Northwest Africa 8785 (NWA 8785)

(Northwest Africa)

Purchased: 2014 Jan

Classification: Enstatite chondrite (EL3)

History: Purchased by Fabien Kuntz in January 2014 from a dealer in Rissani, Morocco.

Petrography: (A. Irving and S. Kuehner, UWS) Well-formed, spherical chondrules are set in a dark, deep red-brown matrix (~40 vol.%). Minerals are orthopyroxene, forsterite, silica polymorph (with enstatite in chondrules), kamacite, troilite (some Cr-bearing), Al-Ti-bearing diopside, schreibersite and minor calcite and gypsum (probably representing altered oldhamite). No CAI were found.

Geochemistry: Olivine (Fa_0.2-1.0, Cr₂O₃ = 0.01-0.28 wt.%, mean 0.15±0.09 wt.%, N = 18), orthopyroxene (Fs_0.1-14.9Wo_0.1-2.6, N = 17), diopside (Fs_0.4-0.5Wo_42.9-42.1, Al₂O₃ 6.9-7.5 wt.%, TiO₂ 1.2-1.0 wt.%, N = 2), metal (Si 0.7 wt.%, Ni 7.1 wt.%, Co 0.5 wt.%, N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of four acid-washed subsamples by laser fluorination gave, respectively, δ¹⁷O 3.180, 2.880, 2.996, 2.922; δ¹⁸O 6.042, 5.707, 5.820, 5.849; Δ¹⁷O -0.010, -0.133, -0.077, -0.166 (all per mil).

Classification: Enstatite chondrite (EL3). Matrix is unusually abundant for an enstatite chondrite.

Specimens: 12.86 g including one polished thin section at PSF; main mass with Kuntz.