Northwest Africa 10472 (NWA 10472)

(Northwest Africa)

Purchased: 2015 Jul

Classification: HED achondrite (Howardite)

History: Found in far-western Algeria in early June 2015.

Physical characteristics: Single stone with fusion crust. A sawn surface shows finely brecciated texture with white, gray, and black clasts.

Petrography: (C. Agee, UNM) This meteorite contains at least six different lithologies: diogenite ~40%, cumulate eucrite ~10%, basaltic eucrite ~50%, carbonaceous chondrite CM2 ~1%, stony-iron (pallasite-like) <1%, and stony-iron (mesosiderite-like) <1%. The CM2 and stony-iron clasts are approximately 500 μm in size. The CM2 clasts are rounded or oval in shape and consist primarily of magnesian-rich chondrules set in a groundmass of phyllosilicates. The pallasite-like clast observed has a typical pallasite texture of rounded olivines suspended in Fe-Ni metal, although the olivine grain size (~100 μm) is much smaller than typical PMG. The mesosiderite-like clast is unbrecciated and consists of equilibrated pyroxenes, plagioclase, silica, and Fe-Ni metal; it most resembles a type A3 mesosiderite. Most HED domains consist of fragmental mineral grains, although there are also a few intersertal basaltic clasts Accessory silica, ilmenite, and chromite were observed.

Geochemistry: (C. Agee and N. Muttik, UNM) Diogenite: low-Ca pyroxene Fs_26.3±4.9Wo_3.1±2.2, Fe/Mn=30±2, n=8. Cumulate eucrite: low-Ca pyroxene Fs_42.8±5.0Wo_3.1±1.2, Fe/Mn=30±1, n=5; high-Ca pyroxene Fs_19.2±0.4Wo_44.1±1.0, Fe/Mn=26±0, n=2. Basaltic eucrite: low-Ca pyroxene Fs_62.9±0.3Wo_2.3±1.0, Fe/Mn=32±1, n=6; high-Ca pyroxene Fs_30.6±3.1Wo_40.9±2.8, Fe/Mn=32±1, n=3, plagioclase An_91.7±3.3, n=5. CM2: forsterite Fa_1.5±1.0, Cr₂O₃ (wt%)=0.46±0.20, n=9; enstatite Fs_1.6±0.5Wo_1.3±0.7, n=6. Pallasite-like clast: olivine Fa_9.7±0.2, Fe/Mn=47±3, n=6. Mesosiderite-like clast: pigeonite Fs_55.7±1.6Wo_11.7±1.6, Fe/Mn=34±1, n=5; high-Ca pyroxene Fs_28.9±3.4Wo_38.0±4.7, Fe/Mn=27±2, n=6; plagioclase An_89.6±4.6, n=2.

Classification: Howardite (xenolith-bearing). Howardite classification based on the presence of diogenite, cumulate eucrite, and basaltic eucrite lithologies. There are also three xenolithic lithologies present: 1) CM2 lithology, 2) main group pallasite-like lithology, 3) A3 mesosiderite-like lithology.

Specimens: 9.6 g including a probe mount on deposit at UNM, DPitt holds the main mass.