The Proterozoic Birimian belt in West Africa hosts nearly all of the known gold deposits in Ghana, Burkino Faso and Cote De Ivoire. The Ashanti Gold Belt of SW Ghana, part of the volcano sedimentary Birimian Belt, includes seven producing mines. Gold mineralisation in the Birimian is mainly in the form of auriferous quartz veins of 'reefs' and as sulphide ore. Tarkwian system rocks consist of a thick series of argillaceous sediments resting unconformably on the Biriman. Gold is found in these sediments, occurring as blanket reefs or conglomerate beds, similar to those of the Witwatersrand in South Africa.
Primary kimberlites have yet to be found.
Constant power supplies to mining operations have been disrupted in Ghana due to drought, resulting in a drop in production of many gold mining operations. The Volta River feeds into the Volta Dam, whose hydroelectric scheme supplies almost all of Ghana's electricity. Ashanti Goldfields has signed an agreement with a consortium led by KMR Power Corporation, a US based power project developer, and the Ghanaian Ministry of Mines and Energy, for support of a 220MW gas fired, combined cycle power plant. Up to 100MW of this plant's energy will be allocated to Ashanti. Construction is underway, and full commissioning was expected to be completed before the end of 1999.