The Tarkwa orebody consists of a series of planar meta-sedimentary palaeoplacer deposits (2,132-2,095 Ma old), similar to those mined in the Witwatersrand Basin of South Africa (2,900-2,700 Ma old) with haematite being the dominant heavy mineral at Tarkwa in place of pyrite seen within the Witwatersrand deposits.

The mineral association of the reefs is consistent throughout all the open pits. The predominant gangue minerals are quartzite (83-90 wt%), muscovite (6-12 wt%) and kaolinite (1-3 wt%). The presence of kaolinite is an indication of the degree of superficial weathering of the orebody. Iron oxide, predominantly haematite, is the most common nonsilicate gangue mineral found in most parts of the deposit, varying between 2-3 wt%, along with minor magnetite. There are also trace amounts of todorokite (a hydrous manganese oxide, < 1 wt%) and copper. Sulphur exists in very minor quantities, especially associated with quartz veining at Pepe North and the Pepe West Limb area, most of which is already mined out. The concentrations are too low to have any detrimental effect on gold cyanidation or the environment. The reefs are interbedded with barren quartzite zones. The major gold bearing horizons are:
• AFc – up to 3.0 m thick, only occurs in the west and subcrops against the A1 in the east. Well sorted with rounded clasts of quartzite and visible gold. The AFc sub-outcrops against the A1 package at Akontansi East and is therefore not developed in the Pepe-Teb ........

In open pit mining, access to the orebody is achieved by stripping the overburden in benches of fixed height to expose the ore below. This is most typically achieved by drilling and blasting an area, loading the broken rock with excavators into dump trucks and hauling the rock and/or soil to dumps. The overburden material is placed on designated waste rock dumps.

Mining operations are carried out by contractor miners using open-pit, conventional drill and blast with truck and shovel methods. Mining occurs from several pits, which haul to the processing facility. Blast restrictions are applied to the Teberebie Cut 4 pit only. Slope stability has been supported by effective wall monitoring and blasting practices.

Four large open pits currently exploit the stacked narrow auriferous conglomerates.

Extraction of the orebody involves a similar activity as in stripping the overburden. Lines are established on the pit floor demarcating ore from waste material and the rock is then drilled and blasted. Post blasting, the ore is loaded into dump trucks, based on a defined ‘dig plan’ demarcating the position of the ore and waste boundaries post the heave and throw movement caused by the blasting, and hauled to interim stockpiles or directly to the crusher at the process plant, while the waste is hauled to waste rock dumps.

Mining at Tarkwa is carried out using conventional selective open pit mining methods which have been highly successful over ........

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