The role of crustal anatexis and magma migration in the thermal evolution of regions of thickened continental crust

Summary The results of numerical thermal models are presented that directly take into account crustal melting and the upward transfer of melts in the thermal evolution of regions of thickened continental crust. The results of these models indicate that in regions of moderate to high mantle heat flow (Q m > 30 mW m −2 ), extensive melting of the lower crust is likely, but will only moderately affect the rise in temperature of the lower crust. They also show that the ascent of those melts will drastically modify the pressure- temperature-time ( P-T-t ) paths followed by horizons in the upper plate, prolonging loading and producing widespread high-grade amphibolite-facies metamorphism. In these models, both the style and timing of metamorphism above zones of melting is controlled by those melts and, as a consequence of melting, as much as 30–50% of the orogenic root is eliminated by removal of the lower plate through the upward transport of melts and their erosion at the surface.