Slab pull,mantle convection,and Pangaean assembly and dispersal |
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| Institution: | 1. EarthByte Group, School of Geosciences, The University of Sydney, Madsen Building F09, Camperdown, NSW 2006, Australia;2. Data61, CSIRO, Australian Technology Park, Eveleigh, NSW 2015, Australia;3. Centre for Tectonics, Resources and Exploration (TRaX), Department of Earth Sciences, The University of Adelaide, Adelaide, SA 5005, Australia;4. The Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin University, GPO Box U1987, WA 6845, Australia;5. Earth Dynamics Research Group, ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), Australia;6. Department of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia, B2G 2W5, Canada;7. Department of Applied Geology, Curtin University, Perth WA 6845, Australia;1. School of Earth Sciences, Damghan University, Damghan 36716-41167, Iran;2. Department of Geosciences, University of Oslo, Blindern, N-0316 Oslo, Norway;3. Département de Minéralogie, Université de Genève, Genève, Switzerland;4. Geosciences Department, University of Texas at Dallas, Richardson, TX 75083-0688, USA;1. Earth Dynamics Research Group, The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;2. Department of Geosciences, Eberhard Karls University Tübingen, Sigwartstr. 10, 72076 Tübingen, Germany;3. School of Earth Sciences and Resources, China University of Geosciences, 29 Xueyuan Road, Beijing 100083, China;4. St. Francis Xavier University, Antigonish, Nova Scotia, B2G 2W, Canada |
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| Abstract: | Two global-scale mantle convection cells presently exist on Earth, centred on upwelling zones in the South Pacific Ocean and northeast Africa: one cell (Panthalassan) contains only oceanic plates, the other (Pangaean) contains all the continental plates. They have remained fixed relative to one another for >400 Ma. A transverse (Rheic–Tethyian) subduction system splits the Pangaean cell. Poloidal plate motion in the oceanic cell reflects circumferential pull of Panthalassan slabs, but toroidal flow in the Pangaean cell, reflected by vortex-type motion of continents toward the Altaids of central-east Asia throughout the Phanerozoic, has resulted from the competing slab-pull forces of both cells. The combined slab-pull effects from both cells also controlled Pangaean assembly and dispersal. Assembly occurred during Palaeozoic clockwise toroidal motion in the Pangaean cell, when Gondwana was pulled into Pangaea by the NE-trending Rheic subduction zone, forming the Appalachian–Variscide–Altaid chain. Pangaean dispersal occurred when the Rheic trench re-aligned in the Jurassic to form the NW-trending Tethyside subduction system, which pulled east Gondwanan fragments in the opposite direction to form the Cimmerian–Himalayan–Alpine chain. This re-alignment also generated a new set of (Indian) mid-ocean ridge systems which dissected east Gondwana and facilitated breakup. 100–200-Myr-long Phanerozoic Wilson cycles reflect rifting and northerly migration of Gondwanan fragments across the Pangaean cell into the Rheic–Tethyian trench. Pangaean dispersal was amplified by retreat of the Panthalassan slab away from Europe and Africa, which generated mantle counterflow currents capable of pulling the Americas westward to create the Atlantic Ocean. Thermal blanketing beneath Pangaea and related hotspot activity were part of a complex feedback mechanism that established the breakup pattern, but slab retreat is considered to have been the main driving force. The size and longevity of the two cells, organised and maintained by long-lived slab-pull forces, favours deep mantle convection as the dominant circulation process during the Phanerozoic. |
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