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Journal of African Earth Sciences (1464343X)230
The structural system related to iron mineralization in the form of skarn and hydrothermal deposits in the Shizan region, northeastern Iran, has a direct relationship with the geometry of deformations, fractures, faults, and intrusive masses, with their penetrative nature serving as the source of fluid motion. This study aims to investigate tectonic structures, analyze them, identify stress trends and mineralization phases, and illustrate the region's structure. A tectonic model related to mineralization in the Shizan region, situated at the eastern end of the intracontinental Doruneh fault, will be presented. Tectonic events in the area are attributed to the activity of this fault, with a particular focus on the Illeh fault. This fault is an important branch that influences mineralization and morphology. By surveying the faults in the region and analyzing the density of each fault series and mineral trends, two main stress trends were identified: one trending NW-SE and the other NE-SW. The change in stress trends has led to the formation of three generations of faults and mineralization. The first mineralization phase, characterized by the N080-120 trend, occurred within the first stress trend along E-W to NW-SE faults. The subsequent mineralization phase with the N350-070 trend was associated with the second stress trend along N-S to NE-SW faults. Following the N015-060 trend, the final mineralization phase occurred when the second stress trend was reactivated along NE-SW faults. The structural evolution during the initial phase of the stress trend resulted in the formation of horsts, grabens, and half-grabens. The results indicate a clear correlation between the open spaces formed in the fault zones and mineralization, facilitating solution flow and promoting iron precipitation in the first and second phases. © 2025
Soleimani m., M.,
Baker j.l., ,
Nadimi, A.,
Dublyansky y., Y.,
Koltai g., G.,
Spötl c., C. Geophysical Research Letters (00948276)51(13)
The regional impact of abrupt glacial climate variability remains poorly constrained for arid southwestern Asia, particularly winter dynamics during Marine Isotope Stage 3, due to limited paleoarchives in the Middle East. Here, we present continuous speleothem records of δ18O and δ13C with robust chronologies for southwestern and central Iran, spanning ∼50–30 ka. Stable-isotope signals in the two stalagmites are generally uncorrelated and do not exhibit a consistent response to Greenland stadials or interstadials; however, both show a positive δ18O excursion that coincides with Heinrich event 4. We explore the potential mechanisms for intermittent coupling of speleothem δ18O across Iran through isotope-enabled atmospheric modeling outputs, from which we utilize the spatial δ18O gradient as a proxy for wintertime westerly versus southerly jet strength. Our results suggest that during Heinrich event 4 and several Greenland stadials, stronger westerly winds enhanced Mediterranean moisture contributions to both sites and reduced aridity in southern Iran. © 2024. The Author(s).
Khademian, F.,
Alaminia, Z.,
Nadimi, A.,
Lentz, D.R.,
Ghasemi, A.,
Sharifi, M. Journal of African Earth Sciences (1464343X)211
Remote sensing data can be utilised for regional mapping of the Earth's surface to enhance structural interpretation and mineral prospecting. To this end, satellite multispectral sensors such as the Advanced Space borne Thermal Emission and Reflectance (ASTER) with six channels in the shortwave infrared and five channels in the thermal area is helpful in detecting alteration and mineralisation zones in areas with good rock exposures. This study has investigated and detected hydrothermal alteration zones and mapped structural elements associated with mafic volcanic rocks-related copper mineralisation in the northwest of the Nain district in Central Iran. In this study, we processed ASTER data (14 bands). We generated maps that depict the distribution of alteration minerals (e.g., sericite, kaolinite, chlorite, and calcite) related to copper mineralisation using various techniques such as different band ratio images, False-colour composition (RGB), Matched Filtering (MF), and Spectral Angle Mapper (SAM). Follow-up ground proofing validated the analysis of results from the ASTER data. The study established the regional distribution of hydrothermal alteration zones (i.e., phyllic, argillic, and propylitic). The regional distribution and extent of these alteration zones are associated with regional structures that served as focusing conduits for the buoyant hypogene mineralizing fluids. The results show that ASTER imagery is useful in mapping the extent of the hydrothermal alteration and lithological units and can thus be used to target hydrothermal ore deposits with large alteration footprints. © 2024 Elsevier Ltd
ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences (21949042)10(4/W1-2022)pp. 631-637
Northwest of Iran, as a tectonically active region, has experienced numerous devastating earthquakes. That is why it is so important to study the earth deformation in this area and to provide more precise insights. So far, most researchers have had the preference of using the invariant component of strain rate tensor for investigating the Earth's shape deformation in the region. However, to examine the efficiency of the variant components of the geodesic strain rate tensor in interpreting deformations of north-western Iran, we have in this article maps of variant components of the geodetic strain rate tensor (normal strain rate along north and eastbound). Using the velocity field gathered from a previous article, and also using a simple and straightforward method, the strain rate tensors were calculated. The obtained contraction along the north direction (from the normal strain along this axis) confirms the Eurasia-Arabia collision. Besides, the obtained extension along the east direction and the derived expansion of the dilatation, show the effect of Anatolian motion to the west and eastward movement of the central Iran plateau on the tectonic structure of the studied area. These two results showed that the variant component of strain rate tensor also provides us with useful information about a region shape deformation. © Author(s) 2023. CC BY 4.0 License.
Turkish Journal Of Earth Sciences (1303619X)32(5)pp. 632-651
Change in the steepness of river profiles caused by tectonic forces (uplift and material weakening in fault zones) causes the formation of the tectonically formed knickpoints (TFKs), which is an important geomorphic feature in bedrock river morphology. In this research, knickpoints in a wide area of the south of Central Alborz using the stream gradient (Gd) and the normalized steepness index (ksn) were identified. According to the location of the knickpoints in relation to the faults in the area, the TFKs were identified. Analysis of the extracted TFKs with the longitudinal profile, logarithm slope-area plots, and natural logarithm gradient-distance plots confirmed their correspondence with the active segments of faults. Investigating the characteristics of TFKs such as length, height and gradient indicated that TFKs related to Mosha and North Tehran faults are high-altitude and the TFKs related to Taleghan and Eshtehard faults are long-distance. The identification of numerous TFKs on the active fault segments of the area and their confirmation based on field observations indicate a high rate of uplift and recent tectonic activity in the southern side of Central Alborz, which shows the importance of seismic studies due to the possibility of destructive earthquakes in the future. © TÜBİTAK.
Keihanizadeh, R.,
Nadimi, A.,
Safaei, H.,
Moradian, A.,
Shafieibafti, S. Journal of African Earth Sciences (1464343X)202
The location of volcanoes in magmatic arcs associated with subduction zones often follows the structures present at the time of magma formation in these zones. The Mozahem stratovolcano, which has been caused by the subduction of the oceanic crust of Neotethys under Central Iran, is one of the Neogene volcanoes located in the southeast of the Urumieh-Dokhtar magmatic arc. The magmatic nature of the rocks forming the volcano is potassium-rich calc-alkaline. In this research, we used petrology, satellite images, and aeromagnetic data to understand the relationship between tectonics and magmatism. Mozahem stratovolcano area is limited to the NW-SE-trending Rafsanjan and Shahr-e-Babak fault zones and cut by the N–S-trending Anar fault. During the Neogene, the activity of the dextral Anar fault, especially in its southern termination areas, has caused changes in the local stress field and created deformations in different parts of this region. The displacement of blocks on both sides of the Anar fault has led to the development of compressive structures (folds and thrusts) at the eastern and tensile structures (dikes and subvolcanic masses) at its western half. The location of minor faults in the southern tip of the Anar fault and different mechanisms on both the eastern and western sides of the fault are comparable with the model of synthetic and antithetic splay faults at the tip. At the confluence of the Anar fault, NE-SW-trending Madvar-Riseh fault, and the NW-SE-trending Mozahem fault, lava, and pyroclastic volcanic materials erupted and the stratovolcano was formed. A tectonic evolution model was prepared to show how the area and the stratovolcano were formed and evolved. © 2023 Elsevier Ltd
Soleimani m., M.,
Nadimi, A.,
Koltai g., G.,
Dublyansky y., Y.,
Carolin, S.,
Spötl c., C. Journal of Quaternary Science (02678179)38(3)pp. 308-318
Glacial periods and their terminations are useful for assessing the full scale of natural climate variability in the diverse climate regions of West Asia (i.e. deserts, mountains, alluvial plains, coastal zones). In this study, we report the first stalagmite stable isotope (δ18O and δ13C) records from the southern Zagros Mountains in southwest Iran. The records partially span the period from the Last Glacial Maximum (LGM) to the early Holocene, 24.2–9.6 thousand years before the present. The southwest Iran stalagmite δ18O and δ13C records indicate that climate and environment in the area differed substantially between the LGM and early Holocene. High stalagmite δ13C values are found at the LGM (7‰ greater compared to the early Holocene), and are attributed to sparse vegetation and reduced soil bio-productivity, and possibly a greater degree of prior calcite precipitation in the epikarst, as a result of a cold and dry climate. Stalagmite δ18O values are also high at the LGM (4‰ greater compared to the early Holocene), and are attributed to lower temperatures (larger water–calcite isotope fractionation) and higher δ18O values of the moisture sources (Mediterranean and Red Seas). Through the deglaciation, stalagmite δ18O, δ13C and/or growth features coincide with the North Atlantic Heinrich Stadial 1, the Bølling–Allerød warm period and the Younger Dryas cold event, supporting a relationship between southern Zagros climate and the North Atlantic millennial events. © 2022 The Authors Journal of Quaternary Science Published by John Wiley & Sons Ltd.
Ahmadi-bonakdar s., S.,
Tabatabaei manesh, S.M.,
Nadimi, A.,
Mirlohi a., A.,
Santos j.f., J.F.,
Parfenova o.v., Geotectonics (15561976)56(6)pp. 791-809
Abstract: The Golpayegan metamorphic complex is located in the Sanandaj-Sirjan Zone, Iran. This complex consists of various metamorphic rocks including schists, marbles, slates, gneisses, and amphibolites, most of them have Neoproterozoic age. The presence of structures such as sigma fabrics, boudinage, folded boudinage and interfering fold patterns indicates the occurrence of more than two deformation phases in the Golpayegan metamorphic complex. The measurement of strain intensity in the folds indicated deep immersion of structures and old Precambrian settings that had been influenced by orogenic events in the Neoproterozoic. These deformed rocks were exposed during extensional movements and, subsequently, sheared. The results based on field works shown geochemical relations and initial εNd(600 Ma) values of amphibolites in three sampling points located in Golpayegan region manifested that the protolith of the first (a') and second (b') sampling points had mantle origin (ortho-amphibolite), whilst protolith of the third (c') sampling point had sedimentary origin (para-amphibolite). Geochemically, the Golpayegan ortho-amphibolites showed sub-alkaline basalt-basaltic andesite compositions of tholeiitic affinity. The negative anomalies of Nb and Ti relative to Pb, La, and Ce in the primitive mantle-normalized spider-diagram and εNd(600 Ma) values revealed the subduction environment for ortho-amphibolites. The ortho-amphibolites exhibited the intermediate chemistry between the normal mid-ocean ridge basalt and island-arc tholeiitic basalt. Enrichment in large ion lithophile elements (LILE), light rare earth elements (LREE), and relative depletion in high field strength elements (HFSE) suggest the back-arc basin setting for the Golpayegan ortho-amphibolites. The primitive magma of the ortho-amphibolites was produced by 8–20% melting of spinel lherzolite. According to the Neoproterozoic age of the Golpayegan ortho-amphibolites and their relationship with the Golpayegan granitic gneiss (596‒578 Ma), it shows that they can be related to the Cadomian back-arc basin in the north of Peri-Gondwana at the Neoproterozoic. The high values of 87Sr/86Sr (0.708450‒0.714986) interpreted as result of seawater hydrothermal alteration. © 2022, Pleiades Publishing, Inc.
Khademian, F.,
Alaminia, Z.,
Ghasemi, A.,
Nadimi, A. Petrological Journal (22285210)13(4)pp. 1-34
Introduction The magmatic evolution of the Urumieh-Dokhtar arc is related to the Neo-Tethys subduction and the continental collision between the Arabian and Eurasian plates, which has led to the creation of diverse and different magmatism along different parts of this belt (Shahabpour, 2005; Agard et al., 2011; Richards, 2015; Karimpour et al., 2021). Volcanic rocks, with various lithological compositions located in the central part of the Urumieh-Dokhtar belt, are part of the extensive Eocene activity, Knowing the nature of basic-intermediate volcanic rocks northwest of Nain requires more detailed investigations. For this purpose, the exploration areas of Chakad, Safafoulad, and Mehrando, located northwest of Nain, were selected for further investigations. The main goal of the present paper is to understand the origin and the tectonic of the volcanic rocks of this part of the Urumieh-Dokhtar magmatic belt using their petrography and geochemical characteristics. Regional Geology Many outcrops belonging to Tertiary volcanic lavas and pyroclastic deposits are widespread 50 km northwest of Nain, within the central part of the Urumieh-Dokhtar magmatic arc (UDMA). The volcanic units are basic to acidic composition ranging in age from Eocene to Oligocene (Chiu et al., 2013) and pyroclastic rocks including tuff, breccia, and ignimbrite, low in altitude, overlain by a sequence of Quaternary alluvium. In the exploration areas of Chakad, Safafoulad, and Mehrando, the Eocene basic-intermediate volcanic rocks with the combination of basalt, basaltic-andesite and pyroclastic rocks exposed and play as the host rocks for copper mineralization. The youngest igneous units observed in the region are a set of parallel diabase and dolerite dikes as swarms, intruded the volcanic rocks. Based on field observations, silica and carbonate veins with different trends are observed along with copper mineralization in basaltic-andesite and basalt units. This ore mineralization occurs mainly as an oxide (malachite and azurite) accompanies with propylitic alteration and less argillic and silicification along and at the intersection of faults and fractures. Materials and methods Following the preparation of thin sections and petrographic and mineralogical investigations of these units, 26 volcanic samples have been analyzed by the ICP-MS method for trace and rare earth elements. Petrography The basic-intermediate volcanic rocks of the region are mostly basalt and basaltic-andesite, as well as diabase and dolerite dikes. The studied basalts, mineralogically, dominated by Euhedral to subhedral phenocrysts of plagioclases (30 to 50 vol%) and clinopyroxene phenocrysts, with porphyritic texture. Small amounts of olivine occur as phenocryst and iddingsite basaltic-andesite consists of plagioclase (40 to 60 vol%), and clinopyroxene (15 to 20 vol%) phenocrysts set in a fine-grained to microlithic groundmass. Clinopyroxene and plagioclase with intergranular texture are the dominant minerals in diabase and dolerite. Chlorite, calcite, epidote, and quartz are the main altered minerals of the rocks under study. Discussion and Conclusion Based on the geochemical data, the basic-intermediate volcanic rocks with the combination of basalt and basaltic-andesite have a calc-alkaline nature, consistent with the features of volcanic arcs in the subduction zone of the active continental margin. In the primitive mantle-normalized multi elements diagram, the patterns of basic-intermediate volcanic rocks show enrichment of LILE (e.g., Ba, K, Rb) and depletion of HFSE (e.g., Nb, Ti, Zr) one of the remarkable features of subduction zone-related magmas (Yang and Li, 2008; Kuscu and Geneli, 2010). In the chondrite-normalized REEs diagram, these rocks exhibit LREE enrichment relative to HREEs. Rare earth elements such as La and Sm are not significantly affected by the mineralogical changes of the source rock, so they can provide information on the chemical composition of the total source rock. The volcanic rocks of the region generated by partial melting of 5 to 10% (Aldanmaz et al., 2006) of the enriched garnet-lherzolite mantle at a depth of 90 to 100 km. It seems that the parent magma has been metasomatized under the influence of fluids and sediments derived from the oceanic lithosphere. As the tectonic setting identification diagrams display the studied samples plotted in the range of magmas related to the subduction zone of the active continental margin. The magmatism under discussion, is the result of the subduction of the Neo-Tethys oceanic lithospheric beneath the central Iranian plate which have given rise to great magmatism during the Eocene and following it. Acknowledgments The authors are very grateful to the esteemed referees of Petrology magazine for their valuable suggestions in improving the scientific structure of the article. © 2023 The Author(s).
Sohrabi, A.,
Nadimi, A.,
Talovina i.v., I.V.,
Safaei, H. Journal of Mining Institute (25419404)236pp. 142-152
In the southern part of the Khur area, there is faults system with predominantly North-West strike. This network of tectonic disturbances is one of the most important fault systems in Central Iran which crosses Paleozoic metamorphic rocks, Cretaceous limestones, and Eocene volcanic rocks. Interpretation of satellite imagery ETM+ (Enhanced Thematic Mapper plus, Landsat) and field observations showed the presence of left-lateral shifts along with fault system. This formed the structure of the branch faults at the northeast end of the main fault. Another feature associated with shear dislocations is the rotation of blocks in the northeastern and southwestern segments of the area under study. There are several basins and positive structures within the area such as a series of uplifts and thrusts, indicating the presence of compressional and extensional tectonics. Another part of the work is devoted to the study of the correlation between active faults and earthquakes. Processing of satellite images, field observations, records of micro-earthquakes within a radius of 17 km made it possible to analyze the earthquakes parameters and the position of tectonic disturbances, and, as a result, confirm the presence of active faults in the region. In addition, we have identified three successive stages of the Khur area tectonics: rifting, contraction, change of convergence and uplift direction. © 2019, Saint-Petersburg Mining University. All rights reserved.
The collision of Arabian-Eurasia continental plates in consequence of Neo-Tethys subduction, produces a zone of very complex tectonic structures in Iran. The study area is hinterland of the Zagros Orogen in central part of the Urumieh-Dokhtar magmatic arc, northeast Isfahan. Major brittle structures in the study area consists of dominant NW-SE-trending longitudinal, N-S and E-W-trending oblique faults sets. Comparison of brittle structures and mineral deposits in the area indicated that the mineralizations are mainly formed along the active tectono-magmatic arc. In the study area, NW-SE trending Zefreh fault and it’s branches faults have created a dextral horsetail splay architecture. Analysis of the lineaments interpreted out of satellite images and field observations is recognized as another technique for locating porphyry type copper mineralization. There is a close correlation between increasing the intensity of fractures and the repoted copper mineralization in the area. © 2019 Taylor & Francis Group, London.
Geotectonics (15561976)52(2)pp. 281-296
The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275–375, 375–500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed. © 2018, Pleiades Publishing, Inc.
Konon, A.,
Nadimi, A.,
Koprianiuk, M.,
Wysocka, A.,
Szaniawski, R.,
Wygladała, M.,
Słaby, E.,
Beygi s., S.,
Barski, M. Geological Society Of America Bulletin (00167606)128(11-12)pp. 1593-1617
The interaction of strike-slip faults in their restraining junctions allowed for the coeval formation of the Tabas and Abdoughi Basins and led to their inversion during the late Cenozoic. The intracontinental basins filled with Neogene and Quaternary deposits were controlled by large-scale dextral transpression along major faults that bounded the Tabas block, which is a part of the Central Iranian block. The anastomosing strike-slip fault pattern facilitated the development of both basins in opposite corners of the Tabas block. The subsided areas were formed as a result of interaction between the restraining junctions of strike-slip faults and thrusts. Flexural loading caused by the uplifted series of thrust sheets resulted in the depression of the opposite fault slabs, which permitted deposition of Neogene sediments. Deformation according to the "bookshelf" mechanism can be considered as a consequence of accommodation of the shortening of the area north of the Main Zagros thrust and externally imposed shearing along the Great Kavir (Doruneh) fault during the collision of the Arabian and Eurasian plates. Related processes of transpression and counterclockwise rotation of the tectonic blocks included in the Central Iranian block favored the interaction of strike-slip faults. The change of far-field stress and continuous transpression caused inversion of the basins and formation of Neogene folds in the northern and southern corners of the Tabas block. The geomorphic features observed along these strike-slip faults and on the thrust surfaces bounding the folds display their recent activity, consistent with present-day seismicity and geodetic measurements within the Central Iranian block. © 2016 Geological Society of America.
Journal of Geosciences (Czech Republic) (18026222)61(2)pp. 127-144
In this paper, we use satellite images, field observations and aeromagnetic data to describe major tectonic features in the central portion of the Urumieh-Dokhtar Magmatic Arc (UDMA) in Central Iran. Most of the analyzed structures such as horsetail splays, rotated blocks, positive flower structures and sedimentary basins have not been previously recognized. The NW-SE-trending Zefreh Fault is the most important dextral transpressional active lineament in the area. Maps of filtered aeromagnetic anomalies confirmed that the fault also affects the basement. Based on our field observations and cross-cutting relationships, tectonic evolution of the central part of the UDMA is interpreted in terms of two main stages: (1) formation of main thrusts during shortening and exhumation of older rocks in the UDMA after Eocene-Oligocene, and (2) transpressional movements reactivating the main thrust faults to reverse-dextral strike-slip faults during the Pliocene-Quaternary. The present-day deformation of the UDMA is mostly dominated by strike-slip movements. These two stages are interpreted as reflecting a change in convergence vector between Arabian and Eurasian plates. © 2016, Czech Geological Survey. All Rights Reserved.
Bahadorinia, S.,
Hejazi, S.H.,
Nadimi, A.,
Ford, D.,
Wainer, K. International Journal of Speleology (1827806X)45(3)pp. 243-257
Kalahroud Cave is located in central Iran, ~50 km north of Isfahan. The landscape is a typical mountain desert morphology of cuestas dissected by ravines and gorges created during rare surface run-off events; crest lines are ~2800 m asl and lowlands at ~2100 m asl. Kalahroud Cave (4500 m of mapped passages, ~60 m deep) is entered through breakdown in the eastern wall of a gorge. The host rock is a Cretaceous limestone and mudstone formation 60 m in thickness, underlain by sandstones and conglomerates and overlain by weakly permeable calcareous marl strata, all dipping 15-20°. Below the entrance breakdown, two corrosion notch chambers give access to a rectilinear, quasi-horizontal maze of joint-guided passages extending ~500 m eastwards. Rock solution morphology created by slowly flowing phreatic waters predominates (solution pockets, partitions, paragenetic forms, etc). Seven shafts are known that discharged water into the maze and chambers from inaccessible passages below. From XRD analysis, the paragenetic sediments derive from the mudstone interbeds. There are small displays of frostwork, helictites and thin flowstones typical of vadose speleothem deposition in arid caves. Below the level of the corrosion notch, more complex sub-aqueous and shelfstone calcites are overlain by accumulations of calcite rafts up to 70 cm in depth. Raft deposition continues today. It is proposed that the cave is of hypogene origin, serving to discharge interformational groundwaters into the gorge, and becoming de-watered as the latter was deepened. The corrosion notches are due to cessation of deepening. From U series dating, the modern phase of raft deposition began about 10,000 years ago. The sequence and ages of older events will be investigated in future work. © 2016, Societa Speleologica Italiana. All rights reserved.
Geotectonics (15561976)49(6)pp. 560-578
Cherty marbles of Hasan-Robat area, northwest of Isfahan, in the Sanandaj–Sirjan Zone of Iran preserves evidences of multiple deformational events. The Sanandaj–Sirjan Zone is the inner crystalline zone of the Zagros Orogen, which has been highly deformed and exhumed during continental collision between the Arabian Plate and Central Iran. The Hasan-Robat area is an example of the exposed Precambrian–Paleozoic basement rocks that stretched along two NW–SE-trending faults and located in the inner part of the HasanRobat positive flower strcuture. The Hasan-Robat marbles record a complex shortening and shearing history. This lead to the development of disharmonic ptygmatic folds with vertical to sub-vertical axes and some interference patterns of folding that may have been created from deformations during the Pan-African Orogeny and later phases. Based on this research, tectonic evolution of the Hasan-Robat area is interpreted as the product of three major geotectonic events that have been started after Precambrian to Quaternary: (1) old deformation phases (2) contractional movements and (3) strike-slip movements. Different sets and distributions of joints, faults and folds are confirmed with effect of several deformational stages of the area and formation of the flower structure. © 2015, Pleiades Publishing, Inc.
Kananian, A.,
Sarjoughian, F.,
Nadimi, A.,
Ahmadian, J.,
Ling, W. Journal of Asian Earth Sciences (18785786)90pp. 137-148
The Kuh-e Dom Pluton is located along the central northeastern margin of the Urumieh-Dokhtar Magmatic Arc, spanning a wide range of compositions from felsic rocks, including granite, granodiorite, and quartz monzonite, through to intermediate-mafic rocks comprising monzonite, monzodiorite, diorite, monzogabbro, and gabbro. The Urumieh-Dokhtar Magmatic Arc forms a distinct linear magmatic complex that is aligned parallel with the orogenic suture of the Zagros fold-thrust belt. Most samples display characteristics of metaluminous, high-K calc-alkaline, I-type granitoids. The initial isotopic signatures range from εNd (47Ma)=-4.77 to -5.89 and 87Sr/86Sr(i)=0.7069 to 0.7074 for felsic rocks and εNd (47Ma)=-3.04 to -4.06 and 87Sr/86Sr(i)=0.7063 to 0.7067 for intermediate to mafic rocks. This geochemical and isotopic evidence support a mixed origin for the Kuh-e Dom hybrid granitoid with a range of contributions of both the crust and mantle, most probably by the interaction between lower crust- and mantle-derived magmas. It is seem, the felsic rocks incorporate about 56-74% lower crust-derived magma and about 26-44% of the enriched mantle-derived mafic magma. In contrast, 66-84% of the enriched mantle-derived mafic magma incorporates 16-34% of lower crust-derived magma to generate the intermediate-mafic rocks. According to the differences in chemical composition, the felsic rocks contain a higher proportion of crustal material than the intermediate to mafic ones. Enrichment in LILEs and depletion in HFSEs with marked negative Nb, Ba, and Ti anomalies are consistent with subduction-related magmatism in an active continental margin arc environment. This suggestion is consistent with the interpretation of the Urumieh-Dokhtar Magmatic Arc as an active continental margin during subduction of the Neotethys oceanic crust beneath the Central Iranian microcontinent. © 2014 Elsevier Ltd.
Bulletin of the Geological Society of America (19432674)124(3-4)pp. 484-498
The Gaw-Khuni Basin is located in the central part of the Sanandaj-Sirjan zone, on the northeastern margin of the Zagros orogen. This basin is one of the continuous zones of Sanandaj-Sirjan zone basins that is filled by Pliocene-Holocene sediments. The Gaw-Khuni Basin is surrounded by an en echelon to parallel arrangement of active faults in dextral strike-slip fault zones that indicate a right-step dilational stepover structure. The boundary faults of this basin are the Eastern and Western Gaw-Khuni, Ramsheh, and Nain-Dehshir faults. Earthquake distribution determined along the faults, dissection and displacement of Holocene sediments, and also the development of pull-apart basins filled with Holocene deposits along the faults confirm that these faults are active. The Gaw-Khuni stepover was formed during transtensional movements produced between two dextral strike-slip faults (Nain-Dehshir and Ramsheh). Also, the Gaw-Khuni pull-apart basin and the Eastern and Western Gaw-Khuni faults developed in a releasing step between the faults and grew in two directions during the time of their formation. © 2012 Geological Society of America.
Journal of Structural Geology (01918141)40pp. 2-16
The Sanandaj-Sirjan Zone (SSZ) is one of the main basement tectonic blocks located close to the northeastern margin of the Zagros Orogenic Belt. New observations in the central part of the zone indicate that the fault pattern is dominated by NW-trending longitudinal faults. The components of movement on the fault planes are interpreted as dextral oblique thrusting and dextral strike-slip. The identified structures along the faults were associated with the strike-slip faults (e.g., Hasan-Robat and Najafabad dextral restraining stepovers) and rotated tectonic blocks (arranged in a 'domino' configuration) near to the Foladshahr and Kolah-Ghazi mountains. Along the longitudinal faults, the dextral offsets of the rock units, streams, alluvial deposits and rivers were measured. The dextral offset values range from 2.4 to 2.7 km, while the estimated offsets based on the geomorphological features are between 50 and 61 m for streams, up to approximately ~50 m for alluvial deposits and up to 2.2 km for rivers. The dextral strike-slip component on the fault planes occurs along the northern and southern margins of the SSZ, as well as directly within the zone, west and east of the study area. The evidence for strike-slip faulting in the internal part of the zone suggests that the central part of the SSZ probably was horizontally sheared in a manner consistent with a simple shear 'card-deck model'. © 2012 Elsevier Ltd.
Journal of Structural Geology (01918141)32(3)pp. 263-263
Konon, A.,
Barski, M.,
Koprianiuk, M.,
Nadimi, A.,
Słaby, E.,
Szaniawski, R.,
Wysocka, A. Przeglad Geologiczny (00332151)58(1)pp. 42-45
Special Paper of the Geological Society of America (00721077)444pp. 105-122
Arabia-Eurasia convergence is accommodated in the Zagros Mountains of southwestern Iran and in the seismic belts of the central Caspian, Alborz, and Kopeh Dagh of northern Iran. The Zagros is a NW-trending fold-and-thrust belt made up of a 6-15-km-thick sedimentary pile, which overlies the Precambrian meta-morphic basement. During the Zagros orogeny, some of the Precambrian basement and Lower Paleozoic strata were exhumed from depth and are now exposed in the Golpayegan region in the northwestern part of the Zagros Mountains. The tectonic evolution of the Golpayegan region and the exhumation of the old rocks are interpreted as the product of three major sequential geotectonic events. (1) Major thrusts formed during shortening and exposure of the basement rocks in the Aligudarz block. The rock units are strongly imbricated and sheared, which suggest a high amount of cumulative shortening in the northern Zagros. (2) NE-SW-trending extensional faults (e.g., Eastern Mute, Western Mute, and Mahallat faults) formed during lateral extensional movement after middle Miocene time. In this event, a set of NE-SW-trending horsts and grabens was formed. In the horsts (e.g., Hassan-Robat, Mute, and Mahallat horsts), the Precambrian basement rocks and Lower Paleozoic strata are exposed. (3) Strike-slip movements began that remain active today. Strike-slip motions are well documented for the late Pliocene-Quaternary period. In the Golpayegan region, the Shazand and Dehagh faults cut through the NE-trending normal faults and through Quaternary deposits. Drainages are displaced by ∼4 km of dextral movement along the Shazand fault and near the city of Golpayegan. © 2008 The Geological Society of America.
Gondwana Research (1342937X)12(3)pp. 324-333
Most of the Infracambrian-Lower Paleozoic sedimentary rocks occurring in Iran cover a crystalline basement. In Central Iran, and the Saghand region along the Chapedony and Poshte Badam faults, the basement complexes show structural vestiges of Precambrian deformational, depositional, erosional, metamorphic and magmatic events. In this region, the basement complexes contain the Chapedony, Poshte Badam, Boneh Shurow and Tashk formations. The prevailing metamorphism, from low grade to high grade, is pre-Pan African Orogeny (i.e. from 2400 to 570 Ma). The presence of greenstone belts, a paleo-suture zone and ophiolitic rocks (i.e. from 2100 to 1500 Ma) around the high-grade metamorphic rocks of the Chapedony Formation, provide evidence that cratonization forming the Iranian basement occurred during the Paleo- and Mesoproterozoic. After formation of the basement complexes, metamorphism of the Precambrian formations and establishment of the Arabo-Iranian coherent platform at the end of Pan African Orogeny, Central Iran broke up during a Neoproterozoic-Early Cambrian extensional tectonic regime. Infracambrian-Phanerozoic sedimentary rocks were then deposited on the basement complexes. The Iranian basement complexes are extensively overprinted by Pan African Orogeny and younger igneous events. © 2006 International Association for Gondwana Research.
Earth and Planetary Science Letters (0012821X)203(1)pp. 93-104
The mantle peridotites of Neyriz record two successive episodes of plastic deformations; the first one related to the igneous accretion of the lithosphere and the second one developed during the first stage of the emplacement of the peridotites. These two events have been distinguished on the basis of microstructural criteria. The diapiric pattern, particularly relevant to the mantle process beneath spreading ridges, features vertical flow lines and elliptic flow plane trajectories in a pipe and extends along the ridge axis about 5 km. These structures rotate to horizontal and diverge in every direction in a narrow transition zone, a few hundred meters thick, below the Moho discontinuity. Such a diapiric pattern has been recognized in a few places along the Neyriz paleo-ridge. A large amount of magma passed through these mantle diapirs that were probably the main zones feeding the overlying magma chamber. The most common pattern features very regular structures over several kilometers along the strike of the paleo-ridge: the flow plane dips away from the ridge axis, and the flow line is parallel to the spreading direction. This flow pattern is frozen during the gradual accretion of the lithospheric mantle away from the ridge in a steady-state spreading regime. A shear-sense inversion at just below the Moho is commonly observed, pointing to forced asthenospheric flow. The reconstructed orientation of the Neyriz paleo-spreading center is 105°, compatible with the geometry and orientation of harzburgite foliations and lineations and sheeted dikes. © 2002 Elsevier Science B.V. All rights reserved.
Physically, Iran is best known for its warm-to-hot, semiarid to arid climatic conditions. In the north (Alborz Mountains) and west (Zagros Mountains) it has mountain ranges rising to 3500-4500. m. a.s.l., however, which supported major alpine glaciers during the Quaternary Ice Ages and maintain a few much smaller ones today. Scientific investigation of caves in the mountains is in its early stages. Two examples with perennial ice have received preliminary study; (1) Yakh-Morad Ice, at 2490. m above sea level in the Alborz, has perennial ice from seepage entering a lower level cold trap and retains seasonal ice into Aug. in warmer upper levels; it is believed that a net loss of the perennial ice is occurring. Dena Ice Cave, at 3900. m. a.s.l. in the Zagros, is a single descending passage with large ice stalactites, stalagmites, and flowstones from seepage. The cave may be experiencing net accumulation of ice today. © 2018 Elsevier Inc. All rights reserved.
