The generation and emplacement of Closepet granite during late Archaean granulite metamorphism in southeastern Karnataka

In the amphibolite-granulite facies transition zone of southeastern Karnataka a typical metamorphic-anatectic sequence is exposed. In this zone large scale melting of basement gneisses during late Archaean granulite metamorphism has led to the generation of the Closepet granite. Field evidence suggests a space-time relationship between charnockite development, migmatite formation and generation of the Closepet granite. Based on texture and cross cutting relationships, four major granite phases are recognised. The P-T conditions inferred from mineralogic geothermometry and geobarometry indicate that granite melts were generated at midcrustal levels. The spatial association of migmatites and gradational contacts suggest that the granite in the transition zone did not rise far from its source region. The occurrence of ductile mylonites and augen gneisses further north of the study area indicates a major shear control in the generation of the Closepet granite. -from Author