Description
Northwest Africa 8687 (NWA 8687)
(Northwest Africa)
Purchased: 2014
Classification: Lunar (troctolite)
History: Purchased by Adam Aaronson in Morocco, 2014.
Physical characteristics: Five pieces, no fusion crust, smooth, light green-tan color, sandblasted exterior, saw cut and polished surface reveals fine-grained, pale green interior with fine shock melt veining.
Petrography: (C. Agee, UNM) Microprobe examination of a ~30 × 15 mm, polished, saw-cut surface of the deposit sample, shows a monomict breccia with approximately 70% plagioclase, 25% olivine, 3% orthopyroxene. Primarily fine grained plagioclase, olivine, and orthopyroxene 5-50 μm, scattered larger plagioclase and olivine 200-500 μm, some poikioblastic plagioclase with fine-grained olivines and pyroxenes. Shock melt veins are found throughout. Scatterered Ti-chromite grains up to 100 μm, other accessory phases include FeNi-metal, troilite, ilmenite, and apatite. Minor pigeonite and augite present.
Geochemistry: (C. Agee and N. Muttik, UNM). olivine Fa21.7±2.2, Fe/Mn=88±5, n=24; low-Ca pyroxene Fs19.6±2.3Wo3.5±1.4, Fe/Mn=54±3, n=11; pigeonite Fs16.8Wo19.1, Fe/Mn=41, n=1; augite Fs11.3Wo37.2, Fe/Mn=41, n=1; plagioclase An96.7±0.8Ab3.1±0.8Or0.2±0.0, n=7; Shock melt (20 μm defocused electron beam, proxy for bulk meteorite composition): SiO2=43.01±0.66, TiO2=0.14±0.03, Al2O3=23.85±2.94, Cr2O3=0.15±0.05, MgO=12.11±3.05, FeO=5.20±1.17, MnO=0.06±0.01, CaO=13.48±1.32, NiO=0.02±0.02, Na2O=0.25±0.05, K2O=0.03±0.00 (all wt%), Fe/Mn=84±29, Mg#=80.5±0.8, n=5.
Classification: Achondrite (lunar troctolite), low weathering grade, high shock stage, likely paired with NWA 5744.
Specimens: A total of 21.5 g including a probe mount on deposit at UNM. Aaronson holds the main mass.
