Late Jurassic–Early Cretaceous Rebangco ophiolite, Tibet: Constraints on the Meso-Tethys Ocean tectonic evolution

Abstract

Ophiolites are widely distributed within the Shiquanhe-Namco-Jiali Ophiolite (SNJO) belt, central Tibet. Further studies on these ophiolites are important for understanding of the Mesozoic tectonic evolution of the Meso-Tethys Ocean. This study presents petrological, chronological, and geochemical data on the ophiolite in the Rebangco area, located at the northern margin of the SNJO belt. Cumulate gabbros of the Rebangco ophiolite contain zircon grains with an age of 152 and they are intruded by diabase with a zircon U-Pb age of 122 Ma. Both diabases and basalts of the ophiolite have geochemical affinity of both island arc and mid-ocean ridge basalts (MORB). Primary magmas were derived from a depleted mantle with contributions from subducted sediments. The source of sandstone surrounding the Rebangco ophiolite originated from a continental magmatic arc in the North Lhasa Terrane. Our study, combined with the previous work, suggest that the ophiolites in the SNJO belt were formed in an oceanic back-arc basin and this belt is an autochthonous mélange zone. This study discusses the tectonic attributes of the SNJO belt and reconstructs the subduction process of the Meso-Tethys Ocean during the Jurassic-Cretaceous. These findings are important for a better understanding of the convergence and closure processes in the Meso-Tethys Ocean.