At
Broadlands-Ohaaki geothermal system, TVZ, mineral distribution patterns in
geothermal wells are analogous to those in epithermal veins. Fluid flow through
geothermal wells is focused over vertical intervals >500 m with discharge at
rates up to 90 l/s. Focused flow at similar rates also occurs in natural systems
where hydrothermal eruption vents provide enhanced vertical permeability. These
vents are commonly aligned with the tectonic fabric, indicating fault control at
depth. We suggest that host rock strength and structural context exert
significant control on the hydrological regime conducive to epithermal
mineralisation.