Recent geophysical exploration of the Kawerau geothermal field, North Island, New Zealand

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Abstract
Resistivity surveys carried out in 1970 have shown that the Kawerau Geothermal Field has a cross-sectional area of 6 to 10 km2 at intermediate depths (approximately ½ km). In the light of these surveys, previously published geophysical data have been reinterpreted, and the geological setting and stratigraphy have been re-examined. Temperature measurements made in wells during the injection of cold water indicate that the best production of hot water comes from andesite at a depth of 750 to 900 m. Because core samples of this andesite have low porosity, the major production is likely to be from fractures in the andesite. The fractures in the andesite are thought to have been caused by recent extrusion of dacite.