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[en] Consistency of radiogenic hypothesis of the the host hematitic zone origin in hydrothermal uranium deposits is rendered to be ambiquous on the base of analyzing series of geological-mineralogical data and experiments on radiogenic irradiation of iron-containing minerals (purite, siderite, chlorite, biotite, ankerite). The minerals were irradiated with a hydraulic GUG-120 M gamma-ray plant. The minerals were irradiated in glass ampoules filled with distilled water or without it. The total radiation dose was equal to 3.5x109 rad. According to the data of X-ray diffraction analysis and infrared spectrometry no changes in the mineral structures were revealed and the indications to neogenic hematite phases were absent. Moessbauer parameters of of the irradiated minerals were identical with the spectra of the intact samples
[en] Samples of magnetite, prepared by standard methods for obtaining of melted ammonia synthesis catalysts have been studied. The samples contain small amounts of additives, such as K2O (0.4-1 mass%), CaO (0.7-1.5 mass%), Al2O3 (0-2 mass%), WO3 (0-1 mass%) and MoO3 (0-0.6 mass%). Some influences of the additives to magnetite, as well as formation of other individual phases were established. (author) 10 refs.; 1 fig.; 2 tabs
[en] The meteorite Orgueil is a carbonaceous chondrite of type CI. Carbonaceous chondrites contain Fe(III), Fe(II) and in some cases metallic iron, indicating that they are in a state far from thermodynamic equilibrium. In Orgueil about 40% of the iron is present in magnetite (Fe3O4). In this work a sample of magnetite grains extracted from Orgueil has been studied by Moessbauer spectroscopy. It has been found that the magnetic phase contains about 11% of maghemite and that the remaining magnetite has a vacancy concentration smaller than 0.006, corresponding to the formula Fe2.994O4. (orig.)
[en] Present article is devoted to study of carbonates of Pakrud deposit (Central Tajikistan). In the Pakrud deposit the siderite, ankerite, dolomite and calcite were found. The dolomite is typomorphic important mineral the presence of which indicating the gold mineralization in deposit.
[en] The objectives of the confirmatory surveys were to provide independent contractor field data reviews and to generate independent radiological data for use by the NRC in evaluating the adequacy and accuracy of the licensee's procedures and survey results.
[en] The low-temperature relaxation process has been investigated in a nonstoichiometric magnetite Fe3−δO4 with δ=0.03. Far below the Verwey transition at TV=90 K, the measurements of AC susceptibility χac display a frequency-dependent anomaly of the shoulder in χ' accompanied with the peak in χ″ and their weak thermal hysteresis. These low-temperature anomalies are related to a thermal relaxation process owing to the domain-wall mobility and extra electron exchange inside the walls. Moreover, the low-temperature relaxation process is revealed to exhibit strong memory effect via field-cooling magnetization measurements. Interesting discrete sudden jumps are observed during the logarithmic decay of magnetization in zero field with aging time, indicating the spontaneous magnetization reversals via adjustment of domain configuration. - Highlights: • At T≪TV, χac displays a shoulder in χ' and a peak in χ″ with a weak thermal hysteresis. • The low-temperature relaxation process is revealed to exhibit strong memory effect. • Discrete sudden jumps are observed in the magnetization relaxation measurements. • Adjustment of domain configuration is suggested for the magnetization reversals
[en] Complete text of publication follows. The crystal symmetry of hematite in the basal plane predicts three easy magnetization axes for the antiferromagnetic spins. Spin canting then leads to three preferred magnetization axes perpendicular to these easy axes. We measured magnetic hysteresis loops and remanence curves on single hematite crystals as a function of rotation angle in order to verify this prediction and to better understand the interplay between spin canting, remanence and magnetic susceptibility. While our results qualitatively coincide nicely with theoretical predictions, a quantitative evaluation requires more complex modeling.
[en] We present a comprehensive experimental characterization of the field and temperature and time dependence of the magnetic response of a powder of nanoscale magnetite particles. The data are analyzed within the framework of the Preisach formalism, and numerical simulations of the field-cooled moment, the zero field-cooled moment, the thermoremanent moment and the isothermal remanent moment, based on two extreme physical scenarios, are compared