Iranian Journal of Crystallography and Mineralogy
Year:2014 | Volume:21 | Issue:4|Papers Count:18

Micro morphological studies were carried out on the surfaces of the ZnS single crystals grown by chemical vapour transport (CVT). Different micro morphological patterns such as layers, steps, kinks, stripes and pits were observed using Scanning Electron Microscope.Formation of these patterns was correlated to the growth of crystals under theoretically predicted optimum and nonoptimum conditions.

The volcanic rocks of Silurian in Khosh yeylagh are located in eastern Alborz structural zone, east of Golestan Province. This volcanic mass is significantly affected by hydrothermal alteration. Propylitic alteration is the most dominant alteration in this area. Based on field observation and X-Ray diffraction studies, four alteration zones of chlorite, epidote, albite and hematite are recognized in the study area. The results of XPMA show that chlorites present in rocks of this area as peninite, talc- chlorite and diabanite. These minerals are formed in temperature ranging from 180 to 250 oC. The average of pistasite amount in epidotes is 31.15 which show that this mineral is magmatic type and is composed of saussuritized plagioclase.Isocon diagrams show the high mobility of some immobile elements during alteration. In albite, alteration zone with an average isocon slope of 1.06 and 1.09 is the highest while in chlorite, alteration zone with an average isocon slope of 1 and 1.03 is the lowest mass transfer which can be observed during alteration. Also based on these diagrams, SiO2 and P2O5 show depletion and L.O.I and Fe2O3 enrichment in all alteration zones. Chemical index of alteration (CIA) indicate that on epidote alteration zone 46.26% to 46.30%, albite alteration zone 47.86% to 51.49%, chlorite alteration zone 46.50% to 47.33% and hematite alteration zone 59.7% to 71.45% have gone under alteration.

The Baft ophiolitic melange, covering an area approximately 150 Km2, is located in the Esfandaghe-Khamrood melange belt. The main part of intrusive rocks in the Baft ophiolitic mélange consists of gabbros, mostly isotropic and occasionally as pegmatitic rocks.Plagiogranites, as veins and small outcrops, are common along with gabbros and doleritic dikes through the area. Plagiogranites consist of trondhjemite, albite granite and granophyre. Based on geochemical studies, gabbros and plagiogranites are belonging to tholeiitic-calc-alkaline magmatic series. Plagiogranites are metaluminous to slightly peraluminous and typologically show characteristics between oceanic ridge (OR) and I-type granites which is consistent with their formation in a supra-subduction zone environment. Chonderite normalized REE patterns of plagiogranites show slight enrichment in LREEs along with flat HREE patterns. Chonderite normalized REE pattern of gabbros are relatively flat with slight enrichment in LREEs compare to HREEs. The derivation of an acidic melt from a gabbroic phase through either fractional crystallization and/or partial melting is less likely. It appears that the origin of Baft ophiolitic melange plagiogranites must be related to doleritic phase, although partial melting of hornblend gabbro and/or amphibolite can be also considered for at least one of the samples.

Late Eocene-Early Oligocene Zouzan granitoid bodies are located in northern part of Lut Block and southeast of Khaf in Khorasan Razavi Province and intruded in metamorphic and sedimentary rocks of Precambrian to Eocene. as a result of subduction of Lut Block under Helman Block, Lut magmatism and Zoozan granitoids have been formed. The granitoid bodies are composed of granodiorite, monzonite, monzodiorite, quartz diorite and also contain microgranular mafic enclaves. Mafic rocks in this area are diorite and gabbro. They are calcalkaline, metaluminous to peraluminous and oxidized I-type (magnetite series) and, have high contents of alkalis. The granitoids characteristics are similar to those of VAG types which probably evolved in a continental margin tectonic setting. Based on chemistry of plagioclase and hornblende in the granitoids, estimated pressure and temperature range from 2.66 to 3.85 Kb and 676 to 717oC, respectively. Due to intrusion of the Zouzan granitoid bodies, the host rocks were metamorphosed and metasomatized also skarn minerals and iron mineralization occurred in the carbonate rocks.

In this research, CaMnO3 powders have been synthesized by solid state reaction and sol-gel methods at calcination temperature of 800oC. Particle size and morphology of the calcined powders have been investigated using XRD and TEM techniques. TEM image showed that the average particle size of the samples, prepared by sol-gel method, is about 85 nm. The optical gap was measured using the absorption spectrum of the powders. The value of the band gap was found for the sample synthesized by sol-gel method is about 3.46eV and that for sample prepared by solid solution to be about 3.40eV. Also the phase formation of the powders has been studied by Fourier transform infrared (FTIR) spectroscopy. Resistivity measurements of the samples between 300-550oK revealed that resistivity of the samples decreases with increasing temperature.

In this research, CdS nanoparticles and core/shell CdS/ZnS nanoparticles were prepared by using aqueous solution method and used 3-mercaptopropionic acid (MPA) as capping molecule. The effect of ZnS shell on optical and structural properties of CdS was investigated. X ray diffraction patterns of CdS nanoparticles at the room temperature and after heat treatment show zinc blende structure. X ray diffraction patterns of CdS/ZnS nanoparticles are wider because of overlapping diffraction patterns of ZnS and CdS. The size of CdS and CdS/ZnS nanoparticles was calculated by using Debay-Scherrer equation which is 2.7 nm and 1.7 nm at room temperature, respectively, and after heat treatment obtained 3.2 nm and 1.9 nm, respectively. FTIR studies were used to indicate coating of the MPA molecule on nanoparticles.In the TEM image of CdS/ZnS nanoparticles, it can be seen small nanoparticles and some agglomeration which is due to nonuniform distribution of particles on the grate sample holder in TEM measurement.

The Kuh-e Mish plutonic complex (KPC) is located about 30 km south of Sabzevar.Based on tectonic division, it is part of Sabzevar zone. The Stratigraphic units of the area are conglomerate, tuff, and sandstone of the Paleogene, radiolarites, andesite and tuff unit of Upper Cretaceous. This collection consists of two plutonic rocks types. (1): The granitoid complex of northern Kuh-e Mish which is composed of monzogranite and pyroxene-granodiorite.Geochemically, these rocks are calc-alkaline, peraluminous and I-type of Post Paleocene. (2): The Gabbro-diorite complex of southern Kuh-e Mish which is composed of various polutonic rocks including gabbro, diorite and gabrbro-diorite. Geochemically, these rocks are tholeiitic, metaluminous and I-type of Upper Cretaceous. These complexes have occurred in volcanic arc in an active continental margin setting. The combinations of field, petrographic and geochemical data indicates that the plutonic complexes have derived from a mantle source. The magma show negative anomalies of Nb, Ti, Ba, and positive anomalies of K, Rb indication of a subduction zone. According to the geological history of the region, likely subduction of Neo Tethyan oceanic crust beneath the Central Iran has occurred in Laramide orogeny (Late Cretaceous). The boundary between these two populations is gradual and sinusoidal shape. This form of occurrence represents metasomatism and chemical reactions between hot granitoid magma and the pre-existing diorite.

Minerals, depending on their composition and origin, contain some radioactive nuclides. Presence of such radionuclides such as 238U, 232Th and 40K in materials are dangerous when they are highly concentrated and influence on human exposure. Bauxites as a raw material for aluminum may contain relatively high amount of those radionuclides, which are more concentrated in remained red-mud after Al production process. Due to high existing of iron oxides in the red-mud, it is preferred to be used in recycled products such as cement and brick.Because of high amount of radionuclides in red-mud, its radioactivity should be determined and decrease their environmental impact before using in industry. Therefore, radiation of red muds from Jajarm bauxite mine, which is the biggest bauxite deposit in Iran (with 1000000 tones redmud annual production), have been determined in this study. Finally, after determination of average radiation of Jajarm red-mud, the mixing ratio of red-mud to low-radiation materials (such as clay minerals) was calculated for using in construction materials, under standard level of radiation.

Firouzkuh prospect area is located about 35 km northeast of Torbat-e- Jam, Khorasan Razavi Province. Geology of the area includes metamorphosed rocks of Miankouhi Formation, which has intruded by monzogranitic to dioritic intrusions. The magnetic susceptibility of the intrusive rocks varies from 0 to 43×10-5 SI and they belong to reduced granitoids of ilmenite series. These rocks are affected by sericitic, silicification, and propylitic alterations in some places. Geochemistry of intrusive rocks indicates that they vary from metaluminous to peraluminous and belong to medium-K to high-K calc-alkalin and shoshonite series. Tectonic setting of intrusions is pre-plate collision to post-collision uplift. Mineralization has controlled by fault zone and formed in the contact between intrusive rocks and metasandstones or in metamorphosed units. Primary minerals consist of gold, arsenopyrite, pyrite, chalcopyrite, and pyrrhotite and secondary minerals include covellite, hematite, and goethite. Geochemical exploration, using chip composite method, shows anomalies of Au (up to 8942ppb), As (up to 74500 ppm), Cu (up to 357 ppm), Pb (up to 45 ppm), and Zn (up to 97 ppm) in the surface samples of the area, which are related to vein mineralization. Core drilling geochemistry indicates that maximum contents of Au (30732 ppb) and Cu (3200 ppm) exist in OBH-7 and high anomaly of As (98670 ppm) and W (133 ppm) are in OBH-2. Au often shows a positive correlation with As in most samples. It mainly exists in arsenopyrite and less as native gold or pyrrhotite and pyrite minerals. Based on presence of reduced intrusive rocks of ilmenite series, reduced mineral assemblages (arsenopryrite and pyrrhotite), type and development of alteration, mineralization form and high concentrations of Au, Cu, As, and W, the area can be part of a reduced intrusion-related gold system, which requires further investigations.

The Cheshme-Bid Granitoids is located in SE Zahedan, Sistan and Balouchestan P Province. These granitoids are in Middle Eocene Neh metamorphosed flysch zone. The main minerals in these granites are quartz, plagioclase, biotite and amphiboles. Based on microprobe analysis, amphiboles are calcic in composition and set on magnesio-hornblende and actinolite classes. Based on chemical classification of micas, these minerals are located between siderophyllite and biotite. The Fe/ (Fe+Mg)>0.33 ratio shows that mica minerals are biotites and they are separated from phlogopites. The composition of plagioclase is between 19.56 to 32.51 an and the average of anorthite is 23.78 %. Estimated pressure and temperature for the formation of the granitoid, based on Al- Barometry in hornblendes, is about 3.8 Kb and the temperature is relatively low, about 751 celsius degree in granodiorite.

The Siyahmansour area is located between longitude 370 46’ 07" to 370 50’ 19" N and latitude 470 53’ 13" to 470 58’ 22" E in northeastern town of Miyaneh Exposure of different igneous rocks in the studied area including Eocene to Miocene volcanic rocks, granitoids and diorites. The granitoids are different including muscovite granites and granite-granodiorite. The muscovite granites are intruded into metamorphic rocks only as dykes. The intrusion age of these muscovite granitoid types could be related to the Precambrian (?) or Early Cimmerian (?) age of the metamorphic rocks. The granite-granodiorites, including alkali-feldespar granites and granodiorites, are intruded into the Cretaceous and Eocene volcano-sedimentary rocks. The geochemistry of variety of granitoids in the studied area indicate that in the view of aluminum saturation index, the muscovite granites and granite-granodiorite are peraluminous to metaluminous respectively. Magmatic series of muscovite granites and granite-granodiorite are determined as calc-alkaline and alkaline respectively. On the basis of mineralogy and geochemical evidences, the muscovite granites and granite-granodiorite are S-type and A-type (A1 subgroup) granitoids. Tectonic setting and petrogenesis of the granite-granodiorite are determined as anorogenic within plate granitoids having mantelic origin but the muscovite granites correspond to the Syn-COLG. REE diagrams of granite-granodiorite show high enrichment of LREE relative to HREE. This indicates that they are likely generated from an enriched source, although crustal contamination and/or fractional crystallization processes can be important too. REE amounts of the muscovite granites are relatively comparable and do not show considerable variations. The spider diagrams of A-type and S-type granitoides of Siyahmansour area are consistent with a crustal source of those rocks.

The Bayazeh ophiolite, with probable Paleozoic age, is cropped out along the Bayazeh fault and located in the eastern margin of the Yazd block (Central Iran). In the field, this ophiolite consists of serpentinized peridotites, metagabbro, ultrabasic metamorphosed dikes, metapicrite, serpentinite and metalistvenite. Development of serpentinization process in the Bayazeh mantle peridotites has been changed peridotites to serpentinized peridotite and serpentinite. Transitional transformation of serpentinite to metalistvenite is obvious in the field.Field and microscopic studies show that the metalistvenites in the Bayazeh ophiolite have been produced by regional metamorphism from old listvenites. After old listvenite formation, during occurrence of regional metamorphism, carbonate listvenites changed to carbonate metalistvenites and silica-carbonate listvenites changed to silica-carbonate metalistvenites with abundant tremolite and actinolite. Chemistry of Cr-spinels in the Bayazeh serpentinites shows that they belong to depleted ophiolitic mantle peridotites.

Upper Jurassic carbonate successions have excellent exposure in Binalud Mountains, west of Bojnurd, northeast and southwest Jajarm area with thickness of about 500m. Chert nodules are present in various shapes such as spherical, elliptical, elongated, discoid and irregular. Silicifications in these deposits are mostly replacement for the carbonate minerals.The presence of carbonate residues in silicified parts of nodules supports this idea. Silica has granular, drusy, radial and mostly microcrystalline fabrics. Microcrystalline quartz in deep facies is mostly containing radiolaria and sponge spicule that indicated organic orgin of silica.Dolomite in these carbonates observed as early and secondary dolomites with different shapes.Four types of dolomites have been identified including fine crystalline (D1) with no allochem and low quartz grains, secondary fine to medium crystalline replacement dolomites (RD1 and RD2) and cements dolomites (CD). On the basis of these data, the studied dolomites have formed penecontemporaneous and early post depositional to shallow burial conditions. Low amount of Na and Sr in dolomites and chert nodules relative to host lime mud indicate the influence of burial diagenetic process on these deposits. In addition, the lower amount of Mn and Fe in chert nodules and dolomites relative to studied limestones that formed in low oxygen conditions, can be related low concentration in dolomitized and silicified fluids and suboxic condition during their formation. Oxygen isotope values of lime mudstones (average -3.1 ‰ VPDB), dolomites (average -3.91 ‰ VPDB) and silica nodules (average -14.82 ‰ VPDB) indicate the influence of burial digenetic process. Based on oxygen isotope values, the formation temperature of studied dolomites is about 54 to 68oC.

Gd2O3 nanoparticles were synthesized for the first time by sol-gel combustion method and YBCO high temperature superconductor by sol-gel method. X-ray powder diffraction pattern of the nanoparticles and prepared superconductor showed single phase by both methods. The average size of Gd2O3 nanoparticles, according to the Scherrer formula, computed 29 nm, which is consistent with the results obtained from the TEM images. The nanoparticles with two weight perecent of 0.05 and 0.1 were added to YBCO superconductor.The morphology, structure and superconducting properties investigated by scanning electron microscopy, X-ray diffraction and AC susceptibility in product powders respectively. Rietveld refinements from X-ray diffraction data and results of characteristic showed that both Gd2O3 and YBCO phases coexisted in the products and critical temperature of superconductor decreased with increasing additive content.

Major rock units of Robat Sefid ophiolitic complex are Late Cretaceous in age. The abundance of rock units in this area in ascending order are: dunit, harzburgite and pyroxenite), gabbro and diabasic dikes (mostly rudenginized). Chromite lenses are generally covered by a few centimeters to several meters of ultramafic rocks mainly of dunite. Primary disseminated and massive textures are abundant in chromite ores and secondary brecite, pulapart and kataclastic textures are present. These textures and dunite pods are confirming that chromite deposits of investigated area are in syngenetic type. Tectonic activities and specially NE-SE direction faults are the major factor for dispersion of chromite lenses. Geochemical analysis indicate that Kuhi chromite deposits samples have an average values of Cr2O3 (49.54%), MgO (20.29%), TiO2 (19.0%) and Al2O3 (2.44 to 7.9%), as well as the ratio of Cr / Cr+Al ranges from 0.86 to 0.95 (average 0.81). These indicate that chromite samples are high in Cr & low in Al type. The percentage of Cr2O3 and MgO in the chromite samples, indicate high partial melting in magma crystallization. Lower amounts of Al2O3 and TiO2 in chromite deposits with their stratigraphic positions in ophiolitic sequence indicate deep chromite zones of the upper mantle- origin of magma. Due to the amounts of major oxides, Kuhi chromite deposits are in Podiform shape which are probably derived from island arc and boninite magmatic series which are associated with Supra-Subduction zones (SSZ). Depletion in Ti and enrichments in Th of samples conform that magma source is related to subduction zone.