Phase separation in seafloor geothermal systems: An experimental study of the effects on metal transport

Experimental investigations were carried out by reacting natural and evolved sea-water with crystalline basalt from the Juan de Fuca Ridge in order to study the effects of vapour-liquid phase separation on metal mobilization in sea-floor geothermal systems in which phase separation occurs between the top of a magma chamber (300-500 bar) and the sea-floor (230-250 bar). The geochemical processes produced by a combination of closed-system phase separation and adiabatic expansion under the conditions characterizing the sea-floor geothermal systems resulted in a significant increase in the acidity and concentration of heavy metals in the liquid phase and strikingly high concentrations of metals in the vapour.