藏南罗布莎蛇绿岩辉绿岩中锆石SHRIMP测年  

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

作　　者：钟立峰[1] 夏斌[1] 周国庆[1] 张玉泉[1] 王冉[1] 韦栋梁[1] 杨之青[2] 

机构地区：[1]中国科学院边缘海地质重点实验室 [2]中国地质科学院地质研究所,北京100037

出　　处：《地质论评》2006年第2期224-229,共6页Geological Review

基　　金：中国科学院知识创新工程项目(编号KZCXZ-SW-117);中国科学院边缘海重点实验室开放研究基金项目(编号MSGL-04-12)资助的成果。

摘　　要：罗布莎蛇绿岩是雅鲁藏布江蛇绿岩带东段出露较好,也是研究程度较高的蛇绿岩片之一。对该蛇绿岩的形成时代至今存在分歧。本文获得该蛇绿岩辉绿岩中的锆石SHRIMPU-Pb定年的结果为162.9±2.8Ma,表明该蛇绿岩的形成时代为中侏罗世,同时发现,在罗布莎地区新特提斯洋形成时,可能存在地幔熔融的岩浆在扩张脊上涌过程中俘获老洋壳或者深海沉积物中锆石的情况;并且在侵位过程中,在该蛇绿岩的局部由于蚀变而产生了变质锆石。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.

关 键 词：SHRIMP锆石年龄 罗布莎蛇绿岩 辉绿岩 西藏 

分 类 号：P597.3[天文地球—地球化学]