Çayeli is a Cretaceous-age volcanogenic massive sulphide deposit that has a known strike length of over 600 metres, extends to a depth of at least 600 metres and varies in thickness from a few metres to 80 metres, averaging about 20 metres. The average dip is 65° to the north northwest.

The deposit is at the contact between altered footwall felsic volcanic flows and pyroclastic and hanging wall mafic volcanic rocks. It consists of massive and stockwork sulphides. The mineralization includes pyrite, chalcopyrite and sphalerite and smaller amounts of galena, dolomite and barite.

The massive sulphide ore is classified into yellow ore, which is copper-rich and zinc-poor; black ore, which is zinc-rich and copper-poor; and clastic ore, which contains copper, zinc and precious metals. In this ore, the sphalerite contains intergrowths and inclusions of chalcopyrite and requires batch processing through the mill.

Ore types which contain either secondary copper minerals or bornite are segregated and processed separately.

Stockwork ore, containing pyrite and chalcopyrite in veins, occurs stratigraphically below the massive sulphide ores.

The mine design is based on underground bulk mining methods with the use of delayed backfill to extract the ore in a sequential manner. A single production shaft located on the footwall side of the orebody and a service ramp provides access to the mine.

The primary mining method for the Çayeli orebody is retreat transverse and longitudinal longhole stoping with paste fill and loose or consolidated waste rock backfill application. The stopes are mined in primary, secondary, and tertiary sequencing. The primary and secondary stopes are mined as transverse and the tertiary as longitudinal stopes. Cut and Fill mining method was applied successfully in 2019 on the upper mine levels in order to eliminate the risk of subsidence to the surface infrastructures and houses. The main levels are developed off the service ramp along the strike of the orebody at 45 to 100 metre vertical intervals. From the top of the mine down to the 800 level, levels are located on the hanging wall side of the orebody. Ore production below 800 level was completed in 2020. The sublevel vertical distance is 20 metres as dictated by the stope height, allowing the development of a 15 metres high by 6 metres wide stope bench for production drilling.

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