Original Research Paper
Volume 23, Issue 91 , June 2014, Pages 1-1
Original Research Paper
Volume 23, Issue 91 , June 2014, Pages 2-2
Original Research Paper
Volume 23, Issue 91 , June 2014, Pages 3-3
Original Research Paper
A.M Rajabi; M Khamehchiyan; M.R Mahdavifar
Abstract
One of the most important effects of the Manjil earthquake (M=7/7, 20/6/1990) has been triggering of the numerous landslides in the area affected by the earthquake. To predict landslides locations during the future earthquakes, it is essential to analyze the distribution of landslides triggered by the ...
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One of the most important effects of the Manjil earthquake (M=7/7, 20/6/1990) has been triggering of the numerous landslides in the area affected by the earthquake. To predict landslides locations during the future earthquakes, it is essential to analyze the distribution of landslides triggered by the Manjil earthquake. In this paper, by employing the Monte Carlo Simulation, an area with 309 km2 including Chahar – Mahal and Chalkasar rectangles (near the Manjil Epicentre) was investigated in order to achieve a probabilistic model to predict earthquake-induced landslides. There is a good correlation between the provided map and the inventory map of landslides occurred during the Manjil earthquake.
Original Research Paper
S Soltaninejad; B Shafiei
Abstract
The Now-Chun deposit, in the Kerman porphyry copper belt, with proved reserve of 268 Mt ore grading 0.034% Mo (100 ppm cut off) and 62 Mt ore grading 0.43% Cu (0.25 cut off), is the first known occurrence of Mo-rich,relatively Cu-poor porphyry mineralization in Iran which is studied from the mineralogical, ...
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The Now-Chun deposit, in the Kerman porphyry copper belt, with proved reserve of 268 Mt ore grading 0.034% Mo (100 ppm cut off) and 62 Mt ore grading 0.43% Cu (0.25 cut off), is the first known occurrence of Mo-rich,relatively Cu-poor porphyry mineralization in Iran which is studied from the mineralogical, l, and genetic point of view. The alteration and mineralization of the Now-Chun deposit is related to the highly differentiated porphyritic stock (rhyodacite) belonging to the Oligo-Miocene Mamzar batholith. Based on the present study, the main part of Mo and Cu mineralization in the Now-Chun deposit occurred more in the form of cross-cutting veinlets (stockwork) and less as dissemination type. The presence of molybdenite with/without chalcopyrite association in quartz-anhydrite-orthoclase-biotite potassic veinlets and chalcopyrite occurrence in primary quartz-magnetite veinlets is indicative of the priority of part of the Cu mineralization respect to the Mo during the primary stage of mineralization. The initial mineralization of Mo in the form of molybdenite occurred in quartz-anhydrite-orthoclase-biotite-pyrite-chalcopyrite. The weak correlation between Mo and Cu in the potassic alteration zone (r= -0.2) especially in the high grade ores indicates the difference between the enrichment conditions of both elements in responsible hydrothermal fluids for this alteration and mineralization zone. The presence of thick quartz-pyrite-chalcopyrite veinlets with sericitic halo and quartz-molybdenite without alteration halo either as independent or as intruded within early veinlets (quartz-molybdenite-anhydrite-orthoclase-biotite) have been associated with increasing of Mo and Cu grades in moderately phyllic alteration zone (sericitic and silicified rocks). The positive correlation between Mo and Cu in moderate phyllic zone (r≥ 0.0 to +0.5) which affected potassic ores indicates the similar behavior of both Mo and Cu during formation and evolution of the hydrothermal solution, which is responsible for the alteration and mineralization in the phyllic zone. This study revealed that the main concentration of Mo occurred in deep parts (potassic zone) of the deposit; whereas, Cu is associated with the shallow parts, especially with moderate phyllic zone which affected the potassic zone. As a result, the high grade Mo ores are not Cu-rich and vice versa. The present study indicated that the Now-Chun deposit in comparison with the Sar Cheshmeh deposit (Cu-Mo porphyry) is categorized within the Mo-Cu porphyry deposits. This sub-group of porphyry Cu and Mo deposit is attributed to the function of the Mo-rich and relatively Cu-poor hydrothermal fluids. The more differentiated composition of the ore-hosting porphyry in the Now-Chun deposit (rhyodacite) in comparison with the Sar Cheshmeh porphyry stock (granodiorite-quartzmonzonite), which indicates the late water saturation in its parent magma, was probably the factor of generating such fluids that could segregate the significant proportion of Mo in respect to Cu from the residual melts into H2O, alkalies and silica-enriched fluid phase which ultimately resulted in forming the Mo-Cu porphyry deposit.
Original Research Paper
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.
Original Research Paper
A Mosavinia; K Seyed-Emami; A.A Aryai
Abstract
The Aitamir Formation follows conformably but with a sharp boundary the dark shales of Sanganeh Formation (Aptian-early Albian) and is followed discontinuously by the whitish marls and chalky limestones of the Abderaz Formation (Turonian-Coniacian). 7 species, 13 genera and 2 subgenera of ammonites are ...
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The Aitamir Formation follows conformably but with a sharp boundary the dark shales of Sanganeh Formation (Aptian-early Albian) and is followed discontinuously by the whitish marls and chalky limestones of the Abderaz Formation (Turonian-Coniacian). 7 species, 13 genera and 2 subgenera of ammonites are reported in this paper. The following genera and species, found in the Iranian Kopeh Dagh region, are reported for the first time: Anahoplites cf. praecox Spath, 1925, Anahoplites mantelli Spath, 1925, Epihoplites aff. trifidus (Spath, 1923) and Hysteroceras orbignyi (Spath, 1922). The described specimen of Dinosauria comes from the upper part of the Aitamir Formation in Zawin Section. The fragment of the Dino was found on the topmost sandstone layer of the section, together with a number of mortonoceratid ammonites, indicating a late Albian (Mortoniceras inflatum Zone) age. So far, it is the first record of marine Dinosauria from the Certaceous of Iran.
Original Research Paper
B Shahbazi; B Rezai; S.M.J Koleini; M Noaparast
Abstract
In this research the effect of bubble surface area flux on flotation rate constant of coal particles was investigated and the results showed that flotation rate constant increased with increasing bubble surface area flux. The obtained Maximum flotation rate constant was 3.30 /min while the particle size ...
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In this research the effect of bubble surface area flux on flotation rate constant of coal particles was investigated and the results showed that flotation rate constant increased with increasing bubble surface area flux. The obtained Maximum flotation rate constant was 3.30 /min while the particle size and bubble surface area flux were -37mm and 25.891/s, respectively. The bubble-particle collision, attachment and detachment efficiency were calculated in order to analyze the results. The obtained Maximum Stokes collision efficiency was 81.57% while the particle size, bubble surface area flux, and flotation rate constant were -500+420mm, 27.431/s, and 1.17/min, respectively. The obtained Maximum Yoon, Stokes and Potential efficiency were 94.66, 56.74 and 45.61%, respectively. Moreover, the obtained maximum detachment efficiency was 34.57% while the particle size, bubble surface area flux and flotation rate constant were -500+420mm, 16.771/s, and 0.85 /min. The collection efficiency increased with increasing of the bubble surface area flux. The collection efficiency was high for the particle size range of -106+37mm and for out of this particle size range it decreased steadily. So, the low efficiency of floating coarse particles can be attributed to the high efficiency of detachment while the low efficiency of floating of the fine particles was due to the low efficiency of collision.
Original Research Paper
K Khaksar; F Rezvannia; M.R Kebriaei-Zadeh
Abstract
The rugose coral Marzanophyllum chalusense gen. and sp. nov. from late Visean (early Carboniferous) in the Vali-Abad section (Central Alborz, N Iran) is described in detail. This solitary coral has thick wall and thick septa with no dissepiment. The genus Zaphrentoides has similar structure, but it possesses ...
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The rugose coral Marzanophyllum chalusense gen. and sp. nov. from late Visean (early Carboniferous) in the Vali-Abad section (Central Alborz, N Iran) is described in detail. This solitary coral has thick wall and thick septa with no dissepiment. The genus Zaphrentoides has similar structure, but it possesses well developed cardinal septum. The new genus is placed in the Subfamily Zaphrentoidinae because of the fossula shape, structure of its septa and incompleted tabulae. This small and undissepimented solitary rugose coral belongs to Cyathaxonia family. They are found at oolitic limestone level. The corals of member C of the Mobarak Formation have endemic character and based on the accompanied fauna and stratigraphic position they are attributed to late Visean.
Original Research Paper
E Hajizadeh Naddaf; B Oveisi; M.R Ghasemi; M.J Bolurchi
Abstract
The analytical models in rock mechanics represent suitable analysis of deformation and failure conditions of the samples bearing simple geometry and mechanical properties. Nowadays different methods of numerical modeling, like finite difference method (FDM), are used for analysis of continuous, non- ...
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The analytical models in rock mechanics represent suitable analysis of deformation and failure conditions of the samples bearing simple geometry and mechanical properties. Nowadays different methods of numerical modeling, like finite difference method (FDM), are used for analysis of continuous, non- and quasi- continuous behavior. This paper represents logical estimate of geomechanical properties of the Asmari formation with usage of the results of triaxial tests on intact rock samples of the upper limy part of this formation and also the finite difference methods. For this purpose, we designed some models containing simple boundary condition and only one rheological unit. To simulate the failure conditions of the samples, a geomechanical simulative software (Flac 2D) was used. The failure of samples under the experienced stress conditions in laboratory were of basic data for simulation of failure conditions by finite difference method. The results show that the cohesion coefficient and uniaxial tensile strength are of sensitive parameters in controlling the failure conditions. This study suggests that the values of Young's and Bulk modulus are 260GPa, 23GPa, respectively, when the uniaxial tensile strength and cohesion coefficient are considered 29MPa and 26MPa, respectively.
Original Research Paper
M Derakhshi; H Ghasemi; T Sahami
Abstract
The Soltan Maydan Basaltic Complex indicates the most important, thickest, and most voluminous early Paleozoic magmatic activity in Iran outcropping in the eastern Alborz structural zone, in the north-northeast of Shahrud. This complex overlies the late Ordovician Ghelli Formation and is overlain by ...
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The Soltan Maydan Basaltic Complex indicates the most important, thickest, and most voluminous early Paleozoic magmatic activity in Iran outcropping in the eastern Alborz structural zone, in the north-northeast of Shahrud. This complex overlies the late Ordovician Ghelli Formation and is overlain by the early Devonian Padeha Formation. The field evidences show more than 50 lava flows erupting frequently in the sub-aerial and submarine environments. This complex comprises of a continuous fractional spectrum including basalt, basaltic andesite, trachybasalt and basaltic trachyandesite that has undergone medium to high degrees of alteration. The geochemical data and diagrams signify transitional to alkaline nature of the primary magma, genetic relationship among all rocks of this complex due to fractional crystallization, none or weak role of magmatic contamination in magma evolution, and generation of primary magma by 15-17 percent partial melting of an enriched garnet peridotitic mantle source in an intra-continental extensional rift setting. This tectonic setting is concordant with the known extensional rift setting governed on the Alborz and Central Iran zones during the early Paleozoic, especially late Ordovician-Silurian, primary stages of generation and development of the Paleotethys.
Original Research Paper
S.T Delavar; I Rasa; M Lotfi; G Borg; N Rashidnejad Omran; P Afzal
Abstract
Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized ...
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Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized in the deposit: 1-layers and lenses, concordant with layering; and 2-discordant secondary forms along the fractures. In Tangedezan deposit two mineralized carbonate facies have been distinguished: 1- dolomitic limestone facies (Microsparite) containing three major mineralization horizons with simple ore mineral paragenesis such as galena, sphalerite and pyrite replacing the host rock and filling the porosities and fractures; and 2- crystallized argillaceous limestone facies with very weak Zn-Pb mineralization in disseminated form. The deposit includes two parts of supergene in surface and sulfides in depth. The simple ore paragenesis comprises of hemimorphite, smithsonite, cerussite, galena, sphalerite and pyrite. Ag and Cd elements have noticeable grade and could be contemplated as by product. All accomplished investigations and evidences such as geological characteristics, mineralized facies, supergene and sulfide development, ore body geometry, ore minerals paragenesis, texture and structures in different scale, existing alterations specially dolomitization and lithogeochemical studies all reveal that Tangedezan deposit is a Zn-Pb Mississippi Valley Type (MVT) deposit.
Original Research Paper
M Sohrabi Mollayousefi; M Sahba
Abstract
The study area includes a part of the northern strip of Persian Gulf coast, a distance of approximately 650 kilometers. The Persian Gulf is a marginal, semi-closed, and shallow sea with salty and warm water. It has a circular flow in a clockwise direction along the coast of Iran, caused by the high range ...
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The study area includes a part of the northern strip of Persian Gulf coast, a distance of approximately 650 kilometers. The Persian Gulf is a marginal, semi-closed, and shallow sea with salty and warm water. It has a circular flow in a clockwise direction along the coast of Iran, caused by the high range of evaporation. The ecology characteristics of The Persian Gulf have created special microfauna among which the hyaline foraminifera were studied in this research. In addition to sampling of coastal sediments, physicochemical properties of water were measured. It was determined that the physicochemical factor affecting the development, abundance, and diversity of foraminifera is dissolved oxygen. In general, 29 genera and 35 species of foraminifera were identified among them the most common foraminifera contain calcareous hyaline shell. The ratio of biocenosis to taphocenosis has a direct relationship with the amount of environmental pollutants. However, as the pollution rate is increased, the quantity and diversity of biocenosis species is decreased and the taphocenosis is upgraded. Another important factor in the abundance of foraminifera is the bed sedimentological characteristics, as the frequency of biocenosis and taphocenosis is higher within the fine-grained beds, whereas, in the low or absence of pollution, the abundance of protoplasm-containing shells within the silty-muddy beds is much higher than the other areas.
Original Research Paper
B Azadbakht; M Zareinejad
Abstract
Water causes erosion of different forms in nature and creates diverse landforms on the earth’s surface depending on the manner it appears in nature. Although water is itself a former factor, it flows under the morphological effect of earth’s surface (Ramasht, 2005). The difference of earth’s ...
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Water causes erosion of different forms in nature and creates diverse landforms on the earth’s surface depending on the manner it appears in nature. Although water is itself a former factor, it flows under the morphological effect of earth’s surface (Ramasht, 2005). The difference of earth’s surface topography and its consequent of water movement on it, cause the formation of sub-basins. In order to recognition of morphology and morphometry of Damavand cone, the region drainage basins must be distinguished. Therefore, in this study 5 drainage basins were identified based on the main criteria including topographic contours with 10 m intervals, drainage system (main and subsidiary rivers, main and subsidiary streams), DEM map of the region, slope map, aspect map and satellite images. Area, perimeter, height classification for classifying the morphological landforms in different levels, hypsometric, drainage density, etc. were then calculated by using the ArcGIS software. The Damavand cone, with a height more than 5,000 m above the sea level, has a very hard-pass slopes. Our purpose in this paper is to identify the effect of drainage basins conditions on the erosion and formation of geomorphological landforms by using of SPOT and ASTER satellite images as well as data analysis o in GIS environment.
Original Research Paper
F Hosseinipour; M.J Hassani; M Dastanpour
Abstract
The Guri limestone member of the Mishan formation in SE of Zagros Basin (N of Bandar-e-Abbas) consists of the thick bedded limestone bearing oyster shells. Seven species of Ostreidae and Gryphaeidae belonging to four genera of Crassostrea, Cubitostrea, Ostrea and Hyotissa were identified as: Cubitostrea ...
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The Guri limestone member of the Mishan formation in SE of Zagros Basin (N of Bandar-e-Abbas) consists of the thick bedded limestone bearing oyster shells. Seven species of Ostreidae and Gryphaeidae belonging to four genera of Crassostrea, Cubitostrea, Ostrea and Hyotissa were identified as: Cubitostrea frondosa, Ostrea (cubitostrea) dubertreti, Cubitostrea digitalina, Crassostrea gryphoides, Hyotissa virleti, Ostrea vesitata and Ostrea plicatula. These fossils are reported from the Zagros Basin for the first time. These deposits assign to a Burdigalian age based on the presence of Borelis melo curdica. The reclining mode of life, adjacent right and left valves and rare erosion traces on shells indicate an in situ buried in hyper saline shallow and near shore water with moderate to low sedimentation rate. The early Miocene oyster assemblages similar to this studied assemblage have been reported from the other parts of Tethys showing a seaway connected to Tethys during the early Miocene. Therefore, the oysters can be used for the Paleogeographical correlation in the early Miocene deposits.
Original Research Paper
A Abbaszadeh Shahri; F Rezaei; K Mehdizadeh Farsad; R Rajablou; N Panaei
Abstract
Liquefaction is a process in which a soil suddenly loses its strength and most commonly occurs as a result of ground shaking during a large earthquake or other rapid loading. The aim of this study is providing and developing of a geotechnical- based computer code for nonlinear site response analysis, ...
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Liquefaction is a process in which a soil suddenly loses its strength and most commonly occurs as a result of ground shaking during a large earthquake or other rapid loading. The aim of this study is providing and developing of a geotechnical- based computer code for nonlinear site response analysis, employing the field and laboratory tests and also combination of several softwares, represents a new method for evaluating the liquefaction potential. In order to verify the proposed method, the Avaj-Changureh earthquake of 2002 was applied on Korzan earth dam in Hamedan province and for determination of its accuracy; it was compared with several known techniques. The obtained results showed proper compatibility with other known methods.
Original Research Paper
E Moosavi; M Mohajjel
Abstract
The North Esfajerd ductile shear zone is exposed in NE Golpaygan in the Sanandaj-Sirjan zone. The shear sense indicators are observed in the both outcrop and microscopic scales in this shear zone. These indicators are representing a NW striking dextral shear. The dynamic analysis and outcrop- scale indicators ...
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The North Esfajerd ductile shear zone is exposed in NE Golpaygan in the Sanandaj-Sirjan zone. The shear sense indicators are observed in the both outcrop and microscopic scales in this shear zone. These indicators are representing a NW striking dextral shear. The dynamic analysis and outcrop- scale indicators of extension direction exhibit a NW extension sub-parallel to the dextral shear and a compression perpendicular to it. The relative simultaneity and parallelism between North Esfajerd ductile shear zone and North Varzaneh thrust shear zone propose the partitioning of strain components in a transpressional deformation. Regarding the geochronologic data and the angular unconformity between the middle Cretaceous and Eocene rock units, the transpressional deformation and its related mylonitization occurred during the Laramide orogeny in late Cretaceous-Paleocene. The gently dipping mylonitic foliations with dextral shear imply an incompatibility between geometry and kinematics in the North Esfajerd ductile shear zone. However, the kinematic and dynamic characteristics of the North Esfajerd ductile shear zone are accommodated with lateral extrusion of material in a dextral domain.
Parallelism between the trends of dominant stretching lineations and the second generation large scale fold axes document that the major mylonitization in the North Esfajerd shear zone occurred during the second generation deformation. These mylonitic fabrics were folded due to the third generation deformation. Two generations of crenulation cleavages, respectively in relation to two refolding events, can be recognized in this shear zone. One of the refolding events with type III interference patterns (coaxial refolding) occurred during the second stage deformation in the late Cretaceous- Paleocene interval, caused the formation of the North Esfajerd shear zone, and can be observed in an outcrop scale. The other has emerged during the third stage of deformation, probably in the post Paleocene-pre Miocene interval, folded the North Esfajerd shear zone and formed the type II (boomerang shape) interference pattern in a map scale.
Original Research Paper
Kh Sarkarinejad; Z Kamali
Abstract
The NE oriented Dasht-e-Arjan graben with orientation is located in 65 Km west of ShirazCity. This graben is resulted from the active Kare-e-Bas fault segmentations. This extensional graben system is part of the Zagros Simply Folded Belt and bounded by two boundary fault system perpendicular to the Shahneshin ...
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The NE oriented Dasht-e-Arjan graben with orientation is located in 65 Km west of ShirazCity. This graben is resulted from the active Kare-e-Bas fault segmentations. This extensional graben system is part of the Zagros Simply Folded Belt and bounded by two boundary fault system perpendicular to the Shahneshin anticline and Salamati anticline. These two boundary faults were named the East-Arjan and West-Arjan faults in this paper. The oriented samples and slabs from slickensides and slickenlines of these two faults were collected in order to reconstruct paleostress orientations for the Dasht-e Arjan graben activities. The paleostress analysis based on the fault-slip inversion method was performed from the striations or the slickenlines data collected from the two faults planes. This showed that the orientations of the maximum principal stress (σ1) of the graben is 70°, N 26° E and the minimum principal stress (σ3) is 25°, S 40°E. Microscopic examination of the oriented thin sections (XY- and XZ- planes) indicated that they consist of the type І and type П calcite e-twins. The measurements of the e- twin and c- axis were carried out using an optical polarizing microscope equipped with 5-axis Universal Stage in order to determine orientations of "Compression"(P) and "Tension" (T) axes. The mean orientation of the sub-vertical maximum principal stress (σ1) is N 35° E ± 11. 72º and mean orientation of the minimum principal stress (σ3) is S 35° E ± 9،32°. The stress field around the boundary faults of the graben is related to the stress field of the Kare-e Bas fault activities.
Original Research Paper
M Sheban; F Ghaemy; A Abbasnejad; F Ghaemy
Abstract
Neotectonics that is a major factor of landform development in tectonically active regions has significantly affected fluvial systems and mountain-front landscapes in the Behabad area of the Central Iran Zone. To assess tectonic activities in the area, we analyzed geomorphic indices including the mountain-front ...
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Neotectonics that is a major factor of landform development in tectonically active regions has significantly affected fluvial systems and mountain-front landscapes in the Behabad area of the Central Iran Zone. To assess tectonic activities in the area, we analyzed geomorphic indices including the mountain-front sinuosity (Smf), stream-gradient index (SL), valley floor width–valley height ratio (Vf), drainage basin shape (Bs) and drainage basin asymmetry (Af). These indices were combined to yield the relative active tectonics indices (Iat). Based on Iat values, the study area was divided into four parts: Class 1 (very high relative tectonic activity, 1.52% in area), Class 2 (high, 68.58%), Class 3 (moderate, 20%), and Class 4 (low, 9.9%). The results are consistent with field observations on landforms and geology. The active tectonics indices and geomorphological evidences indicate that the tectonic activity rate in the studied area is predominantly moderate to high.
Original Research Paper
A.N Pourtaghavi; M Pourkermani; G.R Gharabeigli; Sh Sherkati
Abstract
The western part of Kopet Dagh fold belt is located in NE of Iran. The southern half of this belt is located in Iran and the northern half in Turkmenistan. The Kopet Dagh fold belt can be considered as the second important hydrocarbon province of Iran. Sedimentation in this zone began in Middle Jurassic ...
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The western part of Kopet Dagh fold belt is located in NE of Iran. The southern half of this belt is located in Iran and the northern half in Turkmenistan. The Kopet Dagh fold belt can be considered as the second important hydrocarbon province of Iran. Sedimentation in this zone began in Middle Jurassic due to the intercontinental rifting. The Middle Jurassic sediments lay unconformably on the Paleozoic and Triassic sediments. The geometric pattern of the folds has been studied based on the field work, geological maps, and geophysical data. The results show a thick skin deformation with shortening of about 5% during the tectonic inversion caused by the Pasadenian orogeny phase, which governing the deformation of the region.
Original Research Paper
K Shabani Goraji; R Moussavi-Harami; A Mahboubi; Kh Khosro Tehrani
Abstract
The provenance and tectonic setting of the Eocene turbidite sandstones of the Saravan area in southeast of Iran have been studied based on petrography and geochemistry. These sandstones are very laterally extended and traceable at several kilometers. The sandstones are sharp-based and well-preserved ...
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The provenance and tectonic setting of the Eocene turbidite sandstones of the Saravan area in southeast of Iran have been studied based on petrography and geochemistry. These sandstones are very laterally extended and traceable at several kilometers. The sandstones are sharp-based and well-preserved and generally display Bouma sequences (Tbcde, Tabc, Tbcd, Tabcd) which consist of graded bedding, flute and groove casts, planar cross lamination, current ripples and parallel lamination. The deep water trace fossils (Nereites ichnofacies) are locally abundant. These characteristics support sedimentation by the turbidity current. The petrographical data show that these sandstones are fine to coarse grained, poorly to moderately-sorted, sub-angular to sub-rounded feldspatic litharenite. They contain mono- and poly-crystalline quartz grains, feldspar, volcanic and metamorphic rock fragments and represent Q55F14.7L30.3 proportion. The major, trace and rare earth element concentrations indicate that the source of these sediments were intermediate to felsic igneous rocks. Mean value of chemical index of alteration in analyzed samples (CIA mean ≈ 62) indicate a low to moderate degree of chemical weathering of the source area or during the sediments transportation prior to deposition.The petrographic analysis revealed a recycled orogen and transitional recycled tectonic provenance. Tectonic setting discrimination based on the major, trace and rare earth elements suggest that the Saravan sandstones components derived from an active continental margin and continental arcs.
Original Research Paper
A.R Najafzadeh; H Ahmadipour
Abstract
The Abdasht complex is one of the major ultramafic complexes in south-east Iran (Esfandagheh area). This complex is composed mainly of dunite, harzburgite, lherzolite, chromitite, and subordinate wehrlite. The detailed electron microprobe study revealed very high Cr# (48-86), Mg# (26-56) and very low ...
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The Abdasht complex is one of the major ultramafic complexes in south-east Iran (Esfandagheh area). This complex is composed mainly of dunite, harzburgite, lherzolite, chromitite, and subordinate wehrlite. The detailed electron microprobe study revealed very high Cr# (48-86), Mg# (26-56) and very low TiO2 content (averaging 0.07 wt %) for chromian spinels in peridotites. The Fe3+# is very low (<0.08 wt%) in the chromian spinel of peridotites which reflects crystallization under the low oxygen fugacities. The harzburgite, dunite and lherzolite samples are highly depleted in PGE contents relative to the chondrites. The PdN/IrN ratios in dunites are unfractionated, averaging 0.72, whereas the harzburgites and lherzolites show slightly positive slopes PGE spidergrams, together with a small positive Ru anomaly, and their PdN/IrN ratio averages 2.4 and 2.3, respectively. Moreover, the PGE chondrite and primitive mantle normalized patterns of harzburgite, dunite and lherzolite of this complex are relatively flat which are comparable to the highly depleted mantle peridotites and indicating a high degree of partial melting (about 20-25%) of the mantle source. The mineral chemistry data and PGE geochemistry of Abdasht peridotites indicate that the Abdasht ultramafic complex was generated from an arc-related magma with boninitic affinity above a supra-subduction zone setting.
Original Research Paper
A Zia Zarifi; S Mehri; P Afzal; H.R Jafari
Abstract
Airborne radiometer data is the best to study the distribution of radioactive elements of an area. In this paper, separation of anomaly values have been performed by means of the classical statistics, the tables of frequency distribution of uranium, thorium and potassium have been produced, the frequency ...
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Airborne radiometer data is the best to study the distribution of radioactive elements of an area. In this paper, separation of anomaly values have been performed by means of the classical statistics, the tables of frequency distribution of uranium, thorium and potassium have been produced, the frequency distribution histograms that are introducer of distribution and dispersion of these elements have been plotted, and the statistical parameters of these elements have been estimated. The separation of anomaly value has been done based on the dispersion around the average. The distribution maps of radioactive elements were drawn. These mentioned data were controlled in the field by the radiometric measurements and chemical analysis. Finally, the results of radiometric measurements and chemical analysis revealed non-economic mineralization in the region.
Original Research Paper
S Alipour; A Abedini; Sh Abdali
Abstract
The Heydar-Abad laterite horizon is located at 65 km south of Urmia, West Azarbaidjan province. This horizon was developed as stratiform bed within the carbonate rocks of the late Permian Ruteh Formation. Based on the petrographical and mineralographical studies,the ores of this horizon contain micro-granular, ...
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The Heydar-Abad laterite horizon is located at 65 km south of Urmia, West Azarbaidjan province. This horizon was developed as stratiform bed within the carbonate rocks of the late Permian Ruteh Formation. Based on the petrographical and mineralographical studies,the ores of this horizon contain micro-granular, fluidal-collomorphic, panidiomorphic-granular, spastoidic, pelitomorphic, nodular, and ooidic textures and have an authigenic origin. According to the mineralogical investigations, the ores of this horizon include minerals such as diaspore, corundum, hematite, magnetite, goethite, rutile, paragonite, margarite, amesite, berthierine, montmorillonite, chlorite, chloritoid, muscovite-illite, quartz, pyrite, anhydrite, calcite, and dolomite. The presence of high quantities of silicate minerals indicates immaturity and poor draining system during the development of this residual horizon. The results of chemical analyses show that Eu and Ce anomalies in the ores are within the ranges of 0.67 to 2.74 and 0.86 to 2.16, respectively. The calculations of values of enrichment factor of elements in two selected profiles reveal that two processes of leaching and fixation are major regulators of concentrations of REEs in ores of this horizon. The results obtained from the mineralogical and geochemical studies show that changes of pH of weathering solution, fluctuations of level of ground-waters, alteration intensity, and function of carbonate bedrocks as a geochemical barrier, adsorption, and scavenging have played an important role in distribution of the rare earth elements (REEs) in this deposit. The correlation coefficients show that the secondary phosphates, rutile and muscovite-illite are potential hosts for REEs in the ore.
Original Research Paper
M Asadi; H Alimohammadian; M Oviesy Moakher; N Mirzaei
Abstract
Palaeomagnetic analysis has been applied worldwide on active faults for decades. The palaeomagnetic investigation on the Sahneh Fault, at middle part of the Zagros Main Recent fault, is the main objective of this research. The length of the Sahneh fault, which is about 100 km in study area, cuts the ...
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Palaeomagnetic analysis has been applied worldwide on active faults for decades. The palaeomagnetic investigation on the Sahneh Fault, at middle part of the Zagros Main Recent fault, is the main objective of this research. The length of the Sahneh fault, which is about 100 km in study area, cuts the gabbroic blocks exposed on the both sides with NW-SE trend and connects the Morvarid fault in the NW to the Nahavand fault in the SE of the study area. Tectonically, the mechanism of the Sahneh fault is high angle reverse with dextral strike slip component, and is compatible with the earthquakes focal mechanism solution, movement of the Arabian plate towards the Central Iran and the results of palaeomagnetic data. The paleomagnetic analysis results are based on the drilled oriented samples of 17 selected sites along and on both sides of the Sahneh fault. Nine to eighteen oriented samples were collected from each site. The conducted paleomagnetic analysis includes measurement of NRM, magnetic mineralogy (high temperature), and thermal/ AF demagnetizing. The declination, inclination and ChRM directions of each site separated from the overprint directions by means of the thermal demagnetization method. The mean direction of ChRM and VGP for each site is determined using statistics and palaeomagnetic analysis. For 7 sites the ChRM mean direction is calculated. The obtained mean ChRM directions then compared with the reference palaeomagnetic pole position of the ophioliths of Central Iran, and the sense of rotation were determined for all sites. The dextral strike-slip Movement of the Morvarid and Nahavand faults imposed a compressional and shear stress components on the Sahneh fault, resulted in the formation of transpressional stress regime in the study area. Under this tectonic stress regime, the Riedel of shear systematic fractures may be helpful to interpret the palaeomagnetic data. According to this model, the whole synthetic shear fractures (P, R, D) caused clockwise rotation and the antithetic shear fractures (Ŕ) caused counterclockwise rotation in gabbroic blocks.
Original Research Paper
M.A Sajadi Nasab; M Vosoughi Abedini; M.H Emami; M Ghorbani
Abstract
The studied granitoidic intrusion with about 50 km2 area is located in the SW of Kelardasht, one of the regions in MazandaranProvince. It is one of the pluton masses of the Central Alborz structural zone. The mass has an age between 54±4 and 56±3 million years (late Paleocene to early Eocene) ...
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The studied granitoidic intrusion with about 50 km2 area is located in the SW of Kelardasht, one of the regions in MazandaranProvince. It is one of the pluton masses of the Central Alborz structural zone. The mass has an age between 54±4 and 56±3 million years (late Paleocene to early Eocene) and has intruded in the Mobarak and Shemshak formations. Petrologically it contains of two units of felsic (granite, qz-syenite, and qz-monzonite) and intermediate to mafic (monzonite to monzodiorite, diorite, and gabbro). The rocks of the first group especially granites and q-monzonites show many mineralogical and textural similarities and in which the evidences of magma mixing like rapakivi texture, poikilitic texture, acicular apatite, calcic plagioclase "spikes" in plagioclase, and micro granular mafic enclaves can be seen. These rocks have weak metaaluminous to peralumine nature (granite samples) and are richer in K2O+Na2O, K2O and the elements of Rb, Th, Hf than the second group. Due to the diagram related to REE, the rocks of this group have remarkable enrichment of LREE and related to the behavior of Y, Ba, Ce, and Zr in segregation process, they show the properties of low temperature I-type granites. In the second group, monzonite and monzodiorite rocks also show the evidences of alkaline metasomatism, associated with magma mixing textures including acicular apatite, septum biotites and anortite spikes in plagioclases. These rocks have meta alumine nature and show more richness in FeOT, MgO, CaO, bP2O5, TiO2, and the elements such as Sr, Ba, V, and Y than the first group; and also they show the properties of the high temperature I-type granites. Due to the geochemical evidences and the age of the mass, it can be categorized as post orogenic granite types, which have the properties between VAG and WPG. The isotopic investigation of 143Nd/144Nd revealed that only the granites of the region have can have enriched lithospheric source (negative εNd) and the other rocks have a depleted mantle source (positive). According to the petrographical and geochemical evidences, magma mixing has played an important role in magma evolution, and therefore, the crust melting model by mantle-derived magma is suggested for the magma generation of the area.
