Late Triassic tectonic framework and evolution of Central Qiangtang, Tibet, SW China

Abstract

The Late Triassic Longmu Co–Shuanghu suture zone is a metamorphic belt in Central Qiangtang, SW China, that is interpreted to have formed at the boundary between a Gondwana-derived block and Laurasia during the subduction of Paleo-Tethyan oceanic crust. Recent research has suggested that a Late Triassic (ca. 225–205 Ma) magmatic “flare-up” event took place on both sides of the metamorphic belt within Central Qiangtang coeval with exhumation of the metamorphic rocks. The age-equivalent Gangmari metamorphic belt and Riwanchaka Yangtze-type deposits of the South Qiangtang terrane are located ∼70 km from the Longmu Co–Shuanghu suture zone and the North Qiangtang terrane. We propose that Central Qiangtang underwent postcollisional extension in the Late Triassic. By integrating the geological features described here, we suggest that these complex geological phenomena were triggered by slab breakoff of the northward-subducting lithosphere of the Paleo-Tethys Ocean. Central Qiangtang is therefore an ideal area in which to verify the process of slab breakoff by geological observations.