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The paper examines why voluminous felsic magmas formed during subduction initiation in the Tannuola-Khamsara island-arc system (Tuva, Central Asia), focusing on the Ondum subzone. We report geochemical, Sm-Nd and U-Pb zircon data for plagiorhyolites-plagiodacites, andesibasalts-andesites-dacites, their intrusive equivalents (plagiogranites-tonalites and quartz diorites-diorites), and gabbroic inclusions. Two geochemical types are recognized: depleted Type I (dominant; ε_Nd(t)=+10.4…+6.4, (La/Yb)_N=0.3–0.9) and moderately depleted Type II (subordinate; ε_Nd(t)=+7.7, (La/Yb)_N=1.0–1.7). Type I felsic rocks are consistent with low-pressure, water-saturated partial melting of a gabbroic source, whereas Type II reflects lower degrees of melting and/or weaker fluid input. SSZ ophiolites (580–569 Ma) occur in the forearc, arc and back-arc domains, implying near-synchronous SSZ crust formation at subduction initiation. Xenogenic zircon (571–663 Ma) and metamorphic blocks suggest involvement and partial preservation of an inherited oceanic substrate, possibly with an unusually thick terrigenous-carbonate sedimentary cover. We model spatially heterogeneous SSZ extension: new crust formed in spreading sectors, whereas non-spreading segments retained pre-subduction blocks where hydration and anatexis of gabbroic basement (potentially aided by deep seawater-driven hydrothermal circulation along faults) produced large volumes of felsic melts. Local slab melting is recorded by an adakitic tonalite (556±3 Ma, ε_Nd(t)=+1.0), consistent with a terrigenous sediment component carrying an evolved crustal isotopic signature.

a:2:{s:4:"TEXT";s:1439:"The research develops the classical concept of the skin factor proposed by M.F. Hawkins [Hawkins, 1956]. We demonstrate a fundamental limitation of the Hawkins model, in which the permeability of the drilling mud filtrate invaded zone is assumed to be constant (

A new oil-in-water microemulsion composition has been proposed, incorporating a suite of multifunctional chemical additives (surfactants, improver additives) produced and marketed in Russia. The composition is intended for use as a hydraulic fluid for mechanised mine supports. The physicochemical properties of the developed concentrate and the well-known SOLCENIC GM 20 microemulsion concentrate (Fuchs, Germany) are close to each other. The developed microemulsion concentrate is recommended as a replacement for the foreign-made product.

During the operation of ash dumps, process water at the base of man-made massifs forms a man-made aquifer characterised by high mineralisation, hydrocarbonate-calcium-sodium composition, and a highly alkaline environment. Based on the presented studies of the aquatic environment and previously obtained data on the material composition of the solid phase of man-made deposits, the influence of the aggressive composition of waters in the man-made aquifer on the qualitative composition of ash and slag has been analysed. It is revealed that the ongoing disintegration of carbonates and aluminosilicates in the lower horizon of ash and slag massifs lead to the release of a wide range of hazardous substances. Technogenic processes have a significant impact on the qualitative composition of technogenic filtrate and the migration activity of water-soluble ingredients, which can significantly affect the state of the environment and require systematic environmental monitoring.

The use of high-calcium fly ash (HCFA) as an expanding component of cements contributes to an increase in the level of their utilisation and improvement of binding properties. The influence of HCFA fractions of different size and composition on the expanding effect of binders based on them is studied in the work. The binders based on 100 % of three industrial fractions of high-calcium fly ash of different dispersion and composition, sampled from the 1^st, 2^nd and 4^th fields of the Krasnoyarsk TPP-2 electrostatic precipitators, were studied; the expanding effect of binders based on these fractions was determined with respect to Portland cement (PC) grade CEM I 42.5N. It was determined that an increase in the volume of hardening specimens is 6-19 and 6-42 % after hardening for 5 and 120 days, respectively. An increase in the volume of specimens correlates with the content of CaO and MgO oxide phases in the initial HCFA fractions and is accompanied by a decrease in the average density and compressive strength. The specimens of cement-fly ash compositions with the content of 50 % PC and 50 % HCFA, including a mixture of different fractions of FA, were studied. The positive effect of HCFA fractions on the properties of composite cement, including the regulation of the expansion effect and an increase in compressive strength, was determined.

The procedure for the quantitative determination of F, P, S, V, Cr, Co, Ni, Cu, Zn, As, Pb, Th, and U in the samples of coal and in soil samples containing coal is described. X-Ray fluorescence (XRF) analysis was carried out using wavelength-dispersive X-ray fluorescence spectrometer S8 TIGER (Bruker, Germany). Measurements were carried out in the vacuum mode. The dried samples were prepared in the form of pressed tablets. To obtain calibration characteristics and carry out metrological studies, a set of certified reference materials (CRMs) of shale, coal ash, sediments and soils of different chemical composition was chosen, and mixtures with different CRMs powders and graphite content were prepared. The ratio of CRMs to graphite was determined according to the data on total carbon content in the objects under investigation, and the data on the ash content of coal. To account for mutual influences of the elements, the a-correction method was used, in most cases introducing the fluorescence intensities of elements present in the samples (carbon, etc.) as influencing factors. The calculated values of the detection limits for the elements under determination vary from 0.6 to 20 mg/kg. The accuracy of XRF analysis results was controlled using CRMs of shale (SGR1 and SDC1), anomalous silt (SGH5) and black soil (SP1), as well as the mixtures of SGHM3/graphite (1 : 4) and DVT/graphite (1 : 3). It has been determined with t-test that the results of XRF analysis do not contain significant systematic errors. The procedure for X-ray fluorescence determination of F, P, S, V, Cr, Co, Ni, Cu, Zn, As, Pb, Th and U was used to study the distribution of elements in the samples of coal fractions from the deposits of the Irkutsk Region and in the samples of soils containing these fractions, which were collected in the residential area of the Oktyabrsky district of the city of Irkutsk during summer 2024. Based on XRF data, the conclusion concerning the effect of long-term coal presence in soils on their elemental composition is made.

The results of experiments on the direct oxidation of benzene to phenol using oxygen and air in a barrier discharge under the conditions of efficient removal of reaction products from the reaction zone are presented. In the case of benzene oxidation with oxygen, phenol content in the products reaches ~73 wt%, while arenediols are formed in insignificant amounts (~8 wt% as a total, mainly hydroquinone). The oxidation of benzene with air leads to an increase in the phenol content in the products to ~77 wt% and a decrease in the content of diatomic phenols to ~3 wt%. The conversion of benzene per single pass of the vapour-gas mixture through the reactor reached 0.5 wt% in oxygen and 0.4 wt% in air. The direct oxidation of benzene to phenol with air is accompanied by the formation of a precipitate. Its structure has been studied, and the mechanism of its formation has been discussed. It has been shown that the formation of the precipitate during benzene treatment with air is caused by reactions involving excited nitrogen molecules. The main stages of the mechanism of oxidation are considered in detail, and the results of calculations of electron energy losses in electron-molecular reactions occurring at the discharge initiation stage in the barrier discharge are presented. These calculations allow estimating their contribution to the mechanism of formation of intermediate active particles and stable molecules, as well as the routes of the benzene oxidation process in the barrier discharge plasma. It has been demonstrated that phenol formation occurs as a result of direct interaction between the benzene molecule and atomic oxygen. It has been shown that phenol formation occurs as a result of the direct interaction of the benzene molecule with atomic oxygen. It is demonstrated that benzene oxidation in the barrier discharge surpasses some thermocatalytic methods in terms of reaction rate and exhibits comparable results in terms of phenol formation selectivity.

The effect of low-temperature Ni-Ti eutectics on the mechanochemical in situ synthesis of titanium carbide in a nickel matrix has been studied by X-ray diffraction methods and X-ray spectral microanalysis. When comparing the systems containing 50 wt% Ti-(Ti-C) and 50 wt% Ni-(Ti-C), it has been determined that in the first case the induction period of reaction is 4 min, and in the second case the synthesis proceeds in a mechanically stimulated reaction mode with an induction period of 110 s and is fully completed by 120 s. By the time of reaction completion (120 s), a significant amount of TiC_x (up to 38 wt%) with higher carbon content (C/Ti = 0.83) is detected in the reaction mixture with 50 wt% Ni, and the formed crystallites are larger (~30 nm) than in the mixture 50 wt% Ti + (Ti + C), which justifiably suggests a liquid-phase synthesis mechanism. In the reaction mixture with 50 wt% Ti, by 4 min of mechanical activation, up to 42 wt% TiC_x with crystallite size ~9 nm is formed. In the system 50 wt% Ni-(Ti-C), the dispersed hardening of nickel with titanium carbide is enhanced by solid-solution hardening, as evidenced by the formation of Ni(Ti) solid solution within the same synthesis time intervals (120 s). Shortening of the induction period can significantly reduce the contamination of synthesis products with the material of grinding media and drum walls.

The purpose of this study is to substantiate the existence and prevalence of the phenomenon of dynamic equilibrium in the development of morphological patterns of permafrost landscapes, the related regularities, and the possibilities of their application for forecasting and analyzing processes. The state of dynamic equilibrium in the development of morphological patterns is quite common for certain permafrost landscapes, such as abrasion and thermo-erosional shores, thermokarst plains with fluvial erosion, and floodplains. It is characterized by a combination of constant changes in the elements of the morphological pattern with the constancy of its characteristics (first of all, quantitative) for the landscape as a whole. A promising way to substantiate the existence of dynamic equilibrium of the morphological pattern of a given landscape is to analyze its mathematical model. It is argued that the state of dynamic equilibrium is reflected in a number of specific statistical characteristics. Thus, for thermokarst plains with fluvial erosion, a consistent statistical (integral-exponential) distribution of thermokarst lake areas and a correlation between the average area of thermokarst lakes and the average area of alas depressions (khasyreys) are observed. The obtained information on the state of dynamic equilibrium can be used for planning landscape monitoring, as well as for determining the quantitative parameters of dynamic landscape processes on the basis of the analysis of the quantitative characteristics of its morphological pattern without stationary observations.

An increase in air temperature entails an increase in soil temperature, which is dangerous for buildings and structures constructed with the foundation soils preserved in a frozen state. One of the most common methods of maintaining the frozen state of foundation soils is the construction of a ventilated basement. This system cools the soil by circulating cold atmospheric air. However, with the rise in the mean monthly temperature, the efficiency of the ventilated basement decreases. In a number of regions, the construction of buildings with a ventilated basement without additional measures to cool the foundation soils is already insufficient and may lead to the instability of buildings during their operation. In this paper, analytical calculations are carried out to determine the critical year for the loss of efficiency of ventilated basements according to data from weather stations in the north of European Russia and Western Siberia, as well as in the Central and Eastern Siberia. These calculations are based on representative values of the maximum soil temperature at the base of the pier foundation at the edge of the building with ventilated basement for the beginning of operation in 2025, 2075, and 2125.