The Natural State of Kawerau Geothermal Field

Abstract

Kawerau is a relatively large geothermal field sited on the northeast boundary of the Taupo Volcanic Zone. Subsurface temperatures range to over 31 with the highest measured temperatures occurring inthe south of the fieldtowards Putauaki (Mt Edgecumbe). The highest pressures and in situ chloride concentrations are also towards the south of the field, consistent with deep upflow from this location. Resistivity surveys find a low resistivity anomaly of 19 35 in area at about 500 m depth associated with the field. However most surface thermal activity is located in less than half this area, and the productivity of much of the resistivity anomaly is unproven. The natural surface heat flow from thermal activity is estimatedto be about 100 with possibly an additional subsurface outflow of the order of 50 This outflow may be the cause of anomalous boron and chloride concentrations in groundwaters on the Rangitaiki plains 5-10 north of the field.