Chapter 25: The Sukhoi Log Gold Deposit, Russia

Sukhoi Log, Russia’s largest gold deposit, containing 1,960 metric tons (t) of gold within the deformed Neoproterozoic sedimentary sequences of the Patom passive margin, can be classified as an orogenic gold system. This giant and nearby smaller deposits occur in black shale horizons at several stratigraphic levels. The understanding of Sukhoi Log evolved from a small quartz vein occurrence to a large disseminated gold resource. The genesis of the deposit, originally considered to be related to a granitic intrusion, was later reinterpreted as metamorphogenic, with a significant contribution of synsedimentary gold in pyrite. Recent isotopic studies showed that there may have been more than one early Paleozoic synmetamorphic gold-mineralizing event, so the deposit most likely has a multistage origin. Black shales might have acted either as a synsedimentary and/or synmetamorphic geochemical trap for auriferous fluids. Structurally, the mineralization is confined to the axial portion of the recumbent Sukhoi Log anticline, conjugate with the Kadali-Sukhoi Log shear zone. This imbricate thrust zone marks a major boundary between the Chuya-Nechera anticlinorium and Bodaibo synclinorium, two regional tectonic features in the Patom Highlands.