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1.
The composition of waters from 10 thermal springs located in western Virginia near the 38th parallel lineament have been analysed for major dissolved components and for Sr, Fe, Cu, Zn and Cd; from these analyses, free ion activities have been calculated. The temperatures of the springs range from 17° to 39°C, the heat apparently being derived simply from deep circulation along synclinal, Middle Ordovician limestones. More than 95 per cent of the dissolved solids consist of Ca2+, Mg2+ HCO3?, and SO42?. The concentrations of these components, as well as the spring temperatures, have not changed appreciably in 140 yr in some springs. The waters that have temperatures below 25° are all undersaturated with respect to calcite and dolomite, possibly because they have been contaminated by shallow ground waters. The waters with temperatures above 25° are in equilibrium with calcite and dolomite. Furthermore, in this latter group, the calcium-sulfate activity product and the sulfate-carbonate activity ratio are nearly constant, even though the waters are under saturated with respect to gypsum, anhydrite, celestite and strontianite. This can be explained if CaSO4 is coprecipitated in a mineral such as aragonite. The waters have absorbed some dissolved oxygen near the surface, but at depth they may be anoxic with Eh controlled by the oxidation of pyrite to goethite. The extremely low chloride concentrations of these waters clearly distinguish them from the brines which deposited Mississippi Valley and Appalachian type epithermal ore deposits.  相似文献   

2.
Uttarakhand geothermal area, located in the central belt of the Himalayan geothermal province, is one of the important high temperature geothermal fields in India. In this study, the chemical characteristics of the thermal waters are investigated to identify the main geochemical processes affecting the composition of thermal waters during its ascent toward the surface as well as to determine the subsurface temperature of the feeding reservoir. The thermal waters are mainly Ca–Mg–HCO3 type with moderate silica and TDS concentrations. Mineral saturation states calculated from PHREEQC geochemical code indicate that thermal waters are supersaturated with respect to calcite, dolomite, aragonite, chalcedony, quartz (SI > 0), and undersaturated with respect to gypsum, anhydrite, and amorphous silica (SI < 0). XRD study of the spring deposit samples fairly corroborates the predicted mineral saturation state of the thermal waters. Stable isotopes (δ18O, δ2H) data confirm the meteoric origin of the thermal waters with no oxygen-18 shift. The mixing phenomenon between thermal water with shallow ground water is substantiated using tritium (3H) and chemical data. The extent of dilution is quantified using tritium content of thermal springs and non-thermal waters. Classical geothermometers, mixing model, and multicomponent fluid geothermometry modeling (GeoT) have been applied to estimate the subsurface reservoir temperature. Among different classical geothermometers, only quartz geothermometer provide somewhat reliable estimation (96–140 °C) of the reservoir temperature. GeoT modeling results suggest that thermal waters have attained simultaneous equilibrium with respect to minerals like calcite, quartz, chalcedony, brucite, tridymite, cristobalite, talc, at the temperature 130 ± 5 °C which is in good agreement with the result obtained from the mixing model.  相似文献   

3.
In this paper, the hydrochemical isotopic characteristics of samples collected from geothermal springs in the Ilica geothermal field, Eastern Anatolia of Turkey, are examined and described. Low-temperature geothermal system of Ilica (Erzurum, Turkey) located along the Eastern Anatolian fault zone was investigated for hydrogeochemical and isotopic characteristics. The study of ionic and isotopic contents shows that the thermal water of Ilica is mainly, locally fed by groundwater, which changes chemically and isotopically during its circulation within the major fault zone reaching depths. The thermal spring has a temperature of 29–39 °C, with electrical conductivity ranging from 4,000 to 7,510 µS/cm and the thermal water is of Na–HCO3–Cl water type. The chemical geothermometers applied in the Ilica geothermal waters yielded a maximum reservoir temperature of 142 °C according to the silica geothermometers. The thermal waters are undersaturated with respect to gypsum, anhydrite and halite, and oversaturated with respect to dolomite. The dolomite mineral possibly caused scaling when obtaining the thermal waters in the study area. According to the enthalpy chloride-mixing model, cold water to the thermal water-mixing ratio is changing between 69.8 and 75 %. The δ18O–δ2H compositions obviously indicate meteoric origin of the waters. Thermal water springs derived from continental precipitation falling on to higher elevations in the study area. The δ13C ratio for dissolved inorganic carbonate in the waters lies between 4.63 and 6.48 ‰. In low-temperature waters carbon is considered as originating from volcanic (mantle) CO2.  相似文献   

4.
《Applied Geochemistry》2006,21(2):253-268
The Dalaman and Köyceğiz thermal springs are from karstic limestones belonging to Upper Cretaceous to Burdigalian Beydağları autochthon and Carboniferous to Lutetian Lycian nappes. They have measured temperatures of 24– 41 °C, specific electrical conductivities of 14,310–45,600 μS/cm, and are dominated by Na (1550–8500 mg/kg) and Cl (2725–15,320 mg/kg). The heat source of the geothermal systems of the area is tectonic related and the occurrence of the thermal springs is related to the young normal faults. Meteoric waters and seawaters recharge the reservoir rocks, are heated at depth with increasing geothermal gradient, and move up to the surface through the fractures and faults by convection trend and emerge as thermal springs. While thermal waters move up to the surface, they mix with different proportions of seawater and cold fresh waters. The seawater contribution to the thermal waters varies from 24% to 78%. Lake waters in the area are connected with thermal waters. Consequently, their chemical composition is influenced by the chemistry of thermal waters. Chemical equilibrium modelling based on measured outlet temperatures and measured pH shows that all the waters are oversaturated with respect to quartz and K-mica and undersaturated with respect to Al(OH)3, anorthite, gypsum, siderite and SiO2(a). Albite, alunite, aragonite, Ca-montmorillonite, calcite, chalcedony, chlorite, dolomite, Fe(OH)3(a), fluorite, gypsum, illite, K-feldspar, kaolinite and sepiolite minerals are mostly oversaturated or undersaturated. Mineral saturation studies of the thermal springs indicate that dolomite, chalcedony and quartz are most likely to cause scaling at outlet conditions. Assessments from various chemical geothermometers, and Na–K–Mg ternary and mineral equilibrium diagrams suggest that the reservoir temperature is around 65–90 °C. The temperatures obtained from quartz, quartz-steam loss, Mg/Li geothermometers and mineral equilibrium diagrams give the most reasonable results.  相似文献   

5.
The Sfax Basin in eastern Tunisia is bounded to the east by the Mediterranean Sea. Thermal waters of the Sfax area have measured temperatures of 23–36°C, and electrical conductivities of 3,200 and 14,980 μS/cm. Most of the thermal waters are characterized as Na–Cl type although there are a few Na–SO4–Cl waters. They issue from Miocene units which are made up sands and sandstones interbedded with clay. The Quaternary sediments cap the system. The heat source is high geothermal gradient which are determined downhole temperature measurements caused by graben tectonics of the area. The results of mineral equilibrium modeling indicate that the thermal waters of the Sfax Basin are undersaturated with respect to gypsum, anhydrite and fluorite, oversaturated with respect to kaolinite, dolomite, calcite, microcline, quartz, chalcedony, and muscovite. Assessments from various chemical geothermometers, Na–K–Mg ternary and mineral equilibrium diagrams suggest that the reservoir temperature of the Sfax area can reach up to 120°C. According to δ18O and δ2H values, all thermal and cold groundwater is of meteoric origin.  相似文献   

6.
Semnan thermal springs with high TDS and moderate temperature are located northwest of Semnan, the northern part of Iran. The spatial and temporal variations of physicochemical characteristics of the thermal and cold springs were investigated for the recognition of origin and dominant hydrogeochemical processes. Results show that the thermal springs have the same origin, but due to different ascending flow paths and different conductive cooling mechanism, their temperatures vary. The chemical composition of thermal waters is controlled by dolomite, halite and sulfate minerals dissolution and calcite precipitation and bacterial sulfate reduction. The concentration of major and trace elements in the thermal springs does not change in wet and dry seasons notably because they are derived from old groundwater with deep circulation and high temperature. Seasonal change in the concentration of some trace elements is due to the seasonal variation of pH, Eh, temperature and dilution by shallow waters. Decreasing SO4 and carbonate saturation index and increasing Na/Cl ratios and Ca content in the dry season show dilution effect caused by the previous heavy rainfall events. The temperature of the heating reservoir based on K–Mg, chalcedony, quartz and chemical equilibrium approach was approximately estimated in the range of 60–80 °C. Hydrogeologically, a conceptual model was suggested for the thermal springs. The general groundwater flow direction is probably from the dolomite Lar Formation in Chenaran anticline toward the adjacent syncline in a confined condition, and then a thrust fault acts as a conduit and redirects the thermal water to the emerging springs at the surface.  相似文献   

7.
Thermal waters of northern (18°–27°S) and southern (37°–45°S) Chile occur in two very different climatic, geologic and hydrologic environments: arid closed basins with abundant evaporites in the north; humid climate and well drained valleys in the south. The origin and behavior of the main components of the two groups of waters are examined and compared to each other. The modeling of the alteration of volcanic rocks leads to water compositions very different from those observed both in the north and south. In addition to hydrothermal alteration and deep emanations, the Cl/Br ratio reveals a major contribution of saline waters to the two groups: infiltrating brines from salt lakes in the north; seawater in the south.In the north, concentrations of Cl, Br, Na, K, Ca, SO4, Li, B, Si result from the mixing of alteration waters with recycled brines. Hydrothermal alteration is obscured by this massive saline input, except for Mg. δ34S values are consistent with an origin of sulfate from salar brines, which are themselves derived from deep Tertiary gypsum. In the south, two processes account for the composition of thermal waters: mixing of alteration waters with seawater and deep magmatic contribution. The mixing process controls the concentration of Cl, Br, Na, Alk, Si, K, Ca, Mg. Magmatic inputs are detectable for SO4, Li and B. δ34S suggests that sulfate stems from the mixing of alteration waters with either marine SO4 in coastal waters or with deep SO2 in inland waters. In both the north and south, the Mg concentration is drastically lowered (<1 μmol/L) by the probable formation of a chlorite-type mineral. In the south, very small amounts of seawater (<1% in volume) are sufficient to imprint a clear signature on thermal waters. Not only coastal springs are affected by seawater mixing, but also remote inland springs, as far as 150 km from the sea. Subduction of marine sediments in the accretive margin could be the source of the marine imprint in thermal waters of southern Chile. Seawater may be expelled from the subducted lithosphere and incorporated into the mantle source.  相似文献   

8.
Caldas de Moledo thermal (27–46 °C) spring and borehole waters issue in the region of the famous Port Wine vineyards, in the Douro River valley (Northern Portugal). The most abundant lithotypes are lower Cambrian metasedimentary rocks, Variscan granitoids and aplite-pegmatitic veins. The thermal waters are characterised by pH ≈ 9.0, TDS ranging from 200 to 350 mg/L, and belong to the HCO3–Na facies indicating that the reservoir rock should be mainly granite. Since the local Spa is strongly dependent on water quality, the effects of mixing between local shallow cold groundwaters and deep thermal waters have been properly investigated. In the SO4 2? (mg/L) versus δ18O (‰ vs. V-SMOW) diagram we can observe that some of the thermal springs show evidences of mixing (higher SO4 2? concentrations) with local meteoric waters infiltrated at lower altitude sites (enriched δ18O signatures), showing the “altitude effect” in the isotopic composition of the recharge waters. Similar trends can be found in the K+, NO3 ?, Ca2+ and Na+ (mg/L) versus δ18O (‰ vs. V-SMOW) diagrams. It should be stated that SO4 2?, K+ and Ca2+ are present in the fertilizers and fungicides used in the vineyards in the northern part of the country. Up to now, the thermal waters from boreholes used in the local Spa do not show evidences of mixing with shallow groundwaters contaminated with agrochemicals. The results obtained so far indicate that in the near future, special attention should be put on the possible occurrence of diffuse agricultural contamination (related to the Port Wine vineyards) in the thermal spring waters.  相似文献   

9.
Geothermal water is plentiful in Changbai Mountain region, northeastern China, due to the volcanic activities and widespread faults. For the exploration of geothermal resources, this study uses quartz and cation geothermometer to estimate the temperatures of the geothermal reservoir and uses the tubular models to evaluate the thermal gradient. The hydrogeochemical characteristics of the geothermal resources were also evaluated by hydrogeochemical analysis. The results showed that the geothermal reservoir temperatures of the four major thermal springs in Changbai Mountain region range from 72 to 169 °C. The average geothermal reservoir temperatures of Jinjiang hot springs, Changbai hot springs I, Xianrenqiao hot springs, and Changbai hot springs II are 129.25, 169, 89, and 73.67 °C, respectively. The geothermal gradient values of the four major thermal springs have different characteristics. The geothermal gradient values of Jinjiang hot springs and Changbai hot springs I are 4.6 and 3.1 °C/100 m, respectively. The geothermal gradient values of Xianrenqiao thermal springs and Changbai thermal springs II are both lower than 1.5 °C/100 m, with the values of 1.1 and 1.4 °C/100 m. And the geothermal gradients are influenced by Changbai Mountain Tianchi volcano. In addition, the water chemical analyses showed that the geothermal water types are HCO3-Na with higher concentrations of Na+, Cl?, SO4 2?, TDS, and HCO3 ? than the non-thermal waters, which suggested a deep and long water cycle of the thermal water, and therefore a sufficient water-rock interaction.  相似文献   

10.
Three geothermal systems, Montevago, Castellammare-Alcamo and Sciacca, are located along the main seismogenetic structures in Western Sicily. Concentrations of dissolved species including the gases CO2, N2, He and the results of stable isotope measurements δ18O, δD and δ13CTDIC in water samples collected from six thermal springs and 28 cold discharges were used to characterise their feeder aquifers and to reveal the relationships between water chemistry and regional seismicity. The Sciacca thermal springs differ chemically and isotopically from those of Montevago and the Castellammare-Alcamo areas. The inferred deep end-members of the thermal waters of Montevago and Castellammare-Alcamo are almost similar, suggesting that both systems are fed by carbonate waters and selenite waters. A slight contribution (1–3%) of seawater, during groundwater ascent it is also present. The Sciacca thermal springs are fed by a deep reservoir comprising a mixture of 50% carbonate water and 50% seawater. During ascent towards the surface, these waters interact with NaCl-rich evaporite layers. By combination of published and present data significant temporal variations of temperature and some chemical parameters in the thermal waters of Western Sicily have been recorded. These variations were mostly between 1966 and 1969. Although the data are discontinuous it is still possible to reveal a direct link between physico–chemical changes in the Acqua Pia and Terme Selinuntine springs and the 1968 Belice Valley earthquake. Within the studied springs, two kinds of geochemical behaviour have been recognised. The chemistry of the Montevago thermal springs was permanently changed in response to changes in the groundwater system. Water temperature and dissolved SO4, Cl, Na, and TDS showed minimum values before the earthquake and maximum values after the event. Almost constant values substantially higher than before, were recorded after the seismic event. Conversely, the temporal variations observed in the waters of the Terme Selinuntine spring, from 1965 to 1991, exhibit a transient increase most probably caused by a temporary contribution of deep CO2-rich fluids caused by the strain release during the 1968 earthquake.  相似文献   

11.
The Oylat spa is located 80 km southeast of Bursa and 30 km south of Ineg?l in the Marmara region. With temperature of 40°C and discharge of 45 l/s, the Oylat main spring is the most important hot water spring of the area. Southeast of the spa the Forest Management spring has a temperature of 39.4°C and discharge of 2 l/s. The G?z spring 2 km north of the spa, which is used for therapy of eye disease, and cold waters of the Saadet village springs with an acidic character are the further important water sources of the area. EC values of Main spring and Forest Management hot spring (750–780 μS/cm) are lower than those of Saadet and G?z spring waters (2,070–1,280 μS/cm) and ionic abundances are Ca > Na + K > Mg and SO4 > HCO3 > Cl. The Oylat and Sızı springs have low Na and K contents but high Ca and HCO3 concentrations. According to AIH classification, these are Ca–SO4–HCO3 waters. Based on the results of δ18O, 2H and 3H isotope analyses, the thermal waters have a meteoric origin. The meteoric water infiltrates along fractures and faults, gets heated, and then returns to surface through hydrothermal conduits. Oylat waters do not have high reservoir temperatures. They are deep, circulating recharge waters from higher enhanced elevations. δ13CDIC values of the Main spring and Forest Management hot spring are −6.31 and −4.45‰, respectively, indicating that δ13C is derived from dissolution of limestones. The neutral pH thermal waters are about +18.7‰ in δ34S while the sulfate in the cold waters is about +17‰ (practically identical to the value for the neutral pH thermal waters). However, the G?z and Saadet springs (acid sulfate waters) have much lower δ34S values (~+4‰).  相似文献   

12.
Reservoir fluid compositions have been assessed from analytical data on water samples collected from thermal and cold waters in Balçova geothermal field. The results of mineral equilibrium modelling indicate that the waters, with some exceptions, are systematically supersaturated with respect to calcite, aragonite, dolomite, chalcedony and quartz, but undersaturated with respect to amorphous silica, celestite, anhydrite and gypsum and undersaturated or supersaturated with respect to barite, low-albite, K-feldspar, gibbsite and Fe(OH)3(a). Calculation of mineral saturation states and geochemical analyses of scale and field observations show that carbonate minerals (calcite, aragonite and dolomite) are most likely to be precipitated as a scale type. Besides carbonates, scale formation risk of amorphous silica, Fe(OH)3(a), anhydrite, barite and celestite minerals should be taken into account in some wells and surface equipment. Most of the waters, with some exceptions, have carbonate scaling risk at all temperatures, whereas the other scaling risks only exist over a limited temperature range. While silica, Fe(OH)3(a) and barite show a scaling tendency at low temperatures, anhydrite and celestite scaling occurs at higher temperatures.  相似文献   

13.

A study of thirteen geothermal springs located in the geothermal field of Guelma, northeastern Algeria, was conducted. Samples were collected during the period between January 2014 and February 2016. Geochemical processes responsible for the chemical composition of thermal and mineralized water were evaluated. The hydrochemical analysis shows that the thermal waters are characterized by the presence of two different chemical facies, the first type SO4–Ca in the east, west and south of Guelma, the second type HCO3–Ca in the south. This analysis also attributed to sodium, chlorides, and sulfates to an evaporitic terrigenous origin by the molar ratio Sr2+/Ca2+. The thermal spring waters from Guelma geothermal system have a meteoric origin, and all samples are immature with strong mixing between hot and shallow waters with 19–38.5% rate of mixing. The silica geothermometer shows that these thermal waters have a temperature varying from 84 to 122 °C and that the water came from a depth of 2100–3000 m through a fault system that limits the pull-apart basin of Guelma. Potential environmental effluent from thermal spas could pollute in both the irrigation and drinking waters, and which imposes danger on the health of the inhabitants of the region.

  相似文献   

14.
New major, trace and isotopic geochemical results from a regional study of springs discharging from the major carbonate rock aquifer in the Interlake Region of Manitoba, Canada, are used to understand water–rock reactions, timing of recharge/discharge, tufa formation processes, and as baseline data. Spring waters are fresh with total dissolved solids (TDS) concentrations ranging from 150 to 880 mg/L. Waters discharging in the northern part of the study area have lower TDS, are dominantly Ca–Mg–HCO3 waters with low SO4 concentrations (<< 50 mg/L), and appear to have interacted primarily with Silurian carbonate lithologies. In contrast, waters in the southeastern part of the study area have higher TDS and have elevated SO4 concentrations (up to 210 mg/L). Spring waters have elevated Mg/Camolar (1.23 ± 0.23), typically greater than congruent dissolution of dolomite. Ca and Mg concentrations and Mg/Camolar indicate that groundwater residence times were sufficient to allow equilibration with bedrock dolomite lithologies; elevated tritium in northern waters indicates a significant recharge component in the 1960's and 1970's. Tufa precipitates that have formed from many of the spring waters are low-Mg calcite (MgO = 1.70 to 5.80 wt.%). Sr concentrations are variable (57 to 657 ppm) and tufa Sr/Camolar ratios appear to be entirely controlled by spring water Sr/Camolar. Empirically determined Sr distribution coefficients (DSr = 0.389 ± 0.083) indicate rapid crystallization following CO2 degassing, consistent with heavier δ13CVPDB compared to spring waters. Sulfate concentrations are generally too low for calcitization (dedolomitization) reactions driven by anhydrite dissolution to be the dominant control on the elevated groundwater Mg/Camolar, implying either extensive sulfate reduction along the flow paths (however, δ13CDIC suggests the elevated SO4 is more consistent with Fe-sulfide oxidation), or that other processes are involved. Major ion ratios suggest that the waters in the southern part of the study area are more consistent with interaction with siliciclastic rocks than with anhydrite dissolution. We suggest that calcitization (dedolomitization) reactions driven by anhydrite dissolution may not dominate all carbonate aquifers and that mixing of waters in karst conduits combined with ion exchange reactions are important controls on water chemistry in these systems.  相似文献   

15.
The Diyadin Geothermal area, located in the eastern part of Anatolia (Turkey) where there has been recent volcanic activity, is favorable for the formation of geothermal systems. Indeed, the Diyadin geothermal system is located in an active geodynamic zone, where strike-slip faults and tensional cracks have developed due to N–S regional compression. The area is characterized by closely spaced thermal and mineralized springs, with temperatures in the range 30–64 °C, and flowrates 0.5–10 L/s. Thermal spring waters are mainly of Ca(Na)-HCO3 and Ca(Mg)-SO4 types, with high salinity, while cold groundwater is mostly of Ca(Na, Mg)-HCO3 type, with lower salinity. High contents of some minor elements in thermal waters, such as F, B, Li, Rb, Sr and Cs probably derive from enhanced water–rock interaction.Thermal water samples collected from Diyadin are far from chemical equilibrium as the waters flow upward from reservoirs towards spring vents and possibly mix with cooler waters. The temperatures of the deep geothermal reservoirs are estimated to be between 92 and 156 °C in Diyadin field, based on quartz geothermometry, while slightly lower estimates are obtained using chalcedony geothermometers. The isotopic composition of thermal water (δ18O, δ2H, δ3H) indicates their deep-circulating meteoric origin. The waters are likely to have originated from the percolation of rainwater along fractures and faults to the deep hot reservoir. Subsequent heating by conduction due to the presence of an intrusive cupola associated with the Tendurek volcano, is followed by the ascent of deep waters to the surface along faults and fractures that act as hydrothermal conduits.Modeling of the geothermal fluids indicates that the fluid is oversaturated with calcite, aragonite and dolomite, which matches travertine precipitation in the discharge area. Likewise, the fluid is oversaturated with respect to quartz, and chalcedony indicating the possibility of siliceous precipitation near the discharge areas. A conceptual hydro-geochemical model of the Diyadin thermal waters based on the isotope and chemical analytical results, has been constructed.  相似文献   

16.
Thermal waters of the Usak area have temperatures ranging from 33 to 63°C and different chemical compositions. These waters hosted by the Menderes Metamorphic rocks emerge along fault lineaments from two geothermal reservoirs in the area. The first reservoir consists of gneiss, schists, and marbles of the Menderes Metamorphic rocks. The recorded reservoir is Pliocene lacustrine limestone. Hydrogeochemical studies indicate that thermal waters were mixed with surface waters before and/or after heating at depth. The results of mineral equilibrium modeling indicate that all the thermal waters are undersaturated at discharge temperatures for gypsum, anhydrite, and magnesite minerals. Calcite, dolomite, aragonite, quartz, and chalcedony minerals are oversaturated in all of the thermal waters. Water from the reservoir temperatures of the Usak area can reach upto120°C. According to δ18O and δ2H values, all thermal and cold groundwater are of meteoric origin.  相似文献   

17.
《Applied Geochemistry》2001,16(6):633-649
Water inflows in the Gotthard Highway Tunnel and in the Gotthard Exploration Tunnel are meteoric waters infiltrating at different elevations, on both sides of an important orographic divide. Limited interaction of meteoric waters with gneissic rocks produces Ca–HCO3 and Na–Ca–HCO3 waters, whereas prolonged interaction of meteoric waters with the same rocks generates Na–HCO3 to Na–SO4 waters. Waters circulating in Triassic carbonate-evaporite rocks have a Ca–SO4 composition. Calcium-Na–SO4 waters are also present. They can be produced through interaction of either Na–HCO3 waters with anhydrite or Ca–SO4 waters with a local gneissic rock, as suggested by reaction path modeling. An analogous simulation indicates that Na–HCO3 waters are generated through interaction of Ca–HCO3 waters with a local gneissic rock. The two main SO4-sources present in the Alps are leaching of upper Triassic sulfate minerals and oxidative dissolution of sulfide minerals of crystalline rocks. Values of δ34SSO4 < ∼+9‰ are due to oxidative dissolution of sulfide minerals, whereas δ34SSO4 >∼+9‰ are controlled either by bacterial SO4 reduction or leaching of upper Triassic sulfate minerals. Most waters have temperatures similar to the expected values for a geothermal gradient of 22°C/km and are close to thermal equilibrium with rocks. However relatively large, descending flows of cold waters and ascending flows of warm waters are present in both tunnels and determine substantial cooling and heating, respectively, of the interacting rocks. The most import upflow zone of warm, Na-rich waters is below Guspisbach, in the Gotthard Highway Tunnel, at 6.2–9.0 km from the southern portal. These warm waters have equilibrium temperatures of 65–75°C and therefore constitute an important low-enthalpy geothermal resource.  相似文献   

18.
The reported study contributes to research on earthquake prediction. Between 2007 and 2009, changes were observed in two geothermal and mineral springs located in Eskipazar (～3–5 km to the north of the North Anatolian Fault Zone) in Turkey, in relation to small-magnitude earthquakes. During pre-seismic and post-seismic activities, variations were observed in the hydrogeological parameters of the spring waters. Temperature increases of 0.4–1°C were measured in one of the springs prior to three different earthquakes. There was a slight increase in the spring discharge with respect to the first earthquake, which occurred closest to the spring. This led to a reduction in electrical conductivity (EC), total dissolved solids (TDS), Ca, HCO3, δ13C, Al, Mn, and Fe concentrations in the spring water, whereas tritium and Se values increased. Several days before the third earthquake, which occurred at a shallower depth, a decrease was observed in the discharge, which led to a reduction in tritium, δ13C and Si concentrations. These variations could be explained by changes in the mixing ratio of waters of different genesis, depending on changes in permeability, pore pressure, and flow paths of the aquifer due to regional stress changes.  相似文献   

19.
This study focuses on the hydrochemical characteristics of 47 water samples collected from thermal and cold springs that emerge from the Hammam Righa geothermal field, located in north-central Algeria. The aquifer that feeds these springs is mainly situated in the deeply fractured Jurassic limestone and dolomite of the Zaccar Mount. Measured discharge temperatures of the cold waters range from 16.0 to 26.5 °C and the hot waters from 32.1 to 68.2 °C. All waters exhibited a near-neutral pH of 6.0–7.6. The thermal waters had a high total dissolved solids (TDS) content of up to 2527 mg/l, while the TDS for cold waters was 659.0–852.0 mg/l. Chemical analyses suggest that two main types of water exist: hot waters in the upflow area of the Ca–Na–SO4 type (Hammam Righa) and cold waters in the recharge zone of the Ca–Na–HCO3 type (Zaccar Mount). Reservoir temperatures were estimated using silica geothermometers and fluid/mineral equilibria at 78, 92, and 95 °C for HR4, HR2, and HR1, respectively. Stable isotopic analyses of the δ18O and δD composition of the waters suggest that the thermal waters of Hammam Righa are of meteoric origin. We conclude that meteoric recharge infiltrates through the fractured dolomitic limestones of the Zaccar Mount and is conductively heated at a depth of 2.1–2.2 km. The hot waters then interact at depth with Triassic evaporites located in the hydrothermal conduit (fault), giving rise to the Ca–Na–SO4 water type. As they ascend to the surface, the thermal waters mix with shallower Mg-rich groundwater, resulting in waters that plot in the immature water field in the Na–K–Mg diagram. The mixing trend between cold groundwaters from the recharge zone area (Zaccar Mount) and hot waters in the upflow area (Hammam Righa) is apparent via a chloride-enthalpy diagram that shows a mixing ratio of 22.6 < R < 29.2 %. We summarize these results with a geothermal conceptual model of the Hammam Righa geothermal field.  相似文献   

20.
The study area is located in the northwestern part of Greece, in Aitoloakarnania prefecture. In this region, where no volcanic activity exists, thermal springs such as Kremasta and Kokkino Stefani, well-known for their healing properties occur. The objective of this study was the investigation of these springs, as well as the study of the chemical composition and origin of water. Relationships between these springs were also examined. The geological setting of the area comprises sedimentary rocks of the Pindos, Gavrovo-Tripolis and Ionian geotectonic zones, deformed by orogenic movements followed by Neogene extensional tectonism. The thermal and mineral springs were classified into three main groups. The first group is characterized by Ca-HCO3 water type and low water temperatures. It corresponds to the springs that are hosted in the Ionian zone and their possible enrichment in SO4 is mainly attributed to the evaporites. The other two groups consist of alkaline thermal water mainly hosted in the formations of Gavrovo-Tripolis zone. In these two groups, the very strong reducing conditions that prevail are expressed by high amounts of NH3 and H2S. Moreover, Na, F, Li, Sr and Ba display elevated concentrations. The second includes mineral waters of (Ca)-Na-HCO3 type that are depleted in calcium. Their residence time is rather long and they originate from deep water circulation through siliceous rocks. The third group includes thermal waters of Ca-Mg-Na-HCO3 water type of higher water temperatures that reveal characteristics of deep circulation directly associated with the underlain limestones.  相似文献   

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