Geothermal Groundwater Research Articles

Evaluation of subsurface geothermal groundwater aquifers at Southern Kirthar Range Sindh province Pakistan through the application of vertical electrical sounding

Pakistan has significant geothermal potential but due to poor energy management and low utilization of rich geothermal energy, the country is ranked among the energy deficient nations in the world. In this study, integrated geophysical techniques were used to assess the geothermal energy potential of various hot springs in the Sindh province. The study revealed that Naing Shareef and Gaji Shah hot springs have remarkable potential for geothermal energy having pool water temperature of 43 °C and 45 °C, respectively. Geophysical resistivity survey was carried out at both Naing Shareef and Gaji Shah hot spring to determine depth, thickness and quality of thermal water. At Naing Shareef hot spring, only a single thermal aquifer zone has been pinpointed within the shale composition of the Oligocene Nari Formation, and it is on average 55.07 m depth and 29.8 m thick. At an average depth of 100.66 m and an aquifer thickness of 77.03 m, the Gaji Shah hot springs exclusively possess a thermal aquifer region established within the sandstone composition of the Oligocene Nari Formation.

Hydrogeochemical differences drive distinct microbial community assembly and arsenic biotransformation in unconfined and confined groundwater of the geothermal system

High‑arsenic (As) groundwater in geothermal aquifers poses a serious threat to public health. Assembly processes governing groundwater microbial community related to As biotransformation are still unexplored in geothermal groundwater across different aquifers. To fill this gap, groundwater microorganisms, community assembly processes, and microbially metabolic coupling of carbon (C), nitrogen (N), phosphorus (P), sulfur (S), and arsenic (As) were investigated in unconfined and confined groundwater in the thermal reservoirs of the Guide Basin. The difference in groundwater hydrogeochemicals led to the heterogeneity of the microbial community and microbially mediated C, N, P, S, and As cycling between unconfined and confined groundwater. Higher temperature and As concentrations, low nutrient supply, and reduced conditions in confined groundwater supported stronger interspecific coexistence and environmental selection, thus promoting the proliferation of As-resistant microorganisms (ARMs) and simplifying the community assemblage. Abundant available nutrient supply and oxidizing conditions supported an increased species diversity and metabolic functionality in unconfined groundwater. S oxidizers, C fixation, and C degradation bacteria potentially contributed to the decreased As concentrations in unconfined groundwater. However, ARMs, ammonification, and anaerobic ammonia-oxidizing bacteria potentially caused As mobilization in confined groundwater. Overall, our results give a comprehensive insight into the interaction between As and microorganisms in geothermal groundwater.

New insights on the hydrochemistry, geothermometry, and isotopic characteristics of the hydrothermal groundwater of the SASS basin: case study of the Jérid geothermal field, Southern Tunisia.

Chemical and isotopic indicators were used to recognize the origin of hydrothermal groundwater, to assess the mineralization processes and groundwater quality, to identify the source of solutes and the likely mixing with cold, and elucidate the fluid geothermometry in the Jérid field of Southern Tunisia. The results show that the geothermal groundwater is neutral to slightly alkaline. They are characterized by SO4-Cl-Na-Ca water type. The dissolution of evaporates and pyrite-bearing rocks is the dominant mineralization process. The groundwater quality index indicates that the majority of samples are very hard and belong to poor to unsuitable for drinking classes. Applications and calculations of hydrogeochemical parameters, including SAR, %Na, PI, Kr, and MAR, showed that the majority of samples are unsuitable for agricultural practices. The human health risk was assessed based on hazard quotient and total hazard index through ingestion and dermal contact with iron-rich groundwater. The consumption of CI groundwaters does not present non-carcinogenic risk to adults and children. The δ18 O and δ2H signatures indicate that the geothermal groundwater was recharged by ocean precipitation during cold and wet paleoclimatic periods. The slight enrichment of oxygen-18 and deuterium contents suggests a limited mixing effect between geothermal water and cold groundwater within the same aquifer. This mixing effect is confirmed by the Na-K-Mg and the chloride-enthalpy diagrams. The K-Mg and SiO2 geothermometers provided fairly reliable reservoir temperature values, ranging between 69.6 and 99°C. Calculated geothermal potential values, varying between 469 and 16987 kWth, which allow several applications such as domestic and agricultural heating.

Identifying the genetic mechanism of medium-low temperature fluoride-enriched geothermal groundwater by the self-organizing map and evaluating health risk in the Wugongshan area, southeast China.

Fluoride-enriched groundwater is a serious threat for groundwater supply around the world. The medium-low temperature fluoride-enriched geothermal groundwater resource is widely distributed in the circum-Wugongshan area. And the fluoride concentration of all geothermal samples exceeds the WHO permissible limit of 1.5mg/L. The Self-Organizing Map method, hydrochemical and isotopic analysis are used to decipher the driving factors and genetic mechanism of fluoride-enriched geothermal groundwater. A total of 19 samples collected from the circum-Wugongshan geothermal belt are divided into four clusters by the self-organizing map. Cluster I, Cluster II, Cluster III, and Cluster IV represent the geothermal groundwater with the different degree of fluoride concentration pollution, the different hydrochemical type, and the physicochemical characteristic. The high F- concentration geothermal groundwater is characterized by HCO3-Na with alkalinity environment. The δD and δ18O values indicate that the geothermal groundwater origins from the atmospheric precipitation with the recharge elevation of 1000-2100m. The dissolution of fluoride-bearing minerals is the main source of fluoride ions in geothermal water. Moreover, groundwater fluoride enrichment is also facilitated by water-rock interaction, cation exchange and alkaline environment. Additionally, the health risk assessment result reveals that the fluorine-enriched geothermal groundwater in the western part of Wugongshan area poses a more serious threat to human health than that of eastern part. The fluoride health risks of geothermal groundwater for different group show differentiation, 100% for children, 94.74% for adult females, and 68.42% for adult males, respectively. Compared with adult females and adult males, children faced the greatest health risks. The results of this study provide scientific evaluation for the utilization of geothermal groundwater and the protection of human health around the Wugongshan area.

Arsenic in the Tibetan Plateau’s geothermal systems: a detailed analysis of forms, sources, and geochemical behaviors

In high-altitude tectonic regions, significant geothermal activity influences groundwater arsenic levels, presenting crucial resource and environmental challenges. The present study examines the Gonghe-Guide Basin located in the northeastern region of the Qinghai-Tibet Plateau. The study employs a comprehensive approach encompassing field sampling, hydrochemical analysis, thermodynamic modeling, and statistical analysis to ascertain the composition and origins of arsenic in geothermal groundwater. The research data indicates that the geothermal groundwater in the area displays weak alkalinity and medium to high mineralization, with the principal hydrochemical types being SO4−Cl·Na and Cl·Na. The concentration of arsenic has a notable inverse relationship with Cl− and a positive correlation with water temperature and DO. According to thermodynamic calculations, the most common kind of arsenic is As5+. The hydrochemical properties of the research area are shaped by rock weathering, evaporative concentration, and ion-exchange adsorption working together. These factors contribute to the favorable circumstances for the formation and migration of arsenic throughout the environment. Notably, the ion-exchange between sodium ions and calcium and magnesium ions significantly impacts the arsenic concentration. This study marks the first discovery of a unique arsenic contamination pattern in geothermal groundwater within the Gonghe-Guide Basin in the northeastern Tibetan Plateau, revealing a positive correlation between arsenic levels, water temperature, and dissolved oxygen content. This provides a new perspective on understanding arsenic pollution in geothermal groundwater in high-altitude regions.

Metabolic coupling of arsenic, carbon, nitrogen, and sulfur in high arsenic geothermal groundwater: Evidence from molecular mechanisms to community ecology

Groundwater arsenic (As) poses a global environmental problem and is regulated by complex biogeochemical processes. However, the As biogeochemistry and its metabolic coupling with carbon (C), nitrogen (N), and sulfur (S) in high As geothermal groundwater remain unclear. Here, we reported significant shifts in the geothermal groundwater microbiome and its functional ecological clusters along the flow path with increased As levels and dynamic As-C-N-S biogeochemical cycle from the Guide Basin, China. Strong associations among As(III), NH4+, HCO3−, and corresponding functional microbial taxa suggest that microbe-mediated As transformation, ammonification, and organic carbon biodegradation potentially contributed to the As mobilization in the discharge area. And As oxidizers (coupling with denitrification or carbon fixation) and S oxidizers were closely linked to the transformation of As(III) to immobile As(V) in the recharge area. Our study provides a comprehensive insight into the complex microbial As-C-N-S coupling network and its potential role in groundwater As mobilization under hydrological disturbances.

Lithology controls on the mixing behavior and discharge regime of thermal groundwater in the Bogexi geothermal field on Tibetan Plateau

Geothermal springs within the same geothermal system are naturally considered with similar output manifestation, but usually distinct. A low temperature geothermal spring group (Bogexi) on eastern Tibetan Plateau was investigated and compared with the boiling geothermal spring group (Rekeng) in the same fault zone to get insights into the reasons behind. The Bogexi geothermal springs have quite lower output temperature (25.0–65.3℃) than the boiling Rekeng geothermal springs (84.5–90.0℃). Although all these two geothermal spring groups have the same hydrochemical facies of HCO3-Na, the Bogexi geothermal springs present lower concentration of Na+ and trace elements. The geothermal waters of Bogexi were originated from the precipitation and glacier/snow meltwater of the eastern Haizi mountains with the recharge elevation of 4,400–4,700 m. These recharged waters infiltrate into the geothermal system that with the reservoir temperature of 160-180℃ and are heated by tectonic deformation heat in the depth of 3,100–3,400 m. Lithology determines the fissures development in the shallow and furtherly controls the mixing behaviors and discharge characteristics of geothermal springs in the discharge area. As a result, the thermal groundwaters of Bogexi are mixed with great quantity of shallow cycling cold water with the mixing proportion averaging at 73–76 % during the ascending process, leading to their lower output temperatures and distinct hydrochemical and isotopic features from the boiling Rekeng geothermal springs. A conceptual model was proposed to portray the genesis of low temperature geothermal springs in high temperature geothermal system. The recharged water percolates downward and is heated in the deep thermal reservoir. Heated waters are enriched of chemical elements during this process and then flow upwards under the driving of hydraulic pressure. While the lithology determines the circulation of cold water in the discharge area. Karst lithology, usually with developed fissures and channels, can provide more favorable conditions for cold water cycling in the shallow part than other lithology. This leads to considerable cold water mixed into the upward-flowing geothermal groundwater, and differs these geothermal springs from other ones in the same fault zone in output temperature and hydrochemcial features. This research can improve the understanding of formation mechanism of output discrepancies of various springs within one geothermal system.

Estimation of reservoir temperature and analysis of the mechanism of origin of a granite dome-controlled geothermal system in the western Wugongshan area, southeast China

The escalating issues of worldwide energy scarcity and environmental contamination have brought geothermal resources into the spotlight as a sustainable and eco-friendly energy alternative. The circum-Wugongshan geothermal belt has abundant geothermal resources at a medium-low temperature, offering significant potential for development and utilization. In this study, samples of geothermal groundwater, cold spring water, and surface water were collected from the western Wugongshan area. Hydrochemical and thermodynamic methods were used to estimate the reservoir temperature and analyze its mechanism of origin. The results of these analyses indicated that, in terms of hydrochemical characteristics, most geothermal groundwater samples were Na-HCO3 and Na-SO4, while cold spring and surface water samples were Na-HCO3 and Ca-HCO3, respectively. Quartz and multicomponent geothermometers provided the most reliable estimations of reservoir temperatures, ranging from 64.8°C to 93.4°C. The circulation depth of geothermal water was found to range from 1729.3 m to 2,292.5 m. A mixing model indicated that shallow cold water was blended at a rate of 62.1%–78.8%. The δD and δ18O values validated the conclusion that the geothermal water originates from atmospheric precipitation, with recharge elevations varying between 503.1 m and 1,375.6 m. Based on the above analysis, a conceptual model is proposed to illustrate the mechanism of geothermal groundwater genesis.

Geothermal groundwater study and its energetic potential assessment in Abu Gharadig Basin, North Western Desert, Egypt

The Abu Gharadig Basin (AGB) is one of Egypt's main oil-producing basins, characterized by a range of tectonic structures generated by intense extension and the deposition of a thick sedimentary sequence, making it an ideal location for geothermal energy research. In this study, seven groundwater samples were collected from wells drilled in the AGB to conduct hydrochemical and isotopic analyses. The results indicate that the region's groundwater is dominated by Na+ cations and Cl− anions, which originate from precipitation and runoff. The application of cation geothermometers reveals that all the groundwater samples are in partial equilibrium with the host rock and may also be from mixed sources. The temperature of the deep geothermal reservoir can be estimated using cation geothermometers. The calculated reservoir temperature range deduced from Na–K–Ca geothermometry is 127–184 °C, with an average of 157 °C. The quantities of geothermal power stored in the vicinity of the AGB low-enthalpy geothermal field over the next 25 and 50 years were estimated using stochastic Monte Carlo simulations. For a site with a surface area of 1 km2, the geothermal power potential is 14.3 MWe for a 25-year lifespan and 7.16 MWe for a 50-year lifespan.

Temperature-induced arsenic accumulation in groundwater from Pliocene aquifers of a semiarid continental basin

Contributions of geothermal reservoir and aquifer rock weathering to dissolved arsenic (As) concentrations remain poorly understood. This study investigated geochemical and isotopic characteristics of groundwater from the Quaternary aquifer (Quaternary-GW) and groundwater from the middle-Pliocene aquifer (Pliocene-GW) to reveal As enrichment mechanisms in geothermal groundwater. The results showed that As concentrations in Pliocene-GW were higher than in Quaternary-GW. δ7Li values varied in a wider range in Quaternary-GW than those in Pliocene-GW, and δ11B values were generally lower in Pliocene-GW than those in Quaternary-GW. Normally, δ7Li values in Pliocene-GW showed a negative correlation with the ratio of Li to Na+, and increased along the flow path, which indicated that the prolonged residence time was responsible for high δ7Li. Negative correlations between δ11B and HCO3–, CO32– and B in Pliocene-GW revealed the processes of B desorption and silicate weathering in the middle-Pliocene aquifer. The processes of B desorption and silicate weathering were enhanced by geothermal reservoir, which was evidenced from the negative correlation between δ11B and calculated reservoir temperature. Arsenic concentration increased with increasing δ7Li along the groundwater flow path in the middle-Pliocene aquifer, indicating that prolonged residence time of Pliocene-GW promoted As enrichment. Meanwhile, As concentrations were negatively correlated with δ11B in Pliocene-GW, illustrating that silicate weathering and desorption driven by geothermal conduction were important processes for As mobilization. In samples of Pliocene-GW with similar δ7Li and relatively low δ11B, As was mainly released from the original groundwater-rock interactions, especially desorption and silicate weathering facilitated by geothermal conduction. This study provides quantitative insights into As enrichment mechanisms in geothermal groundwater.

Hydrogeological environments and radon activities of saline geothermal hot spring sites located along eastern and western coastlines of southern Thailand

Hydrogeological settings and natural radionuclides of saline geothermal fields along the coastlines of the Gulf of Thailand and Andaman Sea in Southern Thailand are currently not fully understood. Six saline geothermal springs have been discovered in Surat Thani Province (Southern Thailand's east coast); SR2, SR3, and SR7 sites; Krabi Province (Southern Thailand's west coast); KB2, KB3, and KB4 sites. Based on total dissolved solid contents, we divided the saline geothermal springs into three categories: a) slightly saline geothermal spring had only SR7 (1828 mg/L), b) moderately saline geothermal spring consisted of SR2 (10,196 mg/L) and KB3 (3448 mg/L), and c) very saline geothermal spring comprised SR3 (11,856 mg/L), KB2 (17,014 mg/L) and KB4 (18,070 mg/L). The major ions in the saline geothermal groundwater represent decreasing trends with the distance from the coastline. Stable isotope signatures (δ18O and δ2H) relative to the VSMOW plotted in comparison with the global meteoric water line and local meteoric water line are presumably of meteoric origin and influenced by seawater/brackish water. However, the SR7 and KB3 sites indicated that the isotopic signatures were mainly recharged by rainwater. Significantly, the Na-K-Ca-Mg geothermometer can reasonably estimate the reservoir temperatures for the five saline geothermal springs to be in the range of 120 °C (KB3) to 169 °C (SR2). While the SR7, the silica-quartz geothermometer is proposed of approximately 115 °C. However, the silica-chalcedony and other cation geothermometers fail to estimate suitable reservoir temperatures. On the other hand, the radon concentrations in the saline geothermal groundwater along the Gulf of Thailand and Andaman Sea were assessed by RAD7-H2O, which varied from 18.64 ± 0.96 kBq/m3 (KB2; Andaman Sea side) to 8507.48 ± 1.06 kBq/m3 (SR7; Gulf of Thailand side). A comparison of radon activity with the saltwater intrusion showed that the saline geothermal groundwater on the Gulf of Thailand side had higher levels than that at the Andaman Sea side. The deposition of Quaternary sediments combined with significant saltwater inflow enriched with radon resulted from the decay of uranium from both non-marine and coastal deposits related to granitic mountain weathering along the Gulf of Thailand. Radon concentrations in the geothermal groundwater were highly influenced by the local geological environment and coastal sediments.

Deep submarine infiltration of altered geothermal groundwater on the south Chilean Margin

Submarine groundwater discharge is increasingly recognized as an important component of the oceanic geochemical budget, but knowledge of the distribution of this phenomenon is limited. To date, reports of meteoric inputs to marine sediments are typically limited to shallow shelf and coastal environments, whereas contributions of freshwater along deeper sections of tectonically active margins have generally been attributed to silicate diagenesis, mineral dehydration, or methane hydrate dissociation. Here, using geochemical fingerprinting of pore water data from Site J1003 recovered from the Chilean Margin during D/V JOIDES Resolution Expedition 379 T, we show that substantial offshore freshening reflects deep and focused contributions of meteorically modified geothermal groundwater, which is likely sourced from a reservoir ~2.8 km deep in the Aysén region of Patagonia and infiltrated marine sediments during or shortly after the last glacial period. Emplacement of fossil groundwaters reflects an apparently ubiquitous phenomenon in margin sediments globally, but our results now identify an unappreciated locus of deep submarine groundwater discharge along active margins with potential implications for coastal biogeochemical processes and tectonic instability.

Effects of Seawater Recharge on the Formation of Geothermal Resources in Coastal Areas and Their Mechanisms: A Case Study of Xiamen City, Fujian Province, China

The southeast coastal areas of China have abundant geothermal resources. Most especially, seawater-recharged geothermal systems in the coastal areas have large quantiles of recharge but suffer water salinization and low water temperature. Moreover, the geothermal water development in these areas may induce seawater intrusion. Understanding the genetic patterns of geothermal resources is significant for rational exploration and protection. This study analyzed the hydrochemical and environmental isotopic characteristics of geothermal water, groundwater, and surface water samples collected in the area with geothermal resources in Xiamen Province in the southeast coastal areas of China. Based on this, the recharge of geothermal water circulation and the genetic patterns of geothermal resources were revealed. The results of this study indicate that the geothermal water in mountainous areas and piedmonts in Xiamen is mainly recharged by rainfall infiltration. In contrast, the geothermal water in coastal areas in Xiamen is recharged by seawater mixing to different extents, as indicated by hydrochemical types, isotopic characteristics, and the C1-/Br- ratio of geothermal water. As revealed by the calculation results using the Cl−mixing model, 10 of 13 geothermal fields in Xiamen are recharged by seawater mixing, with a mixing ratio of up to 73.20% in the Pubian geothermal field. After being recharged by rainfall in the low mountainous areas, geothermal water migrates toward deep parts along NW-trending faults. Then, it converges with regional NE-trending deep faults to absorb heat conducted from deep parts to form deep geothermal reservoirs. The deep geothermal reservoirs were estimated to be 185–225°C using the silica-enthalpy mixing model. The geothermal water is mixed with cold water or seawater while rising along faults. The temperature of shallow geothermal reservoirs was estimated to be 71–145°C using SiO2geothermometers.

The genesis of Rare-alkali metal enrichment in the geothermal anomalies controlled by faults and magma along the northern Yadong-Gulu rift

Geothermal water from the hot springs in the Yadong-Gulu rift (YGR) of southern Tibet is extremely enriched in rare-alkali metal (RAM) elements; however, the mechanism of enrichment has long been debated. Much attention has been given to the deep melting magma of the YGR, but no direct evidence indicates whether and how it is connected to the RAM anomaly of hot springs. Determining the mechanism of RAM enrichment and its variations with the time and space of hot springs will contribute to the exploration of the hydrothermal metallogenic systems. This paper presents numerical hydrothermal numerical circulation models constrained by the geological data and the geophysical structure of the YGR. The results illustrate that the depths of boundary faults control the anomalous temperatures of hot springs. High-temperature springs (such as Yangbajing) could be induced by deep faults extending to the middle crust, whereas magma at a depth greater than 10 km has a limited effect on geothermal anomalies. Secondary faults define the extent of hydrothermal circulation and further determine the distribution of thermal anomalies across the rift. We simulate the enrichment and distribution of RAMs from a deep magma source. The pathways of RAMs from the source are consistent with hydrothermal circulation. RAM concentrations are lower in infiltrating groundwater and higher in ascending hot water. In general, deep faults control the hydrothermal circulation of geothermal groundwater. Deep faults and magma further constrain the distribution of RAM anomalies.

Performance investigation of a hybrid ground-assisted desiccant cooling system

This study proposes a novel hybrid ground-assisted desiccant cooling (HGDC) system that integrates a heat pump and shallow geothermal energy. This HGDC system can be used as an efficient alternative for handling the ventilation load in the subtropical monsoon climate. Under the outdoor air conditions of 33.3℃ and 24.9 g kg−1, the system could provide supply air conditions of 23.8℃ and 13.8 g kg−1, and the total coefficient of performance was 4.10. The energy analysis showed that precooling air by shallow geothermal groundwater is helpful for dehumidification, and it accounted for 33–73% of the total cooling capacity. Moreover, this HGDC system also built the control strategy based on outdoor conditions, which contains free ventilation, cooling and desiccant cooling modes. Compared to the conventional vapor compression system, this HGDC system can save 7.7–31.7% on total power consumption of summer period.

The genesis of saline geothermal groundwater in the coastal area of Guangdong Province: Insight from hydrochemical and isotopic analysis

Saline geothermal groundwater is widely distributed in the coastal region of Guangdong Province, China. The present study employed hydrogeochemical (physical parameters, ionic chemistry, and trace elements) and isotopes (H, O, C, and B) analyses to delineate the causes and evolution processes of saline thermal groundwater in different aqueous environments from the coastal region (geothermal groundwater, cold groundwater, seawater, river water, and rainwater). The results showed that meteoric water was the primary origin of the geothermal groundwater. Based on the hydrogeochemical characteristics and TDS values, the geothermal groundwater can be divided into two groups. Group A was mainly Cl-type with TDS values ranging from 1961 to 7752 mg/L and was located around the coastal area. Group B was mainly HCO3-type, which is located in the inland area. The hydrogeochemical differences between group A and group B are primarily caused by groundwater-rock interactions and mixing with seawater. Reservoir temperatures were calculated as 127 to 163 °C for group A and 81 to 140 °C for group B by a quartz geothermometer without steam loss. Besides, the circulation depth of group A (3007 to 4031 m) was much deeper than that of group B (711 to 3965 m) and cold groundwater (394 to 1656 m). The analysis of carbon isotopes (δ13C and 14C) revealed that the circulation times of group A were older than that of group B. Furthermore, seawater intrusion had a significant influence on group A, and the proportions of seawater in group A calculated by Cl (4.90 % to 49.60 %) were closed to that by Br (7.21 % to 53.81 %).

Analysis Water Quality of Springs on the East Slope of Mount Sumbing, Central Java, Indonesia for Sanitation Hygiene Purposes Based on the Physical and Chemical Properties

The eastern slope of Mount Sumbing has many springs used as a source of raw water for hygienic sanitation purposes. However, there has been no scientific research showing the quality of springs. Therefore the purpose of this study is to analyze the quality of springs on the eastern slopes of Mount Sumbing for community sanitation hygiene purposes based on water physical and chemical properties. Water samples were taken from several points in the study area and observed for physical parameters (TDS, smell, taste, and temperature) and chemical parameters (acidity, nitrate, fluoride, and sulfates). The results showed that from 30 samples of springs, only one spring fulfilled the Indonesia Minister of Health Regulation No. 32 in 2017. The spring located at STA 51 Kaliloro, Krajan, Kaliangkrik, Magelang Regency. There was a spring classified as deep geothermal groundwater and the others classified as shallow groundwater. Based on the acidity of water, most of the springs on the eastern slopes of Mount Sumbing could be used as hygiene sanitation by treating the water acidity and regulating the purposes of springs.

2D Electrical resistivity imaging for geothermal groundwater characterization and rejuvenation of the Gaurikund hot spring in the Main Central Thrust (MCT) zone of the Garhwal Himalaya, Uttrakhand, India

Gaurikund is a famous geothermal spring near the Kedarnath Dham in the central Himalaya, Uttarakhand, India. During the Kedarnath Disaster in 2013, the thermal spring and most of the areas surrounding the Kedarnath temple lies ruined and covered by debris. In the present study, an effort has been made to image the debris covered source of the geothermal groundwater potential zones for rejuvenating the Gaurikund thermal spring and to understand the mechanism for enhancing the continuous recharge and flow of this hot spring. We have carried out hydrogeological measurements with these objectives at four locations (points 1–4). The obtained data indicates that spring water temperature varies from 35 to 58 °C and point-2 was observed to be the main source of the spring, situated adjacent to the Gauri Mata temple. Besides this, we performed 2D electrical resistivity imaging (ERI) profile with different configurations in the vicinity of the spring along the right bank of the Mandakini River. ERI reveals two distinct low resistivity horizons with resistivity variation from 20 to 50 Ωm within the depth of 5–15 m. The low resistivity zones have been interpreted to be the thermal spring's potential source, which occurs either along the fractured zones with channelized groundwater flow or along highly weathered zones. The study suggests that the source of the Gaurikund hot spring is located in the hanging-wall of the Vaikrita Thrust, a northerly dipping major structural unit and weak zone that can play a significant role in reviving the Gaurikund geothermal spring.

Обследование скважины жаркентского месторождения термальных подземных вод (скважина 3-т)

Geothermal energy resources, as well as other types of renewable energy sources, are able to satisfy almost any consumer in terms of its potential and quality of its energy. The application and the use of geothermal waters of any deposit depends on the energy potential, the chemical composition, the mineralisation and aggressiveness of the water, the general stock and flow rate of wells, the availability and distance of the potential consumer, the temperature and hydraulic modes of boreholes, the depth of occurrence of aquifers and their characteristics, and much more. This feature is one of the main differences of geothermal energy from other renewable energy sources. The exploration of geothermal groundwater was carried out at the Zharkent basin site, in order to assess the operational reserves of thermal groundwaters. There are several wells on the territory of the Zharkent geothermal deposit that can be used as an energy source. Thus two promising geothermal wells, №1RT and №3T, were identified during the exploration, according to which the studies were carried out.

Analytical Method for Lithium Isotopes Determination by Thermal Ionization Mass Spectrometry: A Useful Tool for Hydrogeochemical Applications

The low temperature realm such as the geothermal systems, characterized by a large variety of near-Earth surface processes, has been the object of several isotopic studies, some of them including lithium isotopes. However, much work can still be done to systematically use lithium as tracer of geochemical processes in deep and shallow Earth reservoirs. A pilot study has been performed for the determination of lithium-isotope ratio by thermal ionization mass spectrometry (TIMS), a technique poorly employed with respect to other methods such as inductively coupled plasma mass spectrometry, being more time consuming. Lithium has been extracted by chromatographic techniques on columns through an ion exchange process from both natural and reference samples. The isotope composition (6Li/7Li) expressed in terms of δ7Li has been determined in dynamic and static mode for comparative purposes, by using two different types of thermal ionization mass spectrometers. The results presented in this work agree with the data reported in the literature, opening a new perspective to future research on continental geothermal systems and groundwater domains, spread over the entire Italian peninsula. This research is based on the use of chemical and isotopic data, whereas it does not include lithium isotopes. These latter may provide a huge contribution in studying both volcanic products and fluids from active volcanic areas, including the superposed geothermal systems, and may represent a new tool for research and surveillance.