Fluid saturation and volatile partitioning between melts and hydrous fluids in crustal magmatic systems: The contribution of experimental measurements and solubility models

This work reviews the experimental constraints on the concentrations of volatiles that can be expected in melts found in the crust and the saturation of such melts with a separate fluid phase. After presenting evidence for volatile concentrations in magmatic source regions in the crust and upper mantle and discussing volatile concentrations in magmatic systems, experimental results on the solubility and partitioning of H2O, CO2, S, Cl, F and a few other minor volatiles at pressures up to 800 MPa are summarized. Many of the important models used to predict the solubility and partitioning of these volatiles are then introduced and two models, both easily available for use, are compared against experimental data. Finally, a model of isothermal, closed system ascent of a granitic composition magma with water, carbon dioxide and chlorine is presented to illustrate the evolution of volatiles in a crustal magmatic system and to demonstrate how this evolution may affect the formation of ore deposits and the vesiculation of ascending magmas.