granulitefacies

Granulite facies is a high-temperature, medium- to high-pressure metamorphic grade of the crust. It records deep crustal metamorphism in environments where temperatures are typically around 700–900°C (sometimes higher) and pressures are about 0.5–1.2 GPa (roughly 5–12 kbar). Rocks that reach granulite conditions often develop granular, high-temperature textures and may undergo dehydration melting, which can produce granitoid melts within the lower to middle crust.

The mineral assemblages common to granulite facies include pyroxenes (orthopyroxene and/or clinopyroxene), garnet, and plagioclase, frequently with quartz and potassium feldspar. Biotite and other hydrous minerals are often scarce or absent, reflecting the relatively dry conditions of granulite metamorphism. Char­nockite and enderbite subtypes are granulite facies rocks characterized by the presence of potassium feldspar in addition to pyroxenes and garnet.

Granulite facies forms predominantly during regional metamorphism in the crust, such as in continental collision zones and ancient orogenic belts. It represents one of the higher-temperature endmembers of metamorphism, and its rocks can record deep-crustal processes, including exhumation and dehydration melting. Granulite facies is distinct from eclogite facies, which forms at higher pressures, and from amphibolite facies, which records lower temperatures. Granulite-grade rocks are widespread in Precambrian shield regions and other areas that have experienced prolonged high-temperature crustal metamorphism.