Iranian Journal of Crystallography and Mineralogy
Year:2006 | Volume:13 | Issue:1|Papers Count:17

Both Sangan and Tannurjeh magnetite deposits are Iron-oxides type. Geochemistry and petrography of source rocks at Tannurjeh and Sangan were studied in detail. The source rocks at Sangan are compused of quartz hornblende alkali syenite porphyry and quartz biotite-hornblende alkali syenite porphyry; while The source rocks at Tannurjeh varies between hornblende quartz diorite porphyry and hornblende granodiorite porphyry. The Au content of Sangan deposit is up to 32 ppb, while Tannurjeh contains up to 700 ppb Au. Based on major oxides analyses, the source rocks at Sangan is ultra-potassic (K2O is 8.5 to 13%), but in Tannurjeh the K2O is lower than 3.5%. The MgO, TFeO, and CaO content of Tannurjeh source rocks is higher, therefore the rocks are slightly mafic in comparison with Sangan source rocks. The content of HFSE elements such as Cu, Ni, Co, Cr, V are higher in Sangan source rocks and the LILE elements such as Th, Zr, Ba, Rb are higher in Tannurjeh source rocks. The La and Ce content of Tannurjeh is higher. At Tannurjeh the Sr and Zn content is higher while at Sangan Nb and Y is higher. The source rocks for IOCG deposits in Chile, coastal belt of Peru, and kirona areain Sweden are high to medium K-content, and alkaline to calc-alkaline diorite-monzonite-granodiorite; there fore the source rocks at tannurjeh have very ligh similarity in composition to these rocks.

Barandagh quadrangle is located in northeast of Zandjan, and is a part of polymetallic region of Tarem-Zandjan. Field evidence and microscopic studies show an intimate relationship between geochemical anomalies and alteration zones in this area. Based on the field observations and mineralogical studis, these zones, in light of extent, locality, and constituent mineral assemblage, differ from one another, and are scattered along the main shear zone of the area and the margin of Ghezel-Ozan river. The major alteration zones in this area are affiliated with the shear zone, and can be categorized into two discrete alteration types: 1) hypogene acid-sulfate (e.g., silicified, alunitized, advanced argillic, sericitic, and propylitic zones) and 2) supergene acid-sulfate (characterized by minerals assemblage such as jarosite, alunite, goethite, gypsum, and native sulfur). Alteration zone along the margin of Ghezel-Ozan river consists of neutral-pH types of alterations (consisting mainly of argillic, calc-silicate-bearing, and zeolitic zones). In general, these alteration zones were developed by the function of a vast geothermal system during the late Oligocene to Mid-Miocene time. Date gathered indicate that the discrepancy in reaction rate between the fluids and the enclosing rocks caused the development of these two types of alterations. Note the type of alteration zones and the obtained results from geochemical exploration, show that this area possesses suitable potential for prospecting of Ag-Au epithermal and polymetallic (Cu, Pb, Zn, Au, Ag) deposits.

The study area is located in northern part of metamorphic belt of Sanandaj-Sirjan in east of Hamedan Batolith. This area is mainly composed of regional metamorphic rocks, such as staurolith, andalusite, silimanite and garnet bearing mica schists and slates, with nearly NW-SE trend. The age of these rocks (tectonites) are Pre-jurassic and have experienced two stages of deformation during ductile deformation. The first schistosity (S1) formed at the first phase (D1). The second phase (D2) was formed by sided forces where the most of structures have formed by this force. The fabric elements of second schistosity (S2) and second lineation (L2) formed in this phase. The subfabric elements of quartz, due to its physicochemical characteristic, was producted at this phase. Quartz grains, first and second schistosity and axes of microfolds all have orthorombic symmetry.

Hydroxyapatite (HA), which is represented by the formula Ca10(PO4)6(OH)2, is one of the inorganic components of the hard tissues of living bodies such as bones, teeth, etc. HA is a calcium phosphate-based bioceramic, which has been used in medicine and dentistry for more than 20 years because of its excellent biocompatibility with human tissues. The precipitation process, considered here, can add orthophosphoric acid solution to a calcium hydroxide solution. The precipitated powder samples were examined by XRD, FTIR, SEM and FESEM (Field emission electron microscopy) methods. The results revealed that the final precipitated powder is HA and using SEM with high magnification showed that these HA consists of small rod-like particles. In addition, the morphology and size of the precipitated particles change during different stages of process. After drying, these nano-particles tend to form small agglomerates.

In this research, the effect of silver doping on 2223 phase of ceramic superconductor Bi1/6Pb0/4Sr2Ca2Cu3Od (BSCCO) has been investigated. To synthesis the samples, we used solid-state reaction method and two different doping methods, namely, doping samples during making processes (batches No.1) and doping samples after making superconductor (batch No.2). With doping Ag to BSCCO, the critical temperature Tc (mid) increases (batch No.1) and also the resistance of the normal state for all samples decreases. For batch No.1 samples, the Jc decreases from pure sample with increasing of Ag doping up to 2% but it increases to maximum value by increasing Ag doping in 5 and 15 percent. The Jc in batch No.2 decreases from pure sample to 5% Ag of doped samples and then increases by increasing Ag doping up to 20% and finally decreases to 60%. The SEM images of samples have shown that all surfaces are porous and the grains are platelike. The EDX analysis confirms that the primary elements in our samples are Bi, Pb, Sr, Ca, Cu, and Ag. The XRD patterns indicated that the silver peaks form separate phase. Also by adding Ag to BSCCO, the BSCCO peaks slightly shifted. Therefore, the lattice parameters slightly change, but the structure of samples has been left orthorhombic.

In this research we measure some of the optical parameters of Barium Titanate crystal (BaTiO3), such as signal beam gain, coupling constant (exponential gain coefficient), change in index refraction and photorefractive sensitivity, which are very significant for optical data storage. In all experiment, two- wave mixing configuration at 632.8 nm (He-Ne laser) were used. Experimental data for change in signal beam gain versus input angle of two beam, beam intensity ratio, pump beam intensity and grating vector, were plotted and compared with Kukhtarev theory. Using of experimental data, we calculated other optical parameters such as exponential gain coefficient, change in index refraction and photorefractive sensitivity. The results are good and the crystal can be used for optical data storage, dynamic holography, etc. For a -wave mixing configuration, the same crystal as a recording medium for real time displacement has been used. For measurement of distant object a high coherent source such as He-Ne laser has can been used. Long coherence length of the laser permit to study the objects which are far away from the crystal. The influence of intervening medium must be negligible.

Optical properties of InxGa1-xN alloy and In0.5Ga0.5N/GaN multi quantum wells have been investigated in the region of far infrared. Far-IR reflectivity spectra of In0.5Ga0.5N/GaN multi quantum wells on GaAs substrate have been obtained by oblique incidence p- and s-polarization light using effective medium approximation. The spectra and the dielectric functions response give a good information about the phonon and plasmon contribution in doped MQW as well as the mole fraction of compounds in the alloys. The changes in position of optical modes are good tools for measurement of the amount of free carrier and the amount of mole fraction in the samples. During study of InxGa1-xN reflectivity spectra, two distinct reststrahl bands with frequency near those of pure InN and GaN were observed over entire composition range. Each band shifts to lower frequencies and decreases in amplitude as the concentration of corresponding compound in alloy decreased. Analysis of dielectric function gives the TO-like and LO-like mode frequencies. The changes in LO mode frequencies, due to coupling of phonon–plasmon, have been observed.

The (Bi0.25 Sb0.75)2Te3 compound is a p-type thermoelectric semiconductor for using in thermoelectric cooling systems. To fabricate this single crystal, elements Bi, Sb and Te with 5N purity melted in quartz capsule at 10-6 torr pressure and rapidly quenched to room temperature are required. The sample was crystallized by zone melting method with the rate of 8 mm per hour at 700 oC and for heat stress relieving annealed at 370 oC. In this presentation, crystal growth processes and effect of dopants on improving the thermoelectric property of crystals will be reported. Structural studies by XRD show that the expected phases have formed in a single phase. Scanning electron microscopy (SEM) used to characterize the quality of the crystal growth. Maximum figure of merit Z = 3.15×10-3 K-1in optimum condition was obtained.

Intrusion of the Chahghand gabbrodiorite in regionally metamorphosed rocks of the Sanandaj-Sirjan zone in NE of Neyriz has caused contact metamorphism. A variety of pelitic hornfelses are formed as a result of thermal metamorphism. Spatial distribution of minerals in the Chahghand aureole defines three mineralogical zones namely cordierite, andalusite and sillimanite zones. Study of metamorphic reactions and phase relations indicate a pressure of 2.5 to 3.5 kbar and temperature of 500-600 oC and ~700 oC for the andalusite and the sillimanite zones respectively. Apart from crystallization of prismatic sillimanite in the sillimanite zone, fibrolite is formed in the other zones. It seems that cation leaching and deformation were the major processes in the formation of fibrolite in the Chahghand aureole. Regarding appearance of fibrolite in altered rocks far from the igneous contact, fibrolite is not crystallized within the sillimanite stability field, but it may has crystallized at lower temperatures. Therefore considering fibrolite in the rocks equivalent to sillimanite existence and estimated pressure and temperature on this basis, at least the altered rocks within the thermal aureoles is fraught with some problems.

Engineering ceramics are often difficult to prepare for observation because of their hardness, wear resistance and chemical inertness. Different silicon nitride containing ‎Y2O3 and Al2O3 are prepared and etched using several different techniques and the most efficient methods are identified. The microstructure and grain-boundary composition were examined by electron microscopy (SEM, TEM), electron diffraction and energy-dispersive X-ray microanalysis. A method has been developed to quantify microstructure consisting of elongated, rod like  Beta-grains to discuss the interdependence between starting materials composition, processing condition, microstructure and resulting mechanical properties of dense Si3N4 materials. It is shown that post-sintering heat-treatment in air in the temperature between 1100-1450 oC results in substantial crystallisation of the glassy phase.

Igneous rocks of the Karaj Dam basement are mainly composed of gabbro, diorite and monzodiorite-monzonite which are locally penetrated by the quartz-monzonitic dikes. The upper and lower margins of the pluton, which has gabbroic composition, show porphyritic texture (chilled margin). The porphyritic texture in chilled margin gradually changes to the equigranular gabbro, diorite and monzodiorite-monzonite. The mineral chemistry (electron microprobe analysis) of the plagioclase and pyroxene in various rock samples from lower contact chilled towards the upper parts suggesting differentiation processes. The Mg ¹ of the pyroxene and An% of plagioclase of the contact chilled samples can be used as an indication of the original magma and plotted between the gabbro and monzonitic samples. In addition, increasing of the Mg¹ within the whole rock samples from the upper of contact chilled, in comparison to the lower one, suggests elements differentiation by the gravity diffusion. Moreover, Na2O, K2O and incompatible elements increase and MgO, Fe2O3 (tot), CaO and compatible elements decrease with the progress of the magma differentiation. The samples in the Log Ni-Log La and Log Ni-Log Zr diagram plot almost as straight horizontal line, which confirms occurrence of the magma differentiation.

One of the main sources of error in sample preparation is contamination resulted by laboratory equipments. Among these equipments, pulverizers and mills have a major impact. In this research, several samples of rock and ore with different abrasive property were pulverized by a tungsten carbide ring mill and analyzed by XRF method. It has shown that some samples were highly contaminated by tungsten and cobalt. The rate of contamination can be directly related to sample abrasiveness and time of pulverizing. Many interference of X-ray fluorescence spectra of tungsten and cobalt with some other elements were also found. In order to get a precise results, it is necessary to reduce or eliminate the interference of these elements by appropriate methods.

Copper-bearing skarn zone in east of Sungun-Chay river is located about 100 km NE of Tabriz, and was developed along the contact of the mineralized porphyry granitoid stock (Oligo-Miocene) with impure carbonate rocks (Upper Cretaceous). Both endoskarn and exoskarn occurred in this zone. Endoskarn is narrow (~0.5-2m) whereas exoskarn is relatively broad (25-55m) and contains minerals such as calc-silicates (grandite, diopside-hedenbergite, tremolite-actinolite, epidote), silicates (quartz, chlorite, and clays), sulfides (pyrite, chalcopyrite, sphalerite, galena, bornite), oxides (magnetite, hematite), and carbonates (calcite, ankerite). Skarnification processes occurred in two distinct stages, including progradation and retrogradation. Calculations of chemical index of alteration (CIA) indicate that the exoskarn underwent metasomatic alteration within the range of 8.41% to 57.29%. Analysis studies of mass changes of elements, on the basis of Nb (as a monitor immobile element), indicate that considerable amounts of elements such as Fe, Si, Mg, S, Cu, Pb, and Zn were added to the skarn system by hydrothermal fluids from the side of pluton, while substantial amounts of Ca was leached out of the system. The overall obtained results show that elements such as Fe, Si, and Mg were introduced into the skarn system by metasomatizing fluids during both progradatian and retrogradatian stages whereas the ore-forming elements such as Cu, Pb, Zn, and S were added to the system mainly during retrograde stage. The inharmonious mass increase of Al and portion of mass changes of Si are due to the local variations of pelitic impurities within the carbonate rocks (as protolith).

In this research, the synthesize possibility of Potassium Nickel Hexacyanoferrate complex on natural clinoptilolite, as a support for removal of Cs+ and Sr+2 from radioactive waste, was investigated. Previous work showed that in the high concentration of sodium ion the sorption of these radionuclides on zeolites is low, therefore we enhance the efficiency for the purpose with loading Potassium Nickel Hexacyanoferrate complex on clinoptilolite. First Potassium Nickel Hexacyanoferrate complex was synthesized and characterized using ICP-AES, XRD and SEM methods. Then the structure of clinoptilolite and the complex loaded zeolite were characterized using IR, EDS, SEM and XRD methods. Sorption of cesium clinoptilolite and potassium nickel hexacyanoferrate-loaded clinoptilolite (CFC) was determined in the presence of various concentration of sodium ion. Results showed the sorption of CFC was improved in comparison to its original natural clinoptilolite.