مجله زمین ساخت
پیاپی 19 (پاییز 1400)

The study area in this research is located in the Central Iran and south of Bayazeh village. Using remote sensing and field studies, the pattern of distribution and evolution of brittle and ductile structures in this part of Central Iran were studied. During remote sensing studies, using different filters, the fracture scattering pattern was investigated. In the field studies section, in order to control and study the faults and folds, structural measurements were performed from different parts of the study area. In the study of folded units, two folding with almost different geometric characteristics were identified that evolved under the influence of NW-SE and E-W convergence directions. Remote sensing and field measurement studies on faults showed three directions of NE-SW, NW-SE and N-S orientations for the main faults in the region. The paleostress field obtained from these studies identified several directions for maximum stress, which with the direction of northwest, northeast, south and east and low to horizontal plunge shows the compressional mechanism prevailing in the region. Hajiabad and Bayazeh faults as the main faults along with minor faults were compared with Riddle fracture pattern and despite the great impact on the spread of faults and folds in the region, it was found that they have not yet reached their structural maturity.

Tarom basin with a general trend of NW-SE is located in the western Alborz structural zone. This basin has been formed due to the extensional stress regime after the collision between the Central Iran and Eurasian block and formation of the Alborz mountain range. In this study, we aimed to identify and introduce of structures toghether with geometric and kinematic analysis of faults and folds to complete the previous researches about the tectonic setting of the eastern part of the Tarom basin. According to our data and previous studies, formation of the Tarom basin started during Oligocene and continued until the early Neogene. The result of this extension is NW striking normal faults in the region. From the Middle Neogene to the Recent, the pressure resulting from the collision of the Arabic plate and Central Iran and the subsequent clockwise rotation of the Caspian block have created two transpressional phases in the western Alborz. One is the dextral transpression with NW compressional component (in the Pliocene) which caused the folds with NE axial trend and the other is the sinistral transpression with NE compressional component (during the Pleistocene to the Recent) which caused the NNW folding and E-W striking normal faults in the Neogene layers. Also the NE striking normal faults and folds with E-W axial trend in the area, show the effect of reactivation of NE stiking left lateral Sefidrud basement fault which continues to the south of Manjil dam.

In this study from the processing and interpretation of the image log (EMI Log) and results integration with the results of the interpretation of conventional reservoir logs (full set logs) In order to describe the reservoir properties of Fahliyan Formation, has been used. Processing and interpretation of full set and image logs in Geolog specialized software. The findings of this study are based on the processing and interpretation of the EMI image log, the dip of the layering is less than 10 degrees and along the northeast. Also, the development of fractures in this limited formation, and generally fractures are open and along the South-West. The maximum tension is also detected in the direction of North East-South-West (NE-SW). The processing and interpretation of conventional reservoir diagrams also shows that the Fahliyan Formation in one of the oil fields of Abadan plain can be divided into 6 layers (F1, F2, F3, R1, F4, and R2). The layers of R1, R2 show weak reservoir potential and F1, F2, F3, and F4 layers are basically lacking reservoir potential due to their very poor porosity or high shale volume. The present study is an applied study. With regard to drilling ranges and reservoir conditions (poor) and considering the costs of drilling, operation and processing, this field is not suitable for development at present and in case of development, due to poor reservoir conditions, it will be necessary to stimulate formation, including acidification.

The study area is in the north of Chelgard city, the central part of Koohrang city in the west of Chaharmahal and Bakhtiari province. The purpose of this study is to evaluate the tectonic evidence related to the activity of Koohrang fault in Zardkooh heights. In this study using indicators Hypsometric integral morphometry (Hi), Drainage basin asymmetry (Af), River gradient (SL), The shape of the basin (BS) is calculated. In order to determine the relative tectonic morphological activity in the study area, The relative active tectonics index (IAT) has been calculated. The map shows the resulting zoning index (IAT) New tectonic activities have not been the same everywhere in the region Basins with different New construction activity are scattered in the area In general Koohrang fault and its sub-faults are active in some sections and basins, according to the obtained results, the area has moderate to low tectonic morphological activity.

Existence of seismic activity history and high rate of tectonic activity in the region, which indicates that the study area is releasing energy in the pre-seismic stage and as a result in some points of stress accumulation, which will lead to high seismic potential in the future. For this purpose, the active faults of the study area have been drawn and the scatter map of the relative tectonic activity level has been evaluated with instrumental seismic data. Finally, the maximum seismic acceleration of the area has been calculated and the area lines have been obtained by PCA method. After examining the area lines, it was found that lines L1, L2, L3, L4, L5 do not have a counterpart in the aerial magnetic map and therefore are a surface fault. L6 has good compatibility with F-9 magnetic line and surface lines L2, L3, L4, L5 do not have any compatibility with any of the faults exposed in the geological map and magnetic line and their faulting needs to be investigated. It has a desert.

In the study area, which is located in the south of Salafchegan, there is a series of intermediate to acidic dykes that have penetrated in two stages of eruption in the Lapilli tuff units and the dark gray andesitic section. according to the age of the host rocks, the injection time of these dykes was late Miocene onwards. In this study, changes in the position of long-term stress axes in this area have been investigated using analysis of slickenline data and slickenside as well as long-term stress trajectories based on dykes’ trend from Miocene onwards. By using the position of the dykes in the area and analyzing the long-term stress data with inversion method, changes in the trend of the main stress axes from Neogene or Plio-Quaternary have indicated, so that the maximum stress direction from north-south direction at the end of Miocene to north east-southwest changed during the Pliocene-Quaternary. This change in trend could be due to the clockwise rotation of the South Caspian block, the impact of which was not limited to Alborz and was also effective in Central Iran. This effect has recently been reported in other studies in the area of the Kushk fault system.