time.« less

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS.

PubMed

Lin, Zhiyong; Sun, Xiaoming; Peckmann, Jörn; Lu, Yang; Strauss, Harald; Xu, Li; Lu, Hongfeng; Teichert, Barbara M A

2017-08-31

Different sulfur isotope compositions of authigenic pyrite typically result from the sulfate-driven anaerobic oxidation of methane (SO4-AOM) and organiclastic sulfate reduction (OSR) in marine sediments. However, unravelling the complex pyritization sequence is a challenge because of the coexistence of different sequentially formed pyrite phases. This manuscript describes a sample preparation procedure that enables the use of secondary ion mass spectroscopy (SIMS) to obtain in situ δ 34 S values of various pyrite generations. This allows researchers to constrain how SO4-AOM affects pyritization in methane-bearing sediments. SIMS analysis revealed an extreme range in δ 34 S values, spanning from -41.6 to +114.8‰, which is much wider than the range of δ 34 S values obtained by the traditional bulk sulfur isotope analysis of the same samples. Pyrite in the shallow sediment mainly consists of 34 S-depleted framboids, suggesting early diagenetic formation by OSR. Deeper in the sediment, more pyrite occurs as overgrowths and euhedral crystals, which display much higher SIMS δ 34 S values than the framboids. Such 34 S-enriched pyrite is related to enhanced SO4-AOM at the sulfate-methane transition zone, postdating OSR. High-resolution in situ SIMS sulfur isotope analyses allow for the reconstruction of the pyritization processes, which cannot be resolved by bulk sulfur isotope analysis.

Spatial and Temporal Variability in Sediment P Distribution and Speciation in Coastal Louisiana

NASA Astrophysics Data System (ADS)

Bowes, K.; White, J. R.; Maiti, K.

2017-12-01

Excess loading of phosphorus (P) and nitrogen (N) into aquatic systems leads to degradation of water quality and diminished important ecosystem services. In the Northern Gulf of Mexico (NGOM), excess P and N loading has led to a seasonally present hypoxic area with less than 2 mg/L O2 in bottom waters, approximating 26,000 km2 in 2017. A sequential extraction (SEDEX) method was performed on surficial sediments from five different coastal and shelf sites as a function of distance from the Mississippi River mouth in the NGOM. To better quantify temporal variability in P distribution and speciation, samples were collected during both low (August) and high (May) river flow regimes. Sequential extraction techniques have been successful in separating pools of P into exchangeable or loosely sorbed P, Fe-P, Authigenic-P, Detrital-P, and Organic-P. Preliminary results suggest Authigenic-P is approximately 3-6 times more concentrated in NGOM sediments than all other P pools. Fractionation results did not show a consistent trend with sediment depth. Sediment samples had an average moisture content of 58.72% ± 12.06% and an average bulk density of 0.582 ± 0.275 g/cm3. Continued analysis of P speciation and cycling in NGOM sediments is critical in understanding the driving force behind coastal eutrophication and informing effective nutrient management strategies.

Burial of redox-sensitive metals and organic matter in the equatorial Indian Ocean linked to precession

NASA Astrophysics Data System (ADS)

Pailler, Delphine; Bard, Edouard; Rostek, Frauke; Zheng, Yan; Mortlock, Richard; van Geen, Alexander

2002-03-01

Authigenic metals (uranium, cadmium, and molybdenum), organic carbon (OC) and total C37 alkenone (totC37) concentrations were measured for the last 350 kyr in core MD900963, located in the eastern equatorial Arabian Sea. Authigenic metal concentrations on a carbonate-free basis range between 1 and 17 ppm, 0.5 and 6 ppm, and 0.5 and 4 ppm for U, Cd, and Mo, respectively. The profiles are characterized by well-defined 23 kyr cycles between oxic and mildly suboxic conditions. The redox-sensitive metal profiles also follow variations in the concentrations of OC (0.2-0.9%) and alkenones (0.2-6.7 ppm). The coupled variations in inorganic and organic constituents are attributed to a 23-kyr cycle in primary production above site MD900963, as suggested by clear correlations with independent micropaleontologic proxies (primary productivity indices based on foraminifera and coccoliths and fragmentation of foraminiferal shells). The 23-kyr cycles do appear to be primarily driven by productivity rather than changes in bottom water oxygen. Comparison with other records indicates that if this interpretation is correct, productivity variations across much of the Indian Ocean have been dominated by precessional forcing, with high productivity in phase with low summer insolation in the Northern Hemisphere. This interpretation contrasts with the traditional attribution of enhanced productivity in the Indian Ocean with periods of high summer insolation.

Fe-SAPONITE and Chlorite Growth on Stainless Steel in Hydrothermal Engineered Barrier Experiments

NASA Astrophysics Data System (ADS)

Cheshire, M. C.; Caporuscio, F. A.; McCarney, M.

2012-12-01

The United States recently has initiated the Used Fuel Disposition campaign to evaluate various generic geological repositories for the disposal of high-level, spent nuclear fuel within environments ranging from hard-rock, salt/clay, to deep borehole settings. Previous work describing Engineered Barrier Systems (EBS) for repositories focused on low temperature and pressure conditions. The focus of this experimental work is to characterize the stability and alteration of a bentonite-based EBS with different waste container materials in brine at higher heat loads and pressures. All experiments were run at ~150 bar and 125 to 300 C for ~1 month. Unprocessed bentonite from Colony, Wyoming was used in the experiments as the clay buffer material. The redox conditions for each system were buffered along the magnetite-iron oxygen fugacity univariant curve using Fe3O4 and Feo filings. A K-Na-Ca-Cl-based salt solution was chosen to replicate deep groundwater compositions. The experimental mixtures were 1) salt solution-clay; 2) salt solution -clay-304 stainless steel; and 3) salt solution -clay-316 stainless steel with a water/bentonite ratio of ~9. Mineralogy and aqueous geochemistry of each experiment was evaluated to monitor the reactions that took place. No smectite illitization was observed in these reactions. However, it appears that K-smectite was produced, possibly providing a precursor to illitization. It is unclear whether reaction times were sufficient for bentonite illitization at 212 and 300 C or whether conditions conducive to illite formation were obtained. The more notable clay mineral reactions occurred at the stainless steel surfaces. Authigenic chlorite and Fe-saponite grew with their basal planes near perpendicular to the steel plate, forming a 10 - 40 μm thick 'corrosion' layer. Partial dissolution of the steel plates was the likely iron source for chlorite/saponite formation; however, dissolution of the Feo/Fe3O4 may also have acted as an iron source, with the steel plates acting as a substrate for chlorite/saponite growth. Trace amounts of pyrite in the bentonite appeared to have reacted to form H2S gas and pentlandite ((Ni,Fe)8S9). Mineral growth on the waste containers was influenced by the container, buffer, and fluid compositions, in addition to pressure and temperature conditions. No significant mineralogical changes were apparent away from the steel-smectite interface. Results of this research show that the waste container may act as a substrate for mineral growth in response to corrosion. However, it is presently unknown whether chlorite and Fe-saponite will act as passivating agents or whether their presence will facilitate further corrosion of the waste containers. The role of these Fe-rich minerals on the stability of steel canisters at elevated heat loads is currently under investigation. LA-UR-12-23845

Application of geochemical logging for palaeoenvironmental research in the Late Cretaceous Qingshankou Formation from the Chinese Continental Scientific Drilling Project-SK-2e, Songliao Basin, NE China

NASA Astrophysics Data System (ADS)

Peng, Cheng; Zou, Changchun; Pan, Li; Niu, Yixiong

2017-08-01

The Chinese Continental Scientific Drilling Project of the Cretaceous Songliao Basin (CCSD-SK) provides an excellent opportunity to understand the response of terrestrial environments to greenhouse climate change in the Cretaceous. We conducted a palaeoenvironmental study of the Late Cretaceous Qingshankou Formation (K2qn) based on geochemical log data from the SK-2 east borehole. According to the characteristic of Ti mainly from terrigenous minerals, the content of authigenic elements was calculated. Correlation space was proposed to study the variation of the correlation between two log curves along the depth. Palaeoenvironmental proxies were selected from log data to study the evolution of the climate and lake, productivity of the paleolake, and organic matter deposition. The results demonstrate that the productivity of the paleolake was driven by chemical weathering in K2qn, in which the first section of the Qingshankou Formation (K2qn1) has higher productivity than the second and third sections of the Qingshankou Formation (K2qn2+3). The high content of pyrite in several thin layers reveals lake water of high sulfate concentration. This may have been caused by acid rain related to large volcanic activity. In K2qn2+3, several periods of high productivity without the formation of source rocks and high organic matter content were identified. This may show that organic matter deposition was limited by low accommodation space or oxidation environment. Therefore, the preservation condition is suggested as the main controlling factor of organic matter deposition in K2qn.

A microbial role in the construction of Mono Lake carbonate chimneys?

PubMed

Brasier, Alexander; Wacey, David; Rogerson, Mike; Guagliardo, Paul; Saunders, Martin; Kellner, Siri; Mercedes-Martin, Ramon; Prior, Tim; Taylor, Colin; Matthews, Anna; Reijmer, John

2018-06-09

Lacustrine carbonate chimneys are striking, metre-scale constructions. If these were bioinfluenced constructions, they could be priority targets in the search for early and extraterrestrial microbial life. However, there are questions over whether such chimneys are built on a geobiological framework or are solely abiotic geomorphological features produced by mixing of lake and spring waters. Here, we use correlative microscopy to show that microbes were living around Pleistocene Mono Lake carbonate chimneys during their growth. A plausible interpretation, in line with some recent works by others on other lacustrine carbonates, is that benthic cyanobacteria and their associated extracellular organic material (EOM) formed tubular biofilms around rising sublacustrine spring vent waters, binding calcium ions and trapping and binding detrital silicate sediment. Decay of these biofilms would locally have increased calcium and carbonate ion activity, inducing calcite precipitation on and around the biofilms. Early manganese carbonate mineralisation was directly associated with cell walls, potentially related to microbial activity though the precise mechanism remains to be elucidated. Much of the calcite crystal growth was likely abiotic, and no strong evidence for either authigenic silicate growth or a clay mineral precursor framework was observed. Nevertheless, it seems likely that the biofilms provided initial sites for calcite nucleation and encouraged the primary organised crystal growth. We suggest that the nano-, micro- and macroscale fabrics of these Pleistocene Mono Lake chimneys were affected by the presence of centimetre-thick tubular and vertically stacked calcifying microbial mats. Such carbonate chimneys represent a promising macroscale target in the exploration for ancient or extraterrestrial life. © 2018 John Wiley & Sons Ltd.

Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy

USGS Publications Warehouse

McLaughlin, P.I.; Brett, Carlton E.; Wilson, M.A.

2008-01-01

Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

Microorganisms meet solid minerals: interactions and biotechnological applications.

PubMed

Ng, Daphne H P; Kumar, Amit; Cao, Bin

2016-08-01

In natural and engineered environments, microorganisms often co-exist and interact with various minerals or mineral-containing solids. Microorganism-mineral interactions contribute significantly to environmental processes, including biogeochemical cycles in natural ecosystems and biodeterioration of materials in engineered environments. In this mini-review, we provide a summary of several key mechanisms involved in microorganism-mineral interactions, including the following: (i) solid minerals serve as substrata for biofilm development; (ii) solid minerals serve as an electron source or sink for microbial respiration; (iii) solid minerals provide microorganisms with macro or micronutrients for cell growth; and (iv) (semi)conductive solid minerals serve as extracellular electron conduits facilitating cell-to-cell interactions. We also highlight recent developments in harnessing microbe-mineral interactions for biotechnological applications.

Facies distribution, depositional environment, and petrophysical features of the Sharawra Formation, Old Qusaiba Village, Central Saudi Arabia

NASA Astrophysics Data System (ADS)

Abbas, Muhammad Asif; Kaminski, Michael; Umran Dogan, A.

2016-04-01

The Silurian Sharawra Formation has great importance as it rests over the richest source rock of the Qusaiba Formation in central Saudi Arabia. The Sharawra Formation has four members including Jarish, Khanafriyah, Nayyal, and Zubliyat. The formation mainly consists of sandstone and siltstone with subordinate shale sequences. The lack of published research on this formation requires fundamental studies that can lay the foundation for future research. Three outcrops were selected from the Old Qusaiba Village in Central Saudi Arabia for field observations, petrographical and petrophysical study. Thin section study has been aided by quantitative mineralogical characterization using scanning electron microscopy - energy dispersive spectroscopy and powder x-ray diffraction (XRD) for both minerals, cements, and clay minerals (detrital and authigenic). The outcrops were logged in detail and nine different lithofacies have been identified. The thin section study has revealed the Sharawra Formation to be mainly subarkosic, while the mica content increases near to its contact with the Qusaiba Formation. The XRD data has also revealed a prominent change in mineralogy with inclusion of minerals like phlogopite and microcline with depths. Field observations delineated a prominent thinning of strata as lithofacies correlation clearly shows the thinning of strata in the southwestern direction. The absence of outcrop exposures further supports the idea of southwestern thinning of strata. This is mainly attributed to local erosion and the presence of thicker shale interbeds in the southeastern section, which was probably subjected to more intense erosion than the northwestern one. The Sharawra Formation rests conformably over the thick transgressive shale sequence, deposited during the post glacial depositional cycle. The lowermost massive sandstone bed of the Sharawra Formation represents the beginning of the regressive period. The shale interbeds in the lower part are evidence of moderate-scale transgressive episodes, while the thin shale interbeds in the middle and upper part of the Sharawra Formation represent small-scale transgressions. Overall, the Sharawra Formation contains a series of repetitive transgressive and regressive events and has been interpreted as a pro-deltaic deposit in previous studies. In the present study, the lowermost sandstone thickly bedded facies lie within the transition zone environment. The siltstone facies and the horizontally stratified facies show a middle shore face environment. The middle shore face environment is present locally. The bioturbation in the uppermost facies is indicative of the upper shore face environment. The porosity values do not vary much, as the average porosity for the sandstone facies is about 15%, for the siltstones it ranges about 7%. The permeability is variable throughout the formation, the values range from 50 to 300 md. Although sandstone has a good porosity and permeability, the siltstone facies exhibit poor petrophysical characteristics. In terms of reservoir characterization, the mineralogical mature, moderately well sorted top most sandstone facies, with appreciable porosity and permeability can be considered as a potential reservoir rock. This study has provided a base for future quantitative studies in this important formation in the area.

76 FR 25277 - Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-04

... 1219-AB64 Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust... to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors. This extension gives... Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors. In response...

Calcic soils and calcretes in the southwestern United States

USGS Publications Warehouse

Bachman, George Odell; Machette, Michael N.

1977-01-01

Secondary calcium carbonate of diverse origins, 'caliche' of many authors, is widespread in the southwestern United States. 'Caliche' includes various carbonates such as calcic soils and products of groundwater cementation. The term 'caliche' is generally avoided in this report in favor of such terms as calcrete, calcic soils, and pervasively cemented deposits. Criteria for the recognition of various types of calcrete of diverse origins include field relations and laboratory data. Calcic soils provide a comprehensive set of characteristics that aid in their recognition in the field. These characteristics include a distinctive morphology that is zoned horizontally and can frequently be traced over tens to hundreds of square kilometers. The major process in the formation of pedogenic calcrete and calic soils is the leaching of calcium carbonate from upper soil horizons by downward percolating soil solutions and reprecipitation of the carbonate in alluvial horizons near the base of the soil profile. The formation of pedogenic calcrete involves many factors including climate, source of carbonate, and tectonic stability of the geomorphic surface on which the calcrete is deposited. Most of the carbonate in pedogenic calcrete is probably derived from windblown sand, dust, and rain. Calcic soils and pedogenic calcretes follow a six-stage sequence morphologic development and is based on a classification devised by Gile, Peterson and Grossman in 1966. The .six morphologic stages of carbonate deposition in soils are related to the relative age of the soil and are as follows: I. The first or youngest stage includes filamentous or faint coatings of carbonate on detrital grains. II. The second stage includes pebble coatings which are continuous; firm carbonate nodules are few to common. III. The third stage includes coalesced nodules which occur in a friable or disseminated carbonate matrix. IV. The fourth stage includes platy, firmly cemented matrix which engulfs nodules; horizon is plugged to downward moving solutions. V. The fifth stage includes soils which are platy to tabular, dense, strongly cemented. A well-developed laminar layer occurs on the upper surface. VI. The sixth and most advanced stage is massive, multilaminar, and strongly cemented calcrete with abundant pisoliths, the upper surface of which may be brecciated. Pisoliths may indicate many generations of brecciation and reformation. In general calcic soils include stages I through III and are friable to moderately indurated; whereas pedogenic calcretes include stages IV through VI and are dense and strongly indurated. In a single pedon the morphologic stage of carbonate deposition decreases downward in the profile. The stage of development may be used in local regions for correlation and determination of relative ages of soils and geomorphic surfaces. Some structures observed in pedogenic calcretes may be present in other types of calcrete but the horizontal zonation typical of deposits of soil processes is absent. Laminar structure in particular is not restricted to pedogenic deposits and is common in many varieties of calcrete. Very little chemical change occurs in the noncalcareous nonclayey fractions of calcretes with age; but clay minerals within calcretes undergo a complex history of authigenesis. There is a depletion of magnesium in the calcareous portion and an enrichment of magnesium in the clayey portion of a calcrete with age. In keeping with this relationship, montmorillonite, or mixed layer montmorillonite-illite, is common in younger calcretes; whereas the high magnesium-silicate clays, sepiolite and palygorskite, are common in older calcretes. This indicates that the magnesium depleted from the carbonate is redistributed authigenically in clay minerals. The mobility of carbonate introduces many problems in attempts to date calcretes directly. Although the relative ages of soils within a province may be determined by quant

Geothermometry, geochronology, and mass transfer associated with hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy

USGS Publications Warehouse

Altaner, S.P.; Ylagan, R.F.; Savin, S.M.; Aronson, J.L.; Belkin, H.E.; Pozzuoli, A.

2003-01-01

A rhyolitic hyaloclastite from Ponza Island, Italy, was hydrothermally altered, producing four distinct alteration zones based on X-ray diffraction mineralogy and field textures: (1) nonpervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the nonpervasive argillic zone, characterized by smectite and disordered opal-CT. The other three zones exhibit more complete alteration of the hyaloclastite. The propylitic zone is characterized by mixed-layer illite-smectite (I-S) with 10 to 85% I, mordenite, opal-C, and authigenic K-feldspar (akspar). The silicic zone is characterized by I-S with ???90% I, pure illite, quartz, akspar, and occasional albite. The sericitic zone consists primarily of I-S with ???66% I, pure illite, quartz, and minor akspar and pyrite. K/Ar dates of I-S indicate hydrothermal alteration occurred at 3.38 ?? 0.08 Ma. Oxygen isotope compositions of I-S systematically decrease from zones 1 to 4. In the argillic zone, smectite has ??18 O values of 21.7 to 22.0??? and I-S from the propylitic, silicic, and sericitic zones ranges from 14.5 to 16.3???, 12.5 to 14.0???, and 8.6 to 11.9???, respectively. ??18 O values for quartz from the silicic and sericitic zones range from 12.6 to 15.9???. By use of isotope fractionation equations and data from authigenic quartz-hosted primary fluid inclusions, alteration temperatures ranged from 50 to 65 ??C for the argillic zone, 85 to 125 ??C for the propylitic zone, 110 to 210 ??C for the silicic zone, and 145 to 225 ??C for the sericitic zone. Fluid inclusion data and calculated ??18 O water values indicate that hydrothermal fluids were seawater dominated. Mass-transfer calculations indicate that hydrothermal alteration proceeded in a relatively open chemical system and alteration in the sericitic zone involved the most extensive loss of chemical species, especially Si. Systematic gains in Mg occur in all alteration zones as a result of I-S clay mineral formation, and systematic losses of Na, Ca, and K occur in most zones. With the exception of Ca, calculations of mass transfer associated with hydrothermal alteration on Ponza agree with chemical fluxes observed in laboratory experiments involving hydrothermal reactions of rhyolite and seawater. The anomalous Ca loss at Ponza may be due to hydrothermal formation of anhydrite and later low-temperature dissolution. On the basis of Mg enrichments derived from circulating seawater, we estimate the following minimum water/rock ratios: 9, 3, 6, and 9 for the argillic, propylitic, silicic, and sericitic zones, respectively. Hydrothermal fluid pH for the propylitic and silicic zones was neutral to slightly basic and relatively acidic for the sericitic zone as a result of condensation of carbonic and perhaps other acids. Copyright ?? 2003 Elsevier Science Ltd.

Mineral facilities of Asia and the Pacific

USGS Publications Warehouse

Baker, Michael S.; Elias, Nurudeen; Guzman, Eric; Soto-Viruet, Yadira

2010-01-01

This map displays over 1,500 records of mineral facilities throughout the continent of Asia and the countries of the Pacific Ocean. Each record represents one commodity and one facility type at a single geographic location. Facility types include mines, oil and gas fields, and plants, such as refineries, smelters, and mills. Common commodities of interest include aluminum, cement, coal, copper, gold, iron and steel, lead, nickel, petroleum, salt, silver, and zinc. Records include attributes, such as commodity, country, location, company name, facility type and capacity (if applicable), and latitude and longitude geographical coordinates (in both degrees-minutes-seconds and decimal degrees). The data shown on this map and in table 1 were compiled from multiple sources, including (1) the 2008 U.S. Geological Survey Minerals Yearbook (Asia and the Pacific volume), (2) minerals statistics and information from the U.S. Geological Survey Minerals Information Web site (http://minerals.usgs.gov/minerals/), and (3) data collected by U.S. Geological Survey minerals information country specialists. Other sources include statistical publications of individual countries, annual reports and press releases of operating companies, and trade journals. Due to the sensitivity of some energy commodity data, the quality of these data should be evaluated on a country-by-country basis. Additional information is available from the country specialists listed in table 2.

Do biofilms and clays alter the chemistry and fabric of a hyper-alklaine, saline, non-marine carbonate precipitate?

NASA Astrophysics Data System (ADS)

Rogerson, Michael; Saunders, Paul; Mercedes-Martin, Ramon; Brasier, Alex; Pedley, Martyn

2015-04-01

Non-marine carbonates comprise a hugely diverse family of deposits, which reflect a constellation of forcing factors from local hydraulics to regional climatology. However, the two dominant controls on precipitation are solution chemistry and benthic microbial biogeochemistry. Here, we present a unifying concept for understanding how these controls influence deposit characteristics, and re-emphasise the importance of biofilms. It is generally accepted that biofilms play an important part in the precipitation of authigenic minerals in a wide variety of settings. In carbonate settings, biofilms are recognised to increase the amount of calcite precipitation and alter the geometry and coarse scale petrography of the precipitate. They determine at what water marginal water chemistries calcite starts to precipitate and microbialites give way to chemical limestones. Biofilms also interact with ambient water, controlling chemical accumulation transport. New evidence, drawn from unique experimental approaches, is demonstrating that biofilm influence extends to control of calcite trace element composition, and crystal scale fabric. Under tightly controlled temperature and chemical conditions, fully replicated experiments show that Mg incorporation into tufa carbonate defies the expected thermodynamic control. However, there is a pronounced influence on (Mg/Ca)calcite from precipitation rate, so that rapidly forming precipitates develop with very low magnesium content indicating kinetic control on fractionation. Calcite precipitation rate in these experiments is controlled by biofilm growth rate and reflects kinetic fractionation arises from the electrochemical activity of extracellular organic acids. These effects are therefore likely to occur wherever these molecules occur, including stromatolites, soil and lake carbonates and (via colloidal organic acids) speleothems. The presence of Extracellular polymeric substances (EPS), even without the presence of cells, also alters precipitation style. Spherular and shrubby calcite growths are well known from the geological record, but their environmental significance is not clear. Sterile, microcosm experiments have shown that these forms occur in saline, hyperalkaline settings ' but only in the presence of organic acid molecules in solution. The presence of inorganic materials (hydrated magnesium clays) does not impact on precipitate morphology, and reduces the precipitation rate of calcite.

An AEM-TEM study of weathering and diagenesis, Abert Lake, Oregon: II. Diagenetic modification of the sedimentary assemblage

USGS Publications Warehouse

Banfield, J.F.; Jones, B.F.; Veblen, D.R.

1991-01-01

This paper compares the mineralogy and chemistry of clay minerals in sediments from various depths and positions in Abert Lake and surrounding playa with those of the weathered materials entering the lake in order to reveal the nature and extent of post-depositional mineralogical modification. Analytical electron microscope (AEM) data from individual clay particles reveal that each sample is comprised of a highly inhomogeneous smectite assemblage. The thin clay flakes (commonly less than 10 nm wide) display a complete range in octahedral sheet compositions from nearly dioctahedral to nearly trioctahedral. The very abundant Mg-rich lake smectites with an estimated composition K0.29(Al0.23-Mg2.16Fe0.30)Si3.80Al0.20O10(OH)2 are not formed by weathering. This confirms the importance of diagenetic Mg uptake. Lattice-fringe imaging failed to reveal distinct brucite-like or vermiculite-like layers, suggesting that interstratifications of this type are rare or absent. Siliceous coatings on clay particles (identified by silica excess in smectite analyses) seem to favor topotactic overgrowth of stevensite rather than addition of brucite-like layers to the dioctahedral nuclei. The growth of K-stevensite dilutes the Al content of the crystal, and thus the increasing diagenetic modification reduces rather than supplements its illite component. Smectite compositions within individual samples were highly variable, yet source-related characteristics such as the abundance of Fe-rich smectite were apparent. Little evidence for systematic K or Mg enrichment with depth was identified in samples from depths of down to 16 feet below the sediment-water interface. The most magnesian assemblages are associated both with weathering sources of Mg-rich smectite and playa environments subjected to repeated wetting and drying cycles. Thus, the observations suggest that clay compositions primarily reflect changes in lake levels, brine composition, and source characteristics, rather than time and depth/compaction effects. Other diagenetic reactions in the sediment include recrystallization of Na-rich silica gel and diatom fragments. Abundant, submicron-sized, untwinned, euhedral crystals of K-feldspar are interpreted to be authigenic in origin. ?? 1991.

Spectroscopic geochemical study of vanadiferous marine sediments of the Gibellini claims, southern Fish Creek Range, Eureka County, Nevada

USGS Publications Warehouse

Böhlke, J.K.; Radtke, A.S.; Heropoulos, Chris; Lamothe, P.J.

1981-01-01

Samples of cuttings from three drill holes in the Gibellini claims were analyzed by emission spectroscopic techniques for a large suite of major and trace elements. Unoxidized siliceous "black shale" from drill hole NGA 7 is strongly enriched in Cd, Mo, Sb, Se, V, and Zn, and also contains relatively high concentrations of As, Ba, Cu, Ni, and Tl compared with nonmetalliferous shales. Analyses of 103 samples plotted against depth in drill holes NGA, NG31, and NGA7, and selected XRD data, show the following: 1. Groups of elements with distinct distribution patterns define most of major mineralogic components of the rocks. The "normal shale" component, which includes several detrital and authigenic phases, is indicated by covariations among Ti, Al, Fe, Na, Mg, K, B, Be, Co, Cr, Ga, La, Sc, Sr, and Zr. The shale component is diluted by varying amounts of the following minerals (and associated elements): silica (Si); dolomite (Mg, Ca, Mn, Sr); apatite (Ca, Be, Cr, La, Sr, Y); barite (Ba, Sr); sphalerite (Zn, Cd, Fe?); smithsonite (Cd, Co, Mn, Ni, Zn); bianchite (Cd, Ni, Zn) ; and bokite (V). Pyrite, gypsum, and jarosite were also identified.2. The highly siliceous kerogenous metalliferous Gibellini facies is underlain by argillaceous and (or) dolomitic rocks. The transition zone deduced from the chemical data is not well defined in all instances, but probably represents the bottom of the black shale deposit. 3. Oxidation has reached to variable depths up to at least 150 ft, and has caused profound changes in the distributions of the enriched metals. Molybdenum, Se, and V have been partially removed from the upper parts of the sections and are concentrated near or slightly above the base of the Gibellini facies. Cadmium, Ni, and Zn have been strongly leached and now occur at or below the base of the Gibellini facies. The variable depth of oxidation, the redistribution and separation of the metals, and the complex mineralogy of the deposit may make development of the claim complicated.

The Chew Bahir Drilling Project (HSPDP). Deciphering climate information from the Chew Bahir sediment cores: Towards a continuous half-million year climate record near the Omo - Turkana key palaeonanthropological Site

NASA Astrophysics Data System (ADS)

Foerster, Verena E.; Asrat, Asfawossen; Chapot, Melissa S.; Cohen, Andrew S.; Dean, Jonathan R.; Deino, Alan; Günter, Christina; Junginger, Annett; Lamb, Henry F.; Leng, Melanie J.; Roberts, Helen M.; Schaebitz, Frank; Trauth, Martin H.

2017-04-01

As a contribution towards an enhanced understanding of human-climate interactions, the Hominin Sites and Paleolakes Drilling Project (HSPDP) has successfully completed coring five dominantly lacustrine archives of climate change during the last 3.5 Ma in East Africa. All five sites in Ethiopia and Kenya are adjacent to key paleoanthropological research areas encompassing diverse milestones in human evolution, dispersal episodes, and technological innovation. The 280 m-long Chew Bahir sediment records, recovered from a tectonically-bound basin in the southern Ethiopian rift in late 2014, cover the past 550 ka of environmental history, a time period that includes the transition to the Middle Stone Age, and the origin and dispersal of modern Homo sapiens. Deciphering climate information from lake sediments is challenging, due to the complex relationship between climate parameters and sediment composition. We will present the first results in our efforts to develop a reliable climate-proxy tool box for Chew Bahir by deconvolving the relationship between sedimentological and geochemical sediment composition and strongly climate-controlled processes in the basin, such as incongruent weathering, transportation and authigenic mineral alteration. Combining our first results from the long cores with those from a pilot study of short cores taken in 2009/10 along a NW-SE transect of the basin, we have developed a hypothesis linking climate forcing and paleoenvironmental signal-formation processes in the basin. X-ray diffraction analysis of the first sample sets from the long Chew Bahir record reveals similar processes that have been recognized for the uppermost 20 m during the pilot-study of the project: the diagenetic illitization of smectites during episodes of higher alkalinity and salinity in the closed-basin lake induced by a drier climate. The precise time resolution, largely continuous record and (eventually) a detailed understanding of site specific proxy formation, will give us a continuous record of environmental history on decadal to orbital timescales. Our data enable us to test current hypotheses of the impact of a variety of climate shifts on human evolution and dispersal.

Hydrological and solute budgets of Lake Qinghai, the largest lake on the Tibetan Plateau

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

Jin, Zhangdong; You, Chen-Feng; Wang, Yi

2009-12-04

Water level and chemistry of Lake Qinghai are sensitive to climate changes and are important for paleoclimatic implications. An accurate understanding of hydrological and chemical budgets is crucial for quantifying geochemical proxies and carbon cycle. Published results of water budget are firstly reviewed in this paper. Chemical budget and residence time of major dissolved constituents in the lake are estimated using reliable water budget and newly obtained data for seasonal water chemistry. The results indicate that carbonate weathering is the most important riverine process, resulting in dominance of Ca 2+ and DIC for river waters and groundwater. Groundwater contribution tomore » major dissolved constituents is relatively small (4.2 ± 0.5%). Wet atmospheric deposition contributes annually 7.4–44.0% soluble flux to the lake, resulting from eolian dust throughout the seasons. Estimates of chemical budget further suggest that (1) the Buha-type water dominates the chemical components of the lake water, (2) Na +, Cl -, Mg 2+ , and K + in lake water are enriched owing to their conservative behaviors, and (3) precipitation of authigenic carbonates (low-Mg calcite, aragonite, and dolomite) transits quickly dissolved Ca 2+ into the bottom sediments of the lake, resulting in very low Ca 2+ in the lake water. Therefore, authigenic carbonates in the sediments hold potential information on the relative contribution of different solute inputs to the lake and the lake chemistry in the past.« less

Carbon, oxygen, and strontium isotopic composition of methane-derived authigenic carbonates in methane seep areas, eastern margin of Japan Sea

NASA Astrophysics Data System (ADS)

Kakizaki, Y.; Ishikawa, T.; Hiruta, A.; Matsumoto, R.

2016-12-01

We report the occurrence, mineralogy, and isotopic composition (δ13C; δ18O) of methane-derived authigenic carbonates (MDACs) from three methane seep areas with shallow gas hydrate (Umitaka Spur, Joetsu Knoll, and off-Tobishima Island), in the southeastern margin of Japan Sea. Furthermore, we present strontium isotopic ratios (87Sr/86Sr) of MDACs, pore waters, and seawater from Umitaka Spur. MDACs range from a few mm to several tens of cm in diameter. Their shape is quite varied, e.g. nodular, platy, and indetermine form. Most MDACs are composed of high-Mg calcite. The δ13C values of MDACs from Umitaka Spur range from -30 to -4 permil. These isotopic values are higher than those of Joetsu Knoll and off-Tobishima Island. This difference is dependent upon the formation depth of MDACs in the sediment column. It probably indicates a difference in the formation environment of MDACs (e.g. methane flux). Meanwhile, range of the δ18O values of MDACs from those three areas is mostly equal. The 87Sr/86Sr ratios in MDACs from shallow sediment depth of Umitaka Spur are equal to those of modern surface seawater just above Umitaka Spur. The 87Sr/86Sr ratios of MDACs from deeper sediment depth are lower, and the Sr-isotopic trend indicates an upward increase. This trend can be correlated to the global Sr-isotopic trend of the seawater from late Pleistocene to present. It means that 87Sr/86Sr ratios of MDACs reflect the 87Sr/86Sr ratio of seawater at the formation age. However, the 87Sr/86Sr ratios in pore water are lower than those of MDACs, yet follow a parallel trend. This would suggest that the pore water includes a source of light Sr, presumably released from tuff and volcaniclastics during diagenetic processes. This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).

Rock magnetic properties of sediments from Lake Sanabria and its catchment (NW Spain): paleoenvironmental implications

NASA Astrophysics Data System (ADS)

Larrasoaña, J. C.; Borruel, V.; Gómez-Paccard, M.; Rico, M.; Valero-Garces, B.; Moreno-Caballud, A.; Soto, R.

2013-12-01

Lake Sanabria is located in the NW Spanish mountains at 1000 m a.s.l., and constitutes the largest lake of glacial origin in the Iberian Peninsula. Here we present an environmental magnetic study of a Late Pleistocene-Holocene sediment core from Lake Sanabria and from different lithologies that crop out in its catchment, which includes Paleozoic plutonic, metamorphic and vulcanosedimentary rocks, and Quaternary deposits of glacial origin. This study was designed to complement sedimentologic and geochemical studies aimed at unraveling the climatic evolution of the NW Iberian Peninsula during the last deglaciation. Our results indicate that magnetite and pyrrhotite dominate the magnetic assemblage of both the sediments from the lower half of the studied sequence (25.6 - 13 cal kyr BP) deposited in a proglacial environment, and the Paleozoic rocks that make up most of the catchment of the lake. The occurrence of these minerals both in the catchment rocks and in the lake sediments indicates that sedimentation was then driven by the erosion of a glacial flour, which suffered minimal chemical transformation in response to a rapid and short routing to the lake. Sediments from the upper half of the studied sequence, accumulated after 12.4 cal kyr BP in a fluviolacustrine environment, contain magnetite and greigite. This points to a prominent role of post-depositional reductive dissolution, driven by a sharp increase in the accumulation of organic matter into the lake and the creation of anoxic conditions in the sediments, in shaping the magnetic assemblage of Holocene sediments. Pyrrhotite is stable under reducing conditions as opposed to magnetite, which is unstable. We therefore interpret that previous pedogenic processes occurred in the then deglaciated catchment of the lake were responsible for the oxidation of pyrrhotite and authigenic formation of magnetite, which survived subsequent reductive diagenesis given its initial larger concentrations. This interpretation is supported by the magnetic properties of Quaternary till sediments, which in some cases retain their original magnetic assemblage (magnetite and pyrrhotite) and in other cases include larger concentrations of magnetite. The Holocene sequence includes some discrete layers with a magnetic signature identical to that of the glacial flour. These layers are interpreted as being deposited during extreme runoff events that eroded Quaternary tills. The sharp change in magnetic properties observed in the lake sediments between 13 and 12.4 kyr BP supports the rapid deglaciation of the catchment of Lake Sanabria inferred in previous studies on the basis of sedimentological, geochemical and geomorphological data.

Minerals

MedlinePlus

Minerals are important for your body to stay healthy. Your body uses minerals for many different jobs, including keeping your bones, muscles, heart, and brain working properly. Minerals are also important for making enzymes and hormones. ...

The fate of nitrogen mineralized from leaf litter — Initial evidence from 15N-labeled litter

Treesearch

Kathryn B. Piatek

2011-01-01

Decomposition of leaf litter includes microbial immobilization of nitrogen (N), followed by N mineralization. The fate of N mineralized from leaf litter is unknown. I hypothesized that N mineralized from leaf litter will be re-immobilized into other forms of organic matter, including downed wood. This mechanism may retain N in some forests. To test this hypothesis, oak...

30 CFR 285.701 - What must I include in my Facility Design Report?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What must I include in my Facility Design Report? 285.701 Section 285.701 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR... Design, Fabrication, and Installation Reports § 285.701 What must I include in my Facility Design Report...

30 CFR 285.645 - What must I include in my GAP?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What must I include in my GAP? 285.645 Section 285.645 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE... Requirements Contents of the General Activities Plan § 285.645 What must I include in my GAP? (a) You must...

30 CFR 285.610 - What must I include in my SAP?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What must I include in my SAP? 285.610 Section 285.610 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE... Requirements Contents of the Site Assessment Plan § 285.610 What must I include in my SAP? Your SAP must...

Diagenetic variation at the lamina scale in lacustrine organic-rich shales: Implications for hydrocarbon migration and accumulation

NASA Astrophysics Data System (ADS)

Liang, Chao; Cao, Yingchang; Liu, Keyu; Jiang, Zaixing; Wu, Jing; Hao, Fang

2018-05-01

Lacustrine carbonate-rich shales are well developed within the Mesozoic-Cenozoic strata of the Bohai Bay Basin (BBB) of eastern China and across southeast Asia. Developing an understanding of the diagenesis of these shales is essential to research on mass balance, diagenetic fluid transport and exchange, and organic-inorganic interactions in black shales. This study investigates the origin and distribution of authigenic minerals and their diagenetic characteristics, processes, and pathways at the scale of lacustrine laminae within the Es4s-Es3x shale sequence of the BBB. The research presented in this study is based on thin sections, field emission scanning electron microscope (FESEM) and SEM-catholuminescence (CL) observations of well core samples combined with the use of X-ray diffraction (XRD), energy dispersive spectroscopy, electron microprobe analysis, and carbon and oxygen isotope analyses performed using a laser microprobe mass spectrometer. The dominant lithofacies within the Es4s-Es3x sequence are a laminated calcareous shale (LCS-1) and a laminated clay shale (LCS-2). The results of this study show that calcite recrystallization1 is the overarching diagenetic process affecting the LCS-1, related to acid generation from organic matter (OM) thermal evolution. This evolutionary transition is the key factor driving the diagenesis of this lithofacies, while the transformation of clay minerals is the main diagenetic attribute of the LCS-2. Diagenetic differences occur within different laminae and at variable locations within the same lamina level, controlled by variations in mineral composition and the properties of laminae interfaces. The diagenetic fluid migration scale is vertical and responses (dissolution and replacement) are limited to individual laminae, between zero and 100 μm in width. In contrast, the dominant migration pathway for diagenetic fluid is lateral, along the abrupt interfaces between laminae boundaries, which leads to the vertical transmission of diagenetic responses. The recrystallization boundaries between calcite laminae act as the main migration pathways for the expulsion of hydrocarbons from these carbonate-rich lacustrine shales. However, because the interaction between diagenetic fluids and the shales themselves is limited to the scale of individual lamina, this system is normally closed. The occurrence of abnormal pressure fractures can open the diagenetic system, however, and cause interactions to occur throughout laminae; in particular, the closed-open (C-O) diagenetic process at this scale is critical to this shale interval. Multi-scale C-O systems are ubiquitous and episodic ranging from the scale of laminae to the whole basin. Observations show that such small-scale systems are often superimposed onto larger ones to constitute the complex diagenetic system seen within the BBB combining fluid transport, material and energy exchange, and solid-liquid and organic-inorganic interactions.

A 1500-year record of climatic and environmental change in Elk Lake, Clearwater County, Minnesota II: Geochemistry, mineralogy, and stable isotopes

USGS Publications Warehouse

Dean, W.

2002-01-01

Most of the sediment components that have accumulated in Elk Lake, Clearwater County, northwestern Minnesota, over the past 1500 years are authigenic or biogenic (CaCO3, biogenic SiO2, organic matter, iron and manganese oxyhydroxides, and iron phosphate) and are delivered to the sediment-water interface on a seasonal schedule where they are preserved as distinct annual laminae (varves). The annual biogeochemical cycles of these components are causally linked through the 'carbon pump', and are recapitulated in longer-term cycles, most prominently with a periodicity of about 400 years. Organic carbon is fixed in the epilimnion by photosynthetic removal of CO2, which also increases the pH, triggering the precipitation of CaCO3. The respiration and degradation of fixed organic carbon in the hypolimnion consumes dissolved oxygen, produces CO2, and lowers the pH so that the hypolimnion becomes anoxic and undersaturated with respect to CaCO3 during the summer. Some of the CaCO3 produced in the epilimnion is dissolved in the anoxic, lower pH hypolimnion and sediments. The amount of CaCO3 that is ultimately incorporated into the sediments is a function of how much is produced in the epilimnion and how much is consumed in the hypolimnion and the sediments. Iron, manganese, and phosphate accumulate in the anoxic hypolimnion throughout the summer. Sediment-trap studies show that at fall overturn, when iron-, manganese-, and phosphate-rich bottom waters mix with carbonate- and oxygen-rich surface waters, precipitation of iron and manganese oxyhydroxides, iron phosphate, and manganese carbonate begins and continues into the winter months. Detrital clastic material in the sediments of Elk Lake deposited over the last 1500 years is a minor component (<10% by weight) that is mostly wind-borne (eolian). Detailed analyses of the last 1500 years of the Elk Lake sediment record show distinct cycles in eolian clastic variables (e.g. aluminum, sodium, potassium, titanium, and quartz), with a periodicity of about 400 years. The 400-yr cycle in eolian clastic material does not correspond to the 400-yr cycles in redox-sensitive authigenic components, suggesting that the clastic component is responding to external forcing (wind) whereas the authigenic components are responding to internal forcing (productivity), although both may ultimately be forced by climate change. Variations in the oxygen and carbon isotopic composition of CaCO3 are small but appear to reflect small variations in ground water influx that are also driven by external forcing.

LA-ICP-MS analysis of isolated phosphatic grains indicates selective rare earth element enrichment during reworking and transport processes

NASA Astrophysics Data System (ADS)

Auer, Gerald; Reuter, Markus; Hauzenberger, Christoph A.; Piller, Werner E.

2016-04-01

Rare earth elements (REE) are a commonly used proxy to reconstruct water chemistry and oxygen saturation during the formation history of authigenic and biogenic phosphates in marine environments. In the modern ocean REE exhibit a distinct pattern with enrichment of heavy REE and strong depletion in Cerium. Studies of ancient phosphates and carbonates, however, showed that this 'modern' pattern is only rarely present in the geological past. Consequently, the wide range of REE enrichment patterns found in ancient marine phosphates lead to the proposition that water chemistry had to have been radically different in the earth's past. A wealth of studies has already shown that both early and late diagenesis can strongly affect REE signatures in phosphates and severely alter primary marine signals. However, no previous research was conducted on how alteration processes occurring prior to final deposition affect marine phosphates. Herein we present a dataset of multiple LA-ICP-MS measurements of REE signatures in isolated phosphate and carbonate grains deposited in a carbonate ramp setting in the central Mediterranean Sea during the middle Miocene "Monterey event". The phosphates are represented by authigenic, biogenic and detrital grains emplaced in bioclastic grain- to packstones dominated by bryozoan and echinoderm fragments, as well as abundant benthic and planktic foraminifers. The results of 39 grain specific LA-ICP-MS measurements in three discrete rock samples reveals four markedly different REE patterns (normalized to the Post Archean Australian Shale standard) in terms of total enrichment and pattern shape. Analyses of REE diagenesis proxies show that diagenetic alteration affected the samples only to a minor degree. Considering grain shape and REE patterns together indicate that authigenic, detrital and biogenic phosphates have distinct REE patterns irrespective of the sample. Our results show that the observed REE patterns in phosphates only broadly reflect water chemistry under certain well constrained circumstances of primary authigenesis. Are these conditions not met, REE patterns are more likely to reflect complex enrichment processes that likely already started to occur during reworking over geologically relatively short time frames. Similarities in the REE patterns of clearly detrital and biogenic phosphate further suggest that the often observed 'hat-shaped' pattern in biogenic phosphates can easily result from increased middle REE (Neodymium to Holmium) scavenging during taphonomic processes prior to final deposition. Finally, cluster analysis coupled with sedimentological considerations proved a valuable tool for the characterization of REE patterns of phosphates in terms of their formation conditions and depositional history, such as the distinction of phosphates formed in situ from reworked and transported phosphate grains.

30 CFR 48.26 - Experienced miner training.

Code of Federal Regulations, 2010 CFR

2010-07-01

... TRAINING AND RETRAINING OF MINERS Training and Retraining of Miners Working at Surface Mines and Surface... must include the following instruction: (1) Introduction to work environment. The course shall include... firewarning signals and firefighting procedures in effect at the mine. (6) Ground controls; working in areas...

Mineral facilities of Europe

USGS Publications Warehouse

Almanzar, Francisco; Baker, Michael S.; Elias, Nurudeen; Guzman, Eric

2010-01-01

This map displays over 1,700 records of mineral facilities within the countries of Europe and western Eurasia. Each record represents one commodity and one facility type at a single geographic location. Facility types include mines, oil and gas fields, and plants, such as refineries, smelters, and mills. Common commodities of interest include aluminum, cement, coal, copper, gold, iron and steel, lead, nickel, petroleum, salt, silver, and zinc. Records include attributes, such as commodity, country, location, company name, facility type and capacity (if applicable), and latitude and longitude geographical coordinates (in both degrees-minutes-seconds and decimal degrees). The data shown on this map and in table 1 were compiled from multiple sources, including (1) the most recently available data from the U.S. Geological Survey (USGS) Minerals Yearbook (Europe and Central Eurasia volume), (2) mineral statistics and information from the USGS Minerals Information Web site (http://minerals.usgs.gov/minerals/pubs/country/europe.html), and (3) data collected by the USGS minerals information country specialists from sources, such as statistical publications of individual countries, annual reports and press releases of operating companies, and trade journals. Data reflect the most recently published table of industry structure for each country at the time of this publication. Additional information is available from the country specialists listed in table 2.

Mineral facilities of Northern and Central Eurasia

USGS Publications Warehouse

Baker, Michael S.; Elias, Nurudeen; Guzman, Eric; Soto-Viruet, Yadira

2010-01-01

This map displays almost 900 records of mineral facilities within the countries that formerly constituted the Union of Soviet Socialist Republics (USSR). Each record represents one commodity and one facility type at a single geographic location. Facility types include mines, oil and gas fields, and plants, such as refineries, smelters, and mills. Common commodities of interest include aluminum, cement, coal, copper, gold, iron and steel, lead, nickel, petroleum, salt, silver, and zinc. Records include attributes, such as commodity, country, location, company name, facility type and capacity (if applicable), and latitude and longitude geographical coordinates (in both degrees-minutes-seconds and decimal degrees). The data shown on this map and in table 1 were compiled from multiple sources, including (1) the most recently available data from the U.S. Geological Survey (USGS) Minerals Yearbook (Europe and Central Eurasia volume), (2) mineral statistics and information from the USGS Minerals Information Web site (http://minerals.usgs.gov/minerals/pubs/country/europe.html), and (3) data collected by the USGS minerals information country specialists from sources, such as statistical publications of individual countries, annual reports and press releases of operating companies, and trade journals. Data reflect the most recent published table of industry structure for each country at the time of this publication. Additional information is available from the country specialists listed in table 2

Transported African Dust to the Amazon: Physiochemical Properties and Associated Nutrients

NASA Astrophysics Data System (ADS)

Barkley, A.; Blackwelder, P. L.; Prospero, J. M.; Gaston, C.

2017-12-01

African dust plays an essential role in fertilizing both oceanic and terrestrial ecosystems by supplying vital biological nutrients such as iron and phosphorus. During Boreal winter, large quantities of African dust are transported across the Atlantic Ocean to the Amazon Basin. It is thought that the Bodélé Depression, part of Paleolake Mega Chad, serves as a major source of this dust, although its importance is debated. The soil in this topographical depression contains a distinctive blend of fluvial and diatomaceous sediments that are thought to supply the Amazon with the nutrients necessary to maintain soil fertility. However, the composition and physical properties of dust transported to the Amazon remain under-explored. Here we present measurements of the size, morphology, and chemical composition of transported dust collected in Cayenne, French Guiana and soil samples collected from the Bodélé Depression using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Inductively coupled plasma mass spectrometry and soluble phosphorus measurements were also performed to investigate the nutrient profiles of filters collected during different air mass transport conditions. In addition to mineral dust, SEM revealed the presence of whole and fragmented freshwater diatoms transported from the Bodélé Depression, or other ephemeral African paleolakes, that were mixed with dust containing iron oxides and micronutrient-rich authigenic clays. Interestingly, transported diatoms were found to the be the largest transported particles with diameters well above 10 μm (up to 70 μm). The low density and high surface-to-volume ratios of diatoms could allow a longer range transport than dust of a comparable size. Therefore, the diatoms could act as a vehicle by which higher micronutrient fluxes could be transported to the Amazon.

Arsenic Incorporation in Pyrite at Ambient Temperature at Both Tetrahedral S-I and Octahedral FeII Sites: Evidence from EXAFS-DFT Analysis.

PubMed

Le Pape, Pierre; Blanchard, Marc; Brest, Jessica; Boulliard, Jean-Claude; Ikogou, Maya; Stetten, Lucie; Wang, Shuaitao; Landrot, Gautier; Morin, Guillaume

2017-01-03

Pyrite is a ubiquitous mineral in reducing environments and is well-known to incorporate trace elements such as Co, Ni, Se, Au, and commonly As. Indeed, As-bearing pyrite is observed in a wide variety of sedimentary environments, making it a major sink for this toxic metalloid. Based on the observation of natural hydrothermal pyrites, As -I is usually assigned to the occupation of tetrahedral S -I sites, with the same oxidation state as in arsenopyrite (FeAsS), although rare occurrences of As III and As II have been reported. However, the modes of As incorporation into pyrite during its crystallization under low-temperature diagenetic conditions have not yet been elucidated because arsenic acts as an inhibitor for pyrite nucleation at ambient temperature. Here, we provide evidence from X-ray absorption spectroscopy for As II,III incorporation into pyrite at octahedral Fe II sites and for As -I at tetrahedral S -I sites during crystallization at ambient temperature. Extended X-ray absorption fine structure (EXAFS) spectra of these As-bearing pyrites are explained by local structure models obtained using density functional theory (DFT), assuming incorporation of As at the Fe and S sites, as well as local clustering of arsenic. Such observations of As -I incorporation at ambient temperature can aid in the understanding of the early formation of authigenic arsenian pyrite in subsurface sediments. Moreover, evidence for substitution of As II,III for Fe in our synthetic samples raises questions about both the possible occurrence and the geochemical reactivity of such As-bearing pyrites in low-temperature subsurface environments.

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).

Apparent overconsolidation of mudstones in the Kumano Basin of southwest Japan: Implications for fluid pressure and fluid flow within a forearc setting

NASA Astrophysics Data System (ADS)

Guo, Junhua; Underwood, Michael B.; Likos, William J.; Saffer, Demian M.

2013-04-01

The Kumano Basin is located in the Nankai Trough subduction zone of southwest Japan. During the past 1.6 million years, approximately 800 meters of sandy turbidites and hemipelagic mud were deposited near the distal edge of the forearc basin, at Site C0002 of the Integrated Ocean Drilling Program. Constant-rate-of-strain consolidation tests yield estimates of in situ permeability that range from 2.6 × 10-17 m2 to 2.5 × 10-18 m2; overconsolidation ratios range from 1.7 to 2.6, and values of the compression index range from 0.39 to 0.78. Several processes contributed to the apparent overconsolidation. Strata dip toward land, and pore fluids probably migrate up-dip and vent along a bathymetric notch near the seaward edge of the basin. Efficient lateral drainage through sandy turbidites has kept pore pressures within interbeds of mudstone at (or close to) hydrostatic. In addition, alteration of dispersed volcanic glass, precipitation of authigenic clay minerals, and collapse of random grain fabric has probably strengthened the bonding among grains. Cementation is particularly likely within the lower basin (unit III), where values of porosity remain anomalously high. If fluid overpressures (and underconsolidation) exist anywhere within the basin, the most likely loci are where sandy turbidites terminate against impermeable mudstones along landward-dipping on-lap surfaces. Those types of on-lap geometries, in addition to structural closures, might provide promising targets for oil/gas accumulation in other forearc basins, particularly where petroleum source rocks have been buried to the optimal depths of catagenesis.

Provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico unraveled by geochemical analysis

NASA Astrophysics Data System (ADS)

Armstrong-Altrin, John S.; Machain-Castillo, María Luisa; Rosales-Hoz, Leticia; Carranza-Edwards, Arturo; Sanchez-Cabeza, Joan-Albert; Ruíz-Fernández, Ana Carolina

2015-03-01

The aim of this work is to constrain the provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico (~1089-1785 m water depth). To achieve this, 10 piston sediment cores (~5-5.5 m long) were studied for mineralogy, major, trace and rare earth element geochemistry. Samples were analyzed at three core sections, i.e. upper (0-1 cm), middle (30-31 cm) and lower (~300-391 cm). The textural study reveals that the core sediments are characterized by silt and clay fractions. Radiocarbon dating of sediments for the cores at different levels indicated a maximum of ~28,000 year BP. Sediments were classified as shale. The chemical index of alteration (CIA) values for the upper, middle, and lower sections revealed moderate weathering in the source region. The index of chemical maturity (ICV) and SiO2/Al2O3 ratio indicated low compositional maturity for the core sediments. A statistically significant correlation observed between total rare earth elements (∑REE) versus Al2O3 and Zr indicated that REE are mainly housed in detrital minerals. The North American Shale Composite (NASC) normalized REE patterns, trace element concentrations such as Cr, Ni and V, and the comparison of REE concentrations in sediments and source rocks indicated that the study area received sediments from rocks intermediate between felsic and mafic composition. The enrichment factor (EF) results indicated that the Cd and Zn contents of the upper section sediments were influenced by an anthropogenic source. The trace element ratios and authigenic U content of the core sediments indicated the existence of an oxic depositional environment.

Combined structural analysis and dating of authigenic/synkinematic illite: A step towards unravelling brittle faulting processes in time and space

NASA Astrophysics Data System (ADS)

Viola, Giulio

2017-04-01

Faulting accommodates momentous deformation and its style reflects the complex interplay of often transient processes such as friction, fluid flow and rheological changes within generally dilatant systems. Brittle faults are thus unique archives of the stress state and the physical and chemical conditions at the time of both initial strain localization and subsequent slip(s) during structural reactivation. Opening those archives, however, may be challenging due to the commonly convoluted (if not even chaotic) nature of brittle fault architectures and fault rocks. This is because, once formed, faults are extremely sensitive to variations in stress field and environmental conditions and are prone to readily slip in a variety of conditions, also in regions affected by only weak, far-field stresses. The detailed, multi-scalar structural analysis of faults and of fault rocks has to be the starting point for any study aiming at reconstructing the complex framework of brittle deformation. However, considering that present-day exposures of faults only represent the end result of the faults' often protracted and heterogeneous histories, the obtained structural and mechanical results have to be integrated over the life span of the studied fault system. Dating of synkinematic illite/muscovite to constrain the time-integrated evolution of faults is therefore the natural addition to detailed structural studies. By means of selected examples it will be demonstrated how careful structural analysis integrated with illite characterization and K-Ar dating allows the high-resolution reconstruction of brittle deformation histories and, in turn, multiple constraints to be placed on strain localization, deformation mechanisms, fluid flow, mineral alteration and authigenesis within actively deforming brittle fault rocks. Complex and long brittle histories can thus be reconstructed and untangled in any tectonic setting.

High-temperature quartz cement and the role of stylolites in a deep gas reservoir, Spiro Sandstone, Arkoma Basin, USA

USGS Publications Warehouse

Worden, Richard H.; Morad, Sadoon; Spötl, C.; Houseknecht, D.W.; Riciputi, L.R.

2000-01-01

The Spiro Sandstone, a natural gas play in the central Arkoma Basin and the frontal Ouachita Mountains preserves excellent porosity in chloritic channel-fill sandstones despite thermal maturity levels corresponding to incipient metamorphism. Some wells, however, show variable proportions of a late-stage, non-syntaxial quartz cement, which post-dated thermal cracking of liquid hydrocarbons to pyrobitumen plus methane. Temperatures well in excess of 150°C and possibly exceeding 200°C are also suggested by (i) fluid inclusions in associated minerals; (ii) the fact that quartz post-dated high-temperature chlorite polytype IIb; (iii) vitrinite reflectance values of the Spiro that range laterally from 1.9 to ≥ 4%; and (iii) the occurrence of late dickite in these rocks. Oxygen isotope values of quartz cement range from 17.5 to 22.4‰ VSMOW (total range of individual in situ ion microprobe measurements) which are similar to those of quartz cement formed along high-amplitude stylolites (18.4–24.9‰). We favour a model whereby quartz precipitation was controlled primarily by the availability of silica via deep-burial stylolitization within the Spiro Sandstone. Burial-history modelling showed that the basin went from a geopressured to a normally pressured regime within about 10–15 Myr after it reached maximum burial depth. While geopressure and the presence of chlorite coats stabilized the grain framework and inhibited nucleation of secondary quartz, respectively, stylolites formed during the subsequent high-temperature, normal-pressured regime and gave rise to high-temperature quartz precipitation. Authigenic quartz growing along stylolites underscores their role as a significant deep-burial silica source in this sandstone.

Paleolimnology of Lake Tubutulik, an iron-meromictic Eocene Lake, eastern Seward Peninsula, Alaska

USGS Publications Warehouse

Dickinson, K.A.

1988-01-01

Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual "iron-meromictic" Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a structural graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Late Cretaceous Darby Pluton, on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the river valley of the ancestral Tubutulik River in early Eocene time. Lake Tubutulik contained a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital layers containing mostly quartz and clay minerals. Both lacustrine facies contain turbidities. The lacustrine sediments graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake apparently occupied a small deep basin in a tectonically active area of high relief. Meromixus was probably stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixus decreased as the lake became shallower from sediment filling. The source of the iron, abundant in the monimolimnion of Lake Tubutulik, was probably the Eocene basalt. Based on carbon isotope analysis of the siderite, the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature (??13C = +16.9) consistent with residual carbon formed during methanogenic fermentation. ?? 1988.

The effects of steam injection in a sandstone reservoir (Etchegoin Formation), Buena Vista field, California

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

Grant, C.W.; Reed, A.A.

1991-03-01

At Buena Vista field, California, 120 ft of post-steamflood core, spanning the middle Pliocene Wilhelm Member of the Etchegoin Formation, was taken to assess the influence of stratigraphy on light-oil steamflood (LOSF) processes and to determine what steam-rock reactions occurred and how these affected reservoir properties. High-quality steam (600F (300C)) had been injected ({approximately}1,700 psi) into mixed tidal flat and estuarine facies in an injector well located 55 ft from the cored well. Over a period of 20 months, steam rapidly channeled through a thin ({approximately}7 ft), relatively permeable (1-1,000 md), flaser-bedded sandstone unit. Conductive heating above this permeable unitmore » produced, in the vicinity of the cored well, a 35-ft steam-swept zone (oil saturation = 0), overlain by a 29-ft steam-affected zone in which oil saturation had been reduced to 13%, far below the presteam saturation of 30%. Steam-induced alteration ('artificial diagenesis') of the clay-rich reservoir rock was recognized using SEM, petrography, and X-ray diffraction. Salient dissolution effects were the complete to partial removal of siliceous microfossils, Fe-dolomite, volcanic rock fragments, and labile heavy minerals. The artificial diagenetic effects are first encountered in the basal 6 ft of the 29-ft steam-affected zone. Based on the distribution of the authigenic phases, the authors conclude that the reactions took place, or were at least initiated, in the steam condensate bank ahead of the advancing steam front. Although these changes presumably reduced permeability, the steamflood process was effective in reducing oil saturation to zero in the steam-contacted portion of the reservoir.« less

30 CFR 253.41 - What terms must I include in my OSFR evidence?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What terms must I include in my OSFR evidence? 253.41 Section 253.41 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE OIL SPILL FINANCIAL RESPONSIBILITY FOR OFFSHORE FACILITIES Requirements for Submitting OSFR Information § 253.41 What terms must I include in my...

30 CFR 254.22 - What information must I include in the “Introduction and plan contents” section?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What information must I include in the âIntroduction and plan contentsâ section? 254.22 Section 254.22 Mineral Resources MINERALS MANAGEMENT SERVICE... must I include in the “Introduction and plan contents” section? The “Introduction and plan contents...

36 CFR 292.68 - Mineral material operations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 36 Parks, Forests, and Public Property 2 2012-07-01 2012-07-01 false Mineral material operations... NATIONAL RECREATION AREAS Smith River National Recreation Area Mineral Materials § 292.68 Mineral material... officer may approve contracts and permits for the sale or other disposal of mineral materials, including...

36 CFR 292.68 - Mineral material operations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 36 Parks, Forests, and Public Property 2 2014-07-01 2014-07-01 false Mineral material operations... NATIONAL RECREATION AREAS Smith River National Recreation Area Mineral Materials § 292.68 Mineral material... officer may approve contracts and permits for the sale or other disposal of mineral materials, including...

36 CFR 292.68 - Mineral material operations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 36 Parks, Forests, and Public Property 2 2011-07-01 2011-07-01 false Mineral material operations... NATIONAL RECREATION AREAS Smith River National Recreation Area Mineral Materials § 292.68 Mineral material... officer may approve contracts and permits for the sale or other disposal of mineral materials, including...

36 CFR 292.68 - Mineral material operations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 36 Parks, Forests, and Public Property 2 2013-07-01 2013-07-01 false Mineral material operations... NATIONAL RECREATION AREAS Smith River National Recreation Area Mineral Materials § 292.68 Mineral material... officer may approve contracts and permits for the sale or other disposal of mineral materials, including...

Some physicochemical aspects of water-soluble mineral flotation.

PubMed

Wu, Zhijian; Wang, Xuming; Liu, Haining; Zhang, Huifang; Miller, Jan D

2016-09-01

Some physicochemical aspects of water-soluble mineral flotation including hydration phenomena, associations and interactions between collectors, air bubbles, and water-soluble mineral particles are presented. Flotation carried out in saturated salt solutions, and a wide range of collector concentrations for effective flotation of different salts are two basic aspects of water-soluble mineral flotation. Hydration of salt ions, mineral particle surfaces, collector molecules or ions, and collector aggregates play an important role in water-soluble mineral flotation. The adsorption of collectors onto bubble surfaces is suggested to be the precondition for the association of mineral particles with bubbles. The association of collectors with water-soluble minerals is a complicated process, which may include the adsorption of collector molecules or ions onto such surfaces, and/or the attachment of collector precipitates or crystals onto the mineral surfaces. The interactions between the collectors and the minerals include electrostatic and hydrophobic interactions, hydrogen bonding, and specific interactions, with electrostatic and hydrophobic interactions being the common mechanisms. For the association of ionic collectors with minerals with an opposite charge, electrostatic and hydrophobic interactions could have a synergistic effect, with the hydrophobic interactions between the hydrophobic groups of the previously associated collectors and the hydrophobic groups of oncoming collectors being an important attractive force. Association between solid particles and air bubbles is the key to froth flotation, which is affected by hydrophobicity of the mineral particle surfaces, surface charges of mineral particles and bubbles, mineral particle size and shape, temperature, bubble size, etc. The use of a collector together with a frother and the use of mixed surfactants as collectors are suggested to improve flotation. Copyright © 2016 Elsevier B.V. All rights reserved.

30 CFR 285.906 - What must my decommissioning application include?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What must my decommissioning application include? 285.906 Section 285.906 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY ALTERNATE USES OF EXISTING FACILITIES ON THE OUTER CONTINENTAL SHELF...

Worldwide Directory of Mineral Industries Education and Research.

ERIC Educational Resources Information Center

Wohlbier, Herbert; And Others

Presented is background knowlege of the institutions of the world involved in mineral industry education and research, including detailed information on the professional staff, research activities, and capabilities of the various mineral industry departments of these institutions. Also included is information on special interest within a…

Early stages of carbonate mineralization revealed from molecular simulations: Implications for biomineral formation

NASA Astrophysics Data System (ADS)

Wallace, A. F.; DeYoreo, J.; Banfield, J. F.

2011-12-01

The carbonate mineral constituents of many biomineralized products, formed both in and ex vivo, grow by a multi-stage crystallization process that involves the nucleation and structural reorganization of transient amorphous phases. The existence of transient phases and cluster species has significant implications for carbonate nucleation and growth in natural and engineered environments, both modern and ancient. The structure of these intermediate phases remains elusive, as does the nature of the disorder to order transition, however, these process details may strongly influence the interpretation of elemental and isotopic climate proxy data obtained from authigenic and biogenic carbonates. While molecular simulations have been applied to certain aspects of crystal growth, studies of metal carbonate nucleation are strongly inhibited by the presence of kinetic traps that prevent adequate sampling of the potential landscape upon which the growing clusters reside within timescales accessible by simulation. This research addresses this challenge by marrying the recent Kawska-Zahn (KZ) approach to simulation of crystal nucleation and growth from solution with replica-exchange molecular dynamics (REMD) techniques. REMD has been used previously to enhance sampling of protein conformations that occupy energy wells that are separated by sizable thermodynamic and kinetic barriers, and is used here to probe the initial formation and onset of order within hydrated calcium and iron carbonate cluster species during nucleation. Results to date suggest that growing clusters initiate as short linear ion chains that evolve into two- and three-dimensional structures with continued growth. The planar structures exhibit an obvious 2d lattice, while establishment of a 3d lattice is hindered by incomplete ion desolvation. The formation of a dehydrated core consisting of a single carbonate ion is observed when the clusters are ~0.75 nm. At the same size a distorted, but discernible calcite-type lattice is also apparent. Continued growth results in expansion of the dehydrated core, however, complete desolvation and incorporation of cations into the growing carbonate phase is not achieved until the cluster grows to ~1.2 nm. Exploration of the system free energy along the crystallization path reveals "special" cluster sizes that correlate with ion desolvation milestones. The formation of these species comprise critical bottlenecks on the energy landscape and for the establishment of order within the growing clusters.

Source/process apportionment of major and trace elements in sinking particles in the Sargasso sea

NASA Astrophysics Data System (ADS)

Huang, S.; Conte, M. H.

2009-01-01

Elemental composition of the particle flux at the Oceanic Flux Program (OFP) time-series site off Bermuda was measured from January 2002 to March 2005. Eighteen elements (Mg, Al, Si, P, Ca, Sc, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Sr, Cd, Ba and Pb) in sediment trap material from 500, 1500 and 3200 m depths were quantified using fusion-HR-ICPMS. Positive Matrix Factorization (PMF) was used to elucidate sources, elemental associations and processes that affect geochemical behavior in the water column. Results provide evidence for intense elemental cycling between the sinking flux material and the dissolved and suspended pools within mesopelagic and bathypelagic waters. Biological processing and remineralization rapidly deplete the sinking flux material in organic matter and associated elements (N, P, Cd, Zn) between 500 and 1500 m depth. Suspended particle aggregation, authigenic mineral precipitation, and chemical scavenging enriches the flux material in lithogenic minerals, barite and redox sensitive elements (Mn, Co, V, Fe). A large increase in the flux of lithogenic elements is observed with depth and confirms that the northeast Sargasso is a significant sink for advected continental materials, likely supplied via Gulf Stream circulation. PMF resolved major sources that contribute to sinking flux at all depths (carbonate, high-Mg carbonate, opal, organic matter, lithogenic material, and barite) as well as additional depth-specific elemental associations that contribute about half of the compositional variability in the flux. PMF solutions indicate close geochemical associations of barite-opal, Cd-P, Zn-Co, Zn-Pb and redox sensitive elements in the sinking flux material at 500 m depth. Major reorganizations of element associations occur as labile carrier phases break down and elements redistribute among new carrier phases deeper in the water column. Factor scores show strong covariation and similar temporal phasing among the three trap depths and indicate a tight coupling in particle flux compositional variability throughout the water column. Seasonality in flux composition is primarily driven by dilution of the lithogenic component with freshly-produced biogenic material during the late winter primary production maximum. Temporal trends in scores reveal subtle non-seasonal changes in flux composition occurring on month long timescales. This non-seasonal variability may be driven by changes in the biogeochemical properties of intermediate water masses that pass through the region and which affect rates of chemical scavenging and/or aggregation within the water column.

Modern and late Holocene dolomite formation: Manito Lake, Saskatchewan, Canada

NASA Astrophysics Data System (ADS)

Last, Fawn M.; Last, William M.; Halden, Norman M.

2012-12-01

Major advances have occurred in our understanding of modern dolomite formation and penecontemporaneous dolomitization over the past several decades. Manito Lake, located in west-central Saskatchewan, Canada, is a large (65 km2), deep (zmax: 22 m) perennial saline (~ 45 ppt TDS) lake in which modern and late Holocene dolomite coexists with other endogenic and authigenic carbonate precipitates, including aragonite, monohydrocalcite, calcite, and Mg-calcite. Like many other lacustrine dolomites, Manito Lake dolomite is microcrystalline (less than 1 μm to 5 μm), Ca-rich and poor to moderately ordered. It occurs as relatively pure hardgrounds and as a component of nearshore microbialites. It also forms isopachous cements in consolidated siliciclastic shoreline sediments. Manito Lake dolomite is most likely forming by mainly biomediated precipitation at or near the sediment-water interface (i) in pore spaces of coarse siliciclastic sediments (i.e., beachrock), (ii) as fine laminae associated with microbialites, and (iii) as a major component of mudstone hardgrounds and pavements.

Lithology, reservoir properties, and burial history of portion of Gammon Shale ( Cretaceous), southwestern North Dakota.

USGS Publications Warehouse

Gautier, D.L.

1981-01-01

In the northern Great Plains, large quantities of biogenic methane are contained at shallow depths in Cretaceous marine mudstones. The Gammon Shale and equivalents of the Milk River Formation in Canada are typical. At Little Missouri field, Gammon reservoirs consist of discontinuous lenses and laminae of siltstone, enclosed by silty clay shale. Large amounts of allogenic clay, including highly expansible mixed-layer illite-smectite cause great water sensitivity and high water-saturation values. Studies show that the Gammon has not undergone thermal conditions sufficient for oil or thermal gas generation. The scarcity of authigenic silicates suggests that diagenesis has been inhibited by the presence of free methane. Shale layers are practically impermeable whereas siltstone microlenses are porous (30-40%) and have permeabilities on the order of 3-30 md. Organic matter in the low-permeability reservoirs served as the source of biogenic methane, and capillary forces acted as the trapping mechanism for gas accumulation. Much of the Gammon interval is potentially economic. -from Author

Clay Mineral Crystal Structure Tied to Composition

NASA Image and Video Library

2016-12-13

This diagram illustrates how the dimensions of clay minerals' crystal structure are affected by which ions are present in the composition of the mineral. Different clay minerals were identified this way at two sites in Mars' Gale Crater: "Murray Buttes" and "Yellowknife Bay." In otherwise identical clay minerals, a composition that includes aluminum and ferric iron ions (red dots) results in slightly smaller crystalline unit cells than one that instead includes magnesium and ferrous iron ions (green dots). Ferric iron is more highly oxidized than ferrous iron. Crystalline cell units are the basic repeating building blocks that define minerals. X-ray diffraction analysis, a capability of the Chemistry and Mineralogy (CheMin) instrument on NASA's Curiosity Mars rover, identifies minerals from their crystalline structure. http://photojournal.jpl.nasa.gov/catalog/PIA21148

30 CFR 285.908 - What must I include in my decommissioning notice?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What must I include in my decommissioning notice? 285.908 Section 285.908 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY ALTERNATE USES OF EXISTING FACILITIES ON THE OUTER CONTINENTAL SHELF...

Regional paleohydrologic and paleoclimatic settings of wetland/lacustrine depositional systems in the Morrison Formation (Upper Jurassic), Western Interior, USA

USGS Publications Warehouse

Dunagan, S.P.; Turner, C.E.

2004-01-01

During deposition of the Upper Jurassic Morrison Formation, water that originated as precipitation in uplands to the west of the Western Interior depositional basin infiltrated regional aquifers that underlay the basin. This regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland/lacustrine successions. A freshwater carbonate wetland/lacustrine succession formed in the distal reaches of the basin, where regional groundwater discharged into the Denver-Julesburg Basin, which was a smaller structural basin within the more extensive Western Interior depositional basin. An alkaline-saline wetland/lacustrine complex (Lake T'oo'dichi') formed farther upstream, where shallower aquifers discharged into the San Juan/Paradox Basin, which was another small structural basin in the Western Interior depositional basin. These were both wetlands in the sense that groundwater was the major source of water. Input from surface and meteoric water was limited. In both basins, lacustrine conditions developed during episodes of increased input of surface water. Inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology. The distal carbonate wetland/lacustrine deposits are well developed in the Morrison Formation of east-central Colorado, occupying a stratigraphic interval that is equivalent to the "lower" Morrison but extends into the "upper" Morrison Formation. Sedimentologic, paleontologic, and isotopic evidence indicate that regional groundwater discharge maintained shallow, hydrologically open, well oxygenated, perennial carbonate wetlands and lakes despite the semi-arid climate. Wetland deposits include charophyte-rich wackestone and green mudstone. Lacustrine episodes, in which surface water input was significant, were times of carbonate and siliciclastic deposition in scarce deltaic and shoreline deposits. Marginal lacustrine deposits include ooid and skeletal packstone-grainstone, siltstone, and sandstone. Distal lacustrine units are skeletal mudstone-wackestone, microbialites, and laminated (siliciclastic) mudstone. Differentiation between wetlands and distal lacustrine units is not always possible. Palustrine features, Magadi-type chert (MTC), and evaporites record episodes of increased aridity and exposure. Farther upstream, during deposition of the upper part of the Brushy Basin Member, the ancestral Uncompahgre Uplift imposed a barrier to shallow, eastward-flowing groundwater that discharged into the San Juan/Paradox Basin on the upstream side of the uplift. This created the closed hydrologic setting necessary for development of an alkaline-saline wetland/lacustrine complex ("Lake" T'oo'dichi'). Silicic volcanic ash, delivered by prevailing winds from calderas west and southwest of the basin, contributed to the pore-water evolution in the sediments. A distinctive lateral hydrogeochemical gradient, reflecting increasing salinity and alkalinity in the pore waters, altered the ash to a variety of authigenic minerals that define concentric zones within the basin. The basinward progression of diagenetic mineral zones is smectite???clinoptilolite???analcime ??potassium feldspar???albite. The groundwater-fed wetlands were shallow and frequently evaporated to dryness. Scarce laminated gray mudstone beds record distinct episodes of freshwater lacustrine deposition that resulted from intermittent streams that carried detritus well out into the basin. ?? 2004 Elsevier B.V. All rights reserved.

43 CFR 3501.5 - What terms do I need to know to understand this part?

Code of Federal Regulations, 2014 CFR

2014-10-01

... hardrock minerals as used here includes mineral deposits that are found in sedimentary and other rocks...) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING OF SOLID MINERALS OTHER THAN COAL AND OIL SHALE Leasing of Solid Minerals Other Than Coal and Oil Shale-General...

43 CFR 3501.5 - What terms do I need to know to understand this part?

Code of Federal Regulations, 2013 CFR

2013-10-01

... hardrock minerals as used here includes mineral deposits that are found in sedimentary and other rocks...) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING OF SOLID MINERALS OTHER THAN COAL AND OIL SHALE Leasing of Solid Minerals Other Than Coal and Oil Shale-General...

43 CFR 3501.5 - What terms do I need to know to understand this part?

Code of Federal Regulations, 2012 CFR

2012-10-01

... hardrock minerals as used here includes mineral deposits that are found in sedimentary and other rocks...) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING OF SOLID MINERALS OTHER THAN COAL AND OIL SHALE Leasing of Solid Minerals Other Than Coal and Oil Shale-General...

43 CFR 3501.5 - What terms do I need to know to understand this part?

Code of Federal Regulations, 2011 CFR

2011-10-01

... hardrock minerals as used here includes mineral deposits that are found in sedimentary and other rocks...) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING OF SOLID MINERALS OTHER THAN COAL AND OIL SHALE Leasing of Solid Minerals Other Than Coal and Oil Shale-General...

Minerals Yearbook, volume I, Metals and Minerals

USGS Publications Warehouse

,

2018-01-01

The U.S. Geological Survey (USGS) Minerals Yearbook discusses the performance of the worldwide minerals and materials industries and provides background information to assist in interpreting that performance. Content of the individual Minerals Yearbook volumes follows:Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Chapters on survey methods, summary statistics for domestic nonfuel minerals, and trends in mining and quarrying in the metals and industrial mineral industries in the United States are also included.Volume II, Area Reports: Domestic, contains a chapter on the mineral industry of each of the 50 States and Puerto Rico and the Administered Islands. This volume also has chapters on survey methods and summary statistics of domestic nonfuel minerals.Volume III, Area Reports: International, is published as four separate reports. These regional reports contain the latest available minerals data on more than 180 foreign countries and discuss the importance of minerals to the economies of these nations and the United States. Each report begins with an overview of the region’s mineral industries during the year. It continues with individual country chapters that examine the mining, refining, processing, and use of minerals in each country of the region and how each country’s mineral industry relates to U.S. industry. Most chapters include production tables and industry structure tables, information about Government policies and programs that affect the country’s mineral industry, and an outlook section.The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the Minerals Yearbook are welcomed.

Surface contamination artificially elevates initial sweat mineral concentrations

USDA-ARS?s Scientific Manuscript database

During exercise in the heat, sweat is initially concentrated in minerals, but serial sweat samples appear more dilute. Possible causes include reduced dermal mineral concentrations or flushing of surface contamination. PURPOSE: To simultaneously sample mineral concentrations in transdermal fluid (T...

Dietary Supplements and Health Aids: A Critical Evaluation, Part 1- Vitamins and Minerals.

ERIC Educational Resources Information Center

Dubick, Michael A.; Rucker, Robert B.

1983-01-01

Evaluates vitamins/minerals, distinguishing whether studies cited used animal or human subjects. Vitamins discussed include niacin and vitamins B-12, C, A, D, E, and megavitamin supplementation (intake of vitamins at levels 10 times the recommended daily allowance). Minerals considered include dolomite/bone meal, chromium (glucose tolerance…

Mineral commodity summaries 2013

USGS Publications Warehouse

,

2013-01-01

Each chapter of the 2013 edition of the U.S. Geological Survey (USGS) Mineral Commodity Summaries (MCS) includes information on events, trends, and issues for each mineral commodity as well as discussions and tabular presentations on domestic industry structure, Government programs, tariffs, 5-year salient statistics, and world production and resources. The MCS is the earliest comprehensive source of 2012 mineral production data for the world. More than 90 individual minerals and materials are covered by two-page synopses. For mineral commodities for which there is a Government stockpile, detailed information concerning the stockpile status is included in the two-page synopsis. Abbreviations and units of measure, and definitions of selected terms used in the report, are in Appendix A and Appendix B, respectively. “Appendix C—Reserves and Resources” includes “Part A—Resource/Reserve Classification for Minerals” and “Part B—Sources of Reserves Data.” A directory of USGS minerals information country specialists and their responsibilities is Appendix D. The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the MCS 2013 are welcomed.

Mineral commodity summaries 2014

USGS Publications Warehouse

,

2014-01-01

Each chapter of the 2014 edition of the U.S. Geological Survey (USGS) Mineral Commodity Summaries (MCS) includes information on events, trends, and issues for each mineral commodity as well as discussions and tabular presentations on domestic industry structure, Government programs, tariffs, 5-year salient statistics, and world production and resources. The MCS is the earliest comprehensive source of 2013 mineral production data for the world. More than 90 individual minerals and materials are covered by two-page synopses. For mineral commodities for which there is a Government stockpile, detailed information concerning the stockpile status is included in the two-page synopsis. Abbreviations and units of measure, and definitions of selected terms used in the report, are in Appendix A and Appendix B, respectively. “Appendix C—Reserves and Resources” includes “Part A—Resource/Reserve Classification for Minerals” and “Part B—Sources of Reserves Data.” A directory of USGS minerals information country specialists and their responsibilities is Appendix D. The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the MCS 2014 are welcomed.

Minerals Yearbook, volume II, Area Reports—Domestic

USGS Publications Warehouse

,

2018-01-01

The U.S. Geological Survey (USGS) Minerals Yearbook discusses the performance of the worldwide minerals and materials industries and provides background information to assist in interpreting that performance. Content of the individual Minerals Yearbook volumes follows:Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Chapters on survey methods, summary statistics for domestic nonfuel minerals, and trends in mining and quarrying in the metals and industrial mineral industries in the United States are also included.Volume II, Area Reports: Domestic, contains a chapter on the mineral industry of each of the 50 States and Puerto Rico and the Administered Islands. This volume also has chapters on survey methods and summary statistics of domestic nonfuel minerals.Volume III, Area Reports: International, is published as four separate reports. These regional reports contain the latest available minerals data on more than 180 foreign countries and discuss the importance of minerals to the economies of these nations and the United States. Each report begins with an overview of the region’s mineral industries during the year. It continues with individual country chapters that examine the mining, refining, processing, and use of minerals in each country of the region and how each country’s mineral industry relates to U.S. industry. Most chapters include production tables and industry structure tables, information about Government policies and programs that affect the country’s mineral industry, and an outlook section.The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the Minerals Yearbook are welcomed.

Minerals Yearbook, volume III, Area Reports—International

USGS Publications Warehouse

,

2018-01-01

The U.S. Geological Survey (USGS) Minerals Yearbook discusses the performance of the worldwide minerals and materials industries and provides background information to assist in interpreting that performance. Content of the individual Minerals Yearbook volumes follows:Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Chapters on survey methods, summary statistics for domestic nonfuel minerals, and trends in mining and quarrying in the metals and industrial mineral industries in the United States are also included.Volume II, Area Reports: Domestic, contains a chapter on the mineral industry of each of the 50 States and Puerto Rico and the Administered Islands. This volume also has chapters on survey methods and summary statistics of domestic nonfuel minerals.Volume III, Area Reports: International, is published as four separate reports. These regional reports contain the latest available minerals data on more than 180 foreign countries and discuss the importance of minerals to the economies of these nations and the United States. Each report begins with an overview of the region’s mineral industries during the year. It continues with individual country chapters that examine the mining, refining, processing, and use of minerals in each country of the region and how each country’s mineral industry relates to U.S. industry. Most chapters include production tables and industry structure tables, information about Government policies and programs that affect the country’s mineral industry, and an outlook section.The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the Minerals Yearbook are welcomed.

The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin

NASA Astrophysics Data System (ADS)

Reinhard, Christopher T.; Planavsky, Noah J.; Wang, Xiangli; Fischer, Woodward W.; Johnson, Thomas M.; Lyons, Timothy W.

2014-12-01

Chromium (Cr) isotopes are an emerging proxy for tracking redox processes at the Earth's surface. However, there has been limited exploration of the Cr isotope record of modern and recent marine sediments. The basic inorganic chemistry of Cr suggests that anoxic marine basins should factor prominently in the global Cr cycle and that sediments deposited within anoxic basins may offer a valuable Cr isotope archive throughout Earth's history. Here, we present δ53Cr data from sediments of the Cariaco Basin, Venezuela-a 'type' environment for large, perennially anoxic basins with a relatively strong hydrological connection to the global oceans. We document a marked positive shift in bulk δ53Cr values following the termination of the Last Glacial Maximum, followed by relative stasis. Based on a suite of independent redox proxies, this transition marks a switch from oxic to persistently anoxic and sulfidic (euxinic) depositional conditions within the basin. We find good agreement between two independent approaches toward estimating the δ53Cr composition of authigenic Cr in euxinic Cariaco Basin sediments and that these estimates are very similar to the δ53Cr composition of modern open Atlantic Ocean seawater. These data, together with considerations of reaction kinetics and mass balance within the Cariaco Basin, are consistent with the hypothesis that anoxic marine settings can serve as a chemical archive of first-order trends in seawater δ53Cr composition. Additionally, the Cariaco Basin data suggest that there has been secular stability in the average δ53Cr value of Atlantic seawater over the last ∼15 kyr.

Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting

NASA Astrophysics Data System (ADS)

Huck, Claire E.; van de Flierdt, Tina; Jiménez-Espejo, Francisco J.; Bohaty, Steven M.; Röhl, Ursula; Hammond, Samantha J.

2016-03-01

Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation. However, combined studies on sediments, pore waters, fish teeth, and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources.

Assessment of the geoavailability of trace elements from selected zinc minerals

USGS Publications Warehouse

Driscoll, Rhonda L.; Hageman, Phillip L.; Benzel, William M.; Diehl, Sharon F.; Morman, Suzette; Choate, LaDonna M.; Lowers, Heather

2014-01-01

This assessment focused on five zinc-bearing minerals. The minerals were subjected to a number of analyses including quantitative X-ray diffraction, optical microscopy, leaching tests, and bioaccessibility and toxicity studies. Like a previous comprehensive assessment of five copper-bearing minerals, the purpose of this assessment was to obtain structural and chemical information and to characterize the reactivity of each mineral to various simulated environmental and biological conditions. As in the copper minerals study, analyses were conducted consistent with widely accepted methods. Unless otherwise noted, analytical methods used for this study were identical to those described in the investigation of copper-bearing minerals. Two sphalerite specimens were included in the zinc-minerals set. One sphalerite was recovered from a mine in Balmat, New York; the second came from a mine in Creede, Colorado. The location and conditions of origin are significant because, as analyses confirmed, the two sphalerite specimens are quite different. For example, data acquired from a simulated gastric fluid (SGF) study indicate that the hydrothermally formed Creede sphalerite contains orders of magnitude higher arsenic, cadmium, manganese, and lead than the much older metamorphic Balmat sphalerite. The SGF and other experimental results contained in this report suggest that crystallizing conditions such as temperature, pressure, fluidization, or alteration processes significantly affect mineral properties—properties that, in turn, influence reactivity, solubility, and toxicity. The three remaining minerals analyzed for this report—smithsonite, hemimorphite, and hydrozincite—are all secondary minerals or alteration products of zinc-ore deposits. In addition, all share physical characteristics such as tenacity, density, streak, and cleavage. Similarities end there. The chemical composition, unit-cell parameters, acid-neutralizing potential, and other observable and quantifiable properties indicate very different minerals. Only one of each of these minerals was studied. Had this assessment included multiples of these minerals, geochemical and mineralogical distinctions would have emerged, similar to the results for the two sphalerite specimens.

Mineral Selection for Multicomponent Equilibrium Geothermometry

DOE PAGES

Plamer, C. D.; Ohly, S. R.; Smith, R. W.; ...

2015-04-01

Multicomponent geothermometry requires knowledge of the mineral phases in the reservoir with which the geothermal fluids may be equilibrated. These minerals phases are most often alteration products rather than primary minerals. We have reviewed the literature on geothermal systems representing most major geologic environments typically associated with geothermal activity and identified potential alteration products in various environments. We have included this information in RTEst, a code we have developed to estimate reservoir conditions (temperature, CO 2 fugacity) from the geochemistry of near-surface geothermal waters. The information has been included in RTEst through the addition of filters that decrease the potentialmore » number of minerals from all possibilities based on the basis species to those that are more relevant to the particular conditions in which the user is interested. The three groups of filters include host rock type (tholeiitic, calc-alkaline, silicic, siliciclastic, carbonate), water type (acidic, neutral), and the temperature range over which the alteration minerals were formed (low, medium, high). The user-chosen mineral assemblage is checked to make sure that it does not violate the Gibbs phase rule. The user can select one of three mineral saturation weighting schemes that decrease the chance the optimization from being skewed by reaction stoichiometry or analytical uncertainty.« less

43 CFR 3583.3 - Applications for hardrock mineral leases.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Applications for hardrock mineral leases... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) SPECIAL LEASING AREAS Shasta and... hardrock mineral leases. No specific form is required. An application shall include the applicant's name...

43 CFR 3583.3 - Applications for hardrock mineral leases.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Applications for hardrock mineral leases... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) SPECIAL LEASING AREAS Shasta and... hardrock mineral leases. No specific form is required. An application shall include the applicant's name...

43 CFR 3583.3 - Applications for hardrock mineral leases.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Applications for hardrock mineral leases... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) SPECIAL LEASING AREAS Shasta and... hardrock mineral leases. No specific form is required. An application shall include the applicant's name...

43 CFR 3583.3 - Applications for hardrock mineral leases.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Applications for hardrock mineral leases... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) SPECIAL LEASING AREAS Shasta and... hardrock mineral leases. No specific form is required. An application shall include the applicant's name...

Minerals Yearbook, volume III, Area Reports—International—Africa and the Middle East

USGS Publications Warehouse

,

2018-01-01

The U.S. Geological Survey (USGS) Minerals Yearbook discusses the performance of the worldwide minerals and materials industries and provides background information to assist in interpreting that performance. Content of the individual Minerals Yearbook volumes follows:Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Chapters on survey methods, summary statistics for domestic nonfuel minerals, and trends in mining and quarrying in the metals and industrial mineral industries in the United States are also included.Volume II, Area Reports: Domestic, contains a chapter on the mineral industry of each of the 50 States and Puerto Rico and the Administered Islands. This volume also has chapters on survey methods and summary statistics of domestic nonfuel minerals.Volume III, Area Reports: International, is published as four separate reports. These regional reports contain the latest available minerals data on more than 180 foreign countries and discuss the importance of minerals to the economies of these nations and the United States. Each report begins with an overview of the region’s mineral industries during the year. It continues with individual country chapters that examine the mining, refining, processing, and use of minerals in each country of the region and how each country’s mineral industry relates to U.S. industry. Most chapters include production tables and industry structure tables, information about Government policies and programs that affect the country’s mineral industry, and an outlook section.The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the Minerals Yearbook are welcomed.

Minerals Yearbook, volume III, Area Reports—International—Asia and the Pacific

USGS Publications Warehouse

Geological Survey, U.S.

2018-01-01

The U.S. Geological Survey (USGS) Minerals Yearbook discusses the performance of the worldwide minerals and materials industries and provides background information to assist in interpreting that performance. Content of the individual Minerals Yearbook volumes follows:Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Chapters on survey methods, summary statistics for domestic nonfuel minerals, and trends in mining and quarrying in the metals and industrial mineral industries in the United States are also included.Volume II, Area Reports: Domestic, contains a chapter on the mineral industry of each of the 50 States and Puerto Rico and the Administered Islands. This volume also has chapters on survey methods and summary statistics of domestic nonfuel minerals.Volume III, Area Reports: International, is published as four separate reports. These regional reports contain the latest available minerals data on more than 180 foreign countries and discuss the importance of minerals to the economies of these nations and the United States. Each report begins with an overview of the region’s mineral industries during the year. It continues with individual country chapters that examine the mining, refining, processing, and use of minerals in each country of the region and how each country’s mineral industry relates to U.S. industry. Most chapters include production tables and industry structure tables, information about Government policies and programs that affect the country’s mineral industry, and an outlook section.The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the Minerals Yearbook are welcomed.

Minerals Yearbook, volume III, Area Reports—International—Latin America and Canada

USGS Publications Warehouse

,

2018-01-01

The U.S. Geological Survey (USGS) Minerals Yearbook discusses the performance of the worldwide minerals and materials industries and provides background information to assist in interpreting that performance. Content of the individual Minerals Yearbook volumes follows:Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Chapters on survey methods, summary statistics for domestic nonfuel minerals, and trends in mining and quarrying in the metals and industrial mineral industries in the United States are also included.Volume II, Area Reports: Domestic, contains a chapter on the mineral industry of each of the 50 States and Puerto Rico and the Administered Islands. This volume also has chapters on survey methods and summary statistics of domestic nonfuel minerals.Volume III, Area Reports: International, is published as four separate reports. These regional reports contain the latest available minerals data on more than 180 foreign countries and discuss the importance of minerals to the economies of these nations and the United States. Each report begins with an overview of the region’s mineral industries during the year. It continues with individual country chapters that examine the mining, refining, processing, and use of minerals in each country of the region and how each country’s mineral industry relates to U.S. industry. Most chapters include production tables and industry structure tables, information about Government policies and programs that affect the country’s mineral industry, and an outlook section.The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the Minerals Yearbook are welcomed.

Minerals Yearbook, volume III, Area Reports—International—Europe and Central Eurasia

USGS Publications Warehouse

Geological Survey, U.S.

2018-01-01

The U.S. Geological Survey (USGS) Minerals Yearbook discusses the performance of the worldwide minerals and materials industries and provides background information to assist in interpreting that performance. Content of the individual Minerals Yearbook volumes follows:Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Chapters on survey methods, summary statistics for domestic nonfuel minerals, and trends in mining and quarrying in the metals and industrial mineral industries in the United States are also included.Volume II, Area Reports: Domestic, contains a chapter on the mineral industry of each of the 50 States and Puerto Rico and the Administered Islands. This volume also has chapters on survey methods and summary statistics of domestic nonfuel minerals.Volume III, Area Reports: International, is published as four separate reports. These regional reports contain the latest available minerals data on more than 180 foreign countries and discuss the importance of minerals to the economies of these nations and the United States. Each report begins with an overview of the region’s mineral industries during the year. It continues with individual country chapters that examine the mining, refining, processing, and use of minerals in each country of the region and how each country’s mineral industry relates to U.S. industry. Most chapters include production tables and industry structure tables, information about Government policies and programs that affect the country’s mineral industry, and an outlook section.The USGS continually strives to improve the value of its publications to users. Constructive comments and suggestions by readers of the Minerals Yearbook are welcomed.

Microbe-Clay Mineral Reactions and Characterization Techniques

NASA Astrophysics Data System (ADS)

Dong, H.; Zhang, G.; Ji, S.; Jaisi, D.; Kim, J.

2008-12-01

Clays and clay minerals are ubiquitous in soils, sediments, and sedimentary rocks. They play an important role in environmental processes such as nutrient cycling, plant growth, contaminant migration, organic matter maturation, and petroleum production. The changes in the oxidation state of the structural iron in clay minerals, in part, control their physical and chemical properties in natural environments, such as clay particle flocculation, dispersion, swelling, hydraulic conductivity, surface area, cation and anion exchange capacity, and reactivity towards organic and inorganic contaminants. The structural ferric iron [Fe(III)] in clay minerals can be reduced either chemically or biologically. Many different chemical reductants have been tried, but the most commonly used agent is dithionite. Biological reductants are bacteria, including dissimilatory iron reducing prokaryotes (DIRP) and sulfate-reducing bacteria (SRB). A wide variety of DIRP have been used to reduce ferric iron in clay minerals, including mesophilic, thermophilic, and hyperthermophilic prokaryotes. Multiple clay minerals have been used for microbial reduction studies, including smectite, nontronite (iron-rich smectite variety), illite, illite/smectite, chlorite, and their various mixtures. All these clay minerals are reducible by microorganisms under various conditions with smectite (nontronite) being the most reducible. The reduction extent and rate of ferric iron in clay minerals are measured by wet chemistry, and the reduced clay mineral products are typically characterized with chemical methods, X-ray diffraction, scanning and transmission electron microscopy, Mössbauer spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), UV-vis spectroscopy, and synchrotron-based techniques (such as EXAFS). Microbially reduced smectites (nontronites) have been found to be reactive in reducing a variety of organic and inorganic contaminants. Degradable organic contaminants include pesticides, solvents, explosives, and nitroaromatic and polychlorinated compounds. Inorganic contaminants include Cr(VI), U(VI), and Tc(VII). Despite significant efforts, our understanding of mechanisms of chemical and microbial reduction of ferric iron in clay minerals is still limited. While some studies have presented evidence for a solid-state reduction mechanism, others argue that the clay mineral structure dissolves when the extent of reduction is higher (greater than 30 percent). The electron transfer process is also dependent on the reducing agent. While chemical reduction of ferric iron appears to occur at the basal surfaces, bacteria appear to attack clay minerals at the edges.

Hair Mineral Analysis and Behavior: An Analysis of 51 Studies.

ERIC Educational Resources Information Center

Rimland, Bernard; Larson, Gerald E.

1983-01-01

Fifty-one studies on the relationship between hair mineral levels and human behavior covered a variety of behavior, including learning disabilities, retardation, hyperactivity, autism, and behavior disorders. High levels of certain minerals (especially lead and cadmium) and low levels of other minerals (especially potassium and sodium) associated…

Anaerobic oxidation of methane in the Concepción Methane Seep Area, Chilean continental margin

NASA Astrophysics Data System (ADS)

Steeb, P.; Linke, P.; Scholz, F.; Schmidt, M.; Liebetrau, V.; Treude, T.

2012-04-01

Within subduction zones of active continental margins, large amounts of methane can be mobilized by dewatering processes and transported to the seafloor along migration pathways. A recently discovered seep area located off Concepción (Chile) at water depth between 600 to 1100 mbsl is characterized by active methane vent sites as well as massive carbonates boulders and plates which probably are related to methane seepage in the past. During the SO210 research expedition "Chiflux" (Sept-Oct 2010), sediment from the Concepción Methane Seep Area (CSMA) at the fore arc of the Chilean margin was sampled to study microbial activity related to methane seepage. We sampled surface sediments (0-30cm) from sulfur bacteria mats, as well as clam, pogonophoran, and tubeworm fields with push cores and a TV-guided multicorer system. Anaerobic oxidation of methane (AOM) and sulfate reduction rates were determined using ex-situ radioisotope tracer techniques. Additionally, porewater chemistry of retrieved cores as well as isotopic composition and age record of surrounding authigenic carbonates were analyzed. The shallowest sulfate-methane-transition zone (SMTZ) was identified at 4 cm sediment depth hinting to locally strong fluid fluxes. However, a lack of Cl- anomalies in porewater profiles indicates a shallow source of these fluids, which is supported by the biogenic origin of the methane (δ13C -70‰ PDB). Sulfide and alkalinity was relatively high (up to 20 mM and 40 mEq, respectively). Rates of AOM and sulfate reduction within this area reached magnitudes typical for seeps with variation between different habitat types, indicating a diverse methane supply, which is affecting the depths of the SMTZ. Rates were highest at sulfur a bacteria mats (20 mmol m-2 d-1) followed by a large field of dead clams, a pogonophoran field, a black sediment spot, and a carbonate rich clam field. Lowest rates (0.2 mmol m-2 d-1) were measured in close vicinity to these hot spots. Abundant massive carbonate blocks and plates hint to a very old seep system with a probably much higher activity in the past. The U-Th age record of these authigenic carbonates reach back to periods of venting activity with more than 150 ka ago. Carbon isotopic signatures of authigenic carbonates (δ13C -50 to -40‰ PDB) suggest a biogenic carbon source (i.e. methane), also in the past. We found several indications for the impact of recent earthquakes within the seep area (cracks, shifted seafloor), which could be an important mechanism for the triggering of new seepage activity, change in fluid expulsion rates and colonization patterns of the cold seep fauna.

Preliminary Model of Porphyry Copper Deposits

USGS Publications Warehouse

Berger, Byron R.; Ayuso, Robert A.; Wynn, Jeffrey C.; Seal, Robert R.

2008-01-01

The U.S. Geological Survey (USGS) Mineral Resources Program develops mineral-deposit models for application in USGS mineral-resource assessments and other mineral resource-related activities within the USGS as well as for nongovernmental applications. Periodic updates of models are published in order to incorporate new concepts and findings on the occurrence, nature, and origin of specific mineral deposit types. This update is a preliminary model of porphyry copper deposits that begins an update process of porphyry copper models published in USGS Bulletin 1693 in 1986. This update includes a greater variety of deposit attributes than were included in the 1986 model as well as more information about each attribute. It also includes an expanded discussion of geophysical and remote sensing attributes and tools useful in resource evaluations, a summary of current theoretical concepts of porphyry copper deposit genesis, and a summary of the environmental attributes of unmined and mined deposits.

Bartering for Minerals.

ERIC Educational Resources Information Center

May, Kathie

2002-01-01

Presents an activity in which students are assigned occupations that rely on specific minerals. To obtain the needed minerals, students learn how to trade services and commodities. Includes details on preparation, modeling behaviors, and printed materials. (DDR)

Phosphorus, Barium and Bioactive Metals (Zn, Cu, Co) in Coral Aragonite: Relationships to Upper Ocean Productivity

NASA Astrophysics Data System (ADS)

Sherrell, R. M.; Lavigne, M. G.; Linsley, B. K.

2006-12-01

Coral records of surface ocean properties related to primary productivity could reveal much about the history of upper ocean biogeochemistry over decades to centuries, but are currently relatively undeveloped. This presentation will explore the utility of high-resolution records of P/Ca, Ba/Ca, and the micronutrient metals Zn/Ca, Cu/Ca, and Co/Ca. Using high sensitivity laser ablation ICP-MS, we have obtained multi-year records of these variables with ~ bi-weekly resolution and seasonal dating for Porites corals from Rarotonga (21S, 159W) and Clipperton Atoll (10N, 109W) Results are compared to data for Porites and Acropora spp. grown in culture at Rutgers University, to explore the applicability of cultured corals for quantifying the effects of seawater chemistry on trace elements in coralline aragonite. The P/Ca results suggest lattice-bound incorporation and encourage the development of a surface ocean PO4 proxy details will be presented by LaVigne et al. elsewhere in this session. At Rarotonga, Ba/Ca shows regular, ~ annual, 2-5 week duration spikes a factor of 2-3 higher than the ~ constant background signal, appearing in austral spring- summer. These are not associated with runoff or authigenic mineral incorporation, and are similar to Ba spikes observed at least twice in the literature. We explore the hypothesis that these signals are related to biogenic organically-bound or barite Ba in the ambient surface water, and might therefore serve as a proxy of phytoplankton bloom intensity during the most productive part of the year. Potential mechanisms of incorporation must include the possibility of suspended particulate elements finding a route to permanent sequestration in the skeleton. Laser ablation values for Zn, and Cu are similar at Rarotonga and Clipperton, and higher by factors of 500 and 15 than literature values for cleaned aragonite analyzed in solution, while our Co/Ca values are the lowest ever determined. Seasonal and shorter scale variations at Rarotonga are muted for Zn, but substantial for Cu and Co, possibly reflecting biologically-driven changes in ambient dissolved metal concentration or speciation. Corals grown in non-metal clean artificial seawater are higher for Zn, but surprisingly lower for Cu and Co. We suggest that the distribution coefficient model of metal incorporation may need to be revised to include aspects of dissolved metal speciation and particulate metal sources. In sum, these results will be used to evaluate the utility of laser ablation data for revealing aspects of open ocean biogeochemistry in the past.

Historical statistics for mineral and material commodities in the United States

USGS Publications Warehouse

Kelly, Thomas; Matos, Grecia; with Buckingham, David; DiFrancesco, Carl; Porter, Kenneth; Berry, Cyrus; Crane, Melissa; Goonan, Thomas; Sznopek, John

2005-01-01

The U.S. Geological Survey (USGS) provides information to the public and to policy-makers concerning the current use and flow of minerals and materials in the United States economy. The USGS collects, analyzes, and disseminates minerals information on most nonfuel mineral commodities.This USGS digital database is an online compilation of historical U.S. statistics on mineral and material commodities. The database contains information on approximately 90 mineral commodities, including production, imports, exports, and stocks; reported and apparent consumption; and unit value (the real and nominal price in U.S. dollars of a metric ton of apparent consumption). For many of the commodities, data are reported as far back as 1900. Each commodity file includes a document that describes the units of measure, defines terms, and lists USGS contacts for additional information End-use tables complement these statistics by supplying, for most of these commodities, information about the distribution of apparent consumption.This publication draws on more than 125 years of minerals information experience. At the request of the 47th Congress of the United States (1882; 22 Stat. 329), the U.S. Government began the collection and public distribution of these types of data. The Federal agencies responsible for the collection of the data have changed through time. For the years 1882-1924, the USGS collected and published these data; the U.S. Bureau of Mines (USBM) performed these tasks from 1925-95; and in 1996, the responsibilities once again passed to the USGS (following the closure of the USBM) (Mlynarski, 1998).The USGS collects data on a monthly, quarterly, semiannual, and annual basis from more than 18,000 minerals-related producer and consumer establishments that cooperate with the USGS. These companies voluntarily complete about 40,000 canvass forms that survey production, consumption, recycling, stocks, shipments, and other essential information. Data are also gathered from site visits, memberships on domestic and international minerals-related committees, and coordination with other government organizations and trade associations.The USGS makes this information available through published products, including monthly, quarterly, and annual Mineral Industry Surveys, the annual Minerals Yearbook (MYB), the annual Mineral Commodity Summaries (MCS), and special mineral commodity studies, including the history of metal prices and materials flow studies. 

43 CFR 3471.2-1 - Disposal of land with a reservation of minerals.

Code of Federal Regulations, 2013 CFR

2013-10-01

... minerals. 3471.2-1 Section 3471.2-1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) COAL MANAGEMENT... reservation of minerals. (a) Where the lands included in a lease or license to mine have been or may be...

43 CFR 3471.2-1 - Disposal of land with a reservation of minerals.

Code of Federal Regulations, 2011 CFR

2011-10-01

... minerals. 3471.2-1 Section 3471.2-1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) COAL MANAGEMENT... reservation of minerals. (a) Where the lands included in a lease or license to mine have been or may be...

43 CFR 3471.2-1 - Disposal of land with a reservation of minerals.

Code of Federal Regulations, 2014 CFR

2014-10-01

... minerals. 3471.2-1 Section 3471.2-1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) COAL MANAGEMENT... reservation of minerals. (a) Where the lands included in a lease or license to mine have been or may be...

Mineral Fiber Toxicology

EPA Science Inventory

The chemical and physical properties of different forms of mineral fibers impact biopersistence and pathology in the lung. Fiber chemistry, length, aspect ratio, surface area and dose are critical factors determining mineral fiber-associated health effects including cancer and as...

An Expert System for Identification of Minerals in Thin Section.

ERIC Educational Resources Information Center

Donahoe, James Louis; And Others

1989-01-01

Discusses a computer database which includes optical properties of 142 minerals. Uses fuzzy logic to identify minerals from incomplete and imprecise information. Written in Turbo PASCAL for MS-DOS with 128K. (MVL)

Mineral concentrations in diets, water, and milk and their value in estimating on-farm excretion of manure minerals in lactating dairy cows.

PubMed

Castillo, A R; St-Pierre, N R; Silva del Rio, N; Weiss, W P

2013-05-01

Thirty-nine commercial dairies in Merced County, California were enrolled in the present study to (1) compare lactating cow mineral intakes (via drinking water and total mixed ration) to the National Research Council (NRC) requirements, (2) evaluate the association between dietary concentrations of minerals with and without drinking water and adjusted for mineral concentrations in milk, and (3) compare 4 different methods to estimate excretion of minerals using either assays or estimations of milk mineral outputs and total daily mineral intake per cow with or without minerals coming from drinking water. Dairies were selected to represent a range of herd milk yields and a range of water mineral contents. Samples of total mixed ration, drinking water, and bulk tank milk were taken on 2 different days, 3 to 7d apart in each farm. Across-farm medians and percentile distributions were used to analyze results. The herd median milk yield interquartile ranged (10th to 90th percentile) from less than 25 to more than 39 kg/d and the concentration of total solids in water interquartile ranged from less than 200 to more than 1,490 mg/L. Including drinking water minerals in the diets increased dietary concentrations by <4% for all minerals except for Na and Cl, which increased by 9.3 and 6.5%, respectively. Concentrations of P and K in milk were essentially the same as the NRC value to estimate lactation requirements. However, NRC milk values of Ca, Cl, and Zn were 10 to 20% greater than dairy farm values; and Na, Cu, Fe, and Mn were no less than 36% below NRC values. Estimated excretion of minerals via manure varied substantially across farms. Farms in the 10th percentile did have 2 to 3 times less estimated mineral excretions than those in the 90th percentile (depending on the mineral). Although including water minerals increased excretion of most minerals, the actual median effect of Ca, Mg, S, Cu, Fe, and Mn was less than 5%, and about 8% for Na and Cl. Replacing assayed concentrations of minerals in milk with NRC constants resulted in reduced estimated excretion of Ca, Na, Cu, Fe, and Zn, but median differences were <5% except for Na which was 7.5%. Results indicate that not including mineral intake via drinking water and not using assayed concentrations of milk minerals lead to errors in estimation manure excretion of minerals (e.g., Ca, Na, Cl, and S). Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Evolution of ribozymes in the presence of a mineral surface

PubMed Central

Stephenson, James D.; Popović, Milena; Bristow, Thomas F.

2016-01-01

Mineral surfaces are often proposed as the sites of critical processes in the emergence of life. Clay minerals in particular are thought to play significant roles in the origin of life including polymerizing, concentrating, organizing, and protecting biopolymers. In these scenarios, the impact of minerals on biopolymer folding is expected to influence evolutionary processes. These processes include both the initial emergence of functional structures in the presence of the mineral and the subsequent transition away from the mineral-associated niche. The initial evolution of function depends upon the number and distribution of sequences capable of functioning in the presence of the mineral, and the transition to new environments depends upon the overlap between sequences that evolve on the mineral surface and sequences that can perform the same functions in the mineral's absence. To examine these processes, we evolved self-cleaving ribozymes in vitro in the presence or absence of Na-saturated montmorillonite clay mineral particles. Starting from a shared population of random sequences, RNA populations were evolved in parallel, along separate evolutionary trajectories. Comparative sequence analysis and activity assays show that the impact of this clay mineral on functional structure selection was minimal; it neither prevented common structures from emerging, nor did it promote the emergence of new structures. This suggests that montmorillonite does not improve RNA's ability to evolve functional structures; however, it also suggests that RNAs that do evolve in contact with montmorillonite retain the same structures in mineral-free environments, potentially facilitating an evolutionary transition away from a mineral-associated niche. PMID:27793980

30 CFR 250.211 - What must the EP include?

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 2 2011-07-01 2011-07-01 false What must the EP include? 250.211 Section 250.211 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF... Information Contents of Exploration Plans (ep) § 250.211 What must the EP include? Your EP must include the...

The Conterminous United States Mineral Assessment Program; background information to accompany folio of geologic, geochemical, remote sensing, and mineral resources maps of the Butte 1 degree x 2 degrees Quadrangle, Montana

USGS Publications Warehouse

Elliott, James E.; Trautwein, C.M.; Wallace, C.A.; Lee, G.K.; Rowan, L.C.; Hanna, W.F.

1993-01-01

The Butte 1?x2 ? quadrangle in west-central Montana was investigated as part of the U.S. Geological Survey's Conterminous United States Mineral Assessment Program (CUSMAP). These investigations included geologic mapping, geochemical surveys, gravity and aeromagnetic surveys, examinations of mineral deposits, and specialized geochronologic and remote-sensing studies. The data collected during these studies were compiled, combined with available published and unpublished data, analyzed, and used in a mineral-resource assessment of the quadrangle. The results, including data, interpretations, and mineral-resource assessments for nine types of mineral deposits, are published separately as a folio of maps. These maps are accompanied by figures, tables, and explanatory text. This circular provides background information on the Butte quadrangle, summarizes the studies and published maps, and lists a selected bibliography of references pertinent to the geology, geochemistry, geophysics, and mineral resources of the quadrangle. The Butte quadrangle, which includes the world-famous Butte mining district, has a long history of mineral production. Many mining districts within the quadrangle have produced large quantities of many commodities; the most important in dollar value of production were copper, gold, silver, lead, zinc, manganese, molybdenum, and phosphate. At present, mines at several locations produce copper, molybdenum, gold, silver, lead, zinc, and phosphate. Exploration, mainly for gold, has indicated the presence of other mineral deposits that may be exploited in the future. The results of the investigations by the U.S. Geological Survey indicate that many areas of the quadrangle are highly favorable for the occurrence of additional undiscovered resources of gold, silver, copper, molybdenum, tungsten, and other metals in several deposit types.

Report on "Methodologies for Investigating Microbial-Mineral Interactions: A Clay Minerals Society Short Course"

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

Maurice, Patricia A.

2010-02-08

A workshop entitled, “Methods of Investigating Microbial-Mineral Interactions,” was held at the Clay Minerals Society meeting at the Pacific Northwest National Laboratory in Richland, WA on June 19, 2004. The workshop was organized by Patricia A. Maurice (University of Notre Dame) and Lesley A. Warren (McMaster University, CA). Speakers included: Dr. P. Bennett, Dr. J. Fredrickson (PNNL), Dr. S. Lower (Ohio State University), Dr. P. Maurice, Dr. S. Myneni (Princeton University), Dr. E. Shock (Arizona State), Dr. M. Tien (Penn State), Dr. L. Warren, and Dr. J. Zachara (PNNL). There were approximately 75 attendees at the workshop, including more thanmore » 20 students. A workshop volume was published by the Clay Minerals Society [Methods for Study of Microbe-Mineral Interactions (2006), CMS Workshop Lectures, vol 14(Patricia A. Maurice and Leslie A. Warren, eds.) ISBN 978-1-881208-15-0, 166 pp.]« less

Race for resources: continuing struggles over minerals and fuels

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

Tanzer, M.

1980-01-01

Analyzing the mineral crisis within the historical context of the workings of the international capitalist system is necessary since capitalism spawned the industrial revolution, which in turn led to the vast expansion of mineral use. The analysis begins with the multinational companies that dominate the international mineral industry because they are generally the leading forces in the struggle for control of mineral resources and profits. The focus is twofold: (1) on those minerals that are important as economic inputs and in money value, including the metals copper, bauxite, nickel, and iron ore; and (2) to a lesser extent, on themore » fuels. The emphasis is on the current picture and likely changes in the future. Case studies illustrate some of the major forces at work. Crucial problem areas of the future will include the roles of technology, the Third World, and socialist countries. 26 references, 24 tables.« less

Program and Abstracts for Clay Minerals Society 28th Annual Meeting

NASA Technical Reports Server (NTRS)

1991-01-01

This volume contains abstracts that were accepted for presentation at the annual meeting. Some of the main topics covered include: (1) fundamental properties of minerals and methods of mineral analysis; (2) surface chemistry; (3) extraterrestrial clay minerals; (4) geothermometers and geochronometers; (5) smectite, vermiculite, illite, and related reactions; (6) soils and clays in environmental research; (7) kaolinite, halloysite, iron oxides, and mineral transformations; and (8) clays in lakes, basins, and reservoirs.

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

D`Agostino, A.E.; Jordan, D.W.; Jordan, D.W.

Shanmugam and Moiola (1995) put forth a new interpretation of sandstone depositional processes in the Jackfork Group exposed in the spillway at DeGray Lake, near Arkadelphia, Arkansas. Their novel interpretation of deposition dominated by sandy, matrix-supported debris flows is at odds with nearly every other investigation of the Jackfork to date. One key to their interpretation is their contention that the Jackfork sandstones have a high matrix content (as high as 25%). The high matrix content is critical to their arguments about the textural characteristics and flow properties of debris flows vs. turbidites. In our guidebook, we presented a largemore » volume of petrographic data collected from samples taken from the Jackfork exposed on the east and west sides of the Spillway at DeGray Lake (and other locations as well). D`Agostino performed nearly al of the petrographic analyses presented in that guidebook. We disagree strongly with the reinterpretations of Shanmugam and Moiola and believe we can confidently address issues of petrography and matrix content. Specifically, we wish to address four points: (1) the amount of petrographic sampling done by Shanmugam and Moiola (1995); i.e., sampling density in a 327-m- (1072-ft) thick section, (2) overall matrix content of Jackfork sandstones, and Shanmugam and Moiola`s misrepresentation of our data, plus their apparent unfamiliarity with pertinent published data on the petrography of the Jackfork, (3) the distinction among authigenic clay, density in a 327-m- (1072-ft-) thick section, (2) overall matrix content of Jackfork sandstones, and Shanmugam and Moiola`s misrepresentation of our data, plus their apparent unfamiliarity with pertinent published data on the petrography of the Jackfork, (3) the distinction among authigenic clay, detrital clay, and other matrix materials, which Shanmugam and Moiola do not adequately discuss, and (4) the relationship of matrix content to their own facies classification scheme.« less

Methane seepage effects on biodiversity and biological traits of macrofauna inhabiting authigenic carbonates

NASA Astrophysics Data System (ADS)

Levin, Lisa A.; Mendoza, Guillermo F.; Grupe, Benjamin M.

2017-03-01

Authigenic carbonate rocks at methane seeps are recognized as hosting diverse and abundant invertebrate assemblages, with potential forcing from fluid seepage and hydrography. Mensurative studies of carbonate macrofauna (>0.3 mm) at Hydrate Ridge, OR revealed little effect of water depth and overlying oxygenation (at 600 m and 800 m) but a large influence of seepage activity on density, taxonomic composition, diversity, and biological traits (feeding, lifestyle, motility, size and calcification). Rocks exposed to active seepage had 3-4× higher total macrofaunal densities than under inactive conditions. Assemblages exhibited higher species richness and reduced evenness (greater dominance) under active seepage than inactive conditions, but no difference in H‧ or rarefaction diversity. Actively seeping sites were characterized by errant (motile), bacterial grazing, small- and medium-sized, heavily calcified species, whereas inactive sites exhibited a greater diversity of feeding modes and more burrowers, sessile, large and lightly calcified species. Active rocks supported more exogonid (Syllidae), ampharetid, and cirratulid polychaetes, provannid snails, pyropeltid limpets, nemerteans, and sponges; whereas inactive rocks supported higher densities of ophiuroids, isopods, gammarid amphipods, hydroids, Typosyllis (Syllidae) and tanaids. Transplant experiments, in which rocks were transferred between active and inactive sites at Hydrate Ridge North (600 m), revealed that assemblages respond within 13 months to increase or cessation of seepage, taking on the feeding, size and calcification characteristics of the background fauna at the new site. Lifestyles and motility patterns shifted more slowly as the sessile, attached species did not track seepage as quickly. Provannid snails and pyropeltid limpets rapidly colonized rocks transplanted to active sites and disappeared when transplanted to inactive sites. Given the known variability of fluid fluxes and rapid community response, a mosaic of communities changing in space and time is hypothesized to generate the relatively high species diversity at methane seeps.

Timing of fluid seepage on summits of Quaker and Conical serpentine mud volcanoes, Mariana forearc: Evidence from U/Th dating of carbonate chimneys

NASA Astrophysics Data System (ADS)

Tong, Hongpeng; Fryer, Patricia; Feng, Dong; Chen, Duofu

2017-04-01

Serpetinization of forearc mantle along deep faults in the Mariana convergent plate margin permits formation of large active serpentinite mud volcanoes on the overiding plate within 90 km of the trench. Fluid seepage on summits of the mud volcanoes lead to the formation of authigenic carbonate chimneys close to the seafloor. Such carbonate chimneys are unique archives of past fluid seepage and assciated envrionemtnal parameters. Here, we report U/Th dating and stable carbon and oxygen isotopes of the chimneys from Quaker and Conical serpentine mud volcanoes. The resulting U/Th ages of samples from Quaker Seamount show three time intervals of 11,081 to10,542 yBP, 5,857 to 5,583 yBP, and 781 to 164 yBP, respectively. By comparison, carbonates from Conical Seamount have U/Th ages between 3,070 yBP and 1,623 yBP. Our results suggest that fluid seepage on the summits of serpentine mud volcanoes are episodic and probably locally controlled. Samples from Quaker seamount show depletion of 13C (δ13C=-7.0-0.4‰ V-PDB), indicating contribution of carbon from anoxic oxidation of abiogenic methane. By contrast, samples from Conical seamount have positive δ18O values (0.6-6.3), suggesting enrichment of 18O in the seepage fluid. The data obtained provide time integrated variation of seepage fluids and seepage dynamics that are archived in authigenic carbonates. This finding adds to the ongoing multidisciplinary effort to better constrain the environment in the Mariana forearc region and to determine the locally dominant biogeochemical processes. Acknowlegment: This study was funded by the CAS (Grant No. XDB06030102).

Post-depositional behavior of Cu in a metal-mining polishing pond (East Lake, Canada).

PubMed

Martin, Alan J; Jambor, John L; Pedersen, Tom F; Crusius, John

2003-11-01

The post-depositional behavior of Cu in a gold-mining polishing pond (East Lake, Canada) was assessed after mine closure by examination of porewater chemistry and mineralogy. The near-surface (upper 1.5 cm) sediments are enriched in Cu, with values ranging from 0.4 to 2 wt %. Mineralogical examination revealed that the bulk of the Cu inventory is present as authigenic copper sulfides. Optical microscopy, energy-dispersion spectra, and X-ray data indicate that the main Cu sulfide is covellite (CuS). The formation of authigenic Cu-S phases is supported by the porewater data, which demonstrate that the sediments are serving as a sink for dissolved Cu below sub-bottom depths of 1-2 cm. The zone of Cu removal is consistent with the occurrence of detectable sulfide and the consumption of sulfate. The sediments can be viewed as a passive bioreactorthat permanently removes Cu as insoluble copper sulfides. This process is not unlike that which occurs in other forms of bioremediation, such as wetlands and permeable reactive barriers. Above the zone of Cu removal, dissolved Cu maxima in the interfacial porewaters range from 150 to 450 microg L(-1) and reflect the dissolution of a Cu-bearing phase in the surface sediments. The reactive phase is thought to be a component of treatment sludges delivered to the lake as part of cyanide treatment. Flux calculations indicate that the efflux of dissolved Cu from the sediments to the water column (14-51 microg cm(-2) yr(-1)) can account for the elevated levels of dissolved Cu in lake waters (approximately 50 microg L(-1)). Implications for lake recovery are discussed.

Occurrence of near-seafloor gas hydrates and associated cold vents in the Ulleung Basin, East Sea

NASA Astrophysics Data System (ADS)

Bahk, J.-J.; Kong, G.-S.; Park, Y.; Kim, J.-H.; Lee, H.; Park, Y.; Park, K.-P.

2009-04-01

During the site survey cruise for proposed drill sites of the Ulleung Basin Gas Hydrate Expedition 01, near-seafloor gas hydrates were discovered in core sediments from both regions of basin plain (2066-2012 m water depth) and southern slope (898 m) of the Ulleung Basin. The gas hydrate-bearing cores were exclusively retrieved from high backscatter intensity areas in processed 13 kHz multi-beam data, implying high seafloor reflectivity. In high-resolution (2-7 kHz) sub-bottom profiles, the coring sites are also characterized by narrow (< about 500 m wide) acoustic blank zones reaching seafloor, where they have surface expressions of low-relief (< about 5 m high) mound. In the data from a 38 kHz split-beam echosounder, which was deployed for acoustic characterization of gas bubbles, there are no apparent gas flares associated with the blank zones. The recovered gas hydrates mainly consist of disseminated nodules or veins in clayey mud, which normally occur from 5-6 m below the seafloor to the maximum penetration depth (<8 m) of the cores. In some cases, they were associated with abundant scattered authigenic carbonate nodules. Compositional and structural analyses of selected gas hydrate samples revealed that they consist of structure I hydrates which contain more than 99% methane with carbon isotope values ranging from -64 to -80 per mil (PDB). The preliminary results of the site survey cruise collectively suggest that the near-seafloor gas hydrates are related to cold vents, where high seafloor reflectivity is caused by presence of gas hydrates and authigenic carbonates. Gas seeping activity in the cold vents appears to be currently dormant.

Contribution of deep sourced carbon from hydrocarbon seeps to sedimentary organic carbon: Evidence from Δ14C and δ13C isotopes

NASA Astrophysics Data System (ADS)

Feng, D.; Peckmann, J.; Peng, Y.; Liang, Q.; Roberts, H. H.; Chen, D.

2017-12-01

Sulfate-driven anaerobic oxidation of methane (AOM) limits the release of methane from marine sediments and promotes the formation of carbonates close to the seafloor along continental margins. It has been established that hydrocarbon seeps are a source of dissolved inorganic and organic carbon to marine environments. However, questions remain about the contribution of deep sourced carbon from hydrocarbon seeps to the sedimentary organic carbon pool. For a number of hydrocarbon seeps from the South China Sea and the Gulf of Mexico, the portion of modern carbon was determined based on natural radiocarbon abundances (Δ14C) and stable carbon isotope (δ13Corganic carbon) compositions of the non-carbonate fractions extracted from authigenic carbonates. Samples from both areas show a mixing trend between ideal planktonic organic carbon (δ13C = -22‰ VPDB and 90% modern carbon) and the ambient methane. The δ13Corganic carbon values of non-carbonate fractions from three ancient seep deposits (northern Italy, Miocene; western Washington State, USA, Eocene to Oligocene) confirm that the proxy can be used to constrain the record of sulfate-driven AOM through most of Earth history by measuring the δ13C values of organic carbon. This study reveals the potential of using δ13C values of organic carbon to discern seep and non-seep environments. This new approach is particularly promising when authigenic carbonate is not present in ancient sedimentary environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support of the deep-sea dives. Funding was provided by the NSF of China (Grants: 41422602 and 41373085).

Post-Depositional Behavior of Cu in a Metal-Mining Polishing Pond (East Lake, Canada)

USGS Publications Warehouse

Martin, A.J.; Jambor, J.L.; Pedersen, Thomas F.; Crusius, John

2003-01-01

The post-depositional behavior of Cu in a gold-mining polishing pond (East Lake, Canada) was assessed after mine closure by examination of porewater chemistry and mineralogy. The near-surface (upper 1.5 cm) sediments are enriched in Cu, with values ranging from 0.4 to 2 wt %. Mineralogical examination revealed that the bulk of the Cu inventory is present as authigenic copper sulfides. Optical microscopy, energy-dispersion spectra, and X-ray data indicate that the main Cu sulfide is covellite (CuS). The formation of authigenic Cu-S phases is supported by the porewater data, which demonstrate that the sediments are serving as a sink for dissolved Cu below sub-bottom depths of 1-2 cm. The zone of Cu removal is consistent with the occurrence of detectable sulfide and the consumption of sulfate. The sediments can be viewed as a passive bioreactor that permanently removes Cu as insoluble copper sulfides. This process is not unlike that which occurs in other forms of bioremediation, such as wetlands and permeable reactive barriers. Above the zone of Cu removal, dissolved Cu maxima in the interfacial porewaters range from 150 to 450 ??g L-1 and reflect the dissolution of a Cu-bearing phase in the surface sediments. The reactive phase is thought to be a component of treatment sludges delivered to the lake as part of cyanide treatment. Flux calculations indicate that the efflux of dissolved Cu from the sediments to the water column (14-51 ??g cm-2 yr-1) can account for the elevated levels of dissolved Cu in lake waters (???50 ??g L-1). Implications for lake recovery are discussed.

Influence of bone mineral density measurement on fracture risk assessment tool® scores in postmenopausal Indian women.

PubMed

Daswani, Bhavna; Desai, Meena; Mitra, Sumegha; Gavali, Shubhangi; Patil, Anushree; Kukreja, Subhash; Khatkhatay, M Ikram

2016-03-01

Fracture risk assessment tool® calculations can be performed with or without addition of bone mineral density; however, the impact of this addition on fracture risk assessment tool® scores has not been studied in Indian women. Given the limited availability and high cost of bone mineral density testing in India, it is important to know the influence of bone mineral density on fracture risk assessment tool® scores in Indian women. Therefore, our aim was to assess the contribution of bone mineral density in fracture risk assessment tool® outcome in Indian women. Apparently healthy postmenopausal Indian women (n = 506), aged 40-72 years, without clinical risk factors for bone disease, were retrospectively selected, and their fracture risk assessment tool® scores calculated with and without bone mineral density were compared. Based on WHO criteria, 30% women were osteoporotic, 42.9% were osteopenic and 27.1% had normal bone mineral density. Fracture risk assessment tool® scores for risk of both major osteoporotic fracture and hip fracture significantly increased on including bone mineral density (P < 0.0001). When criteria of National Osteoporosis Foundation, US was applied number of participants eligible for medical therapy increased upon inclusion of bone mineral density, (for major osteoporotic fracture risk number of women eligible without bone mineral density was 0 and with bone mineral density was 1, P > 0.05, whereas, for hip fracture risk number of women eligible without bone mineral density was 2 and with bone mineral density was 17, P < 0.0001). Until the establishment of country-specific medication intervention thresholds, bone mineral density should be included while calculating fracture risk assessment tool® scores in Indian women. © The Author(s) 2016.

Mineral sources and transport pathways for arsenic release in a coastal watershed, USA

USGS Publications Warehouse

Foley, Nora K.; Ayuso, Robert A.

2008-01-01

Metasedimentary bedrock of coastal Maine contains a diverse suite of As-bearing minerals that act as significant sources of elements found in ground and surface waters in the region. Arsenic sources in the Penobscot Formation include, in order of decreasing As content by weight: löllingite and realgar (c.70%), arsenopyrite, cobaltite, glaucodot, and gersdorffite (in the range of 34–45%), arsenian pyrite (<4%), and pyrrhotite (<0.15%). In the Penobscot Formation, the relative stability of primary As-bearing minerals follows a pattern where the most commonly observed highly altered minerals are pyrrhotite, realgar, niccolite, löllingite > glaucodot, arsenopyrite-cobaltian > arsenopyrite, cobaltite, gersdorffite, fine-grained pyrite, Ni-pyrite > coarse-grained pyrite. Reactions illustrate that oxidation of Fe-As disulphide group and As-sulphide minerals is the primary release process for As. Liberation of As by carbonation of realgar and orpiment in contact with high-pH groundwaters may contribute locally to elevated contents of As in groundwater, especially where As is decoupled from Fe. Released metals are sequestered in secondary minerals by sorption or by incorporation in crystal structures. Secondary minerals acting as intermediate As reservoirs include claudetite (c.75%), orpiment (61%), scorodite (c. 45%), secondary arsenopyrite (c. 46%), goethite (<4490 ppm), natrojarosite (<42 ppm), rosenite, melanterite, ferrihydrite, and Mn-hydroxide coatings. Some soils also contain Fe-Co-Ni-arsenate, Ca-arsenate, and carbonate minerals. Reductive dissolution of Fe-oxide minerals may govern the ultimate release of iron and arsenic – especially As(V) – to groundwater; however, dissolution of claudetite (arsenic trioxide) may directly contribute As(III). Processes thought to explain the release of As from minerals in bedrock include oxidation of arsenian pyrite or arsenopyrite, or carbonation of As-sulphides, and most models based on these generally rely on discrete minerals or on a fairly limited series of minerals. In contrast, in the Penobscot Formation and other metasedimentary rocks of coastal Maine, oxidation of As-bearing Fe-cobalt-nickel-sulphide minerals, dissolution (by reduction) of As-bearing secondary As and Fe hydroxide and sulphate minerals, carbonation and/or oxidation of As-sulphide minerals, and desorption of As from Fe-hydroxide mineral surfaces are all thought to be involved. All of these processes contribute to the occurrence of As in groundwaters in coastal Maine, as a result of variability in composition and in stability of the As source minerals. Arsenic contents of soils and groundwater thus reflect the predominant influence and integration of a spectrum of primary mineral reservoirs (instead of single or unique mineral reservoirs). Cycling of As through metasedimentary bedrock aquifers may therefore depend on consecutive stages of carbonation, oxidation and reductive dissolution of primary and secondary As host minerals.

State summaries: Oklahoma

USGS Publications Warehouse

Krukowski, S.T.

2006-01-01

In 2005, Oklahoma mines produced both industrial minerals and coal. No metals were mined in the state. Based on value, leading industrial minerals include crushed stone followed by cement, construction sand and gravel, industrial sand and gravel, iodine and gypsum. The Oklahoma Department of Mines (ODOM) reported that more than 343 mine operators produced nonfuel minerals from 405 mines in the state. However, 530 mining permitted sites were on file. The Oklahoma Miner Training Institute (OMTI) held 239 classes for 33,768 classroom hours of instruction, in which 84 coal miners and 4,587 metal/nonmetal miners were trained.

Phosphorus K-edge XANES spectroscopy of mineral standards

PubMed Central

Ingall, Ellery D.; Brandes, Jay A.; Diaz, Julia M.; de Jonge, Martin D.; Paterson, David; McNulty, Ian; Elliott, W. Crawford; Northrup, Paul

2011-01-01

Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens. PMID:21335905

Physicochemical characterization of mineral (iron/zinc) bound caseinate and their mineral uptake in Caco-2 cells.

PubMed

Shilpashree, B G; Arora, Sumit; Kapila, Suman; Sharma, Vivek

2018-08-15

Milk proteins (especially caseins) are widely accepted as good vehicle for the delivery of various bioactive compounds including minerals. Succinylation is one of the most acceptable chemical modification techniques to enhance the mineral binding ability of caseins. Addition of minerals to succinylated proteins may alter their physicochemical and biochemical properties. Physicochemical characteristics of succinylated sodium caseinate (S.NaCN)-mineral (iron/zinc) complexes were elucidated. Chromatographic behaviour and fluorescence intensity confirmed the structural modification of S.NaCN upon binding with minerals. The bound mineral from protein complexes showed significantly higher (P < 0.05) in vitro bioavailability (mineral uptake) than mineral salts in Caco-2 cells. Also, iron bound S.NaCN showed higher cellular ferritin formation than iron in its free form. These mineral bound protein complexes with improved bioavailability could safely replace inorganic fortificants in various functional food formulations. Copyright © 2018 Elsevier Ltd. All rights reserved.

Drastic shifts in the Levant hydroclimate during the last interglacial indicate changes in the tropical climate and winter storm tracks

NASA Astrophysics Data System (ADS)

Kiro, Y.; Goldstein, S. L.; Kushnir, Y.; Lazar, B.; Stein, M.

2017-12-01

Marine Isotope Stage (MIS) 5e was a warm interglacial with where with significantly varying insolation and hence varied significantly throughout this time suggesting highly variable climate. The ICDP Dead Sea Deep Drilling Project recovered a 460m record of the past 220ka, reflecting the variable climate along MIS 5e. This time interval is reflected by alternating halite and detritus sequences, including 20m of halite-free detritus during the peak insolation at 125 ka. The Dead Sea salt budget indicates that the Levant climate was extremely arid when halite formed, reaching 20% of the present runoff. The halite-free detritus layer reflects increased precipitation to levels similar to present day, assuming similar spatial and temporal rainfall patterns. However, the 234U/238U activity ratio in the lake, reflected by authigenic minerals (aragonite, gypsum and halite), shifts from values of 1.5 (reflecting the Jordan River, the present main water source) down to 1.3 at 125-122ka during the MIS5e insolation peak and 1.0 at 118-116ka. The low 234U/238U reflects increased flash floods and eastern water sources (234U/238U 1.05-1.2) from the drier part of the watershed in the desert belt. The intermediate 234U/238U of 1.3 suggests that the Jordan River, fed from Mediterranean-sourced storm tracks, continued to flow along with an increase in southern and eastern water sources. NCAR CCSM3 climate model runs for 125ka indicate increases in both Summer and Winter precipitation. The drastic decrease to 234U/238U 1.0 occurs during the driest period, indicating a near shutdown of Jordan River flow, and water input only through flash floods and southern and eastern sources. The 120ka climate model runs shows a decrease in Winter and increase in Fall precipitation as a result of an increased precipitation in the tropics. The extreme aridity, associated with increased flooding is similar to patterns expected due to future warming. The increase in aridity is the result of expansion of the desert-belt and increases in southern precipitation and indicates an important link between the tropical and mid-latitude climate.

Optical properties of mineral dust aerosol including analysis of particle size, composition, and shape effects, and the impact of physical and chemical processing

NASA Astrophysics Data System (ADS)

Alexander, Jennifer Mary

Atmospheric mineral dust has a large impact on the earth's radiation balance and climate. The radiative effects of mineral dust depend on factors including, particle size, shape, and composition which can all be extremely complex. Mineral dust particles are typically irregular in shape and can include sharp edges, voids, and fine scale surface roughness. Particle shape can also depend on the type of mineral and can vary as a function of particle size. In addition, atmospheric mineral dust is a complex mixture of different minerals as well as other, possibly organic, components that have been mixed in while these particles are suspended in the atmosphere. Aerosol optical properties are investigated in this work, including studies of the effect of particle size, shape, and composition on the infrared (IR) extinction and visible scattering properties in order to achieve more accurate modeling methods. Studies of particle shape effects on dust optical properties for single component mineral samples of silicate clay and diatomaceous earth are carried out here first. Experimental measurements are modeled using T-matrix theory in a uniform spheroid approximation. Previous efforts to simulate the measured optical properties of silicate clay, using models that assumed particle shape was independent of particle size, have achieved only limited success. However, a model which accounts for a correlation between particle size and shape for the silicate clays offers a large improvement over earlier modeling approaches. Diatomaceous earth is also studied as an example of a single component mineral dust aerosol with extreme particle shapes. A particle shape distribution, determined by fitting the experimental IR extinction data, used as a basis for modeling the visible light scattering properties. While the visible simulations show only modestly good agreement with the scattering data, the fits are generally better than those obtained using more commonly invoked particle shape distributions. The next goal of this work is to investigate if modeling methods developed in the studies of single mineral components can be generalized to predict the optical properties of more authentic aerosol samples which are complex mixtures of different minerals. Samples of Saharan sand, Iowa loess, and Arizona road dust are used here as test cases. T-matrix based simulations of the authentic samples, using measured particle size distributions, empirical mineralogies, and a priori particle shape models for each mineral component are directly compared with the measured IR extinction spectra and visible scattering profiles. This modeling approach offers a significant improvement over more commonly applied models that ignore variations in particle shape with size or mineralogy and include only a moderate range of shape parameters. Mineral dust samples processed with organic acids and humic material are also studied in order to explore how the optical properties of dust can change after being aged in the atmosphere. Processed samples include quartz mixed with humic material, and calcite reacted with acetic and oxalic acid. Clear differences in the light scattering properties are observed for all three processed mineral dust samples when compared to the unprocessed mineral dust or organic salt products. These interactions result in both internal and external mixtures depending on the sample. In addition, the presence of these organic materials can alter the mineral dust particle shape. Overall, however, these results demonstrate the need to account for the effects of atmospheric aging of mineral dust on aerosol optical properties. Particle shape can also affect the aerodynamic properties of mineral dust aerosol. In order to account for these effects, the dynamic shape factor is used to give a measure of particle asphericity. Dynamic shape factors of quartz are measured by mass and mobility selecting particles and measuring their vacuum aerodynamic diameter. From this, dynamic shape factors in both the transition and vacuum regime can be derived. The measured dynamic shape factors of quartz agree quite well with the spheroidal shape distributions derived through studies of the optical properties.

21 CFR 349.14 - Ophthalmic emollients.

Code of Federal Regulations, 2011 CFR

2011-04-01

... included in the monograph. (2) Lanolin, 1 to 10 percent in combination with one or more oleaginous emollient agents included in the monograph. (b) Oleaginous ingredients: (1) Light mineral oil, up to 50 percent in combination with one or more other emollient agents included in the monograph. (2) Mineral oil...

21 CFR 349.14 - Ophthalmic emollients.

Code of Federal Regulations, 2010 CFR

2010-04-01

... included in the monograph. (2) Lanolin, 1 to 10 percent in combination with one or more oleaginous emollient agents included in the monograph. (b) Oleaginous ingredients: (1) Light mineral oil, up to 50 percent in combination with one or more other emollient agents included in the monograph. (2) Mineral oil...

21 CFR 349.14 - Ophthalmic emollients.

Code of Federal Regulations, 2013 CFR

2013-04-01

... included in the monograph. (2) Lanolin, 1 to 10 percent in combination with one or more oleaginous emollient agents included in the monograph. (b) Oleaginous ingredients: (1) Light mineral oil, up to 50 percent in combination with one or more other emollient agents included in the monograph. (2) Mineral oil...

21 CFR 349.14 - Ophthalmic emollients.

Code of Federal Regulations, 2014 CFR

2014-04-01

... included in the monograph. (2) Lanolin, 1 to 10 percent in combination with one or more oleaginous emollient agents included in the monograph. (b) Oleaginous ingredients: (1) Light mineral oil, up to 50 percent in combination with one or more other emollient agents included in the monograph. (2) Mineral oil...

21 CFR 349.14 - Ophthalmic emollients.

Code of Federal Regulations, 2012 CFR

2012-04-01

... included in the monograph. (2) Lanolin, 1 to 10 percent in combination with one or more oleaginous emollient agents included in the monograph. (b) Oleaginous ingredients: (1) Light mineral oil, up to 50 percent in combination with one or more other emollient agents included in the monograph. (2) Mineral oil...

Geometallurgy of ironsand from the Waikato North Head deposit, New Zealand

USGS Publications Warehouse

Mauk, Jeffrey L.; Cocker, Helen A; Rogers, Harold; Ogiliev, Jamie; Padya, Alex B

2016-01-01

The Waikato North Head deposit produces a magnetic mineral concentrate from Quaternary sands that formed in a coastal setting in the North Island of New Zealand. Detailed examination of the magnetic mineral fraction of the different stratigraphic horizons mined at Waikato North Head shows that the youngest units yield concentrates with significant concentrations of gangue minerals that are included as composite grains, inclusions in titanomagnetite, and as gangue grains with titanomagnetite inclusions. The most abundant gangue minerals in the magnetic fractions of all mined units are pyroxene and amphibole; feldspar, quartz, and biotite are less abundant. The magnetic minerals, which are predominantly titanomagnetite, are used as feed for the Iron Plant in New Zealand Steel’s Glenbrook Steel Mill. From time to time, excessive accretion formation impacts the operation of the rotary reduction kilns of the Iron Plant. Olivine group minerals are the most common silicate phase in these accretions, and we hypothesise that the silicon and magnesium in these minerals are derived from the gangue minerals that are included in the magnetic mineral concentrate from the ironsands. Although various remediation processes are possible, the simplest and most cost effective would appear to be ensuring adequate blending of material from different stratigraphic units, particularly when the youngest strata are being mined in the deposit.

In situ evidence of mineral physical protection and carbon stabilization revealed by nanoscale 3-D tomography

NASA Astrophysics Data System (ADS)

Weng, Yi-Tse; Wang, Chun-Chieh; Chiang, Cheng-Cheng; Tsai, Heng; Song, Yen-Fang; Huang, Shiuh-Tsuen; Liang, Biqing

2018-05-01

An approach for nanoscale 3-D tomography of organic carbon (OC) and associated mineral nanoparticles was developed to illustrate their spatial distribution and boundary interplay, using synchrotron-based transmission X-ray microscopy (TXM). The proposed 3-D tomography technique was first applied to in situ observation of a laboratory-made consortium of black carbon (BC) and nanomineral (TiO2, 15 nm), and its performance was evaluated using dual-scan (absorption contrast and phase contrast) modes. This novel tool was then successfully applied to a natural OC-mineral consortium from mountain soil at a spatial resolution of 60 nm, showing the fine structure and boundary of OC, the distribution of abundant nano-sized minerals, and the 3-D organo-mineral association in situ. The stabilization of 3500-year-old natural OC was mainly attributed to the physical protection of nano-sized iron (Fe)-containing minerals (Fe oxyhydroxides including ferrihydrite, goethite, and lepidocrocite), and the strong organo-mineral complexation. In situ evidence revealed an abundance of mineral nanoparticles, in dense thin layers or nano-aggregates/clusters, instead of crystalline clay-sized minerals on or near OC surfaces. The key working minerals for C stabilization were reactive short-range-order (SRO) mineral nanoparticles and poorly crystalline submicron-sized clay minerals. Spectroscopic analyses demonstrated that the studied OC was not merely in crisscross co-localization with reactive SRO minerals; there could be a significant degree of binding between OC and the minerals. The ubiquity and abundance of mineral nanoparticles on the OC surface, and their heterogeneity in the natural environment may have been severely underestimated by traditional research approaches. Our in situ description of organo-mineral interplay at the nanoscale provides direct evidence to substantiate the importance of mineral physical protection for the long-term stabilization of OC. This high-resolution 3-D tomography approach is a promising tool for generating new insight into the interior 3-D structure of micro-aggregates, the in situ interplay between OC and minerals, and the fate of mineral nanoparticles (including heavy metals) in natural environments.

Geomicrobiology in oceanography: microbe-mineral interactions at and below the seafloor.

PubMed

Edwards, Katrina J; Bach, Wolfgang; McCollom, Thomas M

2005-09-01

Oceanography is inherently interdisciplinary and, since its inception, has included the study of microbe-mineral interactions. From early studies of manganese nodules, to the discovery of hydrothermal vents, it has been recognized that microorganisms are involved at various levels in the transformation of rocks and minerals at and below the seafloor. Recent studies include mineral weathering at low temperatures and microbe-mineral interactions in the subseafloor "deep biosphere". A common characteristic of seafloor and subseafloor geomicrobiological processes that distinguishes them from terrestrial or near-surface processes is that they occur in the dark, one or more steps removed from the sunlight that fuels the near-surface biosphere on Earth. This review focuses on geomicrobiological studies and energy flow in dark, deep-ocean and subseafloor rock habitats.

A world of minerals in your mobile device

USGS Publications Warehouse

Jenness, Jane E.; Ober, Joyce A.; Wilkins, Aleeza M.; Gambogi, Joseph

2016-09-15

Mobile phones and other high-technology communications devices could not exist without mineral commodities. More than one-half of all components in a mobile device—including its electronics, display, battery, speakers, and more—are made from mined and semiprocessed materials (mineral commodities). Some mineral commodities can be recovered as byproducts during the production and processing of other commodities. As an example, bauxite is mined for its aluminum content, but gallium is recovered during the aluminum production process. The images show the ore minerals (sources) of some mineral commodities that are used to make components of a mobile device. On the reverse side, the map and table depict the major source countries producing these mineral commodities along with how these commodities are used in mobile devices. For more information on minerals, visit http://minerals.usgs.gov.

Investigation of sorption interactions between oil shale principal mineral phases and organic compounds

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

Bowen, J.M.

1988-09-01

The interactions between minerals representative of the bulk composition of oil shales and organic compounds that have been found in oil shale leachates were investigated. The method used to directly determine the type of interactions that could take place between organic compounds and oil shale mineral phases was Fourier transform infrared spectroscopy (FTIR) using several advanced detection methods, including diffuse reflectance (DRIFT) and photoacoustics (PAS). The minerals that were investigated include quartz, calcite, and dolomite, which are known to figure significantly in the composition of processed oil shales. The organic chemical compounds used were chosen from a list of compoundsmore » identified in spent oil shale leachates, and they include pyridine, phenol, p-cresol, and acetone. The sorption interactions for the study were prepared by exposing each of the minerals to the organic compounds by three different methods. These were vapor deposition, direct application, and immersion in an aqueous solution at pH 12. 41 refs., 3 figs., 4 tabs.« less

Interaction of divalent minerals with liposoluble nutrients and phytochemicals during digestion and influences on their bioavailability - a review.

PubMed

Corte-Real, Joana; Bohn, Torsten

2018-06-30

Several divalent minerals, including the macroelements calcium and magnesium, are essential nutrients for humans. However, their intake, especially via high-dose supplements, has been suspected to reduce the availability of lipophilic dietary constituents, including lipids, liposoluble vitamins, and several phytochemicals such as carotenoids. These constituents require emulsification in order to be bioavailable, and high divalent mineral concentrations may perturb this process, due to precipitations of free fatty acids or bile salt complexation, both pivotal for mixed micelle formation. Though in part based on in vitro or indirect evidence, it appears likely that high-dose supplements of divalent minerals around or even below their recommended dietary allowance perturb the availability of certain liposoluble miroconstituents, in addition to reducing absorption of dietary lipids/cholesterol. In this review, we investigate possible negative influences of divalent minerals, including trace elements (iron, zinc), on the digestion and intestinal uptake of lipophilic dietary constituents, with a focus on carotenoids. Copyright © 2018 Elsevier Ltd. All rights reserved.

Assessment of critical minerals: Updated application of an early-warning screening methodology

USGS Publications Warehouse

McCullough, Erin A.; Nassar, Nedal

2017-01-01

Increasing reliance on non-renewable mineral resources reinforces the need for identifying potential supply constraints before they occur. The US National Science and Technology Council recently released a report that outlines a methodology for screening potentially critical minerals based on three indicators: supply risk (R), production growth (G), and market dynamics (M). This early-warning screening was initially applied to 78 minerals across the years 1996 to 2013 and identified a subset of minerals as “potentially critical” based on the geometric average of these indicators—designated as criticality potential (C). In this study, the screening methodology has been updated to include data for 2014, as well as to incorporate revisions and modifications to the data, where applicable. Overall, C declined in 2014 for the majority of minerals examined largely due to decreases in production concentration and price volatility. However, the results vary considerably across minerals, with some minerals, such as gallium, recording increases for all three indicators. In addition to assessing magnitudinal changes, this analysis also examines the significance of the change relative to historical variation for each mineral. For example, although mined nickel’s R declined modestly in 2014 in comparison to that of other minerals, it was by far the largest annual change recorded for mined nickel across all years examined and is attributable to Indonesia’s ban on the export of unprocessed minerals. Based on the 2014 results, 20 minerals with the highest C values have been identified for further study including the rare earths, gallium, germanium, rhodium, tantalum, and tungsten.

Vitamin and mineral status in chronic fatigue syndrome and fibromyalgia syndrome: A systematic review and meta-analysis

PubMed Central

Joustra, Monica L.; Minovic, Isidor; Janssens, Karin A. M.; Bakker, Stephan J. L.; Rosmalen, Judith G. M.

2017-01-01

Background Many chronic fatigue syndrome (CFS) and fibromyalgia syndrome (FMS) patients (35–68%) use nutritional supplements, while it is unclear whether deficiencies in vitamins and minerals contribute to symptoms in these patients. Objectives were (1) to determine vitamin and mineral status in CFS and FMS patients as compared to healthy controls; (2) to investigate the association between vitamin and mineral status and clinical parameters, including symptom severity and quality of life; and (3) to determine the effect of supplementation on clinical parameters. Methods The databases PubMed, EMBASE, Web of Knowledge, and PsycINFO were searched for eligible studies. Articles published from January 1st 1994 for CFS patients and 1990 for FMS patients till March 1st 2017 were included. Articles were included if the status of one or more vitamins or minerals were reported, or an intervention concerning vitamins or minerals was performed. Two reviewers independently extracted data and assessed the risk of bias. Results A total of 5 RCTs and 40 observational studies were included in the qualitative synthesis, of which 27 studies were included in the meta-analyses. Circulating concentrations of vitamin E were lower in patients compared to controls (pooled standardized mean difference (SMD): -1.57, 95%CI: -3.09, -0.05; p = .042). However, this difference was not present when restricting the analyses to the subgroup of studies with high quality scores. Poor study quality and a substantial heterogeneity in most studies was found. No vitamins or minerals have been repeatedly or consistently linked to clinical parameters. In addition, RCTs testing supplements containing these vitamins and/or minerals did not result in clinical improvements. Discussion Little evidence was found to support the hypothesis that vitamin and mineral deficiencies play a role in the pathophysiology of CFS and FMS, and that the use of supplements is effective in these patients. Registration Study methods were documented in an international prospective register of systematic reviews (PROSPERO) protocol, registration number: http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42015032528. PMID:28453534

Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming

USGS Publications Warehouse

Day, Warren C.; Frost, Thomas P.; Hammarstrom, Jane M.; Zientek, Michael L.

2016-08-19

Scientific Investigations Report 2016–5089 and accompanying data releases are the products of the U.S. Geological Survey (USGS) Sagebrush Mineral-Resource Assessment (SaMiRA). The assessment was done at the request of the Bureau of Land Management (BLM) to evaluate the mineral-resource potential of some 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming. The need for this assessment arose from the decision by the Secretary of the Interior to pursue the protection of large tracts of contiguous habitat for the greater sage-grouse (Centrocercus urophasianus) in the Western United States. One component of the Department of the Interior plan to protect the habitat areas includes withdrawing selected lands from future exploration and development of mineral and energy resources, including copper, gold, silver, rare earth elements, and other commodities used in the U.S. economy. The assessment evaluates the potential for locatable minerals such as gold, copper, and lithium and describes the nature and occurrence of leaseable and salable minerals for seven Sagebrush Focal Areas and additional lands in Nevada (“Nevada additions”) delineated by BLM. Supporting data are available in a series of USGS data releases describing mineral occurrences (the USGS Mineral Deposit Database or “USMIN”), oil and gas production and well status, previous mineral-resource assessments that covered parts of the areas studied, and a compilation of mineral-use cases based on data provided by BLM, as well as results of the locatable mineral-resource assessment in a geographic information system. The present assessment of mineral-resource potential will contribute to a better understanding of the economic and environmental trade-offs that would result from closing approximately 10 million acres of Federal lands to mineral entry.

Raman spectroscopy of selected copper minerals of significance in corrosion.

PubMed

Frost, R L

2003-04-01

The Raman spectroscopy of selected minerals of the corrosion products has been measured including nantokite, eriochalcite, claringbullite, atacamite, paratacamite, clinoatacamite and brochantite and related minerals. The free energy of formation shows that each mineral is stable relative to copper metal. The mineral, which is formed in copper corrosion, depends on the kinetics and conditions of the reaction. Raman spectroscopy clearly identifies each mineral by its characteristic Raman spectrum. The Raman spectrum is related to the mineral structure and bands are assigned to CuCl stretching and bending modes and to SO stretching modes. Clinoatacamite is identified as the polymorph of atacamite and not paratacamite. Paratacamite is a separate mineral with a similar but different structure to that of atacamite.

Permeability of Granite Including Macro-Fracture Naturally Filled with Fine-Grained Minerals

NASA Astrophysics Data System (ADS)

Nara, Yoshitaka; Kato, Masaji; Niri, Ryuhei; Kohno, Masanori; Sato, Toshinori; Fukuda, Daisuke; Sato, Tsutomu; Takahashi, Manabu

2018-03-01

Information on the permeability of rock is essential for various geoengineering projects, such as geological disposal of radioactive wastes, hydrocarbon extraction, and natural hazard risk mitigation. It is especially important to investigate how fractures and pores influence the physical and transport properties of rock. Infiltration of groundwater through the damage zone fills fractures in granite with fine-grained minerals. However, the permeability of rock possessing a fracture naturally filled with fine-grained mineral grains has yet to be investigated. In this study, the permeabilities of granite samples, including a macro-fracture filled with clay and a mineral vein, are investigated. The permeability of granite with a fine-grained mineral vein agrees well with that of the intact sample, whereas the permeability of granite possessing a macro-fracture filled with clay is lower than that of the macro-fractured sample. The decrease in the permeability is due to the filling of fine-grained minerals and clay in the macro-fracture. It is concluded that the permeability of granite increases due to the existence of the fractures, but decreases upon filling them with fine-grained minerals.

Teleoperated control system for underground room and pillar mining

DOEpatents

Mayercheck, William D.; Kwitowski, August J.; Brautigam, Albert L.; Mueller, Brian K.

1992-01-01

A teleoperated mining system is provided for remotely controlling the various machines involved with thin seam mining. A thin seam continuous miner located at a mining face includes a camera mounted thereon and a slave computer for controlling the miner and the camera. A plurality of sensors for relaying information about the miner and the face to the slave computer. A slave computer controlled ventilation sub-system which removes combustible material from the mining face. A haulage sub-system removes material mined by the continuous miner from the mining face to a collection site and is also controlled by the slave computer. A base station, which controls the supply of power and water to the continuous miner, haulage system, and ventilation systems, includes cable/hose handling module for winding or unwinding cables/hoses connected to the miner, an operator control module, and a hydraulic power and air compressor module for supplying air to the miner. An operator controlled host computer housed in the operator control module is connected to the slave computer via a two wire communications line.

Resolving environmental signatures from a paleovalley sedimentary sequence from arid northwest Australia

NASA Astrophysics Data System (ADS)

Rouillard, Alexandra; Skrzypek, Grzegorz; Dogramaci, Shawan; Grierson, Pauline

2014-05-01

Sediments from paleolakes can retain invaluable archives of past environmental conditions. However, deciphering a depositional signal from digenetic processes can be challenging in arid environments owing to extremely variable rainfall and saline groundwaters, which result in aggressive chemical conditions that often limit the preservation of traditionally used proxies. We investigated the development of hydroclimatic proxies based on sediment geochemistry from the Fortescue Marsh, in the arid Pilbara region of northwest Australia. The Marsh lies in a paleovalley that acts as a terminal basin for the upper part of the Fortescue River and consists of a ~1000 km2 contiguous floodplain with freshwater pools episodically inundated during intense rainfall events. The paleovalley is bound by mountain ranges that contain some of the most Fe-ore rich and ancient deposits on Earth, which we expected to confer unique geochemical characteristics to the sediments. We used a sonic rig to retrieve a 25 m core from one of the deepest sedimentary sections of the Fortescue Marsh (86 m to bedrock). We combined δ34S and δ18O stable isotopes analyses with scanning μXRF and reflectance spectroscopy to quantitatively map the elemental and mineralogical composition of the sedimentary sequence and to identify underlying mechanisms relating to paleoclimate. We found that Fe, Ca and Sr were the most abundant elements identified by μXRF. Typically, layers of up to 1 m that were almost exclusively Fe-dominated alternated with layers of 0.3-2.4 m thickness dominated by Ca and/or Sr, with at least five intervals with distinct peaks in Sr. As expected, the hyperspectral characterization confirmed that Fe oxides were most abundant during the Fe-rich intervals. While clay minerals including kaolinite and montmorillonite were also indicated from the spectral data, this assessment is contradicted by the low relative abundance of Al and Si. Peaks in Sr don't appear to reflect carbonates nor Sr sulfates, thus further analyses are required to confirm their origin. Hyperspectral mapping and strong correlation between S and Ca confirmed that the intervals with high Ca corresponded to gypsum (CaSO4). We suggest that this gypsum is an authigenic sulfate mineral that formed within the top-most sediment due to groundwater fluctuation. Water chemistry measurements taken down the profile show that the conditions are close to saturation of gypsum throughout, and it is likely that such high concentration of crystals would form during prolonged 'dry' periods following very 'wet' periods. Under this scenario, current conditions are 'dry' but there have been significant 'wet' periods during which detrital materials, such as Fe, Rb and other low abundance metals here, have accumulated in the system via transport from the catchment. δ34S and δ18O analyses will help confirm the origins of formation of the crystals. Overall, our findings demonstrate that wetting and drying cycles and de-dolomitization processes are the main mechanisms influencing local geochemistry. Establishment of geochronology for this profile is currently underway. We are also examining other proxies including δ87Sr and particle size. Collectively, a multi-proxy and process-based approach will be used to characterize long-term hydroclimatic change in northwest Australia.