Evidence of lithosphere erosion in the Eastern Indian shield from multi-scale potential field modelling: geodynamic implications

The Precambrian terranes of the Eastern Indian Shield (EIS) comprise the Bundelkhand, Singhbhum, and Bastar cratons with intervening Proterozoic mobile belts such as Central Indian Tectonic Zone, Eastern Ghats Mobile Belt, Singhbhum Mobile Belt and Chotanagpur Granite Gneissic Complex; and the Proterozoic Mahanadi Rift, Chhattisgarh and Vindhyan Basins, with significant coverage of Indo-Gangetic Plain sediments in the northern part. This study presents the results of a seismically well-constrained 2-D multi-scale potential field modelling to delineate the lithosphere structure across different Precambrian terranes of the EIS. The joint interpretation of the potential field data reveals that (i) the mobile belts are bounded by the deep crustal faults with denser crust, (ii) presence of thick underplated crust below Singhbhum Craton, Singhbhum Mobile Belt, Chotanagpur Granite Gneissic Complex and the surrounding rift basin, (iii) localised Moho upwarp at a depth of ~ 36–37 km below the Proterozoic basins, and (iv) the Lithosphere-Asthenosphere Boundary (LAB) varying between 90 and 200 km below the EIS region. The distinct crustal structure and deeper LAB (130–200 km) below the mobile belts suggest the Proterozoic amalgamation and lithosphere reworking. Below the Singhbhum Craton, the LAB is observed at a depth of ~ 145–155 km, which is comparatively thinner than other cratonic areas elsewhere. The observed crustal underplating and the thinner LAB below the Singhbhum Craton indicate that the lithospheric erosion and magmatic upwelling was caused by the major Paleo-Mesoproterozoic and Early-Cretaceous large igneous province events.

Graphical abstract