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The Sea of Japan is a tectonically active region with rift-related destruction of the Earth’s crust and numerous volcanic edifices on the seafloor. Since the 1970s, numerous zones with ferromanganese crusts (FMCs) and phosphorite and barite ore occurrences have been discovered during the repeated expeditions of the Pacific Oceanological Institute, Vladivostok. Analysis of the distribution of these ore occurrences showed that all of them are confined to tectonically active zones of the seafloor: submarine volcanoes, tectonic scarps, or fault zones. In some zones, phosphorites occur together with FMCs, and in one zone, together with FMCs and barites. Ferromanganese hydroxides, phosphorites, or barites are found in the pores of basalts composing submarine volcanic edifices in the Sea of Japan. These data indicate that the ore matter in all zones is supplied with postvolcanic gas-hydrothermal fluids or hydrothermal solutions circulating along deep faults during the destruction of the continental crust in the southern and eastern parts of the sea. Thus, ferromanganese, phosphate, and barite ore occurrences in the Sea of Japan are related to low-temperature hydrothermal-sedimentary processes.

Thermal metamorphism produced an aureole near the early Paleozoic Bayan-Kol gabbro-monzodiorite intrusion in the Erzin shear zone of western Sangilen (Tuva-Mongolia microcontinent, Central Asian Orogenic Belt). Field observation of intrusive contact, structure-textural and mineral transformations of metamorphic rocks, regular changes in the chemical composition of minerals with approaching the intrusive contact, and high temperature gradient from intrusive to wallrocks verified the occurrence of a contact aureole near the Bayan-Kol intrusion. The high-gradient thermal metamorphism (M2) affected garnet-staurolite-kyanite schists that formed during earlier regional metamorphism (M1) at 6.2-7.9 kbar and 600-670 ºC. The 0.5 km wide M2 metamorphic aureole mapped along the northwestern intrusion margin consists of a muscovite-sillimanite zone adjacent to the sedimentary country rocks and a cordierite-K-feldspar zone on the side of the intrusion. The M2 metamorphic reactions occurred within the granulite facies temperature range 880-910 ºC along the contact with monzodiorites and at ~950 ºC along the boundary with gabbronorites; the temperature on the aureole periphery was about 640 ºC. Pressure estimates indicate deep-seated high-grade metamorphism at 6.9-7.8 kbar, while the intrusion itself crystallized at 7.7-7.8 kbar. The suggested numerical model implying the formation of a thermal aureole at a depth of 26 km (7 kbar) in the lower crust is consistent with the temperature pattern determined by geothermobarometry for several key points of the metamorphic zoning and confirms its deep-level origin. Thus, the aureole near the Bayan-Kol intrusion represents a rare case of contact metamorphism in the lower continental crust. The obtained results, along with published petrological and geochronological evidence, reveal two depth levels of the early Paleozoic M2 metamorphism in the Sangilen area: upper (7-15 km, 2-4 kbar) and lower (26-30 km, 7-8 kbar) crust. The Bayan-Kol gabbro-monzodiorite intrusion is likely a small apophysis or a fragment of a deep-crust intermediate magma chamber, while the moderate-pressure (7-8 kbar) M2 granulites in the Erzin shear zone are products of high-gradient metamorphism related to the Cambrian-Ordovician collisional mafic magmatism in the Sangilen area.

The Kolyvan’-Tomsk folded zone (KTFZ) is a late Permian collisional orogen in the northwestern section of the Central Asian Orogenic Belt. The Mesozoic history of the KTFZ area includes Late Triassic-Early Jurassic and Late Jurassic-Early Cretaceous orogenic events. The earlier event produced narrow deep half-ramp basins filled with Early-Middle Jurassic molasse south of the KTFZ, and the later activity rejuvenated the Tomsk thrust fault, whereby the KTFZ Paleozoic rocks were thrust over the Early-Middle Jurassic basin sediments. The Mesozoic orogenic events induced erosion and the ensuing exposure of granitoids (Barlak complex) that were emplaced in a within-plate context after the Permian collisional orogeny. Both events were most likely associated with ocean closure, i.e., the Paleothetys Ocean in the Late Triassic-Early Jurassic and the Mongol-Okhotsk Ocean in the Late Jurassic-Early Cretaceous. The apatite fission track (AFT) ages of granitoids from the Ob’ complex in the KTFZ range between ~120 and 100 Ma (the Aptian and the Albian). The rocks with Early Cretaceous AFT ages were exhumed as a result of denudation and peneplanation of the Early Cretaceous orogen, which produced a vast Late Cretaceous-Paleogene planation surface. The tectonic pattern of the two orogenic events, although being different in details, generally inherited the late Paleozoic primary collisional structure of the Kolyvan’-Tomsk zone.

The paper is concerned with a geochemical study of apoultrabasic metasomatites of the Ospa-Kitoi, Parama, and Ust’-Kelyana ophiolite massifs located in the southern folded framing of the Siberian craton. The isotope (O, C, H, Sr, and Rb) systems of dunites, serpentinites, nephrites, listvenites, and talc-carbonate rocks are studied. The isotopic composition of oxygen in olivines from dunites is characterized by δ¹⁸O = 4.6-5.5 ‰. The δ¹⁸O values of serpentinites (4.67-7.35 ‰) point to the mantle genesis of fluids and might have been inherited from ultrabasic rocks. Nephrites are slightly enriched in heavy oxygen isotope (δ¹⁸O = 6.13-9.54 ‰). This indicates that their fluid phase was transported from serpentinites and captured a small portion of the crustal component. The widest variations in δ¹⁸O values, from 8.12 to 17.46 ‰, are observed in minerals from listvenites. Carbonates from these rocks show a highly heterogeneous isotopic composition of oxygen (δ¹⁸O = 12.9-18.8 ‰) and carbon (δ¹³C = -2.8 to +2.8 ‰). These rocks formed with the contribution of metamorphogenic fluids. According to the isotopic composition of hydrogen, the examined serpentinites are divided into two groups: with δD values specific to “magmatic water” (δD = -73.50 to -85.00 ‰) and those typical of meteoric fluids (δD = -151.90 to -167.20 ‰). The listvenites are characterized by low Rb and high Sr contents. Their ⁸⁷Sr/⁸⁶Sr values (0.70702-0.70971) indicate the contribution of a crustal source. The study of fluid inclusions in minerals from listvenites has shown that the rocks formed under relatively low-temperature conditions. The homogenization temperatures of fluid inclusions in quartz and magnesite from listvenites of the Ospa-Kitoi massif are 184-290 ºC and 122-182 ºC, respectively. In the Parama massif, the homogenization temperature of fluid inclusions in quartz is 130-170 ºC. The solutions that formed listvenites of the Ospa-Kitoi massif were slightly saline (TDS = 2.9-8.4 wt. % NaCl eq.), with NaCl and Na₂CO₃ being the main salt components.

Study of the behavior and distribution of platinum group elements (PGE), along with other data, is necessary for geodynamic reconstructions. There are almost no PGE data for Transbaikalia, one of the large regions of Russia. This work presents the first data on the contents and behavior of PGE in the Cenozoic intraplate alkali basaltoids of southern Transbaikalia. The total PGE contents are 20-40 ppb. The PGE pattern of the studied basanites is similar to those of mafic OIB, including the Hawaiian ones, and rocks of large igneous provinces: tholeiitic basalts of the Siberian Platform and basaltoids of the West Siberian Plate. Based on this similarity and on the intraplate location of the South Transbaikalian basanites, we have concluded that the basanitic melts formed under mantle plume impact.

We present data on dispersed gold and associated disseminated mineralization of leucogranites controlling the location of the Dukat epithermal Au-Ag deposit. The data suggest the formation and burial of small portions of oversaturated gold-bearing fluids in hypabyssal magmatic bodies. The lower (relative to silver) contents of gold in the deposit ores and the high Ag/Au ratios (350-550) are due to the limited occurrence of oxidized gold-bearing fractions of magmatogene fluids. This limitation is explained by the active interaction of late magmatic portions of fluids and the material of the host carbonaceous volcanosedimentary unit and by the formation of an environment favorable for the concentration, migration, and deposition of manganese, silver, and nonferrous-metal compounds.

We present results of petrographic, mineralogical, and geochemical study of all types of rocks of a multiphase pluton and consider the chemical evolution of igneous and metasomatic rocks of the Baga Gazriin Chuluu pluton, based on new precise analytical data. At the early stage of their formation, the pluton granites were already enriched in many trace elements (Li, Rb, Cs, Be, Nb, Ta, Th, and U), F, and HREE relative to the upper continental crust. They show strong negative Ba, Sr, La, and Eu anomalies, which is typical of rare-metal Li-F granites. The geochemical evolution of the Baga Gazriin Chuluu multiphase pluton at the postmagmatic stage was marked by the most intense enrichment of greisens and microclinites with lithophile and ore elements (Sn, W, and Zn) and the formation of ore mineralization. In the permeable rift zone where the Baga Gazriin Chuluu pluton is located, the fluid-magma interaction took place under the impact of a mantle plume. High-temperature mantle fluids caused melting of the crustal substratum, which determined the geochemical specifics of Li-F granite intrusions. Genesis of granitic magma enriched in Li, F, Rb, Sn, and Ta is possible at the low degrees of melting of the lower crustal substratum. The Baga Gazriin Chuluu pluton formed in the upper horizons of the Earth’s crust, where magma undergoes strong differentiation and the saturation of fluids with volatiles can lead to the postmagmatic formation of metasomatites of varying alkalinity (zwitters (greisens), microclinites, and albitites) producing rare-metal mineralization. By the example of the early Mesozoic magmatism area of Mongolia, it is shown that the formation of granites and associated rare-metal minerals is due to the interaction of mantle fluids with the crustal material and the subsequent evolution of granitic magmas.

We examine some issues related to the application of the Monte Carlo method for estimating of errors in calculations of numerical characteristics of the river flow from available series of observations. As a result, it is shown that the adopted Monte Carlo algorithm, which served as the basis of official recommendations for calculating the numerical characteristics of the flow, leads to a significant exaggeration of the negative bias of the numerical characteristics of the dispersion. It is found that the implementation of the above algorithm does not take into account a number of questions, and these authors suggest that special attention should be given to them. Among them are the following four: the first question is related to the fact that the tables of ordinates of the binomial probability curve are used for statistical testing of samples of different durations, which are often not applicable for a large number of tests due to extrapolation beyond the data given in the tables. The second question implies that, in some cases, the Pearson type III probability distribution curves, constructed for time series of the annual flow, negative values are obtained from modeling, which contradicts the physical essence of the river flow. The third question is related to the applica tion of the method of normalization and linearization of G.A. Alekseev’s connections without taking into account the smoothing effect of this method, which leads to an increase in the negative shift of the scattering characteristics. The fourth question is due to the lack of research on the issue of accounting for the spread of empirical points relative to theoretical curves, and the influ ence of the above effect on the final result of modeling. In this context, it is concluded that there is a need for substantial clari fication of these points set out in the four questions as well as for the development of appropriate recommendations.

Ecologo-geochemical conditions of surface water and groundwater are considered in the case of one of the industrially most developed states of India, West Bengal, within the Damodar river basin near Damodar City. The observations were made in the pre-monsoon period of March 2019, a period with the worst conditions of wastewater dilution. To analyze total chemical composition of water samples a standard set of analytical methods was used; trace elements were analyzed by inductively coupled plasma mass spectrometry. Data obtained indicate both the unsatisfactory water quality and the intense self-purification processes. The waters under study are, in general, characterized as freshwaters (except for the stream receiving wastewater from the chemical plant where the water is “brackish”), HCO3-Ca or HCO3-Na (except for the water in the stream near the chemical plant, which is Cl-Na , and groundwater, which is Cl-Ca ). In most cases, the waters are oversaturated with carbonates, compounds with humic acids, quartz and undersaturated with primary aluminosilicates. The main pollutants are organic compounds according to the values of permanganate demand and chemical oxygen demand, Al, F^-, NH4⁺, Fe and Mn . Phosphates, As, Pb and some other chemical elements are also presented in significant concentrations. It is shown that most pollutants settle in bottom sediments of the streams receiving wastewater from industrial enterprises within a few kilometers from the wastewater discharge points. The mechanism of water self-purification is, possibly, associated with co-precipitation and sorption of a great number of substances on particles of poorly soluble carbonates and hydroxides of Ca, Fe and some other metals at relatively high pH values associated with the consumption of carbon dioxide by microorganisms.

The 250 ^th anniversary of the birth of Alexander von Humboldt (1769-1859), the great geographer, traveler, honorary member of the St. Petersburg Academy of Sciences and of the Imperial Russian Geographical Society was widely celebrated in 2019. Special emphasis is placed on the famous travels of the German scientist to Ural, Siberia, and to the Caspian Sea in 1829. An analysis is made of A. Humboldt’s expedition which promoted the achievement of the planned targets. Among them are a highly skilled accompaniment and support from local authorities in regions of Russia, a good transport and route support, a careful preparation of objects for study, a gratuitous availability of samples and cartographic data, command of the German language by most of the respondents, and a wealth of expedition experience by A. Humboldt and his fellow-travelers. The main results of the travel promoting the development of national science and education are considered.