فهرست مطالب m rahgoshay

Narigan area in the southern part of the Bafq-Saghand metallogenic zone in Central Iran is a host of davidite-bearing quartz veins. Davidite is an important key mineral for exploration of not only uranium but also REE's in Central Iran. Narigan granite in the Narigan area is characterized by high-K calc-alkaline nature and its parental magma was partially contaminated by the Precambrian crust. The REE pattern of quartz veins is brought about by REE contents in davidite. The homogenization temperatures of vapor-liquid-solid (V-L-S) fluid inclusions in quartzes are >500˚C in quartz veins. Furthermore, the ∑REE contents (71910 to 90292 ppm) and U/Th ratios (<1000) in the studied davidites indicate upper 450˚C temperature for the generation of them. Based on the similarity of REE pattern of davidite to REE pattern of oxide-uranium minerals in the vein-type ores (characterized by negative Eu anomaly and high LREE/HREE ratio) as well as achievement of the homogenization temperatures for fluid inclusions and davidite formation; mineralization of this mineral can be related to granite related vein-type uranium deposits.

The quest for technology to build submarines equipped with an air-independent propulsion system is increasing. PEM fuel is one of the best options for a submarine power supply system. Durability is one of the main competition factor of polymer fuel cell technology with other power generation technologies. Regarding the importance of polymer fuel cell stack stability tests, for the first time in Iran, performance of polymer fuel cell stack was evaluated over a period of 200 hours. Durability test condition was determined based on universal well-known protocols and according to the intended use, in three sections: assessment of polarization curve, electrochemical impedance spectroscopy and fluoride ions (Fenton test), pH, and electrical conductivity of the anode and cathode side discharge water changes in the intervals of 25 hours. Based on the results, it was found that oxidant shortage, accumulation of water particles in the third cell, and the formation of droplets of water in needles, caused by the design of gas manifolds as well as the applied operation conditions, act as reversible factors for the performance loss of the fuel cell stack. Analyzing the electrochemical impedance spectrum, it was determined that the ohmic resistivity remained almost constant over the 200 hour test (1500mΩ/cm2). The higher charge transfer resistance in the third cell than the others can be attributed to the accumulation of water in the last cell. Investigating the fluoride ions, pH and conductivity of the outlet water from the anode and cathode side of fuel cell stack, it was revealed that performance during 200 hours does not have an effect on the membrane chemical structure, and the chemical degradation of its structure will take place at longer times.

The article aims in the studying of thermal-hydraulic simulation of the VVER-1000 reactor core fuel assemblies’ reaction to the mass flux changes which are caused by the lose of coolant accident and its sudden pressure drop. The analysis of mentioned accident is performed in concise periods (mili second) by the use of the sound effect. Time-related thermal-hydraulic equations were analyzed by the method of a compressible fluid in a single heated channel and were evaluated by the results of the mentioned transient, in a PWR reactor. The mentioned transient was simulated in RELAP5 code and results were compared to the previous ones. Then, 28 reactor fuel assemblies were studied, considering the 1/6 symmetry of VVER-1000 reactor and unique features of every assembly. Mass flux drop was happened the end of the channel, after a few seconds. It was observed that mass flux is at dependent on the role of every assembly in the production of core heat power. The acoustic effect reveals some of the perturbations in mass flux changes, considering every fuel assembly features.

The Sanandaj-Sirjan zone is a NW-SE trending orogenic belt immediately north of the Zagros suture, which represents the former position of the Neotethys Ocean. This zone includes a Pan-African basement similar to the various terranes to the north in Central Iran. The crystalline basement is nonconformably overlain by the Paleozoic-Triassic platform sediments, which in turn are unconformably covered by sedimentary and volcanic strata of the Jurassic arc. The Cretaceous carbonates overlie the older rocks with a regional angular unconformity. The Chadegan high-P metamorphic complex exposed along the upper Zayanderoud and consists of quartz schists, amphibolites, gneisses, marbles and eclogites, and is nonconformably underlain by the fossiliferous Permian carbonates, suggesting a Pre-Permian age. In this paper we present new data including whole rock major and trace element compositions, mineral chemistry and radiogenic isotope data for the selected metabasites. The high field strength element (HFSE) abundances and Sr-Nd-Hf ratios suggest tholeiitic compositions with distinct within plate affinity rather than MORB. We also present new 206Pb/238U zircon age of 568.0 ± 5.3 Ma for a crosscutting orthogneiss reconfirming the Late Neoproterozoic age for the granitic protolith. We conclude that previously presented Ar-Ar ages for white-micas in eclogites and gneisses are indicative of metamorphic crystallization due to the regional plutonic arc activity. A comparison is made with the well-investigated Menderes Massif in Turkey where an orthogneiss-metabsite association with similar age and chemistry makes extensive exposures. We also conclude that this rock complex is extended from Zayanderoud to Khoy and beyond to the Menderes Massif and discuss the connection with the final amalgamation tectonics of the Gondwana near the beginning of the Cambrian Period.

The Zaroo Cu-skarn is located NW of Yazd province, within the Cenozoic magmatic belt of Central Iran. The widespread rocks in the region are Eocene age volcanic with granitoids intrusives. The Cretaceous limestones in western parts of West Zaroo are hosted by skarn – marble mineralization. The skarns are distal type and are characterized by assemblage: Clinopyroxene, garnet, ilvaite, vezovianite, termolite, epidote, chalcopyrite, magnetite, calcite and quartz. The paragenetic relationships of these minerals have revealed a polygenetic nature of skarn assemblage reveal a polygenetic nature. Black crystals and masses of ilvaite have a close association with hedenbergite clinopyroxene and andradite garnet zone, likely as replacement bodieds. The formation of ilvaite is related to following reactions: Andradite + Fe (OH)2 + CO2 = ilvaite + magnetite + quartz + calcite + H2Hedenbergite + magnetite + Fe (OH)2 = ilvaite The early skarn minerals are formed at 550 ºC and the decomposition of early minerals to formation of final hydrous assemblages started below 470 ºC in fO2.