Samah A. M. Abou-alfitooh, M. Ramzi, Mostafa G. Temraz
et al.
Abstract Approaches for enhancing oil recovery are important for maximizing the recovery factor of oil after the vanishing natural pressure of a hydrocarbon reservoir. This study attempted to boost the oil recovery factor at the expense of the saturation of remaining oil after a secondary flood using xanthan gum and its modified form through blending with microcrystalline cellulose (MCC), where their effectiveness was evaluated. To evaluate the effect of MCC on native biopolymer, thermal gravimetric analysis (TGA), interfacial tension (ITF), and rheological studies were assessed. The results indicated that MCC enhanced the rheology properties of the biopolymers. It also reduced the interfacial force between crude oil and polymer slug solution (12.54 mN/m) more than the formation water (18.8 mN/m) and biopolymer solution alone (16.28 mN/m). Full reservoir conditions (confining pressure, reservoir temperature, and actual oil) were applied in this work on two subsurface core samples (A&B), trying to enhance the oil recovery. The original oil in place was evaluated for the reservoir core samples (50.9% p.v. & 60.3% p.v. for A & B, respectively), and the oil permeabilities were 81.6 & 80.97 md at the residual water saturation recorded as the base permeability. To assess the residual oil saturation, the secondary flooding using formation water was carried out up to the stage of no more oil displaced out of the tested samples, where the permeability of water at the residual oil saturation was measured 6.05 & 7.5 md for A & B, respectively. Finally, plug samples were flooded chemically, and additional oil recovery was recorded. The flooding experiments indicated that the MCC with xanthan gum was more effective for enhancing the oil recovery factor (29.09% Sor) than that of the native biopolymer separately (20% Sor), this is due to its higher viscosity, higher ability for IFT reduction, and better emulsion stability. The article’s innovation lies in proving that the presence of microcrystalline cellulose supports the performance of xanthan gum as an enhanced oil recovery agent in severe conditions of oil reservoirs.
Abstract The coupled analysis of multi-field heat and mass transfer in geothermal reservoirs is a pivotal concern within the realm of geothermal rock exploitation. It holds significant implications for the assessment of thermal energy capacity and the formulation of reservoir optimization strategies in the context of geothermal rock resources. Parameters governing production, along with fracture network characteristics (such as injection well temperature, injection well pressure, fracture width, and fracture network density), exert an influence on enhanced geothermal systems (EGS) heat production. In this study, aiming to comprehend the dynamic heat generation of EGS during prolonged exploitation, a coupling of various fields including permeation within the rock formations of geothermal reservoirs and the deformation of these rocks was achieved. In this study, we formulated the governing equations for the temperature field, stress field, and permeability field within the geothermal reservoir rock. Subsequently, we conducted numerical simulations to investigate the heat transfer process in an enhanced geothermal system. We analyzed the effects of injection well temperature, injection well pressure, primary fracture width, and secondary fracture density on the temperature distribution within the reservoir and the thermal power output of the production well. The research findings underscore that ill-conceived exploitation schemes markedly accelerate the thermal breakthrough rate of production wells, resulting in a diminished rate of geothermal resource extraction from the geothermal reservoir rock. Variations in influent well temperature and secondary fracture density exhibit an approximately linear impact on the output from production wells. Crucially, injection well pressure and primary fracture width emerge as pivotal factors influencing reservoir output response, with excessive widening of primary fractures leading to premature thermal breakthrough in production wells.
Abstract Oil well productivity capacity is an important parameter in oilfield development, which is of great significance for efficient development. Traditional oil well productivity capacity prediction methods have a series of problems, such as limited application scope, large prediction errors, difficulty in characterizing changes under the influence of multiple factors. Aiming at these problems, a well productivity prediction method based on machine learning algorithm was proposed. Taking Bohai X oilfield as the research object, 12 factors affecting oil well productivity capacity were selected from three aspects: geology, engineering, and production. The degree of each factor influence on oil well productivity capacity was analyzed by using the mean decrease impurity (MDI) method, the feature parameters were sequentially excluded, and redundant features that do not affect the prediction accuracy of the model were removed. And then support vector machine (SVM) optimized by improved whale optimization algorithm (IWOA) was used to establish prediction model for oil well productivity capacity. The results show that the main control factors of oil well productivity capacity are: permeability, porosity, effective thickness, pressure draw-down, perforation thickness, fracturing sand addition amount, resistivity, oil saturation, sand addition strength and shale content. The model based on SVM optimized by the improved whale algorithm have an average error of 9.3%, while the model based on SVM optimized by grid search and whale algorithm have bigger errors, which are 21.7% and 15.7% respectively. Residual sum of squares (R2) values for SVM optimized by grid search optimization, whale algorithm and improved whale algorithm are 0.372, 0.939 and 0.941 respectively. The model based on SVM optimized by the improved whale algorithm has higher accuracy in predicting oil well productivity capacity. Compared with existing literature, the MDI method was used to optimize the factors affecting oil well productivity, and IWOA was used to improve the accuracy of oil well productivity capacity prediction. The research results can provide reference for the well productivity capacity prediction.
Abstract The key scientific problem to be solved in this paper is the optimal development and utilization model and the economic evaluation model of China's land-phase shale oil and gas resources, and the purpose of the research is to promote the large-scale commercial development and utilization of China's shale oil and gas resources, and to safeguard China's oil and gas energy security and the sustainable development of the economy. The article proposes to adopt the small surface element volume method (oil content rate method) to evaluate the pure shale oil resources, adopt the Cobb–Douglas production function model as the optimization model to measure the boundary production capacity of shale oil and gas, construct the optimal development and utilization model for shale oil and gas resources considering the five first-level safeguard indexes, namely, science and technology (A), capital (K), talents (L), reserves (S) and ecological environment (E), and establish the basic constraint model for the optimal development and utilization of shale oil and gas resources. The basic constraint model, as well as the evaluation model of economic coefficients for the development and utilization of shale oil and gas resources were established. The pure shale oil resources are mainly calculated based on the movable oil content of shale. In the paper, the S 1 of normal pyrolysis (300 °C) is regarded as movable oil, and the sum of S 1 and evaporated hydrocarbon (light hydrocarbon) loss is the movable oil content of shale. The integrated geological-physical exploration-engineering comprehensive evaluation of China’s land-phase shale oil-rich and high-yielding “sweet spot” is an important prerequisite for the realization of shale oil and gas resources to build production scale and effective development, and the least-squares method is used to estimate the average production function, the distance to the maximum value of the residuals, and the boundary capacity production function. The average production function and residual maximum distance are estimated by the least squares method, and the production function of the boundary capacity is derived, and the quotient of the boundary capacity and the actual capacity is calculated to get the capacity utilization rate, which can be used to analyze the potential of future shale oil and gas growth. The development of shale oil and gas resources in a target block requires comprehensive consideration of the first-level guarantee indicators such as science and technology (A), capital (K), talents (L), reserves (S) and ecological environment (E), as well as more than 10 s-level indicators and a number of third-level indicators, in order to ensure that the oil companies maximize their profits by organizing the development and production. The economic coefficient can be expressed as the ratio of economically recoverable resources to geological reserves. The larger the economic coefficient for the development and utilization of shale oil and gas resources is, the better the economy of the area is, and the larger the proportion of shale oil and gas resources that can be exploited. There is little special literature on the optimal development and utilization model of shale oil and gas resources and energy security among many research results at home and abroad. The evaluation of pure shale oil using the small surface element volume method (oil content rate method) and the construction of the boundary capacity calculation model, the optimal development of the basic constraints model and the economic evaluation model that we have determined, although they can not yet fully cover all the links and factors related to the development and utilization of shale oil and gas resources, are not yet fully covered by our research work. However, our research work has given the model more geological and economic theoretical connotations, and provided an economic basis and technical reference for the large-scale and commercial development and utilization of shale oil and gas resources as an effective alternative to oil imports.
Bozhong Sag, the largest hydrocarbon generation sag in the Bohai Bay Basin, is characterized by presence of the third member of the Shahejie Formation (E2s3), which serves as a significant source rock. While previous studies have provided insights into the source material, sedimentary environment, and thermal maturity of the E2s3 source rocks, further investigation is required to deepen our understanding of sedimentary events and biological sources. In this research, nine mudstone core samples from the southwestern Bozhong Sag were thoroughly analyzed using organic-inorganic geochemistry and organic petrology. The results reveal the following key findings: (1) The middle and lower sections of the third member of the Shahejie Formation are characterized by high-quality source rocks, with the lower section exhibiting superior quality. The increase in water salinity during warm and humid climates, and the detection of 24-n-propylcholestane compounds reflected the occurrence of transgression events in the E2s3. These transgressions gradually increased from the lower sections to the middle sections of the E2s3. (2) The studied samples exhibit abundant presence of 4α-methyl-24-ethylcholestanes, 24-n-propylcholestanes, 2α-methylhopanes, oleananeabundant algainite, and a small amount of vitrinite. This diversity of hydrocarbon-forming organisms in the E2s3 source rocks is evident. (3) The moderate marine incursion in the lower part of the E2s3 results in nutrient elements that promote the flourishing of bacteria and algae, providing an abundant material basis for the formation of high-quality source rocks. However, the large-scale marine incursion in the middle of the E2s3 weakens water eutrophication, resulting in a decrease in the quality of source rocks compared to the lower part of the E2s3.
Abstract Surface-active polymer is a novel multifunctional active polymer applied for enhancing oil recovery which has both viscosity-increasing ability and surface activity. Experiments were carried out to indicate basic physicochemical properties of surface-active polymer and to study on differences of properties between surface-active polymer and other chemical flooding agents, and characteristics of increasing displacement efficiency by surface-active polymer flooding have been tested. Experimental results show that the molecular aggregation conformation, viscosity performance and flow capacity of surface-active polymer were significantly different from those of other chemical flooding agents. Positive effects of viscosity and viscoelastic properties and improvements in interfacial chemical properties are basic characteristics of increasing displacement efficiency by surface-active polymer flooding which are basic principles of surface-active polymer flooding for enhancing oil recovery.
Mehdi Ghelichkhanip, Azadeh Malekzadeh Shafaroudi, mohammad Hassan Karimpour
et al.
The Zangalou mine area, a part of NW Bardaskan magmatic assemblage, located south of Sabzevar and northwest of Bardaskan cities in Khorasan Razavi province. The rock units of the area are dominated by sedimentary and volcanic racks (andesite, trachyandesite, latite and andesitic tuff). The dominant minerals are plagioclase, hornblende, pyroxene and alkali feldspar locally affected by argillic and propylitic alterations and the main textures are porphyritic, glomeroporphyritic, amygdaloidal and fine grain. The rocks under study formed in continental volcanic arc related to subduction zone, are calcalkaline in nature, metaluminous in composition and classified as shoshoite series. LREE and LILE enrichment compared to HREE and HFSE of the investigated rocks indicate their magma generation in subduction setting. Both Zr/Ba and Sm/Yb ratios point to lithospheric mantle origin and the rare or the absence of garnet in the origin respectively. The parent magma formed from partial melting of an enriched phlogopite spinel lherzolite. The geochemical properties of Zangalou share many signatures with those of the volacic rocks distributed in other parts of NW Bardaskan volcanic assemblage indicate high similarity in geochemical signatures of volcanic rocks. Studying geochemistry of volcanic rocks in these areas indicates formation of these rocks in a subduction setting.
It is of great significance to clarify the formation mechanism of carbonate cementation and its influence on reservoir physical properties. By means of petrology and geochemistry, the occurrence characteristics and formation mechanism of carbonate cements in Cegai slope of Junggar Basin are analyzed. The results show that the distribution range of <i>δ</i> <sup>13</sup>C<sub>PDB</sub> value is -29.6 ‰~6.7 ‰, that of <i>δ</i> <sup>18</sup>O<sub>PDB</sub> value is -12.5 ‰~19.2 ‰, and it has a large span. All those indicate the material source of carbonate cementation and the complexity of water-rock interaction. <i>δ</i> <sup>13</sup>C<sub>PDB</sub> value has a positive offset with the typical marine or lacustrine phase of carbonate, while <i>δ</i> <sup>18</sup>O<sub>PDB</sub> value has the negative offset. The positive offset of <i>δ</i> <sup>13</sup>C<sub>PDB</sub> value is mainly affected by the carbon isotope fractionation of mixed hydrothermal fluid and the dissolution of a small amount of sedimentary carbonate. The negative deviation of <i>δ</i> <sup>18</sup>O<sub>PDB</sub> value may be caused by the mixing of various fluids—such as precipitation and deep hydrothermal—and the rise of diagenetic temperature. The material source of carbonate cements in Che-Guai slope is related to the CO<sub>2</sub> produced by the decarboxylation of organic acids, compaction and drainage of clay minerals, the dissolution of feldspar debris and the release of a large amount of plasma like Ca <sup>2+</sup>, Fe <sup>3+</sup> and Mg <sup>2+</sup> by conversion among clay minerals. Under the microscope, it is found that the carbonate cements are metasomatic to detrital particles and accompanied by asphaltene appearance, and appear in the form of crystal powder to macrocrystalline grain among the closely arranged clastic particles, as a product of late diagenetic stage, which destroy the physical properties of reservoirs.
Petroleum refining. Petroleum products, Gas industry
Khadijeh Amani, morteza delavari, Sadraldin Amini
et al.
In the Talesh area (western Alborz), a thick sedimentary- volcanic association formed in a littoral- deltaic environment during the Late Cretaceous. The extrusives comprise volcanoclastics (tuffs), lava flows (pillow and massive) and basic dykes. The lava flows are dominated by basalts. Basalts are petrographically diverse including clinopyroxene- and plagioclase- phyric suites. Clinopyroxene is chemically in the ranges of augite to diopside and plagioclase is labradorite to bytownite. Here, using clinopyroxene chemistry, we performed thermobarometry and hygrometry calculations. Thermometric results of different samples are in the ranges of 1000 to 1200 °C. Moreover, barometric calculations show pressure ranges of <2.5 and 2.5 to 6 kbar correlating with crystallization depth of upper to middle continental crust (<10 to 22 km). Regarding parental melt chemistry and the magmatic series, the clinopyroxene and whole rock chemistry suggest two alkaline and subalkaline series. Hygrometric calculations provide H2O contents of 2.7- 2.97 and 2.97- 3.53 wt.% for alkaline and subalkaline basalts, respectively. Tectonically, the alkaline basalts could be related to extensional tectonic regime, asthenosphere upwelling or mantle plume/hot spots, while the subalkaline basalts resulted from subduction- related magmatism probably related to northward subduction of an oceanic basin beneath western Alborz or a Neo-Tethyan branch below southern margin of the Eurasia.
Marzieh Veiskarami, Mahmoud Sadeghian, Habibollah Ghasemi
et al.
Introduction
Thermobarometric models based on the chemical equilibrium among coexisting mineral-mineral or mineral-melts pairs are useful tools widely used to estimate the P-T path and chemical evolution during igneous processes. The high sensitivity of amphibole to physicochemical changes makes it a good tracer for thermobarometric models. Majerad Igneous-Metamorphic Complex with NE-SW trend, 40 kilometer length, and 10 kilometer width is located in the southeast of Shahrood in the northern margin of the Central Iran structural zone. Late Neoproterozoic sequence of Majerad metamorphic complex includes a wide range of metamorphic rocks with extensive compositional variety of metacarbonate, metapsammite, metapelite, metabasite and metarhyolite. Metabasites of the Majerad metamorphic complex consist of a greenschist to garnet amphibolite. Late Iranian Neoproterozoic complexes have been studied by numerous researchers, and a lot of papers have been published related to them (Rahmati Ilkhchi et al., 2011; Balaghi Einalou et al., 2014; Faramarzi et al., 2015; Hosseini et al., 2015; Malekpour-Alamdari et al., 2017). These complexes have cropped out in the different parts of Iran, except the Kopeh Dagh, Makran and the East Iran Flysch structural zones.
Analytical methods
The whole-rock major element compositions were determined by X-ray fluorescence using fused glass disks at the Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China. Trace elements were determined by ICP-MS (Agilent 7500a) at IGGCAS after more than 5-day acid digestion of samples in Teflon bombs. Compositional mineral analyses were performed at the State Key Laboratory of Continental Dynamics, Northwest University, Xian China, using a Cameca JXA-8230 instrument at an acceleration voltage of 15 KV, and beam current of 10 nA.
Results
In the metamorphic environment, aluminous hornblende-bearing assemblages are stable over a wide P-T field that extends from amphibolite to granulite, and high-T eclogite-facies conditions. At lower temperatures, the hornblendic amphibole is replaced by sodic-calcic amphibole at relatively high-P and by actinolite at lower-pressure greenschist-facies conditions (Spear, 1993; Ernst and Liu, 1998; Molina et al., 2015).
Amphibole formulas were calculated with the Amp-Excels spreadsheet using the 13 cations method (Leake et al., 1997). Amphiboles of metabasites are calcic, and Amphiboles of actinolite-schists are in the range of actinolite to magnesio-hornblende, and in amphibolites, they are plotted in the range of magnesio-hornblende to tschermakite. Plagioclase are usually oligoclase to bytownite.
Temperatures range of metamorphism events of amphibolites of the Majerad complex have been estimated by using the hornblende-plagioclase thermometer. This thermometer is based on the Ca and Na equilibrium exchange between plagioclase and amphibole (Holland and Blundy, 1994). The hornblende-plagioclase pair thermobarometer estimates temperatures of 450 to 690ºC and pressures of 4 to 11 Kb for the formation of the Majerad amphibolites. These temperature-pressure ranges correlate with P-T conditions of the greenschist and amphibolite facies in the typical Barrovian type metamorphism.
Abstract The development of heavy oil with high efficiency is a worldwide difficulty for offshore oil field. The technology of rod pumping provides a possible effective way for offshore heavy oil thermal recovery, but the safety of working platform is the prerequisite for the implementation of this new technology. In this paper, the mechanical model of LD27-2 WHPB platform is established, and the safety performance of the platform under hydraulic pumping unit (HPU) load is evaluated. The distribution of the combined HPU load accords with the classical probability model. When the HPUs are all synchronous, the combined load reaches its maximum. The finite element-based platform safety analysis under the extreme condition is carried out. Under the combined action of wave current, wind load and the extreme HPU load, the maximum stress of the jacket is 83.2 MPa, and the safety coefficient is 4.33, indicating the overall strength of LD27-2 WHPB platform meets the safety requirement.
A temporal framework for mineral deposits is essential when addressing the history of their formation and conceptualizing genetic models of their origin. This knowledge is critical to understand how crust-forming processes are related to metal accumulations at specific time and conditions of Earth evolution. To this end, high-precision absolute geochronology utilising the rhenium-osmium (Re-Os) radiometric system in specific sulphide minerals is becoming a method of choice. Here, we present a procedure to obtain mineral separates of individual sulphide species that may coexist within specific mineralized horizons in ore deposits. This protocol is based on preliminary petrographic and paragenetic investigations of sulphide and gangue minerals using reflected and transmitted light microscopy. Our approach emphasizes the key role of a stepwise use of a Frantz isodynamic separator to produce mineral separates of individual sulphide species that are subsequently processed for Re-Os and sulphur isotope geochemistry. • Detailed method and its graphical illustration modified from an original procedure introduced by Saintilan et al. (2017, 2018). • Quality control and validation of monophasic mineral separates made by microscopic investigations and qualitative analysis of aliquots embedded in epoxy mounts. • The present method, which contributed to the successful results presented in the co-publication by Saintilan et al. (2020), demonstrates why other studies reporting Re-Os isotope data for mixtures of sulphide minerals should be considered with caution.
Abstract Polymer flooding and surfactant/polymer flooding (SP flooding) were mainly focused on the improvement in oil–water flow ratio and the reduction in oil–water interfacial tension. Preformed particle gel (PPG) flooding was mainly focused on the reservoir heterogeneity improvement. Each of these technologies has its own limitations. Heterogeneous system flooding (HS–PP flooding) was proposed as a novel flooding method aimed to improve oil–water flow ratio and reservoir heterogeneity at the same time. The HS–PP flooding system was composed of PPG and polymer solution. HS–PP flooding, polymer flooding and SP flooding as different chemical EOR methods were studied in laboratory in physical simulation heterogeneous model. Property of cubic expansion of PPG was researched by laser particle analyzer. The result shows that cubic expansion of PPG in simulation water is obvious and can be controlled. The effect of PPG on the diversion rate modification in double parallel sandstone model was obvious. The oil displacement experiments of the three different flooding systems with the same viscosity in physical simulation heterogeneous model were studied. The results show that the HS–PP flooding improves the oil recovery by 20.04%, comparing the result of 12.67% for polymer flooding and 16.66% for SP flooding, respectively. HS–PP flooding as a novel flooding method shows an excellent ability for stabilizing oil production and controlling water cut. The mechanism of the HS–PP flooding was discussed briefly. In addition to the viscoelastic displacement of polymers, the special circulation ability of “accumulating–deforming (collapsing)–accumulating again” of PPG is the main reason why the HS–PP flooding shows an excellent property for stabilizing oil production and controlling water cut.
Abstract In the past, seismic exploration technique was mainly used for gathering information about subsurface rock structures and fluids by analyzing the travel time, reflection amplitude, and phase variations. However, nowadays, many additional seismic attributes have been introduced by the seismic interpreters, which aid in the visualization of subsurface geological structures, facies, and lithologies. This research aims to identify the pore fluids in the reservoir using post-stacked seismic data without requiring well log data. Gassmann’s equation, a well-known equation for fluid substitution, has been used for fluid substitution in this research. To test the proposed technique, a three-layer geological anticline model has been used. The third layer of the model represents a reservoir which is saturated with water, except its top part which is fully saturated with petroleum. Fluid identification is achieved by using fluid density, velocity changes, and acoustic impedance (AI). P-wave velocity and AI are measured from post-stacked seismic data and its inversion, from which the saturated rock density and compressional modulus (M) are calculated. Using this information, saturated rock density and compressional modulus are inverted for fluid velocity and density, respectively, to identify the pore fluid.
Mohammad Hassan Karimpour, Azadeh Malekzadeh Shafaroudi, Abbas Esmaeili Sevieri
et al.
Introduction
The Irankuh mining district area located at the southern part of the Malayer-Isfahan metallogenic belt, south of Isfahan, consists of several Zn-Pb deposits and occurrences such as Tappehsorkh, Rowmarmar 5, Kolahdarvazeh, Blind ore, and Gushfil deposits as well as Rowmarmar 1-4 and Gushfil 1 prospects. Based on geology, alteration, form and texture of mineralization, and paragenesis assemblages, Pb-Zn mineralization is Mississippi-type deposit (Rastad, 1981; Ghazban et al., 1994; Ghasemi, 1995; Reichert, 2007; Timoori-Asl (2010); Ayati et al., 2013; Hosseini-Dinani et al., 2015). Geology of the area consists of Jurassic siltstone and shale and different types of Cretaceous dolostone and limestone.
The aim of this research is new geological studies such as revision of old geologic map, study of different types of textures and mineral assemblages within carbonate and clastic host rocks, and chemistry of galena, sphalerite, and dolomite. Finally, we combined these results with isotopic and fluid inclusion data and discussed on ore-fluid conditions.
Materials and Methods
In order to achieve the aims of this work, at first field surveying and sampling were done. Then,
200 thin and 70 polished thin sections were prepared. Some of the samples were selected for microprobe analysis and galena and sphalerite minerals were analyzed by using JEOL- JAX-8230 analyzer at Colorado University, USA. The chemistry of dolomite and fluid inclusion data are used after Boveiri Konari and Rastad (2016) and stable isotope is used after Ghazban et al. (1994).
Discussion
The Irankuh mineralization is hosted by carbonate rocks (dolostone and limestone) and minor clastic rocks as epigenetic. Mineralization has occurred as breccia, veinlet, open space filling, spoted, dessiminated, and replacement (carbonate hosted rock). The mineral assemblages are Fe-rich sphalerite, galena, minor pyrite, Fe- and Mn-rich dolomite, bituminous, ankrite, calcite ± quartz ± barite within carbonate host rocks, whereas Fe-rich sphalerite, galena, pyrite, minor chalcopyrite, low Fe-dolomite, quartz, bituminous, ± barite ± calcite are important primary minerals at clastic host rocks.
There is positive correlation between Ag and Sb values within galena mineral. Sb/Bi ratio in galena is up to 20, which is an indicator of low temperature deposits (Malakhov, 1968). The Irankuh homogenization temperature (170 to 260 ºC) is higher than that of US Mississippi-type deposits (80 to 120 ºC). Based on comparison of Th and Fe and Cd contents in sphalerite from Irankuh and US deposits (Viets et al., 1992), homogenization temperature of deposit has a positive relation with Fe values and a negative relation with Cd contents in sphalerite. Fe content in Irankuh sphalerite has reached up to 5% and Cd value is lower than 2000 ppm. In addition, carbonate hosted rock hydrothermal dolomites that are Fe-rich and ankrite have formed at some places. The evidence shows that Irankuh ore-fluid is Fe-rich. However, clastic hosted rock hydrothermal dolomites are low-Fe due to reaction of Fe and S resulting in pyrite formation. Based on O isotope (16–19 ‰) value from hydrothermal dolomites (Ghazban et al., 1994), ore-fluid has been derived from continental crust.
Results
Fe-rich sphalerite and dolomite and ankrite are the most important characteristics of Irankuh mining district. Temperature and Fe-rich nature of ore-fluid and mineralogy signatures of Irankuh area can be used for exploration of this type of mineralization in Iran and the world. The Irankuh mining district is MVT type mineralization.
Acknowledgements
The Research Division of the Ferdowsi University of Mashhad, Iran, supported this study (Project No. 40221.3). Thanks to Bama Co. (especially Mr. Eslami) for the collaborations.
References
Ayati, F., Dehghani, H., Mokhtari, A.R. and Mojtahedzadeh, H., 2013. Geochemistry and mineralogy studies of Gushfil Pb-Zn deposit, Irankuh, Isfahan. Analytical and Numerical Methods in Mining Engineering, 6: 83-91 (in Persian).
Boveiri Konari, M. and Rastad, E., 2016. Nature and origin of dolomitization associated with sulphide mineralization: new insights from the Tappehsorkh Zn-Pb (-Ag-Ba) deposit, Irankuh Mining District, Iran. Geological Journal, DOI: 10.1002/gj.2875
Ghasemi, A., 1995. Facies analysis and geochemistry of Kolah-Darvazaeh, Goud-Zendan, and Khaneh-Gorgi Pb-Zn deposits from south of Irankuh. M.Sc. thesis, Tarbiat Modares University, Tehran, Iran, 158 pp. (in Persian)
Ghazban, F., McNutt, R.H. and Schwarcz, H. P., 1994. Genesis of sediment-hosted Zn-Pb-Ba deposits in the Irankuh district, Esfahan area, west-central Iran. Economic Geology, 89: 1262-1278.
Hosseini-Dinani, H., Aftabi, A., Esmaeili, A. and Rabbani, M., 2015. Composite soil-geochemical halos delineating carbonate-hosted zinc–lead–barium mineralization in the Irankuh district, Isfahan, west-central Iran. Journal of Geochemical Exploration, 156: 114-130.
Malakhov, A.A., 1968. Bismuth and antimony in galena, indicators of conditions of ore deposition. Geokhimiya, 11: 1283-1296.
Rastad, E., 1981. Geological, mineralogical and ore facies investigations on the Lower Cretaceous stratabound Zn – Pb – Ba – Cu deposits of the Irankuh mountain range, Isfahan, west central Iran. Ph.D. thesis, Heidelberg University, Heidelberg, Germany, 334 pp.
Reichert, J., 2007. A metallogenetic model for carbonate-hosted non-sulphide zinc deposits based on observations of Mehdi Abad and Irankuh, Central and Southwestern Iran. Ph.D. thesis, Martin Luther University Halle Wittenberg, Halle, Germany, 152 pp.
Timoori-Asl, F., 2010. Sedimentology and petrology of Jurassic deposits and Basinal brines studies in formation of Irankuh deposit. M.Sc. thesis, Isfahan University, Isfahan, Iran, 120 pp. (in Persian)
Viets, J.G., Hopkins, R.T. and Miller, B.M., 1992. Variation in minor and trace metals in sphalerite from Mississippi Valley-type deposits of the Ozark Region: genetic implications. Economic Geology, 87:1897–1905.
Amir Ali Tabbakh Shabani, Morteza Delavari Kooshan , Mahsa Hajiabdolrahim Khabbaz
Introduction
The Upper Eocene basic volcanic rocks that have cropped out in Karaj formation in the Boumehen and Roudehen area in the east of Tehran are characterized by fibrous zeolites filling their vesicles, cavities and fractures creating amygdale texture. The study area is located structurally in the Central Alborz orogenic belt. The presence of large volumes of shoshonitic magma during the Middle to Late Eocene in southern–central Alborz implies that partial melting to produce shoshsonitic melts was not a local petrological event. Thus, their ages, formation processes, and interpretations are of regional tectonic significance. In this study, we present a detailed petrography, mineral chemistry, and whole-rock geochemistry of high-K (shoshonitic) basic rocks to understand the petrogenesis and source region and to deduce the nature of the tectonomagmatic regime of the Alborz.
Materials and methods
In this study, we present new major and trace element data for a selection of 4 of the least altered samples by a combination of X-ray fluorescence (XRF) and ICP-OES techniques at the Zarazma Mineral Studies Company.
Mineral analyses were obtained by wavelength dispersive X-ray spectrometry on polished thin sections prepared from each rock sample described above for 12 elements using a Cameca SX-50 electron microprobe at the Istituto di Geologia e Geoingegneria Ambientale, C.N.R., University La Sapienza of Rome, Italy. Typical beam operating conditions were 15 kV and probe current of 15 nA. The accuracy of the analyses is 1% for major and 10% for minor elements. A total of 24 point analyses were collected.
Results and Discussion
The extent of alteration in the study rocks varies from slight to severe and shows porphyritic to glomeroporphyritic textures. Pyroxenes are generally subhedral to euhedral and occur as discrete crystals as well as aggregates. Olivine may occur only as relics filled with iddingsite, chlorite and calcite. Plagioclase is subhedral to euhedral and occurs both as pheocrysts and microliths in the glassy groundmass. The plagioclase crystals are variably sassuratised and sometimes replaced by zeolites.
Microprobe data indicate a restricted range of chemical composition for pyroxene falling in diopside and augite fields of ternary pyroxene classification diagram (Morimoto, 1988). The plagioclase composistions have been plotted in the fields of labradorite and bytownite in the orthoclase–albite–anorthite ternary diagram (Deer et al., 1992). On the F1-F2 tectonic discrimination diagram of Nisbet and Pearce (1977), pyroxene compositions plot mainly in volcanic arc basalt field consistent with their whole rock geochemistry. Thermobarometry based on pyroxene composition (Soesoo, 1997) displays a range of temperatures from 1150 to 1250 0C and pressure from 3 to 8 kbar for its crystallization.
Whole rock compositions show that the variations of SiO2 contents are narrow (47.08 – 47.47 wt%) and TiO2 (1.1 – 1.24 wt%). Relatively higher contents of K2O show a shoshonitic affinity in the K2O–SiO2 diagram (Peccerillo and Taylor 1976). Trace element and rare earth element (REE) distribution patterns for the basaltic samples normalized to the primitive mantle (McDonough et al., 1992) and chondrite values (Sun and McDonough, 1989) show similar patterns. The samples are all enriched in large-ion lithophile elements (LILEs), such as Rb, Ba, and K, and light rare earth elements (LREEs) ((La/Sm)N= 2.3–3.2) relative to the more immobile elements (e.g., Hf, Ti and Y). The plot of analyzed samples in a series of different tectonic discrimination diagrams shows that the Boumehen-Roudehen alkaline basalts are consistent with characteristics of subduction related (active continental margins) tectonic environments. In addition, enrichment in LILE and depletion in HFSE on spidergram create patterns which are very similar with the pattern of Andean counterparts indicating an arc setting.
Acknowledgments
Marcello Serracino is thanked for microprobe analyses. The authors are grateful to Journal Manager and reviewers who critically reviewed the manuscript and made valuable suggestions for its improvement.
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