Metamorphic Fluids in Orogenic Settlings

Metamorphic reactions within the Earth’s crust produce fluids of variable composition that play a major role in the evolution of continents. Metamorphic fluids facilitate reactions that alter crustal rheology, reduce melting temperature, cycle elements between geological reservoirs and form ore deposits. These fluids are relatively inaccessible, other than by study of fluid inclusions, so most studies rely on a combination of indirect evidence and predictive thermodynamic models to determine the characteristics and roles of the fluids. In this article, the origins, compositions, controlling phase equilibria, and roles of metamorphic fluids are reviewed, followed by a discussion of selected areas of current and future research.