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1.
Analyses of halogen concentration and stable chlorine isotope composition of fluid inclusions from hydrothermal quartz and carbonate veins spatially and temporally associated with giant unconformity-related uranium deposits from the Paleoproterozoic Athabasca Basin (Canada) were performed in order to determine the origin of chloride in the ore-forming brines. Microthermometric analyses show that samples contain variable amounts of a NaCl-rich brine (Cl concentration between 120,000 and 180,000 ppm) and a CaCl2-rich brine (Cl concentration between 160,000 and 220,000 ppm). Molar Cl/Br ratios of fluid inclusion leachates range from ∼100 to ∼900, with most values between 150 and 350. Cl/Br ratios below 650 (seawater value) indicate that the high salinities were acquired by evaporation of seawater. Most δ37Cl values are between −0.6‰ and 0‰ (seawater value) which is also compatible with a common evaporated seawater origin for both NaCl- and CaCl2-rich brines.Slight discrepancies between the Cl concentration, Cl/Br, δ37Cl data and seawater evaporation trends, indicate that the evaporated seawater underwent secondary minor modification of its composition by: (i) mixing with a minor amount of halite-dissolution brine or re-equilibration with halite during burial; (ii) dilution in a maximum of 30% of connate and/or formation waters during its migration towards the base of the Athabasca sandstones; (iii) leaching of chloride from biotites within basement rocks and (iv) water loss by hydration reactions in alteration haloes linked to uranium deposition.The chloride in uranium ore-forming brines of the Athabasca Basin has an unambiguous dominantly marine origin and has required large-scale seawater evaporation and evaporite deposition. Although the direct evidence for evaporative environments in the Athabasca Basin are lacking due to the erosion of ∼80% of the sedimentary pile, Cl/Br ratios and δ37Cl values of brines have behaved conservatively at the basin scale and throughout basin history.  相似文献   

2.
Twenty-four brine samples from the Heletz-Kokhav oilfield, Israel, have been analyzed for chemical composition and Li isotope ratios. The chemical composition of the brines, together with geological evidence, suggests derivation from (Messinian) seawater by evaporation that proceeded well into the gypsum stability field but failed to reach the stage of halite crystallization. The present salinity of the samples (18-47 g Cl/L) was achieved by dilution of the original evaporitic brine by local fresh waters. Like brines from other sedimentary basins, the Li/Cl ratios in the Heletz-Kokhav samples show a prominent Li enrichment (five-fold to eight-fold) relative to modern seawater. The isotopic ratios of Li, expressed in the δ 6Li notation, vary from −26.3 to −17.9‰, all values being significantly higher than that of modern seawater (−32‰) irrespective of their corresponding Li concentration (1.0-2.3 mg/L). The isotopic composition of Li and the Li/Cl ratio in the oilfield brines were acquired in two stages: (a) The original evaporated seawater gained isotopically light Li during the diagenetic interaction between the interstitial Messinian brine and the basin sediments. A parent brine with an elevated Li/Cl ratio was formed. The brine was later diluted in the oilfields. (b) The δ 6Li values of the final brines were determined during epigenetic interaction with the Heletz-Kokhav aquifer rocks. At the same time, the Li/Cl ratio inherited from stage (a) remained largely unchanged. This work represents the first use of lithium isotopic composition to elucidate the origin and evolution of formation waters in sedimentary basins.  相似文献   

3.
Analyses of fluid-inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75 - 358 and Cl/Br 67 - 394, respectively, and this variation trend coincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br ratios. The average Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are very close to the ratios ( 120 and 233 ) of the residual evaporated seawater past the point of halite precipitation. It is suggested that the original mineralizing brine was derived from highly evapo-rated seawater with a high salinity. However, the inclusion fluids have absolute Na values of 69.9—2606.2 mmol kg^-1 and Cl values of 106.7 — 1995.5 mmol kg^-1. Most of the values are much less than those of seawater: Na, 485 mmol kg^-1 and Cl, 566 mmol kg^-1 , respectively; the salinity measured from fluid inclusions of the deposits ranges from 2.47 wt% to 15.78 wt% NaCl equiv. The mineralizing brine has been diluted. The δ ^18O and δD values of ore-forming fluids vary from -8.21‰ to 9.51‰ and from -40.3‰ to -94.3‰, respectively. The δD values of meteoric water in this region varied from - 80‰ to - 100‰ during the Jurassic. This evidenced that the ore-forming fluids are the mixture of seawater and meteoric water. Highly evaporated seawater was responsible for leaching and extracting Pb, Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted in the formation of ores.  相似文献   

4.
Chemical and isotopic compositions were analyzed in porewater squeezed from a clayey aquitard in Jiangsu coastal plain, eastern China, to interpret the salinity origin, chemical evolution and water-mass mixing process. A strong geochemical fingerprint was obtained with an aligned Cl/Br ratio of 154 in the salinized aquitard porewater over a wide Cl? concentration range (396–9,720 mg/L), indicating that porewater salinity is likely derived from a mixing with old brine with a proportion of less than 20%. Very small contributions of brine exerted limited effects on water stable isotopes. The relationships between porewater δ18O and δD indicate that shallow and intermediate porewaters could be original seawater and were subsequently diluted with modern meteoric water, whereas deep porewaters with depleted stable isotopic values were probably recharged during a cooler period and modified by evaporation and seawater infiltration. The cation–Cl relationship and mineralogy of associated strata indicate that porewater has been chemically modified by silicate weathering and ion-exchange reactions. 87Sr/86Sr ratios of 0.7094–0.7112 further confirm the input source of silicate minerals. Numerical simulations were used to evaluate the long-term salinity evolution of the deep porewater. The alternations of boundary conditions (i.e., the third aquifer mixed with brine at approximately 70 ka BP, followed by recharge of glacial meltwater at 20–25 ka BP, and then mixing with Holocene seawater at 7–10 ka BP) are responsible for the shift in porewater salinity. These timeframes correspond with the results of previous studies on ancient marine transgression-regression in Jiangsu coastal plain.  相似文献   

5.
In the coastal region of Bangladesh, groundwater is mainly used for domestic and agricultural purposes, but salinization of many groundwater resources limits its suitability for human consumption and practical application. This paper reports the results of a study that has mapped the salinity distribution in different aquifer layers up to a depth of 300 m in a region bordering the Bay of Bengal based on the main hydrochemistry and has investigated the origin of the salinity using Cl/Br ratios of the samples. The subsurface consists of a sequence of deltaic sediments with an alternation of more sandy and clayey sections in which several aquifer layers can be recognized. The main hydrochemistry shows different main water types in the different aquifers, indicating varying stages of freshening or salinization processes. The most freshwater, soft NaHCO3-type water with Cl concentrations mostly below 100 mg/l, is found in the deepest aquifer at 200–300 m below ground level (b.g.l.), in which the fresh/saltwater interface is pushed far to the south. Salinity is a main problem in the shallow aquifer systems, where Cl concentrations rise to nearly 8000 mg/l and the groundwater is mostly brackish NaCl water. Investigation of the Cl/Br ratios has shown that the source of the salinity in the deep aquifer is mixing with old connate seawater and that the saline waters in the more shallow aquifers do not originate from old connate water or direct seawater intrusion, but are derived from the dissolution of evaporite salts. These must have been formed in a tidal flat under influence of a strong seasonal precipitation pattern. Long dry seasons with high evaporation rates have evaporated seawater from inundated gullies and depressions, leading to salt precipitation, while subsequent heavy monsoon rains have dissolved the formed salts, and the solution has infiltrated in the subsoil, recharging groundwater.  相似文献   

6.
Cation and anion concentrations and oxygen and hydrogen isotopic ratios of brines in the Asmari Formation (Oligocene–early Miocene) from the Marun oil field of southwest Iran were measured to identify the origin of these brines (e.g. salt dissolution vs. seawater evaporation) as well as the involvement of water–rock reaction processes in their evolution. Marun brines are characterized by having higher concentrations of calcium (11 000–20 000 mg/L), chlorine (120 000–160 000 mg/L) and bromide (600–1000 mg/L) compared to modern seawater. Samples are also enriched in 18O relative to seawater, fall to the right of the Global Meteoric Water Line and local rain water, and plot close to the halite brine trajectory on the δD versus δ18O diagram. Geochemical characteristics of Marun brines are inconsistent with a meteoric origin, but instead correspond to residual evaporated seawater modified by water–rock interaction, most significantly dolomitization. In addition, anhydrite precipitation or sulphate reduction appears to be important in chemical modification of the Marun brines, as indicated by lower sulphate contents relative to evaporated seawater. Extensive dolomitization, the presence of anhydrite nodules and high salinity fluid inclusions in the upper parts of the Asmari Formation fit a model whereby the Marun brines likely originated from the seepage reflux of concentrated seawater during the deposition of the overlying Gachsaran Formation evaporites in the Miocene. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

7.
Concentration and isotope ratios (δ34SSO4 and δ18OSO4) of dissolved sulfate of groundwater were analyzed in a very large anaerobic aquifer system under the Lower Central Plain (LCP) (25,000 km2) in Thailand. Groundwater samples were collected in two different kinds of aquifers; type 1 with a saline water contribution and type 2 lateritic aquifers with no saline water contribution. Two different isotopic compositional trends were observed: in type 1 aquifers sulfate isotope ratios range from low values (+2.2‰ for δ34SSO4 and +8.0‰ for δ18OSO4) to high values (+49.9‰ for δ34SSO4 and +17.9‰ for δ18OSO4); in type 2 aquifers sulfate isotope ratios range from low values (−0.1‰ for δ34SSO4 and +12.2‰ for δ18OSO4) to high δ18OSO4 ratios (+18.4‰) but with low δ34SSO4 ratios (<+12.9‰). Isotopic comparison with possible source materials and theoretical geochemical models suggests that the sulfate isotope variation for type 1 aquifer groundwater can be explained by two main processes. One is the contribution of remnant seawater, which has experienced dissimilatory sulfate reduction in the marine clay, into recharge water of freshwater origin. This process accounts for the high salinity groundwater. The other process, explaining for the modest salinity groundwater, is the bacterial sulfate reduction of the mixture water between high salinity water and fresh groundwater. Isotopic variation of type 2 aquifer groundwater may also be explained by bacterial sulfate reduction, with slower reduction rate than that of the groundwater with saline water effect. The origin of groundwater sulfate with low δ34SSO4 but high δ18OSO4 is recognized as an important topic to be examined in a future investigation.  相似文献   

8.
Groundwater resources in some parts of the lower section of Shire River valley, Malawi, are not useable for rural domestic water supply due to high salinity. In this study, a combined assessment of isotopic (87Sr/86Sr, δ18O and δ2H) and major ion composition was conducted in order to identify the hydro-geochemical evolution of the groundwater and thereby the causes of salinity. Three major end-members (representing fresh- and saline groundwater, and evaporated recharge) were identified based on major ion and isotopic composition. The saline groundwater is inferred to result from dissolution of evaporitic salts (halite) and the fresh groundwater shows influence of silicate weathering. Conservative mixing models show that brackish groundwater samples result from a three component mixture comprising the identified end-members. Hence their salinity is interpreted to result from mixing of fresh groundwater with evaporated recharge and saline groundwater. On the other hand, the groundwater with low TDS, found at some distance from areas of high salinity, is influenced by mixing of evaporated recharge and fresh groundwater only. Close to the Shire marshes, where there is shallow groundwater, composition of stable isotopes of water indicates that evaporation may also be an important factor.  相似文献   

9.
The Castellón Plain alluvial aquifer, Spain, is intensively exploited to meet the demand for agricultural irrigation and industrial water supply. The geochemistry of its groundwater shows complex salinization in the northern and southern parts of the aquifer, with significant pollution from human origin in the central portion. Boron content and B isotope geochemistry are useful for distinguishing between various sources of pollution and their relative importance in different parts of this aquifer. Boron concentrations in the groundwater vary between 0.01 and 0.85 mg/L. In the more saline groundwaters, found at the northern and southern ends of the study area, the presence of B is linked to inputs from seawater and water with a calcium-magnesium sulphate facies, which feed the aquifer and clearly influence the chemistry of its waters. Evidence of B adsorption processes in some samples is shown by the low B/Cl ratios and the high values of δ11B. In the central portion of the aquifer, the high B/Cl ratios and the strongly negative δ11B are related to pollution of human origin.  相似文献   

10.
The major ion hydrochemistry, sodium absorption ratio (SAR), sodium percentage, and isotopic signatures of Hammamet-Nabeul groundwaters were used to identify the processes that control the mineralization, irrigation suitability, and origin of different water bodies. This investigation highlights that groundwater mineralization is mainly influenced by water-rock interaction and pollution by the return flow of irrigation water. The comparison of groundwater quality with irrigation suitability standards proves that most parts of groundwater are unacceptable for irrigation and this long-term practice may result in a significant increase of the salinity and alkalinity in the soils. Based on isotopic signatures, the shallow aquifer groundwater samples were classified into (i) waters with depleted δ18O and δ2H contents, highlighting recharge by modern precipitation, and (ii) waters with enriched stable isotope contents, reflecting the significance of recharge by contaminated water derived from the return flow of evaporated irrigation waters. The deep-aquifer groundwater samples were also classified into (i) waters with relatively enriched isotope contents derived from modern recharge and mixed with shallow-aquifer groundwater and (ii) waters with depleted stable isotope contents reflecting a paleoclimatic origin. Tritium data permit to identify three origins of recharge, i.e., contemporaneous, post-nuclear, and pre-nuclear. Carbon-14 activities demonstrate the existence of old paleoclimatic recharge related to the Holocene and Late Pleistocene humid periods.  相似文献   

11.
《Applied Geochemistry》2001,16(9-10):1269-1284
Chemistry of major and minor elements, 87Sr/86Sr, δD, and δ18O of oilfield waters, and 87Sr/86Sr of whole rock were measured from Paleozoic strata in the Central Tarim basin, NW China. The aim is to elucidate the origin and migration of formation water and its relation to petroleum migration. High salinity oilfield waters in Carboniferous, Silurian and Ordovician reservoirs have maintained the same Na/Cl ratio as seawater, indicative of subaerially evaporated seawater. Two possible sources of evaporitic water are Carboniferous (CII) and Cambrian, both of which contain evaporitic sediments. Geographic and stratigraphic trends in water chemistry suggest that most of the high salinity water is from the Cambrian. Strontium, H and O isotopes as well as ion chemistry indicate at least 3 end member waters in the basin. High-salinity Cambrian evaporitic water was expelled upward into Ordovician, Silurian and Carboniferous reservoirs along faults and fractures during compaction and burial. Meteoric water has likely invaded the section throughout its history as uplift created subaerial unconformities. Meteoric water certainly infiltrated Silurian and older strata during development of the CIII unconformity and again in recent times. Modern meteoric water enters Carboniferous strata from the west and flows eastward, mixing with the high salinity Cambrian water and to a lesser degree with paleometeoric water. The third end member is highly radiogenic, shale-derived water which has migrated eastward from the Awati Depression to the west. Enrichment of Ca and Sr and depletion of K, Mg, and SO4 relative to the seawater evaporation trajectory suggest waters were affected by albitization of feldspars, dolomitization, illitization of smectite, and SO4 reduction. The mixing of meteoric water occurred subsequently to seawater evaporation, main water-rock interactions, and brine migration. The direction of brine migration is consistent with that of petroleum migration, suggesting water and petroleum have followed the same migration pathways.  相似文献   

12.
The study area, the Fasa Plain, is situated in the semiarid region of Fars Province in the south of Iran. The Salloo diapir is a salt dome that crops out in the northwest of the study area. Isotopic and hydrochemical analyses were used to examine the water and how the origin of salinity and the diapir affect the quality of the groundwater quality in the study area. Groundwater was sampled from 31 representative pumping wells in alluvial aquifer and five springs in order to measure their stable isotope compositions, bromide ion concentration, and physical and chemical parameters. The alluvial aquifer was organized into two main groups based on the chemistry, with Group 1 consisting of low-salinity well samples (544–1744 µS/cm) with water type Ca–Mg–HCO3–SO4 which were taken in the center and north of the area, and Group 2 consisting of high-salinity samples (2550–4620 µS/cm) with water type Ca–Mg–Cl–SO4 which were taken from the wells in the south and southwest of the area. A saline spring near the salt dome with an EC of 10,280 µS/cm has water type Na–Cl, while the compositions of the water in the other karstic springs is comparable to the fresh groundwater samples. All groundwater samples are undersaturated with respect to gypsum, anhydrite, and halite and are supersaturated with respect to calcite and dolomite. Stable isotopes (δ18O and δ2H) differentiated four water types: saline springs, freshwater spring, fresh groundwater, and saline groundwater. The results indicate that meteoric water is the main origin of these water resources. Halite dissolution from the salt dome was identified as the origin of salinity. The Na/Cl and Cl/Br ratios confirmed the results. Groundwater compositions in the southwestern part of the area are affected by the intrusion of saltwater from the salt dome. The average saltwater fraction in the some water wells is about 0.2%. In the south and southwestern part of the area, the saltwater fraction is positive in mixed freshwater/saltwater (Group 2). Different processes interact together to change the hydrochemical properties of Fasa’s alluvial aquifer. The main processes that occur in the aquifer are mixing, gypsum dissolution, and calcite precipitation.  相似文献   

13.
In the Schwarzwald area, southwest Germany, more than 400 hydrothermal veins hosting different gangue and ore mineral assemblages cross-cut the crystalline basement rocks. Many of the post-Variscan fluorite-barite-quartz veins are considered to have precipitated through mixing of a deep saline brine with meteoric, low salinity waters. This hypothesis was tested using carbon, sulfur, and oxygen isotope data of sulfides, sulfates and calcite, coupled with fluid inclusion studies. Primary hydrothermal calcites from the deposits show a positive correlation of their δ13C (V-PDB) and δ18O (V-SMOW) values, which range from −12 to −3‰ and from 12 to 18.5‰, respectively. Carbon and oxygen isotope compositions of paragenetically young, remobilized calcite types are shifted towards higher values and range from −12 to −1‰ and from 20 to 25‰, respectively. We developed an improved calculation procedure for modeling the covariation of carbon and oxygen isotopes in calcite resulting from mixing of two fluids with different isotopic compositions and total carbon concentrations. In our model, the carbon speciation in the two model fluid end-members and the fluid mixtures are calculated using a speciation and reaction path code. The carbon and oxygen isotope covariation of primary Schwarzwald calcites can effectively be modeled by a mixing trend of a deep saline brine and a meteoric, low salinity water. Sulfur isotope data of barites from 44 hydrothermal fluorite-barite-quartz veins vary from 9 to 18‰ (CDT), sulfide ore minerals show δ34S values between −14.4 and 2.9‰. Calculated sulfide-sulfate equilibrium temperatures are in the range between 300 and 350 °C. These temperatures differ significantly from the formation temperatures of 150 to 200 °C of most of the deposits as estimated from fluid inclusions, and are interpreted as preserved paleotemperatures of the deep aquifer. This assumption has been carefully checked against possible contamination of an equilibrated sulfide-sulfate system from the deep aquifer with sulfate from surface-derived sources, considering also the kinetics of the sulfide-sulfate isotope exchange. A combination of the S isotopic results with microthermometric fluid inclusion data and constraints on the temperature of the meteoric water was used to calculate mixing ratios of the two fluid end-members. The results indicate that mass fractions of the deep saline brine in the mixed fluid were between 0.5 and 0.75. Considering all geologic, geochemical and isotopic information, we propose that the majority of the post-Variscan hydrothermal veins in the Schwarzwald area were precipitated by district-scale mixing of a homogeneous deep saline brine with meteoric waters.  相似文献   

14.
《Applied Geochemistry》1999,14(1):91-118
The mechanism governing salinization of ground water discharging into the Sea of Galilee in Israel has been the subject of debate for several decades. Because the lake provides 25% of the water consumed annually in Israel, correct identification of the salt sources is essential for the establishment of suitable water-management strategies for the lake and the ground water in the surrounding aquifers. Existing salinization models were evaluated in light of available and newly acquired data including general chemistry, and O, H, C and Cl isotopes. Based on the chemical and isotopic observations, the proposed salt source is an ancient, intensively evaporated brine (21- to 33-fold seawater) which percolated through the valley formations from a lake which had formed in the Rift Valley following seawater intrusion during the late Miocene. Low Na:Cl and high Br:Cl values support the extensive evaporation, whereas high Ca:Cl and low Mg:Cl values indicate the impact of dolomitization of the carbonate host rock on the residual solution. Based on radiocarbon and other isotope data, the dilution of the original brine occurred in two stages: the first took place ∼30 000 a ago by slightly evaporated fresh-to-brackish lake water to form the Sea of Galilee Brine. The second dilution phase is associated with the current hydrological regime as the Sea of Galilee Brine migrates upward along the Rift faults and mixes with the actively circulating fresh ground water to form the saline springs. The spatially variable chemical and isotopic features of the saline springs suggest not only differential dilution by fresh meteoric water, but also differential percolation timing of the original brine into the tectonically disconnected blocks, registering different evaporation stages in the original brine. Consequently, various operations to reduce the brine contribution to the lake may be differentially effective in the various areas.  相似文献   

15.
Evolution of the shallow groundwater quality under saline intrusion in porous aquifer system has been studied with environmental isotopes and geochemistry in the Laizhou Bay area, China. Two campaigns of water sampling from various sources were carried out in spring and winter for environmental isotopic and chemical analyses. The origin of groundwater salinity from intrusion of both modern seawater and deep brine water was identified by analysing the correlations between 18O, D, T, Cl−, SO42− and electrical conductivity. The results indicate that the brine is originated from evaporating and concentrating of intruded seawater and its δD and δ18O are different from modern seawater but similar to those of mixture of seawater with fresh groundwater. It is hard to distinguish the salinity origin in this area by the δD–δ18O relationship alone. The relations between δ18O and conductivity, Cl− and SO42− have been used to identify the salinity origin due to the distinct difference in salinity between the brine and seawater, conjunctively with use of T. A threshold of T = 12 TU was adopted to identify the origin of saline groundwater.  相似文献   

16.
《Applied Geochemistry》2001,16(1):35-55
Formation waters within Upper Carboniferous sandstones in the sub-sea Prince and Phalen coal mines, Nova Scotia, originated as residual evaporative fluids, probably during the precipitation of Windsor Group (Lower Carboniferous) salts which underlie the coal measures. Salinity varies from 7800 to 176,000 mg/l, and the waters are Na–Ca–Cl brines enriched in Ca, Sr and Br and depleted in Na, K, Mg and SO4 relative to the seawater evaporation curve. Br:Cl and Na:Cl ratios suggest that the brine composition corresponds to an evaporation ratio of as much as 30. The brines lie close to the meteoric line on H/O isotopic plots but with a compositional range of δ18O from −4.18 to −6.99 and of δD from −42.4 to −23.5, distant from modern meteoric or ocean water. Mine water composition contrasts with that of nearby salt-spring brines, which are inferred to have originated through dissolution of Windsor Group evaporites by modern meteoric waters. However, a contribution to the mine waters from halite dissolution and from Br in organic matter cannot be ruled out. Present concentrations of several elements in the brines can be explained by water–rock interaction. The original Windsor brines probably moved up into the overlying coal-measure sandstones along faults, prior to the Late Triassic. The high salinity and irregular salinity distribution in the Phalen sandstones suggests that the brines have undergone only modest dilution and are virtually immobile. In contrast, Prince waters show a progressive increase in salinity with depth and are inferred to have mixed with surface waters. Basinal brines from which these modern formation fluids were derived may have been important agents in base-metal and Ba mineralisation from the mid-Carboniferous onwards, as saline fluid inclusions are common in Zn–Pb sulphide deposits in the region.  相似文献   

17.
The present work provides an online Bench II-IRMS technique for the measurement of stable chlorine isotope ratio, which is used to measure the δ37Cl of 38 groundwater samples from the Karst and Quaternary aquifers in Anyang area. The regional distribution and signature of δ37Cl value are characterized on the base of isotopic data. The results suggest that the δ37Cl value of Quaternary groundwater decreases with increasing Cl? concentration, and has no correlation with δ18O and δD values, but closely correlates with the depth to water table. The fractionation mechanism of the chlorine isotope is expounded according to the type of groundwater. The δ37Cl value of karst water is generally positive, which is relevant to the dissolution of evaporite (gypsum mine), and may be caused by the mixing of groundwater and precipitation. The groundwater of Quaternary unconfined aquifer is mainly recharged by precipitation, and the δ37Cl value of groundwater is generally negative. The δ37Cl value of groundwater in Quaternary confined aquifer is more negative with increasing the depth to water level and elevated Cl? concentration, which is possible to result from the isotope fractionation of ion filtration. The groundwater with inorganic pollutants in Quaternary unconfined aquifer has generally a positive δ37Cl value.  相似文献   

18.
Konarsiah salt diapir is situated in the Simply Folded Zone of the Zagros Mountain, south Iran. Eight small permanent brine springs emerge from the Konarsiah salt body, with average total dissolved solids of 326.7 g/L. There are numerous brackish to saline springs emerging from the alluvial and karst aquifers adjacent to the diapir. Concerning emergence of Konarsiah diapir in the study area, halite dissolution is the most probable source of salinity in the adjacent aquifers. However, other sources including evaporation and deep brines through deep Mangerak Fault are possible. The water samples of the study area were classified based on their water-type, salinity, and the trend of the ions concentration curves. The result of this classification is in agreement with the hydrogeological setting of the study area. The hydrochemical and isotopic evaluations show that the groundwater samples are the result of mixing of four end members; Gachsaran sulfate water, Sarvak and Asmari carbonate fresh waters, and diapir brine. The molar ratios of Na/Cl, Li/Cl, Br/Cl, and SO4/Cl; and isotopic signature of the mixed samples justify a groundwater mixing model for the aquifers adjacent to the salt diapir. The share of brine in each adjacent aquifer was calculated using Cl mass balance. In addition, concentrations of 34 trace elements were determined to characterize the diapir brine and to identify the possible tracers of salinity sources in the mixed water samples. B, Mn, Rb, Sr, Cs, Tl, and Te were identified as trace elements evidencing contact of groundwater with the salt diapir.  相似文献   

19.
《Applied Geochemistry》1996,11(3):433-445
Twenty-seven samples from a confined Lower-Middle Jurassic aquifer and an unconfined Oxfordian aquifer of the North Aquitaine Basin (France) have been analysed for their major elements, Br−,18O,2H,13C and14C contents. Hydrochemistry indicates (1) a dissolution of carbonate and anhydrite near the recharge zone and (2) a dilution of a saline water derived from a seawater/halite mixing in the deeper part of the aquifer. The mixing is also visible in a δ18O vs Cl− diagram in which two different groups appear: recent waters and old waters indicating a mixing process between fresh and saline groundwaters. The composition of the saline water is likely to be 34,100±11,200 ppm in Cl, 70±20 ppm in Br and more than −3.5±07‰ vs SMOW in18O.13C contents indicate (1) a C exchange with CaCO3 matrix for groundwaters near the recharge zone and (2) a participation of organic matter in the deep part of the aquifer.Residence times for waters near the area of the aquifer outcrop correspond to Holocene and Late Pleistocene periods. The depletion in stable isotopes of 10 to 15,000 y B.P. waters show a late glacial period infiltration to the aquifer. After a distance of about 10 km in the aquifer, the14C activities are 0 pmc showing the presence of ‘old’ groundwaters.  相似文献   

20.
The Gavbast karstic aquifer located in southern Iran is in direct contact with an exposed salt diapir. To assess the influence of the diapir on the quality of groundwater in the karstic aquifer, electrical conductivity, total dissolved solids, flow rate, temperature and major ion concentrations were measured at 57 sampling sites, including springs, surface waters and wells. A conceptual model of groundwater flow is proposed for the Gavbast karstic aquifer based on the geological setting, water budget, local base of erosion, and hydrochemistry of the sampling sites. The model suggests two subbasins in the Gavbast Anticline draining into two distinct discharging alluvial sections. Unexpectedly, groundwater discharging from the carbonate Gavbast aquifer is saline or brackish and water is of chloride type. The study indicates that the source of salinity of the Gavbast aquifers is infiltration of surface diapir-derived brine into the aquifer. The contribution of the diapir brine in the Gavbast karst aquifer is calculated about 4 L/s, using chloride mass balance. Construction of salt basins to evaporate brine discharging from the diapir springs is proposed to reduce the salinity of karst water. A row of strategically placed wells in the Gavbast karst aquifer would potentially exploit large volumes of fresh groundwater before it is contaminated by the salt. Such low-cost remediation should allow the agricultural exploitation of 40 km2 of currently barren land.  相似文献   

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