Oroch was discovered in 1979 and was extensively explored from 1980 to 2005 through diamond drilling. It is located 110 km from Kubaka and approximately 20 km from the Kubaka-Sopka winter road. Oroch is an epithermal gold-silver deposit. The ore bodies are mainly composed of quartz and carbonate. They have a steep dip and an average width of 6 m.

The Okhotsk-Chukot volcanic belt formed over 25 Ma (middle Albian-Cenomanian) at the boundary between the continental Verkhoyansk-Chukot and Koryak-Kamchatka terranes (Fig.1). This giant belt is 3000 km long is composed of subaerial volcanic rocks.

Relative to the oceanic margin, the Okhotsk Chukot belt is divided into the inner, outer, and perivolcanic zones. The intricate structure of terranes of the basement and the Okhotsk Chukot belt produced a diversity of epithermal deposit types. The inner zone of the belt mainly accommodates porphyry Cu-Mo deposits. The outer and perivolcanic zones include gold silver and silver-tin ore deposits. The gold silver subtype is more widespread in the outer zone (Karamken, Valunisty, Kupol, and Dvoinoi). Deposits of the silver subtype (Dukat, Lunnyi, Arylakh, Golcovy and others) are confined to the volcanic rift located between the Yana Kolyma and Omolon terranes of the Okhotsk Chukot belt.

At Oroch, open-pit mining commenced with a total of 400 Kt of ore mined, ahead of original schedule. The additional volumes will enable optimised throughput at the Kubaka mill in 2016.

The Kubaka plant currently uses only conventional CIP cyanidation technology. Run-of-mine ore is crushed in a jaw crusher, followed by two-stage milling (SAG mill and ball mill), thickening, CIP leaching, desorption, electrolysis, carbon regeneration and doré smelting. This processing option will continue to be utilised in the long term for ores with low silver content, such as ores from the Birkachan and Tsokol mines.