NWA4468

Martian Meteorite / NWA 4468 / NWA4468 / Shergottite Lunar and Planetary Science Conference abstract on NWA 4468: PETROLOGY AND BULK COMPOSITION OF PRIMITIVE ENRICHED OLIVINE BASALTIC SHERGOTTITE NORTHWEST AFRICA 4468. A. J. Irving1, S. M. Kuehner1, R. L. Korotev2 and G. M. Hupé 1Dept. of Earth & Space Sciences, University of Washington, Seattle, WA 98195 (irving@ess.washington.edu), 2Dept. of Earth & Planetary Sciences, Washington University, St. Louis, MO 63130. Description submitted to the Meteoritical Bulletin: Northwest Africa 4468 Western Sahara Find: Summer 2006 Achondrite (Martian, basaltic shergottite) History: Found in Western Sahara in summer 2006 and purchased in Laâyoune by Greg Hupé in July 2006. Physical characteristics: A single 675 g ellipsoidal stone, mostly coated by shiny black fusion crust, and broken at one end revealing the pale yellow-green interior Petrography: (A. Irving and S. Kuehner, UWS) Large ovoid pyroxene oikocrysts (2-10 mm across) enclosing chadacrysts of Ti-poor chromite and olivine are set in an interstitial matrix of 35% olivine, 30% clinopyroxene, 25% maskelynite, Ti-chromite, ilmenite, merrillite, Cl-apatite (as prisms up to 0.8 mm long) and pyrrhotite. Inclusions (up to 300 mm across) surrounded by radial shock relaxation fractures occur within matrix olivine grains; some are quenched melt inclusions and others consist mainly of maskelynite. The specimen is cross-cut by sporadic, thin, dark, glassy shock veins. Geochemistry: Pyroxene oikocrysts are zoned from orthopyroxene cores (Fs24.5Wo4.4, FeO/MnO = 35.4) with mantles of pigeonite (Fs26.3Wo6.3, FeO/MnO = 29.4) to augite rims (Fs17.9Wo33.6, FeO/MnO = 24.9). Olivine chadacrysts (as magnesian as Fa28.8) typically become progressively more ferroan from pyroxene core to rim (up to Fa39.9). Matrix olivine (Fa40.7, FeO/MnO = 50.2), matrix clinopyroxene (Fs31.3Wo8.1, Fs19.6Wo31.3), matrix maskelynite (An38.7-54Or3.9-2.3); maskelynite in inclusions within olivine is inhomogeneous and K-Na-rich (Or52.6Ab40.7An6.7). Classification: Achondrite (Martian, basaltic shergottite). Type specimens: A total of 20.2 g of sample and one large 3.8 cm x 2.8 cm thin section is on deposit at UWS. Mr. G. M. Hupé holds the main mass. Irving, A. J., Kuehner, S. M., Korotev, R. L. and Hupé, G. M. (2007) Petrology and bulk composition of primitive enriched olivine basaltic shergottite Northwest Africa 4468. Lunar Planet. Sci. XXXVIII, Abstract #1526