The spatial distribution of the geothermal fields in the Taupo Volcanic Zone, New Zealand

Abstract

A numerical model of the large-scale water and heat flows within the Taupo Volcanic Zone (TVZ), New Zealand is constructed. In the model the regions of high permeability and heat flow in the TVZ coincide, and lie within the TVZ envelope, defined to contain the Taupo Fault Belt and the most recent caldera collapse structures. The model correctly predicts the absence of geothermal fields in the central region of the TVZ, where cold surface groundwater descends to depths close to 8 km before being heated and ascending in discrete plumes at the permeability barrier which occurs at the boundary of the TVZ envelope. The locations of these plumes can be identified with most of the major geothermal fields in the TVZ (Tokaanu, Lake Taupo, Wairakei and Tauhara, Rotokawa, Ohaaki, Waiotapu and Waikite, Tikitere, Rotoiti and Rotoma, Rotorua, Mokai). In addition, the model predicts two bands of convective upflow across the TVZ, both of which correspond roughly to the known geothermal features of Ngatamariki and Orakeikorako in the south, and Lakes Rotomahana and Tarawera in the north.