Figure 11.

Tectonic model illustrating possible origin of vertical crustal motion and volcanism in the NE Tibetan Plateau in the mid-Tertiary. (A) Asthenospheric mantle flow caused by India-Asia collision was obstructed by the thicker cratonic lithosphere of the Qaidam and Alxa blocks, and the resulting edge-driven convection led to regional surface uplift of the West Qinling and Hoh Xil. (B) The edge convection brought about thinning and/or peeling of lithospheric mantle due to thermal erosion and asthenosphere uprising, and drove surface uplift of the West Qinling and Hoh Xil. Partial melting took place in both the lithospheric mantle and mid-lower crust due to heating of the asthenospheric materials which gave rise to volcanism sourced from the mid-lower crust and lithospheric mantle. Gravitational spreading of the elevated and heated orogenic crust resulted in supracrustal stretching and distributed small extensional basins. (C) Strong crustal shortening began affecting periphery of the NE Tibetan Plateau from the Late Miocene onward and led to thrust-related uplift of structural belts and basin inversion or shrinkage.