Relevance of magnetotelluric method to unlock renewable geothermal energy, A case study from Puga-Chumathang geothermal zone, NW Himalaya, India

The world is striving to achieve net-zero carbon emissions at the earliest possible time. Geothermal energy is one of the renewable energy playing a significant role with its sustainable, consistent and potentially affordable in generating the power and competence in production of green hydrogen. Magnetotellric (MT) method is an excellent way to detect caprock, geothermal fluids and source based on the resistivity models. India’s geothermal resources discloses extensive large number of geothermal provinces with promising energy prospects. However, the present study deals with most promising geothermal province Puga and Chumathag are located in the Indo-Eurasia tectonic collision boundary of NW Himalayan region (altitude ~ 4500m). It is composed of different rock types such as plutonic, basic to ultrabasic, and submarine volcanic rocks (Ophiolites). The Puga valley consists of Precambrian paragneisses, schists, carbonates (Tanglang La) and limestone where as Chumathang region comprises of thick sequence of shallow marine to fluvial deposits of Kuksho formation related to Indus group. A total of 62 MT stations were used in Puga-Chumathang geothermal region to understand the shallow crustal architecture in terms of significant linkage of geothermal fields. The geoelctrical structure derived from the 3D inversion of MT data highlights the different fault structures, lateral extent and upward migration of geothermal fluids at Puga and Chumathang geothermal zones. The study also highlights the presence of secondary magma at a shallow level abducted from Indus Suture zone acts as a possible heat source for these hot springs. 3D MT model along with in observation of negative free air gravity anomaly structural trend signifies the presence of low density material supports the link between both the hot springs. This result greatly helps new pathways in advancing the large-scale plan for geothermal prospecting in India.