New insight into the shallow sub-surface for geothermal prospection of Puga valley, Ladakh, India from electrical resistivity tomography

Abstract

The Puga valley in Ladakh, India, is one of the most significant geothermal fields in the Himalayan belt, marked by extensive hot springs with enriched mineralisation. This study applies a dense coverage of Electrical Resistivity Tomography (ERT) data to investigate the subsurface geological features, structural controls, and hydrogeological conditions influencing geothermal fluid dynamics. In the present study, ten ERT profile results across the valley were analysed, revealing low-resistivity anomalies (<1 to 10 Ω.m) associated with geothermal fluid pathways, particularly in the eastern zone. In contrast, high-resistivity zones (400 – 2500 Ω.m) in the western part of the Puga valley represent compact hard rocks and shallow basement structures of the Tso Morari Crystalline. Two distinct fluid-saturated zones are identified from the ERT model results. The first zone lies parallel to the ground, typically at a shallow level of around 20–30 m. The second fluid-saturated zone delineates a fault structure, as fluid conduits from the near surface zone to as deep as 140 m. Additionally, the 3D resistivity model reveals an ENE-WSW trending linear conductive body on the eastern side of the valley. In contrast, a resistive body, the Tso Morari Crystalline, dominates the western part of the valley. Based on these observations, three potential sites are identified for exploratory drilling for future exploitation of the geothermal resources. These findings provide crucial insights for geothermal energy exploration from the geological and structural understanding as well as the futuristic perspective in Puga valley, highlighting the efficacy of ERT mapping for geothermal prospecting.