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مرکز اطلاعات علمی SID1
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    107
  • End Page: 

    120
Measures: 
  • Citations: 

    0
  • Views: 

    170
  • Downloads: 

    196
Abstract: 

Azna tungsten (copper) ore occurrence is located 2 km west of Azna, in Lorestan province. The region is placed in Sanandaj-Sirjan structural zone of Iran, at the complex deformation sub-zone. In this area, tungsten-copper mineralization occurs as stratiform-stratabound in mylonitic meta-rhyolite and semi-pelitic country rock within upper Triassic volcano sedimentary sequence. The sequence consists of meta-rhyodacite, amphibolite (basic meta-volcanic), black schist, meta-rhyolite and pelitic schist with a predominance of volcanics over sediments. Ore mineral textures cover a wide variety from laminated, disseminated, choloform, bounded to open space filling. Mineralization occurs in several stages concentrated through regional (medium to high grade facies) metamorphism, folding and mylonitization of shear zone (ductile) and fractures of brittle deformation events. In this ore occurrence, metamorphism and deformations process had confused detection of proximal or distal mineralization. But base of comparison of Azna tungsten mineralization with both typical proximal on Felbertal and Austroalpine and distal on Broken Hill and Kleinarltal tungsten mineralizations has shown that they are more similar to the proximal mineral deposits.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    121
  • End Page: 

    130
Measures: 
  • Citations: 

    0
  • Views: 

    329
  • Downloads: 

    94
Abstract: 

Investigation on brachiopods and conodonts of Mobarak Formation in Kalariz section confirms the age of Early Tournaisian to Middle Visean. Some species as Bispathodus aculeatus aculeatus, Bi. stabilis, Spinocarinifera nigra and Shumardella sp. in the lowest part of section show the Early Tournaisisan age, whereas the middle part is Middle to Late Tournaisian on the basis of the presence of Tomiproductus vaughani, Tomiopsis sp., Scabricosta sp., Polygnathus flabellus, P. rostratus, P. longiposticus, Clydagnathus cavusformis. Some faunas as Marginatia kinghirica and Buxtonia cf. praejuresanensis prove the Early to Middle Visean for the upper part of section. Three domestic biozones are recognized on the basis of faunal distribution in the stratigraphic column. Biozone 1 (Early Tournaisian): this zone can be recognized by the association of these species: Spinocarinifera nigra, Rossirhynchus adamantinus, Shumardella sp., Cleiothyridina transversa, Bispathodus aculeatus aculeatus, Bi. stabilis, Polygnathus communis communis, P. inornatus. Biozone 2 (Middle to Late Tournaisian): Tomiproductus vaughani, Tomiproductus elegantulus, Tomiopsis sp., Scabricosta sp., Tylothyris planimedia, Syringothyris altaica, Leptagonia analoga, Leptagonia cf. regularis, Ripidomella michelini, Athyris hibernica, Spirifer missouriensis, Schelwienella sp., Leptagonia cf. regularis, Torynifer sp., Polygnathus flabellus, P. longiposticus, P. inornatus, P. aff. inornatus, P. rostratus, P. sp., P. communis communis, Bispathodus stabilis, Pseudopolygnathus primus, Clydagnathus cavusformis. Biozone 3 (Early to Middle Visean): this zone is identified by the presence of some index species as: Buxtonia cf. praejuresanensis, Megachonetes sp., Actinoconchus lamellosus, Orthotetes batesvillensis, Marginatia cf. kinghirica, Balakhonia sp. Mobarak Formation conformably overlies the Geirud Formation and disconformably underlies the Dorud Formation demonstrating Late Viséan to Gzelian hiatus as the result of Hercynian epeirogenesis.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    13
  • End Page: 

    20
Measures: 
  • Citations: 

    1
  • Views: 

    185
  • Downloads: 

    79
Abstract: 

Determination of the geometry of bedrock, by nonlinear inverse modeling of gravity data, is the aim of this paper. In this method, reliable geological structures can be obtained by minimum geology priori information. The usual practice of inverting gravity anomalies of two-dimensional bodies replaced by n-sides polygon for determining location of the vertical that best explain the observed anomalies. In this method, the geometry of the bedrock is replaced by a series of juxtaposing prisms. Finally the length of each prism is the depth of the bedrock at that point. The algorithm uses a nonlinear iterative procedure for simulation of bedrock geometry. At the first step, the nonlinear problem changes to a linear problem by a proper approximation and standard method. The second step is the parameterization of the model. Finally, an initial model is suggested on the basis of geological and geophysical assumption and using the numerical analysis, Jacobean matrix is calculated. In each iteration the inversion will improve the initial model, considering the differences between observed and calculated gravity anomalies, based on Levenberg-Marquardt's method. The practical effectiveness of this method is demonstrated by inversion of synthetic (free noise and noise contaminated data) and real examples. The real data is acquired over the Moghan area and the results compared with the geological information.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    131
  • End Page: 

    136
Measures: 
  • Citations: 

    0
  • Views: 

    139
  • Downloads: 

    84
Abstract: 

We compute p receiver functions (RF) to investigate the crustal thickness and Vp/Vs ratio beneath the northwest of Iran and map out the lateral variation of Moho depth under this region. We selected data from teleseismic events (Mb ³5.5, 30o<D<95o) recorded since 2000 to present at 8 three component short period stations from Tabriz teleseismic network. RF method is now a well-known tool for studying crustal thickness when such a complete data set is available. As the p-to-s conversion points at the Moho is laterally close to the stations, the Moho depth estimation is less affected by lateral velocity variations and thus provides a good point measurement. First of all, we calculated RFs for each station and then the Moho depth will be estimated only from the delay time of the Moho p-to-s conversion phases. Then we used an H-Vp/Vs stacking algorithm (Zhu & Kanamori, 2000) to estimate crustal thickness and Vp/Vs ratio under each station from P-to-S converted waves in receiver functions. The best value for H and Vp/Vs ratio is found when the three phases (Ps and crustal multiples) are stacked coherently. The average Moho depth is approximately 48 km and varies from 38.5±1 to 53.5±1 km. Deeper and shallower Moho is found under the western and eastern stations beneath SHB and SRB stations respectively. The northwest Iran's crust has an average Vp/Vs ratio of 1.76, with higher ratio of 1.82±0.03 in Tabriz station and lower ratio of 1.73±0.03 in Azarshahr station.

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Writer: 

ATAEI M. | HOSEINIE S.H.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    137
  • End Page: 

    142
Measures: 
  • Citations: 

    0
  • Views: 

    209
  • Downloads: 

    285
Abstract: 

Abrasivity, as one of the most important parameters has great influence on drilling rate. Up to now, four known methods such as "Rock Abrasiveness Index (RAI)", "Cerchar Abrasiveness Index (CAI)", "Schimazek's wear factor (F-abrasivity)" and "Bit Wear Index (BWI)" have been developed for evaluating of rock abrasivity. In this paper, abrasivity of six rock types has been studied using Schimazek's wear factor and Rock Abrasiveness Index. For this purpose, equivalent quartz content and the mean size of rock grains have been calculated using thin section of rocks. All types of rocks have been tested view pointed of compressive and tensile strength (Brazilian test) in laboratory. For evaluating of drillability of rocks, the samples have been drilled using actual percussive-rotary drilling machine. Results reveal that by increasing Schmazek's wear factor, drilling rate decreases logarithmically and by increasing Rock Abrasiveness Index, drilling rate decreases exponentially.

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Writer: 

AYAT M.G. | MOZAFARI A.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    143
  • End Page: 

    148
Measures: 
  • Citations: 

    0
  • Views: 

    269
  • Downloads: 

    918
Abstract: 

Drilling is considered to be an inseparable part of the mine extraction operations, and so far a more appropriate method has not been substituted for these operations. There are different drilling methods which can be used in surface mining such as Rotary, Top hammer, Down the hole, and Coprod. The new drilling method that is used nowadays in surface mining in the developed countries is the Coprod. This method has been designed for drilling under hard geological conditions in surface mines, and innovation of this drilling is to overcome the drilling difficulties under the special geological conditions. In this article, by introducing the new Coprod drilling method and evaluation of its advantages and disadvantages from the technical and economical point of view compared to other conventional drilling methods, the possibility of its application in the dichotomized surface mines of the country has been investigated. In addition, selection method of the appropriate mining machineries with consideration of their application in the surface mines of the country has been thoroughly studied.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    149
  • End Page: 

    156
Measures: 
  • Citations: 

    1
  • Views: 

    275
  • Downloads: 

    111
Abstract: 

The Iranian plateau lies between the Arabian and Eurasian plates and accommodates approximately 22 mm/yr of N-S shortening. About 9 mm/y of this shortening is taken up by folding and thrusting in the Zagros while the remaining 13 mm/yr is taken up in the Alborz and Kopeh-Dagh. The Central Iran block is relatively stable and thus moves to the north with an average velocity of about 13 mm/y. As the stable Afghanistan block lies to the east, the northward motion of Central Iran produces a right-lateral shear in eastern Iran, which is distributed mainly over a few major faults to the west (~ 5 mm/yr) and east (~ 8 mm/yr) of the Lut desert. Limited information is available about the slip rates of individual faults in eastern Iran; therefore in this study we try to combine all geological, geodetic and available Quaternary dating results to estimate the fault slip rates and distribution of active deformation in eastern Iran. Finally, we report the results from OSL dating of samples taken from uplifted plain deposits near the south end of the Bam-Baravat fault. These results show that this fault is growing in the vertical direction with at a rate of ~ 0.5 mmy-1. Considering geometric relation between the Bam-Baravat and the south Bam earthquake fault, we estimate a slip rate of about 2 mm/y for the south Bam earthquake fault.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    157
  • End Page: 

    162
Measures: 
  • Citations: 

    0
  • Views: 

    190
  • Downloads: 

    82
Abstract: 

In this study, foraminifera of the Ilam and Gurpi Formations, from Kuh-e- Assaluyeh section in east Kangan port in Boushehr province and Ivan well in Persian Gulf are investigated. Ilam Formation in Kuh-e-Assaluyeh section with 30 meter thickness and Ivan well with 68 meter thickness composed of limestone and dolomitic limestone. The Ilam Formation in the study sections overlies unconformable the Sarvak Formation and underlies the Gurpi Formation. The Gurpi Formation in Kuh-e-Assaluyeh with 73 meter thickness and Ivan well with 56 meter thickness composed of argillaceous limestone, sandy limestone, shale and limestone. Also the Gurpi Formation in Kuh-e-Assaluyeh section and Ivan well overlies unconformable the Ilam Formation and underlies the Pabdeh Formation. The study of 70 samples from the examined section led to the identification of 13 genera and 19 species of planktonic foraminifera and 12 genera and 12 species of benthonic foraminifera. Planktonic foraminifera are as follow: Heterohelix globolusa, Macroglobigerinelloides ultramicrus, Globotruncanita elevata, Globotruncana bulloides, Globotruncana ventricosa, Muricohedbergella holmdelensis, Heterohelix striata, Macroglobigerinelloides prairiehillensis, Contusotruncana fornicata, spiropelecta sp., Rugoglobigerina rugosa Macroglobigerinelloides bollii, Muricohedbergella monmouthensis, Globotruncana falsostuarti, Gansserina gansseri, Archaeoglobigerina blowi, Globotruncana arca, Contusotruncana contusa, and benthonic foraminifera are as follow: Rotalia sp., Rotalia skourensis, Pseudedomia sp., Minouxia sp., Dicyclina schlumbergeri, Quinqueloculina sp., Marssonella sp., Gavelinela sp., Archaecyclus midorientalis, Ammobaculites sp. On the basis of stratigraphic distribution of index foraminifera, the Ilam Formation belongs to Santonian to Campanian, and the Gurpi Formation in Kuh-e-Assaluyeh section is Campanian to Maastrichtian and in Ivan well is Maastrichtian in age. The studies in Kuh-e-Assaluyeh section let to recognition four foraminifera zone from base to top: Globotruncanita elevata Zone, Globotruncana ventricosa Zone, Globotruncana falsostuarti Zone, Gansserina gansseri Zone. Lacking the main elements of Globotruncanella havanensis and Globotruncana aegyptiaca biozones caused that Globotruncana falsostuarti biozone is introduced on the basis of the first occurances of Globotruncana falsostuarti (at the base) and Gansserina gansseri (at the top). Also in Ivan well, Globotruncana falsostuarti Zone, Gansserina gansseri Zone, Contusotruncana contusa Zone were identified. Abathomphalus mayaroensis in absent at Ivan well and Kuh-e-Assaluyeh. Thus, Abathomphalus mayaroensis biozone is not recognizable, and instead of it Contusoutruncana contusa biozone is introduced. The boundaries of this biozone are identified by the first and last occurrences of Contusoutruncana contuse. Also comparison this study with Biozonation of Wynd, (1965), from base to top: 1- Rotalia sp. 22, Algae assemblage zone, 2- Archaecyclus midorientalis-Pseudedomia sp. assemblage zone, 3- Globotruncanita elevata zone, 4- Globotruncanita stuarti-Pseudotextularia variance assemblage zone. 5- Contusoutruncana contusa zone.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    163
  • End Page: 

    168
Measures: 
  • Citations: 

    0
  • Views: 

    197
  • Downloads: 

    84
Abstract: 

People have paid attention to the use of supportive elements in retrofitting and soil improvement since a long time ego. Nowadays, the capability of reinforcement soil applications has been showed in different civil engineering projects. In order to increase of bearing soil capacity and reduce the settlement of structure, Geosynthetic Cellular System (GCS) has been invented. GCS consists of frame, geosynthetic fabric and soil. In this research, experimental and analytical behavior of small scale geosynthetic cellular systems has been analyzed. Our test case is a cylindrical specimen filled of sand from the beach of Khazar Sea. These cylinders are 10.5 cm in high and theirs base circle diameter are 10 cm in unreinforcement and reinforcement condition. Experimental studies were done with Teri axial test without back pressure and analytical studies were done with finite element soft ware (ABAQUS 6.7). Also in this research, the effect of vertical and horizontal reinforcement, the number of reinforcement, and their arrangement effect in the increase of bearing capacity, the decrease of settlement and lateral deformation of the instance have been presented. The experimental results and analytical studies are completely comparable and analytical results cover the experimental results. Also the results show that the reinforcement elements extremely cause to increase the bearing capacity and decrease settlement and lateral deformation. But, the horizontal reinforcement facilities in construct make it better than vertical reinforcement.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    169
  • End Page: 

    176
Measures: 
  • Citations: 

    0
  • Views: 

    251
  • Downloads: 

    200
Abstract: 

In order to determine the depositional environment and age of the carbonaceous Jahrum Formation, benthic foraminiferal assemblage of upper Eocene in the Jahrum Formation carbonates, located in Gisakan Mountain, 10 km east of the Borazjan city and adjacent fields, were studied. Based on the foraminiferal distribution and abundance, the paleoenvironment were reconstructed. Due to the presence of Nummulites fabianni and based on strontium isotopic analyses, the age between 33.7-35 Ma (Priabonian) was determined. The mean sedimentation rate of ~ 2 m/10000 yr. was calculated. This study indicated Asmari Formation deposited after a hiatus, more than four million years (Rupelian stage). Gradual decreases of the sea level and hence the distribution of large benthic foraminifera resulted in the deposition of six sedimentary facies along the inner-middle to outer carbonate ramp system. These facies, from deep to shallow parts of the basin, include argillaceous carbonates containing planktonic foraminifera that were deposited in a hemipelagic to pelagic environment (which is the transition zone from the Pabdeh to Jahrum Formation), carbonate facies of operculina wackestone to packstone related to the outer carbonate ramp, discocyclina /nummulites wackestone to packstone facies deposited in the middle to outer ramp, nummulites wackestone facies occurred in the middle ramp, nummulites orbitolites wackestone to packstone belong to the middle to inner ramp, and finally the orbitolites/bioclast packstone deposited in the inner ramp.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    177
  • End Page: 

    184
Measures: 
  • Citations: 

    0
  • Views: 

    520
  • Downloads: 

    231
Abstract: 

The NNW-SSE striking Bidhand strike-slip fault system cut and displaced the Cenozoic volcanic and sedimentary rocks of the Urumieh-Dokhtar magmatic arc in south Qom. Structural evidences show that at least 16 km horizontal displacement in the Eocene volcanics has been caused due to dextral strike-slip movement along this fault. The compressional and extensional terminations were developed at the western block and not observed at the eastern one. The reverse and thrust faults associated with the drag folds were generated in the northwestern compressional termination and gabbroic sills were intruded in the southwestern extensional termination. Younger syenitic and granitic intrusive (Miocene) were intruded in the vacant space of the northern compressional termination and releasing zones along the central straight segments of the Bidhand fault. Gabbroic sills in the extensional termination at the south-western area of the Bidhand fault were folded and thrusted towards northeast due to the later deformational events.

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Writer: 

AZIZI H. | AKBARPOUR A.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    21
  • End Page: 

    26
Measures: 
  • Citations: 

    0
  • Views: 

    205
  • Downloads: 

    105
Keywords: 
Abstract: 

Volcanic rocks with mainly andesite composition and lenzoid form outcropped in the Eocene sedimentary host rocks in the east of Sanandaj. Field studies confirm that they are intercalation with the sedimentary host rocks. In thin section, those have porphyritic, glomoroporphyric microlithic and microlithic porphyric textures. Some texture evidences such as glassy inclusion in the center of plagioclase phenocrysts, displacement of plagioclase and mafic phenocrysts with mafic hydrate minerals imply amalgamation of volcanic activity with soft sediments in shallow water; also cracking of plagioclase phenocrysts confirms this subject. Geochemical study shows that these rocks are enriched in incompatible elements such as U, Th, Pb and depleted in Nb, and Ti elements compared with chondrites, primitive mantle and NMORB. If crustal contamination can be responsible for these changes, but as usual these anomalies imply the primary magma generated above the subduction zone. This volcanic rock may have a unique origin the same as Urumieh-Dokhtar volcanic belt.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    27
  • End Page: 

    32
Measures: 
  • Citations: 

    1
  • Views: 

    368
  • Downloads: 

    93
Abstract: 

Destruction and inordinate use of resources causes instability of natural slopes. Policymakers pay high attention to slopes instability investigation in order to supply zoning map to identify susceptible areas and stable location for the development of new settlements in the future. Iran especially in the north and Haraz road is always exposed to landslides hazard because of climatic and physiographic conditions. In order to prepare landslide susceptibility mapping, at first, landslide distribution map and the map of effective factors were supplied by field study. Then prioritization of effective factors was carried out using AHP method and seven factors were selected as most effective factor. Then landslide hazard zoning carried out using information value and AHP models. Results showed that Shemshak formation, fluvial terraces, distance of 500 meters from road, distance of 400 meters from drainage network, the west dip direction, slope of 15-50 percents, elevation of 1500-2100 meters, residential and agriculture-garden landuse have the highest landslide susceptibility.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    3
  • End Page: 

    12
Measures: 
  • Citations: 

    0
  • Views: 

    266
  • Downloads: 

    104
Abstract: 

The Sonajil area is located in ~17 km east of Heris, East-Azarbaidjan. The major lithological units in the area include bodies of volcanic and volcanoclastic rocks (lower to middle Eocene), Sonajil porphyry stock (upper Eocene-lower Oligocene), Incheh granitoid stock (diorite, syeno-diorite, gabbro) (middle-upper Oligocene), and Okuzdaghi volcanic rocks (Plio-Quaternary). The Sonajil porphyry stock hosts a porphyry copper-type mineralization and varies in composition from micro-syenodiorite through micro-gabbro-diorite to micro-gabbro and micro-granodiorite, featuring principally porphyritic to microlithic porphyry textures. The parental magma of these igneous bodies had shoshonitic character (to high-K calc-alkaline), and tectonically belongs to post-collisional volcanic arc. Various generations of banded quartz, quartz-sulfides, quartz-oxides, and sulfides veinlets and micro-veinlets were developed within the porphyry body featuring typical stockwork texture. Veins of sulfide mineralization are also present in peripheral parts of the porphyry body. Alteration and mineralization occurred principally within the Sonaljil porphyry stock. Three types of pervasive hypogene alterations are developed in Sonajil stock: (1) potassic; (2) phyllic; and (3) propylitic. The principal hypogene opaque minerals include pyrite, chalcopyrite, bornite, tetrahedrite, enargite, molybdenite, hematite and magnetite occurring as dissemination and stockwork (veinlets and micro-veinlets). The chief supergene minerals in this body are hematite, goethite, malachite, azurite, chalcocite, covellite, and clay minerals.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    33
  • End Page: 

    44
Measures: 
  • Citations: 

    2
  • Views: 

    267
  • Downloads: 

    144
Abstract: 

The Chenareh Anticline is located between Lurestan Zone (in north) and Dezful Embayment (in south) in the Zagros Folded-Thrust Belt. This anticline is documented and interpreted to constrain the kinematic evolution of a fold. The development of fractures is confined to the Asmari Formation. In the study area, the fracture pattern is interpreted to identify six main fracture sets (from A to F). The first fracture set (A) striking 68o, oblique to the further fold trend, is interpreted as a regional fracture set that predates compression phase. The second set (B) striking 110o, parallel to the fold trend, are found in both limbs and interpreted as extensional fractures. Two other fractures set, (D, E) striking 10o-70o and 80o-140o are conjugate fractures existing in both limbs. The youngest fracture set (E) had formed during the folding process especially at the late stage of fold growth. Later on the first fracture group (A) are reactivated and called as (F) fracture set. Due to geometric characteristics of the Chenareh Anticline, it is categorized as a fault -propagation fold which is affected by the blind Balarud fault zone. The Z-shaped hinge zone of present anticline is attributed to the linkage of the two early individual anticlines.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    45
  • End Page: 

    50
Measures: 
  • Citations: 

    0
  • Views: 

    138
  • Downloads: 

    73
Abstract: 

Characterization of the detailed structure of the crust and upper mantel is an important continuing goal of geophysical studies. Teleseismic body waveforms have been used to infer crust and upper mantel structure. In this study we use teleseismic receiver function method to determine the crustal thickness and Vp/Vs ratio under Kermanshah network in north-west of Zagros using teleseismic data (30o<D<95o, mb³5.5) which have been recorded at five short-period three component stations (2003-2007). The differential travel time between the incident P wave and P to S converted wave (delay time) is used for computation of crustal thickness. Moho depth is not sensitive to crustal P velocity but there is a trade off between Moho depth and Vp/Vs ratio. The ambiguity can be reduced by incorporating the later multiple converted phases, namely, PpPs and PpSs + PsPs. We use the method of Zhu and Kanamori (2000). This method performs a grid search through the Hand Vp/Vs space and searches for the largest summed amplitudes at the predicted times of direct conversions and multiples. By stacking receiver functions from different distances and directions, effects of lateral structural variation are suppressed and an average crustal thickness is obtained. Applying this method to five short period stations in Kermanshah reveals that the Moho depth is 42 km and varies between 36 and 51.5 km. The thinnest crust was found beneath DHR, whereas the deepest crust was observed beneath VIS. We observed that Moho depth increase from west to east (from DHR to VIS) then decrease to KOM. The average Vp/Vs ratio as estimated is about 1.76.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    51
  • End Page: 

    56
Measures: 
  • Citations: 

    0
  • Views: 

    176
  • Downloads: 

    73
Abstract: 

The area that will be discussed in this study is located between Zagros and Arabian structural zones in Iran in which full fold 3D seismic data has been acquired and interpreted using sophisticated techniques. This paper covers the role of structural sensitive seismic attributes including first and Second Derivative attributes, Azimuth attribute, Variance Cube attribute and Seismic Inversion attributes as an advanced stage of the interpretation program in delineating and resolving structural ambiguities in the mentioned field. The result of this study using integrating these attributes shows the interference structural features such as superimposed folding and structural basin in NW nose of the field of study. Hence it seems that an interference folding event to be most probably occurred between Zagros and Arabian structures and made a very gentle refolding belt. Complementary geophysical studies also show a reservoir of good potential in some parts of this belt that located in this field of study.

Yearly Impact:  

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    57
  • End Page: 

    68
Measures: 
  • Citations: 

    0
  • Views: 

    288
  • Downloads: 

    90
Abstract: 

The hypersaline Urmia Lake is the most important intra-continental environment in Iran, with distinctive geological, environmental, and biological, characteristics. The Shahid-Kalantari Highway (under construction) between Urmia and Tabriz cities passes through this lake. Some 14 km dyke is constructed in the lake for this passage and about 1400 meter is left for a bridge construction. The role of the constructed dyke on sedimentation pattern seems significant, as understood from satellite images and field observations. This study deals with sedimentological characteristics and origin of deposits along the Shahid-Kalantary Highway of Urmia Lake. Availability of 4 cores from boreholes drilled for geotechnical studies provided a good opportunity for this study. This study is carried out on the cores of the 4 boreholes (340 m thick in total) and samples collected from the sea floor along the dyke. Mineralogical, textural and structural characteristics of the sediments were studied for determination of chemical, biological and physical processes responsible for their development. Some 396 plugs from the cores (0.7 to 1 m interval) and 15 samples from the sea floor (cores of 20-40 cm long) were selected for these purposes. To investigate the role of surrounding rivers in providing detritus material to the study site, samples from suspension load of the major feeding rivers are collected. Major characteristics of these samples are studied and compared with those from the study area. All available data on the discharge and sediment load of the major feeding rivers are collected and analyzed for this study. Size and shape are two major textural characteristics investigated in this study using petrographic methods (including SEM). Chemical composition of sediments is studied by petrographic (coarse material) and XRD (fine material and clay minerals) methods. Organic mater, carbonate content, and evaporate portion of the sediments are measured using standard techniques introduced in the literature. Results from this study shows that 25 to 40 % of the studied sediments are derived from the land, through feeding rivers and 60 to 75 % of them are formed within the basin by chemical and biological processes. Quartz, feldspar, volcanic lithics, heavy minerals including pyrite and pyroxene, and clay minerals are major detrital constituents of the sediments. Kaolinite, illite, and montmorillonite are common clay minerals in the sediments, which characteristics are similar to those determined in the suspension load of feeding rivers. Some carbonates, as carbonate lithics, and organic material are also found detrital in origin. Gypsum, halite, calcite, and aragonite are the chemical components of the sediments occur as evaporate and mud crusts, or coated grains. Fecal pellets and some coated grains (produced by algae) are the main biological components of the studied sediments. Pyritization of pellets, especially in lower parts of the cores, is commonly observed, so that, pyrite is presented in the sediments both in detrital and diagenetic forms. Distribution pattern of the major constituents along the studied cores reflect the significant role of sea level fluctuation in their development. Results from this study show that the chemical components of sediments developed during the stages of sea level fall, during which the sea was barely receiving sediments from the land (dry periods). The coated grains of this origin were developed in the basin margin, where the wind-induced waves produced a relatively high energy sub-environment in the margin. The biological constituents of the sediments were developed during sea level rise (lower salinity conditions), during which environmental conditions were not suitable for development of chemical sediments. The origin of detrital material is related to the feeding rivers. TalkeRud in the eastern part of the sea had a major role in providing coarse terrigenous particles to the basin. Major characteristics of the detrital quartz, feldspars, pyroxene and volcanic lithics are similar to those find in the volcanic outcrops of the Islami Island and TalkeRud alluvial fans. The Shahr Chay, Nazlu Chay, and Barandoz Chay in the west and ZarinehRud and SiminehRud in the south had significant role in providing fine terrigenous (clay minerals) to the studied area. On the basis of distribution pattern of terrigenous sediments and their ratio to chemical and biological sediments, the feeding rivers around the lake (major suppliers of the terrigenous sediments) are classified into three groups (most, moderate and low effective). This is designed for further investigation on the controls of sediments accumulation along the highway. This study emphasizes on more significant role of chemical and biological processes on the sediments accumulation in the studied area, than that of physical processes. Due to significant role of sea level fluctuation in chemical and biological sediments development, a thorough control on sea level fluctuation (dam construction, artificial evaporation for salt acquisition, and etc.) is vital in this basin. In this regard any program for sedimentation control along the dyke must take greater consideration on chemical and biological deposition.

Yearly Impact:  

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    69
  • End Page: 

    76
Measures: 
  • Citations: 

    0
  • Views: 

    251
  • Downloads: 

    114
Abstract: 

Every year, all over the world, landslides cause considerable damage to life and property. In order to prevent the danger and destruction brought about by landslides, it is important to identify the reasons for the occurrence of this phenomenon. This can only be achieved by conducting a thorough investigation into the geological conditions of the region and a study of the local and global landslides that have occurred in the past across the years. In this research, the reasons for occurrence of land, slides in the region have been studied, in addition to the identification of lithological, geological, morphological and tectonical characteristics of the region around the dam. In abutments, landslides occur due to weak lithologies, discontinuities and a high topographic gradient. Landslides around the reservoir occur due to an increase in pore water pressure and changes in water level of the reservoir, in addition to the reasons mentioned above. Finally, the importance and the role of this phenomenon regarding dams and the region have been studied and explained in this research.

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Writer: 

MOHAJJEL M. | CHOLGOLY A.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    77
  • End Page: 

    84
Measures: 
  • Citations: 

    0
  • Views: 

    169
  • Downloads: 

    73
Abstract: 

Abundant normal faults were locally developed in Pliocene-Quaternary detritus and pyroclastic sediments of Sahand volcano in southeast Tabriz. Well exposed normal faults are synthetic and antithetic, horst and graben and half graben structure systems, drag folds and roll-over anticlines were produced by normal faults. The average strike of these faults changes from dominant N-S in east to ENE- WSW in west. Dip of the fault planes changes due to layer competency and rotated older normal faults and layers were cut by later normal faults. In some cases vertical gashes were produced along fault planes and filled by the sediments of upper strata due to extension. Oversteps and bends also occur along normal faults in cross-section. Field investigations indicate that the syn-depositional extension occurred in Pliocene- Quaternary. Style and growth of normal faults in local distinct area in southeast Tabriz indicate that they were possibly produced by local extension (releasing zone) in relation with dextral strike-slip displacement of North Tabriz Fault.

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Writer: 

MOHAMADI M. | YAZDI M.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    85
  • End Page: 

    90
Measures: 
  • Citations: 

    0
  • Views: 

    134
  • Downloads: 

    79
Abstract: 

There are many precious microremains of chondrichtyans (cartilage fishes) in calcareous beds of Geirud Formation. These micro remains consist of teeth, branchial denticles and sales species and genus of the family and subfamily: Phoebodontidae, Protacrodontoidae, Hybodontoidae and Ctenacanthoidae. Geirud Formation consists of alternating silisiclastics and calcareous beds with 1-2 basaltic units well distributed in Central Alborz. The upper Devonian/Lower carboniferous age assigned to Geirud Formation. The name of the Formation has been driven from type locality - Geirud village in north of Tehran. The upper Devonian/Lower carboniferous deposits have been studied along Alborz Mountain range and Central Iran. Faunal similarity between Famennian deposits of Central Iran and Eastern Alborz with Geirud Formation (Hairapetian & Klug, 2002) confirm the basin relationship between these areas, also faunal relationship between these fauna and the fauna of Famennian in Morocco and Algeria confirm that these deposits belong to shelves of North Gondwanaland (Ginter et al., 2002). These fauna are associated with conodonts of expansa zone.

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Writer: 

EHYA F. | LOTFI M.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    91
  • End Page: 

    98
Measures: 
  • Citations: 

    0
  • Views: 

    143
  • Downloads: 

    79
Abstract: 

The Sarfaryab bauxite deposits occur in karstic depressions at the top of the limestones of the Cenomanian to Lower Turonian Sarvak Formation, which are overlain by the limestones of the Santonian Ilam Formation. In order to determine the possible source rocks of the Sarfaryab bauxite deposits, a few samples were collected from Sarvak Formation, terra rossa and bauxite ore and geochemically and geostatistically analyzed. Plots of chemical data and correlation coefficients show that Al, Ti, Zr, Nb, Cr and V were immobile during the bauxitization process. In the scatter diagrams of Zr and TiO2 versus Al2O3, regression lines pass through the origin and terra rossa falls between the Sarvak Formation and bauxite. Based on this research, it can be stated that the source rock of the Sarfaryab bauxite deposits is the Sarvak Formation and terra rossa is an intermediate product during limestone-bauxite transformation. Post-Turonian uplift had exposed recently deposited limestones of the Sarvak Formation to karst weathering, and a layer of argillaceous debris accumulated on its surface and was partly converted to bauxite. Subsidence followed, and the bauxite was preserved by the deposition of limestones of the Ilam Formation. Uplift in Pliocene time, with ensuing erosion, exposed the bauxite deposits to their present situation.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2010
  • Volume: 

    19
  • Issue: 

    74
  • Start Page: 

    99
  • End Page: 

    106
Measures: 
  • Citations: 

    0
  • Views: 

    136
  • Downloads: 

    110
Abstract: 

The metamorphic rocks around Mashhad city were suffered by several stages of metamorphism and deformation. Special mineral and structural elements were formed in these stages. Metamorphic grade in the pellitic rocks changes from green schist to amphibole facies. Foliations generally are steep toward northeast. Lineations predominantly have gentel to moderate plunge (less than 30o) toward northwest. Kinematic analysis of ductile structures in outcrop and microscopic scale shows dextral strike slip shearing with reverse component from northwest to southeast in shear zones. Contrasting of kinematic analysis of mesoscopic folds coeval deformation with shear sense obtained from ductile shear zones indicates the strain partitioning in the area. Based on field analysis and microscopic studies, the rocks were deformed by two stages of ductile deformation and followed by brittle-ductile and brittle deformation in later stages. The first and second stages of deformation occurred in a progressive and continuous manner accompanied by the higher grade of metamorphism in the area. The main stage of metamorphism is contemporaneous with early Cimmerian orogenic phase.

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