Neoproterozoic to Early Ordovician Evolution of the Paleo-Asian Ocean: Implications to the Break-up of Rodinia |
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| Institution: | 1. Czech Geological Survey, Klárov 3, 118 21 Prague 1, Czech Republic;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. Institute of Petrology and Structural Geology, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic;4. Department of Geosciences, University of Mainz, D-55099 Mainz, Germany;5. Beijing SHRIMP Centre, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, 100037 Beijing, China;6. Institute of Paleontology and Geology, Mongolian Academy of Sciences, P.O. Box 45/650,Ulaanbaatar 15160, Mongolia;7. School of Geology and Mining Engineering, MUST, P.O. Box 654, Ulaanbaatar, Mongolia;8. Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway;1. LSCE, Laboratoire des Sciences du Climat et de l''Environnement, UMR 8212, CNRS-CEA-UVSQ, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France;2. UMR 5563 Géosciences Environnement Toulouse, Observatoire Midi-Pyrénées, CNRS, Toulouse, France;3. Department of Geology and Soil Sciences (WE13), Ghent University, Krijgslaan 281/S8, 9000 Ghent, Belgium;4. UMR 8198 Evo-Eco-Paléo, Université de Lille, Sciences et Technologies, Avenue Paul Langevin, bâtiment SN5, 59655 Villeneuve d''Ascq Cedex, France;1. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;2. Department of Geology and Planetary Science, University of Pittsburgh, 4107 O''Hara Street, Pittsburgh, PA 15260-3332, USA |
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| Abstract: | The paper reviews and integrates the recent geological and geochronological data, which allow us to recognize three stages of the evolution of the Paleo-Asian Ocean.The opening of the Paleo-Asian Ocean at 970-850 Ma is dated by the Nersin Complex in the Aldan shield, plagiogranites of the Sunuekit massif, enderbites of the Sludinsk Lake area, and passive margin sediments of the Patoma or Baikal series. The initial subduction (850-700 Ma) is marked by volcanic rocks, trondjemite and gabbro of the Sarkhoy island arc series. Collisions of microcontinents with Siberia at 660 to 620 Ma are evidenced by the exhumation of Muya eclogites (650 Ma), formation of migmatites and amphibolites of the Njurundukan belt (635 and 590 Ma), metamorphic units of the Near-Yenisei belt (640-600 Ma), and orogenic molasse (640-620 Ma). The Paleo-Asian Ocean maximally opened at 620-550 Ma, because at that time a long island arc composed of boninite volcanic rocks was formed. Primitive island arcs of that age have been reconstructed in Kazakhstan, Gorny Altai, West and East Sayan, and North Mongolia. HP and UHP rocks formed in two stages at 550-520 and 520-490 Ma. At 550-490 Ma oceanic islands and Gondwana-derived microcontinents (Kokchetav, Tuva-Mongolian, Central Mongolian and others) collided with the Cambrian-early Ordovician island arc of the Siberian continent. As a result, the island-arc system was extensively modified. Collision occurred twice at 550-520 and 520-490 Ma during which many HP and UHP rocks formed. At that time, the new oceans - the Junggar, Kazakhstan and Uralian - with an Ordovician island arc were formed. |
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