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Geochemistry of intermediate olivine-phyric shergottite Northwest Africa 6234, with similarities to basaltic shergottite Northwest Africa 480 and olivine-phyric shergottite Northwest Africa 2990

Filiberto, Justin; Chin, Emily; Day, James M. D.; Franchi, Ian A.; Greenwood, Richard C.; Gross, Juliane; Penniston-Dorland, Sarah C.; Schwenzer, Susanne P. and Treiman, Allan H. (2012). Geochemistry of intermediate olivine-phyric shergottite Northwest Africa 6234, with similarities to basaltic shergottite Northwest Africa 480 and olivine-phyric shergottite Northwest Africa 2990. Meteoritics & Planetary Science, 47(8) pp. 1256–1273.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1111/j.1945-5100.2012.01382.x
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Abstract

The newly found meteorite Northwest Africa 6234 (NWA 6234) is an olivine (ol)-phyric shergottite that is thought, based on texture and mineralogy, to be paired with Martian shergottite meteorites NWA 2990, 5960, and 6710. We report bulk-rock major- and trace-element abundances (including Li), abundances of highly siderophile elements, Re-Os isotope systematics, oxygen isotope ratios, and the lithium isotope ratio for NWA 6234. NWA 6234 is classified as a Martian shergottite, based on its oxygen isotope ratios, bulk composition, and bulk element abundance ratios, Fe ⁄Mn, Al ⁄ Ti, and Na⁄ Al. The Li concentration and δ 7Li value of NWA 6234 are similar to that of basaltic shergottites Zagami and Shergotty. The rare earth element (REE) pattern for NWA 6234 shows a depletion in the light REE (La-Nd) compared with the heavy REE (Sm-Lu), but not as extreme as the known ‘‘depleted’’ shergottites. Thus, NWA 6234 is suggested to belong to a new category of shergottite that is geochemically ‘‘intermediate’’ in incompatible elements. The only other basaltic or ol-phyric shergottite with a similar ‘‘intermediate’’ character is the basaltic shergottite NWA 480. Rhenium-osmium isotope systematics are consistent with this intermediate character, assuming a crystallization age of 180 Ma. We conclude that NWA 6234 represents an intermediate compositional group between enriched and depleted shergottites and offers new insights into the nature of mantle differentiation and mixing among mantle reservoirs in Mars.

Item Type: Journal Article
Copyright Holders: 2012 The Meteoritical Society
ISSN: 1945-5100
Keywords: Martian meteorite, REE, lithium isotopes, NWA 6234, oxygen isotopes, geochemistry, major and trace elements
Academic Unit/Department: Science > Physical Sciences
Science
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Related URLs:
Item ID: 34280
Depositing User: Susanne Schwenzer
Date Deposited: 11 Sep 2012 09:49
Last Modified: 25 Sep 2013 13:34
URI: http://oro.open.ac.uk/id/eprint/34280
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