Geothermal exploration in Skardsmýrarfjall, Hengill area, SW-Iceland

Abstract

The present study area is a part of the active Hengill central volcano. It is categorized as a high-temperature area in line with measured and inferred temperature greater than 200°C at less than 1 km. The geothermal manifestations in the area are located above 300-400 m altitude. A boiling reservoir at some depth causes geothermal manifestations like hot ground. The distribution of geothermal manifestations appears to be controlled by faults/fractures almost in a NE-SW direction. In part of the area the bedrock is altered whereas the overlying glacial sediment is fresh, thus indicating declining activity since the area became ice free. Most of the geothermal manifestations lack native sulfur. The extinct hydrothermal alteration has probably reduced the porosity and permeability. This affects the present surface geothermal activity, most of which appears to be related to structural features like faults. Two types of geothermal activity are observed: a) Extinct alteration which is evidenced by greenish- reddish altered hyaloclastites, the alteration minerals are smectite and iron oxides. b) Present geothermal activity, represented by areas of hot geothermal manifestations are characterized by grey or dark brown to reddish brown smectitic clays.