Interpretation of Magnetic Anomalies Over the Reporoa Geothermal Field, Taupo Volcanic Zone, New Zealand

Abstract

The Reporoa geothermal field is located in an area of the Taupo Volcanic Zone (TVZ) which exhibits a complex magnetic source pattern since hydrothermally demagnetised rocks occur together with younger normally magnetised and older reversely magnetised volcanic rocks. No distinct negative residual magnetic anomalies could be observed over the central part of the prospect during our aeromagnetic survey conducted at c.760 m asl. However, when results of detailed geological studies and magnetic studies of cores are considered, it was found that the subdued magnetic anomalies over the Reporoa Field contain a small component reflecting demagnetised rocks which are surrounded, in part, by reversely magnetised rocks at the bottom of the Reporoa Caldera.