Dynamics and storage of brine in mid-ocean ridge hydrothermal systems

• Published in: Journal of Geophysical Research. B. Solid Earth 2006-06, Vol.111 (B6), p.n/a
• Main Authors: Fontaine, Fabrice J., Wilcock, William S. D.
• Format: Article
• Language: English
• Subjects: convection modeling; Earth sciences; Earth, ocean, space; Exact sciences and technology; hydrothermal brines; Marine; mid-ocean ridges
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2005JB003866

Mid‐ocean ridge hydrothermal systems are known to vent fluids with salinities substantially different from seawater as a result of phase separation and segregation of the resulting vapor and brine phases. Time series of vent temperature and salinity (chlorinity) show that some black‐smoker vent fields such as the Main Endeavour Field on the Juan de Fuca Ridge have vented fluids with salinities well below seawater for over a decade, which raises important questions concerning the fate of brines in these systems. One widely accepted model is that high‐density brines formed by supercritical phase separation sink to the base of hydrothermal systems, leading to the development of a two‐layer system in which a recirculating brine layer underlies a single‐pass seawater cell. We first present theoretical arguments to constrain the dynamics of such a deep brine layer in a system still undergoing phase separation, and we conclude that if brines are stored in a basal layer, they are unlikely to convect because they will be stably stratified. One consequence of this result is that the brine layer beneath black smoker systems has to be thin (