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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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| Gillet, P; Barrat, J; Beck, P; Marty, B; Greenwood, R; Franchi, I; Bohn, Marcel; Cotten, J. |
| Northwest Africa (NWA) 1950 is a new member of the lherzolitic shergottite clan of the Martian meteorites recently found in the Atlas Mountains. The petrological, mineralogical, and geochemical data are very close to those of the other known lherzolitic shergottites. The meteorite has a cumulate gabbroic texture and its mineralogy consists of olivine (FO66 to FO75), low and high-Ca pyroxenes (En(78)Fs(19)Wo(2)-En(60)FS(26)W(14); En(53)Fs(16)Wo(31)-En(45)Fs(14)Wo(41)), and plagioclase (An(57)Ab(41)Or(1) to An(40)Ab(57)Or(3); entirely converted into maskelynite during intense shock metamorphism). Accessory minerals include phosphates (merrillite), chromite and spinels, sulfides, and a glass rich in potassium. The oxygen isotopic values lie on the fractional... |
| Tipo: Text |
Palavras-chave: Meteorites; Atlas Mountains; Shergottite; Lherzolitic. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-900.pdf |
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