Magnetic Anomalies over the Wairakei Geothermal Field, Central North Island, New Zealand
- Key words
- Exploration; New Zealand; North Island; Wairakei; Airborne Magnetic Survey; Hydrothermal Alteration; Models; Rhyolites; Andesites; Ignimbrites; Resistivity; Taupo Volcanic Zone
- Location
- Wairakei, New Zealand; Taupo Volcanic Zone
- Conference
- Geothermal Resources Council Transactions
- Year
- 1992
- Session
- Exploration; Geophysical surveys; Magnetic surveys; Computer
- Language
- English
Abstract
A low level airborne magnetic survey (760 m a.s.l) covering the Wairakei area in the Taupo Volcanic Zone (Central North Island of New Zealand) was undertaken in 1984. A detailed analysis showed that both the normal geomagnetic field (IGRF) and a set of long wavelength regional magnetic anomalies had to be removed before second order residual magnetic anomalies, which contain information about the extent of demagnetized volcanic reservoir rocks, could be obtained. A negative residual magnetic anomaly (about 180 nT) in the NW part of the Wairakei field can be interpreted by hydrothermal demagnetization of a sequence of rhyolitic pyroclastics below sea level; this interpretation is supported by magnetization measurements of core samples from deep wells. Hydrothermal demagnetization also occurs within the adjacent Tauhara geothermal field (poorly covered by our aeromagnetic survey) which at greater depth is connected with the Wairakei field.
Copyright 1992, Geothermal Resources Council. Readers who download papers from this site should honour the copyright of the original authors, and may not copy or distribute the work further without the permission of the original publisher.