Northwest Africa 13915 (NWA 13915)

(Northwest Africa)

Purchased: 2021

Classification: Diogenitic melt breccia

History: The meteorite was purchased from a group of meteorites hunters in Nouadhibou, Mauritania, in late 2020.

Physical characteristics: Brownish rock without fusion crust.

Petrography: The meteorite is an achondritic melt breccia predominantly consisting of up to 700 µm sized diogenetic pyroxene, olivine, and calcic plagioclase crystals set in a recrystallized matrix dominated by low-Ca pyroxene displaying mottled compositional zoning and small feldspar grains. Vesicles are abundant in the matrix and the mineral fragments frequently show resorption features at their contact with the melt. Pyroxene and olivine occur as both, compositionally homogeneous and strongly zoned grains that often contain blebby FeS inclusions. Some chromite-orthopyroxene symplectites are present in olivine. Minor phases are silica, chromite, ilmenite, and FeS. No metallic iron has been found. Eucritic material, i.e., exsolved pigeonite is absent.

Geochemistry: diogenetic pyroxene: Fs_20.8±0.1Wo_1.4±0.02 (Fs_20.7-21.1Wo_1.3-1.4, FeO/MnO=25-30, n=8); zoned diogenetic pyroxene: Fs_20.5±5.7Wo_3.2±2.1 (Fs_16.5-30.3Wo_1.8-6.8, FeO/MnO=25-29, n=8); matrix pyroxene displaying patchy zoning: Fs_32.9±1.3Wo_7.8±1.3 (Fs_31.6-35.6Wo_6.3-10.6, FeO/MnO=25-29, n=8); strongly zoned olivine: Fa_17.9±9.1 (Fa_7.4-29.0, FeO/MnO=40±6, n=8); weakly zoned olivine: Fa_35.4±2.3 (Fa_30.9-37.6, FeO/MnO=45±2, n=8); calcic plagioclase: An_93.9±1.1 (An_91.9-95.2, n=10)

Classification: Diogenite (melt breccia)