## 3 Results and Discussion
### Spatial Distribution  
The spatial distribution of the major elements highlights the differences between both synclines (Figure 4). The Guadalmez syncline was found to be more siliceous than that of the Almaden, with higher Si contents in the quartzite-sandstone levels that exhibit a bimodal profile in the violin plot, with higher probabilities in low and high values of the dataset. The distribution of Al was markedly displaced towards the Almaden syncline, related to the greater presence of phyllosilicate-rich shales. Both Ca and Mg showed the highest concentrations in the western part of the study area (the Almaden syncline), where it could be associated with the granite from Garlitos, an area with a geological predominance of igneous rocks (see granodiorites in Figure 1), presenting a general alteration of its primary igneous minerals, replaced by secondary minerals with high concentrations of Ca, Mg, and Fe. Several local anomalies also appeared further east in the Almaden syncline that could be a consequence of the presence of various volcanic tuffs or even localized outcrops of highly altered basalts. The maximum values of Ca-Mg corresponded to various areas heavily anthropized by Pb-Zn-Ag mining. These deposits were exploited in the past and in their surroundings the igneous rocks are highly altered, producing the replacement of primary igneous minerals by carbonates, chlorite, and silica [32].  
Figure 3: (**a**) Correlation matrix for the Almaden and Guadalmez synclines and dendrograms for all samples (**b**), Almaden syncline (**c**), and Guadalmez syncline (**d**). A–D correspond to the different subgroups obtained.  
Figure 4: _Cont_.  
Figure 5 offers the spatial distribution of the most relevant trace elements: Hg, Sb, Pb, and As. The highest concentrations of Hg were found in the Almaden syncline, specifically on the southern branch, drawing a dispersion halo that, on its edges, coincided with the location of cinnab deposits, both stratabound and epithermal. In the violin graphs, it could be observed that the quartzite-sandstone levels contained Hg anomalous values, followed by magmatic rocks and ASQ. However, In the Guadalmez syncline, although the values were lower, the trend of anomalous values continued in the quartzites and ASQ, although not in the magmatic rocks. The distribution of the maximum values of Sb revealed it to be located in areas with low Hg values in both synclines, especially in Guadalmez, where the Sb maximum appears in dark blue areas on the Hg map (Figure 5). The violin graphs also showed a contrasting differentiation for this element, with anomalous values in the quartzite-sandstone levels and ASQ in Guadalmez and in the slates in the Almaden syncline. The other two elements (Pb and As) showed maximum concentrations in localized areas with markedly anomalous contents with respect to the rest of the dataset. The primary mineral samples obtained at the La Balanzona mine were identified with XRD as stibnite (Sb\({}_{2}\)S\({}_{3}\)), with binohimite (Pb\({}_{2}\)Sb\({}_{2}\)O\({}_{6}\)(O,OH)), and stibiconite (Sb\({}^{3+}\)(Sb\({}^{5+}\))\({}_{2}\)O\({}_{6}\)(OH)) as the main oxidized phases. In the Guadalmez syncline, the areas richest in Pb were found to coincide with the Sb maximum. It is not clear whether the presence of Sb and Pb has a genetic relationship or whether small Pb mineralizations were emplaced where Sb deposits would later form, but the result is that the weathering of secondary Sb-Pb minerals occurred [33].  
Figure 4: Spatial distribution maps (**A**) and violin plots (**B,C**) of major elements (all data are expressed as a percentage). ASQ: alternations of shales and quartzites, IR: igneous rocks, QS: quartzites and sandstones, Sl: slates.  
Figure 5: \(Cont\).