Original Research Paper
Petroleum geology
Abstract
In the northern border of Arabian plate exist a complex reverse fault zone in parallel to the Main Zagros Revers Fault. In spit of them, it could be observed another younger fault with dextral strike-slip nearly parallel to the Main Zagros Revers Fault. The young fault is called Main Recent Fault; MRF ...
Read More
In the northern border of Arabian plate exist a complex reverse fault zone in parallel to the Main Zagros Revers Fault. In spit of them, it could be observed another younger fault with dextral strike-slip nearly parallel to the Main Zagros Revers Fault. The young fault is called Main Recent Fault; MRF which shows clear evidences on the surface. The MRF contains many active segments with 100 km length in average from NW to SE which are Piranshahr, Marivan, Sartakht, Morvarid, Dinvar, Sahneh, Nahavand and Droud. Filed data indicates that MRF extended after Droud segment to the SE. They are called Kohrang and Ardal segments. Kohrang fault with 80 km length is separated as en echelon from Droud fault and is oriented with N140 degree trend from 33 north orbit to the Kohrang plain. Ardal fault with 120 km length separates form Kohrang fault. It ends to the SE with N-S trending dextral strike-slip Dena fault. At the end points of Kohrang Fault exist two salt diapirs. It suggests that a part of the segmentation is controlled by salt diapir due to age and mechanical property of sediments above and around of diapirs.
Original Research Paper
Sedimentology
Mohammad Shalalvand; Mohammad Adabi; Afshin Zohdi
Abstract
In this study, the Late Paleocene Taleh Zang Formation in the southwest of Kermanshah hasbeeninvestigatedfor elemental geochemistry and effective diagenetic processes during burial. The thickness of the studied section is 282 meters that mainly composed of shallow marine limestones with interbedded of ...
Read More
In this study, the Late Paleocene Taleh Zang Formation in the southwest of Kermanshah hasbeeninvestigatedfor elemental geochemistry and effective diagenetic processes during burial. The thickness of the studied section is 282 meters that mainly composed of shallow marine limestones with interbedded of marl and dolomite. The main diagenetic processes affecting the TalehZangFormation include micritization, various types of porosity, cementation, dolomitization and compaction. Due to the texture and the abundance of unstable skeletal particles (green algae and bivalve), porosity and cementation aremorecommon among the identified processes. Microscopic and geochemical studies have shown that these processes have taken place in eogenesis and early mesogenesis stages in marine, meteoric and shallow burial environments. Evidences indicate that the carbonates of the TalehZangFormation didnot tolerate deep burial after the deposition during diagenesis. Fluids that affected the lower parts of the formation during burial were mainly marine. Moreover, tothetop ofthe sequence in addition to seawater less meteoric fluids have affected the marine carbonates of the Taleh Zang Formation during diagenesis. The high amounts of Sr/Mn (mean27/51) and Sr/Ca (mean 1/61) and also low Mn (mean 27ppm) and Fe (mean 78ppm) values indicate close digenetic system with low water/rock interaction for the carbonate samples of the TalehZangFormation.
Original Research Paper
Tectonics
Azizollah Bazzi; mohammadmahdi Khatib; mohammadhosein Zarrinkoub
Abstract
The north Makran ophiolite mélange, is located on the northern part of Makran accretionary wedge, southeast of Iran. In this study, we investigate geometry and kinematic properties of structural elements, and analyze the deformation style of the north Makran ophiolite mélange. Based on ...
Read More
The north Makran ophiolite mélange, is located on the northern part of Makran accretionary wedge, southeast of Iran. In this study, we investigate geometry and kinematic properties of structural elements, and analyze the deformation style of the north Makran ophiolite mélange. Based on the results, at least, two stages of deformation were identified in north Makran ophiolite mélange. The first stage, which was accompanied by the development of extension structures, led to the formation of sheeted dykes in crust sequence of oceanic lithosphere. By restoration of these dykes to pre-deformation states, we assigned a SSW-NNE extensional regime that illustrates initial geometry of north Makran ophiolite mélange formed. The second stage, which was formed because of convergence in a compressional or transpressional regime, has been characterized by the development of various types of thrust and strike-slip faults, thrusting of rock units on top of each other and their duplication, and folding of sediment rocks. WNW-ESE thrust faults with 20 to 40 degrees dip toward NNE have the most important influence on current features of the north Makran ophiolite mélange, they reflect the conditions and process that the oceanic basin closed and oceanic lithosphere emplaced.
Original Research Paper
Economic Geology
Ali reza zarasvandi; Mohammad Ali Ali Abadi; Mohsen Rezaei; Houshang Pourkaseb
Abstract
The Mohammadabad deposit is located in vicinity of Delijan in central province and in terms of structural zones of Iran,in the Uremia dokhtar zone. Stratabound Fe-Ce mineralization in brecciated, vein, massive, layered and laminar forms, consists ore minerals such as hematite, pyrite, chalcopyrite and ...
Read More
The Mohammadabad deposit is located in vicinity of Delijan in central province and in terms of structural zones of Iran,in the Uremia dokhtar zone. Stratabound Fe-Ce mineralization in brecciated, vein, massive, layered and laminar forms, consists ore minerals such as hematite, pyrite, chalcopyrite and magnetite ,is seen in lower Eocene volcano sedimentary unites. Amounts , ratios and diagrams of trace elements and rare earth elements show hydrothermal mineralization with the predominance of magmatic fluids. The values of δ34SCDT of sulfide minerals (-2.76 to1.51 ‰) and suggest the magmatic source for sulfur or mineralizing fluid with magmatic sulfur. The values of δ13C (mean 3.61 ‰), δ18O(mean12.946‰) related diagrams show a magmatic source for carbon, hydrothermal genesis for calcite and a mineralizing fluid dominantly magmatic source. above evidences,وthe location of the region in tensile tectonic regime in western edge position of uremia dokhtar magmatic arc during the Eocene and presence of magmatic mass in the depths of the region with high potential for iron and copper mineralization , sulfur supply ,also has played role of a heat engine to circulating and transfer of mineralizing fluids to the sea bed. Offers exhalative-hydrothermal processes model for deposit genesis in Eocene volcano sedimentary units
Original Research Paper
Economic Geology
Hadi Mohammadian; vartan simmonds; kamal Siahcheshm
Abstract
The Sarikhanloo area is located within the Qaradagh metallogenic zone in northwest Meshgin Shahr. Igneous rocks cropped out in this area include successions of Paleocene-Eocene pyroclastic rocks (tuff and andesitic-dacitic lavas with intercalations of ignimbrite) and basaltic andesite lava flows. Igneous ...
Read More
The Sarikhanloo area is located within the Qaradagh metallogenic zone in northwest Meshgin Shahr. Igneous rocks cropped out in this area include successions of Paleocene-Eocene pyroclastic rocks (tuff and andesitic-dacitic lavas with intercalations of ignimbrite) and basaltic andesite lava flows. Igneous rocks show high-K calc-alkaline to shoshonitic nature and are mainly metaluminous, formed in a post-collisional uplift tectonic setting. Hydrothermal activities in this area brought about formation of vast silicic veins and caps, along with silicic, propylitic, phyllic (non-pervasive) and intermediate argillic alterations around the veins, as well as intermediate to advanced argillic alteration halos at the margins of silicic caps. Ore minerals in the silicic veins includes pyrite, arsenopyrite and Fe-oxides, accompanied by minor malachite, formed during four mineralization stages. Fluid inclusion studies indicate that the homogenization temperature of fluid inclusions ranges from 175 to 355 °C, considering the low pressure of fluid inclusions (≤ 0-40 bars), can signify the fluid temperature at the time of entrapment. The estimated salinity values are between 0.2 and 3 wt% NaCleq.
Original Research Paper
Tectonics
babak Samani; Sajad Zareie; Atefeh Ghanbari
Abstract
Split-window algorithm is the effective method for determination of land surface temperature. The results of temperature pattern show that the Gach salt dome has a higher temperature than the Siah Tagh salt dome. From a structural point of veiw, the higher temperature of the Gach salt dome can be related ...
Read More
Split-window algorithm is the effective method for determination of land surface temperature. The results of temperature pattern show that the Gach salt dome has a higher temperature than the Siah Tagh salt dome. From a structural point of veiw, the higher temperature of the Gach salt dome can be related to the rooting of this dome and its relationship with the basement salt column. While the lower temperature of the Siah Tagh salt dome can be due to the lack of connection between the salt dome and the salt source of Hormuz Series. Temperature anomaly maps show the different temperature pattern in these two salt domes. Spatial pattern of temperature anomaly in the Siah Tagh dome show the linear trend in the eastern part of the dome. This temperature linear pattern in the Siah Tagh dome probably is related to the morning sunshine in the eastern slope of this dome. According to the resulting LST map, the highest temperature in the Gach salt dome is 41.87 °C and 36.7 °C in the Siah Tagh salt dome.
Original Research Paper
Economic Geology
Negar Kaboudmehri; Hossein Kouhestani; Mir Ali asghar Mokhtari; Afshin Zohdi
Abstract
The Toryan occurrence is located in the Central Iran zone, 120 km northwest of Zanjan. Pb–Zn mineralization at Toryan occurred as laminated and lens-shaped parallel to lamination of grey sandstone units of the Upper Red Formation. Mineralization often formed around and within the fragments of the ...
Read More
The Toryan occurrence is located in the Central Iran zone, 120 km northwest of Zanjan. Pb–Zn mineralization at Toryan occurred as laminated and lens-shaped parallel to lamination of grey sandstone units of the Upper Red Formation. Mineralization often formed around and within the fragments of the plant fossils, and shows disseminated, replacement, solution seems, intergranoular cement, framboidal, and vein-veinlet textures. At Toryan, ore horizon has 1 m thickness and approximately 350 m length and contains three zones include the red oxidized zone, the bleached zone and the mineralized reduced zone. Galena, sphalerite, pyrite and arsenopyrite are the main ore minerals at Toryan occurrence. Cerussite and goethite are formed during supergene and wethering processes. Comparison of trace elements and REE patterns of barren red and grey host sandstones and mineralized samples indicate that mineralized samples show lower concentrations of trace elements and REE. Based on tectonic setting, sedimentary environment, host rock, presence of plant fossils, geometry, ore texture and mineralogy and alteration, Toryan occurrence can be classified as sediment-hosted Cu deposits of Redbed type, and is comparable with another Redbed type of Cu and Pb–Zn deposits in the Avaj-Zanjan-Tabriz-Khoy belt.
Original Research Paper
Tectonics
Esmail Farahzadi; Seyed Ahmad Alavi; Mohammad Reza Ghassemi; Shahram Sherkati
Abstract
AbstractUnderstanding the history of uplift and folding in an area helps inferring the history of hydrocarbon genesis,migration and trapping and reducing exploratory drilling risks.Thermal model along with structural cross sections help understanding of this history and future plannings for ...
Read More
AbstractUnderstanding the history of uplift and folding in an area helps inferring the history of hydrocarbon genesis,migration and trapping and reducing exploratory drilling risks.Thermal model along with structural cross sections help understanding of this history and future plannings for new exploration. In this paper we have used 3Dseismic reflective lines and geological maps to construct a regional balanced cross section and restore it in several stages. Combining of this cross section and a thermal model produced using vitrinite reflectance and apatite fission track, the history of exhumation and regional erosion is evaluated. Based on the results,unlike the Hormuz Series,the thickness of the Paleozoic sequence is equal throughout the region. This shows that the sedimentary-tectonic events have been the same in this period. The apatite fission track data indicate that the average time of rocks cooling is between14and24 million years ago (Late Oligocene-Middle Miocene).Based on the burial history graph, exhumation rate of the basement decrease from High Zagros to Abadan plain that show the basement in the northern part is involved in deformation earlier than in the southern part of the region. This involvement has affected the formation of structure,change of the sedimentary facies and the regional erosion pattern.
Original Research Paper
Tectonics
MohammadAmir Alimi
Abstract
The Bahlgerd shear zone in the northern margin of Bagheran Mountain is separated Eocene flysch from the Cretaceous ophiolite sequence and Quaternary sediments by southern Birjand and Bahlgerd faults. In the deformation evaluation , sigmoidal array arrays located in sandstone units have been used as strain ...
Read More
The Bahlgerd shear zone in the northern margin of Bagheran Mountain is separated Eocene flysch from the Cretaceous ophiolite sequence and Quaternary sediments by southern Birjand and Bahlgerd faults. In the deformation evaluation , sigmoidal array arrays located in sandstone units have been used as strain markers. Based on the geometry of these arrays, the mathematical equations and R-θ' diagrams of the strain parameters were estimated. The mean values of shear strain (γ), volume change (∆) and convergence across the zone (K) are 0.45, -0.26 and 0.85, respectively. The plotting strain ellipses on the logarithmic Flinn diagram are in the field of flattening, which indicates the simultaneous simple shear and compaction in the region and show a volume reduction of up to 30%. Also, in the Bahlgerd shear zone, the value of θ'> 45 ° and cleavages are created in the direction perpendicular to the opening of the veins, which conforms to the characteristics of the compactional simple shear model. The horizontal strain parameters in the transpression model have similar values the compactional simple shear model. Based on the calculated convergence parameter (0.39), Behlgard shear zone is in the category of slightly convergence zones in which the amount of shortening
Original Research Paper
Economic Geology
Almasi Alireza; Ghasem Nabatian; Amir Mahdavi; Qiuli Li
Abstract
The Maher abad and Khopik porphyry Cu deposits occurred in the Upper Eocene (39-37 Ma) in Lut block. All of them associated with intermediate (mostly monzonite) rocks. Porphyry deposits are closely associated with oxidized magmas. Oxygen fugacity (fO2) is a key factor that controls the formation of porphyry ...
Read More
The Maher abad and Khopik porphyry Cu deposits occurred in the Upper Eocene (39-37 Ma) in Lut block. All of them associated with intermediate (mostly monzonite) rocks. Porphyry deposits are closely associated with oxidized magmas. Oxygen fugacity (fO2) is a key factor that controls the formation of porphyry Cu deposits. The composition of the major and trace elements of zircon grains related to several ore-bearing monzonite were measured in Maher abad and Khopik porphyry copper indices. Zircon grains show moderate to low Ce4+/Ce3+ with a range of 19 to 610 and an average of 155. The average of oxygen fugacity (logfO2) values of Meher abad and Khopik ore-bearing magmas, range ∆FMQ -3.2 to MFMQ -1.3 with mean ∆FMQ -2.2, indicate formation under moderate oxidation conditions (between Ni-NiO (NNO) and Faylite magnetite-quartz (FMQ) buffers, but magnetite-hematite (HM) buffer, which ), which is not ideal for the formation of porphyry deposits. This is supported by whole-rock and Sr-isotopic data, and absence of high oxidation minerals such as hematite, and the poor adakitic charactristic of rocks in both deposits, which are due to factors involved in magma origin such as rock type and partial melting rate (possibly peridotite with low participation of slab).
Original Research Paper
Stratigraphy and Palaeontology
Ali Asaadi; Ali Imandoust; Mehdi Sarfi; Mehdi Ghane Ezabadi
Abstract
The Lower Cretaceous Fahliyan Formation is one of the main oil reservoirs in the Persian Gulf. In this study, for investigating facies characteristics, depositional environment, diagenetic features, sequence stratigraphy and describing factors controlling reservoir quality, the integration of the results ...
Read More
The Lower Cretaceous Fahliyan Formation is one of the main oil reservoirs in the Persian Gulf. In this study, for investigating facies characteristics, depositional environment, diagenetic features, sequence stratigraphy and describing factors controlling reservoir quality, the integration of the results from core description, petrographic studies, and petrophysical data was utilized. Nine main facies were recognized and grouped in four facies belts of lagoon, shoal, patch reef and shallow open marine, indicating deposition of the formation in a carbonate ramp platform. Various diagenetic processes that influenced facies, occurred in marine, meteoric, and burial diagenetic realms. Four main pore types have been identified in the reservoir that include interparticle, moldic, vuggy, and microporosity. From the sequence stratigraphy point of view, three third-order sequences which are correlatable within the Fahliyan Formation were identified. The development of grainstone and algal rudstone/floatstone in shoal/ patch reef sub-environment played an important role in developing the high reservoir. In view of their controls on reservoir quality and pore system, diagenetic features can be categorized into two classes: (1) diagenetic processes enhancing reservoir quality that include dissolution and fracturing, and (2) diagenetic processes reducing reservoir quality that include cementation and compaction.
Original Research Paper
Sedimentology
Alireza Rostami; Mohammad Adabi; Abbas Sadeghi; seyed Ali moallemi
Abstract
In this study, geochemical properties of carbonate sediment in the Dariyan Formation have been consider from original mineralogy aspect, then trace element analysis have been used for stratigraphic interpretations of this succession Petrographic studies led to the identification of 13 microfacies. These ...
Read More
In this study, geochemical properties of carbonate sediment in the Dariyan Formation have been consider from original mineralogy aspect, then trace element analysis have been used for stratigraphic interpretations of this succession Petrographic studies led to the identification of 13 microfacies. These have been deposited in four types of depositional environments, including inner ramp, mid ramp, outer ramp and basin, in a ramp type carbonate platform. Based on petrography, lateral and vertical facies changes, 3 third-order cycles distinguished. An integrated multidisciplinary approach including, petrography, surface gamma-ray spectrometry and trace element analysis have been used for recognition of original carbonate mineralogy and stratigraphic interpretations of this succession. Geochemistry of minor and major elements reveal original aragonitic mineralogy of the Dariyan Formation. Bivariate plot of Mn versus Sr/Ca values illustrated that the Aptian carbonates were affected by semi close diagenetic system with moderate water/rock interaction. Trace elements (Fe and Mn) contents are compared with distribution of sedimentary facies and depositional sequences to investigate and correlate stratigraphic boundaries. The elemental peaks coinciding with the sequence boundaries and elemental peaks are correlated with maximum flooding surfaces.
Original Research Paper
Geophysics
Ghazal Janghorban; Sayyed Mohammad Abtahi Forooshani; Keytash Moshtaghian; Hooshang Asadi Harooni; Hamzeh Sadeghi Sorkhani; Mohammad Hajheidari
Abstract
Kuh-e Lakht epithermal gold index is located on Urumieh-Dokhtar Volcanic Belt in Isfahan province. Geological studies indicate the presence of an epithermal gold mineralization system in the area. The geophysical prospecting of the index includes magnetometry, resistivity, and induced polarization surveys ...
Read More
Kuh-e Lakht epithermal gold index is located on Urumieh-Dokhtar Volcanic Belt in Isfahan province. Geological studies indicate the presence of an epithermal gold mineralization system in the area. The geophysical prospecting of the index includes magnetometry, resistivity, and induced polarization surveys in the study area. To estimate the depths of the possible magnetic sources, the Euler deconvolution process is applied. Then, we implemented Li and Oldenburg algorithm for 3D inversion of the magnetic data. The depth of the largest estimated magnetic susceptibility obtained from data inversion coincides with the average depth of the magnetic sources obtained from Euler deconvolution. Furthermore, we showed a comparison between the estimated 2D models of resistivity and electrical changeability from the inversion of resistivity and IP data and the estimated magnetic susceptibility. The comparison denotes the correlation of the estimated magnetic susceptibility variations with the reduction of resistivity, high electrical chargeability, and alteration zones. A combination of the estimated magnetic susceptibility model with the geochemical analysis of the exploratory boreholes in the area indicates that the mineralization often occurred at the maximum variation of the magnetic susceptibility. Nonetheless, the results indicate the possibility of mineralization along the zones with large variations of magnetic susceptibility.
Original Research Paper
Geophysics
mohammad fouladi; Mir Sattar Meshinchi Asl; Mahmoud Mehramuz; Nima Nezafati
Abstract
Geophysical methods have been developed to study the particulars of physically diffusible fields in the ground. In geophysical studies, the goal is usually to detect inhomogeneities inside the earth using physical values measured at the earth's surface. Geophysicists attempt to reconstruct the Earth's ...
Read More
Geophysical methods have been developed to study the particulars of physically diffusible fields in the ground. In geophysical studies, the goal is usually to detect inhomogeneities inside the earth using physical values measured at the earth's surface. Geophysicists attempt to reconstruct the Earth's interior structure using such data. The present study, which is known as the Third- order Moving Average, is the solution of an inverse problem for simultaneous estimation of the shape and depth of residual magnetic anomalies. The method was applied to the synthetic model, with and without noise, which Superiority this method will show over the Second-order Moving Average. Also, tested by the instance of field data in Geological Survey of Iran (GSI). This method, calculates a nonlinear relationship between depth and shape factor, at seven points with successive window length. Finally, the results showed that this method is very accurate for non-noise data and in has good agreement with the noisy data. which the problem, will showed the superiority of the Third-order Moving Average Method over the Second-order Moving Average method for estimating the shape and depth of buried Magnetic Anomalies. It also showed that it is suitable for real data with 5% error.
Original Research Paper
Exploration and Mining
Keytash Moshtaghian; Sayyed Mohammad Abtahi Forooshani; Hooshang Asadi Harooni; Mohammad Hajheidari; Ghazal Janghorban
Abstract
The Dalli porphyry Copper-Gold deposit consists of two northern and southern indexes located on the Urmia-Dokhtar Volcanic Belt in Markazi province. Due to the presence of magnetite beneath the potassic alteration zone in the center of porphyry mineralization, a magnetometric survey was performed in ...
Read More
The Dalli porphyry Copper-Gold deposit consists of two northern and southern indexes located on the Urmia-Dokhtar Volcanic Belt in Markazi province. Due to the presence of magnetite beneath the potassic alteration zone in the center of porphyry mineralization, a magnetometric survey was performed in the region. In the current study in the northern index, first, we extracted the local anomaly via removing the regional and aliasing effects from the magnetic data. Then, using three-dimensional inverse modeling of the reducted data illustrates the presence of a body with high magnetic susceptibility, in the depth range of 40 to 640 meters of the study area. A comparison between geochemical analysis of two exploratory core drilling with the depth variational model of the estimated magnetic susceptibility in the study area indicates a spatial correlation between increases in the grades of copper and gold and large variations of the magnetic susceptibility. Also, comparison between the magnetic susceptibility model and resistivity and chargeability models estimated from IP/RS data of three parallel profiles indicates a relation between sulfidic and altered mineralized zones and magnetic susceptibility variations. Therefore, the current study shows a high potential for the copper-gold mineralization in the northern Dalli index.
Original Research Paper
Stratigraphy and Palaeontology
elahe zarei
Abstract
The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of ...
Read More
The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of pollen are identified (Middle Jurassic) and presence of some index dinoflagellate species led to the identification of three biozones in the Dalichai Formation. These include in ascending order, Cribroperidinium crispum Total Range Biozone (late Bajocian), Dichadogonyaulax sellwoodii Interval Biozone (Bathonian - early Callovian), Ctenididinium continuum Interval Biozone (early to middle Callovian). Also, this Formation was divided into two biozone on the basis of Lenticulina varians-Ophtalmidium Assemblage zone and Globigerina bathoniana Taxon range zone.The close similarities of fauna assemblages of Dalichai Formation in this region (eastern Alborz ((dinoflagellate cyst, foraminifera, posidonia and radiolar) with assemblages recorded from different parts of Iran (such as central and eastern, western Alborz and Binalud and south of Iran) and other parts of world (northwest of Europe, and the northwestern Tethys and …) confirm the marine connection and faunal exchange between the mentioned basins during Middle Jurassic
Original Research Paper
Petrology
Ziba Khodaean Chegeni; Nematollah Rashidnejad Omran; Ali Akbar Baharifar; Reza Nozaem; Camela Vaccaro
Abstract
AbstractThe Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole-rock geochemistry show that andesitic -basalt ...
Read More
AbstractThe Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole-rock geochemistry show that andesitic -basalt and/or their intrusive equivalents with calc-alkaline to tholeiitic affinity and even a peridotite can be their protoliths. Trace element and Sr-Nd ratios imply that these rocks were from mantle melt sources. In chondrite normalized plots, these amphibolites can be classified into at least two groups. The first group is characterized by LREE depletion relative to HREEs and some with flat patterns. The second has an enrichment of LREEs relative to HREEs. These two different patterns and some other geochemical characters suggest MORB or MORB-like and arc geochemical affinities of the parental magmas. This can be related to the time progressive evolution of magmatism either from MORB or Back-arc to Arc or from Arc to Bak-arc setting.
Original Research Paper
Petrology
mohsen zadsaleh; Fariborz Masoudi; hamed Pourkhorsandi; karen Fontijn
Abstract
To investigate the magmatic processes in the Damavand magmatic reservoir and its evolution over time, the plagioclase mineral textures in pyroclastic flow and ash deposits were studied in this research. Plagioclase minerals with similar dimensions and size but with completely different textures, and ...
Read More
To investigate the magmatic processes in the Damavand magmatic reservoir and its evolution over time, the plagioclase mineral textures in pyroclastic flow and ash deposits were studied in this research. Plagioclase minerals with similar dimensions and size but with completely different textures, and plagioclases with different dimensions but with similar texture characteristics, were observed. Twenty-eight different texture types were observed in plagioclase crystals from lava flows, whereas only three texture types were distinguished in the pyroclastic deposits. A large population of plagioclases in pyroclastic deposits reveal the non-equilibrium conditions in the Damavand magmatic reservoir(s), while in lava flows, a series of plagioclase accumulations present both equilibrium and non-equilibrium conditions in the magmatic reservoir. Changes in the rate of magma ascent, small and large scale convections in magmatic reservoirs, temperature and/or pressure changes, and different volumes of (non-)eruptible mush/melt, are some of the processes and conditions that are revealed by our textural studies. In the period between about 7-450 ky ago, the magmatic reservoir that led to the buildup of the young Damavand volcano, was in non-equilibrium condition as demonstrated by individual crystals in some cases. However, non-equilibrium conditions have not always led to eruptions in Damavand volcano.
Original Research Paper
Sedimentology
Hadi Amin-Rasouli; Nasim Haghighat jou; Mehdi Moradi
Abstract
Kraftu cave, 67 km northwest of Divandareh in Kurdistan province, includes four floors. The bottom of the second floor, in the bat hall, is covered by thick guano deposits. SEM–EDX analyses of the guano deposits showed secondary sulfate (gypsum, cesanite), phosphate (phosphammite, brushite, taranakite, ...
Read More
Kraftu cave, 67 km northwest of Divandareh in Kurdistan province, includes four floors. The bottom of the second floor, in the bat hall, is covered by thick guano deposits. SEM–EDX analyses of the guano deposits showed secondary sulfate (gypsum, cesanite), phosphate (phosphammite, brushite, taranakite, francoanellite, whitlockite, leucophosphite, spheniscidite, pyrocoproite), and nitrate (urea, niter) minerals, along with microorganisms and chitin. Occurrence of these minerals is due to changes in the pH (from acidic to alkaline) and moisture (wet and dry conditions) in the presence of microorganisms. Bat guano has accumulated in Karaftu cave during three different paleoclimate conditions, from base to top, including dry, wet, and dry conditions. A comparison between distributions of secondary minerals and Ce-anomalies along the profile represents that taranakite only forms in wet conditions, but whitlockite, urea, and cesanite only occur in dry ones. Therefore, they are significant indicators of climate in the geologic record, but other minerals, because they can be in both conditions, don't be so. Various reactions between the solutions derived from guano with substrate have resulted in phosphatization and dolomitization of bedrock. The abundance of chitin in the Karaftu cave guano deposits indicates that they are feces of insectivorous bats.
Original Research Paper
Economic Geology
Seyed Mehran Heidari; Sara Safavy; Afshin Akbarpour; Azra Hassanlou; Bahram Mohaghegh
Abstract
Saveh-Razan copper (± gold) area, with WNW direction in the northwest of Urmia-Dokhtar magmatic belt, with the highest reaction to right-sided shear zones and structural trend change during the Oligomyocene, leads to the placement of semi-deep Oligomyocene diorite massifs in shallow rock depths. ...
Read More
Saveh-Razan copper (± gold) area, with WNW direction in the northwest of Urmia-Dokhtar magmatic belt, with the highest reaction to right-sided shear zones and structural trend change during the Oligomyocene, leads to the placement of semi-deep Oligomyocene diorite massifs in shallow rock depths. It is an Eocene volcano. By creating different types of mass-related hydrothermal alteration (propylitic, intermediate-advanced argillaceous, and phyllite) along the fractures, the system concentrates the mineralizations in quartz-sulfide veins, hydrothermal incisions, and concentrated sulfide-bearing filaments. Common features of metallurgy in this area are fluid homogenization temperature between 150 to 350 ° C and salinity range of 6-28% by weight of salt, containing CO2 gas and liquid phase of liquid and the presence of sulfides such as pyrite, chalcopyrite, burnite, chalcocite and sulfosalts in related reserves. There is also more gold than silver. Therefore, these features are most similar to the mass-related intermediate-type epitermal deposits that form in calcoalkalkene magmatic arcs.
