Tectonics
mohammad khalaj
Abstract
Anarak metamorphic complex located east of Nain city. Based on geological, chronological and paleomagnetical data, the complex consists of different metamorphic units from different varity of source. This metamorphic complex also composed of ophiolitic bodies which crop out in the complex as thrust sheets. ...
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Anarak metamorphic complex located east of Nain city. Based on geological, chronological and paleomagnetical data, the complex consists of different metamorphic units from different varity of source. This metamorphic complex also composed of ophiolitic bodies which crop out in the complex as thrust sheets. This study is concerned with structural investigation of metamorphic rocks around Anarak, specially on a Z shape folding in the chahgorbeh mountains. Based on field surveys and microscopic investigations there are at least 3 deformationnal phases in the morghab and chahgorbeh units, all of them occurred in ductile conditions possibly related to “Variscan metamorphism” (late carboniferous). In the basic and ultramafic rocks of chahgorbeh unit, the first deformational phase accompanied with HP/LT metamorphic conditions at amphibolite facies. This phase is accompanied with a relatively low grade metamorphism-green schist facies in the metamorphic pelletic rocks of Morghab and Chahgorbeh units and leads to generation of a low grade (S1) foliation. This phase followed by increasing of intensity of deformation and milonitic foliation and sheath folds developed in the rock units through second phase of deformation. Third phase of deformation continusly affected the pre- deformed rocks in a more low- grade metamorphic and deformational condition than earlier phases.
Tectonics
Amir Shafiei bafti
Abstract
Radon is a radioactive noble gas . The best places for accumulation of radon in groundwater would be geodynamic active areas,deep basement faults and fractures. This paper aims to investigate the relationship between the radon gas concentrations with the behaviors of active tectonic faults. Jorjafk fault ...
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Radon is a radioactive noble gas . The best places for accumulation of radon in groundwater would be geodynamic active areas,deep basement faults and fractures. This paper aims to investigate the relationship between the radon gas concentrations with the behaviors of active tectonic faults. Jorjafk fault with a length of nearly 160 km from North-West to South-East in southern central Iran. This fault shows active tectonics aspects, The distribution of Davaran Mountain seismic centers shows low Seismicity for the region. In addition, the few focus of the events in the south of the mountain and unequal distribution and lack of clear trend is among its seismic properties. For the measurement of radon concentration in water resources leading to the Jorjafk fault,, 35 sampling stations were identified as suitable, and on two occasions the samplings were performed. The highest and lowest concentrations measured in the first stage were 53, 183, and 138 Becquerel's respectively for the stations of 13, 3 and 8, and in the second stage, the highest and lowest concentration were measured with values of 56, 233, and 169 Becquerel's respectively for the stations of 29 and 25. By comparing the obtained concentrations for each station and its compliance with seismic activity in the region, it was observed that in places where seismic activity is higher, the concentration of radon gas is also higher. Therefore, it can be said that the areas with high concentrations of radon gas, have more potential and are more likely to earthquake events
Tectonics
Mohammad Ali Ghanbarian; Ali Yassaghi
Abstract
This research has presented the results of the structural and microstructural analyses of the Faryadoun region which is located in the NE of the Fars province. In this research, a new NW-striking belt has been introduced in the central part of Zagros hinterland and NE of the Sanandaj-Sirjan metamorphic ...
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This research has presented the results of the structural and microstructural analyses of the Faryadoun region which is located in the NE of the Fars province. In this research, a new NW-striking belt has been introduced in the central part of Zagros hinterland and NE of the Sanandaj-Sirjan metamorphic belt. The mean attitudes of the foliation and lineation in this new belt are 315˚, 57˚ NE and 23˚, 116˚, respectively. The study of kinematic indicators revealed the occurrence of a sinistral top-to-the NW shear in this new belt which is different with the known dextral deformation in the central region of the Sanandaj-Sirjan metamorphic belt.
Tectonics
Zeynab Taslimi; Abdollah Saidi; Mehran Arian; A. Solgi; Manouchehr Ghoreshi
Abstract
The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin ...
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The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin of Palo Tethys and Neotethys and it caused the complexity of abundant structural in other way too. The aim of this research is to investigate and analysis of existence structures in east central Alborz from northwest of Damghan (South of Toyeh) to South of Sari (North Alborz fault). The Structural features Analysis indicate that the Alborz Mountains are a fold and thrust belt. During the intense shortening of Alborz crust in the studied area the initial model of folds have been modified or destroyed. Some of these folds could take place in flexural flow folds or Drug folds classes since one limb of folds on the surface of low-angel thrust faults was thrusted recumbently. The thrust faults with south and north dipping is the main controller for variety structures in this part of Alborz. Based on geological and structural properties, construction of folding structures initiated during the Alpine orogeny since the late Eocene (37 million years) and the most shortening and faulting had occurred during at the Late Miocene. Data presented here demonstrate that shortening percent in the study area of Alborz Mountains is about 36.27% and the Rate of Shortening is estimated about 0.93 mm/y.
Tectonics
Mehdi Tavakoli Yaraki; Seyyed Ahmad Alavi; Mohammad Reza Ghassemi; Iraj Abdollahie fard
Abstract
The significance of mechanical stratigraphy of rocks in kinematics of folds has long been of interest to structural geologists. Parameters such as sedimentary facies variations and thickness of incompetent layers play major role in activity of these layers as detachment horizons. The purpose of this ...
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The significance of mechanical stratigraphy of rocks in kinematics of folds has long been of interest to structural geologists. Parameters such as sedimentary facies variations and thickness of incompetent layers play major role in activity of these layers as detachment horizons. The purpose of this study is to investigate the role of mechanical stratigraphy on fold geometry in the Aghajari and Pazanan anticlines within the Dezful Embayment zone. For this purpose, we have used seismic profiles, stratigraphic data and petrophysical logs as well as the previous stratigraphic works in study area. Results show that the Garau Formation is the major intermediate detachment level in the Aghajari structure, and has a significant control on folding geometry of the competent sequences of the Fahliyan to Asmari Formations. The Dashtak Formation and other incompetent evaporatic Formations of Middle-Upper Jurassic also have been active in the Aghajari structure. In contrast, in most parts of the Pazanan structure, the Garau and the Jurassic Formations do not have appropriate mechanical properties to act as intermediate detachment levels due to their change into hemipelagic facies and limestone (Surmeh Formation) respectively. Based on the evidences, the facies change in the abovementioned Formations occurs between the Pazanan and Aghajari anticlines. It seems that activity of the Hendijan-Izeh paleo-high also has some control on facies of the Garau Formation. Based on geometric characteristics and a geometric conceptual model provided for development of these structures, the folding style of the anticlines is suggested as an asymmetric faulted detachment fold type.
Tectonics
Rojin Hamidi; mohamad reza ghassemi; mohammadreza sheikholeslami
Abstract
Continuation of the compressional regime within the convergence zone between the Central Iran and Turan rigid blocks caused thrusting of old rock complexes over the recent sediments. As a result of multiple thrusts and folds, the area uplifted at the same time and the Binalud range have been shortened. ...
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Continuation of the compressional regime within the convergence zone between the Central Iran and Turan rigid blocks caused thrusting of old rock complexes over the recent sediments. As a result of multiple thrusts and folds, the area uplifted at the same time and the Binalud range have been shortened. This study attempts to evaluate the amount of shortening of the Binalud mountains by reconstruction of a balanced cross-section. Field data from the Dulat-Abad-Neyshbur transect, study of the geological units and décollements along the section, and the Move® software environment are used as the basis for this research. Based on these information, four tests were carried out for balancing the cross section in question. The first test, which used the arc and polygon method for the horizons and a listric fault without floor thrust, failed to display the deformed section. In the second test the section was drawn, however the deformed structure did not balance the section in the process of unfolding the fault bend folds. In the third and fourth tests, we used the kink method to restore the deformed state to an undeformed section. For the third test, deformation was proceeded from the hinterland, and in the process of restoration, a shortening of about 65% was revealed. The fourth test was proceeded from the foreland, and taking into account both the foreland uplifts and shortening, the amount of shortening of Binalud range was estimated to about 26%. The final structural model defined a thin-skinned fold and thrust belt which included fault-bend-folds with out-of-sequence and in sequence duplexes. Major décollement horizons defined in the region include: 1) shale horizons within the Silurian-Devonian rock units, 2) medium-bedded dolomite and limestone layers within the Bahram Formation, and 3) evaporitic layers in the Eocene sediments.
Tectonics
Tahmoores Yousefi; Kouros Yazdjerdi; Manouchehr Ghorashi; Alireza Shahidi
Abstract
The current form of the folded Zagros is the result of the oblique collision the Arabian and Iranian plates in Late Cenozoic. In this study, Cenozoic stress field changes in Zagros Simply folded belt and structural evolution after collision in Shiraz Area have been evaluated. The geological formations ...
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The current form of the folded Zagros is the result of the oblique collision the Arabian and Iranian plates in Late Cenozoic. In this study, Cenozoic stress field changes in Zagros Simply folded belt and structural evolution after collision in Shiraz Area have been evaluated. The geological formations under investigation are from Late Cretaceous to Neogene (Late Cenozoic). In this regard, geometry and kinematics of the faults, stylolites and other tectonic and stratigraphic evidence in geological formations outcrops in the study area at 30 stations were taken. The tension main axes (σ1, σ2, σ3) were calculated by Inversion Method for the categorized data. The results of the reconstruction of the paleo stress show compressional and Strike- Slip tectonic regime in Cenozoic. Moreover, anticlockwise rotation of the direction of compressive stress over time is about 60 degrees. As pre-folding compressional stress direction (σ1) is about N60E and its time is Miocene and before that. Whereas syn-folding stress direction is N35E and its age is equivalent to Pliocene that is the same age as old Bakhtiary formation. Stress changes in post-folding indicate N20E and its age equivalent to Pleistocene that is the same age as young Bakhtiary formation. At the present time, the maximum stress direction that is about N-S affects the area.
Tectonics
zahra kamali; hamid nazari; ahad fazeli; faramarz alah vardi migoni; mohamad ali shokri; firooz jafari; hossin iranshahi
Abstract
The Dorud fault, as one of the most important seismic in segments of Zagros main recent fault, near the Arjng area it have northwest-southeast trend and continuity extended in Boroujerd area. Geophysical impressions in 5 profiles, and three resistivity, magnetometric and radionuclide parallel profile ...
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The Dorud fault, as one of the most important seismic in segments of Zagros main recent fault, near the Arjng area it have northwest-southeast trend and continuity extended in Boroujerd area. Geophysical impressions in 5 profiles, and three resistivity, magnetometric and radionuclide parallel profile and parts of one profile were performed. After the completion of field operations and data acquisition, GPR and magnetometer data were final processed in Radexproler and Geosoft software’s, respectively and with combining them in PA software, clearer interpretation of the subsurface structures, especially faults and discontinuities area were obtained. Among these, the F1 fault was considered as the main fault and F2 was the branching branch of the faulty branching out of it. For this reason, the Drood fault in this range is a fault zone with branching fissures branching out to the northeast This fault zone is located at the level of Silakhor plain with a length of several tens of kilometers, a variable height between 50 cm and 7 meters and with approximate dip 60-75 degree toward the north. all of these fault branches have a mechanism and according to their normal slip component.
Tectonics
Zeinab Etemadkhah; Mohammd Mahdi Khatib; Mohammadhossein Zarrinkoub
Abstract
The late Paleocene – early Eocene granitoid intrusions in the northern Sistan suture zone are regarded as potential tools to record tectonic events. A structural study of the Zahri granitoid body, based on the anisotropy of magnetic susceptibility (AMS) technique provides new data to characterize ...
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The late Paleocene – early Eocene granitoid intrusions in the northern Sistan suture zone are regarded as potential tools to record tectonic events. A structural study of the Zahri granitoid body, based on the anisotropy of magnetic susceptibility (AMS) technique provides new data to characterize the internal structure and the kinematic reconstruction. The NW–SE trending body consists basically granite to leucogranite. Based on the results of the analysis of over 360 samples collected from 36 sites, the granitoid body is characterized by a low susceptibility and petrographic observations indicate that paramagnetic minerals such as biotite and amphibole are the most important iron-bearing mineral and can be considered as the main carrier of magnetic susceptibility. Magnetic foliations dominated by moderate dip and foliation strike mostly parallel to the elongated shape of the body, the magnetic lineation mainly trends NE-SW to N-S with plunges to the SW (mean orientation N 197°/32°) and formed during the emplacement and crystallisation of the magma. The Zahri body emplaced in an extensional setting controlled by a NNE-SSW opening direction associated with spaces of the sinistral shear zone in the terminations of Nehbandan fault system during the early Eocene.
Tectonics
Zahra Mohammadyasl; Abdollah Saidi; Mehran Arian; Ali Solgi; taher Farhadinejud
Abstract
The Studied area is located in the small part of the structural zone of Urumieh- Dokhtar Magmatic Arc, at 60km far from south of Qom and 12km far from south east of Kahak. In the beginning, 1:25000 map of the area was prepared, because, region is located in two 1:100000 scale map sheet of Kahak and Aran, ...
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The Studied area is located in the small part of the structural zone of Urumieh- Dokhtar Magmatic Arc, at 60km far from south of Qom and 12km far from south east of Kahak. In the beginning, 1:25000 map of the area was prepared, because, region is located in two 1:100000 scale map sheet of Kahak and Aran, and more rock units were separated. In the next step, in a several step of the field observations, 17 samples of regional volcanic rocks were taken for XRF and ICP chemical analysis, and they main Oxides, heavy metals and rare elements were identife. Most of the samples have been located in the Calk- alkaline series, and some in the Tulleit series. In the lithology diagrams, these samples respectively are arranged in the range of Andesite, Dacite, Trachy Andesite and Rhyolite Rocks. Due to the anomalies and the amount of Nb in the samples of the region, they formation can be related to the subduction zone. On the other hand, the depletion of Nb and Ti is special in magmatism in the subduction zone. Because in the subduction regions released fluids from floating lithospheric rich in LILE, increases in the mantle wedge. Since in the study area rocks exhibit calc- alkaline with moderate to high potassium, it can be concluded that the stones are related to active continental margin associated with subduction.
Tectonics
Masoud Biralvand; Mohammad Mohajjel; Mohammad Reza Ghassemi
Abstract
In Takht-e-Suleiman region, travertine deposits are widespread in the footwall of the Chahartagh fault. Three factors played roles in forming travertine in this area: magmatism and high geothermal gradient, existence of carbonates between thermal source at depth and travertine springs on the ground, ...
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In Takht-e-Suleiman region, travertine deposits are widespread in the footwall of the Chahartagh fault. Three factors played roles in forming travertine in this area: magmatism and high geothermal gradient, existence of carbonates between thermal source at depth and travertine springs on the ground, so that the hydrothermal solution can provide the necessary ingredients for the formation of travertine. The third factor is extensional faults and fractures to conduct water containing dissolved calcium carbonate up to the surface. Absence of travertine on the top of the metamorphic basement, even in the footwall of the Chahartagh fault, highlights the essential role of second factor in formation of the travertine. Sources of travertines in this area are carbonates from the Jangoutaran and Qom formations, with the more emphasis on the latter based on our data. Right-lateral kinematics on the Chahartagh fault led to an NNW extension in the southeastern termination of the fault, paving the way for emergence of the travertine. However, there is evidence for a regional NE extension responsible for NW-SE normal faults in the area. Such an extension may be associated with slab rollback and slab breakoff of the Neotethian oceanic lithosphere, lithosphere delamination deformation or basement-involved thick-skinned deformation in this area.
Tectonics
ahmad lashgari; magmodreza Hayhat; mohammd mahdi khatib; Mahdi Najafi; Jaume Verges
Abstract
Determining the geometry and folding mechanism in Dezful embayment in the southwest of Iran due to the inclusion of a large amount of Iran's hydrocarbon reserves, also its role in the process of structural evolution of Zagros fold- belt, is important. In present study, structural evolution of Jarik anticline ...
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Determining the geometry and folding mechanism in Dezful embayment in the southwest of Iran due to the inclusion of a large amount of Iran's hydrocarbon reserves, also its role in the process of structural evolution of Zagros fold- belt, is important. In present study, structural evolution of Jarik anticline in the northwest of Dezful embayment have been studied based on 3D seismic data, drilling data that has been provided National Iranian Oil Company remote sensing, and the field observations. According to the provided structural cross sections, geometric variations of Jarik anticline across and along the anticline axis, has been investigated. Gachsaran formation as an upper detachment horizon, causes geometric and structural changes along the anticline axis. It seems that, in the nose of anticline, occurred the detachment folding mechanism associated with concentric geometry. And in the middle section of the anticline,that folding process is more advanced, faulted detachment folding mechanism has acted.
Tectonics
Tahmoores Yousefi; Kooros Yazdjerdi; 2Manouchehr Ghorash; Alireza Shahidi
Abstract
Abstract: The brittle tectonic history expresses different tectonic events in the Zagros Simply Folded Belt. Consequence of Mesozoic extension, rifting and the shortening derived from the Cenozoic Eurasia – Arabia collision. In order to reconstruction the ancient tensions in the Mesozoic deposits ...
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Abstract: The brittle tectonic history expresses different tectonic events in the Zagros Simply Folded Belt. Consequence of Mesozoic extension, rifting and the shortening derived from the Cenozoic Eurasia – Arabia collision. In order to reconstruction the ancient tensions in the Mesozoic deposits in the east and south-east of Shiraz, geometry and kinematics of the faults data simultaneously with sedimentation was investigated using the inversion method, to evaluated rifting time, the former of Neo-Tethys and its collisions in Cretaceous and Paleocene. In this regard 21 stations have been exposed in Khanekat to Pabdeh Formations. The resulted geometry and kinematics of the faults data were calculated situation main tension axes (σ1, σ2, σ3 ), tension ellipsoid figure or ratio of difference (ɸ). The results are as follows: from Triassic to upper Cretaceous (Mastrichtian) in Khanekat,Surmeh, Fahlian, Darian, Sarvak, Ilam, Gurpi, Tarbur Formations and Ghorban Member; extensional tectonic regime was dominant and having NE-SW direction (N052°) but in Pabdeh Formation with Paleocene age, tectonic regime has changed into compression with NE-SW compressional stress direction(N045°). So it was concluded that in simply folded Zagros of interior Fars, time of rifting and the forming of Neo-Tethyan basin was Triassic or older (Permian) with NE-SW extensional direction. The beginning of compressional tectonic regime with the same direction has been in Paleocene.
Tectonics
Amir Shafiei bafti
Abstract
. Kouhbanan fault system in south of central Iran is one of the most active and seismic faults, has length of nearly 200km and seismic history from B.C to the present. Epicenter of seismic activities for this fault situated often near fault zone or on the Kouhbanan fault zone branches and other attached ...
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. Kouhbanan fault system in south of central Iran is one of the most active and seismic faults, has length of nearly 200km and seismic history from B.C to the present. Epicenter of seismic activities for this fault situated often near fault zone or on the Kouhbanan fault zone branches and other attached faults. Identify of ruptured and non-ruptured segments can clear the way to finding the areas that have the potential for creating earthquake. Field observation and library data were used for this purpose. According to the spatiotemporal distribution of historical and instrumental earthquakes, may be concluded, the most earthquakes are located where the fault branches or in its bend locations. Earthquake occurred in studied region, often known with absence of high magnitude earthquakes (M≥ 6.5). Interesting point is that in the period of about 160 years ago (Earthquake record time span) along of active faults, especially Kouhbanan fault zone, an area that is less a re-ruptured or be consecutive or earthquake epicenters are few. For earthquake risk assessment, we use Kijko& Sllevoll (1992) method, which show that the earthquake risk and seismicity rate is higher from other regions and earthquake have higher magnitude and less recurrence time. According to the obtained results, for earthquakes (M≥ 7) results should be used with caution.
Tectonics
Marziyeh Khalili; Maryam Ezadi
Abstract
The Kazerun-Burazjan fault is an active strike slip fault with an N-S trending located in the Zagros belt whose performance causes bends and stretches in the folds axis. The obtained results from the seismic profiles of the southern parts of Fars province suggest that there is no evidence as to the continuation ...
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The Kazerun-Burazjan fault is an active strike slip fault with an N-S trending located in the Zagros belt whose performance causes bends and stretches in the folds axis. The obtained results from the seismic profiles of the southern parts of Fars province suggest that there is no evidence as to the continuation of Burazjan fault segment along the Mand Mountain to Persian Gulf as the end part of the Kazerun fault. Studies show that the performance of the faults such as the Mountain Front Fault (MFF) and the rotation of the blocks adjacent to the strike-slip faults caused the Burazjan fault to slip under the Khormuj and Khartang anticlines and the Bangestan Group located in the Khormuj and Siah anticlines to be placed beside the Aghajari formation in the Kaki anticline. The orientation of the long axis of the Khormuj and Namak (Jashak) salt domes with N-S trends can be considered as the activity of the segments of the Burazjan fault system. Surface and subsurface studies have introduced the Darang fault with an N-S trend and strike slip mechanism as the southern terminus of the Kazerun- Burazjan fault system which extends from the Khartng anticline to the Persian Gulf. The fractures result from the fault system performance consists of a series of transverse-shear fractures with NNE-SSW and NW-SE trends with a visible distribution around the folds axis.
Tectonics
Sepideh Rezabeyk; Abdollah Saidi; Mehran Arian; Ali Sorbi
Abstract
In the Northern part of Suture Zone (Kermanshah) the deep sea sediments, oceanic crust remnants, platform carbonates, igneous and metamorphosed rock of active margin and carbonate sequence of passive margin are assembled in this studied area. This convergent area has provided a very complicated structural ...
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In the Northern part of Suture Zone (Kermanshah) the deep sea sediments, oceanic crust remnants, platform carbonates, igneous and metamorphosed rock of active margin and carbonate sequence of passive margin are assembled in this studied area. This convergent area has provided a very complicated structural zone. The main purpose of this study is stress characteristic analysis. A great data has gathered from the faults which are appeared within the rocks specially the radiolaritic rocks. The data includes characteristics of fault surface geometry, fault slip and lineation slip related. By using the method Right Dihedral, the position of main stress was obtained. The great number of reverse faults have a NW- SW trend, while the strike- slip faults, show a NE- SW direction. The Normal faults with a different displacements appeared younger than the other faults. The result of this study that we obtained the situation of main stress σ1, σ2 and σ3 respectively is 059, 305 and 195.
Tectonics
mehdi yousefi; Sayyed Morteza Moussavi; Mohammad Mehdi Khatib; Mohammad yazdani
Abstract
Image logs of 14 wells in Rag sefid anticline are showing 6 main fracture sets treanding N45, EW, N35, N100, N150 and N162 respectively. Development of fractures in the eastern part of the Rag sefid anticline, especially in the frontal edge, are in effect of the propagation fault related folding so that ...
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Image logs of 14 wells in Rag sefid anticline are showing 6 main fracture sets treanding N45, EW, N35, N100, N150 and N162 respectively. Development of fractures in the eastern part of the Rag sefid anticline, especially in the frontal edge, are in effect of the propagation fault related folding so that the most open longitudinal and cross axial fractures show N100 and N10 trends. Due to fold axis rotation 30 degrees to the north In the western part of the anticline the orientation of the fractures have changed and major fractures are longitudinal type and have N160 trend. In the middle and curved part of anticline NE-SW trend fracture sets are more developed by reactivation of hendijan basement fault. Convergence of stress axises as a result of the fault triple interaction In effect of Rag sefid thrust dipping to the north east and dextral shears dut to reactivation of hendijan and southern part of Izef basement faults caused the Restraining bend and dextral shear zone In the western part of the Rag sefid anticline. Creation of this shear zone caused clockwise rotation of anticline axis, rising more in northen west culmination on asmari top formation than southern east culmination, change in fractures orientation and also development and increase the density of fractures in the curved part of Rag sefid anticline.
Tectonics
Golnaz Abbasi; Ali Solgi; Mohsen Pourkermani; Hosein Motamedi; alireza farrokhnia; Keivan Orang
Abstract
We used 2D seismic profiles, field observation and well data to constrain the structural evolution of the Saveh basin during the late-lower Miocene to late Pliocene. During this time period almost 8-9 kilometers of Upper Red Formation (URF) and the Pliocene conglomerates were deposited in the basin depocenter. ...
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We used 2D seismic profiles, field observation and well data to constrain the structural evolution of the Saveh basin during the late-lower Miocene to late Pliocene. During this time period almost 8-9 kilometers of Upper Red Formation (URF) and the Pliocene conglomerates were deposited in the basin depocenter. During the late- lower Miocene (to early- middle Miocene ?), Syn-depositional activity of west-east-northwest-southeast trending high-angle fault zones, with an extensional component, created accommodation space for deposition of lower Upper Red Formation. Since the late- middle Miocene (or late Miocene), initiation of a compressional phase has resulted in regional deformation.The deposition of upper part of the URF and the Pliocene conglomerates was contemporaneous with compressional deformation. During this stage, the middle part of the URF acted as an effective detachment horizon and detachment folds, such as the Saveh and Taraz Naeen anticlines, were formed. The thinning of the Pliocene conglomerates towards the crestal point of these folds indicates late structural growth. According to the top Qom depth map, there are no traps with fault independent closure within the Saveh basin. The top of the Qom Formation is estimated at -4250 m in the Taraz Naeen anticline.
Tectonics
Saeid Hakimi Asiabar
Abstract
Abstract The area of Dona mine is a part of central Alborz. The Dona anticline is a part of pop up structure and located between Kandavan and Azadkuh thrust faults. In this research three sets of major faults are recognized. The first category of faults with W-E trend, dip 40-50, Rake angle more than ...
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Abstract The area of Dona mine is a part of central Alborz. The Dona anticline is a part of pop up structure and located between Kandavan and Azadkuh thrust faults. In this research three sets of major faults are recognized. The first category of faults with W-E trend, dip 40-50, Rake angle more than 70, are parallel to the major fold axes and second category of faults have NE-SW trend with reverse movement and rake angle less than 65. The third category which truncate the first sets, have nearly N30W to N40W direction with dip more than 75 and rake angle more than 70. The aim of this paper is investigation on the structure of Dona mine and investigations on the mechanism of third category of faults which are not popular in Alborz range and did not discussed before. Some of these faults do not have visible slickensides and the mechanism of these faults held on the basis of preparing geologic map on the scale of 1:1000, structural cross sections and implementing Schmidt net with construction methods. The change of tectonic movements from collision into sinstral, on the pop-up structure created this set of young reverse faults with NW-SE trend.
Tectonics
Mohamad Reza Sajadian; Manouchehr Ghorashi; Elahe Javadi Mosavi; Mohsen Pourkermani; Mehran Arian
Volume 28, Issue 110 , December 2018, , Pages 299-306
Abstract
Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculate from ArcGIS and remote sensing packages over large area as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics. ...
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Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculate from ArcGIS and remote sensing packages over large area as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics. This is particularly valuable in west-central Alborz where relatively little work on active tectonics based on this method was done, so this method is new and useful. Based upon values of the stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), index of mountain front sinuosity (Smf) and transverse topographic symmetry factor (T), we used an overall index (Iat) that is a combination of the other indices. The low class of Iat are mainly in the sub-basins no; 6, 10,13,14,21,22,23,24,28 and the rest of the study area has moderate tectonic activities in the other sub-basins. Our results show that he moderate value has located along faulted area, which shows 2 class of relative tectonic activity.
Tectonics
zahra kamali; magmodreza Hayhat; hamid nazari; mohammd mahdi khatib
Abstract
The Dorud fault, as one of the most important seismicin segments of Zagros main recent fault, near the Arjng area it have northwest-southeast trend and continuity extended in Boroujerd area. This area is determined Kinematic dissimilarity fault the fractal analysis of the fractures, the center of earthquakes ...
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The Dorud fault, as one of the most important seismicin segments of Zagros main recent fault, near the Arjng area it have northwest-southeast trend and continuity extended in Boroujerd area. This area is determined Kinematic dissimilarity fault the fractal analysis of the fractures, the center of earthquakes and drainage using the of box method, For this purpose, the study area was divided into two parts based on the difference in distribution of fractures and epicenter earthquakes. Fractal dimensions of fractures, drainage and epicenter earthquakes are calculated and then compared with each other. Kernel density method to investigate the epicenter earthquakes distribution and drainage in the long fault to rate the dissimilar activity that .In the end, the analysis of evidence Morphotectonic that long it’s to determine the horizontal, vertical displacements and net slip to be paid. Fractal analysis on Kernel density method and evidence Morphotectonic. In the end, the analysis of that long it’s to determine the horizontal, vertical displacements and net slip to be paid. So that results of fractal to indicate that the northern segment of the most dynamic segment spread to be identified. Also The results of the kernel analysis and evidence Morphotectonic indicates that neither the fault that along with passing of units of different ages show different behavior and the amount of angle Rick obtained along the fault is different according to the results achieved in three segment to different long can be divided, so that angle Rick segments 1 and2 respectively126°/16° and124°/22° and long segments respectively 18 and48 kilometer, to notice the high values of rick (more of10°) the two segments have a dominant effect of the component dip- slip relative to strike-slip but the angle rick 131°/4° in segment 3indicate of the action component strike slip that the units alluvial are plain Silakhor this segment long is 44 kilometer.
Tectonics
Mojtaba Ershadinia; Saeed Madanipour; Ali Yassaghi
Abstract
Faraghun Mountains are located in the south eastern part of the Zagros orogen. Early Ordovician- Permian rock units are deepest stratigraphic units exposed in the central part of the Faraghun Mountains. High Zagros Fault (HZF) is the main structural feature bordering southern flank of these mountains. ...
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Faraghun Mountains are located in the south eastern part of the Zagros orogen. Early Ordovician- Permian rock units are deepest stratigraphic units exposed in the central part of the Faraghun Mountains. High Zagros Fault (HZF) is the main structural feature bordering southern flank of these mountains. Here we combine detailed mapping, field based structural kinematic analysis and cross sections to reconstruct structural evolution of the Faraghun Mountains. Our new structural and stratigraphic analysis document three kinematically and geometrically different western, central and eastern segments for HZF in the Faraghun Mountains. Eastern and western segments of HZF, those are dipping northward, are connected together with Zakin Fault that dipping to south. Late Paleozoic successions have exposed in the hanging wall of Zakin Fault and central segment of HZF in a pop-up geometry. Stratigraphic records document prominent variation in late Cretaceous sequences including Gurpi Formation in the Hanging wall and footwall of the HZF in the Faraghun Mountains. Higher thickness and basal conglomeratic nature of Gurpi Formation in the hanging wall of HZF with respect to its footwall might reflect normal kinematics of the HZF during late Jurassic-early Cretaceous time. All the stratigraphic and structural evidence represent post late Cretaceous compression accompanied by late Cenozoic right lateral transpression in Faraghun Mountains at SE Zagros.
Tectonics
Mahnaz Sabahi; Ramazan Ramazani Omali; Masoumeh Kordi; Mohsen Dourandish
Abstract
In the past decade, several geophysical, geological and reservoir studies have been done on the Qom formation in the Yortesha field for injection and gas storage purposes. Qom formation in this field has a poor reservoir characteristic (low porosity and permeability); therefore the role of fractures ...
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In the past decade, several geophysical, geological and reservoir studies have been done on the Qom formation in the Yortesha field for injection and gas storage purposes. Qom formation in this field has a poor reservoir characteristic (low porosity and permeability); therefore the role of fractures for increasing permeability and improving reservoir quality is very important. In the current study, fractures’ concentration and strike patterns of the Qom and Upper Red formations as the carbonate reservoir and cap rock, respectively, have been investigated and compared in the Yortesha anticline and its adjacent anticlines (Davazdah Emam and Morreh) using surface and subsurface investigations. In order to achieve this goal, desert data gathering methods, remote sensing, and image log analysis have been used. Subsurface studies and interpretation of FMS and EMI image logs determined that fractures have also a secondary strike of NE-SW in addition to strike of NW-SE. Based on the FMS image log interpretation of well No. 2, three subsurface fracture sets have been identified with the strikes of N55E, N65E, and N15W as well as using the EMI log of well No. 4 shows the two dominant strike of N10E and S45E. The total 1852 specified fractures in the out crops of the Morreh and Davazdah Emam surface anticlines can lead to rose diagrams that show four fracture sets with the strikes of N10E, N45E, N80E, and S45E.
Tectonics
Mohammad Moumeni Taromsari; Maryam Dehbozorgi; Reaza Nozaem; Ali Yassaghi
Abstract
Kalmard fault is considered as one of the fundamental faults in central Iran zone. The Ozbak Kuh mountains with a NE-SW strike are located in central Iran in the Kalmard fault zone. Hence, analyze the folds and faults in this deformed zone can aid in the understanding of structural evolution of this ...
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Kalmard fault is considered as one of the fundamental faults in central Iran zone. The Ozbak Kuh mountains with a NE-SW strike are located in central Iran in the Kalmard fault zone. Hence, analyze the folds and faults in this deformed zone can aid in the understanding of structural evolution of this area in central Iran. In this study, field operations and geometric-kinematic analysis of folds and faults, also study of their structural evolution are integrated in order to provide a better understanding of the structural evolution of the Ozbak Kuh area. The results display that before Cretaceous period the Ozbak-Kuh area was influenced by a compressional regime with a prependicular trend with respect to the Kalmrad fault that it caused the formation of folds and faults paralell to folds axial plane trends, after that compressional regime changing to a dextral strike slip regime in Cenozoic in direction of NE- SW, all structures in the study area such as, faults, folds axial plain and other related structures were influenced by the aforementioned strike slip stress. Generally the geometric- kinematic pattern of faults in the study area regarding to the major and R, P, R', and X faults is kind of simple shear and contraction parallel to deformed zone. In this pattern the simple shear is dominant and compression is trivial component. The mechanism of the faults in the study area shows that the deformation of the Ozbak Kuh mountains is toward the final stages of simple shear. The multiple steps of deformation, simple shear movements and intensity of deformation in the study area caused that the strike of all structures is to be in direction of NE-SW that it is parallel to the main fault zone.
Tectonics
Ali Taghavy; Mahdi Najafi; Najmeh Etemad-Saeed; Mohammad Seddigh
Abstract
A synthesis of 2-D seismic interpretation, exploration well data and field survey permit us to decipher the structural evolution history in the front of Fars paleo-high area, located in SE Zagros fold-and-thrust belt. In the current study, a structural evolution model is proposed for the region, according ...
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A synthesis of 2-D seismic interpretation, exploration well data and field survey permit us to decipher the structural evolution history in the front of Fars paleo-high area, located in SE Zagros fold-and-thrust belt. In the current study, a structural evolution model is proposed for the region, according to a sequential restoration, which was performed based on the growth stratal unit’s pattern, together with constant length and area assumptions. The result of the sequential restoration indicated that in the late Eocene time, Tanbak anticline incepted on the hangingwall of the inverted mountain front basement fault, as an out of sequence forced fold. Although, thin-skinned detachment folding initiated in the lower Miocene, shortening and amplification of anticlines did not accelarated until the late Miocene time, when thrust faults formed on the limb of growing anticlines while Dashtak middle detachment thickened in the fold crestal areas, likely due to an intensified regional shortening.
