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Australian Crustal Research Centre, Department of Earth Sciences, Monash University, Melbourne VIC 3800, Australia
British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK mkrab{at}bgs.ac.uk
Although poly-cyclicity is common, many orogens show a remarkable lack of reworking. In this paper, a review of some factors that may either enhance or inhibit reworking of orogens is presented. As a general rule, orogens are unlikely to rift and rework if their lithospheric strength is higher than adjacent lithosphere. The strength of the lithosphere is strongly dependent on the geothermal gradient and the rheology of the rocks; both these factors can depend on the preceding orogenic evolution, even several hundred Ma after orogenesis. Strong orogenic lithosphere is expected if the crust is composed of material with a low radiogenic heat production capacity, such as island arcs, or if the underlying sub-continental lithosphere is still thickened, as in the Urals. Extensive dehydration metamorphism, a concentration of radiogenic heat production in the upper crust and erosional thinning of the orogenic crust can also strengthen the lithosphere and inhibit reworking. However, proximity of Archean cratons and anomalously high mantle heat flow appear to strongly enhance susceptibility to reworking.
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