## 5 Discussion  
### Geochemical Analyses  
As mentioned in the previous section, the XRF results (Table 2) indicate that the samples fall in the typical range between granoidorites and granites [36], given their SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) contents. The density of the samples also fits with the average values of granoidorites and granites, within the 0.25 percentile [19]. However, the geochemical analyses indicate atypically high concentrations of U, since the expected concentration of U in granoidorites is between 2.2 and 6.1 ppm [27], although the most complete recent study established an average of 3.93 \(\pm\) 3.27 ppm [18]. In all samples, the concentration of U was above this range, except in the case of sample P7 (2.35 ppm), which showed an atypically low value compared to the rest of the samples. In the case of Th, the values obtained were also higher than expected, since the Th content in granoidorites normally ranges between 8 and 33 ppm [27], although [PERSON] [38] indicated that it may be higher in granites. Recent studies place its average concentration at 14.8 \(\pm\) 13.2 ppm [18]. These data allow us to compare the concentration of U with that of Th through the Th/U ratio (Table 4). This ratio is estimated to average 3.7-4.0 in the Earth's crust [39], which implies 3-6 times more Th than U. In the samples studied, the ratio ranged between 0.25 and 0.74 from the geochemical analyses (Table 4), with the average Th/U being 0.49. These values are far from those expected on average for granoidorites and granites, which range between 1 [39] and 3.5-6.3 [27]. Similar values of U and Th have been previously observed in granites from the northwest of the Iberian Peninsula [40]. Therefore, in most samples and for the granoidorites studied, the Th/U ratio was anomalously low [18]. The cause of this anomalous relationship and the abnormally high values of U  
Figure 4: Interpolation maps obtained from the GIS with estimates of radiogenic heat production (RHP) obtained by (**A**) GRS, (**B**) GRS with a collimator, and (**C**) geochemical analyses (XRF + ICP-MS). and Th is the composition of the rock, since other processes--such as weathering or radon losses--tend to decrease the concentration of U and, therefore, increase the Th/U ratio. This also implies that weathering had not reduced the U concentration, as observed in the most weathered sample (P16), where the Th/U ratio was 0.34 and the U concentration was 24 ppm. Recent studies [13; 40] have attributed this high concentration of U to the presence of accessory minerals that contain these elements (i.e., monazite, thorianite, thorite) in granitoids of the area. Similar and anomalously low Th/U ratios have been observed in some Proterozoic granitoids in other areas of the world and, to a lesser extent, in some Palaeozoic ones [18; 41]. For K, the results indicate values more in line with those expected in grandiorites and granites [27; 39; 42], although they are also slightly higher than the average values compiled by [PERSON] et al. [18], which were situated at 2.79 \(\pm\) 1.44%. The average K/U ratio for the Earth's crust has been estimated to be 1.0 \(\times\) 10\({}^{-4}\)[38]. However, in the rocks studied, this ratio was 4.56 \(\times\) 10\({}^{-4}\) for geochemical analyses, 2.60 \(\times\) 10\({}^{-4}\) for those carried out via GRS without a collimator, and 3.41 \(\times\) 10\({}^{-4}\) for those carried out with a collimator (Table 4). These anomalously high ratios have also been observed in some Proterozoic granitoids and, to a lesser extent, in some Palaeozoic ones [18].