SO2 solubility and degassing behavior in silicate melts

We have determined the S contents of 14 different silicate melts equilibrated with Air/SO2 mixtures at 1 atm pressure and temperatures 1473–1773 K in 50 intervals. Under these oxidizing conditions sulfur dissolves predominantly as sulfate (S6+ or SO42–). The quenched products were by EPMA (Electron Probe Micro-Analysis) SIMS (Secondary Ion-Mass Spectrometry) latter being employed for low (i.e., ?60 ppm). Equilibrium found to increase strongly decreasing temperature some compositional parameters, especially CaO content. data used calculate capacity (log CS6+), each melt composition temperature. Sulfate is related equilibrium constant dissolution defined follows terms SO42– concentration fugacities oxygen sulfur: logCS6+=logSO4melt2-(wt.%)-12logfS2-32logfO2 By determining log CS6+ ratios we showed that independent content hence Henry’s Law obeyed experimental range. stepwise linear regression fit an equation incorporating terms. Parameters which did not pass F-test 95% confidence level excluded. This approach led following equation: logCS6+=-12.659+(3692XCaO-7592XSiO2-13736XTiO2+3762XAlO1.5+34483)/T standard error 0.154 R2 0.985. simulate scenarios SO2-degassing from ascending basaltic andesitic compositions. important observations are SO2 partitions into H2O-rich fluid phase most lost relatively high pressures crust. So, example estimate ?85% initial should be before magma reaches 100 MPa pressure.