Location
The Birimian rocks stretch across the countries to the north of the Gulf of Guinea, forming parallel belts that generally trend northeasterly and are 40 to 50 km wide and about 90 km apart. They consist of interlayered sedimentary and volcanic flow rocks metamorphosed to low greenschist facies. Most rivers draining the Birimian rocks hold alluvial gold deposits. They are overlaid in places by quartz-pebble conglomerates within the Tarkwaian System, name after Tarkwa, the second largest source of gold in Ghana. However, recent research indicates that the gold found in the Tarkwaian rocks is not derived from the Birimian terranes.
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