Using equilibrium thermodynamics to understand metamorphism and metamorphic rocks

Abstract

Metamorphic rocks, formed at elevated temperature and pressure from pre-existing rocks inside mountain belts, provide a seemingly unpromising target for the application of equilibrium thermodynamics. This is because metamorphic rocks develop their mineral assemblages along a pressure-temperature (P-T) path, with pressure and temperature continuously changing along the path. However, in a successful model for the formation of such rocks, involving the essential role of fluid or melt, the mineral assemblages observed at the Earth's surface can be considered to reflect a state of frozen-in equilibrium as the rocks are exhumed towards the Earth's surface. Equilibrium thermodynamics applied to su..