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contact metamorphism The recrystallization of rocks surrounding an igneous intrusion in response to the heat supplied by the intrusion. Since there is no significant increase in the pressure gradient around an intrusion, recrystallization processes in the surrounding country rocks are a response only to an increase in the thermal gradient around the intrusion. Hence contact metamorphism is also known as ‘thermal metamorphism’. Metasomatism often takes place during contact metamorphism, unlike regional metamorphism. See also CONTACT AUREOLE.