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The principal features, geotectonic settings and association with near-surface hydrothermal mineral systems of ancient and present subaerial hot springs, fumaroles and geysers are herein reviewed. Fumaroles and geysers usually occur in volcanic craters and are in most cases, part and parcel of hot spring environments. Subaerial hot springs are characterised by siliceous- and carbonate-rich chemical sediments, such as sinters and travertines, respectively. Sinters are commonly enriched in various metalliferous elements. Hot springs surface discharges are also characterised by pools, which exhibit bright colours due to the presence of microorganisms. Present-day examples discussed in this paper, include the fumaroles and hot springs of the White Island volcano (New Zealand), the world-renowned Yellowstone caldera (USA) and the Afar region of the East African Rift System. The Afar triangle, in the northern part of East African Rift System, provides a good example of hot springs associated with evaporative deposits. The Tuli-Sabi-Lebombo triple junction rifts were formed during the ~ 180 ​Ma Karoo igneous event in southern Africa, of which the Tuli arm is the failed rift (aulacogen), as is the Afar region. The Tuli rift is effectively an unusual, if not unique, tectono-thermal setting, because it comprises Karoo-age hot springs systems and associated vein stockworks and breccias, which includes the Messina Cu deposit as well as currently active hot springs with sinter deposits probably due to post-Karoo uplift. Fumarolic pipes in ignimbrites of the Erongo Volcano-Plutonic Complex in Namibia are discussed. This is followed by an example of banded chert rocks in the Killara Formation of the Palaeoproterozoic Capricorn Orogen (Western Australia), interpreted as hot spring chemical sediments, which also show evidence of “fossil” microbial filaments. The paper ends with a brief overview of possible analogues of hot springs on planet Mars.

The hydrochemical characteristics of 15 travertine-depositing hot springs and 7 hot springs that do not deposit travertine in western Yunnan of China are compared to obtain a better understanding of the hydrochemical factors affecting deposition of travertine from hot springs. The analyses of hydrochemical characteristics of the hot springs include the concentrations of Ca and HCO3, the percentage compositions of Ca among cations and HCO3 among anions, the milliequivalent ratio of Ca to HCO3 ( γ Ca/ γ HCO3), the partial pressure of carbon dioxide (pCO2), saturation index (SI) and hydrochemical types of the water samples. All the travertine-depositing hot springs contain high concentrations of CO2, Ca and HCO3. Their partial pressures of CO2 (0.03–0.76 atm) are much higher than that of atmosphere (0.03% atm) and the values of pH range from 5.9 to 7.7. Hydrochemical investigations show that water samples in the travertine-depositing hot springs have relatively high TDS (higher than 590 mg/L) and they are mainly of HCO3–Ca type. The concentrations of Ca and HCO3 are higher than 55 mg/L and 300 mg/L, respectively, and the values of γ Ca/ γ HCO3 are in the range of 0.1–2. The saturation index values of calcite (SIc) are almost positive. By comparison, the concentrations of Ca and HCO3 in the hot springs that do not deposit travertine are relatively low, the range of value of γ Ca/ γ HCO3 is mostly lower than 1 and the hydrochemical types vary greatly. In addition, the concentrations of CO2, Ca and HCO3 decrease along the flow path of the travertine-depositing Nanni hot spring.

A combined cooling heating and power (CCHP) generation system in the San Kamphaeng hot spring, Thailand, is investigated by using a new parameter of levelized energy and exergy costings per life cycle assessment (LCA). The microscale CCHP system, which comprises a 10 kW organic Rankine cycle, a 15 kW absorption unit and a 20 kW centralized drying room, were tested and analyzed. The net output energy and exergy of the CCHP system were found to have 32.62 kWh and 6.98 kWh at average efficiencies of 11.6% and 11.2%, respectively. In the environmental results, the 4 main impacts were essentially driven from the climate change of 3.90 kg CO 2 eq/kJ, human toxicity of 2.96 kg 1,4 DB eq/kJ, metal depletion of 1.20 kg Fe eq/kJ and fossil depletion of 6.47E-01 kg oil eq/kJ. The LCA single score could be integrated as 0.026 Pt. In the economic impact, the levelized energy and exergy costings were 0.069 USD/kWh and 0.323 USD/kWh, respectively. Finally, in the new 3E and 4E models (3,4E-Chaiyat models), the levelized energy and exergy costings per life cycle assessment were found to be approximately 0.002 USD⋅Pt/kWh 2 and 0.008 USD⋅Pt/kWh 2 , respectively.

A comparative study is conducted to understand the hydrochemistry of Beas and Parbati valley Kullu District, Himachal Pradesh, India. Twenty hot spring, sixteen cold spring and twenty four groundwater samples were collected and analysed for physico-chemical parameters. Hot spring samples were slightly acidic to alkaline in nature whereas cold spring and groundwater samples are alkaline type for Beas and Parbati valleys for December 2017 and June 2018.All the three water sources are moderately hard to hard type. Based on LL-diagram, the dominant facies identified for hot spring samples of Beas valley is Na++K+-Cl− + SO42− type while for cold spring and groundwater sample, it is Ca2++Mg2+–HCO3– type for both the seasons. For Parbati valley, the dominant facies identified for hot spring sample is Na++K+-Cl− + SO42− type in December 2017 and Ca2++Mg2+–HCO3– and Na++ K++ HCO3− type in June 2018. For cold spring and groundwater sample of Parbati valley, it is Ca2++Mg2+–HCO3– type in both the seasons.

The reaction of Al and H2O is a promising method for the renewable production of H2 (an environmentally friendly fuel whose combustion produces only water), because it does not directly include fossil fuels conversion. This reaction was studied at extreme pH values as low as 1 and as high as 13.5 with HCl, H2SO4, and NaOH, and at low hydrothermal temperatures of 40-100 °C. Factors such as pH, temperature, and solution medium influenced H2 production, which was considerably greater at higher temperatures and more extreme pH (acidic or alkaline). Alkaline conditions consistently favored more rapid H2 production than acidic conditions. Under the most extreme conditions, the activation energy was ∼60 kJ mol−1 for both acidic and alkaline reactions. A model predicting H2 production in acidic reactions was derived from the reaction mechanism and kinetics. The model yielded a good fit to on-site measurements at the Tamagawa and Zao hot springs in northeast Japan. This study would aid the development of industrial H2 production systems using natural acidic hot springs or alkaline industrial wastewater.

The Tibetan plateau is characterized by a widely and intensively distributed geothermal activity and an extreme enrichment of boron in some geothermal waters. Twenty-five hot spring samples were collected from the Daggyai and Quzhuomu geothermal areas in Tibet to determine their boron concentrations and isotope composition. The boron concentrations and δ11B values for the neutral geothermal waters in Daggyai range from 72.5 to 106.9 mg/L and −16.4‰ to −12.3‰ while the Daggyai acid waters have much lower boron concentrations (1.1–1.2 mg/L) and slightly higher δ11B values (−12.9‰). The hot spring samples from the Quzhuomu geothermal area have boron concentrations varying from 21.9 to 44.6 mg/L and δ11B values from −11.3‰ to −7.1‰. The hydrochemical and B isotopic evidence imply that the boron in Daggyai geothermal waters is contributed by both magmatic fluid input and host rock leaching. In contrast, marine carbonates and granites, especially the former, are confirmed as the major boron sources for the Quzhuomu geothermal waters. In addition, there also exist some secondary processes affecting the boron isotope fractionation in geothermal waters, e.g. water-vapor separation and absorption or incorporation of B into hydrothermally altered minerals. Finally, based on the analysis of B geochemistry in these two typical geothermal areas in Southern Tibet with different heat sources and reservoir lithology, the mechanisms for the accumulation of boron in the Daggyai and Quzhuomu geothermal waters are suggested. This study is promising to provide insight into the sources of boron in the geothermal waters in other Tibetan geothermal areas.

The Rhynie chert provides sublime fossils of cyanobacteria from an Early Devonian hot spring ecosystem. However, only a small fraction of the diversity has been documented. Rhyniotaxillus devonicus nov. gen. et sp., a minute coccoid cyanobacterium from the Rhynie chert, is characterized by cuboid to somewhat irregular colonies of up to 64 cells (cell diameter: 2.5–3.5 μm) arranged into sarcinoid packages, and held together by prominent gelatinous envelopes. Colony morphology parallels that seen in certain present-day species of Eucapsis (Synechococcales) and Entophysalis (Chroococcales), as well as Eoentophysalis belcherensis, a Precambrian fossil equivalent of Entophysalis. The systematic affinities of R. devonicus remain unresolved. Nevertheless, this discovery expands our knowledge of cyanobacterial diversity in early non-marine ecosystems.

The Late Miocene Whitianga Volcanic Centre of the Coromandel Volcanic Zone, North Island, New Zealand, is host to 18 known, siliceous and intensely silicified deposits including: silicified volcanics; sediments of inferred lacustrine, fluvial and mud pool origin; siliceous hot spring deposits, or sinters; and silicic veins. Collectively these siliceous and silicified deposits indicate past geothermal activity that occurred at the Earth's surface and in the shallow subsurface. Sinters, in particular, are of interest because they are derived from deep geothermal reservoirs and precipitate from discharged thermal fluids at the intersection of the water table with the land surface. However, some siliceous and silicified features in hydrothermal paleoenvironments have been misidentified as sinters. By studying textural types, distributions, structural setting, mineral paragenesis and trace elemental composition of the siliceous and silicified deposits in the Whitianga Volcanic Centre, it is possible to differentiate sinters and identify their spring-vent source areas (100–70 °C) from more distal thermal spring discharge locations ( Ag mineralisation may have occurred at depth. This has important implications for the exploration of mineralised epithermal ore deposits at local to regional scales, in particular for the Hauraki Goldfield of the Coromandel Volcanic Zone.

The origin of life on Earth remains enigmatic with diverse models and debates. Here we discuss essential requirements for the first emergence of life on our planet and propose the following nine requirements: (1) an energy source (ionizing radiation and thermal energy); (2) a supply of nutrients (P, K, REE, etc.); (3) a supply of life-constituting major elements; (4) a high concentration of reduced gases such as CH4, HCN and NH3; (5) dry-wet cycles to create membranes and polymerize RNA; (6) a non-toxic aqueous environment; (7) Na-poor water; (8) highly diversified environments, and (9) cyclic conditions, such as day-to-night, hot-to-cold etc.Based on these nine requirements, we evaluate previously proposed locations for the origin of Earth's life, including: (1) Darwin's “warm little pond”, leading to a “prebiotic soup” for life; (2) panspermia or Neo-panspermia (succession model of panspermia); (3) transportation from/through Mars; (4) a deep-sea hydrothermal system; (5) an on-land subduction-zone hot spring, and (6) a geyser systems driven by a natural nuclear reactor. We conclude that location (6) is the most ideal candidate for the origin point for Earth's life because of its efficiency in continuously supplying both the energy and the necessary materials for life, thereby maintaining the essential “cradle” for its initial development. We also emphasize that falsifiable working hypothesis provides an important tool to evaluate one of the biggest mysteries of the universe – the origin of life. Keywords: Origin of Earth's life, Nuclear geyser system, Emergence and evolution of life, Falsifiability

The microbial-assisted dissolution of minerals from low-grade ore resources has been recently developed into interesting processes to recover valuable metals, because of limitation in high- grade ore resources. In the present study, lab-scale column bioleaching of low-grade uranium ore by a new isolated strain of chemolithotrophic Acidithiobacillus Ferridurans, SBU-SH2 KY497231, which is isolated from a sulfur hot spring in Ardabil, NW of Iran, is investigated. Influence of bioleaching parameters is evaluated by setting up continues column experiments and using uranium samples provided from Sghand uranium mine, Yazd, central Iran. Furthermore, response surface methodology is used for statistical optimization of uranium recovery rate and its compliance with empirical results is examined. The statistical results show maximum 95.5% uranium extraction is obtained during 26 days at pH = 2.5, the temperature of 35 °C, at particle size of 4.64 mm, aeration and irrigation rate 0.78 ml/cm2/min and 1.03 ml/cm2/min respectively which are confirmed by experimental results. Analysis of experimental data by a statistical mathematical model indicates the most key factors on column uranium bioleaching are aeration and irrigation rate respectively. Maximum uranium recovery from leaching of control solution without bacterial cells is 11.33% which shows the isolated bacterium has a considerable influence on uranium recovery. In comparison to the other research reporters of column uranium bioleaching, the new strain of Acidithiobacillus Ferridurans, SBU-SH2, KY497231, indicates its salient features.

The Shahin Dezh Region is one of several areas prospective for geothermal energy in the West Azerbaijan Province of Iran. Hot spring spewing fluids at 30 °C is regarded as the first surface signature for the existence of a subsurface geothermal reservoir in this region. To determine the geothermal energy potential for the region we carried out geological, geochemical and geophysical surveys in the study area. Field observation, thin section studies and XRD analysis reveal the existence of a zone of pervasive hydrothermal alteration in this region. Based on the geochemical analysis, the hydrothermal spring fluids falls into the bicarbonate water family. The results of geothermometric calculations indicate that geothermal reservoir temperature ranges between 40 and 51 °C. Euler deconvolution of geophysical data over the region suggests the reservoir is shallow. This shallowness together with groundwater mixing are factors that played a role in decreasing the reservoir temperature. Integrating geological, geochemical and gravity studies revealed that geothermal reservoir contains 2.3 × 10 7 kJ thermal energy.

The rate of silica accumulation on glass slides over 895 days (2 years 5 months and 12 days) was determined using in-situ experiments in the discharge channel of Map of Australia hot pool, located at Orakei Korako, Taupo Volcanic Zone (TVZ), New Zealand. The discharge channel consisted of constantly flowing alkali chloride water with a temperature of 75 °C, pH of 7, 269 ppm silica, a flow rate of 1.4 l/s and mass flow of 1.36 kg/s. One slide was placed parallel to the flow, while another slide was perpendicular to the flow direction. Amorphous silica (opal-A spheres) deposited on both slides to form abiotic, sub-aerial, lily-pad textures which grew on basal sub-aqueous sinter structures. Lily-pad sinter forms by capillary motion of the water reaching and wetting the sub-aerial sinter surface, where the silica accretes to previously formed sinter surfaces parallel to the pool water level. In our experiment, silica deposition was greater in the horizontal direction than the vertical direction. Silica accumulation was up to four times greater on the front face of each slide. The maximum vertical and horizontal growth rates of sinter observed in our experiment were 3.9 and 7.6 mm/year, respectively. The observation that very little sinter grows below the water line is consistent with most of the sinter precipitating as a result of cycles of wetting, evaporation and drying. Quantitative calculations show that the observed growth rates are within the maximum amount of sinter expected to be deposited by evaporation. These measurements provide a constraint on the mass flow and time required to form siliceous sinter deposits of a known thickness, at extinct hot spring sites. Better constraining siliceous sinter growth rates improves our understanding and reconstruction of paleo-hydrological hot spring conditions.

The Cidanau geothermal field is situated in the northern part of Mt. Parakasak in Banten province, West Java, Indonesia. Nine hot spring samples, one river sample, and one cold spring sample were collected and analyzed for their chemical composition and stable isotope ratios of the water. The objectives of this study are to characterize the chemical composition of hot spring water, to estimate the reservoir temperature and to develop a model of a hydrothermal system using chemical composition and water isotope ratios. The geothermal waters were characterized mainly as Na-Cl-HCO3 type of water. The pH of the waters was close to neutral. The temperature of the hot-water discharges varied from 32.2 °C to 61.1 °C. The waters were evaluated to be immature due to mixing with shallow groundwater during the upflow process. Mixing ratios between cold and hot waters were estimated to be 12.2 to 98.3% with Cl concentrations using a mass balance approach. Higher mixing ratios were found for samples at KR-5, KR-37 and KR-43 and can be explained by the existence of fault zones. The δ18O and δD values for geothermal waters in the region ranged between −7.1‰ to −6.4‰, and −43‰ to −38‰, respectively. Isotope signatures of all hot springs suggest a local meteoric origin, and the oxygen shift corresponds to an exchange between circulating meteoric water and reservoir rocks in the geothermal system. A conceptual model of the Cidanau geothermal field hot springs is proposed.

Reshuitang is an important active hydrothermal area in the Tengchong geothermal field and is characterized by many hot springs and their associated deposits. Detailed mineralogical, crystal morphological, and stable isotopic investigations of the smooth slope fossil travertines at Reshuitang and hydrochemical studies of two active springs around the fossil travertines were conducted to study their genesis. The results show that 1) the modern springs discharge waters with high temperature (>70 °C), near-neutral pH (6.3–8.34), and high saturation indices of calcite and aragonite; 2) the fossil travertines contain calcite and small amounts of Mn-Fe oxides, halite, thenardite, and non‑carbonate debris; 3) the calcite include ray crystals, dendrite crystals, platy crystals, and spike crystals; and 4) δ13C and δ18O of the fossil travertines at Reshuitang range from −1.59‰ to −0.87‰ and 6.48‰ to 7.80‰, respectively. According to comparison between the travertines at Reshuitang and other travertines in Tengchong, all these travertines are thermogene travertines, with a large contribution of mantle degassing to their parent CO2, but are formed at different temperatures. The fossil travertines at Reshuitang, similar to those at Shuzhishi, are formed at high temperatures (near 100 °C), which results in weak microbial activities during the formation of the fossil travertines. Most of the calcite crystals at Reshuitang were non-equilibrium products precipitated directly from the spring waters during the deposition process, while the spike crystals originated from diagenetic dissolution of large calcite crystals. Comparison between the fossil travertines at Reshuitang and other smooth slope travertines from other areas shows these smooth slope travertines have different lithofacies and fabrics. In smooth slope environments, temperature may control the distribution and development of microbes and the intensity of CO2 degassing, and consequently cause the precipitation of contrasting fabrics and lithofacies.

An integrated geophysical study consisting of magnetic, very low frequency (VLF) electromagnetic and electrical resistivity tomography (ERT) surveys has been carried out in the vicinity of hot springs at Atri and Tarabalo in central Odisha, India. The study aims to delineate near-surface structural settings of these regions (e.g., faults, fracture network etc.) that controls the flow of geothermal fluids. Processed magnetic data shows distinct low anomaly as well as high-low transition zone near the hot springs and high anomaly away from the hot springs of both the regions. VLF current density sections along the selected profiles reveal existence of conductive fractures near to the hot springs of both the areas. Resistivity study in both the areas advocates three layered subsurface configurations: low resistive ( 700 Ohm.m). Coincidence of low magnetic anomalies, and low resistivity (or high current density) values at same location indicate the existence of alteration/fracture zones. Resistivity models at Tarabalo depict a low resistive (∼75-100 Ohm.m) dipping faulted/fractured zone extending beyond a depth of 80 m. VLF depth sections and reduced to pole magnetic anomaly maps also reveal high current density and low magnetic signatures, respectively in this zone. This fracture zone is extending about 600 m in EW direction with the marshy area at the center and may have acted as a conduit for the warm water movement from depth to surface. Indication of faulted/fractured zones around the Atri hot spring are also there but the inferences are not as conclusive as that of Tarabalo area due to the nearby power line hindrances. Thus, the study provides a cost effective approach to delineate near surface fracture zones as well as helps to understand the thermal fluid flow mechanism of the hot springs.

A substantial volume (c. 5000 m 3 ) of siliceous hot spring deposits (sinter) has been deposited down to 1 m depth in and around the Tokaanu Domain, a 0.2 km 2 , thermally active central area of the Hipaua-Waihi-Tokaanu geothermal field. Associated thermal manifestations in the Domain included geysers, fumaroles, and hot pools with spring outflows depositing sinter from deeply derived NaCl-type waters as already described over 150 years ago. Later observations showed that flat flooded marshes hosting minor sinter deposits decreased in surface areal extent from at least 15,000 m 2 in 1870 to less than 800 m 2 in 2007. Decline in the area of flooded marshland reflects a decline in flow rate of feeding source pools. Depth and thickness (up to 0.5 m) of concealed (i.e. vegetative overgrown or covered in soil) sinter aprons in the Domain were mapped by students of the 1983–1987 Geothermal Diploma (UoA) field classes. The information was used recently to locate sites for coring of two buried sinter aprons. Radiometric dating of the lower Matewai apron yielded a 0.44 kyr age for sinter at 0.2 m depth. Sinter cores from three sites along a c. 60 m long N–S profile, following the apron axis of the Takarea pool source, yielded radiometric ages between 1.2 kyr at 0.25 m depth to 6.2 kyr at 0.35 m depth. Sinter deposition was found to be highly irregular. Sub-rounded sinter clasts at >2 m depth at two drill sites show no genetic relation to sinter found at the top of the cored section. The topmost sinter cap exhibits only minor diagenetic changes; some acidic hydrothermal alteration, however, is visible in the bottom section at >2.5 m depth of the cored sites pointing to a separate geothermal discharge phase. The irregular deposition of sinter in the Domain points to: 1. tortuous fluid flow paths in the shallow subsurface, and/or 2. shifting discharge channel flow directions on top of the developing sinter apron. The present and last sinter depositing episode appears to have come to an end; it probably lasted, with major interruptions, over 6 kyr.

Medium–low temperature geothermal resources are abundant in Southern China, but their heat source and link to fault zones is poorly understood. Consequently, geothermal energy is only used at small scale. In order to broaden the footprint of geothermal energy use in Southern China, it is first necessary to understand and track the geothermal groundwater circulation pattern associated with fault zones. The Heyuan Fault Zone serves as a typical medium–low temperature geothermal system of South China. Here we show that the geothermal groundwater circulation pattern can be traced by using stable hydrogen and oxygen isotopes, helium and neon isotopes, carbon-13 and carbon-14 as well as hydrochemical parameters. The results show that: in the Heyuan Fault Zone, the main hydrochemical type of the hot springs is HCO3-Na + K, while the shallow cold groundwater is mainly enriched in HCO3-Ca. The results of the helium isotope and neon isotope indicate that the geothermal groundwater of this area is derived from the crust, thus excluding the possibility of extremely deep paths of groundwater tapping into mantle helium sources. Furthermore, the characteristics of the stable hydrogen and oxygen isotopes imply that geothermal groundwater is of local meteoric origin, and the recharge area located at the hilly area of the hanging wall of the Heyuan main fault, with the recharge elevations ranging from about 440 m to 670 m. The hot spring geothermometer shows that the highest reservoir temperature is about 157 °C, and the deepest circulation depth is about 6500 m. Carbon-14 isotope age dating suggests that the geothermal groundwater ages are mostly from 9.9 kyr BP to 12.3 kyr BP. According to the geological structural characteristics of the study area, the main upward channel for geothermal groundwater is the Heyuan main fault. Generally, the hot springs in this area are mixed with shallow cold groundwater and surface water, which raises the ratio of the Ca2+ in water and dilutes the heavy hydrogen and oxygen isotopes.

Background and objective According to basic studies, hot spring use has positive effects on the mind and body. However, the association between habitual hot spring use and prevention of long-term care is unknown. Using long-term care insurance data for the residents of Atami City, Japan, who can choose to install hot spring water supply in their homes, this study aimed to determine the association between the installation of a hot spring water supply in the home and prevention of long-term care. Methods 1. Study design: case-control study 2. Subjects: 2719 residents (754 men, 1965 women) of Atami City, Shizuoka Prefecture, Japan, who received long-term care insurance and were certified as “Needing Support” or “Needing Long-Term Care” as of March 2017. 3. Survey methods: Information on long-term care insurance certification was linked to subjects' care level dating back to their initial certification. Also, the installation (or lack thereof) of hot spring water supply in each subject's home was linked to information on Atami household water use as of March 2017. 4. Analysis methods: The age distribution of the subjects was determined. Initial care status and care status as of March 2017 were then compared for the 2194 subjects who received long-term care certification at least twice. These subjects were classified into two groups: those whose care level had not changed or had improved (no change/improvement group) and those whose care level had worsened (worsening group). Subjects were then compared by sex and initial care level in terms of hot spring installation and percentages of no change/improvement or worsening of care level; odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using the chi-square test. Lastly, the same analysis was performed for all subjects grouped together, and ORs and 95% CIs were calculated using the Mantel-Haenszel test. Results Hot springs were installed in the homes of 2359 subjects overall (86.8%). The no change/improvement group and the worsening group comprised 1192 and 1002 subjects, respectively. Overall, improvement or no change in care level was observed in 1050 subjects (55.2%) in the hot spring group and 142 subjects in the no hot spring group (48.5%). Sex-adjusted OR (95% CI) was 1.311 (1.025–1.677, p = 0.036), which represented a significant association. Having a hot spring water supply in the home may be associated with preventing worsening of care level. Conclusion Having a hot spring water supply in the home may be associated with preventing worsening of care level.

The vigorous tectonic activity that affected the Northwestern part of Algeria has generated a Mio-Plio-Quaternary volcanic activity and led to the emergence of several thermal resurgences. These latter consist of thermal springs, travertine deposits and some hydrothermal alteration zones. The chemistry of twenty-one hot spring water samples highlight the heterogeneity of the water mineralization process in NW Algeria. Four major types of water are described. Na+-Cl− and Na+-SO42− with a high salinity up to 3794 mg/L accompanied by higher concentrations of F−, B, Li+, Br− and Cs. These are probably derived from halite and gypsum rich evaporites from the surrounding environment. The other two types are Ca2+-HCO3− and Na+-HCO3−. Chloride rich waters are associated with local carbonate formations. The stable isotopes (δ18O and δ2 H) reveal a fossil system since a large depletion of both isotopes from present-time meteoric waters cannot only be plausibly explained in terms of "inland" and "altitude" effects, we may suppose their recharge under climatic conditions much colder than the present ones taking place probably during the glacial period. The gas mixing models of N2 He*1000-Ar*100 with O2 CO2 He*1000 demonstrate an unarguable meteoric origin for the thermal waters, displaying air-saturated water (ASW) signatures. The collected thermal waters are ‘immature’ while the deep geothermal reservoir temperatures were estimated to be about at 133 °C. The updated geochemical conceptual model indicates two main processes in the flow path of the fossil meteoric water. 1) In the Bouhdjar geothermal zone, the infiltrated meteoric waters are conductively heated at depth because of the high heat flow (∼120 mW/m2), during their ascent, along hydrothermal conduits and towards the ground surface, they have possibly been influenced by heat advection from the underlying magma chambers and/or a percolation with intrusive bodies beneath spring vents. 2) The meteoric waters are recharged from high altitude areas of the Atlasic lands and are deeply circulated and heated at greater depths, hot waters probably mix with cooler Mg-rich waters and/or leach Mg2+ from the surrounding rocks when rising to the surface. Since the locations of the hot springs are close to populated areas, a direct use of this resource is feasible to supply some energy demands that include electricity generation using binary cycles or direct uses of heat.

Microbially-mediated redox reactions have long been known to participate in mineral formation in geothermal systems. In the current study sediment samples collected from an acid-sulfate-chloride thermal spring (pH = 3.5, 78 °C) in Yellowstone National Park, USA were incubated anaerobically in the presence and absence of nutrient enrichment at in-situ temperature and pH for up to 12 months to investigate biomineralization. Neoformation of pharmacosiderite (KFe4(AsO4)3(OH)4·6-7H2O) through the oxidation of ferrous iron and arsenite (or desorbed phase of arsenate) in the hot spring, occurred in nutrient-amended but not in unamended sediment slurries after 6 months of incubation. These reactions are not favored under abiotic, anoxic, or acidic conditions. The reactions are more favorable, however, when mediated biotically by microorganisms such as arsenic and Fe oxidizers. Indeed, 16S rRNA sequence analysis of the sediment slurries revealed the presence of a diverse community of archaea which included a sulfate/thiosulfate reducing Vulcanisaeta sp., the Fe-oxidizer Metallosphaera yellowstonensis MK-1, and members of the heterotrophic iron-reducing genera Sulfolobus and Sulfurihydrogenibium; the latter known to contain members which possess the aioA gene involved in arsenite oxidation. The results suggest that precipitation of pharmacosiderite under ASC hot spring conditions requires the stimulation of heterotrophic members of the microbial community capable of iron and arsenic transformations. Furthermore, in the clay-rich environment such as the present study, kaolinite also have an important role in oxidizing As(III) through a surface complexation providing the favorable conditions for the biotic pharmacosiderite formation compared to the clay-free condition.

The introduction of a heat source water network system using heat from hot spring and drainage water for hot water supply in accommodation facilities in hot spring areas is expected to contribute to increased energy efficiency. In this study, the relationship between the temperature of the heat source water and the energy efficiency of heat pump water heaters introduced in hot spring facilities connected to a single-loop heat source water network was analyzed. The primary energy consumption of the heat source water network system was compared with that of a centralized heat supply system by conducting a dynamic simulation using Modelica in the Dymola environment. The yearly average coefficients of performance of the proposed heat source water network and centralized heat supply systems were estimated to be is 4.56 and 3.24, respectively. The seasonal performance of the proposed system was also investigated based on measurement data. In December, it was estimated that the heat source water network system would achieve a 17.6% reduction in primary energy consumption in comparison with the centralized heat supply system. However, in August, it was estimated that the primary energy consumption of the heat source water network system would be 8.9% higher than that of the centralized system.

One geyser egg (a smooth, oval, siliceous pebble found in alkali chloride hot pools) from the siliceous sinter slope surrounding Old Faithful Geyser was examined to determine its genesis, sinter architecture and elemental composition. The multi-technique approach included Scanning Electron Microscopy (SEM), petrographic microscopy, X-Ray Diffraction, Energy Dispersive Spectroscopy, iTRAX Core Scanner and Computerised Tomography (CT) scans. The geyser egg architecture consists of alternating smooth and porous concentric bands of opal-A silica around a nucleus. These alternating bands are signatures of changes in the degree of silica oversaturation of the discharging fluid. CT scans mapped changes in density throughout the sample and also showed concentric banding of varying density around a core. SEM observations showed the geyser egg has an abiotic origin with subsequent microbial filamentous void infill creating an abiotic-biotic sinter structure. iTRAX scans revealed the geyser egg preserved signatures of changes in fluid chemistry with time, and that the core is rich in arsenic and calcium. iTRAX scans also documented significantly higher concentrations of gallium in the geyser egg compared to those documented in rhyolites and tuffs from the same area. Unravelling geyser egg formation mechanisms and their microbial content provide useful insights on fluid chemistry, water temperature, and flow conditions in these unique hot spring environments.

his work was supported by The Carnegie Trust (REF: 70335), The Leverhulme Trust (REF: RPG-2016-153), and a Royal Society of Edinburgh research fellowship to CRC. EAC thanks the Canadian Space Agency, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the University of Winnipeg, and the Manitoba Research Innovations Fund for supporting the University of Winnipeg's Planetary Spectrophotometer Facility. Silica-rich hydrothermal fluids that experience freezing temperatures precipitate cryogenic opal-A (COA) within ice-bound brine channels. We investigated cryogenic silicification as a novel preservation pathway for chemo- and photo-lithotrophic Bacteria and Archaea. We find that the co-partitioning of microbial cells and silica into brine channels causes microorganisms to become fossilised in COA. Rod- and coccoidal-form Bacteria and Archaea produce numerous cell casts on COA particle surfaces, while Chloroflexus filaments are preserved inside particle interiors. COA particles precipitated from natural Icelandic hot spring fluids possess similar biomorphic casts, including those containing intact microbial cells. Biomolecules and inorganic metabolic products are also captured by COA precipitation, and are detectable with a combination of visible – shortwave infrared reflectance, FTIR, and Raman spectroscopy. We identify cryogenic silicification as a newly described mechanism by which microbial biosignatures can be preserved within silica-rich hydrothermal environments. This work has implications for the interpretation of biosignatures in relic hydrothermal settings, and for life-detection on Mars and Enceladus, where opaline silica indicative of hydrothermal activity has been detected, and freezing surface conditions predominate. Postprint

There are more than one hundred hot spring outcrops around the island of Taiwan, which implies that Taiwan is rich in geothermal resources; however, no commercial geothermal power plants have been established since 1993, the year of the abandonment of a 3 MW geothermal plant in Chingshui. Situated at the oblique collision zone between Eurasia and Philippine Sea plates, most of Taiwan’s hot springs are located in metamorphic terrain rather than volcanic areas. Previous study showed that geothermal resource is also rich in Jinlun area, whereas structural complexity and low permeability pose difficulties to geothermal exploitation. This paper aims to describe a geothermal conceptual model to facilitate the exploitation of the Jinlun geothermal field by integrating results from gravity, temperature surveys, surface geology, and information from recently conducted magnetotellurics survey and a new borehole. Results from the MT survey indicate a deep resistive structure down to 5 km depth. A zone of low resistivity ( 14 C dating data, sources of geothermal brine could be connate water or meteoric water that travelled for a long distance. The main reservoir could be located at the fractured regions instead of porous strata.

Once a geothermal site has been selected for exploration, a full understanding of the formation temperature distribution on the surface and in the underground reservoir is always needed to assess the geothermal capability and productivity. Commercially available electronic measuring instruments cannot overcome the highest downhole temperatures obtained in the world’s deepest and hottest geothermal reservoirs. In this study, fiber optic Bragg grating (FBG) measurement technology is utilized applied in an attempt to replace more expensive electronic sensors and to obtain more accurate downhole pressure and temperature data. This has been our target since 2013. For this purpose, a portable pressure and temperature (P/T) optic fiber wire-line instrument prototype was developed, and it can measure up to 1500 m in depth. The prototype was named SINOTECH-OPTIC-P/T in 2015. It has been tested in various well types, including a hot spring well and a pioneering geothermal exploration well (JY-01). The primary results have proved to be satisfactory. This paper summarizes the temperature and pressure measurement results obtained in JY-01 well at Sanshing geothermal site in I-lan County, Taiwan. The maximum measured well depth was 1200 m, and data measured includes a downhole temperature profile with the maximum temperature of around 75 °C.

Besides temperature, mineralogy, residence time and dilution are crucial for assessing water-rock interaction intensity. The geothermal system at the Villarrica-Quetrupillan-Lanin volcanic chain, Southern Chile, is located across a prominent lithological transition from plutonic rocks of the North Patagonian Batholith (NPB) to volcano-sedimentary units. With the goal to investigate the impact of lithology on medium-enthalpy geothermal fluids, 15 hot spring discharges were sampled and analyzed for anthropogenic tracers and isotopic composition and compared to the analyses of 31 reservoir rock analogues. Comparison of strontium isotope signatures between rock analogues and hot spring discharges allow an allocation of associated reservoir rocks. Chlorofluorocarbons quantify the dilution of the geothermal springs by shallow groundwater, ranging from almost CFC-free samples to dilution with modern meteoric water by up to 50 %. Fluids discharging from plutonic rocks have low proportions of dilution with modern waters, while hot springs discharging from the volcano-sedimentary rocks have a higher and variable dilution with modern waters. The fractionation of oxygen isotopes of the SO 4 -H 2 O system reveals reservoir temperature estimates of 80–100 °C in the plutonic sequence matching discharge temperatures. For the springs discharging from volcano-sedimentary units higher reservoir temperatures of 100–140 °C are calculated. On basis of the analysis, a conceptual reservoir model can be derived. Fast fluid ascent is indicated along Liquine-Ofqui fault system in the NPB by similar discharge and reservoir temperatures and low surficial dilution rates. Large differences in discharge and reservoir temperatures in the Cura-Mallin formation along with a high influx of surficial water may be attributed to a more branched pathway pattern. In conclusion lithology maybe an important factor when coming to the utilisation of geothermal resources.

We are reporting the draft genome sequence of the Geobacillus yumthangensis AYN2 sp. nov. with the genome size of (~ 3.4 Mb) corresponding to 3712 predicted genes with (G + C) content of 42.28%. This bacterium possesses motility and chemotaxis genes, sulfur and denitrifying reductase gene clusters. This thermophilic bacterium was isolated from the Yumthang Hot Spring located in the North district of Sikkim, India.

We report methane (CH4) with variable carbon isotopes (between −60.9‰ and − 26.8‰) from Changbaishan, the most dangerous volcano in NE China. Furthermore, recent chemical and isotopic data of He, CO2, and CH4 in hot spring gases at Changbaishan volcano are also presented. Bubbling gas samples were collected periodically from 2014 to 2019 in three hot spring areas in the Changbaishan volcanic field: one on the shoreline of the Tianchi caldera lake and two on the north and southwest flanks. The helium isotopes of the bubbling gases from the three hot spring areas suggested a major magmatic source, up to 5.8 Ra (where Ra represents the atmospheric 3He/4He ratios). However, the CH4 exhibited a biotic signature in carbon isotopes (δ13C) as low as −60.9‰, and the concentrations of CH4 among the three hot spring areas exhibited remarkable variations from 0.02% to 17.04%. After evaluating the influence of air contamination, crustal and organic contributions, and thermodynamic processes, we suggest that CH4 from the three hot spring areas primarily originated from two sources: (1) a previously formed gas reservoir in the crust with significant contributions from the ancient subductions and (2) the MORB-like materials from the present upwelling asthenosphere. Based on these observations, we propose a model to explain the processes that formed these two sources, which demonstrates the existence of ancient subduction fluids in the subcontinental lithospheric mantle. In addition, our study of volcanic gases does not support the conspicuous material connections between the subducting west Pacific slab and Changbaishan volcano. Finally, based on our results, suggestions for volcanic gas monitoring at the Changbaishan volcano are provided.

To shorten the development period of suitable anti-scaling technology for individual geothermal plants, it is necessary to improve the precision in evaluating the scaling technology through laboratory testing. Therefore, in this study we investigated a method to imitate the structure of magnesium silicate scale that has precipitated in Obama Hot Spring in Nagasaki Prefecture, Japan. Magnesium silicate hydrates were synthesized in an artificial solution at 100°C under different environments (i.e., carbon dioxide, nitrogen, and atmosphere). The synthesized solutions with magnesium silicate hydrates were flowed to the inner surface of a carbon steel pipe, and the scaling propensity of magnesium silicate was evaluated. Among the samples, the ones synthesized under the carbon dioxide environment have a similar structure with the field magnesium silicate scale and exhibited high scaling propensity. We believe that the findings are useful to eliminate the gap between the characteristics of field scaling and laboratory testing., 公開予定日: 2023-07-13

The Pearl River Delta (PRD) region, located in the southern edge of South China Foldbelt, is one of the best known geothermal areas in south China. This study focuses on the hydrogeochemical features and reservoir temperatures of the geothermal waters in the PRD region, which can provide useful information and overall assessments on the geothermal potential. 24 geothermal well waters and 8 hot spring waters were collected from the inland and coastal areas of the PRD region. Hydrochemical and isotopic analysis (δ18O, δ2H, 3H), empirical chemical geothermometer, mineral saturation induce, and silica-enthalpy mixing model have been applied in the PRD thermal waters. The hydrochemical facies of inland geothermal waters are of the bicarbonate-dominated and sulfate-dominated type, and the coastal waters are of chloride-dominated type. Chemical compositions of the geothermal waters reveal strong fluid-rock interactions, the common ion effect, mixture between seawater and thermal waters in coastal waters, and mixing process between cold groundwater and thermal waters in inland waters. Hydrochemical results and enriched heavy isotopes suggest that coastal waters are recharged by local precipitation and seawater. δ18O and δ2H compositions of the inland waters plot along the Local Meteoric Water Line (LMWL), indicating the recharge of local precipitation. The activities of tritium verify that inland and coastal waters have modern meteoric components. Calculations of chalcedony geothermometers, mineral saturation states, and silica-enthalpy models provide the most reliable estimations of reservoir temperature: 90-154 °C for inland thermal waters, 104-156 °C for coastal thermal waters, likely indicating low-moderate temperature geothermal resources in the PRD region.

The formation of springs is vital for understanding the subsurface transport of substances and energy in groundwater circulation. The Xiannvshan hot spring in the sandstone aquiclude near the Tongluoxia anticline in northeast Sichuan Basin of China is an up-flow spring discharging thermal groundwater from the underlying carbonate aquifer of the basin-anticline controlled type. This rarely-encountered up-flow spring neither issues directly from an aquifer, nor is controlled by a fault. The spring water is a very hard (hardness of 1050.069-1835.697 mg/L) and brackish hot spring water (TDS of 1650-2802 mg/L) of SO4-Ca type and low temperature (34-38°C) issuing from a neutral and reduction subsurface environment, and is characterized by high ratios of γNa/γCl (average 1.354) and low γCa/γSO4 (average 0.779), and high concentrations of Sr (7.62-17.183 mg/L) and F (1.87-8.15 mg/L). The ΣMREE of the hot water samples are greater than ΣLREE, and positive Eu and negative Ce anomalies exist. The dissolved constituents in the hot water are derived from the dissolution of calcite, dolomite, anhydrite, gypsum, polyhalite, halite, albite and K-feldspar and small amount of sylvite, epsomite, thenardite, langbeinite, celestite, barite, strontianite, magnesite, and fluorite in the carbonate aquifer, and the dissolution of sulphates prevails in the groundwater system. Hydrochemical similarity is found among the water samples from the two springs’ vents and the flowing borehole near the vents. Faster groundwater circulation caused by the flowing hot water borehole encourages the dissolution of minerals in the carbonate aquifer and slightly increases the TDS and temperature of the hot water from the flowing borehole.

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.

Numerous present-day hot springs and associated ancient Lianghe gold deposit occur in the central Tengchong block, SW China, associated with oceanic crust subduction. From the center outwards, the alteration zones in the hot spring of the Rehai consist of alunite and silica in a breccia zone, a kaolinite and illite zone, and a chlorite, illite, kaolinite zone. The gas phase in the hot spring is dominated by CO 2 with δ 13 C ranging from −4.5‰ to −7.2‰. These features indicate a major magmatic origin of the hot spring gas. The 3 He/ 4 He ratios in the gas from central Tengchong vary from 1.56 to 5.88, approaching to those of the MORB. This is probably related to the ongoing subduction of the Indian plate beneath the Tengchong block. The hot spring waters in the central Tengchong block have much higher content of Au and other elements, e.g., Ag, As, Sb, and Tl, than other typical hot springs, such as Hasbrouck, Sulfer, etc. in the world. The hot springs with more mantle gas contribution and higher water temperature show more elevated Au contents, which implies that the metal in the hot spring was most likely contributed from the magmatic gas. The compiled D-O isotopes of the hot spring waters from previous studies suggest that they are primarily derived from meteoric water. A genetic model for the hot spring system in the central of Tengchong has been tentatively established. The gold-charged hot spring is genetically connected to an active magma chamber, which was produced by subduction of oceanic crust. The chamber is driving long-term surface meteoric circulation and constantly releasing magmatic volatiles enriched with metals. As hot spring water mixed with magmatic volatiles, causing decompression-boiling and forming hydraulic fractures to penetrate the roof of siliceous sinter, which induced the continuing metal deposition and formed the Lianghe hot spring.

Earthquake-related hydrogeochemical changes are considered a possible means of identifying earthquake precursors. This work investigated the time series of hydrogen and oxygen stable isotopes at three hot springs in Kangding with different temperatures, namely, the Erdaoqiao, Longtougou, and Guanding hot springs, located in the Xianshuihe fault zone, one of the most active seismic fault zones in China. The hot springs were observed with a sampling frequency of 3 or 4 days for one year. The results showed that the three hot springs were recharged by meteoric water, and there was a slight water–rock interaction at the Longtougou hot spring. The different isotopic compositions of the three hot springs were related to the recharge and groundwater circulation environment. Temporal anomalies in the stable isotope values at the three hot springs occurred synchronously; these anomalies were closely related to the 2019 Mw 5.8 Changning earthquake, indicating possible earthquake-related changes. Moreover, the amplitudes of stable isotope variations at the three hot springs were closely related to the seismic energy density, and the background isotopic changes were related to the water temperature and flow. These findings reflect the hydrological cycle processes of geothermal water in the Kangding geothermal area on the eastern margin of the Tibetan Plateau. Simultaneously observed temporal variations in hydrogen and oxygen stable isotopes among multiple hot springs may have relevance for distinguishing earthquake precursors.

The Kasane Hot Spring with discharge temperatures of 43–50 °C is characterized by intermittent bubbling accompanied by white precipitant within its vicinity. The hot spring discharges mainly along Chobe River which meets the Zambezi River at the tip of northwest Botswana. In this study the Curie point depth (CPD) was estimated using the spectral centroid method of aeromagnetic data at Kasane Hot Spring and the surrounding regions. The upward continued aeromagnetic data were analyzed to obtain depths to the bottom (CPD) of the magnetic sources. The CPD values were then used to compute the geothermal gradient , subsurface crustal heat flow including radiogenic heat flow distribution in the region. According to the obtained results, the depth to the magnetic bottom varies from 6 to 22 km. These depths are comparable to those obtained from recent regional study of the Okavango Rift Zone . The areas with shallow CPDs of demagnetized rocks at depth are located around Kasane Hot Spring, where high heat flow values in the range 70–90 mW/m 2 were recorded. Moreover, the radiogenic heat production values between 0.50 and 0.60 μWm-3 within the same region may also provide an extra contribution to the geothermal potential of Kasane Hot Spring. The correlation of estimated shallow CPDs with high geothermal gradient, high heat flows, and radiogenic heat flow values at area within Kasane region indicate possible geothermal resource . The CPDs values obtained may be associated with the seismic events in the region and surroundings. The mean earthquake depth of events that occurred within Kasane and surrounding areas from 1987 to 1991 is 10 km, while the mean Curie Point Depth is approximately 11 km. These seismic events in the area could be responsible for possible thermal accumulation at Kasane Hot Spring, resulting in high heat flow values in the area.

More than 70 years observation of the SO42−/Cl− molar ratios of water from the Obuki hot spring in the vicinity of Mt. Akita-Yakeyama volcano indicated that the ratio started increasing rapidly from 1973, peaked in 1980 (SO42−/Cl− = 0.34), remained at high values for about 18 years, then gradually decreased and returned to a normal baseline value (0.14) in 1991. The volcano erupted near the summit in 1948–1957 and again in 1997. The 1980 peak of SO42−/Cl− ratios may reflect the 1948 phreatic eruption of the volcano. Similarly, high SO42−/Cl− ratios were also observed in 2013 lasting for two years. The SO42−/Cl− peak in 2013 appeared 16 years after the 1997 phreatic explosion. The delayed appearance of the SO42−/Cl− peaks may represent slow upward movement of reservoir water to the surface after input of magmatic SO2 into the fluid reservoir which produced HSO4− through disproportionation reaction. The slow movement of water is supported by a long subsurface residence time (13–25 years) of reservoir fluid estimated from tritium measurement of the Obuki hot spring water. One-dimensional channel model was applied to analyze the effect of volcanic activity on SO42−/Cl− ratios of the Obuki hot spring water. The model supported the long travel time of the fluid implying that the effects of the 1997 eruption may appear in the spring water chemistry after about 29 years later, i.e., around 2026.

Yellowstone Lake hydrothermal vent systems have been studied using ROV assets to better understand the chemical and mineralogical evolution of the sublacustrine sediments through which the hot spring fluids discharge to the lake floor. Here we focus on the deposits/alteration and coexisting vent fluid chemistry associated with the Deep Hole on the lake floor, east of Stevenson Island. Remote in its location, at 120 m below the lake surface, this region in the northeast portion of Yellowstone Lake is associated with numerous hydrothermal vents and hot springs, providing evidence of high-temperature fluid-mineral interaction and phase separation phenomena. Vapor-dominated hydrothermal fluids issuing from Deep Hole vents attain temperatures in excess of 150 °C and are enriched in magmatically derived H2S and CO2. Upon mixing with lake water in the root zone of the hydrothermally active vents, the dissolved gases render the mixed fluid, both acidic and reducing, effectively transforming diatomaceous sediment, with detritally sourced Al and Fe components, to an alteration assemblage dominated by kaolinite, pyrite, and lesser boehmite. These alteration processes have been modeled by computer based simulations, coupling fluid flow and mineral dissolution kinetics, to provide insight on the temporal evolution of the vent system. Results predict rapid dissolution of amorphous silica. The magnitude and rate of silica loss, facilitated by the continuous influx of acidic source fluids, yields an increasingly silica poor alteration mineral sequence with time, characterized by quartz, followed by kaolinite and ultimately boehmite. These data are consistent with the observed decrease in SiO2/Al2O3 ratio of the vent deposits with increasing abundance of trace immobile elements, suggesting significant mass loss with reaction progress. Pyrite is predicted to form from sulfidation of magnetite, with noteworthy decrease in magnetic intensity, as measured for hydrothermally altered sediment in the near-field vent environment. Moreover, hydrogen isotope compositional data for kaolinite, together with δD vent fluid data, suggest temperatures in keeping with the high temperatures measured for the vent deposits and discharging fluid, while supporting the potential use of kaolinite as a geothermometer. The predicted and observed transformation of silica-rich protolith to kaolinite, boehmite, and pyrite underscores the large scale dissolution and removal of silica, with possible implications for the temporal evolution of vent deposits on the lake floor in the Stevenson Island Deep-Hole region.

The chemical compositions, including hydrogen and oxygen isotopes, of 35 hot spring waters in Toyama Prefecture, central Japan, were analyzed to examine their geochemical characteristics and geothermal resources. The hot spring water samples were classified into two groups: low and high chloride (Cl−) concentrations of less than and greater than 2000 mg/L, respectively. The samples in the low-salinity group were determined to be of meteoric origin and Ca2+–HCO3− type. The samples in the high-salinity group were determined to be of Na+–Ca2+–Cl− type and assumed to contain a mixture of fossil seawater and meteoric water. In the eastern area of the study region, the Na+/K+ and SiO2 concentrations were lower and higher, respectively, than those in other areas, which corresponded to high-temperature geothermal resources. Thus, the subsurface information obtained in this study enabled effective use of the low to medium geothermal resources in Toyama Prefecture.

A scale sensor was a newly developed using fiber optics to evaluate scale deposition that occurs at hot spring waters and geothermal brines. This proposed sensor is also capable of assessing the effect of various scale suppression methods. The sensor is fabricated by removing the cladding of a multimode fiber to expose the silica core which then detects the scale deposition from the changes in the refractive index. The effectiveness of the proposed sensor was validated using the carbonated water samples at Matsushiro Hot Spring in Nagano Prefecture and brines from three geothermal power stations in Japan. A comparative performance evaluation between the proposed scale sensor and other monitoring devices were investigated at the same locations. The result of the analysis clearly indicates that the silica deposition and depression effects for geothermal brines under standard atmospheric conditions is rapid, ranging from several hours to half a day by the scale sensor. From the results obtained at the Sumikawa geothermal power station, it was found that the silica scale deposition can be sufficiently evaluated by a scale sensor even at high temperatures and pressure.

The Permian Fengcheng Formation is composed of alkaline saline lake deposits in NW China and is tectonically part of the Central Asian Orogenic Belt (CAOB). Cherts are common in this formation and contain abundant fossilized microorganisms. These microfossils occur as individual spheres and clots in chert layers (laterally continuous and commonly parallel to the laminae of the host rocks) and nodules (chert grains formed by shrinkage and desiccation of chert layers). Carbonaceous cell walls have been well preserved in chert layers. Based on petrological and geochemical analyses of chert and their host rocks, the mechanisms of cyanobacterial cell silicification and their significance for hydrocarbon exploration have been discussed. A high concentration of dissolved inorganic silica in brine and high pH values are the premise for microorganism blooms and chert deposition. Hot springs may be an important silica source for chert deposition. Hot springs also create extreme conditions for algal blooms in brine with high temperatures, high salinities and toxic and anoxic conditions. Spheroidal cyanobacterial cells were rapidly silicified, and cell structures, e.g., cell walls and inner division patterns (reproduction of cells), were well preserved. Chert with fossilized spheroidal microorganisms can be considered hydrocarbon source rocks.

Numerous travellers and scientists since the 1st Century B.C. unsuccessfully searched for the hot and cold springs of Troia (Troy)/Turkey mentioned in Homer’s epic poem Iliad. It was therefore suggested that over time, the hot spring might have disappeared after an earthquake. This investigation uses geological, hydrogeological and hydrogeochemical methods to identify potential locations of “hot and cold” springs in the vicinity of Troia. Using statistical analyses of temperature, electrical conductivity, pH-values, redox-potential, and oxygen concentrations, 47 suitable wells and springs were chosen for geothermometric calculations using Si-thermometry based on the equation of Verma. None of the identified springs shows elevated discharge temperatures, no scalings give indication for disappeared springs, and only three springs show elevated reservoir temperatures above 95 °C – none of which is close to today’s Troia. Springs that locals identified as “hot and cold” show nearly constant temperature throughout the measuring period (±0.1–0.3 K) suggesting they appear warm in the winter and cold in the summer months. These results show that a spring sensu Homer never existed in Troia and that Homer possibly meant one spring with warmer and colder temperatures relative to the mean air temperature depending on the time of the year.

Shiretokoiozan volcano in northern Japan is well known for its eruptions, which eject huge amounts of molten sulfur. Watanabe (1940) reported details of the 1936 eruption, but its mechanisms, and how and where the huge amount of sulfur is produced and pushed out remain unknown. The aim of this study is to elucidate the near-surface underground structure of this area and the mechanisms of the molten sulfur eruption. We implemented aerial photographic observations, geological surveys, hot spring analysis, Self-Potential survey and DC resistivity surveys at the western flank of Mt. Shiretokoiozan. The geology of this area is mostly composed of hydrothermally altered boulders, gravels, sand, and clay. Some areas of fumaroles are covered by sulfur cement. Chemical analyses revealed that SO42 − and Cl− are rich in hot water, which imply an area with upwelling hot water/gas below the surface. Results of DC resistivity surveys conducted at several sites show extremely low resistivity, suggesting an aquifer several meters below the surface. Compiling this evidence, we infer a possible mechanism of molten sulfur eruption: the sulfur has been produced and stored in an aquifer located at the eastern hill from Crater I for several decades by chemical reactions of volcanic gases; it gushes out when volcanic activity becomes high.

A thermo-alkalistable and surfactant stable endoglucanase (PHS) gene consisting of 554 amino acids was identified from metagenomic library of Puga hot spring using functional screening. PHS gene was overexpressed and purified to homogeneity using affinity chromatography The purified PHS protein presented a single band of 60kDa on the SDS-PAGE gel and zymogram. The recombinant PHS exhibited activity over a broad range of pH and temperature with optima at pH 8.0 and 65°C, respectively and having optimum stability at 60°C and pH 8.0, respectively. The recombinant PHS showed highest substrate specificity using CMC (218.4U/mg) as compared with Barley β-glucan (89.2U/mg) and Avicel (0.8U/mg). The Km and Vmax of recombinant PHS for CMC were 3.85mg/ml and 370.37μmolmin-1mg-1, respectively. The activity of the recombinant PHS was enhanced by treatment with 10mM non-ionic detergents such as Tween 20, Tween 40, Tween 80, Triton X- 100 and PEG and was inhibited by CTAB, SDS. Its functionality was stable in the presence of Fe3+ but inhibited by Cu2+, Hg2+, Mn2+ and Zn2+. These properties make PHS endoglucanase a potential candidate for use in laundry, textile,paper and pulp industries.

The following work is an attempt to enhance and optimize the potential exploitation of the Hammam Sayala thermal spring (NW Tunisia). This hot spring is located at 10 km of South-western Beja city, with higher temperature values around 42 °C and a low discharge value of about 1 l s −1 . The geological and structural settings of the study area are complex and associated with faults and Triassic intruded salt and evaporate. An integrated geophysical approach using Electrical Resistivity Tomography (ERT), Induced Polarization (IP) and Vertical Electrical Sounding (VES) techniques can provide a high-resolution subsurface image of the principal geothermal plume and associated pathways. These data were used to determine and understand the mechanisms responsible of the rise of hot water flowing out onto the surface. Our results add new information of the hydrothermal system's context in Hammam Sayala area, which can help to create a therapeutic center opening new perspectives in the Beja region and to encourage regional thermal tourism development.

The Mengyejing potash deposit (MPD) is the first significant ancient potash deposit ever found in China, and it was considered to have formed during the middle to late Cretaceous. The 87 Sr/ 86 Sr ratios of potash bulk samples suggest that both bedded and veined potash orebodies of the MPD have been affected by igneous activity resulting from decompression melting of a metasomatically altered, depleted mantle from 16 Ma to present. The Rb-Sr isotopic systematics of the potash bulk samples define several apparent “isochrons” ranging from 0.609 ± 0.026 to 14.23 ± 0.63 Ma, with the maximum age being consistent with previous K-Ar ages of the K-bearing minerals from the MPD. Such isotopic signatures imply that the MPD may have been affected by multiple-stage fluid flow events since the mid-Miocene, consisting of hydrothermal fluids, continental fresh water, and/or hot spring water. It is very likely that the MPD is still affected by fluid flow-events in modern times. The mineral assemblage of halite + sylvite with minor amounts of carnallite was formed due to the recrystallization and diagenetic modification by hydrothermal fluids. Some characteristics of halite photomicrographs and inclusions and the lack of original halite chevron patterns are also supportive of the hypothesis that the deposit has undergone a diagenetic modification and dissolution–recrystallization processes.

Biological removal of hydrogen sulfide (H 2 S) has been widely practiced across the world because it overcomes the drawbacks associated with physico-chemical processes. In this study, the role of a novel MAL 1HM19 strain of a nitrate-reducing, sulfide-oxidizing bacterium (NR-SOB) isolated from the Mae Um Long Luang hot spring (Thailand) was investigated in batch systems for H 2 S removal under different initial N-NO 3 − concentrations (60, 120 and 240 mg N-NO 3 − /L) at 35 °C. The strain MAL 1HM19 was capable of removing 100% of the gas-phase H 2 S within 10 h of incubation. In the liquid-phase, the final products depended on the initial N-NO 3 − concentration: at 120 and 240 mg N-NO 3 − /L, 15% and 18% SO 4 2− formation was detected, while no SO 4 2− was detected at an initial N-NO 3 − concentration of 60 mg N-NO 3 − /L. The identification of strain MAL 1HM19, based on the 16S rDNA nucleotide sequence, revealed it was closely related to Paracoccus sp. (99.93% similarity). The soxB gene was present in strain MAL 1HM19. In addition, strain MAL 1HM19 showed a good capacity to grow at several NaCl concentrations (0.03–7% w/v ), at temperatures varying between 20 and 50 °C and within the pH range of 7.0–9.0.

Hydrothermal systems are increasingly recognized as important fields for the biogeochemical cycling of dissolved organic matter (DOM) in the ocean. While the quantity and quality of DOM have been characterized for various hydrothermal systems, little is known about the temporal variations of DOM and the underlying processes in these systems. Diurnal variations of DOM were investigated for the hot water area and the warm water area of the hydrothermal system in Green Island off southeast Taiwan at 3 h intervals, using measurement of dissolved organic carbon (DOC), absorption spectroscopy, and fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC). The results of temperature, salinity, pH and DOC indicated that the warm water area had a third freshwater source, besides the seawater and the hot fluids from the hot water area, that was probably groundwater. The DOC concentration showed significant diurnal changes within 84–130 μM at the warm water area. A negative correlation between the DOC concentration and temperature was observed at the warm water area, while the DOC concentration at the hot water area was largely independent of temperature and tide. Four fluorescent components were identified by PARAFAC, including tryptophan-like C1 and C4, and humic-like C2 and C3. The fluorescence intensities of C1 and C4 were higher at the hot and the warm water areas than those in the ambient seawater, suggesting that the former two areas were sources of fluorescent DOM for seawater. The fluorescence intensities of C1 and C2 at the hot water area were higher at night than those in the daytime, implying the effects of potential photobleaching. Overall, the low values of the humification index (HIX) and the high values of the fluorescence index (FI) and the autochthonous index (BIX) at the hot and the warm water areas revealed that the DOM might have a mainly autochthonous biological or bacterial origin.

From the 1950s, extraction of thermal fluids to generate electricity at Wairakei, Taupo Volcanic Zone, New Zealand, heralded a rapid transformation of surface manifestations at nearby Geyser Valley, 1 km NW of the power station. Active geysers and hot-springs fed by alkali-chloride waters ceased by 1968, replaced by acidic steam-dominated conditions. Field relationships indicate geothermal features are fault-controlled. Siliceous hot-spring (sinter) deposits represent spring-vent to distal marsh settings. The dominant mineralogy is opal-A, with some minor clay alteration. Some textures show silica dissolution and re-precipitation. Thus, only minor alteration and diagenesis has occurred, with vegetation overgrowing the extinct sinter. Fil: Watts Henwood, Nick. The University of Auckland; Nueva Zelanda Fil: Campbell, Kathleen. The University of Auckland; Nueva Zelanda Fil: Lynne, Bridget Y.. The University of Auckland; Nueva Zelanda Fil: Guido, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina Fil: Rowland, Julie V.. The University of Auckland; Nueva Zelanda Fil: Browne, Patrick R.L.. The University of Auckland; Nueva Zelanda