Intra-oceanic arcs of the Paleo-Asian Ocean |
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| Institution: | 1. Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, 3 Koptyuga ave., Novosibirsk 630090, Russia;2. Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia;3. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography CAS, Urumqi 830011, China;4. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics CAS, Beijing 100029, China;1. Hebei GEO University, Shijiazhuang, Hebei 050031, China;2. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China;3. School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, China;4. Department of Earth Science, University of Adelaide, Adelaide 5005, Australia;1. College of Earth Sciences, Jilin University, Changchun 130061, PR China;2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, PR China;3. College of Marine Geosciences, Ocean University of China, Qingdao 266003, PR China;1. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;2. HKU Shenzhen Institute of Research and Innovation, Shenzhen, China;3. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;4. Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia;5. The Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia;6. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;1. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;2. The Beijing SHIRMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 102206, China;3. Tsinghua-Chinluck Frontier Science Research Center, Tsinghua University, Beijing 100084, China;4. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The paper reviews and integrates geological, geochronological, geochemical and isotope data from 21 intra-oceanic arcs (IOA) of the Paleo-Asian Ocean (PAO), which have been identified in the Central Asian Orogenic belt, the world largest accretionary orogeny. The data We discuss structural position of intra-oceanic arc volcanic rocks in association with back-arc terranes and accretionary complexes, major periods of intra-oceanic arc magmatism and related juvenile crustal growth, lithologies of island-arc terranes, geochemical features and typical ranges of Nd isotope values of volcanic rocks. Four groups of IOAs have been recognized: Neoproterozoic – early Cambrian, early Paleozoic, Middle Paleozoic and late Paleozoic. The Neoproterozoic – early Cambrian or Siberian Group includes eleven intra-oceanic arcs of eastern and western Tuva-Sayan (southern Siberia, Russia), northern and southwestern Mongolia and Russian Altai. The Early Paleozoic or Kazakhstan Group includes Selety-Urumbai, Bozshakol-Chingiz and Baydaulet-Aqastau arc terranes of the Kazakh Orocline. The Middle Paleozoic or Southern Group includes six arc terranes in the Tienshan orogen, Chinese Altai, East-Kazakhstan-West Junggar and southern Mongoia. Only one Late Paleozoic intra-oceanic arc has been reliably identified in the CAOB: Bogda in the Chinese Tienshan, probably due to PAO shrinking and termination. The lithologies of the modern and fossil arcs are similar, although the fossil arcs contain more calc-alkaline varieties suggesting either their more evolved character or different conditions of magma generation. Of special importance is identification of back-arc basins in old accretionary orogens, because boninites may be absent in both modern and fossil IOAs. The three typical scenarios of back-arc formation - active margin rifting, intra-oceanic arc rifting and fore-arc rifting were reconstructed in fossil intra-oceanic arcs. Some arcs might be tectonically eroded and/or directly subducted into the deep mantle. Therefore, the structural and compositional records of fossil intra-oceanic arcs in intracontinental orogens allow us to make only minimal estimations of their geometric length, life span, and crust thickness. |
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