| Summary: | The high-temperature geothermal area of Þeistareykir volcanic system in NE Iceland shows thermal activity by several different heat flow processes. A distinct heat flow process is the transportation of heat through a large groundwater stream across the area. A highly transmissive aquifer is centered within the fractured Þeistareykir fissure swarm. The purpose of this thesis is to estimate the total excess heat flow and relative role of the different heat flow processes in the area, but previous studies on the geothermal system have mainly focused on resource assessments. The excess heat flow refers to heat flow originating from the geothermal system beyond the general ambient heat flow surrounding the area. Heat flow from Þeistareykir occurs by two main processes: heat flow through thermal groundwater, and heat flow through the surface, which is further divided into four different heat flow processes. Heat flow by groundwater streams is estimated using available groundwater model for NE Iceland, and observations and interpolation of temperature measurements of the aquifer, partly considering previously inferred ground resistivity anomalies in the area. For this purpose, results from local resistivity survey interpretations are used to better deduce the relative distribution of thermal groundwater. Along the main groundwater stream along the Þeistareykir fissure swarm, heat flow estimates are carried out at four cross-sections, estimating total excess heat flow and rate of heat loss along the fissure swarm. Next to the Þeistareykir geothermal area, total excess heat flow by groundwater is inferred to be 915 ± 75 MW, considering the methods used. Six km further north along the Þeistareykir fissure swarm, the excess heat flow is 640 ± 4 MW and still 14 km further, at the Lón estuary at the north coast of Iceland, the excess heat flow is estimated 51 ± 4 MW, showing an average heat loss of 43 ± 3 MW/km at the aquifer along the Þeistareykir fissure swarm. The surface heat flow estimates are based on previous work at ...
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