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
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
Affiliations
Ya-ying Wang
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China; Corresponding author: E-mail address: [email protected] (Ya-ying Wang).
Ling-sen Zeng
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Ling-hao Zhao
National Research Center for Geoanalysis, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Li-e Gao
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Jia-hao Gao
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Zhao-ping Hu
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Hai-tao Wang
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Guang-xu Li
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Ying-long Di
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Yu Shen
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
Qian Xu
Institute of Geology, Chinese Academy of Geological Sciences, Ministry of Natural Resources, Beijing 100037, China
ABSTRACT: 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.
