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[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] 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] The thermal stability of the infrared stimulated luminescence (IRSL) signal from a sedimentary K-feldspar was investigated using isothermal decay study. It is observed that the isothermal decay of IRSL signal cannot be described using a first-order exponential decay function. Instead, the decay can be well described by considering the presence of band-tail states. Based on the isothermal decay results, a trap depth of ∼1.92 eV was obtained for the IRSL stimulated at 50 °C and the width of the band-tail states was found to be ∼0.37 eV below the conduction band edge. Deeper trap depths (up to ∼2.06 eV) were obtained for multi-elevated-temperature post-IR IRSL (MET-pIRIR) at elevated temperatures. Based on these observations, the implication for the IRSL dating feldspar was discussed. -- Highlights: ► We investigated the thermal stability of IRSL signal from a sedimentary K-feldspar. ► The isothermal decay of IRSL can be described by considering the band-tail states. ► We obtained a trap depth of ∼1.92 eV for the IRSL stimulated at 50 °C. ► We estimated a band width of ∼0.35 eV for the band-tail states. ► We obtained a trap depth of ∼2.06 eV for the post-IR IRSL at elevated temperature
[en] Induced thermoluminescence (TL) has found useful application in the paleothermometry of primitive meteorites, the thermal histories of chondrules, the ejection mechanism of martian meteorites and arguments about different extraterrestrial sources for meteorites currently falling world-wide and those which fall 105-106 yr ago in the Antarctic. The level of natural TL in meteorites is determined by competition between build-up, due to exposure to cosmic radiation, and thermal decay. Terrestrial conditions should result in lower levels of natural TL compared to those expected in space, and, in principle, natural TL levels should be related to the terrestrial age. Antarctic meteorites tend to have lower natural TL than non-Antarctic meteorites whose fall was observed, presumably because of the large terrestrial ages of the former. A few meteorites have especially low natural TL suggesting that they have recently been reheated. These may have come to earth on orbits with particularly small perihelia, and 26 meteorites with calculated orbits show a correlation between natural TL and perihelion distance. Dose-rate variations due to shielding, heating during atmospheric passage and anomalous fading also cause variations in natural TL levels, but the effects are either relatively small, occur infrequently or can be experimentally identified. (author)
[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 mineralizations described in the Soviet literature are characterized by several phases leading to a distinct mineral zonation. The mineral association depends on the source rock. Important processes are the replacement of quartz and feldspar by albite, formation of Na-hornblendes at the expense of common hornblende and biotite, as well as the development of epidote and aegirine. Cataclastic processes accompany the albitization. In addition to uranium, the formation of zircon is characteristic. The association with phosphate (Itataja) as well as REE and Th (Espinharas) is characterstic for the Brazilian occurrences. The mineralization of uranium follows steeply dipping structures down to depths of more than 1500 m (USSR). The initial investigations of the Kitongo occurrence in northern Cameroon show the presence of four albitite types (arfvedsonite albitite, arfvedsonite-riebeckite albitite, cataclastic riebeckite albitite, and aegirine albitite) which can be assigned to two formation phases. Uranium ore occurs in cataclastic riebeckite albitite and aegirine albitite, as well as together with carbonate along later veinlets. The extent of the occurrence is not definitely determined, the investigations will be continued. (orig./HP)
[en] On feldspathic rock, in Zero Area, Araxa, Minas Gerais, radiocrystalographic studies of Brookite mineral that was found for the first time in this area was made. (L.M.J.)
[pt]Apresentam-se conclusoes do estudo radiocristalografico do mineral Brookita encontrado pela primeira vez na rocha feldspatica da Area Zero, em Araxa, Minas Gerais. (L.M.J.)
[en] This paper presents the results of Curie temperature analyses, high temperature oxidation and electron microscope analyses of titano magnetite grains in volcanic rocks of Kenya. The rocks include basalts, trachytes, nephelinites, melanephelinites, olivine nephelinites,welded tuff and phonolites. The results based on the Curie temperatures and degree of high temperature oxidation of the rocks, age ranging from 1.5 to 13.5 My, may be classified into four broad groups.The correlation of measured Curie temperatures to compositional Curie appears to be significant (author)
[en] Exploration for uranium mineralization in North Rajasthan since late fifties has led to the identification of uranium occurrences at Rohil, Khetri, Khandela, Saladipura, Kundla, Dariba and Ladikabas, all of which form part of the uranium occurrences closely associated with the albitite line. The host rocks quartz biotite schist and albitite contain uraninite as the primary uranium mineral. Fluid inclusions in vein quartz associated with the uraniferous albitites and quartz-biotite schists of North Delhi Fold Belt at Rohil have been studied to understand the temperature, composition and salinity of the hydrothermal fluids responsible for uranium mineralization. The data recorded on minimum temperature of formation (i.e. temperature of homogenization), temperature of first ice melting and final alice melting is indicative of activity of hydrotherms of different generations in this area with varying temperatures of homogenization and differing salinities