H. Jamali; A. Yaghubpur; B. Mehrabi
Abstract
Miveh – Rud area is located 50 km north of Tabriz and 65 km west of Ahar at 36ْْ 33′ 02″to 38ْ, 34′ 52″ N and 46 ْْ 12′ 20″ to 46 ْْ 14′ 35″ E. The oldest rock unit in the area includes a thick sequence of Paleocene sedimentary rocks comprising ...
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Miveh – Rud area is located 50 km north of Tabriz and 65 km west of Ahar at 36ْْ 33′ 02″to 38ْ, 34′ 52″ N and 46 ْْ 12′ 20″ to 46 ْْ 14′ 35″ E. The oldest rock unit in the area includes a thick sequence of Paleocene sedimentary rocks comprising of sandstone, shale, siltstone, marl and marly limestone that have been intruded by a porphyritic intrusive body and dykes of granodioritic to diabasic composition (probably Oligocene in age). The intrusive rocks resulted in the formation of hornfels, skarn and alteration in Paleocene rocks. All of the mentioned rock units are unconformably covered by Pliocene age trachyte, trachyandesite. Alteration of potassic, sericitic, argillic, propylithic and silicification types occurred in the subvolcanic and sedimentary rocks, while there is no observed alteration in the volcanic cover. Anomalies of Au, Ag, Sb, Cu, Bi, W and Mo detected by geochemical investigations are confirmed by field evidences.
The anomalies of Sb, Ag, Au and As are located in the northern part, while the Cu, Co, W and Mo anomalies are in the southern part of the area. The degree of the contact metamorphism decreases toward the north and the potassic alteration can be shown mostly in the southern part of the area. This may suggest uplift and erosion of the southern part compared to northern part of the studied area. Composite halos of As, Pb, Ag / Cu, W and Co confirm the results.The mineralization includes formation of skarn, epithermal and sheeted veins. The epithermal veins cut the skarn and other contact metamorphic rocks.
Economic Geology
S. Maleki; A. A. Calagari; K. Siahcheshm; S. Alirezaei
Abstract
Khak Sorkh iron deposit located about 42 km northwest of Nadushan town in Yazd Province. Host rock include upper Triassic-Jurassic limestone which are intruded by Oligo-Miocene granitoid bodies. Mineralization is dominated by magnetite, and serpentine is the main waste mineral. Skarn mineral assemblages ...
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Khak Sorkh iron deposit located about 42 km northwest of Nadushan town in Yazd Province. Host rock include upper Triassic-Jurassic limestone which are intruded by Oligo-Miocene granitoid bodies. Mineralization is dominated by magnetite, and serpentine is the main waste mineral. Skarn mineral assemblages include clinopyroxene, garnet, tremolite phlogopite and epidote. The characteristics of mineralization are: magnetite mineralization in two generations, presence of serpentine as the main waste mineral, hornfelsed greywacke units which come between intrusive bodies and skarned limestone units, absence of obvious zoning in endoskarn and exoskarn parts, presence of Ni-Co-As sulfides, high amount of Zn, As, Co and Mn in magnetite geochemical results and the increasing Fe along with decreasing Mg contents in magnetite at both deposit and crystal scales from primary to secondary types. Minor elements contents of geochemical results have been used for distinguishing of different mineral deposits (e.g, Dare et al., 2012; Dupuis and Beaudoin, 2011; Nadoll et al., 2012) and they are in good accordance to hydrothermal and skarn type deposits like: low contents of Cr (less than 10 ppm), high contents of Mg (2.2 to 7.5 ppm), low TiO2 (from 0.01 to 0.3 ppm), low amounts of incompatible elements including Ag (
M. Fattahi; S. Rostami Mehraban; M. Talebian; A. Bahroudi; J. Hollingsworth; R. Walker
Abstract
Neyshabour (approximately 200,000 pop.) lies on the southern margin of the Binalud mountains in NE Iran. The city has been destroyed four times by major historical earthquakes (in 1209, 1270, 1389 and 1405 A.D.).Three large faults occur in the region. The Binalud and North Neyshabur faults ...
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Neyshabour (approximately 200,000 pop.) lies on the southern margin of the Binalud mountains in NE Iran. The city has been destroyed four times by major historical earthquakes (in 1209, 1270, 1389 and 1405 A.D.).Three large faults occur in the region. The Binalud and North Neyshabur faults lie at the foot of the Binalud range north of Neyshabour. The Neyshabour fault lies within the valley west of Neyshabour. The Neyshabour fault, which lies 10 km south of the North Neyshabur fault, is 50 km long thrust. At each end of the Neyshabour fault two young, 10 km-long, thrust segments occur. It is close to Neyshabour city; and is a probable source of the 1209 and 1405 earthquakes. It poses a substantial seismic risk to the city because of the potential for future activity. Slip rate is one of the important parameters for seismic hazard assessment which was determined using SRTM for offset measurement and OSL for age calculation. Luminescence was measured through 7 mm Hoya U-340 filters in a Risø (Model TL/OSL-DA-15) automated TL/OSL system. The equivalent dose (De) was obtained using the conventional quartz single aliquot regeneration method (Murray and Wintle, 2000). Twelve aliquots have been processed for the sample, of which only the aliquots were accepted that satisfied the SAR restrictions. De was estimated using analyst program. Age was calculated using a weighted mean De for the sample. The Dose rate was obtained using uranium, thorium and potassium concentrations, which were measured by Micro Nomand portable gamma spectrometer in field. The results are presented in Table 1. Dividing the displacement by the minimum and the maximum ages provided the slip rate to be 0.1-0.2mm/yr.
Economic Geology
Ghodratollah Rostami Paydar
Abstract
The Zarshuran gold deposit in northwest Iran is located in historic gold and arsenic mining area in the Sanandaj-Sirjan geo-structural zone. This area is mainly composed of Precambrian rocks. The Oligo-Miocene granitoid intrusions in Pre-Cambrian formations which are the country rocks of gold mineralization ...
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The Zarshuran gold deposit in northwest Iran is located in historic gold and arsenic mining area in the Sanandaj-Sirjan geo-structural zone. This area is mainly composed of Precambrian rocks. The Oligo-Miocene granitoid intrusions in Pre-Cambrian formations which are the country rocks of gold mineralization have resulted from intensive alteration, milonitization and gold mineralization. The main aim of these study is the separation of gold mineralization zones by using concentration-number (C-N) and concentration- volume(C-V) fractal techniques, which is based on 44 drill hole data and 5800 analyzed samples. Firstly, the logarithmic graph of gold was plotted for each model. Five gold mineralization zones were identified by using concentration-number model and four zones with concentration- volume model, indicate that intense of gold mineralization in wall rock, weak, medium, high and highly enriched zone, respectively. 3D geologic and fractal models show that low mineralized zones occurred in most of the ore deposits, which are often related to the Iman-Khan rock unit. In addition, based on fractal model interpretations and calculation of the overall accuracy matrices, these regions with medium, high and enriched zone have good overlaps to the Jasperoid rock unit, Chaldagh limestone, and Zarshuran shale units, respectively.
Geophysics
Shahrokh Pourbeyranvand; Mohammad Tatar
Abstract
The Alborz, as one of the important seismotectonic provinces in Iran, has a great vulnerability from natural disasters, especially seismic risk point of view, because of the existence of Tehran megacity in its southern edge. The importance of this area has caused a relatively dense GPS network around ...
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The Alborz, as one of the important seismotectonic provinces in Iran, has a great vulnerability from natural disasters, especially seismic risk point of view, because of the existence of Tehran megacity in its southern edge. The importance of this area has caused a relatively dense GPS network around it. In this study, the earthquake focal mechanism data obtained from different resources was used for stress tensor inversion in the Central Alborz. On the other hand, interpolation of the GPS vectors in rectangular grids and differentiation in the center of each grid cell was used for the study of strain rate in this area. The results showed special variation in principal axes of stress and strain rate, and also the changes in areal and maximum shear strain rates in different parts of the Central Alborz, which shows the geodynamic complexity of the study area. Finally, the angular differences between the maximum horizontal stress and strain rate compressive axis directions were calculated in the location of the clusters of the earthquakes. These calculations showed that the extent of the strain partitioning in the middle parts of the mountain range, where strike-slip motions on Mosha and Firuzkuh faults are observed, has more significant effect on the current deformation processes in the Central Alborz. Meanwhile, in the Northern parts of the range, where dominantly sip slip motions on Khazar Thrust and North Alborz fault occurs, deformation partitioning plays a minor role in the region.
Behnaz Hosseini; M. Ghorbani; S. M. Pourmoafi; A. R. Ahmadi
Abstract
Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging from greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, ...
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Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging from greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, these rocks are divided into two groups of "augen geneiss " and "metagranitoid". During the course of previous studies, these two rock groups had been attributed to a magmatic phase in Mesozoic, which experienced different degrees of deformation. In this study we proceed to determine the age of these two granitoid rock groups based on U-Pb age dating method applied on Zircon minerals. As a result, the age of orthogneiss rocks is 514±24 million years old and they belong to Cambrian, whereas metagranitoid rocks are 173±9 million years old and attributed to Middle Jurassic. Based on geological and structural evidences, the magmatism occurred in Cambrian was related to tension tectonics in Late Precambrian to Early Paleozoic, while the magmatism in Middle Jurassic associated with dextral transpression tectonics in the studied area.
H. Amini; M. Fattahi; M. R. Ghassemi
Abstract
Doruneh is an active left- lateral strike- slip fault in North-East Iran. Surface trace of this fault is about 700 km long, and cuts across Quaternary and Tertiary deposits. In some places along the fault, sediments of Paleogene. Neogene, and alluvial fans of Quaternary age are displaced ...
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Doruneh is an active left- lateral strike- slip fault in North-East Iran. Surface trace of this fault is about 700 km long, and cuts across Quaternary and Tertiary deposits. In some places along the fault, sediments of Paleogene. Neogene, and alluvial fans of Quaternary age are displaced by the fault. Left- lateral displacement between 91-457 m are evident in Landsat images between east of Beiragh and east of Khalil-abad. Displacements are also evident in streams that are incised over the above mentioned deposits. We have tried to estimate the recent history of activity on the fault on the basis of the measured displacements and estimated slip rates of the fault. Estimated age of left- lateral movement inception on the fault is very much younger than the displaced geologic units. These observations indicate that Doruneh Fault has been mostly active during the last few millions, which in turn proves the fault to be an active structure.
H. Bahrami; A. Uromiahy; M. Ahmadi; S. Soleymani
Abstract
In a perfect design of underground spaces, amount of total displacement from the point of stability analysis is fundamental. In empirical and numerical stability analysis periphery of excavated area is consider as a continued mass. When an underground space is excavated by blasting process, so periphery ...
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In a perfect design of underground spaces, amount of total displacement from the point of stability analysis is fundamental. In empirical and numerical stability analysis periphery of excavated area is consider as a continued mass. When an underground space is excavated by blasting process, so periphery of tunnel is damaged by that process. As a result, those materials are not continued. In this research this area named "Crashed areola". 3 dimensional distinct element methods has more adapted with this area, while compared to other numerical methods. 3DEC 4.0 which is based on this method was chosen as a numerical codes. 10th kilometers of Gavooshan tunnel which is water conveyance tunnel is considered as a case study. The part of this tunnel which studied in this research is surrounded by ophiolithic gabbro rock mass. For modeling of this tunnel two conditions were considered, first with continue media of rock mass and second discontinue media so called crash areola. One of the advantages of this part of tunnel is installation of instrumentation with very scientific methods and absence of lining in the other hand. The outputs of numerical solution were shown that modeling by considering crash areola is near to data collection by instrumentations.
B. Hosseini; M. Mohammadi Siyani; A. R. Ahmadi
Abstract
Quaternary volcanic activities in Alamut Valley occurred in three stages and covered Neogene red sedimentary rocks. The volcanic rocks are intermediate in composition and are classified as hornblende trachyandesite. The SiO2 content of the rocks varies in a range from 55.48-61.88 wt%. Chondrite normalized ...
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Quaternary volcanic activities in Alamut Valley occurred in three stages and covered Neogene red sedimentary rocks. The volcanic rocks are intermediate in composition and are classified as hornblende trachyandesite. The SiO2 content of the rocks varies in a range from 55.48-61.88 wt%. Chondrite normalized REE patterns exhibit a steep arrangement of LREEs and MREEs (La/Ho)N =85 and a relatively flat HREE (Ho/Lu)N =1.3., Large ion lithophile elements (LILE) do not show strong enrichment compared to LREEs in mantle normalized multi-element spider diagrams. Nb andTa are slightly depleted compared to neighboring light rare earth elements. These rocks have high Sr/Y (140-205), La/Yb (113-142) ratios, accompanied by high K2O/Na2O (0.7-0.9) and resemble C-Type adakites. Geochemical evidence suggest that these rocks are resulted from partial melting of thickened eclogitic lower crust in presence of abundant residual garnet. Partial melting of lower continental crust probably triggered by thickening of crust as a result of late Cenozoic orogenic phases especially the Passadenian Orogenic phase.
Petroleum geology
Seyed Mahmoud Fatemi Aghda; Mashaallah Taslimi; Ahmad Fahimifar
Abstract
The main aim of this study is to examine the feasibility of estimation of flow zone indicator in carbonate rocks by integration of hydraulic flow unit concept a nuclear magnetic resonance technology. The two main permeability models Timur-Cotes and mean T2 models, because of worldwide usage of these ...
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The main aim of this study is to examine the feasibility of estimation of flow zone indicator in carbonate rocks by integration of hydraulic flow unit concept a nuclear magnetic resonance technology. The two main permeability models Timur-Cotes and mean T2 models, because of worldwide usage of these models, were used for evaluating the ability of nuclear magnetic resonance to estimate the flow zone indicator. One of the most important points in this study is the use of the experimental results of the nuclear magnetic resonance in laboratory on core that is never done in Iran. In this study, 24 carbonate samples were selected, and porosity, permeability and nuclear magnetic resonance experiments were performed. Then, using the results of the porosity and permeability tests, the flow zone indicator was determined and was considered as an index for evaluating the accuracy of the nuclear magnetic resonance method. Using the parameters obtained from the nuclear magnetic resonance test and nuclear magnetic resonance permeability models, flow zone indicator was estimated and compared with the core flow zone indicator. According to the results, it seems that the nuclear magnetic resonance permeability models, with the routine coefficients, do not have the proper ability to estimate the flow zone indicator, and it is necessary to correct the coefficients according to the lithology of rocks.
Hadi Amin-Rasouli; Y. Lasemi; M. Ghomashi; S. Zaheri
Abstract
The uppermost layers of the Pabdeh Formation in Kuh e-Asmari section consist of microbial (tufa and stromatolite) facies interpreted to have been deposited in a lacustrine environment. These deposits are unconformably overlain by basal anhydrite and transitional zone of the Asmari and Pabdeh Formations. ...
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The uppermost layers of the Pabdeh Formation in Kuh e-Asmari section consist of microbial (tufa and stromatolite) facies interpreted to have been deposited in a lacustrine environment. These deposits are unconformably overlain by basal anhydrite and transitional zone of the Asmari and Pabdeh Formations. The transitional zone is correlated with the lower Asmari (with a basal unconformity or correlative conformity) in the Gachsaran No. 31 and Aghajari No. 61 wells and in Kuh e-Mish, Shahzadeh Abdullah, Tang-Sorgh and Rag-Sefid surface sections. Therefore the basal anhydrite and transitional zone should be considered as a part of the Asmari Formation. The drastic facies change near the Pabdeh and Asmari contact is due to thrust-loading, relative sea-level changes and climatic variations close to Ruplian-Chattian boundary.
M. Heidari; Ghasem Ghorbani; H. Shafaii Moghadam
Abstract
Abstract Forumad area is located in NW of Sabzevar, in NE of central Iran structural zone and in western part of Sabzevar ophiolite suite. The mantle section of Forumad ophiolite consists mainly of harzburgites, dunites, pyroxenitic dikes and choromititic lenses that contain brown to black Cr-spinels. ...
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Abstract Forumad area is located in NW of Sabzevar, in NE of central Iran structural zone and in western part of Sabzevar ophiolite suite. The mantle section of Forumad ophiolite consists mainly of harzburgites, dunites, pyroxenitic dikes and choromititic lenses that contain brown to black Cr-spinels. The content of Cr2O3 and Al2O3 of Cr-spinels in harzburgites are between 32.6-53.1 and 15.6-34.8 wt%, respectively, and their Cr# ([100 × Cr/(Cr + Al]) atomic ratio]) is between 39- 69%. Relationship between Cr# of Cr-spinels and Fo of coexisting olivine (Fo=91-92%) and low contents of TiO2 (
Z Azimzadeh; A Jahangiri; E Saccani; Y Dilek
Abstract
The Misho gabbroic massif with an east- west trend, 30 Km length and 7 Km wıdth is penetrated in the Infra-Cambrian Kahar formation. The micro-gabbroic dykes have cut this intrusive massif. Gabbros have homogenous compositions and major phases are plagioclase and pyroxene and minor minerals are ...
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The Misho gabbroic massif with an east- west trend, 30 Km length and 7 Km wıdth is penetrated in the Infra-Cambrian Kahar formation. The micro-gabbroic dykes have cut this intrusive massif. Gabbros have homogenous compositions and major phases are plagioclase and pyroxene and minor minerals are olivine, amphibole, biotite, K-feldespar and opaque minerals. Their texture is granular. The results of EMP analysis of clinopyroxenes show that they have diopside to augite compositions. In different diagrams, gabbros mostly show tholiitic composition with MORB affinities in tectonic setting. Pyroxenes generally have high SiO2 (50.02-52.69 wt %), high Mg number [Mg/ (Mg+Fe2+)] (78.59-82.42wt %), variable Al2O3 (1.8–5.09 wt %), low TiO2 (0.53-1.33 wt %), low Na2O (0.21-0.47 wt %) contents and low Al [6]/Al [4] ratios (0-0.39), suggesting relatively low pressure crystallization conditions of the magma. The temperature calculated for the clinopyroxenes in gabbros is 1027-1306oC and pressure is less than 8 Kbars. The investigations of variation trends of clinopyroxene compositions don’t show any zoning in clinopyroxenes and clinopyroxenes are in chemical equilibrium with other minerals in the rocks. The obtained textural and mineral chemical data, suggest that the clinopyroxenes may have crystallized from a tholiitic magma derived from a depleted lithospheric mantle. This is confirmed by the whole-rock chemistry. The gabbroic massif intrusion in a tectonic setting of extensional rifting followed by the opening of Paleotethyan oceanic crust in early Carboniferous in NW Iran.
R. Ghasemi Nejad; R. A. Abbaspour; M. Mojarab
Abstract
Seismic source zones have an important role in hazard assessment in probabilistic seismic hazard analysis. These zones often determined according to judgments by experts are, in most cases, non-uniform across a specific region and typically controversial. Thus, most of the uncertainty in probabilistic ...
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Seismic source zones have an important role in hazard assessment in probabilistic seismic hazard analysis. These zones often determined according to judgments by experts are, in most cases, non-uniform across a specific region and typically controversial. Thus, most of the uncertainty in probabilistic seismic hazard analysis can be related to the delineation of seismic sources. Another problem of probabilistic seismic hazard analysis is the way earthquakes are associated with the faults. Even though it is well-known that earthquakes happen on faults, but most of them are still unknown, this constrains the realization and assessment of seismic risks by experts. This paper attempts to determine seismic sources and associate events to faults using a fuzzy particle swarm optimization clustering algorithm. The algorithm works based on the minimization of two objective functions: distance from events to fault, and distance from events to their center of density (i.e. cluster center). The algorithm is applied on seismic data acquired from northwest of Iran, and its performance is evaluated based on the events assigned to the faults by previous researchers. Comparing associated earthquakes to faults by the algorithm in northwest of Iran with known and documented earthquakes, reveals that, 79.2% of the events are correctly induced by faults. Final result shows that, this methodology will help seismological engineers take a step forward in hazard analysis by determining seismic sources and assigning earthquakes to different active faults.
K. N. Afzali; R. lak
Abstract
United Arab Emirate has recently started to build some artificial islands in the southern part of the Persian Gulf. Constructing of these Islands, such as each marine structure, have special effects on the morphology of the sedimentary Basin. This investigation focused on the documentation of morphological ...
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United Arab Emirate has recently started to build some artificial islands in the southern part of the Persian Gulf. Constructing of these Islands, such as each marine structure, have special effects on the morphology of the sedimentary Basin. This investigation focused on the documentation of morphological and environmental effects of making artificial islands by the UAE in the Persian Gulf. This research is based on remote sensing studies and sedimentology investigation. Remote sensing studies carried out with comparing satellite data related to 1998, 2003, 2007 and 2008. Sedimentology investigation of the three sediment samples taken from the coastal part of the artificial islands was carried out. The deliberations indicate that construction of these islands have negative effects on geomorphological features in coastal part of the Persian Gulf in UAE region. The Sedimentation around the islands leads to the reduction of water depth. The kind of the sediment is usually carbonates and their origin in the western part of the islands is affected by marine longshore currents. However, there are two sources proposed for the sediments in the eastern part of islands; intrabasinal (direct precipitation) and detrical. The construction of linear barriers along the coast leads to the building of restricted lagoons between the coast and barriers. It is estimated the rate of progradation of the coast (sea ward migration of the shoreline) is 120 m from 2008 to 2009.
R. Elyaszadeh; M. Mohajjel
Abstract
High Zagros zone in southeast Kermanshah is bordered between two Radiolarite and Zagros Fold Belt and consist of abundant NW-SE trending thrust faults and folds sub-parallel to Zagros fold belt. Several structural cross-sections were prepared in NE-SW direction perpendicular to the trend of the structures. ...
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High Zagros zone in southeast Kermanshah is bordered between two Radiolarite and Zagros Fold Belt and consist of abundant NW-SE trending thrust faults and folds sub-parallel to Zagros fold belt. Several structural cross-sections were prepared in NE-SW direction perpendicular to the trend of the structures. Main thrusts were cut by some local strike-slip faults due to difference in their displacement. The Kohsefid thrust fault (FA) is one of the main thrusts that divide the northern Radiolarite zone from the High Zagros Zone. This fault is limiting the southern boundary of the Radiolarite zone. It displaced as a reverse fault during contraction tectonic in Late Cretaceous. The flysh facies of Amiran formation in Zagros Fold Belt with Paleocene age contain radiolarite fragments and confirms this event. It seems that the Garo Formation plays a detachment surface role for these thrusts in the High Zagros zone. The foreland in Zagros, commenced to deform by thrusting and folding in Late Cretaceous in the High Zagros zone and by later collision of the Arabian plate with the Iranian plate, rock units in the Zagros Fold Belt were deformed.
Petrology
Mahnoush Bahjati; A. Ahmadi; Habib Biabangard
Abstract
The volcanic rocks of Kuleh sangi-Malek siah kuh igneous complex consist of alkalibasalt, basalt, basaltic andesite, andesite, dacite and trachyte. In the SiO2 versus K2O diagram, the basaltic samples are plotted in the shoshonitic field and the subalkaline samples are plotted in the medium K calc alkaline ...
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The volcanic rocks of Kuleh sangi-Malek siah kuh igneous complex consist of alkalibasalt, basalt, basaltic andesite, andesite, dacite and trachyte. In the SiO2 versus K2O diagram, the basaltic samples are plotted in the shoshonitic field and the subalkaline samples are plotted in the medium K calc alkaline series field. The average La/Yb, Rb/Zr and Cs/Hf ratios in basalts are 7, 47 and 63 times those of N-MORB, respectively. Considerable enrichment of LILEs, LREEs and relative depletion of HREEs indicate that the magmas originated from a mantle source more enriched than that of OIB, where phlogopite and garnet are stable. Using non-modal batch melting model, the compositions of the mafic samples are mainly consistent with about 5% melting of a phlogopite-bearing and garnet-bearing lherzolite with a mixture of about 80% and 20%, respectively. AFC models using Pb versus Ce/Pb and Rb versus K/Rb, show that the fractionated samples have undergone simultaneous crustal assimilation and fractional crystallization. It seems that the assimilation and the fractionation had been taken place with the same rate. Depletion in Y and elevated ratio of Sr/Y of fractionated rocks in addition to Rb/Nb ratio more than 8, could be considered as evidence for crustal assimilation.
M. Rajabi; B. Bohloli; M. Mohammadinia; E. Gholampour Ahangar
Abstract
The shear and compressional wave velocities (Vs and Vp, respectively) have many applications in petrophysical, geophysical and geomechanical studies. Vp is very easily obtained from sonic logs that are available in most of oil and gas wells, but some wells (especially old wells) may not have Vs data. ...
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The shear and compressional wave velocities (Vs and Vp, respectively) have many applications in petrophysical, geophysical and geomechanical studies. Vp is very easily obtained from sonic logs that are available in most of oil and gas wells, but some wells (especially old wells) may not have Vs data. In this study Vs was predicted from porosity well log data (neutron, density and sonic) using fuzzy logic and neuro-fuzzy techniques. For this purpose a total of 3910 data points from Sarvak carbonate reservoir which have Vs and porosity log data were utilized. These data were divided into two parts, one part included 2046 data points used for constructing models and the other part included 1864 data points used for testing models. The results show that fuzzy logic and neuro-fuzzy techniques were useful methods for prediction of Vs in this carbonate oil reservoir.
E. Moghimi; M. Badri Far; M. Zarei Nejad
Abstract
Morphodynamic characteristics of Damavand volcanic cone have been affected by two factors including internal and external morphodynamics. Major goal of this research is based on external morphodynamics. The morphodynamical landforms of this area are divided in two main groups, the first one is climatic ...
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Morphodynamic characteristics of Damavand volcanic cone have been affected by two factors including internal and external morphodynamics. Major goal of this research is based on external morphodynamics. The morphodynamical landforms of this area are divided in two main groups, the first one is climatic processes and the second one is anthropogenic processes. Climatic processes, including glacial erosion, pre-glacial erosion and alluvial erosion, have changed morphology of slopes and spatial landforms. For the special geographic condition of Damavand volcanic cone, few data is available. Therefore by using satellite images ETM+, ASTER, SPOT, several new data layer have been prepared based on base maps and field checking in GIS environment.
M. Ebrahimi; M. Rafiei
Abstract
Eocene pyroclastic-volcanic rocks, ranging in composition from basic to intermediate and acidic rocks, are widely exposed at north of Zavieh, southwest of Karaj. The pyroclastic-volcanic sequence is composed of basalt, trachy-basalt, basaltic trachy-andesite, andesite, trachy-andesite, trachydacite, ...
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Eocene pyroclastic-volcanic rocks, ranging in composition from basic to intermediate and acidic rocks, are widely exposed at north of Zavieh, southwest of Karaj. The pyroclastic-volcanic sequence is composed of basalt, trachy-basalt, basaltic trachy-andesite, andesite, trachy-andesite, trachydacite, dacite and rhyolite along with various pyroclastic rocks including ignimbrite, welded tuff, crystal tuff, lithic tuff, lithic crystal tuff, ash tuff and lapillistone. The pyroclastic-volcanic sequence contains large amount of ignimbrite. Common textures found in the studied volcanic rocks are porphyritic, glomeroporphyritic, cumulophyric, amygdaloidal and trachytic. Rock fragments and broken crystals are usually found in the pyroclastic rocks. Eutaxitic texture is commonly observed in the ignimbrite. Flow banding is seen in the study rhyolitic rocks. Meanwhile, columnar structure is commonly observed in the lava flows and ignimbrites. Pyroxene, amphibole, biotite, plagioclase and quartz are the major minerals in the volcanic sequence along with K-feldspar, opaque minerals and altered olivine as minor minerals. Calcite, chlorite, epidote and sericite are also present as accessory minerals. According to geochemical data the studied volcanic rocks are mainly calc-alkaline, however few samples plot in the alkaline and shoshonitic fields in some diagrams. Negative anomalies of Nb and Ta, Pb positive anomaly, large ion lithophile elements enrichment, rare earth elements enrichments and depletion in high field strength elements all indicate that the parent magma of the studied rocks has originated from a metasomatized asthenospheric mantel over the Benioff-Waddatti zone. Common existence of sieve texture in plagioclase crystals, corroded crystals of plagioclase and pyroxene and dark rim of Fe-Ti oxides around biotite and amphibole crystals all indicate that a disequilibrium condition existed during crystallization which is most probably due to magma mixing. However, assimilation, decompression and rapid ascend of magma may also produce such textures.
I. Monsef; M. Rahgoshay; M. H. Emami
Abstract
The Late Jurassic to Early Cretaceous Orzuieh volcanic sequence is exposed in the southern part of the Sanandaj – Sirjan Zone. Major and trace element geochemistry shows magma evolution from the transitional to the calc-alkaline series. Clinopyroxene compositions are similar to their composition ...
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The Late Jurassic to Early Cretaceous Orzuieh volcanic sequence is exposed in the southern part of the Sanandaj – Sirjan Zone. Major and trace element geochemistry shows magma evolution from the transitional to the calc-alkaline series. Clinopyroxene compositions are similar to their composition in subduction setting and support a volcanic arc related environment. REE and trace element diagrams show enrichment patterns in LREE relative to HREE and depletion in Nb and Ta elements. This magmatic sequence has been originated from the mantle source with effect of liquids and sediment resulted from the subducting slab. The Orzuieh volcanic sequence is probably originated during the subduction of the Neo-Tethyan Oceanic lithosphere under the Sanandaj – Sirjan Zone, during the Late Jurassic to Early Cretaceous time, in the volcanic arc tectonic environment.
Stratigraphy and Palaeontology
Katayoon Barmakizadeh; A. Mahanipour
Abstract
Abstract The lower part of the Garau Formation with a thickness of 212 m at the southwest of the Kabirkuh anticline is investigated with regard to the calcareous nannofossils. Lithology of the studied interval is mainly consists of marl, marly limestone, black shale and limestone. 67 species from 33 ...
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Abstract The lower part of the Garau Formation with a thickness of 212 m at the southwest of the Kabirkuh anticline is investigated with regard to the calcareous nannofossils. Lithology of the studied interval is mainly consists of marl, marly limestone, black shale and limestone. 67 species from 33 genus and 13 families are recognized. Nannofossil events that are recorded from base to top of the section are as follow: the first occurrence (FO) of Calcicalathina oblongata, the last occurrence (LO) of Rucinolithus wisei, the FO of Lithraphidites bollii, the LO of Cruciellipsis cuvillieri, the first occurrence of Assipetra terebrodentarius and the last occurrence of Lithraphidites bollii. According to these index calcareous nannofossils, the studied interval is ranging from the uppermost part of CC2/NK2 biozone to the middle part of CC5b/NC5C subzone Considering these zonations, the age of the studied interval is Valanginian ‒ Hauterivian. According to the calcareous nannofossil data, the Valanginian ‒ Hauterivian boundary can’t be determined. This boundary is located at the base of the Tethyan ammonite Acanthodiscus radiatus at the leading GSSP candidate in the La Charce section of southeastern France.
Stratigraphy and Palaeontology
Ebrahim Mohammadi; Mohammad Javad Hassani
Abstract
Paleoecology of the Qom Formation ostracods in the Bojan and Varkan sections have been studied. The age of the sections has determined base on foraminifera and is Rupelian-chattian for the Bujan and Chattian for the Varkan Section. Ostracoda content of the Bujan and Varkan sections include 44 and 33 ...
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Paleoecology of the Qom Formation ostracods in the Bojan and Varkan sections have been studied. The age of the sections has determined base on foraminifera and is Rupelian-chattian for the Bujan and Chattian for the Varkan Section. Ostracoda content of the Bujan and Varkan sections include 44 and 33 species respectively. The pecies of genus Cytheridea are the most abundant and the most dominant ostracods of the Bujan section. In the lower part of the Bujan section, different species of Cytherella and Cytheridea constitute the dominant ostracods, but upward the abundance of Cytherella is declined and Cytheridea, Neonesidea, and Bairdia are dominant. Podocopids constitute 76% and 86% of the Bujan section ostracods during Rupelin and Chattian, respectively. Neonesidea elegans, Bythocypris pseudoreniformis, Paracypris pandyai, Paracypris sapperi and Paracypris naalunensis constitute the dominant ostracods of the Varkan Section. Podocopid ostracods are dominant in the Varkan marls and constitute 77% of the ostracods. The high percentage of podocopid ostracods indicates that the environment was oxygen-rich and without the ecological stresses in both section; while in the Varkan Section, the ecological conditions are stable but in the Bujan section, the oxygen enriches upward and ecological conditions become closer to normal marin basins.
Z Mohammadipour; F Yaminifard; M Tatar
Abstract
Nearly one-third of the shortening in Iran plateau due to Arabia-Eurasia convergence is accommodated in the Zagros fold and thrust belt, which is seismically one of the most active regions among the continental collision zones in the world. Deploying a temporary seismic network in the north of Bandar ...
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Nearly one-third of the shortening in Iran plateau due to Arabia-Eurasia convergence is accommodated in the Zagros fold and thrust belt, which is seismically one of the most active regions among the continental collision zones in the world. Deploying a temporary seismic network in the north of Bandar Abbas in Hormozgan Province, which consisted of 32 three-component seismograph stations operating for a duration of about 3.5 months, provided appropriate data for studying the upper crustal structure of the easternmost Zagros by usingLocal Earthquake Tomography. Three dimensional velocity model obtained from the conversion of P-wave arrival times indicates southwestward overthrusting of the lower crust of northern parts, supporting active underthrusting of the Arabian plate beneath Central Iran in the easternmost Zagros. A very low velocity zone is also observed in the eastern part of the study area that could be associated with the Zendan-Minab-Palami fault system.
N. Abaasi
