Consulta: creatorFacets:"Rouxel, Olivier"
Registros recuperados: 45
Data/hora: 15/06/2024 14:03:51

Variable Ni isotope fractionation between Fe-oxyhydroxides and implications for the use of Ni isotopes as geochemical tracers
Provedor de dados: 5
Autores: Gueguen, Bleuenn; Sorensen, Jeffry V.; Lalonde, Stefan; Pena, Jasquelin; Toner, Brandy M.; Rouxel, Olivier.
Nickel (Ni) isotopes have recently emerged as a new biogeochemical tracer in marine environments, but our understanding of the mechanisms of Ni isotope fractionation in natural systems with regards to its fractionation by mineral surfaces is incomplete. This study aims to provide experimental constraints on Ni isotope fractionation during adsorption to goethite and 2-line ferrihydrite, two Fe minerals that vary in terms of distinct crystalline properties. We conducted two types of adsorption experiments: one with variable pH (5.0 to 8.0) and constant initial Ni concentration, one at a constant pH of 7.7 and variable initial Ni concentrations. Isotopic measurements were made on both the solid phase and the supernatant solutions in order to determine the Ni...
Tipo: Text
Palavras-chave: Fe-oxyhydroxides; Sorption experiments; Nickel isotopes.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00423/53473/56649.pdf

Ge and Si isotope signatures in rivers: A quantitative multi-proxy approach
Provedor de dados: 5
Autores: 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

Germanium Isotope Geochemistry
Provedor de dados: 5
Autores: Rouxel, Olivier; Luais, Beatrice.
Tipo: Text
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00379/49011/51045.pdf

Coupled Fe and S isotope variations in pyrite nodules from Archean shale
Provedor de dados: 5
Autores: 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

Iron isotope constraints on the Archean and Paleoproterozoic ocean redox state
Provedor de dados: 5
Autores: 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

Depositional setting of the Late Archean Fe oxide- and sulfide-bearing chert and graphitic argillite in the Shaw Dome, Abitibi greenstone belt, Canada
Provedor de dados: 5
Autores: 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

Sulfur and strontium isotopic study of epithermal mineralization: A case study from the SE Afar Rift, Djibouti
Provedor de dados: 5
Autores: Moussa, N.; Rouxel, Olivier; Grassineau, N. V.; Ponzevera, Emmanuel; Nonnotte, P.; Fouquet, Yves; Le Gall, B.
Epithermal mineralization was recently described in synrift volcanic rocks from the SE Afar Rift in Djibouti. To infer fluid sources in this system, coupled sulfur and strontium isotopic analyses were performed on mineralized samples from hydrothermal veins and stockwork zones. Mineralization includes gypsum and chalcedony, and/or quartz ± carbonate containing gold and sulfides. Sulfur isotopic compositions of sulfides and sulfates were determined using Multicollector-Inductively Coupled Plasma Mass Spectrometer (MC ICPMS); Laser Ablation MC ICPMS; and Continuous Flow Elemental Analyzer-Isotope Ratio Mass Spectrometry while strontium isotopes were determined by Thermal Ionisation Mass Spectrometry (TIMS) methods. Sulfur isotopic composition of sulfides...
Tipo: Text
Palavras-chave: Hydrothermal system; Sulfur isotopes; Strontium isotopes; SE Afar rift; Epithermal.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00356/46712/46581.pdf

Origin of red beds in the Paleoproterozoic Franceville Basin, Gabon, and implications for sandstone-hosted uranium mineralization
Provedor de dados: 5
Autores: Bankole, Olabode M.; El Albani, Abderrazak; Meunier, Alain; Rouxel, Olivier; Gauthier-lafaye, Francois; Bekker, Andrey.
Red beds are extensively used as evidence for an oxygenated atmosphere in the Paleoproterozoic. Red beds in the unmetamorphosed, ca. 2.15 Ga FA Formation of the Franceville Basin, Gabon were geochemically, petrographically, and mineralogically characterized to constrain the process of their formation and their relationship to atmospheric oxygenation in the early Paleoproterozoic. Petrographic observations indicate that ferric oxides are dispersed in clay filling intergranular pores and along platy cleavage in altered phyllosilicates. Grain-coating hematite is generally rare to absent in most samples suggesting hematite precipitation after sediment deposition and during burial diagenesis. Textures and geochemical data suggest that iron was likely sourced...
Tipo: Text
Palavras-chave: Red beds; Atmospheric oxygenation; Diagenesis; Iron isotopes; Franceville Basin; Oldest sandstone-type U deposit.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00358/46966/48278.pdf

Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland
Provedor de dados: 5
Autores: 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

Germanium isotopic systematics in Ge-rich coal from the Lincang Ge deposit, Yunnan, Southwestern China
Provedor de dados: 5
Autores: 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

An Intercomparison Study of the Germanium Isotope Composition of Geological Reference Materials
Provedor de dados: 5
Autores: 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

Iron isotope fractionation in iron-organic matter associations: Experimental evidence using filtration and ultrafiltration
Provedor de dados: 5
Autores: Lotfi-kalahroodi, Elaheh; Pierson-wickmann, Anne-catherine; Guénet, Hélène; Rouxel, Olivier; Ponzevera, Emmanuel; Bouhnik-lecoz, Martine; Vantelon, Delphine; Dia, Aliou; Davranche, Mélanie.
Colloids have been recognized as key vectors of pollutants in aqueous environment. Amongst them, those formed by iron (Fe) and organic matter (OM) are of major importance due to their ubiquity in the surface environment and strong affinity for metals. In the recent years, Fe stable isotopes have been increasingly used to elucidate the sources and biogeochemical cycling of Fe in Earth's surface environments. In this study, we aim to elucidate (i) the possible Fe isotopic signature resulting from the Fe/OM colloid formation and (ii) the mechanisms involved in the development of such isotopic signature. For this purpose, Fe-OM associations were synthesized through binding and titration experiments. Various pH levels were used in order to study the isotope...
Tipo: Text
Palavras-chave: Filtration; Size fractionation; Isotope fractionation; Colloidal; Dissolved; Fe isotopes.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00480/59174/61811.pdf

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
Provedor de dados: 5
Autores: 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

Total dissolvable and dissolved iron isotopes in the water column of the Peru upwelling regime
Provedor de dados: 5
Autores: Chever, Fanny; Rouxel, Olivier; Croot, Peter L.; Ponzevera, Emmanuel; Wuttig, Kathrin; Auro, Maureen.
Vertical distributions of iron (Fe) concentrations and isotopes were determined in the total dissolvable and dissolved pools in the water column at three coastal stations located along the Peruvian margin, in the core of the Oxygen Minimum Zone (OMZ). The shallowest station 121 (161 m total water depth) was characterized by lithogenic input from the continental plateau, yielding concentrations as high as 456 nM in the total dissolvable pool. At the 2 other stations (stations 122 and 123), Fe concentrations of dissolved and total dissolvable pools exhibited maxima in both surface and deep layers. Fe isotopic composition (δ56Fe) showed a fractionation toward lighter values for both physical pools throughout the water column for all stations with minimum...
Tipo: Text
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00266/37715/35733.pdf

Geochemical and iron isotopic insights into hydrothermal iron oxyhydroxide deposit formation at loihi seamount
Provedor de dados: 5
Autores: 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 (&lt; 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

Surface-Generated Mesoscale Eddies Transport Deep-Sea Products from Hydrothermal Vents
Provedor de dados: 5
Autores: Adams, Diane K.; Mcgillicuddy, Dennis J., Jr.; Zamudio, Luis; Thurnherr, Andreas M.; Liang, Xinfeng; Rouxel, Olivier; German, Christopher R.; Mullineaux, Lauren S.
Atmospheric forcing, which is known to have a strong influence on surface ocean dynamics and production, is typically not considered in studies of the deep sea. Our observations and models demonstrate an unexpected influence of surface-generated mesoscale eddies in the transport of hydrothermal vent efflux and of vent larvae away from the northern East Pacific Rise. Transport by these deep-reaching eddies provides a mechanism for spreading the hydrothermal chemical and heat flux into the deep-ocean interior and for dispersing propagules hundreds of kilometers between isolated and ephemeral communities. Because the eddies interacting with the East Pacific Rise are formed seasonally and are sensitive to phenomena such as El Nino, they have the potential to...
Tipo: Text
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00035/14629/11973.pdf

Nickel Isotope Variations in Terrestrial Silicate Rocks and Geological Reference Materials Measured by MC-ICP-MS
Provedor de dados: 5
Autores: Gueguen, Bleuenn; Rouxel, Olivier; Ponzevera, Emmanuel; Bekker, Andrey; Fouquet, Yves.
Although initial studies have demonstrated the applicability of Ni isotopes for cosmochemistry and as a potential biosignature, the Ni isotope composition of terrestrial igneous and sedimentary rocks, and ore deposits remains poorly known. Our contribution is fourfold: (a) to detail an analytical procedure for Ni isotope determination, (b) to determine the Ni isotope composition of various geological reference materials, (c) to assess the isotope composition of the Bulk Silicate Earth relative to the Ni isotope reference material NIST SRM 986 and (d) to report the range of mass-dependent Ni isotope fractionations in magmatic rocks and ore deposits. After purification through a two-stage chromatography procedure, Ni isotope ratios were measured by MC-ICP-MS...
Tipo: Text
Palavras-chave: Nickel; Stable isotopes; MC-ICP-MS; Geological reference materials; Bulk Silicate Earth; Abiotic fractionation.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00159/27069/25332.pdf

Molybdenum record from black shales indicates oscillating atmospheric oxygen levels in the early Paleoproterozoic
Provedor de dados: 5
Autores: Asael, Dan; Rouxel, Olivier; Poulton, Simon W.; Lyons, Timothy W.; Bekker, Andrey.
The early Paleoproterozoic witnessed Earth's first major oxygenation, referred to as the Great Oxidation Event or GOE. The GOE began around 2.45 billion years ago (Ga) and progressed over hundreds of millions of years, as evidenced by multiple redox indicators, before coming to an abrupt end by ca. 2.06 Ga. The details of the GOE and the extent of oxygenation are still not resolved, however, and it is not dear how redox conditions across the GOE compare with those during the middle Proterozoic. In order to investigate the evolution of deep-ocean redox conditions during the GOE, we present Mo concentration and isotope data together with Fe speciation values for three key organic matter-rich shale units of the early Paleoproterozoic age (2.32-2.06 Ga). In...
Tipo: Text
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00442/55330/60642.pdf

Origin of the Oligocene manganese deposit at Obrochishte (Bulgaria): Insights from C, O, Fe, Sr, Nd, and Pb isotopes
Provedor de dados: 5
Autores: Dekov, Vesselin M.; Barry Maynard, J.; Kamenov, George D.; Rouxel, Olivier; Lalonde, Stefan; Juranov, Sava.
The large manganese (Mn) deposit at Obrochishte (NE Bulgaria) is part of a cluster of similar Early Oligocene deposits located around present-day Black Sea. They collectively constitute the Earth’s second largest endowment of Mn, after the Kalahari Manganese Field in Africa. We have employed a battery of isotopic techniques (C, O, Fe, Sr, Nd, Pb) to help understand the genesis of this deposit. Carbon isotope data indicates that some sections of the Mn-ore layer have diagenetic MnCO3 mineralization, formed by reaction of Mn oxides with organic carbon (Corg), whereas other sections have MnCO3 precipitated directly from the seawater column. Oxygen isotopes show that the high-grade Mn mineralization had seawater as the fluid source, whereas some lower-grade...
Tipo: Text
Palavras-chave: Mn metallogenesis; C-O-Fe-Sr-Nd-Pb isotopes; Early Oligocene; Submarine groundwater discharge; Water column anoxia; Proto-Black Sea geochemistry.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00624/73591/73025.pdf

Nickel isotope fractionation during tropical weathering of ultramafic rocks
Provedor de dados: 5
Autores: Ratie, G.; Jouvin, D.; Garnier, Julien; Rouxel, Olivier; Miska, S.; Guimaraes, E.; Cruz Vieira, L.; Sivry, Y.; Zelano, I.; Montarges-pelletier, E.; Thil, F.; Quantin, C.
Although Ni isotopes have been shown to be significantly fractionated in terrestrial samples, their use in continental environmental studies has not yet been evaluated. The present study focuses on an ultramafic (UM) massif (Barro Alto, Goias, Brazil) because such areas are naturally rich in Ni. We present developed lateritic weathering profiles. The goal of the study is to evaluate the potential of using Ni isotopes in environmental continental studies by combining its isotopic signature with mineralogy, in order to better understand the geochemical cycling of Ni in UM settings during weathering. As such, Ni isotope values were measured in samples from the Barro Alto UM complex in the main stages of the lateritic weathering profile of UM rocks, including...
Tipo: Text
Palavras-chave: Nickel; Isotope; Weathering; Mineralogy; Soil.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00254/36553/35098.pdf

The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity
Provedor de dados: 5
Autores: El Albani, Abderrazak; Bengtson, Stefan; Canfield, Donald E.; Riboulleau, Armelle; Bard, Claire Rollion; Macchiarelli, Roberto; Pemba, Lauriss Ngombi; Hammarlund, Emma; Meunier, Alain; Mouele, Idalina Moubiya; Benzerara, Karim; Bernard, Sylvain; Boulvais, Philippe; Chaussidon, Marc; Cesari, Christian; Fontaine, Claude; Chi-fru, Ernest; Garcia Ruiz, Juan Manuel; Gauthier-lafaye, Francois; Mazurier, Arnaud; Pierson-wickmann, Anne Catherine; Rouxel, Olivier; Trentesaux, Alain; Vecoli, Marco; Versteegh, Gerard J. M.; White, Lee; Whitehouse, Martin; Bekker, Andrey.
The Paleoproterozoic Era witnessed crucial steps in the evolution of Earth's surface environments following the first appreciable rise of free atmospheric oxygen concentrations similar to 2.3 to 2.1 Ga ago, and concomitant shallow ocean oxygenation. While most sedimentary successions deposited during this time interval have experienced thermal overprinting from burial diagenesis and metamorphism, the ca. 2.1 Ga black shales of the Francevillian B Formation (FB2) cropping out in southeastern Gabon have not. The Francevillian Formation contains centimeter-sized structures interpreted as organized and spatially discrete populations of colonial organisms living in an oxygenated marine ecosystem. Here, new material from the FB2 black shales is presented and...
Tipo: Text
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00202/31356/29754.pdf

Microbial colonization of basaltic glasses in hydrothermal organic-rich sediments at Guaymas Basin
Provedor de dados: 5
Autores: Callac, Nolwenn; Rommevaux-jestin, Celine; Rouxel, Olivier; Lesongeur, Francoise; Liorzou, Celine; Bollinger, Claire; Ferrant, Anthony; Godfroy, Anne.
Oceanic basalts host diverse microbial communities with various metabolisms involved in C, N, S, and Fe biogeochemical cycles which may contribute to mineral and glass alteration processes at, and below the seafloor. In order to study the microbial colonization on basaltic glasses and their potential biotic/abiotic weathering products, two colonization modules called AISICS ("Autonomous in situ Instrumented Colonization System") were deployed in hydrothermal deep-sea sediments at the Guaymas Basin for 8 days and 22 days. Each AISICS module contained 18 colonizers (including sterile controls) filled with basaltic glasses of contrasting composition. Chemical analyses of ambient fluids sampled through the colonizers showed a greater contribution of...
Tipo: Text
Palavras-chave: Colonization module; Basalt alteration; Guaymas basin; Organic-rich sediment; Hydrothermal systems.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00181/29261/27642.pdf

The isotope composition of inorganic Germanium in seawater and deep sea sponges
Provedor de dados: 5
Autores: Guillermic, Maxence; Lalonde, Stefan; Hendry, Katharine R.; Rouxel, Olivier.
Although dissolved concentrations of germanium (Ge) and silicon (Si) in modern seawater are tightly correlated, uncertainties still exist in the modern marine Ge cycle. Germanium stable isotope systematics in marine systems should provide additional constraints on marine Ge sources and sinks, however the low concentration of Ge in seawater presents an analytical challenge for isotopic measurement. Here, we present a new method of pre-concentration of inorganic Ge from seawater which was applied to measure three Ge isotope profiles in the Southern Ocean and deep seawater from the Atlantic and Pacific Oceans. Germanium isotopic measurements were performed on Ge amounts as low as 2.6 ng using a double-spike approach and a hydride generation system coupled to...
Tipo: Text
Palavras-chave: Stable isotopes; Germanium; Silicon; Sponges; Southern Ocean; Chemical oceanography.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00388/49956/50529.pdf

Hydrogen and copper isotope analysis of turquoise by SIMS: Calibration and matrix effects
Provedor de dados: 5
Autores: 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

Comparative geochemistry of four ferromanganese crusts from the Pacific Ocean and significance for the use of Ni isotopes as paleoceanographic tracers
Provedor de dados: 5
Autores: 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

More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland
Provedor de dados: 5
Autores: Lotfi-kalahroodi, Elaheh; Pierson-wickmann, Anne-catherine; Rouxel, Olivier; Marsac, Rémi; Bouhnik-le Coz, Martine; Hanna, Khalil; Davranche, Mélanie.
Although redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes...
Tipo: Text
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00677/78931/81302.pdf

Large nickel isotope fractionation caused by surface complexation reactions with hexagonal birnessite
Provedor de dados: 5
Autores: Sorensen, Jeffry V.; Gueguen, Bleuenn; Stewart, Brandy D.; Peña, Jasquelin; Rouxel, Olivier; Toner, Brandy M.
Manganese oxides are an important sink for Ni in the ocean. To explore the potential of Ni stable isotopes as a geochemical tracer, we conducted two types of sorption reactions between Ni and hexagonal birnessite in 0.05 M NaNO3 media: one where we varied pH from 5 to 8 (constant initial Ni concentration = 170 μmol/L), and a second where we varied the initial dissolved Ni concentration from 17 to 426 μmol/L (constant pH = 7.7). Isotopic measurements were made on both the solid phase and the supernatant solutions to determine the Ni isotope fractionation factors (∆60/58Nimin-aq = δ60/58Nimin − δ60/58Niaq) between the mineral and aqueous phases. Nickel extended X-ray absorption fine structure (EXAFS) spectroscopy showed Ni in two distinct bonding...
Tipo: Text
Palavras-chave: Ni stable isotope fractionation; Ni EXAFS; Surface complexation; Birnessite; Tracer development.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00606/71799/73086.pdf

Comparing orthomagmatic and hydrothermal mineralization models for komatiite-hosted nickel deposits in Zimbabwe using multiple-sulfur, iron, and nickel isotope data
Provedor de dados: 5
Autores: Hofmann, Axel; Bekker, Andrey; Dirks, Paul; Gueguen, Bleuenn; Rumble, Doug; Rouxel, Olivier.
Trojan and Shangani mines are low-grade (&lt;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

Triple iron isotope constraints on the role of ocean iron sinks in early atmospheric oxygenation
Provedor de dados: 5
Autores: Heard, Andy W.; Dauphas, Nicolas; Guilbaud, Romain; Rouxel, Olivier; Butler, Ian B.; Nie, Nicole X.; Bekker, Andrey.
The role that iron played in the oxygenation of Earth's surface is equivocal. Iron could have consumed molecular oxygen when Fe3+-oxyhydroxides formed in the oceans, or it could have promoted atmospheric oxidation by means of pyrite burial. Through high-precision iron isotopic measurements of Archean-Paleoproterozoic sediments and laboratory grown pyrites, we show that the triple iron isotopic composition of Neoarchean-Paleoproterozoic pyrites requires both extensive marine iron oxidation and sulfide-limited pyritization. Using an isotopic fractionation model informed by these data, we constrain the relative sizes of sedimentary Fe3+- oxyhydroxide and pyrite sinks for Neoarchean marine iron. We show that pyrite burial could have resulted in molecular...
Tipo: Text
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00657/76889/78193.pdf

Ni isotope fractionation during coprecipitation of Fe(III)(oxyhydr)oxides in Si solutions
Provedor de dados: 5
Autores: Neubeck, Anna; Hemmingsson, Christoffer; Boosman, Arjen; Rouxel, Olivier; Bohlin, Madeleine.
The dramatic decline in aqueous Ni concentrations in the Archean oceans during the Great Oxygenation Event is evident in declining solid phase Ni concentrations in Banded Iron Formations (BIFs) at the time. Several experiments have been performed to identify the main removal mechanisms of Ni from seawater into BIFs, whereby adsorption of Ni onto ferrihydrites has shown to be an efficient process. Ni isotopic measurements have shown limited isotopic fraction during this process, however, most experiments have been conducted in simple solutions containing varying proportions of dissolved Fe and Ni as NO3 salts, as opposed to Cl salts which are dominant in seawater. Further, Archean oceans were, before the advent of siliceous eukaryotes, likely saturated with...
Tipo: Text
Palavras-chave: Stable Ni isotopes; Ferrihydrite precipitation; Co-precipitation experiment; Banded; Iron Formation; Silica.
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00661/77275/78710.pdf

Native Cu from the oceanic crust: Isotopic insights into native metal origin
Provedor de dados: 5
Autores: Dekov, Vesselin; Rouxel, Olivier; Asael, Dan; Halenius, Ulf; Munnik, Frans.
Ocean drilling has revealed that, although a minor mineral phase, native Cu ubiquitously occurs in the oceanic crust. Cu isotope systematics for native Cu from a set of occurrences from volcanic basement and sediment cover of the oceanic crust drilled at several sites in the Pacific, Atlantic and Indian oceans constrains the sources of Cu and processes that produced Cu0. We propose that both hydrothermally-released Cu and seawater were the sources of Cu at these sites. Phase stability diagrams suggest that Cu0 precipitation is favored only under strictly anoxic, but not sulfidic conditions at circum-neutral pH even at low temperature. In the basaltic basement, dissolution of primary igneous and potentially hydrothermal Cu-sulfides leads to Cu0...
Tipo: Text
Palavras-chave: Cu-isotopes; Deep-Sea Drilling Project; Native Cu; Ocean Drilling Project; Oceanic crust alteration.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00158/26966/25117.pdf

Iron mineral structure, reactivity, and isotopic composition in a South Pacific Gyre ferromanganese nodule over 4 Ma
Provedor de dados: 5
Autores: Marcus, Matthew A.; Edwards, Katrina J.; Gueguen, Bleuenn; Fakra, Sirine C.; Horn, Gregory; Jelinski, Nicolas A.; Rouxel, Olivier; Sorensen, Jeffry; Toner, Brandy M.
Deep-sea ferromanganese nodules accumulate trace elements from seawater and underlying sediment porewaters during the growth of concentric mineral layers over millions of years. These trace elements have the potential to record past ocean geochemical conditions. The goal of this study was to determine whether Fe mineral alteration occurs and how the speciation of trace elements responds to alteration over ∼3.7 Ma of marine ferromanganese nodule (MFN) formation, a timeline constrained by estimates from 9Be/10Be concentrations in the nodule material. We determined Fe-bearing phases and Fe isotope composition in a South Pacific Gyre (SPG) nodule. Specifically, the distribution patterns and speciation of trace element uptake by these Fe phases were...
Tipo: Text
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00278/38965/37505.pdf

A First Look at Dissolved Ge Isotopes in Marine Sediments
Provedor de dados: 5
Autores: 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

Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation
Provedor de dados: 5
Autores: 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

Evidence for Microbial Carbon and Sulfur Cycling in Deeply Buried Ridge Flank Basalt
Provedor de dados: 5
Autores: 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

Determination of the copper isotope composition of seawater revisited: A case study from the Mediterranean Sea
Provedor de dados: 5
Autores: 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

Cobalt and marine redox evolution
Provedor de dados: 5
Autores: 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

Measuring the Form of Iron in Hydrothermal Plume Particles
Provedor de dados: 5
Autores: Toner, Brandy M.; Marcus, Matthew A.; Edwards, Katrina J.; Rouxel, Olivier; German, Christopher R.
Tipo: Text
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00077/18776/16358.pdf

Iron Transformation Pathways and Redox Micro-Environments in Seafloor Sulfide-Mineral Deposits: Spatially Resolved Fe XAS and delta Fe-57/54 Observations
Provedor de dados: 5
Autores: Toner, Brandy M.; Rouxel, Olivier; Santelli, Cara M.; Bach, Wolfgang; Edwards, Katrina J.
Hydrothermal sulfide chimneys located along the global system of oceanic spreading centers are habitats for microbial life during active venting. Hydrothermally extinct, or inactive, sulfide deposits also host microbial communities at globally distributed sites. The main goal of this study is to describe Fe transformation pathways, through precipitation and oxidation-reduction (redox) reactions, and examine transformation products for signatures of biological activity using Fe mineralogy and stable isotope approaches. The study includes active and inactive sulfides from the East Pacific Rise 9 degrees 50'N vent field. First, the mineralogy of Fe(III)-bearing precipitates is investigated using microprobe X-ray absorption spectroscopy (RXAS) and X-ray...
Tipo: Text
Palavras-chave: Hydrothermal; East Pacific Rise; X-ray absorption spectroscopy; Stable isotopes; Micro-environment; Mineral alteration; Iron; Biosignature.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00337/44810/44375.pdf

A late Paleoproterozoic (1.74 Ga) deep‐sea, low‐temperature, iron‐oxidizing microbial hydrothermal vent community from Arizona, USA
Provedor de dados: 5
Autores: 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

Iron isotope systematics in Arctic rivers
Provedor de dados: 5
Autores: 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: https://archimer.ifremer.fr/doc/00273/38402/36865.pdf

Reviews and syntheses: The biogeochemical cycle of silicon in the modern ocean
Provedor de dados: 5
Autores: Treguer, Paul; Sutton, Jill; Brzezinski, Mark; Charette, Matthew A.; Devries, Timothy; Dutkiewicz, Stephanie; Ehlert, Claudia; Hawkings, Jon; Leynaert, Aude; Mei Liu, Su; Llopis Monferrer, Natalia; Lopez Acosta, Maria; Maldonado, Manuel; Rahman, Shaily; Ran, Lihua; Rouxel, Olivier.
he element silicon (Si) is required for the growth of silicified organisms in marine environments, such as diatoms, which consume vast amounts of Si together with N, P, and C, connecting the biogeochemical cycles of these elements. Thus, understanding the Si cycle in the ocean is critical for understanding issues such as carbon sequestration by the ocean's biological pump. In this review, we show that recent advances in process studies indicate that total Si inputs and outputs, to and from the world ocean, are 57 % and 18 % higher, respectively, than previous estimates. We also update the total ocean silicic acid inventory value, which is about 24 % higher than previously estimated. These changes are significant, modifying factors such as the geochemical...
Tipo: Text
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00643/75509/76356.pdf

Enargite-luzonite hydrothermal vents in Manus Back-Arc Basin: submarine analogues of high-sulfidation epithermal mineralization
Provedor de dados: 5
Autores: 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

Ge and Si Isotope Behavior During Intense Tropical Weathering and Ecosystem Cycling
Provedor de dados: 5
Autores: 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

Inter-calibration of a proposed new primary reference standard AA-ETH Zn for zinc isotopic analysis
Provedor de dados: 5
Autores: 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&amp; relative to JMC-Lyon. We suggest that this...
Tipo: Text
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00380/49085/49522.pdf