The Dukat deposit covers 11 sq km and comprises 87 distinct ore veins (only eight of them are fully depleted) and 34 ore zones. Ore bodies dip steeply, with an average width of 0.6 to 21 m. The five largest ore zones display continuity over several hundred metres and account for 85 per cent of ore reserves of the deposit. The largest ore body has a maximum thickness of up to 21 m, a strike length of approximately 1.2 km. Major ore minerals include silver sulphides and silver sulphasalts, as well as native silver and native gold associated with sulphides.
[http://www.minesandprojects.com/reports/annual/Polymetal_International_Dukat_hub_deposits_web_2020.jpg]

The Okhotsk-Chukot volcanic belt formed over 25 Ma (middle Albian-Cenomanian) (Belyi, 1994) at the boundary between the continental Verkhoyansk-Chukot and Koryak-Kamchatka terranes. 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 Dukat, underground mining is now the only source of ore. The conditions for underground mining activites are favourable, with competent ore and host rock made more stable by the permafrost extending to a depth of 300 to 350 m. As a result, very little support is required and a mostly sub-level open stoping mining method is used with minor amounts of ore extracted from manual shrinkage stopes. Underground mining at Dukat is characterised by wide, steeply dipping ore bodies with good wall stability and consistent geometry down-dip and along strike. The Dukat underground mine is accessible by multiple adits located near main ore zones and is relatively shallow, with all current and planned working levels located less than 100 m below the valley floor.

Both underground development and stoping at Dukat are fully mechanised, with the use of trackless equipment. The ore is delivered by trucks to a centralised underground railway. The railway transports the ore to the crusher, which is located immediately at the exit of the railway from the underground mine. Ore from the crusher and the adjacent ore storage yard is then transported to the Omsukchan concentrator by contractors.

The Omsukchan concentrator uses conventional sulphide flotation technology, with each section designed to treat different types of feedstock. To achieve optimal results, extensive geotechnological testing is employed to determine the suitability of a particular ore for one of the sections and to assist in the selection of technological parameters (feed rate and reagent addition).

Section 1 is designed to treat simple metallurgical ores from the Dukat mine which typically yield higher recoveries with lower reagent consumption and generate concentrate that is amenable to cyanidation. The processing circuit comprises three-stage grinding (one SAG mill and two ball mills) followed by flash flotation and conventional flotation.

Section 2 is designed to treat ores that are technically more complicated, including feedstock from Goltsovoye, Lunnoye and old stockpiles. The processing circuit comprises two-stage grinding (one SAG mill and one ball mill) followed by gravity ........