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1.
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   

2.
Mixing is a dominant hydrogeological process in the hydrothermal spring system in the Cappadocia region of Turkey. All springs emerge along faults, which have the potential to transmit waters rapidly from great depths. However, mixing with shallow meteoric waters within the flow system results in uncertainty in the interpretation of geochemical results. The chemical compositions of cold and warm springs and geothermal waters are varied, but overall there is a trend from Ca–HCO3 dominated to Na–Cl dominated. There is little difference in the seasonal ionic compositions of the hot springs, suggesting the waters are sourced from a well-mixed reservoir. Based on δ18O and δ2H concentrations, all waters are of meteoric origin with evidence of temperature equilibration with carbonate rocks and evaporation. Seasonal isotopic variability indicates that only a small proportion of late spring and summer precipitation forms recharge and that fresh meteoric waters move rapidly into the flow system and mix with thermal waters at depth. 3H and percent modern carbon (pmC) values reflect progressively longer groundwater pathways from cold to geothermal waters; however, mixing processes and the very high dissolved inorganic carbon (DIC) of the water samples preclude the use of either isotope to gain any insight on actual groundwater ages.  相似文献   

3.
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   

4.
Thermal waters at the Godavari valley geothermal field are located in the Khammam district of the Telangana state, India. The study area consists of several thermal water manifestations having temperature in the range 36–76 °C scattered over an area of ~35 km2. The thermal waters are Na–HCO3 type with moderate silica and TDS concentrations. In the present study, detailed geochemical (major and trace elements) and isotope hydrological investigations are carried out to understand the hydrogeochemical evolution of these thermal waters. Correlation analysis and principal component analysis (PCA) are performed to classify the thermal waters and to identify the different geochemical processes controlling the thermal water geochemistry. From correlation matrix, it is seen that TDS and EC of the thermal springs are mainly controlled by HCO3 and Na ions. In PCA, thermal waters are grouped into two distinct clusters. One cluster represents thermal waters from deeper aquifer and other one from shallow aquifer. Lithium and boron concentrations are found to be similar followed by rubidium and caesium concentrations. Different ternary plots reveal rock–water interaction to be the dominant mechanism for controlling trace element concentrations. Stable isotopes (δ18O, δ2H) data indicate the meteoric origin of the thermal waters with no appreciable oxygen-18 shift. The low tritium values of the samples originating from deeper aquifer reveal the long residence time (>50 years) of the recharging waters. XRD results of the drill core samples show that quartz constitutes the major mineral phase, whereas kaolinite, dolomite, microcline, calcite, mica, etc. are present as minor constituents. Quartz geothermometer suggests a reservoir temperature of 100 ± 20 °C which is in good agreement with the values obtained from K–Mg and Mg-corrected K–Mg–Ca geothermometers.  相似文献   

5.
This study investigates the origin and chemical composition of the thermal waters of Platystomo and Smokovo areas in Central Greece as well as any possible relationships of them to the neighboring geothermal fields located in the south-eastern part of Sperchios basin. The correlations between different dissolved salts and the temperature indicate that the chemical composition of thermal waters are controlled by, the mineral dissolution and the temperature, the reactions due to CO2 that originates possibly by diffusion from the geothermal fields of Sperchios basin and the mixing of thermal waters with fresh groundwater from karst or shallow aquifers. Two major groups of waters are recognized on the basis of their chemistry: thermal waters of Na–HCO3–Cl type and thermal waters mixed with fresh groundwater of Ca–Mg–Na–HCO3 type. All thermal waters of the study area are considered as modified by water–rock interaction rainwater, heated in depth and mixed in some cases with fresh groundwater when arriving to the surface. Trace elements present low concentrations. Lithium content suggests discrimination between the above two groups of waters. Boron geochemistry confirms all the above remarks. Boron concentration ranges from 60 μg L?1 to 10 mg L?1, while all samples’ constant isotopic composition (δ11B ≈ 10 ‰) indicates leaching from rocks. The positive correlation between the chemical elements and the temperature clearly indicates that much of the dissolved salts are derived from water–rock interactions. The application of geothermometers suggests that the reservoir temperature is around 100–110 °C. Chalcedony temperatures are similar to the emergent temperatures and this is typical of convective waters in fault systems in normal thermal gradient areas.  相似文献   

6.
The Sakarya River is one of the largest rivers in Turkey and is fed mainly from Sakaryabaşı springs. The Sakaryabaşı springs are located in the Central Anatolia and issue from confined/semi-confined karst having a thermal component and therefore, having quite different hydrogeological characteristics as compared to the Taurus Karst region, a typical example of the Mediterranean type of karst. The karstic carbonate rocks that form the groundwater reservoir are overlain by a thick semi-pervious overburden of mainly clastics of Neogene age. Tectonics is the major factor controlling the occurrence of the karst springs in the area where topography is rather flat. This study aimed at explaining the occurrence and movement of the karst groundwater within the system by use of hydrogeological, chemical, and isotopic tools. Isotopic composition of the waters revealed that all waters in the region are of meteoric origin and the thermal component is due to deep circulation. The catchment area of the hydrogeological system extends to the south and groundwater movement is towards the outlets, which are in a depression along a major fault. The movement of the groundwater, based on analysis of remotely sensed images, is controlled mainly by structural elements.  相似文献   

7.
《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   

8.
There are 59 springs at the Gevas–Gurp?nar–Güzelsu basins, 38 of these springs emerge from the fractured karst aquifers (recrystallized limestone and travertine) and 21 emerge from the Yuksekova ophiolites, K?rkgeçit formation and alluvium. The groundwater samples collected from 38 out of the total of 59 springs, two streams, one lake and 12 wells were analyzed physico-chemically in the year 2002. EC and TDS values of groundwater increased from the marble (high altitude) to the ophiolites and alluvium (toward Lake Van) as a result of carbonate dissolution and connate seawater. Five chemical types of groundwater are identified: Ca–Mg–HCO3, Mg–Ca–HCO3, Mg–Na–HCO3, Na–Ca–HCO3 and Mg–Ca–Na–HCO3. The calculations and hydrochemical interpretations show that the high concentrations of Ca2+, Mg2+ and HCO3 ? as predominant ions in the waters are mainly attributed to carbonate rocks and high pCO2 in soil. Most of the karst springs are oversaturated in calcite, aragonite and dolomite and undersaturated in gypsum, halite and anhydrite. The water–rock interaction processes that singly or in combination influence the chemical composition of each water type include dissolution of carbonate (calcite and dolomite), calcite precipitation, cation exchange and freshening of connate seawater. These processes contribute considerably to the concentration of major ions in the groundwater. Stable isotope contents of the groundwater suggest mainly direct integrative recharge.  相似文献   

9.
The origin of groundwater discharging via evapotranspiration and from springs within Oasis Valley, Nevada, is of concern owing to the close proximity of the Nevada Test Site (NTS) and the possible contamination of groundwater as a result of underground nuclear testing. Principal components analysis, cluster analysis, and population partitioning, along with a Geographical Information System, were used to decipher groundwater flow patterns in Oasis Valley, Nevada. These multivariate statistical techniques were applied to the trace element chemistry of groundwater samples collected from 26 springs and wells within Oasis Valley, the NTS, and the Nellis Air Force Range. The results of all statistical analyses showed similar geographical trends in the trace element chemistry of the groundwaters included in this study. Differences are observed between the groundwaters from the NTS and those of Oasis Valley based on the concentrations of the elements Li, Ge, Mo, Rb, Ba, U, and Ru. A concentration gradient is observed from lower concentrations in the NTS to increasing concentrations toward Oasis Valley suggesting groundwater flow in an overall southwestward direction from the NTS. Also, a different trace element signature is observed for the waters collected in the northern and western region of Oasis Valley, suggesting another source of groundwater to this area.  相似文献   

10.
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   

11.

The Mio-Pliocene aquifer of the coastal sedimentary basin of Benin is the most exploited aquifer for water supply to the urbanised region in the southern part of the country. The population explosion is putting increasing pressure on quantitative and qualitative aspects of the groundwater resources. Preventing groundwater contamination caused by surface waters requires a thorough understanding of surface-water/groundwater interactions, especially the interactions between the Mio-Pliocene aquifer and surface waters. This study aimed to investigate the interactions between groundwater and surface waters along the major rivers (Sô River and Ouémé Stream) and brooks in the Ouémé Delta. Field campaigns identified 75 springs located in the valleys which feed the rivers, and thus maintain their base flow. The piezometric results indicated, through flow direction assessment, that the Mio-Pliocene aquifer feeds Ouémé Stream and Sô River. Chemical analyses of groundwater and surface waters show similar chemical facies, and changes in the chemical composition in groundwater are also observed in the surface waters. Moreover, the isotopic signatures of surface waters are similar to those of the groundwater and springs, which led to the identification of potential groundwater discharge areas. As a result of groundwater discharge into surface waters, the fraction of groundwater in the surface water is more than 66% in the brooks, regardless of the season. In the Ouémé Stream and Sô River, the fraction of groundwater is 0–21% between June and September, while from October to March it is 47–100%.

  相似文献   

12.
On the basis of isotopic and chemical analyses of 45 spring, well and meteoric water samples from the El Tatio geothermal field in Northern Chile, four main processes giving rise to the formation of a wide range of thermal discharges can be distinguished. (1) Deep dilution of a predominant, primary high chloride (5500 mg/l, 260°) supply water derived from precipitation some 15 km east of El Tatio with local groundwater produces a secondary chloride water. (4750 mg/l, 190°) feeding springs over a limited area. (2) Single step steam separation from these two waters leads to isotopic shifts and increases in chloride contents to 8000 and 6000 mg/l respectively. (3) Absorption of this separated steam and carbon dioxide into local ground water and mixing with chloride waters at shallow levels produces a series of intermediate temperature (160°), low chloride, high bicarbonate waters. (4) Absorption of steam containing H2S into surface waters leads to the formation of zero chloride, high sulfate waters; the isotopic enrichment observed is governed by a kinetic, steady state evaporation process.  相似文献   

13.
A hydrogeological and geochemical study is presented for the San Severino Lucano region of southern Italy. In this region, groundwater circulation occurs in rocks lithologically different from one another (metaophiolites, carbonate rocks, etc.). Many springs drain this region. The Frido springs are the most important both for their great volume of flow and for their water quality. A water balance estimated for the recharge area of the Frido springs suggests that during the period 1938–1958 the evapotranspiration represents 54.8 percent, runoff 21.2 percent, and infiltration to groundwater 34 percent of rainfall. The springs studied have a meteoric origin and their waters are mostly acid carbonate-alkaline earth type. The reservoir rocks appear to be the only discriminating factors for the chemical composition of the waters analysed.  相似文献   

14.
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   

15.
《Applied Geochemistry》2006,21(2):289-304
Mineral springs from Daylesford, Australia discharge at ambient temperatures, have high CO2 contents, and effervesce naturally. Mineral waters have high HCO3 and Na concentrations (up to 4110 and 750 mg/L, respectively) and CO2 concentrations of 620–2520 mg/L. Calcium and Mg concentrations are 61–250 and 44–215 mg/L, respectively, and Si, Sr, Ba, and Li are the most abundant minor and trace elements. The high PCO2 of these waters promotes mineral dissolution, while maintaining low pH values, and geochemical modelling indicates that the CO2-rich mineral water must have interacted with both sediments and basalts. Amorphous silica concentrations and silica geothermometry indicate that these waters are unlikely to have been heated above ambient temperatures and therefore reflect shallow circulation on the order of several hundreds of metres. Variations in minor and trace element composition from closely adjacent spring discharges indicate that groundwater flows within relatively isolated fracture networks. The chemical consistency of individual spring discharges over at least 20 a indicates that flow within these fracture networks has remained isolated over long periods. The mineral water resource is at risk from mixing with potentially contaminated surface water and shallow groundwater in the discharge areas. Increased δ2H values and Cl concentrations, and lower Na concentrations indicate those springs that are most at risk from surface contamination and overpumping. Elevated NO3 concentrations in a few springs indicate that these springs have already been contaminated during discharge.  相似文献   

16.
The present study identifies the hydrochemical and isotopic properties of the Mahmutlu and Ba?dato?lu mineralized thermal springs in K?r?ehir province, a geothermal field in central Anatolia, Turkey. Based on these properties, a hydrogeological regime is proposed in order to explain the Mahmutlu–Ba?dato?lu geothermal system. The relation between the concentrations of the environmental stable isotopes deuterium and oxygen-18 in the water is similar to the relationship in global meteoric water, indicating that the water is of meteoric origin. Evaluation of the geochemical characteristics of the water reveals that these two thermal springs belong to the same hydrogeological system. The hydrogeological system comprises a fractured limestone member of the Çevirme Formation and the Kervansaray Formation as reservoir rocks, and the Delice?rmak Formation as an overlying aquitard. The waters of the Mahmutlu and Ba?dato?lu springs are mainly of the Na-Cl-SO4 type that originate from the Pohrenk evaporite. The thermal waters are undersaturated with respect to calcite, dolomite, halite, and gypsum. The δ 18O and δ 2H contents indicate a δ 18O shift in the Mahmutlu and Ba?dato?lu waters. The temperature range of the two reservoirs is estimated to be 98–158?°C, on the basis of Na+K+Ca and SiO2 geothermometers.  相似文献   

17.
The dissolved ionic constitutents of groundwaters are,in part,a recored of the minerals and rocks in aquifers through which the water has flowed.The chemical composition and association of these major ions in groundwaters have been used to trace groundwater flow paths and sources,In general,the chemical compostion of water in carbonate-rock aquifers in dominated by calcium,magnesium,and bicarbonate,whereas sodium,chloride,and sulfate can be dominant ions in the water that comes from volcanic aquifers or clay minerals.Since the 1990‘s,we have dealt with the geochemistry of groundwaters from more than 100 springs and wells in southern Nevada and eastrn california ,USA for major solutes and trace elements.This paper compiles the hydrochemical data of major ions of these groundwaters.Based on major ion geochemistry,groundwaters from southern Nevada and eastern California can be classified as carbonate aquifer water,volcanic aquifer water,and mixing water (either mixing of cabonate and volcanic aquifer waters or mixing with local recharges),Piper and stiff diagrams of major ions have graphically shown the general chemical characteristics,classification,and mixing relationships of groundwaters from southern Nevada and eastern California.  相似文献   

18.
Geothermal fields distributed in the southern Tibet Plateau rifts such as Yangbajing - Dangxiong basin, and the Yaluzangbu suture are characterized by intensive hydrothermal activity and high enrichment of trace elements (e.g., Li, Rb, Cs, B and Br) in geothermal springs. However, the origin of these elements and their enrichment mechanisms in those geothermal waters remain unclear. This study presents data for the enriched elements, incompatible elements, and B and Sr isotopes, in the geothermal water in the Tibetan Plateau and compares them with some typical geothermal fields worldwide, in an attempt to provide new insights into the origin and mechanism of the enrichment of these trace elements. The results indicate that all geothermal water samples from the Tibetan Plateau show more negative δ11B values than those from local precipitation and rivers. Considering the wide existence of a high-conductivity zone in the middle or even upper-crust interpreted to correspond to re-melt magmatic fluids in the Tibet, the main sources of the typical chemical composition of geothermal waters in the Tibetan Plateau can be classified into two main types: residual magmatic fluids derived from crustal partial remelting and deep circulated groundwater modified by water–rock interactions. In particular, the possible source of magmatic fluids may play a more significant role for special geochemical compositions of geothermal water in the Tibet. Such resources are beneficial for the development and utilization of the geothermal water itself and also serve as a stable source for feeding the salt lake resources.  相似文献   

19.
《Applied Geochemistry》2001,16(9-10):1153-1163
The waters of the thermal springs at Alhama de Granada vary in temperature between 27 and 45°C. Temporal changes in the composition of the principal spring (Baños Viejos) indicate that a small degree of mixing may occur between deep thermal waters and shallow groundwater. Slight compositional variations also occur between the various thermal springs in the study area. These spatial variations are due to the different local hydrodynamic conditions in the springs. Towards the north in less hydraulically transmissive rocks, cooling of the rising water is more noticeable, as are ion exchange and processes of SO4 reduction. The chemical composition of the water is related to the dissolution of evaporites (SO4 and Cl salts), carbonates and silicates, and to the possible existence of sources of S within the rock. Estimates of the mean residence times have been obtained based on 14CDIC and T. The state of thermodynamic equilibrium at the spring discharge was calculated using the SOLMINEQ.88 program. The results indicate that all the samples are supersaturated with respect to quartz, chalcedony, cristobalite, calcite, aragonite and dolomite, and undersaturated with respect to gypsum, anhydrite and halite. The use of different geothermometers and modelling of saturation indices for quartz, albite and anhydrite indicate temperatures of about 110°C.  相似文献   

20.
In order to identify the origin of the main processes that affect the composition of groundwater in a karstic aquifer, a hydrogeochemical and isotopic study was carried out of water from numerous observation wells located in Sierra de Gador, a semiarid region in SE Spain. Several natural and anthropogenic tracers were used to calculate groundwater residence time within this complex aquifer system. Analysis of major ions enabled the principal geochemical processes occurring in the aquifer to be established, and the samples were classified into four distinctive solute groups according to this criterion. Dissolution of carbonate rocks determines the chemical composition of less mineralized water. In another group, the concurrent dissolution of dolomite and precipitation of calcite in gypsum-bearing carbonate aquifer, where the dissolution of relatively soluble gypsum controls the reaction, are the dominant processes. Marine intrusion results in highly mineralized waters and leads to base exchange reactions. The groundwater enrichment of minor and trace elements allowed classification of the samples into two classes that are linked to different flow patterns. One of these classes is influenced by a slow and/or deep regional flow, where the temperature is generally elevated. The influence of sulphate reduces by up to 40 % the barium concentration due to the barite precipitation. Isotope data (T, 14C) confirm the existence of recent local flows, and regional flow system, and ages of ground water may reach 8000 years. The importance of gypsum dissolution in this aquifer is proved by the δ34S content.  相似文献   

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