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1.
A number of thermal springs with temperature up to 64°C are found in the Western Cape Province of South Africa. The average δ13C value of gas (CO2+CH4) released at three springs is −22, which is consistent with an entirely biogenic origin for the C and supports previous investigations which showed that the springs are not associated with recent or nascent volcanic activity. Most springs issue from rocks of the Table Mountain Group, where faulted and highly jointed quartzites and sandstones of the Cape Fold Belt act as the main deep aquifer. The δD and δ18O values of the springs range from −46 to −18 and from −7.3 to −3.9, respectively. Although the thermal springs have isotope compositions that plot close to the local meteoric water line, their δD and δ18O values are significantly lower than ambient meteoric water or groundwater. It is, therefore, suggested that the recharge of most of the thermal springs is at a significantly higher altitude than the spring itself. The isotope ratios decrease wuth increasing distance from the west coast of South Africa, which is in part related to the continental effect. However, a negative correlation between the spring water temperature and the δ18O value in the thermal springs closest to the west coast indicates a progressive in increase in the average altitude of recharge away from the coast.  相似文献   

2.
One hundred and sixty samples of groundwater from nearly all parts of Egypt have been collected and chemically analyzed in order to assess the country's geothermal potential. The samples considered to be thermal include 20 wells (T > 35°C), 4 springs (T > 30°C) and 1 spring not included in the present inventory. The remaining samples, together with data from the literature, establish background chemistry. The hottest springs are located along the east shore of the Gulf of Suez: Uyun Musa (48°C) and 'Ain Hammam Faraoun (70°C). Additional warm springs are located along both shores of the Gulf of Suez and this region is the most promising for geothermal development. The Eastern Desert of Egypt, particularly the coastal area adjacent to the Red Sea has above normal heat flow ( ~ 72.0 < mWm−2) and therefore some geothermal potential although only one thermal well (Umm Kharga: 35.8°C) could be located, In the major oases of the Western Desert (Kharga, Dakhla, Farafra and Bahariya), the regional temperature gradient is low (< 20°C/km), but many of the wells tap deep artesian aquifers and produce large volumes of water in the 35–43°C range. Such wells constitute a low temperature geothermal resource. None of our samples in northern Egypt can be considered thermal including several reported “hot springs.” Application of the silica, NaKCa. and NaKCaMg geothermometers does not indicate the presence of a high temperature geothermal resource at any area we visited.  相似文献   

3.
Arkosic sandstones and conglomerates of Tertiary age beneath the Challis Volcanics of Eocene age at Basin Creek, 10 km northeast of Stanley, Idaho, contain uranium-bearing vitrainized carbon fragments. The economic potential of these sandstones and conglomerates is currently being assessed. Springs abound at the contacts of rock units, and water from these springs supports abundant growths of bryophytes (mosses and liverworts). Water from 22 springs and associated bryophytes were sampled; two springs were found to contain apparently anomalous concentrations (normalized) of uranium — as much as 6.5 μg/L (ppb) in water and 1800 μg/g (ppm) in ash of mosses. Moss samples from both springs also contained anomalous concentrations of arsenic, and one contained highly anomalous amounts of beryllium. Water from a third spring contained slightly anomalous amounts of uranium, and two species of mosses at the spring contained anomalous uranium (400 and 700 μg/g) and high levels of both cadmium and lead. Water from a fourth spring was normal for uranium (0.18 μg/L), but the moss from the water contained a moderate uranium level and highly anomalous concentrations of lead, germanium, and thallium.These results suggest that, in the Basin Creek area, moss sampling at springs may give a more reliable indication of uranium occurrence than would water sampling. The reason for this may be the ability of mosses to concentrate uranium and its associated pathfinder elements and to integrate uranium fluctuations that occur in the spring water over any period of time.  相似文献   

4.
A theory of two-dimensional geothermic problems is elaborated by the active temperature function at the vertical contact of two horizontally layered media. The approach offered before for oceanic ridges is extended to the case of continental margins and the upper part of a descending slab, i.e. “sink”, in island-arc areas. It is assumed that the plate motion in the oceanic area exists; in a descending area it is directed downward but remains zero on a continental side. Mathematically it symbolizes a “source—span—sink” thermal model. Numerical parameters are given for a theoretical thermal model of the heat-flow profile across the Kuril island arc, from the trench through Iturup Island, Sakhalin Island and the Tatarian Trough.  相似文献   

5.
 Curuksu is a low temperature hydrothermal system located within the upper sector of the B. Menderes Graben. The hydrologic structure of the Curuksu hydrothermal system is largely controlled by major graben faults where it is characterized by the presence of two thermal reservoirs. One is formed by Paleozoic quartzite, schist and marble units, and the second consists of Pliocene limestone-travertine units. The thermal conditions in the Curuksu region indicate that the regional tectonics and resulting local stress field control low temperatures activity. Temperatures of 30 springs emerging in the study area range between 15 and 55  °C. These springs are classified as cold fresh, warm mineral and thermal waters. Pamukkale, Karahayıt and Honaz springs are steam condensate waters, whereas Curuksu springs are commonly steam-heated waters with respect to the major anion concentrations. The reservoir temperatures have been estimated from chemical compositions by utilizing simultaneously, geothermometers and mixing models. According to these thermometric methods, the most probable subsurface temperature is in the range of 62–90  °C. However, the mixing models suggest a temperature level of 80  °C for the parent water. The system has low total dissolved solid (TDS) of ∼1000–1500 mg/l, which indicate that these waters undergo conductive cooling within the reservoir. Received: 9 September 1999 · Accepted: 14 February 2000  相似文献   

6.
An integrated survey program involving geological, hydrogeological and geophysical techniques has been employed to characterize the aquifer geometry, recharge and circulation dynamics of thermal springs within a shallow aquifer system in Ethiopia. The selected springs for the case study are Sodere and Gergedi, which are situated within the tectonically active Main Ethiopian Rift (MER). Geologically, the studied springs are located on Plio-Quaternary volcanic rocks. The geophysical results indicate the presence of subsurface weak zones represented by extensional tectonics and weathering zones which are responsible for thermal water circulation and facilitate recharge from the adjacent surface-water bodies. The structures inferred by the resistivity survey, both sounding and electrical tomography, present contrasts in rock resistivity response. The anomalous zones in the magnetic data are in good agreement with the zones that are revealed by geological mapping and surface manifestation of the thermal water discharge zones. The shallow aquifer of the central MER is under the influence of thermal water, which increases the groundwater temperature and mineral content.  相似文献   

7.

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

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8.
Field and petrologic studies along the Adirondack Lowlands — Highlands boundary near Harrisville, NY, indicate that heat from the synmetamorphic intrusion of the Diana syenite complex (intrusion temperature of 1,050° C) played a major role in the local metamorphic thermal regime and was responsible for extensive partial melting of adjacent metasedimentary units (Major Paragneiss of Engel and Engel). Metamorphic temperatures inferred from two — feldspar and spinel — quartz assemblages decrease from 850–950° C along the Diana — metasediment contact to 650–700° C, 2–3 km away from the contact. Metamorphic pressures are 7±0.5 kb as determined from coexisting plagioclase — garnet — sillimanite — quartz, kyanite — sillimanite, and garnet — rutile — ilmenite — sillimanite — quartz (GRAIL). In the paragneiss, migmatites consisting of quartz — microcline perthite — sodic plagioclase leucosomes are generally concordant with the melanosome consisting of biotite — sillimanite — garnet — spinel — plagioclase ±corundum±cordierite. Qualitatively the amount of partial melt and occurrences of corundum-bearing assemblages decrease away from the Diana contact. Activity of H2O inferred from coexisting biotite — sillimanite — quartz — garnet — K-feldspar ranges from 0.01 to 0.17 and is five to ten times lower in corundum-bearing rocks.Melting proceeded via vapor-absent reactions involving biotite in response to localized heating by synmetamorphic intrusion of magma. This unusually preserved, synmetamorphic contact aureole in a regional granulite terrane supports the concept that granulites owe their origin to magma intrusion and/or the ponding of magmas at the base of the crust.  相似文献   

9.
Compressional wave velocities have been measured in granite, granulite, amphibolite and peridotite specimens under conditions of high temperature up to 700°C and confining pressures up to 6 kbar. In general, velocity increases with pressure and decreases with temperature.Quartz-bearing rocks show an anomalous behavior of their compressional wave velocities. The velocity—temperature relations exhibit a velocity-“deep” due to the high—low inversion of the constituent quartz crystals. The intrinsic effect of temperature on velocities is hard to determine due to thermal expansion and consequent loosening of the structure. The opening of new cracks and the widening of old cracks causes a large decrease in compressional wave velocities. The minimum pressure to prevent damage at a given temperature should, therefore, be about 1 kbar/100°C.The values obtained at these conditions are considered to be most nearly correct as intrinsic properties of the compact aggregates. Velocity anisotropies at high confining pressures and high temperatures correlate with preferred lattice orientation of the constituent minerals. The effect of dimensional orientation and microcracks on seismic anisotropy seems to be of minor importance in dry rocks. It is the more eliminated the higher the confining pressure. The data do not support the concept of a velocity maximum in depth of 10–20 km.  相似文献   

10.
High-precision temperature logging in deep and superdeep wells has permitted the study of the thermal regime in the granite–gneiss layer of the Earth's crust. The long-term logging works have allowed the classification of temperature anomalies recorded in the crystalline basement. Most anomalies have been supposed to be caused by loosely aggregated, permeable zones. The classification reflects main types of processes at a great depth — such as injection, inflow and upward migration of gas-cut fluid. The results of great practical importance are obtained using our classification: some intervals — where temperature anomalies interpreted as inflow reservoirs were revealed — have produced fluid, and others interpreted as injection reservoirs absorbed borehole fluid during tests.  相似文献   

11.
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   

12.
The glass transition temperatures and the thermal expansions both below and above the glass transition temperature region of synthetic glasses of compositions close to those of plagioclases have been determined. The linear thermal expansion coefficient of the rigid glasses decreases on average from 7.4×10–6/dgC for albite glass to 4.9×10–6/dgC for glass close to anorthite composition. The glass transition temperature of the glasses initially decreases from 763° C for albite glass to 752°C for An9.7 glass and then increases nearly linearly with further increasing anorthite content to 813° C for glass close to anorthite composition.—Measurements made for comparison on a glass prepared from Madagascar orthoclase yielded a linear thermal expansion coefficient of 6.1×10–6/dgC and a glass transition temperature of 905° C.The variations in thermal expansion and glass transition temperature of the feldspar glasses with composition are discussed in terms of structural changes which are assumed to be associated with cation replacement.  相似文献   

13.
Three garnet-biotite pairs and eleven garnet-cordierite-biotite triplets from the Steinach aureole (Oberpfalz, North-East Bavaria) were analyzed using an electron probe microanalyzer.The regional metamorphic muscovite-biotite schists contain garnets strongly zoned with Mn-Ca-rich centers and Fe-rich edges, the average composition being almandine 67 — spessartine 4 — pyrope 4 — grossular (+andradite) 25.The first contact garnet that is formed in mica schists of the outermost part of the aureole is small, virtually unzoned, and has an average composition of almandine 52 — spessartine 37 — pyrope 8 — grossular (+andradite) 3. With increasing metamorphic grade, there is a consistent trend to form garnets richer in Fe ending up with a composition almandine 84.5 — spessartine 5.5 — pyrope 7.5 — grossular (+andradite) 2.5. This trend is accompanied by a general increase in grain size and modal amount of garnet. Associated cordierites and biotites also become richer in Fe with increasing grade. While the garnets in the highest grade sillimanite hornfelses are poorly zoned, the transitional andalusite-sillimanite hornfelses contain garnets with distinct but variable zonation profiles.These facts can possibly be explained by the time-temperature relationships in the thermal aureole. In a phase diagram such as the Al-Fe-Mg-Mn tetrahedron, the limiting mineral compositions of a four-phase volume or a three-phase triangle are fixed by T and P (the latter remaining effectively constant within a thermal aureole). Thus, in garnet-cordierite-biotite assemblages, garnet zonation should be controlled by temperature variation rather than by a non-equilibrium depletion process. Taking into account the experimental data of Dahl (1968), a zoned garnet from a transitional andalusite-sillimanite hornfels would reflect a temperature increase of about 40° C during its growth. A hypothetical P-X diagram is proposed to show semi-quantitatively the compositional variation of garnet-cordierite pairs with varying pressures (T constant).  相似文献   

14.
Thermal water springs at Bristol and Bath in west England have come under close scrutiny since the closure of Bath Spa in 1978. In order to protect the hot springs from dewatering and loss of pressure due to largescale quarrying and deep drilling, it is necessary to identify the sources and routes whereby the thermal water travels to its resurgences in the Avon valley. Control over deep water movements is exercised by the structure and size of the aquifers and aquicludes, modified by zones of Quaternary—Recent fracturing along which water movements have not been restricted or blocked by mineralization.  相似文献   

15.
Aquaculture of channel catfish is an industry with an annual worth of hundreds of millions of dollars. Catfish farms in the United States are, for the most part, confined to the south central region and in California. Their commercial success depends on a climate which produces a sufficiently long growing season and an abundant supply of shallow groundwater. The proximity to markets is also essential. The temperature range for maximum growth of the species is 24°C–29°C with the growth rate rapidly decreasing as the upper lethal temperature — about 35°C — is approached. Growth below 13°C is negligible.We review the thermal requirements for growth in catfish and examine the role that climate (air temperature and precipitation) plays in limiting the distribution of profitable fish farms. A model is constructed from these relationships which permits the prediction of changes of this distribution resulting from climate warming.  相似文献   

16.
Gorringe Bank is an anomalously high structure of the eastern part of the north Atlantic, which was known to be composed of mantle-derived peridotites (layer 4) and gabbros (layer 3). During the submersible cruise CYAGOR II in 1981, the contact between layer 4 and layer 3 was observed on Mount Gettysburg and interpreted as tectonic. The overlying series of gabbro was extensively sampled on both mounts composing the bank, Gettysburg and Ormonde. Coarse-grained to pegmatoid clinopyroxene gabbros predominate and are associated with differentiated rocks (ferrogabbros and diorites). Cumulate gabbros are missing. The gabbroic section sampled is therefore interpreted as the upper part of the plutonic section. Most samples were strongly recrystallized during two distinct events. Metamorphism occurred close to the ridge axis, from interaction of a seawater-derived fluid with still hot gabbros. High temperature shear zones favoured fluid circulation, but the water/rock ratio — estimated from the sodium input — was very small in undeformed rocks (<1). The low W/R ratio explains the strong evolution of the fluid phase and therefore some particular compositions of secondary minerals. Low temperature alteration occurred when the gabbros were tectonically emplaced close to the sea bottom.  相似文献   

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

18.
《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   

19.
Jowshan geothermal system comprises 6 thermal springs with outlet temperatures ranging from 39.3 to 46.6°C. The thermal water of these springs is presently used for swimming and as a treatment for rheumatism, sinusitis and skin diseases. The pH value of these springs is slightly acidic to neutral and the electrical conductivities about 1500 μS/Cm. The presence of many faults in the area, the alignment of all springs along the Sirch Fault and the similar chemical and isotopic composition of all springs in combination with the hydrogeological setting and geochemistry of water samples indicate that these springs are associated with deep circulation of meteoric water. According to this heating mechanism, meteoric waters infiltrate through fault openings to depth and after heating by geothermal gradient rise to the ground surface due to the hydraulic and buoyancy forces, a mechanism which is common in the southern parts of Iran. The use of various chemical geothermometers and mineral equilibrium states suggests a range of temperature about 50–90°C for the reservoir of Jowshan geothermal system.  相似文献   

20.
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