# Hydrogeochemistry of Fault-Related Hot Springs in the Qaidam Basin, China
## 5 Conclusions  
In the present manuscript, the hydrogeochemical and gas geochemical characteristics of hot springs in the study region were analyzed using four groups of water samples and two groups of gas samples, in addition to investigating the characteristics of the geological structure. The results of the study revealed the following:  
1. The water chemistry types of the hot springs in the study region were Na\(\cdot\)Mg-Cl, Mg\(\cdot\)Na-Cl\(\cdot\)HCO\({}_{3}\), Na-Cl\(\cdot\)SO\({}_{4}\), and Na-Cl\(\cdot\)HCO\({}_{3}\). Water chemistry types were relatively complex, which could be attributed to the various surrounding rocks distributed along the fault zone. Sr emerged as the most powerful enrichment factor among the trace element enrichment factors. This discovery, combined with the findings of regional lithology analysis, indicated that the hot spring water in the study region was primarily derived from the marl aquifer. The analysis results for the water samples collected in the study region were distributed below the partial balance line, indicating that the degree of water-rock interaction balance was relatively low. This could be due to mixing with cold water during the ascent. 2. The \(\delta\)D values ranged from \(-50.00\%\) to \(-68.60\%\). The \(\delta^{18}\)O values ranged from \(-6.90\%\) to \(-8.60\%\). The hot spring water in the study region was recharged mainly through infiltrating precipitation, with a recharge elevation of 3390-3676 m. These results, combined with the topography and geomorphology of the study region, indicated that the hot spring recharge in the study region occurred mainly due to southern Alpine glacial meltwater and fracture recharge. 3. The strontium isotope ratios of the hot springs varied less and remained nearly constant, whereas the Sr content varied more. This could be because of the similarity of the surrounding rocks along the flow path, as well as the different accumulation times. 4. The thermal reservoir temperatures of the YTBLK, AK, LMY, and GS hot springs were 115.39, 164.91, 66.74, and 73.45 \({}^{\circ}\)C, respectively. The estimated range of circulation  
Figure 11: Time series diagram of AK spring ion detection results. depth for the hot springs at the intersection of the Altun Tagh fault and the East Kunlun fault was 1043-2679 m, while the AK spring circulated at a deeper depth. The thermal storage temperature and the circulation depth of the hot springs in the study region indicated a spatially high east and low west characteristic. * 5 CO2 was the main component of hot spring gas in the study region, with a content of over 95%. The release of mantle-sourced helium from the YTBLK spring was 3.06%, and that from the AK spring was 7.38%. The results of the analysis indicated the presence of mantle-sourced material in the study region. The Altun Tagh fault and the East Kunlun fault belt are excellent channels for mantle-derived helium upward transport. The carbon inventory of the hot spring gas samples (>75%) was dominated by crustal marine limestone, followed by sedimentary organic and mantle sources. The CO2 released from the dissolution of the marl aquifer, and the metamorphism and hydrothermal reactions of the basement lithologies, were the main sources of carbon in the hot springs of the study region. [PERSON]. ([PERSON]), [PERSON] and [PERSON] made equal contributions to this article by analyzing the data, and drafting and revising the manuscript. All authors contributed significantly to the interpretation of the results. All authors have read and agreed to the published version of the manuscript.