K-Ar Biotite age of southern granulite terrene, southern India-Cooling process after High-temperature Metamorphism-

Abstract

The southern India terrene is composed of several Proterozoic granulite blocks dissected by major deep-crustal shear zones welded onto the Archean Dharwar Craton in the north. The existing geochronological studies indicate that the crustal growth occurred at 3000 - 2100 Ma while the peak ultrahigh-temperature metamorphism at 550 - 580 Ma. We estimate the cooling history of various metapelites and orthogenesis collected systematically from north to south of the southern granulite terrene. The Kerala Khondalite Belt gives 451 - 465Ma while the Kodaikanal Metapelite Belt yields 507 - 512 Ma, suggesting the exhumation rate in the south must be slower as compared to that in the northern part of southern granulite terrene.