The geochemical characteristics of geothermically heated water can reveal deep geothermal processes, leading to a better understanding of geothermal system genesis and providing guidance for improved development and utilization of such resources. Hydrochemical and hydrogen oxygen isotope analysis of two geothermal field (district) hot springs based on regional geothermal conditions revealed that the thermal water in the Litang region is primarily of the HCO₃Na type. The positive correlations found between F⁻, Li²⁺, As⁺, and Cl⁻ indicated a common origin, and the relatively high Na⁺ and metaboric acid concentrations suggested a relatively long groundwater recharge time and a slow flow rate. The values of δD and δ¹⁸O were well distributed along the local meteoric line, indicating a groundwater recharge essentially driven by precipitation. The thermal reservoir temperature (152°C–195°C) and thermal cycle depth (3156–4070 m) were calculated, and the cold water mixing ratio (60%–68%) was obtained using the silica-enthalpy model. Finally, hydrogeochemical pathway simulation was used to analyze the evolution of geothermal water in the region. The results were further supported by the high metasilicate content in the region. Of the geothermal fields in the region, it was found that the Kahui is primarily affected by albite, calcite precipitation, and silicate, while the Gezha field is primarily affected by calcite dissolution, dolomite precipitation, and silicate.

There are abundant geothermal resources in the Xiong’an New Area, China. However, the thermal state and geothermal energy accumulation mechanism are not clear. Based on the geological conditions and the characteristics of the present geothermal field, a 2D model was established to analyze the process of mantle-derived heat conduction and to predict the distribution of the deep geothermal field. We calculated the terrestrial heat flow for the Rongcheng uplift and Niutuozhen uplift to be 64 and 75 mW/m², respectively. The geothermal resources in this area are controlled by a four-element model comprising heat conduction, structural uplift, large deep fractures, and convection within the reservoir.

Water resource shortage has been a serious problem since the 1980s in the North China Plain (NCP), resulting in plenty of environmental problems. Estimating the groundwater recharge rate accurately is vital for managing groundwater effectively. This study applied several methods, including chloride mass-balance, tracers (bromide and tritium) and numerical modeling (Hydrus-1D), to estimate groundwater recharge at three representative sites of the NCP: Zhengding (ZD), Luancheng (LC) and Hengshui (HS). The chloride concentration of the soil profile in the ZD site showed that the mean recharge was 3.84 mm/year with the residence time of 105 years for soil water transferring through the vadose area of 45.0 m in depth in the preferential flow model mainly. Considering the influence of preferential flow on the soil water movement in the field scale, the traditional methods (e.g., peak method of bromide and tritium tracers based on piston flow described in the literature) could be unsuitable to estimate groundwater recharge in the LC and HS sites, especially in areas with low recharge rates. Therefore, multi-region and mass balance methods were applied in this study. The results of this investigation showed that the mean values of recharge were 124.3 and 18.0 mm/year in the LC and HS sites, respectively, in 2010. Owing to complexity and uncertainty on the surface resulting from the measuring of evapotranspiration, the upper boundary of 1.4 m (under the ground where most of the plant roots did not reach) was chosen for the numerical modeling of Hydrus-1D, and the result showed that the mean recharge was 225 mm/year from 2003 to 2007, consistent with the result of tracers in the previous literature. The result also showed that the positive relation of groundwater recharge and the sum of irrigation and rainfall was presented in the spatial and temporal scale. Additionally, human activities promoted the recharge rate, and recharge rates increased with greater depths in the LC site generally. However, both cases did not appear clearly in the HS site, showing that the low penetrability of soil controlled the recharge rate in this site.

This study presents a comprehensively analysis of geothermal characteristics in the Xianshuihe geothermal area along the Sichuan-Tibet Railway, using temperature logging, temperature monitoring and thermal conductivity measurement, and regional geothermal geological survey data. The research focuses on the geothermal background, geothermal field, and their potential impact on the surrounding tunnels. The investigation reveals that the average heat flow value in the study area is approximately 73.0 mW/m², significantly higher than the average terrestrial heat flow in mainland China (​​62.5 mW/m²). This high terrestrial heat flow signifies a distinct thermal background in the area. In addition, geothermal anomalies in the area are found to be closely associated with the distribution of hot springs along NW faults, indicating a strong control by the Xianshuihe fault zone. The study concludes that the region's favorable conditions for geothermal resources are attributed to the combination of high terrestrial heatflow background and water-conducting faults. However, these conditions also pose a potential threat of heat damage to the tunnels along the Sichuan-Tibet Railway. To evaluate the risk, the research takes into account the terrestrial heat flow, thermal conductivity of the tunnel surrounding rocks, characteristics of the regional constant temperature layer, as well as the distribution of hot springs and faults. The analysis specifically focuses on the thermal damage risk of Kangding 1^# tunnel and 2^# tunnel passing through the study area. Based on the findings, it is determined that Kangding 1^# tunnel and 2^# tunnel have relatively low risk of heat damage, as they have avoided most of the high temperature anomaly areas. However, several sections of the tunnels do traverse zones with low to medium temperatures, where surface rock temperatures can reach up to 45°C. Therefore, these regions should not be neglected during the construction and operation of the tunnel project, and mitigation measures may be necessary to address the potential heat-related challenges in the area.

High-temperature hydrothermal activity areas in western Sichuan Province, China are ideal objects for studying deep Earth science, extreme ecological environments, and comprehensive geothermal utilization. To understand the geochemical characteristics of rare Earth elements (REEs) in the Chaluo hot springs in western Sichuan Province, the authors analyzed the composition and fractionation of REEs in the hot springs through hydrochemical analysis, REE tests, and North American Shale Composite-normalized REE patterns. Moreover, the composition and complex species of REEs in the geothermal water in the Chaluo area were determined through calculation and simulation analysis using the Visual MINTEQ 3.0 software. The results are as follows. In terms of hydrochemical type, all geothermal water in the Chaluo area is of the Na-HCO₃ type. The cations in the geothermal water are mainly controlled by water-rock interactions and evaporation, the anions are determined by water-rock interactions, and the hydrochemical processes are primarily controlled by the dissolution of silicate minerals. The total REE content of the geothermal water in the Chaluo hot springs is 0.306 ± 0.103 ug/L. It is low compared to the Kangding area and is primarily affected by the reductive dissolution of Fe oxides/hydroxides, followed by pH. The geothermal water in the Chaluo area is rich in light rare Earth elements (LREEs) because of the presence of Fe oxides. It shows positive Eu and Ce anomalies due to the combined effects of the dissolution of Eh and Mn oxides and surface water. Furthermore, the positive Eu anomalies are also caused by the water-rock interactions between the Qugasi Formation and deep geothermal water. Similar to alkaline water bodies, the complex species of REEs in the geothermal water mainly include Ln(CO₃)₂⁻, LnCO₃⁺, and LnOH²⁺, which is caused by the stability constants of complexation reactions.