Integrated gravity-magnetic study in deciphering the subsurface structural setup of Taptapani hot spring region: a case study from the metamorphic terrain of Eastern Ghats Mobile Belt, India

Abstract

The integrated gravity-magnetic study presented here is the first attempt to decipher the subsurface architecture of the region encompassing the Taptapani hot spring location, located within the central part of a high-grade Mesoproterozoic metamorphic terrain in the Eastern Ghats Mobile Belt of India, which is mainly characterized by khondalites and charnockites. The moderate-to-high anomalies observed in the residual gravity and reduced-to-equator magnetic anomaly maps correspond to exposures of charnockite and khondalite rocks near the hot spring. The low-to-intermediate anomalies indicate the presence of migmatite rocks. The depth-estimation techniques using processed gravity-magnetic data highlight shallower sources/features, ranging between 200 and 2000 m below the study area. The deepest depths (~ 1.5 to 2 km) indicate a cratonic rock unit, possibly hosting discontinuities controlling the transfer of thermal waters. The 2D forward model reveals dipping rock units below the profile, along with a contact/discontinuity between two rock units near the hot spring location, corresponding to a sharp gradient observed in the respective gravity and magnetic anomalies. Thus, the observations obtained here suggest that the local structural setup within a high-grade metamorphic terrain controls the flow of thermal water up to the Taptapani hot spring from deeper thermally affected crust and faraway radiogenic rock sources. This study highlights the importance of gravity and magnetic studies in delineating the structural control of the geothermal springs in a metamorphic terrain.