FAVORABLE STRUCTURAL SETTINGS FOR POTENTIAL GEOTHERMAL UPWELLINGS IN THE CENTRAL TAUPO VOLCANIC ZONE, NEW ZEALAND

The Taupo Volcanic Zone (TVZ) in New Zealand is a volcanic and extensional region that contains an abundance of geothermal resources. Previous research has identified favorable structural settings for geothermal activity in extensional tectonic settings. These settings commonly host blind geothermal systems with no surface hot springs or steam vents in some geothermal provinces, such as the Great Basin region of the western USA. In the TVZ, however, it is unclear whether blind geothermal systems host an appreciable amount of the geothermal resources. This study examines the distribution of favorable fault settings in the Rotorua and Ngakuru graben areas of the central TVZ as a proxy for potential blind geothermal systems. We identified four accommodation zones (4%), 22 fault intersections (21%), 40 fault terminations (39%), 12 large step-overs (12%), 24 domes (23%), and one dike termination (1%) as potential favorable settings for geothermal activity. Notably, young volcanic and sedimentary units obscure many structures that may host fluid upwellings. Relatively large favorable structural settings that lack surficial geothermal features include step-overs along the Ngakuru fault and the area north of the northeastern end of the Whirinaki fault. In order to determine if these locations contain deep geothermal fluid upwellings, the fault data analysis of the favorable structural settings performed in this study should be supplemented with other data types, such as gravity, magnetotelluric, and seismic data.