GEOSCIENCES
Year:2010 | Volume:20 | Issue:77|Papers Count:30

VENARCH Manganese Mine is located about 30 Km from south–east of Qom city Volcano–clastic rocks of middle to upper Eocene age make up major outcrops of the region. Sedimentary rocks of Oligo-Miocene age overlie previous rocks, Red earth is found with manganese in the majority of manganese mines of which the most important are Darband & Doctor mines. Their probable reserves are 5760 and 1920 thousand tons. We took Samples were taken from these mines and XRF, XRD studies and microscopic studies were carried out to identify their chemical and physical properties.Dry and Wet sieve and scrubbing analysis were carried out on the samples and in order to decrease the cost and time of project the number of tests was done based on Taguchi method. The concentration of the raw material is increased about 20 percent and a pigment with 70% Fe2O3 was obtained. At least oil absorbtion, covering power and coloured tests carried out. The results show that the pigment has adequate quality.

Cretaceous flysch deposits of the Abshar-e Asyab Kharabeh (30 meters) in west of Siah-rud village in the Jolfa area, NW Iran, consist of conglomerate, sandstone, siltstone and mud-or marlstone layers, which mainly belong to A, B, D and E divisions of Bouma sequence. A divers trace fossils preserved on the lower bedding planes of sandstones and siltstones as positive hyporelief, includes: Bergaueria hemispherica, Bergaueria isp, Cochlichnus isp, Granularia isp, Halopoa imbricate, Helminthoida crassa, Helminthopsis abeli, Imponoglyphus torquendus, Neonereites multiserialis, Paleodictyon latum, Paleodictyon cf. majus, Paleodictyon nodosum, Palaeophycus alternatus, Palaeophycus sulcatus, Phycodes templus, Phycodes isp., Planolites annularis, Planolites beverleyensis, Protovirgularia longespicata, Squamodictyon isp, Strobilorhaphe isp, Thalassinoides isp, Taphrhelminthopsis recta, Taphrhelminthopsis convolute, Treptichnus pollardi. These trace fossils are mainly grazing-feeding or feeding traces of Nereites Ichnofacies and classifiable in six rang/frequency, based ichno-assemblages. Obtained trace fossils were produced during post-event calm periods. So, muddy sediments deposited after turbulence currents and traces have been made on these layers, activates of trace makers were developing when accessible feeding materials or dissolved oxygen increased in environment. Base on founded Nereites trace fossils, these sediments deposited in the deep marine abyssal zone environment.

Sand box models are in order to investigation of circumstance of deformation create in orogenic event. Progressive rigid indenter is as non-plastic continental crust that moves from one side to ward sand hanging wall that is indication plastic crust. The sand primery thickness and angle of rigid indenter are changeable. In the all of models, rises sand in the two side of plan of indenter between fore-slop and back-slop, in the top of indenter progressive edge. The formation rate of anticlinorium folds is related to thickness of sand hanging wall, form of progressive and rate of falling's back-slop plan. Change of primery thickness of sand hanging wall is controler of distance and rate of anticlinorium folds formation. The aim of this experimental work is investigation of thrust belts, progressive indenter, and research of effect's slope in the collision zones and fold-thrusts creation, also comparison of experimental model to natural model.

Geological data are used in a variety of applications. These data have three dimensional (3D) nature and hence 3D modeling, storage, dissemination and presentation of the data not only provide a better understanding of the current situation and the relationship between different features and data layers, but also increase the reliability of decisions. 3D Web Geographical Information Systems (3D Web GIS) are proper tools for managing and sharing geological data. However, current activities on developing geological Web GISs have paid less attention on 3D nature of geological data. In other words, most of the existing geological Web GISs are studied or established based on two dimensional data. One of the important challenges for dissemination of 3D geological data in Web relates to utilization of a proper format for rendering 3D data in Web browsers. Such a format should have the capability of: 1- Conveying geological data, three dimensionally, in Web environment, 2- being displayed by Web browsers, 3- being standard and the standard to be clear for data producers in such a way data conversion to the desired format being possible, 4- conveying attribute data, and 5- providing users with the possibility of querying and analyzing data. Up to the knowledge of the authors, there is not currently any software which can disseminate 3D geological data in Web by employing a proper format respecting all of the above criteria. This paper proposes utilizing X3D, developed by Web 3D Consortium, as a standard text-based format for dissemination and rendering 3D data in Web. Although the format has not been developed for GIS purposes, in this research the applicability of that for modeling and presenting 3D geological data in 3D Web GIS is investigated.

To recognize different species of the genus Orbitolina and determine the age of the Dariyan Formation, the upper limy part of the Dariyan Formation in Dashtak section was sampled and studied. Based on the size, shape and complexity of embryonic apparatus, five species belonging to subgenus Mesorbitolina were recognized as below: Orbitolina (Mesorbitolina) lotzei, Orbitolina (M.) parva, Orbitolina (M.) texana, Orbitolina (M.) subconcava, Orbitolina (M.) sp. cf .M. pervia According to stratigraphic distribution of the mesorbitolinids, the upper part of the Dariyan Formation can be ascribed to the late early Aptian-late Aptian. The early/late Aptian boundary coincides with first occurrence of O. (M.) parva

Separation of alteration zones is one of the important processes in evaluation and identification of mining activities that provide great help to have better view of the region and its mineralization. Most of the alteration separation is based on petrological investigations and the other methods are less applied. Therefore, in this research, there is an attempt by applying RBPNN (Radial Basis Probabilistic Neural Network) to separate these alteration zones. Because of the special structure and easy designing of these networks, they are usually capable to solve the classification problem. The input data were 28 element analyses related to 45 geochemical samples and its outputs were classified alteration zones (potassic, transition, phyllic) that was coding for every inputs data. After selection the training and testing data, the network has been prepared for training and then the data were inputs and the results were outputs. According to the results, the network could distinguish the difficult spatial relation between the inputs, with 28 spatial variables and classify those correctly. The calculated MSE (Mean Square Error) is 0.0163, which shows the good performance of network in this field.

Tehran is the largest and the most populous city of Iran that have been recently regarded from the risk management point of view because of possibility of the earthquake damages. An important destructive phenomenon that may happen in Tehran during an earthquake is liquefaction. In the last two decades, liquefaction of Tehran, especially its southern part, has been extensively studied. These studies are done in different scales and also with different methods. The goal of this paper is consideration of the most important studies which have been done in Tehran up to now and present a practical conclusion. The above mentioned studies are reviewed in the first part of the paper. After that, a network, divided into squares of 1Km×1Km, has been considered in southern part of the Tehran and liquefaction potential for every square of the network is evaluated. Finally, liquefaction hazard map for this part of the city is presented.

Ab-Deraz Formation (Turonian to Santonian) is a marly-Carbonates sequence consists of three marl-chalky limestones intervals. This formation widely crops out in Kopet-Dagh Basin in NE of Iran. Chalk and calcareous marl couplets show decimeter to meter scale cycles. Carbonate content of chalky beds are 80-95% in rhythmic couplets, and about 65-80% in calcareous marly beds. The Ab-Deraz Formation is studied in tow Hamam-Ghale and Padeha outcrops, and also in well No.56 of Khangiran. Three dominate frequency of sediments are identified based on gamma ray log, which are related to three type of Milankovitch cycles including the long eccentricity (413 ka), eccentricity (100 ka) and precession (21-23 ka) cycles. Biostratigraphic age determination based on foraminifera is comparable with orbital chronology calculated by on eeccentricity cycles counting. These cycles are also correlated with carbonate contents in studied sections.

Rudists of the Tarbur Formation, in 7 km southwest of Semirum and 10 km north of Khorramabad, have been studied. Paleontological studies indicate that the age of the Tarbur Formation in both sections is Masstrichtian, and has a rich macrofossil fauna of rudist. The important types of rudist include Radiolites, Hippurites and Caprinidae. The assemblage shows a close similarity with those reported from south Turkey, Mediterranean, Saudi Arabia and Oman.

Landslide and flood are natural disaster which can create tremendous lose of life and properties. The combine occurrence of these events can create debris flow. Due to the repetition of debris flood in different locations of northern part of the country (Neka, 1378, Kolastan, 1380, and 1384), and tremendous destructive power of this natural event, it is essential to assess the effective parameters in development of debris flow. In this paper the condition of masouleh debris flow is reconstructed to assess the effective parameter and suggest possible remedial measures. After a short and intense rainfall a huge flood along with considerable amount of particles ranging from silts to boulder contents striked masouleh town and obstacled the main bridge. This event diverted the debris flood towards the town and caused lose of life and properties. About forty percent of sub basin area is affected by landslides. The rock slides have affected 25.7 percent of the area at the southern part of basin. Various methods were used to estimate the required discharge flow to carry out the material. The optimum method was chosen according to study area condition. The filed investigations clearly demonstrated the river cross sections of upstream can not permit the huge boulders to cross and the big boulder which obstacle the main bridge has been removed from landslide area at downstream at the vicinity of the town.

Mud volcanoes are one of the interesting phenomenons that many researchers in oil field, plate tectonics and geotourism consider the most. In this regard there are many studies in the other countries, especially those which have this phenomenon and published many articles. This article is the output of researches about anatomical characteristics of active, non active mud volcanoes and hidden diapir in the study region. Due to the subduction of Caspian Sea bed under the continental crust in southeast zone of Caspian Sea, there are a series of anticlines and synclinals which located in the west section NW-SE, in the middle section W-E and east section to Turkmanestan NE-SW. Due to the increase in the west thickness of Cheleken and Aghchagyl formations, Apsheron stage and Quaternary series that are calcareous, marl, clay and sandy and consist of gastropod and lamellibranches remains overlaying on each other conformity there are more mud volcanoes in west and southwest of Caspian Sea. There are 3 active, semi-active and few non active diapirs as well as a hidden one. Mud volcanoes at the southeast, semi- active and hidden diapir section of Caspian Sea, are almost in same direction with Caspian Sea fault. The seismic studies in the region show Plio–Quaternary compressive pressures and subsidence in the form of diapir is present on the surface. Anatomy of mud volcanoes of the region shows their history goes back to upper period Pliocene and scientifically their origin are tectonic-sedimentary.

The Ab-Talkh Formation (Campanian-Maastrichtian) is one of the lithostratigraphic units of the Kopeh-Dagh sedimentary basin. So far no high resolution sequence stratigraphy has been done on this formation. In this study, we use the fossil evidences to analyse the formation in the sequence stratigraphy framework. For this purpose, after field studies 39 samples were collected and processed for palynology and palynofacies studies. Accordingly three palynofacies(V:Distal shelf, III:Proximal shelf, II:Marginal shelf) determined. Based on changes in percentages of the three majour constituents of organic matter, the palynofacies and correlation of all data, three second-order sequences were differentiated. Abundance of warm water dinocysts, presence of fungal spores and the ratio of Peridinioids / Gonyaulacoids indicate dominance of warm climate during depositional course of the Ab-Talkh Formation.

Dorouneh Fault System (DFS) is located along northern border of Central Iran microplate. Its mechanism is left-lateral strike-slip with reverse dip-slip component. Considering curve geometry of DFS, it is divided into three major parts: eastern, middle and western. Middle part extends from Torbat-e-Heidarieh city in the east to Anabad village in the west. It passes through Quaternary loose alluviums. DFS is composed of different segments in this part. Bend and right-lateral en echelon geometry at surface and left-lateral strike-slip movement of DFS cause local transpression that is observed as young folding. Fold core is composed of Neogene marl, sandstone and siltstone and fold limbs are composed of Pleistocene loose gravely sediments. Mentioned folds were formed by two different mechanisms: first, Anticlines that formed in right-step bends of DFS and second, pressure ridges that are limited among parallel branches and overlaps of DFS. Estimation of relative uplift rate along mentioned folds indicates that more earthquakes occur in regions with higher uplift rate.

The clastic facies of Kahar Formation were identified in the studied sections of coastal, deltaic and fluvial and also carbonate facies in shallow marine environments. The vertical displacements of Kahar Formation in these study sections show an overall major transgressive upward cycle. The petrography of plutonic and semi- plutonic igneous rocks indicate that they consist mainly of monzogabbro- diorite and in some cases, alkaline syenite. According to the results of Kahar Formation's plutonic rocks petrography and studies of related facies, the basin of this formation was a continental rift.

The Jiroft plain is located at about 230 km from Kerman city in southeast of Iran. As groundwater is the main source for agriculture, industry and drinking in this area, thus its qualitative evaluation is very important. In this study for evaluation of groundwater chemical quality, a combination of statistical method such cluster analysis and correlation coefficients and hydro geochemical methods such ionic ratios and composition diagrams were used. Groundwater samples were grouped with the use of Cluster Analysis method and similar samples were identified. On the basis of cluster analysis results, the groundwater samples fall into four groups, in other words the aquifer has been divided into four zones and each zone has peculiar chemical characteristics. In this paper ionic ratios of (Na+K-Cl)/ (Na+K-Cl+Ca), Na/ (Na+Cl), Mg/ (Ca+Mg), Ca/ (Ca+SO4), Cl/ (sum anions) and HCO3/ (sum anions) and composition diagrams for the characterizing groundwater influencing factors were used. Based on the obtained results, processes such as dissolution of gypsum and halite, Na-rich plagioclase weathering and ion exchange affect the groundwater quality of the study area.

Baba-Ali and Galali iron deposits in west of Hamedan are emplaced within the Songhor volcano-sedimentary sequence of Sanandaj-Sirjan geological-structural zone. Mineralography and SEM-EDAX analyses on magnetite iron ores at both deposits for better understanding of mineralogy and crystal-chemistry of the ores have shown some interesting results. Studies on concentrations of some trace elements such as V, Co, Ni, Cu, Cr, Ti, Au, PGE as well as S and P impurities in the ore indicate that only some of the primary pyrites have considerable concentrations of Pt. It seems that other generations of pyrite and magnetite are depleted in these trace elements. Late stage hydrothermal fluids that lead to mineralization of pyrite in calcite-quartz gangue veins, have also been impotant for gold mineralization and pyrite has actually acted as a favorable carrier for Au. Detection of abundant phlogopite and trace element concentration patterns at Galali iron ore have strengthened volcanogenic magnesian skarn hypothesis.

The Siah-Cheshmeh ophiolites at the north-northwest part of the Khoy ophiolites show a dismembered pile of metamorphic units, mantle sequence, and basaltic-andesitic lavas associated with Late Cretaceous pelagic limestones and cherts. The basaltic-andesitic lavas can be divided into alkaline and calc-alkaline varieties. The presence of Ti-rich amphibole prisms and Ti-bearing clinopyroxenes is characteristic of these lavas. The calc-alkaline lavas are characterized by enrichment in LREE and depletion in HFSE while the alkaline lavas display positive LREE and HFSE anomalies. The interaction between mantle plumes with a spreading center can be considered for generation of alkaline basalts while a subduction zone is responsible for the genesis of calc-alkaline basalts.

Today Helicopter-borne electromagnetic (HEM) data survey play important role for high resolution and fast 3D mapping of resistivity structures within the vast area. The standard method of interpretation of these data is to inverse them frequently. As surveying system is not fixed during the survey, hence noise is accompanying the measured data. To process the measured noisy data they are fed into the several filters to get better data to be used for modeling. During the filtering stage some of signals are also lost. Therefore, it is required to choose modeling techniques that has minimum error and provide accurate subsurface model. In this paper, first the response of the three synthetic layered earth models were calculated by using three different Hankel transform forward modeling methods. Then with adding different percents of random noise to the synthetic data, they were modeled inversely by different methods. The obtained results indicate that the so-called improved Guptasarma-Singh inverse modeling method could provide better responses for all three synthetic models.

The detailed stratigraphical and lithological analysis of the Permian sequence in north Marand, NW of Iran at Harzand village has been studied. At this locating the Permian sequence consist of Dorud (82 m..)  Surmaq (258 m..) and Julfa (108 m.) formations respectively. The main lithology consist of white to red sandstone, grey to dark, biogenetic limestone, marly limestone and thin bedded limestone. The lower boundary is non conformity, so that the Permian sequence is underlying a thick extrusive igneous rocks and at the top, a sequence of Miocene red clastic deposit covers the Permian sequence with disconformably. In this study 52 foraminiferal species belonging to 37 genus and 8 species of 9 Algal genus were recognized and 4 assemblages biozones in Surmaq and Julfa formations have identified. Based on fossils assemblages, the age of the Surmaq formations is Kubergandian-Murgabian (Middle Permian) and the age of Julfa formation is Middian-Early Dzhufian Stages(Late middle–Early late Permian).

In the west and north west of Hassan-Abaad village of Yazd, massive dikes of alkali andesite in the diorite, quartz diorite and granodiorite are observed. Clinopyroxene phenocrysts in these rocks have obvious zoning. Reconnaissance work indicates that groundmass pyroxenes in the alkaline rocks are similar to the more evolved phenocryst rims. Obtained data from core to rim of Clinopyroxene phenocrysts by SEM point analysis, show that Clinopyroxene composition, contains Chrome-diopsides, Salites-ferrosalites and Titanaugite. Clinopyroxene zoning formed during crystal growth. These pyroxenes are believed to record an intricate history of stop-start differentiation, magma-mixing, entry or disappearance of high-pressure precipitates. The salitic and ferrosalitic crystals of the Hassan-Abaad andesite also represent accidental fragments of anomalous upper mantle wall rocks.

Blemish of subsidence and land ruptures such as destroying aquifer systems, damaging structures and disordering water main, are usually irreparable and expensive. One of the regions with a high rate subsidence in Iran is the Yazd-Ardakan plain that subsides with a maximum rate of 12 cm per year based on levelling and InSAR observation. It is obvious that such a high rate subsidence is the result of water extra exploiting and groundwater levels at piezometric wells confirm this in the region. Management of water drafting in this region is a necessary work in this region.

The Kangan Formation is a carbonate-evaporate sequence that is considered as a part of the largest carbonate reservoir in the South Pars Field at Persian Gulf. Petrography analysis led to the recognition of 5 different dolomite types: such as dolomicrite, dolomicrospar, dolospar, dolomite cement and saddle dolomite. Elemental studies on dolomicrite and dolomicrospar samples show a relative increase of Sr and Na and relative decrease of Fe and Mn in comparison with the dolomicrosparite samples. It is notable that the oxygen-carbon isotope trend in dolomite samples are due to slight influence of meteoric diagenesis (about dolomites type I, II and III) and burial diagenesis (about dolomites type IV and V). The dolomicrites have been undergone slight meteoric diagenesis, although they have formed in sabkha environment. The source of Mg for dolomicrites is the magnesium of seawater and interstitial waters equilibrium with seawater and on the other hand probably for the coarser grain dolomites in the Kangan Formation is connate waters and basinal brines. Based on the heaviest oxygen isotope in dolomicrite samples, paleotemperature of depositional environment of the Kangan Formation was around 44.5oC.

The studied sections are located in southwestern of central Iran. Main lithology of these sections are including shale, sandstone and limestone. Four biozones had been recognized base on Conodont. That contain Idiognathodus delicates Zone, Streptognathodus oppletus Zone, Sweetognathus whitei Zone. And Neostreptognathodus pequopensis Zone. Based on recognized conodont, the age reveal for Sardar Formation is Bashkirian-early Gzhelian and the Permian deposits are Artinskian (khan formation age equivalent). In this sections Carboniferous-Permian boundary has been seen paraconformity. Comparison this area with neighborhood showed after Kasimovian we have upward and erosion in these areas and with started melting due to glacial epoch in lower Permian so these areas covered with water although we have shallow basin comparable with another areas in Central Iran.

The Bojnourd earthquake occurred in a mountainous area in North Khorasan provinc. The mainshock produced extensive destruction. Field investigation and aftershocks distribution suggest a NW-SE trend faulting. The distribution of locally recorded aftershocks was extended to a length of about 40-50 km and a depth of about 30 km. Aftershock activity was scattered indicating a complex mode of faulting. The result of waveform inversion indicated that the mainshock followed mainly strike-slip mechanism and the source process included at least two main fault slip. The source time functions indicates that the major amount of seismic energy was released within the first 10 seconds. Considering the field observation, the distribution of aftershocks and the source mechanism, an average source dimension of about 45 km, a NW-SE strike and a SW dipping fault plane could be estimated. The mechanism for the total source is obtained as (strike, dip, rake)=(323, 89, 178). The total seismic moment was calculated to be M0=6.7×1025 dyne cm. The calculated maximum dislocation was about 50 cm and the obtained moment magnitude was Mw=6.5. The average stress drop was estimated to be 25 bar and the average dislocation was 25 cm.