Editor-in-Chief Lecture
Mohammad R. Ghassemi
Original Research Paper
Enayatallah Haghfarshi; Peyman Rezaee; Seyed Reza Moosavi Harami; Mohammad 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 suburb of Tabriz. Its sedimentary facies includes facies groups of fine grains clastics, sandstones, limestones and facies of lignite, tuff and microfacies and petrofacies under ...
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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 suburb 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 studied and 171 samples and 42 thin sections were collected and 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. In the studied 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.
Original Research Paper
Petroleum geology
Haniyeh Ghayeni; Mohamad Hosein Mahmudy-Gharaie
Abstract
Investigating the hydrocarbon generation potential of the Kazhdumi Formation, as the most important oil source rock in the Zagros sedimentary basin, is of great importance. The expansion of the Kazhdumi Formation in the Zagros Basin has been associated with differences in sedimentation depth of the basin ...
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Investigating the hydrocarbon generation potential of the Kazhdumi Formation, as the most important oil source rock in the Zagros sedimentary basin, is of great importance. The expansion of the Kazhdumi Formation in the Zagros Basin has been associated with differences in sedimentation depth of the basin leading to varieties in sedimentary facies and the organic matter preservations. Five black shale samples from Perchestan and Tang-E Maghar sections were selected for analysis by Rock-Eval pyrolysis, and were compared to the data of 25 Kazhdumi samples from different oil fields of Nowrouz, Soroush, Azadegan and Chah-E Binak, previously studied in the Zagros Basin. Additionally, sedimentary environment and depositional conditions were investigated. Sedimentary and geochemical evidences indicate a dominant condition of high organic content shale deposition in the reducing to semi-oxidative environments. The values obtained for total organic carbon (TOC) ranged from 1.2 to 6.9%. Examination of the thermal maturity of the samples showed a wide range from the immature range to the middle oil window, which are often in the range of type II and III kerogens. Finally, the drawing of the TOC vs. S2 diagram represents the higher hydrocarbon generation potential of the Kazhdumi Formation in the Tang-E Magher section, and the TOC vs. HI diagram shows the greater oil generation in the Soroush field, compared to the other studied areas.
Original Research Paper
Geological Environment and Engineering
Abbas Zolfaghari; Mashallah Khamehchiyan; Mohammad Reza Nikoodel; Abdollah Sohrabi-Bidar
Abstract
The combined effect of the number of joints, opening, type and thickness of filling on the amount of vibration caused by the propagation of waves in four identical dry limestone blocks with dimensions of 10*10*50 cm was studied. The maximum vibration of particles in intact and jointed rock blocks in ...
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The combined effect of the number of joints, opening, type and thickness of filling on the amount of vibration caused by the propagation of waves in four identical dry limestone blocks with dimensions of 10*10*50 cm was studied. The maximum vibration of particles in intact and jointed rock blocks in three perpendicular directions was recorded by a three-component geophone. In block number 1 with a joint in the middle of the block, the amount of joint opening was changed from 3-6-9-12-15-18-21 mm and the measurements were made for each amount of opening in two series. In the first series, the joint filled with clay was tested, and in the second series, the joint filled with sandy soil was tested. This series of tests were also performed on blocks No. 2 with two joints, Block No. 3 with three joints, and Block No. 4 with four joints. The results of the tests showed that the presence of joints in rock blocks reduced the maximum vibration of particles in all three directions with different proportions. The relationship between the increase in the joint index and the decrease in the maximum vibration of the particles is nonlinear.
Review Article
Geophysics
Asghar Rastbood; Mohsen Sahebi-Ilekhchi
Abstract
Very Long Baseline Interferometry (VLBI) is one of the essential approaches in geodesy. Significant capabilities of this technique are creation of International Celestial Reference Frame (ICRF), determination of Earth orientation parameters (EOPs), coordinates of station with high accuracy and light ...
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Very Long Baseline Interferometry (VLBI) is one of the essential approaches in geodesy. Significant capabilities of this technique are creation of International Celestial Reference Frame (ICRF), determination of Earth orientation parameters (EOPs), coordinates of station with high accuracy and light deflection. Many attempts could be done to increase accuracy of VLBI data, including technical improvement of equipment, physical models improvement, using optimal data processing methods and increasing number of stations. In this study, in order to reduce the error of EOPs in CONT17 campaign, the appropriate position for a VLBI station in the Middle East is investigated. The results showed that mean error of EOPs in the Legacy-1and Legacy-2 reduced approximately 6.64% and 13.86% by adding two stations in Oman and Egypt countries, respectively.
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. However, 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 a local strike-slip regime in addition to the regional compressional regime in the region.
Review Article
Tectonics
Mohammad R. Ghassemi; Ali Aghanabti; Abdollah Saeidi
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 poorly constrained 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 Ekbatani 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.
Original Research Paper
Petrology
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; Gholam Reza 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 ...
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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
Petrology
Niloofar Nayebi; Dariush Esmaeily; Soroush Modabberi; Ryuichi Shinjo
Abstract
Anomaly 21A, as a part of Bafq iron-apatite ore metallogenic district, is located in Central Iran, and encompasses wide spectrume of igneous, sedimentary and metamorphic rocks. The igneous rocks that show narrow geochemical variations and dominantly plot in the monzonite to monzodiorite fields, are ...
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Anomaly 21A, as a part of Bafq iron-apatite ore metallogenic district, is located in Central Iran, and encompasses wide spectrume of igneous, sedimentary and metamorphic rocks. The igneous rocks that show narrow geochemical variations and dominantly plot in the monzonite to monzodiorite fields, are plotted in the calc-alkaline and high-K calc-alkaline affinities. Geochemical data are characterized by enrichment LILE and LREE as compare to HFSE and HREE, respectively, and depletions in Nb-Ta-Ti imply the mantle-derived melts modified by subduction components. The isotopic signatures of Anomaly 21A samples, e.g., (87Sr/86Sr)i, εNd(t)=, imply the dominant mantle signature. Their initial Pb isotopic composition of study rocks are 18.87 to 20.32 for (206Pb/204Pb), 15.72 to 15.84 for (207Pb/204Pb), and 40.74 to 42.32 for (208Pb/204Pb). The isotopic modellings show less than 4% incorporation of melt-derived subducted sediment into the mantle wedge or variable degrees of contamination by upper continental crust. We suggest partial melting of a sub-arc mantle melt that has been metasomatized by slab-derived sediments and interacted with continental crust en-route the shallower surface as the premise of the geodynamic of Central Iran.
Original Research Paper
Petrology
Saeid Samarbakhsh; Mohammad Hashem Emami; Seyed Mojtaba Mortazavi; Mansour Vosoughi-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
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. The host rocks of Goft and Mohammadabad deposits include red tuff and Marly tuff and limy tuff, 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
Economic Geology
Shayan Akrami; Mohammad Ali Aliabadi; Mohammad Reza Hazareh; Abbas Askari; Tayebeh Ramezani
Abstract
Nineh Pb-Zn deposit is located in the east of the Markazi province, in the Middle to Upper Jurassic rock units of the Malayer-Esfahan metallogenic belt. Stratified and epigenetic mineralization, in the form of veins, replacement and open spaces filling, including the main minerals of galena, sphalerite ...
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Nineh Pb-Zn deposit is located in the east of the Markazi province, in the Middle to Upper Jurassic rock units of the Malayer-Esfahan metallogenic belt. Stratified and epigenetic mineralization, in the form of veins, replacement and open spaces filling, including the main minerals of galena, sphalerite and barite accompanied by dolomite and siliceous alterations are observed. The microthermometry results of fluid inclusions in calcite and barite, display mean homogenization temperature of about 168.6°C and 127.3°C, and a mean salinity of 5.7 and 13.9 wt. % NaCl equiv., respectively, which indicates slight difference in their formation conditions. The homogenization temperature versus salinity diagram suggests a basinal brine fluid mineralizer and mixing and cooling processes for the mineralization. The values of δ34S in galena and sphalerite (7.5‰ to 21.5‰) of this deposit are similar to the values of δ34S in the upper Mississippi deposits, indicating the supply of sulfur during the process of thermochemical reduction of sulfate. The values of δ18OSMOW (-9.2 to -11.2‰) and δ13CPDB (0.1 to 0.5‰) of the calcite veins indicate a multi-origin of oxygen, and the origin of carbon from dissolved and remobilized marine carbonates. According to the evidence obtained during this study, the Nineh deposit can be classified as the Mississippi Valley type deposits, which was formed during the orogeny processes and the movement of basinal brine fluids.