Continental crustal volume,thickness and area,and their geodynamic implications |
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| Institution: | 1. School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC 3800, Australia;2. School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK;3. School of Earth Sciences, University of St Andrews, St Andrews, Fife KY16 9AL, UK;1. Beijing SHRIMP Centre, Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing 100037, China;2. Institute of Geosciences, University of Mainz, 55099 Mainz, Germany;3. Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, Makarova embankment 2, St. Petersburg, 199034, Russia;4. Geological Institute, Russian Academy of Sciences, Pyzhevskiy pereulok 7, Moscow, 119017, Russia;5. Institute of Earth Sciences, Academia Sinica, P.O. Box 1-55, Taipei 11529, Taiwan;6. Department of Geosciences, National Taiwan University, Taipei 106, Taiwan;7. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;1. Department of Applied Geology, Curtin University, Perth WA 6845, Australia;2. School of Geosciences, King''s College, University of Aberdeen, AB24 3UE United Kingdom;3. Department of Earth Sciences, The University of Adelaide SA 5005, Australia;4. School of Earth Science & Resources, Chinese University of Geosciences, Beijing, China |
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| Abstract: | Models of the volume of continental crust through Earth history vary significantly due to a range of assumptions and data sets; estimates for 3 Ga range from <10% to >120% of present day volume. We argue that continental area and thickness varied independently and increased at different rates and over different periods, in response to different tectonic processes, through Earth history. Crustal area increased steadily on a pre-plate tectonic Earth, prior to ca. 3 Ga. By 3 Ga the area of continental crust appears to have reached a dynamic equilibrium of around 40% of the Earth's surface, and this was maintained in the plate tectonic world throughout the last 3 billion years. New continental crust was relatively thin and mafic from ca. 4–3 Ga but started to increase substantially with the inferred onset of plate tectonics at ca. 3 Ga, which also led to the sustained development of Earth's bimodal hypsometry. Integration of thickness and area data suggests continental volume increased from 4.5 Ga to 1.8 Ga, and that it remained relatively constant through Earth's middle age (1.8–0.8 Ga). Since the Neoproterozoic, the estimated crustal thickness, and by implication the volume of the continental crust, appears to have decreased by as much as 15%. This decrease indicates that crust was destroyed more rapidly than it was generated. This is perhaps associated with the commencement of cold subduction, represented by low dT/dP metamorphic assemblages, resulting in higher rates of destruction of the continental crust through increased sediment subduction and subduction erosion. |
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