Researches in Earth Sciences
Year:2019 | Volume:10 | Issue:37 |Papers Count:17

In this study, the variation of daily and monthly non-divergent level in January and July in 1976-2015 long-term periods is investigated in Iran. The non-divergent level is assumed to be the lowest level between 700 and 300 hPa, in which the horizontal divergence is zero. To calculate the horizontal divergence at the standard pressure levels, the zonal and meridional wind components are extracted from the NCEP / NCAR archive. In Iran, nine points were selected in different regions, and the vertical profiles of divergence and Omega are analyzed. The daily survey of vertical profile of divergent in case study shows that, because low pressure (highs) is accompanied with convergence (divergence) in the lower levels and divergence (convergence) at high levels, at least one non-divergent level exists in the areas affected by these systems. The height of non-divergent level depends on the depth of the underlying convergence, so the deeper the underlying convergence or divergence, the height of the non-divergence level will be more elevated. Actually the non-divergent level of the heat lows )highs( are seen in lower levels. The mean monthly height of non-divergent level in the statistical period indicate that it is lower in July in the northwest, west, southwest, center, south, east and south east of Iran. This condition is created by the dominance of the heat low and its shallow convergence in July. In the north and northeastern of Iran, the non-divergent level is lower in January than in July. These areas are less affected by heat lows in July. The study of the trend of changes in the mean monthly height of non-divergent level in the long-term period showed that there is an upward trend in western and north-eastern of Iran and downward trend in southern and central of Iran in July. This condition is indicating an increase convergence depth of the heat low-pressure in southern and central (western and north-eastern) of Iran.

The first and most important step in reducing damages and management of gully erosion, which leads to waste of water and soil resources, is the gully erosion susceptibility mapping. In present study, the potential of gully erosion in the Toroud-Najarabad basin were evaluated using the uncertainty of the theory of evidence method and linear multivariate regression as well as the combination of the above-mentioned methods. In view of this the gully erosion inventory map was prepared using various resources, and from 218 identified gullies, 70% (154 gullies) and 30% (64 gullies) were selected randomly for modeling and validation respectively. In the next step, 14 controling factors in the gully occurrence in the study area including topographic, geomorphometric, environmental and hydrologic parameters were determined for modeling. The results of multivariate regression model showed that land use parameters, slope and distance from the road had the greatest impact on gully occurrence. Susceptibility maps classified to five susceptibility classes of very low to very high. The area under curve (AUC) and Seed Cell Area Index (SCAI) were used to validate the susceptibility maps. The results of the validation showed that the combined model has a higher area under the curve (AUC) (0. 933) toward the evidence-based (0. 914) and multivariate regression (0. 890) models, as well as, the SCAI value in the combined model showed that very low susceptibility to a very high susceptibility has a downward trend that indicating a proper separation of susceptibility classes in this model. Considering the excellent precision of the combined method proposed in this research, the results of this research can be used by decision makers and local managers to reduce losses and the methodology presented in this study can be used in similar areas to determine the areas that are susceptible to gully erosion.

Deposits of terraces and alluvial fans are an important part of the sedimentary series of the Quaternary period that represents the characteristics of their upstream basins. In this study were determined 14 samples of these deposits were collected from the catchment of Kalshoor River in northeastern Iran. In each sample, geochemical and sedimentary characteristics, texture and particle size, element oxides of each of them were investigated. The particle size distribution of the sediments indicates average roundness, poor soreness and normal graining with sand, gravel and sandy gravel. The tectonic setting of these sediments on basing geochemical diagrams placed in the oceanic arc and continental arc setting. Also, determining the effect of weathering in the source area of these deposits using the chemical index of alteration (CIA) suggested the low degree of weathering and dry weather conditions in the source area.

Despotic rule is one of the governmental forms accoss the world. It goes back to the dawn of man’ s political life. In terms of structure, technique of political administration and nature, despotism comprises of a government on top of which there is an authoritative and autocrat person with totalitarian power where no rule and law and tradition and norm may restrict and bar his/ her behavior. Despotic rule is assumed to be different from dictatorship. Dictatorship is the ruling by high class or limited governing group that requires their political power and behavior to observe a series of certain rules and prevalent norms in the community. This makes it different from despotism. For centuries, structure of governments in the Persian Gulf region has been mainly influenced by geographic environment and factors that generally acted as platform to form a rulling system. The present essay has been conducted by descriptive-analytic method in order to identify effective factors in he formation of despotic governments in the Persian Gulf Region. The results of study show that some factors including geographic situation, water and farming status, rentier governing bodies, security pacts, religious system, tribal and ethnic system are led to the formation, composition, development, and persistence of despotic governments in this region.

Production efficiency is a basic factor in the economic and social conditions of each country. It usually leads to further efforts by producers and motivation for innovation and investment. Iran's agricultural situation shows that this sector lacks efficiency in most regions. This problem is rooted in many issues such as dependence of the country on oil revenues, neglating the linkage of agriculture with the industry in macro policies, as well as specific conditions and characteristics of local rural areas. This research was conducted with a qualitative approach with theoretical saturation logic through the participation of 71 farmers and 15 local experts on the basis of an analytical-descriptive method through interviews that identified three categories of factors, issues and the consequences of reducing agricultural efficiency in selected rural areas. The results of the research show that factors such as inappropriate land structure, weakness of work force, lag in mechanization, weak management of water harness and lack of distribution and storage infrastructure are among the main categories of decrease in agricultural efficiency. This is rooted in issues such as: lack of a comprehensive agricultural development plan, lack of serious attention to the issue of education and promotion in agriculture, in efficient investment in agricultural infrastructure, slow growth of mechanization, lack of comprehensive economic programs for adapting systems of planting and harvesting to the environment of the regions, etc. These conditions have affected the agricultural sector in rural areas with consequences such as land use change, the with drawal of agricultural producers from productive activities, rural youth migration, reduced food security and the change in the structure of rualemployment.

To assess the capabilities of historical tourism and improve its performance, it is necessary to analyze the existing and potential capabilities of historical tourism and its role in sustainable rural development. Historical tourism sites require development of infrastructures and welfare and supportive services. The spatial effects of tourism and its environmental, ecological, social, economic, and physical consequences can either be positiveor negative. This affects the development of rural tourist destinations. This study ries to assess the effects of historical tourism capabilities in development of rural settlements. In this descriptive and analytical study, 319 households were randomly selected from12 rural settlements of Soltaniyeh area. The variables used to measure the level of development of rural settlements included 79 items in environmental, ecological, tourism resources, socio-economic and physical dimensions. In addition, the effective component was determined by 14 indicators. The results showed a significant positive relationship between indicators such as capabilities to attract tourists, and the capabilities to create catering units and welfare facilities with indicators of sustainable rural development in Soltaniyeh area. In contrast, the capability of creating tour groups and the capability of creating residential units and supportive services are not found o have a positive place in explaining of sustainable rural development of Soltaniyeh area. Therefore, promoting indicators of historical tourism capabilities components is essential to be considered by policy makers and tourism administrators as an effective strategyfor achieving the sustainable rural development goals.

High ground watertable is one of the main problems that can disrupt the tunnel construction. The prediction of groundwater infiltration into the tunnel is very important subject for preventing problems during drilling and designing drainage system. Therefore, it is necessary to consider the amount of water flow and drainage model in the design, thus, it is necessary to forecast quantity of water flow and the drainage model and consider them in design stage. For this purpose, to present a dewatering design in the eastern part of Tehran Metro tunnel Line 7, the cross-section of 4+ 500 + 4 +600 Kilometers, two drainage galleries with a length of 14 meters were used. Modeling and estimating the entering water into the tunnel requires detailed and accurate information about soil hydrodynamic properties. Also, the accuracy of modeling and numerical analysis and comparison with actual conditions for optimization of the design is very important. One of the best methods for evaluating these parameters in ground mass scale is back analysis according to experimental results. Ground water infiltration into two galleries was calculated for the whole length of the tunnel in steady state, using from finite element and finite difference methods in PLAXIS® and FLAC® softwares. Then, from the data obtained from the Lefranc test, the value of the soil hydrodynamic parameters were estimated by the method of back analysis. The obtained results indicate the value of the method of return analysis compared to the Levfran method for measuring permeability with the same data. The measured value of groundwater infiltration in field tests was 600 cubic of meters per day and the error of the finite element and finite difference methods is equal to 12 and 4/8 percent, respectively, which are in a good agreement with the field measurements. The optimum value of permeability parameter obtained from back analysis equal to 4. 5  10-5 and 3. 6  10-5 meters per second was set for this area as well as optimum transmissivity equal to 117 and 214 meters per day.

The central part of Fars province of the Zagros fold – thrust belt has complex geological structure and geometry probably due to activity of major basement strike slip faults. In this research numerical modelling were used considering different scenarios of the possible roles of Sarvestan, Sabz-Pushan and Nezam-Abad faults for strain distribution modelling. Models were constructed using FEM method and Mathematica software applying local convergence direction of Iranian and Arabian plates in the Fars area and different scenarios of presence of each of three faults. Results revealed vital role of the Nezam-Abad fault in coeval activity of Sarvestan and Sabz-Pushan faults at the time in forming of the geometry of the study area.

Fuzzy analytical hierarchy process (Fuzzy-AHP) technique as a knowledge-driven approach relies on the geologist’ s input to weight the importance of each evidence layer is applied for prospectivity modeling of Au mineralization within the Takhte-soleyman district. Firstly, in current study, all of the criteria and sub-criteria which are gained from exploratory data (geochemistry, remote sensing, geology and tectonic) are weighted by using AHP and thereafter are transformed into [0-1] range based on the fuzzy logic. All fuzzified layers according to the calculated weights were synthesized and prospectivity modeling of Au mineralization based on the Fuzzy-AHP technique was generated. In this study, it was used another fuzzy method based on the fuzzy operators (OR and GAMMA) that called “ Fuzzy-GAMMA” to generate the map of promising areas of Au mineralization in the study area. Finally, in order to evaluate the ability of the applied methods in delineating reliable promising areas, locations of Au occurrences in the study area were used. Consequently, the results demonstrate the more acceptable outcomes for Fuzzy-AHP model by comparison with Fuzzy-GAMMA model.

According to strong evidence based on existence of relationship between rare earth elements and radioactivity, sampling from Baghak anomaly in Sangan mine (NE of Iran, in Khorasan Razavi province and near the border of Iran-Afghanistan) has been carried out based on radioactivity and radiation measurement methods. In fact, the goal of this study, in addition to the presence or absence of such relation in a skarn mine, is introducing and providing an exploration method and optimal sampling pattern to explore REE and investigation of REE distribution in Baghak mine. Results of the microscopic studies and statistical analyses show that there is an acceptable correlation between these elements in Sangan Fe-skarn mineralization in addition to presence of such relation in central Iran’ s mineralization. Chondrite normalized REE pattern shows enrichment of LREE and a positive pattern close to flat HREE due to the entry of LREE ions into allanites network. Moreover, REE patterns show negative Eu anomaly in whole rock. Primitive mantle normalized multi-element patterns are enriched in LREE (La, Ce, Pr, Nd), large ion lithophile (LILE, Cs, Rb, Ba, K), radioactive elements (Th, U), and are strongly depleted in high field strength elements (HFSE, Y, Zr, Ta, Nb, Ti) and HREE (Yb, Lu) compared to the primitive mantle. These features are typical of the subduction related magma.

The Sahneh fault with about 100 km length and strike-slip mechanism is located in the central parts of the MRF and divided into three segments as south-east, central and north-west sections. Firstly, in this study fractures and structural lineaments of the Sahneh fault zone have extracted using remote sensing techniques, Landsat satellite images and digital elevation model. Then, with fractal analysis of the fractures and lineaments of the study area, fractal dimension has computed for determination of high-density fractured area and detailed field studies. Fractures and lineaments of the region have a main trend near the main fault and indicate a high density near the fault zone. A fault plane with N60W/75SE strike, dip and 15S slip vector rake have obtained from the field studies along the south-east segment that indicates right-lateral strike-slip movement of the fault with normal component. Along the central segment, right-lateral movement of the fault caused about 16 km drainages offset. In the north-west segment of the Sahneh fault, a right-lateral offset along the drainages is visible and about 850 m offset have evaluated with restoration of the drainages to the initial stage.

The Shirbit polymetal prospect area is located in 30 km north-east of Ahar city within the Ahar-ore filed in around of Shivardagh batholith. Intrusion of granodiorite igneous bodies into the Eocene trachyte to andesite associated with pyroclastic interlayers caused widespread silicic, argillic and propylitic hydrothermal alteration associated with the Cu, Mo, Pb mineralization as quartz-sulfide (± oxide, carbonate, sulphate) vein and veinlets. Most of chalcopyrite, pyrite and molybdenite veins together with malachite, azurite and iron hydroxides were concentrated in the trachytic-andesitic units with silicic-argillic alteration. The turning point of this study includes investigating the possibility of log-log C-P method for separating geochemical anomalies of ore forming elements from the background, accurately determining the cut-off grade, decreasing the area of anomalies, and determining the number of stages of enrichment of elements in the study area compared to the multivariate statistical methods. For this purpose, 85 stream sediment samples taken from a systematic geochemical network were analyzed using ICP-MS method. In order to identify the susceptible mineralization areas by using of concentration-perimeter double logarithmic method, thee background values and anomalies were separated for each element in the region. Then, elemental anomaly maps were prepared and finally the distribution maps of the ore-forming elements were mapped and the relevant anomalies were distinguished. The results of using C-P fractal method indicates the presence of possible anomalies of Cu, Mo and Ti elements in the eastern, northeastern, and southwest parts of Shirbit area.

In order to understand the dolomitization processes in the eastern margin of the foreland Zagros sedimentary basin, the dolomites of Shahbazan Formation in the outcrop, located 6 kilometers north-west of Semirom, were studied by petrography and geochemistry. The Shahbazan Formation with a thickness of 74 m conformably overlaid on the terrigenous rocks of the Kashkan Formation and was covered disconformably by carbonate rocks of the Asmari Formation. Based on field evidence, petrography (including polarizing microscopes and SEM) and geochemistry of major, minor and rare earth elements (REE), four types of dolomites have been identified in the Shahbazan Formation. The results of this research indicate that the formation of very fine to fine crystalline dolomite occurred in tidal flat and other dolomites have been formed in shallow to intermediate deep burial diagenetic environments by moderately saline marine fluids (mean Na 363 ppm), via seepage reflux of evaporate seawater into the Shahbazan Formation platform. The similar distribution of the trace element versus Mg and REE pattern in the three dolomite types indicate that the Shahbazan dolomites formed a single diagenetic fluid with similar origin. The difference between the dolomite crystals size indicate variable water-rock interaction, temperature and depth of burial.

One of the potential areas for metal indices such as iron is located in the North East part of Isfahanand. There are extensive outcrops of granitoid mass in the studied area and its surroundings (karkas granite) which have been cut most stratigraphic units before Oligo-Miocene. Lithology of the area consists of fine to coarse sandstone, massive dolomite, and cream-colored limestone with fossils and massive intrusive in the region. According to its frequency, quartz monzonit, quartz monzodiorite, granodiorite and granite are the most abundant which are formed from subduction zone before collision and are the type (VAG). In terms of magmatic arc these are calc-alkaline series (CAG), which dactial tails has penetrated through these granites. Volcanic rocks include porfirodacite, andesite and quartz latite with the age of Pilocene to Miocene. Iron was originated from semi-deep magma with high heat, passing fiuids with elements to above horizons and attack limestone and dolomites creating skaran, with mineralogical composition of andradite, gersular, hesonite, epidote, lipidcrolite, zeoizite, and hedenberzite. In addition, hydrothermal fluids resulting in minerals alteration and formation of kaolinite, chlorite, montmorillonite and sericite. The supergene phenomenon has important role in enrichment of iron ore in surface, which main evidences is cap iron (gossan). Kamoo iron mine is located above it and mainly consist of iron ore minerals such as magnetite, hematite, limonite, goethite and other Parageneticmenirals. Magnetite and sulphide mineral such as pyrite and chalcopyrite and with magmatic origin are the first generation of skarn mineralization. Alteration by magmatic fluids is the second generation and supergene phenomenon are third generation of mineralization (forming hematite, limonite, covelite and goethite) in kamoo region. Thus, the main genesis of iron ore in kamoo is epigenetic hydro-thermal.