Lunar Meteorite: Northwest Africa 2200
from The Meteoritical Bulletin, No. 90
Northwest Africa 2200 (NWA 2200)
Achondrite: (lunar, feldspathic breccia)
History: A completely crusted, 552 g, ellipsoidal stone was found in the Atlas Mountains, Morocco, and purchased in Erfoud by a Moroccan dealer for D. Gregory in August 2004.
Petrography and Geochemistry: (S. Kuehner and A. Irving, UWS) Breccia consisting of coarse, greyish-to-whitish lithic and mineral clasts in a darker glassy-to-finely crystalline matrix. Lithic clasts are mainly very fine-grained, quench-textured, feldspathic rocks that probably result from impact melting of anorthositic to gabbroic anorthositic precursors. A small percentage of the clasts are ophitic-textured mare basalts. Mineral clasts include anorthitic plagioclase, olivine (Fa30-60), exsolved pigeonite, irregular grains of metal (Ni = 10–45 wt%), Ti-rich chromite, Ti-poor chromite, pyroxene-like glass, schreibersite (Ni = 5 wt%), clinopyroxene, ilmenite, troilite, and rare zirconolite. Clinopyroxene and orthopyroxene grains in mineral and lithic clasts have Fe/(Fe+Mg) = 0.258–0.482 with Ti/(Ti+Cr) = 0.53–0.75. FeO/MnO ratios measured for olivine (99.7, 105.5), clinopyroxene (73.7), and orthopyroxene (65.4) are unmistakably within the ranges for these minerals in known lunar rocks. Feldspar grains in mineral and lithic clasts have a narrow compositional range of An95.8-97.4.
Classification: Achondrite (lunar, feldspathic breccia). Specimens: A 20.5 g type specimen, one polished thin section, and one polished mount are on deposit at UWS. D. Gregory holds the main mass.
Compositionally, it is a typical feldspathic lunar meteorite
Meteoritical Bulletin Database
Kuehner S. M., Irving A. J., and Gregory D. A. (2005) Lunar feldspathic meteorite NWA 2200; A polymict glassy impact-melt breccia with ferroan anorthosite (FAN) affinities. 68th Annual Meeting of the Meteoritical Society, abstract no. 5137.
Korotev R. L. (2006) New geochemical data for a some poorly characterized lunar meteorites. Lunar and Planetary Science XXVII, abstract no. 1404.
Korotev R. L. and Irving A. J. (2021) Lunar meteorites from northern Africa. Meteoritics & Planetary Science, 206–240.
Korotev R. L. and Zeigler R. A. (2007) Keeping up with the lunar meteorites. Lunar and Planetary Science XXXVIII, abstract no. 1340.
Korotev R. L., Irving A. J., and Bunch T. E. (2008) Keeping up with the lunar meteorites – 2008. Lunar and Planetary Science XXXIX, abstract no. 1209.
Nagaoka H., Karouji Y., Arai T., Shinotsuka K., Ebihara M., and Hasebe N. (2008) A most ferroan feldspathic lunar meteorite NWA 2200. 71st Annual Meeting of the Meteoritical Society, abstract no. 5246, Meteoritics & Planetary Science 43, A107.
Nagaoka H., Karouji Y., Arai T., Ebihara M., and Hasebe N. (2009) Chemical characteristics of the lunar meteorite Northwest Africa 2200. Antarctic Meteorites XXXII, Papers Presented to the Thirty-second Symposium on Antarctic Meteorites, 45-46.
Nagaoka H., Karouji Y., Arai T., Ebihara M., Hasebe N. (2013) Geochemistry and mineralogy of a feldspathic lunar meteorite (regolith breccia), Northwest Africa 2200. Polar Science 7, 241-259.
Nishiizumi K. and Caffee M. W. (2006) Constraining the number of lunar and martian meteorite falls. 69th Annual Meeting of the Meteoritical Society, abstract no. 5368.