## 4 Results and Discussion
### Physiochemical and Hydrochemical Parameters of the Geothermal Springs
It implied that the groundwater chemistry in the studied areas was controlled mainly by the rock-water interaction process, leading to chemical weathering of the rock-forming minerals. This implied that weathering of the aquifer material was the dominant process controlling the chemistry of the springs, resulting in the chemical budget of this water [43]. Along the path of groundwater movement from recharge to discharge areas, several chemical reactions took place with the solid phase. These chemical reactions varied temporally and spatially depending on the chemical nature of the initial water, geological formations, and residence time. In order to assess the major functional source of the dissolved solid in the groundwater, a plot of (Ca + Mg) against (HCO\({}_{3}\) + SO\({}_{4}\)) was done to show the distribution of geothermal water between silicate and carbonate weathering in the system (Figure 7). The plot distinguished between carbonate and silicate weathering controlling factors. The water samples fell below and above the 1:1 line, which showed that they were in the field of silicate weathering and carbonate weathering, respectively (Figure 7). This contradicted findings from [PERSON] et al. [18], which reported that Siloam and Tshipise geothermal springs fell in the silicate weathering zone. However, most of the samples fell above the 1:1 line due to the effects of the reverse ion exchange in the system (carbonate weathering), which supported the Gibb's diagram. The plotted results of Mphephu geothermal spring (MPW and MPS) fell below the 1:1 line, demonstrating the minor ion exchange process. The fact that the ions exchange processes between groundwater and the aquifer materials were relatively high was in good agreement with the Gibb's diagram. Figure 6: Mechanism controlling chemistry of the geothermal springs and other groundwaters—Gibbs plot. Among chloro-alkaline indices, CAI-1 varied from (\(-\)2.38) to 0.55, and CAI-2 ranged from (\(-\)1.08) to 1.57, which were negative in the majority of the samples (67%), suggesting the presence of base-exchange process (Table 2). Ca\({}^{2+}\) and Mg\({}^{2+}\) exchanged Na\({}^{+}\) sorbed on the exchangeable sites on the aquifer minerals, resulting in the decrease of Ca and Mg and the increase of Na in the groundwater by reverse ion exchange [44; 45]. This confirmed that Ca\({}^{2+}\), Mg\({}^{2+}\), and Na\({}^{+}\) concentrations were interrelated through reverse ion exchange. The remaining samples were positive with direct exchange occurrence due to the direct exchange of Ca\({}^{2+}\) and Mg\({}^{2+}\) from the aquifer matrix with Na\({}^{+}\) and K\({}^{+}\) from the groundwater. This supported the fact that alkaline earth elements were abundant. The plot of Na\({}^{+}\) against Cl\({}^{-}\) was used to establish the role of evaporation for higher concentrations of Na in the groundwater. [PERSON] et al. [46] reported that the influence of semi-arid climate as intercalation in the soil zone enhanced active evaporation in the study area. This implied that there was loss of groundwater quantity during the summer by the action of evaporation, resulting in an increase in salt concentration in the groundwater. However, all groundwater samples plotted above the freshwater evaporation line (Figure 8). This study showed that the molar ratios of Na/Cl for the geothermal spring samples generally ranged from 0.4-3.11 compared to the seawater ratio of 0.86, which implied that 67% of the water had a Na/Cl ration higher than that of the seawater, while 33% was lower than that of seawater [9]. The weathering of silicate minerals was thus confirmed as the main source of Na in the groundwater within Soutpansberg. This indicated that evaporation was one of the processes controlling the geochemistry of the geothermal springs [46]. Figure 7: Relation between (Ca + Mg) and (HCO\({}_{3}\) + SO\({}_{4}\)) in the geothermal springs within Soutpansberg.