Geophysical exploration of high-temperature geothermal areas using resistivity methods : case study : Theistareykir area, NE-Iceland

Abstract

Measuring the electrical resistivity, ρ, of the subsurface is the most powerful geophysical prospecting method in high-temperature geothermal exploration and the main method used in delineating geothermal resources. Resistivity surveys using TEM and MT methods have been done in the Theistareykir geothermal area since 2004. In this work, sixteen TEM and MT soundings on two profiles were jointly inverted, based on 1D models. Cross-sections and iso-resistivity maps of the joint inversion models of the TEM and MT data from Theistareykir geothermal area, NEIceland reveal features similar to other high-temperature areas in Iceland, with a resistive zone reflecting unaltered rock formations, a shallow conductive cap and a resistive core reflecting chlorite-epidote alteration. Two deep conductors (<10 Ωm), possibly related to the heat source, were interpreted north of Bóndhólsskard and northeast of Stórihver. Good correlation between the subsurface resistivity and hydrothermal alteration in borehole ThG-05 was confirmed.