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.