SHRIMP Age Determination of the Diabase in Luobusa Ophiolite, Southern Xizang (Tibet)

Luobusa ophiolite in southern Xizang (Tibet) is one of the best outcrop and the most study in east segment of Yarlung Zangbo ophiolite belt. Controversies on its formation age exist among geologists till now. In this paper, by zircon SHRIMP U-Pb age determination, the crystalline age of diabase in this ophiolite,from which the zircons are obtained,is 162.9±2.8 Ma. It suggests that the formation time of the ophiolite is middle Jurassic. It is possible during the formation of the neo-tethys, that there are some older zircons in old oceanic crust or pelagic sediment which have been caught when the mantle magmas upwell beneath mid-oceanic ridges. At the same time, in the course of the emplacement of the ophiolite, the metamorphic zircon was produced in the local of the ophiolite due to metamorphism.