Hydrogeochemical investigation in an arid region of Iran (Tabas, Central Iran)

Groundwater is the most important source of water supply in Iran and understanding the geochemical evolution of groundwater is important for sustainable development of the water resources in Tabas area. A total of 29 samples of groundwater in Tabas area have been analyzed for ions and major elements. Groundwater of the study area is characterized by the dominance of Na–Cl water type. Groundwater was generally acidic to high alkaline with pH ranging from 5.42 to 10.75. The TDS as a function of mineralization characteristics of the groundwater ranged from 479 to 10,957 mg/l, with a mean value of 2,759 mg/l. The Ca²⁺, Mg²⁺, SO₄ ^2? and HCO₃ ^? were mainly derived from the dissolution of calcite, dolomite and gypsum. The Cu, Pb and Zn ions are not mobile in recent pH–Eh, but these conditions controlled dissolved Se, V and Mo in groundwater. The As is released in groundwater as a result of the weathering of sulfide minerals like arsenopyrite.     

Hydrogeochemical processes and multivariate analysis for groundwater quality in the arid Maadher region of Hodna,northern Algeria

Acta Geochimica - This study focused on water quality and hydro-geochemical processes (evolution, origin) in the Maadher region, central Hodna in Algeria. In recent decades, the excessive...     

Hydrogeochemical analysis of salinization processes in the coastal aquifer of Oropesa (Castellón, Spain)

 The coastal aquifer of Oropesa is affected by salinization processes undoubtedly associated with intense groundwater exploitation for agriculture supply. The aquifer corresponds geologically to a tectonic depression with Plioquaternary fill. Hydrogeologically, this aquifer is detrital, with intergranular porosity, which receives substantial recharge from adjacent Mesozoic aquifers. Contact with the sea, in addition to the presence of cultivated soil requiring extreme exploitation of groundwater, frequently give rise to processes of seawater intrusion. The present research is an attempt to understand the saltwater intrusion in this aquifer, using hydrochemical analyses of the behavior of certain minor ions that could help in the characterization process. In the case of the Oropesa sector, groundwater salinization does not appear to be attributable solely to the intrusion of seawater, but there are also anomalies related largely to the geology of the sector and its surroundings, the type of recharge, the hydrodynamic conditions in the specific area, etc. Received: 23 January 1995 · Accepted: 12 September 1995     

Groundwater problems in a semiarid area (Low Andarax river,Almeria, Spain)

The three aquifer units differentiated in the Low Andarax—detritic, carbonated, and deep aquifers—present problems in water quality. This is made worse during the course of development as a result of the appearance of processes of marine intrusion, dissolution of saline rocks present in the stratigraphic series, overexploitation with considerable increase in the boron content, and the continual recycling of water with a resulting increase in total dissolved solids. All this has resulted in the salinization of the majority of the underlying soils that has led to the abandoning of many cultivated areas—especially areas of citrus growth—and/or the substitution of a farming system that is much more tolerant of the salts.     

Water escape structures in the context of a depositional model of a mass flow dominated conglomeratic fan-delta (Abrioja Formation, Pliocene, Almeria Basin, SE Spain)

ABSTRACT Pebbly sediments of the shallow marine Abrioja fan-delta show pockets (bowl-shaped structures, partly filled with pebbles) and pillars (elongate structures, filled with sand and pebbles). These structures are most abundant in pebbly sediments deposited on a steep slope ( ca. 25°-10°) and are absent in conglomerates deposited on a slope of ca . 6° and less, although they are present in the pelitic top of these beds.
The pocket and pillar structures are interpreted as fluid escape structures originating from local liquefaction and fluidization, processes which are favoured by rapid deposition, rapid sediment accumulation, the presence of less permeable layers and an immature sediment texture.
These conditions are met in conglomeratic fan-deltas, which have steep slopes with immature sediments. It is concluded that the presence of fluid escape structures in conglomeratic sediments may indicate a steep depositional slope.     

Selenium content in soils from Murcia Region (SE,Spain)

The objective of this study was to determine the selenium content in soils from the Region of Murcia (SE, Spain) and to study the possible relationship between mineralogical composition, soil properties and selenium content. In addition, generic reference level (GRL) for selenium was determined according to Spanish legislation. For this study, 490 samples were selected in areas subjected to agricultural activity or abandoned agricultural soils with natural vegetation. Five different zones were established in order to study selenium variability. Four different mineralogical groups were established, based on significant relationship with the mineralogical composition, and each sample was included in one mineralogical group. The results showed that the concentration of selenium is correlated with the electrical conductivity, sulphate content and with the mineralogical composition, particularly positively with quartz and in a negative way with calcite percentage. In addition, selenium level was positively correlated with the phyllosilicate content. Established GRL for selenium varies with the mineralogical group, having a great transcendence from the legal and economic points of view.     

Impact of quarrying gypsum in a semidesert karstic area (Sorbas,SE Spain)

The Messinian gypsum of Sorbas is intensively karstified, with hundreds of dolines and numerous, highly unusual exo- and endokarstic forms. Amongst these the tumuli are especially spectacular, as are the large caverns, adorned with numerous speleothems, some of which have not been described anywhere else in the World. The extraction of the gypsum has impacted practically all the elements of the environment (landscape, water, soil, subsoil, flora, fauna, etc.) and, in particular, all of the karstic forms. In addition to endangering the caves and the natural treasures that they contain, it affects the surface waters, markedly modifying the hydrographic network. Groundwaters, which now occur in the bottom of a quarry, are also affected.     

Hydrogeochemical effects of groundwater mining of the Sierra de Crevillente Aquifer (Alicante,Spain)

The groundwater mining of the Crevillente aquifer (southeastern Spain) has resulted in the progressive deterioration of water quality, with particularly significant increases in chloride, sulfate, and sodium. The possibility of a vertical hydrochemical zoning is deduced that would require examining the importance of the geometry and lithology (evaporitic materials) in the salinization process. The time of water-rock contact (residence time) and dilution by infiltration of rainwater also influences the hydrogeochemistry of the aquifer. The hydrochemical data are useful in defining the conceptual model of the aquifer, completely karstified with relative homogeneity.Project AMB92-0211 (CICYT)     

Geochemical characterization of the salinity of irrigated soils in arid regions (Biskra,SE Algeria)

Acta Geochimica - The agriculture in Biskra, southeastern Algeria, is based on traditional practices and characterized by small irrigated fields. In the last decades, the increasing demand in water...     

Hydrogeochemical patterns,processes and mass transfers during aquifer storage and recovery (ASR) in an anoxic sandy aquifer

The hydrogeochemical processes that took place during an aquifer storage and recovery (ASR) trial in a confined anoxic sandy aquifer (Herten, the Netherlands) were identified and quantified, using observation wells at 0.1, 8 and 25 m distance from the ASR well. Oxic drinking water was injected in 14 ASR cycles in the period 2000–2009. The main reactions consisted of the oxidation of pyrite, sedimentary organic matter, and (adsorbed) Fe(II) and Mn(II) in all aquifer layers (A–D), whereas the dissolution of carbonates (Mg-calcite and Mn-siderite) occurred mainly in aquifer layer D. Extinction of the mobilization of SO₄, Fe(II), Mn(II), As, Co, Ni, Ca and total inorganic C pointed at pyrite and calcite leaching in layer A, whereas reactions with Mn-siderite in layer D did not show a significant extinction over time. Iron(II) and Mn(II) removal during recovery was demonstrated by particle tracking and pointed at sorption to neoformed ferrihydrite. Part of the oxidants was removed by neoformed organic material in the ASR proximal zone (0 – ca. 5 m) where micro-organisms grow during injection and die away when storage exceeds about 1 month. Anoxic conditions during storage led to increased concentrations for a.o. Fe(II), Mn(II) and NH₄ as noted for the first 50–200 m³ of abstracted water during the recovery phase. With a mass balance approach the water–sediment reactions and leaching rate of the reactive solid phases were quantified. Leaching of pyrite and calcite reached completion at up to 8 m distance in layer A, but not in layer D. The mass balance approach moreover showed that Mn-siderite in layer D was probably responsible for the Mn(II) exceedances of the drinking water standard (0.9 μmol/L) in the recovered water. Leaching of the Mn-siderite up to 8 m from the ASR well would take 1600 more pore volumes of drinking water injection (on top of the realized 460).     

Towards a Plio-Pleistocene chronostratigraphy in Eastern Betic Basins (SE Spain)

Abstract

The evolution of Neogene and Quaternary littoral basins in the Eastern Betic Cordillera is largely related to tectonic activity along the Eastern Betic sinistral shear zone.

Detailed mapping of sedimentary units in these basins, together with sedimentological and paleomagnetic analysis lead to the proposal of a new chronostratigraphie framework for Pliocene and Quaternary deposits.

This chronostratigraphie setting rejects the synchronous character of the “Pliocene Unite” previously referred to as: “P.I” (grey-blue marls), “P.H” (yellow calcarenites), and “Р.Ш” (variegated silts and clays). Instead, tectonics would have controlled the paleogeographic evolution of the Eastern Betic realms, causing the lithofacies to occur repeated in space and time. The Plio-Pleistocene boundary in these basins is not accompanied by changes in geodynamic behaviour or climatic conditions. According to the paleomagnetic data, these changes occurred at different times during the Pleistocene in the different studied basins.     

Water balance in the playa-lakes of an arid environment,Monegros, NE Spain

The playa-lakes of the Monegros desert in north-east Spain are saline wetlands in an arid environment, a rare phenomenon in Europe. These extremely valuable habitats are threatened by changes associated with agricultural expansion and incorporation of new irrigated areas. An understanding of the present hydrologic regime will enable changes to be identified, particularly those brought about by flooding and pollution caused by irrigation surplus. This study sets out to show the results of applying a daily water balance in three selected playa-lakes. The balance was in two parts and consisted of: (1) the average balance for all the endorheic basin using the BALAN_11 program, and (2) the water balance in some playa-lakes, applying discharge flows obtained from the previous balance. The resulting volumes of water were converted to water depths and contrasted with reference volumes taken from field and Landsat images. The model was calibrated by applying various hypotheses of function which enabled the results to be adjusted. The proposed balance is an acceptable reproduction of field water measurements during this period, and underlines the consistency of the conceptual model. The methodology used is appropriate for understanding the playa-lakes function and for monitoring them for conservation purposes.     

On the tectonics of the eastern Betic Cordilleras (SE Spain)

The tectonically deepest part of the eastern Betic Cordilleras consists of rocks showing medium grade metamorphism of alpine age. In this zone several individual tectonic units are distinguished, each with a basis of polymetamorphic pre-Silurian schists, covered by a sequence of younger metamorphites considered to be partly of Triassic age. The crystalline schists of the Sierra Nevada, together with their cover of younger schists — which represent the deepest part of the mixed zone of previous authors — form a single tectonic unit. It seems appropriate to combine the crystalline schists of the Sierra Nevada and this former mixed zone to a complex of tectonic units, which are characterized by a medium grade metamorphism of alpine age and for which the name Nevado-Filabride units or Nevado-Filabrides is proposed.The Nevado-Filabrides are tectonically overlain by the Alpujarrides, generally characterized by low grade alpine metamorphism, and these in their turn by the Betic of Málaga — merely present as small dispersed remnants — consisting of rocks that are almost devoid of alpine metamorphism.Important movements, that have taken place after the major thrust movements leading to the formation of the nappe structures, have caused horizontal displacements of considerable magnitude, sometimes resulting in changes of the original tectonic succession.

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Zusammenfassung Der tektonisch tiefste Teil der östlichen betischen Kordilleren besteht aus Gesteinen, die eine mittlere Metamorphose alpidischen Alters zeigen. In dieser Zone kann man mehrere selbständige tektonische Einheiten unterscheiden. Bei jeder von ihnen besteht die Basis aus polymetamorphen präsilurischen Schiefern, die überlagert werden von einer Folge jüngerer metamorpher Gesteine, bei denen z. T. triassisches Alter angenommen wird. Die kristallinen Schiefer der Sierra Nevada und die darüber liegenden jüngeren Schiefer (die den tiefsten Teil der Mischungszone älterer Autoren bilden) sind eine telefonische Einheit. Diese kristallinen Schiefer der Sierra Nevada und die früher verwendete Mischungszone faßt man am besten zu einem Komplex tektonischer Einheiten zusammen, die gekennzeichnet sind durch eine mittlere Metamorphose alpidischen Alters. Für sie wird der Name Nevado-Filabride Einheiten oder Nevado-Filabriden vorgeschlagen.Die Nevado-Filabriden werden tektonisch überlagert von den Alpujarriden, die durch einen geringen alpinen Metamorphismus gekennzeichnet werden. Auf diesen liegt das Betikum von Malaga, das vorwiegend in kleinen verstreuten Resten vorliegt und aus Gesteinen besteht, denen eine alpidische Metamorphose fast ganz fehlt.Nach den großen Überschiebungen, die die Deckenstrukturen schufen, haben bedeutende Bewegungen zu Horizontalverschiebungen beträchtlichen Ausmaßes geführt. Bisweilen bewirkten sie eine Änderung der ursprünglichen tektonischen Abfolge.

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Résumé La partie tectoniquement la plus profonde des cordillères bétiques orientales est formée de roches montrant un métamorphisme d'âge alpin de degré moyennement élevé. Dans pette zone on distingue plusieurs unités tectoniques individuelles, chacune avec une partie inférieure constituée de schistes polymétamorphiques pré-siluriens, recouverte par une succession de roches métamorphiques plus récentes considérées partiellement d'âge triasique. Les « schistes cristallins de la Sierra Nevada », avec leur couverture de schistes plus récents — qui représentent la partie la plus profonde de la « Mischungszone » des anciens auteursforment une seule unité tectonique. Il semble convenable de considérer les « schistes crystallins de la Sierra Nevada » et cette ancienne « Mischungszone » comme un seul complexe d'unités tectoniques qui sont caractérisées par un métamorphisme de degré moyen, d'âge alpin, et pour lesquelles l'auteur propose le nom d'unités Nevado-Filabrides ou, simplement, Nevado-Filabrides.Les Nevado-Filabrides sont tectoniquement surmontées par les Alpujarrides, généralement caractérisées par un degré de métamorphisme alpin peu élevé, et celles-ci sont à leur tour recouvertes par le Bétique de Málaga, dont n'existent —dans la région en question — que des témoins dispersés, constitués de roches presque dépourvues de métamorphisme alpin.Des mouvements importants, postérieurs aux grands charriages conduisant à la formation de la structure en nappes, ont causé des déplacements horizontaux de grand ampleur, causant parfois des changements dans la succession tectonique originelle.

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Hydrogeochemical processes affecting groundwater in an irrigated land in Central Tunisia

Detailed hydrogeochemical investigation has provided new information concerning the major factors and mechanisms controlling the groundwater chemistry of Chougafiya basin. The hydrogeochemical characteristics of groundwaters comprise three main types: Cl–SO₄–Ca, Cl–SO₄–Na and Cl–Na. Hydrochemical characteristics based on the bivariate diagrams of major (Cl^?, SO₄ ^2?, NO₃ ^?, HCO₃ ^?, Na⁺, Mg²⁺, K⁺ and Ca²⁺) and some trace (Br^? and Sr²⁺) ions, mineral saturation indices and hierarchical cluster analysis indicate different origins of groundwater mineralization. The water–rock interaction (dissolution of evaporitic minerals), followed by cation exchange reactions with clay minerals, constitute the main processes that control groundwater salinization. However, the chemical composition of brackish groundwater in the central and southern parts of the study area is influenced by a mixing process with Sabkhas salt groundwater. The mixing proportions inferred from chloride mass balance prove that the contribution of Sabkhas groundwater to Quaternary aquifer ranges between 2.7 and 9.1 %. These intrusion rates reflect the progress of the saltwater–freshwater interface, which is mainly controlled by the piezometric level variation and the distance to the Sabkhas.     

Eclogite relics in the Variscan orogenic belt of Bulgaria (SE Europe)

Eclogitic rocks were sampled from two zones in the basement of the Sredna Gora terrane (central western Bulgaria): (1) partially retrogressed eclogites and amphibolites embedded in sillimanite-bearing garnet-micaschists with kyanite relics and migmatites and (2) banded amphibolites associated with muscovite-bearing metagranites within two-mica paragneisses. Rutile relics and oligoclase + green hornblende + epidote ± biotite pseudomorphs after garnet suggest an eclogite facies event. A tholeiitic, transitional affinity was determined for the protoliths, suggesting a continental rift environment, consistent with several eclogite-bearing complexes in the eastern segments of the Variscan belt that arose from the Cambro-Ordovician Gondwana break-up. Decreasing pressure after the eclogite overprint was demonstrated by (a) diopside-albite symplectite, and (b) plagioclase + red–brown to green amphibole kelyphite. The early static re-equilibration, dated to 398 ± 5.2 Ma by ⁴⁰Ar–³⁹Ar technique, was followed by an amphibolite facies foliation, which was pervasive in amphibolites, gneisses and micaschists, and poorly developed in eclogites. The lithospheric PT paths corresponding to higher and lower metamorphic gradients reflect the juxtaposition of crustal and lithospheric mantle units, respectively. In the build-up of the basement of the Balkan orogen, the physical properties of the lithological complexes might have influenced the collisional pattern of involved microplates.     

Interacting tectonics,hydrogeology and karst processes in an intramontane basin: the Jiloca graben (NE Spain)

The Jiloca basin is a NNW–SSE trending, Neogene-Quaternary graben in NE Spain, bounded by normal faults with measurable hectometre-scale throws. Its overall trend truncates previous NW–SE folds. The sedimentary infilling includes Neogene and Quaternary deposits, exceeding 80 m in thickness. The stratigraphical and structural setting controls hydrogeology of the basin. Neogene marls constitute an aquiclude that separates a main Jurassic karstic, confined aquifer from a shallow, unconfined Plio-Quaternary aquifer. The Jurassic aquifer is laterally compartmented by impervious Upper Triassic anticline cores, though its piezometric surface usually lies 30–60 m higher than the Mesozoic-Neogene boundary. The geological, and specifically the hydrogeological features are not significantly compatible with a previously published hypothesis that considers the Jiloca depression as a polje (in which the final topography is the result of suballuvial karstic corrosion) for three reasons. First, the hypothetical corrosion front shows neither a specific relationship with the epiphreatic zone, nor control by the local presence of impervious Triassic rocks. Second, chemistry of groundwater at the underlying Jurassic aquifer would not allow limestone dissolution at rates necessary for producing the supposed erosion deepening of 300 m since the late Pliocene. Finally, no evidence of swallow holes or ponors has been found.     

Hydrostratigraphic framework and hydrogeological behaviour of the Mancha Oriental System (SE Spain)

The Mancha Oriental System (MOS) has a surface area of 7,260 km², making it one of the largest carbonate aquifer systems in Spain. The system sustains about 1,000 km² of irrigated crops and supplies groundwater to 275,000 inhabitants. The economic transformation brought about by the development of extensive irrigated cropland has led to a water-balance disequilibrium of about 75 million m³/year. This input–output deficit has negative consequences in the quantity and quality of the available resources, in the river–aquifer relationship, and in the associated ecosystems as well. To understand the hydrogeological behaviour of the system, it is necessary to design a conceptual model. Further, the conceptualisation of a groundwater flow system is a requirement of the European Water Framework Directive for the characterisation of groundwater bodies. The robustness of the conceptual model depends heavily on the user capability of representing the real system. In this work, a multidisciplinary approach has been used to represent the three-dimensional geological framework and the groundwater flow conceptualisation of the MOS. Data management and three-dimensional visualisation have been carried out by means of geographical information system (GIS) tools and software for contouring and three-dimensional surface mapping.     

Geochemistry and petrogenesis of two-Pyroxene andesites from Sierra de Gata (SE Spain)

Summary The Miocene volcanic suite of Sierra de Gata (Betic Cordillera) is composed of dacites, rhyodacites and rhyolites, besides basaltic andesites and andesites. The latter are very fresh and are the least fractionated rock types; thus they have been investigated in order to put some constraints on the genetic interpretation of the volcanic sequence. These rocks are composed of plagioclase, orthopyroxene, clinopyroxene and magnetite both as phenocrysts and in the groundmass. Olivine and ilmenite occur occasionally. The andesites exhibit orogenic chemical features. They are characterized by very low Ni, Co and Cr contents and show negative Eu anomalies, which support fractionation of mafic phases and plagioclase at depth. The petrogenesis of the andesites, however, cannot be related simply to fractionation processes of a single mafic magma since the lack of good interelemental correlations, the scattering of Sr-isotope ratios and the isotope disequilibrium between the phases conflict with such a simple mechanism. A model which can better explain the petrogenesis of the analyzed andesites considers the intervention of different mafic melts, generated in a heterogeneous mantle and characterized by different chemical and isotopic compositions, which fractionated at depth and concomitantly interacted significantly with the continental crust.

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Geochemie und Petrogenese von Pyroxen-Andesiten der Sierra de Gata (SE Spanien)

Zusammenfassung Die miozäne Vulkanitabfolge der Sierra de Gata (Betische Kordillere) wird von Daciten, Rhyodaciten, Rhyoliten sowie basaltischen Andesiten and Andesiten aufgebaut, letztere sind in einem guten Erhaltungszustand and zeigen die geringste Fraktionierung. Sie wurden daher genauer untersucht, um Aussagen über die Genese dieser Vulkanite machen zu können.Phenokrysten und Grundmasse bestehen aus Plagioklas, Orthopyroxen, Klinopyroxen und Magnetit. Manchmal kommen Olivin und Ilmenit hinzu. Die Geochemie der Andesite folgt typisch orogenen Trends. Sie sind durch sehr niedrige Ni-, Co- und Cr-Gehalte und negative Eu-Anomalien charakterisiert; dies belegt eine Fraktionierung der mafischen Gemengteile und des Plagioklases in der Tiefe. Die petrogenetische Entwicklung der Andesite kann allerdings nicht einfach mit Fraktionierungsprozessen eines einzigen mafischen Magmas erklärt werden. Das Fehlen von Element-Korrelationen, das starke Streuen der Sr-Isotopenverhältnisse und das Isotopenungleichgewicht zwischen den einzelnen Mineralphasen stehen in Widerspruch zu einem derartigen einfachen Modell. Ein Modell, das die Petrogenese der untersuchten Andesite besser erklärt, zieht die Beteiligung verschiedener mafischen Schmelzen-sie bildeten sich in einem heterogenen Mantel und sind durch Unterschiede im Chemismus und ihrer Isotopenzusammensetzung charakterisiert—in Betracht. Dabei kam es zu Fraktionierung dieser Magmen in der Tiefe und zu beträchtlichen Reaktionen mit kontinentalem Krustenmaterial.

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With 5 Figures