Iranian Journal of Crystallography and Mineralogy
Year:2008 | Volume:15 | Issue:2|Papers Count:16

In the west of Marand in Ghekhlar area, the Upper Miocene- Pleistocene volcanic rocks, including intermediate to acidic basic alkaline and lamprophyric, are extensive exposed. Trachy-andesite rocks of this area contain carbonatite-silicate xenoliths, which according to mineralogical studies, arE calcite - carbonatite type. The minerals of calcite, diopside, anorthite, phlogopite, amphibole, apatite, biotite and titano-magnetite are essential minerals, which belong to calcic and hydrous carbonatite types. The dacitic volcanic rocks of this area also contain carbonates globules that formed from calcite and euhedral apatites. These xenoliths are geochemically characterized by high content of CaO, Fe2O3, MgO, P2O5, Cr, Ni, V, Cu, Zn which are related to host rock. REE pattern displays fractionated pattern (CeNb)N =24-29 and lack of Eu negative signature. The source of these xenoliths can be attributed to disequilibrium partial melting of metasomatized mantle by either released fluids from subducted slab or silicate melts derived from melting of subducted slab. Association of silicates and carbonates in xenoliths can be related to mingling and immiscible fluids.

The studied area is situated in southwestern Birjand (South Khorasan). Lithologic units which are studied contains part of the late Cretaceous coloured melange, Cretaceous and Paleogen flysh sediments, Neogen congolmerate and Tertiary volcanic rocks. The listwaenite of this area often appears along fault zone, boundary of units, bedding planes and schistiosity as yellow and brownish vein. The effect of CO2 bearing hydrotermal solutions on mentioned units, in suitable physico -chemical and termodynamic conditions, caused Listwaenitization reactions. Field and microscopic studies revealed that "alteration process comprises pre-stage reactions (specially serpentine and talc forming reactions in ultrabasic rocks) and main reactions of listwaenitization which in primary mineral paragenesis is changed to silisic - carbonate assemblages listwaenite). Abundance and type of minerals is depended on composition of primary rock, PH, Eh, T, Pco2 and PH2O Microscopic studies and XRD analysis show presence of magnesite, breunerite, dolomite, calcite, smithsonite, quartz, clinochlore, talc, muscovite, chromate, pyrite and magnetite. A.lso SEM analysis and polyshed section studies represents Fe, Ni, Fe-Ni-Co sulphur that must be considered as pathfinder minerals for prospecting of Au, Ag, Hg,... .

The Kuh-e- Zar area is located about 75 Km in southeast of Semnan. Electron microprobe analyses of' plagioclases of mafic microgranular enclaves and plutonic host rocks from Kuh-e-Zar area display that they have normal, oscillatory and reverse zoning, so that plagioclase cores of reverse zoning in enclaves have oligoclase and andesine compositions and their rims have andesine and laboradorite compositions, respectively. Investigation of biotite compositions in host rocks show that in the host granodiorite rocks, there are two types of biotites. The first type has high TiO2 (mean 4.8%), Al2O3 mean 12.84%), MgO (mean 15.38%) and low SiO2 (36.89%), which are similar to mafic microgranular enclaves (mean TiO2 4.67%, Al2O3 13.03%, MgO 15.19% and SiO2 37.23%). the second type is depleted in TiO2 (mean 0.04%) and MgO (mean 0.02%) and enriched in Al2O3 (mean 18.09%) and SiO2 (mean 64.5%). Contents of these elements in the biotites of host monzodiorite rocks are similar to enclaves. Chemical compositions of pyroxenes in enclaves are similar in compositions to those of host rocks. These features, in addition to the patterns and abundances of trace elements in enclaves, the presence of inclusions of fine grain biotite and hornblende in feldspares, synplutonic dykes, the nature of the plagioclase zoning and etc. display magma mixing and mingling origin for generation of these enclaves.

Nezamabad region is a part of Boroujerd granitoid complex (western Iran) which has been cut by various quartz-tourmaline veins with approximately 0.5 to 2 m thickness. Mineralogical and electron microprobe analyses of the tourmalines in those veins and quartzdioritic host rock show that they are schorl and dravite one in terms of composition (with a general tendency toward dravite end member) and alkaline and calcic type respectively. The FeO*/ (FeO*+MgO) ratio of the studied tourmalines are between 0.5 to 0.8, demonstrate that the element-rich fluids have originated from£ 1Km for from the veins. Accruing as vein form and showing optical zoning as well as widely varying compositions, they have also more magnesium than iron, fluorine amount similar to hydrothermal veins and tendency away from alkali- and proton-deficient tourmaline. Therefore, it can be concluded that the veins are hydrothermal one and have been formed by dehydration of metamorphosed sedimentary rocks and its mixing with granitic fluids in an open chemical system.

Advanced diode laser consists of a two dimensional thin layer which is about 10 nanometers size. Optical gain of thin layers has a great deal of importance in light amplification. Thin layers cause a modification in conduction and valance bands of bulk materials.' Subbands have been computed through effective mass equations. As a result of this method, particular effective masses are available. These specific equations are formed by numerical methods. Studied structure in this research includes a two dimensional thin layer of GaAs with a quantum well width from 7.5 to 8.5 nanometers, cladded by two layers of AlGaAs which has a larger band gap. Aluminum percentage has been chosen 15 to 45 percent. Results from this study demonstrates that quantum well width should be adjusted according to Aluminum percentage, and the final optimized result, based on the developed optical gain model, is a thin layer of 8.5 nanometers width cladded by a 25 percent of aluminum in AlGaAs materials.

In this research, ZeoliteX (Na86[(AlO2)86(SiO2)106].264H2O) has been prepared from Zonouz Kaolin. Then VOX-Zeolite has been obtained by treatment of ZeoliteX with vanadyl sulfate solution .The Salen ligand has synthesized by condensation reaction of salisylaldehyde and ethylendiamine. The encapsulated complex, VO (salen), in zeolite pores was prepared by reaction of salen with VOX-Zeolite in ethanol at reflux temperatur. The product was characterized by FT-JR, XRD and SEM(EDX) techniques.

One of the metamorphic rocks in the Nain ophiolitic melange is skarn which is formed during the contact metamorphism of intrusive tonalites with their neighboring limestone’s and carbonate parts of banded cherts. Minerals of these skarns consist of carbonate (calcite), clinopyroxene (diopside), garnet (grossular-andradite), wollastonite, sphene and epidote.Also tonalites contain quartz, plagioclase (albite), alkali feldspar (orthoclase), garnet (almandine-spessartine) and prehnite. Based on mineral assemblages of Nain skarns as well as geothermometry of feldspars existing in relevant granites and also applications of different calibrations of garnet clinopyroxene geothermometer, the Nain skarns form at temperatures of about 440 to 650°C at low pressure during a contact metamorphism which has occurred at hornblende hornfels to pyroxene hornfels facies.

The mineralogical and geochemical composition of the soils of three representative pedons formed, on basaltic and esite, andesitic basalt and phyllite were investigated. Results by XRF showed that progressive weathering of rocks have been marked by gradual accumulation of Al, Fe, Ti, Mg, H3O+ and depletion of Na, K, Ca and Si in the soil; although, predominant clay, loss and gain trend of elements was different on the various rocks. Based on x-ray diffraction analysis, minerals in basaltic and esite and andesitic basalt were similar but, the intensity of mica to smectite or vermiculite transformation for latter was relatively higher than the former. This process revealed the degradation mineral because of two reasons: (i) - smectite and vermiculite increased whereas mica decreased in surface horizons. (ii)-Irregular mixed layer of mica-smectite or vermiculite was present in deeper part (170 cm) of the soils from andesitic basalt but shallower depth (75 cm) of the soils from basaltic and esite. Clay minerals in phyllite were mica and chlorite that stratified with vermiculite. However, the absence of smectite in phyllite might be attributed to more acidic condition or position of the Fe ion in the mineral lattice of chlorite (higher Fe in the interlayer hydroxide sheet).

This study was done in the wet marginal part of the Siahkooh playa (Kevir) in Yazd, Iran, which is located in the northwest of Ardakan. The abundance of Ca and S04 iones led to gypsum crystallization near the water table in the soil. From depth to the soil surface, the CaCO3- CaSO4 , 2H2O -NaCl-H2O-PCO2 soil and water system change to CaSO4, 2H2ONa2SO4- NaCl-H2O. From water table (100 cm under soil surface) to the soil surface, ionic power was decreased and activity coefficient was in crased respectively. Therefore, near ground table, gypsum form and high concentration of Ca iones from gypsum lead to low amounts of exchangeable Na. This influence has been continued up to soil surface to achieve a relative balance. Replacement of Na with Ca on the exchangeable surfaces of soil and existance of SO4 iones formed NaSO4 inerals. The precipitation of 1800ton per hectar natrium salts (sulfatic & coloridic) was estimated with respect to the mean of annual evaporation (roughly 900mm) in the studied site. The result also showed that the seventh bands of Landsat 7 are more important to differentiate between sulfate and chloride salts as well as sodium and calcium salts.

The Bit17Sb0.3Sr1.97Ca2.03Cu3.1 Oy superconductors are prepared by sol-gel method and the effect of W03 and MnO2 additives on their properties are studied. Structural studies show that the find samples are homogeneous and are mainly composed of 2223 and lower percents of 2212 phases. Analysis of the X-ray diffraction patterns indicate that the penetration of W6+ ions into superconducting phase considerably increases for more than 2 wt% additives. Also, the penetrating W6+ions preferentially occupy 4e and 2a crystallographic sites of Cu atoms. The electrical measurements show that the best superconducting properties obtain for the sample with 1 wt% of WO3 additive, while superconductivity is weakened for higher amounts of WO3. For the sample with 0.5 wt% of MnO2 additive, the best superconducting properties are obtained after sintering at 830°C.

The Siahkuh playa is one of the greatest deserts in Yazd province and is located in the north-north eastern of Ardakan city. In playa regions, different sub-environments with different mineral potentials can be recognized. In Siahkuh playa, various evaporite minerals such as gypsum in different form (surgery, nodular and euhedral crystals), halite (fibrous, cylindrical, hopper-shaped crystals and ball-shaped), and sodium sulfate were indentified. Sodium sulfate (Thenardite) is a commercial chemical compound which is formed in playas environments. This compound was also found for the first time in mud flat sub-environment of SW of Siahkuh playa. In brine waters of salt lakes sub-environment of Siahkuh playa, various elements such as lithium, magnesium, calcium, potassium and sodium were detected.

The alkaline and calc-alkaline volcanic activities in Mianeh have reactivated the hydrothermal solutions, resulting in the formation of epithermal mineralization in the region. The mineralized zone trending NWSE, and has been affected by NE-SW bended and folded structures. The precious and base metals mineralization are confined to structurally bended zone. Landsat-7(ETM+) data were used to study the alteration zones, structural features and to discriminate the lithological units in the region. The primary corrections were carried out on the images and the data resampled to ISm. Based on spectral pattern of minerals present in the alteration system, such as chlorite, epidote, kaolinite, jarosite, geotite, hydrothermal alteration zones of the area were detected using band ratio and principle component analysis (PCA) techniques, which also well correlated with field studies. The linear and ring structural features along with lithological units were discriminated based on spectral features of minerals. Ultimately, the study reveals that the application of PCA resulted in enhancement of alteration halos. The field checks have confirmed the achievement and indicate the western part of the area as potentially promising zone.

Dodehak granitoid stock with tonalite to granodiorite composition is exposed south of Dodehak village, north of Ab-e-Garm (Mahalat) in Urumieh-Dorhtar volcanic belt of Iran. Based on petrography and point analysis (EPMA), plagioclase crystals show normal zoning with graphic texture is present. Samples from SE of the intrusion are different and myrmekite texture is present in the rocks, while graphic texture is absent and plagioclases have lost their zoning. In samples from SE of the area, myrmekite is rim type and plagioclases show cross shape twinning. Based on whole rock XRF analyses, Rb-SiO2 and K2O-Na2O diagrams show nonlinear trends and EPMA analysis indicate that plagioclases are homogeneous albite. Such petrographical and geochemical features are evidence for alkaline metasomatism in SE of the Dodehak intrusion.

Mantle peridotites are one of the most important rock units of Jandaq ophiolite that are affected by numerous phases of dynamic and static serpentinization, and metamorphism. The main part of mantle peridotites is lherzolite. This ophiolitic association is covered by Paleozoic metamorphic rocks that are schist and marble. All olivines are changed to serpentine. Most of orthopyroxenes are bastitized and some of clinopyroxenes are changed to tremolite by metamorphism. Clinopyroxenes are the most resistant mineral against the metamorphism and alteration. Most of spinels are magnetitized, but in some cases the inner parts are fresh. Composition of chromian-spinels are the same in all mantle peridotites with Cr# = 0.46. Gabbros that intruded the peridotites are rodingitized. Peridotites of Jandaq ophiolite are abyssal peridotites that belong to spinellherzolite facies. Crystallization temperature of pyroxenes in lherzolites ranges from 1041 to 1178°C. One of the most characteristics of these peridotites is absence of chromitite that relates to lherzolitic system of mantle, low degree of partial melting, low activity of mantle in continual ascending melt production, and low Cr content of pyroxenes.

Contact metamorphism in the Shahindezh Metamorphic Core (SMC), which is occurred due to intrusion of Pichaghchi granodiorite during Laramian orogeny (Upper Cretaceous), is studied here. The well developed mineral parageneses at the aureole is quatz + plagioclase + biotite + cordierite±chlorite±K-feldspar±muscovite±and alusite±sillimanite± garnet. Pressure and temperature of the contact metamorphism at the SMC for andalusite + cordierite -bearing assemblages (the most common paragenesis at the aureole) are estimated ~3.5±1.5 kbar and 500±50°C using THERMOCALC computer program. Also the exact position of the muscovite + biotite breakdown reaction at the PT space, is calculated. Temperature for muscovite-biotite breakdown was about 650±40°C at 3.5 kbar. The calculated position of the reaction curve, is in good agreement with published experimental data. The metapelites at the north-eastern part of the SMC contain high-temperature assemblage quartz + biotite + garnet + sillimanite + plagioclase±cordierite±K-feldspar. The mineral assemblages and reaction textures in the aureole rocks record temperature about <750°C at the sillimanite -cordierite zone and pressure ~ 4 kbar, determined using petrogenetic grids. In the partially molten rocks garnet porphyroblasts are associated with coarse-grained quartz. Cordierites occurred both at the rims of residual garnets crystallized during regional metamorphism and in the matrix. All cordierites' are altered to pennite. Fibrolite inclusions in the matrix cordierites are common.