pdf № 333, September

DOI: 10.19110/geov.2022.9.1

It is pointed out that corundum is the only natural modification with corundum Al and O packing motif, which determines the physical and chemical features of noble corundum. Based on the authors' ideas about the genesis of noble corundum with the application of original analytical data, which clarify the consolidated literature data, corundums of the magmatic, metamorphic and detrital series are defined. A scheme of the location of the main deposits of noble corundums of the world is given. It is stated that all properties of noble corundums are determined by their primary indigenous origin. The general condition of corundum formation is protocrystallization from melts in deep magmatic centers under the condition of subsequent rapid solidification of the main mass of the melt. The presented research methods allow determining characteristics and a wide range of application of corundums. Precambrian corundum deposits are of the prevailing genetic type.

Keywords: noble corundum, genesis, magmatism, metamorphism, Precambrian.

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DOI: 10.19110/geov.2022.9.2

This article discusses the results of lithological and geochemical studies of the Artinskian deposits and organic matter, which is a part of the petroleum source rocks of the northern part of the Pre-Ural Foredeep of the Timan-Pechora Province. The rocks are very diverse in composition (clastolites, pelitolites, carbonatolites and mixtolites) and structural and textural features. Mixtoliths are widespread in shallow-marine environments (lower molasse deposits), which are associated with mixed terrestrial and marine organic matter. We recorded the predominance of poor and fair petroleum source rocks due to increasing terrigenous component. Mixtoliths of the Kochmes area (HI of 240 mg HC/g TOC) are characterized by the best generation potential. Organic petrography studies indicate the predominance of bituminite (sapropel base) in the composition of organic matter, the terrigenous components dominates in the eastern regions adjacent to the Urals.

Keywords: Pre-Ural foredeep, artinskian deposits, mixtoliths, petroleum source rocks, organic matter, bituminite, generation potential.

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DOI: 10.19110/geov.2022.9.3

In the Puyva region, located in the southeastern part of the Subpolar Urals, several gold-bearing placers and placer occurrences are known; however, information on gold itself is not complete enough, which makes the research relevant. The study of stream gold from the alluvium of the Khartes, Sertynya, Oika, Dorozhny, and Borovoy areas, has revealed that the gold is predominantly small; the particle shape is lamellar, thickened-lumpy, and complex. Gold roundness is medium; the portion of unrounded and well-rounded particles is insignificant. Silver is almost always present in gold, copper is less often noted. In some samples, electrum of a high silver content is found along with gold. Single gold particles have narrow, discontinuous high-fineness rims due to the removal of silver under exogenous conditions. Placer gold is gold of close wash-down; its original sources are probably represented by hydrothermal gold-sulfide-quartz veins localized in rocks of different composition and age.

Keywords: gold, alluvium, the Puyva region, the Subpolar Urals.

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DOI: 10.19110/geov.2022.9.4

We present a new regional event scale based on a generalized analysis of results of determination of event-stratigraphic boundaries of biotic events of various levels and d¹³C isotope anomalies in studied reference sections of the Subpolar Urals and the Chernov Uplift.

The combined regional curve of carbon isotopic composition allows finding out several isotopic events in the Silurian.

Keywords: carbon isotope record, event stratigraphy, Silurian, Chernov Uplift, Subpolar Urals.

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DOI: 10.19110/geov.2022.9.5

We shortly report on the combinatorial variety of C₆₂ to C₁₅₀ fullerenes, obtained and characterized by symmetry point groups using original computer algorithms. It is established that all 28 symmetry point groups allowed for fullerenes are already realized in the range C₂₀ to C₁₄₀. The criteria of internal verification of the results are proposed.

Keywords: fullerene, combinatorial diversity, automorphism group order, symmetry point group.

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