Rb-Sr geochronology of rocks from the Kolar schist belt, South India

This paper presents the results of whole-rock age measurements based on the Rb-Sr method of one specimen of the 'Champion gneiss' and two specimens of both the 'Patna granite' and biotite-granites from Bisanattam, bordering the main Kolar schist belt. The analysed specimens define an isochron of 2866+-96 my with an initial 87Sr/86Sr ratio of 0.702+-0.002. The ages obtained are much older than those reported by Ramamurthy and Sadashivaiah (1967) and Crawford (1969) for the 'Champion gneiss'. They conform more to the data given by Venkatasubramanian et al. (1971) and confirm that the emplacement of the 'Champion gneiss' and the 'Patna granite' was a very early geological event in the evolution of the Peninsular gneissic complex. (Auth.)