M Sarhangi; A Solgi; A Sorbi; B Fayyazi; Sh Soltani
Abstract
In this paper, the relative active tectonics of the Mordaq-Chai basin has been discussed according to the geomorphic indices using Global Mapper software. The calculated indices are as follows: stream length–gradient index (SL), hypsometric integral (Hi), ratio of valley floor width to valley height ...
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In this paper, the relative active tectonics of the Mordaq-Chai basin has been discussed according to the geomorphic indices using Global Mapper software. The calculated indices are as follows: stream length–gradient index (SL), hypsometric integral (Hi), ratio of valley floor width to valley height (Vf), index of drainage basin shape (Bs),index of mountain front sinuosity (Smf), asymmetry factor (AF), and transverse index of basin topographic symmetry (T). Using above indices results, led to calculation of relative tectonic activity index (Iat).The results show that the Mordaq-Chai basin’s relative tectonic activity index falls into two groups: the first one includes the areas around the Sahand volcano crater (upper part of sub-basin one) and the Goshayesh Valley (upper part of sub-basin three), both of which have high levels of relative tectonic activity. The second one includes high lands located at northern part of the Maragheh fault towards the Kordeh-Deh village (sub-basins one and two), the opening of the Mordaq-Chai river into the Malekan plain (from the Ekiz village to the Sheikh-o-eslam village in central of sub-basin 3) and the southern portion of the Sahand Volcano’s crest (central part of sub-basin one), which all have moderate levels of relative tectonic activity.
Z Solaymani; N Taghipour; R Aharipour
Abstract
This study investigates the organic petrographic of the upper Triassic to Lower Jurassic Olang coal deposits. Olang area is located in 70 km of northeast Shahroud. This area is situated in Gheshlagh Olang synclinal which is a member of eastern Alborz coal basin. Microscopic studies showed that all three ...
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This study investigates the organic petrographic of the upper Triassic to Lower Jurassic Olang coal deposits. Olang area is located in 70 km of northeast Shahroud. This area is situated in Gheshlagh Olang synclinal which is a member of eastern Alborz coal basin. Microscopic studies showed that all three maceral groups of vitrinite, inertinite and liptinite presented in coal deposits of the Olang region and the vitrinite is most important maceral group in these coals. Macerals of vitrinite group include colotelinite, collodetrinite and corpogelinit that collodetrinite is the most abundant of maceral in coal deposits. All of inertinite macerals group observed in these coals which Semifusinite and fusinite are the most abundant in this group. Spornite, cutinite, resinite and lipthodetrinite macerals of liptinite group are present in the coals. Abundance of collodetrinite, presentation of fnginite and the absence of tellinite in these coals are usually thought to indicate deposition in neutral to weakly alkaline waters in an oxygen-rich environment.
D Raeisi; S Dargahi; S.H Moeinzadeh; M Arvin; B Bahrambeigi
Abstract
Gandom-Berian area, located on southern part of the Kavir-e Lut, covers an area around 480 km2 and morphologically is a covered messa by very dark basaltic lava flows. Their major minerals are olivine and clinopyroxene phenocrysts along with plagioclase microlites and their main textures are microlitic ...
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Gandom-Berian area, located on southern part of the Kavir-e Lut, covers an area around 480 km2 and morphologically is a covered messa by very dark basaltic lava flows. Their major minerals are olivine and clinopyroxene phenocrysts along with plagioclase microlites and their main textures are microlitic porphyry to glomeroporphiry with interestal to intergranular groundmass. The in line position of volcanic cones along the line of movements of Nayband fault show its effect on the formation of Gandom-Berian basaltic magma. The genetic realationship of these lava flows with deep seated lithospheric fractures as a result of Nayband fault, the presence of mantle xenoliths and alkaline nature of basalt all reveal a fast deep ascending of magmas. Based on geochemical analysis and occurrence of nepheline in the norm composition the Gandom-Berian basaltic lava flows belong to basanite-tephrite group. The investigation on Gandom-beriyan alkali basalts clearly shows their relationships to an intera-continental extensional environment. Low ratio of Ce/Nb, Th /Nb, U/Nb, Ba/Nb and High levels Zr with mean 234.81 indicate a none depleted asthenospheric mantle source the origin of Gandom-Berian basaltic lava flows. Enrichment and depletion of light and heavy rare earth elements respectively indicate the existence of garnet in the source rock.
P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two ...
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The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two sections are 424 and 440 m respectively and contain red and green sandstone, conglomerate and marl which are bounded unconformably between the Jahrum Formation and Bakhtiari conglomerate. Based on the field and petrographic studies, 14 sedimentary facies related to proximal, mid fan-delta; transition zone, delta slope and prodelta have been recognized for the Miocene succession. Due to the slope facies formed by the turbidity currents, grain fall and debris flows, the coarse grained clasts and poorly sorted texture, a fan-delta model is suggested for the succession. Also, the development of the slope facies indicates a paleo-slope and slope-type, deep-water fan-delta. The frequent intra-formational disconformities, irregular changes in grain size and present of gravity flows indicate an active tectonic sedimentary basin and reflux of coarse grained sediments (catastrophic events) to the proximal parts of Zagros Basin.
A.L Arab; M.R Vaziri
Abstract
A relatively thick sequence of Mid-Cretaceous (Aptian) strata exposed in Baghin area, west of Kerman, Iran. The strata comprise a diverse macro-fauna such as bivalves, echinoids, gastropods, corals and brachiopods. Among the bivalves, presence of a pectinid species, Neithea notabilis is relatively conspicuous. ...
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A relatively thick sequence of Mid-Cretaceous (Aptian) strata exposed in Baghin area, west of Kerman, Iran. The strata comprise a diverse macro-fauna such as bivalves, echinoids, gastropods, corals and brachiopods. Among the bivalves, presence of a pectinid species, Neithea notabilis is relatively conspicuous. The studies show a marked morphological variation in the species. Also, biometric analysis reveals a mark interspecific variation in the studied specimens. Low diversity in the genus Neithea could be due the high isolation of the Baghin area and therefore its limited connection to other water masses during the Mid-Cretaceous or because of its contribution to the diversification trend seen in the Mediterranean region.
M Abdi; M.H Karimpour; M.H Zarinkoob
Abstract
The main purpose of this study is processing of raw data by factor analysis method and having interpretation and integration them by geological, alteration and mineralization data. The distinctiveness of third factor of factor analysis for Au, Mo and W and the coincidence of third factor anomalies by ...
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The main purpose of this study is processing of raw data by factor analysis method and having interpretation and integration them by geological, alteration and mineralization data. The distinctiveness of third factor of factor analysis for Au, Mo and W and the coincidence of third factor anomalies by gold, high primary sulfide bearing area, secondary iron oxide and sericitic and silicic alterationrevealed that the third factor of factor analysis is the agent of mineralization in the study area. The suitable tectonic setting, shallow depth intrusiveswithintermediate composition, calc-alkalineand oxidant magmatism, anomaly of gold and disseminated mineralization in thehost rock and sulfide veinlet accompanied byabundant secondary iron oxide providedproperconditions for porphyry and epithermal type gold mineralization in the study area.
H Amin-Rasouli; Y Lasemi; S Zaheri
Abstract
The middle Cambrian-early Ordovician transgression in the AlborzMountains resulted in the deposition of members 1 through 3 of the Mila Formation showing an overall transgressive trend. This succession is bounded unconformably by the Top-Quartzite of the Lalun Formation at the below and member 4 of the ...
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The middle Cambrian-early Ordovician transgression in the AlborzMountains resulted in the deposition of members 1 through 3 of the Mila Formation showing an overall transgressive trend. This succession is bounded unconformably by the Top-Quartzite of the Lalun Formation at the below and member 4 of the Mila Formation at the top. It consists of tidal flat to open marine facies, which have been deposited in an extensive ramp on the Proto-Paleotethys passive margin of northern Gondwana. It is composed of six depositional sequences aged middle to early- late Cambrian, related to Sauke 2 supersequence. These sequences are correlated with those recognized in other parts of the world including Oman, China, and North America suggesting that they were formed as the consequence of global relative sea level fluctuation.
N Norouzi
Abstract
Regarding to the destructive earthquakes that happened in the world and Iran, potential influence of surface geology on strong ground motion and the damages due to the earthquakes that named as site effect is well known. This study is a section of seismic microzonation of Shahreza city. In this study ...
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Regarding to the destructive earthquakes that happened in the world and Iran, potential influence of surface geology on strong ground motion and the damages due to the earthquakes that named as site effect is well known. This study is a section of seismic microzonation of Shahreza city. In this study we further investigated the site effect by microtremor measurement and for analysis of microtremor data; H/V (Nakamura's technique) was used. Accordingly, the microtremor measurement has been estimated for 64 sites of Shahreza city. Finally, the results are presented in different maps as natural period distribution of site, amplification factors and Vulnerability Index. The calculations revealed that the natural period is differing from 0.04 to 0.38 and the amplification factor differs from 1.21 to 6.88, too. The results showed a relatively acceptable connection with the morphology of the region. Thus, the natural period is decreased by moving toward the mountains around the city, whereas the natural period is increased by moving toward the center of plain. The results of this study as preliminary investigation can be used with detailed investigations in metropolitan planning for Expansion of City, estimation of seismic risks and crisis management due to an earthquake.
T Sarbandi Farahani; M.R Majidifard; M.R Kebriaee- Zadeh; M Mohammadi
Abstract
The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of ...
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The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of the overlying Lar Formation, is completely exposed on the southern slopes of the kuh-e-Rahband. At this area, the sedimentary succession with nearly 122 m thickness subdivided into four members starting with marl and medium to thick-bedded grey limestones to marly limestones. The lower boundary with the siliciclastics of the underlying Shemshak Formation is disconformity, whereas the upper boundary with the light and cliff-forming carbonates of the Lar Formation is rather inconspicuous and transitional. The Dalichai Formation in the east of Mahdishar section is fossiliferous. The ammonite fauna consist of 5 families, 22 genera and subgenera and 40 species, among them 8 species are recorded for the first time from Iran. Based on the ammonite fauna, 9 biozones were recognized that indicated the age of the Dalichai Formation in the investigated area ranges from the Upper Bajocian? to Upper Oxfordian. Pleobigeographically, the fauna shows close relationship to west Europe and sub-mediterranean regions. This indicates a paleogeographic position of the area at the northern Tethys during the Middle Jurassic.
M Biralvand; M Mohajjel; M.R Ghassemi
Abstract
In this study, brittle deformation in Takab complex is discussed. Deformation in the Takab area has been controlled by two sets of major faults. The first set is characterized by NNW-SSE trending steeply-dipping dextral strike-slip faults with reverse component. The second set includes WNW-ESE trending ...
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In this study, brittle deformation in Takab complex is discussed. Deformation in the Takab area has been controlled by two sets of major faults. The first set is characterized by NNW-SSE trending steeply-dipping dextral strike-slip faults with reverse component. The second set includes WNW-ESE trending moderately-dipping reverse faults which have been obviously displaced by the first set. The basement metamorphic rocks are exposed in the hangingwall of the faults indicating thick-skinned type of deformation and exhumation in the area. The major strike-slip reverse faults have resulted in dextral inclined transpression in the Takab complex area. Fault-related folds in hangingwall and footwall of the faults especially in the Cenozoic sediments indicate young activity and uplift in the area. Development of normal faults and local folds, as well asthe occurrence of earthquakes in the area imply that it is tectonically active. Structural analysis in this area reveal that the major steeply-dipping strike-slip reverse faults have controlled deformation and changedthe homogeneous strain to partitioned strain.Deformation of Cenozoic rocks overlying the basement metamorphic rocks indicate a dextral inclined transpression. Deformation in the younger sedimentary cover (Cenozoic sediments) is related to thick-skinned deformation in the basement metamorphic rocks.
V. Esavi; J. Karami; A. Alimohammadi; S. A. Niknezhad
Abstract
In recent decades digging deep wells and a half deep flume was gradually replaced aqueduct that by the relative merits is attended the great environmental effects such as loss underground water level and creating subsidence phenomenon for most regions of interest. Recent studies have been accomplish ...
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In recent decades digging deep wells and a half deep flume was gradually replaced aqueduct that by the relative merits is attended the great environmental effects such as loss underground water level and creating subsidence phenomenon for most regions of interest. Recent studies have been accomplish in order to replace the underground dams instead of medium and small dams in order to optimize storage and use of water resources and reduce the environmental impacts. Site selection of underground dams quite complicated process due to geological, geomorphological and hydrological point of view. Determination of the role adjustment and importance of the variables is based on expert groups thoughts and usually this important is verbalize in linguistic variables form. Analytical Hierarchy process have possible in using the linguistic variables along quantitative variables and essentially is based on expert opinions. In recent years in order to increase the capability of AHP, this method combined with fuzzy method and in the Fuzzy-AHP algorithm is presented. In this paper two methods of AHP and Fuzzy-AHP were used in determining appropriate areas for underground dams. Buckley and Bonissone methodes was used for implementing Fuzzy-AHP method and Yager method was used for defuzzicating fuzzy utility values . From totale 56 outputs points of subbasine in AHP method, 26 points and in Fuzzy-AHP method, 15 points were overlapping with suitable and accessible areas. The results showed that the Fuzzy-AHP method has more flexibility and greater ability to determine appropriate areas dam.
B Taherkhani; H Nazari; M Pourkermani; M Arian
Abstract
The E-W trending North Qazvin Fault is situated in north & northeast of Qazvin city in south-central Alborz. Across the fault, Karaj formation (Eocene) is thrusted over Hezardarreh Formation (A) and the alluvial B Formation. It could be the source for the 1119 AD earthquake with an estimated magnitude ...
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The E-W trending North Qazvin Fault is situated in north & northeast of Qazvin city in south-central Alborz. Across the fault, Karaj formation (Eocene) is thrusted over Hezardarreh Formation (A) and the alluvial B Formation. It could be the source for the 1119 AD earthquake with an estimated magnitude of Ms: 6.5. The North Qazvin Fault is a seismically active fault, therefore it is one of the most important earthquake threats for the Qazvin as an industrial city of Iran. Morphotectonicand detailed field studies along a part of the North Qazvin Fault allows us to measure horizontal and vertical offsets caused by recent movements on this fault. One of the measured horizontal and vertical displacements due to the recent movements on the fault is 4 and 3.5 meters, respectively. The geometry (strike, dip and rake) of the North Qazvin Fault in this part is 090˚, 45˚, 51˚ respectively. Our investigations show that the North Qazvin Fault is a north-dipping compressional fault. The North Qazvin Fault and its surrounding faults such as Najm-abad fault appear as a propagating fault system which has left-lateral compressional kinematics in southern part of the west-central Alborz.
R Ferdowsi; M Moayyed; A Kamali
Abstract
The Kalaibar nepheline syenitic body is located in East Azabaijan, NW of Iran. This alkalic body generally intruded semi-deeply into the Cretaceous and Eocene volcanic and sedimentary rocks. Based upon chemical classification, the composition of studied intrusive bodies are nephelines bearing syenite ...
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The Kalaibar nepheline syenitic body is located in East Azabaijan, NW of Iran. This alkalic body generally intruded semi-deeply into the Cretaceous and Eocene volcanic and sedimentary rocks. Based upon chemical classification, the composition of studied intrusive bodies are nephelines bearing syenite (nepheline syenite), nepheline bearing gabbro (alkalic gabbro), syenite and quartz monzonite (syeno-diorite) in order of abundance. In addition, the composition of accompanying dyke and pegmatitic units are nepheline syenite, syenodiorite and gabbro. Common textures of studied rocks are prophyritic granular and granular and accompanying dykes have fine grained granular, porphyritic and coarse grained granular textures. According to mineralographic studies and XRD analysis results, the main mineral phases contain orthoclase, albite, nepheline, oligoclase, hornblend, augite and Melanite. The nature of parent magma of these intrusives is potassium rich alkaline, metaluminous and miaskitic. Petrographical and geochemical studies based upon accessory and rare elements illustrate that these intrusives formed in a subduction or post collision related tectonic setting, which their lithological variety is justifiable by fractionation crystallization. The studied intrusives show the enrichment of Zn, Ba, Sr, Th and Pb and enrichment of Co, Sr, Pb and V in accompanying dykes. LREEs relative to HREEs show enrichment. Comparison of studied body with some other ones of corresponding type of the world in terms of the amount of accessory and rare elements shows that the Kalaibar nepheline syenitic body is resemble to the central Anatoly (Turkey), Zijinshan (china) and Musale (India) bodies.
B. Oskooi; G.A. Fanaee-Kheirabad
Abstract
Geothermal energy is playing a large role as an alternative energy source for both electricity generation and space heating. Sabalan is a high temperature geothermal region in Ardabil province northwestern of Iran. In this study the conductivity structure of the top crust (depth lower than 2 kilometers) ...
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Geothermal energy is playing a large role as an alternative energy source for both electricity generation and space heating. Sabalan is a high temperature geothermal region in Ardabil province northwestern of Iran. In this study the conductivity structure of the top crust (depth lower than 2 kilometers) is examined using data from collected 212 magnetotelluric (MT) and time-domain electromagnetic (TDEM) soundings across the Sabalan volcano in 1998. The MT data collected between 1-8192 Hz is of useful quality and provides good control on the surface layers in majority of sites. The MT data were corrected for static shift effect using TDEM data. The TDEM data and MT data were jointly inverted to yield 1D and 2D models. In practice for geothermal investigation, measured MT data are never entirely 1D and diagonal elements of the impedance tensor are always non-zero. However, in many cases the Earth response is dominated by an overall 2D structure, permitting data analysis within these lower dimensions. In this study, in order to have the best possible interpretation we used two modes MT data in 2D inversion. Static shift correction and inversion approach accomplished by using WinGlink software. We choose three intersect profiles with 54 MT sites along with, to show resistivity distribution around Sabalan and try to predict the main intrusive magma chamber position as the heat source of the system. MT resistivity images confirmed the findings of previous surveys and the reported geological features in the Sabalan field. To have a better view about resistivity distribution, we combine the 2D models at the intersection points to obtain a 2.5D view about the resistivity in the area. The resulting models reveal the extension of the high conductivity anomalies in the western and southwestern parts of the area that most probably is related to the main heat source of the geothermal system at shallow depths.
Z. Jeddi; Mohammad Tatar; B. Saeedi Razavi
Abstract
The catastrophic December 26, 2003 Mw 6.6 Bam earthquake is one of the most disastrous earthquakes in Iran. This earthquake attracted much attention, and has been far more studied that which would be expected from a moderate magnitude earthquake. Nevertheless, there are doubtful results related to geometry ...
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The catastrophic December 26, 2003 Mw 6.6 Bam earthquake is one of the most disastrous earthquakes in Iran. This earthquake attracted much attention, and has been far more studied that which would be expected from a moderate magnitude earthquake. Nevertheless, there are doubtful results related to geometry and location of the causative fault that produced the Bam earthquake. As very little is known about the 3-D structure of the region and in order to define the 3-D velocity structure and the geometry of the active fault in the Bam area travel time data from the aftershock series of the Bam earthquake are inverted simultaneously for both hypocenter locations and 3-D Vp structure. The data used for this purpose are 6201 P-wave arrival times from 544 selected local earthquakes recorded by temporary 23 short-period seismic stations. 3-D P-wave velocity variations down to 20 km depth were obtained. The acquired tomographic images show that the 3-D velocity structure beneath the region is heterogeneous in that low velocity appears throughout the region down to ~10 km depth, and high velocities occur in western part from ~14 km depth. Velocity structure of seismogenic region is well resolved to a depth of 20 km. Difference in observed velocities in two sides of the Bam fault in depth of 10-20 km is clear in tomographic images and on cross sections. We relate this difference in velocity to the effect of the reverse Bam-Baravat fault which seems influenced the deeper layer down to 20 km depth. This implies that the pre-existing reverse Bam-Baravat fault is a major active structure in the region that could be caused the December 2003 Bam earthquake.
F. Safari; M. Yazdi-Moghadam; F. Sajjadi
Abstract
To recognize different species of the genus Orbitolina and determine the age of the Dariyan Formation, the upper limy part of the Dariyan Formation in Dashtak section was sampled and studied. Based on the size, shape and complexity of embryonic apparatus, five species belonging to subgenus Mesorbitolina ...
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To recognize different species of the genus Orbitolina and determine the age of the Dariyan Formation, the upper limy part of the Dariyan Formation in Dashtak section was sampled and studied. Based on the size, shape and complexity of embryonic apparatus, five species belonging to subgenus Mesorbitolina were recognized as below: Orbitolina (Mesorbitolina) lotzei, Orbitolina (M.) parva, Orbitolina (M.) texana, Orbitolina (M.) subconcava, Orbitolina (M.)sp. cf .M. pervia According to stratigraphic distribution of the mesorbitolinids, the upper part of the Dariyan Formation can be ascribed to the late early Aptian-late Aptian. The early/late Aptian boundary coincides with first occurrence of O. (M.) parva
M. Rahgoshay; J. Mehdipour Ghazi; H. Shafaii Moghadam
Abstract
Peridotites (Cpx-bearing harzburgites, lherzolites, wherlites and dunites) associated with pegmatite gabbros, gabbro impregnations, gabbroic-diabasic dikes, pyroxenites and websterites are the main constituents of the mantle sequence in the Nain ophioliote assemblage. Petrographic and geochemical studies ...
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Peridotites (Cpx-bearing harzburgites, lherzolites, wherlites and dunites) associated with pegmatite gabbros, gabbro impregnations, gabbroic-diabasic dikes, pyroxenites and websterites are the main constituents of the mantle sequence in the Nain ophioliote assemblage. Petrographic and geochemical studies indicate that peridotites in the Nain ophiolites are Cpx-bearing harzburgites with Al-rich spinels (Cr#=16.12-41.55) equilibrated at about 1000˚C. Pegmatite gabbros are found as small pockets within peridotites showing deformed clinopyroxenes and plagioclases. Gabbro-diabase dikes, mostly rodingitized, injected into the peridotites without chilled margins. These dikes are geochemically co-genetic with pillow lavas and micro-gabbros of the crustal sequence, but display variable degrees of partial melting. Based on the geochemistry of the mafic rocks and the peridotites, we suggest that Nain ophiolites were developed in a back arc spreading basin.
E Moosavi; M Mohajjel
Abstract
Two main metamorphic events have occurred within Muteh- Golpayegan metamorphic core complexes (including eastern and western complexes) in the Sanandaj-Sirjan zone. Some grain-scale deformations were also happened in relation to these metamorphisms which have produced various deformation microstructures. ...
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Two main metamorphic events have occurred within Muteh- Golpayegan metamorphic core complexes (including eastern and western complexes) in the Sanandaj-Sirjan zone. Some grain-scale deformations were also happened in relation to these metamorphisms which have produced various deformation microstructures. Microfaults are among the microstructures that were formed during brittle conditions. Bulging recrystallization of quartz and rarely feldspar grains, and bookshelf structure of fragmented feldspar porphyroclasts indicate various deformation and formation of shear zones under low-temperature conditions in the eastern complex. Polygonal granoblastic texture of polycrystalline quartz porphyroclasts documents post-mylonitization annealing at medium- grade conditions in shear zones of eastern complex. Chessboard pattern quartz subgrains propose high-grade metamorphic conditions during the first deformation. However, their undulatory extinction reveals low-grade conditions for the second deformation. Polygonal granoblastic texture of chevron folded feldspar grains also accurately supports these conditions during the two mentioned deformations. In general, considering deformation microstructures and conditions, three stages of recrystallization are respectively recognizable in the Muteh-Golpayegan metamorphic complexes including: 1- high-grade static recrystallization subsequent to early metamorphic event, 2- dynamic recrystallization and related mylonitization under low-grade to locally medium-grade conditions, 3-post-mylonitization static recrystallization in medium-grade conditions. The north Golpayegan intrusive bodies can be considered as the heat source for annealing in the western complex but the cause of annealing is not evident in the eastern complex.
E. Rastad; H. Tajedin; A. Yaghubpur; M. Mohajel
Abstract
The Barika gold (and silver) rich-massive sulfide deposit is located 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are metamorphosed volcano-sedimentary rocks in green schist facies, and include association of meta-andesit, meta-tuffite, ...
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The Barika gold (and silver) rich-massive sulfide deposit is located 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are metamorphosed volcano-sedimentary rocks in green schist facies, and include association of meta-andesit, meta-tuffite, phyllite, and slate rocks. The Barika deposit is metamorphosed to greenschist facies, and underwent Barika shear zone- related deformation. The metamorphism/deformation events have superimposed on the synvolcanic stratiform ore and resulted in a variety of mineralogy and textures. Ore minerals in the deposit were originally composed of pyrite, sphalerite, galena, tetrahedrite- tenantite and stibnite which were deposited during synvolcanogenic hydrothermal activity. Gold probably was occurred as submicroscopic inclusions or invisible gold locked in pyrite and electrum in barite. Prograde metamorphism/deformation obliterated almost the sedimentary textures in the stratiform ore. the regional metamorphism have resulted in the development of granoblastic textures with triple junctions in pyrite which lead to migration of submicroscopic gold to the crystal boundary to form microscopic electrum. Shear zone - related deformation, lead to chemical remobilization of pre-existing mobilizable metallic constituents (e.g., Au, Ag, Pb, Sb, As and Hg) and eventually reconcentrated them as visible electrums associated َwith Ag, As, Sb, Pb, Hg – rich sulfosalt minerals at microfractures and open spaces which have developed during the shearing deformation. Metamorphic/deformation remobilization was important in releasing refractory Au from sulfides and locally concentrating it in a recoverable form (electrum).
Peyman Heidarian; A. Azhdari; M. Jodaki; J. Darvishi Khatooni; R. Shahbazi
Abstract
Significant damages have been caused by dust storm in Iran, particularly in Khuzestan province. Thus, as a primary step to fight with dust storms, it is necessary to map dust sources. The purpose of this study is to identify dust sources using a combination approach of remote sensing, GIS and sedimentology ...
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Significant damages have been caused by dust storm in Iran, particularly in Khuzestan province. Thus, as a primary step to fight with dust storms, it is necessary to map dust sources. The purpose of this study is to identify dust sources using a combination approach of remote sensing, GIS and sedimentology in Khuzestan province. For this, spatial data of soil, land use, climate, slope (collected from related organizations) and sedimentology were used as constraint layers, and vegetation, land surface temperature (LST) and soil moisture constitute the main layers. Sedimentology map was prepared by field sampling (900 samples) and remote sensing techniques. Also the main layers were extracted by performing the necessary computational processes on Landsat 8 satellite images. The constraint layers were applied to remove the areas without any potential of dust source. In next step, main layers weighting was done using pairwise comparison and Fuzzy Analytic Hierarchy Process (FAHP) methods. For preparing map of dust sources, each major layer was multiplied by corresponding weight and were then integrated to present a dust source zonation map. To validate the results, a field work was carried out in 180 points of source areas that verifies high accuracy of the prepared map. Results showed that 9 percent of Khuzestan plain, equivalent to 349254 hectares, are dust-generating sources. Based on land use type and area, the identified zones include destroyed range, rainfed agriculture lands, bare lands, wetlands, dried ponds and irrigated agriculture lands, respectively.
H. Hajialibeigi; S. A. Alavi; J. Eftekharnezhad; M. Mokhtari; M. H. Adabi
Abstract
The Chenareh Anticline is located between Lurestan Zone (in north) and Dezful Embayment (in south) in the Zagros Folded-Thrust Belt. This anticline is documented and interpreted to constrain the kinematic evolution of a fold. The development of fractures is confined to the Asmari Formation. In the study ...
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The Chenareh Anticline is located between Lurestan Zone (in north) and Dezful Embayment (in south) in the Zagros Folded-Thrust Belt. This anticline is documented and interpreted to constrain the kinematic evolution of a fold. The development of fractures is confined to the Asmari Formation. In the study area, the fracture pattern is interpreted to identify six main fracture sets (from A to F). The first fracture set (A) striking 68◦, oblique to the further fold trend, is interpreted as a regional fracture set that predates compression phase. The second set (B) striking 110◦, parallel to the fold trend, are found in both limbs and interpreted as extensional fractures. Two other fractures set, (D, E) striking 10◦-70◦ and 80◦-140◦ are conjugate fractures existing in both limbs. The youngest fracture set (E) had formed during the folding process especially at the late stage of fold growth. Later on the first fracture group (A) are reactivated and called as (F) fracture set. Due to geometric characteristics of the Chenareh Anticline, it is categorized as a fault -propagation fold which is affected by the blind Balarud fault zone. The Z-shaped hinge zone of present anticline is attributed to the linkage of the two early individual anticlines.
Economic Geology
Reza Ghezelbash; A. Maghsoudi
Abstract
Varzaghan district is located in NW of Arasbaran magmatic belt (AMB) which is one of the most highly mineralized region in Iran and host to a significant number of porphyry Cu deposits such as Sungun Cu-Mo porphyry deposit. The main goal of this study is synthesizing diverse raster-based evidence layers ...
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Varzaghan district is located in NW of Arasbaran magmatic belt (AMB) which is one of the most highly mineralized region in Iran and host to a significant number of porphyry Cu deposits such as Sungun Cu-Mo porphyry deposit. The main goal of this study is synthesizing diverse raster-based evidence layers including geochemical, alteration and geological geo-data sets for mineral prospectivity modeling (MPM). For this purpose, firstly, continuous values of six favorable evidential maps as main criteria (geochemical signature of PC1 scores, values of proximity to argillic, phyllic and iron-oxide alterations, values of proximity to Oligo-Miocene intrusions and fault density) were divided into reasonable classes by applying concentration-area fractal model and then discretized layers were integrated using analytical hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS) to generate a final map of porphyry Cu potential within the central part of Varzaghan district. Finally, the success-rate curve of the AHP-TOPSIS model as a quantitative evaluation method according to the locations of known Cu occurrences was drawn. Results revealed the successful performance of AHP-TOPSIS model in portraying the prospective areas related to porphyry Cu mineralization.
M. Esmaeli; M. Lotfi; N. Nezafati
Abstract
Khalyfehlou Cu deposit (southeast of the Zanjan), is the volcanic-hosted vein-type deposit located in the Tarom metallogenic zon,Western Alborz (northwest of Iran) . Tarom zone consist mainly of volcanic and volcaniclastic rocks of the Karaj Formation (Early to Middle Eocone). Regarding the stratigraphic ...
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Khalyfehlou Cu deposit (southeast of the Zanjan), is the volcanic-hosted vein-type deposit located in the Tarom metallogenic zon,Western Alborz (northwest of Iran) . Tarom zone consist mainly of volcanic and volcaniclastic rocks of the Karaj Formation (Early to Middle Eocone). Regarding the stratigraphic position, the Karaj Formation is divided into two members: Kordkand and Amand. The Kordkand member is overlain by the Amand member .The Amand member is divided into six units, Ea1 through Ea6. The Khalyfehlou Cu deposit is located in Ea5 and Ea6 units of Amand member .The Karaj Formation is interrupted by large and linear intrusions with calc alkaline affinities. Host rocks are green tuffs and, rarely, andesites. The patterns of rare earth elements in the studied samples indicate the negative anomaly of Eu element due to plagioclase subtraction. In all the samples, the enrichment of light rare earth elements (LREE) and large lithophil ion (LILE) elements and the depletion of strong field strength elements (HFSE) are observed. This probably indicates the common origin of these rocks. Main minerals include chalcopyrite, bornite, chalcocite, and covellite and gangue minerals including quartz, sericite, and calcite. In this paper the origin of ore-forming fluids and genesis of Khalyfehlou Cu deposit is studied using sulfur and oxygen isotope data. The sulfur isotope values for the chalcopyrite range from −2.0 to −5.3‰. Negative sulfur isotopes values and the occurrence of framboidal pyrite in the tuffaceous sandstone host rocks suggests a sedimentary origin for the sulfur. The oxygen isotope composition of quartz from the veins ranges from 12.3 to 14.3‰. The δ18Ofluid values calculated from the oxygen isotope data range from 0.6‰ to 3.6‰. The O isotopic characteristics indicate that the ore-forming fluids for the Khalyfehlou deposit was meteoric-formational water.This study suggests that mineralization at the Khalyfehlou deposit is similar to cordilleran vein-type deposits.
Mostafa Moradi; Asadollah Mahboubi; Mohammad Khanehbad; Ali Ghabieshavi
Abstract
The Asmari Formation is the main reservoir rock for the Aghajari oilfieild. It is composed of about 400-meter limestone, dolostone and interlayers of sandstones. Study of 1200 meters drilling cores, 2800 microscopic thin sections, 12 SEM analyses along with 125 routine core tests in 5 cored wells indicate ...
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The Asmari Formation is the main reservoir rock for the Aghajari oilfieild. It is composed of about 400-meter limestone, dolostone and interlayers of sandstones. Study of 1200 meters drilling cores, 2800 microscopic thin sections, 12 SEM analyses along with 125 routine core tests in 5 cored wells indicate that the Asmari Formation was effected by various diagenetic processes such as micritization, compaction, cementation, fracturing, dissolution and dolomitization. Some of these processes (e.g. dissolution, dolomitization and fracturing) have constructive effects on the reservoir quality and created wide variety of porosity types including vuggy, intercrystaline and channel in upper parts of the Asmari Formation. Destructive diagenetic processes (micritization, compaction and cementation) have destroyed pore spaces and make the lower parts of the Asmari (specially zone 5) to a non-reservoir unit. Porosity-permeability plots on the Lucia's diagram show sandstones and carbonates rocks with interparticle porosities have good reservoir qualities and always plot on upper parts of classes 1-3. Samples with fracture porosity mainly plot on upper part of class 1. This shows fractures has no considerable role in promoting the porosity, but they strongly increase permeability. Dolostones and the rocks with vuggy porosity have plotted on classes 2 and 3 (high porosity, relatively high permeability). Paragenetic secession of the Asmari Formation shows the diagenetic processes occurred syn-sedimentary on sea floor, after sedimentation during the low-deep burry and uplift. The results of this study can be useful in detection of reservoir zones, increasing of hydrocarbon production and enhanced recovery of this oilfield.
H. Hamzehloo; E. Farzanegan; H. Mirzaei
Abstract
The December 20, 2007 earthquake has occurred three months after the September 16, 2007 earthquake near the Tabriz city in East Azarbaijan province. We have used SH- waves accelerographs data and Brune model to estimate the causative fault plane parameters. The strike, dip and rake have been ...
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The December 20, 2007 earthquake has occurred three months after the September 16, 2007 earthquake near the Tabriz city in East Azarbaijan province. We have used SH- waves accelerographs data and Brune model to estimate the causative fault plane parameters. The strike, dip and rake have been estimated as 310o, 85o and 170o, respectively. The focal mechanism shows right- lateral strike slip, which is consistent with the North Tabriz Fault. This is the first focal mechanis for the North Tabriz fault based on the strong ground motion data.
