New insights into the evolution of the Yarlung Tsangpo suture zone, Xizang (Tibet), China

Abstract

Detailed investigations along the Yarlung Tsangpo suture zone, Tibet result in the following conclusions. (1) Arc, forearc, and subduction complex elements of at least one intra-oceanic island arc which once lay within Tethys and accreted to India prior to its collision with Asia are preserved within the suture. (2) Collision-related tectonic mélange is widespread. (3) Temporally distinct conglomeratic molasse units were developed; they are related to different collision events. (4) Improved radiolarian fossil data place constraints on timing of the development of intra-oceanic terranes and mélange formation. (5) A simple unconformable contact occurs between Upper Oligocene-Lower Miocene conglomerates and the southern Lhasa terrane; the so-called south-directed "Gangdese thrust" does not exist. These new results suggest the former existence of an intra-oceanic subduction system within Tethys and indicate that considerable revision of existing models for the evolution of the Yarlung Tsangpo suture zone is required.