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.

Open pit, conventional drill and blast with truck and shovel. 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 Teberebie cut 4 pit only. Pit wall steepening has been supported by effective wall monitoring and blasting practices.

Four large open pits currently exploit the stacked narrow auriferous conglomerates. Tarkwa has an ore stockpile and ‘spent ore’ on the South Heap Leach pad included in Mineral Resources and Mineral Reserves. Tarkwa has a centralised administrative office, engineering workshops and residence villages.

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.

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 increasing ore production to the heap leach to 7.2Mtpa. Process improvements and optimisations re ........