Northwest Africa 11781 (NWA 11781)

(Northwest Africa)

Purchased: 2017 Aug 09

Classification: Carbonaceous chondrite (CM2)

History: The meteorite was purchased from a meteorite dealer in Moscow, Russia.

Petrography: (S. V. Berzin and K. A. Dugushkina, RAS-UB) Chondrule ~20%, refractory inclusion (CAIs, AOAs, Forsterite rich objects) ~3-5% and fine-grained matrix. Most chondrules are porphyritic. Average chondrule size is 0.3 mm. Chondrule mesostasis is rare. The matrix contains phyllosilicates and calcite. CAIs are small (0.05-0.3 mm in size) and very fine grained. The dominant minerals of CAIs are spinel, Ca-pyroxene, hibonite, with accessory perovskite. Some CAIs have forsterite rims. AOAs mainly has spinel-diopside inclusion. Forsterite rich objects have low-Ca pyroxene rims. Refractory forsterite is zoned. Unshocked, low grade of terrestrial weathering (metal partially oxidized).

Geochemistry: Element composition by ICP-MS (ppm): Li 6.05, Sc 2.93, Ti 427, V 55.9, Cr 2307, Mn 1365, Co 236, Ni 2597, Cu 86.0, Zn 129, Ga 6.82, Ge 8.91, As 2.69, Se 4.82, Rb 0.952, Sr 190, Y 1.87, Zr 5.54, Nb 0.431, Mo 1.33, Ag 0.197, Cd 0.151, Sn 1.180, Sb 0.146, Te 0.949, Cs 0.038, Ba 283, La 0.545, Ce 1.33, Pr 0.194, Nd 0.963, Sm 0.281, Eu 0.104, Gd 0.458, Tb 0.061, Dy 0.409, Ho 0.088, Er 0.267, Tm 0.040, Yb 0.264, Lu 0.041, Hf 0.209, Ta 0.365, W 0.151, Tl 0.053, Pb 7.36, Bi 0.024, Th 0.100, U 0.481.

Classification: CM2 Carbonaceous chondrite