Further discussion on the formation and evolution of the Yarlung Zangbo suture zone, Tibet

Based on a comprehensive study of 1:50000 regional geological survey and relevant data collection, this paper further discusses the formation and evolution of the Yarluzangbo suture zone. The Tethys Ocean in the Yarlung Zangbo had the nature of the back-arc expanded ocean basin. From Early Triassic to mid Middle Triassic period, the oceanic basin was formed preliminarily, completely formed in late Middle Triassic to Late Triassic period, then gradually shrank from Early Jurassic to Late Cretaceous period, and was finally closed in Paleocene-Eocene period. The ophiolite in the southern belt was mainly of the mid oceanic ridge dilatation type (type MORB) formed in late Middle Triassic to Late Triassic period. The ophiolites in the northern belt seem mainly to have been the upper plate of the subduction zone (type SSZ) related to intra-oceanic subduction, formed in the early Middle Jurassic period. The other Jurassic-Cretaceous magmatic rocks in the belt were mainly fore-arc basalt rocks (type FAB). It is shown that the Tethys Ocean in the Yarlung Zangbo began its intra-oceanic subduction in the Early Jurassic, and synchronously subducted actively northward under the Gangdise belt, subducted passively southward under the Himalaya landmass, and then continued to develop until the Late Cretaceous. The Palaeocene-Eocene subduction and collision and extinction were transformed into a binding zone.