First evidence of the Cambrian basement in Upper Peninsula of Thailand and its implication for crustal and tectonic evolution of the Sibumasu terrane |
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| Institution: | 1. Department of Earth Sciences, National Taiwan Normal University, Taipei 116, Taiwan;2. Center for General Education, National Taiwan Normal University, Taipei 106, Taiwan;3. Department of Geosciences, National Taiwan University, Taipei 106, Taiwan;4. Institute of Earth Sciences, Academia Sinica, Taipei 115, Taiwan;5. Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. Centre for Exploration Targeting and Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS), University of Western Australia, Perth, Western Australia 6009, Australia;3. John de Laeter Centre, Curtin University, Perth, Western Australia 6102, Australia;4. Hebei Institute of Regional Geological and Mineral Resource Survey, Lanfang 065000, China;1. School of Earth Science and Geological Engineering, Sun Yat-Sen University, Guangzhou 510275, China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;3. Department of Earth Sciences, University of St Andrews, North Street, St Andrews KY169AL, UK;4. Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;5. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China |
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| Abstract: | Although the Sibumasu terrane in Asia was previously considered to be composed of Phanerozoic rocks with Cambrian crystalline basement, no reliable or direct radiometric dating evidences of such crystalline basement was ever reported. Our new in-situ zircon U/Pb dating of the Khao Tao orthogneiss yields a concordant age of 501.5 ± 7.5 Ma (2σ), which provides the first robust evidence for the Cambrian crust in Upper Peninsula of Thailand. The zircon εHf(T) values range from + 3.7 to ? 6.1 with model ages (TCDM) of 1244–1827 Ma, suggests a mixed crust-mantle source. The chemical similarity and spatial continuity of the Khao Tao orthogneiss with other pre-Neotethys marginal Eurasian and Sibumasu granitoids indicate the linear paleogeographic association under a similar magmatic arc-related regime along the Gondwana India–Australia margin as part of the Pan-African Orogeny system. |
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