Lithospheric mantle deformation beneath the Indian cratons

The nature of deformation of the deep continental roots beneath the Archean -Early Proterozoic terrains opens the question whether these ancient terrai ns have had stable roots since the Precambrian or whether recent plate moti ons have deformed them. In view of this, we make an attempt to study the th ermal structure beneath the cratonic regions of the Indian shield, which va ry in lithospheric thickness from 65 km in the Singhbhum craton to 148 km i n the Archean Dharwars. The average depth of 104 km to the top of the under lying asthenosphere is consistent with other termination methods and is in fact less than half the 200-400-km depth found in other stable areas of the earth. Similarly, the average reduced heat now of about 35 mW/m(2) and Moh o temperature of about 550 degrees C (range: 400 degrees-730 degrees C) for the Indian cratons are also much higher than their counterparts elsewhere. Our study indicates a large-scale deformation of the cratonic mantle litho sphere beneath the Indian shield since the Mesoproterozoic caused by variou s geodynamic causes, challenging the idea of stability of deep continental roots.