| Title | Comparison of Geological and Thermal Structure of Three High-temperature Geothermal Areas in the Neo-volcanic Zone of NE-Iceland |
|---|---|
| Authors | Anette K. MORTENSEN |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | volcanic system, fissure swarm, permeability, glacial loading, temperature reversal, Theistareykir, Krafla, Námafjall, Iceland |
| Abstract | The northern part of the neo-volcanic zone (NVZ) in NE-Iceland consist of four volcanic systems, which are arranged in a right stepping en enchelon formation with a north-south direction. The volcanic systems are dominated by up to 80-90 km long fissure swarms extending from a central volcano, but volcanic eruptions, silicic rocks and high-temperature geothermal systems are focused at the central volcanoes, where calderas can form. Landsvirkjun has explored and developed three high-temperature geothermal areas in NE-Iceland; Theistareykir geothermal area within Theistareykir volcanic system and Krafla and Námafjall geothermal areas within Krafla volcanic system. In this paper similarities and differences in the geological and thermal structure of these three geothermal areas will be highlighted. Krafla high-temperature geothermal area is centred in the eastern part of Krafla caldera, which is intersected by Krafla fissure swarm. Námafjall high-temperature geothermal area is located in the southern part of Krafla fissure swarm and may represent a parasitic volcanic centre within the Krafla volcanic system partially fed by lateral fissure eruptions from Krafla central volcano. Theistareykir high-temperature geothermal area is in the eastern part of Theistareykir fissure swarm and is located within a central volcano, which is dominated by basaltic volcanic shields and table mountains. The high temperature geothermal areas at these three locations have been active during changing glacial and post-glacial climatic conditions. Comparison of alteration with current temperature state in the geothermal systems indicate that the high-temperature geothermal areas have previously been much larger than they are today, which may possibly tie to changing pressure conditions during glacial loading of the crust. On the other hand, areas of subsequent temperature reversal in the geothermal reservoirs are closely tied to the main zone of deformation within the fissure swarms. |