Deep crustal metamorphism during continental extension: modern and ancient examples

Abstract

Granulite facies metamorphism in the lower levels of continental crust which is undergoing extension is indicated by unusually high heat flow in modern-day extensional regimes. For certain geometries of extension, particularly those involving crustal-penetrative detachment zones, this metamorphism may occur on a regional scale. The predicted pressure-temperature-time (P-T-t) paths for such metamorphism involve heating into the granulite facies at constant or decreasing pressure during extension, followed by cooling at constant or increasing pressure after extension stops, and thus they differ considerably from P-T-t paths of metamorphic terrains formed by continental convergence. Many granul..