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The paper discusses possible immiscibility between fluoride salt ("cryolite") and silicate liquids into which the parental melt of the Katugin massif exsolves, and the petrological implications of this phenomenon. Results of a detailed study of the cryolite and zircon are presented. Liquid immiscibility is demonstrated to have triggered the massive crystallization of zircon and, together with the processes of subsequent evolution of the cryolite melt, contributed to the formation of the large cryolite bodies. Data on mineral-hosted inclusions were used to estimate the crystallization temperatures of fluoride salt and silicate melts and outline the pathways of their evolution during the formation of the massif. It is shown that the granites of the Katugin and West Katugin massifs were most likely derived from distinct sources, that differed mainly in fluorine content. Data on the chemical composition of three zircon generations identified in the granites of the Katugin massif are presented. [ABSTRACT FROM AUTHOR]

The level of chromosomal abnormalities in the somatic cells of adult individuals is characterized by significant interindividual variability, which may be partly affected by the genetic and epigenetic background. The epigenetic landscape in cells is largely determined by genome methylation. This study aimed to analyze the relationships between global genome methylation and the frequencies of chromosome abnormalities in lymphocytes of plutonium workers. The frequencies of chromosome aberrations, micronuclei, aneuploidy of chromosomes 2, 7, 8, 12, X, and Y and sister chromatid exchanges were analyzed in the lymphocytes of 40 male workers from a nuclear chemical facility (Seversk, Russia) with incorporated plutonium-239 and 49 healthy male volunteers who had no occupational exposure to ionizing radiation. The long interspersed nuclear elements-1 (LINE-1) methylation index was assessed as a well-known marker of global genome methylation. The frequencies of centromere-negative micronuclei (4.74 ± 2.26 vs. 3.02 ± 1.69‰), chromosome-type aberrations (0.81 ± 0.79 vs. 0.44 ± 0.69%), and total chromosome non-disjunction (0.93 ± 0.43 vs. 0.50 ± 0.25%) were significantly higher in the group of workers than in controls (p < 0.05). The LINE-1 methylation index did not differ significantly between the worker and control groups (74.93 ± 3.63 vs. 73.92 ± 4.62%). Correlations between LINE-1 methylation and the frequency of micronuclei (R = –0.35, p = 0.031) were observed in the control group, whereas correlations of LINE-1 methylation with chromatid-type aberrations (R = –0.42, p = 0.012) (but not chromosome-type aberrations) and with sister chromatid exchanges (R = –0.53, p = 0.004) were observed only in the group of plutonium workers. Thus, LINE-1 hypomethylation after plutonium exposure is associated mainly with chromatid breaks, either repaired or misrepaired. [ABSTRACT FROM AUTHOR]

The issue of the age of rare-metal granites of the Zashikhinskoye field is discussed. To obtain U–Pb (ID TIMS) geochronological data, a modified "chemical abrasion" technique with preliminary high-temperature annealing was used for metamictic zircon. Estimates of the age of alkaline leucogranites and albitites coincide and correspond to the age of formation of rare-metal granites of the Zashikhinskoye field 267 ± 1 Ma. Within East Sayan, igneous rocks with close ages are not yet known. The closest area of magmatic activity of this time was the large zonal Khangai magmatic range, which arose under the influence of the mantle plume and is characterized by widespread development in its peripheral part of alkaline and bimodal associations, including rare-metal magmatic ones. The Zashikhinskoye field is more than 350 km from the edge of its range. Nevertheless, on the basis of geochronological and geochemical data, it was assumed that this field was associated with the activity of the Khangai plume. [ABSTRACT FROM AUTHOR]

The paper presents data on the miaskite syenites of the Lovozero massif, pulaskites of the Khibiny massif, rocks of the larvikite–lardalite series of the Kurga massif, and subalkaline volcanics, which are preserved as remnants in the roof of the massifs. The studied rocks are characterized by a low agpaitic coefficient of <1, the absence of minerals typical of peralkaline rocks (eudialyte, aenigmatite, etc.), and the presence of zircon. The morphological features and chemical composition of zircon from miaskite of the Lovozero massif syenite indicate that the mineral is of magmatic nature. The crystallization age of the miaskites was dated on zircon at 373 ± 5 Мa. The isotope-geochemical characteristics of rocks of the subalkaline series indicate that the miaskites of the Lovozero massif are of mantle origin, show no indications of their crustal contamination, and were produced during the evolution of ankaramite melt. The pulaskites of the Khibiny massif were formed according to an analogous scenario, except their assimilation with crustal material, whose proportion did not exceed, according to model calculations, 10%. [ABSTRACT FROM AUTHOR]