Examination of Heat Flow and Resistivity Values at the Boundaries of the Geothermal System Beneath Lake Taupo, North Island, New Zealand

Abstract

Both the heat flow and resistivity anomalies associated with the hydrothermal system near the Horomatangi reefs in Lake Taupo have abrupt boundaries. A simple thermal model of the boundary to the hydrothermal system, assuming only conductive heat transfer, cannot produce the abrupt horizontal rate of change of heat flow observed, and implies a non-conductive thermal regime. This suggests that cold groundwater adjacent to the hydrothermal system is being drawn into the hydrothermal system producing the abrupt change in heat flow. By analogy the resistivity boundaries observed at several of the geothermal fields may also mark areas where the cold groundwater is or is being entrained into the geothermal fluids.