Northwest Africa 13965 (NWA 13965)

(Northwest Africa)

Purchased: 2020

Classification: Martian meteorite (Shergottite)

History: Purchased by Jay Piatek from a Moroccan meteorite dealer in 2020.

Physical characteristics: Single stone, broken surface reveals a medium-grained mixture of light gray, light green, orange and white grains.

Petrography: (C. Agee, UNM) SEM mapping gave the following 2-D modal abundances 51% pyroxene, 24.5% olivine, 18% maskelynite, 2.5% oxides, 2.2% carbonates, 1.8% phosphates, and trace silica. Igneously zoned pyroxenes are often ~2 mm in size. Pyroxene zoning shows pigeonitic cores and augitic rims, suggesting an early crystallizing, evolving liquidus phase composition. Phenocrystic pyroxene grains often form cumulate masses up to 10mm in size. Phenocrystic olivines are typically less than 1mm and are unzoned. Maskelynlite laths are typically 0.1 × 1 mm in size and often, along with fine-grained pigeonite and olivine, occupy interstitial, later crystallizing zones. Ubiquitous oxides include ilmenite, titano-magnetite, and chromite. Rare silicate melt pockets ~200 μm with concentrated Fe-sulfide blebs were observed. Calcite, presumably from desert weathering, was observed in fractures. Minor amounts of barite were also detected. Secondary alteration patches within pyroxene and olivine were observed in some grains. Some grains of plagioclase had K-rich secondary alteration. It is unknown if these alteration products are of terrestrial or martian origin.

Geochemistry: (C. Agee, UNM) Olivine Fa_45.2±2.2, Fe/Mn=49±4, CaO=0.15±0.04 (wt%), n=4; pyroxene Fs_26.7±4.4Wo_14.0±11.6, Fe/Mn=30±3, n=39; maskelynite An_48.4±5.0Ab_48.9±4.0Or_2.8±1.2, n=10.

Classification: Martian shergottite (olivine-pigeonite phyric basalt).

Specimens: 20.11 g on deposit at UNM, Jay Piatek holds the main mass.