High-heat-producing granites of East Dharwar Craton around Gugi, Karnataka, and their possible influence on the evolution of Rajapur thermal springs, Deccan Volcanic Province, India

High-heat-producing granites of East Dharwar Craton around Gugi, Karnataka, and their possible influence on the evolution of Rajapur thermal springs, Deccan Volcanic Province, India

Background: The thermal springs of Rajapur situated along the west coast of Maharashtra and parts of high-heat-generating granites of Gugi in Karnataka (India) seem to be genetically related. The present investigation involves quantification of the heat generated by the Gugi Granites using the the U, Th and K contents in the rock samples and probing their possible influence on the evolution of the Rajapur springs, based on the geochemistry of the thermal waters, published Bouguer gravity anomaly data, and the overall geological setup. Methods: Fourteen water samples from Rajapur including thermal and groundwater samples were analysed for major ions and five rock samples from the gugi area were analysed for U, Th and K. Results: Rajapur thermal spring is of Na-HCO3 type, while other thermal springs along the west coast are either Na-Cl type or Na-Cl-CO3 type. The stable isotope data of the thermal waters signifies mixing with the ground water. The gravity anomaly data supports the extension of the Gugi Granites below the Deccan Volcanics of the study area. Conclusions: The present investigation suggests that the Gugi Granites could be the main source of heat for these thermal springs, even though the springs issue through the Deccan volcanic flows.