Description
Northwest Africa 11431 (NWA 11431)
Mauritania
Find: 2017 Jun
Classification: Martian meteorite (Shergottite)
History: Found in June 2017 in Mauritania in a region directly south of the NWA 6963 strewnfield (located near Fej Arrih to the north in adjacent Morocco), and puchased by Ben Hoefnagels in July 2017 from a Moroccan dealer.
Physical characteristics: A single stone (524 g) with a flat prismatic shape almost completely coated by black fusion crust. The interior is gray with evident glassy maskelynite.
Petrography: (A. Irving and S. Kuehner, UWS) Medium-grained, diabasic texture. Composed predominantly of zoned clinopyroxene and maskelynite with accessory Fe-bearing merrillite, titanomagnetite, ilmenite (with rare baddeleyite inclusions), silica polymorph, fayalite and pyrrhotite.
Geochemistry: Pigeonite (Fs36.2-51.6Wo8.1-12.8, FeO/MnO = 31-37, N = 4), subcalcic augite (Fs21.6-42.0Wo30.1-31.3, FeO/MnO =30-42, N = 4), fayalite (Fa85.5, FeO/MnO = 60), maskelynite (An38.4-42.3Or4.5-3.0, N = 2). The most ferroan subcalcic augite rims are notably aluminous (Al2O3 = 2.2-2.5 wt.%) and yield low oxide sums plus high cation totals indicative of the presence of minor ferric iron. Magnetic susceptibility (P. Rochette, CEREGE) log χ (× 10-9 m3/kg) = 3.22.
Classification: Martian (shergottite, diabasic). This specimen has many similarities to the NWA 6963 stones and evidently comes from an extension of the same strewnfield into Mauritania.
Specimens: 26.5 g including one polished thin section and one polished thick section at UWB; remainder with Mr. B. Hoefnagels.
