Geological and geothermal mapping in the Trölladyngja field, SW-Iceland

Abstract

The Trölladyngja field in the Krýsuvík area is a part of five high-temperature geothermal fields in the Reykjanes Peninsula in southwest Iceland. The area has undergone extensive research for exploitation of geothermal resources. Findings of this report contribute to the current investigations of the study area and also accomplish the author´s training in Geological Exploration studies at the UNU-GTP, in Iceland 2012. Geological and geothermal mapping of the study area was conducted and both maps are presented. There are three main lithological units: pillow lavas, hyaloclastite tuffs formed during sub-glacial eruptions in the last glacial period (Weichsel), and Holocene lavas during post-glacial eruptions that cover a substantial part of the study area. Normal faults trending N20°-40°E are dense on the hyaloclastite ridges and are covered by the Holocene lava in the valleys. Several fissures and dykes occur in a similar trend to the faults. Geothermal mapping of surface manifestations revealed that most previously active sites have been cooling and the remains of extinct altered clay or hot grounds were mapped. Fumaroles are the only active manifestations that occur linearly along the NE-SW trending faults and fissures, indicating up-flow zones that are controlled by these structures. A geothermal conceptual model is presented from which possible drilling targets for production and/or exploration wells are inferred.