Electromagnetic signatures of collision zones in India

Abstract

Indian subcontinent has experienced intense tectonic activity within the continent in the form of subduction, continent-continent collision, subduction-collision-accretion tectonics. Deep electrical sig� natures of intense tectonic activity are presented for three different regions: Himalayan region, Central Indian Tectonic zone and Southern Granulite terrain. Two long traverses at each region are discussed along with other geophysical data. The geoelectric sections across the Himalayan region have shown a clear north� ward dipping signature of the anomalous conductive features at upper to midcrustal depths. This model gave a clear evidence for the collision and subduction processes. The profiles across the Central Indian tectonic zone constituting major eastwest trending faults and mobile belts provided the evidence for the presence of mantle derived fluids at midcrustal depths and also ga ve a clear evidence for the collision processes between the Bundelkhand craton and the Dharwar craton. The collision-accretion tectonic process is observed in Southern Granulite terrain of south India. Evidence for the exhumation of mantle derived fluids to the mid� crustal depths has been observed along the Vattalakundu-Kanyakumari profile, while the subduction-colli� sion-accretion processes have been observed along Kolattur-Palani geotransect. In all the three tectonically active regions, the deep electrical structure mapped from magnetotellurics, gave a clear evidence for the pres� ence of anomalous conductive structures that can be related to active tectonic regime that has paved a way for better understanding of the evolution of the deep crust. In this paper all the earlier works in three regions with emphasis on tectonics are briefly reviewed.