Birimian

The Birimian rocks are major sources of gold and diamonds that extend through Ghana, Côte d'Ivoire, Guinea, Mali and Burkina Faso.

[1] The Birimian terranes in the southern part of the West African craton are a mix of metamorphosed volcanic, sedimentary, and plutonic rocks and low-grade metavolcanics and metasediments.

They consist of interlayered sedimentary and volcanic flow rocks metamorphosed to low greenschist facies.

They are overlaid in places by quartz-pebble conglomerates within the Tarkwaian System, name after Tarkwa, the second largest source of gold in Ghana.

[4] The Birimian forms two distinct and parallel greenstone belts in southwest Burkina Faso, the Hounde and the Boromo.