40Ar/39Ar dating of the Jiali and Gaoligong shear zones: Implications for crustal deformation around the Eastern Himalayan Syntaxis |
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| Authors: | Te-Hsien Lin Ching-Hua Lo Sun-Lin Chung Fang-Jui Hsu Meng-Wan Yeh Tung-Yi Lee Jian-Qing Ji Yi-Zhau Wang Dunyi Liu |
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| Affiliation: | 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. Department of Geological Sciences, Indiana University, Bloomington, IN 47405, United States;1. Integrated Terrane Analysis Research (ITAR), 18 Cambridge Rd, Aldgate 5154, SA, Australia;2. School of Earth Sciences, University of Tasmania, Hobart, Tasmania, Australia;3. Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. Center for Excellence in Tibetan Plateau Earth Sciences, China;3. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;4. Department of Geology, University of Leicester, Leicester LE1 7RH, United Kingdom;5. Department of Earth and Environmental Sciences, California State University, Fresno, CA 93740, USA;6. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China;7. Myanmar Geosciences Society, Yangon, Myanmar |
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| Abstract: | We conducted a comprehensive 40Ar/39Ar geochronological study of the Jiali and Gaoligong shear zones to obtain a better understanding of crustal deformation and tectonic evolution around the Eastern Himalayan Syntaxis (EHS). The new age data reveal that the main phase of deformation in the Jiali and Gaoligong shear zones occurred from 22 to 11 Ma and from 18 to 13 Ma, respectively. Structural data collected during this study indicate that the Jiali shear zone underwent a change in shear sense from sinistral to dextral during its movement history. Based on a comparison with the deformation histories of other major shear zones in the region, we argue that the initial sinistral motion recorded by the Jiali shear zone was coincident with that of the Ailao Shan–Red River shear zone, which marked the northern boundary of the southeastward extrusion of the Indochina block during the Early Miocene. From the Middle Miocene (～18 Ma), the Jiali shear zone changed to dextral displacement, becoming linked with the dextral Gaoligong shear zone that developed as a consequence of continued northward indentation of the Indian continent into Asia. Since this time, the Jiali and Gaoligong shear zones have been united, defining the southwestern boundary of the EHS during clockwise rotation of the eastward-extruding Tibetan block, as revealed by recent GPS data. The temporal change in regional deformation pattern from southeastward block extrusion to clockwise rotation of crustal fragments may have played an important role in the development of the eastern Himalayan drainage system around the EHS. |
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