ali asghar calagari

The Niaz Cu prospect is located 25 km west of Meshkinshahr, east of the Qaradagh metallogenic zone. The intrusion Oligo-Miocene magmatic bodies into the Paleocene-Eocene rock units has led to alteration and mineralization. The rock units of this area include batholiths Ι and ΙΙ (Khanbaz granodiorite and Khankandi granodiorite), Niaz quartz-monzonite/ quartz-monzodiorite and ore-bearing rhyodacite breccia.

In this research, the geological features, alteration, mineralization and physicochemical conditions of mineralizing fluids have been studied. In this regard, sampling from altered, mineralized zones and drilling cores were carried out and 23 samples were analyzed by XRF and 18 samples by ICP-OES methods and microthermometric measurements were performed on 8 doubly-polished thin sections.

The intrusive units have high-K calc-alkaline to shoshonitic nature, and the geochemical characteristics of their trace elements indicate similarities with subduction-related magmas. The negative anomaly of Ti and Nb in these rocks can be due to the magmatism related to the subduction processes, as well as the stability of the phases containing these elements during partial melting or their separation during the differentiation process. The enrichment of Pb, La, K, U, and Th elements and the depletion of Sr, Ti, and Nb can be attributed to crustal contamination. Hypogene alterations at Niaz include potassic, phyllic, propylitic and intermediate argillic types. Mineralization has occurred during early, middle, and late stages. Based on the mineralogy and paragenetic sequence, at least five types of veins/veinlets can be distinguished in Niaz deposit. Group A veinlets contain quartz+pyrite+chalcopyrite+magnetite, group B veins are also present in the potassic and phyllic alteration zones, veinlets of group C are mainly formed in the middle stage of mineralization, group D veins are mostly observed in the phyllic alteration zone, which are formed in the middle and later stages of hydrothermal activities and group E veins are almost devoid of sulfide minerals and mainly contain bright-color minerals (quartz and/or calcite)±tourmaline and are mostly present in the propylitic alteration zone. Studies on fluid inclusions (FIs) within the quartz veinlets showed that there are four types of FIs at room temperature, (1) mono-phase vapor, (2) liquid-rich 2-phase, (3) vapor-rich 2-phase, and (4) multi-phase solid containing daughter solid phases. The ranges of FIs are about 280-360°C in the potassic, 280-360°C and 280-300°C in phyllic and 170-330°C in propylitic alteration zones.

The petrology and petrogenesis of magmatic host rocks, mineralogy, hydrothermal alteration in the Niaz area testify to a porphyry-type Cu mineralization. The main sulfide mineralization includes vein-type pyrite, molybdenite, chalcopyrite, sphalerite and galena. Fluid inclusion microthermometry results show a Th range of 170-360 °C and salinity values of 0.2-60 wt%NaCl equiv., corresponding to the ranges of porphyry Cu deposits. Boiling and simple colling of ore-bearing fluids were the main processes for ore precipitation.

The Mazraeh manganese deposit (southwest of Maku, north of West-Azarbaidjan Province, NW Iran) is developed in the form of scattered lenses at the contact of pillow basalts and pelagic limestones, belonging to the Khoy-Maku ophiolitic complex. Mineralogically, the ores mainly contain pyrolusite, psilomelane, manganite, and braunite which are accompanied by lesser amounts of hematite, goethite, quartz and calcite. The distribution pattern of REE normalized to chondrite along with some geochemical parameters related to lanthanides, such as La/Ce, (La/Nd)n and (Dy/Nd)n, show a hydrothermal origin for this deposit. This idea is supported by some geochemical diagrams (Co/Zn vs. Co+Ni+Cu, Zn-Ni-Co, and Mn-Fe-[(Co+Ni+Cu)]×10) and elemental ratios such as Mn/Fe, SiO2/Al2O3, U/Th, and Co/Zn. The high concentration of lanthanides in ores (on average of 767 ppm), compared to known hydrothermal manganese deposits, reveals the effects of diagenetic processes on this deposit. The occurrence of negative anomalies of Eu and Ce indicates the low-temperature hydrothermal fluids, responsible for the mineralization. The presence of detrital materials in the ores can be inferred by the concentration values of oxides like Al2O3 and TiO2.

The Neyzar lead-zinc-barium deposit is located about 20 km east of Eshgabad city (South-Khorasan Province, east Iran) and is a part of Tabas-Pushte Badam metallogenic belt. This deposit is hosted by carbonate units of Jamal (Permian) and Shotori (Triassic) Formations. Mineralization was mainly controlled by structural factors (thrust faults) in this deposit. Galena, sphalerite and barite are the principal ore minerals with minor amounts of minerals such as calcite, dolomite, quartz, fluorite, malachite, cerussite, covellite, hemimorphite, hematite, goethite, and manganese oxides. The micro-thermometric studies, using fluid inclusions, on calcite and barite crystals were carried out in this deposit. Both calcite and barite minerals are co-existed and co-genetic with Pb-Zn sulfide mineralization occurrence. Petrographic observations of fluid inclusions show that most of them are of liquid-rich two-phase type. Based upon micro-thermometric analysis, the homogenization temperatures of the fluid inclusions in calcite and barite crystals vary from 120 to 220ºC and from 119 to 199ºC, respectively. The salinities of the fluid inclusions in calcite and barite crystals also show changes within the range of 10.12-23.5 and 19.6-23.1 wt% NaCl eq., respectively. In general, the microthermometric investigations revealed that simple cooling and boiling were the main evolutionary trend for deposition of the ore and gangue minerals by sedimentary-derived hydrothermal fluids. Based on the results obtained from field observations, mineralogy, structure and texture and micro-thermometric data, the Pb-Zn-Ba deposit in the Neyzar area is very similar to those of the Mississippi Valley-type (MVT).

The Gharehkand area is located in the southeast of Maragheh city and in Takab metallogenic district. According to the structural divisions of Iran, this area is situated south of the volcanic Mount Sahand in the Central Iran zone (Stocklin, 1968). This paper aims to investigate the characteristics of gold-bearing vein-veinlets and physicochemical conditions of ore-forming fluids in the Gharehkand area.

About 40 rock samples were collected from mineralized zones and host rocks. The thin and thin-polished sample sections were studied in the geology department of the Mohaghegh Ardebili University, Ardebil. Microthermometric data were obtained from fluid inclusions using the Linkam THMS600 stage at the Payame Noor University of Tabriz.

1) The mineralization in the Gharehkand area took place principally as vein-veinlets within the host sedimentary rocks during two main stages. Mineralization occurred in quartz vein-veinlets during the first stage. The quartz crystals within the quartz vein-veinlets display brecciated, boxwork, drusy, and comb textures. During the second stage barite mineralization occurred as vein-veinlets. The mineralization of sulfides (galena, sphalerite, pyrite, and chalcopyrite) and gold occurred within the quartz vein-veinlets of the first stage.2) The values of homogenization temperature (Th) and salinity of fluid inclusions vary from 80°C to 220ºC and 6 to 13 wt.% NaCl eq., respectively.3) The study of fluid inclusions demonstrated that boiling and simple cooling were the most important mechanisms in the ore deposition at Gharehkand, and the sulfide complexing ligands played an effective role in transporting metals within the ore-forming hydrothermal fluids.4) The quartz crystals textures (brecciated, boxwork, and comb) in quartz vein-veinlets and microthermometric data (low salinity and Th) of the ore-forming fluids indicate that mineralization at Gharehkand is of epithermal type with low-sulfidation style.

The mineralization in the Gharehkand area took place principally as vein-veinlets within the host sedimentary rocks. Two main stages of mineralization were distinguished at the Gharehkand area. Stage-1 mineralization is represented by the quartz vein-veinlets. The quartz crystals within the quartz vein-veinlets display brecciated, boxwork, drusy, and comb textures. The formation of quartz crystals in quartz veinlets and micro-veinlets were temporally divided into three sub-stages: early, middle, and late. Stage-2 mineralization is represented by barite vein-veinlets. The hypogene alteration is mainly observed as the development of silicic halos around quartz vein-veinlets within the host sedimentary rocks. The mineralization of sulfides (galena, sphalerite, pyrite, and chalcopyrite) and gold have occurred within the late sub-stage quartz veinlets and micro-veinlets. Oxidized processes have caused formation of goethite, hematite, jarosite, malachite, and azurite. Copper sulfides (covellite, chalcocite, and digenite) are formed in the supergene zone. Based upon phase content, the studied fluid inclusions in late sub-stage quartz crystals may be classified into three types: liquid-rich two-phase (L+V), mono-phase vapor (V), and vapor-rich two-phase (V+L). The values of homogenization temperature (Th) and salinity of the analyzed liquid-rich two-phase fluid inclusions vary from 80°C to 220ºC and 6 to 13 wt.% NaCl eq., respectively (Fig. 11A, C). Given the Th and salinity values of the fluid inclusions, ore-forming hydrothermal fluids during development of the quartz vein-veinlets at Gharehkand experienced hydrostatic pressures within the range of 20-25 bars. This is almost equivalent to depths of 200-250 meters below the underground water table level. It is consistent with the estimated depths of most epithermal deposits (Bodnar et al., 2014). The Gharehkand microthermometric data points on the bivariate plot of Th versus salinity (Wilkinson, 2001) show that the densities of fluid inclusions vary from 0.9 to 1 g/cm3. The occurrence of boiling and simple cooling are the most effective mechanisms in deposition of ore and gangue minerals at Gharehkand.  The Gharehkand microthermometric data points on the bivariate plot of Th versus salinity (Pirajno, 2009) indicate that the bisulfide complexing ligand most likely played the important role in transporting ore metals (particularly gold).

The monzonitic-syenitic Gowdal intrusive body located in the north of Ahar, East- Azerbaidjan province is a member of the Shivardagh batholithic body and a part of the Alborz- Azerbaidjan- Lesser Caucasus magmatic belt related to the Meso-Tethys (Sevan- Akera- Ghareh Dagh) Ocean. Fe- Cu and Mo skarn mineralization (magnetite, specularite, pyrite, chalcopyrite, and molybdenite) occurred at the contact of the Gowdal intrusive body with limestone- marly limestone units. The supergene copper and iron minerals (malachite, azurite, secondary hematite, and Fe-hydroxides) are superimposed on the hypogene skarn mineralization assemblages. Based upon diagrams of major elements versus SiO2, with mean values, ratios of trace elements, and diagrams of trace elements, the Gowdal intrusive body formed from relatively evolved magma and compositionally lies within the range of intrusive bodies affiliated with copper and to some extent zinc skarns. On the other hand, distribution patterns of trace elements of the Gowdal intrusive body normalized to N-MORB shows considerable similarity to known zinc and to some extent copper skarn-related intrusive bodies. Consequently, despite having dominant iron mineralization at the current level, the Gowdal intrusive body displays the utmost similarity with the bodies associated with copper skarns.

The kaolin occurrence in the Abolhasani-Zereshkouh area (south of Shahroud, northeast of Iran) is a product of alteration of Eocene andesitic rocks. With attention to mineralogical studies, kaolinite, quartz, chlorite, montmorillonite, illite, rutile, calcite, orthoclase, albite, vermiculite, palygorskite, jarosite, and hematite are the mineral assemblege of this alteration occurrence. Calculations of mass balance of elements with assuming Zr as monitor immobile element show that elements such as Si, Fe, Mg, Na, K, Ti, Cr, Ba, Be, Co, Cs, Rb, Sn, U, V, W, Ni and REE were partially depleted and elements such as Hf, Zn and Cd enriched during the kaolinitization processes of andesitic rocks. Other elements including Al, Ca, P, Mn, Ga, Nb, Sr, Ta, Th, Y, Cu, Pb and Tl were undergone both leaching and fixation processes. The mass decrease of Si, Fe, K, Rb, Cs and Ba reveals destruction of plagioclase and hornblende by highly acidic hydrothermal fluids. The presence of two abnormal decreasing and increasing trends for the elements Al, Ga, P, Nb, Ta, and Y can be attributed to the low pH of the altering fluids, the high water-to-rock ratio and the abundance of complexing legands.

The Aghbolagh iron-copper skarn is located in ~21 km north of Oshnavieh, southwest of West-Azarbaidjan province. The intrusion of Cretaceous granitic body into the Cambrian Barut, Zagun, and Lalun Formations (carbonate, shale, and sandstone) was accompanied by development of calcic-type skarn, hornfels, and marble in the study area. The garnets of the Aghbolagh skarn belong to solid solution series of grossularite-andradite in which andradite is the dominant phase (>80%). These garnets are isotropic and lack zonation. The pattern of REE distribution in these garnets shows the enrichment of LREE relative to HREE and also the occurrence of negative anomalies of Eu/Eu* and Ce/Ce*. The comparison of the distribution pattern of REE in garnets with those in igneous (granite and monzonite) and sedimentary (carbonates and sandstones) rocks demonstrates that the REE in garnets were derived mainly from the igneous rocks rather than the sedimentary units. The increase in Pr/Yb ratios in parallel with increase in the ƩREE is indicative of the magmatic origin of the ore-forming fluids in the Aghbolagh skarn. However, the lack of sensible variations between Ce/CE* and ƩREE values indicate that the meteoric waters might have also played a part in skarn-forming fluids at Aghbolagh.

The Gheshlagh bauxitic deposit is located in ~110 km southeast of Gorgan city. Mineralogical studies indicated the presence of minerals such as boehmite, diaspore, kaolinite, hematite, goethite, anatase, rutile, chamosite, calcite, moscovite, clinoclar, provskite, quartz, and dolomite. Based on quantitative mineralogy this deposite made up of (1) bauxitic clay, (2) clayey bauxite, (3) bauxitic clayey iron ore and (4) bauxitic iron ore. Calculations of the enrichment factors, with assumption of upper continental crust (UCC) as parent rocks, showed that elements such as Rb, Cs and Ba were depleted during bauxitization processes whereas elements like Y, Cr, Co, Ni, V and HREEs were encountered enrichment.Elements like Sr, Ga, Zr, Hf, Nb, Ta, U, Th and LREEs underwent both leaching and fixation processes during development of the weathered profile. Combination of the results obtained from mineralogical and geochemical investigations showed that factors such as adsorption, scavenging by metallic oxides and hydroxides, fluctuation of underground water level, type and stability of metal-containing complexes, stability of primary bearing minerals, presence in mineral phases resistant to weathering and changes in chemistry of the solutions responsible for weathering played prominent role in distribution and mobilization of elements in the studied bauxitic ores.

The Bolboli2 copper ore deposit is located about 110 km southwest of Kerman and lies in the Dehaj-Sarduieh metallogenic belt (Kerman Cenozoic Mamatic Arc, KCMA). This ore deposit is hosted by the Eocene extrusive igneous rocks (tuff, agglomerate, andesite, and dacite) and the Oligo-Miocene intrusive igneous body (granodiorite). These rocks are host the propylitic, phyllic, and silicic alteration zones (product of the mineralization fluids). Hypogene mineralization was dominant and occurs mainly as stockwork vein-veinlets and disseminate (chalcopyrite, pyrite, and magnetite). This mineralization is overprinted by supergene assemblages such as hematite, goethite, malachite, and azurite at superficial part of ore deposit. The hypogene minerals show generally vein-veinlet, stockwork, brecciated, granular, and crustiform textures. Microthermometric studies in quartz crystals cogenetic with the ore minerals reveal 4 types (1) L-V, (2) L-V-S, (3) V-L, and (4) V fluid inclusion. Study of fluid inclusions display a Th range of 190-427ºC. The L-V-S fluid inclusions were homogenized with halite disappearance with the Ts(NaCl) ranging from  213ºC to 425ºC which corresponds with salinities within the range of 32-50 wt% NaCl equivalent. The liquid-rich 2-phase inclusions (L-V) show salinities within the range of 0.6-10 wt% NaCl equivalent. Based on microthermometric data, boiling, mixing, and simple cooling of the ore-bearing fluids were the essential mechanisms in deposition and evolution of this ore deposit. The ore-forming fluids were probably of magmatic and mixed magmatic-meteoric sources. The geological setting, structural and textural aspects, alteration and mineralization of mineral assemblages, as well as microthermometric data show that the Bolboli2 ores can be categorized as porphyry copper-type ore deposit.

The Separdeh laterite deposit in the western part of Alborz is about 114 km from the Ramsar city in Mazandaran province. This deposit is located between Triassic limestones (Elika Formation) and Jurassic sandstones (Shemshak Formation). There has been no comprehensive study on the Separdeh deposit. Only studies included 1: 100,000 scale geological map of Javaherdeh and identification of bauxite-laterite and refractory materials of Gilan province by Geological Survey of Iran. Therefore, this paper attempts to study the physicochemical conditions of formation, factors of ore type development and factors affecting the distribution, mobility and differentiation of rare earth elements, Ce and Eu anomalies, and determining the origin of the ore, taking into account the petrographic, mineralogical and geochemical features of the Separdeh deposit.

Based on detailed field observations, 14 ore samples were systematically taken. These were perpendicular to the profile, picked up from the lateritic rocks due to changes in color, texture, and hardness. Thin sections were prepared for textural studies and X-ray diffraction (XRD) analyses of the samples for mineralogical studies at the Iranian Mineral Processing Research Center in Karaj. Geochemical studies of 10 samples were analyzed by ICP-OES and ICP-MS methods to determine the quantities of major and minor earth elements by MS Analytical Company in Canada.

Structural and textural studies in the Separdeh deposit indicate both autochthonous and allochthonous origins for this deposit. Mineralogical investigations revealed that minerals such as siderite, chamosite, kaolinite, boehmite, diaspore, hematite, goethite, clinochlore, and anatase are the main mineral phases accompanied by of minor phase like rutile, moscovite, and lipidocrocite. This mineral assemblage suggests that both underground waters with reducing-alkaline nature and surface waters with oxidizing-acidic nature played an important role in development of this deposit. Based upon chemical analyses, REE values of the ores vary from 58.91 to 846.72 ppm. Values of La/Y, Eu/Eu*, and Ce/Ce* of the ores are within the range of 0.34-3.76, 0.76-1.24, and 0.92-2.41, respectively. Geochemical studies showed that changes in the physico-chemical conditions of formation environment (pH and Eh), carbonate bed rock as a geochemical barrier, complexation with carbonate ligands, difference in the stability of minerals carrying rare earth elements (REEs), and fixation in neomorph phases, play important roles in distribution and mobility of REEs during the formation and evolution of the lateritic horizon at Separdeh. In addition, the Eu anomalies along with ratios of TiO2/Al2O3 and Sm/Nd indicate that upper Triassic rocks with andesitic to basaltic composition could be the potential precursor for this deposit.

Textural, mineralogical and geochemical studies show that the Separdeh deposit is formed in two stages. In the first stage, authigenic lateritization of the upper Triassic basaltic rocks has occurred, such as alteration and decomposing of silicate minerals and formation of clay, iron and titanium minerals. In the second stage, the transfer of lateritic material into karstic cavities and deposition in lagoon and swampy environments was carried out. These conditions have resulted in the formation of minerals such as pyrite, siderite, and facilitated the process of leaching of rare earth elements from the upper parts of the profile and deposited on the lower parts of the Separdeh deposit.

The Kuh-Baba iron ore deposit is located in ~70 km south of Hashtroud, East-Azarbaidjan province, NW Iran. The lithologic units cropped out around this deposit include Oligo-Miocene volcanic-sedimentary rocks, Pliocene intrusive rocks, and Pliocene dacitic domes. The principal host rocks for the Fe mineralization include units of gabbro-norite, pyroxene hornblende gabbro-norite, and monzo-diorite. Remote sensing investigations (using Sentinel satellite images) display the presence of lineaments, NE-SW trending fault structures, and various alteration zones. The dominant hydrothermal alteration in inner parts of the deposit is mainly propylitic (epidote, chlorite, sericite) which gradually changes to argillic outward toward the peripheral parts. Based upon field relations and microscopic examinations, the ores show massive, vein/veinlet, brecciated, and disseminated textures. In the propylitic zone, magnetite is accompanied by epidote and actinolite. The geochemical studies revealed that the FeT content in the diamond drill core samples varies from 3.85 wt% to 63.2 wt%. Ground magnetic survey was conducted in the area and also, the maps of total magnetic field, reduced to pole magnetic, analytic signal, first vertical derivative, and upward continuation were prepared in an attempt to identify the potential deep and shallow subsurface mineralized zones. The obtained results show that two anomalies, one in the north and the other in the central parts of the study area, were recognized which almost correspond with the location of the intrusive bodies.

The Shalang vein-type polymetallic ore deposit is located about 10 km southwest of Kerman and 70 km northeast of Sirjan, and lies in the central part of the Dehaj-Sarduieh metallogenic belt. This deposit is hosted by dacitic and andesitic vitric and crystal tuffs along with andesitic-dacitic lava flows of Eocene age. The alteration zones related to this deposit are propylitic, intermediate argillic, silicic, and carbonatized. Mineralization occurred principally as veins/veinlets in two separate stages, the hypogene (Chalcopyrite, Pyrite, Magnetite) and the supergene (Bornite, Chalcocite, Malachite, Azurite, & Hematite). The hypogene mineralization also took place in two distinct episodes, (1) formation of quartz-sulfide veins/veinlets and (2) development of carbonate-sulfide veins/veinlets. The average concentration values of cu, Pb, Zn, Au, and Ag within the ore-bearing veins/veinlets are 2.5%, 0.26%, 0.16%, 1.3ppm, and 28ppm, respectively. The strong positive anomaly values of Eu (5.03-10.31) and Ce (1.48-5.06) indicate an alkaline pH and reduced nature, respectively for the ore-forming fluids in the depositional environment. The microthermometric studies on fluid inclusions within the cogenetic quartz crystals were carried out. The studied fluid inclusions were chiefly of liquid-rich two-phase type and all of them were homogenized into liquid state. The obtained homogenization temperatures (Th) of the analyzed fluid inclusions varied within the range of 226º-313ºC. The salinities of the studied fluid inclusions range from 3.4wt% to 9.9 wt% NaCl equivalent. Based upon microthermometric results, the boiling concurrent with cooling were two essential mechanisms in development and evolution of this deposit. Presence of colloform, cockad, blabed, and replacement textures in the ores, development of intermediate argillic and carbonatized alteration zones, and the low salinities and temperatures of the studied fluid inclusions provide persuasive evidence that the Shalang vein-type polymetallic ores have the most similarity to the low-sulfidation epithermal deposits.

The Kuh-Baba iron ore deposit is located about 70 km south of Hashtroud, East-Azarbaidjan Province, NW Iran. The deposit is genetically affiliated with intrusive bodies of gabbroic to dioritic composition. The principal host rocks for the Fe mineralization include units of gabbro-norite and pyroxene hornblende gabbro-norite. The widespread alteration zones which are accompanied with Fe-mineralization are actinolitization, chloritization and epidotization. The principal ore mineral is magnetite with subordinate apatite showing massive, vein/veinlet, replacement, brecciated, and disseminated textures. The results of electron probe micro-analysis (EPMA) on 28 points of magnetite crystals show relatively high amounts of elements such as Al, Mn, Ti, and V. The values of components such as TiO2, V2O3, NiO and MgO in massive magnetites are higher than those present in disseminated and veinlet-type magnetites. Studies of primary fluid inclusions in quartz crystals coexisting with magnetite mineralization show that they are mainly liquid-rich 2-phase (L+V) and occasionally monophase-vapor (V). The homogenization temperatures of liquid-rich 2-phase inclusions range from 436ºC to 544ºC (average of 505ºC). Based on temperatures of the last melting point of ice (TM), the obtained average salinity is 15.82 wt% NaCl equ. Considering the measured parameters such as homogenization temperature, salinity, density, and pressure of the fluid inclusion, the depths of magnetite mineralization were estimated to be within the range of 1.3-2.7 (average of 2.3) km (based on the lithostatic pressure). According to the EPMA and fluid inclusion data, the Kuh-Baba iron ores deposit can be classified as a ‘Kiruna-type’ and subtype Iron-Oxide apatite-poor deposits and the origin of magnetite can be conceived as both magmatic and high-temperature hydrothermal.

The Zarshuran Carlin-type gold deposit is located about 30 km north of Takab, West-Azarbaidjan Province, NW Iran. Interaction between the ore-forming fluids and the host carbonates and shales resulted in development of the decarbonatization, argillic, alunite, silicic, and sulfide alteration zones in the study area. Based on mesoscopic and microscopic studies on drill core samples, gold mineralization is mainly associated with Au-bearing pyrite and arsenic-containing pyrite generated during two stages. The mineral assemblages associated with these stages are As-bearing pyrite, realgar, orpiment, cinnabar, stibnite, and colloform sphalerite together with lesser amounts of sulfosalts (tetrahedrite and getchellite) intergrown with jasperoid and quartz. The microthermometric studies on liquid-rich 2-phase fluid inclusions in euhedral quartz crystals intergrown with the Au-bearing sulfides showed that the ore-forming fluids had an average  homogenization temperature (Th) and salinity of about  260°C and 9.2 wt% NaCl equivalent, respectively. The variation trends in salinity and Th of fluid inclusions could be explained by a combination of mixing and dilution of ore-bearing fluids with subsurface waters of meteoric origin. These processes were likely the principal cause for instability of Au-bearing complexes and hence gold deposition in the veins/veinlets. In addition, on the basis of the obtained pressures from microthermometric data the estimated depths for ore formation were within the range of 160 to 300 meters correlated with 40 to 75 bars, which is in agreement with some known Carlin-type gold deposits. In general, the geological, mineralogical, textural, and microthermometric data provided sufficient evidence to categorize the gold mineralization at Zarshuran as Carlin-type

The Noghduz  prospecting area, as a part of the Arasbaran metallogenic zone is located about 20 km east of Ahar, East-Azarbaijan Province. The mineralization host rocks are andesite-trachy andesite with the age of  Late  Eocene. The hydrothermal alterations exposed in this area are silicic, argillic, and propylitic. Pyrite is the main hypogene sulfide mineral which is accompanied by lesser amounts of chalcopyrite and bornite. The most important supergene minerals in this area are iron oxyhydroxides (hematite, limonite and goethite) and malachite that accompany the hypogene mineral assemblage. Gold mineralization occurred within quartz-sulfide veins/veinlets in this area. The microthermometric measurements in the primary 2-phase (L+V) fluid inclusions in quartz crystals associated with  mineralization  indicate that  the mineralizing fluids had temperatures and salinities within the range of 160-334°C and 0.53-3.39 wt% NaCl equivalent. respectively. The presence of hydrothermal breccias, pseudomorph of quartz after bladed calcite, and mono-phase gas inclusions are indicative of boiling of the hydrothermal fluids responsible for mineralization. The sulfur isotopic analysis of pyrite shows  that  the values of isotopic composition of this element  is  close to the range of magmatic source. Also, the oxygen and hydrogen isotopic data demonstrated that  the meteoric waters constituted a great portion of the ore-bearing fluids at Noghduz area. The presence of structural and textural evidence along with fluid inclusion studies (salinity and homogenization temperature) indicate that the gold mineralization at Noghduz area is of epithermal type.

The Siahrudbar deposit is located about 25 km southwest of Aliabad-Katool city in the Golestan Province, north of Iran. This deposit lies between the Triassic limestone (Elika Formation) and Jurassic sandstone (Shemshak Formation). Mineralogical studies indicate the presence of major minerals such as diaspore, hematite, anatase, kaolinite, and chamosite accompanied by minor minerals such as boehmite, goethite, rutile, calcite, moscovite, clinoclar, quartz, and tridymite. Calculation of enrichment factor showed that the bauxitization processes at Siahrudbar were accompanied by enrichment of elements such as Al, Fe, Ti, V, Cr, Co, Ni, Ga, Th, U, Y, Zr, Ta, Nb, Hf, and REEs. While elements such as Si, Mg, Na, K, P, Ba and Rb were leached out of the profile and suffered depletion. Futhermore, elements like Ca, Mn, Sr and Cs experienced both partial leaching and fixation. Based on the results of geochemical studies, changes in pH and Eh of the weathering solutions, adsorption, presence of organic matter, function of carbonate bed rock as a geochemical barrier, existence in resistant minerals, and fixation in neomorph mineral phases played crucial role in distribution of the trace and rare earth elements in the studied ores. Consideration of the correlation coefficients among elements demonstrated that the neomorph phosphate minerals can be conceived as the potential host of rare earth elements.

The Zailic gold-bearing veins are located in the Arasbaran metallogenic zone, east of Ahar, East-Azarbaidjan Province. The most important lithologic units in this area are andesitic and trachy-andesitic tuffs and lavas of Upper Eocene age hosting vein-type gold mineralization. Theses rocks have suffered silicic, argillic, phyllic, and propylitic alterations brought about by hydrothermal fluids. The geochemical study of alteration zones in this area showed that in the silicic zone, due to the acidic nature of altering fluids and hence intense leaching, depletion of most major and trace elements took place. The degree of leaching towards the propylitic zone, owing to the pH increase of the hydrothermal fluids, gradually decreases. The presence of minerals with high adsorption capacity, such as clay minerals, resulted in concentration and fixation of many elements in the argillic, phyllic, and propylitic zones. Consideration of the behavior of rare earth elements (REE) in silicic zone relative to almost fresh volcanic rocks showed that most of REE suffered depletion. Geochemical indices such as TiO2 and (Ce + Y + La)-(Ba + S), showed that the hypogene hydrothermal fluids played an important role in the development of alteration zones at Zailic

The Zaraj-Sou bauxite deposit (southwest of Ramsar, Mazandaran Province, northern Iran) was developed as discontinuous stratified layers and/or lenses along the boundary between carbonate rocks of the Elika (Triassic) and shales and sandstones of the Shemshak (Lower Jurassic) formations. Diaspore, kaolinite, hematite, and anatase are the major mineral phases of the ores. Texturally, the bauxite ores have typical textures of clastic, rounded-grain, and nodular which are often accompanied by certain forms of concretions, ooids, and pisoids in restricted quantities. Concentration values of REEs within the ores in the selected profile vary from 149.97-348.10 ppm and the ratios of Eu/Eu* and Ce/Ce* are within the range of 0.75-1.04 and 0.64-1.28, respectively.  Investigations showed that changes in the values ​​of these parameters are controlled by degree of scavenging hematite. The calculation of mass changes of elements and the study of the trend of variation of elemental ratios in a selected profile across this deposit revealed that the distribution of REE in ores is a function of factors such as changes in pH of ore-making solutions, presence of carbonate bed rock as an active buffer, co-precipitation with metallic oxides, and fixation in neomorph mineral phases. Correlation coefficients among elements suggest that minerals such as hematite and secondary phosphates are the potential hosts for lanthanides in the studied ores.

Khak- Sorkh iron deposit lies about 42 km west of the Yazd city. The area is located in the central part of the Urumieh-Dokhtar magmatic belt and is covered by upper Triassic-lower Jurassic sedimentary units and Oligo-Miocene intrusions. Intrusion of Oligo-Miocene granitoids into Cretaceous limestones resulted in iron skarn mineralization. Magnetite is the main iron ore mineral; minor copper mineralization also occurs locally as malachite staining at surface. Two main structural trends can be distinguished: NW-SE which follows the main trend of the Urumieh-Dokhtar belt, and NE-SW trend that transects the former one and dissects magnetite bodies in some places.
In this study Euler deconvolution and analytical signal methods have been used for interpretation of geophysical data. Depth of magnetic anomalies determined by Euler deconvolution clarified that magnetic bodies are located at shallow depths in the NW of the area. The trends of the detected anomalies correlate very well with the general trend of the Urumieh-Dokhtar belt. This can be used as an exploration tool for magnetic anomalies in the area and likely in other parts of the Central Urumieh-Dokhtar belt. Based on magnetic anomalies 15 diamond bore holes were drilled at the NW part of the region which cut the ore bodies at predicted levels with average ore assay of 39 percent total iron.

Mn-bearing veins of Jonub -ESehchangi are located 200 km southwest of Birjand, Southern Khorasan province (east of Iran). These veins are hosted by andesitic rocks of Eocene to Oligocene ages. Ore minerals identified by XRD method and mineralographic studies and are Pyrolusite, cryptomelane, psilomelane, hollandite, hematite and goethite, displaying colloform and open-space filling textures. Gypsum, halite, barite, carbonate and silica are the gangue minerals. Alteration zones, specifically argillic alteration zone, are developed along the vein within the andesitic wall rocks. Based on the mineralogical and geochemical data, the primary manganese minerals were Mn oxides and hydroxides, which have gradually been converted to psilomelane and hollandite, and finally pyrolusite. The average grade of Mn within the veins is 38.61%. Considering the average Mn/Fe ratio (about 48.55) in the Mn-bearing veins, as well as the positive correlation of Sr, U and Ba with Mn mineralization in this area show hydrothermal origin.

Kaolin deposits in the Nivasht and Kabudkamar areas are located in ~25 km northwest of Saveh, Central province. Field observations along with petrographic examinations revealed that genetically these deposits are alteration products of igneous rocks such as andesi-basalt, trachy-andesite, and andesitic tuff of upper Eocene age. In this study, the physical, chemical, and mineralogical properties of the kaolin deposits in Nivasht and Kabudkamar were investigated on the basis of industrial applications. Based upon mineralogical data, the principal constituent minerals in both deposits are quartz, kaolinite, halloysite, muscovite-illite, Montmorillonite, pyrophyllite, plagioclase, hematite, goethite, anatase, akermanite, alunite and/ or natroalunite, and talc. Further investigations in the studied areas showed that the kaolinitic clays have mostly firing color within the range of milky white to dark gray. Consideration of parameters such as capability of water absorption, resistance in dry state, firing contraction, low thermal efficiency, and the values of major oxides demonstrated that the kaolins at Nivasht and Kabudkamar possess suitable standard conditions for application in ceramic (for floor and wall) industries, however, their application in other industries requires further processing.

The study area is located in the north of Eastern Azarbaidjan (NW Iran). In this area, mineralization of molybdenum-copper is associated with intrusive bodies and developed in the center of Gharehdagh (Gharehchilar-Gharehdarreh) batholith. Petrological and petrographic investigations show that the intrusive bodies have compositions from diorite,through monzonite and granodiorite to granite. These bodies are I-type and mainly metaluminous and calc-alkaline with medium to high potassium belonging to volcanic arcs (VAG) tectonic setting. The principal alterations zones in the mineralized areas include silicic, potassic, phyllic and propylitic. Potassic and potassic-phyllic alterations are frequently seen around the molybdenum-bearing veins and veinlets. The proportions of Mo, Si, K, Rb, Ba and REE's are increased in differentiated biotite-bearing acidic intrusive bodies. Enrichment of K, Rb and Ba and depletion of Zr, Ta, Y, Yb and Nb in intrusive bodies indicate metasomatism of upper mantle materials with subducting oceanic crust and subsequent generation of magma and its passage through relatively thick crustal rocks.The intrusive bodies associated with Mo-mineralization have often quartz-monzonitic to granodioritic composition.

Kamtal skarn is located 15 km northeast of Kharvana, East-Azarbaijan. A quartz-monzonitic stock of Oligocene age intruded the upper Cretaceous sedimentary sequence (claystone, limestone, marl, and siltstone) developing noticeable metamorphic (marble, hornfels) and metasomatic (skarn) alteration zones along the contact. Kamtal skarn is of calcic type and consists of both endoskarn and exoskarn zones. Exoskarn includes two zones of garnet skarn and epidote skarn. Skarnification processes are divided mainly in two major stages (1) prograde and (2) retrograde. During prograde stage, the emplacement of intrusive body caused isochemical metamorphism of the wall rocks and developed marble and hornfels units in enclosing rocks. Crystallization of intrusive body led to evolvement of hydrothermal fluid phase which infiltrated into enclosing rocks. Reaction of these fluids with the early-formed metamorphosed wall rocks brought about extensive progressive metasomatic alteration characterized by the formation of anhydrous calc-silicate minerals such as garnets and pyroxenes at a temperature range of 420-550°C and ¦O2=10-22-10-25. Retrograde stage was accompanied by some physicochemical changes (decrease in temperature to

Kajal kaolin deposit is located ~20 km northwest of Hashtjin، Ardebil province. Field evidence and laboratory investigations show that the deposit is an alteration product of ignimbrites، tuffs، and trachy-andesites of Eocene age. According to mineralogical data، the major rock-forming minerals include kaolinite، montmorillonite، polygorskite، orthoclase، zeolite (stilbite)، quartz، and chalcedony. Mass change calculations of elements، with assumption of Ti as immobile monitor element، indicate that leaching and fixation are two prominent regulators for concentration of major، minor، trace، and rare earth elements in the deposit. The distribution pattern of REEs، normalized to ignimbrite، in kaolin samples illustrates a weak fractionation of LREEs from HREEs coupled with strong negative Eu anomaly during the evolution of the deposit. Calculations of correlation coefficients among elements show that there is a high intrinsic correlation between HREEs in the studied samples. According to geochemical indices، it can be inferred that the hypogene alterations are superimposed by supergene ones in the course of evolution of the deposit. In accordance with the mode of distribution of elements in the deposit، it appears that the behavior of elements during kaolinization of ignimbrites was affected by the function of factors such as pH، redox potential، temperature variations، high fluid to rock ratio، preferential adsorption by clays and iron oxides، discrepancies in the stability rate of minerals، abundance of complex-forming ions (CO32-، F־، Cl־، PO43-، and SO42-)، and isomorphic substitution. The obtained results indicate that epithermal acid-sulfate solutions along with acidic supergene solutions originated from oxidation of hypogene pyrites played an important role in development of the deposit. Further geochemical considerations show that clay minerals along with secondary phosphates like monazite، rabdophane، and xenotime are the potential hosts for REEs in the deposit.

Mehredjan bentonite deposit is located ~33 km southeast of Khoor in Isfehan province. It includes 15 discrete outcrops and occurs as layered and massive forms within a volcano-clastic sequence. Bentonitization process was accompanied with development of minerals such as montmorillonite, quartz, cristobalite, calcite, kaolinite, halite, albite, orthoclase, and muscovite. The collected field and laboratory data indicate that this deposit was developed by authigenic alteration of tuffs ranging in composition from trachyandesite, through andesite to basaltic andesite in a shallow marine environment. The distribution patterns of REEs normalized to chondrite in both bentonite and enclosing tuffs illustrate similar trend indicating the fractionation and enrichment of LREEs relative to HREEs and negative anomalies for Eu. Geochemical data revealed that transformation of tuffs into bentonite took place in an open system where leaching and fixation processes were two basic regulating factors in concentrating of common trace and rare earth elements. By pointing to the obtained results, factors such as differences of alteration intensity of protolith, physico-chemical conditions of alteration environment, adsorbing mechanism, structural incorporation, existing of organic matters, effects of diagenesis, carbonate complexation, ionic exchange, physical concentrations, and existing of resistant minerals played important roles in development of Mehredjan bentonite.