Evaluation of H2O-CO2 solubility models in silicate melts: Precision and accuracy of vapor saturation pressure and composition

Ery Catherine Hughes, Lee Saper

Solubility models for H2O and CO2 in silicate melt are crucial in igneous petrology and volcanology, in particular for calculating the pressure of vapor saturation of melts from their dissolved volatile content as a barometer, as well as melt and vapor compositions and proportions during degassing. We assessed the accuracy and precision of the calculated pressure of vapor saturation and equilibrium vapor composition using various H2O-CO2 solubility models implemented in VESIcal (Dixon, Liu, IaconoMarziano, ShishkinaIdealMixing, and MagmaSat) using a dataset containing 770 vapor-saturated experimental glasses. Experimental and analytical uncertainties were included but model errors were not considered. Across each models’ full calibration range, pressure of vapor saturation calculations using IaconoMarziano and MagmaSat are accurate, whilst Dixon, Liu, and ShishkinaIdealMixing, are quite inaccurate, and all are relatively imprecise. Most models except ShishkinaIdealMixing are accurate for vapor composition, but all are relatively imprecise. Both accuracy and precision for each model tend to be better for specific melt compositions within the range of experimental pressure-temperature conditions. Hence, for application to natural systems, it is important to assess the accuracy and precision of H2O-CO2 solubility models using experimental data that are closely matched to the system of interest.