| Abstract |
The Hengill geothermal system in SW Iceland, 30 km east of Reykjavík, is a major energy source for the Capital Region. Operated by Reykjavík Energy’s subsidiary ON Power, it hosts two co-generation plants with a combined capacity of 423 MWe and 540 MWth. Located within the rifting zone of the Mid-Atlantic Ridge, the nature of its heat sources remains uncertain. To explore the hypothesis that such systems can form via repeated shallow dike intrusions, a numerical modeling study was conducted. Using the iTOUGH2–EOS1sc module, which simulates water under sub- and supercritical conditions, a reservoir model was developed to 4 km depth, incorporating a permeability structure based on Hengill observations. Dike intrusions ~2 km long and ~25 m wide were simulated at depths between 1.2 and 3.0 km b.s.l., representing crustal extension over ~1,250 years. Results indicate that dikes reaching 2.5 km b.s.l. or higher, at 900 °C and under lithostatic pressure, can generate temperature structures broadly consistent with those observed in the Hengill system within 5–10 thousand years, if they intersect permeable zones. These findings support the idea that high-temperature geothermal systems on divergent plate boundaries can form through repeated shallow diking, influencing the development and longevity of supercritical or superheated zones. |