فهرست مطالب

Earth Sciences - Volume:10 Issue:1, 2018
  • Volume:10 Issue:1, 2018
  • تاریخ انتشار: 1397/02/20
  • تعداد عناوین: 8
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  • Bhanwar Choudhary *, Rajesh Arora Pages 1-10
    Front row burden is one of the key parameter to improve the bench blasting results. Improper design of the front row burden can create nuisances in the form of ground vibration, flyrock, back break or it may responsible for breakage of improper fragment size from the rockmass. Therefore, front row burden need to be optimised on the basis of proper scientific assessment. It has been proved that there cannot be a unique blast design that would serve the varied situations prevailing in mines but site specific and customized blast designs can accommodate the different blasting environments encountered in the field under the variegated geo-mining conditions. This study was conducted to know the influence of front row burden on fragmentation, muckpile, excavator productivity and from the study it was found that front row burden range of 0.50-0.70 of designed burden resulted the improved blasting results (fragmentation, Muckpile shape parameters and final wall profile). While, front row burden range of 0.8-1 of designed burden created more congested material, uneven fragmentation and back break in high wall.
    Keywords: Blasting, Surface mines, front row burden, fragmentation, muckpile shape, back break, excavator
  • Fataneh Taghizadeh Farahmand *, Narges Afsari Pages 11-19
    The current geological and tectonic setting of Iran is due to the ongoing convergence between the Arabian and Eurasian Plates, which resulted in the formation of the Iranian plateau, mountain building, extensive deformation and seismicity. The Iranian plateau is characterized by various domains including the continental collision and the oceanic plate seduction. Based on S receiver functions are provided a high resolution image of lithosphere beneath Iran.
    The current geological and tectonic setting of Iran is due to the ongoing convergence between the Arabian and Eurasian Plates, which resulted in the formation of the Iranian plateau, mountain building, extensive deformation and seismicity. The Iranian plateau is characterized by various domains including the continental collision and the oceanic plate seduction. Based on S receiver functions are provided a high resolution image of lithosphere beneath Iran. In the present work, we used data from teleseismic events (at epicentral distances between 60°-85° with magnitude over 5.7 (Mb)) recorded from 1995 to 2011 at 53 national permanent short period stations which are located in the different geological zones of Iran. The Sp phase conversion arriving at times ranging between 8.6 and 13.0 s delay time. In order to enhance the conversions and reduce the error of the depth determination, the S receiver functions stacked in bins. Arrival times of Sp phases were converted into depth domain using the IASP91 reference velocity model. A relatively shallow LAB at about 80-90 km depth was observed beneath the whole plateau with some exceptions. A low velocity zone was found at about 100 km beneath the Zagros fold and thrust belt and reaching 130 km beneath the Sanandaj-Sirjan Zone, whereas other tectonic zones are recognized by a thin lithosphere of about 80-90 km. This technique can introduce an error up to 10 km in the LAB depth determination.
    Keywords: Lithosphere-Asthenosphere Boundary, S Receiver Function, Teleseismic Waves, Iran
  • Javad Raghaghi Gargari *, Ali Solghi, Mehran Arian Pages 20-30
    The Khoy Ophiolitic Complex (KOC) as a part of Tethyan, Izmir-Ankara- Erzincan and Bitlis-Zagros sutures of South East (SE) Turkey is broadly exposed around Khoy region (NW Iran). This complex comprises dismembered fragments of mantle lithosphere, obducted oceanic lithosphere and parts of volcanic arc remnants. The Khoy Ophiolitic Complex can be structurally divided into two major eastern and western blocks which is by NW-SE trending Khoy Faults with right-lateral strike slip kinematics. Also, with regard to heterogeneous crustal properties, KOC can be divided into accreted (stacks of imbricated thrusts) and obducted sections in the tectonic framework. The main tectonic events after opening of South Neotethys Ocean in Mid-Late Triassic include subduction, accretion, obduction and collision in KOC. Therefore, KOC can be regarded as one of the South Neotethyan oceanic relicts (similar to SE Anatolian ophiolites), and it has two distinct types of ophiolite, such that, each type has individual tectonic history related to accretion and obduction processes.
    Keywords: Khoy Ophiolitic Complex, Structure, Accreted, Obducted, Tectonic History
  • Ramin Arfania * Pages 31-38
    Ophiolitic rocks in the southeastern part of the Zagros Orogenic Belt can be separated from southwest to northeast, into two groups: the Neyriz ophiolites and the Naien–Shahrebabak–Baft ophiolites. The southeast sector of Sanandaj-Sirjan wasdelimited by the two nearly synchronous ophiolitic belts in its southwestern and northeastern margins. In this study, new ophiolitic formation models were used to explain a viable geodynamic hypothesis on the development of the southeastern Zagros Orogenic Belt. Supra-subduction zone ophiolites have been of particular importance in the reconstruction of regional tectonic evolution andformed near a main subducting oceanic plate. The history of the southeastern Zagros Orogenic Belt is composed of development of two oceanic crusts, referred to as the Neo-Tethys 1 and Neo-Tethys 2. The process of reconstructing of the plate tectonic evolution of the southeastern Zagros Orogenic Belt was proposed on the basis of "Latest Cretaceous-Neogene collision" hypothesis. The supra-subduction zone ophiolites in the southeastern part of the Zagros Orogenic Belt can be classified into "pull related fore-arc Neyriz ophiolites" and "back-arc Naien-Baft ophiolites".
    Keywords: Ophiolite, Sanandaj-Sirjan, Supra-subduction zone, Zagros Orogenic Belt
  • Mohammad Mobashergermi, Reza Zarei Sahamieh *, Mehraj Aghazadeh, Ahmad Ahmadikhalaj, Gholamreza Ahmadzadeh Pages 39-51
    Petrography and chemistry of minerals showing that Eocene alkaline volcanic rocks in southwestern of Germi (Talesh zone, NW Iran) mostly have basaltic composition. Mineralogically these rocks are composed of diopsidic clinopyroxene and labradoritic plagioclase phenocrysts. The microlithic and glassy groundmass composed of sanidine, clinopyroxene, biotite, pargasitic amphibole and magnetite associated with devitrified glass. Clinopyroxenes show relatively high Mg-numbers (0.76-0.93), low AlVI (mostly
    Keywords: Mineral chemistry, Thermobarometry, Clinopyroxene, Eocene alkaline rocks, NW Iran
  • Mohammad Reza Baghban Golpasand *, Mohammad Reza Nikudel, Ebrahim Asghari-Kaljahi Pages 52-67
    Specifying the soil types and profiling the subsurface soil layers are the excellent examples of CPTu test potentials. In this research, the capability of CPTu test for specifying subsurface soil layers and classification of the sediments in Urmia Lake is investigated. According to previous studies, the sediments of Urmia Lake are commonly fine grained and soft deposits with organic materials. To evaluate the geotechnical parameters of these sediments in Urmia Lake Bridge site, CPTu test was performed and soils were classified applying the results of this test. The results showed that the sediments are mostly composed of clay and silt. To verify the results of CPTu tests for soil classification, the outcomes were compared with the logs of the boreholes and the results of laboratory tests. Comparisons and analysis of findings showed high consistency between the three groups of results; CPTu, boreholes logs, and laboratory tests. Thus, CPTu test can be used, with sufficient confidence and accuracy, to specify and classify the soft soil in lacustrine environments.
    Keywords: CPTu test, Soil classification, Borehole Logging, Laboratory tests, Urmia Lake
  • Rahim Dabiri *, Mohsen Akbari-Mogaddam, Mitra Ghaffari Pages 68-77
    Kashmar granitoids of Taknar zone, in north part of Lut block, intruded into volcanic rocks and consist of granites, granodiorites, monzodiorite and gabbrodiorites. They are composed of mainly plagioclase, alkali-feldspar, quartz, amphibole, biotite and pyroxene minerals. Harker diagram variation, including negative correlations CaO, MgO, FeO, TiO2 and V and positive correlations K2O, Rb, Ba, and Th, with increasing SiO2 and chondrite-normalized REE patterns, suggest that fractional crystallization of gabbrodioritic rocks could have played a significant role in the formation of granites. Their chondrite-normalized REE patterns are characterized by LREE enrichment and show slight negative Eu anomalies. Chondrite-normalized REE modelling indicates that the magma of Kashmar gabbrodiorites were generated with 3–5% of partial melting of a a spinel-lherzolite source. Melting of parental magma located at ~53 km.
    Keywords: Petrogenesis, Geochemical Modeling, Contamination, Granitoids, Taknar Zone
  • Vagif Kerimov, Michael Rachinsky, Rustam Mustaev *, Uliana Serikova Pages 78-89
    The geotemperature factor of the subsurface is among the important reasons for defining hydrocarbon generation conditions, which characterize migration processes and the accumulation of oil and gas in sedimentary rocks. It also has an application aspect, which is very important for potential oil and gas forecasts and the selection of exploration plays. It provides a practical capability to use the data of disruptions in the regional and local geotemperature field for tracking hydrocarbon migration paths, determining discharge zones, areas and foci of geo-fluid-dynamic systems. This is one reason why temperature conditions in the geologic section of oil and gas regions, areas, zones and prospects may be weighty arguments in oil and gas exploration. The study results may benefit planning and conducting exploratory operations in other basins of mobile belts, similar to the studied ones in their tectonotype.
    Keywords: South Caspian basin, Geotemperature regime, Oil, Gas field, Local structures, Basin modelling, Earth's depth heat