Metamorphism associated with igneous intrusions

Abstract

The processes involved in metamorphism are probably most easily understood in cases where surrounding country rocks have been heated by an igneous intrusion. It is increase in temperature which causes the most striking effects on the mineral assemblages in a rock, and in these cases of contact metamorphism, the source of the heat is obvious. It is the heat originally contained in the molten liquid magma of the intrusion. Perhaps the simplest case of all is that of a sheet of basic magma intruded into a planar fracture in the Earth’s crust, which has cooled to form a dyke of dolerite.