مجله بلور شناسی و کانی شناسی ایران
سال سی‌ام شماره 1 (پیاپی 87، بهار 1401)

The Oshvand Skarn deposit is located about 10 km east of Nahavand city in the Sanandaj-Sirjan structural zone. In this area, garnet (grossular-andradite) is the most abundant mineral in the skarn zone and their compositions are in the range of Adr(67.2 - 45.9%) Gro(50.1 - 31.8%) Sps(1.8 - 0.3%) and Prp(2.5 - 0.6%). EPMA data indicate a decrease in andradite and increase in the amounts of grossular and pyralspite group from the core to the margin of the garnet minerals. Increasing the substitution of Al by Fe+ 3 from the core to the rim of the garnet crystals indicates an increaseing FO2 during the growth of the garnet crystals. Pyroxene is the second most abundant mineral in the skarn zone and has a more homogeneous composition than garnet. The main pyroxenes of this deposit are in the range of hedenbergite to diopside with the combination of Fs(41.2 - 30.6%) En(26.6 - 9.5%) and Wo(49.3 - 42.8%) which has an average ratio of Fe/(Fe + Mg) in the range of 0.81 to 0.53. Thermobarometry studies indicate the formation of the progressive stage of skarnification at a pressure of 1 to 2 kbar and a temperature less than 600°C, depth of formation is about 5 km and  FO2 is about -16 to -27. The EPMA results of garnets and pyroxenes of skarn zones indicate that their composition is located at the range of Fe-Cu-Au type skarns.

The volcanic rocks with the Plio-Quaternary age, are exposed in the northern part of the Sanandaj-Sirjan zone, in northwest Urmia. The main mineral phases are olivin + clinopyroxene ± plagioclase, that are present as both phenocrysts to microcrystalline with other minor minerals. The dominant textures of these rocks are porphyry, microlithic porphyry, hyalo-porphyry, glomeroporphyritic and vesicular. Based on geochemistry, the parent magma of these rocks are in the range of trachy-basalt to basaltic trachy andesite, belonging to the alkaline magmatic series. The mantel and chondrite normalised patterns of rare earth elements indicates the enrichment of LILE and LREE as well as the depletion of HFSE and HREE.The spider diagrams show a negative anomaly in Nb, Ta, P, Rb, Zr and Ti and positive anomaly in Pb, La, U, Nd, Th and Cs. These geochemical parameters and tectonic diagrams show that the Plio-Quaternary alkaline magmatism were formed in the post-collision arcs.

The Haft Sandogh alunite deposit is located in the northwest of Takestan (about 60 Km west of Qazvin), and is a part of large Takand alunite deposit. Mineralogical and field study reveal that there is a zonation in the alteration zones of the Haft Sandogh deposit and surrounding area including silica zone in the central part, and quartz-alunite (quartz alunite), kaolinite and propylitic formed toward outer parts. Quartz and alunite are the main minerals of the quartz alunite. Acid-sulfate alteration can be used as a tool in the exploration of epithermal-porphyry ore deposits associated with Cenozoic magmatism in Iran. Regarding to alunite, it can be considered as a potential alternative resource for potassium and alumina production and the decomposition of alunite is a principal step to extract valuable components. Thermal decomposition of alunite was characterized by using differential thermal analysis (DTA), thermogravimetric analysis (TGA) and X-ray powder diffraction (XRD) in this research. The DTA curve shows three endothermic peaks at 546 °C, 787.9 °C and 1195.4 °C and an exothermic peak at 737.2 °C. The first peak is associated with the formation of dehydroxylated basic sulphate (KAl3O3 (SO4)2). The second exothermic peak represents the formation of a new crystalline form of sulphate (KAl(SO4)2). The third endothermic peak represents the massive desulphuration by the formation of a basic aluminium and potassium sulphate (KAlO.SO4). Final endothermic peak represents the formation of Al2O3 and leucite (KAlSi2O6).

Bijvard prospect area is located in the northern part of Central Iran zone, Sabzevar zone, about 40 km north of Bardaskan. The rock units exposed in the area include Cretaceous volcano-sedimentary rocks (andesite, basalt, graywacke and conglomerate) that syenogranite porphyry unit has intruded into them.  Mineralization has structural control, with N35E trending, and has altered the andesitic rock unit. Mineralization in this area has occurred in two parts: 1- Gold-bearing ores, that are mostly associated with silica and argillic alterations within gossan zone, which is surrounded by propylitic alteration 2- Manganese mineralization has occurred within gray wacke unit. Mineralogy is simple and primary minerals are pyrite, chalcopyrite, pyrolusite and braunite and secondary minerals include goethite, hematite, covellite, chalcocite, malachite and various Mn-bearing minerals. Quartz and clay minerals associated with minor calcite are the most important gangue minerals. The maximum value of gold is 1.4 ppm and the minimum value of gold is 0.01 ppm. In addition, the amount of copper is ranging between 88 ppm and 2.2%, arsenic is 21 to 100 ppm, and zinc is 162 to 495 ppm. Based on tectonic setting, host rock, structural control, type of alteration and the absence of high and low sulfide index minerals, Bijvard prospect area is probably an intermediate sulfidation epithermal type.

Fadiheh copper-gold prospect area in northwest of Torbat-e Heydariyeh in Khorasan Razavi Province is located in the central part of the Khaf-Kashmar-Bardaskan magmatic belt. This area includes outcrops of Eocene volcanic-pyroclastic units with felsicintermediate nature. The lavas are andesite and latite, and pyroclastic units include rhyodacitic tuff, andesitic lithic tuff and ignimbrite. Intrusive rocks consist of hornblende monzogranite, synogranite, pyroxene diorite porphyry and quartz monzonite porphyry. Mineralization has structural control and formed as vein-veinlets in accordance with the main trend of NW-SE and NE-SW faults in the region. Mineralization veins have generally N45 ° -75 ° E and N15 ° -30 ° W trending, 2 to 25 m length and 0.2 to 2 m width. The most important veins in the area include quartz + specularite ± pyrite and quartz + specularite ± chalcopyrite. The host rocks are pyroxene diorite porphyry, quartz monzonite porphyry and hornblende monzogranit. The structure and texture of mineralization includes vein-veinlet, open space filling, breccia, secondary replacement, colloform and disseminated. The alteration associated with veins are silicification and chloritization. The propylitic, silicification, chloritization and argillic alteration zones are observed within host rocks and other units in the area. Primary mineralization are specularite, chalcopyrite, pyrite and galena and secondary minerals are malachite, chalcocite, covellite, goethite, hematite, limonite, azurite and chrysocolla. Maximum of geochemical anomalies in veins are up to 5% Cu, up to 3% Pb, 50 g/t Ag, 100 g /t As and up to 791 ppb Au. The geological setting, lithology, mineralogy of mineralized veins, structure and texture, extent and type of alteration zones show that the mineralization in Fadiheh prospect area is iron-oxide copper-gold (IOCG) type.

The Zamin Hossein copper deposit, as a part of the Dehaj- Sarduiyeh metallogenic belt, is located about 170 km southeast of Kerman city. This deposit is accompanied by Eocene volcanic (andesite, andesi-basalt and pyroclastic) and Eocene intrusive body (granodiorite and granite). The propylitic, sericitic, argillic-sericitic and silicic alterations are associated with this deposit. Chalcopyrite and pyrite are the most important hypogene sulfide minerals which are accompanied by supergene mineral assemblages such as goethite, hematite, limonite, malachite, and azurite. The hypogene minerals show generally vein-veinlet, stockwork and crustiform textures. The microthermometric studies in quartz crystalscogenetic with the ore minerals revealed four types of fluid inclusions on the basis of phase content: 1-( L-V), 2-(L-V-S), 3-(V-L), and 4-(V). The results of microthermometric analyses revealed that the fluid inclusions have a wide range of Th (170°C to 530°C). The L-V-S type fluid inclusions displayed Th and salinity ranges of 190-473°C and 31.4-55.6 wt% NaCl eq., respectively. The liquid-rich 2-phase inclusions (L-V) show salinities within the range of 1.74-6.45 wt% NaCl eq. Based upon microthermometric data, boiling, mixing, and simple cooling of the fluids were the essential mechanisms in deposition and evolution of this deposit. The ore-forming fluids were probably of magmatic and mixed magmatic-meteoric sources. According to the structural and textural aspects, alteration and mineralization of mineral assemblages and microthermometric data, the Zamin Hossein ore deposit can be categorized as porphyry copper-type.

Hormuz series in Zendan salt dome, Neoprotozoic-Early Cambrian rocks is located near Bandar-e-Lengeh in western Hormozgan Province. In this salt dome, iron calcic skarns are present near the basic igneous bodies that have copper hydrothermal deposits. Carbonate sedimentary sequences, carbonate tuffs and igneous rocks are the host rocks of these skarns. The calcsilicates in the endoskarn include grandite garnets, feldspars, clinozoicite/epidotes, actinolite, wollastonite and vesuvanite. The calcsilicates in exoskarns are garnets and is mostly andradite, epidote, actinolite and wollastonite. Based on microprobe analysis, the type of garnet within skarn varies from And30Gross70 to And100Gross0. Based on crystal chemistry study, the elements such as Zn, Mn, Cu in exoskarns and endoskarns have a systematicaly distribution. Fluid inclusions study of the andradite mineral have indicated that Zendan skarns are formed at temperatures of 600 to 650°C.

Mehdiabad zinc-lead-barite deposit is located in the Central Iran structural zone and about 116 km southeast of Yazd. The host rock of this deposit is Lower Cretaceous dolomitic limestone of the Taft Formation . The main ore minerals in the Mehdiabad East Ridge ore zone include hemimorphite, hydrozincite, cerussite, and chalcophanite. Ore textures are mainly replacement, brecciated, and open-space filling. As a result of supergene and weathering processes, the sulfide minerals (sphalerite and galena) have been changed to non-sulfide minerals such as hemimorphite, hydrozincite, and cerussite. Statistical analysis of geochemical data indicates that the elements in the ore could be divided into three groups: terrigenous, host rock-forming, and ore-forming elements. Formation of iron-rich dolomite, ankerite, and siderite indicates high concentrations of iron and manganese in the mineralizing fluid. Based on this study, the characteristics of the Mehdiabad deposit are very similar to the Mississippi-Valley type deposits.

The Sebandoon Barite (gold-silver) deposit is located about 20 km NW of the Kashmar in the Central Iran. The rock units exposed in the area consist of Eocene volcano-sedimentary sequences of lithic tuff, rhyolitic tuff, tuffaceouce shale, lapilli tuff and agglomerate associated with pyroxene andesite and trachyandesite. The barite is composed of lenticular, banded and stockwork mineralization and that is hosted in rhyolithic tuff. Lenticular, massive and banded barite contains pyrite, sphalerite,chalcopyrite, galena, tetrahedrite, argentite and electrum. The association of sulphide minerals with the barite indicates sub-oxic conditions during ore forming processes. In this study, the chemistry of sulfide minerals in the barite lenses was studied using Electron Microscope. Accordingly, the narrow range and low iron content within the sphalerite are similar to those of mineralization in a sub-oxic environments. The presence of elements with heavy atomic nuclei, such as gold and silver, in the pyrite indicates that the pyrites are formed in a sub-oxic environment and arsenic in the pyrite is replaced by metal (As3 +). The presence of large amounts of antimony, bismuth, arsenic, and silver in the sulfide and sulfosalt minerals of this deposit indicates that the ore forming fluid was rich in the metal elements.

The Tang Zagh iron deposit is located about 117 km Northeast of Bandar Abbas, Hormozgan Province in the structural folded-thrusted zone of the Zagros basin. Iron mineralization occurs in the form of iron oxides (hematite) within the salt dome and/or in fractures and between the layers of the younger strata with the Tertiary age. Based on the microscopic studies, dolomitic fragments of the host rocks are surrounded by iron oxides during the replacement processes. The texture of ore is vein, veinlets, replacement, and open space filling. Hematite is the most abundant mineral in this deposit and goethite, dolomite and quartz minerals are the minor phases. According to geochemical data, the concentration of Fe2O3 in this deposit reaches up to more than 89 wt%. Low phosphorus and titanium levels and the absence of skarn-related features do not support the magmatic origin for this deposit. According to the field observation, mineralogical and geochemical properties, Tang Zagh iron deposit is formed in 4 stages: 1. Placement of volcanic material and the entrance of iron-bearing fluids of a volcanic origin in the sedimentary basin, 2. Enrichment of iron by hydrothermal fluid activity due to salt diapirism, 3. Reconcentration and redeposition of iron by tectonic activities and finally 4. Hematite, goethite and malachite minerals are formed due to the supergene processes and weathering on this deposit.

Biotite is a common rock-forming mineral and accepts a variety of elements in its structure. The valuable information of crystallization conditions of the biotite mineral obtain on natural biotite composition. The biotite mineral is one of the main mineral phases of pelitic rocks which are formed in a wide range of geological conditions. In this research, microscopic mineralogy, Raman spectroscopy, and X-ray diffraction of biotite minerals from hornfels and migmatites from the Borujerd granitoid aureole in the Sanandaj Sirjan zone investigated. On microscopic studies, mica crystals display common biotite characterizations but the mineral is uniaxial not biaxial as ordinary mica with a monoclinic system. Based on X-ray diffraction, the biotite crystals form in hexagonal crystalline habit. The Raman spectroscopy also reveals the variations in number and shifts on peaks in the range of 500 to 750 cm-1. Based on XRD data, the unit cell lattice parameters have revealed hexagonal mica crystals for the Borujerd migmatite and hornfels. Previous works reported temperatures in the range of 642 to 750 C° for the studied rocks. Investigation on synthetic biotite mineral suggests temperature above 700 C° for monoclinic to hexagonal transformation which confirm the formation of the high-temperature metamorphic event in the Borujerd region.

Zircon is an stable mineral during post crystallization processes and preserves characters of magmatic events. Zircon morphology can give some information about temperature, nature, and source of the magma. Study of the zircon morphology of Cretaceous granitoids and acidic volcanics from the southeast Saqqez area reveals that most of the crystals are P5 and S25 types with high alkalinity (I.A.) and temperature indexes (I.T.) in the range of 672.9 and 637.9 respectively.The minimum temperature of zircon crystallization is estimated to be in the range of 600 to 750 °C based on the morphology, saturation of Zr, and whole-rock chemistry. The presence of apatite inclusions and the mineralogical composition indicate that the source of the magma was relatively hydrous. Typological evolutionary trend (T.E.T.) shows the granites as I-type with calc-alkaline nature, which are in line with geochemical data. The zircon mineral morphology indicates that the granites in the SE Saqqez formed from hybrid magma with crustal and mantle origin.

In this study, meteorite pieces, with total weight of 259 grams, have been studied which is not listed in the world bulletin of meteorites. In order to classify these samples, after preparing microscopic thin sections and performing accurate petrography, using geochemical data of the major elements and trace elements of whole rock, obtained from XRF and ICPMS methods in Zarazma company’s laboratory, have been studiied. At first, the samples which have properties of meteorites are completely separated and other samples and classified according to common petrographic and geochemical methods. As a result, all of the nine of selected meteorite samples belong to the category of chondrite meteorites with petrological type H4. Also, in terms of secondary characteristics, such as special metamorphism and space weathering, the samples have been studied, in addition they are in the group of meteorites with S2 and W2 level of weathering and metamorphism.

Preparation of two-dimensional nanostructures of WTe2 and MoTe2 by chemical solution synthesis methods is of great importance. In different synthesis methods, different precursors and concentrations are used. In this paper, we used the chemical reduction reaction method from solution for our analysis. Binary compounds of WO3 - TeO2 and MoO3 - TeO2 were prepared in two processes with reduction agents: (a) sodium borohydrate (NaBH4) and (b) hydrazine in the presence of nitrogen gas. The structural and optical properties of the nanopowders were studied after chemical reduction. The results of X-ray diffraction (XRD) showed that in the WO3 - TeO2 binary compound, after chemical reduction with NaBH4, the diffraction peaks of the TeO2 and WO3 binary compounds formed independently and after annealing in the presence of hydrazine, and the intensity of the peaks has been significantly increased. Field Emission Scanning Electron Microscopy (FE-SEM) images showed that the morphology of the nanoparticles was uniform in the form of spherical nanoparticles. In the combination of MoO3 - TeO2 with chemical reduction, other phases of Te2O5 and TeMo5O16 are formed in the shape of hemispheres, rods and polyhedrals, which indicates the formation of composite phases. The chemical bond structure and energy gap of samples were studied by FT-IR and UV-Vis spectroscopy.