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Lunar Meteorite: Northwest Africa (NWA) 4472 & 4485 (paired stones)Morocco |
  Two views of NWA 4472. Photos courtesy of Greg Hupé.   Two views of NWA 4485. Photos courtesy of Stefan Ralew and Martin Altmann.
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from The
Meteoritical Bulletin, No. 91, Meteoritics & Planetary Science 42,
A413-A466 (2007)
Northwest Africa 4472AlgeriaFind: 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 (Fa56.6–64.6; FeO/MnO = 91–101), plagioclase (An86.9–97.5 Or0.2–0.6), orthopyroxene (Fs26.9–29.3Wo3.8–4.1; FeO/MnO = 51–62), subcalcic augite (Fs52.6Wo30.5; FeO/MnO = 72), Al-Cr-rich pigeonite (Fs27.0Wo17.1; FeO/MnO = 51.1, Al = 3.10 wt%, Cr = 1.01 wt%), fayalite (Fa90.3; FeO/MnO = 92), barian K-feldspar intergrown with silica (Or80.9–55.6Ab15.3–30.2 Cn0.6–6.3). 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. [should read NWA 4485; RLK] 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. |
from The
Meteoritical Bulletin, No. 91, Meteoritics & Planetary Science 42,
A413-A466 (2007)
Northwest Africa 4485AlgeriaFind: 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 (Fa26.3–63.6; FeO/MnO = 99–121), plagioclase (An88.9–89.7 Or0.3–0.6), orthopyroxene (Fs18.9–19.7Wo4.6–3.7; FeO/MnO = 87–89), pigeonite (Fs37.0Wo10.1; FeO/MnO = 62), subcalcic augite (Fs48.9–49.2Wo26.7–39, FeO/MnO = 59–67), fayalite (Fa90.1, 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. |
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