Subcritical Phase Separation and Occurrence of Deep-Seated Brines at the NW Caldera Vent Field, Brothers Volcano: Evidence from Fluid Inclusions in Hydrothermal Precipitates

Figure 9

Mixing model 1. (a) Salinity-temperature relation for isenthalpic mixing paths of mixtures between phase-separated hydrothermal fluids and ambient seawater at 170 bar. Thin black horizontal curves represent isobaric V+L curves at 135 and 170 bar (calculated after Driesner and Heinrich [57]). The thick black curves denote isenthalpic mixing of the chosen brine-vapor pair. The thin lines represent fluids derived from phase segregation of the phase-separated brine and vapor. The color code gives the mass fraction of the hydrothermal fluid in the mix (i.e., pure hydrothermal fluid to pure seawater). (b) Relationship between temperature and ⁸⁷Sr/⁸⁶Sr for mixing model 1. Vertical lines represent the natural variability of inclusion data in and (dashed lines: min to max, thick lines: ). Note how low-saline high-temperature fluids can precipitate sulfate with near seawater ⁸⁷Sr/⁸⁶Sr. (c) Relationship between salinity and ⁸⁷/⁸⁶Sr for the mixing model.