Northwest Africa 4421                   ~32°19'N, ~4°4'W

Morocco

Find: May 2006

Carbonaceous chondrite (CO3)

History: One sample, said to have been found in the Gourrama area in the province of Er Rachidia, Morocco, and was purchased by P. Thomas in May 2006.

Physical characteristics: A complete stone, weighing 249.73 g, entirely covered with a black, crackled fusion crust.

Petrography: (M. Bourot-Denise, MNHN). The average grain size of chondrules and chondrule fragments is around 100 µm. The largest chondrule is porphyritic and 1000 µm in diameter. Matrix is abundant, fine, and moderately altered; it is sulfide-rich (troilite, pyrrhotite, pentlandite). In the polished section studied, many CAIs and a few AOAs are present, with dimensions comparable to those of chondrules. In BSE images, 90% of the chondrules and chondrule fragments appear FeO-poor, and their olivines are not zoned. The only FeO-rich silicates are in porphyritic (type II) chondrule fragments. Opaque nodules contain metal and sulfides and are associated with magnetite. Small silicate melt pockets are blackened by tiny metal and sulfide droplets.

Geochemistry: Olivine (mean Fa_23.9±22.1, range Fa_0.46-55.1; Cr₂O₃ = 0.28, CaO = 0.25 [both in wt%]); low-Ca pyroxene (mean Fs_8.5±8.2, range Fs_1.4-25.6). Magnetic susceptibility (J. Gattacceca, CEREGE) log χ = 4.57 (10^-9 m³/kg) is consistent with a CO carbonaceous chondrite.

Classification: Carbonaceous chondrite (CO3, estimated subtype 3.2); moderate shock and weathering.

Type specimens: A total of 20.04 g of sample (3 pieces) and one thin section are on deposit at MNHN. Thomas holds the main mass.

Submitted by: M. Bourot-Denise, MNHN.