Diffusion and Redox Reactions of Sulfur in Silicate Melts

Sulfur degassing at Erta Ale (Ethiopia) and Masaya (Nicaragua) volcanoes: Implications for degassing processes and oxygen fugacities of basaltic systems

“…The empirically calculated values for α gas‐melt of 0.9991–0.9997 for Erta Ale are closer to unity than those derived for the theoretical cases of S 2− , FeS, or S 2− /SO 4 2− kinetic fractionation, as has to be the case for diffusion through a complex medium such as melt [ Schauble , ]. Sulfur diffusion is a complex processes involving the breaking and reforming of bonds with cations in the melt and debate still surrounds the effect of melt S speciation (i.e., S 2− versus SO 4 2 ) in controlling S diffusion [ Behrens and Stelling , ].…”

Temperature dependence of sulfide and sulfate solubility in olivine-saturated basaltic magmas

“…Run durations were 18-56 h for Ol container runs (1150-1250°C) and 54 h for runs in Au capsules at 1050°C (Table 3). Liu et al (2007) showed that at 1250°C S-bearing basaltic systems can reach chemical and redox equilibrium after about 6 h. Owing to the small mass of our samples, small size of glass particles, long run duration, high diffusivity of H 2 in the Au 80 Pd 20 capsule material (e.g., Gaillard et al, 2003), relatively high diffusivity of S in Etna basalt (Freda et al, 2005), and fast kinetics of redox reaction involving Fe and S (Gaillard et al, 2003;Behrens and Stelling, 2011), we are confident that our synthetic melt inclusions attained local equilibrium within the Ol container during the runs. In addition, the reproducibility of the experiments was verified by duplicate FeS-saturated runs at 1150 and 1200°C (exp.…”

NanoSIMS results from olivine-hosted melt embayments: Magma ascent rate during explosive basaltic eruptions

“…Nonetheless, existing experiments show no strong fO 2 dependence, perhaps due to the predominance of melt viscosity over speciation on S diffusivity (Behrens and Stelling, 2011). We use an Arrhenius equation derived from experiments conducted on Etna and Stromboli basalts for temperature, pressure, and H 2 O concentrations that are relevant to the Fuego magma (Fig.…”