Northwest Africa 12908 (NWA 12908)

(Northwest Africa)

Purchased: 2019

Classification: Martian meteorite (Shergottite)

History: Purchased by Zuokai Ke from a Moroccan dealer in Chenzhou, China, in May 2019.

Physical characteristics: Single stone, brownish sand blasted exterior with no fusion crust. Cut surface reveals greenish-yellow grains and dark gray grains or domains.

Petrography: (C. Agee, UNM; X. Gu, CSU-China) The two major phases in this meteorite are clinopyroxene and maskelynite. Ubiquitous minor phases are merrillite, apatite, titanomagnetite, ilmenite and troilite. Trace amounts of baddelyite, taenite, chalcopyrite, and molybdenite were detected. The clinopyroxene has a modal abundance of approximately 60%, with significant core to rim zoning observed in backscatter electron images indicating an igneous crystallization trend with Mg-rich pigeonite cores, mantled by augite, and rimmed with ferropigeonite. Clinopyroxene average grain size is approximately 300-500 μm. Maskelynite has modal abundance of approximately 30%, most grains are thin and elongate with maximum length ~1 mm. Merrilite is more abundant than apatite in this sample.

Geochemistry: (C. Agee, UNM; X. Gu, CSU-China: (C. Agee, UNM) Clinopyroxene Fs_45.6±17.2Wo_22.6±7.2, core to rim range Fs_31.1Wo_14.0 (Mg-pigeonite) Fs_22.6Wo_37.0 (augite) - Fs_73.3Wo_17.6 (ferropigeonite), Fe/Mn=38±5, n=24; maskelynite An_47.4±4.8Ab_48.9±3.9Or_3.7±1.4, n=13. Oxygen isotopes (K. Ziegler, UNM): 3 acid-washed fragments analyzed by laser fluorination gave δ¹⁸O= 4.728, 4.967,4.670; δ¹⁷O= 2.780, 2.896, 2.738; Δ¹⁷O= 0.284, 0.273, 0.272 (linearized, all per mil, TFL slope=0.528).

Classification: Geochemically evolved pyroxene-phyric basalt, clinopyroxene compositional zoning trends are similar to QUE 94201. Likely paired with NWA 12522.

Specimens: 18.7 g including a probe mount on deposit at UNM, Zuokai Ke holds the main mass.