Original Research Paper
Economic Geology
Mohammad Boomeri; Somayeh Naruyi; Mohammadreza Ghodsi
Abstract
The Chah Sorbi area is located in the Sistan suture zone. The geology in the Chah Sorbi, from old to young, are flysch type rocks, Zahedan granitoid, subvolcanic granodiorite porphyry, dioritic to granodioritic dikes and recent deposits. The Pb mineralization in the study area occurs as thin and short ...
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The Chah Sorbi area is located in the Sistan suture zone. The geology in the Chah Sorbi, from old to young, are flysch type rocks, Zahedan granitoid, subvolcanic granodiorite porphyry, dioritic to granodioritic dikes and recent deposits. The Pb mineralization in the study area occurs as thin and short galena-bearing veins associated with pyrite, quartz, calcite, goethite and limonite. The host rocks are flysch and the subvolcanics that are undergone phyllic and argillic alteration. Propylitic alteration occurs in most dikes in the area and is characterized by chlorite, calcite and epidote. In northeast part of the area, the subvolcanic rocks were intruded by quartz stockworks and was strongly altered. The most intensive and extensive alteration with these rocks is phyllic alteration that is characterized by pyrite, quartz and sericite. Cu mineralization in the stock is characterized by presence of Cu-carbonate and –sulfides. Galena-bearing veins are probably epithermal type in the Chah Sorbi area that is situated in margin of a porphyry Cu system. Major and minor elements were measured in 7 least altered samples from intrusive rocks. The igneous rocks in the study area are metaluminous that are formed from a calc-alkaline magma in a continental margin volcanic arc setting.
Original Research Paper
Economic Geology
jahangir esmaeili; ahmad khakzad; mansor vosoghi abedini
Abstract
This area has been located in a scene ETM No. 164-37 and ASTER linear band prediction satellite image No. AST-L1A:002:ASTL1A 0108220733380109011021. Such measured images in different band combinations will be used for extracting of geological structures and types of alterations (iron oxide, Argillite ...
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This area has been located in a scene ETM No. 164-37 and ASTER linear band prediction satellite image No. AST-L1A:002:ASTL1A 0108220733380109011021. Such measured images in different band combinations will be used for extracting of geological structures and types of alterations (iron oxide, Argillite and Carbonate) and for detecting different stones and minerals of the ground, a spectrum range of 1.5 to 2.5 μ is very important.This range includes short to average IR range covering six linear band predictions (SWTR bands). On the other side, to use spectral reflectance curves of such minerals in USGSENVI spectral library for spectral analysis, it is necessary to resample the curves to the spectral range of ASTER. Linear Band Prediction methods, LS-Fit, Matched Filtering and BandRATIO used of ASTER images for all Minerals and iron alterations and for iron oxides there were also used visual interpretations and ETM images were used in band combination of RGB:531. Considering the petrological and geological situation of studied area (Scale 1:25000 of Kamoo), the type of Alteration and its index minerals detailed as below; Alteration of iron (Gotit, Hematit and Jarosit and Limotit), alteration of Argilic (Kaolinite, Motmorilonit, Ilite and Haloysite) and carbonate (Calcite and Dolomite) have been considered. Alterations present in remote sensing studies are in conformity with field and results obtained fromtypes of analysis conducted.
Original Research Paper
Economic Geology
Sanaz Ahmadi; Mohammad Ali Salehi; H Jamali
Abstract
The Hassan Abad Zn-Pb deposits is located in the northeast of Isfahan, Central Iran zone. The host rock of this mineralization is the dolomite of Middle Triassic Shotori Formation. Mineralization included galena, sphalerite, sulfosalts, pyrite and barite which associated with dolomitization. Based on ...
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The Hassan Abad Zn-Pb deposits is located in the northeast of Isfahan, Central Iran zone. The host rock of this mineralization is the dolomite of Middle Triassic Shotori Formation. Mineralization included galena, sphalerite, sulfosalts, pyrite and barite which associated with dolomitization. Based on petrographic studies six types of dolomites (in terms of shape and size of the crystals, the distribution of crystal size and shape of the border crystal) has been identified, that including very fine, medium, coarsely crystalline dolomite, Saddle dolomites and filling pore spaces and veins. The first and second type of dolomites were formed as synsedimentary or diagenetic dolomite with sabkha origin. The third type of dolomite in the late stages of diagenesis was formed in shallow burial conditions due to recrystallization of small crystalline dolomite. Coarse-grained and saddle dolomites have been created under the conditions of deep burial and as hydrothermal dolomites and are related to mineralization. Move over, the origin of magnesium for fine crystalline dolomites were seawater, and for coarse crystalline dolomites are probably the brine fluids of the compacted Sorkh Shale Formation and hydrothermal fluid.
Original Research Paper
Petrology
Zohreh Salimi; mohsen moazzen; Robab hajialioghli
Abstract
The ophiolitic-metamorphic complex of Allahyarlu, attributed to pre-Cretaceous, is exposed at the core of Allahyarlu anticline in NW Iran and NE of Meshginshahr. The metamorphic rocks are important constituents of this complex. These rocks include garnet schist, garnet gneiss, amphibolite, marble, associated ...
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The ophiolitic-metamorphic complex of Allahyarlu, attributed to pre-Cretaceous, is exposed at the core of Allahyarlu anticline in NW Iran and NE of Meshginshahr. The metamorphic rocks are important constituents of this complex. These rocks include garnet schist, garnet gneiss, amphibolite, marble, associated with blocks of serpentinite and tectonic slices of gabbro, dunite and diabase. Quartz, garnet, biotite, muscovite and chlorite are the primary minerals in the garnet schists, while zircon, secondary chlorite, opaque minerals and plagioclase make the minor phases. The main minerals in the garnet gneiss samples are K-feldspar, quartz, plagioclase, muscovite, biotite and garnet and tourmaline, zircon and secondary chlorite are the minor phases. Garnet in garnet schists and garnet gneisses is almandine-rich and white mica is muscovite –rich. According to microprobe analyses, brunvigite is the main constituent in chlorite solid-solution. Te average temperature estimated for metamorphism of garnet schists and garnet gneisses, using different methods is 530 to 570 C. Using apetrogenetic grid indicates pressure of ca. 4.5 kbar for the paek of metamorphism. The estimated pressure and temperature are in accordance of Barrovian metamorphic gradient for these rocks, which occurs in crustal thickenning zones such as island arcs, volcanic arcs and collision zones.
Original Research Paper
Economic Geology
Ali Rajabzadeh; Hossein Kouhestani; Mir Ali Asghar Mokhtari; Afshin Zohdi
Abstract
In this study, petrography and major and minor elements geochemical data are presented for sandstone layers of the Upper Red Formation (URF) in the Chehrabad Pb-Zn deposit (NW Zanjan) to investigate sandstone composition, tectonic setting and their source rock. In this area, URF has 980 m thickness and ...
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In this study, petrography and major and minor elements geochemical data are presented for sandstone layers of the Upper Red Formation (URF) in the Chehrabad Pb-Zn deposit (NW Zanjan) to investigate sandstone composition, tectonic setting and their source rock. In this area, URF has 980 m thickness and is conformably overlies the Qom Formation limestones. Based on the microscopic studies, these sandstones mainly composed of fine- to coarse-grained clastic fragments including sedimentary and metamorphic rock fragments (45 %), quartz (38 %) and feldspar (17 %). Based on petrographic studies, these sandstones are feldspathic litharenite and litharenite (mainly chertarenite). Based on the main components and major and minor elements geochemical data, the tectonic setting of these sandstones is an active continental margins and foreland basins. These data represent an intermediate to felsic source rock for these sandstones which was affected by the semi-humid to semi-arid climate and a low chemical weathering.
Original Research Paper
Exploration and Mining
Mehdi Talkhablou; Mehdi Kianpour; Seyed Mahmoud Fatemi Aghda
Abstract
In this study, the efficiency of the compressive wave velocity (Vp) geophysical method for predicting the quality of limestone mass in areas of Zagros formation, has been investigated. For qualitative classification of limestone rock masses, the Q classification system and its modified classification ...
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In this study, the efficiency of the compressive wave velocity (Vp) geophysical method for predicting the quality of limestone mass in areas of Zagros formation, has been investigated. For qualitative classification of limestone rock masses, the Q classification system and its modified classification system for sedimentary rocks (Qsrm) have been used. For this purpose, the data related to Vp, Q and Qsrm were extracted at the site of Karun 2, Karun 4, Khersan 3 and Tangeh Manshoureh dam sites and by using software interpolation methods in ArcGIS has been transformed into information layers. Using simple and multivariable regression analysis on data extracted from information layers and using Fuzzy Inference System (FIS), models for predicting Q and Qsrm in calcareous rock masses are presented. Also, to evaluate the accuracy of the obtained models, in addition to R2, performance indicators (VAF) and root mean square error (RMSE) were used. The results show that since the Qsrm index considers a wider range of massive properties, the prediction of the Qsrm value is closer to reality using geophysical methods than the Q index.
Original Research Paper
Economic Geology
Z. Zandi; A. R. Jafari rad; A. Gourabjeripour; M. Lotfi
Abstract
The Saheb Fe-Cu skarn deposit is located in the Sanandaj-Sirjan metamorphic belt, SE Saqqez, western Iran and has been formed along the contact between the Oligo-Miocene aged Saheb granitoid and the Permian aged impure calcareous rocks and includes endoskarn and exoskarn. Exoskarn is widely developed ...
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The Saheb Fe-Cu skarn deposit is located in the Sanandaj-Sirjan metamorphic belt, SE Saqqez, western Iran and has been formed along the contact between the Oligo-Miocene aged Saheb granitoid and the Permian aged impure calcareous rocks and includes endoskarn and exoskarn. Exoskarn is widely developed and include garnet and epidote skarn zones. The majority of mineralized zones are concentrated in garnet skarn. The relatively oxidizing mineralogical assemblage of the Saheb skarn includes garnet (andradite-grossular), pyroxene (diopside-hedenbergite), magnetite and hematite. Magnetite is the main and abundant ore mineral throughout the ore deposit. Based on field evidences and microscopic studies of skarn zone samples, two stages of prograde and retrograde alteration are distinguishable. According to the results of sample analysis of Saheb skarn productive intrusive body by XRF and ICP-MS techniques, the combination of this body is chiefly granite to granodiorite-diorite and belong to the I-type granitoids, metaluminous and K-rich calc-alkaline series. The Saheb granitoid is related to the VAG (Volcanic Arc Granite) tectonic setting.
Original Research Paper
Petrology
Nargess Shirdashtzadeh; Ghodrat Torabi
Abstract
In this study, some mantle lherzolites of Ashin ophiolite are investigated which contain evidence of a geotectonic/metamorphism during exhumation and obduction of oceanic lithosphere on the continental crust, after closure of Neo-Tethys Ocean. Based on petrography, their primary rock-forming minerals ...
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In this study, some mantle lherzolites of Ashin ophiolite are investigated which contain evidence of a geotectonic/metamorphism during exhumation and obduction of oceanic lithosphere on the continental crust, after closure of Neo-Tethys Ocean. Based on petrography, their primary rock-forming minerals are orthopyroxene, clinopyroxene, olivine, and chromian spinel. Mineralogy and geothermobarometry indicate that these 4-phase lherzolites were formed in the lithospheric mantle (at pressures ~ 21.6 to 8.6 kbar) by melt/wall rock reactions (at temperatures ~ 1012-1183 °C). Then, they were emplaced and obducted on the continental crust along the fault zone of this region, and consequently deformed. The first ductile deformation event occurred in the depth of lithosphere and resulted in high-temperature mylonitization at temperatures higher than 600 to 800 °C. Mineralogical features confirm pressure decreasing of this stage by subsolidus reaction of pyroxene and spinel and substitution of plagioclase and olivine. Therefore, petrography and thermobarometry data are indicative of the spinel to plagioclase lherzolite facies for these rocks. Finally, they partially underwent brittle and cataclastic deformation at temperatures below 600°C and lower pressures and depth during exhumation. However, most of plagioclases were replaced by with prehnite, pumpellyite, chlorite, hydrogrossular and xonotlite minerals by further alterations.
Original Research Paper
Tectonics
Zeynab Taslimi; Abdollah Saidi; Mehran Arian; A. Solgi; Manouchehr Ghoreshi
Abstract
The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin ...
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The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin of Palo Tethys and Neotethys and it caused the complexity of abundant structural in other way too. The aim of this research is to investigate and analysis of existence structures in east central Alborz from northwest of Damghan (South of Toyeh) to South of Sari (North Alborz fault). The Structural features Analysis indicate that the Alborz Mountains are a fold and thrust belt. During the intense shortening of Alborz crust in the studied area the initial model of folds have been modified or destroyed. Some of these folds could take place in flexural flow folds or Drug folds classes since one limb of folds on the surface of low-angel thrust faults was thrusted recumbently. The thrust faults with south and north dipping is the main controller for variety structures in this part of Alborz. Based on geological and structural properties, construction of folding structures initiated during the Alpine orogeny since the late Eocene (37 million years) and the most shortening and faulting had occurred during at the Late Miocene. Data presented here demonstrate that shortening percent in the study area of Alborz Mountains is about 36.27% and the Rate of Shortening is estimated about 0.93 mm/y.
Original Research Paper
Economic Geology
Raziyeh Mahabady; Farajollah Fardoost
Abstract
Abgareh copper deposit located in 140 km southwest of shahrood and part of a volcanic-sedimentary Torud-Chah shirin belt that has facies in the northern edge Structural-sedimentary zones of Central Iran. Field and petrographical studies, deposit area, consist of andesite, basaltic andesite and basalt ...
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Abgareh copper deposit located in 140 km southwest of shahrood and part of a volcanic-sedimentary Torud-Chah shirin belt that has facies in the northern edge Structural-sedimentary zones of Central Iran. Field and petrographical studies, deposit area, consist of andesite, basaltic andesite and basalt and contains less includes tuffit crystal that indicate middle–upper Eocene with with argillitic, sericitic, silicic, carbonatic, chloritic and iron oxides alterations. According to the field observations and mineralogical studies, the mineralization in the region was carried out in two stages: hypogene and supergene and weathering. Hypogen zone minerals are generally pyrite, chalcopyrite and bornite. Because of existence in oxidizing-supergene environment , nearly almost Cu-bearing minerals of the main stage of mineralization have been replaced by secondary Cu minerals such as chalcocite, covellite, malachite and chrysocolla. Fluid inclusion data shows in the temperature range from 145 to 217 °C and salinity between 3.73 and 9.84 Wt%NaCl and depths less than 390 m. The host rocks, ore mineralogy, ore structures and textures, and fluid inclusions characteristics and comparison with similar epithelial deposits indicate that the Abgareh vein system is formed in a low-sulfidation epitermal environment.
Original Research Paper
Geophysics
Vahid Maleki; mohammad reza Hatami; Ali Asghar Mottaghi
Abstract
In this study, we investigate the seismicity of eastern Alborz based on precise location of the earthquakes during the last two decades. In order to reduce the effect of outliers and low quality data on earthquake location results, during phase reading, weighing has been done. Manual readings of seismic ...
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In this study, we investigate the seismicity of eastern Alborz based on precise location of the earthquakes during the last two decades. In order to reduce the effect of outliers and low quality data on earthquake location results, during phase reading, weighing has been done. Manual readings of seismic phases for the desired area have been provided with a seismic data bank in which 5461 phases S and 8523 phases have been read, compared to seismic phases read in The Iranian Seismological Center (IRSC) shows a significant increase. Initial location is based on phase picking and initial weights using a nonlinear probabilistic method (Lomax et al, 2000). After calculation of initial location, the double difference method (waldhauser et al, 2000) is used to enhance the earthquake location quality. The earthquake waveform correlation tool is used to re-find the earthquakes. Transparency correlations are performed for events with a similarity of over 70% in a given time window for phase P and S. As a result, using this technique, the phase reading error for the same events reaches its lowest level, resulting in seismic events in re-location with a much higher accuracy than the initial location and location based only on the catalog data. Results of waveform cross correlation shows that in this area, earthquakes with high similarity occurring at in different times. Investigating the location of earthquakes on the Firoozkouh fault and then Chashm fault and Astaneh Fault in the cross sections.
Original Research Paper
Exploration and Mining
Hassan Bakhshandeh Amnieh; Amirhossein Rostami; Kurosh Shahriar; Hamid Chakeri; Masoud Cheraghi Seifabad
Abstract
When a tunnel passes through weak soil with different conditions, or there is a thin layer of soil on top of the tunnel, the mass of soil or rock must be stabilized. In addition, an excavation method must be chosen and applied in order to control the amount of subsidence and convergence which are among ...
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When a tunnel passes through weak soil with different conditions, or there is a thin layer of soil on top of the tunnel, the mass of soil or rock must be stabilized. In addition, an excavation method must be chosen and applied in order to control the amount of subsidence and convergence which are among the most significant factors in excavation a tunnel especially in urban area, since the soil between the tunnel and the ground moves due to changes in the shape of the tunnel through excavation, and progression of these movements toward the ground is manifested in subsidence of the surface structures. Therefore, in order to choose an excavation method based on the conditions of the project site, providing a decision-making model is essential. The ultimate goal is to select the most suitable subway tunnel excavation method among all available alternatives based on some determining criteria for Isfahan subway tunnel (Line 1). These criteria along with Multi-Criteria Decision Making (MCDM) models helped prioritize suitable alternatives. This model was designed based on technical, financial, executive, social, political and geo-mechanical features of the research site each of which subsumes a number of criteria. On the one hand, alternatives include Open Shield (full face) method, Slurry method, NATM method and excavate twin tunnel with TBM method which are used in the model. Finally, alternative D (excavate twin tunnel with TBM method) was selected as the best alternative of the site in both AHP(D=0.225) and TOPSIS(D=0.676391).
Original Research Paper
Economic Geology
Maryam Kiaeshkevarian; Ali Asghar Calagari; Ali Abedini; GholamHossein Shamanian
Abstract
The Gheshlagh bauxitic deposit is located in ~110 km southeast of Gorgan city. Mineralogical studies indicated the presence of minerals such as boehmite, diaspore, kaolinite, hematite, goethite, anatase, rutile, chamosite, calcite, moscovite, clinoclar, provskite, quartz, and dolomite. Based on quantitative ...
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The Gheshlagh bauxitic deposit is located in ~110 km southeast of Gorgan city. Mineralogical studies indicated the presence of minerals such as boehmite, diaspore, kaolinite, hematite, goethite, anatase, rutile, chamosite, calcite, moscovite, clinoclar, provskite, quartz, and dolomite. Based on quantitative mineralogy this deposite made up of (1) bauxitic clay, (2) clayey bauxite, (3) bauxitic clayey iron ore and (4) bauxitic iron ore. Calculations of the enrichment factors, with assumption of upper continental crust (UCC) as parent rocks, showed that elements such as Rb, Cs and Ba were depleted during bauxitization processes whereas elements like Y, Cr, Co, Ni, V and HREEs were encountered enrichment.Elements like Sr, Ga, Zr, Hf, Nb, Ta, U, Th and LREEs underwent both leaching and fixation processes during development of the weathered profile. Combination of the results obtained from mineralogical and geochemical investigations showed that factors such as adsorption, scavenging by metallic oxides and hydroxides, fluctuation of underground water level, type and stability of metal-containing complexes, stability of primary bearing minerals, presence in mineral phases resistant to weathering and changes in chemistry of the solutions responsible for weathering played prominent role in distribution and mobilization of elements in the studied bauxitic ores.
Original Research Paper
Petrology
J. Ghalamghash; Sara Houshmand; Sayad Jamal Shaikhzakariaee; Hamideh Rashid
Abstract
The Kharsare intrusive mass (South of Ghorveh) is located in the middle part of the Sanandaj–Sirjan zone. The batholith comprises three plutonic units including gabbro- diorite, granite and syenite. In addition, the hybrid rocks with a lot of mixing and minling evidences (including lobate or/and ...
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The Kharsare intrusive mass (South of Ghorveh) is located in the middle part of the Sanandaj–Sirjan zone. The batholith comprises three plutonic units including gabbro- diorite, granite and syenite. In addition, the hybrid rocks with a lot of mixing and minling evidences (including lobate or/and ellipsoidal micro granular mafic enclaves sometimes with chilled margins in granite or in hybrid rocks; net-veining granite; and synplutonic brecciated mafic dikes) crop out in interaction zone between granites and gabbros. The calc-alkaline and metaluminous gabbro-diorite and High-K calc-alkaline and peraluminous granites emplaced in Late Jurassic, simultaneously. The peraluminous A-type syenite formed later and intrude two above mentioned plutonic rocks. Geochemical features suggest that gabbro-diorites and granites formed in an active continental margins. It seems the pioneer mafic magma formed in a subduction setting by partial melting of metasomatized mantle. It ascent and emplace in lower crust to produce the granitic melt. The mingling and mixing evidences that may support local crustal contamination of the mafic melt. The younger syenite is resulted from heating by intrusion of the mafic magma in the end phase of continental arc magmatism.
Original Research Paper
Sedimentology
Zeinab Aalishavandi; Hossain Rahimpour-Bonab; Ali Kadkhodaei; Mehran Arian
Abstract
The Sarvak Formation deposited in the North to Northeastern margin of the Arabian Platform during the Mid-Cretaceous, and is extensively encountered in the Folded Zagros of southwestern Iran. It is the most important reservoir unit after the Asmari Formation in Iran. Petrographic analysis of the drilled ...
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The Sarvak Formation deposited in the North to Northeastern margin of the Arabian Platform during the Mid-Cretaceous, and is extensively encountered in the Folded Zagros of southwestern Iran. It is the most important reservoir unit after the Asmari Formation in Iran. Petrographic analysis of the drilled wells of the Kupal oil field led to recognition of in studied wells led to determination of eight microfacies that deposited in 3 sub-environments; restricted lagoon, lagoon-open marine and shoal in an interior part of Continental carbonate ramp. Petrographic studies revealed that since deposition, the Sarvak Formation experienced several diagenetic realms including marine, meteoric, burial and telogenetic diagenetic environments. Location of the studied wells shows that the relative depth of the Sarvak Formation ramp increases from the east to the west. These diagenetic successions are mainly restricted to the upper and lower parts of the Cenomanian-Turonian disconformity. Meteoric water infiltration below this Cenomanian-Turonian disconfirm boundary and related Dissolution led to development of moldic and vuggy porosity And as a result, the reservoir potential has been increase. In this study Hydraulic flow units were identified firstly using flow zone indicators and secondly using a stratigraphic modified Lorenz plot. The flow units resulting from these two methods are compared, and their close correspondence within the sequence stratigraphic framework is discussed. Base on this results six hydraulic flow units are defined as flow units 1 and 2 of the best reservoir quality and the reservoir potential reduced to the flow unit 6.
Original Research Paper
Economic Geology
Zahra Akbari; ali yarmohammadi; Iraj rassa
Abstract
The Fe-Pb Ahangaran deposit, hosted by tuffaceous siltstone of the Early Cretaceous sedimentary sequence in the northern part of the Malayer-Esfahan Metallogenic Belt (MEMB), Iran. Ore mineralization occurred as stratiform and a widespread veinlet zone in the upper part of Lower Cretaceous terrigenous ...
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The Fe-Pb Ahangaran deposit, hosted by tuffaceous siltstone of the Early Cretaceous sedimentary sequence in the northern part of the Malayer-Esfahan Metallogenic Belt (MEMB), Iran. Ore mineralization occurred as stratiform and a widespread veinlet zone in the upper part of Lower Cretaceous terrigenous unit (Kc). Four different ore types can be distinguished in deposit include: (1) veinlet (feeder) zone, (2) sulfide-Fe- oxide stratiform ore (3) barite ore and (4) vein ore. Ore minerals in the different ore types are pyrite, siderite, magnetite, galena, barite, chalcopyrite and tetrahedrite and rare minerals are pyrrhotite, arsenopyrite, and freibergiteCarbonatization and silicification are the main hydrothermal alterations in this deposit. The orebodies in the Ahangaran deposit have been replaced by iron oxide minerals in supergene process and have been formed a thick gossan zone. The textural and mineralogical data provide evidence of three stages of mineralization (Early, main and late stage) in Ahangaran deposit. According to evidences such as tectonic setting, type of host rock, geometry of deposit, sulfide-Fe oxide ore types, textures and structures indicate that the Ahangaran deposit is compatible with a sub-seafloor replacement mineralization that has been suggested for some Sedex deposits.
Original Research Paper
Stratigraphy and Palaeontology
nahid khodashenas; Fatemeh Hadavi; Marziyeh Notghi Moghaddam; Ahmadreza Khazaei
Abstract
In the present study, Baghamshah Formation in Baghdadeh section located in the eastern margin of Lut Block to biostratigraphic studies based on calcareous nannofossils was sampled. Thickness of Baghamshah Formation in this section is 253m and mainly contains of shale and marl. According to the paleontological ...
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In the present study, Baghamshah Formation in Baghdadeh section located in the eastern margin of Lut Block to biostratigraphic studies based on calcareous nannofossils was sampled. Thickness of Baghamshah Formation in this section is 253m and mainly contains of shale and marl. According to the paleontological studies, 43 nannofossil species belong to 20 genera with well to moderate preservation in Baghdadeh section were identified and photographed. Based on the index calcareous nannofossils and assemblages species, CC1-CC5 biozones of Sissingh (1977) were determined. According to determined biozones, age of the Baghamshah Formation in Baghdadeh section Early Berriasian to Early Barremian was suggested.
Original Research Paper
Hydrology
hojat miranimoghadam; Gholam Hossein Karami; Rahim Bagheri
Abstract
Gonabad area is an arid region where 19.5 mcm of groundwater is annually extracted from 26 qanats. Six major qanats were sampled for hydrochemical and isotopic analyses to determine the origin and flow mechanism of the groundwater.The total dissolved solids vary from 524 to 2375 mg/l. The dominant water ...
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Gonabad area is an arid region where 19.5 mcm of groundwater is annually extracted from 26 qanats. Six major qanats were sampled for hydrochemical and isotopic analyses to determine the origin and flow mechanism of the groundwater.The total dissolved solids vary from 524 to 2375 mg/l. The dominant water types are Na+-Mg2+-HCO3- and Na+-Cl-. The groundwater is saturated with regard to carbonate minerals and under-saturated with regard to evaporate minerals. This means that the composition of the groundwater is highly controlled by the dissolution of carbonate rocks. The deuterium and oxygen 18 isotopes signatures demonstrate the meteoric origin of the groundwater and the flow mechanism is direct infiltration of precipitation before evaporation through fractures in the limestone formations and infiltration of surface water in the coarse grain alluvial cones at the south of the plain. The groundwater recharge originates from an area between 2000 to 2700 m a.s.l. The groundwater of these qanats has depleted stable isotopes in the wet season due to recharge through the infiltration of precipitation and has enriched stable isotopes in the dry season due to recharge through the return flow of qanats and springs used for agricultural activities in the south of the basin.
Original Research Paper
Sedimentology
Samira Akbarzadeh; Abdolhossein Amini; Vahid Tavakoli; Khosro Heydari
Abstract
The Oligo–Miocene Asmari Formation is the most important reservoir rocks of the Dezful embayment oil fields. This study interpret sedimentary environments and sequence stratigraphy of the Asmari Formation in Karun oil field based on changes in facies, gamma-ray log morphology and change in concentration ...
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The Oligo–Miocene Asmari Formation is the most important reservoir rocks of the Dezful embayment oil fields. This study interpret sedimentary environments and sequence stratigraphy of the Asmari Formation in Karun oil field based on changes in facies, gamma-ray log morphology and change in concentration of thorium, potassium and uranium elements of the natural gamma- ray spectrometry. In this regard, 1 evaporate, 9 carbonate facies and 1 mixed facies were recognized. The thorium to uranium ratio used to analyze the oxidation, reduction condition. Based on the vertical distribution of the facies in the sequence stratigraphy framework, three 3rd order sequences were determined. Changing the trend of logs in time reflects the decreasing trend of gamma- ray in the sequence boundary and increasing trend at maximum flooding surface. Five main morphologies including left Box Car shape, Right Box Car shape, Serrated Bell shape, Serrated Funnel shape and serrated shape have been recognized. The conformity of this morphologies with the sequence stratigraphy leads to the relationship between the Left Box Car shape with Low stand system tract, Serrated Bell shape and Right Box Car shape with Transgressive system tract and Serrated Funnel shape with High system tract.
Original Research Paper
Petrology
Shirin Behpour; Abbas Moradian; Hamid Ahmadipour
Abstract
The studied area is located in the SE of Bam and Urumieh-Dokhtar Magmatic Arc. Based on petrographical and geochemical characteristics, studied rocks contain tonalite, granodiorite, granite and alkali granite. These rocks are metaluminous, weakly peraluminous, high-K, and calc-alkaline. The behavior ...
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The studied area is located in the SE of Bam and Urumieh-Dokhtar Magmatic Arc. Based on petrographical and geochemical characteristics, studied rocks contain tonalite, granodiorite, granite and alkali granite. These rocks are metaluminous, weakly peraluminous, high-K, and calc-alkaline. The behavior of Y, Ba, Ce and Zr vs. SiO2 display the properties of the high temperature I-type granites. These granitoids plot in the field of VOG. Enriched LREE and LILE with depleted HFSE show characteristics of subduction related active continental margins. The ratios of Nb/U and Nb/La and Sm/Yb indicate the crustal contamination. Isotopic data and La vs. La/Sm diagram show the role of the lower crust and the old continental crust in magma evolution. According to the phenocrysts assemblage, REE pattern with negative Eu anomaly and La/Yb ratio to crustal thickness, studied rocks are fractionated from relatively dry magma which has undergone from shallow depths. Sm/Yb and La/Yb ratio display the mantle source is garnet-free source. The low to moderate degree of partial melting of garnet-free amphibolite is the source of the studied granitoids. Volatiles that is driven from subduction slab and melt of the subducted sediments play a significant role in the generation and evolution of their magma source.
Original Research Paper
Tectonics
Mehdi Tavakoli Yaraki; Seyyed Ahmad Alavi; Mohammad Reza Ghassemi; Iraj Abdollahie fard
Abstract
The significance of mechanical stratigraphy of rocks in kinematics of folds has long been of interest to structural geologists. Parameters such as sedimentary facies variations and thickness of incompetent layers play major role in activity of these layers as detachment horizons. The purpose of this ...
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The significance of mechanical stratigraphy of rocks in kinematics of folds has long been of interest to structural geologists. Parameters such as sedimentary facies variations and thickness of incompetent layers play major role in activity of these layers as detachment horizons. The purpose of this study is to investigate the role of mechanical stratigraphy on fold geometry in the Aghajari and Pazanan anticlines within the Dezful Embayment zone. For this purpose, we have used seismic profiles, stratigraphic data and petrophysical logs as well as the previous stratigraphic works in study area. Results show that the Garau Formation is the major intermediate detachment level in the Aghajari structure, and has a significant control on folding geometry of the competent sequences of the Fahliyan to Asmari Formations. The Dashtak Formation and other incompetent evaporatic Formations of Middle-Upper Jurassic also have been active in the Aghajari structure. In contrast, in most parts of the Pazanan structure, the Garau and the Jurassic Formations do not have appropriate mechanical properties to act as intermediate detachment levels due to their change into hemipelagic facies and limestone (Surmeh Formation) respectively. Based on the evidences, the facies change in the abovementioned Formations occurs between the Pazanan and Aghajari anticlines. It seems that activity of the Hendijan-Izeh paleo-high also has some control on facies of the Garau Formation. Based on geometric characteristics and a geometric conceptual model provided for development of these structures, the folding style of the anticlines is suggested as an asymmetric faulted detachment fold type.
Original Research Paper
Stratigraphy and Palaeontology
Mahnaz Parvaneh Nejad Shirazi; M. Seddighi; P. Balicheh khorram abadi
Abstract
This study deals with lithostratigraphy, biostratigraphy, microfacies analysis, and depositional setting of the Jahrum Formation in Chellehgah Sepidan section, NW Shiraz. Vertical changes in lithological characteristics led to recognition of 15 lithotypes. The Jahrum Formation, in this area, rests conformably ...
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This study deals with lithostratigraphy, biostratigraphy, microfacies analysis, and depositional setting of the Jahrum Formation in Chellehgah Sepidan section, NW Shiraz. Vertical changes in lithological characteristics led to recognition of 15 lithotypes. The Jahrum Formation, in this area, rests conformably (with a gradational boundary) on the Pabdeh Formation and is overlain unconformably by the Asmari Formation. Micropaleontological analyses based on benthic foraminifera (Nummulites striatus, N. cf. fabianii, N. gr. bullatus-garganicus, Spiroclypeus sp.) suggest a middle-upper Eocene age for the formation. Facies analyses allowed to recognize the 6 facies (including 12 microfacies) for the examined strata. The results also suggest that the Jahrum Formation deposited in a homoclinal ramp.
Original Research Paper
Economic Geology
Maryam Honarmand; Ghasem Nabatian; Mahtab Aflaki; Mohammad Ebrahimi
Abstract
Geology, geochronology and tectonic setting of the Moghanlou mylonite gneiss and granite bodies, west of Zanjan Abstract The Moghanlou mylonite gneiss and granite assemblage is located in the west of Zanjan forming a part of the magmatic-metamorphic association in the Takab area. The Moghanlou assemblage ...
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Geology, geochronology and tectonic setting of the Moghanlou mylonite gneiss and granite bodies, west of Zanjan Abstract The Moghanlou mylonite gneiss and granite assemblage is located in the west of Zanjan forming a part of the magmatic-metamorphic association in the Takab area. The Moghanlou assemblage comprises of leucogranite and biotite granite intrusions which have surrounded the gneiss body. The zircon U-Pb dating shows the ages of 563±6.5 Ma for the mylonite gneiss, 576±13 Ma for the biotite granite and 559±6 Ma for the leucogranite intrusions. Moreover, the samples from the Moghanlou assemblage display high-K calc-alkaline and slightly peraluminous affinities, except those from the leucogranite which are low potassium samples due to the sodic alteration and albitization of the K-feldspars. The trace element patterns suggest LILE and LREE enrichment and HFSE and HREE depletion as well negative anomaly of Nb, Ta and Ti. In general, the geochemical features of the Moghanlou intrusions are comparable with the melts formed from crustal partial melting in magmatic arc environment. The Moghanlou assemblage is analogues to other Late Neoproterozoic-Early Cambrian igneous and metamorphic associations in Iran and Turkey which are related to the igneous activity along the Cadomian magmatic arc, in north of Gondwana supercontinent.
Original Research Paper
Sedimentology
B. Mirzapour; R. Lak; M. Aleali; M. Djamali; R. Shahbazi
Abstract
Lake Urmia is one of the largest salt supersaturated lakes in the world that is located in northwestern Iran. Many wetlands are located around of Lake Urmia, especially in the southern part of the lake. Wetlands are important as a platform for recording environmental and climatic events. The ...
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Lake Urmia is one of the largest salt supersaturated lakes in the world that is located in northwestern Iran. Many wetlands are located around of Lake Urmia, especially in the southern part of the lake. Wetlands are important as a platform for recording environmental and climatic events. The subject of this research is studying sedimentology and statistical parameters of sedimentology in the analysis of different sedimentary environments in the sediments of southern wetlands around Lake Urmia, including Kani Barazan and Solduz wetlands. The purpose of this study is reconstructing the fluctuations of the water table of Lake Urmia and its effect on wetland areas in the Holocene period. For this purpose, sedimentary cores with maximum depth of 12 meters and total depth of about 200 meters using a handi auger and 8 hole cores by a vibra corer were collected and examined. Sedimentary facies were identified and separated based on texture and sediment structure, composition of destructive sediments and organic matter, color, presence of plant remnant and shell residues and other macroscopic components. Sampling was performed based on changes in the type of sediments and sedimentary facies. 150 sediment samples were separated for grain size analysis. The samples were analyzed using two methods, wet sieving and particles smaller than sand (silt and clay) by laser device (Laser particle Sizer Analysette). Statistical parameters of sedimentology were calculated using Sedilizer software and were analyzed by SPSS software. Two samples of plant remnant were dated by C14-AMS isotope method. The results indicate that there are 8 facies, belonging to 3 sedimentary environments of lake, wetland and alluvial. The dating results show the average sedimentation rate in the southern part of Lake Urmia is about 0.5 mm per year. However, sedimentation rates vary in different sediment depths. According to the analysis of different cores, the reconstruction of the paleogeography of the south of Lake Urmia and it`s extention had been done in the last 20,000 years. This study shows that in the late quaternary Lake Urmia has expanded to the beginning of the current Siminehrud. At the late Pleistocene and the early Holocene, the coastline regression in the southern part and the alluvial sediments of the Zarrinehrood and Siminehrood rivers occurred in the south of the region. The late Holocene was associated with decreasing water table, slightly dry conditions (around 4000 years ago) and the expansion of marginal playa. The situation in the region has been permanent for about 2000 years.
Original Research Paper
Economic Geology
Maryam Javidi Moghaddam; M.H Karimpour; Azadeh Malekzadeh Shafaroudi
Abstract
The Rashidi area, which comprises a part of the north Khur in eastern Iran is located at 120 km northwest of Birjand city. Preliminary prospecting in the area using the image processing of ASTER data by Spectral Angle Mapper (SAM) algorithm resulted in the identification of propylitic and argillic alteration ...
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The Rashidi area, which comprises a part of the north Khur in eastern Iran is located at 120 km northwest of Birjand city. Preliminary prospecting in the area using the image processing of ASTER data by Spectral Angle Mapper (SAM) algorithm resulted in the identification of propylitic and argillic alteration zones together with iron oxy-hydroxide minerals. The area consist of outcrops of Eocene pyroclastic rocks ranging from andesitic to rhyolitic in composition, intruded by diorite porphyry dikes. Vein mineralization in the area was mainly occurred along a fracture system hosted by andesitic tuff breccia unit. Vein copper mineralization was formed during two stages including the: (1) quartz-pyrite-chalcocite-tennantite assemblage, and (2) quartz-chalcocite-pyrite-sphalerite assemblage. The values of δ18O for quartz in the first and second stages of vein mineralization was 19.26 and 14.94 and the amount of δ18O water in equilibrium with quartz was 10.96 and 4.94 respectively that shows a magmatic origin and mixing with meteoric water in the second stage. Based on geology, vein geometry, fluid inclusion, and stable isotope geochemistry, the Rashidi Cu deposit can be classified as vein-type copper deposits, which has been formed along fault zones.
Original Research Paper
Economic Geology
mahboobeh yaghobi; sasan bagheri
Abstract
In Eastern Iran, the Eocene platform deposits of northwest of Birjand, are a suitable case; because a thin thrust sheet of Eocene carbonate have had the possibility to slide and fold upon an upper cretaceous plastic footwall. Moreover, this carbonate sheet entirely covered the structural arc, conduct ...
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In Eastern Iran, the Eocene platform deposits of northwest of Birjand, are a suitable case; because a thin thrust sheet of Eocene carbonate have had the possibility to slide and fold upon an upper cretaceous plastic footwall. Moreover, this carbonate sheet entirely covered the structural arc, conduct us to recognize the origin of the bending. Achieving to this goal, we passed the structural arc along the six cross sections; four sections along radial trends and two transversal sections parallel to the inflection line. In these measurements, folds and thrust faults were defined as far as possible. The cross sections have been restored by the "Move Softwear". The amount of shortening along the radial sections were measured respectively from the east to the west are the 30-40% along A, 25-35% along B, 35-45% along C, and 15-25% along D; and along the transversal section are respectively from the south to the north about the 35-55% along E and 25-35% along F. The shortening amount in the platform carbonate at two-facing ends of the structural arc as well as the one along the inflection line are the greatest. The pattern of shortening in the arc seems to follow a buckle folding mechanism.
Original Research Paper
Geophysics
Marzie Shabani; Abolfazl Rezaei; Zohre Masoumi
Abstract
The water table in the Zanjanrood catchment has severely declined recently. Therefore, determination of the groundwater potential zoning map is of great importance for optimal management of water resources. Here, we used seven effective criteria including lithology, slope, drainage, lineament, rainfall, ...
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The water table in the Zanjanrood catchment has severely declined recently. Therefore, determination of the groundwater potential zoning map is of great importance for optimal management of water resources. Here, we used seven effective criteria including lithology, slope, drainage, lineament, rainfall, spring density and landuse to asses groundwater potential. The analytical hierarchical analysis process was used for weighting the criteria. Overlay analysis was implemented using TOPSIS model to prepare the groundwater potential map in four categories of priority including very-good, good, low and poor. In general, the very-good category corresponds with the first priority while the lowest potential of groundwater match with the fourth priority. The high-discharged production wells and the geoelectrical investigations (resistivity and induced polarization) were applied to verify the model. The spatial distribution of the high-discharge production wells has completely coincided with both the very-good and good priorities in the area. The results of resistivity and IP models also are in good agreement with those from the TOPSIS model. Overall, the results suggest there is no rich aquifer in mountains of the Zanjanrood catchment. Furthermore, the most important aquifer in the Zanjanrood catchment is located around the Zanjanrood River where a severe water table decline has occurred.
Original Research Paper
Stratigraphy and Palaeontology
Mir Amir Salahi; Abbas Ghaderi; Alireza Ashouri; Ali asghar siabghodsi
Abstract
To separate the different units of the Paleogene sequences of the Kopet-Dagh basin and their regional correlation with the adjacent areas in the Central Asia, the Oyster bivalves fossils are used in the current research. Also, the study of their paleobiogeography has been considered in this study. Based ...
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To separate the different units of the Paleogene sequences of the Kopet-Dagh basin and their regional correlation with the adjacent areas in the Central Asia, the Oyster bivalves fossils are used in the current research. Also, the study of their paleobiogeography has been considered in this study. Based on this fauna, Pycnodonte-Oestra community in the Chehelkaman Formation uppermost parts represents the late Paleocene age and the first occurrence of Flemingostrea hemiglobosa at the base of the Khangiran Formation confirms the beginning of Eocene epoch. Association of different species and subspecies of Turkostrea in the Khangiran Formation demonstrates the middle part of early Eocene and Sokolowia community near the top of the Khangiran Formation shows the Lotetian-Bartonin ages. These features are in full compliance with the bivalve communities recorded from the other parts of Central Asia such as Amu-Darya, Farghana, Afghan - Tajik and Trim basin of China. It illustrates the same geological history of the mentioned areas during Paleogene, indicates the occurrence of different types of molluscan taxa in the Kopet-Dagh basin is the same as parallel horizons and equivalent time units throughout the extensive Central Asian region.
