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1.
The large volume of groundwater stored in the Tedori River alluvial fan, Ishikawa Prefecture, Japan, is an important source of local drinking and industrial water. The Tedori River was observed to be highly turbid from the beginning of May 2015 to at least November 2017 due to a landslide in the upper reach of the river. After the landslide, the groundwater level was drawn down by several to 10 m near the middle river section during paddy irrigation periods in 2015 and 2016. This study addresses the impacts of the highly turbid water on groundwater recharge from the river and paddy fields. In 2016, we sampled groundwater, river water, paddy irrigation water, paddy ponding water, and precipitation five times at 2-month intervals. We analysed the H, O, and Sr stable isotopic compositions and major dissolved ion (and Sr) concentrations and compared our data to previous data obtained in June 2011. Ca, Sr, Cl, SO4, and TN concentrations and δ18O values were higher in June 2016 than in June 2011; these increases were more extreme along the left bank of the Tedori River than along the right bank. We explored the mixing of Tedori River water with groundwater using a two-endmember mixing model based on their Sr concentrations and isotopic compositions. Compared to June 2011, mixing ratios were decreased near the Tedori River in 2016, and larger decreases were observed along the left bank and in the middle stream area. These results confirm that the contribution to groundwater recharge from the river decreased during the turbidity event, particularly along the left bank.  相似文献   

2.
The deeply buried river‐connected Xishan karst aquifer (XKA) in western Beijing, China, has been suffering from diminishing recharge for several decades, which in turn leads to the disappearing of spring water outflows and continuously lowering of groundwater level in the area. Thus, it is important to correctly recognize the groundwater recharge and flow paths for the sustainable development of the XKA. To investigate these issues, the hydrochemical and isotopic compositions are analysed for both surface water and groundwater samples collected over an area of about 280 km2. Results show that (a) the river water is characterized by high Na contents; (b) the δ2H and δ18O values in the river water are distinctively higher than those of groundwater samples, after experiencing the long‐time evaporative enrichment in the upstream reservoir; (c) the Sr concentrations and 87Sr/86Sr ratios of groundwater clearly indicated the interaction between water and carbonate minerals but excluded the water–silicate interaction; and (d) the groundwater samples in the direct recharge area of the XKA have the lowest Na concentrations and the δ2H and δ18O values. Based on the large differences in the Na contents and 18O values of groundwater and surface water, a simple two‐component mixing model is developed for the study area and the fractions of the river water are estimated for groundwater samples. We find that the distribution pattern of the river water fractions in the XKA clearly shows a change of directions in the preferential flow path of the groundwater from its source zone to the discharge area. Overall, our results suggest that the recharged surface water can be a useful evidence for delineating the groundwater flow path in river‐connected karst aquifer. This study improves our understanding of the heterogeneity in karst groundwater systems.  相似文献   

3.
Some conceptual models suggest that baseflow in agriculturally fragmented watersheds may contain little, if any, groundwater. This has critical implications for stream quality and ecosystem functioning. Here, we (a) identify the sources and flowpaths contributing to baseflow using 222Rn and 87Sr/86Sr and (b) quantify mean apparent ages of groundwater and baseflow using multiple isotopic tracers (CFC, SF6, 36Cl, and 3H) in 4 small (0.08 to 0.64 km2) tributary catchments to the Wabash River in Indiana, USA. 222Rn activities and 87Sr/86Sr ratios indicate that baseflow in 3 catchments is sourced primarily from groundwater; baseflow in the fourth is dominated by a source similar to agricultural run‐off. CFC‐12 data indicate that springs in 1 catchment are discharging significant proportions of water that recharged between 1974 (42 ± 2 years) and 1961 (55 ± 2 years). Those same springs have 36Cl/Cl ratios between 1,381.08 ± 29.37 (×10?15) and 1,530.64 ± 27.65 (×10?15) indicating that a substantial proportion of the discharge likely recharged between 1975 (41 years) and 1950 (66 years). Groundwater samples collected from streambed mini‐piezometers in a separate catchment have CFC‐12 concentrations indicating that a large proportion of the recharge occurred between 1948 (68 ± 2 years) and 1950 (66 ± 2 years). Repeat sampling conducted in September 2015 after above‐average summer rainfall did not show significant decreases in mean apparent age. The relatively old ages observed in 3 of the catchments can be explained by geological complexities that are likely present in all 4 catchments, but overwhelmed by flow from the shallow phreatic aquifer in the fourth catchment.  相似文献   

4.
Oxygen and strontium isotope ratios have been used to characterize source regions for granitic magmas for a transect across the northern Appalachian orogen in central and eastern Maine. The northwestern plutons (Katahdin and Seboeis) have δ18O values of 10.3–13.3 and initial 87Sr/86Sr ratios of 0.7083 and 0.7066, respectively. The central plutons (Bottle Lake and Center Pond) have lower δ18O values (8.2–9.9) and initial 87Sr/86Sr ratios (0.7043–0.7055). The southeastern plutons (Lucerne and Deblois) have δ18O values (9.0–11.0) but initial 87Sr/86Sr ratios (0.7077 and 0.7041, respectively) which are intermediate between the northwestern and central plutons.Source models derived from these results and other petrological and geochemical data reflect the juxtaposition of discrete source regions by transcurrent faulting, which may be related to oblique plate motions. This model illustrates the importance of microplate accretion in the Palaeozoic history of the northern Appalachian orogen.  相似文献   

5.
We used hydrochemistry and environmental isotope data (δ18O, δD, tritium, and 14C) to investigate the characteristics of river water, groundwater, and groundwater recharge in China's Heihe River basin. The river water and groundwater could be characterized as Ca2+? Mg2+? HCO3?? SO42? and Na+? Mg2+? SO42?? Cl? types, respectively. Hydrogeochemical modelling using PHREEQC software revealed that the main hydrogeochemical processes are dissolution (except for gypsum and anhydrite) along groundwater flow paths from the upper to middle Heihe reaches. Towards the lower reaches, dolomite and calcite tend to precipitate. The isotopic data for most of the river water and groundwater lie on the global meteoric water line (GMWL) or between the GMWL and the meteoric water line in northwestern China, indicating weak evaporation. No direct relationship existed between recharge and discharge of groundwater in the middle and lower reaches based on the isotope ratios, d‐excess, and 14C values. On the basis of tritium in precipitation and by adopting an exponential piston‐flow model, we evaluated the mean residence time of shallow groundwater with high tritium activities, which was around 50 years (a). Furthermore, based on the several popular models, it is calculated that the deep groundwaters in piedmont alluvial fan zone of the middle reaches and in southern part of the lower reaches are modern water, whereas the deep groundwaters in the edge of the middle reaches and around Juyan Lake in the lower reaches of Heihe river basin are old water. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

6.
Stable isotopic (δDVSMOW and δ18OVSMOW) and geochemical signatures were employed to constrain the geochemical evolution and sources of groundwater recharge in the arid Shule River Basin, Northwestern China, where extensive groundwater extraction occurs for agricultural and domestic supply. Springs in the mountain front of the Qilian Mountains, the Yumen‐Tashi groundwater (YTG), and the Guazhou groundwater (GZG) were Ca‐HCO3, Ca‐Mg‐HCO3‐SO4 and Na‐Mg‐SO4‐Cl type waters, respectively. Total dissolved solids (TDS) and major ion (Mg2+, Na+, Ca2+, K+, SO42?, Cl? and NO3?) concentrations of groundwater gradually increase from the mountain front to the lower reaches of the Guazhou Basin. Geochemical evolution in groundwater was possibly due to a combination of mineral dissolution, mixing processes and evapotranspiration along groundwater flow paths. The isotopic and geochemical variations in melt water, springs, river water, YTG and GZG, together with the end‐member mixing analysis (EMMA) indicate that the springs in the mountain front mainly originate from precipitation, the infiltration of melt water and river in the upper reaches; the lateral groundwater from the mountain front and river water in the middle reaches are probably effective recharge sources for the YTG, while contribution of precipitation to YTG is extremely limited; the GZG is mainly recharged by lateral groundwater flow from the Yumen‐Tashi Basin and irrigation return flow. The general characteristics of groundwater in the Shule River Basin have been initially identified, and the results should facilitate integrated management of groundwater and surface water resources in the study area. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

7.
Geochemical evaluation of the sources and movement of saline groundwater in coastal aquifers can aid in the initial mapping of the subsurface when geological information is unavailable. Chloride concentrations of groundwater in a coastal aquifer near San Diego, California, range from about 57 to 39,400 mg/L. On the basis of relative proportions of major‐ions, the chemical composition is classified as Na‐Ca‐Cl‐SO4, Na‐Cl, or Na‐Ca‐Cl type water. δ2H and δ18O values range from ?47.7‰ to ?12.8‰ and from ?7.0‰ to ?1.2‰, respectively. The isotopically depleted groundwater occurs in the deeper part of the coastal aquifer, and the isotopically enriched groundwater occurs in zones of sea water intrusion. 87Sr/86Sr ratios range from about 0.7050 to 0.7090, and differ between shallower and deeper flow paths in the coastal aquifer. 3H and 14C analyses indicate that most of the groundwater was recharged many thousands of years ago. The analysis of multiple chemical and isotopic tracers indicates that the sources and movement of saline groundwater in the San Diego coastal aquifer are dominated by: (1) recharge of local precipitation in relatively shallow parts of the flow system; (2) regional flow of recharge of higher‐elevation precipitation along deep flow paths that freshen a previously saline aquifer; and (3) intrusion of sea water that entered the aquifer primarily during premodern times. Two northwest‐to‐southeast trending sections show the spatial distribution of the different geochemical groups and suggest the subsurface in the coastal aquifer can be separated into two predominant hydrostratigraphic layers.  相似文献   

8.
Andesites from the Peruvian Andes and the Banda arc of Indonesia are characterized by unusually high and variable 87Sr/86Sr ratios. The Banda arc samples, including two cordierite-bearing lavas from Ambon, show a clear positive correlation between 87Sr/86Sr and δ18O. The andesitic rocks have δ18O values that range from 5.6 to 9.2‰. Over that range in δ18O, 87Sr/86Sr increases from 0.7044 to 0.7095. The cordierite-bearing lavas have δ18O values of approximately 15‰ and 87Sr/86Sr ratios of approximately 0.717. The similarity between δ18O values and 87Sr/86Sr ratios in total rocks and separated plagioclase phenocrysts of the Banda arc samples indicates that the measured isotope ratios are primary and have not been affected by secondary, low-temperature post-eruptive alteration. The observed variation between O and Sr isotopic ratios can be modeled by two-component mixing in which one component is of mantle isotopic composition. As the crust beneath the Banda arc is probably oceanic, contamination of the manle component may have resulted from the subduction of either continentally-derived sediments or continental crust. Mixing calculations indicate that the contaminant could have an isotopic composition similar to that observed in the cordierite-bearing lavas.The Andean samples, despite petrographic evidence of freshness, exhibit whole-rock δ18O values significantly higher than those of corresponding plagioclase phenocryst separates, indicating extensive low-temperature post-eruptive alteration. The plagioclase mineral separates show a range of δ18O values between 6.9 and 7.9‰. The 87Sr/86Sr ratios of these same samples are, in most instances, not significantly different from those measured for the whole rock, thus signifying that the phenocrysts and groundmass were in isotopic equilibrium at the time of eruption. Unlike the lavas of the Banda arc, the Andean lavas show no strong positive correlation between 87Sr/86Sr ratios and δ18O values, but instead lower 87Sr/86Sr ratios appear to be associated with higher δ18O values. The δ18O and 87Sr/86Sr values of the Peruvian samples are both slightly higher than those of “normal” island arc volcanics.The small proportions of contaminant implied by the O isotope results seem to preclude continental crustal contamination as a primary cause of high 87Sr/86Sr ratios. The most plausible process that can explain both O and Sr isotope results is one in which sediments of continental origin are partially melted in the subduction zone. These melts rise into overlying mantle material and subsequently participate in the formation of calc-alkaline magmas.If the involvement of a sialic component in the genesis of andesitic magma occurs in the subduction zone, melting of that sialic material signifies temperatures of at least 750–800°C at the top of the subducted lithospheric slab at depths of approximately 150 km. The fact that contamination has apparently occurred in the Banda arc samples without producing any simple widespread correlations between Sr and O isotopic compositions on the one hand and major or trace element abundances on the other, shows that isotopic correlations, possibly including pseudo-isochrons, can be produced by mixing without producing trace element mixing correlations. Because O versus Sr isotope correlations are little affected by processes of partial melting of differentiation, they provide a direct means of testing whether Sr isotopic variations in volcanic rocks are of mantle origin or are due instead to mixing with sialic material.  相似文献   

9.
An environmental isotope and hydrochemical study was carried out to conceptualize the surface water and groundwater interaction and to explore the groundwater flow pattern in relation to the geological setting. More emphasis is given to the Afar Depression where groundwater is a vital source of water supply. Conventional field hydrogeological study and river discharge records support the isotope and hydrochemical analysis. The region is tectonically active, comprising rift volcanic terrain bordered by highlands. The result revealed that recent meteoric water is the major source of recharge. Three distinct groundwater zones were identified associated with the highlands, transitional escarpment and the rift. Towards the rift, the ionic concentration and isotopic enrichment (δ2H and δ18degO) increases following the groundwater flow paths, which is strongly controlled by axial rift faults. The groundwater flow converges to the seismically active volcano–tectonic depressions with internal drainage and to the Awash River. Within the Afar Depression, at least four groundwater regimen are identified: (1) fresh and shallow groundwater associated with alluvial deposits ultimately recharged by isotopically depleted recent highland rainfall and the evaporated Awash River; (2) cold and relatively younger groundwater within localized fractured volcanics showing mixed origin in axial fault zones; (3) old groundwater with very high ionic concentration and low isotopic signature localized in deep volcanic aquifers; and (4) old and hot saline groundwaters connected to geothermal systems. The study demonstrated that dependable groundwater can only be obtained from the first two aquifer types in aerially restricted zones in flat plains following river courses, local wadis and volcano–tectonic depressions. The conventional hydrogeological survey and discharge records indicate substantial channel losses from the Awash River, which becomes a more dominant source of recharge in central and lower Awash valleys. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

10.
δ87Sr values and Ca/Sr ratios were employed to quantify solute inputs from atmospheric and lithogenic sources to a catchment in NW Germany. The aquifer consists primarily of unconsolidated Pleistocene eolian and fluviatile deposits predominated by >90% quartz sand. Accessory minerals include feldspar, glauconite, and mica, as well as disperse calcium carbonate in deeper levels. Decalcification of near-surface sediment induces groundwater pH values up to 4.4 that lead to enhanced silicate weathering. Consequently, low mineralized Ca–Na–Cl- and Ca–Cl-groundwater types are common in shallow depths, while in deeper located calcareous sediment Ca–HCO3-type groundwater prevails. δ87Sr values and Ca/Sr ratios of the dissolved pool range from 7.3 to −2.6 and 88 to 493, respectively. Positive δ87Sr values and low Ca/Sr ratios indicate enhanced feldspar dissolution in shallow depths of less than 20 m below soil surface (BSS), while equilibrium with calcite governs negative δ87Sr values and elevated Ca/Sr ratios in deep groundwater (>30 m BSS). Both positive and negative δ87Sr values are evolved in intermediate depths (20–30 m BSS). For groundwater that is undersaturated with respect to calcite, atmospheric supplies range from 4% to 20%, while feldspar-weathering accounts for 8–26% and calcium carbonate for 62–90% of dissolved Sr2+. In contrast, more than 95% of Sr2+ is derived by calcium carbonate and less than 5% by feldspar dissolution in Ca–HCO3-type groundwater. The surprisingly high content of carbonate-derived Sr2+ in groundwater of the decalcified portion of the aquifer may account for considerable contributions from Ca-containing fertilizers. Complementary tritium analyses show that equilibrium with calcite is restricted to old groundwater sources.  相似文献   

11.
The origin and the chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta in semi-arid Botswana were investigated using DIC and major ion concentrations and stable oxygen, hydrogen and carbon isotopes (δD, δ18O and δ13CDIC). The δD and δ18O indicated that groundwater was recharged by evaporated river water and unevaporated rain. The river water and shallow (<10 m) groundwater are Ca–Na–HCO3 type and the deep (≥10 m) groundwater is Na–K–HCO3 to HCO3–Cl–SO4 to Cl–SO4–HCO3. Compared to river water, the mean DIC concentrations were 2 times higher in shallow groundwater, 7 times higher in deep groundwater and 24 times higher in island groundwater. The δ13CDIC indicate that DIC production in groundwater is from organic matter oxidation and in island groundwater from organic matter oxidation and dissolution of sodium carbonate salts. The ionic and isotopic evolution of the groundwater relative to evaporated river water indicates two independent pools of DIC.  相似文献   

12.
Saline seepage zone development, and hence the onset of dryland salinity, is a major environmental problem occurring within the Spicers Creek catchment. The primary objective of this paper was to identify previously unmapped faults and show the correlation between these faults and groundwater salinization. As identified from this study, there is a close association between geological structural features and the formation of saline seepage zones. The most saline groundwaters in the catchment were encountered where two geological structures join and form a fault intersection. These saline groundwaters are found at various depths within the fractured aquifers, and changes in groundwater chemistry in the aquifers are associated with the presence of fault zones. 18O and δ2H stable isotopes, together with 87Sr/86Sr isotopic ratios, indicate that groundwaters within the fault zones are enriched in 18O and have a strontium signature similar to seawater. This study identifies several geological structures in the Spicers Creek catchment and demonstrates that groundwaters with the highest salinity arise where fault intersections occur. The results of this study may be used to interpret further the mechanisms leading to seepage zone formation in dryland salinity‐affected catchments located throughout the Central West region of New South Wales, Australia. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

13.
Groundwater discharges in the western Canadian oil sands region impact river water quality. Mapping groundwater discharges to rivers in the oil sands region is important to target water quality monitoring efforts and to ensure injected wastewater and steam remain sequestered rather than eventually resurfacing. Saline springs composed of Pleistocene‐aged glacial meltwater exist in the region, but their spatial distribution has not been mapped comprehensively. Here we show that formation waters discharge into 3 major rivers as they flow through the Athabasca Oil Sands Region adjacent to many active oil sands projects. These discharges increase river chloride concentrations from river headwaters to downstream reaches by factors of ~23 in the Christina River, ~4 in the Clearwater River, and ~5 in the Athabasca River. Our survey provides further evidence for the substantial impact of formation water discharges on river water quality, even though they comprise less than ~2% of total streamflow. Geochemical evidence supporting formation water discharges as the leading control on river salinity include increases in river chloride concentrations, Na/(Na + Ca) ratios, Cl/(Cl + SO4) ratios and decreases in 87Sr/86Sr ratios; each mixing trend is consistent with saline groundwater discharges sourced from Cretaceous or Devonian aquifers. These regional subsurface‐to‐surface connections signify that injected wastewater or steam may potentially resurface in the future, emphasizing the critical importance of mapping groundwater flow paths to understand present‐day streamflow quality and to predict the potential for injected fluids to resurface.  相似文献   

14.
Characterization of stable isotope compositions (δ2H and δ18O) of surface water and groundwater in a catchment is critical for refining moisture sources and establishing modern isotope–elevation relationships for paleoelevation reconstructions. There is no consensus on the moisture sources of precipitation in the Yellow River source region during summer season. This study presents δ2H and δ18O data from 111 water samples collected from tributaries, mainstream, lakes, and groundwater across the Yellow River source region during summertime. Measured δ18O values of the tributaries range from ?13.5‰ to ?5.8‰ with an average of ?11.0‰. Measured δ18O values of the groundwater samples range from ?12.7‰ to ?10.5‰ with an average of ?11.9‰. The δ18O data of tributary waters display a northward increase of 1.66‰ per degree latitude. The δ18O data and d‐excess values imply that moisture sources of the Yellow River source region during summertime are mainly from the mixing of the Indian Summer Monsoon and the Westerlies, local water recycling, and subcloud evaporation. Analysis of tributary δ18O data from the Yellow River source region and streamwater and precipitation δ18O data from its surrounding areas leads to a best‐fit second‐order polynomial relationship between δ18O and elevation over a 4,600 m elevation range. A δ18O elevation gradient of ?1.6‰/km is also established using these data, and the gradient is in consistence with the δ18O elevation gradient of north and eastern plateau. Such relationships can be used for paleoelevation reconstructions in the Yellow River source region.  相似文献   

15.
Strontium (Sr) concentrations and isotopic ratios have been measured in a series of water and rock samples from most of the major tributaries of the Lake Qinghai basin on the north‐eastern Tibetan Plateau. Dissolved Sr and 87Sr/86Sr show ranges of 488–12 240 nmol/l and 0·710497–0·716977, respectively. These data, together with measurements of major cations and anions in rivers and their tributaries and various lithologies of the catchment, were used to determine the contributions of Sr and its isotopic expense to rivers and lakes. Our results demonstrate that the chemical components and 87Sr/86Sr ratios of the alkaline waters are derived from mixing of carbonate and silicate sources, with the former contributing 72 ± 18% dissolved Sr to rivers. The difference in tributary compositions stems from the lithology of different river systems and low weathering intensity under a semi‐arid condition. Variation in 87Sr/86Sr ratios places constraint on the Sr‐isotopic compositions of the main tributaries surrounding Lake Qinghai. The water chemistry of the Buha River, the largest river within the catchment underlain by the late Paleozoic marine limestone and sandstones, dominates Sr isotopic composition of the lake water, being buffered by the waters from the other rivers and probably by groundwater. However, the characteristic chemical composition of the lake itself differs remarkably from the rivers, which can be attributed to precipitation of authigenic carbonates (low‐magnesium calcite, aragonite, and dolomite), though this does not impact the Sr isotope signature, which may remain a faithful indicator in paleo‐records. Regarding the potential role of groundwater input within the Lake Qinghai systems in the water budget and water chemistry, we have also determined the Sr concentration and 87Sr/S6Sr ratio of groundwater from diverse environments. This has allowed us to further constrain the Sr isotope systematic of this source. A steady‐state calculation gives an estimate for the groundwater flux of 0·19 ± 0·03 × 108 m3/yr, accounting for about 8% of contemporary lake Sr budget. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

16.
We report the results of a detailed study of dissolved Sr isotopes in the Solimões and Beni‐Madeira Rivers of the Amazon basin. This study developed data collected over 8 years indicating large spatial and temporal variations in dissolved Sr isotopes among the rivers of the Amazon basin. The large 87Sr/86Sr variations were found to be correlated with the geology of the source areas of the suspended sediments. The Beni‐Madeira River displays a high average 87Sr/86Sr ratio and large 87Sr/86Sr fluctuations during the hydrological cycle. This large average value and fluctuations were related to the presence of Precambrian rocks and Ordovician sediments in the source area of the suspended sediment of the river. In contrast, the Solimões River displays a narrow range of Sr isotope ratio variations and an average value close to 0.709. This river drains mostly Phanerozoic rocks of northern Peru and Ecuador that are characterized by low Sr isotope ratios. The isotopic fluctuations in the Beni‐Madeira River were observed to propagate downstream at least as far as Óbidos. This signal is characterized by an inverse relationship between the concentration of elemental Sr and its isotopic ratios. We further demonstrate that the Sr isotopic composition and content in the Beni‐Madeira River is controlled by suspended sediments derived from the Andes. Despite draining areas underlain by Precambrian rocks and having high 87Sr/86Sr ratios, such rivers as the Negro and Tapajós play a minor role in the total Sr budget of the Amazon basin. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

17.
The conceptual hydrogeological model of the low to medium temperature Daying and Qicun geothermal fields has been proposed, based on hydrochemical characteristics and isotopic compositions. The two geothermal fields are located in the Xinzhou basin of Shanxi, China and exhibit similarities in their broad‐scale flow patterns. Geothermal water is derived from the regional groundwater flow system of the basin and is characterized by Cl·SO4‐Na type. Thermal water is hydrochemically distinct from cold groundwater having higher total dissolved solids (TDS) (>0·8 g/l) and Sr contents, but relatively low Ca, Mg and HCO3 contents. Most shallow groundwater belongs to local flow systems which are subject to evaporation and mixing with irrigation returns. The groundwater residence times estimated by tritium and 14C activities indicate that deep non‐thermal groundwater (130–160 m) in the Daying region range from modern (post‐1950s) in the piedmont area to more than 9·4 ka BP (Before Present) in the downriver area and imply that this water belong to an intermediate flow system. Thermal water in the two geothermal fields contains no detectable active 14C, indicating long residence times (>50 ka), consistent with this water being part of a large regional flow system. The mean recharge elevation estimated by using the obtained relationship Altitude (m) = ? 23·8 × δ2H (‰ ) ? 121·3, is 1980 and 1880 m for the Daying and Qicun geothermal fields, respectively. The annual infiltration rates in the Daying and Qicun geothermal fields can be estimated to be 9029 × 103 and 4107 × 103 m3/a, respectively. The variable 86Sr/87Sr values in the thermal and non‐thermal groundwater in the two fields reflect different lithologies encountered along the flow path(s) and possibly different extents of water‐rock interaction. Based on the analysis of groundwater flow systems in the two geothermal fields, hydrogeochemical inverse modelling was performed to indicate the possible water‐rock interaction processes that occur under different scenarios. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

18.
Full chemical analyses, including some trace elements and both oxygen and strontium isotope abundance data are presented for samples collected from a traverse across the outcrop of the early Tertiary Loch Uisg Granophyre. Chemically, the body is rhyodacite with very uniform major and trace element composition. In contrast, depleted δ18O values vary widely from +1.5‰ in the south to ?3.7‰ in the north (a distance of about 21/2 km), a range comparable to that for the intrusive rocks of Mull as a whole. This indicates more extensive groundwater interaction (i.e. higher water/rock ratios and/or higher temperatures of isotope exchange) towards the focus of the central intrusive complex. There is some degree of correlation between δ18O and iron oxidation ratios but no other evidence that the primary igneous geochemistry of these rocks has been significantly modified by hydrothermal alteration after emplacement of the pluton. Initial87Sr/86Sr ratios range from 0.71350 ± 9 to 0.71624 ± 6 and correlate with both Rb content and Rb/Sr ratio, the latter correlation yielding a pseudo-isochron of 260 ± 54 Ma at the time of emplacement. These results confirm a major contribution from an old crustal source region, ruling out formation of the granophyre solely from a basic parent magma. However, Rb-Sr data are presented for the Moine schists exposed in Mull and Morvern which also appear to rule out their involvement in the petrogenesis of the granophyre, either as a source region for melting, or as a bulk contaminant for a mantle-derived magma. The only viable hypotheses are assimilation at depth of? Lewisian into a basaltic fractionation sequence or partial melting of a Proterozoic basement such as that involved in the production of Caledonian granites in the Scottish Highlands.  相似文献   

19.
Abstract

Chemical and isotopic data of groundwater of the Upper Cretaceous aquifer in the Orontes basin, Syria, have been used to assess the groundwater geochemistry, the origin of groundwater recharge and groundwater residence time. The chemical data indicate that dissolution of evaporite minerals is the main process controlling groundwater mineralization. The composition of stable isotopes δ18O and δ2H, together with 14C activity, reflect the existence of three different groups: (a) groundwater in the Coastal Mountains with δ18O of –6.65‰, quite similar to modern-day precipitation, and high 14C (>50 pmC); (b) groundwater in the unconfined aquifer of the Hama Uplift, which has δ18O of –5.52‰ and 14C near 20 pmC, and is recharged locally; and (c) groundwater from the confined aquifer of the Homs Depression, which is characterized by more depleted δ18O,, –8.01‰, and low 14C (<7 pmC), and might be recharged in the northern piedmont of the Anti-Lebanon Mountains. The distinctive isotope signatures of the latter two groups indicate different recharge elevations and palaeoclimatic effects. The low recharge rate of the groundwater in the Hama Uplift aquifer, and the even slower recharge rate in the Homs Depression aquifer, are reflected by groundwater 14C residence times of 5 and over 22 Ka BP, respectively.

Editor D. Koutsoyiannis

Citation Al-Charideh, A., 2013. Recharge and mineralization of groundwater of the Upper Cretaceous aquifer in Orontes basin (Syria). Hydrological Sciences Journal, 58 (2), 452–467.  相似文献   

20.
A modified AEI-IM20 ion microprobe has been used to measure87Sr/86Sr ratios in carbonates. A suite of carbonates with varying major elements (Ca, Mg, Fe, Mn) was studied at low and high (M/ΔM ? 3000) mass resolution to determine the types and intensities of molecular species isobaric with Sr peaks; Sr data collected at low mass resolution must be corrected for Ca2 and CaMgO species. Rb/Sr ratios are extremely low, and correction for87Rb is not required (< 0.1‰ of87Sr).Usable Sr isotopic data may be obtained from calcite givenSr≥ 400ppm, and for Sr > 5000 ppm a precision of ～ ± 1‰ (± 0.0007) in87Sr/86Sr (2σ mean) can be achieved under optimum conditions. The corrections for Ca2 and CaMgO are smaller than the within-run precision in calcite, but in dolomite the correction for CaMgO is + 1.5%. Mass fractionation corrections to87Sr/86Sr (based on86Sr/88Sr= 0.1194) are typically +8 to +10‰. Good agreement between ion probe and solid source mass spectrometer results was found for calcites of known Sr isotopic composition: ST4a (～ 400ppm Sr), average ion probe87Sr/86Sr= 0.7267 ± 0.0015, solid source87Sr/86Sr= 0.72680 ± 0.00008 [14]; JCG36 (～ 6000ppm Sr), average ion probe87Sr/86Sr= 0.7056 ± 0.0009, solid source87Sr/86Sr= 0.70588 ± 0.00009 [16]; JCG44 (～ 6000ppm Sr), average ion probe87Sr/86Sr= 0.7057 ± 0.0006, solid source87Sr/86Sr= 0.70540 ± 0.00008 [16]. The ability of the ion microprobe to measure87Sr/86Sr for 10-μm spots in calcite was used: (1) to measure variation in87Sr/86Sr of ～ 0.01 on a centimetre scale in a hydrothermally altered basalt from the Isle of Skye, northwestern Scotland; and (2) to determine the Sr isotopic composition of tiny (< 35 μm) calcite grains in a veined mantle lherzolite from Bultfontein, South Africa. Because of calcite's ubiquitous occurrence in many parageneses this technique may offer many opportunities for the measurement of fine scale heterogeneities in87Sr/86Sr.  相似文献   

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