جستجوی مقالات مرتبط با کلیدواژه "پذیرفتاری مغناطیسی" در نشریات گروه "زمین شناسی"

 One of the processes of the Quaternary era is the glacial and interglacial periods. In the glacial period, loesses deposited and in the interglacial period, Paleosoils were formed. The northern part of Iran is geographically the same as countries such as China, a large part of which has been covered with loess sediments during the Pleistocene glacial period. Loess sediments in northern Iran reflect several cycles of climate changes and the evolution of the earthchr('39')s appearance for the middle to late Quaternary period. In this region, the Loes-Paleosoil sequences are one of the most important terrestrial archives of climate change and provide a bridge between Southeast European and Central Asian loess sediments. To reconstruct paleoclimate changes, magnetic susceptibility is used as a climate proxy. The high magnitude of the magnetic susceptibility indicates the large volume of magnetic minerals. Chemical weathering causes the formation of magnetic minerals such as magnetite and maghemitite. These minerals are abundant in Paleosoils and can be determined by analyzing the magnetic susceptibility of Loess and Paleosoils. The magnetic properties of the Loess-Paleosoil sequence are considered to be evidence of paleo precipitation and weathering.Study area Geographical location of Saadabad sedimentary section in the northern region is 36° 49chr('39') N and 54° 22chr('39') E, at an altitude of 140 m a.s.l. Saadabad sedimentary section is located in the construction zone of Alborz and in terms of the main sedimentary-structural zones of Iran is part of the southern Caspian coast. This zone includes areas, which are located in the north of Alborz fault and block the Caspian Sea coast on the coast of Iran and are covered to the east with thick layers of loess.

In the field work that was carried out in May 2017, after determining the exact location of the sedimentary section, sampling was performed. Before sampling, aerated sedimentary layers are dug up and removed to reveal fresh deposits. Then, using the meter, the layers were divided into 10 cm intervals. 92 samples were prepared at 10 cm intervals from the sequence. Measurement of natural residue magnetic (NRM), by the model rotating magnetometer (JR-6A), and measurement of magnetic susceptibility by magnetic intensity measuring device, in the magnetometry laboratory of the Geological Survey of Iran.

Table 1 shows the measured values of the magnetic parameters. Due to the length of the table, only a few examples are given in the table. Since high magnetic susceptibility can indicate a greater concentration of magnetic minerals in the sample, it can be concluded that the paleosils of the sequence studied have more magnetic materials than the loesses, which are inside the soils. They can be the result of podogenesis processes. Because rising temperatures and humidity cause soil erosion processes and increase oxidation and thus increase the amount of magnetic materials, it can be concluded that in paleosoils with higher magnetic susceptibility, warm and humid climates dominate in the environment. Micromorphological studies of directional clay layers, Fe-Mn hydroxide, show that the palaeosoil of section 5 is moderate to well developed. As the climate changes to higher temperatures and higher humidity, weathering and pedogenesis also increase, leading to the development of a pedogenic oxidation environment as a result this produce the formation of tiny magnetic grains such as maghemite and magnetite in this oxidizer environment and thus increases the magnetic susceptibility. In Saadabad, the high amount of xlf along with the high percentage of xfd suggests that many of the ultra-fine maghemite and magentite grains may have been formed during pedogenesis under a long, humid, warm climate. The findings show that the different behaviors of magnetic susceptibility between the loess of the drier and wetter areas are mainly caused by their different pathogenic environments, which in turn are related to local topography and climatic conditions.

High levels of xlf and xfd indicate high precipitation during the formation of Paleosoils. Post-sedimentation processes may increase the amount of MS by producing new ferromagnetic minerals during the oxidation of wheathered soils, and may also reduce the amount of MS by reducing the processes. The clay material in which the soil is made is the main factor influencing the change in magnetic mineralogy and magnetic susceptibility. This study also shows that magnetic susceptibility is a complex parameter and its use as a precipitation control has certain limitations and conditions, and when the magnetic properties of the loesses are used for paleo climate reconstruction, more attention should be paid to topography, environment. Sediment and weather factors.

In this work, La0.6Sr0.4MnO3 manganite particles with nano and micro scales were prepared by Sol-gel and solid state reaction methods. The results from X-ray diffraction analysis by Fullprof software showed that the samples have been crystallized in the rhombohedral structure with (R-3C) space group. Investigation of magnetic properties showed that this compound belong to soft ferromagnetic materials and Curie temperature of the samples shifted to lower temperatures with particle size reduction. Calculation of the effective magnetic moment using Curie-Weiss model showed the magnetic moment reduction of the samples with particle size decreasing. Using magnetization versus field, magnetic saturation reduction, due to particle size decreasing, was observed. The observed behavior described with Core-shell model and the thickness of magnetic dead layer was estimated.

In this paper Sb2O3 nanoparticles are synthesized by solution method. The effect of these nanoparticles on the Bi-2223 superconductor properties has been investigated. The critical temperature, critical current density and activation energy were measured by the standard four-probe method. Magnetic properties of the samples were measured by using the AC magnetic susceptibility. The microstructure and morphology of samples have been studied by X-ray diffraction, scanning electron microscope and energy dispersive X-ray. The results of X-ray diffraction patterns show that the low amount of Sb2O3 and long annealing time enhance the fraction of Bi -2223 phase. Also the results show that the Sb2O3 nanoparticles do not change the phases and critical temperature of Bi-2223 superconductor, but by increasing the amount of Sb2O3 nanoparticles, the critical current density and the activation energy of the samples increase.

The study area is located 92 Km south-east of Torbat-e-Heydariyeh and 12 Km to the north of Shahrak village in Khaf-Dorouneh volcanic-plutonic belt. Mineralization was formed in fault zones where they cross the intermediate plutonic rocks. Propylitic alteration is widespread and is the dominant type in the area. Magnetite and Specularite with variation in the amount form major portion of mineralization zones. Other primary minerals are Quartz, Calcite, Pyrite, Chalcopyrite and Chlorite. Analysis of a few samples of mineralization for Au, Cu, Pb and Zn elements using the A.A.S method. The amount of copper is 0.2 percent and gold 44 ppb. Microthermometry study of fluid inclusions in Quartz indicated temperature ranges from 160˚C to more than 430˚C and relatively high salinity for mineralization zones. Thermometry study of fluid inclusions in Quartz-Chalcopyrite veins showed Temperatures between 160˚C - 203˚C and relatively high salinity for the solution. Minimum and maximum salinity that obtained were equal to 19 and 31 percent respectively in terms of NaCl. The closest compound system for fluid inclusions was determined H2O-NaCl-CaCl2 triple system. Considering high amount of magnetite and high value of magnetic susceptibility in mineralization, ground magnetic survey was carried out which resulted to the delineation of areas of covered mineralization. Interpretation of magnetic anomalies in profiles, was indicative of the continuation of surface mineralization and increase of magnetite with depth.

KC5 copper exploration prospect is located 80 Km to the northwest of Bardaskan and 4 Km to the Northeast of Dahaneh Siah copper mine in Khorasan Razavi. KC5 and Dahaneh Siah areas belong to Sabzevar geological Zone. Copper mineralization is observable mainly as secondary minerals such as Malachite and Chlorite which fills joints and fractures in a faulty contact at the boundary of the volcanic and Oriyan sedimentary (carbonaceous and tuff) rocks. High intensity ellipsoidal aeromagnetic anomaly overlies the boundary between the volcanic and carbonaceous rocks which follows old abandoned copper mines and extends to the KC5 prospect and Dahaneh Siyah area. Studies indicate the presence of magnetite up to maximum 5% in the volcanic rocks. Magnetic susceptibilities of the volcanic rocks in the KC5 west, KC5 east and Dahaneh Siyah show that this parameter is 2 times smaller in the first area than in the second and third. Magnetic anomalies of the two volcanic units in the KC5 east are similar but their amplitudes are lower than the anomalies produced by the same units in the KC5 west. Anomaly amplitudes of the Dahaneh Siyah volcanic are smaller than those produced by the same volcanic unit in the KC5 west and east. Lower magnetic susceptibilities of surface volcanic samples in the KC5 west and their higher amplitude anomalies in comparison with the anomalies from similar volcanic units in the KC5 east and Dahaneh Siyah implies that the source of the anomaly and main mineralization at KC5 west must be deep. Correlation of aeromagnetic anomaly with old abandoned copper mine (including the Dahaneh Siyah copper mine and the KC5 prospect area), uuper boundary of the volcanic and carbonaceous sediment and geochemical anomaly of the region are indications of the relation of main mineralization with aeromagnetic anomaly.