Original Research Paper
Stratigraphy and Palaeontology
elahe zarei
Abstract
The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of ...
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The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of pollen are identified (Middle Jurassic) and presence of some index dinoflagellate species led to the identification of three biozones in the Dalichai Formation. These include in ascending order, Cribroperidinium crispum Total Range Biozone (late Bajocian), Dichadogonyaulax sellwoodii Interval Biozone (Bathonian - early Callovian), Ctenididinium continuum Interval Biozone (early to middle Callovian). Also, this Formation was divided into two biozone on the basis of Lenticulina varians-Ophtalmidium Assemblage zone and Globigerina bathoniana Taxon range zone. The close similarities of fauna assemblages of Dalichai Formation in this region (eastern Alborz ((dinoflagellate cyst, foraminifera, posidonia and radiolar) with assemblages recorded from different parts of Iran (such as central and eastern, western Alborz and Binalud and south of Iran) and other parts of world (northwest of Europe, and the northwestern Tethys and …) confirm the marine connection and faunal exchange between the mentioned basins during Middle Jurassic.
Original Research Paper
Petrology
Mohsen Zadsaleh; Fariborz Masoudi; Hamed Pourkhorsandi; Karen Fontijn
Abstract
Damavand is a young volcanic edifice with an elevation of 5610 meters formed in the middle of the central Alborz Mountain range (N Iran) during the Quaternary. Its edifice is composed of trachyte and trachyandesite rocks, pyroclastic fall and flow deposits and lahars, formed during several eruptions ...
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Damavand is a young volcanic edifice with an elevation of 5610 meters formed in the middle of the central Alborz Mountain range (N Iran) during the Quaternary. Its edifice is composed of trachyte and trachyandesite rocks, pyroclastic fall and flow deposits and lahars, formed during several eruptions and under different magmatic conditions. To investigate the crystallization trends in the Damavand magma chamber and its evolution over time, plagioclase internal textures in lava flows, pyroclastic flow and ash deposits were studied. Samples from six different lava flows and pyroclastic fall and density current deposits with different ages were collected. Plagioclase crystals with similar dimensions and sizes but with completely different textures, and plagioclases with different dimensions but similar textural characteristics were observed. Twenty-eight different texture types were observed in plagioclase crystals from lava flows, whereas only three texture types were distinguished in the pyroclastic deposits. A large population of plagioclase in pyroclastic deposits reveal the non-equilibrium crstallization in the Damavand magma chamber(s), while in lava flows, a series of plagioclase cumulates present both equilibrium and non-equilibrium crystallization conditions in the magmat chamber. Plagioclase crystals in the source magmas of lava flows have repeatedly remained in a non-equilibrium state without eruption, letting the crystals to overgrow. Changes in the rate of magma ascent, small- and large-scale convection cells in magma chambers, varying temperature and/or pressure, and different volumes of (non-)eruptible mush/melt, are some of the parameters that are revealed by our textural studies. In the period between about 7-450 ky ago, the magma chamber that led to the buildup of the young Damavand volcano, was in non-equilibrium conditions as demonstrated by individual crystals textures and chemistry. However, these conditions have not always led to volcanic eruptions.
Original Research Paper
Geophysics
Mohammad Fouladi; Mirsattar Meshinchi Asl Meshinchi Asl; Mahmoud Mehramuz; Nima Nezafati
Abstract
Geophysical methods have been developed to study the particulars of physically diffusible fields in the ground. In geophysical studies, the goal is usually to detect inhomogeneities inside the earth using physical values measured at the earth's surface. Geophysicists attempt to reconstruct the Earth's ...
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Geophysical methods have been developed to study the particulars of physically diffusible fields in the ground. In geophysical studies, the goal is usually to detect inhomogeneities inside the earth using physical values measured at the earth's surface. Geophysicists attempt to reconstruct the Earth's interior structure using such data. The present study, which is known as the Third- order Moving Average, is the solution of an inverse problem for simultaneous estimation of the shape and depth of residual magnetic anomalies. The method was applied to the synthetic model, with and without noise, which Superiority this method will show over the Second-order Moving Average. Also, tested by the instance of field data in Geological Survey of Iran (GSI). This method, calculates a nonlinear relationship between depth and shape factor, at seven points with successive window length. Finally, the results showed that this method is very accurate for non-noise data and in has good agreement with the noisy data. which the problem, will showed the superiority of the Third-order Moving Average Method over the Second-order Moving Average method for estimating the shape and depth of buried Magnetic Anomalies. It also showed that it is suitable for real data with 5% error.
Original Research Paper
Sedimentology
Alireza Rostami; Mohammad Hossein Adabi; Abbas Sadeghi; Seyed Ali Moallemi
Abstract
The Dariyan Formation with the Aptian age is the youngest reservoir formation of the Upper Khami group which is important in terms of hydrocarbon reservoir potential. This formation is 135 meters thick in the Kuh-e-Mish surface section and consists of thin, thick and massive limestone, marl and shale. ...
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The Dariyan Formation with the Aptian age is the youngest reservoir formation of the Upper Khami group which is important in terms of hydrocarbon reservoir potential. This formation is 135 meters thick in the Kuh-e-Mish surface section and consists of thin, thick and massive limestone, marl and shale. Petrographic studies led to the identification of 13 microfacies. These have been deposited in four types of depositional environments, including inner ramp, mid ramp, outer ramp and basin, in a ramp type carbonate platform. Based on petrography, lateral and vertical facies changes, 3 third-order cycles distinguished. An integrated multidisciplinary approach including, petrography, surface gamma-ray spectrometry and trace element analysis have been used for recognition of original carbonate mineralogy and stratigraphic interpretations of this succession. Geochemistry of minor and major elements reveal original aragonitic mineralogy of the Dariyan Formation. Bivariate plot of Mn versus Sr/Ca values illustrated that the Aptian carbonates were affected by semi close diagenetic system with moderate water/rock interaction. Trace elements (Fe and Mn) contents are compared with distribution of sedimentary facies and depositional sequences to investigate and correlate stratigraphic boundaries, which are determined by sequence stratigraphy in shallow marine carbonate platform of the Dariyan Formation. The elemental peaks coinciding with the sequence boundaries and elemental peaks are correlated with maximum flooding surfaces.
Original Research Paper
Economic Geology
Kourosh Shabani; Nima Nezafati; Morteza Momenzadeh; Mohammad Hashem Emami; Seyed Jamal Shaykhzakaryaii
Abstract
The Tareek Darreh gold Gold & Copper deposit is located 40km north of Torbat- e Jam in the Khorasan-Razavi province,NE-Iran. The study area is mainly comprised of slightly metamorphosed, sedimentary rocks of Jurassic age including alternation of shale, siltstone, and sandstone. These rocks have been ...
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The Tareek Darreh gold Gold & Copper deposit is located 40km north of Torbat- e Jam in the Khorasan-Razavi province,NE-Iran. The study area is mainly comprised of slightly metamorphosed, sedimentary rocks of Jurassic age including alternation of shale, siltstone, and sandstone. These rocks have been intruded by plutonic rocks such as gabbronorite, diorite, quartz-diorite, and rhyodacite. The ore bodies are exposed by trenching and pitting. The alteration minerals quartz, chlorite, albite, and sericite which are observed mostly on the top or margin of the stocks. Alteration is more intensive at the contacts of the stocks where vein type mineralization has occurred. The veins are mainly composed of silica type and calcite type, arsenopyrite, chalcopyrite, and pyrite main ore minerals. Probably more than 2-stages telescopic mineralization occurred in these zones and the conditions of temperature and pressure, as seen below. Appears to be a continuation of tectonic activity in the same place as intrusive and a little later the main cause of this phenomenon. According to our studies, The Tareek Darreh gold deposit is considered to be similar to the "intrusion-related gold "type.
Original Research Paper
Sedimentology
Hadi Amin-Rasouli; Nasim Haghighat jou; Mahdi Moradi
Abstract
Kraftu cave, 67 km northwest of Divandareh in Kurdistan province, includes four floors. The bottom of the second floor, in the bat hall, is covered by thick guano deposits. SEM–EDX analyses of the guano deposits showed secondary sulfate (gypsum, cesanite), phosphate (phosphammite, brushite, taranakite, ...
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Kraftu cave, 67 km northwest of Divandareh in Kurdistan province, includes four floors. The bottom of the second floor, in the bat hall, is covered by thick guano deposits. SEM–EDX analyses of the guano deposits showed secondary sulfate (gypsum, cesanite), phosphate (phosphammite, brushite, taranakite, francoanellite, whitlockite, leucophosphite, spheniscidite, pyrocoproite), and nitrate (urea, niter) minerals, along with microorganisms and chitin. Occurrence of these minerals is due to changes in the pH (from acidic to alkaline) and moisture (wet and dry conditions) in the presence of microorganisms. Bat guano has accumulated in Karaftu cave during three different paleoclimate conditions, from base to top, including dry, wet, and dry conditions. A comparison between distributions of secondary minerals and Ce-anomalies along the profile represents that taranakite only forms in wet conditions, but whitlockite, urea, and cesanite only occur in dry ones. Therefore, they are significant indicators of climate in the geologic record, but other minerals, because they can be in both conditions, don't be so.Various reactions between the solutions derived from guano with substrate have resulted in phosphatization and dolomitization of bedrock. The abundance of chitin in the Karaftu cave guano deposits indicates that they are feces of insectivorous bats.
Original Research Paper
Economic Geology
Seyed Mehran Heidari; Sara Safavy; Afshin Akbarpour; Azra Hassanlou; Bahram Mohaghegh
Abstract
Saveh-Razan copper (± gold) area, with WNW direction in the northwest of Urmia-Dokhtar magmatic belt, with the highest reaction to right-sided shear zones and structural trend change during the Oligomyocene, leads to the placement of semi-deep Oligomyocene diorite massifs in shallow rock depths. ...
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Saveh-Razan copper (± gold) area, with WNW direction in the northwest of Urmia-Dokhtar magmatic belt, with the highest reaction to right-sided shear zones and structural trend change during the Oligomyocene, leads to the placement of semi-deep Oligomyocene diorite massifs in shallow rock depths. It is an Eocene volcano. By creating different types of mass-related hydrothermal alteration (propylitic, intermediate-advanced argillaceous, and phyllite) along the fractures, the system concentrates the mineralizations in quartz-sulfide veins, hydrothermal incisions, and concentrated sulfide-bearing filaments. Common features of metallurgy in this area are fluid homogenization temperature between 250 to 350 ° C and salinity range of 6-28% by weight of salt, containing CO2 gas and liquid phase of liquid and the presence of sulfides such as pyrite, chalcopyrite, burnite, chalcocite and sulfosalts in related reserves. There is also more gold than silver. Therefore, these features are most similar to the mass-related intermediate-type epitermal deposits that form in calcoalkalkene magmatic arcs.
Original Research Paper
Petrology
Reza Jamal Omidi; Saeid Hakimi Asiabar; Shahrooz Haghnazar; Mansour Vosoghi Abedini
Abstract
Tarom mountains are located at the southwestern end of the Alborz mountain range with an approximate northwest-southeast direction. Tashvir region is a part of the northern margin of the Tarom mountains. Most igneous rocks in this area include basalt, andesitic basalt, and interlayers of tuff. Enrichment ...
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Tarom mountains are located at the southwestern end of the Alborz mountain range with an approximate northwest-southeast direction. Tashvir region is a part of the northern margin of the Tarom mountains. Most igneous rocks in this area include basalt, andesitic basalt, and interlayers of tuff. Enrichment of LIL elements with positive anomalies of Ce, P, Sm, and depletion of Nb, Ta, Zr, Hf, and Th, elements and also K2O/Na2O and Ba/Rb ratios in the rock samples of Tashvir area, indicate magma contamination with the lower crust. The evidence of crustal contamination and the ratio of Nb/Y and Zr/Y in the samples indicate that the basalts of the Tashvir region belong to the source of the plume. Alkaline, shoshonitic, and peraluminous nature, REE enrichment (i. e. Ba, Rb, and Sr), low titanium content, origin, and depth of magma indicate they're belonging to the rift environment. In this study, in addition to determining the characteristics of igneous rocks in the Tashvir area, the results of several previous studies are plotted on the map of the Tarom mountains. Accordingly, the tectonic setting of the Tarom range is divided into two parallel sub-regions with magmatic arc and rift-type eruptions, which expansion of this rift zone has stopped before it evolve as a back-arc basin.
Original Research Paper
Geophysics
Ghazal Janghorban; Seyed Mohammad Abtahi Forooshani; Keytash Moshtaghian; Hooshang Asadi Harooni; Hamzeh Sadeghi Sorkhani; Mohammad Hajheidari
Abstract
Kuh-e Lakht epithermal gold index is located on Urumieh-Dokhtar Volcanic Belt in Isfahan province. Geological studies indicate the presence of an epithermal gold mineralization system in the area. The geophysical exploration in the area includes magnetometry, resistivity, and induced polarization ...
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Kuh-e Lakht epithermal gold index is located on Urumieh-Dokhtar Volcanic Belt in Isfahan province. Geological studies indicate the presence of an epithermal gold mineralization system in the area. The geophysical exploration in the area includes magnetometry, resistivity, and induced polarization surveys. Then, we implemented Li and Oldenburg algorithm for 3D inversion of the magnetic data. The depth of the largest estimated magnetic susceptibility obtained from data inversion coincides with the average depth of the magnetic sources obtained from Euler deconvolution. Furthermore, we compared the estimated 2D resistivity and electrical changeability models and the estimated magnetic susceptibility. The comparison denotes the correlation of the estimated magnetic susceptibility variations with the reduction of resistivity, high electrical chargeability, and alteration zones. Combining the estimated magnetic susceptibility model with the geochemical analysis of the exploratory boreholes in the area indicates that the mineralization often occurred at the maximum variation of the magnetic susceptibility. Nonetheless, the results indicate the possibility of mineralization along the zones with large magnetic susceptibility variations.
Original Research Paper
Petrology
Ziba Khodaean Chegeni; Nematollah Rashidnejad Omran; Ali Akbar Baharifar; Reza Nozaem; Carmela Vaccaro; José Francisco Santos
Abstract
Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole- rock geochemistry show that basalt, andesite and/or ...
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Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole- rock geochemistry show that basalt, andesite and/or their intrusive equivalents with calc- alkaline to tholeiitic affinity and even a peridotite could be their protoliths. Trace element and Sr-Nd ratios imply that these rocks were from mantle melt sources. In chondrite normalized plots, these amphibolites can be classified into at least two groups. The first group is characterized by LREE depletion relative to HREEs and some with flat patterns. The second has an enrichment of LREEs relative to HREEs. These two different patterns and some other geochemical characters suggest MORB or MORB-like and arc affinities of the parental magmas. This can be related to the time progressive evolution of magmatism either from MORB or Back-arcto Arc or from Arc to Back-arc setting.
