Supercritical Fluid Geochemistry in Geothermal Systems

Figure 9

Mechanism of conductive boiling of subcritical fluids in cracks near the brittle-ductile transition (BDT). (a) Conductive boiling of a subcritical fluid to supercritical conditions along a single crack. (b) Volumes of secondary minerals (from Heřmanská et al. [31]) formed upon conductive boiling as a function of specific enthalpy along a crack. (c) Time for closure of a crack with a width of 0.05 mm as a function of specific enthalpy and fluid mass flux. Values for the range of fluid mass flux are taken from Norton and Knight [54]. (d) Time for closure of a crack with variable width based on permeability values of Norton and Knapp [53], Lamur et al. [51], and Watanabe et al., [52] using an average fluid mass flux of 10^-5 kg m^-2 s^-1 [54]. Closure of the crack accelerates as soon as quartz starts to precipitate.