Petrology, geochemistry, and cosmic-ray exposure age of lherzolitic shergottite Northwest Africa 1950

Type Article
Date 2005-08
Language English
Author(s) Gillet P1, Barrat J2, Beck P1, Marty B3, Greenwood R4, Franchi I4, Bohn Marcel5, 7, Cotten J6
Affiliation(s) 1 : Ecole Normale Super Lyon, CNRS, UMR 5570, Lab Sci Terre, F-69364 Lyon, France.
2 : IUEM, CNRS, UMR 6538, UBO,Domaine Ocean, F-29280 Plouzane, France.
3 : CNRS, CRPG, UPR 2300, F-54501 Vandoeuvre Les Nancy, France.
4 : Open Univ, Planetary & Space Sci Res Inst, Milton Keynes MK7 6AA, Bucks, England.
5 : CNRS, UMR 6538, IFREMER, Ctr Brest, F-29280 Plouzane, France.
6 : Univ Brest, CNRS, UMR 6538, F-29100 Brest, France.
Source Meteoritics and Planetary Science (1086-9379) (The Meteoritical Society), 2005-08 , Vol. 40 , N. 8 , P. 1175-1184
WOS© Times Cited 44
Keyword(s) meteorites, Atlas Mountains, shergottite, lherzolitic
Abstract 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 line defined by the other SNC meteorites (Delta(17)O = 0.312 parts per thousand). The composition of NWA 1950 is very similar to the other lherzolitic shergottites and Suggests an origin from the same magmatic system, or at least crystallization from a close parental melt. Cosmogenic ages indicate an ejection age similar to those of the other lherzolitic shergottites. The intensity of the shock is similar to that observed in other shergottites, as shown by the occurrence of small melt pockets containing glass interwoven with stishovite.
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Gillet P, Barrat J, Beck P, Marty B, Greenwood R, Franchi I, Bohn Marcel, Cotten J (2005). Petrology, geochemistry, and cosmic-ray exposure age of lherzolitic shergottite Northwest Africa 1950. Meteoritics and Planetary Science, 40(8), 1175-1184. Open Access version : https://archimer.ifremer.fr/doc/00000/900/