Iranian Journal of Crystallography and Mineralogy
Year:2009 | Volume:17 | Issue:3|Papers Count:17

The Natanz plutonic complex is located in north of Isfahan and in the Orumieh – Dokhtar magmatic belt. Based on petrographic studies, the Natanz complex is composed of six rock types, which are granodiorite, quartz-diorite, diorite, gabbro, quartz- monzonite and granite monzogranit. The intrusive rocks of Natanz are related to the calc-alkaline magmatic series and I-type granitoids. These rocks are mainly composed of plagioclase, quartze, amphibole, alkali-feldspar, biotite, and pyroxene. The composition of olivine is Fo67-70. Pyroxene is Na-poor. The Composition of clinopyroxenes is in the diopside – augite range and orthopyroxenes are enstatite. All clinopyroxene analyses display compositional differences between cores and rims. Calcic amphibole with magnesiohornblende composition is one of the mafic minerals in the rocks. Composition of plagioclase is An11 (the minimum value in granite) to An92 (the maximum value in gabbro) and in some samples this mineral has normal zoning. Micas are Mg-rich biotite. Application of Al in hornblende barometry indicates a pressure of  » 2 kbar for the intrusion. Thermometry yields low temperatures, which probably reflects late stage, post - magmatic re-equilibration of the minerals.

In Iran, the most important tin and tungsten mineralization has occurred in Shah-Kuh granitoid pluton (Lut Block, east of Iran), and Nezamabad area (Boroujerd granitoid complex, west of Iran), respectively. Both mineralizations are mainly accompanied by existence of quartz- tourmaline veins. Nezamabad veins- type tourmalines have dravite composition and have been formed in hydrothermal condition on the basis of the following reasons: having more Mg than Fe, fine scale zoning, having low fluorine amount, low X-site vacancy, low Al amount, low Fe/ (Fe+Mg) ratio, tendency away from alkali- and proton-deficient tourmaline and lack of negative correlation between Fe and Mg. Falling their composition in the metapelites and metapsammite zone reveals that the required forming fluids might be originated from host metamorphosed sedimentary rocks of the regions. Quartz-tourmaline veins from Shah- Kuh have been injected into main pluton and sedimentary rocks of Shemshak Formation. Vein- type tourmalines of the sedimentary rocks, have the same hydrothermal properties as Nezamabad tourmaines. Despite of having mostly schorl composition and originating from magmatic fluids, vein- type tourmalines of the granitic pluton represent hydrothermal nature as well.

The Kaleybar alkaline igneous intrusion contains fine- to coarse-grained, anhedral to euhedral brown garnets. Most of the garnets are zoned. Generally, they occur in foid -bearing leucocratic rocks and the phenocrysts typically have analcime inclusions. According to mineral chemistry, the garnets of Kaleybar are Ti-andradites and melanites. The chemical zoning is characterized by a decrease in mole percent grossular, almandine, and spessartine and an increase in andradite from core to rim. On the basis of the present data, it can be concluded that the garnets in the Kaleybar intrusion are in the primary igneous phase that formed during the late magmatic stage and Ti-Si exchange in the tetrahedral site is the main substitution.

TiO2 nanocrystallites in rutile phase with 68 nm dimensions have been synthesized by sol–gel technique. The structure and particle sizes have been determined by X-ray diffracttion and SEM characterizations. Different factors in the rutile phase broadenings and shifts of the Raman modes at different temperatures, especially at high temperatures, have been studied. The effect of particle size, non- stochiometric effect, surface pressure and anharmonic phonon-phonon coupling have been considered and investigated.

The studied area is a small portion of Sanandaj – Sirjan zone. Metasomatism at the contact of intrusive body studied and penetration of Al-rich rocks caused tourmalinization to stratiform tourmalinite in pelitic hornfels. In addition, hydrothermal fluids crystallized tourmaline nodules in monzogranite surface. The Fe/ (Fe+Mg) ratio in varied between 0.4-0.76 in stratiform tourmaline and 0.83-0.96 in tourmaline nodules respectively. The tourmaline composition is schorlite- dravite. Chemical zoning in this mineral show that system is open and crystallization is unequilibrium. The flat trace end rare earth elements imply to mobility of LREE induced to alteration that this phenomena occur to increasing HREE/ LREE in this type tourmalines.

M ineral chemistry of micas from the subduction-related mafic and felsic alkaline rocks of the Kaleybar alkali-gabbro and the Bozqush nepheline syenite was determined. The micas generally occur as large poikilitic grains with Fe-Ti oxides and mafic minerals and give the rocks a spotted texture. Micas in the alkali-gabbro sometimes display a distinct lamination. Based on the International Mineralogical Association (IMA) classification scheme, the mica compositions plot between the siderophyllite and eastonite end members and show high Fe/ (Fe+ Mg) ratio (>0.33), therefore they are biotites. Chemical composition of the biotites varies from Mg-biotite in the Kaleybar alkali-gabbro through Fe-biotite in the Bozqush nepheline syenite. Based on their FeO, MnO, MgO, TiO2, and AlVI content, they are primary magmatic biotites. Despite the alkaline affinity of the biotite host rocks, they plot in the calc-alkaline orogenic suite field on FeO, MgO, and Al2O3 geochemical diagrams.

Determination of stability limits, mineralogical changes and thermal reaction of serpentine minerals are very important for the investigation of magmatism, mechanism and depth of plates of subduction. During the subduction process, serpentine (Lizardite) minerals will release their water due to thermal reactions. This dehydration can play an important role in volcanism processes related to the subduction. In this study, serpentine minerals (Lizardite) collected from the Neyriz Ophiolite Complex (NOC) were dehydrated under the constant atmospheric pressure. These mineralogical changes were determined by X-Ray diffraction and DTA-TG analyses methods. This study shows natural lizardites that heated for about one hour is stable up to 550°C. Dehydration reactions on lizardite started at approximately between 100 to 150°C and dehydroxilation reactions started at approximately 550-690°C. As a result of thermal reaction, the decomposition of lizardite will take place and then changes in to olivine (forsterite). Crystallization of olivine (forsterite) will start at 600°C. This mineral is stable up to 700oC and then crystallization of enstatite will start at 700°C. During this dehydration and crystallization reaction, amorphous processes will start at 600°C and some amount water and silica will release.

The mantle sequence serpentinized peridotites of north of Nain have been converted to carbonate- silica assemblage known as listwaenite at various temperature and pH in response to CO2 and SiO2 bearing fluids. On the basis of carbonate and silica minerals content, three types of listwaenite have been recognized: carbonate, carbonate- silica and silica listwaenites. Generaly carbonate minerals are magnesite, dolomite, ferrite-dolomite and ankerite. Calcite and other carbonate minerals are rare. Silica minerals (including quartz, chalcedony and chert) accompanied by accessory Cr-spinel, chlorite, sulfide minerals also occur in listwaenites. Silica matrix in silica listwaenite containing high amounts of Hg, Ag and As elements and shows that these elements have transported by SiO2 bearing hydrothermal fluids as arsenide complexes.

Bovaki and Aghbolagh tungsten (copper-tin-zinc) ore occurrences are located 12 and 14 km northwest of Azna respectively. The region is located in Sanandaj- Sirjan structural zone of Iran, at the complex deformation sub-zone. There are alternative comsisty Upper Triassic carbonate, quartzite and meta-volcanic rocks (such as meta-tuff). In this area, tungsten-copper mineralization occurs as stratiform- stratabound in metamorphosed cherty, sandy, dolomitic limestone country rocks. In this sequence, the volumetric ratio of sedimentary rocks is more than that of volcanic rocks. Mineral paragenesis in the both areas consists of pyrite, scheelite, maghemite, lepidocrocite, Fe-oxide and hydroxide and occasionally chalcopyrite, chalcocite and malachite. Mineralization types are primary, diagenetic and stratabound veinlet. Ore textures are disseminated, lenticular, replacement and open space filling. Mineralization contaben place by diaganetic processes and regional (low grade facies) metamorphism events. Comparison of Bovaki and Aghbolagh mineralization with both typical proximal and distal mineralizations has shown that they are more similar to the distal mineral deposits.

Loco-granite and granodiorite intrusive bodies have cut the Naiband and Sangestan Formations in Darreh- Zerreshk area in southwest margins of Shirkooh batholite. This intrusion has caused weak metamorphism and copper hydrothermal mineralization in permeable Sangestan Formation. The characteristics minerals are magnetite, chalcopyrite, pyrite, bournite and dyajenite. The studied area is composed of sedimentary strata of Lower Cretaceous up to present. These rocks have been cut by a great variety of extrusive and intrusive rocks. Intrusion of porphyric granitoide of Miocene in volcanic units and Cretaceous limestone units caused Copper mineralization in different parts of studied area. In Darreh- Zerreshk, four different mineralization zones can be recognized as: oxide, leaching, supergene and hypogene. Alteration zones in Darreh- Zerreshk area are potassic, propylitic and phyllic thet can be correlated with Lovell and Gilbert model. This research was carried out for mineralogical, texture and geneses studies of this ore deposit.

The study area is located in Central Iranian volcano-plutonic copper belt (Dehaj-Sarduiyeh belt) about 42 Km northeast of Shahrbabak in Kerman Province. Based on petrographic studies, extrusive rocks have the composition from trachyandesite, andesite basaltic and andesite to dacite with Eocene age. Mineralogically, the rocks contain plagioclase, amphibole, biotite and quartz. Chlorite, calcite, epidote and sericite are secondary phases. The texture of these rocks is normal porphyritic. Geochemically, the rocks mostly belonges to the calc- alkaline series. The ratio of Zr/Y>3 shows that these rocks are similar to active continental margin. Negative anomalies of Ti, Nb, P and positive anomalies Pb, K in spider diagrams are similar to subduction zone and crustal assimilation. These rocks shows enrichment from LILE and LREE elements and are relatively depleted from HFSE elements. These properties can be correlated with subduction volcanic arcs and active continental margins.

In this paper, Bi1.66Pb0.34Sr2Ca2Cu3O superconductor powders have been prepared via sol-gel and solid-state reaction methods. The structural and magnetic properties have been studied by the X-Ray diffraction (Fullprof analysis) and magnetic susceptibility measurements. The superconductivity and structural properties of the samples have been compared with the properties of a commercially available sample from Aldrich Company.

Diffraction line broadening analysis has been proved to be an extremely powerful method to study the defect properties of crystalline materials, since different types of defects produce different types of diffraction line profiles. In other word, the distribution of intensity, especially in tails of line profile, strongly depends on the crystallite size and dislocation structures. In this paper, we have applied the second and fourth order restricted moments methods and analysed the neutron diffraction data collected on Ceria in terms of crystallite size and dislocation density. The values of dislocations density and crystallite size obtained from the second-order restricted moment do not agree with those obtained from the fourth-order restricted moment. This discrepancy is not unexpected when size broadening can not be neglected, the second-order restricted moment does not give correct values for microstructure parameters and therefore these parameters must be evaluated from the fourth-order restricted moment.

In this paper, electronic structure, energy band structure and electronic density in cubic phase for semi-conductor MgSe are studied using WIEN2k package. This employs the Full Potential-Linearized augmented Plane Wave (FP-LAPW) method in the framework of Density Functional Theory (DFT) with generalize different approximations. The results showed a band gap of 2.4 eV at Γ point in the Birrouin zone. The calculated band structure and electronic structure of MgSe agree with the previous experimental and theoretical reports, as do the charge distribution indicated that the bond the Mg and Se is ionic with the one of the properties MgSe.