## 5 Discussion
The elaborations concerning geothermometers (Figure 5 and Supplementary File Table S1), trace elements (Figure 6 and Supplementary File Table S1), and gases (Figure 8 and Supplementary File Table S1) converge in attributing the highest temperatures (>150 \({}^{\circ}\)C), the greatest enrichments in Li and Cs, and traces of mantle-derived He (1-2%) to S5, S11, S13, and S15. These springs are located in peculiar sites within the San Vittorino Plain. Indeed, the waters of S11, S13, and S15 flow precisely in correspondence with the main and deeper structural elements in the area (i.e., the Fiamignano Fault and its conjugate structures; see Figures 1 and 3 BB'). In addition, the water of S5 is fed by a flow influenced by the uprising of deep fluids along one of the main normal faults (orange arrow in Figure 3 AA'). This observation is also corroborated by the depths inferred by geothermometric analyses that are in line with those identified in the cross-section construction. The Cs (S5) and Li (S11, S13, and S15) enrichments (or Li and Cs impoverishments, respectively) shown in Figure 6 are often related to deep processes involving silicates (clays, zeolites, quartz, or chalcogen) that often produce temperature-dependent distributions of these elements [103; 135; 136]. In the same area of this study, Cs enrichment up to 6.5 ppb was also detected in the \"Paulla Bassa\" and \"Paulla 3\" springs [89], which are brackish and reduced (sulphurous), similar to S5. Such a relatively high Cs concentration in old, deep-seated, and saline groundwater could also be ascribed to the long-term weathering of micaceous minerals, typically enriched in Cs, in fracture coatings and wall rock [137]. In addition, the presence of deep sourced He and CO2 found in the same springs confirms the detailed influence of a deep circulation system, largely hidden by the huge contribution to the discharge of the shallow carbonate circulation system (as highlighted by the stability of the water isotopes). In our interpretation, the pressurized nappes can be connected via high-angle Intensive faults, which represent a preferred bottom-up connection path. The remaining two groups of springs (G1 and G2) show a degree of \"deep contribution\", gradually decreasing with respect to the deep fluids uprising. These springs are located at the intersection with secondary structural elements that are probably not able to allow a relevant uprising of deep fluids. In some cases (e.g., S10), the great abundance of shallow waters may hinder the deep signal. Although this area is characterized by intense degassing and evident chemical and isotopic features of mixing of shallow and deep fluids, there are only some springs whose hydrogeochemical features are directly connected with deep structures. In detail, their depth corresponds to the common hypocenters of earthquakes in the Apennine chain (7-10 km) because of the direct connection of the tectonic lines allowing the upward migration of fluids along high-angle faults. Furthermore, the springs of potential interest are those least affected by shallow circulation (also in terms of seasonal variations). For future research, the investigations should be based on high-frequency multiparametric monitoring at different sites and on data cross analysis, through which the dynamics and time evolution of processes in relation to the seismicity of the central Apennines region could be characterized in more detail [100]. In addition, for the management and exploitation of water resources, sites such as the San Vittorino Plain require careful monitoring of the huge quantities of available high-quality water resources, as they could undergo alterations in their chemical-physical properties induced by uprising deep fluids rich in CO2 and heavy metals. For example, the groundwaters of S5, S11, S13, and S15 show concentrations of As between 4 and 60 ppb, probably owing to the greater amount of dissolved CO2. These factors can become relevant for future scenarios of climate change, which can increase heavy metal concentrations.