Tectonics
Khatoun Pirdadi; Maryam Agh-Atabai; Attieh Eshaghi
Abstract
The 2017 Ezgeleh earthquake (Mw: 7.3), which occurred northwest of the Zagros, was followed by many aftershocks. The histogram of the monthly rate of aftershocks shows that, except for the first few months, the aftershock sequence did not follow the Omori law. Therefore, it is necessary to use more complex ...
Read More
The 2017 Ezgeleh earthquake (Mw: 7.3), which occurred northwest of the Zagros, was followed by many aftershocks. The histogram of the monthly rate of aftershocks shows that, except for the first few months, the aftershock sequence did not follow the Omori law. Therefore, it is necessary to use more complex methods to investigate the aftershock sequence. In this research, the temporal multifractal method was used. The results obtained show that the temporal pattern of aftershocks has two short and long-scaling ranges. It seems that short and long ranges are related to the distribution of aftershocks within smaller clusters and the pattern of clusters in the aftershock sequence, respectively. These result showed that the pattern in the longer range is more heterogeneous than the shorter one. On the other hand, by removing the smaller aftershocks, the heterogeneity increases. It seems that the occurrence of several more significant aftershocks with a magnitude of more than 5 has caused an increase in the heterogeneity of the temporal pattern of the aftershock sequence. The results also show that the degree of inhomogeneity of the occurrence time of aftershocks is related to the spatial distribution pattern of aftershocks.
Tectonics
Fereshteh Jafari-Hajati; Maryam Agh-Atabai; Majid Nemati; Ali Biglari-Fadafan
Abstract
In this research, to understand the present-day tectonic situation of Gorgan-plain in the east of the South Caspian basin, the tectonic stress regime of this area and its adjacent areas was estimated using the inversion of the data of the earthquake focal mechanisms. For this aim, in addition to analyzing ...
Read More
In this research, to understand the present-day tectonic situation of Gorgan-plain in the east of the South Caspian basin, the tectonic stress regime of this area and its adjacent areas was estimated using the inversion of the data of the earthquake focal mechanisms. For this aim, in addition to analyzing focal mechanisms solved by different sources, the focal mechanisms were solved for several earthquakes with appropriate and sufficient information. The results indicate the presence of various mechanisms, including thrust, normal, and strike-slip, and as a result, various orientations of kinematic P and T axes, which can indicate the complexity of the region. By analyzing the earthquakes with a minimum magnitude of 4 in the Gorgan-plain, the Kopeh-Dagh in the east of the plain, and the entire eastern region of the South Caspian, a compression regime with a NNW-SSE trend was obtained. However, by analyzing all of the earthquakes (smaller and larger earthquakes) in the Gorgan-plain, a strike-slip regime was obtained, in which the trend of the P and T axes were calculated NE-SW and NW-SE, respectively. The results indicate a local strike-slip regime in addition to the regional compressional regime in the region.
Tectonics
Mohammad R. Ghassemi; Ali Aghanabti; Abdollah Saeidi
Abstract
Correlation of the orogenic and epeirogenic events in Iran with the events that have been identified in different parts of the world and in different tectonic environments, has caused some confusion in the Iranian geological literature. After a brief review of the nature of known orogenic processes in ...
Read More
Correlation of the orogenic and epeirogenic events in Iran with the events that have been identified in different parts of the world and in different tectonic environments, has caused some confusion in the Iranian geological literature. After a brief review of the nature of known orogenic processes in the world, examining issues related to the abovementioned correlations, and considering the tectonic history of various parts of Iran, we have tried to systematically describe and name the important orogenic and epeirogenic events of the country. Most Precambrian orogenic events in Iran are dubious due to unknown age and poorly constrained tectonic setting of the rock units attributed to Precambrian. Paleozoic in Iran has been mostly associated with epeirogenic events, and the only sign of a real orogenic event goes back to the Late Carboniferous in northern Iran. The important Mesozoic and Cenozoic orogenic events have shaped the modern tectonic configuration of Iran. The Paleotethys suture in northern and central Iran formed during the Gorgani orogeny, development of the Central Iranian active margin (Sanandaj-Sirjan) occurred in the Ekbatani orogeny, ophiolite obduction in Central Iran and Zagros developed during the Late Cretaceous events, and collision of the Iranian plate with the Helmand block resulted in the Sistani orogeny. The creation of the Zagros and Alborz Mountain ranges started from Oligocene and Miocene times, respectively, and the deformation due to their shortening continues to this day.
Tectonics
Reza Alipoor; Ali Jahangiri; Zahra Ghasemi
Abstract
The Ghalajeh anticline with about 60 km length and NW-SE trend is located in Lurestan sub-zone and the Zagros fold and thrust belt. Geometry and kinematic of the folds of this zone are controlled by thrust faults and detachment levels. In this research, geometry and deformational style analysis of the ...
Read More
The Ghalajeh anticline with about 60 km length and NW-SE trend is located in Lurestan sub-zone and the Zagros fold and thrust belt. Geometry and kinematic of the folds of this zone are controlled by thrust faults and detachment levels. In this research, geometry and deformational style analysis of the Ghalajeh anticline and the role of the detachment levels on folding style have been investigated interpreting well data and construction of three cross-sections and calculation of geometric parameters. The structure of this anticline is affected by two detachment levels, which include the Pabdeh and Garu formations as the upper and middle detachment levels. Detachment levels and deep-seated and surface thrust faults in the southwestern limb affected the folding geometry and have caused the high thickness of the middle detachment level and inversion of the southern limb which waning southwestern part of the anticline, and the dip of the layers are normal which in turn caused fracturing. Analysis of geometrical parameter along the Ghalajeh anticline indicate that this anticline is an asymmetrical, cylindrical fold is an open half-angle round fold.
Tectonics
Mojtaba Ershadinia; Farzin Ghaemi; Massoud Homam
Abstract
The Fariman complex is located in the northeast of Iran and southeast of Mashhad, contains a variety of rocks from the Permian to the present era that have undergone several stages of deformation. In this paper, the structural geometry of faults and folds of the region is analyzed and based on it, the ...
Read More
The Fariman complex is located in the northeast of Iran and southeast of Mashhad, contains a variety of rocks from the Permian to the present era that have undergone several stages of deformation. In this paper, the structural geometry of faults and folds of the region is analyzed and based on it, the deformation stages of Fariman complex are identified, which indicates its evolution during 3 stages of deformation. In the first stage of deformation, tectonic forces along with the thermal stage have caused the transformation of sediments and the formation of first generation foliation and folds in the region. First-generation thrusts also formed during this phase, thrusting Palaeotethys remnants. The second stage of deformation has led to the formation of the second generation of thrusts and folds in the region. Kinematic analysis of second generation thrusts indicates two reverse motion phases with leftlateral strike-slip component and right–lateral strike–slip with reverse component.Its reverse motions, which result in the formation of misplaced massive carbonate associated with the second stage of deformation, and its dextral motion, which cut and displace previous structures and affect all rock units in the region, the third stage of deformation is analyzed.
Tectonics
Mohammad Reza Sheikholeslami
Abstract
Bajgan metamorphic complex is located at the southeastern termination of the Sanandaj-Sirjan zone in north of Makran. The metamorphic rocks, having igneous and sedimentary origins, are in tectonic contact with ophiolite assemblages and colored mélange. The rocks can be divided in four units based ...
Read More
Bajgan metamorphic complex is located at the southeastern termination of the Sanandaj-Sirjan zone in north of Makran. The metamorphic rocks, having igneous and sedimentary origins, are in tectonic contact with ophiolite assemblages and colored mélange. The rocks can be divided in four units based on lithological characteristics. These units are covered by Pliocene and Quaternary sediments. Structural study indicates the presence of three syn-metamorphic stages of deformation in ductile condition. The main structures elements are different generation of folds, foliation and lineation, each of them has been generated during a specific stage and superimposed on each other. The structural elements in this complex have emerged during subduction, ophiolite obduction and exhumation, respectively.
Tectonics
Mohammad Reza Mazinani; Ali Yassaghi; Reza Nozaem
Abstract
The E-W trending Faghan fault system with >180 km in length located in the northern part of the Lut Block and south of the Dorouneh Fault in central Iran. The fault cut through basement rocks and all other younger units from Cambrian to Cenozoic. Kinematic and dynamic analyses of the Faghan fault ...
Read More
The E-W trending Faghan fault system with >180 km in length located in the northern part of the Lut Block and south of the Dorouneh Fault in central Iran. The fault cut through basement rocks and all other younger units from Cambrian to Cenozoic. Kinematic and dynamic analyses of the Faghan fault system is crucial for understanding the tectonic framework of the northern part of the Lut Block. These field based investigation analyses of the Faghan fault system indicates the E-W trending dextral strike- slip shear kinematics for the fault system and as Principal Deformation Zone (PDZ) along which minor sinistral, dextral and dip slip faults have also formed as second order riedel shears. Therefore, like the Kuh-e-Sarhangi fault zone, the Faghan fault system is considered as one of the fundamental fault zone in the north of the Lut Block caused the deformation partitioning in the block during Late Cenozoic. Accordingly, the Faghan fault system divorces the Bardacan-Kashmar and Gonabad micro-blocks from each other and transfers the deformation from the main Lut Block into its northern micro-blocks by Intraplate escaping tectonics.
Tectonics
Azizollah Tajvar; mohammadmahdi Khatib; mohammadhosein Zarrinkoub
Abstract
The north Makran ophiolite mélange, is located on the northern part of Makran accretionary wedge, southeast of Iran. In this study, we investigate geometry and kinematic properties of structural elements, and analyze the deformation style of the north Makran ophiolite mélange. Based on ...
Read More
The north Makran ophiolite mélange, is located on the northern part of Makran accretionary wedge, southeast of Iran. In this study, we investigate geometry and kinematic properties of structural elements, and analyze the deformation style of the north Makran ophiolite mélange. Based on the results, at least, two stages of deformation were identified in north Makran ophiolite mélange. The first stage, which was accompanied by the development of extension structures, led to the formation of sheeted dykes in crust sequence of oceanic lithosphere. By restoration of these dykes to pre-deformation states, we assigned a SSW-NNE extensional regime that illustrates initial geometry of north Makran ophiolite mélange formed. The second stage, which was formed because of convergence in a compressional or transpressional regime, has been characterized by the development of various types of thrust and strike-slip faults, thrusting of rock units on top of each other and their duplication, and folding of sediment rocks. WNW-ESE thrust faults with 20 to 40 degrees dip toward NNE have the most important influence on current features of the north Makran ophiolite mélange, they reflect the conditions and process that the oceanic basin closed and oceanic lithosphere emplaced.
Tectonics
Esmail Farahzadi; Seyed Ahmad Alavi; Mohammad Reza Ghassemi; Shahram Sherkati
Abstract
AbstractUnderstanding the history of uplift and folding in an area helps inferring the history of hydrocarbon genesis,migration and trapping and reducing exploratory drilling risks.Thermal model along with structural cross sections help understanding of this history and future plannings for ...
Read More
AbstractUnderstanding the history of uplift and folding in an area helps inferring the history of hydrocarbon genesis,migration and trapping and reducing exploratory drilling risks.Thermal model along with structural cross sections help understanding of this history and future plannings for new exploration. In this paper we have used 3Dseismic reflective lines and geological maps to construct a regional balanced cross section and restore it in several stages. Combining of this cross section and a thermal model produced using vitrinite reflectance and apatite fission track, the history of exhumation and regional erosion is evaluated. Based on the results,unlike the Hormuz Series,the thickness of the Paleozoic sequence is equal throughout the region. This shows that the sedimentary-tectonic events have been the same in this period. The apatite fission track data indicate that the average time of rocks cooling is between14and24 million years ago (Late Oligocene-Middle Miocene).Based on the burial history graph, exhumation rate of the basement decrease from High Zagros to Abadan plain that show the basement in the northern part is involved in deformation earlier than in the southern part of the region. This involvement has affected the formation of structure,change of the sedimentary facies and the regional erosion pattern.
Tectonics
MohammadAmir Alimi
Abstract
The Bahlgerd shear zone in the northern margin of Bagheran Mountain is separated Eocene flysch from the Cretaceous ophiolite sequence and Quaternary sediments by southern Birjand and Bahlgerd faults. In the deformation evaluation , sigmoidal array arrays located in sandstone units have been used as strain ...
Read More
The Bahlgerd shear zone in the northern margin of Bagheran Mountain is separated Eocene flysch from the Cretaceous ophiolite sequence and Quaternary sediments by southern Birjand and Bahlgerd faults. In the deformation evaluation , sigmoidal array arrays located in sandstone units have been used as strain markers. Based on the geometry of these arrays, the mathematical equations and R-θ' diagrams of the strain parameters were estimated. The mean values of shear strain (γ), volume change (∆) and convergence across the zone (K) are 0.45, -0.26 and 0.85, respectively. The plotting strain ellipses on the logarithmic Flinn diagram are in the field of flattening, which indicates the simultaneous simple shear and compaction in the region and show a volume reduction of up to 30%. Also, in the Bahlgerd shear zone, the value of θ'> 45 ° and cleavages are created in the direction perpendicular to the opening of the veins, which conforms to the characteristics of the compactional simple shear model. The horizontal strain parameters in the transpression model have similar values the compactional simple shear model. Based on the calculated convergence parameter (0.39), Behlgard shear zone is in the category of slightly convergence zones in which the amount of shortening
Tectonics
babak Samani; Sajad Zareie; Atefeh Ghanbari
Abstract
Split-window algorithm is the effective method for determination of land surface temperature. The results of temperature pattern show that the Gach salt dome has a higher temperature than the Siah Tagh salt dome. From a structural point of veiw, the higher temperature of the Gach salt dome can be related ...
Read More
Split-window algorithm is the effective method for determination of land surface temperature. The results of temperature pattern show that the Gach salt dome has a higher temperature than the Siah Tagh salt dome. From a structural point of veiw, the higher temperature of the Gach salt dome can be related to the rooting of this dome and its relationship with the basement salt column. While the lower temperature of the Siah Tagh salt dome can be due to the lack of connection between the salt dome and the salt source of Hormuz Series. Temperature anomaly maps show the different temperature pattern in these two salt domes. Spatial pattern of temperature anomaly in the Siah Tagh dome show the linear trend in the eastern part of the dome. This temperature linear pattern in the Siah Tagh dome probably is related to the morning sunshine in the eastern slope of this dome. According to the resulting LST map, the highest temperature in the Gach salt dome is 41.87 °C and 36.7 °C in the Siah Tagh salt dome.
Tectonics
Rojan Hemati; Manouchehr Ghorashi; Ali Solgi; Abdollah Saidi
Abstract
The Zagros suture zone is one of Key regions. Continent - Continent collision between Arabian plate and Iranian Block. This region is coincided by High Zagros and Zagros Simply Fold Zones in Western side and in other side is the Sanandaj- Sirjan Zone. The region of this research in situated in Northern ...
Read More
The Zagros suture zone is one of Key regions. Continent - Continent collision between Arabian plate and Iranian Block. This region is coincided by High Zagros and Zagros Simply Fold Zones in Western side and in other side is the Sanandaj- Sirjan Zone. The region of this research in situated in Northern part of suture zone. The Zagros suture is oriented parallel to the other collision Structures as passive and active margins of Neo- Tethys Basin and also to Magmatic Arc (Urmiyeh - Dokhtar Arc).The main Faults in this region which we can mention by name are Zagros Main Thrust Fault and Zagros Main Recent Fault, Which they are also parallel to others structures. This region of suture zone in highly deformed and structures as folds, faults and nappes are the evident of a long compression Tectonics. The aim of this research firstly is analysing of folds and secondly is calculation of shortening rate of crust in this part of collision Zone. Three structural section (Eslam Abad- e- Gharb - Mahidasht, Kamyaran and Gazorkhani) have been balanced and the rate of shortening which is obtained respectively is 6252m , 6530m and 2040m.
Tectonics
Nayyer Bayeste Hasti; Hosein Motamedi; Mahmoud Almasian
Abstract
This study has focused on the result of seismic data. The first stage of basin formation is the opening of Neo- Tethys Sea which is Simultaneous with Dashtak, Kangan and Khaneh kat Formation and after that on the early to middle Triassic sediments an unconformity that can be named as an expansion of ...
Read More
This study has focused on the result of seismic data. The first stage of basin formation is the opening of Neo- Tethys Sea which is Simultaneous with Dashtak, Kangan and Khaneh kat Formation and after that on the early to middle Triassic sediments an unconformity that can be named as an expansion of sedimentary basin in the upper Triassic happened. This stage of basin opening caused the formation of big faults and probably basement faults in the area that studying on this faults and their movements is the main goal of this study. The next stage of evolution of basin starts when the basin began to closure and still there is disagreement about the exact time; but the obvious thing is the four compressional events: first, from Cenomanian- Turonian up to Masstrichtian; second, Late Paleocene- Early Eocene; third, Late Oligocene-Miocene and the forth, Miocene up to Quaternary. All events caused to obduction of Ophiolite and sedimentation of Gurpi with partly erosion and Pabdeh with regional erosion, then disappearing formations such as Asmari and Gachsaran and at the end, the late Zagros orogenic phase which is the compression that is continues to this day.
Tectonics
Ebrahim Gholami; Asghar Ahmadi; mohammadmahdi Khatib; Saeed Madanipour
Abstract
Located at the Arabia-Eurasia collision zone, the E-W trending Bozgoosh Mountain aligned perpendicularly to N-S trending Chehel-Nour Mountain in the northwest of the Iranian Plateau. There is not any thermochronometry study has been performed to determine the initial time of their uplift and exhumation. ...
Read More
Located at the Arabia-Eurasia collision zone, the E-W trending Bozgoosh Mountain aligned perpendicularly to N-S trending Chehel-Nour Mountain in the northwest of the Iranian Plateau. There is not any thermochronometry study has been performed to determine the initial time of their uplift and exhumation. Our low-temperature Thermochronometry analysis in the apatite U-Th/He (AHe) system in combined with previously unpublished data set at central Bozghush Mountains and structural data show that the onset of the Late Cenozoic uplift and exhumation of the Bozgoosh Mountain (~19-25 Ma) is a bit older than Chehel-Nour - Gaflankuh Mountain (~15 Ma). It seems that deformation of the Bozgoosh Mountains started at with respect to middle Miocene unset time of deformation at Chehl-Nour and Gaflankuh Mountain. Then it can be concluded that these two perpendicular maountain ranges have not been formed in a single phase of partitioned deformation. On the other hand N-S trending Chehel-Nour and Ghaflankuh Mountains have similarly deformedsynchronous with the N-S trending part of the southern Talesh Mountains in its eastern border. Our results have also document that the Bozgoosh and Chehl-Nour mountains intersection is actually a part of Bozgoosh mountain.
Tectonics
Marzieh Rostami; Morteza Talebian; Abbas Bahroudi
Abstract
Anticline axes in both orogenic belts of the Zagros and Kopeh Dagh are offset by NW-SE trending transvers faults. These faults are rotating anticlockwise due to their oblique orientation relative to maximum stress vector, causing shortening across the belt and elongation along the strike. The transverse ...
Read More
Anticline axes in both orogenic belts of the Zagros and Kopeh Dagh are offset by NW-SE trending transvers faults. These faults are rotating anticlockwise due to their oblique orientation relative to maximum stress vector, causing shortening across the belt and elongation along the strike. The transverse faults move right laterally and known as prominent faults of Bajgiran, Quchan, Shokranlou, Baghan in central Kopeh Dagh; and Kazerun, Karehbas, Sabzpushan, Sarvestan in central Zagros. Faults in two regions, however, show different pattern of offset. We proposed two different physical models, consist of rotating blocks at the base overlaid by sand with and without silicon layers, resembling variation of stratigraphy in two belts. In the Zagros model, where we have more incompetent layers, offset on the basement faults causes bending of the fold axes at the surface prior to any offset. While in the Kopeh Dagh, where we have less incompetent layers, the fold axes are offset with no major change in their orientation.
Tectonics
mohammadreza sheikholeslami; Shirin Elyasi; Mohamad Reza Ghasemi
Abstract
The Mohr circle is a well-known method for two-dimensional strain analysis. Due to the formation of the boudins during two stages of the progressive deformation (D1 and D4) in cherty marbles, from north Golpaygan metamorphic complex, they have been analyzed for strain in two-dimension. This analysis ...
Read More
The Mohr circle is a well-known method for two-dimensional strain analysis. Due to the formation of the boudins during two stages of the progressive deformation (D1 and D4) in cherty marbles, from north Golpaygan metamorphic complex, they have been analyzed for strain in two-dimension. This analysis is based on estimating of the initial length of the boudins before deformation, and measuring the current length of the boudins, after deformation. Calculation of the longitudinal parameters of the strain and drawing Mohr circles show that the strain ratio varies between 1.06 to 2.35 for D1 stage, and between 1.10 to 2.84 for D4 stage. The mean shear angle for the D1 stage is 22 ° and for the D4 stage is 24 °.
Sedimentology
Parvaneh Faridi; Payman Rezaee; AliReza Piryaei; Mehdi Masoodi
Abstract
Halokinetic Sequences are used for analyzing and connecting endogenous and exogenous influencing factors on the sedimentary sequences around the diapir. The most important effect of the diapir movement is the creation of different sedimentary spaces in the result of uplift and subsidence. So, the Handun ...
Read More
Halokinetic Sequences are used for analyzing and connecting endogenous and exogenous influencing factors on the sedimentary sequences around the diapir. The most important effect of the diapir movement is the creation of different sedimentary spaces in the result of uplift and subsidence. So, the Handun Salt Plug has been selected as a classic example. In the Handun salt plug outcrop Upper Cretaceous to recent sediments. The most important effect of the salt plug movement is during the Eocene of the Jahrum. The initial phase of salt extrusion was observed in the Gurpi Formation. Continuation of salt extrusion carrying on hook forms in the deep- water shale of the Pabdeh Formation in the Paleocene-middle Eocene. In the middle Eocene, when the Jahrum carbonate sedimentation exceeds the salt rise, wedges onlap the salt plug. In addition, thrusting led to the emergence of the salt tongues and forming hook in the Formation. The final phase of salt extrusion has been seen in the hooks in the siliciclastic of the Razak Formation. Finally, ongoing shortening is recorded by Guri member growth strata of the Handun salt plug. Our results provide new insights into using Halokinetic Sequences in tectono-sedimentary analysis of the Zagros diapirs.
Tectonics
Hamid Nazari; Jean-Francois Ritz; Ara Avagyan
Abstract
The Alborz mountain range accommodates some of the convergence between Central Iran and Eurasia. At present, the kinematics of the range involves a strain partitioning mechanism, and is associated with clockwise rotation of the South Caspian Basin. left-lateral strike-slip faulting is present along the ...
Read More
The Alborz mountain range accommodates some of the convergence between Central Iran and Eurasia. At present, the kinematics of the range involves a strain partitioning mechanism, and is associated with clockwise rotation of the South Caspian Basin. left-lateral strike-slip faulting is present along the entire of its central part, while reverse faulting is affects its northern and southern borders. Several slip-rate studies have been carried out along active faults in the internal and southern parts of the range. Our analysis provides new constraints on the activity of this important active thrust fault. We show that the fault generally is a hidden thrust fault, often associated with fault-bend and fault-propagation folds (forebergs). In the central part of the fault near Chamestan, radiocarbon dating on an old elevated terrace allows estimating the minimum vertical slip of 2.0± 0.5 mm / year. Considering a 34 degree slope for the fault, the minimum horizontal slip rate will be 3 mm/yr and the minimum slip rate along the fault plane will be up to 3.6 mm / year. Our results confirm that the Khazar Fault is a major active structure in northern Iran, and represents a significant seismic hazard for the entire Central Alborz region.
Tectonics
shima afkhami; Ahmad Alavi; Mohammad Reza Yamini; Mohamad Reza Ghasemi
Abstract
The main purpose of this study is to investigate and structureral analyzes of Sirri oil field by subsurface geophysical data. In order to Seismic interpretation from 3 seismic lines (LL3, LL4 and LL5) picked up by Iranian Offshore Oil Company and SIC-1 well Data was used. In addition to interpreting ...
Read More
The main purpose of this study is to investigate and structureral analyzes of Sirri oil field by subsurface geophysical data. In order to Seismic interpretation from 3 seismic lines (LL3, LL4 and LL5) picked up by Iranian Offshore Oil Company and SIC-1 well Data was used. In addition to interpreting the geological horizons and understanding the stratigraphic-structural evolution of the region they have also been used. The study area is located in the south of Iran and in the Persian Gulf. In this study, the geological analysis of the area has been studied by two-dimensional seismic surveying method and petrophysical images (up to Darian Formation) and Petrel software. The results show that the rising of the salt dome related to the Hormuz series has affected the overlying Formations in these field, and has created a dome shaped state for most of the Formations. Rising of the salt and folding of the sediments eventually resulted in faulting of the sediments. During the study and measurement of the angle between the edges, it was found that 15.2% of the folds are open and 84.8% are of the soft folds.
Tectonics
M. Kouhpeyma; M. Talebian; L. Chen; A. Ghods; M. Ghorashi
Abstract
The Kopeh Dagh and Binalud-Alla Dagh mountains are important structural elements located in the northeastern boundary of Arabia-Eurasia collision zone. Due to existence of large cities with a long history of civilization, there is a relatively rich body of data on historical seismicity in this area. ...
Read More
The Kopeh Dagh and Binalud-Alla Dagh mountains are important structural elements located in the northeastern boundary of Arabia-Eurasia collision zone. Due to existence of large cities with a long history of civilization, there is a relatively rich body of data on historical seismicity in this area. Nonetheless, little adequate instrumental seismic data were available prior to this study. In this paper, we utilized the temporary China-Iran local seismic network data deployed in the area for 13 months. Based on this data, we determined 37 focal solutions through first motion polarity approach suggesting a combination of strike-slip, reverse and normal mechanisms. There is a significant concentration of epicenters and focal mechanisms around the eastern Alborz - Kopeh Dagh boundary along the Atrak River. The southern and western boundaries of the Binalud Mountains also show relatively high seismic activities. The Local magnitude (ML) of the events ranges from 3.5 to 4.9 with depths of up to 20 km, mostly concentrated at ~10 km. The principal stress axes and slip vectors obtained from the focal mechanisms agree well with kinematic state of main faults and tectonic regime of the area, confirming the seismogenic nature of these faults. In addition, they are consistent with right-lateral component of slip along thrust faults in eastern Kopeh Dagh and Binalud and both laft- and right-lateral motions in the central Kopeh Dagh.
Tectonics
Ali Bandegani; Ali Yassaghi; Mohsen Eliassi
Abstract
In this paper, the structural evolution of Bamu fault zone located in the Zagros folded belt zone is presented as an example of northeast-trending fault zone in the Zagros, using the kinematic and dynamic analysis of accompanied structures. Based on structural and paleostress analyzes two phases of shortening ...
Read More
In this paper, the structural evolution of Bamu fault zone located in the Zagros folded belt zone is presented as an example of northeast-trending fault zone in the Zagros, using the kinematic and dynamic analysis of accompanied structures. Based on structural and paleostress analyzes two phases of shortening were determined as NE and NNE. In order to define the chronology of the deformation stages in the region, the relationship between fault structures and folds in the folded rock formations has been utilized. The result showed that the first compression stress trend in the area was NE that caused formation of the Bamu transverse Fault with left-lateral strike-slip mechanism and its accompanied structures. Since this stage of deformation has affected the Oligocene- early Miocene formations, more likely occurred at this time. During the next phase the shortening direction, due to change in the collision zone direction of the Arabian-central Iran in the Miocene-Pliocene, has changed to NNE which causes development of younger structures in the form of folding and reverse faulting in the fault zone. This shows that the NE-trending fault zones, like other major NW-faults, in Zagros affected by the change in the convergence of Zagros collision.
Tectonics
Firouzeh Shavvakhi; Saeed Madanipour; Ebrahim Rastad
Abstract
South Natanz Area is structurally located in the western part of the Central Iranian structural zone and central part of the Orumieh-Dokhtar magmatic belt at southwestern termination of the Qom-Zefreh Fault. Our structural data represents older generation of E-W to NW-SE thrust faults as Fasakhod Fault ...
Read More
South Natanz Area is structurally located in the western part of the Central Iranian structural zone and central part of the Orumieh-Dokhtar magmatic belt at southwestern termination of the Qom-Zefreh Fault. Our structural data represents older generation of E-W to NW-SE thrust faults as Fasakhod Fault that juxtaposes Permian- Triassic (Jamal, Nayband and Shotori Formations) over younger rock units. Most of the thrust faults have been cross cut with younger generation of strike-slip fault system. These mainly post Eoene strike slip fault systems are structurally linke to Qom-Zefreh Fault zone. On the other hand, they developed as strike slip orders of the Qom-Zefreh Fault system in central part of the Orumieh-Dokhtar magmatic belt. Integration of the structural data set with stratigraphic unconformities observed in the south Natanz represet regional folding of the area during pre Early Cretaceous time. Subsequently, it has experienced regional extension as observed in the other parts of the central Iran during Early Cretaceous time. Major thrust faulting of the area has been occuered during post Late Createcous time. The final post Oligocene strike slip faulting related to the activation of the Qom- Zefreh fault has overprinted and cross cut older structural features.
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. ...
Read More
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 ...
Read More
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 ...
Read More
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.
