Using Numerical Models to Understand What Controls the Locations of Geothermal Systems in the Taupo Volcanic Zone, New Zealand

The Taupo Volcanic Zone (TVZ), located in the central North Island of New Zealand, is an actively rifting volcanic arc. Heat flux in the central part of the TVZ is exceptionally high (700 mW/m), and is focussed at the surface through 23 high-temperature geothermal systems. Many of these systems are closely spaced (~5-7 km) with some appearing to align parallel to the eastern TVZ rift margin, while others appear more randomly located. Understanding what controls the locations of the geothermal systems is important to determine whether systems are connected and interacting at depth, to identify where blind systems might be, and to understand how heat output might change over time. Numerical fluid flow models allow us to test how the locations of geothermal systems are influenced by variables such as rock properties, heat and fluid sources, and faulting. For a region within the TVZ, we have created simplified models and individually varied surface recharge, lithology, permeability, and surface topography. Comparing model outputs with geothermal upflow zones interpreted from geophysical resistivity surveys shows that there is a narrow bulk permeability range within which convective heat flow would occur. Adding topography to a homogeneous model within this permeability range results in a number of upflow zones in very similar locations to those observed in the TVZ.