Geophysical Exploration for Prospective Geothermal Resources in the Tarawera Forest

Abstract

An integrated geophysical survey, involving resistivity, gravity and magnetic measurements, was conducted early in 1987 over a 300km2 area within and north of the Tarawera Forest, to investigate potential geothermal resources for Fletcher Challenge Ltd. Two significant anomalies have been delineated. The first is the Tikorangi resistivity and magnetic low, associated with the north-eastern boundary of the Haroharo Caldera and centered south of the Tikorangi solfataras. The second anomaly, which is situated within the Puhipuhi Basin, east of the caldera, is postulated to represent a separate but cooling geothermal system, with implications of possible epithermal mineralisation. Interpretation of the gravity measurements has led to identification of a north-east trending graben passing through Lake Rotoma, and intersecting the Haroharo Caldera near Tikorangi. combined interpretation Of all available data resulted in a pre-drilling conceptual hydrological model for the Tikorangi system and a target for future exploration drilling.