Paleo-Tethyan evolution of Tibet as recorded in the East Cimmerides and West Cathaysides

Abstract

The Paleozoic-early Mesozoic geology of Tibet was controlled by the rift-drift, seafloor spreading and subduction zone tectonics of a Paleo-Tethyan realm, which evolved between the West Cathaysides (WC) and the East Cimmerides (EC). Different suture zones with ophiolites and ophiolitic mélanges, high-pressure metamorphic belts, magmatic arcs and accretionary prism complexes separating different terranes mark multiple subduction-accretion systems within this Paleo-Tethyan domain, reminiscent of the modern Western Pacific Ocean. Discrete basins separated by different continental blocks and magmatic arcs constituted a complex paleogeography of Paleo-Tethys, and these oceanic strands were closed as a result of subduction with different polarities during the late Paleozoic-Triassic. The Longmu Tso Shuanghu–Changning Menglian Suture zone (LS–CMS) in Tibet represents the main tectonic boundary between the WC and EC that developed in the Devonian. The East Kunlun-A’nyemaqen oceanic slab was subducted northward beneath the East Kunlun terrane in northern Tibet, whereas the Sumdo oceanic slab was subducted northward beneath the South Qiangtang-North Lhasa terrane in southern Tibet. The Longmu Tso Shuanghu–Changning Menglian and Jinshajiang–Ailaoshan–Song Ma ophiolites were developed and emplaced in subduction-accretion systems with opposite polarities (westward and eastward) beneath the North Qiangtang–Qamdo–Simao–Indochina terrane in central Tibet. The Jinshajiang–Ailaoshan–Song Ma oceanic slab was subducted westward beneath the North Qiangtang–Simao–Indochina terrane along the Jinshajiang and Ailaoshan–Song Ma trenches in a trench–ridge–trench triple junction plate configuration. The Emeishan mantle plume produced a large Permian basaltic terrane, developed on the western passive margin of the South China block. The final closure of the Paleo-Tethyan oceanic branches resulted in continental collisions and development of a vast Indosinian orogenic collage in the latest Triassic–Jurassic.