Researches in Earth Sciences
Year:2011 | Volume:2 | Issue:6 |Papers Count:7

NW-SE trending North Siah anticline, a part of Zagros fold and thrust belt (Coastal Fars) is situated in eastern part of Kazeroon fault. In this papar North Siah anticline has studied for structural analysis. In this direction, structural cross sections of this anticline are drawn using structural survey, data from the closely located drilled wells, seismic line and surface stratigraphic sections. Based on geometry analysis by Mitra method, North Siah anticline was located in the range of symmetric faulted detachment fold. For kinematic analysis of mentioned anticline Poblet and McClay methods was used and results indicate that geometry of Kuh-e Siah anticline is the same as geometry of detachment folds presented by Dahlestrom (1990) and therefore its kinematic evolution is valid based on Poblet and McClay models.

Mohsen Ebneh Ali area is located southeast of Borujerd and in the northwest of Sanandaj-Sirjan zone. Main lithology of this area includes Mesozoic volcanosedimentary rocks which were metamorphosed in greenschist facies. The major types of alteration include propylitization, silicification, carbonatization, hematitization and sercitization. Among those, propylitization are pervasive whereas, silicification and carbonatization are usually limited to the mineralization zone. There are close correlations between lineament structures and alteration zones in the area (Base on analysis Landsat ETM+ data). Lithogeochemistry is being routinely applied to gold exploration. Multi-element results undergo one stages of assessment: utilization of minor and trace elements let to identification of anomalous spots for determination of blind gold deposits in the study area. According to the present study, gold-anomalous zone is in the centeral part of map and perpendicular to metavolcanic rocks. Dominant host rocks of the anomaly are intermediate and mafic metavolcanics. Data accomplished enrichment of Ag, As, Sb, Zn, Pb, and Cu in Au anomaly. Calculated correlation coefficient in correlation matrix of elements showed a maximum gold positive correlation with As(+0. 81), Ag(+0. 73), Cu(+0. 68), Pb(+0. 64), Zn(+0. 63). Mineralization is considered a vein type and anomaly is hosted by metavolcanics which are mainly associated with silicic and iron oxide altration. The results of analysis show that gold content ranges from 0. 07 to 0. 5 ppm in quartz-carbonate veins and 1. 74 to 9. 8 ppm in quartz-Fe-oxide veins. The identified minerals in mineralographic studies are pyrite, chalcopyrite, bornite, covolite, malachite, hematite and goethite. Based on alteration, host rock, geometry of mineralization and mineralogy in the study area, gold mineralization is related to lineament structures and faults.

Study area in Saghand fifth anomaly has located in central Iran zone and Bafgh-Posht-e-Badam metalogeny belt. Uranium, thorium and Rare Earth Element mineralization are hydrothermal and metasomatism type related to area intrusion body (granite and gabbro available in north of the study area). Uranium concentration of hydrothermal type followed to deep fractures system and remain around of magnetite body, the cause suitable geochemical, and alkalan metasomatism phenomena with uranium, thorium with rare earth element are important metalogeny cycle in central Iran and study area. Because purpose of article is assessment of radioactive element in area Saghand fifth anomaly, because these elements were lithophile and their concentration is granite magmatism and basic. Radioactive element (U, Th), in metasomatit and igneous rocks, that we separate alterations of uranium and thorium with remote sensing method. Alterations related to U and Th hydrothermal mineralization are hematitization, argillic, carbonate, chloritization and silicates. Total features have processed in this article contain argillic alteration (kaolinite, montmorillonite, illite), prophylitic alteration (epidote, chlorite), siliceous alteration, Fe oxides (hematite, magnetite, goethite) carbonate (calcite, dolomite) and albite, with major and minor lineaments. Using methods for alteration extraction are LS-Fit (Linear Band Prediction), Matched filtering (MF), Spectral Angle Mapper (SAM) and Spectral Feature Fitting (SFF), Ratio band and visual interpretation. The result comparison of different algorithms illustrate that best algorithm for argillic alteration extraction are Matched Filtering (MF) and Spectral Feature Fitting (SFF), Carbonate alterations are Matched Filtering (MF), 7+9/8 band ratio with visual interpretation, argillic and carbonate alterations used visual interpretation with RGB: 468 that carbonate seen yellow and, argillic is pink-red color. Prophylitic alterations are Matched Filtering (MF) and 6+9/7+8 band ratio and best method in identification of siliceous alteration is 12/13, 13/12 band ratio. Fe oxides alteration used with LS-Fit and 2/1, 3/1 band ratio. Best method for albite is Matched Filtering (MF), LS-Fit (Linear Band Prediction). lineament extracted with visual interpretation in color composite RGB: 741, 742 with ETM and Aster satellite image.

The Dalan (Permian) and the Kangan formations (Triassic) which are the largest gas reservoirs, contain 50 percent of gas reserves in the Zagros region and the Persian Gulf. The Dalan Formation with carbonate-evaporate facies overlies the silisiclastic Faraghon Formation and is overlain by the carbonates of the Kangan Formation. This study aims to identify microfacies and interpret the sedimentary environment and diagenetic processes of the Dalan Formation in well #X in the South Pars Oil field. Microscopic studies resulted in identifying four facies with abbreviations A, B, C and D. In terms of sedimentary environment, these facies belong to four facies belts: tidal flat, lagoon, carbonate shoal and open marine. According to identified microfacies, these carbonate successions were laid down on a carbonate platform, a homocline ramp type. The most important diagenetic processes in this study is anhydrite and dolomite formations. Anhydrite cement is very common diagenetic processes after dolomitization. Petrographic studies of the Dalan Formation in this area indicate that anhydrite cement as a diagenetic product, has blocked most of the existing porosity. Among the different textures of anhydrite, the pore filling and pervasive texture has the greatest effect on reservoir quality. Distribution of anhydrite and with its extension within dolograinstone and grain-supported dolopackstone facies, and filling of the entire pore during shallow burial, has greatly reduced their reservoir quality. But on the other hand, due to the solubility of anhydrite cement in the later stages of diagenesis, and creation of secondary porosity, their reservoir quality has improved. The results of this study show that anhydrite cement has formed mostly in dolomitic facies which suggests the effect of sulfate and magnesium-rich brines is in the process of dolomitization. Four types of dolomites have been identified according to the petrographic studies. Four flow units and eight reservoir zones have been recognized for Dalan sequence using porosity and permeability data, petrophysics logs, Lorenz method and log FZI.

Nowadays, the complex dimensions of urban issues and different variables, especially the role of natural factors in urban planning, has resulted in using special models and certain methods. GIS and multi-criteria decision making methods together can be useful tools that are considered in the future development of the town's zoning. Diwandareh is considered as a node connection within the Kurdistan province and is a developing town, which is located in a mountainous region. In this study after the identification and investigation of topography and geomorphologic efficient factors in town developing process, by using the geographical information system and analytical hierarchy process zoning of prone regions of physical development of town has been done. Based on the results of the analysis and modeling by using GIS tools and Expert choice, zoning map of land suitability has been prepared in the Diwandaerh town. In this regard paired-wise matrix method have been used for comparison between criteria; By applying the index coefficient and overlying them, the final map of land suitability is classified into five classes of suitability. According to the study, 28. 2 percent of the study area (33. 8 km2) located in regions with high and very high suitability, are respectively located in the southeastern and eastern part of the case study area.

Extreme temperatures have been analyzed using the daily minimum temperature data from four meteorological synoptic stations including Tabriz, Orumieh, Ardabil and Zanjan, which have long term data and statistics and also the index of north west Iran. In order to identify and analyze the extreme temperatures of the north west region of the Iran, a kind of index called Normalized Temperature Deviations (NTD) is applied, where the NTD has been already introduced by Japanese meteorologist. Using the NTD and considering the intensity of the occurrence and the extent or the comprehensiveness, the 80 days of comprehensive extreme temperature have been identified in the study region. Results obtained by using the NTD index approach which is applied in this research for identification and analyzing of the extreme temperatures and in studies done by using the NTD approach, show that the NTD is a fine procedure for distinguishing, separating and analyzing the daily extreme temperatures of the climate of study region. Considering the idea that the NDT index calculates the daily temperatures changes in each day of a year based on the temperature average deviation of the day in the long term average of that day, one of the most significant advantages of the NDT approach is its usage in the synoptic studies and the selection of days for study.

One of the slope instability forms is land sliding which causes human loss and economic damages. In the basins of northern Iran, a combination of natural and human factors have intensified this phenomenon and resulted in numerous damages One of the main solutions for decreasing the landslide hazards is keeping distance from higher danger areas. For this purpose, it is necessary to prepare the landslide susceptibility map. In this research, after field studies in the Vasetan basin, nine factors including slope gradient, aspect, elevation, precipitation, distance from road, distance from fault, distance from drainage, land use and lithology as effective factors in landslides occurrence have been studied. After preparing the information of these nine factors in GIS environment using Arc View software, every layer has been crossed with the landslide layer to find the role of corresponding layer in the formation of landslide. Then susceptibility mapping was performed with five methods including information value, valuing area accumulation, Analytical Hierarchy Process (AHP), Kopta-Joshi proposed method and multiple regression. Finally, in order to evaluate the verification of the susceptibility mapping, the obtained weights from the Vasetan basin using the above five methods were used for the adjacent basin (Varakee basin), which has similar characteristics to the Vasetan basin. Results showed that Multiple Regression gives better results for landslide susceptibility mapping of the area.