نشریه علوم زمین خوارزمی
سال هشتم شماره 1 (بهار و تابستان 1401)

Karst springs in the western and eastern regions of Ilam province have different physical and chemical characteristics. The springs of the western regions, are sulfuric and thermal with high salinity, while the springs in the eastern regions are fresh and cold. Geological, hydrogeological, hydrogeochemical and isotopic studies were performed to compare and determine the factors affecting the physical and chemical properties of these springs. Monitoring of the springs, including measurement of discharge, temperature, acidity, amount of hydrogen sulfide gas, dissolved oxygen in the field, and analysis of major ion chemistry, was conducted monthly for two years. Deuterium and oxygen-18 stable isotopes were measured during two dry and two wet periods to determine the source of the water. Field studies have shown that the geology of the eastern and western regions of Ilam Province is different. Deep faults have affected the western regions, and some calcareous formations have changed facies so that they have anhydrite members. The deep faults of the western regions of Ilam Province have caused the hydraulic connection of karst formations with the old and lower evaporite formations. The ratios of Na/Cl, SO4/Cl and TDS/Br showed that the salinity of the sulfur springs originates from the dissolution of evaporite formations and is not related to the oil field brines. The results of stable isotope analysis of deuterium (2H) and oxygen-18 (18O) in thermal and sulfur springs showed that the origin of these springs is the local meteoric precipitation. The origin of hydrogen sulfide (H2S) of sulfur and thermal springs was attributed to the activity of sulfate-reducing bacterias. According to the hydrograph of the springs, rainfall affects the discharge increase of fresh and cold springs less than one month; while, the discharge of sulfur and thermal springs increases about two months after rainfalls. In other words, the infiltrating waters that recharge the sulfur springs have a deep circulation. Therefore, the high temperature of the springs in the western regions of Ilam Province is attributed to the deep circulation of infiltrating waters from local precipitation along the faults.

Concerns about dust contamination with potentially toxic elements are especially important in environments such as schools (particularly elementary schools) because children are more vulnerable to contaminants than adults. Therefore, due to the diversity of air pollution sources in Tehran, the present study was conducted to determine the severity of pollution, origin and health risk assessment of some potentially toxic elements in the dust of elementary schools in three districts of Tehran. For this purpose, 27 dust samples were collected from the indoor and outdoor areas of schools, and the concentration of elements was measured by induced coupled plasma mass spectrometer (ICP-MS). Calculation of different geochemical indices showed that the four elements Cu, Zn, Sb and Pb have the highest enrichment and pollution compared to other elements. The results of calculating the health risk index revealed that As, Cu, Ni, Pb and Zn have similar hazard quotient (HQ) values in children and adults. Also, the health risk of exposure to Cr and Mn through dermal contact is higher in adults than in children, and the total hazard index (HI) of all elements in children is higher than in adults. Among the studied elements, two elements, lead and chromium, threaten the health of children more than others. Based on principal component analysis and positive matrix factorization (PMF) model, three geogenic, traffic and mix sources were identified for different elements. Pb, Zn, Cu and Cd were considered as indicators of traffic origin. The results of this study reveal the need for special attention to students' health.

In this paper, metamorphic conditions (T, P and fluid composition) in greenschist to amphibolite facies transition zone are investigated using textural evidence, composition of the minerals and phase diagrams. Metabasites from the south of Kordestan Province were metamorphosed from sub-greenschist to upper amphibolite facies. Field observations and petrography studies show that there are some rocks containing mineral assemblage hornblende + plagioclase + epidote + quartz formed in conditions intermediate between greenschist and amphibolite facies. Electron microprobe analysis and scanning electron microscopy images reveal that the amphiboles have chemical zoning with actinolite cores and hornblende rims and these chemical changes are discontinous. The plagioclases are commonly oligoclase but there is some remnant albite. The epidotes are enriched in Fe with low clinozoisite contents. Geothermobarometry calculations using the amphibole compositions represent 423 °C and 2 kbar for the cores and 543 oC and 4 kbar for the rims. The calculated phase diagram based on whole-rock composition of a sample indicates that it was formed in 450 to 550 °C and 2.1 to 6.8 kbar that fall in the field of epidote-amphibolite facies condition. The O2 and CO2 vs. T variation phase diagrams show that O2 had a significant role formation of the mineral assemblage but the fluid contained very low CO2. Chemical discontinuities in the amphiboles and the plagioclases with different compositions demonstrate that the studied rocks formed in disequilibrium conditions.

The Naft anticline is located in the NW-SE of the N Lurestan sub-zone and the Zagros fold and thrust belt. In this sub-zone, the structural geometry of the folded sequence is significantly influenced by the basemen thrust and strike-slip faults and detachment levels. In this research, for the geometrical analysis of the Naft anticline, we utilized the structural profile perpendicular to the anticline in the central region, information from drilling wells in the study area and neighboring anticlines, and the deformation pattern and structural geometry of the Naft anticline. The anticline has two upper (Amiran Formation) and Middle (Garau Formation) detachment levels. The basement thrust faults and detachment levels in the southwestern limb had a significant impact on the folding geometry and led to the formation of disharmonic folding. An N-S basement strike-slip fault in the middle part of the anticline has shifted the anticline axis from N70W in the northwest to N50W in the southeast. In addition, the minor and shallow thrust faults propagationg from the upper detachment levels or the independent thrusts in the Gurpi Formation resulted in the development ofan axis of two kink and curved hinges in the middle part of the Naft anticline in folded structures. The analysis of the geometrical parameters of the Naft anticline shows that it is an asymmetrical and noncylindrical fold, categorized as an open half-angle fold in terms of tightness.

The continuous development of the oil industry has led to a significant increase in the number of wells that are simultaneously analyzed. For this purpose, it is important to develop methods that improve the integration of all well information at different scales, while reducing the time required for studies. This article examines the integration of image log (FMI) with other conventional logs (gamma, density, neutron and sonic) to determine electrofacies in the Gadwan Formation in one of the oilfields in Abadan plain, SW Iran. Due to the high resolution, the image logs can provide important information regarding sedimentology, texture, and porosity distribution. This information is very valuable in situations where it is not possible to core from the Formation. To accurately estimate, the necessary environmental corrections were applied to conventional logs. In the next step, electro-facies were created by integrating conventional logs and image log using the graphical clustering method (MRGC) in Geolog software and with the FACIMAGE™ module and finally, the model with 8 facies was selected as the optimal model. Among the determined facies, the electrofacies number 8 was recognized as the best reservoir facies (due to high effective porosity and low shale volume). Comparing the results of lithology, shale volume, porosity and water saturation with the facies determined by the cluster analysis method showed that the use of image logs has greatly improved the separation of electrofacies.

The aim of this study is to determine the ambient concentration, content of heavy metals and morphology and mineralogy of PM2.5 samples collected from air pollution monitoring station in Haft-Tir square (central Tehran). For this purpose, PM2.5 samples were collected by means of low-volume sampling device during five months (April-August 2019). Based on the obtained results, there is more loading of PM2.5 on June higher that 10 μgm−3 and showed high to very high pollution level. Variations in metal concentration in the sampling months were relatively similar, showing order of Zn>Ni>Pb>Cr>Cu>Cd. Comparing the mean concentration of metals with international permissible limits the concentration of Pb and Cr in PM2.5 samples was lower than that of recommended by the WHO while the average concentration of Cd and Ni was higher than those of USEPA recommended limit. Calculations of enrichment factor and results of principal component analysis revealed that Cr is of geogenic origin, Cd and Zn are derived from anthropic sources and Pb, Cu and Ni are probably of mixed sources. Based on scanning electron microscopy images, PM2.5 are observed as a shapeless or irregular, rod-shaped, irregular spherical, completely spherical, sheeted, as well as long chain aggregates or single crystals. According to the results of X-ray diffraction analysis, clay minerals, quartz and calcite were found as major minerals, gypsum and dolomite minerals were identified as minor minerals and wüstite and halite minerals were identified as rare mineral phases.