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Registros recuperados: 35
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A First Look at Dissolved Ge Isotopes in Marine Sediments ArchiMer
Baronas, J. Jotautas; Hammond, Douglas E.; Rouxel, Olivier; Monteverde, Danielle R..
The removal of chemical species from seawater during the precipitation of authigenic minerals is difficult to constrain but may play a major role in the global biogeochemical cycles of some elements, including silicon (Si) and germanium (Ge). Here, we present Ge/Si, δ74Ge, and supporting chemical data of pore waters and core incubations at three continental margin sites in California and the Gulf of Mexico. We used these data to partition Ge release and uptake by the various allogenic (delivered via sedimentation) and authigenic (formed in situ) phases in these sediments. About half of the pore water Ge (δ74Gepw = 1.3–2.4‰) is supplied by biogenic silica dissolution (δ74Ge ~ 3‰), with the other half contributed by lithogenic particulates (δ74Ge ~ 0.6‰)....
Tipo: Text Palavras-chave: Germanium; Biogenic silica; Authigenesis; Fe oxides; Isotope fractionation; Continental margin.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00504/61556/65466.pdf
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An Intercomparison Study of the Germanium Isotope Composition of Geological Reference Materials ArchiMer
Escoube, Raphalle; Rouxel, Olivier; Luais, Beatrice; Ponzevera, Emmanuel; Donard, Olivier F. X..
Recent analytical developments in germanium stable isotope determination by multicollector ICP-MS have provided new perspectives for the use of Ge isotopes as geochemical tracers. Here, we report the germanium isotope composition of the NIST SRM 3120a elemental reference solution that has been calibrated relative to internal isotopic standard solutions used in the previous studies. We also intercalibrate several geological reference materials as well as geological and meteoritic samples using different techniques, including online hydride generation and a spray chamber for sample introduction to MC-ICP-MS, and different approaches for mass bias corrections such as samplecalibrator bracketing, external mass bias correction using Ga isotopes and double-spike...
Tipo: Text Palavras-chave: Germanium; Isotope; Intercalibration; Reference materials; Germanium; Isotope; Intercalibration; Materiaux de reference.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00089/20036/21743.pdf
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Cobalt and marine redox evolution ArchiMer
Swanner, Elizabeth D.; Planavsky, Noah J.; Lalonde, Stefan; Robbins, Leslie J.; Bekker, Andrey; Rouxel, Olivier; Saito, Mak A.; Kappler, Andreas; Mojzsis, Stephen J.; Konhauser, Kurt O..
Cobalt (Co) is a bio-essential trace element and limiting nutrient in some regions of the modern oceans. It has been proposed that Co was more abundant in poorly ventilated Precambrian oceans based on the greater utilization of Co by anaerobic microbes relative to plants and animals. However, there are few empirical or theoretical constraints on the history of seawater Co concentrations. Herein, we present a survey of authigenic Co in marine sediments (iron formations, authigenic pyrite and bulk euxinic shales) with the goal of tracking changes in the marine Co reservoir throughout Earthʼs history. We further provide an overview of the modern marine Co cycle, which we use as a platform to evaluate how changes in the redox state of Earthʼs surface were...
Tipo: Text Palavras-chave: Cobalt; Trace element proxies; Ocean redox; Shale; Iron formation; Pyrite.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00174/28575/26986.pdf
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Comparative geochemistry of four ferromanganese crusts from the Pacific Ocean and significance for the use of Ni isotopes as paleoceanographic tracers ArchiMer
Gueguen, Bleuenn; Rouxel, Olivier; Rouget, Marie-laure; Bollinger, Claire; Ponzevera, Emmanuel; Germain, Yoan; Fouquet, Yves.
Ferromanganese (Fe-Mn) crusts are potential archive of the Ni isotope composition of seawater through time. In this study we aim at (1) understanding Ni isotope fractionation mechanisms and metal enrichment processes in Fe-Mn deposits, (2) addressing global vs. local control of Ni isotope composition of these deposits. Two Fe-Mn crusts from the North Pacific Ocean (Apuupuu Seamount, Hawaii) and two Fe-Mn crusts from the South Pacific Ocean (near Rurutu Island, Austral archipelago of French Polynesia) were characterized for their elemental geochemistry and Ni isotope composition. Geochemical analyses were performed at millimeter intervals in order to provide time-resolved record of Ni isotopes. Chronology and growth rates were determined using cosmogenic...
Tipo: Text Palavras-chave: Ferromanganese crusts; Nickel isotopes; Paleoceanography; Pacific Ocean; Biogeochemical cycling.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00341/45255/44696.pdf
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Comparing orthomagmatic and hydrothermal mineralization models for komatiite-hosted nickel deposits in Zimbabwe using multiple-sulfur, iron, and nickel isotope data ArchiMer
Hofmann, Axel; Bekker, Andrey; Dirks, Paul; Gueguen, Bleuenn; Rumble, Doug; Rouxel, Olivier.
Trojan and Shangani mines are low-grade (<0.8 % Ni), komatiite-hosted nickel sulfide deposits associated with ca. 2.7 Ga volcano-sedimentary sequences of the Zimbabwe craton. At both mines, nickel sulfide mineralization is present in strongly deformed serpentinite bodies that are enveloped by a complex network of highly sheared, silicified, and sulfide-bearing metasedimentary rocks. Strong, polyphase structural–metamorphic–metasomatic overprints in both the Trojan and Shangani deposits make it difficult to ascertain if sulfide mineralization was derived from orthomagmatic or hydrothermal processes, or by a combination of both. Multiple S, Fe, and Ni isotope analyses were applied to test these competing models. Massive ores at Shangani Mine show...
Tipo: Text Palavras-chave: Komatiite-hosted nickel deposit; Zimbabwe craton; Archean; Sulfur isotopes; Iron isotopes; Nickel isotopes.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00171/28207/26508.pdf
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Coupled Fe and S isotope variations in pyrite nodules from Archean shale ArchiMer
Marin-carbonne, Johanna; Rollion-bard, Claire; Bekker, Andrey; Rouxel, Olivier; Agangi, Andrea; Cavalazzi, Barbara; Wohlgemuth-ueberwasser, Cora C.; Hofmann, Axel; Mckeegan, Kevin D..
Iron and sulfur isotope compositions recorded in ancient rocks and minerals such as pyrite (FeS2) have been widely used as a proxy for early microbial metabolisms and redox evolution of the oceans. However, most previous studies focused on only one of these isotopic systems. Herein, we illustrate the importance of in-situ and coupled study of Fe and S isotopes on two pyrite nodules in a c. 2.7 Ga shale from the Bubi Greenstone Belt (Zimbabwe). Fe and S isotope compositions were measured both by bulk-sample mass spectrometry techniques and by ion microprobe in-situ methods (Secondary Ion Mass Spectrometry, SIMS). Spatially-resolved analysis across the nodules shows a large range of variations at micrometer-scale for both Fe and S isotope compositions, with...
Tipo: Text Palavras-chave: Pyrite nodules; Fe and S isotopes; Archean; SIMS.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00177/28824/27324.pdf
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Coupled Ge/Si and Ge isotope ratios as geochemical tracers of seafloor hydrothermal systems: Case studies at Loihi Seamount and East Pacific Rise 9°50’N ArchiMer
Escoube, Raphaelle; Rouxel, Olivier; Edwards, Katrina; Glazer, Brian; Donard, Olivier F. X..
Germanium (Ge) and Silicon (Si) exhibit similar geochemical behaviour in marine environments but are variably enriched in seafloor hydrothermal fluids relative to seawater. In this study, Ge isotope and Ge/Si ratio systematics were investigated in low temperature hydrothermal vents from Loihi Seamount (Pacific Ocean, 18°54’N, 155°15’W) and results were compared to high-temperature vents from the East Pacific Rise (EPR) at 9°50’N. Loihi offers the opportunity to understand contrasting Ge and Si behaviour in low temperature seafloor hydrothermal systems characterized by abundant Fe oxyhydroxide deposition at the seafloor. The results show that both Ge/Si and δ74/70Ge in hydrothermal fluids are fractionated relative to the basaltic host rocks. The enrichment...
Tipo: Text
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00273/38403/36728.pdf
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Depositional setting of the Late Archean Fe oxide- and sulfide-bearing chert and graphitic argillite in the Shaw Dome, Abitibi greenstone belt, Canada ArchiMer
Hiebert, R. S.; Bekker, A.; Houle, M. G.; Rouxel, Olivier.
Interbedded chert-rich exhalite and graphitic argillite are the only sedimentary rocks deposited in deep-water settings during long-lived hiatuses in mafic to ultramafic volcanism within the Hart area of the Shaw Dome in the Late Archean Abitibi greenstone belt in Canada. The Fe oxide- and sulfide-bearing, but predominantly cherty, exhalite lithological unit in the Hart area can be traced laterally to iron formation elsewhere in the Shaw Dome. Whole-rock as well as Fe and S isotope geochemistry suggest that the exhalite unit was formed as a result of direct precipitation from seawater, distally from hydrothermal centres. Fractionation of Fe isotopes through the precipitation of iron oxyhydroxides in a neutrally buoyant hydrothermal plume removed the...
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Ano: 2018 URL: https://archimer.ifremer.fr/doc/00436/54758/56206.pdf
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Determination of the copper isotope composition of seawater revisited: A case study from the Mediterranean Sea ArchiMer
Baconnais, Isabelle; Rouxel, Olivier; Dulaquais, Gabriel; Boye, Marie.
A new technique for the determination of dissolved copper isotope composition (δ65Cu) of seawater was applied to examine copper sources and internal cycling in the Mediterranean Sea. A succession of chelating resin with nitrilotriacetic acid functional groups and strong base anion exchange resin, together with optimization of the multi-collector inductively coupled plasma mass spectrometry set-up allowed to isolate copper from seawater matrix and to measure the 65Cu/63Cu ratios in seawater with an external precision of 0.06‰ (2 s.d.). This method was first applied for inter-comparison measurements to surface and deep waters sampled at station BATS in the North Atlantic Ocean. Disparities in δ65Cu reported here and in the literature over these samples...
Tipo: Text Palavras-chave: Copper isotope; Seawater; Mediterranean Sea; Geotraces; Isotope fractionation.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00457/56880/58742.pdf
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Enargite-luzonite hydrothermal vents in Manus Back-Arc Basin: submarine analogues of high-sulfidation epithermal mineralization ArchiMer
Dekov, Vesselin M.; Rouxel, Olivier; Kouzmanov, Kalin; Bindi, Luca; Asael, Dan; Fouquet, Yves; Etoubleau, Joel; Burgaud, Gaetan; Walle, Markus.
Active and inactive hydrothermal chimneys composed almost entirely of enargite and luzonite, rare minerals in seafloor hydrothermal deposits, were found at the summits of two submarine volcanoes, North Su and Kaia Natai, in the Manus Back-Arc Basin. Detailed mineralogical and geochemical studies revealed that most probably these deposits precipitated at T = 200°–330 °C and high fS2. The negative δ34S values (− 8.58 to − 3.70‰) of the enargite-luzonite are best explained by disproportionation reactions of magmatic SO2 and suggest that the high fS2 is likely provided by direct magmatic input of SO2 into the hydrothermal system. Fractionation of Cu stable isotopes during the precipitation of enargite-luzonite (δ65Cu ranges from − 0.20 to + 0.35‰) is inferred...
Tipo: Text Palavras-chave: Enargite; Epithermal; Hydrothermal vent; Luzonite; S-Cu isotopes; Seafloor.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00337/44844/44432.pdf
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Evidence for Microbial Carbon and Sulfur Cycling in Deeply Buried Ridge Flank Basalt ArchiMer
Lever, Mark A.; Rouxel, Olivier; Alt, Jeffrey C.; Shimizu, Nobumichi; Ono, Shuhei; Coggon, Rosalind M.; Shanks, Wayne C., Iii; Lapham, Laura; Elvert, Marcus; Prieto-mollar, Xavier; Hinrichs, Kai-uwe; Inagaki, Fumio; Teske, Andreas.
Sediment-covered basalt on the flanks of mid-ocean ridges constitutes most of Earth's oceanic crust, but the composition and metabolic function of its microbial ecosystem are largely unknown. By drilling into 3.5-million-year-old subseafloor basalt, we demonstrated the presence of methane-and sulfur-cycling microbes on the eastern flank of the Juan de Fuca Ridge. Depth horizons with functional genes indicative of methane-cycling and sulfate-reducing microorganisms are enriched in solid-phase sulfur and total organic carbon, host delta C-13- and delta S-34-isotopic values with a biological imprint, and show clear signs of microbial activity when incubated in the laboratory. Downcore changes in carbon and sulfur cycling show discrete geochemical intervals...
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Ano: 2013 URL: http://archimer.ifremer.fr/doc/00176/28767/32146.pdf
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Ge and Si isotope signatures in rivers: A quantitative multi-proxy approach ArchiMer
Baronas, J. Jotautas; Torres, Mark A.; West, A. Joshua; Rouxel, Olivier; Georg, Bastian; Bouchez, Julien; Gaillardet, Jerome; Hammond, Douglas E..
Solutes derived from the dissolution of silicate minerals play a key role in Earth’s climate via the carbon and other biogeochemical cycles. Silicon (Si) is a unique constituent of silicate minerals and a biologically important nutrient, so tracing its behavior in near-surface environments may provide important insights into weathering processes. However, Si released by weathering is variably incorporated into secondary mineral phases and biota, obscuring signals derived from primary weathering processes. Due to chemical similarities, Germanium (Ge) may help better understand the Si cycle and its relationship to chemical weathering. With this aim, we report new measurements of the concentration and isotopic composition of Ge for both the dissolved and...
Tipo: Text Palavras-chave: Germanium; Silicon; Isotopes; Rivers; Weathering; Fractionation.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00460/57196/59370.pdf
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Geochemical and iron isotopic insights into hydrothermal iron oxyhydroxide deposit formation at loihi seamount ArchiMer
Rouxel, Olivier; Toner, Brandy; Germain, Yoan; Glazer, Brian.
Low-temperature hydrothermal vents, such as those encountered at Loihi Seamount, harbor abundant microbial communities and provide ideal systems to test hypotheses on biotic versus abiotic formation of hydrous ferric oxide (FeOx) deposits at the seafloor. Hydrothermal activity at Loihi Seamount produces abundant microbial mats associated with rust-colored FeOx deposits and variably encrusted with Mn-oxyhydroxides. Here, we applied Fe isotope systematics together with major and trace element geochemistry to study the formation mechanisms and preservation of such mineralized microbial mats. Iron isotope composition of warm (< 60 °C), Fe-rich and H2S-depleted hydrothermal fluids yielded δ56Fe values near +0.1 ‰, indistinguishable from basalt values....
Tipo: Text Palavras-chave: Hydrothermal Systems; Seamounts; Iron Isotopes; Mineral deposits.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00405/51646/52195.pdf
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Germanium Isotope Geochemistry ArchiMer
Rouxel, Olivier; Luais, Beatrice.
Tipo: Text
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00379/49011/51045.pdf
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Germanium isotopic systematics in Ge-rich coal from the Lincang Ge deposit, Yunnan, Southwestern China ArchiMer
Qi, Hua-wen; Rouxel, Olivier; Hu, Rui-zhong; Bi, Xian-wu; Wen, Han-jie.
Organic matter plays an important role in the transport and precipitation of germanium (Ge) in coal-hosted Ge deposits. In this paper. Ge isotopes of coal samples and their combustion products were analyzed in order to investigate the potential use of Ge isotopes as tracers of Ge sources and enrichment mechanisms in coal. Germanium isotopic composition of various samples (mainly Ge-rich lignite) from the Lincang Ge deposit, Yunnan, Southwest China was analyzed using a continuous flow hydride generation system coupled to a Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS) and the standard-sample bracketing approach. Variations of (74)Ge/(70)Ge ratios are expressed as delta(74)Ge values relative to NIST SRM 3120a Ge standard solution....
Tipo: Text Palavras-chave: Germanium; Coal; Stable isotope fractionation; Water-rock interaction; Geochemical tracer.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00041/15249/12676.pdf
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Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation ArchiMer
Schroth, Andrew W.; Crusius, John; Chever, Fanny; Bostick, Benjamin C.; Rouxel, Olivier.
Riverine iron (Fe) derived from glacial weathering is a critical micronutrient source to ecosystems of the Gulf of Alaska (GoA). Here we demonstrate that the source and chemical nature of riverine Fe input to the GoA could change dramatically due to the widespread watershed deglaciation that is underway. We examine Fe size partitioning, speciation, and isotopic composition in tributaries of the Copper River which exemplify a long-term GoA watershed evolution from one strongly influenced by glacial weathering to a boreal-forested watershed. Iron fluxes from glacierized tributaries bear high suspended sediment and colloidal Fe loads of mixed valence silicate species, with low concentrations of dissolved Fe and dissolved organic carbon (DOC). Iron isotopic...
Tipo: Text
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00044/15483/12872.pdf
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Hydrogen and copper isotope analysis of turquoise by SIMS: Calibration and matrix effects ArchiMer
Othmane, Guillaume; Hull, Sharon; Fayek, Mostafa; Rouxel, Olivier; Geagea, Majdi Lahd; Kyser, T. Kurtis.
The hydrogen isotope system is used extensively to provide information on the genesis of minerals (e.g., source of fluids and mechanisms of precipitation). The copper isotopic system is less well understood, but has the potential to provide valuable insight on mineral precipitation, particularly supergene Cu-rich minerals. Here we present a rapid and precise method for measuring hydrogen and copper isotopes in semi-precious gem-quality turquoise (Cu(Al,Fe3 +)6(PO4)4(OH)8 · 4H2O ) by secondary ion mass spectrometry (SIMS). The suitability of standards for instrumental mass fractionation (IMF) calibration was assessed by external precision of SIMS measurements for each standard (2-4‰ for δDIMF and 0.2-0.4‰ for δ65CuIMF). IMF in turquoise was correlated with...
Tipo: Text Palavras-chave: Turquoise; SIMS; Copper isotopes; Hydrogen isotopes; Matrix effects.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00239/35008/33546.pdf
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Inter-calibration of a proposed new primary reference standard AA-ETH Zn for zinc isotopic analysis ArchiMer
Archer, Corey; Andersen, Morten B.; Cloquet, Christophe; Conway, Tim M.; Dong, Shuofei; Ellwood, Michael; Moore, Rebekah; Nelson, Joey; Rehkamper, Mark; Rouxel, Olivier; Samanta, Moneesha; Shin, Ki-cheol; Sohrin, Yoshiki; Takano, Shotaro; Wasylenki, Laura.
We have prepared a large volume of pure, concentrated and homogenous zinc standard solution. This new standard solution is intended to be used as a primary reference standard for the zinc isotope community, and to serve as a replacement for the nearly exhausted current reference standard, the so-called JMC-Lyon Zn. The isotopic composition of this new zinc standard (AA-ETH Zn) has been determined through an inter-laboratory calibration exercise, calibrated against the existing JMC-Lyon standard, as well as the certified Zn reference standard IRMM-3702. The data show that the new standard is isotopically indistinguishable from the IRMM-3702 zinc standard, with a weighted delta Zn-66/64 value of 0.28 +/- 0.02& relative to JMC-Lyon. We suggest that this...
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Ano: 2017 URL: http://archimer.ifremer.fr/doc/00380/49085/49522.pdf
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Iron isotope constraints on the Archean and Paleoproterozoic ocean redox state ArchiMer
Rouxel, Olivier; Bekker, A; Edwards, Kj.
The response of the ocean redox state to the rise of atmospheric oxygen about 2.3 billion years ago (Ga) is a matter of controversy. Here we provide iron isotope evidence that the change in the ocean iron cycle occurred at the same time as the change in the atmospheric redox state. Variable and negative iron isotope values in pyrites older than about 2.3 Ga suggest that an iron-rich global ocean was strongly affected by the deposition of iron oxides. Between 2.3 and 1.8 Ga, positive iron isotope values of pyrite likely reflect an increase in the precipitation of iron sulfides relative to iron oxides in a redox stratified ocean.
Tipo: Text
Ano: 2005 URL: http://archimer.ifremer.fr/doc/00078/18965/16580.pdf
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Iron isotope systematics in Arctic rivers ArchiMer
Escoube, Raphaelle; Rouxel, Olivier; Pokrovsky, Oleg S.; Schroth, Andrew; Holmes, Robert Max; Donard, Olivier F. X..
The input of iron to the Arctic Ocean plays a critical role in the productivity of aquatic ecosystems and is potentially impacted by climate change. We examine Fe isotope systematics of dissolved and colloidal Fe from several Arctic and sub-Arctic rivers in northern Eurasia and Alaska. We demonstrate that the Fe isotopic (δ56Fe) composition of large rivers, such as the Ob’ and Lena, has a restricted range of δ56Fe values ca.–0.11 ± 0.13‰, with minimal seasonal variability, in stark contrast to smaller organic-rich rivers with an overall δ56Fe range from–1.7 to + 1.6‰. The preferential enrichment with heavy Fe isotopes observed in low molecular weight colloidal fraction and during the high-flow period is consistent with the role of organic complexation of...
Tipo: Text Palavras-chave: Iron isotope; Colloids; River; Weathering; Arctic; Iron speciation.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00273/38402/36865.pdf
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