Geological and geothermal mapping of the Slaga-Arnarvatn area , Reykjanes penisula, SW-Iceland

Abstract

Slaga-Arnarvatn area is part of the Krýsuvík geothermal field, one of 27 known high-temperature geothermal fields in Iceland. Geothermal resources in the Krýsuvík field are not exploited today but several research programmes have been carried out intermittently since the 1950s. The research project described here is a part of the author’s UNU-GTP mapping exercise in 2009. This contribution also serves as part of a current geological mapping survey of the Krýsuvík geothermal field, undertaken by ISOR for the HS Orka hf energy company. The geology, geothermal manifestations and surface hydrothermal alteration have been mapped, resulting in two separate maps: a geological map and a geothermal map. The bedrock is composed of four hyaloclastite units, erupted subglacially in Upper Pleistocene time, and three interglacial basaltic lava series and Holocene lavas. The hyaloclastite units form NE-SW trending ridges dissected by normal faults, fissures and fractures which predominantly trend NE-SW. The study area also exhibits eruptive craters of Upper Pleistocene and Holocene ages. The linear distribution of both active and extinct geothermal manifestations correlates to the fault system. The surface alteration grades in intensity from slight to intense. A simple hydrothermal conceptual model is presented at the end of this report, based on the present study and a literary review of earlier and current research in the Krýsuvík field.