Mechanical consequences of granite emplacement during high-T, low-P metamorphism and the origin of "anticlockwise" PT paths

Abstract

High-temperature (T), low-pressure (P) metamorphic belts preserve evidence of metamorphism under extremely perturbed, and hence transient, thermal regimes. PT paths are commonly "anticlockwise"; that is, the maximum T was attained prior to or at the same time as the maximum P with cooling at near constant or increasing P, and, in many terrains, peak metamorphic temperatures prevailed during convergent deformation. Using a simple coupled thermal-mechanical model that assumes a strongly temperature-dependent rheology for the continental lithosphere we show that the coincidence of metamorphism with convergent deformation in high-T, low-P terrains may reflect the thermal weakening attendant with..