جستجوی مقالات مرتبط با کلیدواژه « اسفوردی » در نشریات گروه « علوم پایه »

The use of different geospatial layers In the exploration and determination of the mineralization zones, will lead to more reliable results. In this study, the investigation of iron mineralization zones was done using airborne magnetic data and three types of satellite images (i.e. ASTER, Landast-8 and Sentinel-2) in the Esfordi area. The reduced-to-pole filter, the upward continuation at altitudes of 200, 500 and 1000 meters, the analytic signal, the horizontal tilt angle, and the first vertical derivative were then employed on airborne magnetometry data. Argillic, phyllic and propylitic alterations, iron oxide and gossan zones and structural lineaments were extracted through satellite imagery data processing. The analytical signal and horizontal tilt angle indicators were used as the main geophysics footprints to identify the magmatic intrusions and geological lineaments, respectively. In addition, three satellite imagery indicators were used in final identification of iron-bearing zones. The weight of each layer was calculated by simultaneous analyses of the concentration-area fractal curve, the prediction-area plot, and the use of 22 Fe-bearing occurrences in the studied region. Note that the analytical signal layer with the prediction rate of 76 % has the highest weight among all layers. In other words, this layer has occupied 24% of the study area as favorable zones by which 76% of the known Fe occurrences are delineated. Iron ore potential map was prepared from integration of all geospatial indicators through the weighted multi-class index overlay method. The generated map has an intersection point with a prediction rate of 78% which has higher weight than the other individual indicators. According to this map, new iron mineralization potentials are observed in the east and southeast of the Esfordi area.

The multifractal modelling is an effective approach for separation of geological
and mineralized zones from the background. Following cases are addressed
in this study; Concentration-Distance to Major Fault structures (C-DMF) fractal model
and distribution of the known Fe indices/mines in the Bafgh area to distinguish the Fe
mineralization based on their distance to basement faults, surface faults and master
joints, using remote sensing information, airborne geophysics information and field
surveys. Application of the C-DMF model for the classification of Fe mineralization
in the Esfordi and Behabad 1: 100,000 sheets reveals that the main Fe mineralizations
have a strong correlation with their distance to the major and basement faults.
Accordingly, the distances of Fe mineralization that has the grades upper than 55% in
this area )43%≤S≤60%), are lower than 1 km related to basement faults, while such
distance for this threshold is 2344

The studied area is located at the 30 km northeast of the Bafq city and near the Esphordi phosphate mine. This area composed of Rizu Series rock sequence with Upper Precambrian- Lower Cambrian age. The mentioned sequence has been intruded by some seyenitic and gabbroic intrusions. Petrographical studies indicate that syenites contain hetero- granular, perthite and checkerboard textures and composed of alkali- feldspar (orthoclase), plagioclase, amphibole, pyroxene and biotite. Gabbros contain hetero- granular, and inter- granular textures, and composed of plagioclase, clinopyroxene, amphibole and biotite. Geochemical studies demonstrate that syenites and gabbros have high- K to shoshonitic alkaline nature. Based on the spider diagrams, the two mentioned intrusion have similar trend which can be indicative for their genetic relation. These diagrams indicate enriched LILEs along with negative anomalies of HFSEs. The chondrite normalized REE patterns demonstrate LREEs rich pattern with high ratio of LREE/HREE. The mentioned trends along with positive and negative anomalies of those elements probably are related to lower partial melting degrees of metasomatized mantle along with crustal contamination of this magma. Based on geochemical studies and using the discrimination tectonic setting diagrams, it seems that the studied intrusions were formed at the active continental margins toward post- collisional setting.

Iron-apatite ore deposits well known as Kiruna iron type formed in association with calc-alkaline volcanism from Proterozoic to Tertiary (Hitzman et al.، 1992). Liquid immiscibility in an igneous system was proposed to explain the formation of the iron oxides accompanying apatite in mineralized zones (Förster and Jafarzadeh، 1994; Daliran، 1999). The mode of ore formation however، is a matter in debate. Bafq region in Central Iran is one of the greatest iron mining regions in Iran with 750 million tons of reservoir. The majority of the iron deposits contains apatite as minor mineral and underwent metamorphism-alteration in varying degrees. The mode of formation and geological setting of Esfordi iron-apatite deposit in this region with an average of 13. 9 wt% apatite are discussed using geochemical and mineralogical data along with field description.

Fifty-three samples of mineralized zones and host rocks collected from 7 cross sections were studied by conventional microscopic methods. Seven representative samples were determined by XRD at Department of Physics، Shiraz University. Fifteen and six samples were also analyzed for major and trace elements using XRF at Binaloud Co. Iran، and ICP-MS at Labwest Minerals Analysis، Australia، respectively. Microprobe analyses were carried out on apatite in Geo Forschungs Zentrum Telegrafenberg at Potsdam University، Germany.

Field observation shows that igneous host rocks in Esfordi were intensively altered by hydrothermal fluids. The ores are surrounded by wide altered halos. Petrographic investigation indicated that the most important alterations are of potassic، carbonatitic and silicification types. Magnetite and apatite occur as major minerals، accompanied by minor hematite and goethite in the mineralized zones. Rare Earth Element (REE) minerals are present as minor phases in the ores. Three apatite mineralization types (vein، massive، and disseminated) were recognized. Petrographic data represent three apatite generations: stage 1 which is recognized in the massive and disseminated ore types، stage 2 occurred in brecciated zones and stage 3 which is formed by dissolution and redeposition of the 1 and 2 apatite types in vein-shaped bodies. The correlations among major elements and SiO2 correspond to magmatic differentiation. Cerium is the most abundant REE in the studied samples. Similar REE distribution patterns were observed in the apatite، magnetite and host rhyolite. Electron Probe Micro Analysis (EPMA) shows that the apatites are of fluoroapatite type، enriched in LREE. Low content of Sr was detected in apatites of Esfordi. Low Cd and Na concentrations but high U and Th values were also detected in the studied ore samples.

Esfordi iron-apatite deposit is located NE of Bafq، Yazd Province، and in the Central Iran structural zone hosted by mainly Infracambrian rhyolites. Field evidence such as flow structure of ore and dendritic texture of some minerals، e. g.، actinolite reveal the magmatic origin of iron-apatite deposit. The trends of major element concentrations in ores from different rocks are consistent with magmatic origin of the ores. The absence of sulfides shows an oxidized condition of magma at the time of ore formation. Low Sr in the apatite however، rejects any carbonatitic magma at Esfordi (Belousova et al.، 2002). Similar REE distribution patterns in the apatite، magnetite and host rhyolite indicates the same origin for them. Cerium concentration in the ores from Esfordi is also consistent with magmatic ore types and negatively sloped REE distribution pattern and negative Eu anomaly resemble to the Kiruna type iron-apatite deposits (Hsieh et al.، 2008). Low Cd and variable Th/U in the apatite along with low Na are contradicting with sedimentary environment (Jami، 2005; Alves، 2008). The Esfordi deposit probably formed in an extensional arc-related setting associated with syn-collision granitoids.

The Esfordi magnetite-apatite ore deposit is located in 35 Km northeast of Bafq city in Central Iran. Bafq is an important mining district which hosts more than 45 iron deposits and a few Zn-Pb massive sulfides, Mn and U deposits. The district is restricted by two main strike-slip faults of Kuhbanan to the east and Posht e Bdam to the west. The Esfordi ores occur in an Upper Precambrian-Cambrian volcano-sedimentary complex composed of acidic tuff, carbonates, shale, and sandstone. This complex intruded by granitic rocks and basic dykes and affected by regional and contact metamorphism and hydrothermal alteration. The Esfordi magnetite-apatite ores occur on top of the acidic tuff which is near to a carbonate layer. The Esfordi deposit is the most rare-earth elements (REE)-rich and most P-rich member of the iron deposits in the Bafq district. The main minerals in the Esfordi mine are Iron oxides, apatite, actinolite, diopside, talc, andradite, feldspars, quartz and carbonates. The REE minerals are closely related to apatite and were mainly formed in or around apatite grains and within veins and veinlets. This paper identifies the REE minerals and presents preliminary information on mineral composition and geological and mineralogical features of the deposit. The REE-bearing minerals are mainly of phosphate, fluorocarbonate and silicate groups. The REE minerals are highly enriched in light REE such as Ce, La, Nd and Pr. Apatite contains a few percent REE in its composition. However, the main part of REE may be from apatite as it is the main mineral of the deposit and apatite-rich horizons contain high-grade REE ore. The metasomatic assemblage, one head crystals of apatite and many mineralized veins and veinlets indicate that hydrothermal process were definitely active in the Esfordi deposit at later stages.

According to Atomic Energy Organization of Iran (AEOI) Uranium exploration program in Central Iran, Esfordi 1:100,000 sheet which is located in Yazd province, between Bafq & Behabad cities was prospected. The analysis result of the stream sediment samples which were collected by the Geography Society of Iran (GSI) have been used for radioactive resources of this area. Due to lacking of uranium, thorium and Rare Earth Elements (REE) analysis data, the uranium tracers have been used. The data processing, i.e. normalization, univariate and multivariate analysis were studied and ultimately, anomalies maps were prepared. Three uranium potential areas were introduced. These areas include marl and conglomerate sequence in North-west of region, south of Zarigan granite and sandstone sequence with aplites between Esfordi mine and Kooshk mine. Thus, Esfordi sheet is important as a sediment hosted uranium deposit.

Arash Syenite is located in central Iran and in Bafq metalogenic province, and has intruded into the Precambrian-Cambrian volcanic-sedimentary sequences. Size and distribution of minerals are not uniform in all parts of the body and vary from chilled margins to the central part of the pluton. Effects of tectonic movements, existence of uncommon textures in plagioclase crystals and the appearance of metasomatic textures are the main evidence for metasomatism. Study of elemental concentration deduced from mass balance calculation reveals the effects of alkaline metasomatism in Arash Syenite. Gain in K2O (and Rb) and Al2O3 with parallel losses in Fe2O3, CaO, Na2O, Ba and Sr are shown. Relative increase in Nb and Zr are due to leaching of mobile cations in this pluton.Decrease in Zr and Nb with parallel increase in SiO2, which is one of the most identical factors for the calc-alkaline differentiation, is remarkable in Arash Syenite. There is a clear change in Y, Th and Nb relative to Zr in this pluton and based on the constant ratio of Zr/Nb, the role of contamination and assimilation of country rock is insignificant in the pertrogenesis of this pluton. Negative anomaly for Nb and TiO2 suggest a subduction-related origin for the Arash Syenite.

The Esfordi iron - apatite ore in Central Iran is locAted in Bafq metallogenic province. Stratigraphically most of the rock units belong to Precambrian and Cambrian sequenses which the sedimentary and volcanic series are the most spreading rock types and mineralization took place just within the vOlcanic-sedimentary unit of the mentioned series. Study of REE contents of apatite in Esfordi iron-apatite orc shows high concentration of thClie elements. Zonal distribution of some REEs, e.g. La, is identified which varies from center to the rim of apatite ~ingle crystal. Absence of negative Eu anomaly makes the Esfordi apatite distinctive from the igneous types and may indicate a hydrothermal origin for Esfordi apatites. •