Inherent gravitational instability of thickened continental crust with regionally developed low- to medium-pressure granulite facies metamorphism

Petrological arguments show that regionally developed low- to medium-pressu re, high-temperature granulite facies metamorphism may critically enhance t he lowering of crustal density with depth. This leads to gravitational inst ability of homogeneously thickened continental crust, mainly due to changes in mineral assemblages and the thermal expansion of minerals in conjunctio n with the exponential lowering of the effective viscosity of rocks with in creasing temperature. It is argued that crustal processes of gravitational redistribution (crustal diapirism) contributing to the exhumation of granul ite facies rocks may be activated in this way. (C) 2001 Elsevier Science B. V. All rights reserved.