Petrology of the Neoproterozoic granulites from Central Dronning Maud Land, East Antarctica – Implications for southward extension of East African Orogen (EAO)

Abstract

Suturing of east and west Gondwana occurred during the Neoproterozoic along the East African Orogen (EAO) through continent–continent collision. The southern extension of EAO is projected in central Dronning Maud Land (CDML) in east Antarctica. CDML is considered to be a magmato-metamorphic terrain where high-grade metamorphism occurred during Mesoproterozoic. Granulite grade metamorphic assemblages from metapelites (garnet+sillimanite+K feldspar (perthite)+graphite±plagioclase+quartz±melt), mafic granulite (orthopyroxene+garnet±clinopyroxene+plagioclase+quartz) and granitic orthogneiss (garnet+Fe-clinopyroxene+K feldspar+plagioclase+quartz) in the Humboldt Mountains in CDML have been used to deduce the peak metamorphic conditions as ∼850°C and 6–8kbar pressure. In situ chemical dating of monazite in matrix and inclusions in garnet indicates metamorphism to have occurred between 640 and 580Ma and was partially overprinted at ∼540Ma which is correlatable with extensive charnockite and A-type granite emplacements. This Neoproterozoic metamorphism and its correlation with the coast margin Neoproterozoic granulites at Schirmacher oasis is inferred as the extension of EAO in east Antarctica.