The Origins of the Closepet Granites and the Implications for the Crustal Evolution of Southern Karnataka

The origin of the late Archaean Closepet granites by in situ anatexis of amphibolite facies Peninsular gneisses is discussed.

The Closepet granites which are essentially post-tectonic, cut the high-grade metamorphic fabrics found in the Peninsular gneisses. They show no effects of the regional deformation and of the foliation, forming events found in the Peninsular gneisses. Additionally, the granites have escaped metamorphism except in the south where they are statically overprinted by charnockite. Since the charnockite may be shown to be syn- and post-Closepet granite it follows that there may be two granulite facies events: (1) belonging to the evolution of the Peninsular gneiss; and (2) the late-stage formation of charnockite, which is in some places static whilst in others may be accompanied by deformation.

The Closepet granites may thus be used to clearly separate the charnockite from the early evolution of the Peninsular gneisses.