Northwest Africa 4485

Algeria

Find: September 2006

Achondrite (lunar, KREEP-rich breccia)

History: Stefan Ralew purchased the whole stone in September 2006 from a dealer in Ouarzazate, Morocco.
Physical characteristics: A single 188 g spheroidal stone with a brown weathered exterior. The interior consists of pale gray to whitish clasts in a dark gray matrix, and has visible thin veins of terrestrial carbonate.

Petrography: (A. Irving and S. Kuehner, UWS) Lithic clasts (up to 0.5 cm) are predominantly various types of ophitic to quench-textured basalts (composed of pyroxene(s), plagioclase, olivine, ilmenite, and rare baddeleyite). Granophyre clasts (consisting of subparallel to symplectitic intergrowths of silica and K-feldspar with accessory baddeleyite) are present as a minor component, as well as very fine-grained, quench-textured clasts composed of glass and fine plagioclase microlites. Mineral clasts include pyroxenes, olivine, plagioclase, silica, zircon, baddeleyite, merrillite, Ti-chromite, fayalite, ilmenite, metal (both kamacite and taenite), and troilite (Kuehner et al. 2007).

Mineral compositions and geochemistry: Olivine (Fa_26.3–63.6; FeO/MnO = 99–121), plagioclase (An_88.9–89.7Or_0.3–0.6), orthopyroxene (Fs_18.9–19.7Wo_4.6–3.7; FeO/MnO = 87–89), pigeonite (Fs_37.0Wo_10.1; FeO/MnO = 62), subcalcic augite (Fs_48.9–49.2Wo_26.7–39, FeO/MnO = 59–67), fayalite (Fa_90.1, FeO/MnO = 80). Bulk composition: (R. Korotev, WUSL) INAA on eight ~30 mg subsamples gave a mean composition of: Na = 0.441, Fe = 7.27 (both wt%), Sc = 21.7, La = 31.6, Sm = 14.12, Eu = 1.46, Yb = 11.0, Zr = 443, Hf = 11.4, Ba = 375, Th = 6.37 (all ppm). Although it is possible that there is a minor mare basalt component, this specimen is dominated by materials with KREEP-like compositions, and is essentially identical in bulk composition and petrologic characteristics to Northwest Africa 4472.

Classification: Achondrite (lunar, KREEP-rich breccia).

Type specimen: A total of 20 g and one polished mount are on deposit at UWS. Ralew holds the main mass.