Reaction textures in gneisses from Dallmannfjellet-Conrad area, Orvin range, central Dronning Maud Land, East Antarctica: Implication for metamorphicevolution

Preliminary study of metamorphic reaction textures coupled with thermobarom etry suggests that the metapelites, garnet-clinopyroxene gneisses, calc-sil icate gneisses and orthopyroxene bearing quartzo-feldspathic gneisses expos ed in Dallmannfjellet-Conrad area, central Dronning Maud Land, East Antarct ica were metamorphosed to granulite grade. Peak metamorphic conditions eval uated from core thermobarometry are similar to 900 - 1050 degrees C and pre ssure similar to 9 kbar. Sillimanite and garnet growth over spinel in metap elites suggests cooling of the rocks to 800 degrees C, followed by a mild d ecompression inferred on the basis of orthopyroxene+plagioclase moats aroun d garnet in metanorite pods within metapelite. The metanorite pods record P -T conditions of 7-10 kbar and 750-850 degrees C. Late component of the P-T segments is represented by cooling stage and eventual exhumation of the te rrain.