Review of existing data for the evaluation and estimation of the geothermal potential in the basement of western Spain.

The last few years have been characterized by tremendous global instability due to assure energy supply. Global growth demands more and more resources at the same time as the population´s concern about climate change is increasing. In this context, geothermal energy, a green and renewable energy with the capacity to contribute to the transition of the energy market, is becoming increasingly important. This, together with the improvement in geothermal studies and the development of new exploitation methods, has triggered new geothermal targets to be considered during the last decades.

Geothermal studies in Spain were focused on sedimentary basins and volcanic settings during the 70´s and 80´s. In this framework, few investigations have been done on the western igneous massif of Spain. This study seeks to estimate and resume research on the geothermal potential of the Spanish basement. With that purpose this research analyzes high resolution airborne radiogenic data from Extremadura, Castilla La Mancha and Madrid (Geodata International Inc., 1980), acquired in the 70 and 80´s for uranium exploration, concentration measurements of Uranium, Thorium and Potassium from soil samples (Locutura et al. 2012) and temperature data from widespread hot springs along the studied area.

We have analyzed the concentration of the three heat producing elements in 9 plutons and estimated the heat production of each of them. In this regard, the high airborne-constrained concentrations of the plutons located in the north of Extremadura and west of Salamanca are noteworthy. In this area Uranium reaches 16.43 ppm, Thorium 14.52 ppm and Potassium 6.26 %. Same way a remarkable peak in heat production is located is this area with values up to 5.02 μW/m3. When comparing these data with the values obtained from the soil samples, the correlation between the two is remarkable. Furthermore, the positive radiometric anomalies of both maps coincide with the outcropping of granitic rocks and the location of most of the hot springs.

This work compiles vintage information of diverse origin in order to highlight areas with high geothermal potential in the basement of the westernmost Spain. The results of heat production and their relationship with the hot springs have shown that several of the Paleozoic plutons of the western igneous massif of Spain may have a great potential for geothermal projects.