Gangdese retroarc thrust belt and foreland basin deposits in the Damxung area,southern Tibet |
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| Institution: | 1. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;4. Department of Geosciences, Auburn University, Auburn, AL 36849, USA;1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Economic Geology Research Centre (EGRU), College of Science, Technology and Engineering, James Cook University, Townsville, QLD 4811, Australia;1. Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China;2. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK;1. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China;2. Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, USA;3. Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA;1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. School of Earth and Space Sciences, Peking University, Beijing 100871, China;3. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, CAGS, Beijing 100037, China;4. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China |
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| Abstract: | Geologic mapping and U–Pb detrital zircon geochronologic studies of (meta)sedimentary rocks in the Damxung area (～90 km north of Lhasa) of the southern Lhasa terrane in Tibet provide new insights into the history of deformation and clastic sedimentation prior to late Cenozoic extension. Cretaceous nonmarine clastic rocks ～10 km southeast of Damxung are exposed as structural windows in the footwall of a thrust fault (the Damxung thrust) that carries Paleozoic strata in the hanging wall. To the north of Damxung in the southern part of the northern Nyainqentanglha Range (NNQTL), metaclastic rocks of previously inferred Paleozoic age are shown to range in depositional age from Late Cretaceous to Eocene. The metaclastic rocks regionally dip southward and are interpreted to have been structurally buried in the footwall of the Damxung thrust prior to being tectonized during late Cenozoic transtension. Along the northern flank of the NNQTL, Lower Eocene syncontractional redbeds were deposited in a triangle zone structural setting. All detrital zircon samples of Cretaceous–Eocene strata in the Damxung area include Early Cretaceous grains that were likely sourced from the Gangdese arc to the south. We suggest that the that newly recognized Late Cretaceous to Early Eocene (meta)clastic deposits and thrust faults represent the frontal and youngest part of a northward directed and propagating Gangdese retroarc thrust belt and foreland basin system that led to significant crustal thickening and elevation gain in southern Tibet prior to India-Asian collision. |
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