Northwest Africa 11638 (NWA 11638)

(Northwest Africa)

Purchased: 2017

Classification: CM2.0

History: The meteorite was purchased from a local meteorite dealer in Morocco.

Physical characteristics: Many small and dark-grayish fragments lacking any fusion crust.

Petrography: The meteorite is a carbonaceous chondrite that is composed of chondrule and CAI pseudomorphs set into a fine-grained Fe-rich matrix dominated by phyllosillicates, carbonates and sulfides. It does not contain any anhydrous silicates. Low totals of defocused matrix analyses attest to porosity and the presence of hydrous phases, i.e., phyllosilicates. Abundant mineral phases are up to 50 μm sized Ca-carbonates, often fibrous phyllosilicates, and Ni-bearing pyrrhotite.

Geochemistry: Mean values of defocused (10 μm beam diameter) matrix analyses (all wt%; N=35): SiO₂: 26.5, TiO₂: 0.12; Na₂O: 0.19; Cr₂O₃: 0.46, MgO: 20.5, MnO: 0.25, CaO: 0.68, FeO: 29.5, Al₂O₃: 2.59, NiO: 0.69, P₂O₅: 0.14, S: 0.38, Total: 82.0; Ca-carbonates contain about 1 wt% FeO.

Classification: CM2.0. Subtype following the classification scheme of Rubin et al. (2007)).