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a Compression recorded in the upper Cretaceous rocks. b Compression recorded in the Paleocene rocks. c Compression recorded in the eocene; Φ ratio is indicated in the bracket
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Eastern Iran, including the Sistan suture zone, comprises the boundary between Lut block and Afghan block. This research aims to reconstruct the stress regime evolution from the upper Cretaceous to Quaternary based on the brittle tectonic analysis. In this study, three episodic changes in stress regimes were recognized in the Shekarab Mountain usin...
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... Cretaceous fault kinematics. The Cretaceous rocks are distributed throughout the study area; eastern sites are 13, 17, and 19, and western sites are 33 and 34. There are two outcrops of Cretaceous time in the peridotite and ophiolites rocks (sites 13 and 17), faults observed in these two sites are reverse, and stress regimes are compressional (Fig. 4a). Operations of compressional stress regime in the eastern part of the study area caused the uplifting of peridotites and ophiolites in the east of the study area, and major stress axis (σ1) in sites 13 and 17 had an NW-SE trend. Analysis of data collected from sites 33 and 34 located in the F8 and F9 reverse faults indicates a ...
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This research assessed stress regimes and fields in eastern Iran using fault-slip data and the tectonic events associated with these changes. Our stress analysis of the brittle structures in the Shekarab Mountains revealed significant changes in stress regimes from the late Cretaceous to the Quaternary. Reconstructing stress fields using the age an...
As a part of the Kermanshah ophiolite in western Iran, the Cretaceous Nourabad-Dinavar ophiolitic complex is a remnant of the Neo-Tethys oceanic lithosphere and represents transitional mantle-crust and upper crust units in the Nourabad and Dinavar regions, respectively. All the units were affected by the two metamorphic regimes of static metamorphi...
Abgarm ultramafic complex is a part of the Esfandagheh-Hajiabad coloured melange belt located in the south east of the Iranian segment of Alpine-Himalayan orogenic belt. The complex has faulted contacts with flysch-type sediments of the upper cretaceous ophiolite melange complex. Although Harzburgite is the dominant lithotype, dunites and lherzolit...
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... Moreover, most of the faults in these two splays are thrust with left-lateral components, which were activated as a result of the NE-SW direction stress regime. In the Khousf splay direction of the compression (σ1), it is close to N026° (Ezati et al. 2020(Ezati et al. , 2021. Based on our structural analysis of the Khousf region, a schematic model and related structures have been proposed and drawn (Fig. 4). ...
The Sistan suture zone comprises the boundary between Lut and Afghan blocks. The north-south shear between Iran and Afghanistan is accommodated by several right-lateral strike-slip fault systems. The study area (northern Birjand Mountain range) is a part of Khousf splay; the most important faults in the Khousf splay are sinistral with reverse component and thrust with sinistral component faults; the Khousf splay is a sinistral transpressional zone including shear folds, pop-ups, positive flower structures, and duplexes. In this research, we used field data including geometric and kinematic characteristics of the faults to determine the structural deformation model of the northern Birjand Mountain range. In the northern Birjand Mountain range, several ~E-W striking faults cut through geological units; geometric and kinematic analyses of these faults indicate that almost faults have reverse components which reveal existing of compressional stress in the study area. The northern Birjand Mountain range has been characterized by main reverse faults with ~E-W striking faults. Moreover, most of the faults in the Khousf splay are thrust with left-lateral components, which were activated as a result of the NE-SW direction stress regime. The Khousf splay is a sinistral shear zone, and the beginning of deformation in this splay is from east to west. Structural analysis in the study area indicates that the F1 and F2 reverse faults have southward dips and F3 and F4 reverse faults have northward dips. Investigating the faults in the northern Birjand Mountain range implies that these reverse faults join the Nehbandan fault system. The Nehbandan fault system has splays in the Northern and Southern terminals, and the northern terminals of the Nehbandan fault are reverse faults with nearly E-W striking. The main reverse faults of the study area include F1 to F4 faults which are continuations of the Nehbandan fault system. Therefore, the kinematics and geometry of these faults in the northern Birjand Mountain range suggest pop-up and positive flower structures in a sinistral transpressional zone.
... The northward motion of Arabia with respect to Eurasia is controlling the active tectonics of Iran, as indicated by the current mean direction of σhmax (σ1)~N010 • , measured by GPS motion relative to Arabia-Eurasia convergence [6,15,53]. The active subduction of the Arabian Plate below the Iranian micro-continent is visible on the surface of the Makran tectonic province [54]. ...
This research assessed stress regimes and fields in eastern Iran using fault-slip data and the tectonic events associated with these changes. Our stress analysis of the brittle structures in the Shekarab Mountains revealed significant changes in stress regimes from the late Cretaceous to the Quaternary. Reconstructing stress fields using the age and sense of fault movements showed that during the late Cretaceous, the direction of the maximum horizontal stress axes (σ1) under a compressional stress regime was ~N290°. This stress regime led to the uplifting of ophiolites and peridotites in eastern Iran. During the Eocene, the σ1 direction was NE-SW. The late Eocene and Oligocene stress states showed two distinct transpression and transtension stress regimes. This transition from transpression to transtension in the eastern Shekarab Mountains was the consequence of regional variations in stress regimes. The Quaternary stress state indicates that the tectonic regime in the Quaternary is strike-slip and the σ1 direction is ~N046°, which coincides with the current convergence direction of the Arabia–Eurasia plates. Our paleostress analysis revealed that four distinct stress regimes have been recognized in the area, including compressional, transtensional, transpressional, and strike-slip regimes. Our findings indicated that the diversity of the tectonic regimes was responsible for the formation of a variety of geological structures, including folds with different axes, faults with different mechanisms, and the current configuration of the Sistan suture zone.
... Moreover, in this research, the structural style of the study area was investigated using geometrickinematic analysis. This methodology has been found to be useful in places such as northeast Iran [14,15]; the Himalayan fold-thrust belt [16]; the Andes [17]; the Zagros mountain range [18], the Mosha fault in the Central Alborz range, Iran [19]; NE Ghats Province, India [20], the western Ordos fold-thrust belt, China [21]; the NW Zagros Mountains, Kurdistan Region, Iraq [22]; and Shekarab Mountain in eastern Iran [23,24]. ...
In this paper, faults, one of the most important causes of geohazards, were investigated from a kinematic and geometric viewpoint in the northern part of the Sistan suture zone (SSZ), which serves as the boundary between the Afghan and Lut blocks. Furthermore, field evidence was analyzed in order to assess the structural type and deformation mechanism of the research area. In the northern Birjand mountain range, several ~E–W striking faults cut through geological units; geometric and kinematic analyses of these faults indicate that almost all faults have main reverse components, which reveals the existing compressional stress in the study area. The northern Birjand mountain range is characterized by four main reverse faults with ~E–W striking: F1–F4. The F1 and F2 reverse faults have southward dips, while the F3 and F4 reverse faults have northward dips. Moreover, the lengths of the F1, F2, F3, and F4 faults are 31, 17, 8, and 38 km, respectively. These faults, with reverse components that have interactive relationships with each other, form high relief structures. The study area’s main reverse faults, including F1 to F4, are extensions of the Nehbandan fault system, while their kinematics and geometry in the northern Birjand mountain range point to an N–S pop-up structure.
... The subduction-originated accretionary complex of the Cretaceous to the Oligocene (Tirrul et al., 1983) is a part of the SSZ that shows en echelon structures organized from at least the Oligocene to present as a result of right-lateral motion (Berberian et al., 2000;Ezati et al., 2020Ezati et al., , 2021Freund, 1970). The recent instrumental seismicity and different morphologic indicators of the main faults indicate the SSZ is a tectonically active structure (Berberian et al., 2000;Walker & Khatib, 2006). ...
Geodetic and seismological data are crucial for examining the kinematics and active tectonics in structural zones. The current tectonic stress field can be inferred from the focal mechanism stress inversion (FMSI) and the seismic and geodetic strain rates (SSR and GSR). In this study, a reliable focal mechanism solution for earthquakes from 1968 to 2020 and GPS data from 2006 to 2015 were used to calculate the direction and magnitude of maximum principal strain rates to evaluate the seismic potential of eastern Iran, where more than 10 strong instrumental earthquakes (Mw ≥ 6) have occurred over the past three decades. A new stress map was proposed for the study area by analyzing the weighted average of FMSI, SSR and GSR in which the direction of the mean stress was estimated at ~ N36 E. Results show that the northeast of the Lut block is generally controlled by the transpressional deformation zones with oblique faulting. Moreover, we observed left-lateral and right-lateral shearing as well as dip-slip movements in different parts of the area. According to the stress inversion results of focal mechanism solutions, the study area can be categorized into four main groups of stress regimes: strike-slip (43.75%), thrust (35.41%), normal (4.17%), and unknown or oblique faulting (16.67%). The estimated geodetic shear strain rates (GSSR) show a maximum shearing rate around the Abgarm and the Abiz (Ardakoul) right-lateral strike-slip faults in the boundary of the Sistan Suture Zone (SSZ) with the Afghan block. Seismic and geodetic strain rates were compared with seismic and geodetic moment rates (SMR and GMR) to investigate the seismicity pattern and the structural evolution of the area. The high seismic-geodetic moment-rate ratio of about 92.1% reflects a fully seismic deformation of the study region. According to our calculations, the northern part of the SSZ includes about 89.82% of these ratios, indicating high seismic behavior, while the northern part of the Lut block includes about 2.28%, which indicates an aseismic deformation in this part. The data analysis exhibits more significant seismic hazard along the Dorouneh fault zone and Sedeh, Shekarab, south Birjand, and Birjand faults.
... The Quaternary direction of compression (σ1) is relatively coinciding with the present-day Arabia-Eurasia convergence direction (Jentzer et al. 2017). In the Shekarab Mountains, the Quaternary stress state is strikeslip and the average direction of maximum stress axis (σ1) is toward N026° (Ezati et al. 2020). The NW-SE striking thrust faults and chains are perpendicular to the direction of current maximum horizontal stress (NE-SW) as inferred from earthquake fault plane solutions. ...
In order to evaluate the level of tectonic activities in the Shekarab Mountains, several geomorphic indices such as stream length gradient index (SL), valley floor width to valley height ratio (Vf), hypsometric curve (Hc), hypsometric integral (Hi), drainage basin shape (Bs), and relative tectonic activity (Iat) were calculated. Vf values show fastest uplift, deepest valleys, and highest river incision are associated with the basin 24. The high values of SL in the range of 900 to 3250 on the high resistance rocks related to the western basins indicate that the western part of the Shekarab Mountains has had recent tectonic activities. Moreover, distribution of high Hc and Hi values are related to the highest tectonic activity in the western and northeastern basins. Accordingly, the study area was divided into four subareas based on Iat values, which are the following: class 1, very high relative tectonic activity (10.17%); class 2, high relative tectonic activity (11.77%); class 3, moderate relative tectonic activity (29.96%); and class 4, low relative tectonic activity (48.10%). It can be concluded from the Iat values that different parts of the study area had undergone unequal uplift and tectonic activities in the NE-SW direction are showing the highest uplift rate, which is in consistency with the present time compression direction in the Shekarab Mountains.
Structurally Lut zone is include of the four main trends that N-S and NE-SW trends are more prevalent in the northwest, as well as the magnetic trends confirm these structural trends. In terms of mineralization, the most important parts are related to the eastern and western parts of the Nayband fault zone. The most important mineralizations observed in these parts are lead and zinc. In the Uzbek Kuh areas which are located at the north of Boshrouyeh, the remains of ancient and today mines are considered by geologists and miners. Fault zones with the general NE-SW trend are the most important structures that caused movement and placement of the mineralized solutions. By evaluating and recognizing the relationships between the structural and geophysical features of this part of the Lut structural zone, it is possible to identify suitable areas for the continuation of lead and zinc mineralization.
سنگ¬های آذرین در راستای پهنه گسلی نهبندان یکی از منابع بی پایان انرژی در خراسان جنوبی هستند. واحدهای سنگی زیرپهنه سیستان در استان¬های خراسان جنوبی و سیستان و بلوچستان، مجموعه ای از واحدهای دگرگونی، رسوبی، آذرین و آذرآواری¬ها هستند که در اثر فعالیت پهنه اصلی گسل نهبندان و سرشاخه¬های آن دچار دگرشکلی و برش خوردگی شدید شده اند. واحدهای آذرین مربوط به دوره چهارم زمین شناسی در خاور ایران می¬توانند یکی از منابع مهم زمین گرمایی محسوب گردند. یکی از جوانترین واحدهای سنگی در خاور ایران که می¬تواند نقش موثری در تولید انرژی ایفا نماید واحدهای آذرین از نوع بازالتی هستند که در نقاط مختلف و از جمله راستای گسل نهبندان در سطح زمین دیده می¬شوند. بدلیل اینکه پهنه گسلی نهبندان دارای شیب زیاد و سازوکار امتدادلغز راستگرد می¬باشد، تداوم آن به اعماق زمین باعث گردیده است که این پهنه گسلی به هجره های ماگمایی راه یابد. فعالیت گسل مذکور و اتصال سرشاخه های آن باعث ایجاد فضای مناسب برای بالاآمدن مواد مذاب ایجاد کرده¬اند. هندسه¬ی پهنه اصلی با راستای شمالی – جنوبی و سازوکار راستگرد و همچنین چرخش بلوک¬های گسلی ناشی از اتصال شکستگی¬های وابسته به آن در رفتار شکننده¬ی سنگ¬ها، باعث ایجاد فضای خالی در حاشیه بلوک¬های گسلی و راه یافتن مواد مذاب به سطح زمین گردیده است. بدلیل جوان بودن حرکات گسل نهبندان از نظر زمین شناسی، واحدهای آذرین در راستای آن در اعماق بسیار کم پوسته ای جای گرفته¬اند و درجه زمین گرمایی نیز در آنجا بالا و دستیابی به منبع انرژی آسان خواهد بود.
In the Central part of the Kopeh Dagh, there are a set of active right-lateral strike-slip faults that obliquely intersect the range and cause displacement in geomorphological and geological structures. In order to evaluate the rate of tectonic activities in the Central Kopeh Dagh, T, SL, Vf, HI and RIAT morphometric indices were evaluated. The average value of T index is equal to 0.25, and the main rivers are tilted toward the south. So, the E-W trending folds and thrusts, which are parallel to the basins, have caused the main river to tilt to the south. The highest value of the SL index is related to the intersection of the strike-slip faults which cut the sixth and seventh order rivers. The lowest values of the Vf index are related to the northern part of the studied region; hence, the V-shape valleys and high incision rates are associated with the high degree of tectonic uplift in the Shirinrood basin. Moreover, high values of the SL index and low values of the Vf index are related to the intense tectonic activities in the northern part of the Central Kopeh Dagh. The hypsometric integral (HI) indicates that the highest rock uplifts rate happened in the Shirinrood basin. Neotectonic analysis of the Central Kopeh Dagh shows that the northern part of the study area has the highest tectonic activity and earthquake risk.
