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1.
Integrated hydrochemical assessment of the Quaternary alluvial aquifer of the Guadalquivir River, southern Spain 总被引：2，自引：0，他引：2
M. Lorite-Herrera R. Jimnez-Espinosa J. Jimnez-Milln K.M. Hiscock 《Applied Geochemistry》2008,23(8):2040-2054
The alluvial aquifer of the Guadalquivir River comprises shallow Quaternary deposits located in the central-eastern part of the Province of Jaén in southern Spain, where groundwater resources are used mainly for crop irrigation in an important agricultural area. In order to establish the baseline hydrochemical conditions and processes determining the groundwater quality, groundwater and river water samples were collected as part of an integrated investigation that coupled multivariate statistical analysis with hydrochemical methods to identify and interpret the groundwater chemistry of the aquifer system. Three main hydrochemical types (Mg–Ca–HCO3, Ca–Mg–SO4–HCO3–Cl and Na–Ca–Mg–Cl–SO4) were identified. Further interpretation, using R-mode principal components analysis (PCA) conducted with 13 hydrochemical variables, identified two principal components which explain ⅔ of the variance in the original data. In combination with the hydrochemical interpretation, mineralogical analyses of the aquifer sediment together with inverse geochemical modelling using NETPATH showed that dedolomitization (calcite precipitation and dolomite dissolution driven by gypsum dissolution) is the principal hydrochemical process controlling the regional groundwater chemistry. Other processes such as silicate weathering, ion exchange, mixing between river water and groundwater, and agricultural practices also affect the groundwater chemistry. 相似文献
2.
Hydrochemical appraisal of groundwater and its suitability in the intensive agricultural area of Muzaffarnagar district,Uttar Pradesh,India 总被引：1，自引：0，他引：1
Muzaffarnagar is an economically rich district situated in the most fertile plains of two great rivers Ganga and Yamuna in
the Indo-gangetic plains, with agricultural land irrigated by both surface water as well as groundwater. An investigation
has been carried out to understand the hydrochemistry of the groundwater and its suitability for irrigation uses. Groundwater
in the study area is neutral to moderately alkaline in nature. Chemistry of groundwater suggests that alkaline earths (Ca + Mg)
significantly exceed the alkalis (Na + K) and weak acids exceed the strong acids (Cl + SO4), suggesting the dominance of carbonate weathering followed by silicate weathering. Majority of the groundwater samples (62%)
posses Ca–Mg–HCO3 type of hydrochemical species, followed by Ca–Na–Mg–HCO3, Na–Ca–Mg–HCO3, Ca–Mg–Na–HCO3–Cl and Na–Ca–HCO3–SO4 types. A positive high correlation (r
2 = 0.928) between Na and Cl suggests that the salinity of groundwater is due to intermixing of two or more groundwater bodies
with different hydrochemical compositions. Barring a few locations, most of the groundwater samples are suitable for irrigation
uses. Chemical fertilizers, sugar factories and anthropogenic activities are contributing to the sulphate and chloride concentrations
in the groundwater of the study area. Overexploitation of aquifers induced multi componential mixing of groundwater with agricultural
return flow waters is responsible for generating groundwater of various compositions in its lateral extent. 相似文献
3.
In this study, reservoir temperatures of Balıkesir geothermal waters in northwestern Turkey are estimated with various geochemical
models. The geothermal fluids in the region are represented by Na–SO4, Na–HCO3 and Ca–HCO3 type waters with discharge temperatures up to 98°C. It was determined that the solubility of silica in most of the waters
is controlled by the chalcedony phase. Equilibrium states of the Balıkesir thermal waters studied by means of Na–K–Mg–Ca diagram,
mineral saturation calculations and activity diagrams in the system composed of Na2O–CaO–K2O–Al2O3–SiO2–H2O phases approximate a reservoir temperature of about 120°C. Most of the waters are found to be equilibrated with calcite,
chalcedony ± quartz and muscovite at predicted temperature ranges, similar to those calculated from the chemical geothermometers. 相似文献
4.
Maozhong Min Xinjian Peng Xianlin Zhou Haiming Qiao Jinping Wang Li Zhang 《Journal of Geochemical Exploration》2007,93(2):91-108
Groundwaters and surface water in the Shihongtan sandstone-hosted U ore district, Xinjiang, NW China, were sampled and analyzed for their major-, and trace element concentrations and oxygen, hydrogen, boron and strontium isotope compositions in order to assess the possible origins of the waters and water–rock interactions that occurred in the deep aquifer system. The waters in the study district have been grouped into three hydrochemical facies: Facies 1, potable spring-water, is a pH neutral (7.0), Na–Ca–HCO3 type water with low total dissolved solids (TDS; 0.2 g/l, fresh) and has δ18O of − 8.3‰, δD of − 48.2‰,δ11B of 1.5‰, and 87Sr/86Sr of 0.70627. Facies 2 groundwaters are mildly acidic to mildly alkaline (pH of 6.5–8.0, mean 7.3), Na–Ca–Mg–Cl–SO4 type waters with moderate TDS (8.2 g/l–17.2 g/l, mean 9.3 g/l, brackish) and haveδ18O values in the − 5.8‰ to − 9.3‰ range (mean − 8.1‰), δD values in the − 20.8‰ to − 85.5‰ range (mean − 47.0‰),δ11B values in the + 9.5‰ to + 39.1‰ range (mean + 17.1‰), and 87Sr/86Sr values in the 0.70595 to 0.70975 range (mean 0.70826). Facies 3, Aiting Lake water, is a mildly alkaline (pH = 7.4), Na–Ca–Mg–Cl–SO4 type water with the highest TDS (249.1 g/l, brine) and has δ18O of − 2.8‰, δD of − 45.8‰,δ11B of 21.2‰, and 87Sr/86Sr of 0.70840. The waters from the study district show a systematic increase in major, trace element and TDS concentrations and δ11B values along the pathway of groundwater migration which can only be interpreted in terms of water–rock interaction at depth and strong surface evaporation. The hydrochemical and isotopic data presented here confirm that the groundwaters in the Shihongtan ore district are the combined result of migration, water–rock interaction and mixing of meteoric water with connate waters contained in sediments. 相似文献
5.
Contribution to the study of Greek thermal springs: hydrogeological and hydrochemical characteristics and origin of thermal waters 总被引：1，自引：0，他引：1
A large number of chemical analyses of Greek thermal waters were evaluated in order to investigate spring water origin, water–rock interaction mechanisms, and estimate the thermal potential of the geothermal areas. Four water types were distinguished from geochemical diagrams. The relatively fresher waters include samples of Ca–HCO3 and Mg–HCO3 type waters originating from the schistose Rhodope Massif and the Quaternary basin of Aridea, respectively. Samples of the Na–HCO3 water type are typical of springs located in the post-orogenic basins of northern Greece. These hot, deep-rising Na–HCO3
waters circulate in a CO2-rich environment that favours the solubility of alkaline ions such as Na from siliceous rocks. Most of the samples belong to the Na–Cl water type and originate from Greek islands and coastal springs. These are characterized by the mixing of deep thermal solutions with seawater and fresh water. The presence of CO2 in thermal and mineral springs is due to the metamorphism of buried marine carbonate horizons while H2S is due to both local pyrite oxidation and the reduction of sulphates. The use of geothermometers suggested that the investigated geothermal areas have low enthalpy fluids at depth, while higher temperatures are likely present in Milos, Lesvos, Nisyros islands and Xanthi Basin.
Resumen Se ha evaluado un gran número de análisis químicos de aguas termales griegas con objeto de investigar el origen del agua en los manantiales, los mecanismos de interacción agua-roca, y estimar el potencial termal de las áreas geotérmicas. Se distinguieron cuatro tipos de aguas a partir de diagramas geoquímicos. Las aguas relativamente frescas incluyen muestras de agua tipo Ca–HCO3 y Mg–HCO3 que se originan en los esquistos del Macizo Rhodope y la cuenca Cuaternaria de Aridea, respectivamente. Las muestras de agua tipo Na–HCO3 son típicas de manantiales localizados en las cuencas post-orogénicas del norte de Grecia. Estas aguas calientes y profundas, de tipo Na–HCO3, circulan en un ambiente rico en CO2 que favorece la solubilidad de iones alcalinos, tal como Na proveniente de rocas silícicas. La mayoría de las muestras pertenecen al tipo de agua Na–Cl y se originan en islas y manantiales costeros griegos. Estas aguas se caracterizan por la mezcla de soluciones termales profundas con agua de mar y agua dulce. La presencia de CO2 en manantiales termales y minerales se debe a el metamorfismo de horizontes carbonatados marinos enterrados mientras que el H2S se debe a oxidación local de pirita y reducción de sulfatos. El uso de geotermómetros sugiere que las áreas termales investigadas tienen fluidos de baja entalpía a profundidad, mientras que las temperaturas más elevadas es probable que se presenten en Milos, Lesvos, islas de Nisyros y la cuenca Xanthi.
Résumé Un grand nombre danalyses chimiques des eaux thermales grecques ont été menées de manière à investiguer lorigine des eaux des sources thermales, les mécanismes dinteraction avec les roches traversées, et destimer le potentiel des zones géothermiques. Quatre types deau ont été distinguées sur base des diagrammes géochimiques. Les eaux les plus fraîches correspondent respectivement aux échantillons des eaux calco et magnéso carbonatées du massif schisteux de Rhodope et du bassin quaternaire dAridea. Les échantillons deaux sodi carbonatées proviennent typiquement des sources localisées dans les bassins posts-orogéniques du Nord de la Grèce. Ces chaudes et très profondes eaux sodi carbonatées circulent dans des environnements riches en CO2 qui favorisent la solubilité des ions alcalins, tel que le sodium, des roches siliceuses. La plus part des échantillons ont un facies chloruré sodique et proviennent des îles grecques ou des environnement côtier. Ces eaux sont caractérisées par des mélanges entre eaux profondes avec des eaux de mer et des eaux de surface. La présence de CO2 dans les eaux de sources thermales et minérales est due au métamorphisme des horizons de calcaires marins et couverts, tandis que la présence de H2S est due à loxydation locale de la pyrite et à la réduction des sulfates. Lutilisation de géothermomètres suggère que les zones géothermiques étudiées contiennent des eaux à faible enthalpie en profondeur, bien que des températures assez élevées soient rencontrées à Milos, Lesvos, sur les îles Nisyros et dans le bassin de Xanthi.相似文献
6.
The Kali-Hindon is a watershed in the most productive central Ganga plain of India. The whole area is a fertile track with
sugarcane being the principal crop. Systematic sampling was carried out to assess the source of dissolved ions, impact of
sugar factories and the quality of groundwater. Thirty-six samples were collected covering an area of 395 km2. The quality of groundwater is suitable for irrigational purposes but is rich in SO4 which is not best for human consumption. Graphical treatment of major ion chemistry helps identify six chemical types of
groundwater. All possible species such as Na–Cl, K–Cl, Na–HCO3, Na–SO4, Ca–HCO3, Mg–HCO3, Ca–SO4 and Mg–SO4 are likely to occur in the groundwater system. The most conspicuous change in chemistry of groundwater is relative enrichment
of SO4. The interpretation of data reveals that SO4 has not been acquired through water–rock interaction. The source of SO4 is anthropogenic. Sugar factories alone are responsible for this potential environmental hazard. 相似文献
7.
Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca–HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquifer water with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium-3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge.The online version of the original article can be found at 相似文献
8.
Ünsal Gemici Gültekin Tarcan Cahit Helvac&#x; A. Melis Somay 《Applied Geochemistry》2008,23(8):2462-2476
This study documents the environmental impacts of borate mines in Bigadiç district, which are the largest colemanite and ulexite deposits in the world. Borate-bearing formations have affected the concentrations of some contaminants in groundwater. Groundwater quality is directly related to the borate zones in the mines as a result of water–rock interaction processes. Calcium is the dominant cation and waters are Ca–SO4 and HCO3 type in the mine (Tülü borate mine) from which colemanite is produced. However in the Simav and Acep Borate Mines, ulexite and colemanite minerals are produced and waters from these open pit mines are Na–HCO3–SO4 types. High SO4 concentrations (reaching 519 mg/L) might be explained by the existence of anhydrite, gypsum and celestite minerals in the borate zone. Groundwater from tuff and borate strata showed relatively low pH values (7–8) compared to surface and mine waters (>8). EC values ranged from 270 to 2850 μS/cm. Boron and As were the two important contaminants determined in the groundwaters around the Bigadiç borate mines. Arsenic is the major pollutant and it ranged from 33 to 911 μg/L in the groundwater samples. The concentrations of B in the study area ranged from 0.05 to 391 mg/L. The highest B concentrations were detected at the mine areas. The extension of the borate zones in the aquifer systems is the essential factor in the enrichment of B and As, and some major and trace elements in groundwaters are directly related to the leaching of the host rock which are mainly composed of tuffs and limestones. According to drinking water standards, all of the samples exceed the tolerance limit for As. Copper, Mn, Zn and Li values are enriched but do not exceed the drinking water standards. Sulfate, Al and Fe concentrations are above the drinking water standard for the groundwater samples. 相似文献
9.
Benony K. Kortatsi Collins K. Tay Geophrey Anornu Ebenezer Hayford Grace A. Dartey 《Environmental Geology》2008,53(8):1651-1662
Alumino-silicate mineral dissolution, cation exchange, reductive dissolution of hematite and goethite, oxidation of pyrite
and arsenopyrite are processes that influence groundwater quality in the Offin Basin. The main aim of this study was to characterise
groundwater and delineate relevant water–rock interactions that control the evolution of water quality in Offin Basin, a major
gold mining area in Ghana. Boreholes, dug wells, springs and mine drainage samples were analysed for major ions, minor and
trace elements. Major ion study results show that the groundwater is, principally, Ca–Mg–HCO3 or Na–Mg–Ca–HCO3 in character, mildly acidic and low in conductivity. Groundwater acidification is principally due to natural biogeochemical
processes. Though acidic, the groundwater has positive acid neutralising potential provided by the dissolution of alumino-silicates
and mafic rocks. Trace elements’ loading (except arsenic and iron) of groundwater is generally low. Reductive dissolution
of iron minerals in the presence of organic matter is responsible for high-iron concentration in areas underlain by granitoids.
Elsewhere pyrite and arsenopyrite oxidation is the plausible process for iron and arsenic mobilisation. Approximately 19 and
46% of the boreholes have arsenic and iron concentrations exceeding the WHO’s (Guidelines for drinking water quality. Final
task group meeting. WHO Press, World Health Organization, Geneva, 2004) maximum acceptable limits of 10 μg l−1 and 0.3 mg l−1, for drinking water. 相似文献
10.
Mixing of shallow and deep groundwater as indicated by the chemistry and age of karstic springs 总被引：1，自引：0，他引：1
Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca–HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquifer water with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium-3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge.An erratum to this article can be found at 相似文献
11.
Slovakia has many areas rich in thermal waters one of which is the Hornonitrianska kotlina depression. At four localities
three types of waters are found. The first belongs to the Ca–Mg–HCO3 type with T.D.S. 0.7 g/l, the second to the Ca–Mg–SO4 type with T.D.S. 1.37–2.01 g/l and the third to the Ca–Mg–SO4–HCO3 type with T.D.S. 0.97 g/l. Discharge at individual localities varies up to 30 l/s and temperatures of water reach 32.5–66.6 °C.
The waters are predominantly used for healing, rehabilitation purposes, recreation and heating.
Received: 8 March 1999 · Accepted: 7 June 1999 相似文献
12.
Groundwater geochemical evolution in the northern portion of the Guarani Aquifer System (Brazil) and its relationship to diagenetic features 总被引：1，自引：0，他引：1
The groundwater flow pattern in the northern portion of GAS (Guarani Aquifer System) is characterized by the existence of four regional recharge areas located in São Paulo, Mato Grosso do Sul and Goiás states. From these areas of recharge the regional flow is radial and directed toward the center of the Paraná Sedimentary Basin. Local discharge occurs in portions of outcrop regions. The groundwater has low mineralization and can be classified as Ca or Ca–Mg–HCO3 type, Na–HCO3 type and Na–HCO3/Cl/SO4 type, this sequence represents the hydrochemical evolution. The mechanisms responsible for this evolution are dissolution of feldspars and removal of the carbonate cement from the sandstone mineral framework, followed by ion exchange, responsible for the increase in the Na concentration and decrease of Ca, and, finally, enrichment in Cl and SO4 derived from underlying aquifer units. The hydrochemical evolution is consistent with diagenetic features that are observed in the sandstones, with the presence of siliceous cement in the outcrop areas, and carbonate cement toward the center of Paraná Basin. 相似文献
13.
Peter Torssander Carl-Magnus Mrth Risto Kumpulainen 《Journal of Geochemical Exploration》2006,88(1-3):64
The possible contamination of a groundwater system with industrial wastewater originating from a paper mill factory has been investigated in Piteå, N. Sweden. Six samples were collected from the wastewater in the waste dump and twelve samples from the adjacent groundwater were analyzed for chemistry and sulfur isotopes. The industrial wastewater is a saline water consisting mainly of Na–HCO3–SO4, having a high pH and showing δ34S values between 7‰ and 9‰ affected by bacterial sulfate reduction. The groundwaters are relatively dilute, dominated by Na+, Ca2+ and HCO3−, but with varying concentrations as exemplified by sulfate with concentrations varying between 3 and 69 mg L− 1 while the δ34S values range from − 0.5‰ to 14.3‰. The data suggest that the main S sources in the waters are the bedrock sulfides and/or atmospheric deposition, which, sometimes, are overlapped by bacterial sulfate reduction. Contamination from the waste dump does not occur. 相似文献
14.
Hand-pump wells in the Tarkwa gold mining district and the geologically similar Bui area were chemically analysed and compared in an effort to determine whether groundwaters in the Tarkwa area have been affected by mining. Significant chemical differences attributed to mine water discharges have been observed in streams in the Tarkwa area. Groundwater chemistry from hand-pump wells in Tarkwa and Bui areas reveal similar hydrochemical facies, predominantly Ca–Na–Mg–HCO3–Cl. However, except for SO42–, ionic concentrations of groundwaters from Bui are greater than those from Tarkwa probably due to differences in (1) water availability during sedimentation (2) water-rock interactions and/or residence times for water. No demonstrable impact of mining on groundwaters from hand-pumped wells in the Tarkwa area has been noted. Hydrogeological inference suggests that the main streams which receive mine water discharges are both gaining and are groundwater divides. The overwhelming majority of population centres and mining operations are located on opposite sides of these groundwater divides, therefore, it is unlikely aquifers tapped for drinking by these communities would be affected by mining. 相似文献
15.
Björn S. Frengstad Kaj Lax Timo Tarvainen Øystein Jæger Börge J. Wigum 《Journal of Geochemical Exploration》2010
Twenty-two bottled mineral and spring waters from Norway, Sweden, Finland and Iceland have been analysed for 71 inorganic chemical parameters with low detection limits as a subset of a large European survey of bottled groundwater chemistry (N = 884). The Nordic bottled groundwaters comprise mainly Ca–Na–HCO3–Cl water types, but more distinct Ca–HCO3, Na HCO3 and Na–Cl water types are also offered. The distributions for most elements fall between groundwater from Fennoscandian Quaternary unconsolidated aquifers and groundwater from Norwegian crystalline bedrock boreholes. Treated tap waters have slightly lower median values for many parameters, but elements associated with plumbing have significantly higher concentrations in tap waters than in bottled waters. The small dataset is able to show that excessive fluoride and uranium contents are potential drinking water problems in Fennoscandia. Nitrate and arsenic displayed low to moderate concentrations, but the number of samples from Finland and Northern Sweden was too low to detect that elevated concentrations of arsenic occur in bedrock boreholes in some regions. The data shows clearly that water sold in plastic bottles is contaminated with antimony. Antimony is toxic and suspected to be carcinogenic, but the levels are well below the EU drinking water limit. The study does not provide any health-based arguments for buying bottled mineral and spring waters for those who are served with drinking water from public waterworks. Drinking water from crystalline bedrock aquifers should be analysed. In case of elevated concentrations of fluoride, uranium or arsenic, most bottled waters, but not all, will be better alternatives when treatment of the well water is not practicable. 相似文献
16.
Groundwater samples were collected from 25 sampling sites of the Oropos–Kalamos basin aiming to describe the groundwater quality
in relation to geology, lithology and anthropogenic activities of the study area. Chromium speciation analysis, factor analysis,
GIS database and geochemical data proved successful tools for the identification of natural and anthropogenic factors controlling
the geochemical data variability and for the identification of the redox couple controlling Cr speciation. A Durov diagram
is used to classify groundwater quality into five types: Ca–HCO3, Mg–HCO3, Na–Cl, Mg–Cl and Ca–Cl. The groundwater quality of Oropos–Kalamos is influenced by various natural and anthropogenic factors.
Evaluation of water quality for drinking and irrigation purposes is discussed. 相似文献
17.
Water samples from 72 wells tapping the Jilh aquifer were collected and analyzed for 10 different water quality parameters. Using these data, a regional irrigation water quality was assessed using three techniques: (i) United States Department of Agriculture method (USDA), (ii) Food and Agriculture Organization (FAO) guidelines for water quality assessment, and (iii) Water-Types approach. The USDA method revealed that the aquifer water salinity, as represented by electrical conductivity, ECw, ranges from high salinity (C3: ECw > 0.75–2.25 dS/m) to a very high salinity (C4: ECw > 2.25 dS/m). The sodium adsorption ratio (SAR) varied from low (S1) to very high (S4) sodicity. Therefore, the water of the Jilh aquifer is dominantly of the C4–S2 class representing 56% of the total wells followed by C4–S1, C4–S3, C3–S1 and C4–S4 classes at 19%, 14%, 8%, and 3% of the wells respectively. The FAO system indicated moderate to severe restriction on the use for irrigation and slight to moderate ion toxicities for Na+, Cl−, B+, NO3− and HCO3−. It is clear that, both USDA and FAO systems condemn the Jilh groundwater as hazardous for irrigation due to its high salt content, unless certain measures for salinity control are undertaken. The dominant salt constituents in the water are Mg–Cl2, Na–Cl and Ca–Cl2 as per the Water-Types method. However, due to the complexity in classifying the aquifer groundwater for irrigation, a simplified approach acknowledging three class groups (I-suitable water, II-conditionally suitable water and III-unsuitable water) adopted from the three methods, is suggested in this paper. The simplified approach combines C–S classes of the USDA method among these three groups according to the lowest ratings. The salinity of the FAO method has been split arbitrarily into slight and moderate subclasses with values of 0.7–2.25 and >2.25 dS/m, respectively; to match with the C3-class of the USDA system. The Water-Types were classified assuming that Ca–Cl2 is the least hazardous salt, followed by Mg–Cl2 and Na–Cl. Using this integrated hydrochemical method, the majority of the wells (92%) contain unsuitable water for irrigation (Group III) while the remaining wells (8%) are in Group II with water considered conditionally suitable for irrigation. 相似文献
18.
J. M. S J. M. Bertrand J. Leterrier M. H. F. Macedo 《Journal of South American Earth Sciences》2002,14(8):676
Proterozoic metamorphosed sequences are identified in the Transversal Zone (TZ) domain of the Borborema geological province, Northeast Brazil. This TZ domain is located between the well-known E–W Patos and Pernambuco continental shear zones. In its eastern part, in the Taquaritinga region, a large mass of augen gneisses with a conspicuous horizontal to subhorizontal tectonic foliation forms one of the most important rock types in the region that displays U–Pb zircon ages ca. 1.52 Ga. Paleoproterozoic orthogneisses dated by U–Pb on zircon at ca. 1.97 Ga and older paragneisses and banded gneisses represent basement rocks, which were cross-cut by these Mesoproterozoic augen gneisses, and have been in turn intruded by plutonic rocks in upper Neoproterozoic (U–Pb and Rb–Sr, ca. 0.6 Ga) times.Chemical analyses of major, minor, and trace elements (including REE) for the basement orthogneisses indicate calcalkaline affinities and a signature very similar to volcanic arc granites, representing crustal accretion during the Paleoproterozoic Transamazonian/Eburnean orogenesis in the region. In turn, the chemical data for augen gneisses indicate that they are relatively homogeneous and evolved metaluminous metaplutonic rocks with characteristics very similar to A-type granites generated and emplaced in an extensional anorogenic setting. Relatively high 87Sr/86Sr initial ratio and negative Nd(t) are signatures of crustal components in these rocks.Based on geochemical, geochronological, and structural data, the Taquaritinga region is composed of Paleoproterozoic (>1.97 Ga) rocks intruded by Mesoproterozoic (ca. 1.5 Ga) anorogenic granites and Neoproterozoic granites (ca. 0.6 Ga). These data also suggest that the tectonometamorphic structures displayed by Meso and Neoproterozoic suites were developed by the Brasiliano/Pan-African orogeny and that the record of Transamazonian/Eburnean orogeny is restricted to basement rocks. This means that there is no evidence for a compressional event in Mesoproterozoic times (Cariris Velhos=Grenville) as suggested for the central and western part of the TZ. It is important to remark that the Taquaritinga augen gneisses are, up to now, the only unit that represents magmatic pulses associated with extensional episodes with this age (ca. 1.5 Ga) in the TZ and in the whole Borborema Province.
Resumen
A zona Transversal da Província Borborema está geologicamente situada entre os lineamentos Pernambuco e Patos. Na sua parte oriental, na região de Taquaritinga (PE), dominam augen gnaisses com uma penetrativa e proeminente foliação tectônica subhorizontal, com idade de cristalização de 1.52 Ga obtida em zircão. Estas rochas são intrusivas em ortognaisses e paragnaisses do embasamento com idade mínima em torno de 1.97 Ga, e são intrudidas por rochas plutônicas associadas ao Ciclo Brasiliano (ca. 0.6 Ga).Análises de elementos maiores, menores e traços (incluindo terras raras) nos augen gnaisses mostram caráter metaluminoso para esta suíte ígnea e fortes semelhanças com os granitos tipo-A gerados em ambiente anorogênico. Razões iniciais 87Sr/86Sr relativamente altas e Nd(t) negativos são assinaturas indicadoras de forte contribuição crustal nestes augen gnaisses.A conjunção dos dados geoquímicos, geocronológicos e de campo indicam que na região de Taquaritinga onde são identificadas rochas de idades paleo (>1.95 Ga), meso (ca. 1.5 Ga) e neoproterozóicas (ca. 0.6 Ga), o ciclo orogênico Transamazônico é restrito às rochas do embasamento, e que todas as estruturas dúcteis identificadas nas rochas meso e neoproterozóicas foram desenvolvidas durante o Ciclo orogênico Brasiliano. Não foram encontradas evidências que atestem a existência do Ciclo Cariris Velhos nesta parte da Província Borborema. Contudo, está bem marcado que nesta Zona Transversal e na Província Borborema, os augen gnaisses de Taquaritinga são, até o momento, os únicos marcadores de pulsos magmáticos associados com eventos extensionais crustais datados do Mesoproterozóico inferior. 相似文献19.
Geochemistry constraints of Mesozoic–Cenozoic calc-alkaline magmatism in the South Shetland arc, Antarctica 总被引：1，自引：0，他引：1
A. Machado E.F. Lima F. Chemale Jr. D. Morata O. Oteiza D.P.M. Almeida A.M.G. Figueiredo F.M. Alexandre J.L. Urrutia 《Journal of South American Earth Sciences》2005,18(3-4):407-425
Geochemical data from basalts, basaltic andesites, and andesites of the Mesozoic–Cenozoic (143–44 Ma) from Livingston, Greenwich, Robert, King George, and Ardley Islands of the South Shetland archipelago, Antarctica, are presented. The rocks have variable SiO2 of approximately 46–61 wt%, Al2O3 of 15–26 wt%, and total alkali (K2O+Na2O) of 2–6 wt%. Most samples have low Mg#, Cr, and Ni, which indicates that they have undergone significant fractional crystallization from mantle-derived melts. The presence of olivine cumulatic in the samples from Livingston and Robert Islands explains some high MgO, Ni, and Cr values, whereas low Rb, Zr, and Nb values could be related to undifferentiated magmas. N-MORB-normalized trace element patterns show that South Shetland Islands volcanic rocks have a geochemical pattern similar to that found for other island arcs, with enrichment in LILE relative to HFSE and in LREE relative to HREE. The geochemistry pattern and presence of calcic plagioclase, orthopyroxene, Mg-olivine, and titanomagnetite phenocrysts suggest a source related to the subduction process. The geochemical data also suggest magma evolution from the tholeiitic to the calc-alkaline series; some samples show a transitional pattern. Samples from the South Shetland archipelago show moderate LREE/HREE ratios relative to N-MORB and OIB, depletion in Nb relative to Yb, and high Th/Yb ratios. These patterns probably reflect magma derived from a lithospheric mantle source previously modified by fluids and sediments from a subduction zone.
Resumo
Dados geoquímicos de basaltos, andesitos basálticos e andesitos mesozóicos–cenozóicos (143–44 Ma) das ilhas Livingston, Greenwich, Robert, King George e Ardley do Arquipélago Shetland do Sul, Antártica são discutidas neste artigo. As rochas tem conteúdos de SiO2 variando de 46 a 61%, Al2O3 de 15 a 26% e álcalis (K2O+Na2O) de 2 a 6%. A maior parte das amostras tem conteúdos baixos de Mg#, Cr e Ni, indicando que sofreram significante cristalização fracionada de fusões derivadas do manto. A presença de fases cumuláticas nas amostras das ilhas Livingston e Robert explicaria os elevados valores de MgO, Ni, Cr, enquanto que baixos valores de Rb, Zr e Nb observados nas amostras destas ilhas poderiam estar relacionados a magmas não diferenciados. Os padrões de elementos-traço normalizados pelo N-MORB mostram que as rochas vulcânicas das Ilhas Shetland do Sul têm padrão geoquímico similar àqueles encontrados em outros arcos de ilhas com enriquecimento em LILE em relação aos HFSE e em ETRL em relação aos ETRP. O padrão geoquímico e a ocorrência de fenocristais de plagioclásio cálcico, ortopiroxênio, olivina magnesiana e titanomagnetita sugerem origem relacionada a processos de subducção. Dados geoquímicos obtidos para as amostras do arquipélago Shetland do Sul sugerem um magma evoluindo de toleítico para cálcico-alcalino, observando-se em algumas amostras um padrão transicional. As amostras do arquipélago Shetland do Sul mostram em relação ao N-MORB e OIB, moderadas razões ETRL/ETRP, empobrecimento em Nb relativo a Yb e elevada razão Th/Yb Estes padrões refletem, provavelmente, magma derivado de uma fonte mantélica litosférica, que foi modificada por fluídos e sedimentos da zona de subducção. 相似文献20.
Eliane Guedes Monica Heilbron Paulo M. Vasconcelos Cludio de Morisson Valeriano Júlio Csar Horta de Almeida Wilson Teixeira Antonio Thomaz Filho 《Journal of South American Earth Sciences》2005,18(3-4):371-382
New K–Ar and 40Ar/39Ar data of tholeiitic and alkaline dike swarms from the onshore basement of the Santos Basin (SE Brazil) reveal Mesozoic and Tertiary magmatic pulses. The tholeiitic rocks (basalt, dolerite, and microgabbro) display high TiO2 contents (average 3.65 wt%) and comprise two magmatic groups. The NW-oriented samples of Group A have (La/Yb)N ratios between 15 and 32.3 and range in age from 192.9±2.2 to 160.9±1.9 Ma. The NNW-NNE Group B samples, with (La/Yb)N ratios between 7 and 16, range from 148.3±3 to 133.9±0.5 Ma. The alkaline rocks (syenite, trachyte, phonolite, alkaline basalts, and lamprophyre) display intermediate–K contents and comprise dikes, plugs, and stocks. Ages of approximately 82 Ma were obtained for the lamprophyre dikes, 70 Ma for the syenite plutons, and 64–59 Ma for felsic dikes. Because Jurassic–Early Cretaceous basic dikes have not been reported in SE Brazil, we might speculate that, during the emplacement of Group A dikes, extensional stresses were active in the region before the opening of the south Atlantic Ocean and coeval with the Karoo magmatism described in South Africa. Group B dikes yield ages compatible with those obtained for Serra Geral and Ponta Grossa magmatism in the Paraná Basin and are directly related to the breakup of western Gondwana. Alkaline magmatism is associated with several tectonic episodes that postdate the opening of the Atlantic Ocean and related to the upwelling of the Trindade plume and the generation of Tertiary basins southeast of Brazil. In the studied region, alkaline magmatism can be subdivided in two episodes: the first one represented by lamprophyre dykes of approximately 82 Ma and the second comprised of felsic alkaline stocks of approximately 70 Ma and associated dikes ranging from 64 to 59 Ma.