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Through the examination of calcite twins, this research outlines the tectonic development and paleo stress patterns of the Paleozoic Routshon complex situated in the southeastern segment of the Sanandaj-Sirjan zone, a hinterland region of the Zagros orogeny in southeastern Iran. The study of orogenic phase indicates that the deformation event affecting the southern sector of the Sanandaj-Sirjan zone aligns with the Cimmerian orogenic phase of the Late Triassic period. A variety of structural features at both map and outcrop scales highlight the importance of slip partitioning in the structural evolution of this region, driven by inclined transpression. Observations suggest that the deformation related to contractional components includes steeply to moderately plunging folds, dipslip domain deformation primarily involving thrusts, and ongoing deformation by strike-slip component motion, which results in thrust-related ductile shear zones. The analysis of calcite c-axis fabrics from mylonite samples obtained from these shear zones indicates a low-temperature monoclinic pattern of non-coaxial deformation. This deformation type underscores the impact of the strike-slip component in the development of progressive simple shear within thrust-related shear zones in this segment of the Sanandaj-Sirjan zone. Dynamic analysis of caxis fabric data reveals a NE-SW orientation for the principal compressive axes (σ1) in this area. This direction, corroborated by additional data such as fault surface, GPS, and earthquake focal mechanism data, confirms that the orientation of the compressive axes (σ1) has remained consistent from the Late Triassic to the present. [ABSTRACT FROM AUTHOR]

Azizi, H., Daneshvar, N., Asahara, Y., Minami, M. & Anma, R. (2023). The generation of Eocene mafic dike swarms during the exhumation of a Core complex, Biarjmand area, NE Iran. Journal of Petrology 64 , 1–18 have attributed the E–W-oriented mafic dike swarm in the Biarjmand metamorphic core complex to an Eocene extensional event which is much younger than a previously suggested Late Jurassic–Early Cretaceous age. They proposed that the emplacement of these dikes occurred in a rapid extensional regime coeval with the exhumation of the core complex after gravitational instability in the Central Iran/Eurasia collision zone. I appreciate the opportunity this article provides to shed light on specific aspects of the Late Mesozoic–Early Cenozoic continental extension within the Eurasian sector of the Neotethys subduction system. However, I here bring to attention certain discrepancies within Azizi et al. 's publication. Specifically, the assignment of an Eocene age to the emplacement of the E–W-oriented dike swarm, even though purportedly supported by U–Pb zircon dating, appears to be at odds with field observations and previously published geochronological data. Furthermore, the article contains internal contradictions in its presentation of the core complex model for the study area. It is important to note that Malekpour-Alamdari, A., Axen, G. J., Heizler, M. T. & Hassanzadeh, J. (2017). Large-magnitude continental extension in the northeastern Iranian plateau: insight from K-feldspar 40Ar/39Ar thermochronology from the Shotor Kuh-Biarjmand metamorphic core complex. Geosphere 13 , 1207–1233 previously documented the geochronological-based metamorphic core complex model of the area. Regrettably, despite its direct relevance, these earlier works have not been acknowledged in Azizi et al. 's paper. In this comment, I outline the problems with the structural and regional geology, the zircon U–Pb age of the dike samples, the age of the dike swarm, and the geodynamic interpretations in Azizi et al. 's work. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In recent decades, there has been a growing emphasis on assessing aquifer vulnerability. Given the availability of spatial data and the GIS advantages, mapping the groundwater vulnerability has become a common tool for protecting and managing groundwater resources. Here, we applied the GIS indexing and an overlay method to explore a combination of the potential contamination factors needed to assess groundwater vulnerability in the Mosha aquifer. The data from a borehole data logger and chemical analysis of spring water show groundwater responses to the surface contaminating sources. To assess the aquifer vulnerability, the potential contaminating sources were classified into three groups, namely (1) geological characteristics such as lithology and structural geology features; (2) the infrastructures induced by human activities such as roads, water wells, and pit latrines; and (3) land use. By considering these components, the risk maps were produced. Our findings indicate that the aquifer is very responsive to the anthropogenic contaminants that may leak into the aquifer from urbanized areas. Additionally, roads and pit latrines can significantly release pollutants into the environment that may eventually leak into the aquifer and contaminate the underlying groundwater resources. [ABSTRACT FROM AUTHOR]

The Asmari reservoir in Haftkel field is one of the most prolific naturally fractured reservoirs in the Zagros folded zone in the southwest of Iran. The primary production was commenced in 1928 and continued until 1976 with a plateau rate of 200,000 bbl/day for several years. There was an initial gas cap on the oil column. Gas injection was commenced in June 1976 and so far, 28% of the initial oil in place have been recovered. As far as we concerned, fracture network is a key factor in sustaining oil production; therefore, it needs to be characterized and results be deployed in designing new wells to sustain future production. Multidisciplinary fracture evaluation from well to reservoir scale is a great privilege to improve model's accuracy as well as enhancing reliability of future development plan in an efficient manner. Fracture identification and modeling usually establish at well scale and translate to reservoir using analytical or numerical algorithms with the limited tie-points between wells. Evaluating fracture network from production data can significantly improve conventional workflow where limited inter-well information is available. By incorporating those evidences, the fracture modeling workflow can be optimized further where lateral and vertical connectivity is a concern. This paper begins with the fracture characterization whereby all available data are evaluated to determine fracture patterns and extension of fracture network across the field. As results, a consistent correlation is obtained between the temperature gradient and productivity of wells, also convection phenomenon is confirmed. The findings of this section help us in better understanding fracture network, hydrodynamic communication and variation of temperature. Fracture modeling is the next step where characteristics of fractures are determined according to the structural geology and stress directions. Also, the fault's related fractures and density of fractures are determined. Meanwhile, the results of data evaluation are deployed into the fracture model to control distribution and characteristics of fracture network, thereby a better representation is obtained that can be used for evaluating production data and optimizing development plan. [ABSTRACT FROM AUTHOR]

Earth fissure structures are a common type of geohazard associated with geotechnical surface ruptures that can occur almost anywhere on the ground surface due to a variety of different mechanisms, and in most cases, these hazardous cracks have resulted in severe damage to infrastructure. Investigation of the structural characteristics of fissures in an active tectonic area (such as Birjand in eastern Iran) can improve our understanding of connections between the fissures and structural geology. The first reported earth fissures in NW Birjand are distributed along the North Birjand fault. Field observations and analysis of the detailed topography cross-sections using the real-time kinematic (RTK) technique have been used to infer the fissure development. Morphometric analysis of faults and fissures shows that the long axis of most fissure structures is distributed perpendicular to the strike of the North Birjand fault. The average volume strain in the study area was calculated to be 14.68 percent based on fissure geometry studies, with the maximum volume strain corresponding to the location of the North Birjand fault's youngest splay. This splay formed fault-propagation folds with exposed fissure structures. This study shows that the fault-propagation folds in this system are subjected to the activity and evolution of the ground fissure as a result of the expansion of tensile stress. [ABSTRACT FROM AUTHOR]

The morphotectonic analysis is a useful time-saving and cost-effective method to assess tectonic activity, especially in large regions. In this paper, the morphotectonic study was carried out in Kerman city which is in the southeast of Iran and is a part of the Central Iran structural zone. Despite the occurrence of numerous historical and instrumental earthquakes around Kerman city, there is a gap in earthquake records of this city that has obscured its seismicity status. The aim of this study is to identify active faults and the associated seismic hazard to Kerman city. For this purpose, seven geomorphic indices namely 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) were examined for 51 basins of the study area, using digital elevation model (DEM) and geological maps in a GIS environment. Then, two kinds of relative tectonic activity indices were calculated for each basin, i.e., Iat and Iat_T, from the combination of these indices. The Iat_T was chosen because its results show better agreement with the structural geology and seismic records of this region. Finally, the study area was divided into three regions according to the Iat_T values. The morphotectonic analyses indicate that the Kuhbanan fault system, especially its southern splays, has the potential to produce serious seismic hazards to Kerman city in the future; the Mahan-Jupar fault-related folds, the southern tip of the Jorjafk fault, the probable fault of Zangi-Abad, the Rafsanjan-Zarand fault system, and Gowk fault are considered as other threats to Kerman city. Furthermore, this study reveals that morphotectonic analysis is a reliable tool to evaluate fault capability and to determine the fault types, and therefore to estimate seismotectonic hazard. [ABSTRACT FROM AUTHOR]

The application of multivariate statistical analysis (MSA) in analyzing drainage basin morphometry, in conjunction with seismic events (focal mechanism) and associated tectonic influences, has been discussed less in the framework of existing geomorphometric studies. Hence, in this study, an integrated approach was designed combining the geomorphometric analysis with MSA, focal mechanism and associated structural lineaments (using a remote sensing and GIS framework) to address the role of active tectonism on the drainage network characteristics in Qorveh-Dehgolan basin located in western part of Iran (Kurdistan province). Eight watersheds were delineated from burnt ASTER DEM using SWAT model and categorized into high-altitude watersheds and low-altitude watersheds. Four-sets of the drainage network were extracted from satellite imageries (Landsat 7 and 8) over a period of 17 years (2000–2017) to monitor the temporal stream network behavior. Overall, nineteen morphometric parameters were calculated (and categorized into linear, aerial, and relief aspects) exhibiting significant changes in the drainage network from 2000 to 2017 (the stream order declined from 5th to 4th order). The higher-altitude watersheds showed various anomalies in the calculated indices (indicating the potential influence of tectonic activity), while the lower altitude watersheds did not exhibit any specific anomalies. In addition, higher concentration of longer lineaments was observed in areas where the relatively resistant, fractured bedrock lithology (meta-volcanic and meta-sedimentary rocks) provided favorable conditions for origin and propagation of the lineaments. Further analysis of focal mechanism solutions (FMS, beachball diagrams) showed that the study area is primarily influenced by moderate earthquake events (3 ≤ Mw ≤ 6) and is influenced by a complex fault mechanism (primarily normal faults and strike slip faults). The morphometric parameters were further subjected to the factor analysis (principal axis factoring using Varimax rotation transformation) resulting in derivation of "factor of basin magnitude", "factor of steepness" and "factor of texture" as three principal factors impacting the drainage network. Finally, it was concluded that "factor of steepness" played a decisive role in defining hydrology of higher-altitude watersheds (an indication of tectonic influences in these watersheds) and thereby defining the overall hydrology of the study area as well. Overall, this study highlighted the significant role of the tectonic activity associated with structural lineaments and the seismic events in defining the nature and behavior of the drainage network and certain anomalies caused in the basin hydrology under these structural controls. [ABSTRACT FROM AUTHOR]

Bajalia Anticline is located about 60km northeast of central Amarah city in the Al-Teeb area near the Iraq-Iran border. Field and laboratory works were conducted to study topography, geomorphology, stratigraphy, and structural geology of Bajalia Anticline. The Anticline has a longitudinal shape with about 29km in length and 5-7km in width. Injana, Mukdadiya, and Bai Hassan formations are the three formations that were recognized in the study area. The geometrical structural analysis depicts that the Anticline is non-cylindrical, asymmetrical, close, subhorizontal, steeply inclined, and linear fold. Most of the fractures in the Anticline are joints. These joints were classified based on the tectonics axes, which are a, b, and c, into ac, be, and hol. A major reverse fault is located at the margin of the southwestern limb parallel to the fold axis with about 25km length. This fault is responsible for the vergence of the Anticline and overturned part of the southwestern limb. The Anticline was formed as a result of the collision between the Arabian and Iranian plates during the Late Tertiary. The maximum stress axis, which is caused by collision, is perpendicular to the hinge line. The geometrical and genetic classification indicates that the Anticline was formed by the high folding intensity and with a role of evaporites layers. [ABSTRACT FROM AUTHOR]

Among the many factors causing damage to lifelines, there are active faults along the pipeline route that can cause fracture and breakdown of the pipeline if it is justified. Thus, during pipeline route study phase, detailed geological work on the route should be undertaken and fault paths identified. It is, therefore, essential to study the structures of the study area to select the appropriate path. Due to crossing of Iranshahr–Mirjaveh gas pipeline in the eastern part of Iran at the intersection with the southern terminals of the Nosrat-Abad fault system, careful study of the geology and structural interpretation of these faults in terms of damage to the pipeline is necessary. Therefore, in this study, fault displacements and damages considering fault width at intersection with lifelines (buried gas pipelines) are modeled and evaluated by special software programs. Therefore, in this paper, considering a specific area in eastern Iran and using available software to simulate the active fault and analyze their effects on pipelines and considering the impact of active fault zones on three issues selected (strike-slip, strike-slip–reverse and reverse faults) have been investigated to improve the design parameters routing of lifelines (buried gas pipelines) in the future. [ABSTRACT FROM AUTHOR]

The groundwater may recharge the surface water bodies through seepage faces and springs. The spatial correlation between the fault zones and the groundwater seepage faces results in deep understanding of the hydrogeologic regime, especially where there is no monitoring boreholes. Locating these recharging zones by conventional methods is a challenging task; particularly in areas where (1) there is no hydrogeologic monitoring boreholes or reliable data, (2) private pumps withdraw the stream, and (3) intense canopy limits the use of drones and satellite images. This paper aims to study the relationship between the fault zones and occurrence of the groundwater seepage faces by using the high resolution handheld thermal imaging cameras as a tool to locate the seepage faces along a small river in the Damavand County, north of Iran. The correlation between the structural geology features and occurrence of the groundwater seepage faces revealed that the stream in the study area is being recharged by the groundwater at extensive fault zones. Additionally, this study suggests that the handheld thermal imaging cameras are a useful robust tools to evaluate the surface-groundwater interaction. However, it is essential to use the field structural geologic and hydrogeologic observations to interpret the thermal images. [ABSTRACT FROM AUTHOR]

Mélanges are formed by sedimentary, tectonic and diapiric processes and are generally found in collisional belts. The Zagros Orogeny provides an intriguing geological laboratory for the study of mélange‐forming processes during the progressive tectonic evolution of the Neotethys Ocean. Different types of tectonic and sedimentary mélanges occur in specific structural positions within the Zagros orogenic belt in the Neyriz Region (Iran). Based on their block‐in‐matrix fabrics, and tectonostratigraphic positions, we differentiated 14 different mélange types, which mark different episodes of the tectonic evolution of the Neyriz Region from the Cretaceous subduction to the Miocene collision. The Cretaceous subduction stage is recorded by volcanic‐sedimentary mélanges (Mv). Sedimentary mélanges characterized by megabreccia from the Cretaceous limestone (Ms1) and Eocene polymictic megabreccia (Ms2) represent epi‐nappe mélanges formed during the Palaeocene–Eocene in wedge‐top basins. The ophiolite emplacement in the Oligocene resulted in local extensional tectonics in the upper part of the ophiolitic nappe, and deposition of a polymictic megabreccia (Ms3, Ms4). As the final production of the Neotethys Ocean closure and the Eurasian‐Arabian collision, the sedimentary mélanges characterized by different types of chaotic rock units (Ms5, Ms6, Ms7 and Ms8 facies) were developed in front of the Cretaceous–Eocene nappes due to growth of the orogenic wedge in the Miocene. Our findings indicate that the recognition and distinction of different types of mélange may provide additional constraints for a better understanding of the tectono‐sedimentary evolution of the Neotethyan region. [ABSTRACT FROM AUTHOR]

Reservoir connectivity has a considerable effect on reservoir characterization, plans for field developments and production forecasts. Reducing the uncertainties about the lateral and vertical extension of different pay zones is the main step in developing and managing the reservoirs. Nearly all the proposed methodologies for the verification of reservoir connectivity are limited to the study of the communication of different compartments in one field. In the presented paper, first a comprehensive procedure is proposed to study the reservoir connectivity between nearby fields. The steps in this procedure are not necessarily hierarchy, but all the considerations in each step are studied to cover all the uncertainties that affect the reservoir communication. This procedure mainly comprises the study of reservoir extension, pressure communication in the hydrocarbon column, fluid similarity, top seal efficiency and faults sealing. Then, to apply this procedure for proving the communication between nearby fields, a case study of Ilam Formation in southwest of Iran is presented. The results confirm the lateral connectivity of the three pre-explored distinctive oil fields in Ilam Formation. The established connectivity leads to an increase in the pre-estimated oil-in-place volumes. This incorporated case study demonstrates how different data including geophysics, structural and petroleum geology, production and reservoir engineering are integrated to prove the communication of Ilam reservoir between these fields. This manifested technique is a powerful road map for other cases worldwide and is extremely recommended to be performed before developing those fields that are suspicious to lateral connectivity. [ABSTRACT FROM AUTHOR]

Complex geology and tectonics of the NW Iran, the Caucasus region, and Eastern Turkey, are responsible for the present‐day landscapes of the region. The Aras drainage basin located in Iran, Azerbaijan and Armenia borders, provides an appropriate geographical environment for systematically studying the landforms produced or modified by active tectonic processes. Several morphometric indices were calculated for 114 sub‐basins to assess relative tectonic activity levels. Results were evaluated using two different methods; Index of Active Tectonics (IAT) and Analytical Hierarchy Process (AHP) methods. IAT results show that 2% of the sub‐basins belong to very high, 25% to high, 46% to moderate and 27% to low tectonic activity classes. AHP results, display that 12% of the sub‐basins belong to very high, 25% to high, 43% to moderate, and 20% to low tectonic activity classes. Results of both methods show approximate consistency and indicate that the tectonic activity along the Aras drainage basin is moderate to high and decreases from southwest to the northwest which is probably due to terminating fault branches in young unconsolidated deposits or strain partitioning processes. The major fault zones (e.g., Aras, Pambak–Sevan–Sunik, Akera, and Moghan fault zones) include areas with very high and high tectonic activity classes. Accordingly, the uplift rates have been estimated as >0.5 mm/yr for central and western parts, whereas the uplift rates are relatively less in the eastern part (<0.5 mm/yr). The Aras fault zone includes five active structural segments that the main Aras and Horadiz segments of them show relatively higher tectonic activity. [ABSTRACT FROM AUTHOR]

The 2017 April 5 M w 6 Sefid Sang earthquake occurred east-northeast of the town of Fariman between the Binalud Mountains, at the northeast boundary of the Arabia-Eurasia collision zone, and the Doruneh Fault which defines the northern limit of the Lut Block. The pattern of present-day deformation in this area is not well understood. We combine results from studies of earthquake location, focal mechanism solutions and Interferometric Synthetic Aperture Radar (InSAR) to investigate the coseismic displacements. The active deformation of the source region is investigated through a synthesis of the structural geology, complimented by geological fieldwork. Our results reveal that the mainshock nucleated at a depth of ∼15 km on a reverse fault plane dipping north-northeast, with a component of dextral faulting. Rupture in the mainshock was almost unidirectional towards the southeast. The temporal growth of the 24-km long aftershock cloud reflects migration of seismicity towards the southeast. Analysis of ascending and descending interferograms of TOPS S1 SAR images show a maximum of 9 and 11 cm of surface deformation, respectively. A rupture model based on the inversion of the InSAR interferograms features a maximum slip of 83 cm on the NNE-dipping fault plane. Inversion of fault-slip data from earthquake focal mechanisms and geological field measurements indicates a contemporary regional transpressional tectonic regime characterized by a NE-trending maximum compression (mean direction of N020°E for seismological slip data and N029°E for geological fault kinematics). This implies a transpressional active kinematics according to which the Central Iran–Eurasia convergence is taken up by reverse dextral faulting on several NW-striking faults such as the eastern termination of the Doruneh fault and the southeast termination of the Chakaneh-Neyshabur fault systems. Our seismological, geodetic and geological results consistently indicate accommodation of active deformation by oblique-slip reverse faulting that is distributed in the region connecting the distinct block-bounding fault systems of northeast and eastern Iran. We propose a transpressional relay zone structural model to explain the nature, kinematics and structural pattern of the boundary of the collision zone between the Doruneh Fault and the Binalud Mountains. Our observations and results could shed light on structural aspects of other intracontinental collision zone boundaries, where deformation is taken up by discontinuous continental block boundaries. [ABSTRACT FROM AUTHOR]

This research presents an integrated study of 2D seismic reflections and calibrated well data to outline the structural development of the Gorgan Plain on the border of the South Caspian hydrocarbon basin, in the Alborz and Kopeh-dagh ranges of northeast Iran. Eight seismic horizons, including two unconformities, have been identified, ranging in age from Early Jurassic to Quaternary. Analysis and interpretation of geophysical data provide an understanding of the structural geology of the Gorgan Plain, crucial for investigation of structural traps. Seismic interpretation indicates structural features such as deep reverse listric faults (inverted normal faults) for older formations; strike-slip and normal faults in younger sequences; dome and basin interference patterns of folding for all the top formations. Well data demonstrate the occurrence of a disconformity at the base of Upper Cretaceous beds and an angular unconformity at the base of Paleogene. Evidence identified in well and seismic-reflection data proves a complex pattern of tectonic phases since the Early Jurassic. It seems reasonable to suppose that these structural patterns are related to a change in direction of tectonic compression, which in turn has produced structural hydrocarbon traps in crests of domes in the Gorgan area. [ABSTRACT FROM AUTHOR]

Highlights • Ongoing and active subduction in the western Makran. • Fracture zones divide Makran into two different subductions of two different dipp of sinking plates. • A mature Aleutian type for the eastern and a Kuril type of subduction for the western Makran. • Size of the plate boundary earthquakes are geometrically limited by different size of coupling areas in eastern and western Makran. • Makran plays important role in seismotectonic of triple junction between Eurasian, Indian and Arabian plates. Abstract The present study combined spatial distribution and mechanism of seismicity, seismicity parameters, geomorphology in satellite imagery and tectonic features in Makran inland to show that the Makran low angle thrust fault is divided into two separate segments. Depth dispersal of earthquakes, especially relocated events, shows that the sinking plate is steeper in the west than in the east of Makran. Significant facts were identified from the variation of Moho depth between west and east, slip rates of the inland faults and crustal shortenings in the north of Makran. The Sistan suture zone plays a significant role in dividing the overriding plate into a non-deforming Helmand block and a less deforming Lut block. These blocks have different resistances against the northward subduction. Large and great events, such as the 1989 Chabahar (M W 5.5) and 1945 Gwadur (M W 8.1), occurred in the south of subduction fronts of the western and eastern Makran, respectively. They occurred in shallow depth and were the pieces of evidence of weak and strong coupling between the oceanic and continental crusts on a low angle and a very low angle reverse faults, respectively. Spectral analysis and depth determination of the instrumental and pre instrumental earthquakes, respectively, helped to separate some plate boundary and intraplate events. This separation, geometry and non-characteristic behavior of the subduction zone, revealed from spatial and temporal distribution of the earthquakes, probably dedicate a mature Aleutian type for the subduction zone in the east. Missing great (M > 6.1) earthquakes, less slip rate of the continental faults and steeper dipping of the sinking plate in the west probably indicate a Kurile type for the Iranian part of subduction. Makran is a bimodal subduction, because geomorphological and seismic pieces of evidence indicate a NNW surficial and right lateral fracture zone in the continental crust and a NW deep and left lateral fracture zone in the oceanic crust, respectively. The fractures and geometry of subductions showed that the eastern Makran has seismotectonically a wider area for potential coupling of a larger earthquake than the western Makran. [ABSTRACT FROM AUTHOR]

Highlights • Quantifying the strike- and dip-slip subcomponents of the Mashhad earthquake. • Assessment for the future seismic hazard for the Mashhad regions. • Provide a new tectonic implications for the strain partitioning dynamics of NE Iran. Abstract The outward expansion of the northeastern Iranian Plateau is mainly accommodated by a series of widely distributed range-normal thrust and range-parallel strike-slip faults. However, the role of the strike-slip faults in this region's strain-partitioning kinematics remains unclear. The occurrence of the 5 April 2017 Mw 6.1 Mashhad earthquake provides us a rare opportunity to study this topic because this earthquake struck the southern Binalud Mountains, which are experiencing an oblique convergence between the northward-moving Lut Block and the NW-striking Binalud and Kopeh Dagh mountain ranges. We process two paired ascending and descending Sentinel-1A radar-image observations to determine the relative contributions from the dip and strike-dip subcomponents in such an oblique collisional domain. The interferograms along the line-of-sight direction and their converted horizontal and vertical displacements indicate that a thrust with a right-lateral strike-slip fault controlled the rupture process of the Mashhad earthquake, with the maximum dextral shearing and vertical displacements reaching 19.5 cm and 14 cm, respectively. Coseismic surface deformation measurements are also used to estimate the fault geometry and invert the slip distribution along the underlying seismogenic fault. Our best-fit faulting model suggests that the coseismic rupture occurred on a fault plane with a dip angle of 37.5° and strike angle of 324°. The strike-slip subcomponent was more significant than the dip-slip, approaching ∼95 cm, and the dip-slip varied from 10 cm to 47 cm. The seismic-moment release of our preferred fault model is 1.71 × 1018 Nm, equivalent to a Mw 6.16 earthquake event. We also use the preferred fault model to calculate the Coulomb failure stress (CFS) change at the nearby receiver faults. Combined with an analysis of historical earthquakes and the consistent dextral river deflections along the strike-slip fault systems of the southern Binalud and Kopeh Dagh Mountains, we speculate that the seismogenic structure that triggered the Mashhad earthquake should have been one strand fault of the NW–SE-striking Kashafrud fault system. The strike-slip faults in NE Iran play an important role in accommodating the lateral transport of crustal material from the convergence front of the Lut Block and Binalud fragments and providing commonly distributed anticlockwise rotation around a vertical axis. [ABSTRACT FROM AUTHOR]

NW Iran is among the most interesting and complex areas within Arabian-Eurasia collision zone. Historical and instrumental earthquake records in this region indicate that active faults have the potential to produce serious seismic hazards in the future. The North Bozgush Fault Zone, an anastomosing fault zone, consists of several parallel and sub-parallel faults which have developed in a right lateral strike-slip system with a reverse component. Our structural analysis shows that faulting occurs along a strong dominant compressional strike-slip regime and is predominantly related to NW-SE shortening along the zone. This paper represents an analysis of the morphometric indices to depict the tectonic activity of the northern part of the Bozgush Mountains, an area with a typical tectono-morphology. The result of the morphometric analysis shows that relative tectonic activity along the North Bozgush Fault Zone decreases significantly from west to east. Measured uplift rates show that the uplift rate is higher than 0.5 mm/yr in the western and central parts and decreases in the eastern part to between 0.5 and 0.05 mm/yr. The structural and morphometric data are indicative of the relation between the North Bozgush Fault Zone and the Tabriz Fault Zone during Quaternary time. [ABSTRACT FROM AUTHOR]

This paper presents an approach to stream length-gradient index analysis to identify tectonic signatures. The graded profile of the Dez River in Zagros Mountains, Iran, indicates that the area has been tectonically disturbed, and it triggers landslide hazards. The high-gradient index shows that a steeper gradient could be potentially a signature for landslides identification. The digital surface models acquired by airborne LiDAR were used in this study to generate the HRDEM. Our result shows a great potential for improving landslide investigations by implementing stream length-gradient index derived from the HRDEM in conjunction with the landslide inventories data-set in the GIS environment. We also identified a correlation between the stream length-gradient index and the graded topographic profile with slopes and landslides. This empirical approach was verified by geodata analytics and landslide inventories data-set in conjunction with field observations. This study has identified the locations of high-gradient indices with susceptible to landslides. [ABSTRACT FROM AUTHOR]

The 300 km long arc of the Fars province is located to the south east of the NW-SE trending and SW vergent orogen of the Zagros Mountains. This region is one of the largest hydrocarbon reserves worldwide, and also as a territory of high quality outcrops. Geological cross-sections of the Zagros belt are usually based on very large scale geological maps (1:1.000.000 or 1:250.000), and on few subsurface data and aim at describing the decoupling relationship between cover and basement rocks and the subduction/collision history of the Arabian – Eurasia plates. In this paper, we present a 253 km long cross-section across the Fars province on the basis of detailed geological maps (1:100.000 scale), field and subsurface data. Our purposes are to: 1) investigate the link between shortening inferred from our original cross-section (from a maximum of 9,1% to a minimum of 4,4%. for different sectors of the belt) and rift-related and flexure-related extensional faults, which in turn, control thickness and lateral facies variations; 2) describe the geometries of folds and thrusts and their relationship with pre-thrusting normal faults, that were inverted during shortening as transpressional or strike slip faults. Moreover, we present for the first time new field data showing evidences of syn-collisional normal faults likely related to the bending of the Arabian plate in the Fars area. [ABSTRACT FROM AUTHOR]

The Jahani Salt Diapir (JSD), with an area of 54 km2, is an active diapir in the Simply Folded Belt of the Zagros Orogeny, in the south of Iran. Most of the available studies on this diapir are focused on tectonics. The hydrogeology, schematic model of flow direction and hydrochemical effects of the JSD on the adjacent water resources are lacking, and thus, are the focus of this study. The morphology of the JSD was reevaluated by fieldwork and using available maps. The physicochemical characteristics of the springs and hydrometric stations were also measured. The vent of the diapir is located 250 m higher than the surrounding glaciers, and covered by small polygonal sinkholes (dolines). The glacier is covered by cap soils, sparse trees and pastures, and contains large sinkholes, numerous shafts, several caves, and 30 brine springs. Two main groups of caves were distinguished. Sub-horizontal or inclined stream passages following the surface valleys and vertical shafts (with short inlet caves) at the bottoms of nearly circular blind valleys. Salt exposure is limited to steep slopes. The controlling variables of flow route within salt diapirs are the negligible porosity of the salt rocks at depth more than about ten meters below the ground surface and the rapid halite saturation along the flow route. These mechanisms prevent deep cave development and enforce the emergence points of brine springs with low flow rates and small catchment area throughout the JSD and above the local base of erosion. Tectonics do not affect karst development, because the distributions of sinkholes and brine springs show no preferential directions. The type of spring water is sodium chloride, with a TDS of 320 g/l, and saturated with halite, gypsum, calcite and dolomite. The water balance budget of the JSD indicates that the total recharge water is 1.46 MCM (million cubic meter)/a, emerges from 30 brine springs, two springs from the adjacent karstic limestone, and flows into the Firoozabad River (FR) and the adjacent alluvium aquifer. The FR cuts through the northern margin of the salt diapir, dissolving the glacier salts at the contact with JSD, increasing the halite concentration of the 17.7 MCM/a of the FR from 100 mg/l to 12,000 mg/l. This is a permanent process because the active glacier flows rapidly down the steep slopes into the river gorge from the nearby vent. The possible relocation of the FR channel would enhance the FR water quality, but disrupt the natural beauty of the diapir. [ABSTRACT FROM AUTHOR]

The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeling and many researchers have worked on this topic. This study is an effort to define linear and area seismic sources for Northern Iran. The linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes. Time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on Poisson process. GIS functionalities are used in this study to introduce and incorporate spatial-temporal and geostatistical indices in delineating area seismic sources. The proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around Tehran. Previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible. All events are transformed to uniform magnitude scale; duplicate events and dependent shocks are removed. Completeness and time distribution of the compiled catalog is taken into account. The proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of Northern Iran. [ABSTRACT FROM AUTHOR]

In this study, biostratigraphy and paleoecology of the Asmari Formation have been investigated. The study area is located in the Izeh zone, Zagros Basin. Four outcrop sections (Halayjan, Kuh Shur, Kuh-e Bad and Gharibi Ha) have been sampled. Based on distribution of the larger benthic and planktonic foraminifera, five assemblage zones have been recognized. Assemblages 1 and 2 indicate Chattian; assemblage 3 is restricted to Aquitanian and assemblages 4 and 5 suggest Burdigalian. During the Chattian, the carbonate deposits of the Asmari Formation are mostly composed of coralline red algae and large and flat benthic foraminifera. The common components of the Aquitanian are abundant imperforate foraminifera and Favreina asmaricus. The Burdigalian is characterized by coral, coralline algae, and perforate and imperforate foraminifera. During the Burdigalian toward the SE of study area (Gharibi Ha section), the shallow water deposits are abruptly overlain by pelagic limestone. It is interpreted as the result of a regional tilting that started in the upper part of the Burdigalian. The biotic associations suggest that carbonate sedimentation occurred in tropical to subtropical waters under oligotrophic to mesotrophic conditions. The carbonate grain associations in the Asmari Formation suggest heterozoan association. According to paleoecological parameters (such as: nutrient, depth, light and salinity) in the study area, the Asmari Formation belongs to nannofor--foralgal to foramol association which were deposited in slightly hyper to normal saline environment. In the euphotic zone, abundant imperforate foraminifera are present. Basinward, lens shaped rotalids developed in mesophotic conditions, and large lepidocyclinid-nummulitids characterize the sediments of the deeper oligophotic zone. [ABSTRACT FROM AUTHOR]

Evaluation of active tectonism by means of geomorphic indices has provided crucial semi-quantitative data for evaluating seismic hazards in a fault zone in a semiarid area of the Zagros Mountains of Iran where tectonic rates are low-to-moderate and there are few Quaternary dates. Quaternary activity along the seismically active but poorly understood Sabzpushan fault zone (SFZ) has been investigated. The SFZ consists of two dextral strike-slip faults, the Zafarabad and Kafari faults. Geomorphic indices including mountain front sinuosity, valley asymmetry factor, hypsometric integral, valley floor width to valley height ratio and stream length gradient index were used to assess the effects of active reverse faults which control the topographic relief and Quaternary activity. Geomorphometric and field evidence reveal that the Quaternary activity and topographic relief of the study area are controlled by two reverse faults, the North and South Sabzpushan reverse faults, which have formed a pop-up structure in the contractional step-over area between the Zafarabad and Kafari dextral strikeslip faults as a consequence of oblique convergence between the Afro-Arabian and Iranian plates accommodated by the North and South Sabzpushan thrust faults. [ABSTRACT FROM AUTHOR]

The North Qazvin region is a part of the Central Alborz Mountains in Iran and has experienced destructive earthquakes. This region is a popular and industrial zone near Tehran, capital of Iran. To identify the highest and lowest seismic hazard location and consequently the seismic zonation of this region, different parameters, such as topography, geology, tectonics and seismicity, have been focused. Accordingly, the north of Qazvin region can be divided into three subzones: western, eastern and southern. Seismic activity of the western zone is higher than the other ones and seismic potential of the eastern zone is higher than the other two zones. This zoning is also necessary for all seismic active areas to find the most dangerous zone. [ABSTRACT FROM PUBLISHER]

Motivated by the desire to have more information following the occurrence of damaging events, the main purpose of this article is to study aftershock sequence parameters in the Iranian plateau. To this end, the catalogue of the Iranian earthquakes between 2002 to the end of 2013 has been collected and homogenized among which 15 earthquakes have been selected to study their aftershock decay rates. For different tectonic provinces, the completeness magnitudes ( M) of the earthquake catalogue have been calculated in different time intervals. Also, the M variability in spatial and temporal windows has been determined for each selected event. For major Iranian earthquakes, catalogue of aftershocks has been collected thanks to three declustering methods: first, the classical windowing method of Gardner and Knopoff (Bull Seismol Soc Am 64:1363-1367, ); second, a modified version of this using spatial windowing based on the Wells and Coppersmith (Bull Seismol Soc Am 84:974-1002, ) relations; and third, the Burkhard and Grünthal (Swiss J Geosci 102:149-188, ) scheme. Effects of the temporal windows also have been investigated using the time periods of 1 month, 100 days, and 1 year in the declustering method of Gardner and Knopoff (Bull Seismol Soc Am 64:1363-1367, ). In the next step, the modified Omori law coefficients have been calculated for the 15 selected earthquakes. The calibrated regional generic model describing the temporal and magnitude distribution of aftershocks is of interest for time-dependent seismic hazard forecasts. The regional characteristics of the aftershock decay rates have been studied for the selected Iranian earthquakes in the Alborz, Zagros and Central Iran regions considering their different seismotectonics regimes. However, due to the lack of sufficient data, no results have been reported for the Kopeh-Dagh and Makran seismotectonic regions. [ABSTRACT FROM AUTHOR]

Chromitite bodies of various sizes associated with dunite envelopes have been found in the Dehsheikh ultramafic massif, in the southeastern part of the outer Zagros ophiolite belt. The chromitites occur as layered and lenticular bodies, and show both magmatic and deformational textures, including massive, disseminated, banded and nodular types. The Dehsheikh chromitites display a variation in Cr# [100 × Cr / (Cr + Al)] from 69 to 78, which is typical of high-Cr chromitites. The Al 2 O 3 and TiO 2 contents of chromites range from 10.3 wt.% to 16.9 wt.% and 0.12 wt.% to 0.35 wt.%, respectively. The Al 2 O 3 , TiO 2 , and FeO/MgO values calculated for parental melts of Dehsheikh chromitites are within the range of boninitic melts. Chondrite-normalized distribution patterns of platinum-group elements show relative enrichments in Ru, Ir, and Os, and depletions in Rh, Pd, and Pt that are typical of chromitites associated with ophiolites formed by high degrees of mantle partial melting. The presence of Na-rich amphibole inclusions in chromite grains, together with the mineralogical and chemical composition of the chromitites and estimates of their parental melt compositions are used to help establish the tectono-magmatic setting. It is shown that the Dehsheikh massif is an ophiolite formed in a suprasubduction zone setting. We suggest that the composition of the rocks in this section was influenced by hydrous partial melts which might be formed in the subduction zone. Variable melt/rock interaction produced melt channel networks in the dunite which allowed the parental melt of the chromitite to percolate through them. Similar characteristics have been observed in other ophiolite complexes from the outer Zagros Iranian ophiolitic belt; these are believed to be the product of magmatism in a fore-arc environment. [ABSTRACT FROM AUTHOR]

A major magmatic flare-up is documented along the Bitlis–Zagros suture zone in Eocene–Oligocene times. The Cenozoic magmatism of intraplate Central Iran is an integrant part of this tectono-magmatic scenario. The Cenozoic magmatism of the Sabzevar structural zone consists of mostly intermediate to felsic intrusions and volcanic products. These igneous rocks have calc-alkaline and adakitic geochemical signatures, with nearly coincident zircon U–Pb and mica Ar–Ar ages of ca. 45 Ma. Adakitic rocks have quite low HREE and high Sr/Y ratio, but share most of their geochemical features with the calc-alkaline rocks. The Sabzevar volcanic rocks have similar initial Sr, Nd and Pb isotope ratios, showing their cogenetic nature. Nd model ages cluster tightly around ~ 0.2–0.3 Ga. The geochemistry of the Sabzevar volcanic rocks, along with their isotopic signatures, might strangle that an upper mantle source, metasomatized by slab-derived melts was involved in generating the Sabzevar calc-alkaline rocks. A bulk rock trace element modeling suggests that amphibole–plagioclase–titanite-dominated replenishment-fractional crystallization (RFC) is further responsible for the formation of the middle Eocene Sabzevar adakitic rocks. Extensional tectonics accompanied by lithospheric delamination, possibly assisted by slab break-off and melting at depth was responsible for the Eocene formation of the Sabzevar magmatic rocks and, more in general, for the magmatic “flare-up” in Iran. [ABSTRACT FROM AUTHOR]

In this work we present new AMS and structural results from the Ferdows active fold–thrust system (Lut block, Central Iran). AMS analyses show that the Miocene units of the Upper Red Formation have a well defined magnetic fabric of tectonic origin, with both magnetic lineation and magnetic foliation oriented parallel to the regional fold axes. In most of the cases the magnetic fabric, acquired when the bedding was still horizontal, is related to different degrees of LPS shortening. In some other cases, the magnetic foliation is vertical and oblique to the bedding, suggesting that in the Ferdows thrust–fold structure a cleavage system, not visible at the outcrop scale, has been developed as a consequence of later shortening related to the activity of the thrust system, responsible of the recent earthquakes in the area. Results from this study establish a relationships between the recent tectonics of the area and the evolution of the magnetic fabric and demonstrate that a well defined magnetic fabric of pure tectonic origin can also develop in poorly deformed rocks lacking field evidence of pervasive internal deformation. [ABSTRACT FROM AUTHOR]

The structure, age and petrogenesis of plutonic basement rocks from the Kuh-e-Sarhangi region, located in the Kashmar-Kerman tectonic zone of Central Iran are described. These intrusive rocks consist of a sub-alkaline, dominantly high-K calc-alkaline acidic suite, characterised by high SiO 2 (72.60–77.17 wt%), and alkalis (up to 8 wt%) and low Mg# (07-35). They are also enriched in Th, U and light rare earth elements, and depleted in Nb, Ta, and Ti, thus showing a geochemical fingerprint compatible with arc magmatism. The U–Pb zircon geochronology constrains magma crystallisation and emplacement during Ediacaran-Cambrian (ca. 575–535 Ma) times, under a tectonic regime dominated by transpressional tectonics as constrained by analysis of field structures. Combined inverse and forward modelling thermobarometry indicates pluton emplacement occurred in a thickened crustal environment, suggesting the Kuh-e-Sarhangi magmatic belt exposes the exhumed roots of a volcanic arc. This magmatism is interpreted as part of the Cadomian, subduction-related magmatism and framed within an oblique convergence scenario during formation of an Andean-type active margin all along the northern (proto-Tethyan) margin of the Gondwana Supercontinent. [ABSTRACT FROM AUTHOR]

The occurrence in Iran of several ophiolite belts dating between Late Palaeozoic to Triassic poses several questions on the possible existence of various sutures marking the closure of the Palaeotethys ocean between Eurasia and this Gondwana-derived microplate. In this scenario, the Anarak region in Central Iran still represents a conundrum. Contrasting geochronological, paleontological, paleomagnetic data and reported field evidence suggest different origins for the Anarak Metamorphic Complex (AMC). The AMC is either interpreted, as: (1) relict of an accretionary wedge developed at the Eurasia margin during the Palaeotethys subduction as part of the Cimmerian suture zone of NE Iran, displaced to Central Iran by a large counter-clockwise rotation of the central Iranian blocks; (2) autochthonous unit forming a secondary branch of the main suture zone. Our structural, petrographic and geochemical data indicate that the AMC consists of several metamorphic units also including dismembered “ophiolites” which display different tectono-metamorphic evolutions. Three main ductile deformational events can be distinguished in the AMC. The Morghab and Chah Gorbeh complexes preserve a different M 1 metamorphism, characterized by blueschist relics in the S 1 foliation of the former unit, and greenschist assemblages in the latter. They share a subsequent similar D 2 deformational and M 2 metamorphic history, showing a prograde metamorphism with syn- to post-deformation growth of blueschist facies mineral assemblages on pre-existing greenschist facies associations. High pressure, low temperature (HP/LT) metamorphism responsible for the growth of sodic amphibole has been recognized also within marble lenses at the contact between the Chah Gorbeh Complex and serpentinites. Evidence of HP/LT metamorphism also occurs in glaucophane-bearing meta-pillow lavas and serpentinites, which contain antigorite and form most of the “ophiolites” within the AMC. Structural relationships show that the Chah Gorbeh and Morghab units and the “ophiolites” were tectonically coupled within an accretionary wedge before the D 2 folding stage. The other units of the AMC lack evidence of HP metamorphism in the area around Anarak, especially the Lakh Marble, a large thrust sheet that occupies the uppermost structural position in the AMC. Available radiometric ages of trondhjemite dikes and stocks that intruded the accretionary wedge, as well as our new data, constrain the subduction event at the end of the Carboniferous, before 290 Ma. These data suggest that the AMC is part of an allochthonous crustal fragment belonging to the Variscan belt developed along the southern Eurasian margin before the Cimmerian collision of Iran. Subsequent deformational events that occurred during the Mesozoic and the Cenozoic, up to the Miocene and possibly later, resulted in folding, thrusting and faulting that dismembered the original structure of the wedge accompanying its displacement to the present day position. [ABSTRACT FROM AUTHOR]

The structural evolution of the Sanandaj-Sirjan zone is the result of the convergence of the Iranian microcontinent and the Afro-Arabian continent. The study area at Khabr in the SE Sanandaj-Sirjan zone, in the hinterland of the Zagros orogen, consists of Paleozoic, Mesozoic and Cenozoic rocks. In this area, deformation phases were distinguished in different rock units based on structural and stratigraphical evidence, and the deformational events are divided into two stages: (1) a Late Triassic event and (2) a Late Cretaceous to Miocene event. The Late Triassic deformation event caused regional metamorphism in the Paleozoic units. These units are overlain by unmetamorphosed Jurassic clastic sequences. Fabrics and structural evidence confirm that the F folding recumbent and refolded folds were synchronous with the metamorphism of the Paleozoic units and terminated in the Early Jurassic. The time table of the orogenic phases shows that this deformation event is related to the Cimmerian orogenic phase. From a geodynamic point of view, the early Cimmerian deformation in the southeastern Iranian margin suggests that the SE Sanandaj-Sirjan zone was an active margin at that time. The early Cimmerian discordance recorded the onset of a contractional component related to the oblique subduction of Neo-Tethys beneath the central Iranian microcontinent. Structures related to the Late Cretaceous to Miocene deformation phase are observed in Jurassic to Oligocene units, which contain moderately inclined and plunging folds. Comparing these folds with domains of deformation generated in models of transpression shows that the folding was caused by a combination of contractional and dip-slip components of movement, eventually resulting in the formation of a thrust system. The Khabr thrust systems consist of five sheets of oblique thrusts, duplex structures and shear zones. The shear zones generally strike E-W and dip moderately N (30°-40°). The occurrence of asymmetric folds with hinges that are either parallel to strike or plunge down dip demonstrates an oblique-slip component in these thrust shear zones. The stretching lineation in the mylonites within the shear zones is defined by the long axes of ellipsoidal grains of quartz, calcite, plagioclase and garnet. In general, stretching lineations trend from N40°W to N80°W with an intermediate (35°) plunge. The geometry of foliation and lineation within these shear zones shows the effect of dip- and oblique-slip shearing. Deformation continued with strike-slip faulting becoming important during the last stages of deformation from the Miocene to the present day. The results of this study demonstrate that the evolution of the SE Sanandaj-Sirjan zone, from Late Triassic to Miocene, is compatible with an inclined dextral transpression along this zone. [ABSTRACT FROM AUTHOR]

We present a detailed stratigraphic and structural study of the Kopeh Dagh fold-and-thrust belt in NE Iran, which is an investigation of the complex polyphased tectonic history of this belt and its links with the adjacent South Caspian Sea and Amu Darya basins. Based on numerous field surveys, a large amount of 2D and 3D seismic data, borehole data and more than 150 new biostratigaphic datings, a new detailed biostratigraphic chart and 4 main regional cross-sections illustrate the importance of lateral facies variations and structural inheritance in the present-day structure of the belt. After the Cimmerian orogeny corresponding to the closure of the Paleotethys Ocean in Late Triassic/Early Jurassic times, a Middle Jurassic post-collisional rifting event was associated with the deposition of one of the main source rocks of the Kopeh Dagh and the Amu Darya Basin (Kashafrud Formation). Following this rifting event, over 7 km of sediments were accumulated until the Tertiary above a regional post-Triassic unconformity. The occurrence of local uplifts during the Late Cretaceous-Early Paleocene is interpreted as a consequence of regional-scale modification of plate-slab coupling in the Neotethys subduction zone. The main inversion of the Kopeh Dagh occurred at Late Eocene times, when the far-field deformation developed in Eurasia as a consequence of the locking of the Neo-Tethys subduction. This folding phase is sealed in the western part of the belt by a major Eocene-Oligocene unconformity at the base of the thick sedimentary series belonging to the South Caspian Sea Basin. The bulk of sedimentary infill in the South Caspian Sea Basin is Oligocene and younger, and it is probably related to syn-compressional downward flexure of the resistant basement basin at the onset of the Alpine phase. In the eastern part of the Kopeh Dagh, this deformation is characterized by Middle Jurassic graben inversion with evidence of forced folding, short-cuts and as well by larger scale basement uplifts. In contrast, the northwestern part of the belt shows thrust faults involving basement and fault-propagation folds within the sedimentary sequence. The Kopeh Dagh presents tectonic structures that are parallel to the Paleotethys suture zone, which emphasizes the importance of the structural inheritance and inversion processes during the structural evolution of the belt. Finally, a change from a mostly dip-slip to a mostly strike-slip tectonics occurred during the Pliocene within the Kopeh Dagh as a consequence of a major tectonic reorganization in North-East Iran. [ABSTRACT FROM AUTHOR]

The Kashafrud Formation was deposited in the extensional Kopeh-Dagh Basin during the Late Bajocian to Bathonian (Middle Jurassic) and is potentially the most important siliciclastic unit from NE Iran for petroleum geology. This extensional setting allowed the accumulation of about 1,700 m of siliciclastic sediments during a limited period of time (Upper Bajocian-Bathonian). Here, we present a detailed facies analysis combined with magnetic susceptibility (MS) results focusing on the exceptional record of the Pol-e-Gazi section in the southeastern part of the basin. MS is classically interpreted as related to the amount of detrital input. The amount of these detrital inputs and then the MS being classically influenced by sea-level changes, climate changes and tectonic activity. Facies analysis reveals that the studied rocks were deposited in shallow marine, slope to pro-delta settings. A major transgressive-regressive cycle is recorded in this formation, including fluvial-dominated delta to turbiditic pro-delta settings (transgressive phase), followed by siliciclastic to mixed siliciclastic and carbonate shoreface rocks (regressive phase). During the transgressive phase, hyperpycnal currents were feeding the basin. These hyperpycnal currents are interpreted as related to important tectonic variations, in relation to significant uplift of the hinterland during opening of the basin. This tectonic activity was responsible for stronger erosion, providing a higher amount of siliciclastic input into the basin, leading to a high MS signal. During the regressive phase, the tectonic activity strongly decreased. Furthermore, the depositional setting changed to a wave- to tide-dominated, mixed carbonate-siliciclastic setting. Because of the absence of strong tectonic variations, bulk MS was controlled by other factors such as sea-level and climatic changes. Fluctuations in carbonate production, possibly related to sea-level variations, influenced the MS of the siliciclastic/carbonate cycles. Carbonate intervals are characterized by a strong decrease of MS values indicates a gradual reduction of detrital influx. Therefore, the intensity of tectonic movement is thought to be the dominant factor in controlling sediment supply, changes in accommodation space and modes of deposition throughout the Middle Jurassic sedimentary succession in the Pol-e-Gazi section and possibly in the Kopeh-Dagh Basin in general. [ABSTRACT FROM AUTHOR]

This paper presents the role of tectonic and karstic processes in the formation and evolution of Barm Firuz Lake within the Zagros Mountains of Iran. This lake with elevation of 3 340 m from sea level is located in the crest of the Barm Firuz anticline. Results show that the structural evolution of the Barme Firuz Lake is related to both tectonic and karst processes. Therefore the term of tectonokarstic has been used for structural evolution of the lake. Structural studies especially on the stylolite structures revealed the occurrence of an important component of simple shear deformation in the study area. Based on structural and karstic evidence around the lake, the fault-dissolution sink model with oblique pure shear component is suggested as kinematic model of the Barm Firuz Lake evolution in the Zagros Mountains of Iran. [ABSTRACT FROM AUTHOR]

The record of conodonts related to the Mississippian/Pennsylvanian boundary interval was investigated in four sections in Central Iran from two different structural units. Two sections from the Sanandaj-Sirjan trend zone (Asad-abad, and Darchaleh sections) and two from the East-Central Iran Microplate (Shesh-angosht and Kale-Sardar sections) exhibit a nearly complete record previously described across the Mississippian/Pennsylvanian boundary in Iran. The investigated sections can be subdivided in three formations (Ghaleh-, Absheni-, and Zaluda Formation) which belong to the Sardar Group. The mid-Carboniferous boundary was defined by the occurrence of Declinognathus noduliferus s.l.. Bio-event characteristics of the Carboniferous conodont fauna (Mississippian genera Gnathodus and Lochriea have been replaced by Pennsylvanian genera Declinognathus and Idiognathodus) as well as sedimentological changes within overall shallow water deposits were located approximately 33° S of the paleoequator and suggest sea-level changes within the framework of the Late Paleozoic Ice Age (LPIA). Furthermore, a widespread crinoid marker horizon previously described from two localities in Iran can be subdivided into three units of different ages. [ABSTRACT FROM AUTHOR]

The Zagros fold-and-thrust belt of SW Iran represents deformation of the former Arabian passive margin since Permian-Triassic opening of the Neo-Tethys ocean. The Zagros belt is characterized by a present-day structural salient-recess setting inherited from past marginal embayment-promontory geometry, which was involved in discontinuous ophiolite obduction and diachronous continental collision. We examine outcrop-scale Mesozoic extensional brittle tectonics, preserved as syn-depositional normal faults within the folded strata, in terms of stress tensor inversion. The result is then integrated with belt-scale isopach, seismic and topographical data to delineate the geometry of a major irregularity along the passive margin originating from oblique oceanic opening. The implication of this configuration within the tectonic framework of oceanic closure is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Various studies have been conducted thus far to classify the seismicity regions of Iran into zones that share similar seismic characteristics. In these studies, seismotectonic models have been presented that implement various information layers based mostly on human expert judgment. The purpose of the present research is to develop a seismotectonic model using all of the available information about the layers along with an automated smart clustering algorithm. In this paper, based on a review of past research studies, a combined model is presented, which involves the combination of the four most-referenced seismotectonic models. To build upon past studies, a smart algorithm called the self organizing map (SOM) was selected for clustering the seismotectonic data of provinces. Input layers, such as earthquake coordinates, seismicity, faults distribution, topography, gravity, and magnetism, were used to execute the SOM smart algorithm. Based upon previous studies, the number of clusters was selected in the range of 5–25. Three of the SOM algorithm outputs, which were more compatible with the combined model, were selected for use in this study. According to the clustering validation methods and expert judgments, the highest compatibility belongs to the models that were produced either by all of the information or by the combination of seismicity, faults, and topography layers. Implementation of the clustering validation methods indicated that the optimum number of seismotectonic zones is between 9 and 13. This study emphasizes that the application of smart methods along with various geological, structural, subsurface, and aerial information layers will produce informative and reliable results. [Copyright &y& Elsevier]

The neotectonics of the Zanjan-Kazvin area are dominated by the region-wide E-W trending left lateral strike-slip faults. These faults create restraining and releasing stepovers indicating strain partitioning. Instead of the NW-SE trending long range-parallel continuous thrust faulting suggested in previous studies, this paper demonstrates that there are E-W trending range-crossing left lateral strike-slip faults creating short range-parallel thrust faults in the restraining stepovers. Establishing this strike-slip-induced structural style might contribute to an understanding of the nature of the Elburz (Alborz) Mountains located between the Central Iran and Caspian blocks. [ABSTRACT FROM AUTHOR]

One of the major strengths of a GIS is the ability to integrate and combine multiple layers of geoscience data for producing mineral potential maps showing favorable areas for mineral exploration. Once the data is prepared properly, the GIS, jointly with other statistical and geostatistical software packages, can be used to manipulate and visualize the data in order to produce a mineral prospectivity map. Many spatial modeling techniques can be employed to produce mineral potential maps. This paper demonstrates a technique to define favorable areas for REE mineralization with AHP technique using geological, geochemical, geophysical, alteration and faults density spatial data in the Kerman-Kashmar Tectonic Zone of central Iran. The AHP is a powerful and flexible multi-criteria decision-making tool for dealing with complex problems where both qualitative and quantitative aspects need to be considered. This approach is knowledgedriven method and can be applied in other areas for conventional use in mineral exploration. [ABSTRACT FROM AUTHOR]

Abstract: The morphology of six adjacent major catchments draining the onshore Makran accretionary wedge in southeast Iran and southwest Pakistan was studied to examine how the channel pattern and the length profiles may reflect the recent and active growth of the wedge. Qualitative field surveys were combined with the quantitative analysis of channel steepness and concavity measured from digital elevation models. These profiles were compared with modelled profiles using a stream power approach assuming homogeneously uplifting, uniform rock substratum. Results show a distinct difference between the studied western and eastern catchments. The three western rivers are in morphological equilibrium; whereas the two eastern rivers exhibit profiles with prominent convexities and knickpoints, thus notably diverging from equilibrium concave-up shapes. All the studied catchments share the same base level, flow on similar lithologies, and developed under uniform climate conditions. Therefore, we interpret the morphometric differences in terms of differential rock uplift rate as a response to local tectonic activity. This interpretation is consistent with both uplift rates of marine terraces along the coast of Makran and the recorded seismicity. The geomorphological analysis presented here extends coastal information to wide inland areas and documents longer term tectonic behaviour than the seismotectonic record. Hence, the steeper surface slope and faster surface uplift rates recorded by the eastern catchments compared to equilibrium of the western catchments are regional, long-term signals relevant for a wide part of the Makran accretionary wedge. We attribute the regional geomorphic difference to Quaternary variations in tectonic regimes that forced differential uplift rates of the wedge surface. We hypothesize that the different tectonic regimes are related to different subduction rates. [Copyright &y& Elsevier]

Abstract: Photogrammetry is becoming a highly efficient alternative technique to laser-scanning for creating virtual outcrop models. It is easy to create a 3-dimensional digital model of an outcrop and extract geological information contained in it by using photos taken from different locations and integrating few free and/or cheap software. Subsequently, both the virtual outcrop and the geological data can be easily uploaded into Google Earth for sharing purposes. This is opening a door to the use of virtual outcrops in geology, for both research and teaching, which due to the costs and computers' skill requirements, was limited to a few. The aim of this paper is to present methodologies involved in the creation, analysis and sharing of low-cost easily-built virtual outcrops, which can be extensively used for the introduction to the 3D geology. An example from the Khaviz Anticline (Iran) is used to create a 3D digital model from a set of non-oriented images, using Agisoft Photoscan photogrammetry software. The obtained geopositioned model is then imported into OpenPlot, from which geological surfaces can be extracted. These data, together with the 3D model, can be later exported in Google Earth format. [Copyright &y& Elsevier]

Highlights: [•] AMS used to solve the ambiguity on the tectonic or sedimentary origin of magnetic lineation. [•] Comparison of magnetic fabric with available tectonic and sedimentary data. [•] The magnetic lineation in the Shemshak Group sandstones is tectonically originated. [•] AMS is a valuable tool to study deformation processes in sedimentary rocks. [Copyright &y& Elsevier]

We present a velocity field compiled from a network of 27 permanent and 20 campaign GPS stations across NE Iran. This new GPS velocity field helps to investigate how Arabia–Eurasia collision deformation is accommodated at the northern boundary of the deforming zone. The present-day northward motion decreases eastward from 11 mm/yr at Tehran (∼52°E) to 1.5 mm/yr at Mashhad (∼60°E). N–S shortening across the Kopeh Dagh, Binalud and Koh-e-Sorkh ranges sums to at longitude 59°E. The available GPS velocities allow us to describe the rigid-body rotation of the South Caspian about an Euler pole that is located further away than previously thought. We suggest that two new stations (MAVT and MAR2), which are sited far from the block boundaries, are most likely to indicate the full motion of the South Caspian basin. These stations suggest that NW motion is accommodated by right-lateral slip on the Ashkabad fault (at a rate of up to 7 mm/yr) and by up to 4–6 mm/yr of summed left-lateral slip across the Shahroud left-lateral strike-slip system. Our new GPS results are important for assessing seismic hazard in NE Iran, which contains numerous large population centers and possesses an abundant historical earthquake record. Our results suggest that the fault zones along the eastern Alborz and western Kopeh Dagh may accommodate slip at much faster rates than previously thought. Fully assessing the role of these faults, and the hazard that they represent, requires independent verification of their slip-rates through additional GPS measurements and geological fieldwork. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ophiolitic extrusive sequence of Sabzevar area comprise of three main units. [•] Sheet flow of lower unit and pillow lava of middle unit show OIB affinities. [•] Lava flows from upper unit and supra-ophiolitic series show subduction characters. [•] These rocks probably formed from a marginal arc to a backarc basin. [Copyright &y& Elsevier]

Abstract: Late Cenozoic strike–slip tectonics and active faulting in Central Iran have been extensively described in the last decades. This study presents results of integrated structural and geomorphological analyses along the Kuh-e–Sarhangi Fault, a major NE–SW striking brittle deformation zone that cuts across the basement and Neogene–Quaternary cover successions at the north-western edge of the Lut Block. Structural investigations document post-Neogene NE–SW dextral transpressive tectonics and geomorphic evidence support a Late Quaternary age for the faulted alluvial fan deposits along the bedrock range fronts. Northward, the nearly parallel Great Kavir (Doruneh) Fault is known to have active left-lateral strike–slip kinematics, and its easternmost segment was considered as the northern margin of the Lut Block. The new findings impose reconsideration of the current regional kinematic models, with implications on the seismogenic fault networks of Central Iran. [Copyright &y& Elsevier]

Abstract: The Kashmar–Kerman Tectonic Zone (KKTZ) is an arcuate zone located between the Tabas and Yazd blocks in Central Iran. Detailed structural analysis and mapping of the metamorphic basement rocks of the KKTZ on the Boneh-Shurow, Tashk, Saghand and Sarkuh Metamorphic Complexes, as well as 40Ar/39Ar cooling ages on the Boneh-Shurow Metamorphic Complex indicate three deformation stages in the tectonometamorphic evolution of the KKTZ during the Cimmerian orogeny. The D1–1 event corresponds to continental accretion through the progressive formation of dextral shear zones, which is equivalent to an Early Cimmerian event during Late Triassic–Early Jurassic times. The D1–2 event is characterized by top-to-NE normal shear zones due to syn-collisional exhumation within the KKTZ and is considered to be a Mid-Cimmerian Middle Jurassic event at ca. 168Ma. The progressive regional compressional deformation is continued by the D2–1 and D2–2 events through formation of reverse shear zones and faults, with their SW movement. The progressive D2 event is considered to be Late Cimmerian and has taken place during Early Cretaceous. It is proposed that the mapped long-lived dextral shear zones within the KKTZ acted as block bounding faults between the Tabas and Yazd blocks in Central Iran. [Copyright &y& Elsevier]