NWA 4734

NWA 4734 Erfoud Morocco Find : october of 2006 Major classification (group) Achondrite (Lunar monzogabbro) History: bought from nomads in Erfoud (Morocco) in October 2006 and february 2007. Physical characteristics: One complete crusted stone freshly broken into several pieces for a TKW of 1439 g. Dull black/brown fusion crust. It is a light gray, coarse grained, pristine magmatic rock consisting of millimetric phenocrysts mainly of pyroxene and plagioclase. The few patches where crust is missing are light tanned. Petrography: A. Jambon, O. Boudouma and D. Badia. UPVI . The texture is best described as shergottitic like. Pyroxene are highly fractured while plagioclase laths, partly transformed to maskelynite, are only affected by a small number of fractures. Silica and silica-feldspar glass are minor components. A few impact melt patches underline the similarity with shergottites further. Ilmenite, baddeleyite, zirconolite, tranquilityite, pyrrhotite and metal. Fayalite associated with silica probably results from the dissociation of iron rich pyroxene. Minor terrestrial alteration. Mode (vol %): Cpx 50, Plagioclase + Kspar 32, silica + glass 7.5, opaques (ilmenite, Ti-magnetite, pyrrhotite) + fayalite 7, voids + fractures 3. Geochemistry: Mineralogy by EMP and SEM.(Trace -ICP-MS- and major -ICP-AES- element analyses, J-A Barrat UBO). Pyroxene exhibit a complex zoning from En65Fs21Wo13 to En2Fs83Wo15 with a FeO/MnO of 78 on the average. A few compositions correspond to pyroxferroite. Plagioclase is normally zoned from An 91 to An 75 with a sharp rim. Average composition An 89. Fayalite (Fa 80 to 95). Chondrite normalized REE pattern with an enrichment of 53 (La) to 40 (Yb). Trace element pattern with negative anomalies of Sr and Eu. Interstitial glass high in silica (75%) containing microcrysts of K feldspar with a significant celsian component. Classification: According to the grain size, the texture, the plagioclase composition, the core composition of pyroxenes, the FeO/MnO ratio in pyroxene and the chemical identity with lunar basalts, it is classified as a highly shocked lunar gabbro (Mare basalt). Type specimens: A total of 20 g of sample and one polished section is on deposit at UPVI. _________________________________________________ To understand how it’s classified as monzogabbro: http://www.uwgb.edu/DutchS/PETROLGY/classification_of_igneous_rocks.htm Lunar Meteorite with some similarities?: LaPaz Icefield (LAP) 02205, 02224, 02226, 02436, 03632, & 04841 (paired stones)