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1 School of Earth and Environment, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
2 Institut für Geowissenschaften, Universität Mainz, 55099 Mainz, Germany
3 School of Earth Sciences, James Cook University, Townsville, Qld 4811, Australia
4 Department of Earth and Atmospheric Sciences, St. Louis University, St. Louis, MO 63103, USA
5 US Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, USA
6 Department of Geology, University of Leicester, Leicester LE1 7RH, UK
* Corresponding author (e-mail: Peter.Cawood{at}uwa.edu.au)
Accretionary orogens form at intraoceanic and continental margin convergent plate boundaries. They include the supra-subduction zone forearc, magmatic arc and back-arc components. Accretionary orogens can be grouped into retreating and advancing types, based on their kinematic framework and resulting geological character. Retreating orogens (e.g. modern western Pacific) are undergoing long-term extension in response to the site of subduction of the lower plate retreating with respect to the overriding plate and are characterized by back-arc basins. Advancing orogens (e.g. Andes) develop in an environment in which the overriding plate is advancing towards the downgoing plate, resulting in the development of foreland fold and thrust belts and crustal thickening. Cratonization of accretionary orogens occurs during continuing plate convergence and requires transient coupling across the plate boundary with strain concentrated in zones of mechanical and thermal weakening such as the magmatic arc and back-arc region. Potential driving mechanisms for coupling include accretion of buoyant lithosphere (terrane accretion), flat-slab subduction, and rapid absolute upper plate motion overriding the downgoing plate. Accretionary orogens have been active throughout Earth history, extending back until at least 3.2 Ga, and potentially earlier, and provide an important constraint on the initiation of horizontal motion of lithospheric plates on Earth. They have been responsible for major growth of the continental lithosphere through the addition of juvenile magmatic products but are also major sites of consumption and reworking of continental crust through time, through sediment subduction and subduction erosion. It is probable that the rates of crustal growth and destruction are roughly equal, implying that net growth since the Archaean is effectively zero.
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