Lunar Meteorite: Northwest Africa 10783

northwestern Africa

Two slices of NWA 10783. “The type specimen is mostly light colored with metal specks, and there is a dark zone at one end” (MetBull description, below). There appears to be a ~1-mm metal grain in the bottom photo. Photo credit: Luc Labenne

A slice of NWA 10783. The rusty spots are iron-nickel metal. Thanks to Luc Labenne for the sample. Photo credit: Randy Korotev

from The Meteoritical Bulletin, No. 105

Northwest Africa 10783 (NWA 10783)

(Northwestern Africa)
Purchased: 2015 May 01
Mass: 22.0 g (1 piece)

Lunar Meteorite (anorthosite)

History: Found in the Almahbas region near the frontier between Morocco and Algeria.

Physical characteristics: The stone is a breccia with no visible fusion crust. The type specimen is mostly light colored with metal specks, and there is a dark zone at one end.

Petrography: (R. Hewins, S. Pont, B. Zanda, MNHNP) Most of the prepared section is a poikilitic anorthosite resembling Apollo 77017. It consists of plagioclase phenocrysts up to 2 mm in length set in pyroxene poikilitic to stubby tiny plagioclase laths (down to 20 μm) and to olivine granules (~50 μm). Both pigeonite and augite are present, but with no obvious exsolution. Minor minerals include chromite, ilmenite, baddeleyite, taenite and kamacite. There is a dark sliver of breccia matrix at the end of the section containing a huge variety of clast types, 1 mm or smaller. These include crystal clasts (olivine, pigeonite, augite, anorthite, chromite and a silica polymorph), breccia clasts, and lithic clasts often with elongated plagioclase laths.

Geochemistry: Mineral compositions and Geochemistry: (R. Hewins and S. Pont, MNHNP) The olivine composition is Fa34.1±1.5, with FeO/MnO 119±14. Pyroxenes are pigeonite Fs25.4Wo11.1 and augite En49.6Fs19.2Wo31.2. Plagioclase is An94.0±0.6Ab5.5±0.6Or0.5±0.2. Taenite contains ~37% Ni. Mineral compositions are similar to those of Apollo 77017, but olivine is a little less ferroan.

Classification: (R. Hewins MNHN, L. Labenne Paris) Lunar poikilitic anorthositic breccia.

Specimens: The type specimen consists of 3.78 g and 0.63 g at MNHNP. The remaining 17.6 g minus sawdust has been sold in the form of thin slices by Labenne.

Randy Says…

My sample of Northwest Africa 10783 is from the light colored clast (lower photo above), which I would call a KREEP-bearing, feldspathic impact-melt breccia on the basis of the texture and composition (6.0% FeO, 3.4 ppm Sm, 16 ppb Iridium). NWA 10783 appears to be another meteorite that, like SaU 169 and NWA 7022, is a regolith breccia dominated by a large clast of impact-melt breccia. Compositionally, NWA 10783 is most similar to the NWA 8641 clan and may, in fact, simply be a large clast in from the NWA 8641 meteorite.

More Information

Meteoritical Bulletin Database

NWA 10783 

References

Korotev R. L. and Irving A. J. (2021) Lunar meteorites from northern Africa. Meteoritics & Planetary Science, 206–240. 

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