Black shale formations in the Sayan-Baikal mountainous province (Kotera depression in Northern Baikal and Ilchir and Oka depressions in southeastern East Sayan) are considered in terms of their geochemistry and metallogeny. The rocks formed in Late Riphean-Early Paleozoic time in active continental margin (turbidite terrane), back-arc spreading (oceanic terrane), or shelf (carbonate deposition) geodynamic environments. Some intervals of the section bear precious-metal mineralization. The C-rich deposits associated with ophiolites host high-Au sulfides similar to sulfides from sediment-covered spreading centers. The continental-margin deposits show platinum and palladium enrichment attributed to zones of high Ba, Mo, and U abundances in which δ34S is +3…+6.8‰, against –10…–17‰ outside these zones.

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