Jurassic tectonic evolution of Tibetan Plateau: A review of Bangong-Nujiang Meso-Tethys Ocean

Abstract

The Jurassic subduction of the Bangong-Nujiang Tethys Ocean is recognized as a significant event in the geotectonic evolution of Tibetan Plateau. This study focuses on the Mesozoic ophiolites, magmatic rocks, sedimentary strata, and metamorphic features, and discusses their relationship with the evolution of the Bangong-Nujiang Ocean. Two stages of Jurassic northward subduction are identified. The first stage is represented by the Early Jurassic subduction of the Amdo-Jiayuqiao subterrane. Slab break-off triggered the Middle-Late Jurassic exhumation of the subducted subterrane as well as the eclogite and high-pressure granulite. This process promoted the initiation of the second stage subduction at the southern margin of the South Qiangtang and Amdo-Jiayuqiao subterranes. For the western-central Bangong-Nujiang Ocean, we interpret the second stage as flat or shallow angle subduction and suggested that it was triggered by break-off of the subducted slab. The Bangong-Nujiang Tethys Ocean experienced southward ocean-continent and intra-oceanic subduction in the eastern and central-western segments, respectively, which are represented by the Shiquanhe-Yongzhu-Jiali mélange zone. The western and central-eastern segments of the Shiquanhe-Yongzhu-Jiali oceanic basin represented an immature to mature back-arc basin. The Bangong-Nujiang Ocean experienced a complex subduction evolution during Jurassic. Both northward and southward subduction zones were initiated during Late Triassic perhaps in response to the closure of the Paleo-Tethys oceans to the south and north.