Metapelitic migmatites from Brattstrand bluffs, east Antarctica - Metamorphism, melting and exhumation of the mid crust

Metapelitic migmatites at Brattstrand Bluffs, East Antarctica, preserve granulite assemblages and a complex deformational history. Crystallized granitic melt accounts for similar to 25% of exposed rocks, and was produced by biotite dehydration-melting reactions in the host metapelite. Variable degrees of melt production and extraction resulted in a range of bulk compositions in the residual metapelite, from quartz-rich migmatites to restitic quartz-absent pelite. Decompressional reaction textures indicate similar to 11 km of exhumation after Peak metamorphism al P-T conditions of similar to 6 kbar and similar to 860 degrees C. Decompression occurred during a single cycle of partial melting and melt crystallization at similar to 500 Ma, and was synchronous with tectonic unroofing of the Brattstrand Bluffs migmatites along ductile shear zones. Exhumation has been proposed as a cause of dehydration melting in the Himalaya and elsewhere, but melting at Brattstrand Bluffs was ultimately driven by the tectonic perturbation and subsequent thermal relaxation responsible for high metamorphic temperatures. Exhumation did not drive melting reactions, but it is likely that the presence of melt focused deformation in the migmatites and thus Promoted exhumation.