| Title | Geochemistry and Origin of Geothermal Waters in NE Borgarfjördur, W-Iceland |
|---|---|
| Authors | Hrefna KRISTMANNSDÓTTIR, Axel BJÖRNSSON, Ãrný E. SVEINBJÖRNSDÓTTIR |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | geochemistry, geothermal water, stable isotope ratios, earthquake activity, recharge areas |
| Abstract | There is an extensive geothermal activity in the NE part of the Borgarfjördur region associated with an extensive earthquake activity connected with both the Western volcanic zone and the Snæfellsnes transverse zone. The reservoir temperatures are up to 150 °C.The main features in bedrock geology are Quaternary basaltic lavas, 0.8-3My old, closest to the active rift zone and Tertiary basalts older than 3My further to the west and north. Some postglacial lava-flows, younger than 11000y are encountered and both active and extinct central volcanos occur in the area. About once a year earthquake swarms of low magnitude with direction NNE-SSW connected to the western volcanic zone occur in the eastern part of the area. In the north and western parts earthquakes up to magnitude 6 have occurred. To the east on the border of the intern highland there are two big glaciers, Langjökull and EirÃksjökull. The hot springs in the Reykholtsdalur valley towards west appear to occur at the intersection of north¬westerly oriented young faults and northeasterly trending faults or dykes. The Húsafell geothermal field in the eastern part is associated with an extinct central volcano and the thermal manifestations occur along a layer of acidic tuff. Between those two fields are several others with lower temperatures. In the northern part of the area there is also extensive geothermal activity. There is a distinct difference in geochemistry of waters in the different geothermal fields and the recharge areas can clearly be differentiated by the stable isotope ratios. The water in most of the fields is classified as sulfate water with a few samples falling on the border line to bicarbonate water. The Húsafell water has the highest concentration of fluoride of any geothermal water in Iceland due to reaction with acidic rocks within the extinct central volcano. The recharge areas are both local and the glaciers and mountains in the eastern highlands. |