The carbon dioxide solubility in alkali basalts: an experimental study

Experiments were conducted to determine CO2 solubilities in alkali basalts from Vesuvius, Etna and Stromboli volcanoes. The basaltic melts were equilibrated with nearly pure CO2 at 1,200A degrees C under oxidizing conditions and at pressures ranging from 269 to 2,060 bars. CO2 solubility was determined by FTIR measurements. The results show that alkalis have a strong effect on the CO2 solubility and confirm and refine the relationship between the compositional parameter I devised by Dixon (Am Mineral 82:368-378, 1997) and the CO2 solubility. A general thermodynamic model for CO2 solubility in basaltic melts is defined for pressures up to 2 kbars. Based on the assumption that O2- and CO (3) (2-) mix ideally, we have:Then, from the thermodynamic model, we obtain ln K (0) = 0.893 I - 15.247. The new CO2 solubility model yields saturation pressures lower by as much as 50% relative to some existing models when applied to volatile-rich alkali basalts.