Northwest Africa 11562 (NWA 11562)

(Northwest Africa)

Purchased: 2017 Oct

Classification: Ungrouped achondrite

History: Purchased in Temara, Morocco, by Adam Aaronson in October 2017.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) The specimen consists of coarser, protogranular regions (mean grainsize 0.25 mm) composed of forsterite and enstatite with some interstitial diopside, altered kamacite and blade-like cohenite, plus much finer-grained, quench-textured regions with the same mineralogy.

Geochemistry: Olivine (Fa_1.0-1.1, FeO/MnO = 3-4, N = 3), orthopyroxene (Fs_0.9-1.0Wo_1.0-2.3, FeO/MnO = 2-3, N = 3), diopside (Fs_0.2-0.9Wo_36.3-40.5, Al₂O₃ = 2.0-3.6 wt.%, TiO₂ = 0.5-0.6 wt.%, N = 3). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively δ¹⁷O 1.567, 1.396, 1.479; δ¹⁸O 6.345, 6.084, 6.291; Δ¹⁷O -1.783, -1.816, -1.843 per mil.

Classification: Achondrite (ungrouped). The oxygen isotope composition plots between the trends for CR and CV chondrites, and far from the trends for most achondrites (except for some ureilites); however, the highly magnesian silicates and evidence for partial melting would seem to preclude any affinity to ureilites.

Specimens: 20.5 g including one polished thin section at UWB; remainder with Ke Zuokai.