卷 68, 编号 4 (2023)

Knowledge of mineral–melt partition coefficients (D) is necessary for geochemical modeling of magma formation and evolution. The main source of these parameters is experiments on equilibrium between minerals and silicate melt. The database on mineral–melt equilibrium experiments has grown continuously, which allows one to refine partition coefficients and reveal the most important factors affecting them. This paper reports the analysis of available experimental data on trace element partitioning between olivine and melt (7000 experiments from 587 publications were used). Based on the statistical processing of the data array, the dependence of D on melt and olivine composition and P–T conditions was evaluated. It was found that most of incompatible elements are either insensitive or moderately sensitive to these parameters. Among the compositional parameters, CaO content in melt is most significant. It was shown that D estimates can be significantly improved by using ratios of D values for different elements. Such ratios are often independent of experimental parameters and much less variable than D values for particular elements. The obtained D estimates for basaltic compositions vary within six orders of magnitude, from <10–5 (U, Th, and La) to ~5–10 (Co and Ni). The low D values for most elements (<0.1) indicate that many trace element ratios in melts do not change significantly even at high degrees of olivine crystallization. The obtained estimates were compared with data on element partitioning between high-pressure (Mg,Fe)2SiO4 phases (wadsleyite and ringwoodite) and silicate melt and between olivine and carbonate–silicate melts. In both cases, there is a close similarity to element partitioning between olivine and silicate melt. One exception is REE. DREE values for the wadsleyite/ringwoodite–melt and olivine–carbonate melt systems are approximately one order of magnitude lower than those for olivine–silicate melt partitioning.

Obtained data on the composition and properties of ash nanoparticles from Klyuchevskoy, Tolbachik, Kizimen, and Shiveluch volcanoes (Kamchatka, Russia) are generalized. It has been shown that the concentration of toxic and potentially toxic metals and metalloids (Ni, Cu, As, Se, Ag, Cd, Sn, Te, Hg, Tl, Pb, Bi) in volcanic ash nanoparticles can be 10–535 times higher than their concentration in bulk polydisperse samples. The most volatile elements such as As, Sn, Te, Hg, Tl, and Bi have the highest concentration factors in the range of 100–535. Based on the data on single particle inductively coupled plasma mass spectrometry, it is assumed that the listed metals and metalloids are accumulated in the fraction of volcanic ash nanoparticles mainly through the condensation of these elements or their compounds from the gaseous phase and the formation of individual (single) nanophases with an average size in the range of 12–74 nm. It should be noted that approximately an order of magnitude less nanoparticles have been isolated from the acidic volcanic ashes of the Kizimen and Shiveluch volcanoes as compared to those of basic ashes of the Tolbachik and Klyuchevskoy volcanoes. This fact is inconsistent with published data showing that the fraction of fine ash is usually larger for acidic explosive eruptions compared to basaltic eruptions. The Pearson correlation coefficients between the basicity index of volcanic ash and the concentration of more than 50 elements in the ash and ash nanoparticles have been calculated. Some elements have a correlation coefficient |R| > 0.7, which, according to the Chaddock scale, indicates the high degree of correlation. It is noted that a number of elements have an opposite correlation between the basicity index of ash and the concentration of elements in ash and ash nanoparticles. For example, Hg and Tl content in ash have a negative correlation with basicity index, that is, their concentration decreases with increasing basicity index of the ash, whereas their concentrations in nanoparticles positively correlate with ash basicity index. The concentration of Ca, Ho, and Er in the ash increases with an increase in the ash basicity index, whereas ash nanoparticles show an opposite correlation. The revealed regularities are unexpected and confirm the unique features of nanostructures and raise new questions of nanogeochemistry.

The 1-D burial and thermal history of the Korotaikha depression in the Timan–Pechora basin was numerically simulated for the sedimentary sequences of three wells: Korotaikhinskaya 1, Labogeyskaya 15, and Khavdeiskaya 1. This made it possible to numerically assess the conversion history of the hydrocarbon (HC) potential of source rocks in the southwestern flank of the Korotaikha depression in the northeastern Timan−Pechora basin. The modern modified kinetic spectrum of vitrinite maturation was used in calculations of the vitrinite reflectance to clarify the thermal history of the sedimentary cover of the study area. The occurrence of episodes of hydrothermal activity follows from comparison of the calculated and measured values of the vitrinite reflectance and explains the jumps in the maturity of organic matter at the boundaries of the unconformity of Quaternary and Triassic sediments, as well as the Permian and Carboniferous sediments. The simulations suggest a high conversion of the initial HC potential of the source rocks of the Silurian and Domanic horizons, Tournaisian, and Visean ages in the Korotaikhinskaya and Labogeiskaya areas and moderate generation in the Havdeyskaya area. The simulation shows that the high grades of the catagenesis (MC5 and higher) of the main source rocks and the significant role of secondary cracking of liquid HC fractions in the central part of the Korotaikha depression (wells Korotaikhinskaya 1 and Labogeyskaya 15) suggest that the possible HC accumulations should contain only gas. Accumulations in the southern part of the depression (Khavdeiskaya area), where secondary cracking was minimal and source rocks occur within the oil window, should contain both oil and gas (due to Permian rocks with terrigenous organic matter).

The article considers the distribution of mobile forms and bulk concentrations of Zn, Cu, Ni, Co in the genetic horizons of the studied soils at the studied area in the central part of the Valday Upland. The contents of easily soluble, exchangeable, and sum of potentially mobile forms of elements were determined by extraction method. It was found that in all genetic soil horizons, the bulk Zn content and the concentration of its mobile forms are higher than those of other elements, but Cu demonstrates the most intense migration. The predominant form of Cu migration is complexes with organic compounds. According to the calculated data of the extraction criterion (EC), the studied soils are background. The availability of Zn, Cu, and Co in the soils was estimated, which characterizes the potential reserves of elements as plant nutrients.