Baddeleyite and zircon U-Pb ages of the ultramafic rocks in Chigu Tso area,Southeastern Tibet and their constraints on the timing of Comei Large Igneous Province  

作　　者：Ya-ying Wang Ling-sen Zeng Ling-hao Zhao Li-e Gao Jia-hao Gao Zhao-ping Hu Hai-tao Wang Guang-xu Li Ying-long Di Yu Shen Qian Xu 

机构地区：[1]Institute of Geology,Chinese Academy of Geological Sciences,Ministry of Natural Resources,Beijing 100037,China [2]National Research Center for Geoanalysis,Chinese Academy of Geological Sciences,Ministry of Natural Resources,Beijing 100037,China

出　　处：《China Geology》2020年第2期262-268,共7页中国地质（英文）

基　　金：The authors thank and appreciate Qiu-li Li and Ke-jun Hou for their help in guiding the dating work.This study was supported by National Science Foundation of China(41425010,41430212);China Geological Survey Project(DD20190057);National Key Research and Development Project of China(2016YFC0600304);Basic scientific research fund in Institute of Geology,CAGS(J1901-1,J1901-10).

摘　　要：A suite of ultramafic and mafic rocks developed in the Chigu Tso area,eastern Tethyan Himalaya.Baddeleyite and zircon U-Pb ages acquired by SIMS and LA-ICP-MS from olivine pyroxenite rocks in the Chigu Tso area are 138.9±3.0 Ma and 139.0±1.9 Ma,respectively.These two Early Cretaceous ages are similar with the ages of the more abundant mafic rocks in the eastern Tethyan Himalaya,indicating that this suite of ultramafic and mafic rocks in the Chigu Tso area should be included in the outcrop area of the Comei Large Igneous Province(LIP).These ultramafic rocks provide significant evidence that the involvement of mantle plume/hot spot activities in the formation of the Comei LIP.Baddeleyite U-Pb dating by SIMS is one reliable and convenient method to constrain the formation time of ultramafic rocks.The dating results of baddeleyite and zircon from the olivine pyroxenite samples in this paper are consistent with each other within analytical uncertainties,suggesting that baddeleyite and zircon were both formed during the same magmatic process.The consistency of baddeleyite U-Pb ages in the Chigu Tso area with zircon U-Pb ages for a large number of Early Cretaceous mafic rocks in the eastern Tethyan Himalaya further support that zircon grains from such mafic rocks yielding Early Cretaceous ages are also magmatic in origin.

关 键 词：U-Pb dating BADDELEYITE ZIRCON Ultramafic rock Comei Large Igneous Province Kerguelen plume Tethyan Himalaya Geological survey engineering TIBET China 

分 类 号：P588.1[天文地球—岩石学]