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Thermal Springs (thermal + spring)
Selected AbstractsThe influence of poorly interconnected fault zone flow paths on spring geochemistryGEOFLUIDS (ELECTRONIC), Issue 2 2008J. C. ROWLAND Abstract Thermal springs commonly occur along faults because of the enhanced vertical permeability afforded by fracture zones. Field and laboratory studies of fault zone materials document substantial heterogeneities in fracture permeabilities. Modeling and field studies of springs suggest that spatial variations in permeability strongly influence spring locations, discharge rates and temperatures. The impact of heterogeneous permeability on spring geochemistry, however, is poorly documented. We present stable isotope and water chemistry data from a series of closely spaced thermal springs associated with the Hayward Fault, California. We suggest that substantial spatial variations observed in ,18O and chloride values reflect subsurface fluid transport through a poorly connected fracture network in which mixing of subsurface waters remains limited. Our measurements provide insight into the effect of fracture zone heterogeneities on spring geochemistry, offer an additional tool to intuit the nature of tectonically induced changes in fault zone plumbing, and highlight the need to consider local variations when characterizing fracture zone fluid geochemistry from spring systems with multiple discharge sites. [source] Geochemistry of the Bagnères-de-Bigorre thermal waters from the North Pyrenean Zone (France)GEOFLUIDS (ELECTRONIC), Issue 1 2002S. Levet Abstract Thermal springs are poorly known in the sedimentary sites of the Pyrenees. In this paper, we describe the ,Bagnères-de-Bigorre' springs which occur in a remarkably active seismotectonic context. A chemical and isotopic study of 15 spring waters (both cold and thermal, ranging in temperature from 7.0 to 49.9°C), and continuous monitoring of a single spring allow us to characterise water,rock interactions, fluids paths and mixing processes. Three groups of waters are distinguished: (I) SO42+,Ca2+,Cl, thermal waters (II) SO42+,Cl,,Ca2+ thermal waters and (III) HCO3,,Ca2+ cold shallow waters. Their characteristics suggest interactions with Mesozoic evaporite and carbonate formations. O and D isotopes from thermal waters indicate a local meteoric origin of Atlantic signature and a recharge elevation of 800 to 1000 m, which corresponds to a single feeding area. Their ,13C values (,2.8 to ,9.6,) are consistent with carbonate dissolution, slight fractionation and a surficial organic input leading to ,13C depletion. Sr isotopes (0.70751 to 0.70777), Na+/Cl, and (Ca2+ + Mg2+)/SO42, ratios as well as thermodynamic calculations show that the dissolution of anhydrite and halite-bearing Triassic layers control the chemical composition of group-I and -II waters. The contrasting trends of cation/Cl, ratios and TDS of waters from groups I and II suggest the existence of two different circulation paths at depth as well as dilution with surficial waters similar to group III. Calculated mixing proportions show that three waters from group I are diluted from 17 to 66%, whereas all waters from group II are mixed. The aquifer temperature is estimated to be in the range 55,64°C using the retrograde and prograde solubilities of anhydrite and chalcedony, respectively. Accordingly, the mean depth of the reservoir is around 1.7 km, which allows us to constrain the depth of the Triassic layer. [source] Geothermal prognoses for tunnels in the Andes / . Geothermische Prognose für AndentunnelGEOMECHANICS AND TUNNELLING, Issue 5 2010Mag. Giorgio Höfer-Öllinger Geothermal energy - Geothermie; Reconnaissance - Baugrunderkundung; Hydrology - Hydrologie; Geology - Geologie Abstract Geothermal prognoses were carried out for two tunnel projects in the Andes, each running between Argentina and Chile. Different methods were applied in accordance with the different project phases. For the feasibility study of a 52 km long railway tunnel, hydrogeological mapping and hydrochemical analyses were carried out as well as isotope analyses on a thermal spring. An attempt to use silica and ionic solute geothermometers produced different results. For the central section of the tunnel temperatures are assumed to reach 50 to 70 °C and further investigations are recommended. The second tunnel project is now in the design phase. Two investigation phases have been completed including geological/ hydrogeological mapping, water sampling and analysis and core drilling. The geothermal gradient is well known from borehole temperature measurements. The thermal conductivity of the rocks was determined from core samples in a laboratory, and an average heat flow of approximately 100 mW/m2 was calculated. During the driving of the tunnel, temperatures of just over 50 °C are expected. Für zwei Tunnelvorhaben in den Anden, jeweils zwischen Argentinien und Chile, wurden geothermische Prognosen durchgeführt. Für verschiedene Projektphasen kamen entsprechend unterschiedliche Methoden zur Anwendung: Für eine Machbarkeitsstudie eines 52 km langen Eisenbahntunnels wurde eine Quellkartierung mit Probennahme durchgeführt sowie Isotopenanalytik an einer Thermalquelle. Ein Versuch, Geothermometer anhand der Lösungsfracht des Quellwassers zu verwenden, scheiterte. Für den zentralen Bereich des Tunnels werden Temperaturen von 50 bis 70 °C vermutet, weitere Erkundungen wurden empfohlen. Das zweite Tunnelvorhaben ist in der Planungsphase deutlich weiter. Neben Kartierungen liegen zwei Erkundungsphasen mit Kernbohrungen vor. Aus Bohrlochmessungen ist der geothermische Gradient bekannt, die Wärmeleitfähigkeit der Gesteine wurde anhand von Bohrkernen im Labor ermittelt. Es konnte ein durchschnittlicher Wärmefluss von etwa 100 mW/m2 errechnet werden, für den Tunnelvortrieb werden Gebirgstemperaturen von maximal knapp über 50 °C erwartet. [source] Volcanic calderas delineate biogeographic provinces among Yellowstone thermophilesENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Cristina Takacs-Vesbach Summary It has been suggested that the distribution of microorganisms should be cosmopolitan because of their enormous capacity for dispersal. However, recent studies have revealed that geographically isolated microbial populations do exist. Geographic distance as a barrier to dispersal is most often invoked to explain these distributions. Here we show that unique and diverse sequences of the bacterial genus Sulfurihydrogenibium exist in Yellowstone thermal springs, indicating that these sites are geographically isolated. Although there was no correlation with geographic distance or the associated geochemistry of the springs, there was a strong historical signal. We found that the Yellowstone calderas, remnants of prehistoric volcanic eruptions, delineate biogeographical provinces for the Sulfurihydrogenibium within Yellowstone (,2: 9.7, P = 0.002). The pattern of distribution that we have detected suggests that major geological events in the past 2 million years explain more of the variation in sequence diversity in this system than do contemporary factors such as habitat or geographic distance. These findings highlight the importance of historical legacies in determining contemporary microbial distributions and suggest that the same factors that determine the biogeography of macroorganisms are also evident among bacteria. [source] The influence of poorly interconnected fault zone flow paths on spring geochemistryGEOFLUIDS (ELECTRONIC), Issue 2 2008J. C. ROWLAND Abstract Thermal springs commonly occur along faults because of the enhanced vertical permeability afforded by fracture zones. Field and laboratory studies of fault zone materials document substantial heterogeneities in fracture permeabilities. Modeling and field studies of springs suggest that spatial variations in permeability strongly influence spring locations, discharge rates and temperatures. The impact of heterogeneous permeability on spring geochemistry, however, is poorly documented. We present stable isotope and water chemistry data from a series of closely spaced thermal springs associated with the Hayward Fault, California. We suggest that substantial spatial variations observed in ,18O and chloride values reflect subsurface fluid transport through a poorly connected fracture network in which mixing of subsurface waters remains limited. Our measurements provide insight into the effect of fracture zone heterogeneities on spring geochemistry, offer an additional tool to intuit the nature of tectonically induced changes in fault zone plumbing, and highlight the need to consider local variations when characterizing fracture zone fluid geochemistry from spring systems with multiple discharge sites. [source] Contribution to the study of thermal waters in Greece: chemical patterns and origin of thermal water in the thermal springs of LesvosHYDROLOGICAL PROCESSES, Issue 2 2008N. J. Lambrakis Abstract The occurrence of thermal/spa waters on Lesvos Island is related to the presence of a major faulting system. Thermal waters are the result of mixing of meteoric and infiltrating seawater at great depth, and their total salinity depends on the percentage of seawater in their composition. According to the diagrams of main elements, trace elements and environmental isotopes, most of the components that determine the chemical composition of thermal waters such as sodium, chloride and sulphates originate from seawaters. On the other hand, the concentration of calcium, magnesium, boron, lithium, etc., was affected by water,rock interaction under high temperature conditions. Moving towards the surface, thermal waters may become polluted by influx of recent seawater, allowing their chemical composition to become similar to that of seawater. The thermal waters of Lesvos Island present relatively high concentrations of ammonia and redox sensitive metals because they are hosted in a reducing environment. They also exhibit low nitrate concentrations due to their mixture with recent fresh water. Finally, they show increased radon concentrations, ranging from 20 to 60 kBq m,3 in the eastern and southern parts of the island, and about 230 kBq m,3 in the north, in the area of Eftalou,Argenos. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||