Evidence for Ordovician subduction-related magmatism in the Truong Son terrane,SE Laos: Implications for Gondwana evolution and porphyry Cu exploration potential in SE Asia |
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| Institution: | 1. School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia;2. Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, Sydney, Australia;3. PT (Sole) Company Ltd, Vientiane, Laos;4. School of Earth Sciences, University of Melbourne, Melbourne, Australia;1. Guangdong Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;3. Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;4. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;5. Department of Earth Sciences, University of St Andrews, North Street, St Andrews KY169AL, UK;1. School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou, 510275, China;2. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan, 430074, China;3. Department of Applied Geology, Curtin University, Perth, 6102, Australia;4. School of Geotechnology, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand;1. School of Earth Sciences and Engineering, Sun Yat–sen University, Guangzhou 510275, China;2. Guangdong Key Lab of Geodynamics and Geohazards, Guangzhou 510275, China;3. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;4. Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;5. Department of Applied Geology, Curtin University, Perth 6102, Australia;1. Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606–8502, Japan;2. Division of Evolution of Earth Environment, Faulty of Social and Cultural Studies, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819–0395, Japan;3. Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan;4. National Institute of Polar Research, 10–3 Midori-cho, Tachikawa, Tokyo 190–8518, Japan;5. Department of Earth Sciences, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814–0180, Japan;6. Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand;7. Japan Oil, Gas and Metals National Corporation, Toranomon Twin Building 2-10-1 Toranomon, Minato-ku, Tokyo 105–0001, Japan;1. Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, United Kingdom;2. Department of Geology, Chiang Mai University, Thailand;3. Swedish Museum of Natural History, and Nordic Center for Earth Evolution, Box 50007, SE-104 05 Stockholm, Sweden;4. NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, United Kingdom;1. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;2. School of Earth Science and Geological Engineering, Sun Yat-Sen University, Guangzhou 510275, China;3. School of Geotechnology, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand |
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| Abstract: | The Truong Son Fold Belt (TSFB) is characterised by Late Carboniferous-Late Triassic metamorphic, volcanic and plutonic rocks, the product of accretion of the Indochina Terrane onto the South China Terrane and a range of composite subduction, collision and extensional events. This study discusses geochronological and geochemical data obtained from a dioritic intrusion and rhyolitic tuff mapped in the Donken area of SE Laos, and previously assigned to the Permian Antoum Granodiorite rock suite within the TSFB. Magmatic zircon U-Pb Q-ICP-MS dating undertaken in this study suggests ages of ca 470 ± 2 Ma for the diorite and ca 476 ± 1.5 Ma for a proximal rhyolitic tuff.Whole-rock geochemistry of both units suggests a subduction-related island arc environment, with calc-alkaline and tholeiitic affinities for the diorite and tuff respectively. The intrusion also exhibits an adakitic signature (high Sr, low Y and HREE contents) suggesting that Ordovician magmatism also occurred within the Indochina Terrane, associated with an enigmatic, early Gondwana subduction event. This intrusion appears part of a broader, bilateral Early Ordovician magmatism, newly linked to the south-east subduction of the Tamky-Phuoc Son Ocean underneath the Kontum terrane, and a north-west subduction beneath the Truong Son terrane. Significantly, sub-economic hydrothermal Cu mineralisation observed within the dioritic intrusion, hints at the presence of local Ordovician, porphyry-style base metal enrichment. |
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