pdf № 308, August

DOI: 10.19110/geov.2020.8.1

The results of mineralogical investigation of glauconite from the Yangyssko-Bayguskarovskaya zone (Bashkortostan) have been presented. Grains were studied by the complex of chemical and physical methods: X-ray diffraction, ⁵⁷Fe Mössbauer spectroscopy, scanning electron microscopy and microprobe analyses.

Special attention was given to the crystal-chemical features of mineral and processes of glauconite formation.

Glauconite was characterized by a relatively high content of K, Fe, Mg. Content of total iron and potassium displayed a direct correlation (k=0.87). According to Mössbauer spectroscopy data Fe²⁺ occupied not more than 3% of the total iron content in glauconite. Average crystal-chemical composition of mineral was Ca_0.04K_0.49 [Fe³⁺_1.05Fe²⁺_0.04Al_0.50Mg_0.43] {(Si_3.80Al_0.16Fe_3+0.04)₄O₁₀}(OH)₂ and corresponded to evolved (less mature to mature) glauconite. Glauconite contained a small (<10 %) amount of swelling layers.

Keywords: glauconite, crystal-chemical features, glauсonite maturity, ⁵⁷Fe Mössbauer-spectroscopy, X-ray diffraction.

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DOI: 10.19110/geov.2020.8.2

The Upper Emsian deposits in the northern part of the Urals are mainly composed of normal-marine clayey limestones with abundant organic remains. However, there are rare, predominantly clayey sections, which conditions of sedimentation remain unclear. The object of the study is one of such atypical Upper Emsian deposits, exposed at the Ilych River near the mouth of the Shezhim-Yu River. These rocks were studied by petrographic (optical microscopy) and geochemical (silicate and X-ray diffraction) methods. The argillites include kaolinite, ferruginous chlorite and muscovite. The interpretation of the chemical analysis data showed that the clayey material of the argillites correspond to the continental clays of the tropical climate with a high degree of chemical decomposition of the original rocks (weathering crusts), probably formed before the Late Emsian time. During the Late Emsian transgression, this clay material was eroded, transported and accumulated in the coastal shallow-water conditions of the passive continental margin. Fragments of the Upper Emsian sections containing similar kaolinite-bearing argillites form a strip along the western slope of the Urals from the Ilych River middle course to the Shchuger River. We concluded about the location of the removal source in the Verkhnepechorskaya depression southern part, where the Upper Emsian rocks with stratigraphic unconformity overlaid the Upper Silurian strata.

Keywords: Northern Urals, Upper Emsian, kaolinite, chemical composition, geochemical coefficients, formation conditions, products of weathering crust destruction.

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 DOI: 10.19110/geov.2020.8.3

The Solikamskaya depression and adjacent territories have significant groundwater resources and huge fresh water reserves, which are a unique source for drinking, industrial and industrial water supply. Therefore, the issues of formation of the composition of groundwater water in the Solikamskaya depression are relevant.

The main purpose of this work is to study the features of the formation of isotopic (d²Н and d¹⁸О) and chemical compositions of groundwater in the Lower Permian sediments of the Solikamskaya depression and the adjacent Kolvinskaya saddle, which are unloaded within the Solikamskaya depression.

Groundwater is mainly hydrocarbonate-magnesium-calcium and sulfate-hydrocarbonate-magnesium-calcium composition with mineralization 213—431 mg/dm³, their isotopic composition varies from –14.2 to –16.3 ‰ in d¹⁸О and from –107.3 to –119.4 ‰ by d²H. Seasonal changes in the isotopic composition (heavy composition in summer, light — in spring) of groundwater confined to the Lower Permian sediments of the Solikamskaya depression and Kolvinskaya saddle indicate the meteogenic impact on them. In this case, a time delay (one to three months) of the transmission of the isotope signal from precipitation to groundwater is recorded. An increase in mineralization in winter, spring and summer periods, as well as an increase in the content of sulfates and chlorides, suggests that water flows from the underlying horizons through zones of increased fracturing. Thus, groundwater in the Lower Permian deposits of the Solikamskaya depression has a mixed supply.

Keywords: Solikamsk depression, Lower Perm aquifer, groundwater, isotopic and chemical composition, Spearman's correlation coefficient, correlation analysis.

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 DOI: 10.19110/geov.2020.8.4

The article shows that consideration of 7 symmetry groups of borders in a university course in crystallography is advisable for a number of reasons. On their example, the simplest symmetry groups of infinite figures are easily constructed. The theorem on the compositions of planes and axes of symmetry with orthogonal translations generating homogeneous symmetry elements is clearly explained. An analysis of the symmetry groups of borders in nature and urban landscapes (fences, lattices, ornaments, mosaics, etc.) address students to the fundamental problem of the prevalence of 230 space symmetry groups in the mineral world.

Keywords: endless figure, border, symmetry group, theorem on the composition of symmetry elements, frequency analysis.

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