A mafic intrusion is an igneous body composed predominantly of mafic minerals, such as pyroxene and olivine, that has intruded into the Earth’s crust. These intrusions are significant for studying the processes of magma emplacement, the formation of ore deposits, and the thermal evolution of the crust.
Source Best, M. G. (2003). “Igneous and Metamorphic Petrology.” Wiley-Blackwell.