pdf № 311, November

DOI: 10.19110/geov.2020.11.1

The data obtained for the first time on the isotopic composition of oxygen and carbon of calcites and graphites of dolomitecalcite rocks of the Ilmeny Mountains and dykes of a similar composition in the Plastovsky district have confirmed their magmatic genesis. The temperature of formation of carbonate bodies (590—1000 °C), determined from the isotopic ratios of C and O in calcite and graphite, corresponds to the temperature range (600—900 °C) of the formation of carbonatite associations. According to the same ratios of isotopes in calcites, the protoliths of carbonate rocks are located within the carbonatite fields of the folded regions and in the transition zone to carbonates of marine origin. This is probably due to the fact that these rocks are a product of carbonate magma during remelting of sedimentary carbonate rocks in subduction zones, or under the influence of the heat of granite intrusions.

Keywords: carbon and oxygen isotopes, calcite, graphite, dolomite-calcite carbonatites. Ilmeny Mountains, Plastovsky district, South Urals.

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DOI: 10.19110/geov.2020.11.2

Hydrothermal processes play an important role in the reprecipitation of ore elements, but it is difficult to characterize their qualitative and quantitative parameters for large objects. The compact homogeneous internal structure of the ultramafic massif Malyutka of the Khudolaz differentiated complex provides a good opportunity to characterize the features of the hydrothermal reprecipitation of mobile elements in it.

The geochemical features of barren and ore-bearing variously altered rocks of the Malyutka massif have been studied using the methods of X-ray fluorescence (XRF) and mass spectrometry with inductively coupled plasma (ICP MS) analyzes. The results show a strong depletion of ores by siderophile (Ni, Co) and chalcophile (S, Cu, As, Se, Cd, Bi, Pb and many others) elements under hydrothermal influence, which is consistent with the postmagmatic dissolution and replacement of sulfide minerals not only by secondary sulfides, but also silicates. Leaching led to a reprecipitation of these elements, mainly to dispersion, both inside the intrusion and outside it. Most lithophile macro- and microelements have not reprecipitated significantly in hydrothermal conditions.

Keywords: Khudolaz complex, Malyutka massif, hydrothermal metasomatism, geochemistry, siderophile and chalcophile elements.

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DOI: 10.19110/geov.2020.11.3

The article is devoted to Svyatoslav Sergeevich Savkevich¢s scientific activities in connection with his 90th anniversary. He was a famous scientist in the field of mineralogy and geology of amber and other fossil resins. We briefly reviewed his life path, prime research lines and the most important achievements of the scientist. We focused on the results of his comprehensive scientific-organizational and public activity.

Keywords: S. S. Savkevich, amber, fossil resins.

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DOI: 10.19110/geov.2020.11.4

We analyzed the history of the fossil reefs study expressed in various thematic conferences and accompanying field geological sessions, general publications on this problem, starting from the mid-60s of the last century. The role of individual researchers in the development of the reef theme is noted.

Keywords: reefs, meetings, paleoecological-lithological sessions, geological excursions.

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