3D Basement (Visualisation) Model of the Taupo Volcanic Zone

Abstract

The Taupo Volcanic Zone (TVZ; ~350 km long, ~60 km wide) constitutes the southern portion of the active Lau-Havre-Taupo extensional back arc basin, and formed by extension of crust above the Hikurangi subduction zone. The fault-controlled volcano-tectonic depression is infilled by Quaternary volcanic rock and sediments, with underlying basement greywacke faulted to 1-2 km below sea level.

A geological basement model of TVZ Torlesse greywacke is presented. The 3D model, generated using Leapfrog Geothermal software, is based on revised interpretation of acquired TVZ gravity data, and constrained by geological information used to establish recently updated regional 250,000-scale (Q-map), geological maps of the area and geothermal drillhole logging data collected over the last 60 years from several geothermal fields (including Kawerau, Ngatamariki, Ohaaki and Wairakei-Tauhara).

The 3D visualisation model of the TVZ Torlesse greywacke basement provides part of the story for establishment of the geological and structural framework of the TVZ, supports our understanding of the deep rheology and controls on deep-seated permeability, and represents an important output from an integrated, multi-disciplinary study that aims to support future development of New Zealand’s high enthalpy (>250°C) geothermal resources, which are hosted in some fields (e.g. Kawerau) by fractured Torlesse greywacke.