from The Meteoritical Bulletin, No. 110
Northwest Africa 14446 (NWA 14446)
Lunar feldspathic breccia
History: Purchased on September 14, 2021, by Edwin Thompson, Patrick Thompson, and Paul Stahurg by a meteorite dealer in Morocco.
Physical characteristics: Single stone with absent fusion crust. The middle of the stone has a light-colored lithology that forms a crude layer ~2.5 cm thick sandwiched between a dark-colored lithology.
Petrography: (D. Sheikh, A. Ruzicka, Cascadia; A. Greshake, MNB) This sample is a dimict breccia composed of two distinct lithologies (light and dark lithologies) separated by a sharp boundary composed of broken up clasts, isolated mineral fragments, devitrified glass, and maskelynite. Light lithology: This lithology is a crystalline melt breccia composed of sub-angular feldspathic lithic clasts (Av. 1.0±0.2 mm diameter, n=11) and relict Mg-Al spinel grains (Mg#=68.9±0.8, Cr#=12.3±0.1, Av. 550±10 µm diameter, n=4) set within a microcrystalline matrix exhibiting a sub-ophitic texture composed of irregular olivine and pigeonite (some weakly zoned) grains and fractured and smooth (possibly maskelynite) plagioclase grains (silicate grain size Av. 100±40 µm diameter, n=51). Shock melt veins are visible throughout, some of which are associated with localized areas containing melt pockets, and some of which crosscut into the dark lithology. Accessory phases include ilmenite, apatite, troilite, and carbonate (from weathering veins). Dark lithology: This lithology is a crystalline melt breccia composed of sub-angular feldspathic lithic clasts and isolated mineral fragments (Av. 190±90 μm diameter, n=51) set within a cryptocrystalline matrix exhibiting a sub-ophitic texture composed of irregular pyroxene, olivine, and plagioclase (some lath-like) grains (silicate grain size Av. 6.0±3 µm diameter, n=40). Some flow banding of matrix minerals is evident along clast boundaries. Accessory phases include ilmenite, apatite, troilite, kamacite, spinel, baddeleyite, and carbonate (from weathering veins). Some plagioclase grains in lithic clasts have been transformed into maskelynite.
Geochemistry: Mineral compositions and geochemistry: Light lithology: Olivine (Fa36.8±0.3, range Fa36.1-38.6, FeO/MnO=96±5, n=20), Pigeonite (Fs27.0±1.9Wo12.7±3.4, range Fs23.8-31.6Wo9.1-21.8, FeO/MnO=54±2, n=19), Augite (Fs48.4Wo31.5, FeO/MnO=20, n=1), Calcic plagioclase (An97.0±0.6, range An96.1-97.9, n=15); Dark lithology: Olivine (Fa29.5±4.4, range Fa17.9-38.6, FeO/MnO=94±14, n=21), Low-Ca Pyroxene (Fs32.5±17.1Wo3.6±0.5, range Fs21.8-52.2Wo3.2-4.1, FeO/MnO=58±4, n=3), Pigeonite (Fs36.8±15.3Wo7.8±2.3, range Fs19.1-46.9Wo6.5-10.5, FeO/MnO=56±3, n=3), Augite (Fs21.1±16.0Wo34.1±11.4, range Fs9.8-32.4Wo26.1-42.2, FeO/MnO=47±8, n=2), Homogeneous low-Ca pyroxene (Fs29.1±0.2Wo4.2±0.0, range Fs28.9-29.4Wo4.2, FeO/MnO=52±3, n=5), Low-Ca pyroxene host to augite exsolution (Fs43.9±0.6Wo4.1±0.7, range Fs40.8-44.9Wo2.8-5.7, FeO/MnO=58±3, n=8), Augite exsolution lamellae (Fs16.9±0.1Wo41.7±0.2, range Fs16.7-17.6Wo41-42.1, FeO/MnO=50±4, n=8), Calcic plagioclase (An96.4±1.9, range An92.3-98.8, n=12).
Classification: Lunar (dimict feldspathic crystalline melt breccia). This sample has the appearance of an intrusive dike structure in hand specimen, representative of a dimict breccia (Stöffler et al., 1980). In this case, both lithologies appear to represent feldspathic crystalline melt breccias, but there are distinct textural and compositional differences between the light and dark lithologies.
Specimens: 20.3 g and a thin section at Cascadia; main mass with Edwin Thompson, Patrick Thompson, and Paul Stahurg.
I have not studied Northwest Africa 14446. From the description, it seems unique.
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