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The early stages of basic–ultrabasic magmatism in Sarmatia are characterized by the appearance of ultrabasic rocks formed from the mantle with an abnormally high iron content. Therefore, it is important to study them as the source of information about the stages and causes of the activity of the mantle and its possible composition. This magmatism has been recorded in Sarmatia since the beginning of the Eoarchean. The relics of Eo- and Paleoarchean basic and ultrabasic rocks were found in the Dniester–Bug, Kursk, and Azov provinces, which underwent tectonic reconstruction in the Mesoarchean and Paleoproterozoic. Mesoarchean basic–ultrabasic magmatism is manifested in all provinces of Sarmatia and is represented by effusive and intrusive facies. The Mesoarchean greenstone belts composed of komatiites and basalts have been well preserved in the Middle Dnieper province; in other provinces, they are strongly deformed and form narrow linear structures. The Paleoproterozoic endogenous activity in Sarmatia differs from that in other regions in the almost complete absence of magmatism in the period 2.5–2.3 Ga and its significant manifestation 2.1–2.0 Ga. The magmatism in Sarmatia at this stage is similar in the ratios of basic–ultrabasic and granitoid complexes to the magmatism in South Africa but differs from that in Fennoscandia and Canada. The volume of granitoids coeval with basic rocks is larger than the volume of mantle magmatism. The igneous complexes formed 2.1–2.0 Ga in Sarmatia and South Africa are also similar in the presence of norites, the enrichment in Ni and platinum group elements, and the ratio of granitoids and basic–ultrabasic rocks. Magmatic activity (first of all, basic–ultrabasic magmatism in ancient cratons) is not a synchronous phenomenon on a planetary scale and varies greatly in the volume of produced material within the same time intervals. Early Precambrian basic–ultrabasic rocks (volcanics of greenstone belts, intrusions of large igneous provinces, and layered massifs) resulted from plumes, whose derivates formed within the lower and upper mantle and/or the upper mantle and crust, which determined the heterogeneous composition of igneous rocks. The spatial heterogeneity and nonsynchronic occurrence of basic–ultrabasic magmatism might have been due to impact events serving as the triggers of plumes.

Based on our new U–Pb isotope data (SHRIMP-II) for the Voronezh Crystalline Massif (VCM) and on published U–Pb data for the Archean rocks of the Ukrainian Shield (USh), we have substantiated the main stages of the Archean evolution of the Sarmatian crust, a fragment of the basement of the East European Platform. New data have been obtained for 20 indicative rocks of the Kursk block (KB) of the VCM. We compared the Eoarchean and Paleoarchean KB rocks (mafic rocks and tonalites of the Oboyan’ complex), orthogneisses of the USh Dniester–Bug province (Bug granulite complex), and tonalites and mafic rocks of the USh Azov Province and have established the existence of ancient continental crust (3.75–3.60 Ga) in Sarmatia. The presence of Paleoarchean xenogenic zircons in younger intrusions indicates a wide spread of Paleoarchean rocks in the deep VCM crust section. In the Mesoarchean (3.2–3.0 Ga), eastern Sarmatia (KB and Azov and Middle Dnieper provinces) was a single granite–greenstone terrain. Two stages of felsic magmatic activity have been dated: 3.15–3.10 Ga (volcanics in the greenstone belts and tonalite–trondhjemite granites in the VCM and USh) and 3.05–3.00 Ga (volcanics and tonalite–trondhjemite granites in the USh and granites in the VCM KB). Magmatic and tectono-metamorphic processes (2.95–2.85 Ga) have been established throughout the eastern part of Sarmatia. The latest Mesoarchean endogenic activity (2.85–2.80 Ga) testifies to the tectonic differentiation of the area. Mafic and felsic magmatism, deformations, metamorphism, and ultrametamorphism under amphibolite and granulite facies conditions took place in the most part of the KB and in the Azov and Bug areas. It is shown that ultrametamorphic granites formed from an ancient (3.0–3.5 Ga) protolith. The USh Middle Dnieper province had a different tectonic position. Here, intrusion of post-tectonic granites and formation of mature sediments proceeded at 2.81–2.86 Ga. Our geochronological data show that most of the Sarmatian continental crust formed in the Mesoarchean as a result of both the intrusion of juvenile material and the reworking of the older protolith rocks. Neoarchean events (2.8–2.5 Ga) are weakly expressed in Sarmatia in contrast to Baltia, another large fragment of the East European Platform basement, where endogenic processes at 2.65–2.75 Ga were the major crust-forming geologic events.

Garnet-bearing aluminous gneisses in the Vasil’kovka area of the Orekhov–Pavlograd zone of the Ukrainian Shield were studied using the THERIAK-DOMINO, THERMOCALC, and WINTWQ software and mineral geothermobarometry methods. The stability fields of parageneses formed at the initial, peak, and post-peak metamorphic stages have been estimated: T = 500–650 °C and P > 7 kbar, T = 800–850 °C and P ≈ 8 kbar, and T = 600–670 °C and P = 4.0–5.5 kbar, respectively. A “clockwise” PT path has been established. Based on the aluminous gneiss, the age of metamorphism is determined as Paleoproterozoic (2014 ± 11 Ma). Unique regularly oriented acicular goethite microinclusions were described in garnet. In contrast to other known oriented Ti-bearing mineral inclusions in garnet, these goethite inclusions suggest not only extremely high P and T values (necessary for the formation of oriented Ti-bearing inclusions) but also a high oxygen fugacity. The obtained data broaden the concepts of the ways and conditions of formation of regularly oriented mineral phases in garnet.

We present results of study of organic matter in the coastal and bottom sediments of the Laptev Sea (Buor-Khaya Gulf). The study has shown the regularities of organic-matter distribution in the shelf zone adjacent to the glacial coast. The coast composed of a glacial rock complex supplies the largest amount of organic material to the sea as compared with other types of the coast. The average content of organic matter in these strata is ~2–3%. The bottom sediments of the shallow littoral zone are significantly depleted in organic carbon (0.1–0.3%) as a result of their active rewashing and the transition of finely dispersed material (mainly organic one) toward the deep sea zones. The content of organic carbon in the bottom sediments increases to 1–2% as the sea deepens to 7–10 m at 5–12 km from the coast. There are frequent local anomalies of organic-carbon contents (up to 4–5%) in the deltaic zones of the sea. The highest contents of organic carbon (up to 3%) have been found in the recent marine sediments in the central, relatively deep zones of the bays.

We performed a regional analysis of the effect of anthropogenic (acid precipitation) and natural (climatic changes, endogenous methane) factors on the hydrochemical composition and phytoplankton of mountain lakes in East Siberia for the last 210 years. The lacustrine diatom community responded to the intense acid precipitation that led to the acidification of lakes in Europe and North America in 1950–1985: Cyclotella-complex was partly replaced by more pH-tolerant species of diatoms, such as Aulacoseira lirata, A. italica, and Tabellaria flocculosa. This anthropogenic impact, however, was not dramatic for the ecosystem of mountain Lake Oron. The diatom records distinctly show a tendency for the reduction of lacustrine-alga population since the end of the Little Ice Age. We assume that the decrease in the Oron bioproductivity was mainly due to a deficit of nutrients caused by the inflow of ultrafresh waters from the thawing glaciers, snow patches, and seasonal snow cover of the Kodar Ridge during the Recent global warming in the Northern Hemisphere. In addition, the changes in the lake ecosystem might have been accelerated by emissions of endogenous methane.

A simple, reliable, and high-performance method has been proposed for direct determination of the isotopic composition of authigenic uranium in silica lacustrine sediments. The method is based on studying the kinetics of the selective extraction of authigenic uranium from sediments with weak solutions of ammonium hydrocarbonate followed by the ICP-MS analysis of the nuclides. To estimate the contamination of authigenic uranium by terrigenous one, the contents of 232Th and some other clastogenic elements in the extracts were measured simultaneously. The selectivity of extraction of authigenic uranium from the sediments treated with a 1% NH4HCO3 solution appeared to be no worse than 99%. The method was used to analyze the isotopic composition of authigenic uranium at several key horizons of a core dated before. The measurements directly prove that the 234U/238U values in Baikal water varied depending on climate, which contradicts the previous statements. The measured 234U/238U ratios in paleo-Baikal water match the values reconstructed from isotopic data for total uranium in the sediments on the supposition that the U/Th ratio is constant in the terrigenous part of the sediment. Direct experimental determination of total and authigenic nuclides in sediments enhances the potentiality of the method for absolute 234U-230Th dating of carbonate-barren lacustrine sediments, including those from Lake Baikal, within the intervals corresponding to the periods of glaciation, where the sediments contain a large fraction of terrigenous component. Given the fractions of terrigenous and authigenic uranium are accurately determined, we have an opportunity to study the variability of the sources of terrigenous matter and to refine the previous model for reconstructing the climate humidity in East Siberia.