Northwest Africa 15508 (NWA 15508)

Morocco

Find: 2014

Classification: HED achondrite (Eucrite, unbrecciated)

History: This meteorite was found near Tirhert in Morocco in 2014, and was purchased by Luc Labenne in Agadir from an anonymous Moroccan dealer.

Physical characteristics: (T. Shisseh, R. Hewins, FSAC, MNHNP) A single stone with a black and shiny fusion crust. The interior shows white plagioclase grains, brown pyroxenes and black opaques.

Petrography: (T. Shisseh, R. Hewins, B. Zanda, E. Jacquet, S. Pont, H. Chennaoui Aoudjehane, FSAC, MNHNP) An unbrecciated rock with a subophitic texture. The fusion crust is up to 150 µm in thickness, and it contains vesicles (40 µm in diameter) and mineral fragments. The main mineral phases are plagioclase and pyroxene. Minor mineral phases include silica, chromite, ulvöspinel, ilmenite, troilite and metal. Plagioclase laths are up 2 mm long and 0.5 mm wide, and they contain pyroxene, silica and oxide inclusions following crystallographic directions. The main pyroxene phase is pigeonite, but scarce augite grains are also present. Mosaicism in pyroxene is observed. Pigeonite contains 8-40-µm-thick augite lamellae, as well as discontinuous rods and lenses of plagioclase and oxides. Remnant Ca-zoning in pyroxene is abundant, with augite lamellae decreasing in thickness toward the pyroxene cores. In some cases, augite lamellae in pigeonite are bended or faulted. Granular late-stage mesostasis is composed of silica, augite and ilmenite, and mostly occurs between plagioclase laths.

Geochemistry: (T. Shisseh, R. Hewins, FSAC, MNHNP) Low-Ca pyroxene is En_35.54±0.5Fs_58.3±0.5Wo_6.1, with Fe/Mn=32 and Mg# =38 (n=2). Augite is En_29.3±0.1Fs_28.8±0.3Wo_{41.8± 0.5} (n = 2). Plagioclase is An_88.9±0.8Ab_10.68±0.7Or_0.42±0.1 (n=4). The TiO₂ and FeO contents of ilmenite are 55.9 wt% and 44 wt%, respectively (n=1).

Classification: (T. Shisseh, R. Hewins, FSAC, MNHNP) Unbrecciated eucrite. The meteorite contains anorthite, and pyroxene with Fe/Mn ratios matching eucrites, plus typical eucritic textures.