Regimes of subduction and lithospheric dynamics in the Precambrian: 3D thermomechanical modelling |
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| Institution: | 1. Sorbonne Universités, UPMC Univ Paris 06, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F-75005 Paris, France;2. CNRS, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F-75005 Paris, France;3. Dublin Institute for Advanced Studies, Geophysics Section, 5 Merrion Square, Dublin 2, Ireland;4. Géosciences Rennes, CNRS UMR 6118, Université de Rennes 1, F-35042 Rennes, France;1. Key Laboratory of Submarine Geosciences and Prospecting Techniques, MOE and College of Marine Geosciences, Ocean University of China, Qingdao 266100, PR China;2. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, PR China;3. Key Laboratory of Computational Geodynamics, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China;4. UCD School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland;5. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, PR China;6. Institute of Geophysics, ETH-Zurich, Zurich 8092, Switzerland;7. School of Earth Science and Resources, China University of Geosciences Beijing, Beijing 100083, PR China;1. Key Laboratory of Continental Tectonics and Dynamics, Institute of geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Key Laboratory of Computational Geodynamics, College of Earth Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;3. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;4. Institute of Geophysics, Department of Earth Sciences, ETH-Zurich, Zurich 8092, Switzerland;5. State Key Laboratory of Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210046, China;1. Department of Earth Science, Karl-Franz University of Graz, Austria;2. ETH-Zurich, Institute of Geophysics, Switzerland;3. Adjunct Professor of Geology Department, Moscow State University, Moscow 119199, Russia;4. Department of Geology, University of Maryland, College Park, MD 20742, USA;1. University of WA, Center for Exploration Targeting, Australia;2. Swiss Federal Institute of Technology, Switzerland |
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| Abstract: | Comparing the early Earth to the present day, geological–geochemical evidence points towards higher mantle potential temperature and a different type of tectonics. In order to investigate possible changes in Precambrian tectonic styles, we conduct 3D high-resolution petrological–thermomechanical numerical modelling experiments for oceanic plate subduction under an active continental margin at a wide range of mantle potential temperature TP (? TP = 0 ? 250 K, compared to present day conditions). At present day mantle temperatures (? TP = 0 K), results of numerical experiments correspond to modern-style subduction, whereas at higher temperature conditions important systematic changes in the styles of both lithospheric deformation and mantle convection occur. For ? TP = 50 ? 100 K a regime of dripping subduction emerges which is still very similar to present day subduction but is characterised by frequent dripping from the slab tip and a loss of coherence of the slab, which suggests a close relationship between dripping subduction and episodic subduction. At further increasing ? TP = 150 ? 200 K dripping subduction is observed together with unstable dripping lithosphere, which corresponds to a transitional regime. For ? TP = 250 K, presumably equivalent to early Archean, the dominating tectonic style is characterised by small-scale mantle convection, unstable dripping lithosphere, thick basaltic crust and small plates. Even though the initial setup is still defined by present day subduction, this final regime shows many characteristics of plume-lid tectonics. Transition between the two end-members, plume-lid tectonics and plate tectonics, happens gradually and at intermediate temperatures elements of both tectonic regimes are present. We conclude, therefore, that most likely no abrupt geodynamic regime transition point can be specified in the Earth's history and its global geodynamic regime gradually evolved over time from plume-lid tectonics into modern style plate tectonics. |
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