Determining the pressure-temperature-composition (P-T-X) conditions of magma storage

Determining the pressures and temperatures at which melts are stored in the crust and upper mantle, and the major element composition, redox state and volatile contents of these melts, is vital to constrain the structure and dynamics of magmatic plumbing systems. In turn, constraining these parameters helps understand the geochemical and structural evolution of the Earth’s lithosphere, and periods of unrest at active volcanoes. We review common thermobarometers, hygrometers and chemometers based on mineral and/or liquid compositions, before discussing recent advances in melt and fluid inclusion barometry, Raman-based elastic thermobarometry, and thermodynamic modelling methods. Where possible, we investigate the accuracy and precision of each technique, and the implications for the application of each method to different research questions.