Volume 70, Nº 4 (2025)

CaSiO₃ inclusions in diamonds from the Juina area in Brazil have low Fe (0.08–0.53 wt. % FeO) and Al (0–1.52 wt. % Al₂O₃) concentrations; they belong to the ultramafic association. Two different types exist among CaSiO₃ grains. Type I has a normal REE_n pattern, while type II has a sinusoidal REE_n pattern. Type I CaSiO₃ associates with high-Mg – high-Ni protogenetic ferropericlase, and type II associates with high-Fe – low-Ni syngenetic ferropericlase. Thus, type I CaSiO₃ grains are protogenetic, formed, like high-Mg – high-Ni ferropericlase, in the upper part of the lower mantle as davemaoite (CaSi-perovskite), and type II CaSiO₃ were formed in the transition zone as breyite. The enrichment of CaSiO₃ in REE, particularly in LREE, corresponds to high values of their partition coefficient CaSiO₃/melt and shows the Ca-SiO₃’s origin from a mantle material under high pressures. The isotope characteristics of the studied CaSiO₃ demonstrate strong geochemical heterogeneity in the inclusions. The ⁸⁷Rb/⁸⁶Sr ratios in type II CaSiO₃ (0.127–3.23) are 3–4 orders higher than in type I (0.0008). Even within a single diamond, different CaSiO₃ grains have ⁸⁷Rb/⁸⁶Sr ratios varying from 0.014 to 3.23. The same is true for U/Pb isotope systematics (e. g., ²³⁸U/²⁰⁶Pb varies in one sample in an order of magnitude from 0.031 to 0.312) and, to some extent, for Sm/Nd ratios. This implies the geo-chemical heterogeneity in Deep Earth on a very small scale.

New data on the content of humic substances (HS) in the East Siberian Sea are presented. The results of the studies showed that the degree of humification of organic matter (OM) in the studied samples of the upper layer of bottom sediments of the sea varies from 21 % to 9 % and averages 15 %, which is typical of low-productivity Arctic seas. It was found that the average HA values (for the considered profiles) were 0.16 and 0.20 %, which is typical of oxidized marine sediments. The concentration of organic carbon (C_org) varied from 0.34 % to 1.89 % depending on the granulometric type of sediment. It is shown that the total C_org consists of 10–40 % HS, the HS themselves consist of 12–30 % humic acids (HA) and 70–88 % fulvic acids (FA), which indicates early humification of sediments. НAs were determined only in the sediments of the coastal part of the sea. FAs were determined in all studied bottom sediments.

For the first time, a comprehensive study of urban dust collected in Krasnoyarsk city was carried out. The results obtained enabled the features of elemental composition of urban dust and their natural and anthropogenic sources to be investigated. Dust samples (n = 68) were collected in different functional areas of the city. The content of 70 elements was determined in the collected samples of urban dust. The diagrams of the (CaO + + Na2O) – Al2O3 – K2O and (CaO + Na2O + K2O) – Al2O3 – (Fe2O3 + MgO) composition showed that the mineral part of most of the studied Krasnoyarsk dust samples is represented by plagioclases. Values of enrichment factors and geoaccumulation indices showed contamination of Krasnoyarsk dust by Co Sn, Bi, Pb, Mo, Cu, As, Zn, Cd, W, Ag and Sb. Regularities of microelement accumulation depending on sampling locations were found. Sb accumulates to a large extent in samples collected on major highways of Krasnoyarsk, while elevated contents of As, Cu and Co are typical for samples collected in industrial areas of the city. The principal component analysis and Pearson matrix allowed to identify 6 groups of elements in the dust samples, which can be attributed to various natural and anthropogenic sources: Al, Ti, Cr, Fe and Ni – weathering of soils and rocks; Fe, Co, Ni, Cu and As – emissions from metallurgical plants and coal-fired thermal power plants; W, Bi, Zn and Mo – heavy metallurgical and mechanical engineering industries; Cu, Cd, Sn and Pb – emissions from motor and rail transport, as well as wear of metal parts and structures; Sn and Sb – wear of brake pads and tires and industrial emissions; Hg – weathering of soils and rocks.