FIRST REPORT OF PAN-AFRICAN SM-ND AND RB-SR MINERAL ISOCHRON AGES FROM REGIONAL CHARNOCKITES OF SOUTHERN INDIA

Mineral and whole-rock isotope data for a massive charnockite from Kottaram in the Nagercoil Block at the southern tip of Peninsular India yield Sm-Nd and Rb-Sr ages of 517 +/- 26 Ma and 484 +/- 15 Ma respectively. The Nd model age calculated for the charnockite is c. 2100 Ma. Our study reports the first Pan-African mineral isochron ages from regional charnockites of Peninsular India, which are in good agreement with the recently obtained ages of incipient charnockites in the adjacent blocks, as well as alkaline plutons within the same block. Our results indicate that the Pan-African tectonothermal event in the granulite blocks south of the Palghat-Cauvery shear zone was regional, with terrain-wide rejuvenation. These results correlate with similar Pan-African tectonothermal events reported from Sri Lanka and East Antarctica, and have an important bearing on Gondwana reconstructions.