The Gydratny Fault, extending in SW-NE over 60 km, is situated in the central basin of Lake Baikal. This fault governs a distribution of hydrocarbon gas discharge zones on the lake bottom, many of them are hydrate-bearing. During the Class@Baikal-2019 expedition gas samples were obtained from bottom sediments along the fault zone, molecular and isotopic properties of the gases were studied. It is concluded that the fault zone is permeable for hydrocarbons and serves as an important fluid flow conduit from deep sources to the surface. The most intensive gas seepage was determined along the central and north-eastern segments of the fault zone where it is associated with the MSU hydrate-bearing structure and the Novosibirsk and Ukhan mud volcanoes. Within these structures the highest concentrations of methane and C2+ components were detected, the heaviest isotopic composition of methane carbon (–57‰ VPDB) were identified and near-surface gas hydrate accumulations were observed. The south-western segment of the fault is characterized by the lowest concentrations of gases in sediments with light carbon isotopic composition of methane (–76‰ VPDB).

A dominant gas migration mechanism (advection or diffusion) in the upper part of the basin sedimentary section conditions the registered concentrations of methane and its homologues in sediments and their carbon isotopic composition. Diffusion and dispersion of migrated thermogenic gases and significant portion of microbial methane in seeping gases are characteristic for the areas where the fault is buried under relatively thick modern sediments. Focused gas migration followed by its focused discharge are specific for the areas where the fault propagates to the lake floor and is well-expressed in a bottom relief. Two models of hydrocarbon gases migration to the surface explaining the observed gas-geochemical characteristics of bottom sediments are described and discussed. Obtained results can help in enhancing interpretation of data of gas geochemical prospecting for offshore oil and gas.

The inefficiency of short-term forecasting of strong earthquakes is obvious. New methods and hypotheses of preparation of seismic events are interesting, but exact and reliable forecasts will not follow. Unpredictability is undoubtedly predetermined by nonlinearity, self-similarity, by a chaotic (not stochastic) and by bifurcations dynamics of seismic process in fractal geomedium. Superdependence of dynamic systems on initial conditions, vagueness of distinctions of background and abnormal structures and conditions, at rigid requirements to adequacy and representativity of forecasts, inevitably lead, to the negative decision of a problem. This article continues the long-standing scientific discussion about earthquake prediction, which was resumed after the our publication [Koronovsky et al., 2019].

The results of geochemical research of the cyclic section of the Upper Cretaceous deposits near Staryi Oskol town at Belgorod province and paleogeographical and paleoclimatic interpretation of these data were given for the first time.

This article presents the results of studies of the material constitution and physical properties of rocks of foundation of the West Siberian Plate. It is shown that anthraxolite and kerite groups are present in bitumen rocks. We assume that the bitumens create a Late Paleozoic paleo-deposit, transformed under the conditions of apocatagenesis. Impregnation with highly transformed organic matter leads to a significant decrease in electrical resistivity to values of 1–30 Ohm metre, which must be taken into consideration when interpreting low-resistivity zones on log data.

Three series of experiments were carried out to study the possibility of replacing quartz sand in the initial charge for the production of glass with a silica clay. The experiments were carried out at atmospheric pressure and temperatures of 900–1200 С. It is shown that the complete replacement of quartz sand with a silica clay and the use of the presented initial compositions based on silica clay in the glass industry will lead to an increase in the temperature in the technological scheme of production, an increase in energy consumption and is economically unprofitable.

Production schemes are promising, in which, along with the silica clay, the original charge contains cullet. It is shown that the disappearance of crystalline phases in this case in the samples with the addition of the silica clay occurs at a lower temperature than in the samples without the silica clay.

Natural processes contradictive to the common organic (sedimentary and migrational) theory of oil formation were concluded to take place based on the study of the hydrocarbons-biomarkers distribution regularities at the molecular level in the dispersed organic matter of rocks, petroleum and kerogen thermolysis products.

Here specific examples of the generation of oil (concentrated organic matter) directly in the reservoir, i.e. reduced scheme of naphthydogenesis, excluding the process of migration were presented. At the same time, these examples do not exclude the migration of organic matter from the «oil source strata», but are an exception that confirms the general rule. It was shown that the study of organic matter, organic carbon (TOC), chloroform-soluble bitumen, pyrolysis “Rock-Eval”, etc., necessarily supporting the conclusions with data from a detailed study of the hydrocarbon composition at the molecular level.

Experiments on the melting of samples of fluorite-containing ongonites from the Ary-Bulak massif at 700–800 °C at a pressure of 100 MPa and oxygen fugacity corresponding to the Ni–NiO and Mt–Hem buffers were carried out. In all experiments, the limit of fluorine content in the aluminosilicate melt and saturation with respect to fluorite and topaz were reached. The change in oxygen fugacity does not qualitatively affect the phase relations in the studied samples, but leads to a slight increase in the solubility of topaz and a decrease in the solubility of fluorite in the silicate melt. In the composition of the silicate melt, there is a corresponding change in the value of the agpaite coefficient Ka and the content of CaO.

The distribution of lithium between aluminosilicate and alkali-alumina-fluoride salt melts in a granite system with the limiting contents of water and fluorine at temperatures of 700– 800° C and pressures of 10–50 MPa has been experimentally studied. It is shown that lithium is distributed in favor of the salt melt under all conditions. An increase in the water content in the system by more than 20 wt.% and a pressure from 10 to 50 MPa leads to a decrease in the partition coefficients of lithium between the salt and aluminosilicate melts by 2–4 times.

Researchers’ views on the causes of mud volcanism have evolved over time. In the early stages, mud volcanoes were considered common to volcanoes. Later, they began to be associated with processes in sedimentary basins, although attempts to link mud volcanism with magmatic manifestations and replenishment of juvenile components still exist. Findings of mercury, native gold, silver, sulfur, copper, iron and accessory minerals in the products of mud volcanoes in recent years allow a number of researchers to assume the existence of deep-seated flows of hydrocarbons from the mantle, and to consider mud volcanoes as a kind of degassing pipes. The results of the analysis of trace element composition of mud volcanoes sediments in different regions of the world (Kerch Peninsula, North-West Caucasus, Sakhalin, Dzhungar Basin, Andaman Islands, Cadiz Bay, Eastern Mediterranean and Eastern Java) confirm the idea that in them, as in the mud volcanoes fluids (water, methane, carbon dioxide, and helium), traces of the mantle/juvenile component are not observed.

The paper presents the experimental results of the rare earth elements and yttrium (REY) biosorption in the natural surface waters and groundwater in the presence of living and inactivated organotrophic bacteria (Curtobacterium sp., Ralstonia sp., Pseudomonas sp., Bacillus sp., Brevibacterium sp., Microbacterium sp.,) under different environmental pH conditions. We find that the biosorption process is mainly regulated by two factors: the aqueous solution’s pH and the bacteria strains concertation. The water acidity significantly effects on the bacteria sorption capacity for all studied strains. We discover a decrease in REY sorption with an increase in pH due to lower absorption of REY on the cell walls of bacteria. The process of REY biosorption proceeds more intensively by living bacteria than in the presence of inactivated microorganisms. We observe that at neutral pH values all studied bacterial strains sorb light REY (lanthanum, praseodymium, neodymium), in more acidic solutions (pH 2) the heavy ones (lutetium, europium). The REY sorption decreased with an increase in the living and inactivated bacterial concentration.

The paper presents the results of numerical simulation of cluster pumping test in an heterogeneous aquifer with transmissivtyvariability described by the model of a stationary random field of its logarithm with a given scale of correlation in the plan. The case of comparable planar distance to observation wells and correlation scale is considered. Parameters of the model of transmissivity heterogeneity of the simulated aquifer are obtained from the data of experimental tests carried out within the limits of the South Voronezhskoye groundwater field. The simulation has shown that the average results of interpretation of these cluster pumping data correspond to the geometric value of the transmissivity, which confirms the previously obtained approximate theoretical result for the model of small-scale heterogeneity and extends it to an almost important case of similarity of cluster well test planar sizes and spatial scale of heterogeneity. Thus, the present study has confirmed the possibility to apply standard methods in processing of cluster pumping data under planned heterogeneity conditions to estimate the equivalent aquifer transmissivity in the well cluster location area.