Geochronology and isotope analysis of the Late Paleozoic to Mesozoic granitoids from northeastern Vietnam and implications for the evolution of the South China block |
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| Institution: | 1. SE Asia Research Group, Department of Earth Sciences, Royal Holloway University of London, Egham TW20 0EX, UK;2. Minerals and Geoscience Department Malaysia (JMG) Sarawak, Jalan Wan Abdul Rahman, Kenyalang Park, P.O. Box, 560 93712 Kuching, Sarawak, Malaysia;3. Research School of Earth Sciences, The Australian National University, Canberra 2601, Australia;4. Department of Earth Sciences, University College London, London, WC1H 0BT, UK;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. Department of Astronomy, Space Science and Geology, Chungnam National University, Daejeon 34134, South Korea;2. Department of Geology and Earth Environmental Sciences, Chunganm National University, Daejeon 34134, South Korea;3. Faculty of Geology, University of Science VNU-HCM, Vietnam;4. Division of Earth and Environmental Sciences, Korea Basic Science Institute, Ochang, Chungbuk 28119, South Korea |
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| Abstract: | In northeastern Vietnam, Late Paleozoic and Permo-Triassic granitic plutons are widespread, but their tectonic significance is controversial. In order to understand the regional magmatism and crustal evolution processes of the South China block (SCB), this study reports integrated in situ U–Pb, Hf–O and Sr–Nd isotope analyses of granitic rocks from five plutons in northeastern Vietnam. Zircon SIMS U–Pb ages of six granitic samples cluster around in two groups 255–228 Ma and 90 Ma. Bulk-rock εNd (t) ranges from ?11 to ?9.7, suggesting that continental crust materials were involved in their granitic genesis. In situ zircon Hf–O isotopic measurements for the granitic samples yield a mixing trend between the mantle- and supracrustal-derived melts. It is suggested that the granitic rocks were formed by re-melting of the continental crust. These new data are compared with the Paleozoic and Mesozoic granitic rocks of South China. We argue that northeastern Vietnam belongs to the South China block. Though still speculated, an ophiolitic suture between NE Vietnam and South China, so-called Babu ophiolite, appears unlikely. The Late Paleozoic to Mesozoic magmatism in the research area provides new insights for the magmatic evolution of the South China block. |
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| Keywords: | Northeastern Vietnam South China block Triassic orogen Zircon SIMS dating Hf–O isotopes Eastern Paleotethys |
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