COMPUTERISED TOMOGRAPHY (CT) SCANNING OF CORE FROM TAUHARA GEOTHERMAL FIELD, NEW ZEALAND: A PILOT STUDY

Abstract

Computerized Tomography (CT) was used to scan core from the Tauhara geothermal field, Taupo Volcanic Zone, New Zealand. Six samples, representing the Mid and Lower Huka Falls Formation, Waiora Formation, Taupo Formation and the Crown Road Breccia were chosen for analysis. CT scans imaged individual 0.02 mm incremental slices, which provided a 3D image of the cored rock. CT imaging is sensitive to density changes, a property that readily changes in rocks as they undergo hydrothermal alteration. CT scanning has tracked zones of hydrothermal alteration within the Tauhara core and shown that even within one centimetre thick slices of rock, hydrothermal alteration and thermal fluid flow through a rock, is spatially patchy. This technique also enabled the mapping of void and fracture size, dimensions and connectivity. Scanning Electron Microscopy and petrographic microscopy provide supporting information for the CT scan observations.