SUBDUCTION OF ASIAN LITHOSPHERIC MANTLE BENEATH TIBET INFERRED FROM MODELS OF CONTINENTAL COLLISION

The relative northward motion of the Indian subcontinent that followed the onset of continental collision with Asia has produced extensive deformation of the Earth's crust, giving rise to the world's highest mountains in the Himalayan chain and the world's largest high-elevation region, the Tibetan plateau. The formation of the broad mountain belt implies that, contrary to the original tenets of plate tectonics, the lithospheric plates have experienced widespread deformation far from the plate boundary(1). Several models have been proposed(2-6) to explain the manner in which this post-collisional deformation is distributed within the continental lithosphere of the Indian and Asian plates. Here we propose an alternative model in which subduction of the Asian lithospheric mantle develops following the collision of India. Our model is supported by numerical calculations of crustal deformation and thickening, and is consistent with available geological and geophysical data(7-9). This picture suggests that lithospheric mantle is not deformed along with the crust, and would imply that continental collision zones are more analogous to oceanic subduction zones than was previously believed.