contactmetamorfose

Contactmetamorfose, commonly referred to as contact metamorphism in English, is the type of metamorphism that occurs when rocks are heated by the intrusion of magma at relatively shallow crustal depths. The process is driven by heat from the igneous body and, in many cases, by chemically active fluids released from the magma, which can alter mineral compositions and generate new minerals near the intrusion.

The metamorphic effects form a zone, or aureole, around the intrusion. Temperature decreases with distance from the magma, so metamorphic grade is highest closest to the intrusion and diminishes outward. Because the confining pressure is usually low to moderate, the resulting rocks are often non-foliated or only weakly foliated. Metasomatic changes are common where fluids migrate into surrounding rocks, creating calc-silicate assemblages in carbonate rocks.

Common products of contact metamorphism include hornfels, a class of dense, fine-grained, non-foliated rocks produced by rapid heating. In carbonate rocks, metasomatism can produce skarns with minerals such as diopside, garnet, and calc-silicates. The overall texture is typically granoblastic, with recrystallized grains forming within the original rock.

Geologically, contact metamorphism contrasts with regional metamorphism, which is driven by large-scale pressure and temperature changes during mountain building. Economically, contact aureoles can host mineral deposits associated with skarns, including copper, iron, and tungsten ore.

The term is used across languages; in English the standard term is contact metamorphism, while in Portuguese the equivalent is metamorfose de contato.