Magmatic volatiles in the Yellowstone Plateau volcanic field: The knowns, the unknowns, and the uncertainties

The Yellowstone Plateau volcanic field has a large magmatic system supplying heat and mass into the overlying hydrothermal system. To interpret changes in the composition and/or emission rates of hydrothermal fluids as possible indicators of volcanic unrest requires discriminating between magmatic, crustal, hydrothermal, and hybrid sources and processes. Significant progress in characterizing the composition and rates of hydrothermal fluid discharge has been made over the past two decades but many uncertainties about sources and processes remain.