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Lunar Meteorite: Northwest Africa (NWA) 4734Morocco |
 A sawn face of NWA 4734 (Photo courtesy of Chladni's Heirs)  Chips of basalts LAP 04841 (left) and NWA 4734 (right), same scale. The two meteorites are compositionally and texturally identical and almost certainly were ejected from a common crater on the Moon by a single impact. (Photos by Randy Korotev) |
from The
Meteoritical Bulletin,
no. 93, Meteoritics & Planetary Science 43,
571-632 (2008)Northwest Africa 4734Rissani, MoroccoFind: October 2006 Achondrite (lunar) History: Two pieces were purchased from nomads in Erfoud, Morocco in October 2006 and February 2007. Physical characteristics: A. Habibi purchased two pieces, with a total mass of 477 g, in Rissani, Morocco, and several other pieces of the same stone totaling 895 g are with M. Oumama in Rissani, Morocco. Dull black/brown fusion crust nearly complete and inside slightly tarnished where absent. It is a gray, coarse grained, pristine magmatic rock consisting of millimeter-sized phenocrysts, mainly of pyroxene and plagioclase. Petrography: (A. Jambon, O. Boudouma and D. Badia, UPVI). The texture is best described as shergottite-like. Pyroxene grains 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 patches of impact melt are also observed. Ilmenite, baddeleyite, zirconolite, tranquilityite, pyrrhotite and metal. Fayalite associated with silica probably results from the dissociation of iron rich pyroxene. Modal mineralogy (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 and major element analyses ICP-MS and ICP-AES, J-A Barrat, UBO). Pyroxene grains are complexly zoned (En65Fs21Wo13 to En2Fs83Wo15; FeO/MnO = 78 [average]). A few compositions correspond to pyroxferroite. Plagioclase is normally zoned from An75-91 (average An89) with minor olivine (Fa80-95). 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 is high in silica (75 wt%) and contains microcrysts of K-feldspar with a significant celsian component. The chemistry, major and trace elements, is identical to NWA 032-479-773 and LAP 02205-02224-02226-02234-02436-03632. The texture is very similar to that of the LAP specimens. The very low abundance of olivine and the relative abundance of silica in NWA 4734 are the main differences beside the grain size and the slightly different composition of the major phases. Classification: Achondrite (lunar); extensive shock. Type specimens: A total of 20 g of sample and one polished section is on deposit at UPVI. Mbarek Ait Elkaid hold the main masses. |
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