Segregation of tonalitic-trondhjemitic melts in the continental crust: the mantle connection

Abstract

Rates of melt segregation into fractures during fluid-absent partial melting above a mafic heat source are investigated numerically over a range of viscosities appropriate for tonalitic-trondhjemitic melts. Static melt segregation is dependent upon large tensile stresses set up during fluid-absent partial melting reactions. Melt segregation into veins and fractures is likely to be most effective near the intrusion-protolith interface, where high temperatures result in relatively low melt viscosities and high porosities. For relatively low viscosity tonalitic melts, extraction may occur at values below the critical melt fraction, provided the melt is everywhere interconnected. Larger veins may propagate upward as dikes to feed high level plutons. -from Author