Gold mineralisation at Tarkwa is hosted by Proterozoic Tarkwaian metasediments, which overlie but do not conform to a Birimian greenstone belt sequence. Gold mineralisation is concentrated in conglomerate reefs and has some similarities to deposits in the Witwatersrand Basin in South Africa. The deposit comprises a succession of stacked, tabular palaeoplacer units consisting of quartz pebble conglomerates. Approximately 10 such separate economic units occur in the concession area within a sedimentary package ranging from 40 metres to 110 metres in thickness. Low-grade to barren quartzite units are interlayered between the separate reef units. The Tarkwaian belt has been subject to moderate folding and at least five episodes of deformation have been recognised. In 2019 and 2020, exploration scoped to target extensions to the existing pits and to define palaeoplacer extensions, specifically in the Akontansi Underlap area, has successfully extended Tarkwa’s LoM to 2034.

The mine utilises selective surface mining methods to optimise the extraction of the mineralised conglomerate units. Short-term mine planning and forecasts are based on grade controlled models. During mining, fresh rock and transitional zones are drilled and blasted in six-metre lifts, with excavation in three metre flitches.

The mine is owner-operated and has its own load and haul fleet of 13 excavators, which range from 120 to 400 tonnes. The haul fleet includes 67 dump trucks with a payload of 146 tonnes, eight dump trucks with a payload of 240 tonnes and nine dump trucks with a payload of 90 tonnes. The load and haul fleet are supported by an ancillary fleet consisting of dozers, graders, water carts and compactors. A total of 22 owneroperated drill rigs are used for blast hole drilling. Maintenance of the fleet is carried out by Tarkwa mine, while maintenance of the excavators is carried out by contractors.

Mining operations are carried out using contractor mining. Mining occurs from several pits which haul to the processing facility. Blast restrictions are applied to the Pepe 8, Atuabo and Mantraim pits, which will be complete in 2020. Pit wall steepening has been supported by effective wall monitoring and blasting practices. [2019 Mineral Resources and Mineral Reserves Supplement to the Integrated Annual Report. P.96]

Gold Fields operates the mine with a conventional carbon-in-leach (CIL) plant, with a gyratory crusher feeding a semi-autogenous (SAG) mill and ball mill. Gold Fields processes the ex-pit mined ores through a conventional gold recovery plant, that consists of two parallel crushing circuits (a single primary gyratory crusher and a separate gyratory/cone tertiary crushing circuit), both feeding a single SAG, ball mill and pebble crusher (SABC) grinding circuit.

Ore is processed utilising a conventional CIL plant, with a gyratory crusher feeding a SAG mill and ball mill. Gold is recovered from solution by electro-winning and smelted in an induction furnace. Current plant capacity is 13.5Mtpa.

LoM tailings deposition requirements are catered for in the short term by wall raise sequences at the operating TSF 1, 2 and 5 facilities. The TSF 5 starting facility, whose downstream construction commenced in 2016, was completed in 2018. In the longer term, LoM tailings deposition requirements will be catered for by planned extended expansions to TSF 1, 2 and 5 and establishment of a new TSF 5 Annex that is planned to be constructed adjacent to TSF 5. [2019 Mineral Resources and Mineral Reserves Supplement to the Integrated Annual Report. P.96]

The initial development, Tarkwa Phase 1, was completed in April 1998 processing 4.7 million tonnes per annum (Mtpa) heap leach feed ore. An expansion, Phase 2, was completed in July 1999 inc ........