Northwest Africa 8331 (NWA 8331)

Morocco

Purchased: 2002

Classification: Carbonaceous chondrite (CV3)

History: The meteorite was bought in 2002 in Sainte-Marie-aux-Mines, France, from a Moroccan dealer

Physical characteristics: A single dark stone without fusion crust. Cut face display abundant orange and brownish chondrules in a dark brown matrix.

Petrography: (J. Gattacceca, B. Devouard, CEREGE) Chondrule mean apparent size 934±914 μm (N=57), up to 6 mm. Most chondrules are surrounded by fine-grained dark rims. Modal abundances by point counting: 45 vol% chondrules, 40 vol% matrix, 13 vol% opaques. Opaques consist mostly of troilite (11 vol%), both in matrix and chondrules, in grains up to 500 μm. Metal is very scarce. Magnetic measurements (hysteresis) indicate the presence of about 5 wt% magnetite, present as fine grains in the matrix. Rare refractory inclusions up to 1 mm.

Geochemistry: Chondrule olivine Fa_6.4±5.2, PMD 62%, range 0.7-20.5, mean FeO/MnO=53, mean NiO 0.08 wt.%, N=19. Cr₂O₃ in ferroan olivine 0.18±0.11 wt.% (N=13). Matrix olivine Fa~56. Orthopyroxene Fs_1.7±0.6Wo_1.0±0.4, PMD 36%, mean NiO 0.15 wt.%, N=10. FeNi metal Ni=60 wt.% (N=2). Oxygen isotopic compositions: (J. Gattacceca and C. Sonzogni, CEREGE) analysis of four 1.5 mg acid-washed chondrule samples (from two different chondrules) by laser fluorination gave δ¹⁷O = -5.67, -5.54, -3.71, -3.48; δ¹⁸O = -1.50, -1.34, -0.36, 0.11; Δ¹⁷O = -4.89, -4.84, -3.52, -3.53 (all per mil). Magnetic susceptibility log χ = 4.36 (c in 10^-9 m³/kg).

Classification: Carbonaceous chondrite (CV3), oxidized subgroup.

Specimens: 8.7 g and a polished section at CEREGE. Main mass with N. Tourment.