postmetamorphic

Postmetamorphic is an adjective used in geology and petrology to describe rocks, processes, or events that occur after metamorphism has taken place. Metamorphism encompasses mineralogical and textural changes driven by elevated temperature and pressure, whereas postmetamorphic stages refer to the rock’s subsequent history and alteration.

Postmetamorphic processes can include tectonic uplift and exhumation that bring metamorphic rocks toward the surface, erosion that removes overburden, and surface weathering or diagenetic alteration that modifies exposed rocks. Hydrothermal or metasomatic activity that occurs after peak metamorphism may introduce new minerals or alter existing assemblages without requiring high-temperature metamorphism again. In many studies, retrograde metamorphism is treated as a postmetamorphic phase, because it occurs during cooling after peak metamorphism, although some authors classify it within the metamorphic sequence.

Using a postmetamorphic perspective helps geologists reconstruct tectonic histories, timing of exhumation, and landscape evolution, and it clarifies which rock textures and mineral assemblages reflect earlier metamorphic conditions versus later overprints. The term is used mainly in scholarly discussions of metamorphic belts, orogenic cycles, and crustal evolution. See also metamorphism, retrograde metamorphism, exhumation, and metasomatism.