Wairakei: a Natural Geochemical Laboratory

Abstract

The Wairakei-Tauahara geothermal system (as it is now called but here abbreviated) is justly world famous, and not only for its being the first hot water geothermal system to generate electricity and the advances in engineering that this entailed.

Wairakei is also a large, open-ended, natural laboratory. Helping solve its practical problems greatly expanded our scientific knowledge of:
.. The geology, structure and evolution of the Taupo Volcanic Zone.
.. The principles and products of fluid/mineral interactions.

Drilling at Wairakei resulted in the recovery of many cores that yielded much important stratigraphic information. Staff of the New Zealand Geological Survey of the Department of Scientific and Industrial Research (DSIR) studied these cores, notably George Grindley, Jim Healy and Alfred Steiner (petrologist). On occasions, Bill Watters, Ted Lloyd and Don Rishworth assisted. George and Jim had many healthy disagreements, especially about the role of faults in providing permeability, with others of us either taking sides or sitting on the fence.

Mr Steiner (he was always called Mr, even when he received his DSc) also found that many of the cores were hydrothermally altered as a result of reactions between the thermal fluids and the primary minerals. He used the identities of the secondary minerals to predict some of the reservoir conditions, for example, subsurface temperatures, and permeability within