Lithogeochemical characteristics of the pelitic and silty–pelitic bottom sediment samples, collected during Cruise 89 of the R/V Akademik Mstislav Keldysh (September 2022), from several areas in the southwestern Kara Sea (Baidaratsk Bay, Pukhuchansk Depression, West Kara Step, and Novaya Zemlya Depression) are discussied. It has been established that the muds contain a significant proportion of the lithogenic component. This conclusion agrees well with the localization of sediment data points on various discriminant diagrams near the reference points of average Paleozoic graywackes and PAAS. Such component could be sourced either from the fine-grained suspended particulates of the Ob River or from the sedimentary rocks and friable sediments of the Yamal and Yugra Peninsulas, Vaigach, and Novaya Zemlya. Although the upper layer of bottom sediments in the southwestern Kara Sea contains a noticeable amount of the mafic igneous rock fragments from Novaya Zemlya, which should make a significant contribution to their erosion products in the mud composition, parameters of the chondrite-normalized REE distribution in the sediments are inconsistent with such assumption.

Modern data on the formation of the mineral composition, geochemical and isotope-geochemical features of sediments from large rivers in Africa (Zambezi, Nile, Congo), as well as U–Pb isotope ages of detrital zircon populations in sands, obtained during complex long-term studies by Prof. E. Garzanti (Universita’ Di Milano-Bicocca, Italy) and his colleagues are considered. Ideas about the influence of chemical weathering on the composition of both silts and sands of the named large rivers are briefly summarized. The influence of river segmentation on the composition of the transported aluminosiliciclastics is discussed. The key points of the research results presented in the overview are outlined for specialists studying ancient sedimentary sequences.

Sands make up 5-7% of the surface bottom sediments in the West Kara zone and slightly more in the Ob-Yenisei zone. Analysis of the bulk chemical composition of the sands has shown that they contain greywackes, lithites, and subarkoses. This suggests that there is currently no significant clastic averaging in the Kara Sea and that sand composition is largely determined by the composition of the provenance. The concentrations of a number of trace elements, normalized to the composition of the average Phanerozoic cratonic sandstone, indicate their significant difference from this reference material. This difference is also confirmed by the localization of data points of sands from different areas of the Kara Sea on discriminant diagrams. The REE systematics of sands suggest that the contribution of erosion products of major igneous rocks is significant only for the Yenisei Bay sands. The sands from other areas have (La/Yb)(N) and Eu/Eu* values indicating the predominant role of erosion products of felsic igneous rocks in their composition.

On the basis of data on the geochemical characteristics ((La/Yb)N, Eu/Eu*, and content of Th) of clay rocks of Podolian Transnistria, Southeastern Poland, Belarus and Volyn, Lithuania, the vicinity of St. Petersburg, Southeastern White Sea region, and Arctic Norway, categories of rivers that transported fine-grained aluminosilicate clastic material to sinks that existed during the Vendian and Early Cambrian were reconstructed in the west of the East European Platform. The distribution of data points of clay rocks of the Volhynian time on the (La/Yb)N–Eu/Eu* diagram with the fields of the composition of the pelitic fraction of bottom sediments in the mouth of modern rivers of various categories allows us to assume that, for Lithuania and Podolian Transnistria, the feeding provinces were, among other things, paleowatersheds composed of volcanic formations. For Eastern Belarus and the Southeastern White Sea region, the influence of erosion products supplied by rivers flowing through igneous/metamorphic terranes (crystalline basement) is noticeable. A significant part of the clastic material was carried by rivers that drained sedimentary formations, as well as large rivers, i.e., rivers whose length exceeded 1000 km and whose drainage area was more than 100 000 km2. The existence of the latter is confirmed by the presence of detrital zircon in the rocks of the Zhukov Formation of Southeastern Poland, borrowed possibly from the rocks of Fennoscandia. In the Redkinian time, along with large rivers (rivers of category 1) and rivers fed by the products of erosion of sedimentary formations (rivers of category 2), transport of fine-grained clastic rocks was also carried out by rivers that drained rocks of the crystalline basement (rivers of category 3; this is typical of Belarus and Volyn, the Southeastern White Sea, and Arctic Norway) and by rivers flowing through areas of distribution of volcanic associations (rivers of category 4). The distribution of data points of the clay rocks of the Kotlin stage on the (La/Yb)N–Eu/Eu* diagram suggests that the main agents of transport of fine-grained aluminosilicate clastic material to sinks at that time were large rivers and rivers fed by fine-grained particulate matter owing to the erosion of predominantly sedimentary rocks. The Early Cambrian paleowatersheds were apparently composed not only of crystalline rocks but also of sedimentary formations. All of the above is in fairly good agreement with the previously established fact of a gradual increase in the contribution of erosion products of sedimentary rocks to the formation of Vendian–Early Cambrian sedimentary sequences from Podolian Transnistria to Arctic Norway.

The first of two communications is devoted to the study of lithogeochemical features of the pilot collection of Upper Precambrian sandstone and siltstone samples taken from four boreholes: Bogushevskaya 1, Bykhovskaya, Lepel 1, and Kormyanskaya (Belarus). This article analyzes the general features of their bulk chemical composition and shows the possibilities and limitations for further reconstructions. It has been established that Riphean and Vendian rocks included in the pilot collection, visually identified as sandstones, are actually quartz, feldspar–quartz, and arkosic varieties with different cement types. In terms of geochemical characteristics, the Vendian “siltstones” correspond to the coarse- and fine-grained siltstones and, to a greater extent, mudstones with a predominance of illite, as well as various admixtures of berthierine, kaolinite, and smectite. Based on the comparison of enrichment factor (EF) of the trace element, these rocks are marked by several dissimilarities related to both variations in the source rock composition and sedimentary environment. Data points of the samples on the Zr/Sc–Th/Sc diagram indicate that all of the studied Riphean and Vendian rocks are dominated by the first sedimentation cycle material, suggesting that the lithogeochemical characteristics of the pilot collection rocks quite correctly reflect similar features of the source rock complexes. Therefore, they can be used to reconstruct the paleogeodynamic and paleoclimatic factors that controlled the accumulation of Riphean and Vendian sedimentary sequences in Belarus.

The article analyzes the lithogeochemical features (content and distribution of the main rock-forming oxides, as well as a number of the trace elements) of clay rocks of the Volyn, Redkino, Kotlin and Lower Cambrian stratigraphic levels of the west part of the East European Platform (Belarus and Volyn, east part of the Baltic monocline, Moscow syneclise). Usage (1) various lithogeochemical approaches and methods; (2) data on the U–Pb isotopic age of detrital zircon populations present in mudstone-associated sandstones; (3) the geochemical features of the supposed source rocks of fine-grained aluminosiliciclastics (magmatic associations of different composition and age in Sarmatia and Fennoscandia) made it possible to express considerations about their possible contribution to the formation of the Vendian and the Early Cambrian clay rocks.

Lithogeochemical characteristics of limestones of the Uk Formation (uppermost unit of the Riphean stratotype section in the Southern Urals) are considered. Data points of limestones (40 samples), accumulated on the middle and inner ramps have a quite contrasting distribution on the (La/Sm)sh, (La/Yb)sh, and (Sm/Yb)sh diagrams based on the systematization of numerous analytical data on carbonate sequences in various plate-tectonic (paleogeographic in the broad sense) environments, according to (Zhang et al., 2017). The data points of limestones of the Medved Member of the Uk Formation deposited on the middle ramp, according to a detailed lithofacies analysis, are shifted in these diagrams toward the field of limestones of open ocean, whereas limestones of the Manaysu Member (inner ramp) correspond to the near-coastal deposits in terms of their geochemical characteristics. Thus, the geochemical characteristics of the Uk limestones generally confirm the conclusions based previous reconstructions. In the described example, the distribution of trace elements in the inner ramp limestones was controlled apparently by the fine-grained aluminosiliciclastic material transported from the continent, whereas influence of the open ocean environment is already perceptible in geochemical features of the middle ramp limestones deposited in the deeper sea.

The lithogeochemical peculiarities (content and distribution of main rock-forming oxides, as well as some trace elements) of clayey rocks of the Volynian, Redkinian, Kotlinian, and Lower Cambrian stratigraphic levels of the west of the East European Plate (Belarus and Volyn, east of the Baltic Monocline, and Moscow Syneclise) are analyzed. Using various lithogeochemical approaches and methods and data on U–Pb isotopic age of detrital zircon populations, which occur in sandstones associated with mudstones, and taking into account geochemical peculiarities of possible source rocks of fine-grained alumosiliciclastic material (igneous associations of different composition and age of Sarmatia and Fennoscandia), we provided ideas on a possible contribution of the latter associations to the formation of the Vendian and Early Cambrian clayey rocks.

This paper completes the examination of results of the study of lithogeochemical characteristics of a pilot collection of the Riphean–Vendian sandstones, siltstones, and claystones (last one based on the interpretation of results) in Belarus. Data on the age of detrital zircon published in recent years suggest that Upper Precambrian rocks of this region were sourced from the Osnitsk–Mikashevichi and the Trans-Scandinavian igneous belts, the Volyn–Brest large igneous province, rapakivi granites, as well as various rock associations of Sarmatia, Danopolonian orogen and Svecofennides. Based on the lithogeochemical characteristics, the distribution of data points of the studied clastic rocks on discriminant diagrams provides insight into the possible provenance, paleogeodynamic, paleogeographic, and paleoclimatic settings and suggests several conclusions. The considered Riphean–Vendian stratons in Belarus are composed mainly of erosion products of within-plate granitoids, as well as various island-arc and syncollisional felsic igneous rocks. The share of erosion products of mafic rocks among them generally does not exceed 30

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23060144

The Lower Сarboniferous volcanogenic-terrigenous strata on the eastern slope of the Middle and Northern Urals have been studied. It is shown that these formations are confined to the zones of regional strikeslips and were formed in the conditions of transtension. The geochemical parameters of volcanites show similarities with igneous rocks of both suprasubduction and intraplate environments, which does not contradict the ideas about their formation in the rear of the active continental margin.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070413

The results of a comparison of various indicator ratios of trace elements-indicators of the composition of provenances for clay rocks of the Middle Riphean Avzyan Formation and the Upper Riphean Biryan Subformation of the Zilmerdak Formation (Bashkirian meganticlinorium, Southern Urals) are analyzed. The formation of these two objects is separated by a hiatus, the maximum duration of which can reach 250 Ma. The study is based on data on the content of trace elements in 28 and 16 samples of clay/fine-grained clastic rocks, respectively, of the Avzyan Formation and the Biryan Subformation from the collections of E. Z. Gareev and the author, obtained by the ICP-MS method at the IGG Ural Branch of the Russian Academy of Sciences (Yekaterinburg). Distribution of individual and average data points of clay rocks of named objects on diagrams La/Sc – Th/Co, Sc – Th/Sc, Eu/Eu* – Th/Sc, Ni – V – 10*Th, Th – La – Sc, Y /Ni – Cr/V, Cr/Th – Th/Sc, and Hf – La/Th are largely comparable. The spectra of rare earth elements normalized to chondrite are also comparable. Only on the Th – Th/U diagram the distribution of the data points has a slightly different form. This either indicates the invariance of the composition of the provenances for almost 250 Ma, or suggests that the duration of the pre-Upper Riphean hiatus was not so long, or the author’s analytics is“lame”, or there are other reasons. Проанализированы результаты сопоставления различных индикаторных отношений редких и рассеянных элементов-показателей состава пород палеоводосборов для глинистых пород авзянской свиты среднего рифея и бирьянской подсвиты зильмердакской свиты верхнего рифея (Башкирский мегантиклинорий, Южный Урал), разделенных перерывом, максимальная длительность которого может достигать 250 млн лет. В основу исследования положены сведения о содержании редких и рассеянных элементов в 28 и 16 образцах глинистых / тонкозернистых обломочных пород соответственно авзянской свиты и бирьянской подсвиты из коллекций Э. З. Гареева и автора, полученные методом ИСП-МС в ИГГ УрО РАН (г. Екатеринбург). Распределение индивидуальных и средних фигуративных точек глинистых пород названных объектов на диаграммах La / Sc — Th / Co, Sc — Th / Sc, Eu / Eu* — Th / Sc, Ni — V — 10*Th, Th — La — Sc, Y / Ni — Cr / V, Cr / Th — Th / Sc и Hf — La / Th в существенной степени сопоставимо. Сопоставимы также нормированные по хондриту спектры распределения редкоземельных элементов. Только на диаграмме Th — Th / U распределение фигуративных точек имеет несколько отличающийся вид. Это, либо указывает на неизменность состава палеоводосборов на протяжении почти четверти миллиарда лет, либо дает основание предполагать, что длительность предверхнерифейского перерыва была не столь велика, либо «хромает» авторская аналитика, либо есть иные причины.

The Lower Carboniferous volcanoterrigenous sequences of the eastern slope of the Central and Northern Urals are studied. It is shown that these rocks are confined to zones of regional strike–slip faults and formed under transtension conditions. The geochemical parameters of volcanic rocks are similar to those of igneous rocks of both suprasubduction and intraplate settings, which is in agreement with ideas about their formation in the rear of the active continental margin.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070218

This work presents new data on the Sm–Nd age of the Ishlya (1470 ± 62 Ma) and Misaelga (1481 ± 58 Ma) mafic/ultramafic complexes distributed along the western slope of the Southern Urals. The ages obtained are close to the Calymmian–Ectasian boundary ( 1400 Ma) of the International Chronostratigraphic Scale. Based on calculated data, it is shown that the area of magma generation for the melts that formed the named complexes has been located in the “head” of a plume, which is the primary cause of the Mashak “magmatic event” in the Southern Urals.

Based on lithogeochemical data related to the fine-grained clastic rocks of the Volyn, Valdai, and Baltic groups in the western part of the East European Platform (Belarus and Volyn, partly Lithuania), categories of rivers that transported the fine-grained aluminosiliciclastics to the sinks were reconstructed. It is concluded that the formation of Vendian and Lower Cambrian sedimentary sequences in this area was controlled mainly by river systems similar to modern large rivers (catchment area >100 000 km2) and rivers draining sedimentary rocks (catchment area <100 000 km2). The fine-grained aluminosiliciclastics transported by them was delivered mainly from areas composed of rocks of the platform crystalline basement and, in part, sedimentary rocks. The distribution of data points of Vendian–Lower Cambrian mudstones on the (La/Yb)N–Eu/Eu* and (La/Yb)N–Th diagrams with fields of the pelitic and silty–pelitic sediments at the mouths of modern different-category rivers shows that mafic rocks of the Volyn–Brest large igneous province, apparently, were not suppliers of the fine-grained aluminosiliciclastics in the indicated time intervals.

Several geochemical characteristics ((La/Yb)N, Eu/Eu*, and Th content) of gray silts of the Volga River, suspended particulate matter of the Lena River, and silt–pelite fraction of bottom sediments in the Yangtze River are analyzed. It has been established that the above parameters of the chondrite-normalized lanthanide spectra and the Th content turn out in almost all cases to be comparable with their values determined for the specially prepared (removal of nonterrigenous carriers of rare earth elements (carbonate minerals, Fe–Mn oxyhydroxides, and organic components) pelite fractions of bottom sediments deposited near the mouths of named major rivers, and are retained over thousands of kilometers upstream from their deltas/mouths. The regulation of the Volga and Yangtze flows does not have a significant impact on parameters of the suspended particulate matter and bottom sediments under consideration.

The systematics of REE, Sc, Cr, Zr, and Th in silty-pelitic and pelitic surface bottom sediments sampled during cruises 71, 75, 77, and 80 of the R/V Akademik Mstislav Keldysh in the Nordic Seas is considered. It is shown that the geochemical features of silts in a number of regions (the southern part of the Kolbeinsei Ridge, the continental slope of Norway, the northern end of Mona Ridge) indicate the presence in their composition of a significant (30–40

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.