metasomatism
Noun
Meaning
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.
Source: Webster's dictionaryExamples
There is also a tendency for metasomatism between the igneous magma and sedimentary country rock, whereby the chemicals in each are exchanged or introduced into the other.
Metasomatism is the drastic change in the bulk chemical composition of a rock that often occurs during the processes of metamorphism.
Metasomatism will change the original composition.
The formation of important ore minerals may occur by the process of metasomatism at or near the contact zone.