New heat flow data from the Veiholmen and Raudsand boreholes, middle Norway

Abstract

New thermal data for Fennoscandia have been recently acquired in two boreholes, Veiholmen and Raudsand 5, which are located in the northern part of Møre and Romsdal county of middle Norway. The calculated values of the uncorrected average heat flow density are 55 and 56 mW/m2 within the Veiholmen and Raudsand 5 boreholes, respectively. But, the values of average heat flow density, corrected for topography and palaeoclimate, are the following: 71 mW/m2 within the Veiholmen borehole and 79 mW/m2 within the Raudsand 5 borehole. The estimated palaeoclimatic corrections are relatively high and reach almost 20 mW/m2, showing the significance of taking into account the influence of the last glacial periods on the present-day thermal regime within the uppermost crust of Fennoscandia for geothermal calculations. The heat flow density is slightly higher in the Raudsand 5 borehole than in the Veiholmen borehole, most likely, due to the presence of the massive gneisses within the Raudsand area, which are characterized by higher radiogenic heat production compared to the diorites on the Innveien Island, where the Veiholmen borehole is located. The latter demonstrates the importance of internal heat production within the crust in addition to the heat coming from the Earth’s interior.