magmatisiin

Magmatisiin is a geologic concept describing the processes by which magma forms, evolves, and interacts with surrounding rocks to produce igneous rocks. The term is closely related to, and often considered a variant of, magmatism; in English literature the standard term is magmatism.

Generation and evolution of magma occur mainly through partial melting of existing rocks in the mantle or crust, sometimes aided by subduction or mantle plume activity. As magma ascends, it may pool in magma chambers where crystallization begins. Differentiation through fractional crystallization, assimilation of surrounding rock, and magma mixing can change the chemical composition, yielding a spectrum from felsic to mafic magmas.

Crystallization and storage in chambers produce a range of igneous rocks. Intrusive or plutonic magmatism forms rocks such as granites, diorites, and gabbros, with features like dikes, sills, and batholiths that intrude preexisting rocks. Extrusive or volcanic magmatism erupts as lava flows, ash falls, volcanic domes, and pyroclastic deposits. The texture and mineralogy depend on cooling rate and chemical composition.

Geological settings for magmatism are closely tied to plate tectonics and occur at subduction zones, continental rifts, and oceanic ridges; mantle plumes can create hotspot-related volcanism. Magmatism also drives crustal growth and ore-forming processes, including porphyry copper systems and granitic pegmatites rich in rare earth elements.

See also: igneous rocks, partial melting, crystallization, plate tectonics, ore deposits.