Deep Thermal Water Research Articles

Hydrochemistry and geothermometry of thermal groundwater of southeastern Tunisia (Gabes region)

Given the vital importance of water and energy in desert regions, we undertook a study dealing with the deep reservoirs in Gabes area, which is located in the southeastern part of Tunisia. Geothermal resources are taken from the Intercalary Continental [or Continental Intercalaire (CI)], known as the largest deep aquifer in Tunisia and are used in a number of applications, mainly in agriculture. Previous investigations performed on the thermal waters of this area focused on the genesis of the deep waters with regard to the thermal features of geothermal reservoirs. A more detailed investigation has been carried out, considering both deep and shallow waters. In order to estimate the potential temperatures of deep reservoir in the Gabes area, we developed a synthetic study including chemical geothermometers, multiple mineral equilibrium approach, and other approaches. Chemical types of the thermal waters and effects of mixing between shallow cold waters with deep thermal waters were also discussed. In fact, the application of Na–K–Mg diagram relative to deep geothermal reservoir capitulate estimated temperatures (about 90°C). In addition, the multiple mineral equilibrium approach submits a similar estimated temperature ranging between 65 and 70°C, showing a disequilibrium status which indicates a possibly mixing with surface water. Indeed, wells exploiting the CI aquifer in the south part of the studied area showed the same characteristics, corroborating the reliability of the applied methods.

Comparative study on humic substances isolated in thermal groundwaters from deep aquifers below 700 m

Copyright © 2012 by The Geochemical Society of Japan. as spectroscopic characteristics was discussed in some studies (Wassenaar et al., 1990; Gron et al., 1996; Artinger et al., 2000). Thurman (1985) studied several properties of HS isolated from Ca(HCO3)2 and CaSO4-rich groundwater originating from different depths in sandy, dolomitic or limy aquifers. He found that groundwater containing organic carbon concentration greater than 1 mg/L either may originate from aquifers receiving recharge from organic-rich waters or may be in contact with sediments rich in kerogen. However, the investigation of HS from deep groundwater or geothermal water has received relatively little attention compared with other environments (Thurman, 1985). The isolation of humic acid (HA) and fulvic acid (FA) fractions from thermal waters circulating in deep aquifers of the Pannonian Basin has been carried out recently (Kovacs et al., 2010). Based on our knowledge, our group was the first who isolated HS from deep thermal waters. However, thermal waters from Pannonian Basin were studied earlier by Sajgo et al. (1998), Karpati et al. (1999) and Fekete et al. (2009) that found several aromatic families in hot waters with outflow temperature over 70–80°C. They suggested that the appearance and abundance of aromatic hydrocarbons, alkyphenols and fatty acids in thermal waters is controlComparative study on humic substances isolated in thermal groundwaters from deep aquifers below 700 m

Reconstruction of groundwater flows and chemical water evolution in an amagmatic hydrothermal system (La Léchère, French Alps)

Summary A detailed picture of the hydrogeochemistry of an alpine thermal area (La Lechere, French Alps) was drawn up from new and complete analyses of shallow and deep groundwater, including major and trace elements, gases, and stable (δ 18 O, δD, δ 13 C, δ 34 S) and radiogenic isotopes ( 14 C), combined with data on the trace and stable isotope (δ 18 O, δ 34 S) contents of the aquifer rocks. Three different groundwater facies were recognized: (1) the shallow groundwater in the carbonate and crystalline rocks presents a poorly mineralized Ca–HCO 3 facies; (2) the shallow groundwater from the evaporitic fault zone presents a mineralized Ca–Mg–SO 4 facies; (3) and the deep thermal water presents a highly-mineralized Ca–Na–SO 4 facies. The evolution from facies 2 to facies 3 is controlled by three phenomena: (i) the presence or absence of evaporitic deposits along the fault, which governs whether or not the water can interact with carbonates and dolomites, (ii) interactions with micaschists and Permo-Carboniferous rocks, which lead to Ca–Na exchanges and enrichment in some trace elements and gases (CO 2 , CH 4 and H 2 S), and (iii) the long residence time (several thousand years) and high temperature (90 °C) of the thermal water.

Major ion hydrochemistry and environmental isotope signatures as a tool in assessing groundwater occurrence and its dynamics in a fractured volcanic aquifer system located within a heavily urbanized catchment, central Ethiopia

Summary Hydrochemical and environmental isotope ( 2 H, 18 O and 3 H) data were used to characterize the groundwater flow, occurrence and major ion chemistry in a complex fractured volcanic aquifer system located at the edge of the Ethiopian rift. The study has been supported by conventional hydrogeological mapping. The result clearly indicates the presence of two distinct groundwater systems: (1) The shallow groundwater characterized by low ionic concentration and in places isotopically enriched younger waters; and (2) The deep thermal waters with relatively older age showing negative 18 O shifts and higher ionic concentration. The deep groundwaters are manifested as thermal springs and deep confined and artisan wells mainly aligned along major regional faults. The first group of groundwater is further divided into four subgroups indicating clear geo-hydrological patterns along the groundwater flow path representing different lithologies, residence time and anthropogenic influences. The classification shows different degrees of rock–water interaction and aquifer composition. There are indications of aquifer recharge from highly evaporated surface waters. This integrated study enabled to conceptualize the groundwater flow system vertically in to three zones: namely shallow fast circulating fresh water; mixed and moderately mineralized groundwaters representing the majority of wells and the deep old and mineralized thermal waters. This study has very important implications on possible location and depth of future boreholes, well head protection and in understanding the spread of pollutants that may originate from urban areas.

Geochemical implication of 87Sr/86Sr ratio of high-temperature deep groundwater in a fractured granite aquifer

The Dongrae thermal water area located at the southeast margin of the Korean Peninsula is one of the oldest hot springs in Korea and has been used in spas since the 9th Century. In this paper, a geochemical significance of 87Sr/86Sr ratios from deep thermal water, groundwater, surface water and rainwater in the Dongrae area is discussed. The bedrock of this thermal water-bearing aquifer is composed of Mesozoic granitoids. For temperatures up to 71°C, the thermal water is Na-Cl type, whereas shallow cold groundwater is Ca(-Na)-HCO3 type. 87Sr/86Sr ratios of the thermal water are in the 0.705651 ± 11-0.705696 ± 12 range and have remained nearly unchanged over the past 4 years (2004-2007). 87Sr/86Sr ratios of the shallow cold groundwater, surface water and rainwater range from 0.705781 ± 26 to 0.705789 ± 12, 0.706700 ± 14 and 0.707375 ± 11 respectively. 87Sr/86Sr ratios of the thermal water in the Dongrae area are lower than those of groundwater, surface water, rain water as well as aquifer bearing granite. These Sr isotopic signatures indicate that the circulation rate between thermal water and current meteoric water, including groundwater, surface water and rain water in the Dongrae area should be very slow. Therefore, the thermal water might be derived from a high temperature paleo-groundwater reservoir rather than from circulation of young meteoric water heated by current heat sources. Our data show that 87Sr/86Sr ratios may become an important time lag indicator for the groundwater cycle between deep and shallow groundwater in a fractured granite aquifer system.

HYDROCHEMICAL CONDITIONS AND ENVIRONMENTS PROBLEMS IN THE LOW LAND ZONE OF PINIOS RIVER OF ILIAS DEPARTMENT

The lower Pinios basin at the eastern coast of the Peloponnesus, hosts a system of alternative aquifers in the Pleistocene sediments of "Kalatha" formation. The elaboration of chemical analyses of the principal and trace elements of groundwater samples shown that a Redox environments and the presence of deep thermal water affect the groundwater quality. The aquifers sectors with reducing conditions are characterized by high concentrations of alkalinity, ammonia, total iron and total manganese groundwater. In the aquifers sectors with oxidizing conditions the values of the above parameters are low and the dominance of the chemical elements oxidizing forms are obvious.

Geochemistry, geothermics and relationship to active tectonics of Gujarat and Rajasthan thermal discharges, India

Most thermal spring discharges of Rajasthan and Gujarat in northwestern India have been sampled and analysed for major and trace elements in both the liquid and associated gas phase, and for 18O/ 16O, D/H (in water), 3He/ 4He and 13C/ 12C in CO 2 (in gas) isotopic ratios. Most thermal springs in Rajasthan are tightly associated to the several regional NE–SW strike-slip faults bordering NE–SW ridges formed by Archaean rocks at the contact with Quaternary alluvial and aeolian sedimentary deposits of the Rajasthan desert. Their Ca–HCO 3 immature character and isotopic composition reveals: (1) meteoric origin, (2) relatively shallow circulation inside the crystalline Archaean formations, (3) very fast rise along faults, and (4) deep storage temperatures of the same order of magnitude as discharging temperatures (50–90°C). Thermal spring discharges in Gujarat are spread over a larger area than in Rajasthan and are associated both with the NNW–SSE fault systems bordering the Cambay basin and the ENE–WSW strike-slip fault systems in the Saurashtra province, west of the Cambay basin. Chemical and isotopic compositions of springs in both areas suggest a meteoric origin of deep thermal waters. They mix with fresh or fossil seawater entering the thermal paths of the spring systems through both the fault systems bordering the Cambay basin, as well as faults and fractures occurring inside the permeable Deccan Basalt Trap in the Saurashtra province. The associated gas phase, at all sampled sites, shows similar features: (1) it is dominated by the presence of atmospheric components (N 2 and Ar), (2) it has high crustal 4He enrichment, (3) it shows crustal 3He/ 4He signature, (4) it has low CO 2 concentration, and (5) the only analysed sample for 13C/ 12C isotopic ratio in CO 2 suggests that CO 2 has a strong, isotopically light organic imprint. All these features and chemical geothermometer estimates of spring waters suggest that any active deep hydrothermal system at the base of the Cambay basin (about 2000–3000 m) has low-to-medium enthalpy characteristics, with maximum deep temperature in the storage zone of about 150°C. In a regional overview, both thermal emergences of Rajasthan and Gujarat could be controlled by the counter-clockwise rotation of India.

Geochemical Signature of the Kizildere Geothermal Field, Western Anatolia, Turkey

The Kizildere thermal waters are located in the northern part of the Büyük Menderes rift zone. The Paleozoic metamorphic rocks form the basement of the studied area and are discordantly overlain by Pliocene clastic sediments. The thermal waters are associated with NE-SW- and NW-SE- oriented faults, representing a compressional event that followed extensional formation of the rift zone. The hydrothermal alteration includes phyllic, argillic, silicic, hematitized, and carbonatized alteration zones. Precambrian to Cambrian metamorphic and Pliocene sedimentary rocks are distinguished from one another by enrichment patterns for Hg, Sb, As, Tl, Ag, and Au, and depletion patterns for alkaline and alkaline-earth elements in connection with degree of hydrothermal alteration. The thermal waters have surface temperatures of up to 100°C and reservoir temperatures from 148 to 198°C in the Sazak formation and from 200 to 212°C in the Igdecik formation. Hydrogeochemically, Kizildere thermal waters are of the Na-HCO3-(SO4) type. Metalloids of As and Sb and some trace elements (e.g., B and F, indicating high-temperature water-rock interaction), are found in high concentrations. Isotopic data reveal that Kizildere thermal waters do not contain measurable 3H. Conversely, some nearby thermal springs with temperatures of up to 88°C contain atmospheric and anthropogenic 3H (up to 6.5 TU). Therefore, there is evidence for a mixing process between the fresh groundwater and deep thermal water. The Kizildere thermal waters are of meteoric origin. Stable isotope values of σD and σ18O show that the mixed groundwater-thermal water systems lie along the meteoric water line, whereas high-temperature, deep groundwater systems deviate from the meteoric water line in showing a water-rock interaction at high-temperature conditions. These data agree well with the results of hydrogeochemical analyses indicating intensive water-rock interaction and reactions with silicates. Due to the deep circulation, the water is heated by recent subvolcanic activity. Overprinting by reactions with crystalline rocks was intensified by outgassing of magmatic CO2 and H2S, proven by isotope analyses of σ13C, σ34S, and σ11B. Although intense geochemical near-surface reactions occur, the geochemical features of high-temperature, water-rock interaction dominate the chemical and isotopic characteristics of the studied waters.

Use of hydrochemistry and environmental isotopes for evaluation of groundwater in the Paleogene limestone aquifer of the Ras Al-Ain area (Syrian Jezireh)

Atmospheric precipitation and groundwaters from the Paleogene aquifer system in northeastern Syria (Jezireh) have been investigated using major ions and environmental isotope methods to interpret the hydrogeological features characterizing this system. Based on the chemical ratios and isotopic compositions, the groundwater bodies are differentiated into three main groups: (1) fresh, cold, and shallow groundwater; (2) brackish, thermal, and deep groundwater, and (3) an admixed groundwater. The fractions of deep thermal water in the total discharge of admixed groundwaters were estimated and the elevations of recharge zones for the Paleogene aquifer were determined. Based on tritium content in atmospheric precipitation and by adopting a model with exponential time distribution function, the mean residence time of groundwater is evaluated. Radiocarbon groundwater ages were calculated and corrected according to the most commonly used models. The extensive declining of major karst springs discharge in the Ras Al-Ain area is the consequence of a severe groundwater pumping from the Paleogene aquifer. The remaining groundwater resources in this aquifer are subject to be exhausted in the future years, in the absence of any real rational treatment and suitable management strategies.

Geochemistry of thermal springs, Alhama de Granada (southern Spain)

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 SO 4 reduction. The chemical composition of the water is related to the dissolution of evaporites (SO 4 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 14C DIC 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.

Origin of salinity of deep groundwater in crystalline rocks

Deep groundwater in fractured crystalline basement has been reported from deep mines and from scientific deep wells. Highly saline brines have been described from several km depth in the continental basement of the Canadian, Fennoscandian and Ukrainian shields and elsewhere in the world. The origin of salinity is unknown and many different possibilities have been presented. We compare the compositional evolution of deep waters in the Black Forest basement, SW Germany, with those of other deep crystalline waters, and use halogen systematics (e.g. Cl/Br ratios) and other parameters of the waters to deduce the origin of their salinity. In the Black Forest the composition of deep thermal waters results from chemical interaction of surface water with the rock matrix (mainly weathering of plagioclase and mica) and from mixing of the reacted water with stagnant saline deep water. Here we show by Na/TDS‐and Cl/TDS‐investigations, by molality‐ratios of the Na and Cl concentrations, and by Cl/Br systematics that these deep saline waters have a marine origin. The Cl/Br ratios in deep crystalline waters are very close to normal marine ratios (Cl/Br = 288 ppm basis). In contrast, Cl/Br ratios of other possible sources of salinity show distinctly different Cl/Br ratios: water derived from dissolved Tertiary halite deposits of the rift valley is in the order of Cl/Br = 2400 and water from dissolved Muschelkalk halite deposits has values of about Cl/Br = 9900. Leaching experiments on crystalline rocks, on the other hand, show that the average Cl/Br ratio of crystalline rocks is far below Cl/Br = 100.

Geochemical and hydrogeological characterization of thermal springs in Western Sicily, Italy

Thermal and cold waters from Castellammare–Alcamo (Western Sicily-Italy) were collected between May 1994 and May 1995 and studied for their chemical and isotopic composition. During the same period, mean monthly samples of meteoric water were also collected and measured for their isotopic composition. The main purpose of this study was the characterization of the acquifers and, if possible, of their recharge areas. According to the results obtained, the acquifers were divided into three main groups: (a) selenitic waters, (b) cold carbonatic waters, and (c) deep thermal waters resulting from the mixing of the other two types. Besides a mixing process between carbonatic and selenitic waters, contamination processes of thermal waters by seawater take place during their ascent. The water temperature of the acquifer feeding the thermal springs was estimated by means of various geothermometers to range between 60°C and 97°C. Isotope data on rainwater samples show a wide seasonal variation of both δ 18 O and δD values. The fairly constant values of thermal waters through time and the lack of an apparent correlation with the isotopic values of rainwater suggest the existence of a deep circuit determining an almost complete homogenisation of the seasonal variations of the isotopic values.

Chemical geothermometry and fluid–mineral equilibria for the Ömer–Gecek thermal waters, Afyon area, Turkey

Thermal waters of the Ömer–Gecek geothermal field, Turkey, with temperatures ranging from 32 to 92°C vary in chemical composition and TDS contents. They are generally enriched in Na–Cl–HCO 3 and suggest deep water circulation. Silica and cation geothermometers applied to the Ömer–Gecek thermal waters yield reservoir temperatures of 75–155°C. The enthalpy–chloride mixing model, which approximates a reservoir temperature of 125°C for the Ömer–Gecek field, accounts for the diversity in the chemical composition and temperature of the waters by a combination of processes including boiling and conductive cooling of deep thermal water and mixing of the deep thermal water with cold water. It is also determined that the solubility of silica in most of the waters is controlled by the chalcedony phase. Equilibrium states of the Ömer–Gecek thermal waters studied by means of the Na–K–Mg triangular diagram, Na–K–Mg–Ca diagram, K–Mg–Ca geoindicator diagram, activity diagrams in the systems composed of Na 2O–CaO–K 2O–Al 2O 3–SiO 2–CO 2–H 2O phases, log SI diagrams, and finally the alteration mineralogy indicate that most of the spring and low-temperature well waters in the area can be classified as shallow or mixed waters which are likely to be equilibrated with calcite, chalcedony and kaolinite at predicted temperature ranges similar to those calculated from the chemical geothermometers. It was also observed that mineral equilibrium in the Ömer–Gecek waters is largely controlled by CO 2 concentrations.

Hydrology and Geochemistry of Thermal Waters in the Upper Napa Valley, California

AbstractShallow low‐to‐moderate temperature geothermal waters are found in the upper part of the Napa Valley near the town of Calistoga, California. The geology of the upper Napa Valley is dominated by Jurassic to Cretaceous eugosynclinal Franciscan assemblage and the late Tertiary (Pliocene) Sonoma Volcanic rocks. Minor post‐Pliocene normal faulting is evident in the volcanic rocks north and southeast of the study area. The thermal waters which have a sodium chloride chemistry with elevated concentrations of chloride, boron, and fluoride, are attributed to fault‐controlled hydrothermal circulation. The cold waters are characterized as mixed‐cation bicarbonate type with high concentrations of calcium, magnesium, and iron. The geothermal aquifer is believed to be recharged by the upwelling of thermal water along a linear fault zone aligned with the topographic axis of the Napa Valley. Data from 140 domestic water wells were used to evaluate the chemical character of the geothermal resource and to construct maps of chloride and boron concentrations. These maps were subsequently used to locate the source of the deep thermal water and zones of cold and hot water mixing, and to develop a conceptual model of the geothermal system.

Water/rock interaction in the Larderello Geothermal Field (Southern Tuscany, Italy): an [formula omitted] and [formula omitted] isotope study

Stable isotope and fluid inclusions investigations were carried out on metamorphic rocks belonging to the Southern Tuscany Paleozoic basement that constitutes the main deep fluid reservoir (> 1000 m below ground level) of the Larderello Geothermal Field. Whole-rock samples have δ 18O and δD values ranging from +2.9 to +11.6‰ and from −65 to −76.‰, respectively; most negative δ 18O and δD values have been obtained on rocks from highly fractured levels. Calculated δ 18O and δD values for the fluids in equilibrium with the rocks are from +3 to +8‰ and −31 to −43‰ respectively, temperatures of homogenization of fluid inclusions range from 245°C to 324°C and salinities from 1.0 to 12.8 wt.% NaCl eq. The combined data are consistent with mixing between a deep circulating (> 2500 m below ground level) meteoric-hydrothermal water and a deep thermal water of probable magmatic or metamorphic origin. After mixing and exchange the water/rock mass ratios are small, typically <0.3. These 18O-rich hydrothermal fluids at T>250°C in the deeper explored levels contrast with the much less strongly 18O-shifted meteoric-hydrothermal waters which circulate in the upper 1000 m or so of the system at T<250°C. These new stable isotope data and other petrological, geophysical and geochemical data are all consistent with the existence of two apparently separate hydrothermal systems (and productive horizons) at different depths bearing fluids of different physico-chemical characteristics. The “shallow” upper meteoric system may not be continuosly connected to the lower meteoric-magmatic system because, at least locally, fluid pressures in the lower levels are higher than hydrostatic pressures.

Oxygen and hydrogen isotopes in deep thermal waters from the south meager creek geothermal area, british columbia, canada

Deuterium and oxygen-18 ( 18O) have been measured in deep thermal, shallow thermal and non-thermal water samples collected at various times between 1982 and 1989 from the Meager Creek area, with the aim of assessing the origin of the thermal waters. The isotopic composition of the reservoir waters ( δ 18 O = −13‰ and δ D = −114.8‰ ) was calculated from data on post-flash deep thermal waters, using a two-stage steam loss model. The reservoir composition shows an oxygen shift of 2.4‰ relative to the local meteoric water line. The composition of the recharge, obtained by removing the oxygen shift, is isotopically heavier than the average local meteoric waters, suggesting that the recharge may be from an area to the west of Mt Meager where isotopically heavier ground-waters are likely to be found. The small δ 18O shift of the deep high-temperature waters is indicative of dominance of fracture-related permeability in the reservoir. Analysis of the chemistry and the temperature of the waters from hot springs and shallow thermal wells suggests that these waters have evolved from the deep geothermal waters through dilution by meteoric waters and about 40°C adiabatic cooling (steam loss).

Chemical and stable isotopic models for boundary creek warm springs, southwestern Yellowstone National Park, Wyoming

Abstract Thermal springs of the Boundary Creek hydrothermal system in the southwestern part of Yellowstone Park outside the caldera boundary vary in chemical and isotopic composition, and temperature. The diversity may be accounted for by a combination of processes including boiling of a deep thermal water, mixing of the deep thermal water with cool meteoric water and/or with condensed steam or steam-heated meteoric water, and chemical reactions with surrounding rocks. Dissolved-silica, Na + , K + and Ca 2+ contents of the thermal springs could result from a thermal fluid with a temperature of 200 ± 20°C. Chloride-enthalpy and silica-enthalpy mixing models suggest mixing of 230°C, 220 mg/l Cl − thermal water with cool, low-Cl − components. A 350 to 390°C component with Cl − ≥ 300 mg/l is possibly present in thermal springs inside the caldera but is not required to fit observed spring chemical and isotopic compositions. Irreversible mass transfer models in which a low-temperature water reacts with volcanic glass as it percolates downward and warms, can account for observed pH and dissolved-silica, K + , Na + , Ca 2+ and Mg 2+ concentrations, but produces insufficient Cl − or F − for measured concentrations in the warm springs. The ratio of a Na / a H , and Cl − are best accounted for in mixing models. The water-rock interaction model fits compositions of acid-sulfate waters observed at Summit Lake and of low-Cl − waters involved in mixing. The cold waters collected from southwestern Yellowstone Park have δD values ranging from −118 to −145 per mil and δ 18 O values of −15.9 to −19.4 per mil. Two samples from nearby Island Park have δD values of −112 and −114 per mil and δ 18 O values of −15.1 and −15.3 per mil. All samples of thermal water plot significantly to the right of the meteoric water line. The low Cl − and variable δD values of the thermal waters indicate isotopic compositions are derived by extensive dilution with cold meteoric water and by steam separation on ascent to the surface. Many of the hot springs with higher δD values may contain in addition a significant amount of high-D, low-Cl − , acid-sulfate or steam-heated meteoric water. Mixing models, Cl − content and isotopic compositions of thermal springs suggest that 30% or less of a deep thermal component is present. For example, the highest-temperature springs from Three Rivers, Silver Scarf and Upper Boundary Creek thermal areas contain up to 70% cool meteoric water and 30% hot water components, springs at Summit Lake and Middle Boundary Creek spring 57 are acid-sulfate or steam-heated meteoric water; springs 27 and 48 from Middle Boundary Creek and 49 from Mountain Ash contain in excess of 50% acid-sulfate water; and Three Rivers spring 46 and Phillips could result from mixing hot water with 55% cool meteoric water followed by mixing of acid-sulfate water. Extensive dilution by cool meteoric water increases the uncertainties in quantity and nature of the deep meteoric, thermal component.

Survey on Invasion Point of Deep Thermal Water at Motomachi Area of Izu-0shima Island

Survey on Invasion Point of Deep Thermal Water at Motomachi Area of Izu-0shima Island

Dirty-water events at Rocky Mountain Hot Springs and their correlation with other short-lived phenomena

The Radium (British Columbia) and Miette (Alberta) hot springs occasionally produce "dirty" water that carries varying amounts of solid particles in suspension. Dirty-water events in the period 1959–1983 were caused either by heavy rains (or rapid snowmelt) or by earthquakes with magnitudes of 6.9 or greater, between 740 and 2300 km distant from the springs, in Alaska, Idaho, and Montana. Rainfall-induced events at Miette appear to require at least 34 mm of rain within a 48 h period. Associated decreases in water temperatures and dissolved-solids concentrations and changes in the ionic and isotopic compositions of the spring waters result from mixing of deep thermal water with cooler, less mineralized shallow water. By contrast, the earthquake-triggered events did not have significant thermal or geochemical effects. Suspended solids in the dirty waters represent surficial materials (including vegetation debris) and possibly residues from dissolution of carbonate rocks. At Miette Hot Springs the dirt contains secondary sulfur species (native sulfur and gypsum) derived from the HS− content of the spring water.

Isotopic and chemical evidence for water sources and mixing in the Cerro Pando geothermal area, Republic of Panama

The Cerro Pando geothermal area in Chiriqui Province is situated just to the south of the continental divide in western Panama. Three groups of thermal springs are associated with lineations in a complex of late Tertiary and Quaternary extrusives. Spring temperatures reach maximum values of 66°C at Los Pozos, 67°C at Cotito and 41°C at Catalina; flow-rates are low, ranging up to 1.5 l/s. However, total heat output is estimated at around 7 MW from calculations incorporating measured spring discharges with river-bed discharges inferred from stream conductivity anomalies. In all cases the spring hydrochemistries become of a more dominantly Na-Cl character as mineralization increases; the highest salinities are found in samples from test boreholes in which 4500 mg/l Cl − has been measured. 18O/ 16O and 2H/ 1H data for all thermal springs are roughly colinear, plotting on the δ-diagram with a slope around 3.6 and intersecting the meteoric water line within the compositional range of local surface water. Moreover, δ 18O data are found to correlate with Cl − concentrations, although separate linear trends represent the Los Pozos/Cotito and the Catalina groups of springs. These data are interpreted as indicating that deep thermal ground water feeds the thermal spring systems, with differing isotopic compositions and/or salinities in the Los Pozos/Cotito and Catalina groups. These end-member compositions have evolved by sub-surface steam loss, possibly without any δ 14O shift due to water - rock exchange. The observed spring compositions are all mixtures between the deep thermal and shallow cool end-member ground waters. The importance of resolving mixing relationships before applying geothermometric calculations is illustrated.