pdf № 304, April

DOI: 10.19110/geov.2020.4.1

The article is devoted to studying the chemical composition of the main rock-forming minerals of basalts from the island of La Palma, xenolith from the island of Lanzarote of the Canary Archipelago (Spain). The main task of the research is the diagnosis of mineral composition of these rocks. Peridodite xenoliths can be of several types reflecting their mantle or crust origin. The chemical composition of the main rock-forming minerals is described, which testifies to a cumulative genesis of these formations in deep magmatic chambers with possible inclusion of xenogenic crystals from lithospheric mantle material.

The main research methods were petrographic diagnostics and micro X-ray spectral analysis of the chemical composition of the main rock-forming minerals by Tescan Vega II LMU electron microscope equipped with INCA Energy 350 energy dispersive spectrometer (with Si (Li) Standart detector). We found that the olivines and pyroxenes of basalts were characterized by a typical composition of volcanic rocks, which had been formed in near-surface conditions or as a result of direct outpouring. Variations in the composition of plagioclase from labrador to oligoclase allowed classifying these formations as subalkaline bases characteristic of intraplate oceanic magmatism. The study of the petrostructure of peridotite xenolith and the composition of its constituent minerals revealed the peculiarities of their formation. There are several versions of the nature of peridotite xenoliths, reflecting their mantle or crustal origin. The obtained results suggested the cumulative genesis of these formations in deep magma chambers, with the possible involvement of xenogenic crystals from lithospheric mantle material. The magmatic nature of xenolith was supported by the presence of endiopside and plagioclase in the intergranular space of large olivine and orthopyroxene grains. The elements of intracrystalline deformations and their high magnesian composition, corresponding to restite hyperbasites of ophiolite association, can be used to explain the mantle nature of large crystals of olivine and orthopyroxene.

Keywords: rock-forming minerals, chemical composition, xenolith, mineral type, basalts, peridotite.

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DOI: 10.19110/geov.2020.4.2

We present our results of petrographic, mineralogical, spectral, chemical and elemental analysis of the meteorite. We determined that according to structural and textural features mineral and elemental composition, the studied meteorite is an ordinary olivine-enstatite chondrite of H4 petrological type. The predominant minerals are rhombic pyroxene and olivine. We determined the presence of sodium plagioclase, feldspar glass, chromespinelides, apatite, chlorapatite, barite, calcite, zircon, titanite, pyrrhotine, kamacite and taenite. Chondres were predominantly represented by radiant-fibrous, grate, cryptocrystalline and porphyry olivine and pyroxene monomineral varieties. We found chondres composed of fine-grained rocks and surrounded by a rim of carbonaceous matter. We determined inclusions of native platinum in the carbon matter and chromespinelides. The regularity of changes in the distribution of iron in the mafic minerals, composing the chondre, was established.

Keywords: meteorite, chondrite, mineral composition, olivine, pyroxene, native metals.

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The features of the composition of minerals formed during the albitization and cancrinitization of rocks in the calcite-nepheline-feldspar pegmatite vein (southwestern endocontact of the Ilmenogorsky miaskite massif) are studied. Albite formed together with annite, pyrite, strontianite, barite, and fluorapatite. Annite revealed a low content of TiО₂ and MgО (up to 1.0 wt. %) and a high content of Fe (31.2—41.4 wt. %). Fluorapatite is characterized by an increased amount of rare earths, ∑ REE = 2.9—4.8 wt. %, and an increase in the content of SrО to the edge of the grain, up to 5.4 wt. %. The content of BaО increases from 0.6—1.0 to 2—7 wt. % in the composition of orthoclase at the border with albite. The development of late fluorite-calcite formations with the sulfide-rare-earth mineralization is associated with the processes of the cancrinitization of nepheline.

Keywords: minerals, albitization, cancrinitization, calcite-nepheline-feldspar pegmatite vein, carbonatite, Ilmenogorsky miaskite massif.

DOI: 10.19110/geov.2020.4.3

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DOI: 10.19110/geov.2020.4.4

The object of study — the rocks of the Yulinsk complex, as exemplified by the Kotursky massif, located on the southeastern slope of the Batenevsky ridge of Kuznetsk Alatau. The massif under study consists mainly of rocks of syenite-granosyenite magmatic formation. The relevance of the study is conditioned by new data on the composition of the Yulinsk complex with copper-molybdenum ore occurrences. The petrogeochemical characteristics of the rocks of the Kotursky massif was given mainly according to the original results of silicate and ICP-MS analyzes to elucidate the patterns of composition variation and to establish their evolutionary orientation. The established petrogeochemical features of the rocks of the Kotursky massif reflect their crystallization from differentiated magmatic melts, which are contaminated to varying degrees by the material of the earth's crust. The regularities of the distribution of petro- and microelements indicate that the rocks of the massif belong to the island-arc collision and, mainly, to intraplate granitoids. The rocks of the Kotursky massif are typical of the Yulinsk igneous complex of small intrusions.

Keywords: Batenevsky ridge, Yulinsk complex, petrography, syenites, granosyenites, granites, petrogeochemistry, evolution.

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DOI: 10.19110/geov.2020.4.5

Based on the experience of using broadband seismic equipment for monitoring the ground of the base of the railway track for the Northern Railway using the train as a source of the probing signal, the possibility of monitoring the state of the soil of the base of the roadbed by passive seismic methods was experimentally shown and confirmed by modeling. Field observations showed that recordings at low frequencies (0.01 Hz) significantly differ in neighboring sections of the path — favorable and unfavorable, with the horizontal components being the most informative. Records at frequencies of 2–8 Hz are characterized by significant changes in the ratio of the amplitudes of the vertical and horizontal components during seasonal watering. The parameters of seismic monitoring are determined: equipment and data processing methods by which in situ it is possible to judge the change in the state of soils, the possibility of identifying stages of soil freezing and thawing and the associated negative processes is discussed.

Keywords: low-frequency vibrations of a roadbed railway, seismic test, seismic equipment, stability of the roadbed railway.

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DOI: 10.19110/geov.2020.4.6

The article is devoted to the morphological systematics of icosahedral viruses. It is shown that fixation of capsids by the triangulation numbers does not distinguish the isomers. Description of capsids by symmetry point groups (–5–3m and 532) is greatly detailed. In their diversity, homologous series connected in pairs are distinguished. Within the series, capsids are linked by a similarity transformation. The series are connected by the transition to the dual polyhedra. Capsid generators that are not reducible to simpler forms and produce the entire variety of icosahedral capsids are defined.

Keywords: icosahedral viruses, capsid morphology, symmetry point group, triangulation number, homological series, capsid generators, similarity transformation, dual polyhedra.

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