Reservoir Geology of the Nesjavellir High Temperature Fields in SW-Iceland

Abstract

The geological structures that aflect the flow of geothermalfluid in the Nesjavellir system are deduced from variable data sources The eruptive lithology consists of basaltic hyaloclastites and lava series. Intrusive rocks dissect the succession below about 800 m depth and become dominant part of the strata below 1.500 m depth. The hydrothemal alteration depicts two outfow zonesflorn the Hengill mountain, the main one lying on the east side of the Kyrdalshryggur ridge. The aqugers in the reservoir appear to be related to sub-vertical faults and eruptivejssures, stratigraphic boundaries of eruptive units in the upper 800 m and basalt and intermediate intrusive rocks below that depth.