Coupled Reaction and Flow in Subduction Zones: Silica Metasomatism in the Mantle Wedge

Abstract

Large quantities of H 2 O are carried to great depth during subduction of sediment and hydrated oceanic crust. Much of this H 2 O is bound in hydrous minerals. When dehydration reactions proceed, the liberated fluid may migrate back up the slab or into the overlying mantle wedge (eg Peacock, 1990a, 1993a, b; Bebout, 1991a, b). Regardless of the fluid's trajectory, the strong dependence of mineral solubility on pressure and temperature suggests that this flow may lead to extensive metasomatism. This is supported by field and~…