The Siguiri orebodies are early Proterozoic orogenic quartz-vein hosted deposits located in the Siguiri Basin of West Africa. Generally poorly exposed, the basin sediments have been subject to greenschist facies metamorphism and consist of a well-bedded turbiditic sedimentary sequence, with some brecciated and possibly volcanic members. Mineralisation also occurs as secondary gold in alluvial and colluvial gravels in laterite cover.

Three main sedimentary packages are recognised in the Siguiri district, the Balato, Fatoya and Kintinian formations. The Balato Formation is dominated by centimeter scale alternations of shale-siltstone and greywacke. The overlying Fatoya Formation consists of meter scale beds of greywacke fining towards the west. The Kintinian Formation is a thick package of shale and sandstone with a basal clast-supported conglomerate.

The orebodies are structurally controlled and the area has undergone at least three distinct phases of deformation, with initial N-S compression developing minor folds, the second and largest deformation event is associated with E-W to ENE WSW directed compression leading to N-S structural architecture, and the third event was a NW-SE compression that led to refolding of existing structures.

A deep oxidation (weathering) profile is developed in the region, varying between 50m to 150m. The mineralised saprolite currently provides the main oxide feedstock for the CIP processing plant, although a new treatment option has been approved to mine the fresh-rock extensions of the ore deposits.

Primary gold mineralisation occurs in all three lithostratigraphic units of the Siguiri region although the majority of known mineralisation is found in the central and more competent Fatoya Formation. In some deposits the mineralisation shows strong lithological control and is preferentially developed in coarser-grained units that have higher fracture/vein densities relative to fine-grained rocks.

Two styles of primary mineralisation have been recognised at Siguiri. The first is characterised by precipitation of gold-bearing pyrite associated with proximal albite and distal carbon alteration, and opening of carbonate-pyrite veins. The second style corresponds to ENE-WSW trending native gold bearing quartz veins with carbonate selvages which crosscut carbonate pyrite veins and show arsenopyrite (±pyrite) halos.

Siguiri Gold Mine (Siguiri) is an open-pit operation, located in the Siguiri district in the north-east of the Republic of Guinea, West Africa.

Siguiri is currently a multi-pit fresh rock and oxide gold mining operation with active mining currently occurring largely in Kami, Bidini and Tubani pits.

The mining method is selective conventional mining using excavators and trucks on 3m high flitches. Three Caterpillar 6020B excavators are the main loading equipment matched with Caterpillar 777G dump trucks. In some deposits, a selective mining unit (SMU) of 10 x 10 x 3m has been defined based on historical grade control, the deposit type, and the mining equipment used to simulate the expected mining dilution and ore losses.

Siguiri includes a processing plant, a TSF, and other infrastructures such as a mine village, a water supply system, roads, power supply by on-site generators and communications systems. Additional infrastructure includes on-site offices, accommodation and workshops to support remote mining

Since February 2019, the Siguiri combination plant was commissioned, in which the ore reception section consists of three off-loading pads, ROM(Run-of-Mine) 1, ROM 2 and ROM 3 where dump trucks directly tip ore into tipping bins or stockpile the material on the pads. Ore from the tipping bins is withdrawn at controlled rates by hydraulically powered variable apron feeders in close loop with mass meters to feed MMD (company name) sizers at ROM 1&2. ROM 3 treats the hard, transitional material in three-stage crushing, comprising a primary jaw crusher in open circuit with buffer stockpile, and the secondary and tertiary cone crushers which are in close circuit with vibrating screens.

Crushed products from ROM 2&3 crushers are transported in a series of overland conveyor belts onto a crushed ore stockpile located near the process plant. The stockpiled ore is withdrawn by the west apron feeder to CVR04, feeding the new Ball Mill 2. The second apron feeder-east, located underneath the stockpile, is capable of feeding both the existing Scrubber and the new Ball Mill 2, depending on Scrubber power and ore requirements. The existing ROM 1 continues to feed oxide material directly into the Scrubber/Ball Mill 1.

Scats generated from the scrubber are crushed in existing Symons 7 ft. short head cone crushers (running and standby), one crusher via a 6,000t live scats stockpile. New ball mill scats are also stockpiled near the existing scats stockpile. Crushed scats are returned, at a controlled rate, to the existing scrubber and/or new Ball Mill 2.

Crushed ore is fed to a 6.15m diameter x 11.1m length Scrubber, equipped with a 2500 kW installed drive. Scrubber discharge, controlled at approximately 50% solids by weight, is fed onto a vibrating double deck scrubber screen, fitted with 35mm/15mm square aperture polyurethane panels to scalp off scats. Scrubber screen oversize ore discharges go to a scat stockpile via a conveyor, whilst the undersize goes into a mill sump.

As a part of the comminution circuit, there is a 6.15m diameter x 9.0m length Ball Mill 1 which operates in closed circuit with a cluster of cyclones. The ball mill is equipped with a 6000 kW installed drive and takes its feed predominantly from cyclone cluster underflow. The ball mill discharges onto a trommel screen from where the undersize gravitates to the mill sump to join the scrubber screen undersize before both are pumped to the cyclone cluster. Ball Mill 1 trommel screen oversize discharges into a scats bunker. The mill cyclone cluster overflow gravitates to the new trash screen with the underflow being split as gravity circuit and ball mill feed. Trash screen undersize gravitates to the CIL(Carbon-in-Leach) feed pump which discharges to the leach circuit.

Processing began in 1997 via heap leaching and was continued for eight years, after which the long-term potential of the site as a heap leach became limited. As the percentage of heap-leachable ore declined (and to be able to exploit saprolitic ores that extended below the base of the existing pits), a CIP (Carbon-in-Pulp) plant was built.

The current processing plant treats both oxide and fresh sulphide material via a hybrid CIL circuit plant converted from CIP in 2018. The plant is capable of processing blends of hard and soft ore post commissioning a new ball mill and three-stage crushing plant in 2019. Unit operations include comminution, leaching, carbon adsorption and desorption, smelting and tailings disposal. Further modification of three leach tanks to CIL tanks was done in the fourth quarter of 2020 giving a total of seven tanks in the hybrid circuit.

Since February 2019, the Siguiri combination plant was commissioned with following updates:
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