Interpretation of gravity–magnetic anomalies to delineate subsurface configuration beneath east geothermal province along the Mahanadi rift basin: a case study of non-volcanic hot springs

Abstract

Gravity and magnetic studies have been carried out over a non-volcanic hot spring zone consisting of Atri and Tarabalo hot springs along the intracontinental Mahanadi rift basin to delineate the subsurface structures and to understand their effect on the geothermal activities over a stable continental region. Calculated gravity and magnetic anomaly maps unveil the presence of hot springs along Mahanadi fault. The four-layer subsurface configuration as observed using radially averaged power spectrum analysis and 3D Euler solutions of both gravity and magnetic data indicates occurrence of multi-phases sedimentation and tectonic events. 2D forward, 2D inverse, and 3D inverse residual gravity models have delineated high-density igneous intrusive bodies surrounded by comparatively less dense Khondalites and Charnockites rich altered zones. The sharp high to low density transition zones are identified as the regional Mahanadi fault. The India–Antarctica rifting, existence of two hot springs along the Mahanadi fault of the rifted basin, and similarity in water chemistry strongly indicates an interconnection between these two hot springs. Igneous intrusions and radiogenic element-rich metamorphosed shallow formations combinedly acting as the heat source. Deciphered altered zone, deeper intrusion and deeply connected regional fault along the hot springs confirmed that this regional fault is providing the major pathway for water circulation through radioactive element-rich altered zones while the local and shallow fractures connecting the Mahanadi fault feed the hot springs of the study area.