NORTHWEST AFRICA 4734

Two partially fusion-crusted fragments, weighing 409 g and 68 g, were purchased from nomads in Rissani, Morocco by A. Habibi. Additional fragments of this same meteorite, having a combined weight of 895 g, are in the possession of M. Oumama. A portion of the meteorite was submitted by Mr. Habibi for analysis and classification to UPVI, Paris (A. Jambon, O. Boudouma and D. Badia) and UBO (J-A Barrat) under the designation NWA 4734. Northwest Africa 4734 was determined to be of lunar origin.

Not unexpectantly, separate analyses of this unique and unusual lunar mare basalt have resulted in some differences in the classification nomenclature among the various investigating teams. The initial analysis conducted in France on a portion of NWA 4734 resulted in its classification as a highly shocked lunar monzogabbro (inferring a plutonic crystallization origin rather than a volcanic/basaltic origin), with a measured anorthite content within the monzogabbro field (89%). However, the minimum amount of alkali feldspar (10%) was not observed in NWA 4734, and therefore the "monzo" modifier is not supported (R. Korotev). Given the close compositional, mineralogical, and textural similarities that exist between NWA 4734, NWA 032/479, the LaPaz 02205 lunar mare basalt pairing group, and the NWA 773 pairing group, it is considered that these stones, recovered from distinct continents, may be source-crater paired. Through Pb–Pb dating utilizing zirconolite and baddeleyite, Wang and Hsu (2010) determined a crystallization age for NWA 4734 of 3,074 (±16) m.y., and an age for the LAP pairing group of 3,044 (±12) m.y. These ages are consistent with results obtained by other chronometry methods, and support a concomitant formation with a concurrent ejection of both NWA and LAP members during the same event.

Further information can be found on the NWA 032 page, as well as the lunar meteorite website of the Department of Earth Sciences, Washington University.

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