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| 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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| 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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| Le Goff, Samuel; Barrat, Jean-alix; Chauvaud, Laurent; Paulet, Yves-marie; Gueguen, Bleuenn; Ben Salem, Douraied. |
| Gadolinium-based contrast agents (GBCAs), routinely used in magnetic resonance imaging (MRI), end up directly in coastal seawaters where gadolinium concentrations are now increasing. Because many aquatic species could be sensitive to this new pollution, we have evaluated the possibility of using shellfish to assess its importance. Gadolinium excesses recorded by scallop shells collected in Bay of Brest (Brittany, France) for more than 30 years do not reflect the overall consumption in GBCAs, but are largely controlled by one of them, the gadopentetate dimeglumine. Although its use has been greatly reduced in Europe over the last ten years, gadolinium excesses are still measured in shells. Thus, some gadolinium derived from other GBCAs is bioavailable and... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00615/72758/72029.pdf |
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| 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 |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00278/38965/37505.pdf |
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| 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 |
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| Mahan, Brandon; Moynier, Frederic; Siebert, Julien; Gueguen, Bleuenn; Agranier, Arnaud; Pringle, Emily A.; Bollard, Jean; Connelly, James N.; Bizzarro, Martin. |
| Chondrites and their main components, chondrules, are our guides into the evolution of the Solar System. Investigating the history of chondrules, including their volatile element history and the prevailing conditions of their formation, has implications not only for the understanding of chondrule formation and evolution but for that of larger bodies such as the terrestrial planets. Here we have determined the bulk chemical composition-rare earth, refractory, main group, and volatile element contents-of a suite of chondrules previously dated using the Pb-Pb system. The volatile element contents of chondrules increase with time from similar to 1 My after Solar System formation, likely the result of mixing with a volatile-enriched component during chondrule... |
| Tipo: Text |
Palavras-chave: Cosmochemistry; Planetary formation; Pebble accretion; Solar System evolution; Meteorites. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00638/74979/75756.pdf |
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| Brugier, Yann-aurélien; Barrat, Jean-alix; Gueguen, Bleuenn; Agranier, Arnaud; Yamaguchi, Akira; Bischoff, Addi. |
| The Ureilite Parent Body (UPB) was a C-rich planetary embryo disrupted by impact. Ureilites are fragments of the UPB mantle and among the most numerous achondrites. Zinc isotopic data are presented for 26 unbrecciated ureilites and a trachyandesite (ALM-A) from the same parent body. The δ66Zn values of ureilites range from 0.40 to 2.71 ‰ including literature results. Zinc isotopic compositions do not correlate with the compositions of olivine cores, with C and O isotopic compositions, with Zn abundances, nor with shock grades. The wide range of δ66Zn displayed by the ureilites is chiefly explained by evaporation processes that took place during the catastrophic breakup of the UPB. During breakup, the high temperatures of the UPB mantle allowed Zn to... |
| Tipo: Text |
Palavras-chave: Ureilite; Zinc isotopic composition; Isotope fractionation; Shock. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00472/58335/60889.pdf |
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