Geothermal mapping in Middalur field, Hengill area, SW-Iceland

Abstract

Middalur area is a part of the Hengill volcanic massif located in the western branch of the volcanic rift zone in SW-Iceland. It is a high-temperature geothermal field endowed with impressive geothermal manifestations which include warm and hot springs, mud pools, steam vents (fumaroles), warm grounds, hot grounds and clay alterations. The geothermal exploration carried out in the area involved mapping surface geothermal manifestations and shallow soil temperature measurements around the active manifestations to delineate the warm (>15°C) and hot (>50°C) isotherms within which many hot springs, mud pools, steam vents and warm springs occur. The results indicate that tectonic features control geothermal activity in the area. Eight faults, inferred faults and fracture were mapped based on aerial photographs, field studies and alignment of the geothermal manifestations. The trends of the geothermal manifestations are N-S, NE-SW and E-W. Most of hot springs precipitate calcite. The proposed geothermal model of the area shows the geothermal activity associated with active faults and fractures.