Northwest Africa 3163

Mauritania or Algeria

Find: August 2005

Achondrite (lunar, feldspathic granulitic impactite)

History: In August 2005, G. Hupé purchased a 1634 g stone from a Moroccan dealer in Ouarzazate.

Petrography and Geochemistry: (A. Irving and S. Kuehner, UWS) The exterior is almost completely coated by a thin, transparent, greenish fusion crust. The pale gray interior has multiple shock fractures (with very minor calcite coatings) and some thin glass veins. Poikiloblastic recrystallized breccia, with larger grains of plagioclase (~70 vol%) enclosing much smaller grains (less than 100 µm across) of pyroxenes (~20 vol%), olivine (~10 vol%), and accessory Ti-chromite (Cr/(Cr+Al) = 0.714–0.736; Mg/(Mg+Fe) = 0.121– 0.143; TiO₂ = 9.1–18.4 wt%), ilmenite, troilite, and metal (Ni = ~15 wt%). Anorthitic plagioclase (An_97.4–98.2) has been converted by shock almost entirely to maskelynite (although domains of birefringent, less-shocked feldspar remain). Pigeonitic pyroxene grains have very fine-scale exsolution lamellae of augite (Fs_14.5–16.1Wo_40.2–40.5; FeO/MnO = 41.7– 43.8) within orthopyroxene (Fs_32.0–33.9Wo_4.4–5.8; FeO/MnO = 55.5–61.2). Olivine (Fa_38.0–40.9; FeO/MnO = 91.7–110).

Classification: Achondrite (lunar, feldspathic granulitic impactite).

Specimens: A 20.1 g type specimen and one polished thin section are on deposit at UWS. GHupé holds the main mass.