THE TRANS-HUDSON OROGEN OF NORTH AMERICA AND THE HIMALAYA-KARAKORAM-TIBETAN OROGEN OF ASIA, PART 2: STRUCTURAL AND THERMAL EVOLUTION OF THE UPPER PLATE
In the Himalaya, the upper plate includes the vast Tibetan Plateau north of the Indus-Yarlung Tsangpo suture zone, and its extensions to the west, and the Karakoram and Hindu Raj - Hindu Kush Ranges. The geology of the plateau comprises mainly sedimentary and volcanic rocks, rarely deep crustal metamorphic rocks, whereas the Karakoram Range exposes extensive lower crustal rocks and pre- and post-collisional granites. Pre-collisional, 150-95 Ma Andean-type granite-diorites are related to subduction of the Tethyan ocean crust beneath the southern margin of Asia. Post-collisional granites include the Baltoro Bt-monzogranite and Grt-Bt-Ms leucogranites formed 25-18 Ma by melting of lower crust gneisses. St, Ky, and Sil metamorphism is sporadic and semi-continuous from 70-0 Ma along the southern margin of the Karakoram, following collision of the Kohistan arc during the Late Cretaceous, and India in the earliest Eocene.
Late thick-skinned folding and cross-folding in THO is constrained at 1758-1742 Ma. Himalayan manifestations might be the >1cm/year erosion rates in the Nanga Parbat syntaxis of Pakistan, and the Miocene-Pliocene Sil grade gneiss domes in the southern Karakoram.