جستجوی مقالات مرتبط با کلیدواژه « ree » در نشریات گروه « زمین شناسی »

Saghand Anomaly 2 is located in 180 km NE of Yazd, 40 km east of Saghand village and east of Tashk mountain. This area is part of the Bafgh-Saghand metallogenic zone in the Central Iran Zone. The early Cambrian volcano-sedimentary unit consisting of intermediate- acidic volcanics, dolomitic limestone and small amounts of gypsum layers hosts iron-uranium mineralization in Sagand region. Uraninite is the main host of uranium associated with magnetite and pyrite. Molybdenite is rarely present in some parts f mineralization zones. Fe and U mineralizations occurr in two separate stages. coarse-grained Magnetite and pyrite are related to the Fe-mineralization stage while their fine-grained types form in the U-mineralization stage. The U content varies between 1365 and 4764 ppm in the analysed samples. As well as, Ce, Fe, Hf, Nb, S, Sc, Ta, W, Yb and Zr show enrichment, and Fe and S have the largest ranges of changes. The major and rare earth elements can be divided into two groups according to their association with U. The first group includes S, Fe, Ce, Dy, Er and Gd that show positive correlation with U and form in the same condition. The second group including Ti, Hf and Nb, have negative correlation with U and probabely form in the different condition. The rare-earth elements diagram show depletion in Eu and Pr and enrichment in Ce and Sm. The chemical composition of uraninite and the similarity of the distribution pattern of rare earth elements in uraninite of Saghand Anomaly 2 with metasomatic deposits show that the uranium mineralization in Saghand Anomaly 2 is metasomatic type and based on the chemical composition and distribution pattern of rare earth elements in the uraninite its formation temperature is between 200 and 350 ̊C.

Shotorsang iron skarn is located in 60 km northwest of Neyshabour (Khorasan Razavi, Iran) in Quchan-Sabzevar magmatic belt. Subvolcanic intrusion rocks have intruded into Cretaceous limestones and created skarnization. These rocks are divided into syenite porphyry and granodiorite porphyry based on their geochemical characteristics. They are I type oxidizing, metaluminous, and tectonic. Setting of the subvolcanic rocks are the subduction zone of the continental margin (VAG). Comparing the mineralization potential of the subvolcanic rocks of this area based on the use of the graph of SiO2 against K2O, MgO, Na2O+K2O, and Ni-V shows that they are fertile in terms of the formation of Fe and Cu skarn. Syenite porphyry is the origin of this mineralization, and magnesium in skarn is taken from hydrothermal fluid. The diagram of Eu/Eu*, Ce/Ce*, (Pr/Yb)n ratios also confirms the presence of meteoric water in the formation of the skarn zone. The primary fluid, which has a positive anomaly of Ce/Ce* and Eu/Eu* had acidic and oxidant conditions and high temperature, and formed pyroxene skarn. A part of magnetite mineralization is formed in this zone, and in this condition, the highest amount of REE entered the pyroxene skarn zone and diluted the fluid in terms of REE. This issue has led to a sharp decrease in the amount of REE in the mineralization zone. Negative Ce/Ce* and Eu/Eu* anomalies indicate alkaline conditions with less concentrated REE content, consistent with chlorite skarn. The highest amount of Fe mineralization is formed in this zone.

Temelieh area is located about 20 Km northwest of Selseleh (Lorestan Province). Geologically, the area is a small part of the Harsin radiolarite complex. Petrography consists of radiolarite, peridotite, gabbro, plate dikes, basalt and andesite, limestone, and marble. Manganese mineralization occurs as vein-veinlet and is mainly formed in faults, joints, and fractures that crosscut in radiolarites. Based on mineralogical studies, the manganese paragenesis is composed of pyrolusite, psilomelane, todorokite, cryptomelane, lepidocrocite, and manganese oxide-hydroxide (housmanite, hydrohousmanite, Manganite). The essential waste minerals are calcite and quartz. Based on geochemical data from major and trace elements, using different distinguishing charts and elemental ratios, there is a good relation between the manganese-rich region and the hydrothermal deposits. On the other hand, calculation of element designated ratios like Mn/Fe )mean 0.92), Ti/Al (mean 0.01), Co/Ni (mean 0.97), Co/Zn (mean 0.28), U/Th (mean 0.73), La/Ce (mean 0.32), LREE/HREE (mean 8.64) and ΣREE (mean 56.53) indicate Temelieh manganese ore is hydrothermal. Comparison of the REE normalized pattern of Temlieh manganese ore with other manganese deposits in the world indicates the hydrothermal origin of this deposit. REE distribution pattern indicates Ce positive anomaly with mean 24.5 and Eu negative anomaly with mean 0.54 that is compatible with hydrothermal manganese deposit. Accordingly, ore-forming fluids could be originated from meteoritic or magmatic water circulating through volcanic rocks, dissolve manganese and other metals and, while rising from suitable areas, deposits them in along the fault planes and fractures.

Karafs iron index is located 5Km north of the Karafs village in Hamedan province, Iran and geologically in the Sanandaj-Sirjan structural zone. Iron deposits in Sanandaj- Sirjan structural zone have been discussed and their origin is controversial. In this paper, geological, mineralogical, textural and geochemical properties, especially the geochemical behavior of rare earth elements in Karafs iron index are investigated and the mineralization type and its origin are determined.
During the field studies, 70 samples were taken for petrographic and mineralogical studies. Petrographic and mineralogical studies were performed in the Bu-Ali Sina University mineralogical laboratory. Geochemical study of iron ore was analyzed by ICP-MS at SGE company of Canada. XRD analyzes were performed at Bu-Ali Sina University.
Based on field observation,rock units in the area include volcanic rocks, phyllite, schist, skarn and limestone. Iron deposit is formed in lower Cretaceous limestone formation. The Karafs iron index consists of several small goethite-hematite sac-shaped masses which are accompanied by minor magnetite. Goethite and hematite are the main ore minerals. Most hematites formed in the ore are hypogene (first generation). Secondary hematites caused by conversion of magnetite to hematite (second generation) are very rare.
Replacement textures such as corrosion, marginal and island mainland are seen in hematite crystals. Two generations of goethite were observedin microscopic sections. The first generation goethites are macrocrystalline with an internal reflection of yellow brick and are usually amorphous and crushed and in some parts have a flowing state. Second generation goethites are found at the crystal boundaries of hematite and pyrite or fill its joints and fractures.
In the Karafs iron index, magnetite is seen with primary hematite in the form of amorphous crystals, in the size of 25 to 100 microns and with mass texture. Quartz, chlorite, epidote and sericitic are gangue minerals in the area. The correlation diagrams show positive correlation of Mg, Mn, P, Cu, Zn and negative correlation of Si, Co, Ni, Ti, V with Fe. Geochemical studies showed that the Ni / Co ratio is between 0.2 and 7, which is a characteristic of hydrothermal iron ore (Bajwah et al., 1987). Sr-Y diagram indicates that samples are plotted in the granitoid section, which shows that the hydrothermal fluids are derived from granitoid (Belousova et al., 2002). LREE is enriched in all samples. Enrichment of LREE elements related to HREE and Negative Eu anomalies in the deposit related to hydrothermal fluid have been reported in various parts of the world (Marschik and Fontbote, 2001; Galoyan et al., 2009).
Karafs iron index is located 5Km north of the Karafs village in Hamedan province and geologically in the Sanandaj-Sirjan structural zone. Rock units in the area include andesite, phyllite, schist, skarn and limestone. Iron deposit is formed in lower Cretaceous limestone formation. Goethite and hematite are main ore minerals which are accompanied by minor magnetite. The correlation diagrams show positive correlation of Mg, Mn, P, Cu, Zn and negative correlation of Si, Co, Ni, Ti, and V with Fe. Sr-Y and Co-Ni diagrams. Parameters of REE as well dispersion pattern, variance, diagrams and correlation coefficient of elements indicate hydrothermal origin derived from granitoid system and that the deposit has been hydrothermally leaching after the formation.

The majority of recent works accept that agates are formed at temperatures <100˚C (Moxon and Reed, 2006) and consist of a variety of silica minerals. The Reza Abad agates are located 150 km from SE Shahrood in the northern parts of Central Iran structural zone with geographic coordinates of 56˚ 25′ 22.52″ to 56˚ 47′ 2.50″E longitudes and 35˚ 55′ 32.68″ to 36˚ 07′ 5.54″N latitudes. The area is a part of the magmatic belt of northern Central Iran, containing a main period of magmatic activities from Eocene to late Miocene in a subduction related volcanic arc setting (Ghasemi and Rezaei-Kahkhaei, 2015). Analyses of the distribution of trace elements and stable isotopes should provide important information concerning the geochemistry of agate and genetic aspects of agate formation. Therefore, in this study, we tried to study the geochemical characteristics of Reza Abad agates, the origin and formation temperature based on the oxygen stable isotope data.

In this research more than 300 samples of agates were collected and six samples of them and three samples of their host rocks were selected for analysis by ICP-AES and ICP-MS methods. The samples were powdered and sent to ALS Chemex Company in Loughrea, Ireland. The oxygen stable isotope studies have been conducted on six samples in black, green, white, gray, red, and yellow agates. Oxygen isotope analyses were carried out on powdered agate using the conventional fluorination method at the Stable Isotope Laboratory in the Department of Geological Sciences, the University of Cape Town, South Africa.

Geochemistry of the agates The studied agates have 97.1 to 99.6 wt.% SiO2 with minor amounts of Al2O3 (0.01-0.13 wt.%), Fe2O3 (0.01-0.59 wt.%), Na2O (0.01-0.06 wt.%), and CaO (0.05-1.08 wt.%). The amount of aluminum is reduced by increasing the percentage of silica in most agates (except black agates) as illustrated in Figure 6. The amount of sodium oxide in brown, red, yellow and white agates is also reduced by increasing the silica content. The trace element analyses of Reza Abad agates and associated volcanic parent were carried out to obtain more information about the geochemistry of agates and their mineral-forming fluids. For this purpose, trace elements and rare earth element values are normalized to chondrite values. The general REE trend is characterized by a negative slope from La to Nd with enriched light REE contents (e.g., La, Ce). Most of the agate samples show a positive Eu anomaly except for white agates (Figure 7). The Reza Abad agates host rocks show an LREE-enriched pattern on the chondrite normalized REE diagram. The similarities in the shape and slope of the rare earth element patterns of the agates and the host volcanic rocks show that the elements forming the agates may have originated from fluids circulating in the host volcanic rock.

The East Sanadaj magmatic rocks of the northern Sanandaj-Sirjan Zone, part of Zagros Orogen, comprise several intrusive bodies that were generated during northeastward subduction of Neo-tethys beneath the Iranian sector of the Eurasian plate. From the east Sanadaj to Galali, mafic- intermediate intrusions of Late Jurassic age, have significant out crops in Kangareh, Saranjianeh, Ghorveh, Shanevareh and Galali. These rocks are calc-alkaline, metaluminous (ASI=0.51-0.95) and mostly magnesisan. As SiO2 increases, the chemistry of rocks changes to ferroan and high-K. These rocks present enrichment of LILE relative to HFSE, the low LREE/HREE fractionation ((La/Lu)N=1.5-14.6) considerably flatter chondrite-normalized REE profiles, Eu positive anomaly (Eu/Eu*= +0.63-+3.75). Primitive features of Sr - Nd isotopes Combined with HFSE and REE ratios, as source indicators, prove the mantle derived magma as a source of these rocks. Geochemical modelings indicate mafic- intermediate rocks of east Sanadaj, originated from spinel lherzolithic magma with hydrous components such as amphibole. Fractionation of these hydrous minerals have important role in evolution of magma. The combined monitoring of geochemical data and REE patterns, isotopic data were performed in order to unravel the compositional changes from calc-alkaline-magnesisn rocks to high alkaline-ferroan rocks of this area. The results denied bimodality of source magma and confirmed the important role of differentiation in magma evolution.

The Aderba leucogranite in the Golpayegan metamorphic core complex (GMC)¡ a part of Sanandaj-Sirjan zone¡ host lentiform small (2*4 cm)(Type 1) and large (7*14 cm)(Type 2)tourmaline nodules. In terms of mineralogical features¡ the core of these two types tourmaline nodules is different. The Type 1 composed of small blue-green tourmaline¡ quartz¡ K-feldspar (microcline) and apatite while the Type 2 is characterized by tourmaline coarse crystals accompanied by quartz. Based on major and trace elements data the tourmalines under discussion are classified as alkaline¡ schorl (Type 1) and schorl-dravite (Type 2). The mean REE values displays a negative slope and a negative (Type 1) and positive (Type 2) Eu anomalies. The overall petrographic observations and geochemical results indicate that the Type 1 is likely influenced by two mechanisms of liquid immiscibility in the evolved melt followed by biotite breakdown in the final stages of tourmaline crystallization to complete consumption of B (closed system). For nodules¡ Type 2¡ breakdown of biotite in equilibrium with the external fluid (open system) is proposed.

The study area is located at the center of the Lut area and the southern part of the Eocene- Oligocene Lut volcano-plutonic belt. The main exposed igneous rocks include widespread and thick units of Middle Eocene and Eocene-Oligocene volcanic Lavas (basaltic andesite, andesite and trachy-andesite), volcanic-subvolcanic (dacite and rhyodacite) with related tuffs, are intruded by microdioritic stock and dykes with gabbrodiorite to quartzdiorite compositions. Texture is dominantly porphyritic and the main minerals are plagioclase, clinopyroxene, hornblende, K-feldspar, quartz and minor amounts of biotite with apatite, zircon, rutile and opaque minerals as accessory phases. These rocks with predominant K-high calc-alkaline to shoshonitic affinities, are I type and metaluminous and are characterized by LILE, LREE and Th enrichment relative to HFSE, depletion in Nb,Ti,Ta and weak depletion in HREE and Y. These features are characteristic of the post-collisional calc-alkaline rocks along with a continental active margin tectonic setting. In spite of the low ratios of Nb/U, Nb/La and Ce/Pb, the Sm/Yb (1.6-2.1) ratio reveals low contamination of magmas with relatively thin crust which is in accordance with low crustal thickness in this area (36-38Km). According to geochemistry of trace elements and REEs, the main cause of magmatism in Mahour was melting of a metasomatized lithospheric mantle (E-MORB like) with spinel lherzolite composition accompanied by very small amount of garnet in the presence of phlogopite. On the basis of the phenocrysts assemblage, REE pattern with negative Eu anomaly (Eu/Eu= 0.63- 0.9) and also La/Yb calibration to crustal thickness, magmas have undergone relatively dry crystallization in the magma chamber at shallow depths (

Fluorite mineralization occurred in Central Alborz in Elika and Tizkooh Formations. The genesis of these deposits are considered to be epigenetic to sedimentary-diagenetic type. The obtained results show that all sedimentary-diagenetic and epigenetic fluorits are with similarities normalized patterns. These similarities can be considered from solution, transportation or recrystalization of former fluorites (sedimentary-diagenetic) epigenetic fluorite originated. The pattern similarity of fluorite and host rock, it can be concluded that remobilization of F element occurred and differential patterns between fluorite and igneous rock described their independency. In Kamarpohst ore deposit, the amount of REE is increasingly from fluorite zone to alteration and finally to basalt. Also the highest amount of REE identified in basalt and the lowest amount find in fluorite. Moreover, there was a complete similarity between normalized pattern of basalt, alteration halo and fluorite vein in Kamarposht deposit. This can show the leading of REE from the basalt and transported to fluorite vein. The dissimilarity in normalized pattern in black shale, sandstone and fluorite can be explained as differently origins. This result can be supported by the low amount of REE in sandstone and shele.Because of negative anomaly of Eu and positive anomaly for Ce, the environment of fluorite in Elica Formation was reduction.

A total of 50 boreholes have been drilled in the sediments of the study area in south west of Marvast. Based on heavy minerals investingation, the amount of monazite in these sediments rangs from 50 to 525 gram per tons. Analysis of monazites from Marvast and sediment samples with ICP-MS and normalization of some data with upper earth crust and chondrite showed that Marvast monazite enriched in all of REE specially LREE. The source rock of monazite is Upper Triassic black shale which is interbedded with sandstone, limestone and conglomerate. Erosion and weathering of these rocks have released monazite and enriched them in the sediments nearby. Iso-grade maps of  monazite in different depths from 1 to 6 m showed that the strongest and the most widely anomalies are at the depth 1 m, and with increasing the depth, intensity and distribation of the anomalies decreased, as the deepest anomaly has 5 meters thickness. Also, with the simple comparison, a good correlation exists between the presence of anomalies and the thickness of sediments or the depth of bed rock.

Iron oxide - apatite deposits are one of the most important REE resources that occurred in the Posht-e-Badam and Zanjan regions of Iran. REE mineralization in the Zanjan region is associated with Sorkhe Dizaj, Aliabad, Morvarid, Zaker, Oskand and Golestanabad iron oxide-apatite mineralization. The deposits are located in the Tarom area, which is a part of western Alborz - Azarbaijan zone. The Eocene volcanic sequences such as olivine basalt, trachyandesite, andesite as well as volcanoclastic rocks are the main units in the area which are intruded by the late Eocene plutonic rocks. Plutonic rocks in the region include porphyric micro-quartzdiorite and quartz-monzonite to quartz-monzodiorite. Magnetite-apatite mineralization in the Zanjan region is related to quartz-monzonitic to quartz-monzodioritic rocks. The mineralization is observed in the form of vein and stockwork (irregular veins and veinlets of magnetite-apatite). In the Tarom magnetite-apatite deposits, apatite crystals are associated with magnetite some of which have sizes up to 20 cm. Monazite is the main REE-bearing mineral at these deposits occurring as inclusion in the apatite. The apatite minerals contain 0.4-1.6 wt% REE, and have an REE distribution pattern with a strange LREE/HREE enrichment. The results of this research indicate that the iron oxide - apatite mineralization in the Zanjan region is formed by a quartz-monzonitic magma with calk-alkaline affinity, which occurred in a magmatic arc setting. This research shows that the magnetite - apatite mineralization in the Zanjan region is an important REE concentration in Iran.

The Sungun Cu-porphyry deposit is located in the East Azarbaiyjan province، 75 Km NE of Ahar city. The porphyry type mineralization is related to the Miocene monzonite-quartz monzonite and diorite-granodiorite intrusive rocks. There are four distinguished alteration zones in the Sungun deposit which nearly envelope the ore body concentrically. The present research is concerned on the behaviour of REE in potassic، phyllic and argillic zones regarding their geochemical and economic potentials. Geochemical evidences of trace elements share many similarities between alteration zones. LREE enrichment and HREE depletion are well clear in three alteration zones. Eu anomaly in potassic zone is weakly negative، in phyllic is nearly positive but the argillic zone doesn’t show any Eu anomaly. Lower ratio of Ce/Ce* (0. 95) in potassic and the higher ratio in phyllic and argillic zones reveal prevailing reduced and oxidized conditions respectively. Similar physicochemical conditions such as pH، the availability of suitable complexes in fluids، and the occurrence of secondary minerals for REE uptake، have been prevailed on the evolution of these three alteration zones.

Zafarabad iron deposit is located northwest of Divandareh، in the northern margin of Sanandaj-Sirjan plutonic-metamorphic zone. The deposit is in lentoid to tubular shape، within a shear zone and occrrued in host rocks of calc-schist and limestone. Magnetite with massive، cataclastic and replacement textures are the main phases، while pyrite and other sulfide minerals are found. Major and trace elements are measured by ICP-MS and ICP-AES methods. Based on some ratios of trace elements in the ore samples and (Ti+V vs. Cal+Al+Mn and Ti+V vs. Ni/(Cr+Mn)) diagrams which are used for classification of iron deposit types، Zafarabad iron deposit fall in the range of skarn deposits. Spider diagrams show a steady decline from LREE to HREE elements with Eu (mean value of 0. 06 ppm) and Ce (mean value of 0. 94 ppm) negative anomalies. Comparing the distribution patterns of REE for the Zafarabad magnetites with those of various types of iron deposits shows that the REE pattern for Zafarabad is similar to these deposits. Analysis of calculated parameters for REE shows that the hydrothermal fluids responsible for mineralization are mainly of magmatic origin through fractionation and crystallization processes of a deep iron rich fluid phase and its emplacement within the carbonate rocks، forming iron skarn.

Garnet is the most abundant calc-silicate mineral in the Darreh Zereshk skarns, and occurs as grained euhedral, to massive anhedral, isotropic to anisotropic crystals and display concentric and sector zoning or no zoning. Based on mineralogical investigations and paragenetic relations, garnet formed during progrademetasomatic stage of skarn formation. Geochemically they display two different patterns, i.e: (1) LREE-enriched and HREE-depleted, with strong positive Eu anomaly and (2) HREE-enriched and LREE-depleted with small Eu anomalies characteristic of andraditic and grassuleritic garnets, respectively. Electron probe micro analyzer (EPMA) identifies the garnets from Darreh Zerreshk skarn as grossular–andradite (grandite) solid solution series, with a less contents of spessartine and pyrope components. This is significant of a composition similar to Cu, Fe and Au skarn.

Base-metals sulfide mineralization in Galena and sphalerite forms with little amount of pyrite, in Mobarak and Elika formation have been occurred in the studied region. Chemically, all deposit phases have compositing hemogen region. Mineralization has been followed the fault general process in the region, and the main textures in the ore are vein texture and open space filing. Genetically, studied deposits are epigenetic. Field features essentially have resulted mineralogical investigations and geochemical surveys on trace elements and rare earth elements (REE), they have included ore metals source in sulfide Pb-Zn mineralization in Kelardasht region showed carbonate - hosted mineralized rocks (upper Paleozoic, lower Triassic) in deposit. In genetic relation between Pb-Zn mineralization in this deposit with Akapol monzonit quartz - monzodiorite intrusion (aged to upper Eocene - lower Paleocene), Were located near to studied Pb-Zn deposits, Akapol intrusion have played as required heating source that heated ore fluids. According to Eu negative anomalies in ore and host rock samples,and were seemed The source of hydrothermal fluids in the studied region have been the surface and atmospheric full - oxygen water (meteoric) have been warm through closing Akapol intrusion and have been solved the elements and then have been deposited them in the host rock fault crushes, cracks and joints, and then circulation in base-metals have enriched carbonate hosted units.

Antimony mineralization occured in Hamedan district (Faghireh) which is related to Alvand Granitoids. The mineralization occurcd as a series of veins. Thickness of veins are variable and reach up to 0.7m. The veins are emplaced along high angle faults. These faults acted as a pathway for migration of are nuids. Veins are composed of stibnite, pyrite, realgar and orpiment with quartz as a gangue. The textures of veins are open space filling, however brecciations also occured. Monzogranites, which formed the main part of Alvand pluton, is the host of quartz - stibnite veins. Monwgranites are composed of quartz, sodium plagioclase (oligoclase), orthoclase, biotite and sometimes muscovite. The veins arc composed of 30.5% antimony , 0.83 ppm gold and 498 ppm arsenic. Based on geochemical studies, Sb, Au, AS, Ag, Hg, Sn, Ni, Co and Cr contents of host rocks are much higher than the world chr('39')s average monwgraniets and have probably anomalies. Spiderdiagrams show an identical pattern for host rocks and veins, which strongly suggests that these veins are cogenetic with the intrusive rocks (monzogranite). 1n summary, with all geological evidences In the region, it can be concluded that the mineralization is probably occured in the epithermal type.