Mining Institute, Ural Branch, Russian Academy of Sciences, Perm, Russia:

S. S. Andreiko, Head of Laboratory, Professor, Doctor of Engineering Sciences
I. I. Chaikovsky, Head of Laboratory, Doctor of Geological and Mineralogical Sciences, ilya@mi-perm.ru

Belaruskali, Solegorsk, Belarus:
V. N. Getmanov, Director of Mine Manegment 2
A. B. Chayanov, Director of Mine Manegment 1

The object of the study was fluid and mineral inclusions, as well as the composition of components of occluded gases in salt rocks of Starobin deposit using the example of Krasnoslobodsky mine of Belaruskali OJSC. Sylvinites, underlying rock salt, as well as rocks of the zone of replacement, leaching and recrystallization were studied. To identify the morphology and spatial localization of inclusions, a VEGA 3 LMH scanning electron microscope with an Oxford Instruments INCA Energy 250/X-max 20 X-ray energy-dispersive microanalysis system was used, and a 450-GC gas chromatograph was used to determine the gas content and components of occluded gases. Three groups of inclusions were identified. The primary ones were captured inside (spherical and cubic) and at the grain boundaries (smooth-walled slit-like cavities, bay-shaped, worm-shaped, drop-shaped, faceted). Secondary salts were formed during partial recrystallization (large intraand intergranular irregular shapes) and deformation of salts (elongated along dislocations and cleavage planes). Epigenetic channels, associated with the transit of undersaturated calcium chloride brines, were slit-like channels with a corrosion-regenerated wall surface, in which free gas can be localized, provoking gas-dynamic phenomena. The methane–nitrogen composition of occluded gases in salt rocks in Krasnoslobodsky mine, typical of Starobin deposit, was determined. Nitrogen of fluid inclusions is associated with atmospheric gas dissolved in the brine of the saline basin, hydrocarbons are associated with thermogenic transformation of buried organic matter, and hydrogen is associated with radiolysis of water. The increased content of carbon dioxide in the zones of leaching (dip troughs) and recrystallization is associated with the inflow of subsalt fluids along rift faults.

The study was supported by the Russian Foundation for Basic Research, project No. 20-45-596017 r_NOTs_Perm Krai.

1. Lupinovich Yu. I., Protopopov A. L. Petrography of carnallite and carnallite–sylvinite rocks at Starobinsk deposit. Lithology, Geochemistry and Minerals of Belarus and the Baltic Countries. Minsk : Nauka i tekhnika, 1968. pp. 199–206.
2. Protopopov A. L. Secondary structures of some rocks of potassium stratum III at Starobinsk potassium salt deposit. Some Issues of Mineral-Salt Production Theory and Practice : VNIIG Transactions. Leningrad, 1971. Vol. 55. pp. 15–23.
3. Petrov E. V., Protopopov A. L. Role of sedimentation genesis water in post-sedimentation transformations of potassium strata at Starobinsk deposit. Formation and Transformation of Material Constitution of Rocks at Potash Deposits : Collection of Scientific Papers. Leningrad : VNIIG, 1982. pp. 5–24.
4. Proskuryakov N. M. Rock and Gas Outbursts in Potash Mines. Moscow : Nedra, 1980. 264 p.
5. Kislik V. Z. Post-sedimentation transformation of potassium strata at Starobinsk deposit. Prediction, Prospecting and Exploration of Chemical Raw Materials Deposits in the USSR : Collected Works. Moscow : Nedra, 1971. pp. 209–218.
6. Baryakh A. A., Andreiko S. S., Fedoseev A. K. Gas-dynamic roof fall during the potash deposits development. Journal of Mining Institute. 2020. Vol. 246. pp. 601–609.
7. Andreyko S. S., Lyalina T. A. Rockburst from Floors. Soils and Rocks. 2019. Vol. 42, No. 1. pp. 77–82.
8. Bobrov D. A., Litvinovskaya N. A., Nesterov E. A. Gas content and gas-dynamic characteristics of rocks of the IV-p horizon of the Starobin deposit of potash salts. IOP Conference Series: Earth and Environmental Science. 2022. Vol. 1021. 012056. DOI: 10.1088/1755-1315/1021/1/012056
9. Duchrow G. Der 100-jährige Rhönmarsch in die Kohlensäurefelder des Südthüringischen Kalibergbaus. Der Anschnitt: Zeitschrift für Kunst und Kultur im Bergbau. 1997. Vol. 49, Heft 4. ss. 123–147.
10. Siemann M. G. Herkunft und Migration mineralgebundener Gase der Zechstein 2 Schichten in Zielitz. Kali- und Steinsalzbergbau. 2007. Heft 3. ss. 26–41.
11. Ivanov O. V. Research-and-training measurement facility for the occluded gas content analysis of rocks. Strategy and Processes of Development of Georesources : Collection of Scientific Papers. Perm : GI UrO RAN, 2012. Vol. 10. pp. 223–225.
12. Ivanov O. V. Procedure and results of occluded gas content analysis of rocks by dry mechanical disintegration method. Strategy and Processes of Development of Georesources : Collection of Scientific Papers. Perm : GI UrO RAN, 2016. Vol. 14. pp. 312–314.
13. Lewis S., Holness M. Equilibrium halite-H2O dihedral angles: High rock-salt permeability in the shallow crust? Geology. 1996. Vol. 24, No. 5. pp. 431–434.
14. Warren J. K. Evaporites: A Geological Compendium. 2^nd ed. Cham : Springer, 2016. 1813 p.
15. Roedder E. The fluids in salt. American Mineralogist. 1984. Vol. 69, No. 5-6. pp. 413–439.
16. Сhaikovskiy I. I., Ivanov O. V., Bubnova M. V., Fedorov T. V. On the nature, composition and gas content of epigenetic mineralization in the salt column of the Verkhnekamskoe deposit (on the example of the Usolsky mine). Litosfera. 2023. Vol. 23, No. 1. pp. 117–132.
17. Zemskov A. N., Kondrashev P. I., Travnikova L. G. Natural Potash Gases and Preventions. Perm : Tipografiya kuptsa Tarasova, 2008. 413 p.
18. Bo Liu, Dongqi Yan, Xiaofei Fu, Yanfang Lü, Lei Gong et al. Investigation of geochemical characteristics of hydrocarbon gas and its implications for Late Miocene transpressional strength – A study in the Fangzheng Basin, Northeast China. Interpretation. 2018. Vol. 6, Iss. 1. pp. 83–96.
19. Savchenko V. P. Formation of free hydrogen in the crust due to reducing action exerted by products of radioactive change of isotopes. Geochemistry. 1958. No. 1. pp. 14–21.