Geothermal exploration in Tindar and western side of Gufudalur, Hveragerdi, SW-Iceland

Abstract

The study area of Tindar and western side of Gufudalur is a part of the Hveragerdi central volcano area, which is located on the eastern margin of the western rift zone and the western margin of the South Iceland Seismic Zone (SISZ). Hyaloclastites and lava flows dominate the lithological units in the study area. Earthquakes with epicentres in the Hveragerdi central volcano are quite common. The most recent large-size earthquakes in the SISZ happened on the 29th of May 2008 with magnitudes of 5.5 a nd then 6.3, located between the towns of Selfoss and Hveragerdi (Khodayar et al., 2008, Brandsdóttir et al., 2010). These earthquakes created new geothermal manifestations and caused an increase in geothermal activity. New surface manifestations are still forming in the study area. Geothermal activity is widely distributed in the mapped area, the main manifestations being fumaroles and steam vents, mud pools, hot, warm and cold springs, and hot, warm and steaming grounds. The manifestations are mainly controlled by faults or fractures. The major alignment of manifestations is striking in the NE-SW direction, which coincides with the direction of major faults and fractures. In addition, NW-SE, NNW-SSE and N-S oriented faults/fractures are also present and play an important role in the enhancement of geothermal activity as well as the expansion of manifestation areas. The main purpose of this study was to map the surface manifestations, soil temperatures, and CO2 emission measurements, and investigate the relationship between the geothermal manifestations and geological structures such as faults, fractures and lineaments. There were 365 GPS locations of geothermal manifestations taken and divided into 12 separate manifestation areas. In addition, the present result was compared to results of previous geothermal investigations done in 1995 and in 2008, soon after the earthquakes.