Metal-rich slurries
discharged from excess-enthalpy geothermal wells at Kawerau (NZ) indicate that
an efficient ore precipitation mechanism operates in some feedzones. In our
conceptual model, which takes into account the relative permeabilities of liquid
and gas phases in boiling fluids, a metal-precipitating liquid phase is
effectively immobilised along boiling fronts, leading to the formation of highly
concentrated ore. Chemical equilibrium and heat/mass transport modelling
demonstrate the general applicability of this conceptual model to hydrothermal
eruption environments.