Northwest Africa 11697 (NWA 11697)

(Northwest Africa)

Purchased: 2017 Nov

Classification: Rumuruti chondrite (R3-6)

History: Purchased by Bob Falls in November 2017 from a dealer in Zagora, Morocco.

Petrography: (A. Irving and S. Kuehner, UWS) Breccia composed predominantly of small unequilibrated Type 3 lithic clasts (containing separated chondrules with apparent diameter 560±350 µm, N = 10) and related debris (including isolated chondrules), plus rare fine grained, recrystallized Type 5 and Type 6 chondrite clasts, in a finer grained matrix. Minerals in addition to olivine and pyroxenes include albitic plagioclase, pentlandite, troilite and minor ilmenite. Metal is absent. No CAI were observed in the studied thin section, but several chondrules were found to contain highly aluminous pyroxenes.

Geochemistry: Olivine in Type 3 clasts and isolated chondrules (Fa_1.5-48.4, N = 4), orthopyroxene (Fs_1.9-14.5Wo_0.3-2.9, N = 3), augite (Fs_10.7Wo_45.4), Al-rich subcalcic clinopyroxene in chondrule (Fs_3.5Wo_29.2, Al₂O₃ = 7.7 wt.%, TiO₂ = 1.0 wt.%), Al-rich diopside in chondrule (Fs_1.8Wo_41.9, Al₂O₃ = 7.7 wt.%, TiO₂ = 0.9 wt.%), Al-rich low-Ca pyroxene in chondrules (Fs_1.9-2.2Wo_2.9-3.2, Al₂O₃ = 11.6-13.8 wt.%, TiO₂ 0.5-0.7 wt.%; Fs_16.6Wo_3.7, Al₂O₃ = 16.0 wt.%, TiO₂ = 0.4 wt.%; N = 4), plagioclase (An_6.5-10.0Or_2.0-2.9, N = 2).

Classification: R3-6 chondrite. The high content of Mg-Tschermak’s component in low-Ca pyroxenes in some chondrules is an anomalous feature of this specimen.

Specimens: 20.5 g including one polished thin section at UWB; remainder with Mr. R. Falls.