Northwest Africa 4422                   ~32°16'N, ~3°28'W

Morocco

Find: May 2006

Carbonaceous chondrite (CK4)

History: P. Thomas purchased one stone, said to have been found in Beni Tajjite in the province of Figuig, Morocco, in May 2006.

Physical characteristics: One complete, pyramid-shaped stone weighing 147.72 g, entirely covered with a very black fusion crust; the crust is very thin on one face.

Petrography: (M. Bourot-Denise, MNHN) Chondrule and CAI dimensions are between 500 and 1000 µm; CAIs are relatively abundant. Magnetite is the most abundant opaque; it rims chondrules and CAIs, makes up big nodules in association with sulfide, or is scattered as small angular grains in matrix and chondrule rims. Matrix is completely recrystallized. BSE images show that all silicates are equilibrated, even though the chondritic texture is well preserved. The polished section studied contains a 3000 µm diameter chondrule whose core of pyroxene laths is surrounded by a double rim peppered with small magnetites.

Geochemistry: Olivine (mean Fa_30.2±0.3) and low-Ca pyroxene are homogeneous. Magnetite, Cr₂O₃ = 3.79, MgO = 0.16 (both in wt%), in the equilibrated CK domain. Plagioclase, An in the range 34.8-72.3. Magnetic susceptibility: (J. Gattacceca, CEREGE) = log χ = 4.93 10^-9 m³/kg.

Classification: Carbonaceous chondrite (CK4); minimal shock, moderate weathering.

Type specimens: A total of 21.4 g of sample (1 sawn fragment with crust) and one polished mount are on deposit at MNHN. Thomas holds the main mass.

Submitted by: M. Bourot-Denise, MNHN.