Gold in Africa: Exploring West Africa’s Birimian Greenstone Belt

Precious Metals
birimian greenstone belt

The Birimian greenstone belt of West Africa represents one of the world’s most prospective yet underexplored regions for gold mining and discovery.

In recent years, West Africa has been the target of widespread gold exploration by many mining companies, and a staggering number of new finds have been made. This is not surprising—many of West Africa’s natural resources have gone untapped due to political unrest, poor access or inadequate infrastructure.

As a result, modern tools and techniques are screening highly prospective geology for the very first time. In fact, while known gold resources in the US have decreased in recent years, West African gold ore has increased by nearly 60 percent due to modern discoveries.

Many countries in West Africa now recognize the benefit to be reaped from resource development and have revisited and rewritten their mining laws to meet modern standards. For example, requirements for ownership have now changed in such a way that mining companies can make a substantial profit while offering high-paying jobs to local citizens.

The goldfields of West Africa run across a number of countries, including Burkina Faso, Ghana, Gambia, Nigeria, Sierra Leone, Liberia and 11 others. While each country carries its own set of mining rules and regulations, mining companies have gravitated towards the enormous potential for undiscovered gold ore.

Some countries have already made their mark in the global gold market. South Africa, for example, exported US$4.6 billion worth of gold in 2019. When combined, Ghana, Mali and Burkina Faso produce a total of 6.7 million ounces of the precious metal per year.

Introducing the Birimian Greenstone Belt

While Africa is home to a number of productive greenstone gold belts, the Birimian greenstone belt of West Africa is the best known and most prolific on the continent.

The Birimian greenstone belt formed during the collision of tectonic plates, the heat and pressure from which created the gold-bearing fluids that eventually became deposits. The primary goldfields of the Birimian being explored in West Africa involve the Proterozoic rocks situated in the southern portion of the West African Craton.

To date, the most productive gold-bearing zone within the Birimian greenstone belts has been the Ashanti belt in Ghana. The Ashanti belt has been actively mined for centuries—ever since European operations began in the 1800s.

Gold in the Ashanti belt is associated with metamorphosed volcanic and sedimentary rocks referred to as greenstone. Major gold deposits in the rest of West Africa are almost always associated with greenstone. Likewise, gold mineralization is also associated with quartz vein swarms and stockwork zones forming along structural weaknesses in the stratigraphies. Mineralized zones within greenstone belts can continue for long distances.

The majority of Birimian-hosted gold deposits occur in corridors that are 10 to 15 kilometers wide. These corridors represent the transition between volcanic rock and sedimentary lithologies and are typically characterized by regionally extensive shear zones.

Due to the age of these highly mineralized areas, large regions of the Birimian greenstone belt have been flattened by weathering and erosion. While some areas remain heavily vegetated, the vast majority of gold-bearing regions are arid and savannah-like, owing to its proximity to the Sahara desert.

The modern era of mining in the Birimian began in the 1980s, with the discovery of very fine gold in the Loulo and Syama gold deposits in Mali. These prolific discoveries underlined the significant discovery potential of West Africa’s Birimian belt, which, until the 1990s, remained underestimated outside of Ghana.

Major players to watch

A range of mining companies, from smaller exploration outfits to established operators, have set up camps in West Africa for the purpose of finding and mining gold. Commercial exploration is often based on native miners who have already tested surrounding areas for paying deposits. The purpose of drilling is often to search for deeper extensions of surface gold showings, which has led to many valuable finds.

African Gold Group

The African Gold Group (TSXV:AGG) is an exploration and development company focused on their advanced-stage Kobada gold project in Southern Mali, which has the potential to produce up to 100,000 ounces of gold per year. The project offers a low-cost profile and a large, and growing, mineral resource estimate. The Republic of Mali remains Africa’s third largest gold producer and has been EITI-compliant since 2011.

The company’s Kobada project is located within the Birimian greenstone belt and, unlike many other West African mining projects, benefits from excellent transportation links to Bamako, the capital city of Mali, and established logistics routes to West African ports. Southern Mali is widely considered a stable jurisdiction and is home to a number of gold producers.

Recent drill results have yielded a number of high-grade findings at unexpected depth, confirming the project’s significant exploration upside potential. Ongoing exploration in Mali since the 1980s has led to world-class discoveries, including the Morila deposit, which contains 8.5 million ounces of gold at grades of up to 6.28 grams per tonne.

Indigo Exploration

Indigo Exploration (TSXV:IXI) holds two gold exploration permits within the Birimian greenstone belts. The projects are located in Burkina Faso, which remains underexplored in comparison to countries like Ghana and Mali, where world-class discoveries have been unearthed at grades of up to 7.59 grams per tonne gold.

Indigo owns a land package that includes two properties: the 191 kilometer Hantoukoura permit and the 184 kilometer Lati permit. The Hantoukoura property hosts gold mineralization in the form of stacked veins while the Lati property offers shear hosted veins.

Hummingbird Resources

Hummingbird Resources (OTC Pink:HUMRF) acquired the Yanfolila gold project in 2014. This project is a high-grade open-pit mining operation that’s located in southern Mali. The company’s second project is the Dugbe gold project situated in the Republic of Liberia, the first country in Africa to become EITI-compliant.

The Yanfolila gold mine, while in its early stages of production, officially yielded gold in December 2017. Hummingbird Resources expects to mine over 676,000 ounces of reserve gold and believes the mine’s resource base could yield an additional 2 million ounces. The company’s current five year rolling mine plan anticipates mining over 100,000 ounces of gold per year until 2024.


The Birimian greenstone belt of West Africa represents one of the world’s most prospective yet underexplored regions for gold mining and discovery. As mining rules and regulations continue to shift in favor of widespread, large-scale development, mining companies that have established their position in West Africa’s fast-growing industry are well-positioned to benefit from the influx of new discoveries.

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