Delineating geothermal upflow from surface features: a Wai-O-Tapu case study

HAMILTON, AYRTON; CAMPBELL, K.; GUIDO, D.; DOBSON, M.; HAMILTON, T.; PENROSE, L.; DRAKE, B.; ROWE, M.

Congreso; 16th Biennial Meeting SGA 2022; 2022

The Waiotapu geothermal system has the largest area of surface alteration of the >20 active high enthalpy geothermal systems in the Taupō Volcanic Zone, New Zealand, with the greatest variety of active and preserved surface manifestations. These surface features have been formed by varied subsurface water-rock interactions, including geothermal upflow and outflow. This study examines a preserved siliceous sinter sheet, known as Northern Waiotapu and dated in this study at 1,111 (±20) years BP, which formed from near neutral alkali pH fluids. The Northern Waiotapu sinter sheet is currently being overprinted by 20 newly active hot springs, with temperatures ranging from 38.4°C to 99.3°C and pH ranging from 2.56 to 8.77, including the first reported high temperature, neutral pH hot springs within the Waiotapu geothermal field. In this study, we examine the textures, trace elemental concentrations, including gold, as well as fluid chemistry of the preserved and active hot springs at the Northern Waiotapu site, and compare these data to Champagne Pool in the main tourist area, to understand the spatial and temporal association of sinter in relation to delineating primary geothermal upflow and potential subsurface mineralization. The chemical, textural and traceelemental results of this study suggest that Northern Waiotapu preserved and active deposits represent geothermal upflow with potential for mineralization at depth. This maybe analogous to the Miocene Favona epithermal deposit in the Hauraki Goldfield, New Zealand.