Home – Home – Jornals – Russian Geology and Geophysics 2002 number 4

Black shale formations in 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 the Late Riphean-Early Paleozoic in different geodynamic environments of active continental margin (turbidite terrane), back-arc spreading zone (oceanic terrane), or shelf (carbonate deposition). Several intervals of the section show noble-metal mineralization. The black shales associated with ophiolites typically demonstrate a high auriferous potential of sulphides, which are equivalents of sulphides from back-arc spreading zones. The carbonaceous shales of continental margins show platinum and palladium enrichment, their elevated concentrations being attributed to zones of high Ba, Mo, and U abundances. The isotope composition of sulphide sulphur varies from -10÷17 – outside these zones to +3-+6.8 within them.