Tectonic Evolution of the Tibetan Plateau: A Working Hypothesis Based on the Archipelago Model of Orogenesis

Abstract

The geology of the Tibetan Plateau is interpreted within the framework of archipelago orogenesis, with the relief of the plateau owing its origin to the Neogene subduction of the Indian continental lithosphere under Tibet. Late Precambrian back-arc spreading resulted in the genesis of island arcs and back-arc basins south of the Angaran craton. A magmatic front is located at or near the position of the Kunlun Mountains. The part including and south of the Tianshan and Neimonide was separated from the Angaraland and formed microcontinents as well as numerous back-arc basins and remnant arcs in China. The Early Paleozoic basins collapsed behind the Kunlun magmatic front to form the Tianshan, Qilian, and other mountains. A part ofthe accretionary complex to the south of the Kunlun Arc was split off to form Late Paleozoic and Early Mesozoic island arcs and back-arc basins to the northeast of the Bangong/Nujiang suture. The collapse of those basins before the end of the Triassic caused the accretion of the archipelago rocks to the Cathaysian continent. A Late Paleozoic magmatic front on the northern edge of Gondwanaland was responsible for arc volcanism and back-arc spreading in Tibet. The microcontinent became separated from the rest of Gondwanaland during the Early Mesozoic when the Neotethys ocean came into existence. The northern magmatic front produced a belt of arc magmatism just south and west of the Bangong/Nujiang suture. Jurassic and Cretaceous back-arc basins were formed in northern Tibet by back-arc spreading. Those basins collapsed to form mountains before the mid-Cretaceous collision of Tibet and Cathaysia along the Bangong/Nujiang front. The Zhanbo ophiolites represent the relics of two rows of back-arc basins that came into existence as the Neotethys ocean floor was subducted under the Himalayas. Those back-arc basins collapsed in the Eocene, but the Neotethys was consumed only in the Early Miocene. The continued northward displacement of the Indian plate caused the subduction of the Indian continentallithosphere under the Himalayas and Tibet, thus causing uplift of the Tibetan Plateau.