Hydrogeological framework and estimation of aquifer hydraulic parameters using geoelectrical data: a case study from West Iran

Detailed local geological, geophysical, and hydrogeological investigations were carried out for the alluvial aquifer in the Kangavar basin, West Iran to delineate the architecture of different subsurface geological horizons using lithologs and generated vertical electrical sounding (VES) data. An attempt has also been made to estimate aquifer transmissivity from resistivity data. Forty VESs were recorded with the Schlumberger electrode configuration in the study area; 28 of these were selected for evaluation. The maximum current electrode spacing was 400–500 m. The data obtained were interpreted by computer iterative modeling with curve matching for calibration purposes. In order to ascertain the subsurface geological framework, the general distribution of resistivity responses of the geological formations was obtained and geoelectrical sections along a number of lines were prepared. Probable aquifer horizons from these sections were identified. The transmissivity of the unconfined aquifer was computed by determining the Dar-Zarrouk parameters (longitudinal unit conductance and transverse unit resistance) and were compared with the actual field transmissivity. The results showed a direct relation between aquifer transmissivity and modified transverse resistance.     

Groundwater utilization through the centuries focusing οn the Hellenic civilizations

Groundwater has been utilized since the Prehistoric times. Water supply of some Minoan settlements on the eastern side of the island of Crete (Greece) was based on groundwater. Later on, many wells were constructed in several areas of Greece and their use expanded through subsequent periods. The greatest achievement in groundwater exploitation by ancient Greeks was the construction of long underground galleries or qanats, which collected water from springs and alluvial deposits. In Classical times, most of the wells were on private properties and their owners were forced by regulations to maintain the wells in good condition and ready for use in wartime. During that period, the first scientific theories of Aristotle and Theophrastus were developed in regards to hydrological phenomena, and the processes involved in the formation of surface water and groundwater were clarified. Wells played a major part in urban water supply during the Roman period, in which famous aqueducts were constructed to transfer water; however, several regions of Greece were self-sufficient in water, supplied by many wells from the Prehistoric to the Byzantine period. People understood the local geological conditions and, according to their culture, constructed and managed their own types of wells. In addition to the wells and aqueducts, the hydraulic technology included cisterns to store rainwater, and systems to capture spring water for transport by aqueducts. The examples of hydro-technologies and water management practices described in this paper may have some relevance for water engineering even in modern times.     

Re–Os isotope evidence for mixed source components in carbonate-replacement Pb–Zn–Ag deposits in the Lavrion district,Attica, Greece

The Lavrion ore district contains carbonate-replacement and vein-type Pb–Zn–Ag deposits as well as low-grade porphyry Mo, Cu–Fe skarn, and minor breccia-hosted Pb–Zn–Cu sulfide mineralization. These ore types are spatially related to a Late Miocene granodiorite intrusion (7 to 10 Ma), and various sills and dikes of mafic to felsic composition. Samples of sphalerite and pyrite from the Ilarion carbonate replacement deposit, and galena from Vein 80 (vein-type mineralization) in the Adami deposit show heterogeneous Re–Os values. These values were partially disturbed by hydrothermal activity associated with the formation of hydrothermal veins (e.g., Vein 80). A plot of initial ¹⁸⁷Os/¹⁸⁸Os versus 1/Os_common ratios for pyrite and sphalerite from the Ilarion deposit form a mixing line (r²?=?0.78) between high concentration crustal-like and low concentration mantle-like end-members, or two crustal end-members one of which was more radiogenic than the other. Based on the Re–Os systematics and previously published geological and geochemical evidence, the most plausible explanation for the Re–Os isotope data is that ore-forming components were derived from mixed sources, one of which was a radiogenic crustal source from schists and carbonates probably near intrusion centers and the other, intrusive rocks in the district that are less radiogenic. Although the Re and Os concentrations of galena from Vein 80 are above background values they cannot be used as a chronometer. However, the results of the current study suggest that although pyrite, sphalerite, and galena are poor geochronometers in this ore deposit, due to partial open-system behavior, they still yield valuable information on the origin of the source rocks in the formation of bedded replacement and vein mineralization in the Lavrion district.     

Mineralogy of telluride-bearing epithermal ores in the Kassiteres-Sappes area, western Thrace, Greece

Summary The Kassiteres-Sappes district represents a multi-centered, porphyry-epithermal system developed during the Oligocene to Miocene at a composite calc-alkaline to high-K calc-alkaline volcanic edifice. Precious and base metal mineralization postdates the emplacement of dacite and rhyolite porphyries and is partly superimposed on earlier microdiorite-related porphyry-style mineralization exposed at the Koryfes Hill prospect. A second mineralized porphyry-type system genetically related to a dacite porphyry body developed near the St Demetrios deposit. Tellurides occur mainly at the St Barbara prospect and the St Demetrios deposit. Based on petrographic, electron microprobe, and scanning electron microscope analyses, hessite, petzite, sylvanite, altaite, stützite and native tellurium occur in the St Barbara prospect. These tellurium-bearing minerals are hosted in intermediate-sulfidation type veins and accompanied by pyrite, chalcopyrite, tetrahedrite-group minerals, galena and native gold/electrum. The St Demetrios mineralization includes hessite, altaite, stützite, and tetradymite in close spatial relation to a high-sulfidation assemblage composed of enargite, chalcopyrite, goldfieldite, and native gold. Tellurides were deposited at logfTe₂ values of −8.5 to −7.1 and logfS₂ values of −10.7 to −7.9 (275 °C). The ore systems are characterized by Au, Ag, Te, Bi, and Mo, which suggests a magmatic contribution to the mineralizing fluids. Ore-forming components were likely derived from both the dacite and rhyolite porphyries.     

A cervelleite-like mineral and other Ag-Cu-Te-S minerals [Ag2CuTeS and (Ag,Cu)2TeS] in gold-bearing veins in metamorphic rocks of the Cycladic Blueschist Unit, Kallianou, Evia Island, Greece

A cervelleite-like mineral, two unnamed silver sulfotellurides in the system Ag-Cu-Te-S [Ag₂CuTeS, (Ag,Cu)₂TeS], Te-rich polybasite and cadmian tetrahedrite occur in gold-bearing quartz veins in metapelites and faults within brecciated marbles of the Cycladic Blueschist Unit in the Kallianou area (southern Evia Island, Greece). The quartz veins and faults are discordant to syn-metamorphic structures and formed during ductile to brittle deformation in the final stages of exhumation of the Styra Nappe extrusion wedge (~21?Ma). Te-rich polybasite (up to 7.4 wt. % Te), cadmian tetrahedrite (up to 12.4 wt. % Cd), together with electrum (23?C54 wt. % Ag) and the sulfotellurides, are the main silver carriers in the mineralization. The two unnamed sulfotellurides, Ag₂CuTeS and (Ag,Cu)₂TeS are believed to be new quaternary minerals in the system Ag-Cu-Te-S. These minerals and the cervelleite-like phase could have exsolved from galena during cooling (below 200°C). Initial temperatures for the formation of the sulfotellurides, in the form of hessite-intermediate solid solution, at Kallianou may be up to 300°C under logfS₂ values between?~ ?11.5 to ?8.3, and logfTe₂ from?~ ?14.8 to ?7.8. The values of logfTe₂ and logfS₂ during re-equilibration (at ~200°C) were constrained to ?19.5 to ?15.2 and to ?15.8 to ?11.5 respectively.     

Groundwater quality in the semi‐arid region of the Chahardouly basin,West Iran

Chahardouly basin is located in the western part of Iran and is characterized by semi‐arid climatic conditions and scarcity in water resources. The main aquifer systems are developed within alluvial deposits. The availability of groundwater is rather erratic owing to the occurrence of hard rock formation and a saline zone in some parts of the area. The aquifer systems of the area show signs of depletion, which have taken place in recent years due to a decline in water levels. Groundwater samples collected from shallow and deep wells were analysed to examine the quality characteristics of groundwater. The major ion chemistry of groundwater is dominated by Ca²⁺ and HCO₃^?, while higher values of total dissolved solids (TDS) in groundwater are associated with high concentrations of all major ions. An increase in salinity is recorded in the down‐gradient part of the basin. The occurrence of saline groundwater, as witnessed by the high electrical conductivity (EC), may be attributed to the long residence time of water and the dissolution of minerals, as well as evaporation of rainfall and irrigation return flow. Based on SAR values and sodium content (%Na), salinity appears to be responsible for the poor groundwater quality, rendering most of the samples not suitable for irrigation use. Copyright © 2007 John Wiley & Sons, Ltd.