مجله زمین ساخت
پیاپی 15 (پاییز 1399)

Structurally, the Tarom Metallogenic Zone is located in an NW-SE trending anticline with 50 km wave-lenght, consists of the Karaj formation equivalent units and Neogene red beds. This anticline was created during the Alborz orogen formation- related phase has multiple fractures with NW-SE, NE-SW, and E-W trend. Detailed mesoscopic and microscopic investigations of the existing fractures for studying their propagations during folding, including their relative age, sequential deformation of the fractures in various beds, distribution of the fractures, and their changes during the following geological events, were performed many times. Comparison of various fracture patterns in folded layers not only illuminates the brittle deformation successions but also resulted in the detection of the main fold formation mechanism of the studied area. Based on the existing evidence at limbs of the anticline including 1- The existence of parasitic folds in soft layers, 2- Creation of layer- parallel shearing related strata-bound fractures in soft layers on various scales. Dyke intrusion into pre-existing fractures at fold limbs, preferentially has been happened in soft beds, especially in the Karaj formation equivalents pencil shales. While at the hinge zone, they have been created in hard layers, for example, andesite and basalt. The flexural slip mechanism is proposed for the Tarom Anticline.

The Kashan fault zone is located 30 km Southeast of Kashan with strike NW-SE and 80 km lengt that propagated in the middle part of Urumieh-Dokhtar magmatic arc. This fault zone intersects Eocene-volcanic intrusive, Oligocene conglomerates, Oligo-Miocene carbonate masses, Neogene and Quaternary sedimentary Units. In this research, reconstruction of paleo and neo-stress and structural evolution of Kashan fault zone has been assessed.  The collected structural data indicates the NW-SE trend and right-lateral transpression for main Kashan fault as the main fault zone in the region. The result of paleo-stress inversion and collected structural data indicate that after likely Middle Miocene (ca. Upper Miocene) the regional stress regime has been changed in which the direction of the maximum compression changed from NE-SW to N-S. The new N-S directed maximum compression caused the propagation of the E-W trending folds of the Neogene sediments and right-lateral kinematics of Kashan fault zone in the area. Furthermore, new N-S directed maximum compression formed the N-S trending grabens that have been filled by Pliocene and Quaternary detrital deposits.

The study area is located in sheet 1: 100,000 Ghaenat, 15 km east of Ghaen, South Khorasan province. Interpretation of aerial magnetic data and extraction of magnetic lines along with processing of satellite data indicate the orientation of fractures and major structures in three important directions NS NW-SE, and NE-SW in the region, respectively. The The purpose of this study is to investigate the structural elements in the region such as faults, joints, veins, dikes and to determine the characteristics of faults in the region by emphasizing the mineralization potential of faults and to identify promising areas for copper exploration in the region. The application of a compressive-shear regime creates a tensile space followed by the infiltration of mineralized hydrothermal solutions and extensive alterations. With the development of green schist facies in the area, silica and carbonate are released and the cavities are replaced by malachite (copper oxide), which has led to the formation of malachite nodules within andesitic units. The junction of joints and faults in the study area (faults with northwest-southeast direction and joints with northeast-southwest direction) has high grade mineralization.

Fracture intensity map is important in quarries for correct location of face, reduce stone crushing and economic efficiency. In this study, the fractures surveyed in Lashotor stone quarry complex, 20 km south of Isfahan city as one of the most famous building stone quarries in Iran. Strike of major fractures are N-S, E-W and others are showing mostly NW-SE strike. The fracture intensity map was drawn in Arc GIS software for identified fractures based on augmented circular scaling method. Then Faces were mapped in fracture intensity map which demonstrate inactive faces exist in high fracture intensity areas .Thus, this kind of study is very important and needed for primary stages of exploration and extraction of building stone quarries. Also, Riddle model was drawn considering Kolah- Ghazi fault with strike of 135° and reverse and dextral strike- slip components. Identified fractures are almost fitted perfectly with the Riddle system of the Kolah- Ghazi fault.

Behlgard shear zone in eastern Iran has deformed Eocene flysch on the border with the ophiolite sequence south of Birjand. In field studies of the region, small-scale structures that are formed in brittle-ductile deformation have been considered as strain marker for assessing local deformation. For this purpose, first analytical methods based on the geometry of pattern of extension fractures, foliations, deflection of markers and initially elliptical particles have been used then these methods are compared and the limitations of their use are discussed. In the estimated values of strain using extension fractures and the curvature of foliation, the area under the distance-strain curve determines the mean shear strain (γ mean), which should be introduced by parameter of the intensity of strain localization (Iloc). In using foliations in determining the strain, recognizing the relationship of this type of fabric with regional structures, the difference of strain patterns in shear zones with parallel and wedge-shaped walls, foliation refraction affected by the behavior of rocks, It is important and should be considered on a regional scale. Graphical methods such as Lisle (2013) due to the simplicity and calculated parameters of shear strain and volume change as compared to other methods is preferred. Methods for calculating the mean of Rf data due to the simplicity of determining the Rf parameter in elliptical markers and simple mathematical calculations to determine deformation at the regional scale. In applying different methods for determining deformation parameters, in order to control the validity of the assumptions and accurate assessment of multiple markers and strain should be used.

The Sarvak and Ilam Formations in the Zagros sedimentary basin are known as hydrocarbon reservoir formations. More than half of the hydrocarbon fields in the Zagros Basin on the Sarvak and Ilam horizons contain hydrocarbons. In this research, to identify areas with hydrocarbon potential of the horizon of Sarvak and Ilam at Bandar Abbas hinterland, parameters such as outcrops of formations, main faults, salt plugs, isopach maps and upper sediment volume of formations from the geological map of the region and well data were extracted. With designing a network inference among data and using Fuzzy logic method with the high hydrocarbons, potential of the Sarvak and Ilam horizons were identified in the Bandar Abass hinterland. This area identified as a relatively weak area in terms of exploratory potential in Sarvak and Ilam reservoir horizons. 68% of the hinterland region has low hydrocarbon potential, 18% has medium hydrocarbon potential and only 14% has high hydrocarbon potential for exploration in Sarvak and Ilam horizons. However, considering the effect of anticlines, the mentioned percentages for areas with high hydrocarbon potential reduced to 4.3%. Together, it seems that the anticlines of South Gashu, Bastaneh, Kisn, West Namak and Suru have hydrocarbon potential in Sarvak and Ilam horizons.