Why is there a lot gold in west Africa?

Militaries which have taken energy in Africa’s Sahel area – notably Mali, Burkina Faso and Niger – have put strain on western mining corporations for a fairer distribution of income from the profitable mining sector.

Gold is likely one of the assets on the coronary heart of those tensions. West Africa has been a famend gold mining hub for hundreds of years, courting again to the traditional Ghana empire, which earned its status because the “Land of Gold” due to its plentiful reserves and thriving commerce networks. The area stays a worldwide chief in gold manufacturing. As of 2024, west Africa contributed roughly 10.8% of the world’s complete gold output.

However why is there a lot gold on this area? The Dialog Africa requested geologist Raymond Kazapoe to clarify.

How is gold fashioned?

The easy reply right here is that we’re not sure. Nevertheless, scientists have some concepts.

Gold, like all components, fashioned by excessive vitality reactions that occurred in varied cosmic and house environments some 13 billion years in the past, when the universe began to type.

Nevertheless, gold deposits – or the focus of gold in massive volumes inside rock formations – are believed to happen by varied processes, defined by two theories.

The primary idea – described by geologist Richard J. Goldfarb – argues that massive quantities of gold had been deposited in sure areas when continents had been increasing and altering form, round 3 billion years in the past. This occurred when smaller landmasses, or islands, collided and caught to bigger continents, a course of known as accretionary tectonics. Throughout these collisions, mineral-rich fluids moved by the Earth’s crust, depositing gold in sure areas.

A more moderen, complementary idea by planetary scientist Andrew Tomkins explains the formation of some a lot youthful gold deposits throughout the Phanerozoic interval (roughly 650 million years in the past). It suggests that because the Earth’s oceans turned richer in oxygen throughout the Phanerozoic interval, gold bought trapped inside one other mineral generally known as pyrite (typically known as idiot’s gold) as microscopic particles. Later, geological processes – like continental development (accretion) and warmth or strain adjustments (metamorphism) launched this gold – forming deposits that may very well be mined.

The place in west Africa is gold discovered and what are its sources?

Most gold manufacturing and reserves in west Africa are discovered inside the west African craton. This is likely one of the world’s oldest geological formations, consisting of historic, continental crust that has remained largely unchanged for billions of years.

The craton underlies a lot of west Africa, spanning elements of Mali, Ghana, Burkina Faso, Côte d’Ivoire, Guinea, Senegal and Mauritania. In actual fact, most west African international locations which have important gold deposits have near 50% of their landmass on the craton. Notably, between 35% and 45% of Ghana, Mali and Côte d’Ivoire’s territory sits on it – which is why these areas obtain a lot consideration from gold prospectors.

Gold deposits had been fashioned inside west Africa’s craton rocks throughout a significant tectonic occasion, generally known as the Eburnean Orogeny, 2.2 billion to 2.08 billion years in the past. This occasion was accompanied by the temperature, strain and tectonic situations which promote gold mineralisation occasions. Many of the gold assets within the west African craton are discovered inside historic geological formations fashioned by volcanic and tectonic processes about 2.3 billion to 2.05 billion years in the past. These are generally known as the Rhyacian Birimian granitoid-greenstone belts.

These gold-bearing belts in Ghana and Mali are by far probably the most endowed compared with different international locations within the area. Ghana and Mali at the moment, cumulatively account for over 57% of the mixed previous manufacturing and assets of all the west Africa sub-region.

Ghana is considered residence to 1,000 metric tonnes of gold. The nation produces 90 metric tonnes every year – or 7% of worldwide manufacturing. Gold manufacturing in Mali reached round 67.7 tonnes in 2023. Mali has an estimated 800 tons of gold deposits.

By comparability, the world’s two largest gold producers are China (which mined roughly 370 metric tonnes of gold in 2023) and Australia (which had an output of round 310 metric tonnes in 2023).

What are among the trendy exploration instruments used to seek out gold?

Gold was historically discovered by panning in riverbeds, the place miners swirled sediment in water to separate the heavy gold particles, or by digging shallow pits to extract gold-rich ores. Over time, strategies have advanced to incorporate geochemical exploration strategies, superior geophysical surveys, and chemical extraction strategies, like cyanide leaching.

Geological mapping strategies are all the time evolving, and for the time being, there may be lots of curiosity in combining distant sensing information with cutting-edge information analytics strategies, like machine studying. By combining these two strategies, geologists can get round among the issues brought on by conventional strategies, just like the reliance on subjective judgement to create dependable maps and the necessity to spend cash prospecting in areas with low probabilities of success.

In recent times, deep studying laptop strategies have made important progress. They study varied geological data-sets to scale back uncertainty and improve the probabilities of discovering gold mineralisation by superior synthetic intelligence strategies. These strategies have proved extremely useful in figuring out particular options and discovering new mineral deposits when utilized to distant sensing information.

One other technique, which I’ve researched and which might function a complementary gold exploration software, is using secure isotopes. Steady isotopes are components – like carbon, hydrogen and oxygen – that don’t decay over time. Some are accountable for serving to to hold gold, in fluids, by rocks to type the deposits. Because the gold-bearing fluids work together with the rocks, they switch the secure isotopes to the rocks, thereby imbuing them with their distinctive signature. The considering right here is to determine the signature after which use it as a proxy for locating gold, since gold itself is difficult to determine instantly.

Developments in analytical strategies have lowered the associated fee, quantity, and time concerned. This makes it a viable different to geochemical approaches – probably the most broadly used and comparatively environment friendly technique.

Raymond Kazapoe obtained his PhD in mineral exploration from the Pan African College on the College of Ibadan, Nigeria. This text is republished from The Dialog.