Iranian Journal of Crystallography and Mineralogy
Year:2013 | Volume:21 | Issue:2|Papers Count:18

In this work, Ce-YIG nanoparticles with nominal composition of Y3-xCexFe5O12 (x=0, 0.1, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were first fabricated by sol-gel method and then the influence of the cerium substitution on the structural and magnetic properties of garnet nanoparticles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, vibrating sample magnetometer (VSM) and Mossbauer spectroscopy. The XRD results showed that the maximum amount of the Ce3+ substitution in YIG structure is x=0.6. Magnetic measurement shows that room temperature saturation magnetization of nanoparticles increases up to x=0.3 firstly and then decreases by increasing Ce content. The variation of saturation magnetization can be explained according to mossbauer studies. The mossbauer analysis showed that due to Ce substitution a and d sub lattice split into two pairs of distorted and undistorted sublattice. So reduction in saturation magnetization is disscused.

Thomsonite along with other zeolite minerals such as natrolite, mesolite, analcime and rarely stellerite in cavities and veins of mafic alkaline lavas in Hormak area, north of Zahedan, eastern Iran, is formed in there distinct habits of blocky, bladed, and waxy-growth.Chemical composition of Hormak thamsonite is reasonably comparable with those of other reported thomsonites. Si/Al ratio of the thomsonite is 1.16 on average. The minerals show high Sr contents, up to 2.94 atoms per formula unit. Na and Ca are the main extra-framework cations with average values of 4.73 and 6.01, respectively. Calcium was most probably provided after either alteration of groundmass component or dissolution of secondary calcite, while sodium was mainly provided from saline and alkaline lake waters where the magma was poured.Hormak thomsonite was formed at low temperatures, about 100±40 oC.

The study area is located at the Soghanchi village (east of Miyandoab city, NW of Iran). The Oligocene age Soghanchi stock is intruded into Permian carbonate rocks during Pyrenean orogenic epoch. Petrographically, the main minerals of this intrusive are plagioclase, biotites, pyroxenes, olivines, hornblendes, and alkali-feldspars. The microscopic and geochemical assessments of intrusive, show gabbro-dioritic, monzo-gabbroic and monzonitic composition with high potassic- calc-alkaline to shoshonitic and meta-aluminous characters.Based on this investigation, the Soghanchi pluton has formed in a continental arc setting.Intrusion of this stock into the Permian limestones, results in different degrees of recrystalization and skarnification. The Soghanchi calcic skarn is mainly composed of anhydrous calc-silicates, retrograde metasomatic products, some calcite, and quartz. Magnetite and minor hematite are the main metallic minerals in this area. Physco-chemical investigations showed 450-650oC for skarnification (prograde stages) and 400-450oC for retrograde metasomatic event and iron mineralization.

The studied area is located about 35 KM north-west of Rafsanjan (Kerman Province) and belongs to Hezar volcanic complex (in Uromieh-Dokhtar volcanic belt) and consists of Eocene folded lava flows (basalt, basaltic andesite, andesite) and pyroclastic rocks. Plagioclase phenocrysts show evidences of disequilibrium textures such as sieve texture, resorption and oscillatory zoning. These features can be formed by magma mingling, PH2O variations and decompression, as magma rises to the surface. Geochemical Studies indicate that lava flows belong to calc-alkaline magmatic series and their parent magmas have not extensively fractionated. The highly enrichment of LREE compared to HREE, high contents of LILE to HFSE and significant anomalies of Nb, Ti and P suggest a subduction-related volcanism.Chemical composition and phenocryst assemblages of these rocks indicate that these magmas probably derived from mantle, and then, have been erupted in a form of continental volcanic and they have passed some stages of their crystallization’s history in the crustal reservoirs During these stages, crustal contamination affected them.

Neyzar iron deposit is located about 50 km southwest Mashhad, northeast Iran. It was developed as layered and discontinuous lenses in a fault zone within quartz-arenite and sublitharenite sandstones of Lalun Formation (Lower Cambrian). Mineralographical studies show that hematite is the principal iron ore mineral accompanied by goethite and lesser amounts of pyrite. Microscopic examinations confirm the presence of skeletal, relic replacement, marginal replacement, and pseudomorphic textures within the ores. Based on petrographical data, two series of alteration minerals, hypogene (sericite, pyrite, pyrophyllite, barite, chalcedony, and calcite) and supergene (goethite, jarosite, gypsum, limonite, and hematite) were developed in this deposit. Based on the results obtained from field works, mineralographical and geochemical studies, it appears that the evolution of the studied ores is genetically related to the host rocks.Both hydrothermal processes and fault systems (existing in the host rocks) played important roles in leaching of elements and depositing of the ores. Results of chemical analyses show that the REE values vary in the iron ores from 6.97 to 18.26 ppm. Eu and Ce anomalies in the ores are within the ranges of 0.01-1.36 and 0.28-1.89, respectively. Geochemical considerations reveal that distribution of rare earth elements within Neyzar iron ores was controlled by pH, abundance of complex-forming ions (CO32-, F-, Cl-, PO43-, and SO42-), scavenging processes, and fixation in neomorph mineral phases.

The hydrothermal method due to advantages of low reaction temperatures and achieving fine particles in synthesized samples was used. Li2SiO3 has orthorhombic structure with Cmc21 space group and cell parameters a=9.392, b=5.397 and c=4.660A. The structure, size and morphology of nano particles were investigated by XRD, FT-IR and SEM analysis methods. In addition, the cell parameters of lithium metasilicate nano particles were determined by CELREF software version3. Optical properties of synthesized silicates were investigated by UV-vis and Pl analysis methods.

The ophiolitic complex of Sahneh-Harsin is composed of rock units such as gabbro, basalt, diabasic dikes, diorite and plagiogranite. The geochemical studies show that primitive magma has been sub-alkaline tholeiitic Mg-rich and K-poor. These data show enrichment of light rare earth elements (LREE) and depletion of heavy rare earth (HREE). The ratio of NbTa in the basalts is between 16.19 and 18.88; therefore these high amounts indicate the magma derived from the contaminated mantle. Lithological and geochemical studies show that there are genetic connections between the rocks and their origin from the same magma. Magmatic contamination and differentiation had important role in evolving of rocks and they formed during melting of more than 16% of a garnet peridotite. Petrogenesis of pillow lavas shows they are of MORB type; based on spider diagarms this complex is formed from a oceanic tholeiitic magma of EMORB Enriched (MORB).

Khut skarn deposit, located in the 50 Km NW of Taft, has formedin the result of Khut granodiorite intrusion into the upper Triassic impure carbonate rocks.Field evidences and mineralogical studies show Khut skarn is calcic type and exoskarn is the major skarn zone in area which associated with ore mineralization.The microprobe analyses show that there are two major types of garnet at garnet-pyroxene skarn zone: (1) Anisotropic garnets with 51.76-63.17 mol% grossular and (2) Isotropic garnets with 17.77-28.10 mol% grossular. Petrographic observations of anisotropic garnets show marked zoning and sector twining.Study of garnet zonation with electron microprobe in Khut skarn show chemical variations in Ti, Al, Fe, Mn, and Mgvalues form core to rim. In various zones, variations of Al, Ti and Fe are repeated alternatively. Hence, garnet zonation is caused by alternative variations of Fe, Al and Ti in composition of the fluid phase. This indicates multiple pulses of hydrothermal fluid flow.

Mishan Formation with grey marl and sandy lime composition is one of the most important raw material for cement production. Remote sensing is approved as a low-cost and rapidly developing method in exploration of mineral resources. The sub-pixel mixture tuned matched filtering (MTMF) and the whole-pixel spectral angle mapper (SAM) algorithms were used on 6 and 9 bands of the ASTER data from Mishan type section and a part of outcrops of this formation in Jamileh village, northern Boushehr province, to determine the abundance of clay (illite) and carbonate (calcite and dolomite) minerals in marl. The image end members were extracted using the Sequential Maximum Angle Convex Cone algorithm and the Iterative Spectral Unmixing; and the abundances of clay and carbonate of marl were detected using the extracted end members. Although the output results of algorithms enhanced similar districts for the dominant minerals of marl, the sub-pixel outputs determined pixels with high abundances of carbonate, comparing to illite. The results of sub-pixel processing on 6-bands data set highly corresponded field observations, spectral characteristics, and the XRD results of samples, making this method as an efficient approach for exploration plans.

Dust is one of the environmental problems in Kerman city. Due to the major aspect of mineralogy in environmental studies, mineralogy and chemical studies of dust in different regions of the city performed by microscopic thin sections, x ray diffraction (XRD) and ICPMS.In all areas of the city, minerals such as calcite, quartz, feldspar, pyroxene, micas, Jaffeite, gismondine and clay mineral were most abundant in the dust. Decreases of size and roundness of quartz and Calcite from west to east, indicating the major source of dust is from the west of city. Jaffeit in dust of the central region may be originated from the cement factory in the west and abundant of gismondin (a zeolite) in the north of city dust can be orginated from playa surfaces. Chemical studies indicating high concentration of pb, As, Cr, Sn, Zn, Cd in the dust of western region may be originated from anthropogenic activity, industrial such as cement factory and traffic.

The Bayazeh ophiolite, with Paleozoic age, is located in the eastern margin of the Yazd Block (Central Iran). This ophiolite consists of serpentinized peridotites, metagabbro, ultrabasic metamorphosed dikes, metapicrite, serpentinite and metalistvenite. Rock forming minerals of the metapicrites in the Bayazeh ophiolite are olivine (completely altered to serpentine), clinopyroxene (diopside, augite), phlogopite, apatite, opaque (ilmenite, magnetite), amphibole (tremolite, actinolite, and tremolitic hornblende), chlorite (clinochlor, penninite) and prehnite. Main textures in these rocks are granular and poikiloblastic. Chemical composition of clinopyroxenes indicates that crystallization of clinopyroxenes has occurred during ascending of the magma. Geochemical analysis of the Bayazeh metapicrites conclude high values of MgO (25.8 to 28 wt %) and low values of SiO2 (37.5 to 39.4 wt. %) that reveal their ultramafic nature.Presence of phlogopite as a primary hydrous mineral together with geochemical criteria of the studied rocks, reveal amphibole presence in the source rock of the Bayazeh metapicrites.Amount of REEs, enrichment from HFSEs and LREEs associated with high value of Mg# and Ni in these metapicrites indicate metasomatic enrichment of a mantle source. Metasomatic enrichment of this mantle source could be affected by fluids related to the Paleo-Tethys subduction. Geochemical characteristic of metapicrites in the Bayazeh ophiolite show that these rocks generated from 40% of partial melting of a metasomatized asthenospheric spinel lherzolite.

Outcrops of the Upper Ordovician igneous rocks, as basaltic lava and microgabbroic dyke and sill, present within the Abarsej and Ghelli formations in north and southwest of Shahrood. These rocks have basaltic, trachybasaltic and basaltic trachyandesitic composition with alkaline nature. Their parallel patterns on the primitive mantle and chondrite normalized spider diagrams indicate the common source of these rocks and the role of fractional crystallization in their generation. These rocks plot on the field of alkali basalts related to intracontinental rift on various discrimination tectonic setting diagrams. This tectonic setting corresponds to paleogeography of the Alborz during early Paleozoic (occurrence of Turan intracontinental Paleotethys rift) in Ordovician- Silurian times. Geochemical investigations indicate the magma forming of these basaltic rocks generated from 14-16% partial melting of an enriched garnet peridotitic astenospheric mantle source in 100-110 km depths. This magma has not contaminated by continental crust during ascending to the earth surface.

The Kermanshah Ophiolite Complex (KOC) lies in the structural - tectonic zone of western Iran in northern part of Zagros main thrust and is a part of highly dismembered Kermanshah - Panjvin Ophiolitic belt. The best outcrops of the sheeted and isolated dykes in this complex are present in south of Sahneh area. They are basic in composition. The geochemical studies show parent magma is in its initial melt stage with LIL elements enriched signature. Also, this magma belongs to high Mg and low K, tholeiitic sub alkaline series. The patterns of incompatible trace elements demonstrate an island arc affinity for these dykes. The N-MORB- normalized multi-elements plots indicate nearly flat patterns for HFSE. Geotectonic diagrams reveal transitional characteristics between mid-oceanic ridge basalts and island-arc tholeiites. Therefore, the dykes of the KOC may be originated in a back-arc basin tectonic setting.

Evaporite minerals form when evaporation is more than precipitation. One of the most important evaporate minerals are calcium sulfate, that have extensive distribution in geologic time. Sedimentary and digenetic processes, operating within different environments such as shallow margins to deep water, have an important role in the formation of these minerals. Due to the presence of anhydrite as a cement, as well as distributeon of this mineral in sedimentary facies of the Asmari Formation in Mansouri oil field, this mineral can affect on the reservoir quality in the studied reservoir. In this study, the fabric of anhydrite in production zones in the Mansouri oil field has been investigated. Microscopic studies led to the identification of 11 microfacies that are formed from sabkha to open marine environment. Note that the textures of anhydrite is partly related to sabkha and lagoon environments (felted fabric and acicular crystals) and partly are related to digenetic processes operated in shallow to deep burial (coarse crystals of anhydrite with cleavage) in grain-supported facies. Other anhydrite textures identified in the Asmari Formation include layers, poikilotopik, pore filling and inclusive, nodular, nodular - burial, scattered and fracture filling.

The study area is located in northwest of Birjand, northern part of the Sistan suture zone in eastern Iran. There is well preserved outcrops of an ophiolite melange in this area. This complex is composed of harzburgite, layered gabbro and spilitic basalt with flysch type rocks.Microprobe analyses of olivine, clinopyroxene, orthopyroxene and spinel in harzburgites show that olivine is forsterite (Fo90.15-Fo90.75), clinopyroxene is diopsidic augite (Mg#=95.8), orthopyroxene is enstatite (Mg#=91.58), and spinel (Cr#=41) is Al-Cr bearing type. Based on thermobarometry of clinopyroxene and orthopyroxene minerals, crystallization temperature of peridotites is 1016±100 oC at 25 Kbar pressure.

Bagham pluton is located in 23 km of the southeastern of Ardestan and it is near the main road of Esfahan-Ardestan. The study area is a part of central Iranian zone and Urumieh- Dokhtar magmatic belt. Minerlogically, the rocks include plagioclase, pyroxene, amphibole and opaque. The rocks have SiO2=44.75-47.08 and occur in gabbroic field. The chondrite normalized REE pattern show low enrichment in the LREEs relative to HREEs. The negative Nb and Ti anomalies in primitive mantle and MORB-normalized multi-element diagrams of the rocks are characteristic of island arc magmas. Also, enrichment in LILE and depletion of HFSE may indicate a subduction-related tectonic setting. Moreover, on based of the values of specific ratios (e.g. low Ti/V, Ti/Sc and high CaO/TiO2 and Al2O3/TiO2) can define a depleted or refractory magma source and on other hand, demonstrate the similarity of the mentioned rocks to tholeiitic rock with low boninitic affinity.