The First Example of Kyanit-Staurolite-Garnet–Bearing Metapelites from the Hoggar (Egéré Terrane, South Algeria)

Abstract

Metapelites containing kyanite, garnet, staurolite, biotitecordierite, and spinel are relatively rare. However, theyhave been reported from a numerous metamorphicterranes around the world. kyanite-garnet-staurolite–bearing metapelites have been identified among thevarious lithologies featuring the Egéréarea (CentralHoggar). These rocks contain mineral assemblages con-sisting of garnet, kyanite, quartz, staurolite, spinel,cordierite, biotite,±plagioclase and muscovite. Theserocks display complex symplectites and coronas reactiontextures comprises spinel and cordierite resulted from thebreakdown of the peak paragenesis formed by garnet,kyanite and staurolite. Garnets porphyroblasts with inclu-sions of quartz, biotite, plagioclase, and rutile reveal anobvious compositional core–rim–outr-rim zonation, par-ticularly in grossular, and pyrope, which is related to themetamorphic evolution of their host metapelitic rocks.Phengitic white micas display high-Si content thatindicates crystallization under relatively high pressureconditions. The textural observations and mineral chem-ical compositions described in this contribution areinterpreted via the application of P–T pseudosections,which were calculated in the system MnO–Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2(MnNCKFMASHT). The obtained results indicate that the metamorphicevolution recorded in these rocks started at pic conditions