EVOLUTION OF OCEANIC CRUST OF MESOZOIC TETHYS IN THE LIGHT OF TWO SUITES OF VOLCANIC ROCKS IN THE YARLUNG ZANGBO OPHIOLITE BELT

The Yarlung Zangbo ophiolite represents the ocean crustal residue of the Mesozoic Tethys. In this ophiolite belt, there are two suites of volcanic sequences. One is Late Jurassic-Early Cretaceous metabasalts, and the other is Early Cretaceous pillow basalts. These two suites of volcanic rocks are significantly different in time and space patterns and geochemistry. Based on an investigation on their geochemical characteristics, the authors would have a discussion on the two stages of the ocean crustal evolution of the Mesozoic Tethys.The evolution of the Mesozoic Tethys went through three stages, namely the early rift valley, the intermediate ocean crustal development and the last closing stage. The development of oceanic crust experienced the early discontinuous spreading stage which formed the metabasalt and the late continuous spreading stage which produced the Early Cretaceous oceanic crust.