Authors: M. Skursky, R. Veits, A. Voznaya, G. Gribanova, N. Kizhaeva

Title of the article: Sedimentary continental mechanogenic terrigenous formations of placer mineral deposits

Year: 2021, Issue: 4, Pages: 4-39

Branch of knowledge: 25.00.16 Mining and oil and gas geology, geophysics, surveying and subsoil geometry

Index UDK: 551.263:553.2:553.6

DOI: 10.26730/2618-7434-2021-4-4-39

Abstract: According to the classical theory of placer formation, the foundations of which are laid in the works of W. Lindgren, K. Rayborn, G. Milner, E. Dunn, Y.A. Bilibin, I.S. Rozhkov, humid environments provide deep chemical weathering of rocks and opportunities for transportation, sorting and accumulation of relatively strong and heavy minerals in the water environment (in river valleys and coastal zone) and therefore have the priority in formation of placer deposits. These views underwent a significant transformation in the mid-1960s during the study of gold placers in the Russian North-East. It turned out that the permafrost also does not prevent the formation of placers, and physical and chemical changes of rocks in the zone of permafrost and features of slope and fluvial processes impose an imprint on the structure of placer deposits. Periglacial (near-glacial) lithogenesis, determining the specific mechanisms of movement of clastic masses and concentration of heavy minerals, contributes to the appearance of special morphogenetic types of placer deposits, largely differing from the placers of humid areas. Areas of periglacial lithogenesis occupy 34.5 million km² (23% of land), including more than 22 million km² in the Northern Hemisphere alone (of which more than 11 million km² in Russia). It was also believed that semi-arid (half-arid), arid (dry climate) environments, which now occupy almost 23% of the land surface, were also poorly favorable for the formation of large placers due to the reduction or complete absence of surface runoff. Meanwhile, by the end of the 1980s, a sufficient number of facts had accumulated indicating the release of placer-forming minerals, their transfer, sorting and concentration in various environments of arid and semi-arid regions. Formations of placer mineral deposits are considered below. Their names omit the geological and ore formations producing them due to the fact that the placers, especially those of distant drift, have completely and often partially lost their connection with the indigenous sources. In the text they are restored as far as possible.

Key words: placer deposits formations natural resources minerals precious metals sedimentation placer formation

Receiving date: 17.09.2021

Approval date: 23.10.2021

Publication date: 24.12.2021

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