# Hydrogeochemistry of Fault-Related Hot Springs in the Qaidam Basin, China
## 4 Discussion  
### Hydrochemical Characteristics of the Hot Springs  
#### 4.1.1 Major Components in the Spring Water  
The results of the study revealed that the average EC value of the samples was 4665.8 uS/cm. These values were particularly high for the AK spring samples. This high EC is actually primarily determined by the content of major anions and cations that are usually incorporated into the water via geochemical processes, such as ion exchange, evaporation, and silicate weathering. A second factor that plays a role in EC is the temperature, as specific ion conductivity increases with temperature. Water temperature is indeed higher in AK than in YTBLK, and this could explain part of the twofold increase in EC, in spite of the significantly higher ion concentrations in YTBLK. The dominating cations in the hot spring water at the sampling sites were the Na\({}^{+}\) ions. The normality concentration of Mg\({}^{2+}\) ions in the YTBLK spring sample was relatively high. The normality concentrations of Ca\({}^{2+}\), Na\({}^{+}\), and Mg\({}^{2+}\) ions in the AK spring samples were also relatively high. The cation compositions of the LMY and GS springs were relatively consistent, with the percentage of the Na\({}^{+}\) ion normality concentration reaching over 60% (Figure 2a). The main anion in the TYBLK spring water was Cl\({}^{-}\), which accounted for approximately 60% of the total anions, and its salinity was also relatively high. The main anions in the AK spring water were HCO\({}_{3}\)\({}^{-}\) and Cl\({}^{-}\). The main anion in the LMY spring water was SO\({}_{4}\)\({}^{2-}\), which accounted for approximately 50% of the total anions. The main anions in the GS spring water were HCO\({}_{3}\)\({}^{-}\) and SO\({}_{4}\)\({}^{2-}\) (Figure 2b). The main elements in the hot springs located at the Wenquan Ditch of Da Qaidam Area were Na, Cl, and SO\({}_{4}\)\({}^{2-}\), and this composition is relatively similar to the chemical composition of the hot spring water samples from the study region, all of which were relatively rich in Ca and low in Mg; this is a typical characteristic of several deep hot waters, such as the typical oil field water in the western Qaidam Basin and the Tibetan geothermal water [39]. The same phenomenon was discovered in a study of hot springs in Canada's White Lake Basin and Mexico's eastern volcanic belt, where the cations in the hot spring water were primarily Na, followed by Ca, with very low concentrations of other cations. The anions were dominated by Cl, SO\({}_{4}\), and HCO\({}_{3}\)[40, 41]. This phenomenon could be linked to the distribution of geological formations and the lithology surrounding them. Different water types may be defined according to the composition of the water. The Piper diagram depicted in Figure 2c was constructed using AquaChem Scientific Software (AquaChem 11.0) and presents the relative concentrations of different ions in individual water samples. It may be observed that the hydrothermal components in the study region were spatially complex along the fracture. The [PERSON] classification method for groundwater chemistry based on EXCELS was employed [42], and all water samples were classified into the following four chemical types: Na-Mg-Cl, Mg-Na-Cl-HCO\({}_{3}\), Na-Cl-SO\({}_{4}\), and Na-Cl-HCO\({}_{3}\) (Table 1). Magnesium ions were dominant among the cations detected in the AK and YTBLK spring water samples. The common sources of magnesium ions in natural water include dolomite, olivine, hornblende, etc., and also calcium carbonate (CaCO\({}_{3}\)). The Mg(Ca)-HCO\({}_{3}\)- and Ca(Mg)-HCO\({}_{3}\)- type waters are usually only located in the distribution areas of dolomite or dolomite limestone. Therefore, it was inferred that the western part of the region is formed of magnesium-bearing carbonate rocks in the presence of CO\({}_{2}\). The concentrations of HCO\({}_{3}\)\({}^{-}\), SO\({}_{4}\)\({}^{2-}\), and Cl\({}^{-}\) in the water samples