Research subject. This article considers accessory minerals, which, unlike zircons, are present in the vast majority of common clastic rocks. Materials and methods. The data on the chemical composition of minerals (garnet, tourmaline, chromespinelide, rutile, chloritoid and clinopyroxene) extracted from the Riphean and Vendian, as well as Upper Permian and Lower Triassic sandstones of the Southern Urals, were used to illustrate the features of applying various methods and techniques. In addition, numerous examples from publications are presented. Results. A number of modern methods for studying accessory minerals, which might be used to elucidate the composition and characteristics of the provenance rocks for terrigenous strata, were reviewed. Conclusions. It is shown that, similar to zircons, accessory minerals possess a significant potential in terms of providing important data on parent rocks.
Research subject. The article discusses the analysis results of correlations between the calcium oxide content and a number of other rock-forming oxides in the Asselian sandstones and in the Middle–Upper Permian clay rocks of the Pre-Ural trough with some of their inherent ratios of rare and trace elements (La/Sc, Th/Cr, Th/Co, Ce/Cr, etc.), which act as traditional indicators of source rocks composition.Methods. Our main method is to analyze the correlation coefficients values between different pairs of oxide-indicator ratios. During the discussion, we proceeded from the fact that a statistically significant (both positive and negative) correlation between calcium oxide, ignition loss, or magnesium oxide, on the one hand, and the values of indicator ratios of rare and trace elements, on the other hand, suggest the dependence of the noted ratios on the features of the aluminosilicate matrix replacement with carbonate minerals.Results. We have established, there is a statistically significant positive or negative correlation between the calcium oxide content in Permian terrigenous rocks (different sedimentary intervals of the Pre-Ural Foredeep) and some indicator ratios of rare and trace elements (Asselian sandstones – Th/Cr, Ce/Cr and Eu/Eu*, Urzhum–Viatsk clay rocks – La/Sc, Th/Co, (La/Yb)N, etc.). As a result, the values of these ratios depend to some extent on the carbonate minerals content (mainly calcite) in terrigenous rocks. These carbonate minerals corrode the aluminosilicate matrix and in one way or another change the primary contents and ratios of impurity elements. On the contrary, there is no significant correlation between the CaO content in the Asselian sandstones and the values of La/Sc, Th/Co, etc. There is no correlation between the CaO content and the Ce/Cr ratio in the Urzhum–Viatsk clay rocks.Conclusions. We suggest, the correlation (not statistically significant at 5% confidence level) between calcium oxide content (in sandstones and clay rocks) and some indicator ratios of rare and trace elements can be considered as an indication that such ratios can be used to reconstruct the source rocks composition.
The crystallochemical characteristics of Cr spinels and tourmalines in combination with U-Pb isotope data on detrital zircons from the Upper Permian and Lower Triassic sandstones of the Belskii Depres sion showed that the main provenances of the molasse sequence in the southern part of the Cis Uralian fore deep were Lower Paleozoic (Sakmara zone) and Precambrian (Uraltau zone) complexes. The absence of Late Paleozoic zircons in the Tatarian (Upper Permian) sandstones, as well as their small amount in the Lower Tri assic psammites together with geochemical and petrographic data, suggest that granite massifs of the Main Granitic Axis of the Urals, as Middle-Upper Paleozoic magmatic complexes of the Magnitogorsk Mega zone, were not involved in erosion. At the same time, the significant amount of Precambrian zircons is indic ative of the presence of metamorphic complexes in the provenance of the Uraltau zone.
The 12th Ural lithological meeting “Sedimentary geology of the Urals and surrounding regions: today and tomorrow” and the 3rd All-Russian School of students, graduate students, young scientists and specialists on lithology “Lithology and me: from idea to conclusions” took place in Yekaterinburg, in the oldest in the region Ural State Mining University (USMU), united by the common name “Ural lithological Biennale-2018” in October 22–26, 2018. The events were organized by the Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences and the USMU. Financial support for the Organizing Committees of the lithological meeting and the School was provided by the RFBR.
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