F. Bagheri; A. Saeidi; S. Bouzari
Abstract
Meyamey fault, one of the major faults in the northeast of Iran, has played an important role in the regional depositional basin development and created many geomorphologic features. This fault has proved to be an important subject for study in terms of structural ...
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Meyamey fault, one of the major faults in the northeast of Iran, has played an important role in the regional depositional basin development and created many geomorphologic features. This fault has proved to be an important subject for study in terms of structural geology, fault mechanisms, fault interactions and the relation between faults and folds. Field measurements in the eastern part of the Meyamey fault zone depict that faults are mainly striking towards NE with dips of up to 50º and gentle lineation. Folds also follow the same trend. Calculated maximum stress axis in Armain fault is in NE direction, whereas in Meyamey and Ghods faults are in SE direction and are horizontal. Moreover, in the eastern Meyamey fault area, this fault shear zone Chah Seidabad fault, in which X and R, R fractures are evident.
Gh Ghadami; M Poosti; F Babai
Abstract
Few More than 5 dacite to andesite volcanic masses with Mio-Pliocene age are exposed to older volcanic rocksat the south and east of the Mozahem volcano, in south-east of Urumieh- Dokhtar magmatic belt, north-east of Shahre-Babak. These rocks show hyaloporphyritic- trachytic texture and consist of pPhenocrysts ...
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Few More than 5 dacite to andesite volcanic masses with Mio-Pliocene age are exposed to older volcanic rocksat the south and east of the Mozahem volcano, in south-east of Urumieh- Dokhtar magmatic belt, north-east of Shahre-Babak. These rocks show hyaloporphyritic- trachytic texture and consist of pPhenocrysts of plagioclase, amphiboles and biotites. Based on geochemical data and multi elements patterns, these rocks are medium to high K calc-alkaline suite and they show LILE and LREE enriched normalized multi-element patterns, and negative Nb, Ti and Ta anomalies. Chondrite normalized REE patterns display a steep decrease from LREE to HREE without any Eu anomaly. They have higher SiO2 and Sr contents and Sr/Y and La/Yb ratios and low MgO, Y and Yb contents than the normal calc-alkaline volcanic rocks. These volcanic rocks are formed in the a subduction zone in an active margin, and showing full complete of HSA(high SiO2 adakites) characteristics. HREE and Y depleted patterns suggest the existence of garnet and amphibole as a residue in the source. The source of these rocks was probably amphibole-eclogite or garnet-amphibolite possibly generated during subduction or slab break of the Neo-Tethyan oceanic slab beneath the Central Iran microplate in Neogene.
SH Habibimood; M.N Gorgij; KH Khosrotehrani; A Saidi; S.A Aghanabati
Abstract
The studied section is located in the vicinity of the village Daghal on the Zabol – Nehbandan road, 100 kilometersfrom Zabol. The strata under study are 55.57 meters thick here and lie nonconformably on the igneous rocks while the upper contact is now known. In this study the mentioned strata are ...
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The studied section is located in the vicinity of the village Daghal on the Zabol – Nehbandan road, 100 kilometersfrom Zabol. The strata under study are 55.57 meters thick here and lie nonconformably on the igneous rocks while the upper contact is now known. In this study the mentioned strata are divided into four units lithologically. The results of macroscopic and microscopic studies and the microfacies analysis show that the strata were deposited in four sub-environments including, lagoon, tidal channel, submarine fans and open marine. The thickness and extent of the marine sub-environment is greater than the other sub-environments. The study of microfacies and their constituent sub-environments implies that the mentioned section is formed in a homoclinal carbonate ramp. This study indicates that during the late cretaceous there was a relatively shallow sea covered the area. The existence of microfossils such as Orbitoeides, Omphalosyclus and globutruncana indicates the age of Maastrichtian for the rock unit studied.
Petrology
Maryam Dorani; Mohsen Arvin; Roland Oberhänsli; Hadi Omrani; Sara Dargahi
Abstract
Bajgan Complex is a part of Iranian Makran including many kinds of metapelites, metabasites, calcsilicates, amphibolites, marbles, meta volcanosediments, felsic, mafic and ultramafic intrusives. The calcsilicates are divided into amphibole bearing epidote schist, epidote - amphibole schist, epidote – ...
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Bajgan Complex is a part of Iranian Makran including many kinds of metapelites, metabasites, calcsilicates, amphibolites, marbles, meta volcanosediments, felsic, mafic and ultramafic intrusives. The calcsilicates are divided into amphibole bearing epidote schist, epidote - amphibole schist, epidote – amphibole - garnet schist and carbonate bearing mica schist. Among of all calc silicates the epidote – amphibole - garnet schist shows the highest metamorphic condition and consists of garnet, amphibole, epidote, calcite, quartz, secondary chlorite and minor amount of titanite, apatite, white mica and magnetite. In this study the mineral chemical compositions, temprature, pressure and fluid activity in different metamorphic stages of epidote – amphibole - garnet schist were detected. In according to chemical data, garnet has almandine, grossular, spessartine and pyrope solid solution (Alm 35-50, Grs 23-31, Sps 14.6-36, Prp < sub> 2.6-9.8 ; mol%) and shows chemical zoning as almandine and spessartine have an increasing and decreasing trend, respectively, from core to rim. Amphiboles are classified in sodic- calcic group and are Barroisite. Chlorites are kown as Ripidolite and epidotes are classified in Clinozoisite subgroup. Peak metamorphic condition of epidote – amphibole - garnet schist has been estimated about 610° C and 8 kbar and molar fraction of Co2 and H2O have been calculated about 0.32 and 0.68, respectively. The retrograde metamorphic condition are about 525° C, 4.5 kbar and molar fraction of Co2 and H2O have been calculated about 0.31 and 0.69, respectively. The epidote – amphibole - garnet schist followed a ‘clockwise’ P–T path during prograde and retrograde metamorphism.
S. Alipour
Abstract
Yarim-ghayeh cave, located in the border of Iran and Turkey, is hosted by the Oliogocene-Miocene limestone body. Its in and outside rough topography implies that the cave is very young and infact in the beginning stage of its formation. Overall volume is 9600 m3 with 631 ...
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Yarim-ghayeh cave, located in the border of Iran and Turkey, is hosted by the Oliogocene-Miocene limestone body. Its in and outside rough topography implies that the cave is very young and infact in the beginning stage of its formation. Overall volume is 9600 m3 with 631 m2 dry area and 4700 m3 occupied by water with 4 to 6 meters in depth. Structurally, the cave has been formed by a fault system cause a sinkhole form on the top of the cave aproximately of 10000 m2. Its water is clean and clear with pH of 7.36 and its fluorine is only 1.7 ppm compared to 4.5 ppm in Maku area. Yarimghayeh playa with an area of 5 m2 is in the close eastern part of the cave with permenant water flow. Elevation of the water surface of playa is 1414 m which is 2 m higher than the water surface of the cave (1412 m). 500 m3 water is daily pumped out without any change in water level. Since there is no any other water flowing to the cave, therefore, the playa is supplying the cave water system. The ecosystem of the cave and playa are tight together and any change in one will affect the other. To protect its water quality from contamination, access to this small scale cave must be restricted except for scientific research.
Petrology
Mohammad Fadaeian; Aminollah Kamali; Kourosh Mohammadiha
Abstract
The studied area is located in Ardabil province and the northeast of Meshkinshahr city and structurally in Alborz-West-Azerbaijan zone. Tephritic dykes have pyroxenite and gabbro xenolites. Mineralogy of tephritic dykes and xenolites includes plagioclase, clinopyroxene, analcime, amphibole, olivine and ...
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The studied area is located in Ardabil province and the northeast of Meshkinshahr city and structurally in Alborz-West-Azerbaijan zone. Tephritic dykes have pyroxenite and gabbro xenolites. Mineralogy of tephritic dykes and xenolites includes plagioclase, clinopyroxene, analcime, amphibole, olivine and phlogopite. Porphyric, microcrystalline, granular and cumular microlytic textures are their main textures. According to the mineral chemistry data as well as the presence of shaped, homogeneous and coarse analcime crystals, it can be concluded that the analcime crystals are secondary and as a result of delayed magmatic reactions under hydrothermal conditions have been formed on the primary leucite crystals. The composition of olivine in gabbro xenoliths is chrysolite. The chemical composition of pyroxene mineral in tephritic dykes and gabbro xenolites is diopside. The studied clinopyroxenes with alkaline composition show good adaptation to the tectonic environment of the magmatic arc. Clinopyroxenes are also formed at low to medium pressures, indicating their crystallization during magma ascent and at different depths. The amount of ferric iron in clinopyroxenes indicates high oxygen fugacity of magma. Clinopyroxenes of Tephritic and Gabbroic dykes are formed at 10 and 12 kbar pressure, temperature between 950 and 1100 ° C and depth between 35-35 and 40-50 km. The chemical composition of amphiboles related to pyroxenite xenolite is calcic and magnesiohastingsitic amphiboles type . The average geometry of the barometer based on the amount of aluminum for pyroxenite xenoliths is 7-9 kbar. Thermometric studies indicated that the amphiboles were formed at 900-950 ° C. The chemical composition of mica is phlogopite, and the number of magnesium in mica is 0.77.
L Ebadi; A Alavi; M.R Ghassemi
Abstract
The study area is located in the SW Rafsanjan city and central Iran. In the area, strike- slip faults effected the Cenozoic unites. This paper analysis subsidiary fault data collected from damage zones associated with the Cenozoic Rafsanjan intraplate right-lateral strike-slip fault systems in SW Rafsanjan ...
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The study area is located in the SW Rafsanjan city and central Iran. In the area, strike- slip faults effected the Cenozoic unites. This paper analysis subsidiary fault data collected from damage zones associated with the Cenozoic Rafsanjan intraplate right-lateral strike-slip fault systems in SW Rafsanjan city. Fault sets, arranged in a consistent kinematic architecture that is compatible with the Cenozoic regional strike-slip environment. In the paper, kinematic architecture of fault zone interpret in the subsidiary fault. The results show that five peaks is prominence. Angular and kinematic relation among subsidiary fault set show that right-lateral strike- slip and revers fault are the dominant kinematic type in the area. Based on, the angular analysis in the damage zone, we have 5 subsets. 2 subsets of 5 subsets named 1rev (NW-SE trending) and 2rev (E-W trending). In the strike- slip fault mechanism, 3 subsets is demined, three azimuth named 1rl (NW-SE striking), 2rl (E-W striking) and 3rl (WNW-ESE striking). Average strike of set 1rl and 1rev indicate the orientation of the PDZ for fault systems and the PDZ be produced by early localization of the principal displacement zone along pre-existing mechanical discontinuities inherited. Early formation of the PDZ by re-activating pre-existing mechanical discontinuities.The azimuthal value of the faults set in the kinematic architecture are similar to predicted by the simple shear Reidel model. By analysis with kinematic architecture in damage zone of strike- slip fault system indicated that the linking damage zone is very important to increase permeability and created void. The void is low pressure stress and magma can intrude in the area and the dikes formed. The PDZ induced stress and the second and third order fracture is created. Stress analysis in the study are show shear – compression regime convert to compression. The maximum principle axis show N20E to N-S in the Cenozoic. The change of stress regime is correlated by formation fault and fold with E-W trend. The change regime caused reactive pre-exiting fault.
Economic Geology
Monireh Sakhdari; Mehrdad Behzadi; Mohammad Yazdi; Nematollah Rashidnejad-Omran; Morteza Sadeghi Naeini
Abstract
The Godar Sorkh area is located in the central part of the Sanandaj-Sirjan zone, 20 km southwest of the Muteh region. Gold mineralization at Godar Sorkh occurs in quartz-sulfide veins that hosted in metasedimentary rocks. Veins of mineralization typically formed along normal faults. Rock sequences ...
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The Godar Sorkh area is located in the central part of the Sanandaj-Sirjan zone, 20 km southwest of the Muteh region. Gold mineralization at Godar Sorkh occurs in quartz-sulfide veins that hosted in metasedimentary rocks. Veins of mineralization typically formed along normal faults. Rock sequences are affected by several deformation phase, gold mineralization occurs in ductile to ductile-brittle shear zones and had been under poly-phase metamorphism. The main alterations are Sulfidation, carbonization, silicification, chloritization, and sericitization. Ore-mineral assemblages include pyrite and chalcopyrite, arsenopyrite, sphalerite, galena, and Fe-oxide. Mean homogenization temperature in gold-bearing quartz range between 275oC and 300oC. Fluid inclusions in quartz veins are dominated by CO2-H2O-NaCl fluid. Salinity ranges from 9 to 17 wt. % NaCl equivalent. Corresponding to a depth of <2 km, Godar Sorkh deposit is formed in epizonal environment. Measured δ18O values for the gold-bearing quartz range between 12.7 to 14.3 permil, estimated δ18Ofluid values range from +6.4 to +7.3 permil, δ34S values range from –16 to +5 permil, and estimated δ34Sfluid values range from +4.2 to -17.3 permil. Fluid inclusion and stable isotope studies on ore-bearing quartz-sulfide veins indicating the major role of metamorphic fluids. Gold derived from metasedimentary rocks. Gold mineralization in the Godar sorkh deposit classified as an orogenic gold deposit.
E Ghanavati; A Karam; E Taghavi Moghdam
Abstract
Ground assessment to identify and map of susceptible land are as to slope movements especially landslides is of studies related to natural geographers, particularly geomorphologists. Determining and recognition of susceptive areas to sliding could prevent making loss as well as facilitating slope stability ...
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Ground assessment to identify and map of susceptible land are as to slope movements especially landslides is of studies related to natural geographers, particularly geomorphologists. Determining and recognition of susceptive areas to sliding could prevent making loss as well as facilitating slope stability operations. In this study, the variables such as slope, the aspect of slope, petrology, land use, rainfall, and distance from river, fault, and road were used to map the risk of landslide in the Taleghan watershed. After constructing and analyzing the information layers by means of Arc GIS Software, the fuzzy membership functions were used for weighting the layers. The standardized fuzzy layers were overlapped in GIS environment and the landslide risk mapping was produced by means of fuzzy logic operators. The results of this study indicated that gamma function 0.7 is more appropriate than other fuzzy operators. Based on the abovementioned gamma, 18.91% of the area was identified as the high-risk areas. Obviously, allocating these areas for housing, facilities, etc. increases financial and physical damages.
K Hashemi; B Oveisi; A Saeedi
Abstract
The Zagros fold-thrust belt is a young orogenic belt which is characterized by extensive folding in its sedimentary cover, and abundance of earthquakes in which, intends to inner parts of Zagros like a band. The Lar anticline is one of the active folds in this belt which is situated in the coastal Fars ...
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The Zagros fold-thrust belt is a young orogenic belt which is characterized by extensive folding in its sedimentary cover, and abundance of earthquakes in which, intends to inner parts of Zagros like a band. The Lar anticline is one of the active folds in this belt which is situated in the coastal Fars arc of the Zagros simple folded belt and intends to inner parts. Earthquakes have several times destroyed Lar town in the northeast of this structure. The most important event was 1960 earthquake (mb~6.0) that caused lots of destruction and casualties. The nearest fault to Lar town, which probably caused this earthquake, was the Lar fault. In order to illustrate the geometry of the Lar fault-related fold a structural cross section with ~27 km length was prepared. Percentage of total shortening along the cross-section obtained 17.3 % which is equal to 4.6 km. The maximum amount of this shortening equals to 15 % (~4 km) has been absorbed by the Lar anticline. Geometrical comparison between the Lar anticline and fault propagation fold models showed that the Lar anticline kinematically corresponds to a fixed axial surface fault propagation fold that associated with thinning in its forelimb. Investigations showed that the Lar anticline is a mature fault propagation fold, which its core is converting to an immature fault bend fold. This kinematic reorganization has led to elimination of the low viscosity Hormuz salt from anticline core and elimination of the low viscosity units in turn has led to changing ductile behaviour to rigid behaviour. According to the structural cross section, such a mechanical behaviour in the Lar anticline can occur in contact boundary of the Paleozoic rocks in anticline core which can lead to seismic potential increase in the sedimentary cover. So, it is expected that the depth of 1960 earthquake was low (6-9 km) and occurred in the core of the Lar anticline, in relation to its rigid mechanical behaviour. By using geometric equations, we showed that long term relative shortening rate for the Lar anticline is 2 ± 1 mm/yr which is associated with 4±1 mm/yr average slip rate upon the Lar fault.
S. Z. Hosseini; M. Arvin
Abstract
Neogene volcanism in the Tel Gorban-Chah Breshk area, north of Shahre-Babak, occurs as dacitic to andesitic lava flows and domes. Petrographically the rocks consist of plagioclase, hornblende ±biotite and quartz phenocrysts setting in porphyritic and hyalopilitic matrix. Opacitization of hornblende ...
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Neogene volcanism in the Tel Gorban-Chah Breshk area, north of Shahre-Babak, occurs as dacitic to andesitic lava flows and domes. Petrographically the rocks consist of plagioclase, hornblende ±biotite and quartz phenocrysts setting in porphyritic and hyalopilitic matrix. Opacitization of hornblende and biotite and zoning and sieve texture in plagioclase are signatures of disequilibrium conditions through the magma cooling. Geochemical data and petrological diagrams show their medium potassic calc- alkaline nature. Enrichment in LILE’s and depletion in HFSE’s (eg. Nb,Ta,Ti) points to a subduction tectonic environment for Tel Gorban-Chah Breshk dacitic to andesitic rocks. Furthermore, their Al2O3>16,Sr/Y>80 and chondrite normalize REE pattern are quite similar to dakites. Distinctive geochemical features such as Rb/Sr< 0.04, La/Yb> 18, Yb< 1, (Sr/Y)n> 80, and Y
B Rahimzadeh; F Masoudi; Sh Ranjbar
Abstract
Scoria is one of the main pyroclastic units in Damavand volcano, which its main crystals are plagioclase, olivine and pyroxene. In this study, characterization of bubbles and their formation during the eruption considered using Bubble Size Distribution (BSD) method including study of volume, 3D modeling, ...
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Scoria is one of the main pyroclastic units in Damavand volcano, which its main crystals are plagioclase, olivine and pyroxene. In this study, characterization of bubbles and their formation during the eruption considered using Bubble Size Distribution (BSD) method including study of volume, 3D modeling, nucleation and bubble growth. For selected sample, thebubbles investigated in 3 perpendicular dimensions (X-Y-Z) and in total 16830 bubbles (X=7357, Y=5385, Z=4088) were measured and drawn. The Bubbles volumes calculated in 3 dimensions are X=47.21, Y=40.27, Z=40.01 percent. The Bubbles axes were calculated: X=1:1:4, Y=Z=1:1:3.4 and the 3D schematic shape is ellipsoid which the longest axis (L) is about 4 times longer than the other two axes (I, S). The L axis is parallel to the lowest pressure dictated on magma and the bubbles could be grown 4 times more in that direction. The bubbles shape of Damavand scoria is an ellipsoid with an average of 1:1:3.7 for its axes. The presence of 3 peaks in frequency distribution versus bubble size diagram, suggesting polymodal events of bubbles generation and in the Damavand volcano the bubbles nucleation occurred in 3 events(F1, F2, and F3). The nucleation density increased from F1 to F3 but the bubbles growth reduced in the same direction. The first group of bubbles formed in the magma chamber and the second group formed during the magma ascent. The third group of bubbles could form either in the space between earlier groups or in the last stage of magma eruption.
S Soltaninejad; B Shafiei
Abstract
The Now-Chun deposit, in the Kerman porphyry copper belt, with proved reserve of 268 Mt ore grading 0.034% Mo (100 ppm cut off) and 62 Mt ore grading 0.43% Cu (0.25 cut off), is the first known occurrence of Mo-rich,relatively Cu-poor porphyry mineralization in Iran which is studied from the mineralogical, ...
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The Now-Chun deposit, in the Kerman porphyry copper belt, with proved reserve of 268 Mt ore grading 0.034% Mo (100 ppm cut off) and 62 Mt ore grading 0.43% Cu (0.25 cut off), is the first known occurrence of Mo-rich,relatively Cu-poor porphyry mineralization in Iran which is studied from the mineralogical, l, and genetic point of view. The alteration and mineralization of the Now-Chun deposit is related to the highly differentiated porphyritic stock (rhyodacite) belonging to the Oligo-Miocene Mamzar batholith. Based on the present study, the main part of Mo and Cu mineralization in the Now-Chun deposit occurred more in the form of cross-cutting veinlets (stockwork) and less as dissemination type. The presence of molybdenite with/without chalcopyrite association in quartz-anhydrite-orthoclase-biotite potassic veinlets and chalcopyrite occurrence in primary quartz-magnetite veinlets is indicative of the priority of part of the Cu mineralization respect to the Mo during the primary stage of mineralization. The initial mineralization of Mo in the form of molybdenite occurred in quartz-anhydrite-orthoclase-biotite-pyrite-chalcopyrite. The weak correlation between Mo and Cu in the potassic alteration zone (r= -0.2) especially in the high grade ores indicates the difference between the enrichment conditions of both elements in responsible hydrothermal fluids for this alteration and mineralization zone. The presence of thick quartz-pyrite-chalcopyrite veinlets with sericitic halo and quartz-molybdenite without alteration halo either as independent or as intruded within early veinlets (quartz-molybdenite-anhydrite-orthoclase-biotite) have been associated with increasing of Mo and Cu grades in moderately phyllic alteration zone (sericitic and silicified rocks). The positive correlation between Mo and Cu in moderate phyllic zone (r≥ 0.0 to +0.5) which affected potassic ores indicates the similar behavior of both Mo and Cu during formation and evolution of the hydrothermal solution, which is responsible for the alteration and mineralization in the phyllic zone. This study revealed that the main concentration of Mo occurred in deep parts (potassic zone) of the deposit; whereas, Cu is associated with the shallow parts, especially with moderate phyllic zone which affected the potassic zone. As a result, the high grade Mo ores are not Cu-rich and vice versa. The present study indicated that the Now-Chun deposit in comparison with the Sar Cheshmeh deposit (Cu-Mo porphyry) is categorized within the Mo-Cu porphyry deposits. This sub-group of porphyry Cu and Mo deposit is attributed to the function of the Mo-rich and relatively Cu-poor hydrothermal fluids. The more differentiated composition of the ore-hosting porphyry in the Now-Chun deposit (rhyodacite) in comparison with the Sar Cheshmeh porphyry stock (granodiorite-quartzmonzonite), which indicates the late water saturation in its parent magma, was probably the factor of generating such fluids that could segregate the significant proportion of Mo in respect to Cu from the residual melts into H2O, alkalies and silica-enriched fluid phase which ultimately resulted in forming the Mo-Cu porphyry deposit.
F Mousivand; E Rastad; M.H Emami; J.M Peter
Abstract
Various types of volcanogenic massive sulfide (VMS) deposits occurred within the northern and southern parts of the Sanandaj-Sirjan zone (SSZ). The most important VMS deposits of the south SSZ includes the Bavanat Cu-Zn-Ag (pelitic mafic- or Besshi-type), Sargaz Cu-Zn (bimodal mafic- or Noranda-type), ...
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Various types of volcanogenic massive sulfide (VMS) deposits occurred within the northern and southern parts of the Sanandaj-Sirjan zone (SSZ). The most important VMS deposits of the south SSZ includes the Bavanat Cu-Zn-Ag (pelitic mafic- or Besshi-type), Sargaz Cu-Zn (bimodal mafic- or Noranda-type), and Chahgaz Zn-Pb-Cu (silicicalstic felsic-or Bathurst-type) deposits, and the north SSZ hosts the Barika gold-rich (bimodal felsic- or Kuroko-type) VMS deposit. Comparison of the VMS deposits, and investigating of possible relationship between formation of these deposits and tectono-magmatic processes within the SSZ indicate formation of all the deposits within intra-arc rift basins related to subduction of the Neo-Tethyan oceanic crust beneath the Iranian plate during Mesozoic period. Main reasons for formation of the different VMS types within the SSZ might be due to evolution of magma nature and intra-arc rift basins. Comparison between the deposits in many aspects including host and associated rock types and ore mineral paragenesis indicate clear differences between the Bavanat and Sargaz deposits and the Chahgaz deposit. It is inferred that the differences could be due to variations in magma compositions, i.e., felsic in the Chahgaz, and mafic in the Bavanat and Sargaz host sequences. Indeed, development of the intra-arc rifting was at early/nascent stage in the Bavanat and Sargaz regions and at mature stage in the Chahgaz area.The SSZ (particularly the southern part) due to hosting various VMS type deposits and involving the known largest and majority VMS deposits in Iran is the most attractive structural zone for VMS exploration.
M Kianpour; M Sayari; A Uromeihy; M.R Nikudel
Abstract
Shear strength is one of the most important properties of mudrocks and shales in rock engineering and engineering geology. Because of the difficulty to obtain undisturbed samples of shales as required for determination of shear strength parameters, it is also the most difficult to evaluate. This research ...
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Shear strength is one of the most important properties of mudrocks and shales in rock engineering and engineering geology. Because of the difficulty to obtain undisturbed samples of shales as required for determination of shear strength parameters, it is also the most difficult to evaluate. This research investigated properties that can be used to predict the shear strength parameters of Shemshak formation shales. Thirty samples of shales from various depths were collected from boreholes in Shemshak formation in the site of Siahbishe pumped storage powerhouse. Shear strength parameters (c and ϕ), tensile strength (TS), quartz percent (Qz %), porosity (n) and density (ρ) were determined in lab for each sample. Data were analyzed statistically and with fuzzy inference system to determine the relationships between shear strength parameters with other properties. Results show that cohesion and friction angle of shales can be meaningfully predicted from a few engineering properties by fuzzy inference system. The adjusted R2 values between measured and predicted values for cohesion and friction angle are 0.95 and 0.84 respectively. Also the variation of regression coefficient (R2), performance indices (VAF) and root mean square error (RMSE) with were calculated as for the shear strength parameters, obtained from the multiple regression modeland the fuzzyinference system, revealed that the prediction performance and accuracy of the fuzzy models are high and multiple regression equations not have performance in prediction of shear strength parameters of shales.
A Khodabakhshnezhad; M Pourkermani; M Arian; A.A Matkan; A Charchi
Abstract
Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics in an area. These indices have the advantage of being calculated using ArcGIS and RS (Remote Sensing) packages over large areas as a reconnaissance tool to identify geomorphic anomalies possibly related ...
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Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics in an area. These indices have the advantage of being calculated using ArcGIS and RS (Remote Sensing) packages over large areas as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics. This is particularly valuable in Great Karoun River Basin of Zagros, where relatively little work on active tectonics based on this method was done. The study area in central Zagros fold- thrust-belt of the southwestern Iran is an area with NW–SE oriented structures provides an ideal location for testing the concept of an index to predict relative tectonic activity on a basis of river system or mountain front. Based upon values of the stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf), overall index as index of relative active tectonic (Iat) was resulted that is a combination of the other indices. This indices are used to divide the landscape into four classes of relative tectonic activity. After measuring indices it is concluded that this part of the Zagros zone has variable rates of active tectonics. Based on corrected Iat values, the study area was divided into three parts: class 1 (very high relative tectonic activity, %24 in area; such as some parts of the east and central zone where Main Zagros Reverse Fault and Dezful embayment fault have the most influence); class 2 (high relative tectonic activity, 63% in area; such as most parts of the area in east, west, north and center where action of faults are lower than the previous class); class 3(moderate, 10% in area; such as most parts of the area in north and south where action of faults are the lowest). Therefore, we don't have class 4 in this area, and 1% of basin is not measured for the indices because it is located in coastal plain of Khuzestan.
E Zarei; E Ghasemi-Nejad
Abstract
The Gurpi Formation at Farhadabad section in west of Darehshahr, was studied in detail for environmental changes and water–level fluctuations via using organic matter contents of the rock samples. Depositional environment interpretation was done based on integration of evidences derived from ...
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The Gurpi Formation at Farhadabad section in west of Darehshahr, was studied in detail for environmental changes and water–level fluctuations via using organic matter contents of the rock samples. Depositional environment interpretation was done based on integration of evidences derived from organic geochemistry analysis (TOC, TIC and Aliphatic n-alkane (short, mid and long chain n-alkane to sum of n-alkane, TAR (terrigenous-aquatic ratio), CPI(Carbon Preference Index), ratio of C17 to C27 and Isoperinoids (pr/ph,pr+ph/nC17+nC18, pr/nC17and ph/nC18) and palynofacies data (Amorphous organic matter, marine palynomorphs and palynomaceral). Statistical studies on palynomorphs confirm the results gained from the organic geochemical analysis. High ratio of palynomaceral and high TAR and CPI and dominance of long chain n- alkane and low ratio of C17/C27 (C17 relative to C27) and high ratio of Pr/Ph (>1) indicate regression condition at the base of the Gurpi Formation, Lopha Member, top of Emam-Hassan Member and Cretaceous – Tertiary boundary. On the other hand high abundance of marine palynomorphs and transparent amorphous organic matter and unimodal n-alkane with a marked even over odd predominance (CPI <1) and TAR <1 and high C17/C27 (C17 relative to C27) and low ratio of pr/nC17<0.5 indicate transgressive condition in upper part of Globotruncanita stuartiformis biozones, black shales between Lopha and Emam- Hassan, upper part of Contusotruncana contusa biozones and at the base of purple shale of the Pabdeh Formation. Maximum flooding surface probably equates the 70 Ma MFS K175, 68 Ma MFS K180 and 58 Ma MFS Pg10 of Sharland et al., 2001 that is recorded in many parts of the Arabian Plate. The relative sea level curve resulted in form this study is well in accord with the existing eustasy curves especially for the Campanian- Maastrichtian boundary indicating effect of eustasy on relative sea- level changes during this period. Combining all these data, an open marine environment with terrestrial organic input under suboxic to anoxic conditions can be concluded for the depositional course of the Gurpi Formation.
M Mojarab; H Memarian; M Zare; V Kossobokov
Abstract
The earthquake of 23 October 2011, near the Turkish city of Van, had 600 victims and caused great damages in Van, Argis, Moradiyeh and Caldiran. Review of 20th century and historical earthquakes in eastern Anatolian plate and west of Iranian plateau confirmed the activity of this area with the notable ...
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The earthquake of 23 October 2011, near the Turkish city of Van, had 600 victims and caused great damages in Van, Argis, Moradiyeh and Caldiran. Review of 20th century and historical earthquakes in eastern Anatolian plate and west of Iranian plateau confirmed the activity of this area with the notable earthquake of 24 November 1976 in Caldiran. The main objective of this paper is evaluation of predictability of earthquakes in this region. Presently, the two main approaches for predicting extreme events are precursory and pattern recognition algorithms. For this study, we applied M8 algorithm that is based on pattern recognition. In this respect,a 49 point network were designed around the epicenter of Van earthquake and M8 algorithm applied to this network. The end result was four zones with some overlaps that were proposed as CTIP (current time of increase probability). This study could predict the Van earthquake with 1/1/2008 to 30/12/2012 time window, 281 km local radius and magnitude of more than 7. In addition, forward prediction in this area shows there is no alarm for magnitude 7+ in next 5 years. This study showed the strength of M8 algorithm for predicting earthquakes in the Middle East. It can be concluded that using algorithms based on pattern recognition can play an important role for mitigation of damages in seismic events.
K. Mohammadiha; M. Moazzen; U. Altenberger; R. Hajialioghli
Abstract
The Mashhad ultramafic complex with a Permo-Triassic stratigraphic age is exposed at the NE of Binaloud Mountain and at the vicinity of the Mashhad city. This area is mainly composed of mafic and ultramafic rocks, metamorphosed carbonate and pelitic rocks and granitoids with a NW- SE trend. Serpentinized ...
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The Mashhad ultramafic complex with a Permo-Triassic stratigraphic age is exposed at the NE of Binaloud Mountain and at the vicinity of the Mashhad city. This area is mainly composed of mafic and ultramafic rocks, metamorphosed carbonate and pelitic rocks and granitoids with a NW- SE trend. Serpentinized peridotites are the main types of ultramafic rocks in this area. Minerals in these rocks include olivine, orthopyroxene, clinopyroxene, brown amphibole and opaque minerals as the original minerals and serpentinite group minerals (lizardite and antigorite), tremolite-actinolite, chlorite, talc and carbonate minerals are the secondary minerals. High pressure-low temperature metamorphic rocks, which are indicative of subduction are not present in this area, but according to the major, minor and rare earth elements chemistry of the Mashhad serpentinites, these rocks show subducted serpentinites features, with a peridotite protolith derived from lherzolite or olivine-poor harzburgite. The protolith of these rocks metasomatized and refertilized by melt formed in a subduction zone before serpentinization.
A. Rastbood; B. Vosooghi
Abstract
In this research, fracture mechanic concepts and dislocation modeling is used to examine the velocity field of GPS observables on the oblique collision zone of Arabia-Eurasia plates. For this purpose, the significant active faults in the study area were selected and proper boundary conditions applied. ...
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In this research, fracture mechanic concepts and dislocation modeling is used to examine the velocity field of GPS observables on the oblique collision zone of Arabia-Eurasia plates. For this purpose, the significant active faults in the study area were selected and proper boundary conditions applied. Numerical boundary element method with green functions obtained from Okada analytical solution were used to distribute strike slip rates among selected active faults. Velocity field obtained from the model was compared with GPS velocity field of Iranian campaign global geodynamic network and by changing boundary conditions using try and error a better coincidence were generated between model and GPS velocity field. At the final stage the difference of most of GPS observations from model results were inside of 95% confidence ellipse. Regarding accordance among model and geological slip rates, in continue of estimates we tried to get better accommodation between model and GPS velocity fields. For this purpose we tried to get better accordance between deduced slip rates by two methods with changing of boundary conditions and introducing some of geological slip rates as boundary conditions. Slip rates of other faults obtained by initial modeling were considered as boundary conditions for final modeling. These boundary conditions were changed by try and error to get close and close to geological slip rates such that the accommodation of model with GPS velocity field were retained and even get better too. Modeling results show that most of faults modeled slip rates are consistent with slip rates obtained by geological methods. The numerical results also show that most of strike slip faults in Iran are dextral. Regarding that final modeled slip rate for North Tabriz fault (6.4 mm/yr) is more than modeled slip rate for Main Recent Fault (2.2 mm/yr), the model shows that North Tabriz Fault is continuation of North Anatolian Fault in Iran.
A Mehrabi; M Dastanpour; Sh Radfar; M.R Vaziri; R Derakhshani
Abstract
In the Zagros structural zone of Iran, there is a broad range of emergent salt domes, a unique morphology in the world that is developed in tectonic environment. In the Zagros fold-thrust belt, emergent salt domes exhibit the linear patterns. Such trends indicate their relation to the linear structural ...
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In the Zagros structural zone of Iran, there is a broad range of emergent salt domes, a unique morphology in the world that is developed in tectonic environment. In the Zagros fold-thrust belt, emergent salt domes exhibit the linear patterns. Such trends indicate their relation to the linear structural features which are observable by Landsat imagery. Detection of fault lineaments and their spatial relationship with salt dome locations have been the matter of this study on statistically viewpoints. Based on the remote sensing analysis, horizontal displacements of parts of folded structures and distribution of Hormoz series salt domes, 33 fault lineaments were detected. A statistical method called the weight of evidence modeling is used for determination of the relationship between salt domes places and fault lineaments trends. For this purpose, the fault lineaments map and the center of salt domes map are converted to the raster one and buffers extracted around the fault lineaments; then, the spatial relationship between the salt domes and fault lineaments are quantified using weights of evidence method. The salt domes are associated spatially with the fault lineaments within distances of 1 km in horizon. Weights of evidence method show that the fault lineaments could be the most important foci for emplacement of salt domes in the study area.
R Ramazani Omali; N Hafezi Moghaddas; K Heidari
Abstract
Rock falls are the usual forms of slope instability in hill slopes. The high velocity and rapid occurrence are the main differences of rock fall and other rock instability. Therefore, the rock falls are among the most destructive mass movements and results in high loss of lives and heavy damage to the ...
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Rock falls are the usual forms of slope instability in hill slopes. The high velocity and rapid occurrence are the main differences of rock fall and other rock instability. Therefore, the rock falls are among the most destructive mass movements and results in high loss of lives and heavy damage to the structures, roads, residential area, farms and etc. In this research, rock fall in rocky slopes of the TepalMountain in northwest of Shahrood city was investigated. For this, the large scale geological map of area (scale of 1:10000) was produced and joint studies in 12 sections performed. Then, the slope instability was analyzed by two methods of stereographic (using Dips 5.103 software) and analytical method (by Swedge 4.078 and rock fall 4.039 softwares). The results show that all of the slopes are stable in static conditions and become instable in dynamic state. In critical states of huge raining and earthquake intense instability will be occurred and the big problems could be created for the down area of slopes. Based on the results of analytical and using the Arc GIS 9.3 rock fall hazard zonation map was produced. In addition, by overlaying of landslide hazard map and land use map, the area affected by rock falls was distinguished. The results of this study show that Salamaty road, Mazar Shohaday Gomnam and its access road, some part of AzadiPark, the tourism hotel, some of the residential area down of the Salamaty road and some parts of the AbsharPark are located in the hazard zones.
N Badri; A.L Kani
Abstract
The Gurpi Formation has a wide extent in the Zagros Sedimentary Basin.It has received considerable attention due to its unique stratigraphic position, chronostratigraphic importance, and floral and faunal diversity and abundance.In order to biostratigraphically classification and correlation of theGurpi ...
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The Gurpi Formation has a wide extent in the Zagros Sedimentary Basin.It has received considerable attention due to its unique stratigraphic position, chronostratigraphic importance, and floral and faunal diversity and abundance.In order to biostratigraphically classification and correlation of theGurpi Formation in Kuh-e-Gach andKuh-e Kurdeh sections (Lar region, Fars province), this study concentrated on the calcareous nannofloral content of sediments.From the prepared 300 microscopic slides, a total of 53 species from 30 genera belonging to 15 families were determined, described and photographed. The distribution of nannofloral assemblage of the Gurpi Formation in Kuh-e Kurdeh reveals presence of CC18 to CC24 zones indicating an Early Campanian to Early Maastrichtian age, while in Kuh-e Gach CC19 to CC24 zones with an age range of Early Campanian to Early Maastrichtian are present. Occurrence of various speciesof low latitude affinities points toward such positioning of depositional basin of the Gurpi Formation.
M. Paknia; Habib Alimohammadian; M. R. Majidifard; J. Sabouri; A. Aghanabat
Abstract
The Golbini section comprising of continuous succession of sediments ranging in age from Triassic – Jurassic formations, is situated at 35 Km north – east of Jajarm city. On the bases of studies on Dalichai Formation at this section and at about Middle Jurassic (Bathonian–Callovian ...
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The Golbini section comprising of continuous succession of sediments ranging in age from Triassic – Jurassic formations, is situated at 35 Km north – east of Jajarm city. On the bases of studies on Dalichai Formation at this section and at about Middle Jurassic (Bathonian–Callovian boundary), 3 Member, 31 Genus and 13 species of Ammonite, has been identified. For paleomagnetic analysis, with the help of portable coring machine, the total number of 155 oriented core samples were collected from limestone and clayey– limestone of this section. Then the samples were prepared for paleomagnetic analysis at Environmental and Paleomagnetic Laboratory based at Geological Survey of Iran, Tehran, Iran. The conducted paleomagnetic analysis include measurement of NRM, Susceptibility, Thermal and AF demagnetizing, Virtual Geomagnetic Polarity (VGP), identification of normal and reversal magnetic polarities and calculation of sedimentation rate. The obtained paleomagnetic results then composed with GPTS and also with proposed Bathonian–Callovian boundaries in Russia and Germany. This comparison reveals that the magnetic polarity of Golbini section is co-relatable with GPTS and also with Bathonian–Callovian boundary in Russia and Germany.
A. Naeimi; Gh. Heidarzadeh; M. R. Sheikholeslami
Abstract
The ~100km-long NE-SW Cheshmeh nay fault zone is located in Alborz-Allah Dagh Mountains. This fault zone is composed of several faults with dips between 40 to 85° toward NW or SE. The Cheshmeh nay fault zone belongs to the Shahrud fault system and has a left-lateral motion. Geomorphic evidence such ...
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The ~100km-long NE-SW Cheshmeh nay fault zone is located in Alborz-Allah Dagh Mountains. This fault zone is composed of several faults with dips between 40 to 85° toward NW or SE. The Cheshmeh nay fault zone belongs to the Shahrud fault system and has a left-lateral motion. Geomorphic evidence such as deflected streams, bisected alluvial fans and cut Quaternary deposits shows that this fault zone has been active during Quaternary. Exposure of Paleozoic and Mesozoic formations over or in contact with younger units as well as abundant thrust fault planes present in the fault zone indicate that there seems to have been a thrust faulting along the fault zone sometime during its evolution. In addition, the Cheshmeh nay fault zone coincides with the F-431 aeromagnetic lineament, indicating that the fault zone is supposed to be an old basement fault. Making part of the boundary between the Alborz and Kopeh Dagh basins, this fault zone was a basin-bounding normal fault zone which changed the kinematics into a thrust fault zone. This kinematics change resulted likely from the Iran Block moving toward the Turan and Kopeh Dagh regions and/or in Late Cretaceous. Following the regional reorganization in the Arabia-Eurasia collision zone between 3-7 Ma and/or in Quaternary, the Cheshmeh nay fault zone became a fault zone with a dominant left-lateral movement.
