Regional framework and tectonics of the Yarlung Zangbo suture in southern Tibet

Abstract

A synthesis of regional framework and tectonic characteristics of the Yarlung-Zangbo Suture in Southern Tibet has been attempted. The Yarlung-Zangbo Suture lies between the Tethys Himalayan zone to the south and the Lhasa Terrane to the north. In the northern part of the Tethys Himalaya, a belt of Neogene granites and older (Cambrian and Pre-Cambrian) orthogneiss is located. The Xigaze ophiolite, the ophiolite tectonic breccia and the Xigaze Group are the principal tectono-stratigraphic units of the Yarlung-Zangbo Suture. The Xigaze Group represents the remanant of the Neotethyan oceanic crust of Jurassic-Cretaceous age, deposited in a fore-arc basin. Magmatism of the Gangdise plutonic-volcanic arc began around 90 Ma and paroxysmal activity took place between 50–60 Ma. The magmatic arc owes its origin to northward Tethyan subduction beneath the Lhasa block. In Lhasa Terrane, the Precambrian Nyainqentanglha group crystallines are succeeded by Carboniferous to Cretaceous sequence of sedimentaries and volcanics. The Yarlung-Zangbo Suture contains crustal fragments of the Neotethys ocean that originated through rifting in Triassic and opening of the ocean basin in the Jurassic-Cretaceous times. The suture was closed as a result of the collision between the Indian continent and the Lhasa block at 45 Ma.