Delineation of Shallow Structural Features Controlling the Flow of Geothermal Fluids at Butchers Pool, Reporoa, New Zealand

Abstract

The shallow (<200m) resistivity structure around the “Butchers Pool” hot spring area, Reporoa, New Zealand has been determined using time domain electromagnetic soundings. A 3-D resistivity model was developed in Earthvision using 1-D inversions of TEM soundings collected at 26 sites. The resistivity data and 3-D model suggest that Butchers Pool is an upwelling of geothermal fluids near the edge of a rhyolitic dome. The geothermal fluids penetrate a capping layer of lacustrine sediments (Huka Falls formation) and appear to pass along a NW trending corridor of higher permeability probably originating from the Reporoa geothermal system. The source of geothermal fluids from the northwest is interpreted to be from an aquifer at about 90m depth (approx. 220m RL).