Golden Star Resources has reported the results from a feasibility study of development of an underground mine on the high-grade West Reef deposit on its Prestea property in southwest Ghana. The Prestea property hosts a previously operated underground mine that Golden Star acquired and placed on care and maintenance in 2002. Extensive surface infrastructure and underground development are in place and can be used in developing a new mine on the West Reef deposit.
Prestea is located 16 km from Golden Star’s existing Bogoso processing plant. West Reef ore will be hauled along an existing private haul road to a new plant at the Bogoso site. Golden Star initiated mining from a pit on the Prestea property in the third quarter of 2015 and currently hauls that ore to the Bogoso plant.
Gold production from the West Reef deposit will average about 80,000 oz/y over a mine life of 5.5 years based on current probable reserves. Life-of-mine all-in costs are estimated at $756/oz. The initial capital outlay is estimated at $63 million, with a development timeline of approximately 19 months to commercial production. The payback period is estimated at 2.9 years from the start of the project.
The West Reef deposit hosts probable mineral reserves totaling 1.04 million mt at a grade of 14 g/mt gold for a total of 469,000 oz of contained gold. The deposit ranges in depth from 550 m to 1,025 m below surface. The mineralization dips 60° to 85° to the west and varies in width from 0.5 to 3.5 m, with an average width of approximately 1.8 m.
The primary access shaft for mining the West Reef deposit will be the existing Central shaft in the town of Prestea, approximately 2 km to the north of the deposit. This shaft will be used for personnel access, materials transport, dewatering, and hoisting. The existing Bondaye shaft 3 km to the south of the deposit will provide a secondary means of egress and will also be used for dewatering.
The feasibility study proposes shrinkage stoping for mining the West Reef. An incline/decline system will be developed in the footwall of the mineralization to access sublevels at a vertical spacing of approximately 35 to 40 m.
A stand-alone, 500-mt/d processing plant to treat West Reef ore will be built at Golden Star’s Bogoso site, with a standard comminution circuit followed by gravity and carbon-in-leach sections. Gravity concentrate will be treated in the Bogoso plant’s existing Acacia recovery circuit. Gold recovered from the carbon-in-leach circuit will be further processed in the existing elution circuit, and doré will be smelted in the existing gold room.