Northwest Africa 1296

Morocco

Found 2001 spring

Achondrite (angrite)

The single stone weighs 810 g and appears quite fresh with a very thin and shiny, dark-grey, typical fusion crust. It was found in Morocco in spring 2001 by an anonymous finder and afterwards bought by a dealer in Bouarfa (Morocco). Petrography, mineralogy, chemistry and classification (A. Jambon, UPVI; J.-A. Barrat, UAng; O. Boudouma, UPVI): The rock has a fine-grained magmatic texture, indicating rapid cooling, and is significantly different from other angrites. Numerous small vesicles are present, some of which filled with carbonate. Olivine (≈Fo50) was the first phase to crystallize, as feathery chains a few micrometers in thickness. It is closely associated with anorthite (An98–100) overgrowing the olivine crystals. These composite chains are separated from one another by intergrown elongated Al, Ti-rich diopside. Both olivine and pyroxene are normally zoned up to mg# <0.01. The most magnesian pyroxene and olivine have mg# of 0.52. The Fe-rich olivines also contain up to 12 wt% CaO, a typical feature of angrites; they appeared after plagioclase crystallization stopped at the end of the crystallization sequence when co-crystallization of olivine with sub-calcic kirschsteinite is observed. Minor phases are pyrrhotite, Ca-phosphate, a silico-phosphate similar to that found in d’Orbigny and titanomagnetite. The bulk rock analysis is that of a typical angrite like d’Orbigny or Sahara 99555, with a (Ca/Al)CI of 1.52. Extensive trace element data confirm that alkali elements are strongly depleted. Ba is slightly enriched probably as a result of terrestrial alteration; Sr is not. All refractory lithophile incompatible elements exhibit a flat chondrite normalized pattern with an enrichment of 13 × CI. Specimens: main mass, Moroccan Import, Asnières, France; type specimen, 49 g, UPVI.