Justification of underground gold placer development parameters for the Konevinsky deposit

The Konevinsky deposit is located in the Eastern Sayan highlands in a poorly developed area of the Far North. The deposit is being developed by Khuzhir Enterprise LLC. The deposit is a thin steeply dipping vein characterized by the extremely irregular metal content and a low ore-bearing coefficient. Ore is extracted using the underground method at a depth of 300 m in the permafrost zone. Steeply dipping ore deposits with a complex morphology and a discrete distribution of metal are developed using the ore shrinkage system which involves longwall stoping without supporting enclosing rocks. Longwall stoping with a small extraction space eliminates rock cleavage along the cracking system that results in high dilution of ore (up to 67%). Due to this fact, the existing mining geotechnology of balance reserves development has become unprofitable and production has been suspended. The purpose of this article is to identify new parameters of the balance reserve extraction method that will improve quality of ore and increase profitability of metal production. Studies of geological environment and analysis of causes of ore quality deterioration showed that along with the excessive sticking of wall rocks under the minimal excavation width of 1m, ore dilution is affected by inrushes from block sides with an increased rock fracturing and an internal chocking with low-grade ores. These disadvantages can be eliminated using sublevel drifts, the breast-and-bench method and a descending order of reserves excavation. The article substantiates and develops parameters of the system which can increase ore production quality without increasing production costs.