Mixing Of Thermal Waters Research Articles

The feasibility of harnessing the geothermal areas of the Indian State of Odisha: Hydrochemical characteristic and stable isotope systematics of the waters

To meet the increase in global energy consumption in an eco-friendly and sustainable manner more emphasis has been put on non-conventional energy resources, such as geothermal energy. India aims to significantly increase the contribution of geothermal energy to its energy mix. In order to do so, a thorough investigation into the geothermal resources of India is of utmost importance. Here we report the hydrochemistry and stable isotope systematics of thermal springs located in the state of Odisha, Eastern India, to evaluate the feasibility of harnessing the geothermal reservoirs. Water chemistry and stable isotope ratios of surface-, non-thermal and thermal water were studied to access the origin and chemical evolution of the thermal waters. The waters had a pH of 5.9 to 8.6 and a suggested meteoric origin based on their δ18O and δD ratios. Chemical geothermometers indicate reservoir temperatures in the range 96–128°C, caused by a high radiogenic heat production at depth coupled with the deep circulation of meteoric water through faults. Processes such as water-rock-interaction, mixing of thermal water with the shallow groundwater and mineral precipitation and dissolution were found to be responsible for the chemical evolution of the thermal waters.

Geochemical Survey of low- temperature geothermal resource of the Reşadiye Spa (Tokat, Northern Turkey)

The low-temperature geothermal area of Reşadiye is located within the Kelkit Valley in the middle of the Black Sea region of Turkey. The area is covered with widespread travertine deposits which are acquired immediately on deposition from hot spring waters. Thermal waters have temperatures between 42 °C and 49 °C and the discharge rate is 3 L/sec. Total dissolved solids range from 3686 to 4204 mg/L. These thermal waters are of Na-HCO3-Cl type. A geothermal reservoir having probable temperature of about 100° is the source of thermal water for the springs. Before emerging along the margins of exposed carbonate formations through the faults and fractures, the waters interacts sometimes with Na-rich Neogene sediments and/or with B-rich rising geothermal fluids as confirmed by high concentrations of Cl, and, to a greater degree, by the presence of B. The conductive process along with the mixing of thermal waters with shallow groundwaters is the main cooling mechanism. Deuterium and oxygen-18 signatures of thermal groundwater indicate its meteoric origin. Equilibrium states of the Reşadiye thermal waters studied by means of the Na–K–Mg triangular diagram, K–Mg–Ca geoindicator diagram, and finally the activity diagrams in the systems composed of Na2O–CaO–MgO-K2O–Al2O3–SiO2–CO2–H2O phases indicate that the springs and low-temperature geothermal well waters in the area can be classified as shallow or mixed waters which are likely to be equilibrated with muscovit at temperature similar to those calculated from the chemical geothermometers. It was also observed that mineral equilibrium in Reşadiye waters is largely controlled by CO2 concentration. Based on acquired data, a conceptual model of the geothermal system of Reşadiye is proposed.

Isotope hydrology and geothermometry of the thermal springs, Damavand volcanic region, Iran

The chemo-isotopic characteristics, geothermal activity and water origin of the 5 thermal and 7 non-thermal springs have been investigated in Damavand volcanic region, northern Iran. The Damavand thermal waters are characterized by outlet temperature values of 23 to 65 °C and the Ca–Cl or Ca-SO4 water types. Stable isotope values of 49 monthly precipitation samples from 5 stations at 2500 to 3200 m elevations were also measured in the study area and Damavand meteoric water line (DMWL) was drawn as δD = 7.64 × δ18O + 8.93 (R2 = 0.98, n = 49). It has a lower slope and intercept than the global meteoric water line (GMWL) due to isotope kinetic fractionation effects during precipitation. The δ18O = (−0.0018 × H(m.a.s.l.) − 3.12) equation was derived based on precipitation data. The reservoir temperature was estimated to be 110–135 °C based on different geothermometers. Damavand volcano can be considered as the main heat source for the thermal springs in the region. The conductive process along with the mixing of thermal waters with shallow cold groundwaters is the main cooling mechanisms. Almost, all the thermal waters fall near the LMWL and within prediction interval area, indicating meteoric origin and no significant effect of water-rock interaction. The Damavand geothermal reservoir is fed by local meteoric water from altitudes of 2500 to 4100 m and circulates at least 500 m deep, near the magma chamber.

The hydrogeochemical assessment of hot springs in Mahallat region, central Iran

The Mahallat hot springs are located in the city of Mahallat, central Iran. This region is famous for its balneotherapy and health tourism attractions. They are located in the transitional zone between the Sanandaj–Sirjan (mainly metamorphosed zone) and the Orumieh–Dokhtar (mainly volcanic zone) structural zones. The host rocks of the region include sedimentary to volcanic rocks (Permian to Quaternary), but Quaternary-aged alluvium and travertine layers are the main outcrops. Additionally, these features reveal that thermal and shallow ground waters had been mixed before hot springs exposure. The chemistry data show that these waters are enriched in Ca2+, Mg2+, Na+, Cl−, HCO3−, and SO42− as well as U and NO3−. The chemistry of thermal and shallow groundwater samples are graphed in the Cl−–SO42−–HCO3− ternary and other diagrams. In addition, hot springs having high NO3−-concentrations indicate that thermal waters mix with shallow groundwater, which are attributed to agricultural and other anthropogenic activities. The hot springs have high U concentration that may result in shallow groundwater mixing with andesitic tuff, granodiorite, shale, and schist of the region. Therefore, the local farms and agricultural crops as well as local residents’ health could be at risk of exposure to the U and NO3− pollution.

Hydrogeology and hydrogeochemistry of a coastal low-temperature geothermal field: a case study from the Datça Peninsula (SW Turkey)

The thermal springs at the Golbasi geothermal field located in the southwest coastal region of Turkey discharge from the Mesozoic-aged fissured carbonate aquifer. The temperature, specific electrical conductivity and pH values of the thermal waters are, respectively, 21.6–29.4 °C, 4020–57,200 µS/cm and 6.85–7.35. Thermal waters are Na–Cl-type brackish to saline waters. The Golbasi geothermal system is fed by meteoric waters and local seawater. The waters are heated at depth by high geothermal gradient caused by the recent tectonic activity in the deep and ascend to the surface through fractures and faults by convection and emerge as thermal springs. The thermal waters mix in different proportions with seawater (5–58 %) and fresh cold waters during the moving up to the surface. Isotope data (δ18O, δ2H and tritium) show that the thermal waters are of meteoric origin, and the residence time at the reservoir is at least 50 years. Almost all the waters are saturated with respect to Ca-montmorillonite, gibbsite, K-mica, illite, kaolinite, Fe (OH)3(a), calcite, dolomite and barite minerals. The most expected minerals that cause scaling at outlet conditions during the production and utilization of Golbasi geothermal waters are calcite, dolomite and some barite. Various chemical geothermometers, Na–K–Mg ternary diagram and mineral equilibrium diagrams suggest that the reservoir temperature is around 50–100 °C.

Stable isotopes (δ13CDIC, δD, δ18O) and geochemical characteristics of geothermal springs of Ladakh and Himachal (India): Evidence for CO2 discharge in northwest Himalaya

Geothermal fields are common in the north-western part of the Himalaya encompassing Himachal Pradesh and Ladakh region, owing probably to their link to the northward migration of the Indian plate and due to under plating. Twenty geothermal springs along the Indus and Nubra valleys of Ladakh region, Sutlej, Beas, and Parbati valleys of Himachal region have been studied. The major & trace element characteristics and stable isotopic composition (δ13CDIC, δ18 O & δD) of these springs were employed to trace their origin and process of metamorphic CO2 degassing. Surface temperature of these springs varies from 21 to 95°C, with an average of 56°C, whereas pH ranges from slightly acidic to alkaline 6.2–8.9 with an average of 7. Hydro-chemically these springs fall under the categories of HCO3: Cl: SO4 and Na+K: Mg: Ca types. Abundance of trace element in these spring waters, such as Fe, B, Li, Sr, Mn, Al, Mo, Zn, and As, were found in considerable amount, possibly due to the rock-water interaction. Springs of the study area contain high ratios of dissolved inorganic carbon (DIC) with concentrations of HCO3− ranging from 1300 to 13400, (average of 5297) μE. The δ13CDIC ratios of these springs vary from −8.4‰ to +1.7‰VPDB, which points towards the deeper source of their origin. δ18O composition of these springs range from −16 to −7.3‰vsmow with corresponding variation in δD varies from −123.5 to − 44.8‰vsmow indicating mixing of thermal water with a meteoric dominated reservoir as most of these samples fall on the line defined by Global Meteoric Water Line (GMWL). In the present study we have estimated the metamorphic CO2 flux using concentration of HCO3≈DIC of these springs and have found that the geothermal springs of the northwest Himalaya have potential to degas ∼2.9×107mol CO2 per year in the atmosphere. Further reservoir temperatures for these springs were also estimated applying standard dissolved silica geothermometers which varies from 42 to 107°C indicating their application in space heating and to generate electricity in certain cases.

A hydrochemical study of the Hammam Righa geothermal waters in north-central Algeria

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.

Differentiating natural and anthropogenic impacts on water quality in a hydrothermal coastal aquifer (Mondragone Plain, Southern Italy)

Groundwater from the Mondragone Plain (Southern Italy) has been investigated by a monthly sampling regimen over the course of a hydrologic year in order to analyze geochemical signatures and has been experienced methods for detecting natural and anthropogenic contamination dynamics that affect resources for human water supply. The Mondragone Plain aquifer is characterized by (1) anthropogenic land uses, (2) varying degrees of hydrothermal interactions, and (3) the potential for seawater intrusion. Anomalies induced by anthropogenic pollution produce non-normally distributed time series and an alteration of the natural SO42− background of groundwater. Variables depending on natural processes are related to water–rock interactions along groundwater flow path, i.e., the hosting aquifer lithology of hydrothermal systems, the recharging massifs of Mt. Petrino and Mt. Massico, and more recent volcanic and alluvial formations. Solute transport in groundwater affects the urban aquifer, both by mixing of thermal waters and by ions deriving from agricultural activity (NO3−, SO42−, NH4+), compromising the quality of a resource largely used by locals. The two thermal systems in the studied area [Levagnole and Padule–San Rocco] are two different aquifers with an independent circulation and chemical composition. Seawater intrusion, both into thermal systems and into shallow aquifers, seems to be unlikely despite the detected increase of salinity in the LEV system close to the shoreline.

Geochemical patterns and origin of alkaline thermal waters in Central Greece (Platystomo and Smokovo areas)

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.

Hydrology, hydrochemistry and geothermal potential of El Chichón volcano-hydrothermal system, Mexico

Fluid and heat discharge rates of thermal springs of El Chichón volcano were measured using the chloride inventory method. Four of the five known groups of hot springs discharge near-neutral Na–Ca–Cl–SO 4 waters with a similar composition (Cl ∼ 1500–2000 mg kg −1 and Cl/SO 4 ∼ 3) and temperatures in the 50–74 °C range. The other group discharges acidic (pH 2.2–2.7) Na–Cl water of high salinity (>15 g/L). All five groups are located on the volcano slopes, 2–3 km in a straight line from the bottom of the volcano crater. They are in the upper parts of canyons where thermal waters mix with surface meteoric waters and form thermal streams. All these streams flow into the Río Magdalena, which is the only drainage of all thermal waters coming from the volcano. The total Cl and SO 4 discharges measured in the Río Magdalena downstream from its junction with all the thermal streams are very close to the sum of the transported Cl and SO 4 by each of these streams, indicating that the infiltration through the river bed is low. The net discharge rate of hydrothermal Cl measured for all thermal springs is about 468 g s −1, which corresponds to 234 kg s −1 of hot water with Cl = 2000 mg kg −1. Together with earlier calculations of the hydrothermal steam output from the volcano crater, the total natural heat output from El Chichón is estimated to be about 160 MWt. Such a high and concentrated discharge of thermal waters from a hydrothermal system is not common and may indicate the high geothermal potential of the system. For the deep water temperatures in the 200–250 °C range (based on geothermometry), and a mass flow rate of 234 kg s −1, the total heat being discharged by the upflowing hot waters may be 175–210 MWt.

Genesis of thermal groundwaters from Siping'an district, China

Thermal groundwaters (40–52°C, pH = 7.4–7.8, Eh = 210–245 mV) from Siping'an district, Shanxi Province, northwestern China, are hydrogeochemically unique. Their occurrence is controlled by faulted structures in Precambrian host rocks. Their hydrochemical type (5 springs and 2 wells) is mainly Cl SO 4 Na, with TDS values around 1.0 g/l. Some minor elements such as Si, Br, Sr, and Li, as well as neutral and acid bituminous substances are so enriched that the thermal waters can also be regarded as mineral waters. Their origin is meteoric, as indicated by 3 lines of geochemical evidence: (1) their δD and δ 18O compositions are very close to the Craig meteoric line; (2) their dissolved gas compositions are N 2-dominated, with less O 2 and CO 2; and (3) the 3He/ 4He ratios are low (0.028). Geochemical processes responsible for the genesis of the hydrochemical features of the waters include dissolution, mixing, and oxidation. The most important water-rock interaction is dissolution or hydrolysis of alumino-silicate minerals in the magmatic and metamorphic host rocks, since the waters are still undersaturated with respect to albite, anorthite, K-spar, and chlorite, as shown by saturation indices. The tritium contents of some thermal waters (46–53 TU), higher than the tritium concentration of local meteoric water, result from the mixing of thermal waters with cold, shallow-lying groundwaters that are from the 1960s. The predominant species of Fe in the thermal waters is Fe(OH) 3, as a result of oxidation processes under aerobic conditions of the aquifers.