Bibiani Gold Project

The Bibiani underground gold mine is expected to produce approximately 100,000oz of gold a year. Image courtesy of Alchemist-hp.

The Bibiani gold project is an underground mine located in the western region of Ghana. The mineral concessions of the deposit are located approximately 80km south-west of Kumasi, the capital city of Ashanti Region.

Feasibility study of the gold project was completed in June 2016, and the second phase of resource drilling started in December 2016. Infill and extensional drilling at the mine is expected to be started in the fiscal year 2017 to bring the historic mine back into production.

The project is expected to produce up to 1.2 million tonnes per annum (Mtpa) of underground ore and approximately 100,000oz of gold a year over its initial operating life of five years.

Mensin Gold Bibiani Limited (MGBL), a subsidiary of Resolute Mining, is the owner of the project. Resolute Mining owns 90% of MGBL, while the Ghana Government owns the remaining 10%.

Resolute gained control over the Bibiani project through a deed of company arrangement (DOCA) with Noble Mineral Resources. The ownership was transferred to MGBL in June 2014.

Bibiani mine geology and mineralisation

The gold mine is found within a series of fine-grained graded turbidites containing localised interbeds of fine to medium-grained turbiditic sandstones. The orebody is classified as a mesothermal lode-type deposit and is much identical to the lode deposits of the Konongo-Axim belt that host the Obuasi deposit.

The ore body is hosted within a shear zone, filled with quartz, within Lower Birimian sediments close to the eastern contact with Upper Birimian rocks.

Mineralisation in the main pit area occurs within a vertical to steeply east dipping zone extending over approximately 2,300m of strike length.

Majority of the mineralisation is associated with quartz veins and quartz stockworks, and is closely associated with sulphides and photomicrographs. Gold is predominantly fine and is found mostly along edges or cracks in pyrite and arsenopyrite sulphide minerals.

Reserves at Bibiani gold deposit

The Bibiani gold mine is estimated to contain probable ore reserve of 5.4 million tonnes (Mt), containing 640,000oz of gold.

Mining and processing of ore from Bibiani mine

Long hole open stoping mining method will be applied at the underground Bibiani mine. The developer proposes to use longitudinal method, wherever the width of the planned stope is less than 15m.

Am estimated 100,000t of ore a month is expected to be mined, which includes approximately 25,000t of waste and a total rock movement of 125,000t.

Ore from the mine will be processed at the existing processing plant. The ore will be primarily crushed and delivered to the reclaim stockpile. Front-end loaders (FEL) will be used to reclaim the stockpiled crushed ore and fed into the 1Mtpa milling circuit.

The milling circuit comprises a semi-autogenous grinding (SAG) mill, which operates in a single-stage closed circuit. The mill will reduce the product size to P80 106μm. The mill discharge will be classified by new 400mm hydrocyclones, wherein a portion of the cyclone underflow will be fed to the skim-air flash flotation cell for initial sulphide recovery.

Cyclone overflow will be screened to remove trash prior to scavenger flotation, and the resulting flotation and skim-air concentrates diverted to the fine grinding circuit.

Concentrate will then be pre-cycloned in new 150mm cyclones, with the overflow transferred to the concentrate thickener. Cyclone underflow will be directed to the Metprotech stirred mill for regrinding to a P80 of 25μm before pumping to the new carbon-in-leach (CIL) circuit comprising three tanks.

The concentrate leach tailings will be combined with the flotation tailings in the new flotation tailings leach circuit. The final tailings will be pumped to the tailings storage facility.

Carbon will be advanced through the flotation tail leach circuit and onto the concentrate leach circuit before being removed for elution.

Gold will be recovered from the loaded carbon in a 4t-capacity AARL elution plant, which is then deposited on to stainless-steel cathodes in an electro-winning circuit.

Infrastructure facilities at Bibiani gold mine

Access to the gold mine is from the eastern region, along the Kumasi – Bibiani – Sefwi Bekwai highway.

Power supply for the mine is provided from the national grid, while two fresh water dams already existing on the mine property will be used to meet the water needs.

The mine is serviced by two well equipped coastal ports namely Tema, which is located to the east of Accra, and Takoradi, which is on the western region of Ghana.

Key players involved

Resolute Mining engaged African Underground Mining Services (AUMS) for conducting drilling as part of the Bibiani feasibility study.

Minelogix developed the processing system for the Bibiani gold mine.