Raman spectroscopy as a tool to study the solubility of CO_2 in magnesium sulphate brines: application to the fluids of Europa's cryomagmatic reservoirs

摘要

The solubility of CO_2 in water at different temperature and pressure conditions has been studied for more than 150 years because of the common presence of this system in the Earth, and its importance for engineering and in several biological and geological processes. However, there are many contradictions in the literature with regard to the solubility of CO_2 in salt-rich aqueous solutions, and associated effects such as the salting out have been studied in detail for only few salts such as NaCl or Na_2SO_4. In this study we introduce Raman spectroscopy as a useful tool to measure gas solubility in brines. We have obtained the solubility of CO_2 in aqueous solution of MgSO_4 at different concentrations (5 and 17 wt %), in the range of temperatures from 5 to 20 ℃ and pressures up to 50 bar. The results allow one to approach different aqueous reactions and processes that are relevant in geochemical phenomena of some planetary objects. Thus, we have modelled the degassing processes that could occur through the crust of Europa, a satellite of Jupiter.