Geochemistry of the Archaean Metavolcanic Rocks of Kolar and Hutti Gold Fields, Karnataka, India

Geochemical data on Archaean goldfields metavolcanics (2.7 b. yrs) have been plotted on major and minor element discriminant diagrams to define the magma type and to formulate the tectonic environment model for the origin of these ancient volcanic rocks. The meta basalts of Kolar and Hutti (Karnataka, South India), Norseman (Eastern Goldfields, Western Australia). Steynsdorp (Barberton, South Africa) and Yellowknife (Canada), plot within the field of mid-ocean ridge basalts (MORB). The marginal basin basalts (MBB) of South Sandwich Islands of Scotia Arc Region of Phanerozoic age also plot within the field of MORB. Unlike the depleted MORB, the MBB are enriched in certain large ion lithophile (LIL) elements with higher Rb/Sr, Ba/Sr and lower K/Ba ratios. Further, in contrast to MORB, they exhibit slightly enriched LREE patterns. The LIL element enriched goldfield volcanics of Kolar, Hutti, Norseman, Steynsdorp and Yellowknife, with their slightly enriched LREE patterns, compare more favourably with MBB than with MORB. Based on geochemical features and geological setting, marginal basin model is proposed as the most favourable tectonic environment for the generation of gold bearing Archaean greenstone belts of Kolar and Hutti.