Fluid chemistry and circulation patterns from typical convective hydrothermal system on the northeastern Tibetan Plateau

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Understanding the causes of these differences is crucial. This research specifically examines the Wahongshan-Wenquan Fracture Zone (Area Ⅰ) and the Zhiduo-Yushu Mountainous Zone (Area Ⅱ) in Qinghai Province. Hydrochemical and gas isotope data were collected from convective hydrothermal systems in these distinct tectonic settings. A comparative analysis of geothermal fluid geochemical characteristics and sources was conducted using fluid geochemistry methods. Results show that hot water in the igneous rocks of Area Ⅰ is mainly of Cl-Na type, while in the carbonate rocks of Area Ⅱ, it is primarily of HCO 3 -Ca•Mg type. The salts in the former come from silicate mineral dissolution, while the solutes in the latter are primarily influenced by carbonate rock breakdown. Igneous thermal reservoirs have higher temperatures and greater fluid circulation depths than carbonate reservoirs. Geothermal gases in both regions are dominated by N 2 of atmospheric origin. Most of He originates from the crust, with mantle contributions not exceeding 5%. High CO 2 content (14%) in certain carbonate reservoirs is mainly of inorganic metamorphic origin. Both regions are medium-low temperature convective geothermal systems, primarily driven by crustal heat. However, isotopic analysis suggests that the carbonate reservoirs in the Zhiduo-Yushu Mountains have a higher mantle contribution than those in the Wahongshan-Wenquan Fracture Zone. This study summarizes the fluid circulation patterns in these two regions, revealing regional and tectonic influences on fluid sources and transport mechanisms. It provides a theoretical framework for developing and utilizing geothermal assets on the northeastern Tibetan Plateau. Convection geothermal systems Geothermal fluid geochemistry Fluid circulation patterns Northeastern Tibetan Plateau Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Introduction Geothermal energy, a clean and sustainable energy with vast reserves, has multiple uses, such as electricity production and heating. Its utilization has become crucial for global energy restructuring and sustainable development (Korucan et al., 2024 ; Soltani et al., 2019 ). The northeastern part of the Tibetan Plateau is a crucial section for the long-term impacts of the Indo-Eurasian plate collision as well as the transitional edge for the lateral expansion of plateau uplift. (Zhou et al., 2023 ). Research into geothermal resources in this region began during the early 1960s. Geologists have conducted comprehensive surveys and gathered data regarding the locations of natural thermal springs throughout the region, including their temperatures, flow rates, and other fundamental physical characteristics. The results indicate that hot springs are often found in linear clusters where geological formations overlap or where primary and secondary faults intersect (Cheng & Jin, 2013 ). Hydrothermal resources in the northeastern Tibetan Plateau show significant variations in terms of fluid chemistry, thermal reservoir types, and genesis mechanisms in different regional and tectonic contexts. Lei et al. ( 2022 ) researched the hydrochemistry of carbonate reservoir thermal springs in Yaoshuitan, Xining Basin, and proposed a mechanism for the weakly acidic water. Results suggested that the bottom crack of Laji Mountain’s northern edge directs the heat flow from deep crustal and mantle sources. This leads to a thermal metamorphism reaction of the buried thick carbonate rock and silicate at high temperatures. The hot springs are weakly acidic due to the high concentration of inorganic ions created by the metamorphic dissolution of CO 2 . Liu et al. ( 2023 ) used helium isotopes and isotope dating methods to identify the sources of geothermal fluids and heat from the Gonghe basin. The findings revealed that the hot spring water combines sub-modern and modern recharge sources. The fluids passed through silicate reservoirs and surrounding rocks, undergoing aqueous-rock reactions. After being heated by deep crustal heat sources, the fluids finally gushed out of the surface in the form of SO 4 -Cl-Na-type weakly alkaline high-temperature mineral springs. There are significant differences in local tectonic hot springs that are controlled by the same deep, major fault. Li et al. ( 2022 ) explored the connection between the hydrochemical features of hot springs and fracture activities along the Qilian-Haiyuan fault. The findings revealed the hydrochemistry of thermal water along the fault has a direct connection to the surrounding rocks as well as hydrodynamic and hydrothermal circumstances. Furthermore, the hydrochemical composition of thermal water in different segments of the fault is influenced by local tectonic activities, leading to distinctive hydrochemical characteristics. Liu et al. ( 2022 ) established a conceptual framework for fluid transport by investigating the fluid chemistry and dissolved carbon characteristics of hot springs along the Yushu-Ganzi-Xianshuihe fracture. The study revealed a spatial pattern of hydrothermal fluid chemistry, circulation paths, and thermal reservoir temperatures along the fracture system, which is controlled by the regional fault structure. However, past research has primarily concentrated on a single geothermal field or a single deep and broad fracture zone, with no systematic assessments or comparative studies on the fluid features and genesis processes of geothermal systems across different tectonic contexts. These studies were analyzed using a single methodology and mainly employed hydrogeochemical methods. Nowadays, gas geochemistry and its isotope methods have been widely used to analyze fluid sources and heat source mechanisms in geothermal systems in the southern and eastern Tibetan Plateau (Fan et al., 2019 ; Guo et al., 2017 ; Li et al., 2024 ; Zhang et al., 2017 ). However, few studies have applied these methods to explore the formation factors of geothermal systems in the northeastern Plateau. This study collected natural thermal water and volatile gas samples from the Wahongshan-Wenquan Fracture and the Zhido-Yushu deep Fracture. The geochemical features of geothermal water and gases in both places will be systematically compared and analyzed by combining hydrological, gas geochemical, and isotopic methods. The similarities and differences in the sources and causes of the fluids in these two areas will be analyzed, and the geothermal fluid circulation models of the two areas will be constructed. The study's findings are intended to expand the theoretical basis for geothermal research on the northeastern Tibetan Plateau. Geological background The study area includes the Wahong Mountain in east-central Qinghai Province (Fig. 1 a) and the mountains along the Zhiduo-Yushu region in southwestern Qinghai Province (Fig. 1 b). Area Ⅰ is geotectonically located in the northeastern Tibetan Plateau East Kunlun orogenic belt, and hot springs along the fracture zone are exposed in a string of beads in the Indo-Chinese granite, including Xinghai Sangchugou hot springs (XH2, 78°C), Ulaanba hard Geli hot springs (WL1, 44°C), Dulan Chahanwusu hot springs (DL1, 87°C), Anguotan hot springs (DL2, 67°C), and Xinghai Wenquan hot springs (XH1, 64°C) along the southernmost part of the fracture exposed stratigraphy lithology in sandstone. Except for XH1, which has a high flow rate of 25.31L/s, the other granite thermal reservoir hot springs have flow rates that vary between 0.221 and 4.132L/s. Area Ⅱ is geotectonically positioned in the northeastern part of the Yangzi River Plate, between the Bayan Lola orogenic belt and the North Qiangtang-Sanjiang orogenic belt, with hot springs dispersed along the main NW-oriented fracture. From north-west to south-east, there are the Sagongsi hot spring (ZD1, 24°C), the Baihailuo hot spring (ZD2, 27°C), the Riqingdangjiang hot spring (ZD3, 19°C) in Zhiduo County, and the Chatong hot spring (YS1, 65°C), Batanghe hot springs (YS2, 12.5°C), Angpusi hot springs (YS3, 33°C), and Shabajiugongzhu hot springs (YS4, 24°C) in Yushu City. Hot springs are found in Triassic carbonate rocks, except for YS1 (65°C), which has the highest water temperature, where the exposed stratigraphic lithology is sandy slate. The flow rate varies considerably, spreading between 0.7 and 200 L/s. The Wahongshan-Wenquan Fracture is a NNW-trending dextral slip crustal fracture. It starts from the southern edge of Lake Harrah in the north and ends at southern Wenquan Town in Xinghai County, covering more than 300 km. This fracture truncates the Zongwulongshan-Qinghai Southern Mountains Fault in the north, forming the eastern and western boundaries of the Qaidam and Gonghe basins, respectively. This fracture also exists along the Gonghe Basin-East Kunlun Magma Belt intersection, managing the transitional contact between each of them. (Wang & Burchfiel, 2004 ). The go-slip of the Wahongshan-Wenquan Fracture caused the mountain to rise. Influenced by magmatic activities, a tectonic-magmatic uplift zone with a nearly north-south orientation was formed (Dong et al., 2019 ; Lu et al., 2024 ). The tectonic magma belt runs north-south from the Wahongshan-Wenquan Fracture and consists of volcanic rocks of the Triassic Erlangshan Formation and neutral acidic rocks of the Indo-Chinese-Yanshanian period, which form the main body of the mountain (Sun et al., 2011 ). The geomorphological type of the Zhido-Yushu study area is dominated by tectonic erosion of the mountain plateau, and the tectonic lines and stratigraphic regions in the area are basically in the same direction of spreading, presenting a northwest-southeast oriented strip spreading. Fracture tectonic development in this area is mostly NW-SE-oriented pressure or pressure-twisting fracture, including the southern edge of the Hoh Xil active Fault and the Xijinwulanhubei-Yushu Fault. The fracture of the southern edge of Hoh Xil is generally near NNW for the Bayan Lola orogenic belt and the North Qiangtang-Sanjiang orogenic belt of the division of the fracture. The Xijinwulanhubei-Yushu Fracture extends in a northwesterly direction, with obvious fault geomorphological features, and is a Holocene-acquired left-rotating retrograde fracture (Huang et al., 2011 ). The widespread stratigraphy in this region is Triassic, followed by Jurassic. Materials and methods Sample collection Figure 1 shows the location of sampling points. The hot spring water samples for the majority of the study area were collected between May and July 2022. Only three sets of samples (ZD3, YS1, and YS3) were collected in July 2023. Water temperature, pH, and TDS were determined through a multiparameter water quality tester (WTWMulti340i/SET, Germany) before sample collection in the field. Geothermal gases were collected using the drainage gas collection method. The specific operation is as follows: insert a thin plastic tube into a high-temperature-resistant thin-mouthed glass bottle filled with 500 mL of sampled hot spring water (to avoid air contamination) and connect it with a reversed Teflon funnel, immerse it in the hot spring water, and then seal when the gas content is approximately 2/3 of the volume of the glass bottle. Due to field conditions, H 2 S and SO 2 were not measured on-site. Sample testing Water chemistry and stable isotope tests were performed at the Geochemical Analysis and Testing Centre, Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences. The hot water cation fraction was detected by inductively coupled plasma emission spectrometry (Optima 8000 ICP-OES), Cl − and SO 4 2− were detected by ion chromatography (ICS-2500), and HCO 3 − was measured by acid-base titration. Deuterium-oxygen isotopes were analyzed with an ultra-high-precision hydroxide-oxygen isotope analyzer (L2130-i) with a testing accuracy of 0.025%. Gas samples were analyzed by the Oil and Gas Resources Research Centre of the Northwest Institute of Ecology and Environmental Resources, Chinese Academy of Sciences. Constant gas components were measured by the MAT271 mass spectrometer with a relative standard error of less than 5%. Gas rare components and isotopes were analyzed with a Noblesse Rare Gas Isotope Mass Spectrometer (RGIMS). The testing error for He isotope measurements was ± 10% for R-values exceeding 1 × 10 − 7 and ± 15% for R-values between 1 × 10 − 8 and 1 × 10 − 7 . Carbon isotopes were analyzed and tested on a Delta Plus XL mass spectrometer and expressed as PDB standards. The test results are shown in Table 1 and Table 2. Results Hydrochemical and isotopic composition Based on Table 1 and Fig. 2 , the geothermal water temperature in the Wahongshan-Wenquan Fracture Zone (Area I) ranges from 44°C to 87°C. The pH value falls between 7.46 and 8.82, and the dominant cations in the geothermal water are Na + , with significant variation in the anions, primarily Cl − and SO 4 2− . The hot spring water in Area Ⅰ contains three chemical types: the Cl-Na type, the Cl•SO 4 -Na type, and the SO 4 •Cl-Na type (Fig. 3 ). Combined with the geographic location of the hot springs, it can be found that the springs located distant near the Wahongshan-Wenquan Fault belong to the Cl-Na kind. The Cl − concentration increases with distance from the main fault, with the maximum value appearing in DL1, reaching 1461 mg/L. The hot springs around the fault primarily contain Cl•SO 4 -Na and SO 4 •Cl-Na type water, with significantly elevated SO 4 2− levels. The temperature of the geothermal water in the Zhiduo-Yushu hot spring concentration area (Area II) ranges from 12.5°C to 65°C. The pH values range from 6.93 to 7.84, and all samples are weakly alkaline except for YS3, which is weakly acidic. The geothermal water in Area II contains a high concentration of HCO 3 − . The water in the greywacke reservoir is mainly composed of Ca 2+ and Mg 2+ . The hydrochemistry includes HCO 3 -Ca, HCO 3 -Ca•Mg, HCO 3 -Mg•Ca, and HCO 3 -Mg, as well as HCO 3 -Ca•Na types (Fig. 3 ). The cations in the geothermal water of the sand slate reservoir YS1 are dominated by Na + , and the hydrochemical type exhibits the HCO 3 -Na type. The δD and δ 18 O values in the geothermal water samples from Area I range from − 92‰ to -88‰ and − 12.2‰ to -11.6‰, respectively. The composition of δD and δ 18 O values in the samples from Area II range from − 108‰ to -101‰ and − 14.4‰ to -14‰, respectively. Geothermal gas chemistry and isotopic composition Geothermal gases have two groups based on their main components, one is rich in N 2 , while the other is dominated by CO 2 . The results of component and isotope analyses of the gases (Table 2) indicate that their components display a wide range of variations and are primarily dominated by N 2 , which is a type of gas classified as N 2 . The main gas components in Area Ⅰ were N 2 (73.67 ~ 83.63%), O 2 (13.87 ~ 18.53%), and CO 2 (0.19 ~ 7.83%), with traces of Ar (0.96 ~ 1.16%), CH 4 (0.01 ~ 0.04%), and He (0.0052 ~ 0.1753%). The gases from the hot springs in Area Ⅱ were dominated by N 2 , with an average concentration of over 61.19%. The CO 2 content was higher than that in Area Ⅰ, with the highest sample reaching 34.14%. Additionally, there were trace amounts of O 2 , Ar, CH 4 , and He (Fig. 4 ). The small amount of O 2 detected in the gas components may be due to irregular sampling and storage, atmospheric mixing, and other factors. Therefore, the O 2 contents fail to accurately reflect the actual amount of the spilled geothermal gases. The 3 He/ 4 He ratio in Area I ranges from 1.8×10 − 8 to 1×10 − 7 , equivalent to 0.013 ~ 0.07Ra (Ra represents the 3 He/ 4 He proportion in the modern standard air). The He isotope ratios of ZD2 and YS1 in Area II are 0.203 Ra and 0.429 Ra, respectively. The \(\:{{\delta\:}}^{13}{\text{C}}_{{\text{C}\text{O}}_{2}}\) values have a wide range of distribution. The samples collected in Area I have \(\:{{\delta\:}}^{13}{\text{C}}_{{\text{C}\text{O}}_{2}}\) values between − 16‰ and − 10‰, while the geothermal gases in Area II have values ranging from − 6.8‰ to -4.8‰. Discussion Sources of chemical components of geothermal water Generally, high levels of Cl − in thermal water are principally caused due to the mixing with magmatic fluids (Guo, 2012 ; Pan et al., 2021 ). Guo et al. (2020) concluded that the hydrochemistry of a non-carbonate thermal reservoir containing a magmatic heat supply is distinguished by the simultaneous occurrence of acidic, neutral, and weakly alkaline geothermal water. Area I, where the anion is dominated by Cl − , does not satisfy the occurrence of these three types of water at the same time, so the possibility of its geothermal fluids being affected by magma water is very low. Cl − may originate from the leaching process of surrounding salt minerals during geothermal water runoff (Ma et al., 2020 ), which is associated with evaporative concentration. The water temperature of DL1 is reaching 87°C, close to the local boiling point. Its water chemistry is significantly concentrated by evaporation, resulting in the highest Cl − content. The gradual increase of SO 4 2− in geothermal water close to the main fault may be related to the intrusion of sulfate minerals during hydrometamorphism. The hydrological interaction of thermal water from the Greywacke stratum in Area II regarding the carbonate rocks during circulation is the decisive factor controlling the type of water chemistry. Bivariate plots of different anions and cations can further reveal the sources of solutes in the water column (Hui et al., 2023 ; Li et al., 2021 ; Luo et al., 2022 ; Ma et al., 2023 ). Figure 5 a reveals that the samples in Area I are scattered along the 1:1 line, with most of them tilted towards the Na + K axis. This phenomenon suggests that the presence of Na + is not solely due to rock salt dissolution but also from other sources such as the dissolution of silicate rocks or ion exchange interactions. Figure 5 b shows that the hot spring sites in Area II exhibit a trend closer to the 1:1 line trend. This implies that the weathering dissolution of carbonates and sulfates possesses a crucial function in controlling Ca 2+ and Mg 2+ levels in the geothermal waters of the Zhiduo-Yushu mountains. Most samples are shifted towards the HCO 3 + SO 4 axis, indicating that there are also varying degrees of silicate mineral contributions. The YS1 deviation is most pronounced for sandstone thermal reservoirs, with the largest contribution from silicate rock dissolution. The process of weathering and hydrolysis of dolomite and calcite also releases Ca 2+ , Mg 2+ , and HCO 3 − . In Fig. 5 c, several of the hot springs points in Area II are located near the 1:1 line, indicating that calcite weathering is the main process of mineralization. Additionally, some points fall between the 1:1 and 1:2 lines, suggesting that the hydrochemistry of these hot springs is affected by both calcite and dolomite weathering. The points in Fig. 5 d all deviate from the 1:1 line, demonstrating that the dissolution of sulfate rocks like gypsum is not the main cause of SO 4 2− enrichment in some of the geothermal waters in Area I. Sulfurous gas odor is evident in these hot springs during field collection, and SO 4 2− can also be formed by geothermal fluids interacting with shallow, oxygen-rich groundwater during ascent (Daniele et al., 2020 ). Sources of water recharge in hot spring The stable isotope values of the geothermal waters from the study area are all close to the global meteoric water line (GMWL). The deuterium excess parameter (d) values of the samples are between 0 and 15%, with a higher concentration in the 0 to 10% range. This suggests that atmospheric rainfall is the most probable supply of replenishment for these thermal waters. (Fig. 6 ). The isotopic compositions of different areas have obvious spatial variability, and the mean values of isotopes gradually decrease from the Wahongshan Fracture Zone (Area I) to the southwestern Zhiduo-Yushu Mountainous area (Area II). This reflects differences in the sources of atmospheric precipitation, which are related to elevation. Isotopic values decrease with increasing elevation, indicating that hot spring water in Area II comes from precipitation recharge at higher elevations. The elevation of monsoon water vapor due to altitude can also impact δ 18 O values (Yao et al., 2013 ). The higher δ 18 O values in the northern regions result from water vapor cycling in the inland areas. In comparison, the lower δ 18 O values in the southern regions may be linked to monsoon-driven oceanic water vapor (Tian et al., 2001 ). The thermal waters are refilled by atmospheric precipitation, therefore their isotopic distribution is comparable to that of precipitation. Overall, the δ 18 O excursion for all water samples is not significant, especially in Area II. This represents that groundwater circulation is insufficiently deep to allow for significant water-rock interaction. Reservoir temperature and circulation depth Reservoir temperature Deep reservoir temperatures can be calculated from geochemical temperature scales. The commonly used chemical temperature scales include cationic scales such as Na-K geothermometers, K-Mg geothermometers, and Na-K-Ca geothermometers (Fournier, 1977 ; Fournier, 1981 ; Giggenbach, 1988 ; Giggenbach, 1989 ), SiO 2 temperature scales, and multi-component mineral equilibrium methods. Estimates using cationic geothermometers are more precise only when the chemistry of the groundwater is in equilibrium after an extended period of water-rock interaction. It is considered that hot water remains in equilibrium even after it has reached the surface. The Na-K-Mg ternary diagram can be used to make a preliminary determination of whether the thermal water chemistry is in equilibrium. Figure 7 illustrates that all water samples in the study area fall within partially mature or immature zones, indicating that the water-rock interaction has not yet reached complete equilibrium. In this case, the cation temperature scale estimation results will have a large deviation, so the use of the SiO 2 temperature scale and the multi-component mineral balance method is considered to estimate the reservoir temperature. The multi-component mineral equilibrium method involves modeling the change in the saturation index of multiple minerals at various temperatures. The thermal reservoir temperature is the temperature at which the saturation index (SI) values for different minerals approach 0 (Reed & Spycher, 1984 ; Tole et al., 1993 ). The multi-component mineral balance diagram of the geothermal water is depicted in Fig. 8 , and Table 3 shows the estimated thermal reservoir temperature. The results indicate that the calculated chalcedony temperature scale yields lower results. The quartz temperature scale results are similar to those derived from estimation using the multimineral equilibrium graphical method. By combining these two sets of results, we can determine the range of thermal reservoir temperatures of the samples. The thermal reservoir temperatures estimated for all hydrothermal water samples were higher than the actual measurement temperatures. The reservoir temperature in Area Ⅰ ranges from 88 to 156℃, significantly higher than that in Area Ⅱ. The granite thermal reservoir is significantly higher than the greywacke thermal reservoir, while the two hot springs (XH2, YS1) exposed in sandstone in the study area have reservoir temperatures between the granite reservoir and the greywacke reservoir. Circulation depth Underground hot water is typically heated by deep thermal sources during transportation, and determining the circulation depth of thermal water is useful for analyzing the formation of hot springs. The depth of underground circulation can be calculated based on the estimated thermal reservoir temperature with the following formula: $$H=\frac{{T - {T_0}}}{K}+{H_0}$$ 1 Where H is the circulation depth (m), T is the thermal reservoir temperature (℃), T 0 is the local average annual air temperature (℃), K is the local geothermal gradient (℃/100 m), and H 0 is the thickness of the constant temperature zone (m). According to the information from previous studies, the multi-year average annual air temperature in Area Ⅰ is 3.8°C, the thickness of the constant temperature zone is 50m, and the local geothermal gradient is taken as 4.5°C/100m (Wang et al., 2023 ); The average annual temperature in Area Ⅱ is 2.9°C, the thickness of the constant temperature zone is 50m, and the local geothermal gradient is taken as 3.4°C/100m (Wang et al., 2024 ). Calculation results (Table 3) indicate that the Wahongshan-Wenquan Fracture hydrothermal system circulates at a depth of 1921 to 3432m. The sandstone thermal reservoir YS1 has a deeper circulation depth. Additionally, the geothermal water in other remaining greywacke reservoirs in Area II circulates at depths ranging from 989 to 2168m. Table 3 Reservoir temperature (℃) and circulation depth (m) of geothermal systems in the study area. Area ID Chalcedony Quartz no loss Quartz maximum loss Multicomponent mineral equilibria Temperature range Circulation depth Ⅰ XH1 95.5 123.6 121.2 128 123.6–128 2712–2810 XH2 94.7 122.8 120.6 121 120.6–121 2646–2654 WL1 64.7 95.1 96.8 88 88-95.1 1921–2079 DL1 118.7 144.5 138.9 156 144.5–156 3177–3432 DL2 115.6 141.8 136.6 147 141.8–147 3117–3232 Ⅱ ZD1 19.6 52 58.8 60 58.8–60 1744–1780 ZD2 31.6 63.6 69.1 70 69.1–70 2056–2083 ZD3 15.2 47.7 54.9 50 47.7–50 1408–1477 YS1 71.4 101.3 102.2 100 100-101.3 2992–3032 YS3 41.2 72.8 77.3 63 63-72.8 1871–2168 YS4 -8.4 24.5 33.9 37 33.9–37 989–1083 Sources of geothermal gases Ar in geothermal gases is mainly of atmospheric origin (Fischer et al., 1998 ; Lowenstern et al., 2015 ). Harrison et al. ( 1999 ) reported values of 295.5 for atmospheric 40 Ar/ 36 Ar and 7300 ± 900 for mantle 40 Ar/ 36 Ar. The geothermal gases in the research region have 40 Ar/ 36 Ar values ranging from 289.6 to 304.3, which are similar to atmospheric values, indicating that the Ar in this area is primarily of atmospheric origin. As seen in Fig. 9 , all of the samples’ N 2 /Ar values are greater compared to the atmospheric precipitation value of 38 and close to the atmospheric value of 84. This indicates that the N 2 is predominantly atmospheric. The comparatively elevated N 2 /Ar values are explained by three primary points: (1) magmatic gas input, (2) crustal organic metamorphic genesis, and (3) Ar depletion. Although the N 2 /Ar value of YS1 (87) in the sandstone reservoirs of Area II is greater than the atmospheric value of 84, the likelihood of magmatism can be ruled out. Typical magmatic gases have N 2 /Ar ratios between 800 and 2000 (Zhao et al., 2002 ). The higher N 2 /Ar value of YS1 than the atmospheric value may be related to organic genesis. The sample points in Fig. 9 are evenly distributed along the line connecting He to the atmospheric value, showing that the gas is mostly produced by the mixing of atmospheric and crustal sources and that He is a byproduct of the radioactive elements disintegration. Isotopic characterization of geothermal gases Geothermal gases from various sources have varied chemical and isotopic signatures, and studying the isotopic compositions of the gases can help identify the sources of geothermal gases. Helium isotopes He has two naturally occurring stable isotopes, 3 He and 4 He, each with a unique origin. Mantle degassing releases the element 3 He, which is native to the Earth, while crustal sources of 4 He are formed by the radiative disintegration of the radionuclide (U and Th). He isotopes are an important parameter for determining the source of He and are often described as 3 He/ 4 He values (R). The atmospheric 3 He/ 4 He value (Ra) is commonly used as a reference, Ra = 1.43×10 − 6 (Sano & Wakita, 1985 ). Geothermal systems contain three main sources of He: atmosphere, crust, and mantle, with 3 He/ 4 He ratios of Ra, 0.005–0.02 Ra, and 8 ± 1 Ra, respectively (Sano & Marty, 1995 ). The 4 He/ 20 Ne ratio combined with the R/Ra ratio is widely used to quantitatively identify helium from various sources (Karakuş, 2015 ; Wang et al., 2020 ). In Fig. 10 , the YS1 sample is near the air end, suggesting that the sample may have been subjected to severe atmospheric pollution, leading to a predominantly atmospheric genesis of its He. Other sample points with less air pollution are near the 100% crustal end, and the proportion of mantle-sourced He to total He for a few samples does not exceed 5%, indicating that He is predominantly of crustal origin in the two regions, while some samples contain small amounts of mantle-sourced incorporation. The three-component mixing model (Eq. 2 –Eq. 4 ) (Sano et al., 1982 ) can quantify the contribution of various He sources to total He. The results are reported in Table 4 . where A, M, and C represent the proportion of atmospheric, mantle, and crustal sources, respectively. Ra, Rm, and Rc values are 1.4 × 10 − 6 , 1.1 × 10 − 5 , and 1.5 × 10 − 8 , respectively. ( 4 He/ 20 Ne) a , ( 4 He/ 20 Ne) m , and ( 4 He/ 20 Ne) c are the 4 He/ 20 Ne ratios for the atmosphere, mantle, and crustal end, with values of 0.318, 1000, and 1000, respectively. According to Fig. 10 and Table 4 , it can be seen that crustal source He accounts for 92.17%~99.46% of all the samples from the Wahongshan-Wenquan Fracture Zone, and only two hot springs contain a small amount of mantle He (0.26%, 0.13%), indicating the He gas from Area I is mainly derived from crustal and atmospheric. The less air-polluted ZD2 in Area II possesses a high mantle contribution of about 2.19%. This hot spring has a relatively high R/Ra value (0.429), implying that the fracture system in the Zhiduo section extends deeper compared to the geothermal system in Area I and that the deep, large fractures provide upward pathways for deep volatiles such as mantle He (Tian et al., 2021 ). Overall, the vast majority of samples He in the research area come from crustal sources, with an average contribution of 96.55%. This finding is consistent with the conclusion that the stacking of radioactively enriched strata in the Tibetan Plateau crust results in a significant contribution of crustal heat (Tian et al., 2018 ; Zhou et al., 2017 ). Mantle source contributions in the Zhiduo-Yushu Mountains are higher than in the Wahongshan-Wenquan Fracture Zone, and north-west-south-east-trending faults in Area Ⅱ have deep volatile fluxes. Table 4 Helium sources of geothermal gases Area ID He sources(%) A M C Ⅰ XH1 0.28 0.26 99.46 XH2 7.83 0 92.17 WL1 4.35 0 95.65 DL1 0.67 0.13 99.20 DL2 2.51 0 97.49 Ⅱ ZD2 2.47 2.19 95.34 YS1 93.59 0 6.41 Carbon isotopes CO 2 in geothermal fluids consists of three main sources: the mantle, metamorphic inorganic carbon, and organic carbon in sediments. The range of \(\:{{\delta\:}}^{13}{\text{C}}_{\text{C}{\text{O}}_{2}}\) varies depending on the source of CO 2 . Carbon isotope values can identify CO 2 genesis. Mantle sources (mid-ocean ridge basalts) have \(\:{{\delta\:}}^{13}{\text{C}}_{\text{C}{\text{O}}_{2}}\) values ranging from − 9‰ to -4‰, metamorphic decarbonization of marine carbonates has \(\:{{\delta\:}}^{13}{\text{C}}_{\text{C}{\text{O}}_{2}}\) values of 0 ± 2‰, and organic sediment genesis has lower values of \(\:{{\delta\:}}^{13}{\text{C}}_{\text{C}{\text{O}}_{2}}\) generally less than − 20‰ (Sano & Marty, 1995 ). Due to the overlap of carbon 13 values from different sources in practice and the fact that CO 2 release is also related to many factors such as magma degassing, material differentiation, alteration of the surrounding rocks, and geotectonic effects (Yang, 1999), it is not possible to accurately identify the cause of CO 2 based on carbon isotope values alone. Combined CO 2 -He isotopes can accurately determine CO 2 sources (O'nions & Oxburgh, 1988 ). Figure 11 shows that the \(\:{{\delta\:}}^{13}{\text{C}}_{\text{C}{\text{O}}_{2}}\) values of hot spring samples in Area I vary from − 20‰ to -10‰. The low CO 2 concentration is primarily a mixture of two sources: organic sediments and marine carbonate rocks. ZD2 has a higher \(\:{{\delta\:}}^{13}{\text{C}}_{\text{C}{\text{O}}_{2}}\) value (>-10‰) and is closer to the MORB end than the Area I samples. Combined with the results of the He isotope analysis, it is concluded that the CO 2 in ZD2 has a mantle source genesis in addition to the weathering and decarbonization of the marine carbonate rocks as the main controlling factors. The northwesterly spreading Hoh Xil Southern Margin Fault near the hot spring outcrop site transports CO 2 from a deep mantle source, whereas the deep big fracture is the primary condition for deep heat conduction. Conceptual model of geothermal fluid circulation The Wahongshan-Wenquan Fracture Zone (Area I) represents a typical igneous thermal reservoir hydrothermal convection system (Fig. 12 ). The hot springs are replenished by atmospheric precipitation from Wahong Mountain. Cold water flows downward through fault fracture zones, receiving heating from convective heat sources and radiogenic heating of intrusive rocks, and the water temperature rises continuously. Salt rock dissolution and cation exchange provide a fluid source for the production of Cl-Na-rich geothermal water. The gaseous components (N 2, Ar, and He) are continuously introduced, while the 4 He created by the thicker crust's radioactive disintegration is constantly dissolved in the water. The fluid upwells when it encounters a torsional fracture, mixes with varying proportions of cold groundwater as it rises, and is continuously mixed with atmospheric components, eventually flowing out to the surface. The thermal fluids in the Zhiduo-Yushu Mountains (Area II) are affected by tectonic activity, and the carbonate rocks near the deep and large fractures constitute karst-fissure-type thermal storage (Fig. 13 ). The thermal water is replenished with atmospheric precipitation from neighboring mountains, and the underground hot water dissolves with dolomite, calcite, and other carbonate rocks in the surrounding rocks during transport, accumulating water chemical components. Some groundwater absorbs the radioactive decay of crustal rocks as well as a tiny amount of mantle-conducted thermal energy during infiltration and transfer to depth via conductive fractures or fissures, accumulating gaseous components. Influenced by the tectonic underplate water blockage, the underground hot water upwelled along the tectonic channel and was enriched in the carbonate rock tectonic fracture zone. During this period, due to the conduction effect of the fissures near the fracture zone, the hot water mixed with quite a bit of shallow groundwater, causing changes in the water chemistry, and was finally exposed to the surface at a low water temperature. Conclusions The hydrochemical kinds of geothermal resources differ significantly between the two tectonic environments. The igneous hot spring water in the Wahongshan-Wenquan Fracture Zone has a Cl-Na chemistry that is mostly regulated by evaporation and concentration, with salts derived primarily from the breakdown of silicate rocks. The water chemistry of the carbonate hot springs throughout the Zhiduo-Yushu mountain region consists predominantly of HCO 3 -Ca type, and the component content is simultaneously controlled by water-rock action (carbonate rock dissolution) and evaporation and concentration. The hydroxide stable isotope characterization data indicates that atmospheric precipitation recharges the geothermal water in both study areas. The isotopic composition shows obvious geographic fluctuations. The isotope distribution values gradually decrease from the Wahong Mountains in the northeast to the Zhiduo-Yushu Mountains in the southwest, consistent with the elevation effect, implying that the geothermal water is replenished via atmospheric precipitation in nearby high mountains. The Wahongshan-Wenquan Fracture Zone has a thermal reservoir temperature of 88–156℃ and a hot water circulation depth of approximately 1921-3432m. The reservoir temperature of carbonate rocks in the Zhiduo-Yushu mountainous area ranges from 33.9 to 72.8℃, and the circulation depth is 989-2168m. None of the water-rock interactions of the thermal water has yet reached equilibrium. The temperature and depth of hot water circulation in individual hot springs of the sandstone thermal reservoirs are between those of the igneous and carbonate reservoirs. The geothermal gases in the research area are all dominated by atmospheric N 2 . The small amount of CO 2 in the hot springs of the Wahongshan-Wenquan Fracture Zone is mainly from a mixture of two sources: organic sediments and marine carbonate rocks. He is mostly the result of radioactive element decay in the Earth's crust, with less than 0.5% coming from the mantle. The high CO 2 level (14%) of the ZD2 hot springs in the Zhiduo-Yushu Mountains is due to a minor amount of mantle-source origin, with weathering and decarbonization of marine carbonate rocks acting as the primary regulating mechanisms. He-C isotope investigations reveal that He is primarily from the crust, with the mantle-source component not exceeding 5%, implying that the deep northwestern-trending fractures in the Zhiduo-Yushu area are linked to the mantle. By synthesizing the above analyses and engaging in discussions about the fluid circulation patterns of two convective geothermal systems with different tectonic backgrounds in the study area, we can provide a scientific foundation for the development and utilization of geothermal resources in this area, as well as for future research. In the future, it will be necessary to improve the complex transportation mechanism of geothermal fluids in the research area using the findings of existing hydrogeologic and geothermal geologic surveys, as well as more sophisticated geophysical approaches. Declarations Acknowledgments We thank the laboratories of the Oil and Gas Resources Research Center of the Northwest Institute of Ecology and Environmental Resources, Chinese Academy of Sciences for their assistance in gas testing. Author contributions LY: conceptualization, investigation, data analysis, visualization, writing - original draft. RL: data curation, project administration, validation. BL: data curation, investigation. WX: investigation, validation. JZ: resources, supervision. WL: funding acquisition, investigation, supervision, visualization, editing and revising the manuscript. All the authors read and approved the final manuscript. Funding This study was supported by the National Key Research and Development Program of China (Grant No. 2021YFB1507401), Qinghai Province Clean Energy Minerals Special Project (No. 2022013004qj004 and No. 2023086020qj002), and the Geological Survey Project of China Geological Survey (No. DD20221676, No. DD20230019). Availability of data and materials All data generated or analyzed during the study are included in this published article. Competing interests The authors declare that they have no competing interests. Ethics and consent to participate declarations Ethics and Consent to Participate declarations: not applicable. References Cheng G, Jin H. Permafrost and groundwater on the Qinghai-Tibet Plateau and in northeast China. Hydrogeology Journal. 2013;21:5-23. https://www.sci-hub.ee/10.1007/s10040-012-0927-2. Daniele L, Taucare M, Viguier B, Arancibia G, Aravena D, Roquer T, Sepúlveda J, Molina E, Delgado A, Muñoz M, Morata D. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5592114","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":391758590,"identity":"e8b8525a-dc3e-4d03-bddd-3a133d352bbe","order_by":0,"name":"Lu Yang","email":"","orcid":"","institution":"School of Environmental Studies, China University of Geosciences","correspondingAuthor":false,"prefix":"","firstName":"Lu","middleName":"","lastName":"Yang","suffix":""},{"id":391758591,"identity":"a6d48a2c-c801-410f-b874-e8c9275c3733","order_by":1,"name":"Rui Lu","email":"","orcid":"","institution":"Qinghai Geological Survey Bureau","correspondingAuthor":false,"prefix":"","firstName":"Rui","middleName":"","lastName":"Lu","suffix":""},{"id":391758592,"identity":"5d7ca6c1-0322-4007-9c71-f0c65b06a717","order_by":2,"name":"Bo Liu","email":"","orcid":"","institution":"Qinghai Geological Survey Bureau","correspondingAuthor":false,"prefix":"","firstName":"Bo","middleName":"","lastName":"Liu","suffix":""},{"id":391758593,"identity":"20c242de-b9a1-4809-a800-6f2d9c022229","order_by":3,"name":"Wenping Xie","email":"","orcid":"","institution":"Qinghai Geological Survey Bureau","correspondingAuthor":false,"prefix":"","firstName":"Wenping","middleName":"","lastName":"Xie","suffix":""},{"id":391758594,"identity":"54d9835c-8448-4f59-a91f-c7025e80aa96","order_by":4,"name":"Jinshou Zhu","email":"","orcid":"","institution":"Qinghai Geological Survey Bureau","correspondingAuthor":false,"prefix":"","firstName":"Jinshou","middleName":"","lastName":"Zhu","suffix":""},{"id":391758595,"identity":"0d552de4-4079-4e9e-a397-1581c815609c","order_by":5,"name":"Wenjing Lin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDUlEQVRIiWNgGAWjYBACPmYwxcbDwMB8gIHBwIKwFjaEFrYEoBYJIrQgmDwGQIIYLey8xyQ+7uCTMedf83XDjwIJBv7+5Q8Yv1QcZuCf3YDDYXxpkjPPsPFYzni77WYP0GESN94YMMucOcwgcecADi08Zrd529h4DG6c3XaDB6jFQOIMA7NkWxqQkYBby1+wljPPbv4Bazn+gLAWRpCW8z1st8G28DcYMH5ss8GnxfxnL9gWNrPbMgYSPBJA5x1mOGMDZGDXws9/xtjgZ9sxe4Pzh5/dfPPHRo6///jDhz8qJOT4Z2DXAgXHgDECUcADYhzmATHwgxqgfQdgFh9gYPxBQP0oGAWjYBSMKAAAfSlUFI+U0V4AAAAASUVORK5CYII=","orcid":"","institution":"Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Science","correspondingAuthor":true,"prefix":"","firstName":"Wenjing","middleName":"","lastName":"Lin","suffix":""}],"badges":[],"createdAt":"2024-12-06 08:38:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5592114/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5592114/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":71920069,"identity":"46c4e92d-ddc8-4046-a333-94b57ec0f65a","added_by":"auto","created_at":"2024-12-19 17:19:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":366168,"visible":true,"origin":"","legend":"\u003cp\u003eGeology of the study area and locations of sampling points (The data for the base map comes from (Steinshouer et al., 1999)). Fig. a. shows the Wahongshan-Wenquan Fracture Zone (Area I); Fig. b. shows the Zhiduo-Yushu Mountain Zone (Area II); Fault numbers: F1-Kangle-Tianshui Fault; F2-Zongwulanshan-Qinghai Southern Mountains Fault; F3-Wayuxiangka-Lagan Fault; F4-Wahhongshan-Wenquan Fault; F5-Kunzhong Fault; F6-South margin of Hoh Xil Fault; F7-Dangjiang-Zhimenda Fault; F8-Xijinwulanhubei-Yushu Fault; F9-Bamuqu-Gela Fault.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/c3c1cf809f4567d32983444d.png"},{"id":71920068,"identity":"a0741515-36db-4cbe-8335-786596c24acc","added_by":"auto","created_at":"2024-12-19 17:19:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":143534,"visible":true,"origin":"","legend":"\u003cp\u003eSchoeller diagram of water macronutrient ion fraction\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/efa3f00410e61e1f1441ce71.png"},{"id":71920071,"identity":"63ed56b2-8b35-493c-885a-524289f8a8aa","added_by":"auto","created_at":"2024-12-19 17:19:24","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":141809,"visible":true,"origin":"","legend":"\u003cp\u003ePiper diagram of waterchemistry\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/16efd794c3d6cb86b4502831.png"},{"id":71920998,"identity":"0b846073-19a4-4c86-a687-ebd2124f9b3f","added_by":"auto","created_at":"2024-12-19 17:27:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":111818,"visible":true,"origin":"","legend":"\u003cp\u003eSchoeller diagram of geothermal gases composition\u003c/p\u003e","description":"","filename":"floatimage41.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/424703cdce22ce2d99ee257d.png"},{"id":71921516,"identity":"9227b016-8d80-4853-88fe-faa7161f56d2","added_by":"auto","created_at":"2024-12-19 17:35:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":255312,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation diagram of major ions in geothermal water\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/7865b1a516fb9dffa75a96ea.png"},{"id":71920105,"identity":"5842ea15-c5b8-48f9-ba31-dc4434a16d78","added_by":"auto","created_at":"2024-12-19 17:19:25","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":92933,"visible":true,"origin":"","legend":"\u003cp\u003eδ\u003csup\u003e2\u003c/sup\u003eH vs. δ\u003csup\u003e18\u003c/sup\u003eO diagram of geothermal water\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/5316e1ff0bdb5311fd2868b4.png"},{"id":71920073,"identity":"95f7db7b-1181-406b-acc8-9233db6c7eed","added_by":"auto","created_at":"2024-12-19 17:19:24","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":133328,"visible":true,"origin":"","legend":"\u003cp\u003eNa-K-Mg diagram of geothermal water\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/4d0db23c1cc62148c6bbaa7a.png"},{"id":71920101,"identity":"4e27318d-1da4-4e93-b0ae-e87989c8c622","added_by":"auto","created_at":"2024-12-19 17:19:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":312382,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature vs. SI diagram of geothermal water\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/2b3ed931604ba3f9d73afcc3.png"},{"id":71920076,"identity":"28288746-67b9-43a7-a343-45e5b52d1323","added_by":"auto","created_at":"2024-12-19 17:19:24","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":130791,"visible":true,"origin":"","legend":"\u003cp\u003eTriangle diagram of He, Ar, and N\u003csub\u003e2\u003c/sub\u003e relative contents\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/07643b7d96a0e1eee44ce415.png"},{"id":71920075,"identity":"9a0780cf-aee6-4e04-bb0b-f620cf4df0d0","added_by":"auto","created_at":"2024-12-19 17:19:24","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":134792,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e4\u003c/sup\u003eHe/\u003csup\u003e20\u003c/sup\u003eNe vs. R/Ra of geothermal gases\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/b853698d3509f558bc5b5602.png"},{"id":71920083,"identity":"ff3d3db1-9a20-4496-bd4b-df3af842045c","added_by":"auto","created_at":"2024-12-19 17:19:24","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":74805,"visible":true,"origin":"","legend":"\u003cp\u003eδ\u003csup\u003e13\u003c/sup\u003e C\u003csub\u003eCO2\u003c/sub\u003e vs. R/Ra of geothermal gases\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/bcd3c8b68056368836cb2be0.png"},{"id":71920074,"identity":"5c6fb6ee-7a57-43c3-99c3-447a369c4ba8","added_by":"auto","created_at":"2024-12-19 17:19:24","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":215245,"visible":true,"origin":"","legend":"\u003cp\u003eGeothermal fluid circulation pattern in Area Ⅰ\u003c/p\u003e","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/13a238ff7fad1559fbc1d475.png"},{"id":71920106,"identity":"b91ba3cb-854f-4ffd-97af-e9a964557e9f","added_by":"auto","created_at":"2024-12-19 17:19:25","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":241390,"visible":true,"origin":"","legend":"\u003cp\u003eGeothermal fluid circulation pattern in Area Ⅱ\u003c/p\u003e","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/c0a690295ce023ec66da8032.png"},{"id":84767682,"identity":"5f6f0834-121f-4813-9a0f-93275cbc27c2","added_by":"auto","created_at":"2025-06-17 07:25:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3379903,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/845ddec1-fcc5-4b57-8149-d3bc8fb7fb8d.pdf"},{"id":71920067,"identity":"72405b2c-c521-4de1-8d3e-df93f03a36d9","added_by":"auto","created_at":"2024-12-19 17:19:23","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":48422,"visible":true,"origin":"","legend":"","description":"","filename":"Table1and2.docx","url":"https://assets-eu.researchsquare.com/files/rs-5592114/v1/9300cea5e8f1eb27f85f6e10.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Fluid chemistry and circulation patterns from typical convective hydrothermal system on the northeastern Tibetan Plateau","fulltext":[{"header":"Introduction","content":"\u003cp\u003eGeothermal energy, a clean and sustainable energy with vast reserves, has multiple uses, such as electricity production and heating. Its utilization has become crucial for global energy restructuring and sustainable development (Korucan et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Soltani et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The northeastern part of the Tibetan Plateau is a crucial section for the long-term impacts of the Indo-Eurasian plate collision as well as the transitional edge for the lateral expansion of plateau uplift. (Zhou et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Research into geothermal resources in this region began during the early 1960s. Geologists have conducted comprehensive surveys and gathered data regarding the locations of natural thermal springs throughout the region, including their temperatures, flow rates, and other fundamental physical characteristics. The results indicate that hot springs are often found in linear clusters where geological formations overlap or where primary and secondary faults intersect (Cheng \u0026amp; Jin, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Hydrothermal resources in the northeastern Tibetan Plateau show significant variations in terms of fluid chemistry, thermal reservoir types, and genesis mechanisms in different regional and tectonic contexts. Lei et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) researched the hydrochemistry of carbonate reservoir thermal springs in Yaoshuitan, Xining Basin, and proposed a mechanism for the weakly acidic water. Results suggested that the bottom crack of Laji Mountain\u0026rsquo;s northern edge directs the heat flow from deep crustal and mantle sources. This leads to a thermal metamorphism reaction of the buried thick carbonate rock and silicate at high temperatures. The hot springs are weakly acidic due to the high concentration of inorganic ions created by the metamorphic dissolution of CO\u003csub\u003e2\u003c/sub\u003e. Liu et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) used helium isotopes and isotope dating methods to identify the sources of geothermal fluids and heat from the Gonghe basin. The findings revealed that the hot spring water combines sub-modern and modern recharge sources. The fluids passed through silicate reservoirs and surrounding rocks, undergoing aqueous-rock reactions. After being heated by deep crustal heat sources, the fluids finally gushed out of the surface in the form of SO\u003csub\u003e4\u003c/sub\u003e-Cl-Na-type weakly alkaline high-temperature mineral springs. There are significant differences in local tectonic hot springs that are controlled by the same deep, major fault. Li et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) explored the connection between the hydrochemical features of hot springs and fracture activities along the Qilian-Haiyuan fault. The findings revealed the hydrochemistry of thermal water along the fault has a direct connection to the surrounding rocks as well as hydrodynamic and hydrothermal circumstances. Furthermore, the hydrochemical composition of thermal water in different segments of the fault is influenced by local tectonic activities, leading to distinctive hydrochemical characteristics. Liu et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) established a conceptual framework for fluid transport by investigating the fluid chemistry and dissolved carbon characteristics of hot springs along the Yushu-Ganzi-Xianshuihe fracture. The study revealed a spatial pattern of hydrothermal fluid chemistry, circulation paths, and thermal reservoir temperatures along the fracture system, which is controlled by the regional fault structure. However, past research has primarily concentrated on a single geothermal field or a single deep and broad fracture zone, with no systematic assessments or comparative studies on the fluid features and genesis processes of geothermal systems across different tectonic contexts. These studies were analyzed using a single methodology and mainly employed hydrogeochemical methods. Nowadays, gas geochemistry and its isotope methods have been widely used to analyze fluid sources and heat source mechanisms in geothermal systems in the southern and eastern Tibetan Plateau (Fan et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Guo et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). However, few studies have applied these methods to explore the formation factors of geothermal systems in the northeastern Plateau.\u003c/p\u003e \u003cp\u003eThis study collected natural thermal water and volatile gas samples from the Wahongshan-Wenquan Fracture and the Zhido-Yushu deep Fracture. The geochemical features of geothermal water and gases in both places will be systematically compared and analyzed by combining hydrological, gas geochemical, and isotopic methods. The similarities and differences in the sources and causes of the fluids in these two areas will be analyzed, and the geothermal fluid circulation models of the two areas will be constructed. The study's findings are intended to expand the theoretical basis for geothermal research on the northeastern Tibetan Plateau.\u003c/p\u003e"},{"header":"Geological background","content":"\u003cp\u003eThe study area includes the Wahong Mountain in east-central Qinghai Province (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) and the mountains along the Zhiduo-Yushu region in southwestern Qinghai Province (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Area Ⅰ is geotectonically located in the northeastern Tibetan Plateau East Kunlun orogenic belt, and hot springs along the fracture zone are exposed in a string of beads in the Indo-Chinese granite, including Xinghai Sangchugou hot springs (XH2, 78\u0026deg;C), Ulaanba hard Geli hot springs (WL1, 44\u0026deg;C), Dulan Chahanwusu hot springs (DL1, 87\u0026deg;C), Anguotan hot springs (DL2, 67\u0026deg;C), and Xinghai Wenquan hot springs (XH1, 64\u0026deg;C) along the southernmost part of the fracture exposed stratigraphy lithology in sandstone. Except for XH1, which has a high flow rate of 25.31L/s, the other granite thermal reservoir hot springs have flow rates that vary between 0.221 and 4.132L/s. Area Ⅱ is geotectonically positioned in the northeastern part of the Yangzi River Plate, between the Bayan Lola orogenic belt and the North Qiangtang-Sanjiang orogenic belt, with hot springs dispersed along the main NW-oriented fracture. From north-west to south-east, there are the Sagongsi hot spring (ZD1, 24\u0026deg;C), the Baihailuo hot spring (ZD2, 27\u0026deg;C), the Riqingdangjiang hot spring (ZD3, 19\u0026deg;C) in Zhiduo County, and the Chatong hot spring (YS1, 65\u0026deg;C), Batanghe hot springs (YS2, 12.5\u0026deg;C), Angpusi hot springs (YS3, 33\u0026deg;C), and Shabajiugongzhu hot springs (YS4, 24\u0026deg;C) in Yushu City. Hot springs are found in Triassic carbonate rocks, except for YS1 (65\u0026deg;C), which has the highest water temperature, where the exposed stratigraphic lithology is sandy slate. The flow rate varies considerably, spreading between 0.7 and 200 L/s.\u003c/p\u003e \u003cp\u003eThe Wahongshan-Wenquan Fracture is a NNW-trending dextral slip crustal fracture. It starts from the southern edge of Lake Harrah in the north and ends at southern Wenquan Town in Xinghai County, covering more than 300 km. This fracture truncates the Zongwulongshan-Qinghai Southern Mountains Fault in the north, forming the eastern and western boundaries of the Qaidam and Gonghe basins, respectively. This fracture also exists along the Gonghe Basin-East Kunlun Magma Belt intersection, managing the transitional contact between each of them. (Wang \u0026amp; Burchfiel, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). The go-slip of the Wahongshan-Wenquan Fracture caused the mountain to rise. Influenced by magmatic activities, a tectonic-magmatic uplift zone with a nearly north-south orientation was formed (Dong et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Lu et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The tectonic magma belt runs north-south from the Wahongshan-Wenquan Fracture and consists of volcanic rocks of the Triassic Erlangshan Formation and neutral acidic rocks of the Indo-Chinese-Yanshanian period, which form the main body of the mountain (Sun et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The geomorphological type of the Zhido-Yushu study area is dominated by tectonic erosion of the mountain plateau, and the tectonic lines and stratigraphic regions in the area are basically in the same direction of spreading, presenting a northwest-southeast oriented strip spreading. Fracture tectonic development in this area is mostly NW-SE-oriented pressure or pressure-twisting fracture, including the southern edge of the Hoh Xil active Fault and the Xijinwulanhubei-Yushu Fault. The fracture of the southern edge of Hoh Xil is generally near NNW for the Bayan Lola orogenic belt and the North Qiangtang-Sanjiang orogenic belt of the division of the fracture. The Xijinwulanhubei-Yushu Fracture extends in a northwesterly direction, with obvious fault geomorphological features, and is a Holocene-acquired left-rotating retrograde fracture (Huang et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The widespread stratigraphy in this region is Triassic, followed by Jurassic.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eSample collection\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the location of sampling points. The hot spring water samples for the majority of the study area were collected between May and July 2022. Only three sets of samples (ZD3, YS1, and YS3) were collected in July 2023. Water temperature, pH, and TDS were determined through a multiparameter water quality tester (WTWMulti340i/SET, Germany) before sample collection in the field. Geothermal gases were collected using the drainage gas collection method. The specific operation is as follows: insert a thin plastic tube into a high-temperature-resistant thin-mouthed glass bottle filled with 500 mL of sampled hot spring water (to avoid air contamination) and connect it with a reversed Teflon funnel, immerse it in the hot spring water, and then seal when the gas content is approximately 2/3 of the volume of the glass bottle. Due to field conditions, H\u003csub\u003e2\u003c/sub\u003eS and SO\u003csub\u003e2\u003c/sub\u003e were not measured on-site.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSample testing\u003c/h3\u003e\n\u003cp\u003eWater chemistry and stable isotope tests were performed at the Geochemical Analysis and Testing Centre, Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences. The hot water cation fraction was detected by inductively coupled plasma emission spectrometry (Optima 8000 ICP-OES), Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e were detected by ion chromatography (ICS-2500), and HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e was measured by acid-base titration. Deuterium-oxygen isotopes were analyzed with an ultra-high-precision hydroxide-oxygen isotope analyzer (L2130-i) with a testing accuracy of 0.025%. Gas samples were analyzed by the Oil and Gas Resources Research Centre of the Northwest Institute of Ecology and Environmental Resources, Chinese Academy of Sciences. Constant gas components were measured by the MAT271 mass spectrometer with a relative standard error of less than 5%. Gas rare components and isotopes were analyzed with a Noblesse Rare Gas Isotope Mass Spectrometer (RGIMS). The testing error for He isotope measurements was \u0026plusmn;\u0026thinsp;10% for R-values exceeding 1 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e and \u0026plusmn;\u0026thinsp;15% for R-values between 1 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e and 1 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e. Carbon isotopes were analyzed and tested on a Delta Plus XL mass spectrometer and expressed as PDB standards. The test results are shown in Table\u0026nbsp;1 and Table\u0026nbsp;2.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eHydrochemical and isotopic composition\u003c/h2\u003e \u003cp\u003eBased on Table\u0026nbsp;1 and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the geothermal water temperature in the Wahongshan-Wenquan Fracture Zone (Area I) ranges from 44\u0026deg;C to 87\u0026deg;C. The pH value falls between 7.46 and 8.82, and the dominant cations in the geothermal water are Na\u003csup\u003e+\u003c/sup\u003e, with significant variation in the anions, primarily Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e. The hot spring water in Area Ⅰ contains three chemical types: the Cl-Na type, the Cl\u0026bull;SO\u003csub\u003e4\u003c/sub\u003e-Na type, and the SO\u003csub\u003e4\u003c/sub\u003e\u0026bull;Cl-Na type (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Combined with the geographic location of the hot springs, it can be found that the springs located distant near the Wahongshan-Wenquan Fault belong to the Cl-Na kind. The Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e concentration increases with distance from the main fault, with the maximum value appearing in DL1, reaching 1461 mg/L. The hot springs around the fault primarily contain Cl\u0026bull;SO\u003csub\u003e4\u003c/sub\u003e-Na and SO\u003csub\u003e4\u003c/sub\u003e\u0026bull;Cl-Na type water, with significantly elevated SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e levels. The temperature of the geothermal water in the Zhiduo-Yushu hot spring concentration area (Area II) ranges from 12.5\u0026deg;C to 65\u0026deg;C. The pH values range from 6.93 to 7.84, and all samples are weakly alkaline except for YS3, which is weakly acidic. The geothermal water in Area II contains a high concentration of HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e. The water in the greywacke reservoir is mainly composed of Ca\u003csup\u003e2+\u003c/sup\u003e and Mg\u003csup\u003e2+\u003c/sup\u003e. The hydrochemistry includes HCO\u003csub\u003e3\u003c/sub\u003e-Ca, HCO\u003csub\u003e3\u003c/sub\u003e-Ca\u0026bull;Mg, HCO\u003csub\u003e3\u003c/sub\u003e-Mg\u0026bull;Ca, and HCO\u003csub\u003e3\u003c/sub\u003e-Mg, as well as HCO\u003csub\u003e3\u003c/sub\u003e-Ca\u0026bull;Na types (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The cations in the geothermal water of the sand slate reservoir YS1 are dominated by Na\u003csup\u003e+\u003c/sup\u003e, and the hydrochemical type exhibits the HCO\u003csub\u003e3\u003c/sub\u003e-Na type. The δD and δ\u003csup\u003e18\u003c/sup\u003eO values in the geothermal water samples from Area I range from \u0026minus;\u0026thinsp;92\u0026permil; to -88\u0026permil; and \u0026minus;\u0026thinsp;12.2\u0026permil; to -11.6\u0026permil;, respectively. The composition of δD and δ\u003csup\u003e18\u003c/sup\u003eO values in the samples from Area II range from \u0026minus;\u0026thinsp;108\u0026permil; to -101\u0026permil; and \u0026minus;\u0026thinsp;14.4\u0026permil; to -14\u0026permil;, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eGeothermal gas chemistry and isotopic composition\u003c/h2\u003e \u003cp\u003eGeothermal gases have two groups based on their main components, one is rich in N\u003csub\u003e2\u003c/sub\u003e, while the other is dominated by CO\u003csub\u003e2\u003c/sub\u003e. The results of component and isotope analyses of the gases (Table\u0026nbsp;2) indicate that their components display a wide range of variations and are primarily dominated by N\u003csub\u003e2\u003c/sub\u003e, which is a type of gas classified as N\u003csub\u003e2\u003c/sub\u003e. The main gas components in Area Ⅰ were N\u003csub\u003e2\u003c/sub\u003e (73.67\u0026thinsp;~\u0026thinsp;83.63%), O\u003csub\u003e2\u003c/sub\u003e (13.87\u0026thinsp;~\u0026thinsp;18.53%), and CO\u003csub\u003e2\u003c/sub\u003e (0.19\u0026thinsp;~\u0026thinsp;7.83%), with traces of Ar (0.96\u0026thinsp;~\u0026thinsp;1.16%), CH\u003csub\u003e4\u003c/sub\u003e (0.01\u0026thinsp;~\u0026thinsp;0.04%), and He (0.0052\u0026thinsp;~\u0026thinsp;0.1753%). The gases from the hot springs in Area Ⅱ were dominated by N\u003csub\u003e2\u003c/sub\u003e, with an average concentration of over 61.19%. The CO\u003csub\u003e2\u003c/sub\u003e content was higher than that in Area Ⅰ, with the highest sample reaching 34.14%. Additionally, there were trace amounts of O\u003csub\u003e2\u003c/sub\u003e, Ar, CH\u003csub\u003e4\u003c/sub\u003e, and He (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The small amount of O\u003csub\u003e2\u003c/sub\u003e detected in the gas components may be due to irregular sampling and storage, atmospheric mixing, and other factors. Therefore, the O\u003csub\u003e2\u003c/sub\u003e contents fail to accurately reflect the actual amount of the spilled geothermal gases. The \u003csup\u003e3\u003c/sup\u003eHe/\u003csup\u003e4\u003c/sup\u003eHe ratio in Area I ranges from 1.8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e to 1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e, equivalent to 0.013\u0026thinsp;~\u0026thinsp;0.07Ra (Ra represents the \u003csup\u003e3\u003c/sup\u003eHe/\u003csup\u003e4\u003c/sup\u003eHe proportion in the modern standard air). The He isotope ratios of ZD2 and YS1 in Area II are 0.203 Ra and 0.429 Ra, respectively. The \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{{\\text{C}\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003e values have a wide range of distribution. The samples collected in Area I have \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{{\\text{C}\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003e values between \u0026minus;\u0026thinsp;16\u0026permil; and \u0026minus;\u0026thinsp;10\u0026permil;, while the geothermal gases in Area II have values ranging from \u0026minus;\u0026thinsp;6.8\u0026permil; to -4.8\u0026permil;.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cstrong\u003eSources of chemical components of geothermal water\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGenerally, high levels of Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e in thermal water are principally caused due to the mixing with magmatic fluids (Guo, \u003cspan\u003e2012\u003c/span\u003e; Pan et al., \u003cspan\u003e2021\u003c/span\u003e). Guo et al. (2020) concluded that the hydrochemistry of a non-carbonate thermal reservoir containing a magmatic heat supply is distinguished by the simultaneous occurrence of acidic, neutral, and weakly alkaline geothermal water. Area I, where the anion is dominated by Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e, does not satisfy the occurrence of these three types of water at the same time, so the possibility of its geothermal fluids being affected by magma water is very low. Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e may originate from the leaching process of surrounding salt minerals during geothermal water runoff (Ma et al., \u003cspan\u003e2020\u003c/span\u003e), which is associated with evaporative concentration. The water temperature of DL1 is reaching 87\u0026deg;C, close to the local boiling point. Its water chemistry is significantly concentrated by evaporation, resulting in the highest Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e content. The gradual increase of SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e in geothermal water close to the main fault may be related to the intrusion of sulfate minerals during hydrometamorphism. The hydrological interaction of thermal water from the Greywacke stratum in Area II regarding the carbonate rocks during circulation is the decisive factor controlling the type of water chemistry.\u003c/p\u003e\n\u003cp\u003eBivariate plots of different anions and cations can further reveal the sources of solutes in the water column (Hui et al., \u003cspan\u003e2023\u003c/span\u003e; Li et al., \u003cspan\u003e2021\u003c/span\u003e; Luo et al., \u003cspan\u003e2022\u003c/span\u003e; Ma et al., \u003cspan\u003e2023\u003c/span\u003e). Figure \u003cspan\u003e5\u003c/span\u003ea reveals that the samples in Area I are scattered along the 1:1 line, with most of them tilted towards the Na\u0026thinsp;+\u0026thinsp;K axis. This phenomenon suggests that the presence of Na\u003csup\u003e+\u003c/sup\u003e is not solely due to rock salt dissolution but also from other sources such as the dissolution of silicate rocks or ion exchange interactions. Figure \u003cspan\u003e5\u003c/span\u003eb shows that the hot spring sites in Area II exhibit a trend closer to the 1:1 line trend. This implies that the weathering dissolution of carbonates and sulfates possesses a crucial function in controlling Ca\u003csup\u003e2+\u003c/sup\u003e and Mg\u003csup\u003e2+\u003c/sup\u003e levels in the geothermal waters of the Zhiduo-Yushu mountains. Most samples are shifted towards the HCO\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;SO\u003csub\u003e4\u003c/sub\u003e axis, indicating that there are also varying degrees of silicate mineral contributions. The YS1 deviation is most pronounced for sandstone thermal reservoirs, with the largest contribution from silicate rock dissolution. The process of weathering and hydrolysis of dolomite and calcite also releases Ca\u003csup\u003e2+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e, and HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e. In Fig. \u003cspan\u003e5\u003c/span\u003ec, several of the hot springs points in Area II are located near the 1:1 line, indicating that calcite weathering is the main process of mineralization. Additionally, some points fall between the 1:1 and 1:2 lines, suggesting that the hydrochemistry of these hot springs is affected by both calcite and dolomite weathering. The points in Fig. \u003cspan\u003e5\u003c/span\u003ed all deviate from the 1:1 line, demonstrating that the dissolution of sulfate rocks like gypsum is not the main cause of SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e enrichment in some of the geothermal waters in Area I. Sulfurous gas odor is evident in these hot springs during field collection, and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e can also be formed by geothermal fluids interacting with shallow, oxygen-rich groundwater during ascent (Daniele et al., \u003cspan\u003e2020\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSources of water recharge in hot spring\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe stable isotope values of the geothermal waters from the study area are all close to the global meteoric water line (GMWL). The deuterium excess parameter (d) values of the samples are between 0 and 15%, with a higher concentration in the 0 to 10% range. This suggests that atmospheric rainfall is the most probable supply of replenishment for these thermal waters. (Fig. \u003cspan\u003e6\u003c/span\u003e). The isotopic compositions of different areas have obvious spatial variability, and the mean values of isotopes gradually decrease from the Wahongshan Fracture Zone (Area I) to the southwestern Zhiduo-Yushu Mountainous area (Area II). This reflects differences in the sources of atmospheric precipitation, which are related to elevation. Isotopic values decrease with increasing elevation, indicating that hot spring water in Area II comes from precipitation recharge at higher elevations. The elevation of monsoon water vapor due to altitude can also impact \u0026delta;\u003csup\u003e18\u003c/sup\u003eO values (Yao et al., \u003cspan\u003e2013\u003c/span\u003e). The higher \u0026delta;\u003csup\u003e18\u003c/sup\u003eO values in the northern regions result from water vapor cycling in the inland areas. In comparison, the lower \u0026delta;\u003csup\u003e18\u003c/sup\u003eO values in the southern regions may be linked to monsoon-driven oceanic water vapor (Tian et al., \u003cspan\u003e2001\u003c/span\u003e). The thermal waters are refilled by atmospheric precipitation, therefore their isotopic distribution is comparable to that of precipitation. Overall, the \u0026delta;\u003csup\u003e18\u003c/sup\u003eO excursion for all water samples is not significant, especially in Area II. This represents that groundwater circulation is insufficiently deep to allow for significant water-rock interaction.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReservoir temperature and circulation depth\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReservoir temperature\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDeep reservoir temperatures can be calculated from geochemical temperature scales. The commonly used chemical temperature scales include cationic scales such as Na-K geothermometers, K-Mg geothermometers, and Na-K-Ca geothermometers (Fournier, \u003cspan\u003e1977\u003c/span\u003e; Fournier, \u003cspan\u003e1981\u003c/span\u003e; Giggenbach, \u003cspan\u003e1988\u003c/span\u003e; Giggenbach, \u003cspan\u003e1989\u003c/span\u003e), SiO\u003csub\u003e2\u003c/sub\u003e temperature scales, and multi-component mineral equilibrium methods. Estimates using cationic geothermometers are more precise only when the chemistry of the groundwater is in equilibrium after an extended period of water-rock interaction. It is considered that hot water remains in equilibrium even after it has reached the surface. The Na-K-Mg ternary diagram can be used to make a preliminary determination of whether the thermal water chemistry is in equilibrium. Figure \u003cspan\u003e7\u003c/span\u003e illustrates that all water samples in the study area fall within partially mature or immature zones, indicating that the water-rock interaction has not yet reached complete equilibrium. In this case, the cation temperature scale estimation results will have a large deviation, so the use of the SiO\u003csub\u003e2\u003c/sub\u003e temperature scale and the multi-component mineral balance method is considered to estimate the reservoir temperature.\u003c/p\u003e\n\u003cp\u003eThe multi-component mineral equilibrium method involves modeling the change in the saturation index of multiple minerals at various temperatures. The thermal reservoir temperature is the temperature at which the saturation index (SI) values for different minerals approach 0 (Reed \u0026amp; Spycher, \u003cspan\u003e1984\u003c/span\u003e; Tole et al., \u003cspan\u003e1993\u003c/span\u003e). The multi-component mineral balance diagram of the geothermal water is depicted in Fig. \u003cspan\u003e8\u003c/span\u003e, and Table 3 shows the estimated thermal reservoir temperature. The results indicate that the calculated chalcedony temperature scale yields lower results. The quartz temperature scale results are similar to those derived from estimation using the multimineral equilibrium graphical method. By combining these two sets of results, we can determine the range of thermal reservoir temperatures of the samples. The thermal reservoir temperatures estimated for all hydrothermal water samples were higher than the actual measurement temperatures. The reservoir temperature in Area Ⅰ ranges from 88 to 156℃, significantly higher than that in Area Ⅱ. The granite thermal reservoir is significantly higher than the greywacke thermal reservoir, while the two hot springs (XH2, YS1) exposed in sandstone in the study area have reservoir temperatures between the granite reservoir and the greywacke reservoir.\u003c/p\u003e\n\u003ch3\u003eCirculation depth\u003c/h3\u003e\n\u003cp\u003eUnderground hot water is typically heated by deep thermal sources during transportation, and determining the circulation depth of thermal water is useful for analyzing the formation of hot springs. The depth of underground circulation can be calculated based on the estimated thermal reservoir temperature with the following formula:\u003c/p\u003e\n\u003cdiv id=\"Equ1\"\u003e\n \u003cdiv id=\"FileID_Equ1\" name=\"EquationSource\"\u003e$$H=\\frac{{T - {T_0}}}{K}+{H_0}$$\u003c/div\u003e\n \u003cdiv\u003e1\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eWhere H is the circulation depth (m), T is the thermal reservoir temperature (℃), T\u003csub\u003e0\u003c/sub\u003e is the local average annual air temperature (℃), K is the local geothermal gradient (℃/100 m), and H\u003csub\u003e0\u003c/sub\u003e is the thickness of the constant temperature zone (m). According to the information from previous studies, the multi-year average annual air temperature in Area Ⅰ is 3.8\u0026deg;C, the thickness of the constant temperature zone is 50m, and the local geothermal gradient is taken as 4.5\u0026deg;C/100m (Wang et al., \u003cspan\u003e2023\u003c/span\u003e); The average annual temperature in Area Ⅱ is 2.9\u0026deg;C, the thickness of the constant temperature zone is 50m, and the local geothermal gradient is taken as 3.4\u0026deg;C/100m (Wang et al., \u003cspan\u003e2024\u003c/span\u003e). Calculation results (Table 3) indicate that the Wahongshan-Wenquan Fracture hydrothermal system circulates at a depth of 1921 to 3432m. The sandstone thermal reservoir YS1 has a deeper circulation depth. Additionally, the geothermal water in other remaining greywacke reservoirs in Area II circulates at depths ranging from 989 to 2168m.\u0026nbsp;\u003c/p\u003e\n\u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"8\"\u003e\n \u003cp\u003eTable\u0026nbsp;3 Reservoir temperature (℃) and circulation depth (m) of geothermal systems in the study area.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eArea\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eID\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eChalcedony\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eQuartz\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eno loss\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eQuartz\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003emaximum loss\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMulticomponent\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003emineral equilibria\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTemperature\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003erange\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eCirculation depth\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"5\"\u003e\n \u003cp\u003eⅠ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXH1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e95.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e123.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e123.6\u0026ndash;128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2712\u0026ndash;2810\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXH2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e94.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120.6\u0026ndash;121\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2646\u0026ndash;2654\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWL1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e64.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e95.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e96.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e88-95.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1921\u0026ndash;2079\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDL1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e144.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e138.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e156\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e144.5\u0026ndash;156\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3177\u0026ndash;3432\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDL2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e115.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e141.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e136.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e147\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e141.8\u0026ndash;147\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3117\u0026ndash;3232\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"6\"\u003e\n \u003cp\u003eⅡ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eZD1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e58.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e58.8\u0026ndash;60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1744\u0026ndash;1780\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eZD2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e69.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e69.1\u0026ndash;70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2056\u0026ndash;2083\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eZD3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e47.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e54.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e47.7\u0026ndash;50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1408\u0026ndash;1477\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYS1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e101.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e102.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100-101.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2992\u0026ndash;3032\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYS3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e41.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e72.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e77.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63-72.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e1871\u0026ndash;2168\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYS4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-8.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33.9\u0026ndash;37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e989\u0026ndash;1083\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cdiv id=\"Sec11\"\u003e\n \u003ch2\u003eSources of geothermal gases\u003c/h2\u003e\n \u003cp\u003eAr in geothermal gases is mainly of atmospheric origin (Fischer et al., \u003cspan\u003e1998\u003c/span\u003e; Lowenstern et al., \u003cspan\u003e2015\u003c/span\u003e). Harrison et al. (\u003cspan\u003e1999\u003c/span\u003e) reported values of 295.5 for atmospheric \u003csup\u003e40\u003c/sup\u003eAr/\u003csup\u003e36\u003c/sup\u003eAr and 7300\u0026thinsp;\u0026plusmn;\u0026thinsp;900 for mantle \u003csup\u003e40\u003c/sup\u003eAr/\u003csup\u003e36\u003c/sup\u003eAr. The geothermal gases in the research region have \u003csup\u003e40\u003c/sup\u003eAr/\u003csup\u003e36\u003c/sup\u003eAr values ranging from 289.6 to 304.3, which are similar to atmospheric values, indicating that the Ar in this area is primarily of atmospheric origin. As seen in Fig. \u003cspan\u003e9\u003c/span\u003e, all of the samples\u0026rsquo; N\u003csub\u003e2\u003c/sub\u003e/Ar values are greater compared to the atmospheric precipitation value of 38 and close to the atmospheric value of 84. This indicates that the N\u003csub\u003e2\u003c/sub\u003e is predominantly atmospheric. The comparatively elevated N\u003csub\u003e2\u003c/sub\u003e/Ar values are explained by three primary points: (1) magmatic gas input, (2) crustal organic metamorphic genesis, and (3) Ar depletion. Although the N\u003csub\u003e2\u003c/sub\u003e/Ar value of YS1 (87) in the sandstone reservoirs of Area II is greater than the atmospheric value of 84, the likelihood of magmatism can be ruled out. Typical magmatic gases have N\u003csub\u003e2\u003c/sub\u003e/Ar ratios between 800 and 2000 (Zhao et al., \u003cspan\u003e2002\u003c/span\u003e). The higher N\u003csub\u003e2\u003c/sub\u003e/Ar value of YS1 than the atmospheric value may be related to organic genesis. The sample points in Fig. \u003cspan\u003e9\u003c/span\u003e are evenly distributed along the line connecting He to the atmospheric value, showing that the gas is mostly produced by the mixing of atmospheric and crustal sources and that He is a byproduct of the radioactive elements disintegration.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\"\u003e\n \u003ch2\u003eIsotopic characterization of geothermal gases\u003c/h2\u003e\n \u003cp\u003eGeothermal gases from various sources have varied chemical and isotopic signatures, and studying the isotopic compositions of the gases can help identify the sources of geothermal gases.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\"\u003e\n \u003ch2\u003eHelium isotopes\u003c/h2\u003e\n \u003cp\u003eHe has two naturally occurring stable isotopes, \u003csup\u003e3\u003c/sup\u003eHe and \u003csup\u003e4\u003c/sup\u003eHe, each with a unique origin. Mantle degassing releases the element \u003csup\u003e3\u003c/sup\u003eHe, which is native to the Earth, while crustal sources of \u003csup\u003e4\u003c/sup\u003eHe are formed by the radiative disintegration of the radionuclide (U and Th). He isotopes are an important parameter for determining the source of He and are often described as \u003csup\u003e3\u003c/sup\u003eHe/\u003csup\u003e4\u003c/sup\u003eHe values (R). The atmospheric \u003csup\u003e3\u003c/sup\u003eHe/\u003csup\u003e4\u003c/sup\u003eHe value (Ra) is commonly used as a reference, Ra\u0026thinsp;=\u0026thinsp;1.43\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e (Sano \u0026amp; Wakita, \u003cspan\u003e1985\u003c/span\u003e). Geothermal systems contain three main sources of He: atmosphere, crust, and mantle, with \u003csup\u003e3\u003c/sup\u003eHe/\u003csup\u003e4\u003c/sup\u003eHe ratios of Ra, 0.005\u0026ndash;0.02 Ra, and 8\u0026thinsp;\u0026plusmn;\u0026thinsp;1 Ra, respectively (Sano \u0026amp; Marty, \u003cspan\u003e1995\u003c/span\u003e). The \u003csup\u003e4\u003c/sup\u003eHe/\u003csup\u003e20\u003c/sup\u003eNe ratio combined with the R/Ra ratio is widely used to quantitatively identify helium from various sources (Karakuş, \u003cspan\u003e2015\u003c/span\u003e; Wang et al., \u003cspan\u003e2020\u003c/span\u003e). In Fig. \u003cspan\u003e10\u003c/span\u003e, the YS1 sample is near the air end, suggesting that the sample may have been subjected to severe atmospheric pollution, leading to a predominantly atmospheric genesis of its He. Other sample points with less air pollution are near the 100% crustal end, and the proportion of mantle-sourced He to total He for a few samples does not exceed 5%, indicating that He is predominantly of crustal origin in the two regions, while some samples contain small amounts of mantle-sourced incorporation.\u003c/p\u003e\n \u003cp\u003eThe three-component mixing model (Eq. \u003cspan\u003e2\u003c/span\u003e\u0026ndash;Eq. \u003cspan\u003e4\u003c/span\u003e) (Sano et al., \u003cspan\u003e1982\u003c/span\u003e) can quantify the contribution of various He sources to total He. The results are reported in Table \u003cspan\u003e4\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv id=\"Equ2\"\u003e\n \u003cdiv id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Equ4\"\u003e\u003cimg src=\"https://myfiles.space/user_files/122228_c8a1650c59388082/122228_custom_files/img1734628526.png\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003ewhere A, M, and C represent the proportion of atmospheric, mantle, and crustal sources, respectively. Ra, Rm, and Rc values are 1.4 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e, 1.1 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e, and 1.5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e, respectively. (\u003csup\u003e4\u003c/sup\u003eHe/\u003csup\u003e20\u003c/sup\u003eNe)\u003csub\u003ea\u003c/sub\u003e, (\u003csup\u003e4\u003c/sup\u003eHe/\u003csup\u003e20\u003c/sup\u003eNe)\u003csub\u003em\u003c/sub\u003e, and (\u003csup\u003e4\u003c/sup\u003eHe/\u003csup\u003e20\u003c/sup\u003eNe)\u003csub\u003ec\u003c/sub\u003e are the \u003csup\u003e4\u003c/sup\u003eHe/\u003csup\u003e20\u003c/sup\u003eNe ratios for the atmosphere, mantle, and crustal end, with values of 0.318, 1000, and 1000, respectively.\u003c/p\u003e\n \u003cp\u003eAccording to Fig. \u003cspan\u003e10\u003c/span\u003e and Table \u003cspan\u003e4\u003c/span\u003e, it can be seen that crustal source He accounts for 92.17%~99.46% of all the samples from the Wahongshan-Wenquan Fracture Zone, and only two hot springs contain a small amount of mantle He (0.26%, 0.13%), indicating the He gas from Area I is mainly derived from crustal and atmospheric. The less air-polluted ZD2 in Area II possesses a high mantle contribution of about 2.19%. This hot spring has a relatively high R/Ra value (0.429), implying that the fracture system in the Zhiduo section extends deeper compared to the geothermal system in Area I and that the deep, large fractures provide upward pathways for deep volatiles such as mantle He (Tian et al., \u003cspan\u003e2021\u003c/span\u003e). Overall, the vast majority of samples He in the research area come from crustal sources, with an average contribution of 96.55%. This finding is consistent with the conclusion that the stacking of radioactively enriched strata in the Tibetan Plateau crust results in a significant contribution of crustal heat (Tian et al., \u003cspan\u003e2018\u003c/span\u003e; Zhou et al., \u003cspan\u003e2017\u003c/span\u003e). Mantle source contributions in the Zhiduo-Yushu Mountains are higher than in the Wahongshan-Wenquan Fracture Zone, and north-west-south-east-trending faults in Area Ⅱ have deep volatile fluxes.\u0026nbsp;\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 4\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eHelium sources of geothermal gases\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eArea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eID\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eHe sources(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"5\"\u003e\n \u003cp\u003eⅠ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXH1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e99.46\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXH2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e92.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWL1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e95.65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDL1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e99.20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDL2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e97.49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eⅡ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eZD2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e95.34\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYS1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e93.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.41\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\"\u003e\n \u003ch2\u003eCarbon isotopes\u003c/h2\u003e\n \u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e in geothermal fluids consists of three main sources: the mantle, metamorphic inorganic carbon, and organic carbon in sediments. The range of \u003cspan\u003e\u003cspan\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{\\text{C}{\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003e varies depending on the source of CO\u003csub\u003e2\u003c/sub\u003e. Carbon isotope values can identify CO\u003csub\u003e2\u003c/sub\u003e genesis. Mantle sources (mid-ocean ridge basalts) have \u003cspan\u003e\u003cspan\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{\\text{C}{\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003e values ranging from \u0026minus;\u0026thinsp;9\u0026permil; to -4\u0026permil;, metamorphic decarbonization of marine carbonates has \u003cspan\u003e\u003cspan\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{\\text{C}{\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003evalues of 0\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026permil;, and organic sediment genesis has lower values of \u003cspan\u003e\u003cspan\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{\\text{C}{\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003e generally less than \u0026minus;\u0026thinsp;20\u0026permil; (Sano \u0026amp; Marty, \u003cspan\u003e1995\u003c/span\u003e). Due to the overlap of carbon 13 values from different sources in practice and the fact that CO\u003csub\u003e2\u003c/sub\u003e release is also related to many factors such as magma degassing, material differentiation, alteration of the surrounding rocks, and geotectonic effects (Yang, 1999), it is not possible to accurately identify the cause of CO\u003csub\u003e2\u003c/sub\u003e based on carbon isotope values alone. Combined CO\u003csub\u003e2\u003c/sub\u003e-He isotopes can accurately determine CO\u003csub\u003e2\u003c/sub\u003e sources (O\u0026apos;nions \u0026amp; Oxburgh, \u003cspan\u003e1988\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan\u003e11\u003c/span\u003e shows that the \u003cspan\u003e\u003cspan\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{\\text{C}{\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003e values of hot spring samples in Area I vary from \u0026minus;\u0026thinsp;20\u0026permil; to -10\u0026permil;. The low CO\u003csub\u003e2\u003c/sub\u003e concentration is primarily a mixture of two sources: organic sediments and marine carbonate rocks. ZD2 has a higher \u003cspan\u003e\u003cspan\u003e\\(\\:{{\\delta\\:}}^{13}{\\text{C}}_{\\text{C}{\\text{O}}_{2}}\\)\u003c/span\u003e\u003c/span\u003e value (\u0026gt;-10\u0026permil;) and is closer to the MORB end than the Area I samples. Combined with the results of the He isotope analysis, it is concluded that the CO\u003csub\u003e2\u003c/sub\u003e in ZD2 has a mantle source genesis in addition to the weathering and decarbonization of the marine carbonate rocks as the main controlling factors. The northwesterly spreading Hoh Xil Southern Margin Fault near the hot spring outcrop site transports CO\u003csub\u003e2\u003c/sub\u003e from a deep mantle source, whereas the deep big fracture is the primary condition for deep heat conduction.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\"\u003e\n \u003ch2\u003eConceptual model of geothermal fluid circulation\u003c/h2\u003e\n \u003cp\u003eThe Wahongshan-Wenquan Fracture Zone (Area I) represents a typical igneous thermal reservoir hydrothermal convection system (Fig. \u003cspan\u003e12\u003c/span\u003e). The hot springs are replenished by atmospheric precipitation from Wahong Mountain. Cold water flows downward through fault fracture zones, receiving heating from convective heat sources and radiogenic heating of intrusive rocks, and the water temperature rises continuously. Salt rock dissolution and cation exchange provide a fluid source for the production of Cl-Na-rich geothermal water. The gaseous components (N\u003csub\u003e2,\u003c/sub\u003e Ar, and He) are continuously introduced, while the \u003csup\u003e4\u003c/sup\u003eHe created by the thicker crust\u0026apos;s radioactive disintegration is constantly dissolved in the water. The fluid upwells when it encounters a torsional fracture, mixes with varying proportions of cold groundwater as it rises, and is continuously mixed with atmospheric components, eventually flowing out to the surface.\u003c/p\u003e\n \u003cp\u003eThe thermal fluids in the Zhiduo-Yushu Mountains (Area II) are affected by tectonic activity, and the carbonate rocks near the deep and large fractures constitute karst-fissure-type thermal storage (Fig. \u003cspan\u003e13\u003c/span\u003e). The thermal water is replenished with atmospheric precipitation from neighboring mountains, and the underground hot water dissolves with dolomite, calcite, and other carbonate rocks in the surrounding rocks during transport, accumulating water chemical components. Some groundwater absorbs the radioactive decay of crustal rocks as well as a tiny amount of mantle-conducted thermal energy during infiltration and transfer to depth via conductive fractures or fissures, accumulating gaseous components. Influenced by the tectonic underplate water blockage, the underground hot water upwelled along the tectonic channel and was enriched in the carbonate rock tectonic fracture zone. During this period, due to the conduction effect of the fissures near the fracture zone, the hot water mixed with quite a bit of shallow groundwater, causing changes in the water chemistry, and was finally exposed to the surface at a low water temperature.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe hydrochemical kinds of geothermal resources differ significantly between the two tectonic environments. The igneous hot spring water in the Wahongshan-Wenquan Fracture Zone has a Cl-Na chemistry that is mostly regulated by evaporation and concentration, with salts derived primarily from the breakdown of silicate rocks. The water chemistry of the carbonate hot springs throughout the Zhiduo-Yushu mountain region consists predominantly of HCO\u003csub\u003e3\u003c/sub\u003e-Ca type, and the component content is simultaneously controlled by water-rock action (carbonate rock dissolution) and evaporation and concentration.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe hydroxide stable isotope characterization data indicates that atmospheric precipitation recharges the geothermal water in both study areas. The isotopic composition shows obvious geographic fluctuations. The isotope distribution values gradually decrease from the Wahong Mountains in the northeast to the Zhiduo-Yushu Mountains in the southwest, consistent with the elevation effect, implying that the geothermal water is replenished via atmospheric precipitation in nearby high mountains.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe Wahongshan-Wenquan Fracture Zone has a thermal reservoir temperature of 88\u0026ndash;156℃ and a hot water circulation depth of approximately 1921-3432m. The reservoir temperature of carbonate rocks in the Zhiduo-Yushu mountainous area ranges from 33.9 to 72.8℃, and the circulation depth is 989-2168m. None of the water-rock interactions of the thermal water has yet reached equilibrium. The temperature and depth of hot water circulation in individual hot springs of the sandstone thermal reservoirs are between those of the igneous and carbonate reservoirs.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe geothermal gases in the research area are all dominated by atmospheric N\u003csub\u003e2\u003c/sub\u003e. The small amount of CO\u003csub\u003e2\u003c/sub\u003e in the hot springs of the Wahongshan-Wenquan Fracture Zone is mainly from a mixture of two sources: organic sediments and marine carbonate rocks. He is mostly the result of radioactive element decay in the Earth's crust, with less than 0.5% coming from the mantle. The high CO\u003csub\u003e2\u003c/sub\u003e level (14%) of the ZD2 hot springs in the Zhiduo-Yushu Mountains is due to a minor amount of mantle-source origin, with weathering and decarbonization of marine carbonate rocks acting as the primary regulating mechanisms. He-C isotope investigations reveal that He is primarily from the crust, with the mantle-source component not exceeding 5%, implying that the deep northwestern-trending fractures in the Zhiduo-Yushu area are linked to the mantle.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eBy synthesizing the above analyses and engaging in discussions about the fluid circulation patterns of two convective geothermal systems with different tectonic backgrounds in the study area, we can provide a scientific foundation for the development and utilization of geothermal resources in this area, as well as for future research. In the future, it will be necessary to improve the complex transportation mechanism of geothermal fluids in the research area using the findings of existing hydrogeologic and geothermal geologic surveys, as well as more sophisticated geophysical approaches.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank the laboratories of the Oil and Gas Resources Research Center of the Northwest Institute of Ecology and Environmental Resources, Chinese Academy of Sciences for their assistance in gas testing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLY: conceptualization, investigation, data analysis, visualization, writing - original draft. RL: data curation, project administration, validation. BL: data curation, investigation. WX: investigation, validation. JZ: resources, supervision. WL: funding acquisition, investigation, supervision, visualization, editing and revising the manuscript. All the authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the National Key Research and Development Program of China (Grant No. 2021YFB1507401), Qinghai Province Clean Energy Minerals Special Project (No. 2022013004qj004 and No. 2023086020qj002), and the Geological Survey Project of China Geological Survey (No. DD20221676, No. DD20230019).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during the study are included in this published article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics and consent to participate declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthics and Consent to Participate declarations: not applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCheng G, Jin H. 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Applied Geochemistry. 2017;79:17-26. https://doi.org/10.1016/j.apgeochem.2017.01.022.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table 1 and 2","content":"\u003cp\u003eTable 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Convection geothermal systems, Geothermal fluid geochemistry, Fluid circulation patterns, Northeastern Tibetan Plateau","lastPublishedDoi":"10.21203/rs.3.rs-5592114/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5592114/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe northeastern Tibetan Plateau is abundant with intermediate to low-temperature geothermal resources, with hot springs varying significantly among locations and tectonic conditions. Understanding the causes of these differences is crucial. This research specifically examines the Wahongshan-Wenquan Fracture Zone (Area Ⅰ) and the Zhiduo-Yushu Mountainous Zone (Area Ⅱ) in Qinghai Province. Hydrochemical and gas isotope data were collected from convective hydrothermal systems in these distinct tectonic settings. A comparative analysis of geothermal fluid geochemical characteristics and sources was conducted using fluid geochemistry methods. Results show that hot water in the igneous rocks of Area Ⅰ is mainly of Cl-Na type, while in the carbonate rocks of Area Ⅱ, it is primarily of HCO\u003csub\u003e3\u003c/sub\u003e-Ca\u0026bull;Mg type. The salts in the former come from silicate mineral dissolution, while the solutes in the latter are primarily influenced by carbonate rock breakdown. Igneous thermal reservoirs have higher temperatures and greater fluid circulation depths than carbonate reservoirs. Geothermal gases in both regions are dominated by N\u003csub\u003e2\u003c/sub\u003e of atmospheric origin. Most of He originates from the crust, with mantle contributions not exceeding 5%. High CO\u003csub\u003e2\u003c/sub\u003e content (14%) in certain carbonate reservoirs is mainly of inorganic metamorphic origin. Both regions are medium-low temperature convective geothermal systems, primarily driven by crustal heat. However, isotopic analysis suggests that the carbonate reservoirs in the Zhiduo-Yushu Mountains have a higher mantle contribution than those in the Wahongshan-Wenquan Fracture Zone. This study summarizes the fluid circulation patterns in these two regions, revealing regional and tectonic influences on fluid sources and transport mechanisms. It provides a theoretical framework for developing and utilizing geothermal assets on the northeastern Tibetan Plateau.\u003c/p\u003e","manuscriptTitle":"Fluid chemistry and circulation patterns from typical convective hydrothermal system on the northeastern Tibetan Plateau","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-19 17:19:18","doi":"10.21203/rs.3.rs-5592114/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0ba02c14-cf75-40cf-833a-15e1bdeddc69","owner":[],"postedDate":"December 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-06-17T07:24:41+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-19 17:19:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5592114","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5592114","identity":"rs-5592114","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}