granitization, formation of granite or closely related rocks by metamorphic processes, as opposed to igneous processes in which such rocks form from a melt, or magma, of granitic composition. In granitization, sediments are transformed in their solid state or in a partially molten state. The solid-state process requires the addition and removal of various chemical components by solid-state diffusion, vapour transport, or the movement of certain fluids such as aqueous solutions.
Granitization may occur on a small, localized scale, as in the formation of migmatite in which igneous rocks of granitic composition are intermixed with high-grade metamorphic rocks.