Name: Wassa mine.
Location: The project is located in the Wassa East district, in the Western region of Ghana.
Mine Owner/s: Golden Star Resources (90%) and the Ghana government (10%).
Brief Description: Wassa is an operating underground mine with the required services, infrastructure and community support already in place.
Brief History: The Wassa mine was originally developed as an openpit operation. Production from the surface operation started in 2005. Openpit mining was temporarily halted in January 2018.
Wassa transitioned into an underground-focused operation in early 2018.
The mine plan assumes underground mining will continue until the end of 2024 and that openpit mining will start in 2023 and continue until 2028.
Primary Metals/Minerals: Gold.
Secondary Metals/Minerals: None stated.
Geology/Mineralisation: The Wassa lithological sequence is characterised by lithologies belonging to the Sefwi Group and comprises intercalated meta-mafic volcanic and meta-diorite dykes, with altered meta-mafic volcanic and meta-sediments that are locally characterised as magnetite-rich, banded-iron formation-like horizons. The sequence is characterised by the presence of multiple ankerite-quartz veins, which run subparallel to the main penetrative foliation. The lithological sequence is also characterised by Eoeburnean felsic porphyry intrusions on the south-eastern flank of the Wassa mine fold.
Mineralisation within the Wassa mine is structurally controlled and related to vein densities and sulphide contents. The mineralisation generally comprises broadly tabular zones containing dismembered and folded ribbon-like bodies of narrow quartz vein material, with zones typically 10 m to 50 m wide within a 900 m mineralised corridor.
Reserves: Total proven and probable reserves as at December 31, 2020, were estimated at 18.41-million tonnes grading 2.38 g/t of gold.
Resources: Total measured and indicated resources as at December 31, 2019, were estimated at 48.81-million tonnes grading 2.34 g/t of gold. Inferred resources were estimated at 61.74-million tonnes grading 3.79 g/t gold.
Mining Method: Sublevel open stoping using unconsolidated waste backfill in the early stages and converting to cemented paste backfill in 2020.
Major Infrastructure and Equipment: The underground design uses a twin decline access from the base of the openpit.
Mining is undertaken using trackless, diesel-powered equipment, including twin-boom jumbos for development and longhole drills for production drilling. A combination of 17 t capacity loaders and 40 t capacity trucks is used for materials handling to surface.
The 2.7-million-tonne-a-year processing plant comprises a crushing, milling, gravity and carbon-in-leach gold recovery circuit.
The operation also features two tailings facilities.
Grid power from the State-owned power utility GridCo is supplied using a 161 kV line to supply a local substation, where power is transformed through a 33 MVA transformer to 34.5 kV. Two feeders provide electricity for the Wassa mine substation at 34.5 kV. Back-up generator power is available for the plant and underground mine.
Prospects: The Wassa underground mine has exploration upside through extension drilling of B Shoot North, step-out drilling on B Shoot South, step-out drilling on the 242 Trend and the extension of the F Shoot. This work is expected to increase the Wassa underground mine life in the short, medium and long term.
Contact Details:
Golden Star Resources
Tel +1 233 302 779 040
Email siteoperations@gsr.com
Website http://www.gsr.com