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.     

从雅鲁藏布江蛇绿岩带中的两套火山岩探讨中生代特提斯洋壳的演化

雅鲁藏布江蛇绿岩代表中生代特提斯的洋壳残余,其中包括两套火山岩:一套为晚侏罗—早白垩世的变玄武岩;另一套为早白垩世的枕状玄武岩。两套火山岩具有不同的时空格局和明显的地球化学差异。通过对两套火山岩的地球化学研究,讨论了中生代特提斯洋壳演化的两个阶段。中生代特提斯的演化经历了早期裂谷阶段、中期洋壳发育阶段以及末期闭合阶段。洋壳的演化包括早期的不连续扩张阶段,形成了变玄武岩和晚期的扩张阶段,发育了枕状玄武岩。