Contact metamorphism

Contact metamorphism is the alteration of rock, chiefly by heat from nearby magma, within a relatively limited zone around an intrusion.

Thermal aureole: A zone of rock altered by heat around an igneous intrusion. It is the characteristic spatial footprint of contact metamorphism.
Igneous intrusion: A body of igneous rock formed when magma solidifies within pre-existing rock. An intrusion supplies the heat that drives the surrounding metamorphism.
Hornfels: A hard, fine-grained metamorphic rock commonly formed by heating near an igneous intrusion. It is a characteristic product of contact metamorphism in many aluminosilicate-rich rocks.
Regional metamorphism: Metamorphism affecting broad regions, commonly during mountain building under elevated pressure and temperature. Unlike contact metamorphism, it typically spans large areas and involves substantial tectonic pressure.
Metamorphic grade: A measure of the pressure and temperature conditions recorded by metamorphic rocks. Temperature generally falls outward from the intrusion, producing changing metamorphic grades.
Country rock: Pre-existing rock surrounding or enclosing an igneous intrusion. Its composition determines which minerals can form in the aureole.
Skarn: A calc-silicate rock formed by chemical reaction between carbonate rock and magmatic or metamorphic fluids. It records fluid-assisted reactions where intrusions meet carbonate host rocks.
Dynamic metamorphism: Metamorphism concentrated in fault zones, where intense deformation and friction alter rocks. Its deformation and shear dominate, rather than heat from a nearby magma body.
Metasomatism: Chemical alteration of rock through the addition or removal of material by fluids. Magma-derived fluids can change aureole chemistry as well as heat the host rock.
Magma: Molten or partly molten rock beneath Earth’s surface, containing crystals and dissolved gases. Its temperature and composition set the initial conditions for heating and fluid release.

Linked from 16 pages