جستجوی مقالات مرتبط با کلیدواژه "origin" در نشریات گروه "زمین شناسی"

due to the increasing progress of today 's technology and the use of rare earth elements and strategic elements of these elements as well as the need of the country 's industry to these elements, the study and discovery of these elements is of great importance. Senj polymetal deposit is located 57 km northwest of Karaj city in Alborz province and in the central part of Alborz magmatic arc. In this region, the magmatic mass from monzonite to monzodiorite is of Oligocene age and due to the Middle Alpine orogeny phase, it has been injected as a sill into the igneous rocks of tuff to andesite-tuff porphyry. The geochemical investigations of the deposit show that the concentration of some elements such as molybdenum, copper, gold and rare earth elements is exceptionally high. One of the remarkable points in this deposit is the high anomalies of light rare earth elements (Ce, La) as well as Y, Th elements. The concentration of La in high grade samples varies from 400 ppm up to 23700 ppm and Ce from 420 up to 37900 ppm. Rare earth elements are mainly concentrated in two minerals, allanite and apatite. The comparison of 34S δ sulfur isotope changes in the Senj deposit with the ore-forming type of sulphide deposits showed that it is most compatible with volcanic-hydrothermal deposits.

Carbonate deposits of members 1 to 2 of the Mila Group (Middle Cambrian) in Central Alborz that call the Deh-Sufiyan Formation in this research, were studied in Shahmirzad, Tueh-Darvar, Mila-Kuh and Deh-Molla sections. The Unit 2 of Deh-Sufiyan Formatrion in Central Alborz of Northern Iran consists mainly of shallow marine carbonates and contains a variety of limestone conglomerates. Limestone conglomerate is an important component of Unit 2 of Deh-Sufiyan Formatrion, but its origins remain enigmatic. These limestone conglomerates have a diverse set of characteristics that range clast to matrix supported with scattered flat pebbles. These conglomerates are largely comprised of oligomictic, rounded lime–mudstone clasts of various sizes and shape (equant, oval, discoidal, tabular, and irregular). According to composition and characteristic sedimentary structures and fabric, limestone conglomerates in the Unit 2 of Deh-Sufiyan Formatrion consist of: (1) Intraformational limestone conglomerate beds were formed by depositional processes (2) Limestone pseudoconglomerate beds were produced by diagenetic processes. The common characteristics of the Unit 2 of Deh-Sufiyan Formatrion pseudoconglomerates, such as oligomictic lithology of lime–mudstone clasts, mosaic fabric, disorganized/edgewise fabric, variable and gradational fabric, transitions adjacent or underlying facies and the complete lack of depositional structures, are typical of pseudoconglomerates formed by early diagenetic sediment deformation under shallow burial conditions. These characteristics are different those of intraformational limestone conglomerate showing primary depositional features such as normal or inverse grading, internal stratification, (hummocky) cross-stratification and sharp erosional bases. Diagenetic conglomerates in ribbon rocks resulted soft-sediment deformation of ribbon rocks during early diagenesis. In contrast, the dimension and thickness, sizes of the clasts, clast-rich beds, size ingredient of matrix, tendency to amalgamate with amalgamation scours within depositional conglomerates suggest that high energy and strong erosion above storm wave base was responsible for the disintegration of the carbonate material.

In the following research 19 samples were collected from dust of the main streets of Ray City in dry conditions of the summer and wet conditions of the winter in heavy traffic time of evening. The samples were analyzed by ICP-OES for 49 elements such as Pb, Zn, and Cu, As, Fe, Ni, Cr, Cd, Mn and Bi. Also, 15 samples were analyzed by XRF to determine major oxide and minor elements. The enrichment factors and Muller geoaccumulation index were calculated for these samples. Data processing shows enrichment in Ag ٬Pb ٬Zn ٬ Cu ٬As ٬S ٬Ba ٬U ٬Zr ٬Sr, Hf levels relative to earth's crust. The results of enrichment factors indices indicate that Ag ٬Pb ٬Zn ٬Cu, Hg ٬S٬ have the highest enrichment level. Muller geoaccumulation index is represented high pollution range for Ag ٬Pb ٬Zn ٬S in all streets. The results show that this high pollution are related to Tehran refinery, metallurgical activities, erosion of Holly Shrine of Abudalazim and vehicles (fossil fuel combustion). Finally we used one-step chemical separation method to calculate the anthropogenic and non- anthropogenic ratio. The samples were analysed by ASS for Pb, Mn, Fe, Cu, Zn, Ni, Co. The results show that the anthropogenic effects of these elements are more than that of non- anthropogenic factors. It is because of the great influence of using natural resources in the productions of concrete factory.

The Gelmandeh Massive is a low relief high located north-east of Saghand, in Yazd province..From the point of view of structural geology, it is part of "Central Iran" the Kalmard_Posht-e Badam Block, east of the Posht-e-Badam Fault. This structural high is composed of a combination of metamorphosed sedimentary rocks, amphibolites and pink quartzific and feldspatic gneissic. The characteristic of the mica schist is the high percentage of re-criticized quartz and large, bent muscovite crystal. This unit is seen in close proximity of muscovite of an amphibolites complex, which is divided in two the fallowing three parts: 1) hornblendite with excess of 90% hornblende 2) garnet-amphibolites (containing) oligoclase, tschermakite and hastingsite variety of hornblende and large, brown garnets of almandine-grossularite type 3) Grey banded amphibolitic gneiss with augen texture. Field observations and geochemical studied point to a magmatic protolite for the amphibolites but of two different origins: 1) Basaltic with calcalkaline & potasic calcalkaline affinity derived from an enriched mantle 2) basaltic with calcalkaline to tholeitic affinity with crustal contamination. Both are of within plate variety, produced by "hot spot affected the crest in two different time