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A First Look at Dissolved Ge Isotopes in Marine Sediments 5
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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A late Paleoproterozoic (1.74 Ga) deep‐sea, low‐temperature, iron‐oxidizing microbial hydrothermal vent community from Arizona, USA 5
Little, Crispin T. S.; Johannessen, Karen C; Bengtson, Stefan; Chan, Clara S; Ivarsson, Magnus; Slack, John F; Broman, Curt; Thorseth, Ingunn H.; Grenne, Tor; Rouxel, Olivier; Bekker, Andrey.
Modern marine hydrothermal vents occur in a wide variety of tectonic settings and are characterized by seafloor emission of fluids rich in dissolved chemicals and rapid mineral precipitation. Some hydrothermal systems vent only low‐temperature Fe‐rich fluids, which precipitate deposits dominated by iron oxyhydroxides, in places together with Mn‐oxyhydroxides and amorphous silica. While a proportion of this mineralization is abiogenic, most is the result of the metabolic activities of benthic, Fe‐oxidizing bacteria (FeOB), principally belonging to the Zetaproteobacteria. These micro‐organisms secrete micrometer‐scale stalks, sheaths, and tubes with a variety of morphologies, composed largely of ferrihydrite that act as sacrificial structures, preventing...
Tipo: Text Palavras-chave: Arizona; Fe-oxidizing bacteria; Hydrothermal vents; Jasper; Late Paleoproterozoic; Verde mining district.
Ano: 2021 URL: https://archimer.ifremer.fr/doc/00680/79162/81674.pdf
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An Intercomparison Study of the Germanium Isotope Composition of Geological Reference Materials 5
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 5
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 5
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 5
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 5
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 5
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 5
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...
Tipo: Text
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 5
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 5
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 5
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...
Tipo: Text
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00176/28767/32146.pdf
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Ge and Si Isotope Behavior During Intense Tropical Weathering and Ecosystem Cycling 5
Baronas, J. Jotautas; West, A. Joshua; Burton, Kevin W.; Hammond, Douglas E.; Opfergelt, Sophie; Pogge Von Strandmann, Philip A. E.; James, Rachael H.; Rouxel, Olivier.
Chemical weathering of volcanic rocks in warm and humid climates contributes disproportionately to global solute fluxes. Geochemical signatures of solutes and solids formed during this process can help quantify and reconstruct weathering intensity in the past. Here, we measured silicon (Si) and germanium (Ge) isotope ratios of the soils, clays, and fluids from a tropical lowland rainforest in Costa Rica. The bulk topsoil is intensely weathered and isotopically light (mean ± 1σ: δ30Si = −2.1 ± 0.3‰, δ74Ge = −0.13 ± 0.12‰) compared to the parent rock (δ30Si = −0.11 ± 0.05‰, δ74Ge = 0.59 ± 0.07‰). Neoforming clays have even lower values (δ30Si = −2.5 ± 0.2‰, δ74Ge = −0.16 ± 0.09‰), demonstrating a whole‐system isotopic shift in extremely weathered systems....
Tipo: Text
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00643/75484/76330.pdf
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Ge and Si isotope signatures in rivers: A quantitative multi-proxy approach 5
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 5
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 5
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 5
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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Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland 5
Baronas, J. Jotautas; Hammond, Douglas E.; Bennett, Mia M.; Rouxel, Olivier; Pitcher, Lincoln H.; Smith, Laurence C..
Glacial environments offer the opportunity to study the incipient stages of chemical weathering due to the high availability of finely ground sediments, low water temperatures, and typically short rock-water interaction times. In this study we focused on the geochemical behavior of germanium (Ge) in west Greenland, both during subglacial weathering by investigating glacier-fed streams, as well as during a batch reactor experiment by allowing water-sediment interaction for up to 2 years in the laboratory. Sampled in late August 2014, glacial stream Ge and Si concentrations were low, ranging between 12–55 pmol/L and 7–33 µmol/L, respectively (Ge/Si = 0.9–2.2 µmol/mol, similar to parent rock). As reported previously, the dissolved stable Ge isotope ratio...
Tipo: Text Palavras-chave: Glacial weathering; Germanium; Isotope fractionation; Amorphous silica; Experimental dissolution.
Ano: 2021 URL: https://archimer.ifremer.fr/doc/00684/79577/82249.pdf
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Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation 5
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 5
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: https://archimer.ifremer.fr/doc/00239/35008/33546.pdf
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