مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Title: 
Author(s): 

Journal: 

علوم زمین

Issue Info: 
  • Year: 

    0
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    -
Measures: 
  • Citations: 

    1
  • Views: 

    1409
  • Downloads: 

    0
Keywords: 
Abstract: 

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Title: 
Author(s): 

Journal: 

علوم زمین

Issue Info: 
  • Year: 

    0
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    -
Measures: 
  • Citations: 

    2
  • Views: 

    2418
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 2418

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Author(s): 

FATEMIZADEH A. | TATAR M.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    2-11
Measures: 
  • Citations: 

    0
  • Views: 

    999
  • Downloads: 

    0
Abstract: 

Crustal velocity structure has a very important role in precise locating of seismic events. In this study attempt has been made to investigate the velocity structure of the crust and the upper mantle in the Ghir-Karzin region of the central Zagros using local earthquakes recorded by a temporary network of 30 seismological stations operated for two months. The geometry of the Moho discontinuity is planned to be investigated using all readings of Pn phases and applying relative time-distance method. Therefore, first using arrival times of refracted Pg from different layer interfaces, a P-wave velocity of 5.9 and 6.45 km/s was obtained for second and third layer respectively. Relative time-distance curves of Pn arrival time for 3 regional earthquakes located enough away from our network reveal an apparent velocity of 8.0 km/s for the upper mantle beneath the seismic network. Using same method, we demonstrated that the crustal thickness increases toward NE. A dip of (2±1) degree was estimated for the Moho beneath our seismological network.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    12-21
Measures: 
  • Citations: 

    0
  • Views: 

    946
  • Downloads: 

    0
Abstract: 

In this study the undrained shear strength of soft soils of Uromieh Lake Bridge site is measured by CPTu and compared with the results of laboratory tests conducted on undisturbed and remolded samples. The CPTu tests conducted in 8 boreholes up to 100m. Unconfined compression test conducted on the undisturbed samples from the depth 20 to 30 m showed 0.3 to 0.4 kg/cm2 for undrained shear strength; meanwhile they are resulted 0.4 to 0.7 kg/cm2 from CPTu tests for the same depths. In spite of the undisturbed samples are obtained by thin wall tubes, but a reduction in strength due to sample disturbance are appeared. This reduction is about 30 to 70 percent. The results of remolded samples showed about 0.1 to 0.12 kg/cm2 for undrained shear strength. The difference between these values and the values resulted from undisturbed samples is about 4 times and the value of CPTu tests is about 5 times. Therefore the soft soils of Uromieh Lake are sensitive and in situ tests like CPTu is suitable and reliable for testing of them.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    22-31
Measures: 
  • Citations: 

    0
  • Views: 

    2832
  • Downloads: 

    0
Abstract: 

Monazite is a member phosphate group, and a phosphate of Th and REE. Monazite is a rare mineral and occurs as an accessory mineral in granites, gneisses, aplites, pegmatites and as rolled grains in the sands derived from decomposition of such rocks. Due to the high content of turium and rare earth elements this mineral is the most important and economic mineral in placer deposits. Marvast monazite placer has been identified through the regional geochemical exploration in Yazd- Sabzevaran zone. Detailed exploration shows that younger gravel fan and recent alluvium contain monazite grains. The grade of monazite in this placer varies from 50-525 g/ton. The reserve of placer is 8866425 t. with a grade of 150 g/ton of monazite. Monazite concentrates samples analysed by mass spectrometry and microprobe techniques. The results show that Marvast monazite enriched in light rare earth elements (Ce, La, Nd, Pr, Eu, Sm) and the content of REE203 is about 55.45%. In this placer deposit, Monazite accompaniedby hematitizedpyrite, epidotes, celestie, cerisite, rutile, magnetite, garnets, ilmenite, pyroxens, amphibols and sometime with zircon and apatite. Black shales are the host rock of monazite in the Marvast area, interbeded with calcareous sandstone, limestone and conglomerate. Monazite nodules, occurs sporadically in shales. Monazite grains are released by weathering and erosion of these rocks and are concentrated in younger gravel fan and recent alluvium.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    32-47
Measures: 
  • Citations: 

    2
  • Views: 

    963
  • Downloads: 

    0
Abstract: 

Boroujerd granitoid mass belongs to Sanandaj - Sirjan zone (SSZ). It consists of granodiorites, quartz diorites and monzogranites.The country rocks into which the Boroujerd granitoid was emplaced consist of greenschist rocks of the regional metamorphism. The statistical technique of discriminant analysis, using major element differences alone, shows that this mass has characteristics of orogenic granitoids (R>O).The Boroujerd granitoid has geochemical characteristics typical of arc intrusive e.g. I-type, high-K calc-alkaline series, metaluminous to weakly peraluminous, a greater enrichment in LILEs (Cs, K, Rb, U, Th) compared to HFSEs (Nb, Ta), depletion in Sr, Ba, P and Ti relative to other trace elements. High Th/Yb (>5) ratios correlated to high values (>10, up to ca. 100) for LalYb and plot as volcanic arc granites on various discriminant diagrams. This granitoid is a typical representative of a volcanic arc environment, spatially related to an active continental margin. Crustal contamination processes provide a further complicationin the interpretation of the Boroujerd rocks. The rarity of primitive magma compositions in arcs, particularly continental margin arcs, points to the important and consistent role of such processes. Probably, Boroujerd granitoid is the result of the subduction of Neo- Tethyan oceanic plate below the Iranian microcontinent.

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Author(s): 

PASHAEI A.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    48-55
Measures: 
  • Citations: 

    1
  • Views: 

    766
  • Downloads: 

    0
Abstract: 

Our investigation on the clay mineral compositions of the Loess materials in the NE of Iran, presents the following results: The main clay mineral components of the Loess materials in the area are illite and chlorite accompanied by lesser amount of kaolinite and expounding minerals such as smektite. However, with increasing moisture in Minoo-Dasht and Gorgan area, the content of kaolinite in the A-horizon increases to 25%, while smektite is still low and reaches to about 1-7%with traces of mixed layer minerals in all horizons. In contrast, in semiarid area under the steppic conditions, particularly in the B-horizons, the quantity of smektite increases to 15%. The traces of palygorskites in the loess materials of the area, indicates that the conditions for formation of the materials are not exceedingly arid and saline.

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Author(s): 

BAYATI KHATIBI MARYAM

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    56-71
Measures: 
  • Citations: 

    0
  • Views: 

    928
  • Downloads: 

    0
Abstract: 

In the study area, the development of gullies and gulling processes are very complex regarding geological structures, lithological factors and surface materials. Soil condition, topographic and climatological factors represent very vulnerable base for gulling processes. In this study, all these factors were examined in the lab orator and the field. The results show that the role of soil moisture and climatological factors (e.g storms and temperature) are important in gulling processes. In the region, gullies develop at the foot of slopes because the surface of slopes is not covered with plant in the early spring and autumn or disturbed by human activity. The role of litological factors and type of surface materials are very important parameters in gulling processes. The major portion of gulling, especially linear one head - gulling and polymorph gulling are growing on old alluvial, Silt and Marl.

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Author(s): 

BEHNIA P.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    72-79
Measures: 
  • Citations: 

    2
  • Views: 

    1125
  • Downloads: 

    0
Abstract: 

The metallogeny of Central Iran is mainly characterized by the presence of several iron, apatite, and uranium deposits of Proterozoic age. Neural network method is used as a data-driven method for GIS-based predictive mapping of Proterozoic iron oxide (CU-U-AU-REE) mineralization in Central Iran. The radial based function link network (RBFLN) which is a modification of radial basis function neural networks (RBFNN) is employed as a neural network system. The evidential maps comprising of stratigraphic, structural, geophysical, and geochemical maps are used as n-dimensional vectors input to the RBFLN. A number of 58 deposits and 58 non-deposits are employed to train the network. The operations for the application of neural networks applied in this study involve both multiclass and binary representation of evidential maps. Running RBFLN on different input data shows that the increase in the number of evidential maps and classes leads to higher classification sum of squared error (SSE). As a whole the increase in the number of iterations results in the improvement of training SSE. The results of applying RBFLN show that a successful classification depends on the existence of well distributed deposit and non-deposit sites through the study area.

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Author(s): 

AZARMSA S.A. | RAZMKHAH F.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    80-87
Measures: 
  • Citations: 

    2
  • Views: 

    1476
  • Downloads: 

    0
Abstract: 

Managing coastal zones needs accurate and updated information about coastline position. Coastlines continuously change due to wave, tide, and etc. actions. Therefore, it is necessary to have enough information on coastline position not only in the present time, but also in the past and future in order to organize scientific and engineering activities in a coastal zone. Satellite data are the best and most economic method for collecting such data. In this paper, three images provided by TM sensor of Landsat satellite were used for extracting coastline positions and investigating their changes in a period of 13 years. The images were prepared for further processing like radiometric corrections and geocoding. Then shoreline position corresponding to each image was extracted and compared with others. Moreover, different prediction methods were employed to estimate shoreline position in 2005 and 2010. Data are not timely equidistant, therefore, the results of the least square method are not accurate enough. However, the results of other methods are acceptable.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    88-97
Measures: 
  • Citations: 

    1
  • Views: 

    1273
  • Downloads: 

    0
Abstract: 

Chahghand complex is located in the northeast of Neyriz and southwest of Shahre-Babak. This complex consists of granitoid and metamorphic rocks, ultramafic, mafic and intermediate intrusive rocks, in which pyroxenite, olivine gabbro and diorite occur.Alkaline character of the complex is revealed by detailed petrography, geochemistry, multielement patterns (trace and rare earth elements) and tectonomagmatic diagrams. It seems that the generation of these rocks corresponds to the lower degree of partial melting from a lehrzolitic mantle source rock.The enrichment of LREE, LILE and depletion of HFSE elements coincide with patterns characteristics of intraplate continental setting; as a result, an intracontinental rift environment in Sanandaj-Sirjanzone during Triassic Jurassic for Chahghand complex magmatismis suggested.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    98-109
Measures: 
  • Citations: 

    1
  • Views: 

    1435
  • Downloads: 

    0
Abstract: 

Pahnavar skarn, located in the east of Siahrood, is a typical magnetite-rich skarn developed along the contact of Qolan granitoid (quartz diorite) I-type intrusive body (Oligo-Miocene) with carbonate (principally limestone) rocks. Field evidence and mineralogical study show that Pahnavar skarn is of calcic-type and includes two distinct zones: 1) endoskarn and 2) exoskarn. Exoskarn is the major skarn zone and by itself includes two separate zones: a) garnet skarn in igneous contact side and b) epidote skarn in parts farther from the contact. Two general stages of skarnification were recognized in Pahnavar: 1) prograde and 2) retrograde. Prograde stage was developed within the temperature ranges of 470-550°C and includes two discrete stages: a) isochemical formation of hornfelsic skarnoid (bimetasomatic) and recrystallized limestone (marble) and b) formation of metasomatic skarn during which a series of medium to coarse-grained anhydrous calc-silicates were developed. Retrograde stage commenced at temperatures <470°C and includes two distinct stages: 1) early retrograde stage during which anhydrous calc-silicate assemblages (formed during prograde stage) were replaced by a series of hydrous calc-silicates(epidote, tremoliteactinolite), silicates (quartz), carbonates (calcite), and opaques (magnetite, hematite, and pyrite). Magnetite was principally developed during this stage. 2) Late retrograde stage during which most of minerals formed during previous stages were altered into a series of fine-grained aggregates of chlorite, calcite, quartz, hematite, and clay minerals.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    110-119
Measures: 
  • Citations: 

    0
  • Views: 

    1526
  • Downloads: 

    0
Abstract: 

Khosrow-Abad iron deposit is located in the northeast of Kermanshah in Sanandaj-Sirjan geotectonic zone. Theunits outcropped in the area are the (iron-rich) andesitic volcanicsat the lower part of the sequence overlaying limestone. The aforementioned complex by the name of Songhor volcanosedimentarycomplex has been metamorphosed up to greenschist facies. Iron rich andesiteand limestone-units have been intruded by a granitic body led to a contact metamorphism and subsequent alteration by hydrothennal fluids, extracting iron from basaltic andesite and deposited it in the limestone adjacent to basaltic andesite and at the contact of granite. Iron occurrence confined to the contact of granite in carbonate and existence of skarn mineralogy support the occurrence of an iron skam deposit, but detailed studies on textures and structures suggest the source of the iron from the volcanosedimentarycomplex and its basaltic andesites.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    120-129
Measures: 
  • Citations: 

    0
  • Views: 

    983
  • Downloads: 

    0
Abstract: 

The Strike-slip faults are not linear and straight features visible on the map view and nature, as they become bent in their path. Bending causes compressional or tensional stress becomes predominant in the region. Astaneh and Firuzkuh faults are the two active strike-slip faults with ENE-WSW trend. Between these two active left-lateral faults, an imbricate fault zone with thrust component occurs. Furthermore, this zone cuts and offsets an anticline. The region is uplifted in this regime and forms a compressional horst between Chashm and Bashm faults; moreover, an additional horst is forming in the south east of the zone.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    130-141
Measures: 
  • Citations: 

    0
  • Views: 

    2873
  • Downloads: 

    0
Abstract: 

The Torghabeh gold mineralized area is part of collision zone formed during Late Paleozoic-Early Triassic time due to collision of Iran and Turan Plates. Oldest exposed rocks are meta-ophiolite and meta-flysch (Paleo- Tethys remnants). Dehnow- Vakilabad - Torghabeh tonalite- granodiorite (Early Mesozoic age) intruded low grade regional metamorphosed rocks of Late Paleozoic. Different types of schists were formed around the contact. Tonalite-granodiorite has low values of magnetic susceptibility [(1.5 to 2.5) * 10-5SI], therefore, it belongs to ilmenite series or reduced-type granite.Mineralization is found within shear zones. The shear zones cut all of the exposed rocks, then, mineralization is younger than these rocks. Gold mineralization was associated with silica rich fluid. Parageneses from depth to the surface are: 1) arsenopyrite - pyrrhotite - gold, (2) pyrite - arsenopyrite - gold and (3) pyrite - gold- galena. Gold is mainly associated with pyrite and arsenopyrite. The elemental content of Ag, Bi, Cu, Sb, Sn, Pb, Zn and W is low. Gold grade varies between 0.5 to 56 ppm and is less than 5 ppm on average. The width of mineralization is between 0.4 to 2.5 meters.Torghabeh deposit is mesozonal orogenic type gold deposit. The ore bearing solution was in reducing stage, low in Sand T=420oC, pH=7, Log fO2<-40, Log fS2<-14.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    142-165
Measures: 
  • Citations: 

    2
  • Views: 

    2446
  • Downloads: 

    0
Abstract: 

Chah-Bagh gold deposit is located in central part of Sanandaj-Sirjan zone, 60 km southwest of Delidjan, in Mutehmining district. Rock units exposing in the area underwent greenschist to lower amphibolite metamorphism. They consist of NW-SE trending deformed and metamorphosed volcano-sedimentary and acidic volcanic rocks. These units, thought to be of Devonian or pre-Devonian age have been intruded by basic sills and dikes.The rock units are characterized by several phases of intense deformation that lead to the generation of different fabrics and structures. The most important structure in the area is caused by WNW (N280-N290') trending inverse dextral ductile shear zone. Mylonitization, extension of mylonitic foliation, penetrative stretching lineation, chevron folds, and etc. are generated by ductile deformation in the area.Gold mineralization occurs in ductile and brittle shear zones. The maximum gold concentration occurs along 1 km long, 60 meters wide NW-SE trending (N40-50E) ductile shear zone. Ductile gold mineralization, reported for the first time in Chah- Bagh, has NW (N60-80W) dipping lenticular shape. Samples taken from silicified parts of this zone contain 1.8-13.2ppmgold. Deformation in this zone occurs as protomylonite, mylonite and ulteramylonite. Brittle mineralization, including gold-bearing siliceous-sulfidic zones, occurs alongN40Wtending, NE dippingnormal faults. The main gold-bearing siliceous sulfidiczone in Chah-Bagh is 100 meters long and 3-5 meters wide with N35Wgeneral trend. Geochemical analysis of samples taken from this sulfide-siliceous zone indicates near 1.82ppm of gold grades. The rock units hosting the above mentioned shear zones consist mainly of intensely deformed meta-acidic volcanic and volcano-sedimentary rocks (meta-rhyolite and felsic schist).These rock units have experienced different types of alteration with various intensities. The most important ones are sericitization, kaolinitization, epidotization, tourmalinization, silicification and solfidization. Silicified and sulfide alteration observed in the inner parts of alteration zones coincide with the ore-bearing zones. Studies suggest temporal and spatial relation between alteration and deformation. Spatial relations are interpreted by overlapping i alterationand deformation zones. Hydrothermal quartz and pyrites filled foliation parallel open spaces (generated during ductile, deformation and mylonitization) and also micro-fractures of porphyroclasts (with grain cataclastic flow origin) simultaneously. These facts reflect temporal correlation between deformation and alteration. High gold contents are related to silicified highly deformedmylonitic and ultramylonitic units and also sulfide-bearing zones coinciding with the inner parts of alteration zones. Simpleore-mineral assemblages include pyrite and chalcopyrite in ductile shear zone and pyrite, arsenopyrite and chalcopyrite in brittle ones. Iron hydroxides and other weathering products accompany these sulfide minerals in the alteration zones. Based on microscopicstudies, quartz, the main rock-forming mineral in Chah-Bagh deposit, is considered to be of three generations: predeformation quartz, first stage hydrothermal quartz and hydrothermal quartz accompanied by sulfide (late stage), respectively. Based on microscopic structural and textural studies, sulfide minerals can be divided into two different generations. The first generation consists of euhedral and coarse grain pyrite, arsenopyrite and chalcopyrite occurring in the form of segregated grains or along weak surfaces (such as fractures and grain boundaries) of second stage and pre-deformation quartz grains. The second generations of sulfides are characterized by unreformed disseminated fine grain anhedral pyrite and chalcopyrite in altered rocks. In elevated gold-bearing samples, gold cannot be observed in siliceous gangue and altered sulfide mineral margins, however, electron microprobe analysis indicates invisible gold within the sulfide minerals. Based on these studies, gold has been observed with both pyrite and chalcopyrite phases. Silver exists as invisible within sulfide minerals and in the form of native one within siliceous gangue.Lithogeochemical survey perpendicular to ore-bearing zones shows positive correlation between silica, titanium, sulfur, iron, arsenic, molybdenum, tungsten and chromium and high-grade zones are accompanied by deformation and alteration. Light rare earth elements (LREE except Eu) are enriched in sulfidized and silicified parts with elevated gold contents. Controlling parameters for mineral concentration in Chah-Bagh deposit are shear zones (ductile and brittle) and alteration (silicification and sulfidization). Comparing Chah-Bagh main characteristics with orogenic gold deposits, Chah-Bagh has the most similarities with orogenic gold mineralization therefore it is considered to be of this type.

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Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    166-177
Measures: 
  • Citations: 

    0
  • Views: 

    1186
  • Downloads: 

    0
Abstract: 

Pre-feasibility and feasibility studies are vital in mining projects. One major part of these studies is capital cost estimation of project, especially the cost related to equipments. Due to possibility of several technical alternatives, estimation of costs should be fulfilled separately for each alternative. For this reason, suitable models or software's may be useful to do these studies in shortest possible time with sufficient accuracy.In this study, after a brief comparison of the cost estimation models a software has been developed for estimating the capital costs of equipments in open pit mines. Basically, this software is designed using western mining engineering institute cost models. Visual basic programming language is applied for development the software which can be run in the windows- XP, 2000, 98 and NT environment.Application of this software to some of the metal mines has shown that the results of cost estimation obtained from this software are credible and this software has a good conformity with run conditions.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

ASHOURI ALI REZA | YAMINI A.

Journal: 

GEOSCIENCES

Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    60
  • Pages: 

    187-178
Measures: 
  • Citations: 

    0
  • Views: 

    1065
  • Downloads: 

    531
Abstract: 

This paper attempts to describe a cephalopod fauna from the "Cephalopod Beds" in the Shotori Range, Central Iran. The fauna contains 5 genera of nautiloid cephalopods and 12 genera of ammonoids. Among these, 7 ammonoid genera (Tornoceras, Cheiloceras, Maeneceras, Gonioclymenia, Cyrtoclymenia, Staffites, and Falcitornoceras) and 5 nautiloid genera (Ormoceras, Mooreoceras, Sycoceras, Michelinoceras, and Macroloxoceras) are reported for the first time from Iran. Ammonoid faunas indicate a Middle (?)/Late Frasnian to Late Famennian age for the "Cephalopod Beds", confirmed by conodont (Ashouri, 1990, 1995 & 1997) and brachiopod (Rastkar, 1996) studies. Microfacies analysis of the sections indicates that sedimentation occurred in a mostly shallow and high energy sedimentary environment. The distribution of goniatite fauna in eastern as well as northern Iran suggests similar paleobiological condition and a marine connection of the two regions during the Famennian stage. A paleogeographical map of the Late Devonian and comparison of the goniatite fauna of the study area with Alborz, Kazakhstan, China, North Africa and Europe indicate that these areas were in low latitudes during this time.

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