Thermobarometric implications of silica-chloride contents of the Bio9 hydrothermal vent across two eruptive cycles. Measured silica (mmolal) and chloride (molal) data are superposed onto the Fontaine et al.  model to predict temperatures and pressures of equilibration. After each eruption, the vapors are noticeably chloride-poor. The top figure in the inset shows measured exit temperatures (open squares) compared to modeled reaction temperatures (filled squares), derived from temperatures predicted by the silica-chloride model (at left) across the eruptive cycle. Note that the extremely low exit temperatures are from fluids with high end-member Mg contents, suggesting dilution with seawater prior to sampling. The modeled pressures (bottom figure in the inset) correspond to the depth of equilibration for the fluid and oceanic crust as derived from application of the Fontaine et al.  model. In the inset, the red vertical lines indicate the 1991-1992 and 2005-2006 eruptions.
Media Type: Graph
Investigator: Julie Bryce