Crustal resistivity architecture beneath the Sikkim Himalaya and Foreland Basin, NE India: Constraint from magnetotellurics data

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The manifestation of the hydrocarbon reserves in the Himalayan fold-thrust belts is essential for revealing the thermal and tectonic parameters. The broadband magnetotelluric (MT) studies were conducted in the Sikkim Himalaya and Himalayan foreland basin regions to identify the complex tectonic and architectural features. The joint TE, TM-modes, and tipper data from 17 sites were used to obtain the electrical model along the SW-NE profile. The data were inverted using a 2-D non-linear conjugate gradient algorithm. The high conductivity features associated with thrust, fault, and lineament are delineated in the electrical model of the upper crust. The Himalayan foothill contains an anomalous conductor (C1) and a conductive layer (C2) in the region of the Indo-Gangetic plain. The Lesser Himalaya upper crust is heterogeneous and characterized by high resistivities lower grade metamorphic rocks. The middle crust contains a conductive feature (C4) in the Lesser Himalaya's roof by anticline structure interpreted as Ramgarh Thrust (RT) and also characterized by intense microseismic activity along the single fault known as Main Himalayan Thrust (MHT) or basal detachment. The Main Frontal Thrust (MFT) and Main Boundary Thrust (MBT) are reflected in the Outer Himalayan region through a remarkable conductor (C3). The NNW-SSE trending Tista lineament joins the MHT ramp up to ∼10 km depth and northeast dipping between features R2 and C3. The Main Central Thrust (MCT) exhibited a low resistivity feature. The partial melting of deep crustal rocks due to the high-temperature regime is attributed to high conductivity as frictional heat is generated during the collision between India and Asia.