جستجوی مقالات مرتبط با کلیدواژه "phase diagram" در نشریات گروه "علوم پایه"

The Qori metamorphic complex in the northeast Neyriz (Sanandaj-Sirjan zone) formed due to the different metamorphic phases during the Jurassic to Cretaceous as a result of the subduction of the Neotethys oceanic crust beneath the Iran microplate. The whole-rock compositions revealed that some of the complex units formed from the metamorphism of basic protoliths. Petrographic investigations showed that the metabasites contain assemblage actinolite + zoisite + plagioclase + chlorite + epidote + quartz ± titanite in the lowest metamorphic grade (green schist facies) that was replaced by hornblende + plagioclase + garnet + clinopyroxene + quartz ± titanite assemblage at the peak of the metamorphism (lower granulite facies). Based on the thermodynamic phase diagrams (pseudosection) calculated for these rocks, the metamorphism at the green schist facies occurred at T < 550 C° and P < 5 kbar, while the peak condition occurred T and P 640 to 750 C° and 6.5 - 10 kbar, respectively. The other phase diagrams indicate that the low MgO content in the protolith and CO2</sub> content in the metamorphic fluid played an important role in the formation and stability of the metamorphic assemblages observed in the metabasites of the Qori metamorphic complex.

Migmatites are silisic rocks form in middle to high degree metamorphic territories, at lower to middle continental crust and through water producing reactions (Makrygina, 1977; Brown, 1979; Ashworth, 1985). During intrusion of Chah-Bazargan batholith in the Barrovian-type Qori-Neyriz regional metamorphic rocks at 170 Ma (Fazlnia, 2017), some pieces of these rocks were trapped in the magma and endured intense metamorphism and anatexis. They show stromatic and nebulitic magmatic structures. In the present study, the stable mineral assemblages, conditions, and factors affected partial melting in the Chah-Bazargan migmatites are investigated using phase diagrams and petrographic evidence.

The nebulitic migmatites representing the highest metamorphic degree and close and gradational relationships with peraluminous granites in the area were sampled. Petrographic studies were performed on the thin sections to determine mineral assemblages of peak metamorphic condition. The phase diagrams were calculated using whole-rock analyses reported in Fazlnia (2017) and TheriakDomino software (de Capitani, 2010).

PetrographyThe main textures of nebulitic migmatites are granoblastic and poikilioblastic, although porphyroblastic texture can be observed in places. Stabe mineral assemblage cordierite + spinel + garnet + prtithic K-feldspar + plagioclase together with dissolved silimanites and biotites inclusions represent the peak metamorphic condition. Corundum + spinel sympetectic around the cordierites also form in high metamorphic degrees (Whittington et al, 1998). With increasing metamorphic degree, the biotites and cordierites become less and the more, respectively.Phase diagramsThe P-T phase diagram was calculated in Na2O-CaO-K2O-FeO-MgO-SiO2-H2O (NCKFMASH) chemical system with fluid as pure water and in excess. According to it, mineral assemblage feldspar + chlorite + biotite + muscovite + quartz was stable at temperatures below 550 °C and represents hornblende hornfels zone of the area metapelitic rocks. Partial melting occurs at 700 that increases up to 750 °C with pressure increasing. The assemblage feldspar + garnet + biotite + cordierite + quartz melt + H2O observed in the xenoliths occurs a pressures below 5 kbar. Although, comparing calculated almandin isopleth for garnet and phlogopite for biotite with chemical compositions of these minerals represented in Fazlnia (2017) indicates that anatexis could onset in lower temperatures.According to the calculated T-XCO2 diagram, the partial melting occurs in lower temperatures with increasing in CO2 content of the fluid. Also, T-XO2 diagram show that presence of sufficient O2 in the environment could decrease the partial melting temperatre to below 700 °C. Moreover, the T-Mg# diagram (Mg# = MgO/MgO+FeO) reveals that low Mg# contents of these rocks (0.2 – 0.3) could trigger anatexis in temperatures below 700 °C.

Falling of metapelitic xenoliths in Chah-Bazargan batholith producing magma caused intense contact metamorphism and partial melting. In the peak condition, the assemblage cordierite + spinel + K-feldspar + garnet + palgiocasle together with corundum + spinel intergrowth on cordierite formed. Based on the calculated phase diagrams, anatexis occured in temperatures 700 – 750 °C and pressures less than 5 kbar, however, chemical compositions of the garnets and biotites from the xenoliths show that it could onset in lower temperatures. The T-XCO2, T-XO2, T-Mg# diagrams reveal that increasing CO2 and O2 and high FeO contents of the protolith probably triggered anatexis in lower temperatures.

Based on the density functional theory and the GGA approximation, by applying the improved potential of TB-mbJ the structural, electronic, optical, and thermodynamic properties of the XVSi semiconductor compounds (X = Co, Rh) and its [001] films Were studied. These two heusler compounds with the non-magnetic semiconductor behavior are stable in the MgAgAs-type cubic structure with F4-3m space group. Due to the good responses of the real and imaginary parts of the dielectric function for CoVSi and RhVSi in the visible spectrum range and the low electronic loss function, these two heuslers will be suitable for optical applications in this energy range. An examination of the stability phase diagram of [001] films showed that all 6 of its possible terminations would be thermodynamically stable. The electronic structure of these films indicates the emergence of half-metallic magnetic behavior only for two terms of V-Si: CoVSi [001] and   V-Si: RhVSi[001]. The responses of the dielectric function, as well as the absorption spectra of the two terms, are similar to those of the Bulk state, but with less intensity, while the electron loss in these two films is greater than that of the Bulk.

In this paper, metamorphic conditions (T, P and fluid composition) in greenschist to amphibolite facies transition zone are investigated using textural evidence, composition of the minerals and phase diagrams. Metabasites from the south of Kordestan Province were metamorphosed from sub-greenschist to upper amphibolite facies. Field observations and petrography studies show that there are some rocks containing mineral assemblage hornblende + plagioclase + epidote + quartz formed in conditions intermediate between greenschist and amphibolite facies. Electron microprobe analysis and scanning electron microscopy images reveal that the amphiboles have chemical zoning with actinolite cores and hornblende rims and these chemical changes are discontinous. The plagioclases are commonly oligoclase but there is some remnant albite. The epidotes are enriched in Fe with low clinozoisite contents. Geothermobarometry calculations using the amphibole compositions represent 423 °C and 2 kbar for the cores and 543 oC and 4 kbar for the rims. The calculated phase diagram based on whole-rock composition of a sample indicates that it was formed in 450 to 550 °C and 2.1 to 6.8 kbar that fall in the field of epidote-amphibolite facies condition. The O2 and CO2 vs. T variation phase diagrams show that O2 had a significant role formation of the mineral assemblage but the fluid contained very low CO2. Chemical discontinuities in the amphiboles and the plagioclases with different compositions demonstrate that the studied rocks formed in disequilibrium conditions.

Phase equilibrium systems are important topics in physical chemistry. As the practical training of phases contributes to a deeper understanding of this part of science, planning an agenda with a green chemistry approach and attention to human health is essential. In this study, a simple solid-liquid phase equilibrium system, palmitic acid - oleic acid, replaced the naphthalene - benzene or naphthalene - toluene system. This system not only can this system meet the educational goals of this department, but it also has the capability to recycle consumables and use waste as raw materials in other training laboratories. It is also affordable for an undergraduate training lab. From this simple experiment, the melting point of palmitic acid was 64° C and the melting enthalpy of this material was 40.69 kJ / mol. Compared to the actual values, due to the simple tools and the purity of the material used, it has an acceptable error percentage. It is noteworthy that the same uncertainty also is observed in the results of naphthalene-toluene system.

The study area is a part of the Sanandaj- Sirjan zone that is located in the NW of Azna city and NE of the dimension stone mine of Jan between 49° 11' 41"and 49° 16' 07" E longitude and 33° 36'35" and 33° 38'12" N latitude., A pluton of mylonitic granite-gneiss is exposed in the area which contains abundant tourmalines as black and patchy or subgrain association. Geochemically, the studied granite-gneiss is A-type, peraluminous to slightly metaluminous and calc – alkaline to slightly alkaline (Moradi et al., 2017). The electron microprobe analyses of the tourmalines display shorl-dravite in composition with more tendency to shorl (Moradi et al., 2015). In this paper we try to study the petrological sites of tourmaline formation with associated minerals, controller factors of crystallization using mineral chemistry of tourmaline, comprehensive behavior of trace elements in the tourmaline, synthetic phase diagrams and finally relationships between the associated minerals.
The results of trace-element and major-element analyses were obtained from one polished thin section including 2 tourmaline grains. Major-element analyses of tourmaline were obtained at Oklahama City University of America using the JEOL 8200 electron microprobe with a spot size of 5 μm and trace-element analyses were performed on just a sample by Laser Ablation-Inductively Coupled Plasma-Mass Spectroscopy (LA-ICP-MS) a 193nm ArF excimer laser ablation system (MicroLas GeoLas 200Q) in combination with a quadrupole ICP-MS (Micromass Platform ICP) at Utrecht University of Netherland. Representative EMP and LA-ICP-MS analyses of tourmaline samples are presented in Tables1 and 2.
The results of LA-ICP-MS on tourmalines of Jan mine in the North east of mylonitic granite-gneiss body show that distribution and diffusion of trace elements during the growth of tourmaline trend is positive on the plots of binary Mn versus Fetot / (Fetot ) and it represents the formation of the tourmaline mineral from the melt is along with the progress of the differentiation (Jolliff et al., 1987; Kontak et al., 2002). Also the average composition of tourmaline – bearing mylonitic granite-gneiss pluton normalized spider diagram for the studied tourmaline shows positive anomaly and negative anomaly in Eu that indicates tourmaline minerals surrounded by quartz and feldspar grains (Copjakova et al., 2013). Secondary phases such as zircon and allanite very much effect on the REE patterns (Rollinson, 1993). Therefore, in the final stages of differentiation, allanite appeared earlier than it appeared in areas without tourmaline crystalliziation and LREE soon after tourmaline crystalized and they are deposited (Cuney and Friedrich, 1987). Using a combination of phase diagrams, the controlling factors of creation of tourmaline associated with biotite-tourmaline can be assessed, and the relationship between tourmaline and associated minerals, chemistry of tourmaline – bearing granitoid pluton, and location of petrological minerals tourmaline can be sought (Pesquera et al., 2005).
The results of LA-ICP-MS on tourmalines of mylonitic granite-gneiss body in the north east of Jan mine in Sanandaj – Sirjan Zone represents tourmaline crystallization from the melt along with the progress of the differentiation. Also, the average composition of tourmaline – bearing mylonitic granite-gneiss pluton normalized spider diagram for the studied tourmaline shows positive anomaly and negative anomaly in Eu that indicates that tourmalines are surrounded by quartz and feldspar grains. According to petrographic evidence of tourmaline and biotite, it can be seen with muscovite. Therefore, where tourmaline is dominant, biotite and associated minerals are limited or do not exist. Using a combination of phase diagrams controlling factors of tourmaline crystallization associated with biotite-tourmaline can be assessed, and the relationship between tourmaline and associated minerals, chemistry of tourmaline – bearing granitoid pluton, and location of petrological of tourmaline minerals can be sought.