Академическое издательство «Гео»

Keywords: minerals of light and heavy fractions, aggregates, carbon-bearing inclusions, meteoritic particles, coefficients of maturity and stability, clay minerals.



GEOGRAPHY AND NATURAL RESOURCES, 2018, № 2, p. 102-110

Lithological records of unique natural events in argillo-arenaceous sediments of the Gorome cave (Oka plateau)

T.G. Ryashchenko

Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Sciences,
ul. Lermontova, 128, Irkutsk, 664033, Russia, ryashenk@crust.irk.ru

Argillites, clays and fine-grained sands with traces of connectivity and sandy alluvium from the Gorome cave (Oka plateau in Eastern Sayan) were studied. Results on the mineral composition of terrigenous components of light and heavy fractions of these sediments are considered for the first time. They were obtained by the method of quantitative immersion analysis. The morphological features of minerals indicated that there were no traces of roundness; a predominance of ore components is responsible for the increased mass of heavy fraction in clays and sands; the highest degree of chemical maturity was observed in argillites. The general and particular features of light and heavy minerals were established; the presence of a large number of aggregates and carbon-bearing inclusions with the structure of wood in the composition of light fraction as well as meteoritic particles among heavy components was observed. The method of phase X-ray diffraction analysis was used to determine the composition of clay minerals among which smectite of a weak degree of transformation prevailed. A high content of aggregates in cave argillites, clays and fine-grained sands was confirmed by results of studies using the “Microstructure” method. The assumptions (hypotheses) concerning carbon-bearing inclusions, meteoritic particles and the formation of aggregates were considered. The woody microstructure in carbon-bearing inclusions can give evidence for fire sites in the cave, and the presence of meteoritic particles is likely due to redeposition of “above-ground” sedimentary rocks. Two variants of the formation of epigenetic aggregates are suggested: in conditions of positive temperatures as a result of variable moisturizing or drying out of the precipitate; at negative temperatures, as a result of the microstructure rearrangement under the influence of physicochemical processes.

Keywords: minerals of light and heavy fractions, aggregates, carbon-bearing inclusions, meteoritic particles, coefficients of maturity and stability, clay minerals.

DOI: 10.21782/GiPR0206-1619-2018-2(102-110)

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