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[en] The first data on the discovery of Th–Sc mineralization in the pyritic complexes of the Southern Urals are presented. The minerals of Th (thorite) and Sc-containing thorium minerals are described. The conclusion is made that the Th–Sc mineralization formed due to crystallization of a residual melt in the local volume.
[en] A collaborative project named SUCON to investigate the radiological impact of the MAYAK complex on the Southern Urals region was initiated by the European Commission in 1996 as part of the Fourth Framework Programme of the European Commission on Nuclear Fission Safety. Under Work Package 4 of the SUCON project, recommendations on future remedial actions in the contaminated areas of the Southern Urals are required. This report contains these recommendations. On the basis of a dose assessment which has estimated current typical and most exposed group doses to inhabitants of three towns in the area, it is concluded that current average doses are relatively low and the introduction of new, or more intensive and expensive, measures is not justified by the levels of dose. However, current restrictions relating to the Techa river are successful in terms of the dose reduction they achieve, and these should therefore continue. A key recommendation is the establishment of a continual monitoring system that will provide an alert if environmental levels of activity should for any reason increase in the future. (author)
[en] Detrital zircons (DZs) from arkose sandstones of the Upper Riphean Zilmerdak Formation (Southern Urals) yielded ages in the range of 3039–964 Ma. Grains with Late Karelian and Early and Middle Riphean ages compose 35, 34, and 26% of the total number of the analyzed zircons, respectively. This is similar to the age spectra of the Vendian sandstones (Asha Group), but it differs significantly from the age distribution typical of the Riphean stratotype sandstones.
[en] In order to resolve the age of Navysh volcanics (NV), which is usually attributed to the Lower Riphean of the Ai Formation, we have used geochronological, petrologic, and mineralogical methods of zirconology, apart from the SHRIMP isotopic data of single zircon grains. Moreover, TIMS isotope age analyses have been conducted, the results of which can be regarded as both controlling and providing the most correct information. The TIMS and SHRIMP data make it possible to suggest a polychronous character of the NV, which include not only Riphean, but also Paleozoic groups of volcanics. In this situation, an assessment of the scales of such polychroneity of NV and, correspondingly, of the Ai Formation as a whole becomes urgent.
[en] We have been the first to study in situ the U–Pb isotopic system of aeschynite identified in the gold-bearing magnetite–chlorite–dolomite rocks of the Karabash serpentine massif in the Southern Urals. In the concordia diagram, the U–Pb LA–ICP–MS data on aeschynite are characterized by a considerable discordance, which is consistent with the regression line, the lower crossing of which with the concordia corresponds to an age of 298 ± 18 Ma, whereas the figurative ellipses of coexisting monazite reveal an almost concordant cluster corresponding to the U–Pb age of 317.3 ± 3.3 Ma. It has been established that the closure temperature of the aeschynite system is lower than that of the coexisting monazite.
[en] Corundum-containing and corundum-free plagioclasites localized in chromite-bearing ultramafites of the Rai-Iz Massif were explored for the composition and age. The composition of rock-forming minerals was studied, and the geochemical characteristics of the rocks were ascertained. The isotope age of plagioclasites determined by zircons using the U–Pb mode with a SHRIMP II device was equal to 398 ± 3 Ma. The age found conformed to the boundary on most of the Rai-Iz Massif took place against the background of a starting powerful collision, which caused the formation of the chromium mineralization of a high-chromic type, as well as the separation of a series of essentially plagioclase rocks of ruby mineralization at the discharge zones of the vein series.
[en] Complete text of publication follows. Advances in magnetotelluric sounding (MTS) have provided the possibility to study deep parts of the planet and obtaining information on electroconductivity of the Earth tectonosphere which is very sensitive to lithology of rocks in the upper part of the crust, as well as to the phase state of substance, the temperature, concentration, and a mineralization of fluids. Introduction of modern broadband digital measuring and computation equipment, as well as programs of computational modeling allowed us to realize more completely the possibilities of geoelectric methods. The material on the study of fields of natural sources (AMTS-MTS-DMTS methods) and the induction electromagnetic sounding (IEMS) method with a controlled source along a traverse about 1000 km long from the Settlement of Askino (Bashkortostan) in the west to Tjukalinsk (Omsk oblast) in the east with an a posteriori test of the previously obtained results was generalized for the first time in this work. Major faults and zones of higher fracturing in the crust and mantle, as well as relationships between electroconductivity and the tectonic structure of regions were studied. New data is obtained on particularities of tectonosphere construction of all the main structural formational zones of the Urals part proper and the adjacent areas of the East-European platform, Preduralian foredeep and the West Siberian platform. The originality of the studies performed lies in the fact that peculiarities of tectonosphere stratification were traced by electric parameters within a depth from 10 m to 600 km, and traces of events that proceeded there over a large time interval were revealed. (author)
[en] For refining the data on the age of metamorphic rocks of the Murzinka metamorphic complex and the earliest stage of their formation the age of zircons within plagiogneisses of the rocks was identified. The age was identified by two methods, i.e. laser ablation (LA-ICP-MS) and classical U-Pb method. It is shown that the oldest dating of the gneisses by the method of laser ablation, which is 1600-1800 mln. years, agrees well with the data provided by U-Pb method (1639 ± 42 mln. years)
[ru]С целью уточнения данных о возрасте метаморфических пород Мурзинского метаморфического комплекса и наиболее раннем этапе их образования определен возраст цирконов в составе плагиогнейсов этих пород. Определение возраста проводили двумя методами - лазерной абляции (LA-ICP-MS) и классическим U-Pb-методом. Показано, что древнейшие датировки этих гнейсов методом лазерной абляции, составляющие 1600-1800 млн. лет, согласуются с данными U-Pb-метода (1639 ± 42 млн. лет)