GRC Transactions, Vol. 38, 2014 Overprinting Hydrothermal Systems in the Taupo Volcanic Zone Sarah D. Milicich1, Isabelle Chambefort2, Greg Bignall2, and John Clark3 1GNS Science, Lower Hutt, New Zealand 2GNS Science, Wairakei Research Centre, Taupo, New Zealand 3Mighty River Power Ltd, Rotoru, New Zealand
[email protected] Keywords and evolution. Numerical modelling (e.g., Kissling and Weir, New Zealand, Taupo Volcanic Zone, Kawerau, geothermal 2005; Kissling et al., 2009) suggest TVZ geothermal systems system, longevity, heat source, stable isotopes, fluid inclusions have lifetimes similar to that of the TVZ (i.e., ~2 Myr), with the heat fed from depths of ~8 - 10 km (i.e., below the inferred brittle- ductile transition: Bryan et al., 1999). These studies suggest the Abstract hydrothermal systems are fixed in their geographic position, but are not positioned above a localised heat source. Rather, heat driv- Numerical reservoir modelling point to geothermal systems ing the hydrothermal systems results from deep ‘under-plating’ in the Taupo Volcanic Zone (TVZ, New Zealand) having life- of magma. Recent work undertaken at the Kawerau geothermal times similar to that of the TVZ itself, with heat fed from below system (Fig. 1), where age data can be used to pin the geological the brittle-ductile transition in the TVZ crust (~8-10 km). The history, suggests that the lifetime of individual high-temperature models suggest the geothermal systems are relatively fixed in hydrothermal systems are characterised by episodic thermal geographic position, but are not positioned above a localised events, impacting on the order of tens of thousands of years, heat source.