Geological Survey of Iran
  • Tehran, Tehran, Iran
Recent publications
During the last two decades, the number of tropical cyclone (TC) events in the Arabian Sea has increased dramatically. These events have led to severe human and economic damage in Oman, Iran and Pakistan. Within this context, Gonu, Phet and Shaheen were the Arabian Sea's most destructive TCs on record, leading to a total of 6.07 billion USD in damages and 159 fatalities. Previous studies have mainly focused on atmospheric, sea surface temperature (SST) and anthropogenic impacts of TC generation and intensification. By contrast, oceanographic currents, Persian Gulf water outflow and the role of ocean-atmospheric interactions on the distribution of outflow water into the Arabian Sea and their impacts on TC intensification, are poorly understood. In order to address this issue, we use historical TC records, satellite data, atmospheric and reanalyzed oceanographic data to shed new light on the relationship between large-scale atmospheric forcing and ocean currents on TC intensification in the Arabian Sea. The results demonstrate that pre-monsoon TCs mainly occurred during co-existing La Niña, cold Indian Ocean Basin Model (IOBM) and anomalous northern hemisphere circulations over the Persian Gulf. By contrast, post-monsoon TCs were generally generated during warming acceleration period. Poleward movement of the monsoon belt provided the required humidity and energy for TC generation and increased upwelling events. Water salinity and temperature have increased in the north and northwestern parts of the Arabian Sea following rising upwelling events and a decrease in Persian Gulf outflow water depth. Rapid TC intensification has increased noticeably since 2007 and >72 % of cyclones have reached category 3 or more. We find that the rate of SST rise in the Arabian Sea is higher than the other parts of the northern Indian Ocean since 1998. SST and salinity in the Arabian Sea have been controlled by Persian Gulf outflow water and oceanographic currents. TC intensity is controlled by warm and saline (>36.6 PSU) water distribution patterns, mediated by eddy and jet currents. Rapid intensification of pre-monsoon TCs occurred by tracking to the north and northwest, with most landfalls occurring during this period. Post-monsoon TCs generally affect the center and the southwest of the Arabian Sea. The risk of intensive TCs manifests an increasing trend since 2007, therefore education programs via international platforms such as the International Ocean Institute (IOI) and UNESCO are required for the countries most at risk.
In this study, 2,7-Diaminophenazine supported on nanocellulose (DAP@CNC) was designed. The prepared nanocatalyst was characterized with various analytical techniques such as FTIR, XRD, TGA, SEM, TEM, and CHN. Nanocatalyst used for the synthesis of isoxazolo[4,3-e]indazole derivatives via the nucleophilic substitution of a hydrogen in 5-nitro-1-p-tolyl-1H-indazole with different 2-phenylacetonitrile derivatives in basic medium. Also, we did this reaction with KOH as other catalyst. The mechanism of the reaction investigated by density functional theory based modeling is also reported. Simple procedure, high yields, short reaction time and environmentally benign method are advantages of this protocol. The nanocatalyst was readily separated by filter and reusable without significant loss of its catalytic efficiency.
The purpose of this study is to improve the efficiency of decontamination using BaSO 4 as a piezocatalyst. Three techniques are employed in this study to enhance the piezocatalytic activity of BaSO 4 . The first method involves coupling BaSO 4 with BaTiO 3 . The acid red 151 and acid blue 113 decontamination rates improved from 56.7% and 60.9% to 61.3% and 64.4%, respectively, as a result of this strategy. Additionally, the composite of BaSO 4 and BaTiO 3 was doped with copper, iron, sulfur, and nitrogen. By doping BaTiO 3 , acid red 151 and acid blue 113 achieved 86.7% and 89.2% efficiency, respectively. Finally, the nanostructures were modified with sucrose. These strategies improved degradation efficiency for acid red 151 and acid blue 113 to 92.9% and 93.3%, respectively. The reusability results showed that the piezo-catalytic activity of the m-S–BaSO 4 –BaTiO 3 catalyst did not show a significant loss after five recycles for the degradation of AB113.
In order to reduce water consumption (especially in remote areas) for the self-cleaning dust removal systems, the efficiency of a three-phase traveling electromagnetics wave for some designed Electrodynamics Dust Shield (EDS) setups are simulated and also experimentally tested. The designed Fresnel rings electrodes EDS system showed about 25% enhancement on light collecting power and a substantial improvement on dust removal efficiency, as well. On the other hand, for the fabricated EDS systems the dust removal efficiency has been tested as a function of the dust particle size, respectively. In this study, the removal dust particles has been sampled from three different Iran's desserts with a vast size ranges, which matches with many of the remote areas in the world. It was confirmed that the sweeping frequency range from 5 to 100 Hz improved the cleaning efficiency and also the sweeping time lasting reduced about half for the zigzag electrode EDS system in comparison to a simple parallel bar one. For designing the different EDS systems, the well-known Finite Element calculation method (COMSOL Multiphysics software) has been employed, respectively.
The Achaemenids and Sasanian 'Persian' Empires were significant political, economic, and social forces in the Late Iron Age and Late Antiquity Eurasia, respectively, which have left marks on the heritage of the Mediterranean and Middle Eastern world. While attention is often focused on military and political conditions when discussing the prosperity and decline of these imperial powers, their realms, which crossed a variety of environmental settings, were highly dependent on the predictability of rainfall that drove agriculture and effective provisioning. Here, we present a multi-proxy sedimentological, geochemical, and palynological record from a 2.5-m long peat deposit near the excavation site in Konar Sandal near Jiroft in southeastern Iran, covering 4000-850 cal yr BP. Around 3950 cal yr BP a wet period prevailed based on elemental ratios, stable C isotope, pollen, and diagnostic lipids. Between 3900 and 3300 cal yr BP, wet/semi-wet conditions developed with the appearance of Cerealia-type pollen. Dry and windy conditions followed (ca. 3300-2900 cal yr BP), which coincided with the Siberian anticyclones and climatic shifts developing in the Eastern Mediterranean region. Consequently, the Bronze Age settlements around Jiroft, dependent on agriculture, underwent a steady decline. A prolonged wet period followed (ca. 2900-2300 cal yr BP) with the abundance of Sparganium-type pollen and the aquatic lipid proxy (Paq). This change coincided with intensive agricultural practices and the flourishing of the powerful Median and Achaemenid empires. The shift to high Ti/Al ratios coeval with the lowest δ13COM values suggests an increase in aeolian activity and dry conditions ca. 2100-1650 cal yr BP. The Jiroft valley again experienced wet conditions between 1550 and 1300 cal yr BP, which overlapped with the economic prosperity of the middle to late Sasanian empire. The paleoenvironmental reconstruction indicates that wet periods and intensive agriculture coincide with the Persian empires' zenith, political influence, and economic affluence. Therefore, contextualized and detailed paleoenvironmental records are desirable to explore the interplay of political and climatic factors in the development and fragmentation of the ancient settlements and imperial powers in Eurasian history.
The southern Sanandaj-Sirjan Zone (SSZ) forms the core of the Zagros orogen and consists of a stack of four major tectonic units, all of which were thrust southwestward over the Neyriz ophiolites. Precambrian and early Paleozoic rocks were affected by high-grade metamorphism, whilst the late Paleozoic (Carboniferous and Permian) and Mesozoic rocks are of low grade to unmetamorphosed. Geothermobarometric results indicate that the investigated area experienced peak temperature–pressure conditions of ~ 650 °C and 8–9 kbar, before being partly overprinted by greenschist facies conditions. We identified two main deformational phases (D2, D3) and some relics of an older one (D1) in the southern SSZ. D1 is inferred based on local evidence of tight D2 folds that fold a pre-existing schistosity (S1), associated with prograde- and peak metamorphism. D2 shows large-scale, tight-to isoclinal F2 folds and a penetrative S2 foliation, forming the dominant foliation in our study area. The P–T path is clockwise and associated with a geothermal gradient of ~ 20 °C/km, suggesting a collision-related geodynamic setting, preceding D2, and possibly linked to an early stage of D1. D3 is characterized by open folds (F3) and thrusts developed after greenschist facies metamorphism. Based on the metamorphic grade and stratigraphic age of folded units, D2 is inferred to be Eo-Cimmerian, and D3 post-Cretaceous, coeval to the Zagros orogeny. Concerning the oldest phase (D1), for which only circumstantial structural evidence exists, we discuss whether its age is pre-Cimmerian, possibly Variscan, or Eo-Cimmerian as suggested in previous literature. This study uses metamorphic assemblages and structures of the southern SSZ, to retrace its geodynamic evolution, which started with burial associated with high-temperature metamorphism, followed by Eo-Cimmerian shortening, and finally terminated with additional shortening related to the Zagros collisional event.
Magnetic properties of root, bark, and leaf of mangrove (Avicenna marina) and sediment were determined for pollution assessment at three locations in the northern coast of the Persian Gulf. The study revealed that the sources of the particles deposited on leaf surfaces can be discriminated via saturation isothermal remanent magnetization (SIRM) values and heavy metal. However, different factors including wind direction, size of the magnetic particles and crown density, play a role using SIRM for biomonitoring of atmospheric particulate matter. For leaves, the significant correlations between SIRM and leaf elemental contents indicated that the deposited particles on their surface mainly have geogenic sources. The magnetic analyses revealed that leaves are more suitable than bark for monitoring atmospheric pollution using mangrove trees due to the effect of different factors including dense crown of trees, washing of tree trunk by sea waves, and elements translocation from roots and sediments. Instead, the positive and significant correlation between the SIRM values for sediments and mangrove roots, and no or negative correlation between sediments and roots with barks and leaves indicates that the magnetic properties of the sediments and mangrove roots are suitable indicators of pollution in aquatic environment.
The Sarvak and Ilam Formations in the Zagros sedimentary basin are known as reservoir ROCKs. Over 50 hydrocarbon fields are in the Zagros basin at the Sarvak and Ilam hydrocarbon Formations, and the Fars region is about 5%. This research identifies areas with hydrocarbon potential of the Formation of Sarvak and Ilam at Fars area parameters such as Formations outcrop, main faults, isopach maps, and volume of upper Formations sediments extracted from geology map of the area. With fuzzification of the layers and overlapping them with each other, the areas with high hydrocarbon potential were identified in the Ilam and Sarvak Formations. Regarding exploration potential in the Sarvak and Ilam Formations, the Fars region was identified as an area with poor hydrocarbon potential. Somehow 75.25% of the Fars area has inferior hydrocarbon potential, 18.5% has standard hydrocarbon potential, and only 6.25% has high hydrocarbons potential for exploration at the Sarvak and Ilam Formations. While considering to fault effect and their outcrops, the percent of areas with high hydrocarbon potential decreased to 3.6%. Also, Fuzzy logic as a multi-value logic from masters knowledge and designed inference network could identify all fields with hydrocarbons potential in the Sarvak and Ilam Formations in the Fars area and recognize those areas as a high hydrocarbons potential.
The Neo-Tethys subduction and subsequent Arabia-Eurasia continental collision invoked widespread Cenozoic tectono-magmatism throughout the Iranian Plateau. We herein develop a new method to image the shallow crustal S-wave velocity (Vs) structure by joint inversion of multifrequency waveforms and horizontal-to-vertical ratios around the direct P phase in P-wave receiver functions. Synthetic tests demonstrate the validity of our method in constraining the absolute Vs values beneath single stations down to ~12-km depth. By applying this method to a seismic array of 63 stations with an average spacing of ~10 km along the main profile, we construct a detailed shallow crustal Vs model across the northwestern Iranian Plateau. The model is characterized by distinct high- and low-velocity anomalies beneath the Iranian hinterland and the Zagros foreland fold and-thrust belt, respectively. In combination with geological observations and laboratory data, the imaged high-velocity anomalies (with Vs of 3.2-3.9 km/s) may denote arc to intraplate magmatism beneath Central Iran and Alborz to the north, whereas the low-velocity anomalies (with Vs of ~1.65 km/s) probably represent the marl/shale layers in Late Cretaceous and Paleocene beneath Zagros. The magmatic rocks at the Iranian hinterland exhibit strong variations in absolute Vs, reflecting different bulk compositions with more mafic inland. The shale/marl layers could have acted as décollements to accommodate crustal deformation. Our observations underline both the key role of lithology-controlled layering in sedimentary deformation at the Zagros fold-and-thrust belt and the change in compositions and forming-environments of magmatic rocks at the Iranian hinterland.
Ardestan-Arak axis is situated in the Urmia-Dokhtar magmatic belt and Sanandaj-Sirjan zone. Exposed magmatism in Urmia-Dokhtar magmatic belt in study area often includes plutonic (granodiorite, granite, and gabbro with calc-alkaline composition) and volcanic rocks (rhyolite, dacite, trachydacite, andesite, and basalt with porphyry texture). Geochemical analysis shows that the primary magma have characteristics of I-type magmatism which produced in volcanic arc. All volcanic rock samples collected have SiO2 values from 50 to77 wt% and are metaluminous. NMORB-normalized trace element spider diagrams and chondrite-normalized REE patterns show negative Nb, Ta, and Ti anomalies, enrichment in large ion lithophile elements (LILEs), and light rare earth elements (LREEs) relative to high field strength elements (HFSEs) which are characteristics of calc-alkaline composition of the rocks in subduction zone. Plutonic and volcanic rocks in the Ardestan-Arak axis have slightly LREE-enriched pattern with (La/Yb)n variation in 2.36–10.92 and 2.7–7.7, respectively, which support a subduction nature for most of the samples. Also, low Sr/Y in magmatic rocks (with typical values of the Sr/Y ratio Less than 30) is similar to non-adakite and barren-type igneous rocks in subduction zone in the Urmia-Dokhtar Magmatic Arc. Also, the geochemistry results of plutonic rocks in study area show minor negative to slightly positive Eu/Eu* anomaly varying from 0.9 to 1.2, similar to unprodutive magmas. On the other hand, the average copper grade at the plutonic and volcanic rocks at Ardestan-Arak axis is 32 and 29 ppm, respectively. Another evidence related to barren-type magmas in Ardestan-Arak axis is enrichment in Cs, Rb, Ba, Th, U, Nb, K, and Pb and depletion in Zr, Ti, and P in the NMORB-normalized diagram. These similar values also indicate a similar source for the plutonic and volcanic rocks in Ardestan-Arak axis or show the mantle enrichment processes before melting. Therefore, it could be concluded that magmatism in the study area was not favorable for the formation of porphyry copper mineralization.
The Sistan orogen (Eastern Iran) separates the Afghan and Lut continental blocks and stretches along ~700 km from north to south, at a high angle with respect to other, dominantly E-W trending Alpine-Himalayan orogens. This study reappraises the tectono-metamorphic evolution of the northern part of the orogen, as well as its significance within the Neotethyan realm. Detailed inspection of the Sistan ophiolite indicates that the Sistan Ocean was of a slow- spreading type and that, given its structural patterns, petrological characteristics and age, it opened in a transtensional setting ~125 Ma ago. Closure of the Sistan Ocean took place through a major NE-dipping subduction zone, formed no later than 90 Ma, as shown by the location and age of bimodal juvenile arc magmatism, the SW vergence of the orogen and the location and age of subducted fragments. The discovery of a metamorphic sole at the base of the ophiolite (~750°C-0.65 GPa) argues for the onset of an additional intra-oceanic thrust/subduction zone around 74-72 Ma, which resulted in the south-westward obduction and preservation of the ophiolite onto the continental Lut block. The Sistan Ocean therefore appears to have recorded two major geodynamic events that accompanied the closure of the Neotethys, i.e. the major change in kinematics at ~105 ±5 Ma and the northward migration of India from ~75-70 Ma onwards. Subsequent collision, likely started during the Paleocene and mostly completed by the Oligocene, was accompanied by a drastic change of the Eocene sedimentation yet by only moderate shortening (~30-50 km in total). Since the Late Miocene onwards, post-collisional deformation is dominated by far-field stresses related to the Zagros collision.
The Jazmurian Playa in southeast Iran is a sediment archive that has preserved a record of climate and environmental changes since the late Pleistocene. The late Pleistocene was dominated by sub-arid to arid climate interspersed with short periods of warm and humid conditions that impacted the vegetation cover and landscape. This study used sedimentological variations in a sediment core, supported by geochemical and mineralogical characteristics, to reconstruct climate change impacts and water-level fluctuations in the playa. These changes were inferred using grain-size data, magnetic susceptibility, total organic matter content, carbonate content, elemental concentrations, and mineralogical composition in a ¹⁴C-dated sediment core. Based on the inferred water level fluctuations in the playa, the core was divided into two major units. Unit 2 belonged to the late Pleistocene, characterized by a cold and dry climate. In contrast, Unit 1 was deposited during the Holocene, a time marked by prevailing warm and humid conditions, with short periods of intense dust storms. Since the late Holocene, the IOSM (Indian Ocean Summer Monsoon) has played a dominant role in regional climate. Water-level fluctuations related to humidity significantly influenced the sedimentological variables, including grain-size distribution, sorting, skewness, and roundness. During cold and arid conditions, the water level was low, and coarse sediments were deposited in the playa, with low organic matter content, low concentrations of Cu, Mn, P, and V, and evaporite minerals. In contrast, high organic matter content, presence of illite, and high concentrations of Cu, Mn, P, and V and low values of ICV (Index of Compositional Variability) imply a warm and humid climate during the Holocene. The paleoclimate reconstruction in the playa provides evidence about ongoing changes that are closely related to the paleohydrological conditions in this region.
We present the source mechanisms and rupture processes for the damaging 23 February 2020 earthquake doublet of Mw 5.8 and Mw 5.9 that occurred near the Turkish-Iranian border regions of Qotur-Goharan-Mir'Omar-Ravian (NW Iran), extending towards Saray and Başkale (Eastern Turkey), as obtained from seismological waveform analysis and space geodesy imaging. Seismotectonic characteristics of the sequence highlight the role of indentation tectonics developed within regional-scale compressional environment where the Arabian microplate collides with the Eurasian plate. Here we report optimal finite-fault slip distribution patterns of the 2020 Qotur-Ravian earthquake doublet revealing complex co-seismic rupture propagation along the fault planes with maximum displacements ranging from 20 to 50 cm, stretching from the hypocentre to the surface. Analysis of aftershocks based on 3.5 months-long seismicity confirms distributed deformation. This energetic earthquake sequence demonstrates the distinct rupture characteristics illuminating differences in seismogenic properties and seismic hazard. Coulomb stress transfer modelling predicts triggering of the second event of Mw 5.9 by the first event of Mw 5.8. The zone of negative Coulomb stress changes attributed to varying pore pressure linking to geothermal water resources in the region as a driving force, may have an impact on the nucleation of triggered faulting. Evaluation of Interferometric Synthetic Aperture Radar (InSAR) data reveals the activated fault with evident post-seismic slip. Specifically, (1) we detected a rare case in earthquake-induced ground deformation where there is overlapping surface deformation due to sequential shallow events located closely in the crust, (2) the initial event ruptured a fault located towards W-NW of the latter inferred fault and (3) the conjugate system of faults is closely placed at a few km apart. The frequent Sentinel-1 interferograms enhanced our imaging abilities of geometry and kinematics of shallow moderate-size M < 6.0 earthquakes and to trace seismogenic structures in remote and mountainous earthquake prone regions.
Land subsidence (LS), which mainly results from poor watershed management, is a complex and non-linear phenomenon. In the present study, LS at a country-wide assessment of Iran was mapped by using several geo-environmental conditioning factors (namely, altitude, slope degree and aspect, plan and profile curvature, distance from a river, road, or fault, rainfall, geology, and land use) into a machine learning algorithm-based artificial neural network (ANN), and a powerful group method of data handling (GMDH). The total dataset includes historical LS and non-LS locations, identified by the interferometric synthetic aperture radar (InSAR). The whole dataset was divided into two subsets at a ratio of 70:30 for training and validating the model, respectively. ANN- and GMDH-based LS maps were evaluated using receiver-operator characteristic (ROC) curves. The information gain ratio (IGR) was calculated to determine the relative importance of the conditioning factors. The results showed that all of the considered factors contributed significantly to the LS mapping in Iran, with geology having the strongest impact. According to the ROC curve analysis, both ANN and GMDH-based LS maps were accurate, but the map obtained by the GMDH approach had a higher accuracy than that of ANN. Southwestern, northeastern, and some parts of the central region of Iran were shown to be susceptible to LS in the future. According to the GMDH susceptibility map, 10% of Iran exhibits high or very high susceptibility to LS in the future. The provinces of Hamedan and Khouzestan had the highest percentage of areas at risk of LS. According to the InSAR data, 39%, 20%, 25%, 13%, and 3% of the investigated areas are subject to a yearly LS of -1 to -2.5, -2.5 to -5, -5 to -7.5, -7.5 to -10, and -10 to -20 cm, respectively. The province of Razavi Khorasan in the northeast of Iran had the largest area (about 3500 km2) vulnerable to LS occurrence. Based on the LS susceptibility map, the provinces of Ardebil, Kurdistan, West and East Azerbaijan, Sistan and Baluchistan, and Kermanshah, although not currently undergoing a high rate of LS, will be at high risk of severe LS in the future.
The Central Iranian Micro-plate (CIM) is a dismembered piece of northern Gondwana. The aim of this study is to reconstruct the post-Early Cretaceous structural evolution of the western edge of CIM in the light of the integration of regional to the micro-scale structural data with minor Anisotropy of Magnetic Susceptibility (AMS) analyses. Our original field measurements on the structural architecture of the study area show main NW-SE and E-W structural trends that are accompanied by structural evidence for superposition. However, paleostresses obtained from fault and fold analysis (stress inversion method on faults and statistically π‐plane and β‐axis solution on folds), statistical Fry center-to-center analysis on the oriented thin-sections integrated with AMS results suggest that the study area has experienced a NE-SW-directed compressional regime since Paleocene time followed by a post-Early Miocene, roughly N-S-directed, regional compressional regime. Furthermore, the results of this work confirm the consistency between regional-micro structural analysis and AMS analysis. The most of samples show composite (sedimentary + tectonic) magnetic fabric and intermediate arrangement in the orientation of the magnetic fabric. Reconciling our results with published structural and AMS data suggests the changes in the regional stress regime in the western CIM has been occurred in response to the long-term stress transition from the infant Late Cretaceous–Paleogene subduction of the Neo-Tethys Ocean to the mature Cenozoic stages of the Zagros collision and the consequent Neogene tectonic reorganization in the hinterland domains of the southern Eurasian plate
Expansion of agriculture and industry has led to the growing exploitation of groundwater resources and groundwater level decline in the Isfahan-Borkhar plain. The steady decline in groundwater in susceptible areas has resulted in land subsidence. In this research, the subsidence level of the plain was measured between 2014 and 2017 using radar interferometry technique. On the other hand, the effects of groundwater level decline and aquifer parameters (e.g., alluvium thickness, fine-grained sediments percentage, hydraulic conductivity, storage coefficient, water level, and water level decline) on the subsidence were evaluated. To this end, the deformation in areas where the radar interferometry technique has failed to measure due to significant vegetation cover was estimated using an artificial neural network (ANN)-based model. This model was developed to predict the subsidence amount at any point, assuming that all parameters affecting the occurrence of this phenomenon are known. Next, the sensitivity analysis was performed using trained model parameters to determine the parameter with the highest impact on the subsidence event in the study area. The modeling results showed that the model could predict the subsidence with high accuracy. The most effective parameters in the subsidence event in this area were water level decline and fine-grained sediments percentages. Overall, comparing the subsidence level estimated from time series analysis with changes in groundwater level at some piezometers demonstrates the high impact of fine-grained sediments on the subsidence event in the area.
The pre-Alpine evolution of the Tethyan domains between Gondwana and Laurasia, and in particular that of the Cimmerian continental blocks, remains poorly constrained. Central Iran is a key area to constrain the closure of the Paleotethys and the collision of Laurasia with the Cimmerian blocks drifted from Gondwana. The present study provides a combined metamorphic and geochronologic approach focused on two areas of Central Iran: the Kashmar-Kerman Tectonic Zone (KKTZ) and the Jandaq area, whose tectonometamorphic units are affected low- to middle-pressure high-temperature metamorphism. We performed in-situ texturally constrained U/Pb dating on titanite and Rb/Sr dating on mica to quantify the timing and intensity of burial and exhumation of these metamorphic rocks. Results show that metamorphism in the central and eastern KKTZ (7-9 kbar; ∼700°C) is synchronous or slightly postdates the Cimmerian orogeny (∼190-180 Ma) and relates to the collision following the Paleotethys closure, whereas metamorphism in the Jandaq complex (12-13 kbar; ∼450°C) relates to the Paleotethys subduction. Based on paleogeographic reconstructions, the KKTZ lied hundreds of kilometers south of the Paleotethys suture zone. As such, we propose that metamorphism along the KKTZ results from the closure and shortening of a rheologically weak domain located outboard of the main suture. In-situ Rb/Sr dating of biotite yields precise and accurate cooling ages (± 2-5 Ma) ranging from 170 to 140 Ma. These cooling ages document the exhumation of these terranes from the Mid-Cimmerian event onward (∼170 Ma), coeval with the widespread extension distributed across Iran and thought to reflect upper plate extension above the Neotethyan subduction system.
Cenozoic tectono‐magmatism in Iran is widely considered to be related to subduction of the Neo‐Tethys Ocean. We employed whole‐rock and mineral geochemistry and isotopic data of intrusive rocks from Tafresh, central Urumieh‐Dokhtar magmatic arc, to evaluate the role of the mantle in magmatism, to assess the timing of emplacement, and to interpret the tectonic setting. Rock compositions range from gabbro or gabbro‐diorite (plagioclase + pyroxene ± olivine), to diorite (plagioclase + amphibole ± pyroxene), to granodiorite (quartz + plagioclase + K‐feldspar + amphibole + biotite), exhibiting high‐alumina calc‐alkaline affinity. Major oxide and trace element variations vary systematically from less to more evolved rocks suggesting a major role for fractional crystallization processes. Zircon LA‐ICP‐MS U–Pb ages of major rock types are in the range of 24–19 Ma, whereas those of gabbroic dikes are ~17.5 Ma. ԐNd values range between −1.8 and 3.7, and (87Sr/86Sr)i is narrowly restricted to 0.705–0.706, suggesting a common mantle source. The enrichment in light rare earth element (REE) enrichment and flat heavy REE patterns couple depletion of Nb–Ta–Ti indicate that subducting oceanic crust had interacted with the overlying mantle wedge. High‐alumina, mid‐Mg# Tafresh plutonic rocks formed from hydrous melts from which Ca‐pyroxene and magnetite crystallized earlier than plagioclase, whereas late‐crystallizing zircon nucleated while magma traversed through lithospheric mantle and Cadomian crust. Modelling of isotope and incompatible‐element patterns suggests the contribution of no more than ~5% molten sediment or other crustal components in Tafresh magma, at a developmental stage before most plagioclase and amphibole had crystallized. The Miocene Tafresh plutons originated during the final stages of subduction, before the collision between the Arabian and Eurasian plates. Schematic diagram showing the Miocene geodynamic evolution of the Tafresh magmatic rocks.
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119 members
Nasser Naimi Ghassabian
  • Department of Geology
Shabnam Najafi AsliPashaki
  • Department of Chemistry
Hamid Nazari
  • Research Institute for Earth Sciences
Mohammad Hashem Emami
  • Institute for Earth Sciences Research
Mahmoud Reza Majidifard
  • Stratigraphy and Palaontology
Meraj St, Azadi Sq., Tehran, Tehran, Iran