pdf № 325, January

DOI: 10.19110/geov.2022.1.1

The article presents the first U-Pb data on the age of detrital zircon from clastic sediments of Khobeyu Formation in the Subpolar Urals. Age data for 102 zircon grains (LA-ICP-MS) cover the range of 862—2656 Ma. Weighted average age of the three youngest grains yields the age of 927 ± 54 Ma which provides grounds to assume that sediment deposition took place in Late Riphean. Significant similarity of the ages of detrital zircon grains from the terrigenous rocks of the Khobeyu Formation and underlying Puyva Formation indicates that the rocks were formed in the same sedimentary basin, and the detrital material came from source areas similar in age. In terms of the prevalence of zircon grains of Middle–Late Riphean age, the Khobeyu and Puyva Formations are comparable to the Upper Precambrian sandstones and siltstones of the Barmin Group of the Northern Timan, and Chetlas and Vym Groups of the Middle Timan. It is assumed that the sources of detrital zircon in all these stratigraphic units were igneous and metamorphic rocks of Fennoscandia and the Central Russian Belt.

Keywords: detrital zircon, U-Pb dating, Late Riphean, Khobeyu Formation, Subpolar Urals.

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DOI: 10.19110/geov.2022.1.2

The article presents novel results of studies of the mineral composition of placer samples, morphological and chemical study of native gold from alluvial deposits in the Pokyu River (Middle Timan). The main minerals in the heavy fraction of concentrates are garnet and ilmenite. Most samples contain gold from occasional particles to certain grades. Small (0.25—1.0 mm) medium-rounded gold of plate and tabular form prevails. The only impurity is silver, the content of which is 0.5—27 wt. %. Almost all gold particles have a high-grade rim. The gold contains microinclusions of galena and gersdorffite.

Keywords: gold nugget, placer, alluvial sediments, Volsko-Vymskaya ridge, Middle Timan.

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DOI: 10.19110/geov.2022.1.3

We carried out experiments on the synthesis of nanocomposite materials based on supramolecular silica structures, consisting of monodisperse spherical particles 300 nm in diameter and Group I metals of the periodic system Au and Ag. We determined basic conditions (preliminary preparation, type of reducing agent used, metal concentration and holding time) that allowed producing nanocomposite materials with various degrees and forms of entering of metal particles, both on surface of silica spheres and in  packing voids between them. The obtained nanocomposite materials can find wide application in various fields of optics, electronics and catalysis.

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DOI: 10.19110/geov.2022.1.4

The article is devoted to the applications of the entropy category in the natural sciences, mainly in mineralogy and crystallography to describe the complexity of mineral parageneses and crystal structures. It is shown that thermodynamic, informational and statistical entropy, defined independently in different disciplines, do not copy each other. They are not recalculated into each other and agree at the level of general principles. Statistical entropy as a measure of the complexity of systems characterized by probability distributions of parameters is always their convolution with loss of information. As a scale of complexity, it is unevenly curved in different areas of the probability field. The article is dedicated to the 85^th anniversary of the birth of N. P. Yushkin.

Keywords: thermodynamic entropy, informational entropy, statistical entropy, disorder, complexity, additivity, semi-additivity, antisemi-additivity.

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DOI: 10.19110/geov.2022.1.5

Synthesized titanium oxide nanotubes from titanium raw materials are efficient nanoreactors for photocatalysis in comparison with macroanalogues. The dependence of the geometry of titanium oxide structures on the redistribution of the density of electronic states was studied. The presence of natural iron ligands leads to the appearance of midgap states inside the bandgap of titanium oxide.

Keywords: nanoreactor, low-dimensional structures, titanium oxide, nanotubes, photocatalytic activity, titanium raw.

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