When Continents Collide: Geodynamics and Geochemistry of Ultrahigh-Pressure Rocks

Abstract. The evolution of the Taiwan orogeny is often described in terms of deformation of rocks above a shallow decollement, either in a continuously deforming wedge or a discretely deforming stack of thrust sheets. Recently acquired evidence from seismic tomography, earthquake locations and focal mechanisms, GPS geodesy, leveling, and exhumed shear zones suggest that such models are inadequate. We propose that these observations are better explained by a model of continental subduction followed by crustal exhumation. In the context of this model, the Eastern Central Range is the locus of active crustal exhumation. Simple thermal modeling shows that the observed seismicity patterns across Taiwan and the high heat flow in the Eastern Central Range are well explained by this crustal exhumation model