فهرست مطالب

Volume:10 Issue: 2, Summer- Autumn 2020

  • تاریخ انتشار: 1399/11/05
  • تعداد عناوین: 12
  • Amirhossein Enayati Bidgoli *, Hossain Rahimpour Bonab, Amin Navidtalab Pages 227-243

    The Upper Cretaceous Ilam carbonate Formation has been analyzed for its coated grains (fine ooids and rhodoids) in oilfields of SW Iran. The recognized coated grains are morphologically classified into several types. Petrographic and geochemical characteristics indicate that the ooids were originally composed of low-magnesium calcite (LMC; consistent with global observations), but rhodoids consisted originally of high-magnesium calcite (HMC). The overall primary mineralogy of the intervals containing coated grains has been a mixture of HMC and LMC. Co-occurrence of these mineralogies and allochemical (both ooids and rhodoids and other bioclasts) components indicates a rhodalgal-like grain association and a relatively temperate paleoclimatic conditions.

    Keywords: Coated grains, Ooid, Rhodoid, Ilam Formation, Upper Cretaceous
  • Saeed Saadat *, Ahmad Mazaheri, MohamadReza Heidarian, Hojat Jahangiri, Mohammad Foudazi, Seyed Jafar Omrani Pages 245-261

    The Ghaleh-Rigi complex is located in northern margin of the Sanandaj–Sirjan Zone (western Iran) and the southern part of the Central Iran Micro-continent block. The study area is covered by pillow and massive lava flows associated with micro gabbro and pelagic sediments including mudstone and radiolarian ribbon chert. Geochemical analysis indicates similar mantle source for magmatic rocks. These rocks show tholeiitic affinity with depletion in high-field strength elements (HFSEs) and light rare-earth elements (LREEs). They also show enrichment in large-ion lithophile elements (LILEs) in primitive mantle normalized multi-element diagrams. All samples show variable depletion in Th followed by depletion of HFSE and trace element concentrations and negative Nb anomaly (Th/Nb=0.23-035), which is a typical characteristic from magmas related to subduction zone. In addition, ratio of Y/Nb against Zr/Nb and Ce/Y against Zr/Nb and also REE flat patterns are similar to N-MORB-like source. These features suggest generation of magma in the back-arc basin. According to geochemical and petrogenesis studies, these rocks shows around 10% partial melting of a mixed spinel–garnet-bearing source composed of 50% PM and 50% MORB source. Based on bio-chronological investigation, the radiolarian cherts associated with volcanic rocks show Early Bajocian to Berriasian; Callovian- Valanginian; and Oxfordian- Valanginian ages.

    Keywords: Pillow lava, radiolarian biostratigraphy, Early Middle Jurassic, Central Iran, Ghaleh-Rigi
  • Parivash Mahdavi, Alireza Jafari Rad *, Soraya Heuss Aßbichler, Mohamad Lotfi, Nima Nezafati Pages 263-275

    Shadan copper-gold deposit is located in nearly 65km Southwest of Birjand. The area is a part of eastern margin tertiary volcano-plutonic belt in Lut Block. The oldest units in this area are tertiary andesite, tuff, rhyolite, and rhyolitic tuff. The units are intruded by late Eocene–Oligocene Shadan subvolcanic, granite, and granodiorite intrusion rocks. The rocks are again overlined by Quaternary deposits. Shadan mine is considered as Cu-Au porphyry in which mineralization was controlled by tectonic strictures. The deposit is hosted by dacite, rhyodacite and micro granodiorite subvolcanic rocks which are mainly associated with potassic, sericitic, argillic and propylitic alterations. Mineralization mostly occurs as disseminated, stockwork, veins and veinlets in host rocks. The paragenesis in veins and veinlets includes quartz, chalcopyrite, pyrrhotite, magnetite, hematite and covellite, gold, iron-hydroxide and rare abundances of other minerals. Gold grains are between 1-150μm in diameter commonly occurring within the quartz and in some places occur in

    Keywords: : Shadan, Porphyry copper-gold, mineralogy, Fluid inclusions
  • Ali Kadkhodaie *, Saeed Yarmohammadi Pages 277-287
    Finding and quantifying microscopic features such as matrix and grains, fabrics, porosity, fossil contents and diagenesis are crucial to improving the results of a microfacies study. Moreover, the application of image processing seems essential in analysis of hydrocarbon fields. There is a wide range of available image processing algorithms. However, these algorithms are dealing with many difficulties when faced with complex microfacies study objectives.In this paper, 170 thin section photographs from a Permo-Terias formation of Salman field in South-west of Iran were analyzed. Using the suggested histogram equalization algorithm, the selected thin section images were improved in a way to be comparable with the reference photographs. Afterward, the main microfacies major features such as matrix texture, boundaries, fossil content and appearance are characterized by applying functional image processing algorithms and sensitivity analysis of the algorithm results. Accurate grain size is measured in a designed Graphical User Interface (GUI). Next, pore detection and 2D porosity values are calculated by K-means clustering of A and B parameters in L*A*B color image space. Finally, different minerals in the matrix, cement, and porosity are classified and distribution of them are visualized and plotted on a scatter plot to determine the exact facies types.
    Keywords: Microfacies, image processing, Edge detection, k-means clustering, K nearest neighboring classifier
  • Masoomeh Zaheri, Behrouz Rafiei * Pages 289-303
    The evaporite deposits examined in this study are located in the Eshtehard area (SW of the Alborz Province). Four outcrop sections (Mard Abad, Eshtehard, Salt Mine and Rud Shur) and thirty gypsum samples were selected for facies analysis, petrographical and mineralogical investigation in combination with the geochemical analyses. The Neogene evaporites are composed of massive, selenite, nodular and satin-spar gypsum lithofacies. Three different textures were recognized under microscope: porphyroblastic, alabastrine, and fibrous gypsum. Petrographical investigations and X-ray diffraction analysis showed the evaporite beds are mainly composed of gypsum, with no anhydrite relics. The characteristics of these litho- and microfacies indicate gypsum deposited in the lacustrine and sabkha settings. The ICP-OES analysis shows significant differences in major and trace element contents of the four types of gypsums. The concentrations of Sr, Fe, Al, Mg and Na were increased in massive gypsum, while the crystals represent a decreased in size. The contents of these elements were also decreased in nodular, fibrous and selenite gypsums. These are probably indicating an increase and decrease in brine concentration, respectively. Paleoclimate condition is simply determined for the Neogene evaporites using geochemical approach. The results suggest a shift from semi-arid (bottom) to arid (top) paleoclimate conditions.
    Keywords: Gypsum Texture, Lacustrine Environment, strontium, Neogene Deposits, Eshtehard. Alborz Province
  • Vesal Yahya Sheibani, Asadollah Mahboubi *, Reza Muossavi Harami, Mohammad Khanehbad Pages 305-332
    Parvadeh Formation (Bathonian) in Tabas block is formed of mixed siliciclastic-carbonate deposits. Six stratigraphic sections have been selected in this formation which dominantly composed of conglomerate, sandstone, shale and limestone. Integration of field and microscopic studies resulted in identifying two facies association including 4 siliciclastic and 10 carbonate facies in this formation. Analyzing facies and sea level fluctuations caused identification of two 3rd order sedimentary sequences in each of the sections. The low-stand system tracts of the recorded sequences are characterized by tidal flat and lagoon facies and shallowing-upward para-sequences. Highstand and transgressive systems tracts are generally both represented by dominantly intertidal and sub-tidal lagoon, shoal and open marine facies. The upper and lower boundaries in all stratigraphic sections of middle Jurassic successions are SB1 that are distinguished by erosional evidences and sometime red conglomerate and sandstone horizons. On the basis of detailed facies and depositional sequences analysis, global sea level fluctuations and tectonic events are the most important factors that affected system tracts and depositional sequences in the Tabas block. Local tectonic activities (mostly related to Kalmard and Nayband Faults) also have an effective role on the thicknesses of siliciclastic and carbonate deposits in different parts of study areas.
    Keywords: Parvadeh Formation, Middle Jurassic, sedimentary environment, Microfacies, sequence stratigraphy
  • Hengameh Erfanian Kaseb, Habib Allah Torshizian *, Davod Jahani, Mohammad Javanbakht, Nader Kohansal Ghadimvand Pages 333-349
    The Petergan Playa lies in east of Iran, covering an area of 212.5 km2. The playa is located 135 km from the city of Qayen at the border area known as Shahrakht. Thus, in the present study, to study the brines and their evolution, sampling was conducted from some of 95 brines based on an ordered network. The brines were analyzed using the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) method. The cations found in the brines showed abundance in the amounts of Na^+,Ca^(2+), Mg^(2+),〖and K〗^+.For the anions an abundance was observed in the amounts of Cl^-, SO_4^(2-), and HCO_3^-. The type of brines was as follows: Na^+-SO_4^(2-)-Cl^- , by pondering fairly neutral acidity and chemical investigation of the ingress waters, it can be inferred that, the waters are of Ca^(2+)>CO_3^(2-), Cl^-+ SO_4^(2-)>HCO_3^-,HCO_3^-≪Ca^(2+)+ Mg^(2+) molar ratios, following the geochemical route П in the brines’ geochemical evolution diagram, which is similar to the brines in Saline Valley and the Dead Valley in the United States. X-Ray Diffraction (XRD) results revealed that, the most abundant minerals in the brines are Quartz, Gypsum, Halite, and Calcite. Accordingly, source of the brines would be meteoric waters as well as neutral waters and brines with hydrothermal source.
    Keywords: playa, Dead Valley, east of Iran, Hydrogeochemistry, Brine Evolution
  • Saeed Maleki Porazmiani *, Ebrahim Ghasemi Nejad, Taghi Farmani Pages 351-365

    The Albian-Cenomanian strata of the Koppeh-Dagh Basin were investigated for their marine palynomorphs and palynofacies contents and used for palaeoclimatic, palaeoenvironmental and sequence stratigraphical purposes. Various palynofacies criteria such as Palynological Marine Index (PMI), chorate/proximate, proximochorate and cavate ratio (C/PPC) and outer neritic/inner neritic index (ON/IN) were applied as alternative indicators to monitor the proximal-distal trends. Higher values of the former proxies versus low continental/marine ratio (CONT/MAR) were documented during periods of relative rise of sea-level. Increasing values of the marine palynological proxies such as the PMI, C/PPC and ON/IN were consistent with maximum flooding surfaces (MFS). A relatively diverse dinoflagellate cyst assemblage was reported at MFS, whereas, during the periods of relative sea-level fall, the dinocyst diversity decreased and coincided with those above-mentioned marine palynological ratios that reinforced terrestrial conditions. Palaeovegetation reconstruction showed the predominance of the pteridophyte spores. This palynoflora indicates a humid and warm climate during the Albian-Cenomanian time. Three deducted depositional sequences correspond with those suggested in previous studies based on surface and subsurface geological data. Sea-level changes correspond well with those reported from other parts of the Tethys.

    Keywords: Palynology, sequence stratigraphy, Albian-Cenomanian, Tethys, Koppeh-Dagh Basin
  • Seyedeh Razieh Jafari *, Ali Sepahi, Yasuhito Osanai Pages 367-380
    A narrow zone of migmatitic rocks forms part of the metamorphic complex associated with the Boroujerd plutonic complex in the north-western part of the Sanandaj-Sirjan zone, Iran. It includes stromatic, dyktionitic, schollen and massive migmatite, metatexites and diatexites. Leucosome (alkali-feldspar granitic and trondhjemitic) and mesosome are well developed, melanosome less so. Detrital zircon cores from one mesosome range in age from ~ 2540 to 210 Ma, with a major sub-population at ~ 250 Ma. The detrital zircon is probably derived from igneous bodies from the Iranian micro-plate (southern Eurasia) and possibly Pan-African and Arabian-Nubian basement no longer exposed. Metamorphism at 170–160 Ma recorded by thin metamorphic zircon rims is similar in age to the adjacent plutonic rocks from the Boroujerd area (172–169 Ma), both occurring in a middle Jurassic continental arc setting.
    Keywords: Geochronology, Migmatite, Boroujerd, Sanandaj-Sirjan zone, Zircon
  • Hassan Azmi *, Moarefvand Parviz, Abbas Maghsoudi Pages 381-394
    The selection of an appropriate estimation method is a crucial decision in resource estimation processes. There are multiple resource estimation methods of which the most important one is block modelling. Among the block modelling methods used for the estimation of gold resources, three methods have a broader application. These methods include Inverse Distance Weighting (IDW), Ordinary Kriging (OK), and Full Indicator Kriging (FIK). We compared the results of these three techniques and selected the most appropriate method for resource estimation of the Damanghor gold deposit. For this purpose, we prepared the geometric model of the deposit based on geological continuity and then, conducted the variography procedure to determine the grade continuity and the amount of gold resource. The dataset of the Damanghor area included eight diamond drilling boreholes and eight exploratory trenches comprising the grade results of 405 samples. The results show that FIK is the best method for resource evaluation of this case study. The OK method, however, is not suitable for this deposit. The IDW method provides reliable results when the drilling spacing is less than the variography range. This results can be used for the estimation of inferred resources when the geological continuity is appropriately determined.
    Keywords: Damanghor Gold deposit, Grade continuity, Geological continuity, Full indicator kriging, ordinary Kriging
  • Shiva Shahsavar, Alireza Jafari Rad *, Peyman Afzal, Nima Nezafati Pages 395-404
    The main purpose of this research is a comparative study among four different fractal models including Concentration-Perimeter/Area (C-P/A), Concentration-Number (C-N), Concentration-Area (C-A) and Concentration-Perimeter (C-P) for delineation of stream sediments Au anomalies based on catchment basins in Aghkand region, NW Iran. In this study, a total of 920 stream sediment samples were utilized to determine the geochemical anomalies of Au using the fractal models for selection of optimum model. As a result, the Au anomalies were correlated with geological units located in the western and SW parts of the region that mainly consist of andesite rocks and tuffs. To certify this, 78 litho-geochemical sets of data were utilized to validate the C–P/A, C–N, C–A and C–P fractal models for Au by logratio matrix. The overall accuracy rates are 0.97, 0.96, 0.95 and 0.95 for the C– P/A, C–N, C–A, C–P fractal models, respectively. It showed that the C–P/A model was the optimum fractal model in the study region.
    Keywords: Fractal models, Stream sediments, Aghkand
  • Farkhondeh Askari Malekabad, Reza Jahanshahi *, Rahim Bagheri Pages 405-418
    The Bazman volcano in the southeast of Iran is considered to be a dormant volcano. To study the hydrogeochemistry and geothermometry, sixteen water samples were collected from the thermal and cold springs. Temperature of the cold springs range from 28.1 to 36.6 C while mean temperature of the thermal spring waters is ~42 C. Generally, the salinity values of the water samples vary from 1102 in the cold spring to 10250 µS/cm in the thermal springs. The water samples are categorized into three types: Cl -Na, Cl-HCO3-Na-and SO4-Na. The composition values of δ2H and δ18O in the thermal springs were resulted from water-rock interaction or underground evaporation in the deep depths. Since the thermal springs have a different temperatures but similar chloride content, it seems that a conductive cooling mechanism is occurring in the geothermal system. Based on the geothermometry results, the equilibrium temperature of the deep reservoir estimated from ~120 to 145 C. The fraction of the cold water mixed with the warm water ascending is estimated to be ~0.94. Finally, the depth of thermal water circulation is estimated to ranging from 1.9 to 3 km under two different scenarios.
    Keywords: Geothermometry, stable isotopes, Geothermal field, Water-rock interaction, Bazman Volcano