Northwest Africa 10154 (NWA 10154)

(Northwest Africa)

Purchased: 2015 February

Classification: HED achondrite (Diogenite, anomalous)

History: Discovered in January 2015 at the border of Western Sahara and the southeastern corner of the Al Hamada region. Purchased from a dealer in Mauritania.

Physical characteristics: One piece with no fusion crust present. A saw-cut surface shows pale green pyroxene crystals up to 1-cm in size. Numerous dark-gray patches of maskelynite are observed throughout.

Petrography: (C. Agee, UNM) Orthopyroxene makes up approminately 70% of this meteorite, followed by ~20% plagioclase and 5-10% clinopyroxene. The pyroxene is heavily fractured with many cleavage partings, The plagioclase composition domains appear smooth and unfractured in BSE images, consistent with maskelynite. Accessory troilite, Low-Ni metal, iron oxide, and chromite were observed. Thin calcite weathering veins are present.

Geochemistry: (C. Agee and N. Muttik, UNM) orthopyroxene Fs_32.6±0.3Wo_3.4±0.5, Fe/Mn=30±1, n=14; clinopyroxene Fs_14.2±0.0Wo_43.5±0.5, Fe/Mn=25±1, n=3; plagioclase (maskelynite) An_93.7±0.4Ab_5.8±0.4Or_0.4±0.1, n=10. Oxygen isotopes (K. Ziegler, UNM) laser fluorination of acid-washed bulk subsamples gave (average) respectively, δ¹⁷O = 1.332, δ¹⁸O = 3.086, Δ¹⁷O = -0.305 ‰ (linearized).

Classification: This is an equilibrated, unbrecciated, gabbronoritic diogenite with anomalously low ?17O and ?18O, and an anomalously high percentage of plagioclase or maskelynite.

Specimens: 22.5 g including a probe mount on deposit at UNM, DPitt holds the main mass.