Iranian Journal of Crystallography and Mineralogy
Year:2011 | Volume:19 | Issue:1|Papers Count:20

The study area (Bornaward granite) is located in northeast of Iran (Khorasan Razavi province), about 280 km southwest of Mashhad city. Taknar zone is an exotic block, bordered by two major faults, Great Kavir fault (Drouneh) to the south and Rivash fault in the north. A complex of granite, granodiorite, monzonite and diorite crop out at the center of Taknar zone. They are named as "Bornaward granite". Published data using Rb–Sr whole-rock and biotite isotopic methods on granitoid rocks (Bornaward granite) gave ages of 154 to 111 Ma. The results of U-Pb zircon dating of granodiorite is 552.69 ± 10.89 Ma and granite is 538.22 – 1.82, +4.28 Ma (Late Neoproterozoic time). Both granite and granodiorite are classified as belonging to the ilmenite-series of reduced S-type granitoids. Chemically, they are per-aluminous, high-K calc-alkaline with relatively enriched in LILE, Rb, K and depleted in Sr, Ba, Nb, Ti, Ta, Y and Yb. Chondrite-normalized Rare Earth Element (REE) plots indicate minor enrichments of light REE in composition with heavy REE, with (La/Yb)N between 3.5-5.6 and high total REE (193-252) with strong negative anomaly of Eu. They have a initial 87Sr/86Sr and 143Nd/144Nd ranging from 0.713566 to 0.716888 and 0.511791 to 0.511842, respectively, when recalculated to an age of 553 and 538 Ma, consistent with the new radiometric results. Initial eNd isotope values for granite and granodiorite range from -2.62 to -2.01. Granite and granodiorite of Bornaward yields a TDM age of 1.4-1.41 Ga. This indicates that the granites and granodiorite being derived from partial melting of distinct basement source regions with very high initial 87Sr/86Sr.

Mehrabad bentonite deposit appears to be derived from the volcano- sedimentary materials of Oligo-Miocene age by transformation in a lagoon environment. Based on analysis, bentonite samples contain minerals such as montmorillonite, albite, clinoptilolite, quartz, cristobalite, calcite, gypsum, halite, muscovite and nantronite. Conversion of shard glasses to bentonite and zeolite has occurred under diagenetic conditions with acidic to intermediate composition. The bentonite deposit is halmyrolytic clays in type. According to geochemical studies, bentonite's magmatic series is subalkaline (calc- alkaline) and their tectonic setting is volcanic arc and syn- collision.

Type of clay minerals determines the stage of soil evolution. Palygorskite is a dominant clay mineral in soils of arid and semi-arid regions. This study aims to identify the distribution and genesis of palygorskite in some soils developed on Tertiary parent materials in the Isfahan Province. Six soil profiles and their Tertiary parent materials were studied, described and sampled for X-ray diffraction analysis and scanning electron microscopy examinations. Physico-chemical characteristics of both soils and parent materials were also determined. Different quantities of palygorskite were found in soils and parent materials. The highest amount of palygorskite was found in soils and parent materials where both gypsum and carbonates precipitated. Much less quantity of palygorskite was found in salic and calcic horizons. Results revealed that occurrence of palygorskite in the studied soils are mainly related to the inheritance from parent Tertiary sediments. Besides, it seems that palygorskite has partly been formed through pedogenesis processes. Using principal component analysis, the Mg/Ca ratio, pH, H4SiO4 and gypsum contents were identified as the most important factors affecting the distribution and genesis of palygorskite in the soils and parent materials. This may suggests that the neoformation of palygorskite by precipitation from solution can take place where the evaporation fluxes are very high.

The study area is located about 45 km of southwest Neyshabour and east of Arghash village. Both intrusive and volcanic rocks are exposed in the study area and they are intensively altered due to hydrothermal fluid. The alteration zoning in the study area consists of potassic, sericitic, carbonatization, silicification and propylitic. More than 10 intrusive rocks with composition in the range of monzonite to diorite are identifined. Chemically, they are met-aluminous and calc-alkaline. Based on mineralogy and high values of magnetic susceptibility, granitoid rocks of the area are belonging to ilmenite-series and I-type. Both disseminated and vein type mineralization is rcognized. Pyrite is the dominante sulfide. Stream sediment and rock chip geochemical exploration carried out in the area. Highest Cu anomaly (Cu = 108 ppm) is associated with quartz hornblend diorite porphyry. Based on alteration, type of intrusive rocks and geochemical anomalies, Arghash area has potential for Cu- porphyry mineralized system.

Clay mineralogy of paleosols provides more information about Quaternary climatic changes and paleoenvironmental conditions. Clay minerals of an alluvial fan in eastern Isfahan were studied, using x-ray diffraction analysis. Studied paleosols are located on old Qf1 and Qf2 geomorphic surfaces. Qf1 geomorphic surface is older and topographically higher than Qf2. The results of clay mineralogy show dominance of palygorskite and smectite in calcic (Bk) and argillic (Bt) horizons of Qf1 geomorphic surface, respectively. Calcrete (Bkm) in the paleosol of the Qf1 surface was formed in the semi-arid paleoclimate. It seems that during more humid periods, carbonates enhancement and porosity decreases in calcrete (Bkm) horizon have caused increase in ionic activity and formation of pedogenic smectites in this horizon. In the next drier periods, the calcrete (Bkm) horizon was enriched in palygorskite via translocation and autogenic formation. The palygorskite fibers in calcrete (Bkm) have been protected by calcite crystals. The comparison of the argillic horizons of Qf1and Qf2 geomorphic surfaces indicates dominance of smectite in Qf1 argillic (Bt) horizon and palygorskite in Qf2 argillic-calcic (Btk) horizon. Regarding to Uniformity of parent material and landform, this difference is due to high weathering in the argillic (Bt) horizon of Qf1 and protection of palygorskite in the argillic-calcic (Btk) horizons in the soil of Qf2 surface. It is recommended to use clay mineralogy of calcic horizons, argillic horizons and calcretes as a powerful tool in geomorphology investigations.

The Heydarabad bauxite-laterite deposit is located in 63 km southeast of Urmia city. This ore deposit occurs as a concordant layer within the boundaries of Upper Permian and Lower Triassic carbonate units (limestone and dolomite), although it has been suffered some tectonic displacements along its direction. The studied horizon varies from 15-20 m in thickness and has an east-west trend with a length of 3.5 km. This deposit consists primarily of two parts of dark and light in color. The former is rich in hematite and corundum, (upper horizon) and the latter in phyllo-aluminosilicates (lower horizon) with an gradual boundary, respectively. Common textures are mostly pisolitic, nodular, oolitic and massive. Based on the microscopic studies and XRD analysis, the main mineral components are hematite, diaspore, chloritoid, and corundum. On the other hand, chlorite, rutile, magnetite and pyrite are found as accessory phases. The Heydarabad bauxite-laterite horizon is different from those occurred into the Iran-Himalayan belt based on the absence of boehmite, kaolinite and other clay minerals, and the abundance of corundum, chloritoid and chlorite. The geological and mineralogical evidences indicated that a thermal metamorphic event was responsible for the formation of this special mineralogical composition after bauxitization processes. Based on geological, mineralogical, and chemical characteristics, it can be proposed that the probable parent rocks for the Heydarabad bauxite are mafic sills and diabasic dykes. Due to considerable accumulation of minerals which their hardness is greater than 6, this ore deposit can be presented as a potential for abrasive applications.

Based on field observation, magnetic data results and chemical analysis of the samples in the Haj - Elyas area northwest of Nehbandan, an iron ore body within the Lower Cretaceous dolomitic limestone, was identified. The intrusion of a Fe-bearing porphyritic diorite into the dolomitic limestone caused the occurrence of iron mineralization in the area. Studies of 750 meters of diamond drill Core logs, indicated that the mineralization occurred at the contact of porphyritic diorite and dolomitic limestone. The ore minerals in this zone are magnetite, hematite and limonite. Gangue minerals are plagioclase, quartz, calcite, dolomite, garnet, clinopyroxene, hornblende, tourmaline, hercynite, serpentine, epidote, pyrite, sphalerite and chalcopyrite. Garnet is more andradite in composition. Magnetite is altered to hematite and limonite in fractures. The average iron grade within mineralized zone is about 70 percent. Copper and zinc show very low grade. Based on mineralogical data, the mineralization at Haj - Elyas is associated with calcic – magnesian skarn type.

Sahand volcanic rocks, with Plio-Quaternery age, is located southeast Tabriz in the northwest part of Central Iran. These rocks are mainly composed of pyroclastics (tuff and ignimberite) and lava flows (rhyolite, rhyodacite, dacite and andesite) that unconformably cover the Miocene sedimentary formations. The major constituent minerals include plagioclase and hornblende which are surrounded by a matrix of fine grain and glassy. Their textures are porphyritic. Heterogenous mineralogy, field and textural evidences such as sieve texture in plagioclase, resorption rims in crystals, oscillatory zoning in plagioclase, high normative quartz and rounded enclaves suggest that the primary magma undergone magmatic evolution including fractional crystallization, fractionation, contamination and magma mixing during ascending. There are mineralogical as well as geochemical evidences that AFC-type processes were involved in the evolution of the Sahand volcanic rocks. The chemistry of the felsic- intermediate volcanic rocks indicates that the parent magmas are medium-K calc-alkaline and metaluminous in nature. The volcanic rocks display highly fractionated REE patterns, with no negative Eu anomaly. Their geotectonic environment is post-collision and continental margin arcs.

Sheykh Abad area is located in South Khorasan Province, about 90 km south-west of Birjand. The geographical coordinates of area is 59o 00' 50" to 59o 06' 20" longitude E and 32o 26' 20" to 32o 29' 32" latitude N. The study area is located in geotectonic Lut Block zone. Eocene sub-volcanic units are altered by hydrothermal solotions in Skeykh Abad area. Kaolinite, Montmorillonite and quartz are the major and muscovite, albite, orthoclase and gypsum are the minor mineralogical compositions. The chemical composition of Sheykh Abad kaolin deposit shows that the percentage of SiO2 is higher (63.18%) and the amount of Al2O3 is lower (22.06%), than the theoritical composition of kaolin. The kaolinic clay raw materials from Sheykh Abad deposit, by having the average amounts of 0.53% Na2O, 3.90% K2O and 0.88% TFeO, Module of Rupture (MOR) between 49 to 56.1 Kgf/ cm2, white to pale yellow colour, low LOI (4.69%) and zero percentage of water absorption, can be used as floor tile. Wet or dry processing are necessary for making the kaolin from Sheykh Abad suitable for ceramic and paper industrials.

Analcime along with other zeolite group minerals such as: Tetranatrolite, Natrolite, Mesolite, Scolcite, Heulandite, Stilbites and, levyne occur as vein and cavity filling minerals in the intermediate to basic volcanic rocks in South Kahrizak. Scanning Electron Microscopy (SEM) of microcrystaline analcime reveal pseudo-cubic prismatic faces of [211] containing laminations perpendicular to the elongation of the crystals. These laminations are due to crystal growth mechanism and are characteristics of hydrothermally formed analcime (H-type). X-ray diffraction study has revealed a pseudocubic symmetry for analcime with unit-cell parameters of: a = 13.6974(51) Å, b = 13.6874(124) Å, C = 13.6637(311) Å, V = 2561.695 Å3.Raman spectrum of the sample shows vibrational mode frequency for H2O molecules in analcime at about 3500 cm-1.

Shurab polymetal ore deposit is located in 77 km south of Ferdows in north of Lut structural zone. Geology of the area includes a Jurassic sedimentary rocks, comprises shale and sandstone of Shemshak Formation, Badamo limestone, and andesite, dacite, rhyodacite and rhyolite volcanic and subvolcanic-calc-alkaline Tertiary rocks as a hydrothermal mineralization host rock. In these rocks, mineralization occurs as both series of NW-SE and E-W trending fault and fracturing. Galena, sphalerite, stibnite, chalcopyrite and pyrite are present as major sulfide ore mineral and frequently shows open-space filling, vein-type and crustified textures. The mineralization is subdivided into two stages, base metal-bearing assemblage (Pb>Zn>Cu) accompanied by first generation pyrite and second stage, stibnite-bearing minerals (stibnite, chalcostibnite, tetrahedrite and bournonite) with subordinate arsenopyrite and late generation pyrite sulfide minerals. Microtermometric measurement of fluid inclusions in cogenetic quartz and sphalerite shows homogenization temperatures (Thtotal) between 114oC and 275oC and salinities between 4.2 to 17.2 wt.% NaCl equiv. Geochemistry of oxygen isotope (relative to SMOW) indicate ranging  between +12.5‰ to +14.8‰ (mean 13.6‰) which assume that mineralizing solutions in the area were a mixture of meteoric and magmatic waters. This study indicated that, mixing, cooling and fluid-rock interactions were the main controlling factors in formation of the Shurab polymetal ore deposit.

Hololeucocratic granitoids of Alvand main granitoids crops out as veins with low thickness. They are scattered in the south and west of Hamadan with latitudes of 34o 30'- 35o00' N and longitudes of 48o00'- 48o 45' E. This granitoids, based on petrological studies, are in the ranges of leucotonalite, leucogranodiorite and leucoquartz- monzodiorite. The investigation, based on the grain size, show that hololeucocratic granitoids can be divided into two groups: 1) coarse- graind and 2) fine- graind. Sharp contact between hololeucocratic granitoids and Alvand main granitoids indicate that hololeucocratic granitoids are younger than main granitoids (Paleocene to Late- Paleocene). Mineralogical and geological studies show that they are I- type, alkaline-calc and based on saturation degree of aluminum (ASI), they are metaluminous to slightly peraluminous. These granitoids enriched in Sr and depleted in Ba, Rb, Nb and Ti which are obvious in the spider diagrams. They are also poor in K2O, FeO, MgO and enriched in CaO, Na2O with respect to Alvand main granitoids. These rocks show enrichment from LILE and LREE elements and are depleted from HFSE elements. These properties are an indication of subduction zones and active continental margins. The Rb vs. Ta + Nb, Nb vs. Y, Rb vs. SiO2 geotectonic affinity discrimination diagrams support an I- type, volcanic arc environment for the hololeucocratic granitoids of Alvand Complex. With regard to geological history of this area, it can be attributed to subduction of oceanic crust of Neotethys under the Central Iran.

In this research, NTC thermistors with composition of NiMn2-xCoxO4 (x = 0.4, 0.8, 1.2, 1.6) prepared by two methods: solid state reaction and sol-gel (gel-combustion). The average particle size was monitored and structure of the calcinated powders have been investigated using x-ray diffraction (XRD) and tunneling electron microscopy (TEM) techniques. The average particle size was estimated to be about 65nm with the cubic and cubic + tetragonal phases for low and high cobalt concentrations, respectively. The grain size of samples verifies with scanning electron microscopy (SEM) images. Upon increasing the cobalt fraction, the grain size of samples increases from about 2mm to a few mm in size. The electrical properties of these thermistors depend on the grain size. The grain size of samples made from sol-gel is smaller than from solid state reaction under the same condition. For longer sintering time of the samples prepared by gel-combustion method, the grain size was increased then the electrical parameters of nanopowder improved and we obtain better results than the samples prepared from solid state reaction.

The Naghadeh metamorphic complex at the West-Azerbaijan Province is located at termination of the NW Sanandaj-Sirjan Zone. Major varieties of the metamorphic rocks in this area are: amphibolites, greenschists, marbles and metaperidotites. The metaperidotites are classified into two groups, serpentinised metaperidotites and serpentinites. Orthopyroxene, clinopyroxene, olivine and spinel are the magmatic relict minerals in the serpentinised metaperidotites. Mineral chemistry of the orthopyroxene has been determined as Ca0.03-0.06 Mg1.68-1.69Fe2+0.17-0.18 Cr0.02 Al0.07-0.09)M (Al0.02-0.05Si1.95-1.98)TO6. Chemical formula of the analysed clinopyroxenes is Di 96-98Hd1.0-3.0Ae 0.0-1.0. The composition of olivine is considerably homogeneous (Fo86.50 Fa13.50). On the basis of the mineralogical and textural evidence, the protolith composition in the investigated metaperidotites could be considered as lherzolite and rarely harzburgite and dunite. The serpentine polymorphs in the studied metaperidotites are distinguished based on the mineralogical and textural features. In this regards, chrysotile and lizardite are the low temperature polymorphs which occur within paragenesis, containing talc and calcite/magnesite. During prograde metamorphism, chrysotile and lizardite are disappeared as antigorite co-existing with termolite/actinolite and clinochlore are formed. The metamorphic events in the Naghadeh peridotites can be considered in two stages, (1) metasomatic stage under H2O-bearing fluid conditions at T<280oC and (2) the prograde regional metamorphism under inception of amphibolite facies (T ~500oC and P ~7kbar). Considering the Naghadeh metamorphic complex in northwestern extension of the Sanandaj-Sirjan Zone, the prograde metamorphic stage of the Naghadeh metaperidotites can be considered comparable to the metamorphic events from the Sanandaj-Sirjan Zone, corresponding to the closure of Neotethys and final continental collision.

The investigated area is a part of Sabzevar ophiolite melang of North Eastern Iran which is important from two points of view, geology and its potential of Economic Mineral deposits. The main geological units in both Chah Yabu and Cheshmeh Palang areas are serpentinized peridotite, gabbro, diabasic dykes of Upper Cretaceous and Tertiary volcanic rocks which are mainly altered. Cheshmeh Palang area contains more harzborgite and less dunite units than Chah Yabu. Reflected light microscopy investigations indicate that chromite ores in both Chah Yabu and Cheshmeh Palang deposits show primary and secondary textures. The major primary textures are massive, banded, disseminated, and integrated while the main secondary textures are cataclastic and pull-apart. Geochemical analysis show that chromite ores of Chah Yabu and Cheshmeh Palang deposits have average amount of Cr2O3 53.15% and 42.93%, Al2O3 6.15% and 8.92%, MgO 15.92% and 22.42% and TiO2 0.14% and 0.19% respectively. The ratio of [Cr/(Cr + Al)] in Chah Yabu and Cheshmeh Palang chromite deposits are more than 0.91% and 0.76% respectively which are demonstrating these deposits of high chromite and low aluminum types. High amount of Cr2O3 and MgO and also low amount of Al2O3 and TiO2 from chromite ores correspond to deep stratigraphic situation of their ore bodies in ophiolitic sequence (tectonized peridotite) and indicates that the parent magma for both of Chah Yabu and Cheshmeh Palang deposits were primary melting materials from upper mantle. Regarding the standard chemical properties of chromite to be used in ferrochrome production and chemical industries (Cr2O3>46%, Cr/Fe>3 and Cr2O3>44%, Cr/Fe>1.5) respectively, chromite ores from Chah Yabu and Cheshmeh Palang deposits can be used mainly for metallurgical and chemical applications.

Mazraeh granidiorite is part of Shyvardag plutonic batholith which is located in eastern Azarbajan, 20 km north of Ahar town and 5 km north of Mazraeh Village. It is a part of Mesozoic –Tertiary igneous belt of the Sanandaj-Sirjan. From petrography and geochemical point of view, rocks are acidic to intermediate and the main part of the body is granodiorite. Texturally, the rock is mainly granular, containing plagioclase, alkali feldspars, quartz, and hornblende. The accessory minerals include biotite, sphene, magnetite, apatite and epidote. Geochemicaly, this granodioritic rocks are calk alkaline an I type series and is Metaaluminous with VAG characteristic. Based on Harker type diagrams, the incompatible elements as well as compatible elements have a continuous trends, which indicate fractional crystallization of magma during the evolution of intrusion of the rock in the region and other processes are in second order. The presence of amphibole minerals indicate that the primary magma was rich in water (%3). In addition, enrichment of magma from elements like Fe, Ca, Mg, Co, Ni   and reduction of elements like K,Na, Th in low Si  samples proved that the amphibole have been crystallized at the intail stages of fractional crystallization but minerals like albite, alkali feldspar and biotite were crystallized at the final stage. Intrusion of this body to in the carbonate rocks caused the skarn mineralization which indicate the potential of mineralization of these grandiorities. Comparison of Mazraeh granodiorite with other granodiorite, such as Qulong of Chinese, Rio_Narcea belt in Spain, Celebi in Turkey, Songun and Tokmedash in Iran indicate that Mazraeh granodiorite enriched in elements like Th,Nb,La,P,Pb. These geochemical differences with other granodiorite could be due to their different shares from enriched mantel and crust during the formation of these granodiorites.