Petrography and geochemistry of the chassignite Northwest Africa 2737 (NWA 2737)

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doi: 10.1016/j.gca.2006.01.016
Authors:Beck, P.; Barrat, J. A.; Gillet, P.; Wadhwa, M.; Franchi, I. A.; Greenwood, R. C.; Bohn, M.; Cotten, J.; van de Moortèle, B.; Reynard, B.
Author Affiliations:Primary:
Ecole Normale Supérieure, Laboratoire des Sciences de la Terre, Lyon, France
Other:
Universite de Bretagne Occidentale-IUEM, France
Field Museum, United States
Open University, United Kingdom
Volume Title:Geochimica et Cosmochimica Acta
Source:Geochimica et Cosmochimica Acta, 70(8), p.2127-2139. Publisher: Elsevier, New York, NY, International. ISSN: 0016-7037
Publication Date:2006
Note:In English. 45 refs.; illus., incl. 3 tables
Summary:We report on the petrology and geochemistry of the Northwest Africa 2737 (NWA 2737) meteorite that was recovered from the Morrocan Sahara in 2000. It is the second member of the chassignite subclass of the SNC (Shergotitte-Nakhlite-Chassignite) group of meteorites that are thought to have originated on Mars. It consists of black olivine- and spinel-cumulate crystals (89.7 and 4.6 wt%, respectively), with intercumulus pyroxenes (augite 3.1 wt% and pigeonite-orthopyroxene 1.0 wt%), analbite glass (1.6 wt%) and apatite (0.2 wt%). Unlike Chassigny, plagioclase has not been observed in NWA 2737. Olivine crystals are rich in Mg, and highly equilibrated (Fo = 78.7 ± 0.5 mol%). The black color of olivine grains may be related to the strong shock experienced by the meteorite as revealed by the deformation features observed on the macroscopic to the atomic scale. Chromite is zoned from core to rim from Cr83.4Uv3.6Sp13.0 to Cr72.0Uv6.9Sp21.1. Pyroxene compositional trends are similar to those described for Chassigny except that they are richer in Mg. Compositions range from En78.5Wo2.7Fs18.8 to En76.6Wo3.2Fs20.2 for the orthopyroxene, from En73.5Wo8.0Fs18.5 to En64.0Wo22.1Fs13.9 for pigeonite, and from En54.6Wo32.8Fs12.6 to En46.7Wo44.1Fs9.2 for augite. Bulk rock oxygen isotope compositions confirm that NWA 2737 is a new member of the martian meteorite clan (Δ17O = 0.305 ± 0.02 ppm, n = 2). REE abundances measured in NWA 2737 mineral phases are similar to those in Chassigny and suggest a genetic relationship between these two rocks. However, the parent melt of NWA 2737 was less evolved and had a lower Al abundance. Abstract Copyright (2006) Elsevier, B.V.
Sections:Meteorites and tektites
Subjects:Achondrites; Chassignite; Chassigny Meteorite; Chemical composition; Chemical ratios; Cosmochemistry; Crystal chemistry; Geochemistry; ICP mass spectra; Martian meteorites; Mass spectra; Melts; Metals; Metamorphism; Meteorites; Mineral assemblages; Mineral composition; Northwest Africa Meteorites; Petrography; Rare earths; Shock metamorphism; Silicates; SNC Meteorites; Spectra; Stony meteorites; TEM data; Textures; Trace elements; Africa; Morocco; North Africa; Sahara; NWA 2737
Abstract Numbers:06M/2420
Record ID:2007058293
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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