Northwest Africa 8632 (NWA 8632)
Classification: Lunar meteorite (basalt)
History: Purportedly found near Chwichiya in 2013 and purchased by Luc Labenne in June 2014 from a dealer in Ouarzazate, Morocco.
Physical characteristics: A single, small, dense black stone (23.8 g) with a flat, squarish shape and no fusion crust. Magnetic susceptibility log ? = 3.08 (X in nm3/kg) (J. Gattacceca, CEREGE).
Petrography: (A. Irving and S. Kuehner, UWS) Porphyritic texture. Subhedral zoned olivine phenocrysts (up to 2.3 mm long, yellowish in thin section) are set in a groundmass composed mainly of elongate, zoned clinopyroxene grains (clear with pink rims), smaller olivine grains and interstitial regions (opaque in thin section) consisting of ilmenite needles, Ti-chromite, fine clinopyroxene, fayalite and glass. No plagioclase was found. Small patches and veinlets of pale yellow devitrified glass are present.
Geochemistry: Olivine phenocrysts (cores Fa32.5-32.8, FeO/MnO = 90-100, N = 3; rim Fa48.8, FeO/MnO = 98), groundmass olivine (Fa72.6-74.1, FeO/MnO = 91-97, N = 3), augite (Fs23.7-27.1Wo40.1-40.5, FeO/MnO = 53-55, TiO2 = 2.4-2.6 wt.%, Al2O3 = 5.9- 6.1 wt.%, N = 2), subcalcic augite (Fs26.6-27.0Wo30.8-36.1, FeO/MnO = 54-60, TiO2 = 1.9-2.1 wt.%, Al2O3 = 4.7-5.6 wt.%, N = 2), ferroan subcalcic augite rim (Fs41.9Wo34.1, FeO/MnO = 63, TiO2 = 3.2 wt.%, Al2O3 = 8.1 wt.%).
Bulk composition: (R. Korotev, WUSL) INAA of subsamples gave the following mean abundances (in wt.%) FeO 22.6, Na2O 0.28; (in ppm) Sc 51.1, Ni 70, La 7.8, Sm 4.7, Eu 0.89, Yb 4.1, Lu 0.58, Hf 3.4, Th 1.25.
Classification: Lunar (mare basalt).
Specimens: 4.6 g including one polished thin section, one polished thick section and one polished mount at UWB. The main mass is held by Labenne.
Northwest Africa 8632 compositionally distinct from any other basaltic lunar meteorites. The major-element composition, however, is matched well by a mixture of 83% NWA 032/479, 13% Fo68 olivine, and 3% ilmenite, so it may be a sample from the bottom of the NWA 032 basalt flow, one that contains denser minerals and slightly less trapped liquid than NWA 032. We suspect that NWA 8632 and NWA 032/479 are launch pairs with each other and NWA 4734/10597 and the LAP basalts of Antarctica (Korotev & Irving, 2021).
Meteoritical Bulletin Database
Cato M. J., Fagan A. L. Gross J. (2016) Crystal size distribution of low-Ti lunar basalt-Northwest Africa 8632. 47th Lunar and Planetary Science Conference, abstract no. 2751.
Fagan A. L., Gross J., Ramsey S., and Turrin B. (2018) Northwest Africa 8632- Recording young lunar volcanism. 49th Lunar and Planetary Science Conference, abstract no. 2584.
Fagan A. L., Udry A., Gannon J. P., Cato M. J., and the Spring 2017 WCU Petrology (GEOL 355) class1 (2018) Northwest Africa 8632 – Crystal size distribution variation & potential link to Northwest Africa 032. 49th Lunar and Planetary Science Conference, abstract no. 2601.
Korotev R. L. and Irving A. J. (2021) Lunar meteorites from northern Africa. Meteoritics & Planetary Science, 206–240.
Korotev R. L., Irving A. J., Wittmann A., Kuehner S. M., Chennaoui-Aoudjehane H., and Labenne L. (2015) Petrology and composition of lunar mare basalt meteorite Northwest Africa 8632 from Chwichiya, Morocco. 46th Lunar and Planetary Science Conference, abstract no. 1195.
Schiller M., Bizzarro M., and Fernandes V. A. (2018) Isotopic evolution of the protoplanetary disk and the building blocks of Earth and the Moon. Nature 555, 507-510.
Tang C. P, Sawchuk K, and Warren P. H. (2018) A textural/mineralogical gradient within vitrophyric mare basalt Northwest Africa (NWA) 8632. 49th Lunar and Planetary Science Conference, abstract no. 2029.
Webb S., Neal C. R., Gawronska A., and Day J. M. D. (2019) Crystal size distribution patterns for lunar meteorites Northwest Africa 12008, 4898, 8632, 3136 and three LaPaz Icefield lunar meteorites. 50th Lunar and Planetary Science Conference, abstract no. 2686.