فهرست مطالب

Earth Sciences - Volume:11 Issue:2, 2019
  • Volume:11 Issue:2, 2019
  • تاریخ انتشار: 1398/03/11
  • تعداد عناوین: 7
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  • Separation of geochemical anomalies by Concentration-Area and Concentration-Number methods In the Saqez 1:100,000 Sheet, Kurdistan
    Fatemeh Zadmehr, Seyed, Vahid Shahrokhi * Pages 0-0
    Regional exploration and identification of anomalies can be done by geochemical data resulted from stream sediments. In this paper, fractal methods of concentration-number and concentration-area were used for regional studies, and abnormalities of elements including gold, arsenic, bismuth and mercury were studied. Statistical processing of these elements took place with the help of 1063 samples of stream sediments in the Saqez 1:100,000 sheet (Kurdistan Province). The elements were analyzed in the laboratory of the Geological Survey and Mineral Exploration of Iran by ICP-OES method and Au element was analyzed by Emission Spectrograph method. According to the position of geology, existing structures and the dominant rock type, the comparison between the map prepared methods of concentration-number and concentration-area was conducted in Saqez sheet. In general, the results of the two methods showed that in the south, southwest, center and west of the region, the concentration of these elements is increased, and presence of ore promising areas is high in these areas. Concentration-number method showed a good overlap with concentration-area method; making extensive geochemical halos and encompassing known ores of Qolqoleh, Kervian and Qabghlojeh, it follows the expected process of mineralization in Sanandaj-Sirjan zone.
    Keywords: Concentration-Area(C-A), Concentration-Number(C-N), multifractal modeling, Stream sediments, Saqez
  • Wadhah Mahmood Shakir AL, Khafaji *, Hayder Abdul Zahra Al, Dabbagh Pages 95-103
    This research study deals with the processing and interpretation of the total Bouguer anomaly and the total count iso-radiation data for a region located in the western desert of Iraq. The research aims to delineate the approximate locations and the effective depth of faults and how does rocks radioactivity act nearby the faults. The graphical method adopted to separate the residual fields from regional’s, in order to be processed later by applying the horizontal gradient filter. The results displayed as maps and profile section which delineate qualitatively the approximate locations of faults and quantitatively the high radio counts and major faults effective depth within the region. The results of this study showed that the major faults within the region extend with the directions NW-SE, with effective fault depth ranges of 1.7 – 4.9 Km. High radiometric anomalies detected near or between fault locations as they detected after conducting a gravity-radiometric profile section across the region. Peaks of high radiation total counts are located over the elevated blocks which produced by faulting action. The detected faults penetrate the main groundwater aquifer in the region and this considered responsible for transporting radioactive elements to the surface over and nearby the detected fault locations to form spots of accumulated radioactive deposits.
    Keywords: Faulting Gravimetry, Faulting Radioactivity, W- Desert Iraq
  • Rahim Mahari *, Rahim Shabanian, Farahnaz Reihani, Hamideh Shetabifard, Somaieh Sadigh Pages 104-112
    The Cretaceous deposits in Morakan, located in the northeast of Khoy, a town in western Azerbaijan province, Iran, are primarily made up of carbonate rocks. These deposits, which are of 717 meters thick, lie on the clastic facies of Jurassic and are covered with beneath the pelagic beds of the Upper Cretaceous. To investigate the facies, sedimentary environment and sequential stratigraphy of these successions, a stratigraphic section was made in the south of Morakan village. Carbonate facies in this section have deposited in open marine, bar, lagoon, and tidal flat facies belts. The study of these facies and comparing them with old and modern sedimentary environments reveals that these succes-sions have deposited in a carbonated platform of rimmed shelf type. The study of the vertical succes-sion of microfacies shows four main sequences in the form of system tracts of TST and HST, which are made up of shallowing and deepening parasequences. The first lower boundary of the sequences is the type SB1 unconformity, and other identified sequences are the type SB2 unconformity.
    Keywords: Cretaceous, sequence stratigraphy, microfacies, sedimentary environments, Azerbaijan
  • Gholamreza Asgari, Farzin Ghaemi *, Bahman Soleimany, Behnam Rahimi, Mehrdad Maleki Pages 113-125
    Lali sub-surface structure, with a NW-SE Zagros trending is located in Dezful Embayment. To determine the folding mechanism, structural geometric parameters including limbs dip, amplitude, wavelength, and crestal length were determined in four stages during deformation. In order to investigate the lateral folding mechanism, these geometric parameters were analyzed in three parts in the Lali structure including northwest, central and southeast. Lali structure in all three sections, show detachment folding mechanism. At the initial stage, due to the rheology of the region's stratigraphic units, the folding mechanism was fault-bend fold and due to the thickness of incompetent units, folding mechanism changes from the fault-bend fold to fault detachment fold and growth of this structure continues with this mechanism. As the deformation continues, detachment folding, the Dahlstrom type inclined to migration type. By identifying the folding mechanism of the Lali structure, determination of the detachment depth was necessary with two computational and graphical methods. Therefore, the depth of this surface was estimated at about 7500-8500 m for Lali structure. This amount is determined at the maximum thickness of the stratigraphic sequence of the region due to the migration of incompetent units to the core of the Lali structure.
    Keywords: Geometry parameters, Folding mechanism, Detachment depth, Dezful Embayment, Zagros
  • Sahar Tarabi, Sourosh Modabberi *, Mohamad Hashem Emami, Seyed Jamal Sheikh Pages 126-140
    This study investigates petrology and major, minor, and rare earth elements ‎geochemistry of ‎East Iranian Eocene–Oligocene volcanic rocks in Sistan suture ‎zone, to examine their ‎petrogenesis and magma evolution. The volcanic rocks include andesite, trachy-andesite, dacite ‎and rhyolite. ‎These calc-alkaline rocks of high-K series are enriched in Large ‎Ion Lithophile ‎Elements of Rb and Ba and depleted in High Field Strength Elements  ‎(e.g. Ti and Nb). The REE ‎pattern shows Eu negative anomaly. These ‎features are comparable with rocks in subduction ‎zone of continental ‎margin setting. ‎The petrographic features and the geochemical variation ‎of major oxides and trace ‎elements against SiO2 can be related to fractional ‎crystallization in parent magma. The trace ‎element ratios, e.g. Nb/La, Nb/U, Ba/Rb, Nb/Y and Rb/Y, verify crustal ‎contamination with a remarkable upper ‎crustal contamination as the main ‎process in the ‎formation of volcanic series. ‎The ratios of Nb/Ba and Nb/Zr indicate that magmatic activity in Momen Abad had ‎resulted ‎from sub-continental lithospheric mantle. In addition, Nb/Y and Zr/Yb versus ‎Ta/Yb reveals an ‎E-MORB like mantle source. A spinel lherzolite composition ‎with significant role of the ‎AFC processes are deduced from the concentrations of Yb and ‎Y, and the ratios of Th/Yb and ‎La/Yb. ‎The Ba/Nb, Ba/Th and Th/Nb ratios presume a metasomatized mantle source ‎resulted from ‎the melting of upper crust sediments inherited from the subduction of ‎Neotethys ocean beneath ‎the Lut Block. ‎
    Keywords: Volcanics, Rare Earth Elements (REE), Fractional crystallization, East of Iran, Momen Abad
  • Mehdi Reza Poursoltani *, Mahin Harati Pages 141-159
    The Upper Jurassic carbonates of the eastern part of the Kopet-Dagh Basin, with thickness of 470 m, are the major gas-bearing reservoir in NE Iran. The objectives of this study are recognition of diagenetic history and estimation of porosity related to dolomitization. Based on field and laboratory study, four carbonate facies associations have been identified at the Mazdavand outcrop. Most of the carbonate rocks were deposited in an open marine, tidal channel and barrier, lagoon and tidal flat setting. Using petrographic and CL analyses, the main diagenetic processes that affected these rocks are micritization, cementation, compaction, fracturing, dissolution, neomorphism, silicification, and dolomitization. Dissolution of grains and calcite cement generated secondary porosity, whereas compaction and cementation are the primary cause of porosity reduction. The average porosity of core plugs is 15.78% and match well with two-dimensional estimates from thin sections. The more porous samples are either highly fractured or contain interparticle and intercrystalline porosity, within the lower strata that contain more dolostone.
    Keywords: porosity, diagenesis, carbonate, Mozduran Formation, Iran
  • Feridon Ghadimi *, Massume Khavari Pages 160-170
    The Haft Saravan area is located in 90 km SE Arak in the central Iran. This area is a part of Malyer-Isfahan metallogenic belt. The article's objective is determining the most suitable method for identifying mineralized zones using original singularity and weighted singularity methods in three-dimensional space. In weighted singularity method, mineralized zones have a greater volume relative to original singularity method. Coefficient of areal association showed that percentage of overlapping of two methods is less than 50% for Pb, Fe and Mn and less than 55% for Zn. Two methods were compared by modified singularity method in order to select the best method. Percentage of overlapping is more than 98% both original and modified singularity methods for Pb, Zn and Mn and is less than 45% for weighted singularity method. Therefore, it can be said that original singularity method is suitable relative to weighted singularity in identifying mineralized zones due to the high overlapping of original and modified singularity method.
    Keywords: Original singularity, Weighted singularity, Mineralized zones, Haft Savaran