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[en] Thermoluminescence (TL) is a well established method to determine the energy dose absorbed by natural minerals, such as quartz and feldspar. A key aspect in the accuracy of luminescence dating is the reproducibility of natural processes in the laboratory. But dose rates applied in the laboratory differ by several orders of magnitude from the dose rate in nature. The effect of different dose rates on TL signals of quartz were investigated in different studies: McKeever et al (2002) reported a considerable decrease of TL response in powdered samples of Brazilian crystalline quartz when irradiated with a 60Co source at dose rates ranging from 1.4 mGy s-1 to 3.3 Gy s-1. Valladas and Ferrera (1980) investigated rock crystal TL by applying different filters: peak at 320 C decreases by 40% when dose rate increases, while peak at 360°C increases by 60% but peak at 370°C presents a small increase.
[en] Thermoluminescence (TL) properties of irradiated quartz and feldspar have been investigated in this work. Samples were irradiated at two different dose rates of 60Co source. TL intensity of both quartz and feldspar did not show dependence from the dose rate. Hence this property may be used for the dating of archaeological artifacts.
[en] Ab initio calculation of the XANSE/ELNES spectra for α quartz and stishovite were carried out using a large-supercell approach that includes the electron--core--hole interaction. Excellent agreements with experimental spectra were obtained for Si--K, Si--L2,3, and O--K edges. The usual interpretation using orbital-resolved local density of states in the conduction band is unsatisfactory
[en] Amphiboles and biotites from some cal-alkaline granitoid rocks ranging in composition from quartz-diorite (QD), through tonalite (TON), granodiorite (GD) to monzogranite (MGR) exposed at Wadi Akhdar-Wadi El-Sheikh area have been analyzed for major, trace and REE. Both the amphiboles and biotites cover a wide compositional range which reflects the magmatic evolution of their host rocks. The amphiboles belong to the calcic-type, ranging from magnesio-hornblende in QD and TON, actionolitic hornblende in GD and actionolite in MGR. Biotite varies from 45 to 64 mol-% phlogopite and classified as Fe-rich merox-ene in QD, TON and GD and Fe-poor lepidomelane in MGR. The proposed conditions of crystallization range from <1-3Kb and 650-850C for the amphibole and a lower pressure and 800-600 C for the biotic equilibrium. Generally, the amphibole and biotite are characterized by an increase in Si, Fe, K and HFSE, a decrease in Ti, Ca, Mg and the third transitional element contents relative to Fe/(Fe+Mg) ratios. They also show a great parallelism with successive enrichment of both the total REE contents and negative Eu anomalies, suggesting a progressive crystal fractionation from the more mafic melt to constitute the felsic QD-TON-GD-MGR crystallization trend. The examined amphiboles and biotites from Wadi Akhdar-Wadi El-Sheikh granitoid complex are chemically similar to those from the orogenic calc-alkaline (I-type) suites. (author)
[en] Beypazari Granitoid represents one of the widest exposure bodies within the Sakarya continent. It has several exposure bodies at Beypazari, Oymaagac, Tahir, Kirbasi and Yalnizcam of Eskisehir city. Although Beypazari Granitoid has several independence outcrops, the field geology and the aeromagnetic anomaly reveal that they are a unique body at the lower part of the crust. Field observations, mineralogical and petrographical investigations reveal that Beypazari Granitoid is composed of five different units these are monzonite, quartz monzonite, granodiorite, granite and alkali feldspar granite. Alkali feldspar granite cuts all the other subunits in the form of aplitic dyke. All the other subunits have gradual contact with the each other. Excluding alkali feldspar granite mafic enclaves are observed within the other 4 subunits as angular and elliptical in shape and changing from mm up to 20 cm in size. These enclaves can be divided genetically into three different types according to the field observation, textural features and mineralogical compositions. The first type has igneous texture, sharp contact with host rock, rimmed by fine crystalline mafic minerals and represents the abundant enclave type within the monzonite, quartz monzonite, granodiorite and granite as elliptical to sub-angular in shape. These enclaves mostly have subophitic texture in the composition of diorite, quartz diorite and monzodiorite. Ocellar quartz, acicular apatite, poiclitic feldspars and blade shaped biotite are the most characteristic features of the first type of these enclaves, which may represent the magma mixing/mingling enclaves in origin. The second type of these enclaves has a cumulate texture and is representing a segregation of early crystallization processes of mafic minerals. The second type of these enclaves is the product of the early crystallization of magmatic differentiation and is forming the magma segregation enclave types. The third type of the enclaves have metamorphic texture with clear metamorphic lineation, sharp contact with host rock and mostly observed at the northwest part of Kirbasi and Tahir region in the form of xenolithic enclaves. They have angular to sub-angular in shape. These types of the enclaves have hornfels in composition at the contact with the host rock as a product of contact metamorphism and amphibolites in composition at the core as a product of high temperature and middle pressure metamorphism. The textural features and mineral composition of the third type of the enclaves may indicate a fragment of metapelitic rocks, which caught by the granitoid magma in the form of xenolithic enclaves. Whole rock geochemistry reveals that Beypazari granitoids are subalkaline and calcalkaline in nature. They are enriched in Light-REE and LIL with respect to High-REE and HFS elements. Tectonic discrimination diagrams of Beypazari granitoid suggest a product of plate convergence and probably belong to Volcanic Arc Granitoid (VAG). The field observations, mineralogy, petrography with the whole geochemical data reveal that the Beypazari Granitoid magmas are derived from a subduction-modified magma and metasomatized mantle source with considerable crustal contribution
[en] Based on the concept of χ -matrix and Choi–Jamiólkowski states we develop the approach of quantum process reconstruction. The key part of the work is devoted to the adequacy of applied reconstruction models. The approach is tested with the statistical reconstruction of the polarization transformations in anisotropic and dispersive media realized by means of quartz plates and taking into account the spectral structure of input polarization states. (paper)
[en] The radioluminescence (RL) spectra of three types of quartz have been compared to those obtained from wavelength resolved thermally stimulated luminescence (TSL) measurements. A detailed numerical deconvolution into Gaussian components allowed to identify which of the bands are involved in either types of luminescence processes. The blue “A band” at 2.51 eV was confirmed to dominate both RL and TSL spectra in samples exposed to prolonged irradiation. The UV emission of the 110 °C TSL peak was found to be composite. Analogously to what previously reported for RL spectra, an annealing at 500 °C for 10 min induced a strong enhancement of the “C band” at 3.42 eV. This effect was particularly evident in natural and pre-irradiated quartz. A second intense UV component, the “M band” at 3.7 eV, was found to contribute to both TSL and RL spectra of samples annealed at 1000 °C for 10 min. A further broad UV emission seems to be involved only in RL emission but not in the TSL one.
[en] An FPGA based hardware system for imaging both Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) is described. This system allows spatial investigation of luminescent materials as it uses EMCCD which is one of the most sensitive detectors for low level light imaging. User-interface, graphical display of data, and instrument control has been implemented using LabVIEW. The details of this system and the results of its performance tests are enumerated in this paper. Dose recovery tests were done for quartz and feldspar and the results for most of the grains were found to be within ±10% of the real value
[en] The difficulties to recovery very small particles by conventional flotation need the development of all methods likely to give the best results. And this owing to the actual tendency which consists in including in the stocks of valorized ores, those with mineral particles finely scattered needing a very advanced grinding. Among these methods (va cum flotation, ionic flotation, column flotation, etc...), the electro flotation, which uses the electrolysis of pulp for it's airing seems to have a great interest but in fortunately its still on a laboratory scale. The passage to the industrial scale needs the putting in a conspicuous position of all possibilities of the method. However the studies have shown that the method should particularly be effective in recovering of several minerals finely ground. In this article, we have confirmed the fact in the case of galene. We have furthermore showed that the rate of recuperation increases with the decreasing of the size of the particles. The recovering is maximal for the particles under μm. This phenomen is different from the one observed in conventional flotation. We have given the reasons of this difference in this article.