The Geothermal Exploration of the -Oxarfjordur High-Temperature Area, Ne-Iceland

Abstract

The Oxarfjordur lowlands in NE-Iceland are characterized by sediments from a glacial river and by fissure swarms from active central volcanoes further inland. A major graben is associated with the recently active Krafla fissure swarm in the central part of the area, where the sediments may be up to 1000 m thick. Rather insignificant surface geothermal activity in the form of warm springs and warm ground is encountered at a few locations within the fissure swarm. A systematic geothermal exploration in the eighties and the nineties has confirmed the existence of high-temperature geothermal activity within the Krafla fissure swarm. Resistivity soundings have outlined an area of at least 10 km2 with a very low resistivity, 1-5 É?m. The low resistivity surrounds a high-resistivity body which is associated with alteration minerals forming at or above 250ÅãC. Another low-resistivity area is seen near the coast. Geochemical analysis and calculations based on mixing models indicate temperatures above 200ÅãC. This has been supported by studies of alteration minerals in samples from shallow exploration wells. Seismic refraction measurements also show a high-velocity an omaly associated with the high-temperature activity as well as anomalously high seismic noise.