Zircon U-Pb Geochronology of the Cenozoic Granitic Mylonite along the Ailaoshan-Red River Shear Zone:New Constraints on the Timing of the Sinistral Shearing  

作　　者：Xiaofei Guo Yuejun Wang Huichuan Liu Jianwei Zi 

机构地区：[1]State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]School of Earth Science and Geological Engineering,Sun Yat-sen University,Guangzhou 510275,China [4]CAS Center for Excellence in Tibetan Plateau Earth Sciences,Beijing 100101,China [5]School of Earth and Environment,University of Western Australia,Crawley 510275,Western Australia

出　　处：《Journal of Earth Science》2016年第3期435-443,共9页地球科学学刊（英文版）

基　　金：Supported by the National Basic Research Program of China(No.2014CB440901);the China National Natural Science Foundation(No.41190073);the Fundamental Research Funds for the Central Universities to SYSU

摘　　要：The Ailaoshan-Red River（ASRR） shear zone in SW China represents an important discontinuity believed to have accommodated eastward extrusion of the Tibetan Plateau in response to the collision of the Indian and Eurasian plates. The onset timing and duration of the ASRR sinistral strike-slip shearing have been hotly disputed. In this paper we present new zircon LA-ICP-MS U-Pb geochronological data from six syntectonic granitic mylonite and leucosomes samples from the ASRR shear zone. Our data reveal a metamorphic age of ~40 Ma, most likely suggesting the maximum age of the shearing initiation. Rocks showing syn-kinematic signatures yield crystallization ages of 38–22 Ma, with inherited components ranging from 716 to 108 Ma. These results, together with existing geological and geochronological data, indicate that the sinistral shearing along the ASRR zone probably began at 40 Ma, mainly activated at 29–22 Ma and lasted at least to ~22 Ma. Our data suggest a continuous extrusion between the Indochina and South China blocks during ~35–17 Ma. The ASRR sinistral shearing has accommodated large scale eastward displacement of the southeastern Tibetan syntaxis, and is likely responsible for the opening of the South China Sea.The Ailaoshan-Red River（ASRR） shear zone in SW China represents an important discontinuity believed to have accommodated eastward extrusion of the Tibetan Plateau in response to the collision of the Indian and Eurasian plates. The onset timing and duration of the ASRR sinistral strike-slip shearing have been hotly disputed. In this paper we present new zircon LA-ICP-MS U-Pb geochronological data from six syntectonic granitic mylonite and leucosomes samples from the ASRR shear zone. Our data reveal a metamorphic age of ~40 Ma, most likely suggesting the maximum age of the shearing initiation. Rocks showing syn-kinematic signatures yield crystallization ages of 38–22 Ma, with inherited components ranging from 716 to 108 Ma. These results, together with existing geological and geochronological data, indicate that the sinistral shearing along the ASRR zone probably began at 40 Ma, mainly activated at 29–22 Ma and lasted at least to ~22 Ma. Our data suggest a continuous extrusion between the Indochina and South China blocks during ~35–17 Ma. The ASRR sinistral shearing has accommodated large scale eastward displacement of the southeastern Tibetan syntaxis, and is likely responsible for the opening of the South China Sea.

关 键 词：Ailaoshan-Red River zircon U-Pb dating mylonite and migmatite sinistral shearing eastward extrusion 

分 类 号：P588.332[天文地球—岩石学] P597.3[天文地球—地质学]