Iranian Journal of Crystallography and Mineralogy
Year:2004 | Volume:12 | Issue:2|Papers Count:11

In this research work a rather new method was used to detect trace elements of small quantities. For this, X-ray intensity enhancement effect and standard samples of BAS Company were employed. In the standard sample a small amount of Rubidium was present, which by adding some quantities of SrCo3 to the sample the XRF characteristic peaks of Rubidium were enhanced. This effect proved to be applicable for detecting trace elements.

In the Ardakan barite ore deposits, two groups of copper ore minerals have been identified in the barite veins. The hypo gene ore minerals consist of chalcopyrite and chalcocite, which are associated with pyrite. The Super gene ore minerals are mainly composed of secondary Cu-sulfides (such as covellite, yarrowite and anilite), Cu-carbonates (malachite and azurite) and Cu-oxides (cup rite). Chalcopyrite is the most important hypo gene Cumineral which has been altered to Cu-super gene minerals. Chalcopyrite tarnishing were developed along the joints, fractures and grain boundaries as films and veinlets. The tarnish color on the chalcopyrite varies from deep blue, pale blue, pink, yellow and dark gray. The tarnish phases in the chalcopyrite were studied using SEM - EDXA. Sequences of the chalcopyrite alterations by the continued oxidation are as following: chalcopyrite (CuFeS2), covellite (CuS), yarrowite (CU9S8),spionkopite (CU39S28),geerite (Cu l.6S) and anilite (Cu 1.75S).Alteration and oxidation caused a series of changes from chalcopyrite to anilite. These changes include general fluctuations in the Cu/Fe and Cu/S ratio, so that some new minerals form by Fe and S depletion and Cu enrichment. Weathering of chalcopyrite to covellite results in a decrease in iron content with simultaneous increase in copper. Subsequent weathering of covellite to anilite caused an increase in the Cu/S ratio from 0.9 in covellite, to 1.12 in yarrowite, 1.45 in spionkopite, 1.64 in geerite, and to 1.77 in anilite. Super gene weathering in the chalcopyrite of the Arakan barite is mainly due to galvanic reactions.

It has been the aim of this project to produce refractory calcium aluminate cement (CAC) with 70% alumina in the laboratory. Pure calcined alumina and lime were mixed and fired at different temperatures and times in a rotary kiln. When the clinker was formed, it removed out of the furnace and cooled rapidly. The presence of optimized amounts of monocalcium aluminate (CA) and Dicalcium aluminate (CA2) as the major anhydrous phases in clinker were examined by X-ray diffraction method, and the hydraulic properties of powdered samples were measured by evolved heat measurement versus time during setting times. Based on the data acquired by various test methods, 1550 ° c and 90 min. were the optimized conditions for preparation of this type of refractory calcium aluminate cement.

The bentonites of Aftar region, with average of 15 meters thickness and about 10 km long, are volcanoclastic sequence of Semnan Formation that formed in a shallow sea water environment. Based on the field, XRD data, microscopic and scanning electron microscopic (SEM) studies, as well as chemistry, the bentonite beds contain zeolites (clinoptilolite and mordenite), gypsum, calcite, celestine, opal, quartz, crystobalite and aragonite associated with clay minerals. XRD data of airdried, glycolated and heated of clay fractions show the majority of the clay minerals are of swelling and of dioctahedral, smectite types. FTIR spectra, in agreement with chemical analyses data, reveal that the smectites are of Wyoming type (SWy-2) montmorillonite. The structural formula unit of representative clay of Aftar region, based on 11 oxygens, is:(Ca0.057 Na0.270K0.030)( AI1.515Mg0.313Fe0.109Ti0.010)( Si4.015O10)(OH)2.Based on the composition of tuff and bentonites, the bentonites appear to be derived from alteration of acidic (dacitic to rhyolitic) tuffs of Eocene age in a relatively basic environment. Relatively stable smectites and zeolites are formed by dissolutim of less stable glass of vitric ash that was present in tuff during variation in basic environmental conditions.

The mineralogy and origin of the scapolite crystals of the Panj-Kuh area (S-E Damghan) has been investigated. Based on textural and field observations, two types of scapolite have been identified. Type 1 scapolite consists of fine to coarse grain crystals which are mainly replaced for plagioclase in the pluton body. The type 2 as veinlet and vein ranging in thickness from few milimeters inside the body to about few hundred meters in the margin of the body that present close to the iron ore deposit. It seems that the formation of the first type of scapolites is related to the circulation of NaCl rich fluid around of the intrusive body, and the second type has directly been precipitated from the hydrothermal fluids. The extensive abundance of scapolite-albite zone in intrusive rocks and specially between body and a volcano-sedimentary sequence suggest that the formation of scapolite was accompanied by an alkali metasomatism which has been derived from the evaporate sediments of that sequences.

The study area is a part of central Iranian Cenozoic magmatic belt. The dominant rock type in the area is rhyodacite with Eocene in age. These rocks have been effected by Qum-Zefreh fault as well as alteration by hydrothermal solutions. Due to sulfate - acid alteration, the following minerals are formed: pyrite + alkali feldspar + sericite + pyrophyllite + barite + jarosite + hematite + quartz. The presence of abundant jarosite mineral and the high heavy elemental content, as well as the high K/Na ratio, we suggest that the Rangan jarosite may have a magmatic - hydrothermal ongm.

Pressure and temperature of metamorphism in the Mahneshan area were estimated in order to determine the type of metamorphism and tectonic setting of the rocks. Biotite, muscovite, plagioclase, garnet, quartz, andalusite and staurolite minerals are crystallized together in metapelites in the regional metamorphic rocks of southwest Mahneshan. Chemistry of coexisting minerals is studied using microprobe analysis. Using multiple equilibria calculations and THERMOCALC program, temperatures of ~520°C and pressure of ~3 kbar have been calculated for the formation of these rocks. Using these data, geothermal gradient of 60°C/km has been calculated for the upper crust of the Mahneshan. Based on calculated geothermal gradient, the Buchan type metamorphism is suggested for the metamorphic rocks of southwest Mahneshan.

In PZT thin film devices, with silver oxide electrodes, the diffusion of silver atoms into the PZT structure is very possible which may change the properties of the device. In the present work, this effect on PbZr1-xTix03 with x = 0.47 has been investigated. The samples were prepared by mixed oxide method. After calcination the mixed powders, Ag2O with different weight percent were added. All the samples were calcinated and sintered under the same conditions. Electrical measurements revealed that the electrical conductivity of the samples, depending on the weight percent of Ag2O, has increased. X-ray diffraction patterns showed that silver atoms have not produced new phases. Investigating the structure of the samples by SEM proved that adding silver oxide causes the growth of the grains.

Single crystals of Cd96Zn0.04Te(CZT) with 14 mm in diameter were grown by seedless modified Bridgman method. Also, crystals with the same chemical composition were grown by vapor phase inert gas-transport method (VPGT), and single crystals up to 3.5 mm in diameter were obtained. Structural studies by XRD and back reflection Laue method show that the grown crystals are single phase with high purity, which preferentially have been grown along [111] crystal axis. The energy gap of as-grown crystals is about 1.2 eV. The electrical properties measured by Van der Pauw method, show that the resistivity is in order of 104Ω.cm. The electrical conductivity of crystals grown by Birdmen method is p-type, and for VPGT-crystals is ntype.

Rock unites which are exposed in Tak-I mine area are: Taknar formation (Ordovician), Mid-late Paleozoic and younger intrusive rocks. Taknar formation consists of sericite schist, chlorite schist, chlorite-sericite schist and some meta-diabase- gabbro-diorite. Taknar Polymetal (Cu-Zn-Au- Ag-Pb) Massive sulfide deposit formed at certain horizon of Taknar formation. Three style of mineralization are: stockwork, layered and massive. Due to strong tectonic activity in the area, dimension and geometry of deposit are being changed. Para genetic minerals within the massive and layered are: magnetite + pyrite + chalcopyrite ± sphalerite ± galena ± sulphosalt ±gold + chlorite ± carbonate± Seri cite. Magnetite is the main mineral in the massive zone. Par agenesis within stock work are: pyrite + chalcopyrite ±magnetite + chlorite + quartz + sericite ±carbonate. Based on mineral par agenesis, the ore bearing solution had the following condition: T≥ 270°C, pH= 5 -7, Logƒ02 = (-29) to (-30). Also, The range of chemical composition of some elements within Tak-I massive sulfide is as follow :Cu = %0.01 - %5.86, Zn = 269 -15600 (ppm), Pb = 27 - 4400 (ppm), Au = 0.86 - 7.53 (ppm), Ag = 2.4 - 95.1 (ppm), Bi = 34 - 2200 (ppm).Based on the par agenesis, alteration, style of mineralization, petrography, geochemistry, and structure, Tak-I is part of massive sulfide deposit. Due to high content of Cu, Zn, Au, Ag and Pb, Taknar massive sulfide deposit is a polymetal deposit. Based on high magnetite within sulfides and lack of pyrrhotite, Taknar is a special massive sulfide deposit.

The first crystal structure of a phenylcyanamide cobaltoxime (cobaloxime) complex is reported. This compound is trans- [Co((DO)(DOH)pn)(2,5-Cl2pcyd)2],and consits of an imine-oxime equatorial ligand ((DO)(DOH)pn) and two 2,5-dichlorophenylcyanamide ligands in axial positions. Crystals of trans- [Co((DO)(DOH)pn)(2,5-Cl2pcyd)2]were grown by ether diffusion into an acetonitrile solution of the complex. Crystal structure of this complex is orthorhombic (space group: Pbca) with a = 13.6800, b = 13.7434, c = 29.892 A, and Z = 8. The structure was refined by using 2946 independent reflections with I>2σ(I) to a R factor of 0.0606. Both phenylcyanamide ligands are coordinated to Co(III) through the terminal nitrile nitrogen of the Cyanamid group. Inaddition, the cobalt(III)-cyanamid (Co(III)- N=C=N-ph) bond angle is significantly bent while the cyanamide group(N=C=N-) is largely coplanar with the phenyl ring. These geometries can be ascribed to the relative importance of π bonding.