Temporal and spatial radiogenic heat production rate of granitic plutons from the Eastern Pontides Orogenic Belt, NE Turkey: Constraints for the geothermal resources

In Turkey, an evaluation of the geothermal potential of the granitic rocks is important in long-term sustainable renewable energy projects due to increasing energy demand. Therefore, granitic plutons are gaining importance due to their ability to generate a substantial amount of geothermal potential. The Eastern Pontides Orogenic Belt in NE Turkey contains a variety of granitic plutons changing in age, size, and composition. In this study, we examined the temporal distribution of radiogenic heat production by using the contents of heat-producing elements (U, Th, K) of the granitic plutons. The average U, Th, and K concentrations for the granitic plutons are 2.97±0.95 ppm, 13.48±3.48 ppm and 2.69±0.47 % for Paleozoic plutons, 1.83±0.98 ppm, 8.58±5.10 ppm and 1.77±0.80 % for Jurassic plutons, 5.24±1.64 ppm, 26.02±6.43 ppm and 3.17±0.49 % for Cretaceous plutons, and 3.82±0.90 ppm, 15.79±4.27 ppm and 2.88±0.40 % for Eocene plutons, respectively. Radiogenic heat production rates are 1.43-2.73 µW/m3 (a mean value = 1.93±0.53 µW/m3) for Paleozoic plutons, 0.74-1.70 µW/m3 (a mean value = 1.22±0.67 µW/m3) for Jurassic plutons, 0.66-6.28 µW/m3 (a mean value = 3.41±0.91 µW/m3) for Cretaceous plutons and 1.15-5.22 µW/m3 (a mean value = 2.32±0.30 µW/m3) for Eocene plutons. Generally, the studied plutons are classified as low- to moderate heat-production granitoids. However, some Cretaceous and Eocene granitic plutons with radiogenic heat production values of 5.22-6.28 µW/m3 are considered as high heat-producing granitoids. The thermal indications in the region can be related to radiogenic heat generation and the neotectonic activity of the region. Considering the large volume of the Cretaceous- and Eocene- aged granitic plutons in the EPOB, the moderate to high radiogenic heat production of the granitic plutons in some areas has a significant geothermal impact and can be considered as the potential of enhanced geothermal systems (EGS) for the future energy demand of the region.