Iranian Journal of Crystallography and Mineralogy
Year:2007 | Volume:15 | Issue:1|Papers Count:17

In this study, strain and microstructures of quartz grains have been used for deformational analysis of thrust sheets in the eastern Alborz. Structural studies resulted in recognition of eight thrust sheets (Gorgan, Siahkhani, Tazereh, Shahdar, Anbankuh, Shirband, Anjirlu and Sefidkuh) in ascending order from north to south. Microstructural studies and strain analyses on samples across the sheets were carried out for interpretation of deformation conditions. Detail microstructural analysis of quartz grains indicated that the grains are deformed by intracrystalline deformation. Accordingly, it is proposed that the thrust sheets in the southern portion of Tazereh (i.e. Shahdar, Anban-kuh, etc) and the Siahkhani to be generated in shallow depth. However, Tazereh and Gorgan sheets postulated to have deeper origin, presumably from a depth in which the transition from brittle to ductile deformation occurs. The low values of finite strain indicate that emplacement mechanism of the sheets was assumed to be compatible with the model proposed for foreland sheets. That is, the sheets were emplaced on their basal thrust as rigid blocks. Consequently, the area of study is governed by thin skinned tectonics.

Upper Eocene shoshonitic rocks have very good exposures in the Qaleh-Khargooshi area. These rocks have a wide range of SiO2 content (absarokite to toscanite) and belong to fifth phase of Eocene volcanism in this area. Clinopyroxene is present in all members of shoshonitic group as phenocryst, but they have altered in toscanites. The study of clinopyroxenes composition shows that this mineral has been crystallized before occurrence of contamination and magma mixing. These minerals are enriched in REE, specially in LREE, and show negative anomaly of Eu. Primary magma of these shoshonitic rocks was formed by low degree melting of an enriched upper mantle source, and experienced the contamination and magma mixing during ascending through the thick continental crust.

Glauconies are typically sand-sized and ellipsoidal green pellets in shape that have an earthy or lustrous appearance and is one of the major components of all siliciclastic facies in the Aitamir Formation. Studies of glaucony in this Formation led to identification of two types (allocthonous and autochthonous). Based on maturation, the glauconies in the Aitamir Formation can be divided into slightly evolved, evolved and highly evolved. Study of cutting samples from Gonbadli well-9 and Khangiran wells-6 and 35 show that morphology of glaucony is useful for reservoir potential quality assessment. Rate of compaction and types of grains associated with glaucony can control the morphology of glaucony and its effect on reservoir quality. Glauconies in the Aitamir Formation are autochthonous and   types II and III. Therefore these sandstone units have suitable reservoir potential. This study showed that the morphology of glaucony can be used for evaluation of reservoir quality.

Acid and saline seeps are an increasing problem in most parts of the World and Australia as well. They are areas of bare soil or reduced crop production. Recent laboratory, field, and remote sensing studies have explored the use of visible to short – wave infrared (VIS- SWIR; 400-2500 nm) reflectance data for characterizing the mineralogy of mine wastes, surface mineralogy of acid-saline affected areas and for evaluating waste impacts on hydrologic and biologic systems. Seasonal surface sampling through topo-sequence of the study area and analytical results of XRD, SEM and VNIR indicate that morphological and mineralogical changes within a natural acid saline seep affected landscape revealed that seasonal differences in surface mineralogy. The visible near infra-red (VNIR) reflectance spectra of the surface minerals from unaffected, salt crusted and acid seep areas, showed spectral differences expressed in the VNIR region due to absorption bands of iron oxides and hydroxides. This difference in the surface mineralogy during summer can be readily identified via multi-spectral and hyper-spectral remote sensing methods, and therefore regional mapping com be done for identification of surface mineralogy due to spatial and temporal distribution of acid seeps, which has caused degradation of agricultural lands is suggested.

Exposed rocks at Hired gold-tin prospecting area are mainly Mesozoic and Paleocene sedimentary and Eocene volcanic rocks. Oligo-Miocene Granitoids are intruded the Eocene and older rocks. Based on petrology and physical characteristics of rocks, granitoids are two types: 1) S-type and 2) I-type. Mineralization is seen as stockwork, fault mineralized zone, skarn and in replacement. Stockwork mineralization is exposed in the eastern part of target (1) and it is found within S-type granite and silicified – tourmaline rich shale. Hypogene minerals are: pyrite, arsenopyrite, pyrrhotite, chalcopyrite, ± galena, ± sphalerite, tourmaline, quartz, chlorite, calcite and sericite. Gold is mainly found in veinlets contain sulfide, quartz and tourmaline. Based on S-type granite, stockwork mineralization, tourmaline alteration and Sn anomalies (581 ppm), Hired is a Tin – Gold mineralized system. Geochemical data from drill holes in target (1) and (3) indicate that the high value of Au, Ag, Cu, Zn, Pb, As and Sb are found mainly between depth of 50 to 100m in eastern part of target (1), therefore this area is close to the source of fluid. Tin – Gold mineralized system at Hired is associated with S-type granite.

Cretaceous succession of Bashm mountain, located in south of Centeral Alborz, is a part of Alpine-Himalayan orogeny belt. In this paper, Cretaceous at the age of Albian-Turonian which consists well-beded dolomite and limestone, cherty limestone and massive limestone and which have become host rock for Lead and Zinc deposits is studied. 6 profiles of this Cretaceous were selected from Reza-Abad, Heydar-Abad and Reza-Barak abandoned mines, and Bozmolla occurrence. Their outcrops thickness varies between 290-540 m. Petrography of the studies area revealed that the sediments are consist of 15 carbonate facies. Most likely this facies have been deposited in inner, outer and mid ramp. Beside this, tectonic characteristics of forland basins which is dominant in Cretaceous time for this area, has revealed the presence of carbonate ramp. The most important diagenetic processes in these studied facies were biogenic processes, compaction, dissolution, cementation, neomorphism, dolomitization, dedolomitization and silicification. The most important mineralization processes related to porosities were found in intergranular, intercrystalline (in dolomite), joints, faults and karsts. Formation TD-ICP chemical analysis of Ca, Mg, Sr, Mn, Zn, Pb elements and INAA chemical analysis of Fe, Na elements for 6 samples of Cretaceous showed decreasing in Sr and Na and increasing in Fe and Mn elements. These result may suggest, the comparison of aragonites of warm areas and calcites of recent temperate during diagenes process. Comparing values of these elements with warm water Ordovician Gordon Limestone (Tasmania) and Mozduran carbonates (Upper Jurassic) showed mineralogy similarity between shallow carbonates of studied area and those which is mostly observed as an indicator of mineralogy of primary aragonite.

Amphibolites are one of the metamorphic rock units of Jandaq ophiolite and exposed in a considerable volume. These rocks are metamorphism products of basalts, pillow lavas and diabasic dikes of Jandaq ophiolite. Amphibolites contain amphibole, plagioclase, garnet, alkali feldspar (orthoclase), magnetite, biotite, muscovite, sphene, quartz, epidote and calcite minerals. These rocks contain very good lineation and foliation. By metamorphic differentiation, mafic and felsic minerals are separated in some locations. Metasediments that are present in Jandaq area were originaly sedimentary cover of Jandaq ophiolite, before the metamorphism has taken place. Mineralogical studies, hornblende barometry, and amphibole – plagioclase thermometry, conclude that the metamorphism of Jandaq ophiolite amphibolites occured in upper part of amphibolite facies condition (7.98 to 9.01 Kbars and 714 to 737oC). Temperature of metamorphism in Jandaq ophiolite amphibolites is higher than amphibolites that are in Jandaq metamorphic rocks (8.58 to 10.87 Kbars and 619 to 668oC).

In this work, the epitaxially grown, lattice–matched p-Si/Si1-xGex/Si inverted remote doped structures have been characterized using X-ray and electrical techniques. The Si cup layer thickness (lc) and Ge content (x) have been determined from computer simulation of intensity and angular sepration of (004) peaks observed in the X-ray diffraction pattern due to misorientaion of corresponding Bragg planes of Si and SiGe layers. On the other hand, a quasi two dimensional hole gas (2DHG) is formed in the compressively strained alloy of these structures and its areal density (ns) has been measured by Hall expriment and can be controlled by applying a voltage (Vg) to the artificial gate. In the electrical technique, x and lc chractristics have been obtained using theoretical calculations of the linear dependence of ns versus Vg. Finally, the uncertainity and partial inconsistent of the results have been explained in terms of the affecting effects.

Detailed studies on micro-texture and microprobe analysis of Fe-Ti oxides from Qareaghaj mafic-ultramafic intrusion (QMUI) is the basis of this investigation. The QMUI is mainly composed of non-mineralized mafic and Fe-Ti-P-rich ultramafic rocks (FTP). The FTP with high proportion of ilmenite (~11-19 modal %) and magnetite (~2-13 modal %) show an unusual bulk composition. Fe-Ti oxides are divided into three distinct generations on the basis of their micro-texture: 1) small-sized rounded to ellipsoid-shape inclusion in olivine and clinopyroxene, 2) coarse interstitial grains and 3) late stage veinlets. The ilmenite grains (0.1-2mm) commonly contain fine hematite lenses arranged in [0001] planes. Primary Ti-magnetites contain ilmenite lamellae along the [111] planes and exhibit wide variety of exsolution textures (e.g., trellis- and sandwich-types). Ilmenite in FTP show Xilm range from 0.82-0.91 and has high MgO (0.82-2.38 wt %). Most Ti-magnetites (bulk composition) have low Xusp (0.03-0.13) and therefore high Xmag (0.79-0.93). Two oxide geothermobarometer in the ILMAT program, resulted in re-equilibration temperature range of 450-700ْ C and ƒO2 (nearly -19±3) during subsolidus cooling for FTP rocks.

In this research the  ion exchange potential of natrolite towards K+, Tl+, Cs+, Ca+2, Ni+2, Cu2+, and Co2+ in their melted salts was investigated. The effect of temperature, reaction time and zeolite to salt ratio on the exchange relation was studied. The exchange of Ca2+, Ni2+, Cu2+, and Co2+ was negligible and was equal to 2.59, 6.29, 3.14 and 5.04 percent respectively whereas the exchange of K+, Tl+, Cs+ was relatively high and equal to  82.36, 66.67 and 42.98 percent respectively.

The crystal-chemistry of the plagioclase, alkali feldspar, biotite, amphibole and whole rock geochemistry of Akapol granitic massif are investigated in this paper. The chemical composition of biotites and amphiboles ploted in the annite-siderophyllite, magnesiohornblende and actinolite fields, respectively. Comparison of the chemical composition of biotites and amphiboles with similar minerals from the California granitic batholith indicate that the monzogranitic unit of Akapol belongs to the strongly contaminated I-type granites. Accordingly, these rocks are highly contaminated and may have derived from upper mantle and/or lower crustal sources. They have experienced magma mixing or are affected by contamination with upper crustal rocks. These results are consistent with the curve like logarithmic diagrams of compatible/incompatible elements; the presence of the sieve, poikilitic and rapakivi textures; the partial absorption of the plagioclase phenocherists; the presence of mafic microgranular enclaves and needle apatite in the samples. Based on this study, two types of plagioclase in monzogranitic unit can be recognized in the monzogranitic unit: the first generation occur in the alkali feldspar phenochrysts and the second generation is in the form of covering crystals in rapakivi and sieve textures which probably formed during magma mixing.

The studied intrusions with parallel northwest – southeast trend, are located in southwest of Robat Village, Shahr-babk. General exposure of the northern trend is massive and consists of urallitized gabbro, hornblende gabbro, olivine gabbro, anortosite and plagiogranitic dikes and are highly altered. The composition of rocks in the southern trend consists of dunite, pyroxenite, olivine gabbro and troctolite and is very fresh and has cumulate textures. On the base of chemical analysis, using of ICPAES and ICP-MS method, these rocks are located in the low potassium tholeiitic filed. Also by using of tectonic setting diagrams, the studied intrusions display extensional marginal basin characteristic. The rare and trace elemental pattern of these rocks have a descending trend from low to high elements and the examples of anomalies are the positive crest of Sr and the negative crest of Nb. Also the study of REE trend show that the tholeiitic magma may have formed in the upper pridotitic mantle.

CdS thin films were deposited by thermal evaporation in a vacuum of ~ 10-5 torr at room temperature. Samples were subjected to annealing in the range of temperatures 100-300oC for 1 hour in air. The crystal structure of CdS films was characterized by XRD technique. Only hexagonal phase with the preferred (002) plane was found in CdS films.

Mafic rocks including basalts and gabbros are the main constituents of Birjand ophiolites. They are found in several places and show low grade metamorphism in the field and under the microscope. Chondrite-normalized REE patterns for basalts and gabbros indicate that these rocks are transitional-enriched to depleted mid-oceanic ridge basalts respectively. Otherwise, N-MORB normalized trace elements patterns for basalts and gabbros are considered to be enriched in some LIL elements. Depletion in Ti and also in Nb (in gabbros) is other characteristic of these rocks. Therefore an incomplete short-lived subduction regime for generation of those heterogeneities can be suggested. The primary mantle-normalized trace elements pattern for Birjand harzburgite also confirms some LIL enrichments.

The Kashmar granitoid (43.5–42.4 Ma) forms an extensive part of iron–oxide type magmatic belt in northern side of the Doruneh Fault. It includes plutons of tonalite, granodiorite, granite and alkali feldspar granite which are metaluminous (ASI ≤ 1) in nature. They contain dominantly felsic minerals, representing I–type granites with low–temperature and low–pressure characteristics. According to microscopic studies and electron microprobe analyses, all amphiboles in Kashmar are monoclinic calcic hornblende which is common mafic mineral in distinction of I–type granites. The calculated structural formula for Kashmar amphiboles show characteristics of magnesio-hornblende as follow:Ca(M4)+Na(M4)>1.34,Na(M4)<0.67,Mg*>0.50,(Na+K)A<0.50,Ti<0.50apfu.They are low in Al2O3 and TiO2, high in Mg* (0.6–0.75), extremely low in AlVI (<0.1 apfu) but significantly higher in Fe3+, features indicating low temperature, low pressure and oxidized conditions. Using appropriate thermo barometers for Kashmar amphiboles, average temperature of 650oC, pressures of ≤ 3 kb and logfO2 = –16.59 to –19.40 were calculated. These results define a thermal boundary of ~700oC between felsic and mafic low–temperature I–type granites.

In this study, the YBa2Cu3O6+x samples at temperatures 200 and 300oC, as the value of x ( the oxygen content in 0the basal plane)  increased under nearly thermodynamical equilibrium condition, the structure changed from the well- known tetragonal (T) to a mixed-phase (T+OII) region (orthorhombicII phase is a superstructure). This mixed-phase region suggests a first order T/OII phase transition with the expected linear change in the volume fraction of each phase (phase lever rule). The existence of a stable whole OII phase region around x» 0.7 at 300oC, which is indicated by extrapolation, implies a substantial correction on the YBCO’s structural phase diagram. From the full analyses of the data by Reitveld Method, the possibility of the formation of another superstructure along the c direction can not be ruled out (broadening of [00l] reflections which, presumably comes from anti phase boundary effects). By inserting the structure factor of the OII phase, we have been able to study this phase quantitatively.