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

Beck, P.; Barrat, J.A.; Gillet, P.; Wadhwa, M.; Franchi, I.A.; Greenwood, R.C.; Bohn, M. and Cotten, J. (2006). Petrography and geochemistry of the chassignite Northwest Africa 2737 (NWA 2737). Geochimica et Cosmochimica Acta, 70(8) pp. 2127–2139.

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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 Cr(83.4)Uv(3.6)Sp(13.0) to Cr(72.0)UV(6.9)Sp(21.1). Pyroxene compositional trends are similar to those described for Chassigny except that they are richer in Mg. Compositions range from En(78.5)Wo(2.7)Fs(18.8) to En(76.6)WO(3.2)Fs(20.2) for the orthopyroxene, from En(73.5)Wo(8.0)Fs(18.5) to En(64.0)Wo(22.1)Fs(13.9) for pigeonite, and from En(54.6)Wo(32.8)Fs(12.6) to En(46.7)Wo(44.1)Fs(9.2) for augite. Bulk rock oxygen isotope compositions confirm that NWA 2737 is a new member of the martian meteorite clan (Delta O-17 = 0.305 +/- 0.02 parts per thousand, 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.

Item Type: Journal Item
ISSN: 0016-7037
Extra Information: Some of the symbols may not have transferred correctly into this bibliographic record and/or abstract.
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 5789
Depositing User: Ian Franchi
Date Deposited: 03 Nov 2006
Last Modified: 01 May 2019 13:23
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