Geological Features Of Neothyan Ophiolites In Tibetan Plateau And Its Tectonic Evolution

Ophiolites in the Yarlung Zangbo Suture Zone ( YZSZ) and the Bangong-Nujiang Suture Zone ( BNSZ) represent remnants of the Neotethyan oceanic crust and upper mantle, they are original producers of chromitite and ophiolite-type diamonds in China. However, the origin and relationship of the YZSZ and BNSZ remain controversial. In this paper, we summarize temporal and spatial occurances, ophiolitic rock assemblages and tectonic settings of ophiolites and ophiolitic melanges within the YZSZ, BNSZ, Shiquan River-Numdo ophiolitic melange zone ( SNMZ ) and Sumdo suture zone, overview magmatic rocks distribution since Late Paleozoic in the Lhasa block. We propose that : (1) Panjal mantle plume likely have prompted the contemporaneous opening of the Bangong-Nujiang ocean and Yarlung Zangbo West Ocean (YZWO) during the Early Permian Kungurian Period (283 similar to 272Ma). (2) Yarlung Zangbo East Ocean bounded by the Saga-Cuoqin with the YZWO, opened in Late Triassic due to the southward subduction of the Songdo Paleo-Tethys Ocean, and created the 245 similar to 200Ma magmatic events along the southeastern Gongdese island arc. (3) Closure of Bangong-Nujiang ocean and collision between Southern Qiangtang and Northern Lhasa blocks at similar to 140Ma led to accelerate the spreading rate of the Yarlung Zangbo ocean and triggered flat subduction southword the Lhasa block, which further led to the drifting and spreading of the Bangong-Nujiang ocean and the formation of a short-lived (133 similar to 104Ma) small ocean basin. (4) Ophiolites in the southern belt of the western YZSZ are thrust nappes from the northern belt. (5) Ophiolites along the BNSZ and SNMZ belong to the same oceanic basin, the latter represents remnants of the main mature oceanic basin of the Bangong-Nujiang ocean in the late Jurassic.