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| Decitre, S; Deloule, E; Reisberg, L; James, R; Agrinier, P; Mevel, C. |
| [1] Analyses of Li and Li isotopes in serpentinized peridotites have been performed using Thermo-Ionisation Mass Spectrometry (TIMS) and Secondary Ion Mass Spectrometry (SIMS) techniques on samples collected from the southwest Indian Ridge (SWIR). In the bulk samples, Li concentrations range from 0.6 to 8.2 ppm, while whole rock delta(6)Li values range from -2.9 to -14parts per thousand. In situ analyses display a greater range in both Li concentration (0.1-19.5 ppm) and Li isotopic composition ( -27 to +19parts per thousand), with the serpentinized portions having higher Li concentrations than the associated relict phases. These variations may reflect changes in Li partitioning and isotopic fractionation between serpentine and fluid with temperature and... |
| Tipo: Text |
Palavras-chave: Lithium; Isotopes; Geochemical cycle; Oceanic crust; Serpentinization. |
| Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/00223/33403/31860.pdf |
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| Beck, Pierre; Chaussidon, M; Barrat, J.a.; Gillet, Ph.; Bohn, Marcel. |
| Ion-microprobe was used to measure Li abundances and isotopic compositions in pyroxenes from three Martian meteorites belonging to the nakhlite family. The profiles performed across augite crystals from Northwest Africa 817 show a large isotopic zoning from crystal cores (delta Li-7 similar to 0 parts per thousand) to rims (delta Li-7 similar to +20 parts per thousand) while Li abundances are almost constant (similar to 9.2 mu g/g). Unlike NWA 817, the pyroxene studied in the Miller Range 03346 nakhlite shows a zoning in Li abundance, with concentrations increasing from similar to 2.5 mu g/g in the core to similar to 9 mu g/ g in the rim. The augite rim (delta Li-7 = +7 parts per thousand) is slightly enriched in Li-7 with regard to the core (delta Li-7 =... |
| Tipo: Text |
Palavras-chave: Magma; Pyroxene; Lithium; Geochemistry; Mars planet; Isotopic composition. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1955.pdf |
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| Beck, Pierre; Barrat, J; Chaussidon, M; Gillet, P; Bohn, Marcel. |
| Lithium abundances and isotopic compositions were measured by ion microprobe in individual grains of pyroxene, and in a few maskelynites and Ca-phosphates grains, from the Martian meteorite Northwest Africa 480 (NWA 480). In pyroxenes Li abundances are nearly constant from core to rim with concentrations ranging between 3 and 4 mug/g. In contrast, a significant isotopic zoning is observed with delta(7)Li values increasing within single crystals from similar to -17parts per thousand in the core to similar to +10parts per thousand in the rim, most of the variability being observed in the core. Plagioclase (now maskelynite) and phosphate crystals, which co-crystallized with the pyroxene rims, display similar delta(7) Li values. Because of the incompatible... |
| Tipo: Text |
Palavras-chave: Mars planet; Magma; Pyroxene; Isotopic composition; Lithium; Geochemistry. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-735.pdf |
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| Reitz, Anja; Thomson, John; De Lange, Gert J.; Hensen, Christian. |
| [ 1] The residual dark unit of the most recent eastern Mediterranean sapropel (S1) is usually overlain by sediments with enhanced concentrations of MnO(x) in two separated layers. The variability and magnitude of the Mn enrichment at different locations and water depths indicate that Mn must have been added preferentially to sediments at intermediate ( 1 - 2 km) water depths. We propose a two-stage mechanism for the Mn enrichment that involves decreasing oxygenation with increasing water depth. This mechanism involves the loss of reduced Mn(2+) from the deepest sediments (> 2 km water depth) into overlying anoxic waters and a variable gain of MnOx in sediments in contact with oxygenated waters at shallower depth. In the S1 unit that receives the extra... |
| Tipo: Text |
Palavras-chave: Manganese; Sapropel S1; Eastern Mediterranean; Molybdenum; Lithium. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00234/34529/33426.pdf |
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