The Proterozoic Greenstone Belts of West Africa (also known as Birimian Greenstone Belts) encompass a vast area of approximately 350,000 square kilometres. World-class gold deposits situated within the Birimian Greenstone Belts have been discovered in the countries of Côte d’Ivoire, Burkina Faso, Ghana, Guinea, Mali, Niger, Senegal and Côte d’Ivoire (See Figure 1).
Geology & Mineralisation
The geology of West and Central Africa is dominated by Precambrian shields or cratons of Archean and Lower Proterozoic age, Pan-African mobile zones of Upper Proterozoic age and intracratonic sedimentary basins ranging from the Proterozoic to the Quaternary.
Birimian is a term to describe a collection of Paleoproterozoic metasedimentary and metavolcanic units and associated intrusive complexes that are the dominant hosts of gold deposits in West Africa.
Birimian gold mineralisation is often concentrated along the margins of volcanic belts, with mesothermal gold deposits localised along faults and shears that cut through the greenstone sequences, and are defined by zones of alteration and quartz +/- carbonate veining.
Types of Birimian hosted gold deposits
Most Birimian hosted gold deposits occur in corridors 10 to 15 kilometres wide, in the transition zone between volcanic belts and sedimentary basins which are characterized by regionally extensive shear zones. Two major styles of gold mineralisation occur in the Birimian
- Structurally controlled quartz vein style deposits, and
- Chemical sediment hosted deposits where gold is associated in selvages to quartz veins.
Commercial mineralisation is dominantly quartz vein-controlled and may be found in a variety of rocks and structural settings with metasediments being the most common host rock, particularly where intruded by felsic dykes and sills. Important mineralisation is also found in intermediate to mafic intrusive volcanic rocks and, volcanoclastic units. Quartz veins may contain both free gold and mineralisation associated with sulphides.
List of mining companies operating within the Birimian Greenstone Belts
Today there are many exploration companies prospecting in West Africa, such as:
- African Gold Group,
- African Queen Mines Ltd,
- Alecto Minerals Ltd,
- AngloGold Ashanti Ltd,
- Asante Gold Corporation,
- Asanko Gold Ltd,
- Aurora Minerals Ltd,
- Avnel Gold Mining Ltd,
- Avocet Mining plc,
- Azumah Resources Ltd,
- B2 Gold Ltd,
- Birimian Gold Ltd,
- Cardinal Resources,
- Castle Peak Mining,
- Centamin Mining,
- Desert Gold Inc,
- Endeavour Mining Corporation,
- Golden Star Resources
- Gold Fields
- Gryphon Minerals Ltd,
- HummingBird Resources,
- Iamgold Corp,
- Merrex Gold Inc,
- Newmont Mining,
- Oklo Resources Ltd,
- Perseus Mining Ltd,
- Pinsapo Gold S.A.
- Predictive Discovery Ltd,
- RandGold Resources,
- Sarama Resources Ltd,
- Savary Gold,
- Semafo Inc,
- Taruga Gold Ltd,
- True Gold Mining,
- West African Resources Ltd, and
- West End Mining,
List of gold deposits in the Birimian Greenstone Belts:
|Bissa Hill||Burkina Faso||5,100,000|
|Batie West||Burkina Faso||3,100,000|
|Samira Hill||Burkina Faso||2,500,000|
Source: Company Reports
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