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Li isotopic variations in single pyroxenes from the Northwest Africa 480 shergottite (NWA 480): a record of degassing of Martian magmas?
Provedor de dados: 5
Autores: 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

Diffusion induced Li isotopic fractionation during the cooling of magmatic rocks: The case of pyroxene phenocrysts from nakhlite meteorites
Provedor de dados: 5
Autores: 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