Mechanisms underlying sulfate concentration variations in geothermal waters around the Wugongshan area

Experimental and geochemical evidence for magmatic origin of Li-Rb-Cs in geothermal waters of the Yangbajing-Gulu Rift, Tibet

Hydrochemical fingerprints, source apportionment and genesis mechanism of geothermal waters in the Gaoligong Geothermal Belt, southeastern Tibetan Plateau

This study explores the hydrochemical and thermal characteristics of a fault-controlled geothermal field within the Northern Qinghai Lake Coalfield Area on the northeastern Qinghai–Tibetan Plateau (QTP). This research integrates hydrochemical analyses, isotopic tracers, and the regional geological framework to define hydrochemical signatures, identify recharge sources and flow paths, assess cold–hot water mixing, estimate reservoir temperatures, determine circulation depths and residence times, and explain the geothermal system’s formation. Systematic sampling included geothermal waters, cold springs, and surface waters, followed by laboratory analysis of major ions, stable isotopes (δ2H, δ18O), radiocarbon (14C), and tritium (3H). The geothermal water is categorized as a low-temperature, weakly acidic to near-neutral HCO3-Ca•Mg type, exhibiting temperatures from 35.6 to 46.2 °C. Isotopic analyses indicate that cold spring and river waters align with the local meteoric water line, while geothermal waters display distinct isotopic signatures, suggesting deeper circulation. A silica–enthalpy mixing model reveals substantial cold-water mixing during upwelling, with mixing ratios between 74.5% and 85.6%. The corrected recharge elevation is estimated to be 4378–4456 amsl, implying a primary recharge zone in the branch of the Qilian mountains—the middle section of Datong Mountain to the northeast. Geothermometry, employing quartz and chalcedony temperature scales and accounting for mixing, estimates reservoir temperatures of 150–202 °C. The calculated circulation depth spans 3211–4291 amsl. Low tritium levels and carbon dating suggest a deep-cycling system predating 1952, characterized by deeply circulating “ancient water”. The geothermal system’s development is associated with regional tectonics, fault systems, and the Kesuer Formation (Jxk) acting as the reservoir. This study provides a scientific foundation for the development and sustainable use of geothermal resources in the northern Qinghai Lake region and offers insights applicable to comparable fault-controlled geothermal systems across the QTP.

ABSTRACT Groundwater contamination in western Türkiye’s basins remains poorly understood because geogenic and anthropogenic influences overlap. This study assesses sources and human health risks associated with groundwater contamination in the Kula–Selendi region (Manisa), where geothermal, cold mineral-rich, and cold fresh groundwater types coexist. Thirty water samples (27 groundwater and 3 surface water) were analyzed for major ions, trace metal(loid)s (TMs), and physicochemical parameters. Principal component analysis (PCA) identified four dominant hydrogeochemical processes: silicate weathering, carbonate dissolution, anthropogenic contamination, and arsenic mobilization. Geothermal waters in the Vezirler mélange contained low arsenic (≤2 µg L−1), whereas cold groundwater in sedimentary aquifers reached 3050 µg L−1, indicating that arsenic enrichment is decoupled from the Kula Geothermal System. Elevated nitrate (up to 454.7 mg L−1) in shallow aquifers reflects inputs from agricultural and livestock activities. Health risk assessment (HRA) showed that arsenic in sedimentary aquifers posed high carcinogenic risk and dominated non-carcinogenic risk via drinking water, followed by lithium, nitrate, and boron. Dermal exposure generally posed low risk, although boron and lithium made relatively greater contributions. The combined PCA–HRA approach links hydrogeochemical processes to human health risks and supports targeted monitoring of naturally enriched TMs (As, B, Li) and mitigation of nitrate pollution.

This study highlights the hydrogeochemical characteristics and geothermometry of the Taptapani geothermal spring, located along the lineament in the Eastern Ghats Granulite terrain of Ganjam district, Odisha (India). Water samples were collected during pre-monsoon, monsoon, and post-monsoon periods in 2021. Various physico-chemical parameters, including temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), major ions (Ca2+, Mg2+, Na+, K+, HCO3 −, F−, SO4 −), and toxic trace elements (Fe, Cr, Zn, Cd, Cu, Mn, Ni, and Pb), were measured. Spring exhibits a natural sulfurous odour and is slightly basic, with a pH of 7.2 and a temperature of 42 °C, exceeding ambient levels due to deep meteoric fluid circulation influenced by a high geothermal gradient. TDS and EC values were recorded as 243.3 mg/l and 380.1 µS/cm, respectively. Geochemical characteristics of the spring water are governed by the lithology of the region. Sodium (Na⁺) dominates the cation budget, while bicarbonate (HCO₃⁻) dominates the anion budget, classifying the geothermal water as Na-HCO₃ type. Reservoir temperatures estimated using Na–K and Na–K–Ca geothermometers ranged from 122–135.4 °C and 140.5–152.4 °C, respectively. Based on the Water Quality Index (WQI), the spring was categorized as having poor water quality (WQI > 100), establishing a baseline reference for environmental forensic applications. While most ionic compositions were within permissible limits, except for fluoride (F⁻: 3.8–4.7 mg/l, average 4.20 mg/l), cadmium (Cd: 17–22 ppb, average 19.3 ppb), and nickel (Ni: 32–53 ppb, average 43 ppb) levels exceeded WHO (2022) and BIS (2012) standards. Parameters such as sodium percentage (Na%), sodium absorption ratio (SAR), residual sodium carbonate (RSC), magnesium absorption ratio (MAR), and Kelly Index (KI) were analyzed to assess irrigation suitability. Effective treatments like adsorption, membrane filtration, electrocoagulation, photocatalysis, and ion exchange can remove elevated elemental concentrations from thermal water.

Although the therapeutic and health benefits of geothermal water are widely recognized by the public, the risks associated with its components have also drawn attention. However, in the eastern part of Shandong Province where low-temperature geothermal water is widely distributed, the risks to residents' health posed by harmful components in the geothermal water have not yet been fully recognized and effectively addressed. In the eastern part of Shandong Province bounded by the Tanlu Fault (EST), the concentrations of fluoride (F) in all geothermal waters and arsenic (As) in some geothermal waters exceed the permissible limits set by the national standard (GB 5749-2022), with As at 0.01mg/L and F at 1mg/L. This study employs multivariate statistical analysis, hydrogeochemical methods, and a health risk assessment model coupled with Monte Carlo simulation to reveal the driving factors of F and As enrichment in geothermal waters and their associated health risks. This study reveals that, in addition to natural mechanisms (dissolution and precipitation, cation exchange, alkaline environment) influencing the concentrations of F and As in geothermal water, anthropogenic factors (agricultural activities) have also become important drivers for As enrichment in geothermal water. Hierarchical clustering categorized the water samples into two groups. Both deterministic and probabilistic health risk assessments indicated that children faced higher risks than adults. The risk from ingestion exposure far exceeded that from dermal contact, with more than 91% and 99% of the non-carcinogenic and carcinogenic risks due to ingestion reaching alert or unacceptable levels, respectively. While the risk from dermal contact was negligible for most samples, attention should be paid to the carcinogenic risk in Cluster A, which has reached an alert level. This research can provide insights into the enrichment mechanisms of F and As in geothermal water and offer valuable references for government departments in the risk management and rational application of geothermal water.

Technical lessons learned from the usage of geothermal mine water for heat supply and economic scenarios to predict feasibility

A comparative study of hydrochemical signatures and formation mechanisms of geothermal waters in the tensile and shear faults of the Tibetan plateau

The hydrochemical mechanism of multiple types of geothermal water in the same fault zone in western Guangdong, Southern China

Ambient Synthesis of La Embedded ZIF-8 Core-Shell Adsorbent for Selective Fluoride Removal from Tanzanian Geothermal Water: Performance, Kinetics, and Isotherms

Competitive thiolation kinetics of antimony, arsenic, and tungsten controlling antimony speciation in sulfidic hot springs.

The Xinding Basin is located in the high-heat-flow geothermal anomaly zone in the north-central part of China. Revealing the geothermal origin mechanism of the basin is of great significance for filling the measurement gap in heat flow values in China and providing a scientific basis for the evaluation and utilization of regional geothermal resources. Based on the hydrogeochemical characteristics of thermal reservoirs and borehole data in the Xinding Basin, this paper analyzes water–rock interaction process between geothermal water and heat reservoirs and discusses the types of geothermal systems in the basin. The results indicate that the fault structures in the basin are well-developed. The hydrochemical type of typical geothermal fields is dominated by the Cl·SO4-Na type. Geothermal water is mainly immature water and receives recharge from shallow cold water with relatively rapid circulation. The discovered magma intrusion residues in the basin indicate that sections of the upper mantle with a shallow burial depth serve as the dynamic heat sources for regional thermal reservoirs. Intense extensional stretching in the Cenozoic Era resulted in high terrestrial heat flow values and an upward arching phenomenon of the Curie isothermal surface in the basin. Neotectonic movement is active in the basin. The regional geothermal reservoirs in the Xinding Basin occur in the glutenite beds of the Cenozoic Erathem and the rock formations of the New Archaean Erathem. The thick-layered Cenozoic loose sediments serve as the thermal cap rocks in this area. An efficient heat-convergent geothermal system integrating a heat source, heat channel, thermal reservoir, and cap rock (the “four-in-one” system) has promoted the formation of geothermal resources in the Xinding Basin.

Cesium (Cs) is a strategic metal used in high-precision timing and advanced electronics technologies, but current supply comes mainly from a few pegmatites as associated minerals. This concentration, together with rising demand, creates clear risks for global supply chains. In this context, this study reviews the geological setting, enrichment processes and resource potential of unique geothermal-type Cs resources on the Tibetan Plateau, and its relevance for critical metal security and the energy transition. Hydrochemical, isotopic, petrological and geophysical data show that southern Tibet hosts a distinct geothermal Cs province, where high-temperature systems along Yarlung Zangbo Suture and N–S trending rifts are consistently enriched in Cs in both fluids and siliceous deposits, well above levels in most other geothermal fields worldwide. The evidence supports a crustal evolved magmatic–hydrothermal fluid source model: Himalayan crust undergoes partial melting and magmatic differentiation, releases Cs-rich fluids that rise along fault zones, and the mixed geothermal waters are then trapped in opal-rich siliceous sinters, ancient siliceous rocks and sediment-hosted units. Tibetan geothermal systems therefore contain a dual Cs resource, with both a dissolved flux and a shallow solid inventory in siliceous sinters and sedimentary rocks. Geothermal Cs on the Tibetan Plateau represents a separate geothermal-type deposit, marked by high enrichment, shallow occurrence and close coupling to geothermal heat. Its dispersed, small- to medium-scale nature makes it best suited to co-production with geothermal development. It can enhance the diversity and resilience of Cs supply, while supporting integrated strategies for low-carbon energy deployment and critical metal security.

Introduction The Taiyuan Basin of North China, as a typical intermountain fault basin, is located in the middle part of the Fen-Wei graben system-an extensional faulting belt. It is one of the areas where high-quality karst thermal storage is developed to match urban heating demand. The formation of its karst geothermal system and the study of its thermal storage characteristics are of great significance for analyzing the distribution pattern of this type of geothermal resource and its overall development. Methods Based on the synthesis of previous research results and the latest geothermal well data, this article analyzes the heat source, karst geothermal reservoir distribution, and hydrothermal dynamic characteristics of the karst geothermal system in the Taiyuan Basin, and evaluates the geothermal resources in 8 units. Results The results show as flow: (1) The karst geothermal reservoir strata in the Taiyuan Basin are mainly composed of the Lower Paleozoic Ordovician, widely distributed in the North China Plate. The evolution of karst geothermal systems has gone through five stages from the Early Paleozoic to the Quaternary. (2) The heat source comes from the high-altitude heat flow (>71 mW/m 2 ) in the asymmetric fault basin of the Cenozoic era, and the heat transfer mode can be divided into the basin edge strong convolution type and the basin internal heat conduction type. (3) The cumulative thickness of the geothermal effective reservoir section is 160–180 m, including the main water bearing sections of 3-4 layers, which are prone to overflow during migration. (4) Controlled by the structure and topography of mountain fault basins, the geothermal water supply and transport mode of karst geothermal systems has the characteristics of bidirectional, near source, and rapid. Discussion According to the evaluation method of karst geothermal reservoir volume, the total geothermal resources of the karst geothermal system in Taiyuan Basin are estimated to be 83.03 × 10 8 GJ, equivalent to 2.83 × 10 8 t standard coal, and the annual mining output can meet the heating area of 15 million square meters.

Multi-perspective visualization of flow and membrane fouling in membrane distillation in geothermal brackish water

Control mechanism of regional structure on geothermal water chemistry, geothermal field and thermal hazard in a coal mine

Formation mechanism of high arsenic geothermal water in Gonghe basin, Northwest China

Hydrochemical appraisal, formation mechanism, and sustainable development of fold-type geothermal waters: Insights from hydrochemistry and isotopes

Decarbonizing the heating sector is a critical component of the European Union’s energy transition strategy aimed at achieving climate neutrality by 2050. Renewable technologies play a pivotal role in this effort, with district heating systems serving as vital platforms for integrating diverse renewable energy sources such as geothermal, bioenergy, solar thermal, and large-scale heat pumps. These technologies enhance system flexibility and support thermal-electric sector coupling by efficiently utilizing recovered energy from waste heat and various renewable heat sources, including geothermal energy, surface water, wastewater, and industrial waste heat. This article presents an analysis of large-scale heat pump installations connected to district heating networks, drawing on case studies across Europe. Key parameters and the number of installations are summarized. The findings emphasize that achieving high system efficiency and significant emissions reductions depends on the careful selection and inte- gration of renewable technologies. Large-scale heat pumps, as part of a broader renewable technology portfolio, are essential enablers of Europe’s decarbonized and climate-resilient sustainable development goals.