Editor-in-Chief Lecture
Volume 17, Issue 67 , February 2008, Pages 1-1
Original Research Paper
A. Asghari Moghaddam; E. Fijani
Abstract
Maku area is located in the north of West Azarbaijan, northwest of Iran. In this area, groundwater supplies main water demands for different purposes such as drinking, agriculture and industry. The aim of this research is to study the groundwater hydrochemistry, hydrogeological relation between karstic ...
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Maku area is located in the north of West Azarbaijan, northwest of Iran. In this area, groundwater supplies main water demands for different purposes such as drinking, agriculture and industry. The aim of this research is to study the groundwater hydrochemistry, hydrogeological relation between karstic and basaltic aquifers, determination of probable hydrochemical anomalies and their genesis and suitable methods for removal of these anomalies. For this purpose, in adition to available hydrochemical data, 72 water samples were collected from wells and springs in high and low level groundwater durations and were been analyzed for some trace elements. The results indicate fluoride anomaly in this area. In order to examine the hydrochemistry of the study area, graphical and mass balance methods were used. Both of these methods confirm the basaltic origin of fluoride anomalies. Consequently, hydrogeological relation between karstic and basaltic aquifer is established. Petrologic studies show that basaltic rocks of the area have appropriate conditions for occurrence of fluoroapatite; as a result, fluoroapatitic origin for high concentration of fluoride is identified. The most suitable methods for removal of the fluoride proposed to be adsorption on Defluoron2 and exchanging Cl- with F- by anionic resin in the study area.
Original Research Paper
S. H. Tabatabaei; A. Aghaei Araei
Abstract
This paper describes the result of a study on the determination of geotechnical properties of improved soil treated by quick lime and hydrated lime. Soil samples are mixed with quick lime and hydrated lime in various portions. The geotechnical properties investigated are ...
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This paper describes the result of a study on the determination of geotechnical properties of improved soil treated by quick lime and hydrated lime. Soil samples are mixed with quick lime and hydrated lime in various portions. The geotechnical properties investigated are compaction characteristics, Atterberg limits, compressive strength and CBR. It is observed that the dry density of soil treated with hydrated lime decreases and the optimum water content increases, while there is no noticeable change in dry density and optimum moisture content of soil treated with quick lime. The plasticity index of admixtures indicates a descending trend; however, it is more pronounced in samples treated by quick lime. Addition of small amount of lime causes significant increase in compressive strength of admixtures and increases with curing time. The effect of the quick lime is more significant than the hydrated lime. CBR tests show a trend similar to that observed for compressive strength tests. The optimum amount of hydrated and quick lime for improvement of the soil is presented.
Original Research Paper
M. Saadat; S. A. Alavi; A. Saeedi
Abstract
To analyze the paleostress in Sorkheh Hessar – Khodjir area, different shear – fault planes and the associated slickenside lineations are measured. The stress tensor and the variation of the stress direction in the upper Triassic to Oligocene formations are discussed. Numerous shear data ...
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To analyze the paleostress in Sorkheh Hessar – Khodjir area, different shear – fault planes and the associated slickenside lineations are measured. The stress tensor and the variation of the stress direction in the upper Triassic to Oligocene formations are discussed. Numerous shear data are determined from different locations in the study area and categorized into 16 sites according to the stratigraphic age. The main criteria used to identify the sense of slip are accretionary mineral steps, tectonic tool marks, polished and rough facets, and riedel shears. According to the inversion method which includes determination of the mean stress tensor orientation and sense of slip on numerous faults ,all data are classified based on tectonic events and the principal stress axes and corresponding compressional and extensional directions are calculated.
Based on the derived results from the diagrams, it is suggested that a prominent NE- SW compressional stress direction, which is obvious in Mesozoic and the younger Cenozoic formations, caused the deformation of the Mesozoic strata after Mesozoic and was continuous in Tertiary (Oligocene). It seems that a younger N-S stress direction exists and has had effects on both older and younger formations. It is believed that it would be related to one of the last Alpine orogenic phases.
Original Research Paper
A. R. Sayadi; M. Yavari; N. Solgi
Abstract
Exploration projects need considerable investments. These projects are associated with high techno-economical risks. Therefore, Evaluation of exploration potential is necessary. It is determined in primary stages of exploration whether the deposit reserve is not economic or the ...
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Exploration projects need considerable investments. These projects are associated with high techno-economical risks. Therefore, Evaluation of exploration potential is necessary. It is determined in primary stages of exploration whether the deposit reserve is not economic or the grade is less than normal grade, and it may be decided to stop the project. The minimum acceptable target reserve is known as a criterion for determining the economic potential of deposit regarding to techno-economical environment of project. In this research a new model is proposed for determining minimum acceptable target reserves in gold projects. This model is verified through the economic filed data from Zarshpran gold mine. The graph of grade versus tonnage and internal rate of return versus tonnage are demon stared through Excel software. The results of this research could be used as powerful decision making tools in gold exploration projects.
Original Research Paper
M. Ahrari rudi; Zh. Shahrokhi khargerdi
Abstract
Regarding different and beautiful geological features, Chabahar is one of the most important geotouristic sites in Iran. The attractive geological landforms are so spectacular that always attract a lot of tourists to the area. Some of the important geomorphological features are mud-volcano, ...
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Regarding different and beautiful geological features, Chabahar is one of the most important geotouristic sites in Iran. The attractive geological landforms are so spectacular that always attract a lot of tourists to the area. Some of the important geomorphological features are mud-volcano, ties cave, Mars land, cliff, lagoons, sand dune, erosion columns, bedding and etc. These geomorphologic features are introduced in details as follow.
N. Abbassi; A. H. Amini
Abstract
The Upper Miocene Upper Red Formation in the Evan-e-Key Section is composed of conglomerates, sandstones, mudstones, and thin lenses of evaporates (gypsum). The formation is dominated by gypsiferous mudstones and characterized by fining-up cycles in this area. The whole ...
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The Upper Miocene Upper Red Formation in the Evan-e-Key Section is composed of conglomerates, sandstones, mudstones, and thin lenses of evaporates (gypsum). The formation is dominated by gypsiferous mudstones and characterized by fining-up cycles in this area. The whole formation occurs as a fining upward megasequence, in which the sandy facies dominate the lower half and muddy facies the upper half. Gypsum layers, up to 10 meters thick, are locally observed in the basal part. The formation has suffered an extensive weathering in the region, as a result of which primary features (e.g. sedimentary structures, trace fossils) are partially obscured. In the sandy units of the middle part of the formation some vertebrate footprints are observed, which are locally deformed due to intensive weathering of the rocks. Two types of Carnivoripedida footprints however, are distinguished and described here, so that well preserved Chelipus isp. is related to Felidae. Depositional environments including alluvial fans with abundant debris flows, gravelly bed load braided systems with wide flood plains and local swamps provided a good opportunity for development of the track makers. The transverse and longitudinal bars within the channels, levees, and over-bank sub-environments were found more suitable for development and preservation of the footprints. Comparing with other sections of the formation (e.g. Qum area), desirable climate was found a major control on development of the vertebrate track maker in the Evan-e-key area.
Original Research Paper
H. Ghasemi; A. Ramazani; A. Khanalizadeh
Abstract
Silijerd intrusion with an age of Late Eocene – Oligocene (39.23.2 Ma) is located in Uromeyeh-Dokhtar magmatic arc, central Iran structural zone, northwest Saveh. This intrusion is composed of a continuous compositional range including: diorite/gabbro, ...
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Silijerd intrusion with an age of Late Eocene – Oligocene (39.23.2 Ma) is located in Uromeyeh-Dokhtar magmatic arc, central Iran structural zone, northwest Saveh. This intrusion is composed of a continuous compositional range including: diorite/gabbro, granodiorite, syeno-monzogranite and alkali granite intruded into the Eocene volcanic and pyroclastic rocks.
Variation diagrams showing trends of major and trace elements indicate a continuous compositional range and a comagmatic origin for these rocks. Trends of compatible- incompatible elements indicate the important role of fractional crystallization in the genesis of these rocks. All samples are metaluminous with medium-high K with calc-alkaline nature. High values of Rb, Sr, K, U, Th, Zr and Ba and high ratios of K2O/Rb and FeO/MgO indicate the similarity of the rocks of this intrusion with the rocks of continental margin magmatic arc intrusions. Depletion in Nb,P,Ta and Ti and enrichment in K,Sr,Rb,Cs and Ba are obvious in the spider diagrams of these samples. The enrichment in LILE and depletion in HFSE reveal the I-type metaluminous magmatism of volcanic arcs (VGA). Whole rock 87Sr/86Sr ratios of this intrusion range from 0.704759 to 0.705166 and it can be correlated with the values of these ratios in the mantle and lower crust sources and low contamination of their magmas with upper crust.
Existence of K-feldspar megacrysts and mafic microgranitoid inclusions in this intrusion, high abundances of La and Ce , V enrichement in mafic terms and low whole rock 87Sr/86Sr ratios of this body, suggested a partial melting of mantle wedge, subducted oceanic crust (metabasaltic sources) or lower continental crust (metatonalitic sources) origins for it. The discrimination tectonic setting diagrams also indicate an I-type continental volcanic arc magmatism for this intrusion.
Original Research Paper
M. Maanijou; I. Rasa; D. Lentz
Abstract
Chehelkureh copper deposit is located in Kuh-e-Lunka area, 120 km NW of Zahedan (SE of Iran). The host rocks of mineralization are intercalated Eocene turbiditic greywackes, siltstones, and shales (flysch). They are folded with N-S trend and the eastern limb of this fold has ...
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Chehelkureh copper deposit is located in Kuh-e-Lunka area, 120 km NW of Zahedan (SE of Iran). The host rocks of mineralization are intercalated Eocene turbiditic greywackes, siltstones, and shales (flysch). They are folded with N-S trend and the eastern limb of this fold has been drag folded. Several stocks and dykes of granodiorite to quartz monzodiorite and granite compositions intruded the turbidites, converting them locally to hornfels. These intrusions are oriented parallel to the major NW-SE fault set. The Chehelkureh ore field comprises numerous irregular lenses and veins. The ore field extends for 1500m in N23°W direction, and is displaced by late brittle faults striking roughly E-W. The fault and fracture filling ores include quartz, dolomite, ankerite, siderite, calcite, and lesser amounts of pyrrhotite, arsenopyrite, pyrite, chalcopyrite, sphalerite, galena, Se-rich galena, marcasite, molybdenite, ilmenite, and rutile. Assay data from 39 drill holes show high contents of base metals, with an average of 1.48% Cu, 1.77% Zn, 0.85% Pb (4.1% Cu+Zn+Pb), and silver (average 22 ppm in 45 samples). The ores are not so enriched in gold (0.14 ppm on average in 45 samples).
A composite sample of least-altered greywackes and shales (host rocks) is used for comparison with mineralized samples. Mass-balance calculations were carried out to quantify chemical changes resulting from different alteration episodes. With the low solubility and low variance of Al (Al2O3) in moderately altered sedimentary country rocks compared with many other immobile trace components, Al2O3 is used as an immobile component for mass-balance calculations. There is a net mass increase in Fe2O3T, and MgO and a net mass decrease in Na2O, CaO, K2O, and SiO2 with chloritization. Carbonatization shows Fe2O3T, and MgO enrichment and SiO2 and Na2O depletion, implying that ankerite, siderite and dolomite are predominant phases. SiO2 is enriched in silicified samples and depleted in other alteration types. There is no mass change in Cu, Pb and Zn with kaolinization, but these elements are enriched in other alteration types. Hg is enriched in all alteration types except kaolinization, which may even show a slight depletion. Samples from gossan with silicification showed an increase in SiO2, Fe2O3T, Cu, Pb, Hg, and Zn and a decrease in MgO, Na2O, CaO, and K2O. Some trace and major elements have high variance in different alterations and are more complicated to interpret, such as P2O5, MnO, Ni, Co, and Rb.
The REE contents of the composite host rock sample are enriched in the LREE relative to the HREE and moderately depleted in Eu and Ho. As a whole, samples with kaolinization and carbonatization (ankerite and siderite) have been enriched in REE contents and other wallrock alteration, including chloritization, dolomitization, kaolinization, minor sericitization, and silicification, are depleted in REE. SEM-EDS evidence indicates that enrichment of REE-bearing phosphates, such as monazite, occurred with carbonatization and kaolinization assemblages.
Original Research Paper
H. Atashy; J. Rahnama-Rad
Abstract
The effect of temperature, mixer ratio and acid thickness on the rate of magnesite dissolution in nitric acid was investigated in this laboratory research. The result shows dissolution rate increases with rising temperature when the size of particles is reduced. At ...
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The effect of temperature, mixer ratio and acid thickness on the rate of magnesite dissolution in nitric acid was investigated in this laboratory research. The result shows dissolution rate increases with rising temperature when the size of particles is reduced. At the beginning of the reaction, thicker acid increases the rate of dissolution but as the acid grows thicker not only there is no overwhelming changes obvious but also extends the duration due to product layer formed on the mineral grain surface during the reaction. This has less effect on thinner acid and smaller particles. The kinetic results shows that magnesite minerals dissolution in nitric acid follows the kinetic model , Optimized laboratory conditions are a temperature of 30 oC, nitric acid thickness of 50 %, size of particles: 250-297 ., mixer ratio of 300 rounds per min. and reaction duration of 170 min.
Original Research Paper
Z. A. Pur-Abrishami; A. H. Kokabi-Nezhad; G. R. Zare; O. Dabiri
Abstract
Maragheh informal Formation is widely extended on the Sahand hillside and Maragheh city. Based on lithology and sedimentary facies, Maragheh Formation is divided into two members: lower member in the studied area (Mordagh area - Aghajery) consists of marl, tuff, tuffaceous ...
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Maragheh informal Formation is widely extended on the Sahand hillside and Maragheh city. Based on lithology and sedimentary facies, Maragheh Formation is divided into two members: lower member in the studied area (Mordagh area - Aghajery) consists of marl, tuff, tuffaceous sandstone with several fossiliferous layers. Upper member has more extent and thickness than the lower member and the facies variation are accompanied by increase of tuffaceous layers with diatomit and fish debries. In the Gorg Darreh –Mordagh area four geologic sites were excavated and investigated for vertebrate fossils. The samples obtained in this study from above mentioned sites consist of Ivory of mastodont, Ivory of phiomia, Monkey teeth, radius and ulana bones of elephant, cervid, gazelle and hipparions. The sequence of Maragheh Formation mostly consists of fluvial deposits, therefore its dating is difficult. However, it displays different ages from 7Ma to 12.5Ma respectively based on the vertebrate fossils such as hipparion sp. ,.
Original Research Paper
Kh. Tahmasbi Poor; M. Poormoafi
Abstract
In this study, samples from Zefreh dolomite mine were characterized by X-ray diffraction and microscopic study. Dolomite samples were heated up to 1700ºC to produce doloma. Zircon and zirconia were used for preparation of dolomite – zirconia refractories. ...
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In this study, samples from Zefreh dolomite mine were characterized by X-ray diffraction and microscopic study. Dolomite samples were heated up to 1700ºC to produce doloma. Zircon and zirconia were used for preparation of dolomite – zirconia refractories. Samples containing different contents of zirconia and zircon were heated up to 1600 ºC. Apparent porosity, bulk density, X-ray diffraction, cold compressive strength, hydration resistance tests and SEM studies were carried out on the fired samples. Results show that samples containing zirconia have higher quality than samples containing zircon without additives.
Original Research Paper
S.H. Vaziri; D. Jahani; M. Safdari; F. Chegeni
Abstract
The Ilam Formation in southwestern Khorram Abad with a thickness of up to 204 meters consists of uniform limestones with Middle Turonian to Early Campanian age which were deposited in a continuous sedimentation process. In this section, the Ilam Formation has continuous ...
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The Ilam Formation in southwestern Khorram Abad with a thickness of up to 204 meters consists of uniform limestones with Middle Turonian to Early Campanian age which were deposited in a continuous sedimentation process. In this section, the Ilam Formation has continuous and transitional contacts with the Sourgah Formation in the lower boundary and the Gurpi Formation in the upper boundary. In the present study, 9 genera, 30 species and 2 biozones of the planktonic foraminifera have been recognized. The Ilam Formation in the studied section consists of a shaly facies and three carbonatic microfacies include mudstone, wackestone and packstone containing planktonic foraminifera. Shaly facies and mentioned microfacies were deposited in deep-open marine, which formed in a quiet environmental condition and increased environmental energy in microfacies with mudstone texture toward microfacies with wackestone and packstone textures. Whereas in the studied section recognized microfacies are not related to parts of continental shelf,such as ; bar, lagoon and tidal flat, therefore it could be said that, the studied area was part of profound depositional basin in Middle Turonian to Early Campanian.
Original Research Paper
M. Eliassi; S. Ahmadian
Abstract
Analysis of paleostress history in Kan_Karaj Area is the main object of this research. Paleostress phases were determined and categorized by numerous mesoscale faults containing slickenside lineations .The results were controlled and supported by some other geological features such as orientation of ...
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Analysis of paleostress history in Kan_Karaj Area is the main object of this research. Paleostress phases were determined and categorized by numerous mesoscale faults containing slickenside lineations .The results were controlled and supported by some other geological features such as orientation of axial plane of folds, intrusion and stylolitic planes. The orientation of finite principal stress axes and geometrical shape of stress ellipsoid in a 4-D stress space were analyzed by determination of rotational axis of each sub-area, according to Anderson Theory. Two different stress phases were separated and geometrical configuration of the maximum compressional stress trajectory were illustrating on the structural map. The resulting trajectory shows north- south trend with an outstanding convergence to the north which reflects incremental intensity of stress in that direction during the fault system activities.
Original Research Paper
A. Ghaderi; A. Aghanabati; B. Hamdi; J. F. Miller
Abstract
The Shirgesht Formation is one of the fossiliferous units of Central Iran which in the type section is defined (informally) in the terms of 3 members. This formation is mainly composed of limestone, marl, siltstone, shale and dolomite, conformably overlay on the upper part of the Derenjal Formation with ...
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The Shirgesht Formation is one of the fossiliferous units of Central Iran which in the type section is defined (informally) in the terms of 3 members. This formation is mainly composed of limestone, marl, siltstone, shale and dolomite, conformably overlay on the upper part of the Derenjal Formation with a gradual contact, composed of brachiopods limestone bearing (Billingsella limestone). The Shirgesht Formation is overlain by sandy limestone and volcanic rocks of the Niur Formation.
To do biostratigraphy studies on the first and second members of Shirgesht Formation in the type section, totally 99 rock samples were selected. The conodont fauna of lower part of its first member contain some species of Westergaardodina, Furnishina and prooneotodus which show an age of late Cambrian. Several species of Cordylodus, Oistodus, Drepanodus, Proconodontus and Paroistodus in distance of middle part of the lower member to the end of the second member represent an age of Tremadocian – Arenigian. According to conodont content of the first and second members of Shirgesht Formation, 7 conodont assemblage zones were determined in the type section which show an age of Late Cambrian – Early Ordovician. The recognized biozones are as follow:
1. Furnishina - Westergaardodina Assemblage Zone.
2. Proconodontus - Oneotodus Assemblage Zone.
3. Cordylodus proavus - Cordylodus oklahomensis Assemblage Zone.
4. Cordylodus lindstromi Assemblage Zone.
5. Cordylodus angulatus Assemblage Zone.
6. Drepanodus - Paltodus deltifer Assemblage Zone.
7.Paroistodus proteus Assemblage Zone.
The mentioned conodont assemblage zones are equivalent to Cordylodus spp., Deltiferand Proteus global standard conodont biozone. In contrast with the previous reports, the Cambrian – Ordovician boundary is located in the first member of the Shirgesht Formation. Thus, the Shirgesht Formation in type section is diachronous formation.
Original Research Paper
M. Moazemi; B. Rezai; A. Amini
Abstract
In this research firstly ore characterization studies from ore dressing point of view have been conducted and then increase in module ratio i.e. ratio of Al2O3 to SiO2 of the bauxite samples from Boolboolieh area of Kerman province investigated by the means of ore dressing techniques. Obtained ...
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In this research firstly ore characterization studies from ore dressing point of view have been conducted and then increase in module ratio i.e. ratio of Al2O3 to SiO2 of the bauxite samples from Boolboolieh area of Kerman province investigated by the means of ore dressing techniques. Obtained results from ore characterization studies revealed diaspore and hematite were major mineral phases and Al2O3, Fe2O3 and SiO2 contents of head sample were 36.6, 27.02 and 20.32 % respectively and consequently module ratio was determined to be 1.8. Mineralogical studies on all prepared microscopic sections show clastic texture that contains pisolith and oolith particles inside microcrystalline matrix formed from hematite, clay minerals and fine bauxite particles. In ore dressing studies, physical separation methods, selective grinding, heavy media separation and tabling have been investigated. Obtained results from selective grinding revealed that alumina to silica ratio increases from 1.8 to 1.91 with alumina recovery about 69.3 %. Heavy Liquid separation tests proved that alumina to silica ratio increases to 3.32 with 64.02% alumina recovery by adjusting heavy liquid density to 3.22. Tabling tests approved increase in concentrate module ratio to 2.64 with reduction in alumina recovery to 21%.
Original Research Paper
A. Afsharian; Y. Naeimi; M. Ataei
Abstract
Slope stability studies is one of the most considerable parameter of safety and economical factors of open pits.
Because the pit walls usually consist of different characteristics of lithology and structure, using only one slope for all walls is not enough and reasonable.
So ...
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Slope stability studies is one of the most considerable parameter of safety and economical factors of open pits.
Because the pit walls usually consist of different characteristics of lithology and structure, using only one slope for all walls is not enough and reasonable.
So they need carefull geological and geotechnical studies to determine the geotechnical limits of the pit.
By using MRMR methods, SlopeW 2004 and FLAC 4.0 softwares and comparing the results,optimum slopes for North western wall of Chadormalu Iron mine have been calculated.
On the basis of all available data,the following geotechnical domains have been distinguished for North western wall of Chadormalu Iron mine:
• Lithology and Structure
• Pit Wall Orientation
• Rock Mass Rating and conditions
North western open pit wall is bounded by metasomatite, albite metasomatite, and ore. The structure of this domain is distinguished by steep normal faults with great displacement and brecciate limestone.The results of geotechnical boreholes, modeling and studies indicate that the overall slope of this domain could be increased from 52, to 60 degrees.
Original Research Paper
M. V. Valizadeh; H. R. Abdollahi; M. Sadeghian
Abstract
The intrusive bodies of Central Alborz constiute speciale distribution. And they are located near major faults, and also they are accompnied by pyroclastic rocks of the Karaj Formation.Moreover they display lithological diversity and they occur as sill, lopolith, stock ...
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The intrusive bodies of Central Alborz constiute speciale distribution. And they are located near major faults, and also they are accompnied by pyroclastic rocks of the Karaj Formation.Moreover they display lithological diversity and they occur as sill, lopolith, stock and plug.
These intrusive bodies blong to post upper Eocene and they are related to the Pyrenean- equivalent orogenic phase.
Rregarding the geochemical results obtained by other researchers, as well as determining the nomenclature, definiton of granitoid and gabbroic bodies the composition of the above mentioned masses, fall within the calc - alkaline to alcaline range.
However, most specimens are plotted in the field of type I granitoids.From the tectonic viewpoint, all of the intrusive bodies are Considered as syntectonic. Moreover, they are often of continental subduction Zone(CAG)origin , while other may be long to continental collision type(CCG), and a few are located to the island arcs(IAG).
Original Research Paper
M. Hosseini-Barzi; R. Alinejad-Kurdi; H. Ghalavand
Abstract
The calcimeteric analysis of samples from Pabdeh Formation, in type section (north of Dezful embayment subzone), represent a marl and shaly marl lithology. SEM images from these samples represent chlorite flakes with diagenetic origin (transformation of illite to chlorite) and imply the possible existence ...
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The calcimeteric analysis of samples from Pabdeh Formation, in type section (north of Dezful embayment subzone), represent a marl and shaly marl lithology. SEM images from these samples represent chlorite flakes with diagenetic origin (transformation of illite to chlorite) and imply the possible existence of other detrital clay minerals (include chlorite). However, XRD analysis of selected samples indicates the existence of montmorillonite, illite and chlorite showing a descending trend for clay percent and montmorillonite and ascending one for illite and chlorite from bottom to top of these deposits. Based on these evidences, we introduced the possibility for cooling in climate condition and shoaling in depth of deposition, from bottom to top of the Pabdeh Formation.
Study of Th, K & Th/K peaks of NGS log represents the existence of montmorillonite and illite, as common clay mineral. Calculating clay mineral percent, shale percent and uranium trend imply an anomaly at the uppermost part of the Pabdeh Formation which could be related to fault activity in Central Dezful embayment subzone and sediment supply probably due to Pyrrenean orogeny.
Therefore, investigation of clay mineral represent difference in sedimentary framework between northern Dezful embayment subzone and central Dezful embayment subzone and their different response to change in geological condition.
Original Research Paper
F. Tutti; S. Yazdani; K. Bazargani-Guilani
Abstract
South Kahrizak volcanic rocks with Eocene age are located in the north part of Central Iran. These rocks are mainly composed of pyroclastics (tuff and ignimbrites) and lava flows (rhyolite, trachyandesite, basaltic trachyandesite and basalt). Petrographic evidence such as: zoning, ...
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South Kahrizak volcanic rocks with Eocene age are located in the north part of Central Iran. These rocks are mainly composed of pyroclastics (tuff and ignimbrites) and lava flows (rhyolite, trachyandesite, basaltic trachyandesite and basalt). Petrographic evidence such as: zoning, sieve texture and rounded crystals in plagioclase and pyroxene phenocrysts show the non-equilibrium conditions between melt and crystals during magma cooling. Geochemical characteristics indicate that these rocks locate in the subalkaline to alkaline domain. The highly enrichment of LREE compared to HREE, high content of LILE relative to HFSE and significant anomalies of Nb, Ta and Ti reveal the characteristics of a subduction - related volcanism. Whereas, the alkaline affinity of rocks shows that they may have formed in an extentional region, most probably a back-arc basin.
