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《Geotectonica Et Metallogenia》 2009-02
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SHRIMP U-Pb Dating for the Gabbro in Qunrang Ophiolite,Tibet:The Geochronology Constraint for the Development of Eastern Tethys Basin

LI Jianfeng1,5,XIA Bin1,LIU Liwen2,XU Lifeng1,5,HE Guansheng3,WANG Hong1,ZHANG Yuquan1 and YANG Zhiqing4(1.Guangzhou Institute of Geochemistry,CAS,Guangzhou 510640,Guangdong,China;2.719 Geological Team,Guangdong Bureau of Geological Exploration,Zhaoqing 526020,Guangdong,China;3.Geological Team No.261 of Jiangxi Nuclear Industry,Yingtan 335001,Jiangxi,China;4.Beijing SHRIMP Centre,Beijing 100037,China;5.Graduate School,CAS,Beijing 100049,China)  
Along the Yarlung-zangbo River valley,the Yarlung-zangbo Suture zone in Southern Tibet lasts along more than 2,000 kilometers from west to east,which is also the longest ophiolite belt in China.This ophiolite belt has drawn more and more attention from the geologists,due to its younger age and better reservation.But limited by the past analytical technology,the precise report about its formation time is singularly.And as product of the magmatic event during the extension period of the middle ocean ridge,the gabbro in ophiolite possess a formation age corresponding to the extension time,and this age also represents the formation time of the ophiolite.In this paper,zircon SHRIMP U-Pb technique was applied to the gabbro in Qunrang ophiolite,west of the Yanglung Tangbo suture zone.A 206Pb/238U mean age 125.6±0.88Ma(2σ,MSWD=1.9)was obtained,which is the crystallization time of the gabbro.Compared with the former reported ophiolite ages in the Yanglung Tangbo suture zone(122.3±2.4Ma for Xiugugabu ophiolite in the western part,126±1.5 Ma for the Dazhuka ophioilte and 123±1.8Ma for the Jiding ophiolite in the middle part,while 162.9±2.8Ma for Luobusha ophiolite in the eastern part),this age suggests that the extension time of Tethys oceanic basin in Qunrang region was consistent with the formation time of the Dazhuq and Tiding oceanic basin in the middle part,which indicates that the development of the oceanic basin was isochronous both in the middle part and the western part while was later than the development of oceanic basin in the eastern part of the Yanglung Tangbo Suture zone.From the geochronology data,we can deduce that the open time of the eastern tethys basin was characterized by the east earlier and the west later.
【Fund】: 国家自然科学基金重点项目(No.40534019)资助
【CateGory Index】: P597.3
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