SHRIMP U-Pb zircon geochronology of granulites at Rimana(Southern Tibet)in the central segment of Himalayan Orogen  

作　　者：LIDewei LIAOQunan YUANYanming WANYusheng LIUDemin ZHANGXionghua YIShunhua CAOShuzhao XlEDefan 

机构地区：[1]FacultyofEarthSciences,ChinaUniversityofGeosciences,Wuhan430074,China [2]InstituteofGeology,ChineseAcademyofGeosciences,Beijing130073,China

出　　处：《Chinese Science Bulletin》2003年第23期2647-2650,共4页

基　　金：supported by the Geological Survey Program with a Scale of 1:250000 in the Unmapped Area of the Qinghai-Tibetan Plateau,the China Bureau of Geological Survey

摘　　要：High-pressure mafic granulites, occurring as lenses within gneisses and quartzite in the central segment of the Himalayan orogen, were dated using SHRIMP U-Pb technique. 13 analyses out of a total of 15 are plotted along a concordia line and yield a mean 206Pb/238U age of 17.6 0.3 Ma. This age indicates adiabatic decompression and a metamorphic event associated with rapid uplift of granulites in a tectonic environment resulted from the collision between India and Eurasia, synchronous with large-scale thrusting, extension, detachment as well as emplacement of leu-cogranite. One analysis gives a 206Pb/238U age of 29.5 0.4 Ma that is interpreted to represent the timing of the final closure of the Neo-Tethys. Another age is 1991 26 Ma that represents the age of the protolith of the granulites. In sum-mary, dating results show that granulites in this area under-went multiphase metamorphism and complex geological evolution.High-pressure mafic granulites, occurring as lenses within gneisses and quartzite in the central segment of the Himalayan orogen, were dated using SHRIMP U-Pb technique. 13 analyses out of a total of 15 are plotted along a concordia line and yield a mean 206Pb/238U age of 17.6 0.3 Ma. This age indicates adiabatic decompression and a metamorphic event associated with rapid uplift of granulites in a tectonic environment resulted from the collision between India and Eurasia, synchronous with large-scale thrusting, extension, detachment as well as emplacement of leu-cogranite. One analysis gives a 206Pb/238U age of 29.5 0.4 Ma that is interpreted to represent the timing of the final closure of the Neo-Tethys. Another age is 1991 26 Ma that represents the age of the protolith of the granulites. In sum-mary, dating results show that granulites in this area under-went multiphase metamorphism and complex geological evolution.

关 键 词：锆石 地球年代学 麻粒岩 西藏 喜玛拉雅山脉 大陆运动 

分 类 号：P542.2[天文地球—构造地质学]