Northwest Africa 4472

Algeria

Find: July 2006

Achondrite (lunar, KREEP-rich breccia)

History: G. Hupé purchased the sample July 2006 from a dealer in Tagounite, Morocco.

Physical characteristics: A single 64.3 g stone with visible pale gray to whitish clasts in a dark gray matrix. Fusion crust is not evident, but the exterior has fractures and thin coatings of desert varnish on exposed surfaces.

Petrography: (A. Irving and S. Kuehner, UWS) Lithic clasts (up to 0.65 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 “ribbon-like” subparallel intergrowths of silica and K-feldspar with accessory baddeleyite and rare tranquillityite) are present as a minor component, as well as clasts composed mainly of fayalite (with associated glass, silica, K-feldspar, and merrillite) and spherical to ellipsoidal glass objects (up to 60 µm across). Mineral clasts include pyroxenes, olivine, plagioclase, silica, zircon, baddeleyite, merrillite, Ti-chromite, fayalite, ilmenite (with baddeleyite inclusions), metal (both kamacite and taenite), troilite, and schreibersite (Kuehner et al. 2007).

Mineral compositions and geochemistry: Olivine (Fa_56.6–64.6; FeO/MnO = 91–101), plagioclase (An_86.9–97.5 Or_0.2–0.6), orthopyroxene (Fs_26.9–29.3Wo_3.8–4.1; FeO/MnO = 51–62), subcalcic augite (Fs_52.6Wo_30.5; FeO/MnO = 72), Al-Cr-rich pigeonite (Fs_27.0Wo_17.1; FeO/MnO = 51.1, Al = 3.10 wt%, Cr = 1.01 wt%), fayalite (Fa_90.3; FeO/MnO = 92), barian K-feldspar intergrown with silica (Or_80.9–55.6Ab_15.3–30.2 Cn_0.6–6.3). Bulk composition: (R. Korotev, WUSL) INAA on nine ~30 mg subsamples gave a mean composition of: Na = 0.448, Fe = 7.14 (both wt%), Sc = 20.9, La = 44.7, Sm = 19.51, Eu = 1.50, Yb = 13.4, Zr = 438, Hf = 11.1, Ba = 601, Th = 7.49 (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 12.87 g and 3 polished thick slices are on deposit at UWS. G. Hupé holds the main mass.