A potential deep geothermal reservoir in eastern Ladakh as inferred from the upper crustal geoelectric structure of the region

Abstract

The Ladakh Himalaya is a repository of the evolutionary history of the India-Eurasia convergent plate margin. We present the results of a magnetotelluric (MT) study carried out in Eastern Ladakh along a 40-km-long profile traversing across various tectonic domains of this plate margin. We modeled the MT dataset by two-dimensional (2-D) and three-dimensional (3-D) inversion algorithms. The upper crustal geoelectric model obtained by 2-D inversion of distortion corrected and decomposed data of 18 sites shows an excellent match with the surface geology. In this model, the Indus Suture Zone (ISZ) appears as a steeply dipping contact and the Ladakh batholith is about 10 to 12 km thick. The model yields a prominent electrical conductor of ~6 km diameter at 4 km depth beneath the Tso Morari Crystallines with an offshoot of a small conductor that rises upward along the ISZ. The geoelectrical model obtained by 3-D inversion is broadly consistent with the 2-D model but also reveals off-profile features and a connectivity of the shallow conductors with a widespread conductive zone at deeper level of the upper crust. In view of the presence of Puga and Chumathang hot springs towards west and Demchok hot springs towards east of our study region, we infer these conductors to be representing a potential major geothermal reservoir system connected to the widespread deeper conductive zone of partial melts, which extends from the southern Tibet to the eastern Ladakh region.