CONCEPTUAL MODEL OF THE FORMATION OF THE UNIQUE SUKHOI LOG GOLD DEPOSIT BASED ON A DETAILED GEOSTRUCTURAL ANALYSIS

This paper presents several opposing points of view on the ore-controlling structure of the large (~2000 t) Sukhoi Log gold deposit, as well as data on a detailed geostructural analysis. The deposit is located in the southern margins of the Siberian Craton in black shale deposits of the Khomolkha Formation (610‒600 Ma) on the territory of the Baikal-Patom fold belt. It is revealed that the Baikal-Patom belt is characterized by a complex regional structure resulting from the accretion of the Baikal-Muya belt to the Siberian Craton. The formation of industrial ores of the Sukhoi Log deposit and ore-controlling folding dates back to the Late Ordovician-Early Silurian (~450‒420 Ma). The second stage of the development of weakly gold-bearing ores falls on the Early Carboniferous (340‒300 Ma). The study demonstrates the absence of an ore-controlling fault zone of the syn-folding stage (450–420 Ma). It is shown that the internal structure of the gold ore zone is comprised of intensely deformed rocks in the anticline core with bedding-plane gold-quartz-pyrite veinlets. It is concluded that the Sukhoi Log deposit is a classic example of disharmonic folding of plastic rocks in the anticline core, where the signs of two stages of structure formation are combined: buckle folding with flow and laminar flow. The present geostructural studies of the deposit and the previously published data suggest that this is an orogenic deposit with metamorphic-metasomatic redistribution of ore matter.