Deep Electrical Structure Beneath the Taupo Volcanic Zone and the Source of Geothermal Heat

Abstract

Electrical resistivity surveys now provide images of the electrical structure beneath the Taupo Volcanic Zone (TVZ) to depths that exceed those of the base of the geothermal systems. Multiplesource bipole-dipole surveys show there are three distinctive zones in the upper crust across the TVZ. Highly conductive basins up to 5 km deep, found on both the east and west sides of the TVZ, are separated by a resistive structure beneath the (cold) Taupo Fault Belt. At greater depths, inversion of magnetotelluric data along a profile crossing the TVZ shows a significant conductive structure at a depth of about 10 km. This conductor may be associated with magma within the crust and hence may represent the ultimate source of geothermal heat.