Evolution of eastern segment of the Central India Tectonic Zone: an insight from a magnetotelluric study

The collision process between the South Indian Block (SIB) and North Indian Block (NIB) resulted in the development of the complex crustal nature of the Central India Tectonic Zone (CITZ). The evolutionary past of CITZ covers a long geological time (similar to 1000 Ma), which corresponds to the assembly and spreading of Columbia and Rodinia supercontinents. Despite several studies in the western and central parts of the CITZ, the location of the suture zone between the SIB and NIB is still under debate. In addition to that, the crustal structure in the eastern segment of CITZ is yet to be resolved. Therefore, for the first time, a dense station coverage magnetotelluric (MT) study is carried out along a 275 km transect in the eastern segment of CITZ from Pandaria to Rewa. The complexity of the Central Indian Shear (CIS) and Tan Shear Zone (TSZ) are reflected as anomalous phases (beyond 90 degrees) in the MT data. A deep crustal resistivity model derived from 2-D and 3-D inversion of the MT data brought out a high-to-moderate conductivity structure (10-100 omega-m) in the middle of the surface expressions of CIS and TSZ. The conductive structure could be related to a deformation zone formed by tectonic interaction of the CIS and TSZ or multiple tectonic boundaries in the middle of the CIS and TSZ. The conductive structure observed in the southern limit of the CITZ also may indicate the tectonic boundary between the SIB and NIB. The high conductivity in the deformation zone may be explained by the collision-related metallic rich sediments and/or mylonite associated with interconnected fluids. Moderately conductive vertical features delineated from the MT model correlate with the intrabasinal faults which might have acted as the pathways for Deccan volcanism. This study suggests that the CITZ could have been developed under the transition of oceanic subduction to continental collision processes at multiple geological times.