H. Ghasemi; A. Ramazani; A. Khanalizadeh
Abstract
Silijerd intrusion with an age of Late Eocene – Oligocene (39.23.2 Ma) is located in Uromeyeh-Dokhtar magmatic arc, central Iran structural zone, northwest Saveh. This intrusion is composed of a continuous compositional range including: diorite/gabbro, ...
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Silijerd intrusion with an age of Late Eocene – Oligocene (39.23.2 Ma) is located in Uromeyeh-Dokhtar magmatic arc, central Iran structural zone, northwest Saveh. This intrusion is composed of a continuous compositional range including: diorite/gabbro, granodiorite, syeno-monzogranite and alkali granite intruded into the Eocene volcanic and pyroclastic rocks.
Variation diagrams showing trends of major and trace elements indicate a continuous compositional range and a comagmatic origin for these rocks. Trends of compatible- incompatible elements indicate the important role of fractional crystallization in the genesis of these rocks. All samples are metaluminous with medium-high K with calc-alkaline nature. High values of Rb, Sr, K, U, Th, Zr and Ba and high ratios of K2O/Rb and FeO/MgO indicate the similarity of the rocks of this intrusion with the rocks of continental margin magmatic arc intrusions. Depletion in Nb,P,Ta and Ti and enrichment in K,Sr,Rb,Cs and Ba are obvious in the spider diagrams of these samples. The enrichment in LILE and depletion in HFSE reveal the I-type metaluminous magmatism of volcanic arcs (VGA). Whole rock 87Sr/86Sr ratios of this intrusion range from 0.704759 to 0.705166 and it can be correlated with the values of these ratios in the mantle and lower crust sources and low contamination of their magmas with upper crust.
Existence of K-feldspar megacrysts and mafic microgranitoid inclusions in this intrusion, high abundances of La and Ce , V enrichement in mafic terms and low whole rock 87Sr/86Sr ratios of this body, suggested a partial melting of mantle wedge, subducted oceanic crust (metabasaltic sources) or lower continental crust (metatonalitic sources) origins for it. The discrimination tectonic setting diagrams also indicate an I-type continental volcanic arc magmatism for this intrusion.
M. Heydari; Sharafi M.
Abstract
The use of remote sensing combined with field surveys can be used as an economic approach to detect the areas that are susceptible to the influx of water into tunnels. This study aims at investigating potential zones of groundwater influx in part 1-A of the Nosoud water-transport tunnel located in the ...
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The use of remote sensing combined with field surveys can be used as an economic approach to detect the areas that are susceptible to the influx of water into tunnels. This study aims at investigating potential zones of groundwater influx in part 1-A of the Nosoud water-transport tunnel located in the NW of Kermanshah province. Stratigraphic units of the area are composed of limestone and shale layers, which have formed alternating hard and soft sequences at the tunnel site. Fractured brittle limestone layers alternating with impermeable shale layers are the most important factor controlling the influx of water into the Nosoud tunnel. The danger of possible mine explosions prevented us from a survey along the whole length of the tunnel. Hence we classified these lithologies into two types labeled as Li and Sh which representing limestone and shale respectively. In order to explore layers that could potentially lead to water influx, we used ASTER satellite images to analyze the geohydrologic evidences across the area. Results suggest that the tunnel has a high risk of groundwater influx in places where the Li3 and Li-Sh3 units are encountered. Moreover, observations during tunnel excavation show that the major cause of water influx into the tunnel are preferentially concentrated in zones where hard layers with open fractures are crossed. This is considerably compatible with the results of satellite image processing model.
Hanieh Mardomi; Mir Sattar Meshinchi Asl; Hamid Reza Siahkoohi
Abstract
Magnetotellurics is an exploration method which is based on measurement of natural electric and magnetic fields of the Earth and is increasingly used in geological applications, petroleum industry, geothermal sources detection and crust and lithosphere studies. In this work, discrete wavelet transform ...
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Magnetotellurics is an exploration method which is based on measurement of natural electric and magnetic fields of the Earth and is increasingly used in geological applications, petroleum industry, geothermal sources detection and crust and lithosphere studies. In this work, discrete wavelet transform of magnetotelluric signals was performed. Discrete wavelet transform decomposes signals into coefficients in multi-scales. Noise and signal portions are separable in multi-scale mode. Therefore, noise can be discarded in each scale; a threshold value is constructed dependent to coefficients of the scale then, the noise coefficients are discarded by thresholding the coefficients with the proper values. Proportional threshold values can be used to remove white and 1/f noise from time series. After that, a new signal is constructed using clean coefficients. This method is widely used in various fields of sciences from image processing to seismic studies. This work tried to show the effectiveness of this technique in decreasing pervasive noise from magnetotelluric signals. The results emphasized the advantageous effect of wavelet techniques in magnetotelluric data noise removing process.
A. Zamani; M. Agh-Atabai
Abstract
The 31 March, 2006 earthquake with Mw=6.1 destroyed villages in the Darb-e-Astaneh (Silakhor) region of the Lurestan province. The epicenteral area of this earthquake lies near the Main Recent Fault (MRF) and its right lateral mechanism indicates that it belongs to this fault zone. The main shock was ...
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The 31 March, 2006 earthquake with Mw=6.1 destroyed villages in the Darb-e-Astaneh (Silakhor) region of the Lurestan province. The epicenteral area of this earthquake lies near the Main Recent Fault (MRF) and its right lateral mechanism indicates that it belongs to this fault zone. The main shock was followed by relatively large number of aftershocks. In this research, the aftershock sequence of this earthquake has been studied by measuring quantitative indices of coefficient of variations (CV), the exponent of the power spectral density function, and the generalized multifractal dimensions. The results reveal the presence of fractal structure in the temporal and spatial distribution of aftershock sequence. The multifractal behavior of the aftershock sequence indicates the clustering of the earthquake activity and the degree of the heterogeneity in the seismotectonic and geodynamic processes in the focal region. The results show that the multifractal dimensions of the aftershock sequence decreases and the multifractal dimensions of aftershock epicenters increases with time. It seems that these changes in the multifractal dimensions are related to the activity of secondary and sympathetic faults and changes in the tectonic stress regime of the region. The results also indicate that the multifractal method rather than monofractal approaches is a powerful tool for quantitative analysis of aftershock process's clustering behavior.
M. Moazemi Goodarzi; B. Rezaei; A. Amini
Abstract
In this paper, iron removal studies on high iron diasporic bauxite by thermochemical treatment was investigated for the first time. For this purpose, bauxite samples were calcined in temperatures between 600 and 1100°C and then leached with hydrochloric acid. Obtained results revealed, in spit of ...
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In this paper, iron removal studies on high iron diasporic bauxite by thermochemical treatment was investigated for the first time. For this purpose, bauxite samples were calcined in temperatures between 600 and 1100°C and then leached with hydrochloric acid. Obtained results revealed, in spit of gradual decrease in both iron and aluminum extraction with rising calcination temperature, iron extraction to aluminum extraction is selective at calcination temperature above 900°C. Leaching studies of calcined sample at 900°C proved that leaching temperature is the most important parameter for iron dissolution in acid and rising leaching temperatures from 20 to 95°C increases iron extraction over 70%. The other optimum parameters are: leaching time120 minutes, acid concentration 50% V/V, grinding size of 210 µm, pulp density of 15% solid by weight. As a result of optimizing parameters, 96.5% of bauxite iron content removed successfully with 88.5% aluminum recovery and solid residue iron content, i.e., the obtained concentrate, decreased from 27.02 to 1.59%.
Economic Geology
S. Amani Lari; I. Rassa; A. Amiri
Abstract
Ahmadabad Zn-Pb deposit is one of the Pb-Zn deposits in the Kouhbanan-Bahabad metollogeny Belt, which is located 10th Km northwest of Bahabad City in the Posht-Badam Block in Centeral Iran Zone. Ore deposits consist of Zn, Pn, Mo and Sr non-sulfide minerals with large amount of Fe oxide-hydroxide ...
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Ahmadabad Zn-Pb deposit is one of the Pb-Zn deposits in the Kouhbanan-Bahabad metollogeny Belt, which is located 10th Km northwest of Bahabad City in the Posht-Badam Block in Centeral Iran Zone. Ore deposits consist of Zn, Pn, Mo and Sr non-sulfide minerals with large amount of Fe oxide-hydroxide minerals occurred in dolomitic host rock of the Shotori Formation. A quartz-calcite vein accompanies ores in the host rock. This study is focused on C-O isotopic variation in the host rock, quartz-calcite vein and hydrozincite. Isotopic variation of C indicates that the source of carbon is different in the host rock and quartz-calcite vein. The most important source of carbon for hydrozincite formation was carbonate rocks of the area and regarding this aspect this deposit is different from others Zn-Pb non-sulfide deposits that studied in the world. According to oxygen isotopic variation, the temperature for hydrozincite formation was between 14-44˚C. The oxygen isotopic variation suggests marine basin water as the source of quartz-calcite vein. The dolomitic host rock was formed in equilibrium with fluids of a mixture of marine and magmatic waters, based on oxygen isotopic variation.
Tectonics
Nayyer Bayeste Hasti; Hosein Motamedi; Mahmoud Almasian
Abstract
This study has focused on the result of seismic data. The first stage of basin formation is the opening of Neo- Tethys Sea which is Simultaneous with Dashtak, Kangan and Khaneh kat Formation and after that on the early to middle Triassic sediments an unconformity that can be named as an expansion of ...
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This study has focused on the result of seismic data. The first stage of basin formation is the opening of Neo- Tethys Sea which is Simultaneous with Dashtak, Kangan and Khaneh kat Formation and after that on the early to middle Triassic sediments an unconformity that can be named as an expansion of sedimentary basin in the upper Triassic happened. This stage of basin opening caused the formation of big faults and probably basement faults in the area that studying on this faults and their movements is the main goal of this study. The next stage of evolution of basin starts when the basin began to closure and still there is disagreement about the exact time; but the obvious thing is the four compressional events: first, from Cenomanian- Turonian up to Masstrichtian; second, Late Paleocene- Early Eocene; third, Late Oligocene-Miocene and the forth, Miocene up to Quaternary. All events caused to obduction of Ophiolite and sedimentation of Gurpi with partly erosion and Pabdeh with regional erosion, then disappearing formations such as Asmari and Gachsaran and at the end, the late Zagros orogenic phase which is the compression that is continues to this day.
A. Mansourian; M. Zareinejad; E. Moghimi; S. Omidian
Abstract
Damavand volcano is one of the most important geological features in Iran. Although a variety of studies are available about this volcano, there are different problems associated with existing data from Damavand including: they are not stored in a consistent and organized way, they are not directly ...
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Damavand volcano is one of the most important geological features in Iran. Although a variety of studies are available about this volcano, there are different problems associated with existing data from Damavand including: they are not stored in a consistent and organized way, they are not directly applicable in users' information systems (such as GIS), and they are not easily accessible and sometimes not accessible to users. In addition, clear and accurate studies about geomorphological-environmental specifications of Damavand are not still available. Considering these facts, this paper aims to describe design and implementation of Damavand geomorphological-environmental database and then disseminating it using WebGIS. In this research project, firstly, required spatial and attribute data were identified. Then, using available maps, satellite imageries, aerial imageries, and field works, required data were produced, completed and complemented. After that, the proposed database was designed and implemented and finally the mentioned data were stored in the database. By conducting these stages, the Damavand geomorphological-environmental database was established. At the next stage, an interactive WebGIS was designed and implemented in Geological Survey of Iran (GSI). At the last stage, the database was linked to the WebGIS and disseminated via that. At the time of writing this paper, the Damavand WebGIS and hence the geomorphological-environmental database is accessible via GSI intranet. The WebGIS can also be connected to internet in order to make the database accessible for public. Establishing such database for other geological-related datasets and its dissemination using WebGIS can significantly resolve current problems associated with these datasets from storage, accessibility and applicability perspectives.
Economic Geology
Mohammad Amin Jafari; Ahad Nazarpour; Ghodratollah Rostami Paydar
Abstract
In this research, using fuzzy logic (gamma) methods, analytic hierarchical analysis (AHP), and based on the weighting of exploratory layers by the opinion of geoscientists, modeling of mineral potential for lead and zinc metals in the Khondab sheet. The geochemical layer related to Pb-Zn metals has been ...
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In this research, using fuzzy logic (gamma) methods, analytic hierarchical analysis (AHP), and based on the weighting of exploratory layers by the opinion of geoscientists, modeling of mineral potential for lead and zinc metals in the Khondab sheet. The geochemical layer related to Pb-Zn metals has been prepared using the singularity index (SI) method, which has high accuracy in detecting weak and hidden anomalies. All exploratory layers and substrates including lithology, geochemistry, the density of lead and zinc deposits and mineral signs, the density of faults and silica and carbonate alterations were weighted using the fuzzy logic (gamma) method and ranged from 0 to 1 and fuzzy layers with gamma value (γ) of 0.95 were combined with each other and prepared the potential maps for Pb-Zn metals in the study area. Then, using the AHP method and forming a suitable matrix for the exploratory layers, the layers were weighed and a potential map of the desired metals was obtained. The results showed that the AHP method identified more anomalies compared to the fuzzy logic (gamma) method and the anomalies obtained from this method show more compliance with the Pb-Zn deposits in these regions.
A. Saki; M. Moazzen; M. Modjtahedi; R. Oberhänsli
Abstract
Mahneshan Complex in the northwest of Iran was affected by regional and contact metamorphism. Microstructural and petrographical features as well as field relations show that Mahneshan Metamorphic Complex has been affected by four episodes of metamorphism (M1 to M4) and at least two ...
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Mahneshan Complex in the northwest of Iran was affected by regional and contact metamorphism. Microstructural and petrographical features as well as field relations show that Mahneshan Metamorphic Complex has been affected by four episodes of metamorphism (M1 to M4) and at least two deformational phases (D1 and D2). The M2 metamorphic stage is characterized by a strong preferential orientation of minerals (S2) and development of a peak metamorphic assemblage. This metamorphismis temporally associated with D2 deformational phase. The M3 metamorphism was contact metamorphism and M4 metamorphism is retrograde. The mineral assemblages of peak metamorphism M2 are muscovite, biotite, garnet, staurolite, andalusite and sillimanite. Pressure and temperature of metamorphism in the Mahneshan Complex were estimated by multiple equilibria calculations, cation exchange reaction thermometry and net transfer reaction in order to determine the geothermal gradients and type of metamorphism. The temperature of M1 metamorphism is estimated 420-450ºC and pressure of 3-4 kbar. M2 (peak metamorphism) temperature is 600-620ºC and pressure of 5-7 kbar. The temperature of M3 metamorphism is 520-560 ºC and pressure of 2.-3.5 kbar. The Geothermal gradients for the peak of metamorphism show high value for the upper crust (33° C/ km) indicating a Barrovian type of metamorphism for the study area. Tectonic setting of metamorphism is related to continental crust and magmatic arc.
GH Abbasi; M Ebrahimi; M Sharifi; N Shirdashtzadeh; J Ahmadian
Abstract
The studied volcanic rocks to the northeast of the Gavkhuni playa lake are composed of rhyolite, trachydacite, trachyandesite and pyroclastic rocks including lithic tuff and volcanic breccia. Rhyolitic rocks have flow structure and hyalophyric texture with glassy to cryptocrystalline ...
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The studied volcanic rocks to the northeast of the Gavkhuni playa lake are composed of rhyolite, trachydacite, trachyandesite and pyroclastic rocks including lithic tuff and volcanic breccia. Rhyolitic rocks have flow structure and hyalophyric texture with glassy to cryptocrystalline matrix in which quartz and feldspar crystal are present. The dominant texture in trachydacitic and trachyandesitic rocks in porphyritic texture in which plagioclase and rarely sanidine phynocrysts are set in a glassy to microcrystalline groundmass containing feldspar microlites. In trachydacites, quartz is present as small crystals and rarely as microphynocrysts. Plagioclase phynocrysts in trachydacitic and trachyandesitic rocks display sieve-texture. Amphibole and biotite are the mafic minerals of the volcanic rocks and they are partialy, at rims, or completely altered to Fe-Ti oxides. All of the studied rocks are high- K calc-alkaline in nature. According to the geochemical data, the volcanic rocks are depleted in high field strength elements such as Nb, Ti and Ta and enriched in large ion lithophile elements like Cs, K, Ba, Rb and Th which are characteristics of subduction related volcanic rocks. Nb negative anomaly is characteristic of continental rocks and indicates the continental crust involvement in the magmatic processes. The rocks are enriched in Cs, Rb, Ba and Pb indicating mantle metasomatism by fluids released from subducting oceanic lithosphere. Therefore, magma contamination and mantle metasomatism have affected the magma from which the volcanic rocks of the Gavkhuni playa lake have were generated. The calc-alkaline magmatism in the study area was associated with the closure of the Neotethyan Ocean.
M Mirzaei; L Soheili; V Ebrahimzadeh Ardestani; A Teymorian Motlagh
Abstract
The main objective of interpretation of acquired gravity data on the Earth's surface is to determine the contrasts in density or shape/dimension of mass anomalies. Interpretation of gravity data can be done through an inversion process. In this research, a block model has been considered for the subsurface ...
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The main objective of interpretation of acquired gravity data on the Earth's surface is to determine the contrasts in density or shape/dimension of mass anomalies. Interpretation of gravity data can be done through an inversion process. In this research, a block model has been considered for the subsurface anomalous mass. By considering a constant initial density (about 2.6 gr/cm3) for all blocks and by using inversion method, distribution of density of the anomalous mass was estimated and interpreted. In this research, Occam method is used to invert 246 gravity data collected in 2007. Results of the gravity data inversion show sufficient fit between observed and calculated gravity data. Using this inversion method, distribution of density in the subsurface layers related to sediments and basement are estimated in this area. Since there is a density contrast between sedimentary layers and basement, the estimated density distribution can help to explore the lithology of formations as well as the discontinuities in them. Densities less than 2 gr/cm3 in horizontal and vertical sections obtained from the inversion are attributed to the alluviums. The depth of these sediments, which include sand, silt and clay of different percentages, is estimated to be less than about 200 m. Unequal density distribution along the layers is taken to indicate fractures. In fact, these fractures are associated with part of the Tabarteh fault in this area, which caused numerous earthquakes (but less than 5 Richters in magnitude) around the Arak and Dawood Abad cities in past years.
M. Talkhablou; N. Hafezimoghaddas; M. Nikodel; A. Uromeihy; M. shafiefar
Abstract
Rocks are natural materials used in a variety of coastal protection structures, especially in rubble mound breakwaters. Engineering properties of rocks, such as durability and resistance to degradation factors of the marine environments are important properties which ...
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Rocks are natural materials used in a variety of coastal protection structures, especially in rubble mound breakwaters. Engineering properties of rocks, such as durability and resistance to degradation factors of the marine environments are important properties which construction material of marine structures should behave. Rock durability is a function of rock properties and condition of environment in which the rock will be used. Regarding the economical importance of constructed coastal ports and facilities in coast lines of south Iran, it is necessary to evaluate the engineering properties of rocky construction materials in such structures from durability and degradation point of view. In this study, by investigating and sampling the used rock material in 27 constructed rubble mound breakwaters along the 1000 km south Iran's coastlines, from Amery Port in western part to Pasabandar Port in 85 km east Chabahar, and regarding the observations that collected in field visual investigations and engineering tests of durability examination, the experimental relationship between physical, mechanical and durability parameter of studied rocks have been concluded and consequently criterion to select the suitable rock of three groups of rocks limestone, igneous rock and bioclastic sedimentary rock (lomashell) have been presented individually.
Petrology
Elahe Namnabat; Mansour Ghorbani; Seyed hassan Tabatabaei
Abstract
The Youseflo pluton, a part of Ahar - Arasbaran magmatic belt, is located in south east of Ahar city in north east of East Azarbayejan province of Iran. The pluton is mainly composed of quartz monzonite, granodiorite and granite, however, the major investigated rock is granodioritic in composition. Quartz, ...
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The Youseflo pluton, a part of Ahar - Arasbaran magmatic belt, is located in south east of Ahar city in north east of East Azarbayejan province of Iran. The pluton is mainly composed of quartz monzonite, granodiorite and granite, however, the major investigated rock is granodioritic in composition. Quartz, Plagioclase, biotite, amphibole, K-feldspar, chlorite, zircon, sphene, apatite and opaque minerals are the minerals of these rocks. Biotites, as a significant ferromagnesian mineral in Youseflo pluton, are Mg- rich, Cl-poor where all are primary types. Considering Fe/(Fe+Mg) (from 0.36 to 0.43) and Al IV (average 2.32 apfu), minerals are classified as biotite between Annite- siderophyllit endmembers. The study of mineral chemistry of biotites demonstrates that the calculated pressure based on total Al content in biotites varies from 0.19 to 0.89 kb which is indicative of a shallow emplacement depth. Crystallization temperature of biotites based on Ti content and Ti/Fe+2 ratio suggests an average temperature of 735 oC.
A. Moradzadeh; F. Tahmasbi; M. Fateh
Abstract
The magnetotelluric (MT) method is a natural source electromagnetic geophysical technique, which is used mainly in petroleum, mineral and geothermal exploration. As in this method, the quantity of the measured data is bulky and have a complex structure, their modeling, ...
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The magnetotelluric (MT) method is a natural source electromagnetic geophysical technique, which is used mainly in petroleum, mineral and geothermal exploration. As in this method, the quantity of the measured data is bulky and have a complex structure, their modeling, compared with the modeling of the other electrical data, is a very complex task or even impossible in some instances.
The main objective of this paper is to use the ability of the artificial neural networks (ANN) to find a solution for two-dimensional (2D) joint TE (transverse electric) and TM (transverse magnetic) modes inverse modeling of MT data. To achieve the goal, a multilayer perceptron (MLP) network with back propagation (BP) learning algorithm is used. In order to learn the designed network, many synthetic 2D models with the same category, have been created and their responses have been calculated for each polarization mode by forward modeling. Synthetic data include apparent resistivity and impedance phase in 9 stations and 11 frequencies in two polarization modes. After a comprehensive study, a perceptron with 3 layers and architecture of 396-9-9 has been designed and used to model the data.
This study show that the designed network is capable enough to produce an acceptable 2D underground model so that the correspondence mean relative modeling error is 3.9% and 6.9 % respectively for noise free data and 5 percent randomly added noisy data. This indicates that if ANN is designed and trained properly, then it would be capable enough to perform 2D inverse modeling of MT data. It has also shown that once the designed network has been trained properly it is able to perform the inverse modeling precisely in a short time. At the end, the performance of the designed network has been evaluated by a set of field MT data and its results has been compared with those produced by a common smooth rapid relaxation inversion (RRI) method. The comparison indicates that the results of these two different procedures are in close agreement.
M Mohajjel; S Houshmand, Ma
Abstract
A NW-SE trending ductile shear zone has been generated in the metamorphic rocks of the southwest Golpaygan. Different pellitic and psammitic schists, meta-carbonates and igneous rocks were strongly deformed in this ductile shear zone and produced mylonites and ultra-mylonites. Structural analysis indicates ...
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A NW-SE trending ductile shear zone has been generated in the metamorphic rocks of the southwest Golpaygan. Different pellitic and psammitic schists, meta-carbonates and igneous rocks were strongly deformed in this ductile shear zone and produced mylonites and ultra-mylonites. Structural analysis indicates three stages of foliations in the metamorphic rocks. Geometry and kinematics of the fabrics in Nowgan shear zone are divided into two northeastern and southwestern parts (limbs of Nowqan antiform). Mylonitic foliation moderately to steeply dip towards northeast in the northeastern part but dips to the southwest in the southwestern part. Mineral and stretching lineation, are shallowly to moderately plunging to the east-southeast in the northeastern part of the shear zone and, to the west-northwest in the southwestern part. The microstructural indicators of shear sense cleared that the northeastern part dextrally displaced along strike with normal component and the southwestern part sinisterly displaced with reverse component at the present situation. The fabrics evidence clear that this ductile shear zone were originally right-lateral strike–slip shear zone and during its structural evolution it was rotated around its strike during later folding stage. Structural analysis of the surrounded rocks of the shear zone indicates three superposed foliations. The mylonitic foliation in the shear zone and the axial plane foliations of the second stage folding are sub-parallel. Plunge directions of the second stage folds axes and the mineral/stretching lineation are also sub-parallel. Therefore, the initiation and development of the shear zone were synchronous with the second stage folding event.
Tectonics
Mohammad Reza Mazinani; Ali Yassaghi; Reza Nozaem
Abstract
The E-W trending Faghan fault system with >180 km in length located in the northern part of the Lut Block and south of the Dorouneh Fault in central Iran. The fault cut through basement rocks and all other younger units from Cambrian to Cenozoic. Kinematic and dynamic analyses of the Faghan fault ...
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The E-W trending Faghan fault system with >180 km in length located in the northern part of the Lut Block and south of the Dorouneh Fault in central Iran. The fault cut through basement rocks and all other younger units from Cambrian to Cenozoic. Kinematic and dynamic analyses of the Faghan fault system is crucial for understanding the tectonic framework of the northern part of the Lut Block. These field based investigation analyses of the Faghan fault system indicates the E-W trending dextral strike- slip shear kinematics for the fault system and as Principal Deformation Zone (PDZ) along which minor sinistral, dextral and dip slip faults have also formed as second order riedel shears. Therefore, like the Kuh-e-Sarhangi fault zone, the Faghan fault system is considered as one of the fundamental fault zone in the north of the Lut Block caused the deformation partitioning in the block during Late Cenozoic. Accordingly, the Faghan fault system divorces the Bardacan-Kashmar and Gonabad micro-blocks from each other and transfers the deformation from the main Lut Block into its northern micro-blocks by Intraplate escaping tectonics.
Petrology
Arefeh Heidarianmanesh; Seyed Mohsen Tabatabaimanesh; Narges Shirdashtzadeh
Abstract
Based on field observation and petrographic evidence, by progress in metamorphic degrees, a wide variety of metabasites have formed following the metamorphism at amphibolite facies (metamorphism M1) in the east of Jandaq. Thermobarometry of plagioclase- amphibole pairs indicate temperature ranges were ...
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Based on field observation and petrographic evidence, by progress in metamorphic degrees, a wide variety of metabasites have formed following the metamorphism at amphibolite facies (metamorphism M1) in the east of Jandaq. Thermobarometry of plagioclase- amphibole pairs indicate temperature ranges were 642-692ºC and 688-712 ºC for epidote amphibolites and garnet amphibolite, respectively, in a pressure range of 8 and 11 Kbar, correlating with transition from middle amphibolite to upper amphibolite facies. In addition to this metamorphic phase, petrographic signatures indicate further metamorphic phases concerning this region's geological phenomena. Based on brittle deformation in amphiboles, and epidote and quartz formation in their fractures, these rocks have undergone some degrees of retrograde metamorphism (<700 ºC; metamorphism M2) at greenschist to lower amphibolite facies. Rock foliation and mineral orientation, aggregate shape preferred orientation (ASPO) of titanite crystals along foliation, and syn-tectonic euhedral garnets indicate prograde metamorphism toward amphibolite-upper amphibolite facies (metamorphism M3). Finally, under greenschist facies condition, minerals such as chlorite and actinolite were formed in these rocks (metamorphism M4). The formation of chlorite and actinolite in the rims of the primary crystals shows that these rocks were finally affected by metamorphism at greenschist facies (M4 metamorphism).
R. Shabanian
Abstract
The Permian sequences of Aru and Bibishahrbanoo sections comprise the Dorud, Ruteh and Nesen formations respectively. A precise dating of the formations was provided based on the analysis of smaller foraminifers and fusulinid assemblages. The clastic Dorud Formation refered to Asselian and Sakmarian ...
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The Permian sequences of Aru and Bibishahrbanoo sections comprise the Dorud, Ruteh and Nesen formations respectively. A precise dating of the formations was provided based on the analysis of smaller foraminifers and fusulinid assemblages. The clastic Dorud Formation refered to Asselian and Sakmarian stages. The platform limestone of Ruteh Formation corresponds to Kubergandian – Murgabian stages. The Laterite and Bauxite horizon in the studied area attributed to Midian and finally, the uppermost beds of Permian in Bibisharbanoo corresponds to Early Dzhzulfian, based on the proposed of international subcommission on Permian stratigraphy concerning Tethyian stage bourdaries. Biolithic limestones of Ruteh Formation lying transgressively and disconformably on the underlying clastic and continental Dorud Formation with a great hiatus consists of Yachtashian and Bolorian stages. In both stratigraphical sections, thin vermiculate and oolithic limestone of Elika formation belonge to Early to Middle Triassic lying disconformably on the Permian sequence with hiatus. The hiatus between Permian and Triassic in Aru comprise Dzhulfian and Dorashamian stages and in Bibi Shahrbanoo stratigraphical section include Late Dzhulfian and Dorashamian stages. In this study 45 species belonging to 40 genus related to fusulinid families, smaller foraminifers and calcareous algae were recognized.
K Solaimani; J Zandi; M Habibnejad
Abstract
Over the last few decades, many studies have been resulted in landslide susceptibility maps using different techniques including the probability method (frequency ratio), the Analytical Hierarchy Process (AHP), bivariate, multivariate, logistic regression, fuzzy logic and artificial neural network (ANN). ...
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Over the last few decades, many studies have been resulted in landslide susceptibility maps using different techniques including the probability method (frequency ratio), the Analytical Hierarchy Process (AHP), bivariate, multivariate, logistic regression, fuzzy logic and artificial neural network (ANN). This study aimed to evaluate the susceptibility of the occurrence of landslides in the Vazroud watershed located in MazandaranProvince, north of Iran. The achieved results were based on three methods of frequency ratio model, statistical index (Wi) and weighting factor (Wf), which integrated to Geographical Information System (GIS) and remote sensing techniques. Vazroud as mountainous watershed morphologically is with increasing occurrence of landslides and it caused many failures of the mass movement, which seem continues now. In order to reduce the effects of this occurrence, it is necessary to scientifically assess the area where are susceptible to the landslide. For this reason, landslide susceptible areas were mapped and the landslide occurrence parameters were analyzed using three different methods. The results of these analyseswere confirmed using the relative operating characteristics curve (ROC). The validation process showed that the value for the area under the ROC curve for the Wf method was found to be 0.962, with an estimated standard error of 0.002 and is better in prediction than the other methods of frequency ratio and the statistical index (Wi) model.
Z Sadeghi; M.J Valadanzouj; M Dehghani
Abstract
Temporal and geometrical decorrelation often prevents SAR conventional interferometry from being an operational tool for surface deformation monitoring. Persistent Scatterer Interferometry (PSI) techniques presented to overcome the limitation of SAR conventional interferometry and use ...
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Temporal and geometrical decorrelation often prevents SAR conventional interferometry from being an operational tool for surface deformation monitoring. Persistent Scatterer Interferometry (PSI) techniques presented to overcome the limitation of SAR conventional interferometry and use amplitude analysis and considering temporal deformation model for PS pixel selection fail to identify PS pixels in rural areas lacking man-made structures. On the other hand, the high subsidence rates lead to not be fulfilled the required condition for unwrapping (Nyquist sampling criterion) and significant phase unwrapping errors in novel PSI algorithm (StaMPS) that applies amplitude analysis as well as phase stability in order to select the PS pixels without using a pre-define deformation model. Therefore, in this paper we present an enhanced algorithm based on PSI in order to estimate deformation rate in rural area undergoing high and nearly constant deformation rate using the available SAR images. The proposed approach integrates the merits of all existing PSI algorithms in PS pixel selection and phase unwrapping. PS pixels are selected based on the amplitude information and phase stability and their phase are compensated for APS and nonlinear deformation contribution by applying temporal filter. Deformation rate is then estimated using LAMBDA method that is a fast and optimal without considering Niquist sampling criterion. The approach was applied to the ENVISAT ASAR images of Southwestern Tehran basin and the results were evaluated with leveling data and the maximum difference rate across the leveling stations was 5 cm/yr demonstrating the high performance of the proposed algorithm in comparison with the obtained results from other interferometry methods. Moreover, the presented algorithm was applied to the simulated data and the value of RMSE was obtained 0.003 m/yr confirming this success.
R Khavari
Abstract
Stream gradients of rivers bedrock in the Khuzestan province were calculated, using GIS and 50-m digital elevation models to discuss the distribution of knick zones. Gradients were classified into local and regional types based on the measurement lengths of stream gradients for 474 rivers having at least ...
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Stream gradients of rivers bedrock in the Khuzestan province were calculated, using GIS and 50-m digital elevation models to discuss the distribution of knick zones. Gradients were classified into local and regional types based on the measurement lengths of stream gradients for 474 rivers having at least 10-km long in the study area. The transition rate from the local to regional gradients, i.e. the decreasing rate of gradient with increasing measurement length, is then obtained as the indicator of relative steepness of a river segment, which permits the objective identification of fluvial knick zones. Knick zones occur widely in the study area. The knick zones with large relative steepness near the outlets of large watersheds are related to the tectonic activity and most of them are actually close to the known locations of the active faults. The most important active faults in the study area are Mafaron, Agha-jari, Andakan, Lahbari, Mordehfel, Maron, North Behbahan Dezfol and Mishdagh. Knick zones occur along upstream steep reaches can be related to active hydraulic and erosional conditions regardless of geological or tectonic conditions. Effects of rock properties on the frequency and form of knick zones are observed, but they seem to play only a subordinate role. This study concludes that tectonics and geology are more important than topographic and hydraulic conditions in knick zone existence.
S Alaei Moghadam; M Karimi; M Mesgari; N Saheb Zamani
Abstract
Due to the extensive areas of potential mineral reserves in the country, it seems necessary to have a systematic approach to identify and convert indices of mineral deposits into mines. Existing various conceptual models of mineral deposits, variety of both quantitative and qualitative data to explore ...
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Due to the extensive areas of potential mineral reserves in the country, it seems necessary to have a systematic approach to identify and convert indices of mineral deposits into mines. Existing various conceptual models of mineral deposits, variety of both quantitative and qualitative data to explore mineral deposits and the expertise and different interests, cause the mineral potential mapping process to be very complicated. So far, various methods such as the overlap index, fuzzy logic, neural networks and weights of evidence are used for modeling this complexity. Consideration the fuzzy nature of mineral exploration in the process of modeling exploratory data, applying expert knowledge and flexibility for all types of mineral deposits in the form of an integrated system is essential. Compared with other methods fuzzy inference system has stated characteristics. To verify this, in this study, a fuzzy inference system for modeling mineral potential was proposed and for the Chah Firoozeh copper deposit was implemented. The main stages of this research include fuzzifying factor maps using the appropriate membership functions and linguistic variables, combining factor maps using fuzzy inference (by creating if_then fuzzy rules database and using an appropriate decision-making model) and generating mineral potential map with defuzzification output.
In the resulted mineral potential map, porphyry copper mineralization prone area is located in the central regions with north-south extension. For evaluation, 24 exploration boreholes in the area are complying with the mineral potential map. Based on the four classification types of mineral potential map, the compliance rate was calculated as 63.64%, 75%, 63.95% and 80.23%. Obtained mineral potential map is more accurate in the very low potential areas and 81.52% of the holes with very low state are located properly. In addition, resulted mineral potential map was compared with the mineral potential map generated using only fuzzy operators and without fuzzifying factor maps. The comparison shows that the mineral potential map that was generated using fuzzy inference system, in four classifications used in this study has 6% greater compliance with the exploration boreholes in average.
K Khaksar; F Rezvannia; M.R Kebriaei-Zadeh
Abstract
The rugose coral Marzanophyllum chalusense gen. and sp. nov. from late Visean (early Carboniferous) in the Vali-Abad section (Central Alborz, N Iran) is described in detail. This solitary coral has thick wall and thick septa with no dissepiment. The genus Zaphrentoides has similar structure, but it possesses ...
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The rugose coral Marzanophyllum chalusense gen. and sp. nov. from late Visean (early Carboniferous) in the Vali-Abad section (Central Alborz, N Iran) is described in detail. This solitary coral has thick wall and thick septa with no dissepiment. The genus Zaphrentoides has similar structure, but it possesses well developed cardinal septum. The new genus is placed in the Subfamily Zaphrentoidinae because of the fossula shape, structure of its septa and incompleted tabulae. This small and undissepimented solitary rugose coral belongs to Cyathaxonia family. They are found at oolitic limestone level. The corals of member C of the Mobarak Formation have endemic character and based on the accompanied fauna and stratigraphic position they are attributed to late Visean.
R Behbahani; R Lak; N Chanani; G Hosseinyar
Abstract
In order to study of organic geochemistry of bed sediments in Khowr-e-Mussa and its adjacent marine areas, 61 surface sediment samples were collected. Based on granulometric analysis of the sediments, 4 major sedimentary types comprising mud, sandy mud, muddy sand, and slightly gravelly muddy sand were ...
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In order to study of organic geochemistry of bed sediments in Khowr-e-Mussa and its adjacent marine areas, 61 surface sediment samples were collected. Based on granulometric analysis of the sediments, 4 major sedimentary types comprising mud, sandy mud, muddy sand, and slightly gravelly muddy sand were determined. The bed sediments are mainly composed of terrigenous (quartz, feldespar, rock fragments, carbonate lithics and clay minerals) and chemical – biochemical (bivalve, gastropod, foraminifera, ostracod and bryozoa) particles. Based on the organic geochemistry studies, the total organic carbon (TOC) varies from 0.11 to 0.70 %wt, which increases in the muddy sediments. The studied kerogens (based on S2/TOC diagram) indicate that the kerogen types III (%33) and mixture of III-II (%55) are the most abundant. In addition, the hydrogen index versus Tmax diagram, revealed the similar results. The studied kerogens indicated that this part of the Persian Gulf affected by the transportation of terrestrial (fluvial, III type) rather than the marine organic matter (II type).
