Archaean high-grade gneiss complex from Satnur-Halagur-Sivasamudram areas, Karnataka, southern India: petrogenesis and crustal evolution

Abstract

The high-grade gneiss complex of the Satnur-Halagur-Sivasamudram area in southern Karnataka forms a part of amphibolite-granulite facies transition zone of southern India. The major lithologies are metasediments, amphibolite facies gneisses, foliated charnockites, mafic granulites, granite sheets. All these lithologies show a prominent N-S fabric which appears to have been produced during late Archaean shear deformation. Rb-Sr whole rock isochron and U-Pb zircon and monazite ages suggest that much of the crust accreted during 2.96 Ga magmatic event followed by the 2.5 Ga granulite facies metamorphism; the occurrence of a previous high-grade metamorphism close to 2.9 Ga remains debatable. -from Authors