Northwest Africa 7892 (NWA 7892)

Morocco

Purchased: 2012

Classification: Carbonaceous chondrite (CO3.0)

History: Purchased by Abdelhadi Aithiba in Morocco, 2012.

Physical characteristics: Single stone, distinctive polygonal, dark brown weathered fusion crust, saw-cut reveals many small chondrules in a very fine-grained dark-brown matrix.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows many PP, POP, and PO chondrules, most 50-300 μm, irregular shaped or fragmental chondrules common.

Geochemistry: (C. Agee and L. Burkemper, UNM) Random chondrule olivine range Fa_0.3-56.8, mean=Fa_17.5, n=22, chondrule ferroan olivine mean Fa_30.7±13.4, Cr₂O₃=0.39±0.19 wt%, Fe/Mn=95±25, n=35; low-Ca pyroxene range Fs _0.8-41.3, mean Fs_8.0, n=17; aluminous diopside Al₂O₃=8.76 wt%. (Karen Ziegler, UNM) Oxygen isotope mean values of analyses on 2 acid-washed aliquots of bulk sample, 1.2, 1.1 mg, gave δ¹⁷O= -8.851, -9.836, δ¹⁸O= -5.849, -6.906, Δ¹⁷O= -5.763, -6.190, (linearized, all permil).

Classification: Carbonaceous chondrite (CO3.0) estimated 3.05, based on mean Cr₂O₃=0.39 wt% in 35 chondrule ferroan olivines which is higher than that measured in the most primitive CO3 chondrite currently known (ALH 77307), but with higher standard deviation (σ-Cr₂O₃), analogous to the higher σ-Cr₂O₃ reported in type 3.05 ordinary chondrites QUE 97008, MET 00526, and EET 90161 (Grossman and Brearley, 2005). Oxygen isotopes values significant lower than literature CO bulk values, and slightly above the CCAM.

Specimens: 21 g including a probe mount on deposit at UNM, Abdelhadi Aithiba holds the main mass.