نشریه علوم زمین خوارزمی
سال نهم شماره 2 (پاییز و زمستان 1402)

The present study aims to investigate the environmental geochemistry, source, and health risk of potentially toxic elements in urban soils of Shahrood, Semnan Province. For this purpose, the total concentration of major and trace elements in 26 topsoil samples was determined using an ICP-MS device. The average concentrations of As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb and Zn are 7.9, 0.1, 7.4, 77.5, 59.8, 448.9, 0.8, 31.5, 35.7 and 104.1 mg/kg, respectively. On the basis of the geochemical indices (i.e., enrichment factor, geoaccumulation index, single-factor analysis, nemerow integrated pollution index, and potential ecological risk index), the studied soils are polluted with potentially toxic elements, especially As, Pb and Cu, and the most polluted sites are located in the northern parts of the city. Statistical analyses (cluster analysis and principle component analysis) indicate that Co and Mn are mainly from natural sources, while Cr, Mo, Ni, Zn, Cu, As, Cd and Pb are probably from anthropogenic sources (especially industrial inputs and traffic). The health risk assessment shows that there is a non-carcinogenic risk of Pb for children through the ingestion route. The carcinogenic risk of As, Cr and Ni for children through the ingestion route is higher than the reference value (1×10-4). In conclusion, the pollution of the studied soils with As, Pb, Cu, Cr and Ni must be considered as a concern in the study area.

Mining is a necessary activity for the development of countries, but it imposes direct and indirect negative impacts on the exploited areas and their surroundings. Sangan iron mine is one of the largest iron ore deposits in the Middle East, where the ore is extracted by open pit mining. The present study aims to investigate the soil’s concentration of heavy metals and to assess the level of soil’s contamination in the Sangan mining area. For these purposes, 44 samples of the soils (including both topsoils and subsoils) of the Sangan mining area were collected, and were analyzed by an ICP-MS device. The obtained data were analyzed by calculating the geochemical indices and statistical methods. On the basis of descriptive statistics of the analytical data, Pb with an average content of 138.39 mg/kg and Cd with an average concentration of 0.19 mg/kg had the highest and lowest concentrations in top soils, respectively. Moreover, Cr with an average value of 102.19 mg/kg, showed the highest, and Cd with an average of 0.2 mg/kg showed the lowest concentrations in subsoils. The average concentrations of As, Cr and Fe in the study area were higher than their respective values in the World-Soil Average composition. Among the elements, Pb had very high and severe enrichment in two stations with enrichment factor values of 149 and 23.85. The results indicated no severe soil pollution and ecological risk in the study area, except in some sampling sites. The most polluted soils were collected near the placer extraction units and tailing ponds of Ehya-Sepahan Company, as well as the waste rock pile of Sanabad Comprehensive Development Industrial and Mining Company.

The high K-volcanic rocks of the Eslamieh Peninsula (Saray) are exposed in the northwestern Urumieh-Dokhtar magmatic belt. They mainly include phonolitic lavas and related xenoliths. The xenoliths can be subdivided into two types with basaltic and trachyandesitic compositions. ​ The phonolites and related xenoliths are characterized by enrichment in large ion lithophile elements (LILEs: Th, Ba, Rb and K) and light rare earth elements (LREE), depletion in high field strength elements (HFSE: Eu, Ta, Nb and Ti) and flat patterns in heavy rare earth elements (HREE). They have typical high–K and shoshonitic signatures formed in ​ post-collisional arc setting. The studied pyroxenes from phonolitic hosts were crystallized at moderate to high pressures (6-15 kbar) and temperatures of 1200-1300 ̊C, whereas those from trachyandesite and basaltic xenoliths were formed at lower pressures (6-10 kbar and 2-5 kbar) and temperatures (1150-1200 ̊C and 1100-1150 ̊C), respectively. Due to the lack of evidence for melting, dissolution and the presence of accumulated microcrystals at the mineral boundary, it seems that the xenoliths were detached from the walls and been transported to the surface during magma ascent

The felsic intrusive rocks in the Piranshahr plutonic complex consist of three groups: syenite, nepheline-syenite, and alkali-feldspar granite. They are co-genetic and formed approximately 40 million years ago. Textural relationships, major oxides, and trace element composition of the selected felsic rock samples were studied using SEM, EPMA, and LA-ICP-MS methods. In the studied samples, apatite appears as euhedral to subhedral crystals with prismatic forms and has a homogeneous texture without zonation. The low amounts of MnO and the REE pattern of apatites confirm their magmatic nature, indicating that post-crystallization processes did not affect the composition of apatites. All apatite crystals fall into the fluorapatite category. The amounts of fluorine and chlorine vary in different felsic rocks, and the F/Cl ratio decreases from granites towards syenites and nepheline-syenites. The determination of the apatite saturation temperature indicates that alkali feldspar granites have a higher crystallization temperature range (858-844°C) than both syenites (818-783°C) and nepheline syenites (668-610°C). Analyzing the manganese levels in the examined apatites suggests a consistent oxidizing setting with minimal fluctuations in fO2 conditions (logfO2= -8 to -9.8). Trace elements in different apatites show significant differences; for instance, apatites in granitic samples are enriched with HFSE and rare earth elements (REE), while apatites in nepheline-syenites have a higher concentration of components such as silica, Cr, Ni, and V. The composition of trace elements and the F/Cl ratios in apatites demonstrate consistent variations and alignment with the host rock composition. The results of the apatite mineral composition confirm previous petrological findings regarding the impact of volatile phases separation on magmatic evolution in the Piranshahr felsic rocks.

The outcropping mica schists from the Silvana region, which are a component of the Silvana colored mélange complex, are situated southwest of Urmia. This region is located in the northwesternmost part of the Sanandaj-Sirjan metamorphic belt. Mica schists can be classified into three sub-types based on petrographic studies: muscovite schists, biotite-muscovite schists and fibrolite-biotite-muscovite schists. Mylonitic zone can be identified by the presence of mylonitic foliation and microstructures such as mica fish, dynamic recrystallization, asymmetrically tailed porphyroclasts, kink bands, and microfolds. The Silvana mylonites are categorized as low to medium grade mylonites based on textural and microstructural evidence. According to the structural and microstructural relations, the study area appears to have been impacted by three main phases of deformation. The first phase can be characterized by a transpressional deformation regime, leading to the formation of S1 foliation in mica schists. The dextral main simple shear component can be attributed to the second phase. During this phase, S2 foliation, mylonite zones and various folds and microfolds were developed. Ultimately, multiple fractures and microfaults were caused by the third phase of brittle deformation that affected the study area.

The Band-e-Cherk exploration area is located in the structural zone of central Iran, northeast of the city of Ardestan, and the Anarak metallogenic zone. The outcropping rock units in this area include Kuh-e-Dom metamorphic schist complex and recrystallized limestone, Cretaceous limestone sediments, Paleocene conglomerate, Eocene volcanic rocks composed of andesite, andesite-basalt, trachyte, as well as tuff and diorite intrusions. The Kuh-e-Dom metamorphic complex is of lower Paleozoic age, and includes muscovite schist to graphite-muscovite schist, epidote-hornblende-calc schist, muscovite-chlorite schist, calc schist, crystalline limestone and marble. Graphite mineralization is concentrated along the schistose surfaces of graphite-muscovite schist units, and quartz, kaolinite, illite, muscovite (sericite), orthoclase and dickite minerals are other minerals. Comparison of the temperature range for the formation of high-quality flake graphite, which is formed at temperatures above 450°C, mainly between 470 and 560°C (in the amphibolite facies), with the temperature obtained by interpreting the results of Raman spectroscopy on high-quality graphite-bearing samples from the Band-e-Cherk area, shows that graphitization in the Band-e-Cherk area is of an amorphous type and at a temperature lower than 450°C (436°C). Therefore, it was formed under the temperature conditions associated with the greenschist metamorphic facies.

The curved fold-thrust belt of North Birjand contains some outcrops of Upper Paleozoic to Cenozoic sequences that have undergone several stages of deformation. Thrusting, large-scale parallel and radial folds, penetrative shear cleavage, tectonic klippes, tensile fractures, and conjugate strike-slip faults are exposed in this structural arc. The Chah-hoz region consists of Upper Cretaceous mélanges and listvenites with NW-trending thrust sheets dipping to the NE. The Mousavieh area includes pre-Cretaceous metamorphic rocks belonging to the basement of the Lut block, Cretaceous ophiolite, and turbidite complex, and Eocene platform limestone. The dip of thrust planes in the outer part of this arc is SSE and in the inner part of the arc is generally NNW indicating the direction of regional tectonic transport towards the interior of the arc. The abrupt boundary between the Eocene-Oligocene continental deposits in the north of this arc is either thrust or characterized by two types of major folds: The first type is the parallel folds with the edge of the arc, which are often cylindrical, but under the influence of the younger generation folds, they have become non-cylindrical, and the second type is the conical folds with a radial arrangement, the apex of the cone is plunged towards the NNW.Therefore, it seems that the structures of the northern curved border of the Lut and Sistan terrains do not follow the model of common structures in linear collision mountains i.e., eastern Iran continental crust rifting and subsequent linear collision of the Lut and Afghan blocks. According to this research, it seems that the NW movement of the North Birjand platform was caused by buckling in the Late Eocene-Oligocene.

The Early Jurassic (≈180 Ma) Gowd-e-Howz (Siah-Kuh) granitoid stock is located in the southern part of the Sanandaj-Sirjan metamorphic belt, southeast of Iran in Kerman Province. This granitoid stock is intruded into the Upper Paleozoic metamorphic and Triassic igneous-sedimentary rocks and covered by Jurassic rock units and Lower Cretaceous limestones. The main part of the stock is granodiorite with medium- to coarse-grained anhedral granular texture and mineral assemblage of amphibole, biotite, plagioclase, alkali feldspar, and quartz. Biotite, as one of the main ferromagnesian minerals of this body, has a primary igneous origin and iron rich composition. The different magmatic series and tectonic discrimination diagrams indicate that the magma was of subduction zone-related I-type calc-alkaline series, crystallized under medium to high oxygen fugacity, and equilibrated at temperatures and pressures of 589 to 875 °C and 0.45 to 2.27 kbar, respectively, during magma emplacement in the crust.

The Zhaveh dam is located on the Sirvan River containing two main branches of Gaveh Rood and Qeshlaq. The dam was designed for industrial and agricultural use. Surface sediment samples were collected at 5 selected stations in the two branches of the Sirvan River, Qeshlaq and Gaveh, as well as in the dam reservoir. In this study, nine sediment parameters (different forms of nitrogen and phosphorus, TOC, pH, Eh) were investigated to determine the quality and the prediction of the eutrophication trend of the Zhaveh Dam. The quality of sediments in different stations showed that they contain high organic and mineral pollution. Based on the TOC% of the sediment, the region was considered as slightly to highly polluted, especially in stations 2 and 3, but station 4 (Gaveh Rood branch) was classified as moderate quality. The changes in the OPI and ONI indices and comparison with the organic index standard also indicated the high pollution of the sediments in this region. These conditions are due to the high mean concentration of total phosphorus (2075±178 mg/kg.dw) and bioavailable phosphorus (666±142 mg/kg.dw) in the rivers feeding the dam, which deal with a high risk of eutrophication. In addition, after the water intake of the Zhaveh Dam and the high concentration of organic and mineral pollutants during the retention time of the water, it will be difficult to control the eutrophication

The existing landfill site for Sari city is situated in an unhygienic manner in a village, at the southernmost point of the provincial capital. Unfortunately, this location has led to numerous environmental incidents affecting the local residents. In this study, a multi-criteria approach was employed using analytic network analysis (ANP) to identify the optimal waste landfill site. The evaluation process involved considering 24 layers of information, including geology, engineering geology (such as erosion, lithology, soil science, and seismicity), hydrology, hydrogeology (including rivers, dams, and well depths), topography (elevation and slope), socio-economic factors (distance from urban areas, villages, main roads, side roads, mines, and airports), climate (rainfall), and environmental aspects (protected areas and land use). Based on the findings, we selected five potential locations, with ‘Site 1’ in the southeast of Sari city receiving the highest average score and being recommended as the most suitable landfill site.

Spatial distribution of groundwater quality data and a reasonable monitoring network, which are usually collected from monitoring wells, are required for the management of groundwater resources. However, since the maintenance cost of groundwater monitoring networks is extremely high, an optimal design of those is necessary. This study aimed to find a qualitatively optimal monitoring network with a minimum number of wells in the Rafsanjan aquifer so that it could provide sufficient spatial distribution in terms of groundwater quality. For this purpose, electrical conductivity (EC) was selected as a quality parameter in the design of the monitoring network in this study. In the first step, to identify the risk and assess the vulnerability of the aquifer, the DRASTIC method was used. Then, the average Kriging standard deviation was used as a criterion for the determination of network density, and the GIS-based approach was analyzed. In this step, semi-variograms were tested to ascertain the best-fitted model accuracy measures, average standard error, root mean square error, and root mean square standardized error. The results showed that the spherical model is more reliable than other models due to the root mean square standardized error (RMSSE) being close to one, the average standard error (ASE) being close to the root mean square error (RMSE), and the less RMSE than other models. Also, based on cross-validation of data and a quality monitoring map resulting from the overlap of prediction and standard error maps with the DRASTIC map, 60 wells were sufficient as groundwater quality monitoring stations for the Rafsanjan aquifer. Removing 10 wells in different parts of the aquifer and adding 6 wells in the northwest of the aquifer will help to complete the quality monitoring network.

Deformation of microcontinents occurs during collision with a larger stable continent. Deformation is usually concentrated at the boundaries of the deforming microcontinent and depends on mechanical stratigraphy and pre-existing structures. The Alborz Mountains, located in the northern margin of central Iran underwent various deformations including Cimmerian, Laramide and Alpine compressions since the Triassic and its highest exhumation occurred in Cenozoic, as a result of the Alpine orogeny. Relocation of the Alborz Mountain front is visible in the satellite images in the Qazvin-Rasht area, where the geophysical maps also indicate changes in the basement at the subsurface. The aim of this study is to investigate possible factors responsible for this large displacement of the mountain front, using 2D numerical modeling. We designed and run five 2D models considering different parameters, such as the presence of basal and middle detachments and the effect of their thickness as well as the involvement of basement faults. The experiments show a faster movement of the deformation towards the foreland in the presence of basal detachment compared to the case without basal detachment. The addition of intermediate detachment intensifies this process. Increasing the thickness of the middle detachment increases the exhumation and deformation, especially towards the foreland. The model with a pre-existing basement fault shows very clear localization of deformation on the basement fault which causes developing the deformation towards the foreland. According to the cross sections constructed across the area on both sides of the change in the mountain front, there is an increase in the thickness of the Jurassic shale (Shemshak Formation) as a detachment level in the central Alborz, where higher exhumation and extensive outcrops of Paleozoic rocks is observed compared to the western Alborz. The numerical models with different thickness of intermediate detachments (1 and 2 km) have simulated this difference between the central and western Alborz. Considering the larger displacement of deformation front toward the foreland in the numerical model in the case of a pre-existing fault, the presence of a basement fault in the western Alborz could be assumed to cause the larger southward displacement of the mountain front compared to the central Alborz.