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contact aureole (metamorphic aureole) A region in which country rocks surrounding an igneous intrusion have been recrystallized in response to the heat supplied by the intrusion. The widths of contact aureoles are quite variable and partly depend on the size of the igneous intrusion—the larger the intrusion, the wider the aureole. For intrusions of similar size, an aureole formed in response to simple conduction of heat will, in general, be thinner than an aureole formed in response to the more efficient convective transfer of heat in escaping mineralizing fluids. See also CONTACT METAMORPHISM.