Crustal density structure across the Central Indian Shear Zone from gravity data

Abstract

The Central Indian Shear Zone is a distinct tectonic feature in the central part of India that separates the Central Indian Tectonic Zone from the Bastar Craton. The complete Bouguer anomaly map of the region encompassing Central Indian Shear Zone is characterised by a broad relative gravity high over Central Indian Tectonic Zone as compared to the Bastar Craton. The paired gravity anomaly across the two crustal domains signifies that the Central Indian Shear Zone is a locus of density discontinuity along which the two crustal domains accreted. Horizontal gravity gradient analysis further demonstrates the northward subduction of the Bastar Craton beneath the Bundelkhand Craton. 2½D gravity modelling along Mungwani–Rajnandgaon profile, constrained by Seoni–Kalimati seismic section, delineates a thick crust beneath the Bastar Craton as compared to the Central Indian Tectonic Zone. Northward dipping contact of the two crustal domains when projected on the surface coincides with the Central Indian Shear Zone. With a well defined Moho offset and crustal density discontinuity, Central Indian Shear Zone represents a suture zone that separates the Bastar Craton from the Central Indian Tectonic Zone. A low-velocity (6.4 km/s)/density (2.90 g/cm 3) layer at the base of the crust and relatively lower density (3.21 g/cm 3) subcrustal mantle may be the imprint of thermal remobilization beneath the Central Indian Tectonic Zone.