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

The ever-increasing demands of the steel industry for iron ore and the reduction in the grade and tonnage of existing large active mines raise the motivation for exploring small-scale or hidden iron deposits. The present research deals with prospecting a case of these deposits in Yazd province. The area is close to Marvar village in Meybod county, with an area of circa 720 m2. The rock type in the study area comprises of andesitite, dacite, and riodacite volcanic rocks with Eocene age. The hematite and magnetite outcrops also mainly occur within the andesites and andesitic tuffs. Therefore, the first step was the remote sensing for reconnaissance of the iron oxide zones, and ENVI 5.3 software created false color composites and the band ratios of Aster and Landsat 8 satellite images. The band ratio of 2/1 and 4/2 revealed the ferric iron oxides in the Aster and Landsat 8 images, respectively. In contrast, calculated band ratios of 1/2+5/3 for Aster and 7/5 in Landsat images illustrated the ferrous iron oxide zones. Besides, a false-color composite consisting of R=4, G=6, and B=8 showed the propylitic and argillic alteration zones via green and yellowish-pink colors, respectively. Comparing iron oxides and alteration zones revealed a spatial correlation between propylitic alteration and magnetite mineralization and another correlation between argillic alteration and hematite mineralization. Meanwhile, the magnetic data were processed via subtraction of the IGRF from the magnetic data and removing small and noisy features with a low pass filter of 100 m. Then, an upward continuation to 250 m exposed the regional effects in data. The subtraction of the regional effect from the filtered data gave the residual magnetic anomaly. In addition, the reduction-to-pole filter was also implemented and revealed the actual location of magnetic anomalies. In the next step, calculating the analytical signal of magnetic data in the area illustrated the boundaries of magnetic anomalies. Comparing the analytical signal and iron oxide zone from the remote sensing studies illustrated a significant spatial correlation between the ferrous-iron oxide zones and the magnetic analytical signal. Furthermore, the results of Euler deconvolution and power spectrum techniques indicate that most magnetic sources have a depth of circa 65 meters. Later, the estimated depth was used to define depth weighting in a 3D inversion of the magnetic data. Using Li and Oldenburg's algorithm via UBC Mag3D software, this inversion gave a three-dimensional shape of the magnetic susceptibility distribution in depth. According to the estimated model, the zones with high magnetic susceptibilities commonly occur at 50 to 100 meters depths, and their locations coincide well with the reduced-to-pole magnetic anomalies. Besides, comparing the iron grade of the geochemical analyses along three exploratory core samples confirmed that the zones with the biggest estimated magnetic susceptibilities within the model match the position of high grades of iron along the exploratory wells. Therefore, the area's main type of iron ore is magnetite, not hematite.

The Shamsabad manganese-bearing iron deposit is located 36 km south-east of Arak city, in the Sanandaj-Sirjan Zone. In order to determine the origin and ore-forming processes of the deposit, in addition to petrographic and mineralogical studies, geochemical studies for major, trace and rare earth elements (using LA-ICP-MS method) were done on ore samples. The ore is lens form and strataband, occurring in thick-bedded to massive, orbitolina-bearing Early Cretaceous limestones. Hematite, limonite, goethite and pyrolusite are the main ore minerals. Hematite is more abundant than other minerals. The colloform texture and lamination of the ore are evidences for volcanic-sedimentary origin of the deposit, and deposition in a marine environment. The presence of todorukite as a primary mineral is indicative of the hydrothermal mediated mineralization. The high Mn/Fe and Si/Al ratios, As, Ba, Cu, Pb and Zn enrichments, and depletion of Co and Ni are similar to hydrothermal deposits. The normalized REE patterns and low ΣREE values (31.40 ppm in average) support that Shamsabad deposit is of hydrothermal origin. Negative Ce and positive Eu anomalies indicate that low temperature hydrothermal fluids have an important role in mineralization. The Co/Ni, Co/Zn, La/Ce, LaN/NdN, DyN/YbN, Y/Ho ratios, and the discriminative diagrams for trace element concentrations are in the range of hydrothermal deposits. this study, it is suggested that the Shamsabad deposit is deposited from submarine hydrothermal fluids.

There is an iron mining complex called Shahrak 60 km east of the Takab town, NW Iran. The exploration in the Shahrak deposit (general name for all iron deposits of the area) started in 1992 by the Foolad Saba Noor Co. and continued in several periods until 2008. The Shahrak deposit is comprised of 10 ore deposits including Sarab-1, Sarab-2, Sarab-3, Korkora-1, Korkora-2, Shahrak-1, Shahrak-2, Shahrak-3, Cheshmeh and Golezar deposits (Sheikhi, 1995) with a total 60 million tons of proven ore reserves. The Fe grade ranges from 45 to 65% (average 50%). The ore reserves of these deposits are different. Sarab-3 ore deposit with 9 million tons of 54% Fe and 8.95% S is located at the northeast of Kurdistan and in the Sanandaj-Sirjan structural zone at the latitude of 36°20´ and longitude of 47°32´.
Sixty thin-polished, polished and thin sections are made for the study of mineralogy and petrology, and among them six thin-polished sections were selected for EPMA (Electron Probe Micro Analysis) on magnetite and hematite. EPMA was performed using the Cameca Sx100 electron microprobe at the Iran Mineral Processing Research Center (IMPRC) with wavelength-dispersive spectrometers.
Based on field observations and petrographic studies, lithologic composition of intrusion (Miocene age) ranges within the diorite-leucodiorite, monzodiorite-quartz monzodiorite, granodiorite-granite. With the intrusion of those igneous bodies into carbonate rocks of the Qom Formation, contact metamorphism was formed. The formation of Sarab-3 iron deposit occurred at the three stages of metamorphism, skarnification and supergene. Based on field geology of the deposit, it is composed of endoskarn, exoskarn including Fe ore±sulfides. At the metamorphic stage, after intrusion of intrusive bodies in carbonate rocks, recrystallization took place and marble was formed. With more crystallization of magma, evolved hydrothermal fluids intruded into host rocks. Skarnification occurred at the two stages of progressive and regressive. At the progressive stage, the reaction of fluids and host rocks turned to the formation of anhydrous calc-silicate minerals such as garnet and clinopyroxene. At the regressive stage with the change of physicochemical conditions like decreasing temperature, these minerals converted to hydrous silicates (tremolite-actinolite, epidote) and phyllosilcates (chlorite, serpentine, talk, and phlogopite). Also, minerals such as oxides (magnetite and hematite), sulfides (pyrite and chalcopyrite) and calcite were formed. At a late stage, with activations of fluids, quartz-calcite mineralized veins formed. At the supergene stage, the oxidation process leads to the formation of alteration minerals from the main mineralization. Although there are magnesian minerals in the skarn, its main composition is calcic. The shape of the deposit is lentoid to horizontal and in some places bed formed along with some alteration halos. The ore minerals include low Ti-magnetite (with an average of 0.02 wt % Ti), hematite and sulfide minerals such as pyrite, pyrrhotite and chalcopyrite. Magnetite is the most important mineral with disseminated, vein, open-space filling, aggregate, accumulation, island and cataclastic textures. The magnetite at Sarab-3 is generated in 2 stages: At the first stage, magnetite has mass to mosaic textures that indicate the first phase of deposition in the area and at the second stage magnetite is gray magnetites that are placed as narrow bands around hematite or on the primary magnetite. Hematite in the area is formed either as hypogene hematite with plate or blade texture that is formed before the formation of early magnetite or supergene hematite that itself is formed due to alteration and weathering of magnetite in the superficial and shallow part of the deposit. In the surface area of the deposit, ore minerals are strongly altered to mixtures of oxide and hydroxide minerals like hematite, limonite and goethite which changed the color of the ore body to yellow, deep orange, red and brown. Pyrites are the most important sulfide minerals in the area that are formed in five stages respectively, mass texture (Py1), Melnikovity (py2), vein-veinlet (py3), inclusion (py4), and mineralized veins (py5). Sericitization, calcitization, serpentinization, chloritization, epidotization, uralitization, argilitization, propylitization and actinolitizion are the important alterations in the area from which chloritization-epidotization and calcitization in the ore and propylitic and argilitization alteration in the plutonic rocks are dominant. The EPMA analytical results on 23 points on magnetite and hematite mineral suggest that the amounts of TiO2 and V2O5 (0.03 wt % and 0.01 wt % in average, respectively) are low in contrast to MnO and Al2O3 (0.09 wt % and 1.59 wt % on the average, respectively). Therefore, it fits in the skarn ore deposit domain on Ni/(Cr) versus Ti and Caɟ versus Ti discrimination diagrams of iron ore deposits (Dupuis and Beaudoin, 2011). High Mn in the rock samples of Sarab-3 may have resulted from the substitution of Fe by Mn in magnetite and hematite structure that can be a sign of hydrothermal skarn. Manganes, Al, Cu, Mg, and Ca show a negative correlation with Fe that may have resulted from the concentration and the substitution of these elements in tremolite-actinolite, epidote, chlorite, calcite, phlogopite and chalcopyrite. According to the chemistry of magnetite and plotting them on V2O5 versus TiO2 and V2O5 versus Cr2O3 diagrams, it can be recognized that the samples of the Sarab-3 deposit resemble to exoskarn magnetite of Goto and endoskarn Karakaen deposit of Senegal. Mineralographical and geochemical evidence from ore, the occurrence of iron in contact with the carbonates and calc silicates such as garnet, pyroxene, secondary calcite, epidote and chlorite suggest iron skarn genesis for the Sarab-3 deposit.

Siriz iron deposit is located in Central Iran structural zone, 75 km northwest of Zarand, Kerman Province. Iron mineralization occurred mainly as irregular ore bodies, lenses and veins in Paleozoic metamorphosed dolomitic limestone known as Kuhbanan Formation and the skarn units at the contacts of Siriz granitoid pluton. The Siriz iron deposit shows a simple mineralogical composition including magnetite, pyrite, chalcopyrite, hematite and iron hydroxides. The Siriz granitoid pluton is composed of quartz syenite, quartz monzonite, syenite and syenogabbro, with a calc–alkaline origin. Based on geochemical studies and classification, this pluton shows A-type characteristics with A1 subclass, originated from a mantle source. The Siriz skarn mineralization system consists of Siriz granitoid pluton as heat and mineralization source, skarn zone, massive magnetite iron ore lenses and veins, and metamorphosed dolomitic limestone (marble). An advance contact metamorphism between Siriz pluton and the dolomitic limestone of Kuhbanan Formation originated a calcic marble with granoblastic texture with garnet-wollastonitemarble (calcite) assemblage in limestone and garnet-clinopyroxene-phlogopite assemblage in dolomitic limestone. The Ca(-Mg) silicate minerals formed at this stage are mainly anhydrous and are not associated with iron mineralization. The peripheral high temperature magmatic-hydrothermal system changed to lower temperature system during the progressive cooling of the Siriz granitoid pluton,. This stage was recognized by formation of epidote, tremolite–actinolite, biotite, muscovite, chlorite, talc, calcite and quartz mineral assemblage in the Siriz iron deposit skarn unit. The association of iron mineralization and the late retrograde mineral assemblages, suggests that the iron mineralization is probably related to the fluid mixing with cooler meteoric water and decline in ore fluid temperature.

The Sadrabad iron deposit is located 28 km west of Sadrabad village (west of Yazd) at the Urumieh-Dokhtar magmatic arc. The Upper Triassic-lower Jurassic sedimentary rocks (dolomitic limestone, sandstone, shale and marl), the Cenozoic granite to dioritic intrusive bodies and the Quaternary unconsolidated deposits outcrop in the study area. The intrusive bodies are of I-type calc-alkaline series formed in syn-collision to post collision settings of continental margin subduction zone. The later quartz monzodiorite intrusions played a significant role in iron mineralization. The location of mineralization controlled by NW-SE and NE-SW fault systems. Olivine, clinopyroxene, garnet, tremolite-actinolite, epidote, serpentine, talc, phlogopite, calcite, dolomite, brucite and hydromagnesite are the main skarn minerals. The ore bodies consist mainly of magnetite with minor pyrite, chalcopyrite and pyrhotite which occur as massive, vein-veinlets, brecciate and disseminated magnetite. Skarn formation occurs in two prograde and retrograde stages. Olivine, clinopyroxene and garnet formed in prograde and the remaining minerals in retrograde stages. The temperature and salinity of fluid inclusions in quartz veins associated with serpentine (in retrograde stage) range from 217 to 280˚c and 8 to 16 (wt %) NaCl respectively, indicating the mixing of magmatic and meteoric water in retrograde stage. The Mg-bearing silicates such as serpentine, phlogopite, diopside and talc in the Sadrabad skarn, point to the mineralization of magnesian type.

OjatAbad iron ore located in north east of Semnan city. Old indications of mining are evident in the area. Belich and Bragin (1993) introduced Semnan iron ores as hydrothermal deposits. Recent studies show that the iron ores are related to Oligo-Miocene magmatism. Most iron ores have magnetite which has high magnetic susceptibility; therefore, magnetic method is a conventional method for geophysical exploration of iron.
In order to identify and detect this deposit, a magnetic survey was carried out in OjatAbad area. The magnetic data corrected for diurnal change of magnetic field and then total magnetic field of the Earth has been reduced. To do this, a reduce to pole (RTP) filter was implemented on the grid for locating the anomalies and their sources. This method entails removing the dependence of magnetic data to the magnetic inclination, i.e., converting the data which were recorded in the inclined Earth’s magnetic field to what they would have been if the magnetic field had been vertical. This method simplified the interpretation because for sub-vertical prisms or sub-vertical contacts (including faults), it transforms their asymmetric responses to simpler symmetric and anti-symmetric forms. The symmetric “highs” are directly centered on the body, while the maximum gradient of the anti-symmetric dipolar anomalies coincides exactly with the body edges.
For depth estimation of anomalies, the upward continuation filter was implemented. This is a mathematical technique that projects the data taken at an elevation to a higher elevation. The effect is that the short-wavelength features are smoothed out because one is moving away from the anomaly. The upward continuation is a way of enhancing large scale (usually deep) features in the survey area. It attenuates the anomalies depending on their wavelengths; the shorter the wavelength, the greater the attenuation. Also upward continuation tends to accentuate the anomalies caused by deep sources at the expense of the anomalies caused by shallow sources. For 3D imaging of magnetic data, we chose the inversion method of Li and Oldenburg (1998) that minimizes a function composed by (1) the data-misfit function defined in the data space as the L2 norm of the difference between the observed and predicted data, and (2) the stabilizing function defined in the parameter model space as the L2 norm of the first-order derivative of the weighted density distribution in both vertical and horizontal directions. They introduced a depth-weighting function to counteract the spatial decay of the kernel function with depth by giving more weight to rectangular prisms as depth increases.
On the RTP magnetic map of study area we can see 8 magnetic anomalies (A, B, C, D, E, F, G and H) which are located at the northeast to the southwest trend. The H one has the lowest amplitude. The results of upward continuation filter show that the anomalies of F and G are shallower than the other anomalies. Also, H and B are only deeper than 100m. The inversion results recovered all of the 8 anomalous bodies and confirm the above results. They showed that the anomalous body H has lower magnetic susceptibility and is deeper than the others and it seems likely that it is an intrusive body. So, iron mineralization is probably happened in the other bodies. The anomalous body B is the deepest mineralized body which elongates to 100 meter.

There is an iron mining complex called Shahrak 60 km east of Takab town، NW Iran. The exploration in the Shahrak deposit (general name for all iron deposits of the area) started in 1992 by Foolad Saba Noor Co. and continued in several periods until 2008. The Shahrak deposit comprising 10 ore deposits including Korkora-1، Korkora-2، Shahrak-1، Shahrak-2، Shahrak-3، Cheshmeh، Golezar، Sarab-1، Sarab-2، and Sarab-3 deposits)Sheikhi، 1995) with total 60 million tons of proved ore reserves. The Fe grade ranges from 45 to 65% (average 50%). The ore reserves of these deposits vary and the largest one is Korkora-1 with 15 million tons of 55% Fe and 0. 64% S. The Korkora-1 ore deposit is located in western Azarbaijan and Urumieh-Dokhtar volcanic zone، at the latitude of 36°21. 8´، and longitude of 47°32´. Six thin-polished sections were made on magnetite، garnet، and amphibole for EPMA (Electron Probe Micro Analysis). EPMA was performed using a JEOL JXA-733 electron microprobe at the University of New Brunswick، Canada، with wavelength-dispersive spectrometers. Outcropped units of the area are calc-alkaline volcanics of rhyolite، andesite and dacite and carbonate rocks of Qom Formation in which intrusion of diorite to granodiorite and quartzdoirite caused contact metamorphism، alteration plus skarnization and formation of actinolite، talc، chlorite، phlogopite، quartz، calcite، epidote and marblization in the vicinity of the ore deposit.

Gol-Gohar mining complex, located southwest of Sirjan (Kerman Province) and within the Sanandaj-Sirjan structural zone, has a number of iron-rich deposits that provides 30% of steel demand in the country. The main ore in this deposit is magnetite with subordinate amounts of hematite and accessory pyrite and chalcopyrite phases. Comparison of rare earth element (REE) distribution patterns of Gol-Gohar magnetite with those of magmatic magnetite (Kiruna) and also magnetite associated with granite and basalts show similar enrichment in light REE relative to the heavy REE and negative Eu anomaly. Such features can also be observed in apatite from Kiruna, Iron Spring, Choghar and Esfordi Fe ore deposits, the origin of all of which have been ascribed as magmatic due to a lack REE distribution patterns similar to phosphorites. Based on these characteristics, it seems that the magnetite in Gol-Gohar Fe deposit has dominantly originated from a magmatic fluid.

Gol-Gohar metamorphic complex, the major host rock for Gol-Gohar Fe ore deposit, belongs to east part of Sanandaj-Sirjan magmatic-metamorphic zone. The complex consists of mica-schist, quartzite, marble, amphibole-schist, graphite-schist, calc-schist and amphibolite. Amphibolite forms intermittingly with Gol-Gohar orebody, and thus determining the origin of this unit can shed some light on the origin of amphibolite and the condition under which Fe-ore was formed. Field, petrographic and geochemical studies indicate that metapelites originated from iron-bearing shale while amphibolites’ protolith were marl-type sediments. In addition, the position of amphibolite samples on various diagrams (e.g., mg vs. c, Cr, Ni and si vs. alk, al, and mg) which support their para-amphibolite origin, also confirms that the protolith of Gol-Gohar amphibolites formed in a sedimentary environment.

There are a few iron deposits in the north and northeastern part of Semnan city that none of them has a systematic exploration background. Ojat_Abad deposit is one of them located in 63 km of north-east of Semnan at the southern side of Semnan - Damghan main road. A magnetic survey including 1200 measuring points has been recently performed to explore the deposit within an area of 89 acres. The prepared total and residual magnetic field maps clearly demonstrate the existence of iron anomaly at seven locations in a zone with northeast - southwest trend. In this paper, attempt has been made to obtain more qualitative and quantitative information for the recognized anomalies by performing two and three dimensional (2D, 3D) numerical modeling. To achieve the goal, the residual anomaly map, obtained by professional software called Modelvison Pro is used. It was found that the results of 2D and 3D modeling confirm each other in the most cases and in addition are in quite good agreement with the results of existing mining excavations. The obtained results also demonstrate the explored anomalies locate separately, and except one of them, all are located at a depth less than 35 meters.

Panj-kuh iron ore deposit is located in 50 km southeast of Damghan. volcanic and pyroclastic rocks of the Eocene with composition of andesite–trachyte are the main host of the ore deposit. Injection of quartz monzonitic intrusion into volcano–sedimentary and volcanic rocks of the Eocene in the center and south of the study area has resulted in skarnization and formation of Panj-kuh iron deposit.Pyroxene, epidote and amphibole are the main silicate minerals and magnetite (and hematite), pyrite, chalchopyrite, malachite and azurite are the ore minerals. Extensive abundances of the sodi–calsic alteration which is defined by presence of albite, scapolite, and Mg-Ca-mafic minerals (diopsid), and constricted potasic alteration with minor distribution which is defined by orthoclase and biotite, major magnetite accompanied with minor pyrite and chalchopyrit, formation of malachite and azurite within the volcanic rocks are the most important features of the area. Also, geochemical investigations show that the intrusive rock samples of Panj Kuh have high MgO, SiO2, Ni, V, Sc and lower contents of K2O and Rb/Sr. The samples plot in the chalk alkaline and alkaline in the AFM and SiO2-(Na2O+K2O) diagrams respectively. They show metalminus and oxidation characteristics. These features are indications of the metasomatic skarn mineralization which formed by metasomatic fluid. Major and trace elements comparison of the Panj-kuh intrusion with other intrusions associated with skarn mineralization of the world, indicate some features of the gold and copper bearing skarns in the Panj-kuh skarn that recommend new exploration projects for the copper and gold in the Panj-kuh district.

The Jalal Abad iron ore deposit is one of the seven most important iron ore deposilS in the central Iran. with a probable are reserve of 200.4 million tons of iron ore in which the average grades are estimated as 44.28% Fe, 0.83% Sand 0.07%P. In the Jalal Abad deposit two types of orebodies are identified: the orebodies which are concordant with respect to the sedimentarY most rocks (Jalal Abad I). and the orebodies which are discordant with respect to their carbonate host. rocks (Jalal Abad II). In this deposit the primary ore minerals are magnetile and hematite. Hematite is also formed from the oxidation of magnetite. It is proposed that the deposit was rormed in two stages as describled below. 1) The principal orebodies were chr('39')formed contemporaneous with the sedimentation. from the exbalites and precipitates associated with volcanic activity within an intracontinental sources. This pan of the deposit is named Jalal Abad l. 2) After formation of the Jalal Abad orebodies. due to emplacement or the igneous rocks within the ore zone, the meteoric and/or connate water contained in the Jalal Abad J:then iron was redeposited from the upwelling iron bearing solution as replace,m ent orebo<1ies within the carbonate rocks. 1n this manner JalaJ Abad II orebodies were formed.