pdf № 342, June

DOI: 10.19110/geov.2023.6.1

Glaucophane-bearing rocks — indicators of high-pressure metamorphism — were earlier found in the Polar Urals in the Neoproterozoic deposits of the Nyarovey series, in the northern part of the Marunkeu eclogite-amphibolite-gneiss complex, and in the foot of the ultramafic massifs of the Main Ural Fault (MUF) zone. We have discovered high-pressure rocks in the western endocontact of the Kharbey amphibolite-gneiss complex, where they are represented by garnet-glaucophane, garnet-glaucophane-barroisite rocks and garnet-barroisite amphibolites formed during progressive zonal metamorphism. From the western boundary of the complex to the east, temperature gradually increases from 400—480 °C (for garnet-glaucophane rocks) to 495—570 °C (for garnet-glaucophane-barroisite rocks and garnet-barroisite amphibolites) at a pressure of 11—16 kbar. We determined that the high-pressure metamorphism had an areal distribution within the Kharbey metamorphic complex and, apparently, marked the Paleozoic subduction-collision processes of formation of Uralides.

Keywords: garnet-glaucophane rocks, high-pressure metamorphism, Polar Urals, phengite.

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DOI: 10.19110/geov.2023.6.2

Rare-metal and thorium mineralization (uranium pyrochlore, niobaeschynite-(Ce), aeschynite-(Ce), thorite, and thorianite) was studied in the dike complex of fluid-explosive rocks of the Middle Timan. The source of thorium and rare-metal-rare-earth elements was carbonate-alkaline solutions of carbonatites, paragenetically associated with the formation of dike rocks.

Keywords: fluid-explosive dikes, rare-metal and thorium mineralization, Middle Timan

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DOI: 10.19110/geov.2023.6.3

The results of mineralogical studies of the Besapantau deposit, typical of the Muruntau ore field (Central Kyzylkum), belonging to the low-sulfide gold-quartz geological-industrial type, are discussed. The most productive for gold is the early sulfide (pyrite-arsenopyrite) stage of mineralization. The minerals associated with gold and silver include pyrite, arsenopyrite, galena, fahlore, sulfoantimonides, and tellurides. Native gold varies in composition from electrum to very fine gold. Silver is present in the forms: native, gold-bearing, hessite, argentite, stephanite, pyrargyrite. Arsenopyrite can serve as an effective search indicator for gold in the conditions of forms, and also as the Central Kyzylkum, and the content of arsenic in ores can serve as a criterion for the degree of gold enrichment.

Keywords: Uzbekistan, Central Kyzylkum, Muruntau ore field, Besapantau deposit, gold and silver minerals.

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DOI: 10.19110/geov.2023.6.4

The law of cosmogeochemical differentiation discovered by the remarkable Russian geochemist Yu. G. Shcherbakov and the geochemical classification of elements formulated on its basis on the scale of the Periodic system of D. I. Mendeleev are analyzed. Based on new research results, it is shown that signs of the fundamental cosmic distribution code of chemical elements are quite clearly preserved in terrestrial geological and biological objects.

Keywords: Yu. G. Shcherbakov, law of cosmogeochemical differentiation of elements, discovery of sulfide-indium-manganese deposit.

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DOI: 10.19110/geov.2023.6.5

Monodisperse spherical silica particles, as a basis for creating supramolecular 3D matrices, are currently of increasing interest due to the prospects for their wide application in the synthesis of new nanocomposite materials. At the same time, one of main problems of their large-scale synthesis is associated with the unstable behavior of tetraethoxysilane (TEOS) during hydrolysis, which leads both to the deviation of the particles from a given size and their shape from a spherical one. In this paper, on the basis of the study of tetraethoxysilane from various manufacturers, we continued to work on determining factors that can influence the process of hydrolysis of tetraethoxysilane and, as a result, the monodispersity and size of the formed particles, and also other factors. To solve this task, all TEOS samples were studied by various physicochemical methods of analysis, including Fourier IR and Raman spectroscopy, gas chromatography-mass spectrometry. As a result of the studies, we showed that the presence of di- and trisiloxanes in the system did not significantly affect the size of the formed silica particles, while significantly accelerating the rate of formation of silica spheres. Moreover, the presence of methoxyl groups in the initial silane, and an insignificant content of ethanol in the system did not affect the size stability of the formed particles. At the same time, the replacement of part of the ethoxy groups in the initial TEOS by methyl or ethyl groups, as they are not capable of participating in the hydrolysis reaction, largely contribute to the deviation of sizes of the formed silica particles from each other. The results obtained on the effect of impurities on the size of the formed silica globules are important, among other things, for understanding the processes of formation of natural supramolecular structures of silica.

Keywords: monodisperse spherical silica particles, supramolecular structures, physicochemical methods of analysis.

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DOI: 10.19110/geov.2023.6.6

The article is devoted to the search for a concise answer to the question: how does the nucleus of a crystal arise? Although a simple and complete answer is impossible at the same time, an attempt has been made to clarify the problem in three aspects: according to which principle particles are combined into a nucleus, which nucleus have a chance to become crystal, and from which atomic configuration it can be recognized. To model the small polyhedral clusters, the principle of equal immediate environment is proposed. It is shown that such clusters with an odd number of atoms are impossible. Small polyhedral clusters should grow by attaching pairs of atoms. Previously, this was known for fullerenes because of their specific geometry. The topic is important because of the coverage of various quasi- and non-crystalline structures by crystallography and mineralogy.

Keywords: crystallography, mineralogy, nucleus, crystal, symmetry, polyhedral cluster, principle of equal immediate environment.

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