Original Research Paper
Petrology
saeid samarbakhsh; mohamad hashem emami; Seyed mojtaba Mortazavi; mansor vosoghi abedini
Abstract
The study area, situated 50 km north of Ghaemshahr, structurally belongs to the Central Alborz tectonic zone. The volcanic rocks of the area, including basalt, andesite, trachyandesite, and dolerite are the products of fractional crystallization and some contamination processes. Clinopyroxene, olivine, ...
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The study area, situated 50 km north of Ghaemshahr, structurally belongs to the Central Alborz tectonic zone. The volcanic rocks of the area, including basalt, andesite, trachyandesite, and dolerite are the products of fractional crystallization and some contamination processes. Clinopyroxene, olivine, and plagioclase are the main minerals of these rocks. Porphyritic to mega-porphyritic texture with microlithic, glomeroporphyritic, and amygdaloidal matrix are observed in these rocks. Plagioclase, hornblende, and pyroxene can be considered the main mineral phases of these rocks. The rocks are enriched in LIL and LREE elements and depleted in HFS elements. The ratios of trace elements and rare earth elements in the studied region indicate that the basalts were formed by melting a garnet bearing peridotite at great depths and pressures. Negative Ce anomaly, Nb negative anomaly, Pb positive anomaly the role of continental lithosphere in contaminating the magmatic sources of volcanic rock in the study area. The Pb/Ce ratio similar to ocean island basalt (OIB) sources, induces OIB sources, the asthenospheric mantle, in the initial formation of basaltic magma. it can be concluded that the volcanic rocks of the area have formed in an intra-plate environment in an extensional regime.
Original Research Paper
Economic Geology
Shayan Akrami; Mohammad Ali Aliabadi; Mohammadreza Hezaree; Abbas Asgari; Tayebeh Ramezani
Abstract
The Nineh deposit is a Pb-Zn deposit located in the Malayer-Esfahan metallogenic belt (MEMB) as stratabound and epigenetic mineralization hosted by middle-Jurassic limestone. The replacement and vein mineralization of galena, sphalerite with a minor amount of pyrite occurred in the foreland basin within ...
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The Nineh deposit is a Pb-Zn deposit located in the Malayer-Esfahan metallogenic belt (MEMB) as stratabound and epigenetic mineralization hosted by middle-Jurassic limestone. The replacement and vein mineralization of galena, sphalerite with a minor amount of pyrite occurred in the foreland basin within the Orumieh-Dokhtar zone. The microthermometery results of fluid inclusions trapped in calcite and barite, respectively, show homogenization temperature peak of 107 to 137°C and 150 to 170°C , and a salinity mode of 12.9 to 14.9wt.% NaCl equiv. and 4 to 6wt.% NaCl equiv.. The salinity vs. homogenization temperature diagram attests to cooling and mixing as the main mineralization mechanisms. The δ34S values of sphalerite and galena are within the range of 9.5 to 21.5‰ and 7.5 to 19.5‰, respectively and is about 43.7‰ for barite, the wide range of the sulfur isotope values is consistent with originating from different sources. Additionally, the δ13C (0.1 to 0.5 ‰) and δ18O (-9.5 to -11.5‰) values of calcite samples are in accordance with marine carbonate source and a high interaction of the ore fluids with different sources. Accordingly, the deposit could be classified as Mississippi Valley type (MVT) deposit which undergone more W/R interaction due to multiple orogenic
Original Research Paper
Tectonics
Mohammad Reza Ghassemi; Seyed Ali Aghanabati; Abdollah Saidi
Abstract
Correlation of the orogenic and epeirogenic events in Iran with the events that have been identified in different parts of the world and in different tectonic environments, has caused some confusion in the Iranian geological literature. After a brief review of the nature of known orogenic processes in ...
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Correlation of the orogenic and epeirogenic events in Iran with the events that have been identified in different parts of the world and in different tectonic environments, has caused some confusion in the Iranian geological literature. After a brief review of the nature of known orogenic processes in the world, examining issues related to the abovementioned correlations, and considering the tectonic history of various parts of Iran, we have tried to systematically describe and name the important orogenic and epeirogenic events of the country. Most Precambrian orogenic events in Iran are dubious due to unknown age and tectonic setting of the rock units attributed to Precambrian. Paleozoic in Iran has been mostly associated with epeirogenic events, and the only sign of a real orogenic event goes back to the Late Carboniferous in northern Iran. The important Mesozoic and Cenozoic orogenic events have shaped the modern tectonic configuration of Iran. The Paleotethys suture in northern and central Iran formed during the Gorgani orogeny, development of the Central Iranian active margin (Sanandaj-Sirjan) occurred in the Alvandi orogeny, ophiolite obduction in Central Iran and Zagros developed during the Late Cretaceous events, and collision of the Iranian plate with the Helmand block resulted in the Sistani orogeny. The creation of the Zagros and Alborz mountain ranges started from Oligocene and Miocene times, respectively, and the deformation due to their shortening continues to this day.
Review Article
Petroleum geology
Hanie Ghayeni; Mohamad Hosein Mahmudy Gharaie
Abstract
Investigating the hydrocarbon generation potential of the Kazhdumi Formation, which is one of the most important source rocks of the Zagros sedimentary basin, is very important and necessary, Because the tectonic movement of the main faults of Zagros, both during the deposition of Kazhdumi and after, ...
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Investigating the hydrocarbon generation potential of the Kazhdumi Formation, which is one of the most important source rocks of the Zagros sedimentary basin, is very important and necessary, Because the tectonic movement of the main faults of Zagros, both during the deposition of Kazhdumi and after, caused differences in the depth and sedimentation conditions of the different zones of this basin, and changes such as diversity in the way of sedimentation, biological facies and It has resulted in the preservation rate of organic matter. Therefore, 30 samples of this formation were selected and evaluated from different areas of Izeh zone (Perchestan ) and Dezful Embayment (Tang-E Magher , Nowrouz , Soroush , Azadegan and Binak). In this study, in addition to comparing the data of Kazhdumi Formation in different zones of Zagros, it has been tried to study the conditions of sedimentation and sedimentation environment. The recorded values for total organic carbon range from 1.2 to 6.9% and the examination of the thermal maturity of the samples shows a wide range from the immature range to the middle of the oil window,
Original Research Paper
Economic Geology
Shaghayegh Sadat Hashempour; Sajjad Maghfouri; Ebrahim Rastad
Abstract
The Goft and Mohammadabad manganese deposits are located in the southwestern part of Sabzevar, whitin the Late Cretaceous volcano-sedimentary sequences. This sequence is located inside a 100 km long folded structure with northeast-southwest trend. Mohammadabad manganese deposit located in the southeastern ...
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The Goft and Mohammadabad manganese deposits are located in the southwestern part of Sabzevar, whitin the Late Cretaceous volcano-sedimentary sequences. This sequence is located inside a 100 km long folded structure with northeast-southwest trend. Mohammadabad manganese deposit located in the southeastern edge of the southern anticline in the unit 4 of regional stratigraphic column and Goft manganese deposit is occurred in the southeastern edge of the northern anticline in the first unit of the regional stratigraphic column. respectively. According to geochemical studies, tectonic environment of manganese deposits in the southwest of Sabzevar is a rifting environment that has been formed in the Sabzevar back-arc basin. The rocks of the region have a wide range of basalt, rhyolite, dacite, olivine-basalt, andesite-basalt and trachy-andesite, which formed aligned with pyroclastic sediment and Late Cretaceous sedimentary units. Dacite rocks are the thickest felsic rock unit in the area. The values of major oxides, the pattern of rare earth elements (REE), and the changes in trace elements in spider diagrams indicate the bimodal and tholeiitic nature of the volcanic rocks of the region, which are deposited in extension environment with a mixed range from basalt to rhyolite.
Original Research Paper
Stratigraphy and Palaeontology
Ali Jalali; Hamed Yarahmadzahi; Mehran Arian; Abdollah Saidi; Seyed Mohsen Aleali
Abstract
the Shishtou section is located in the north of Tabas . Ghezelin and Asselian sequences of Zaladou Formation with 60 m thickness are divided into five units, includes sandstone, limestone, shale, sandy limestone and limestone. The lower boundary of the Gzhelian deposits with disconformity on top of the ...
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the Shishtou section is located in the north of Tabas . Ghezelin and Asselian sequences of Zaladou Formation with 60 m thickness are divided into five units, includes sandstone, limestone, shale, sandy limestone and limestone. The lower boundary of the Gzhelian deposits with disconformity on top of the Moscovian deposits of the Abshani Formation. The upper boundary of these deposits with the Tighe-Madanou Formation is continuous. Assembelage of fusulinids in the Shishtou section such as Ruzhenzevites-Rauserites-Triticites are identified in the upper part of Gzhalian previously reported from equal deposits in Darvaz, Fergana, Southern Urals, Donetsk and Carnic of Alps, as well as, Central Iran , Central Alborz and Sanandaj-Sirjan zones. Also, different species of Sphaeroschwagerina, Pseudoschwagerina and Likharevites, which illustrate the Asselian age, represent the Carboniferous-Permian boundary in the studied section and allow for comparability with other structural-sedimentary zones of Iran, including Central Iran , Central Alborz (Doroud Group) and Sanandaj-Sirjan zone.This equivalence expresses the transgressive of sea level in different parts of Iran in the late Carboniferous and early Permian periods.In Shishto section 15 genera ,35 species and 2 subspecies of Fusulins have been identified, some of which are reported for the first time from Iran.
Original Research Paper
Economic Geology
Amir Esna-Ashari; Massimo Tiepolo
Abstract
The Malayer-Boroujerd plutonic complex (MBPC) is part of the Sanandaj-Sirjan continental arc of Iran resulted from subduction of Neotethys oceanic crust below Central Iran microcontinent. A number of adakitic samples have recently been reported in the MBPC. This study shows that among the various petrogenetic ...
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The Malayer-Boroujerd plutonic complex (MBPC) is part of the Sanandaj-Sirjan continental arc of Iran resulted from subduction of Neotethys oceanic crust below Central Iran microcontinent. A number of adakitic samples have recently been reported in the MBPC. This study shows that among the various petrogenetic processes responsible for the formation of adakitic rocks, two have been suggested in the genesis of those from the MBPC. i) interaction of crust-derived magma with ultramafic rocks and ii) crystallization of amphibole from a more basic magma. The former process leads to formation of intermediate to basic magma that subsequently crystallized amphibole in the ultramafic rocks. Amphibole growth was associated with textural and chemical changes toward the rim. Chemical modeling shows that amphibole growth was coeval with assimilation of olivines that their residue are remained as inclusions in the amphibole. The magma that formed the rim of amphiboles had higher Th, Zr, Ta and LREE but lower Ti and HREE than the core-forming magma. Assimilation of olivine during the amphibole growth prevented a decrease in Ni and Co content of the remained magma. Comparable chemistry of the rim-forming melt and MBPC adakitic rocks suggest that they are of the same origin.
Original Research Paper
Petrology
zeinab rahmanian; gholamreza ghadami; hamid Ahmadipour; Mohammad Poosti
Abstract
Dalfard granitoids are located in the south-east of Kerman province and in the margins mainly include quartz diorite. Quartz diorites contain main minerals plagioclase, amphibole and biotite and this work reveals that the rocks in this area are I type granitoides and they belong to calc-alkaline magmatic ...
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Dalfard granitoids are located in the south-east of Kerman province and in the margins mainly include quartz diorite. Quartz diorites contain main minerals plagioclase, amphibole and biotite and this work reveals that the rocks in this area are I type granitoides and they belong to calc-alkaline magmatic series. The enrichment of LREE relative to HREE, high contents of LILE relative to HFSE and anomalies of Nb and Ti in spider diagrams show that the Dalfard quartzdiorites are formed in an arc setting environment. The CaO/(MgO+FeOt) and Al2O3/(MgO+FeOt) ratios (0.55 and 1.36 respectively) show that the parent magmas were formed by the partial melting of basaltic rocks of the lower crust and mantle fluids/melts also participated in their formation. Based on geochemical data such as La/Yb(N) and Th/Yb(N) ratios (4.4 and 6.5 respectively), these magmas are related to pre-plate collision environment and formed in the mature Volcanic arc setting at a depth of about 40 km at the supra subduction zone of the Neothetys oceanic lithosphere and then, they ascent to the higher levels of the crust and passed fractional crystallization.
Original Research Paper
Sedimentology
AFSHIN KARIMKHAMI BAHADOR; SADAT FEIZNIA; Mohsen Aleali; Mehran Arian
Abstract
To prepare sedimentological data, 98 surface sampling stations have been designed from the seabed in the continental shelf in the southern part of the Caspian Sea and along the coast of Iran. Indicators such as the type and amount of sediment load transported to the sedimentation environment, the energy ...
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To prepare sedimentological data, 98 surface sampling stations have been designed from the seabed in the continental shelf in the southern part of the Caspian Sea and along the coast of Iran. Indicators such as the type and amount of sediment load transported to the sedimentation environment, the energy of waves and sea currents, as well as how the slope of the seabed changes, play a role in the production and diversity of the sedimentary facies. 9 sedimentary facies are the most abundant in the surface deposits of this area and on average, in the sediments of the continental shelf, there are 1% by weight of coarse-grained particles, 25% by weight of medium-grained particles and 74% by weight of fine-grained particles. The composition of sedimentary facies in this area is controlled by indicators such as the size of sedimentary particles, the amount of sedimentary load carried to the environment, the energy of waves and sea currents, and how the slope of the seabed changes. In the marine environment of the study area, sub-sedimentary environments, Backshore, Foreshore, Shoreface, Offshore transition zone and Offshore can be identified. The two facies of slightly gravelly Mud and Mud are more abundant than other facies.
Original Research Paper
Tectonics
Fereshteh Jafari Hajati; Maryam Agh-Atabai; Majid Nemati; Ali Biglari Fadafan
Abstract
In this research, to understand the present-day tectonic situation of Gorgan-Plain in the east of the South Caspian basin, the tectonic stress regime of this area and its adjacent areas was estimated using the inversion of the data of the earthquake focal mechanisms. For this aim, in addition to analyzing ...
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In this research, to understand the present-day tectonic situation of Gorgan-Plain in the east of the South Caspian basin, the tectonic stress regime of this area and its adjacent areas was estimated using the inversion of the data of the earthquake focal mechanisms. For this aim, in addition to analyzing focal mechanisms solved by different sources, the focal mechanisms were solved for several earthquakes with appropriate and sufficient information. The results indicate the presence of various mechanisms, including thrust, normal, and strike-slip, and as a result, various orientations of kinematic P and T axes, which can indicate the complexity of the region. By analyzing the earthquakes with a minimum magnitude of 4 in the Gorgan-plain, the Kopeh-Dagh in the east of the plain, and the entire eastern region of the South Caspian, a compression regime with a NNW-SSE trend was obtained. But by analyzing all of the earthquakes (smaller and larger earthquakes) in the Gorgan-Plain, a strike-slip regime was obtained, in which the trend of the P and T axes were calculated NE-SW and NW-SE, respectively. The results indicate that there is a local strike-slip regime in addition to the regional compressional regime in the region.
Original Research Paper
Sedimentology
Enayat Allah Haghfarshi; Payman Rezaee; Seyed Reza Moosavi Harami; Mohamad Faridi
Abstract
Lignite Beds of Tabriz are among of the Neogene formations in the northwestern area of the Iran, which is spread in the eastern suburbs of Tabriz. Its sedimentary facies includes facies groups of fine grains clastics, sandstones, limestones and facies of lignite, tuff and microfacies and petrofacies ...
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Lignite Beds of Tabriz are among of the Neogene formations in the northwestern area of the Iran, which is spread in the eastern suburbs of Tabriz. Its sedimentary facies includes facies groups of fine grains clastics, sandstones, limestones and facies of lignite, tuff and microfacies and petrofacies under them. In this study, two stratigraphic sections of these sediments in the eastern part of Tabriz were collected and studied. 171 samples and 42 thin sections were studied. XRD analysis for mineralogy and SEM electron microscopy for 3-dimensional studies were used to identify microfossils. Identified fossils include the genera and species of gastropods, Pelecypods, ostracods, fish, diatoms, charophyte algae, and foraminifera. The studied fossil assemblages includes species from freshwater to euryhaline and marine. The identified sedimentary environments include the lake basin environment, the shallow coastal environment and the marshy lake environment. Studied in sedimentary strata, strong fossil evidence and sedimentological evidence of the marine environment are not observed, at least during its lifetime. Therefore, it is concluded that the marine taxis in these deposits remain and are adapted from a former marine environment.
