metasomatism

The process by which the chemical composition of a rock is changed by interaction with fluids; replacement of one mineral by another without melting.

Same as metasomatosis.

chemical change occurring in a body of ore or in a rock-mass at a considerable depth in the earth’s crust: distinguished from weathering, which occurs at or near the surface.

An alteration in a mineral or rock mass when involving a chemical change of the substance, as of chrysolite to serpentine; — opposed to ordinary metamorphism, as implying simply a recrystallization.

the process by which the bulk chemical composition of a rock is changed by the introduction of components from an external source, especially by a hydrothermal fluid