Why is there so much gold in west Africa?
Gold is one of the resources at the heart of these tensions. West Africa has been a renowned gold mining hub for centuries, dating back to the ancient Ghana empire, which earned its reputation as the 'Land of Gold' because of its abundant reserves and thriving trade networks. The region remains a global leader in gold production. As of 2024, west Africa contributed approximately 10.8% of the world's total gold output.
But why is there so much gold in this region? The Conversation Africa asked geologist Raymond Kazapoe to explain.
The simple answer here is that we are not certain. However, scientists have some ideas.
Gold, like all elements, formed through high energy reactions that occurred in various cosmic and space environments some 13 billion years ago, when the universe started to form.
However, gold deposits – or the concentration of gold in large volumes within rock formations – are believed to occur through various processes, explained by two theories.
The first theory – described by geologist Richard J. Goldfarb – argues that large amounts of gold were deposited in certain areas when continents were expanding and changing shape, around 3 billion years ago. This happened when smaller landmasses, or islands, collided and stuck to larger continents, a process called accretionary tectonics. During these collisions, mineral-rich fluids moved through the Earth's crust, depositing gold in certain areas.
A newer, complementary theory by planetary scientist Andrew Tomkins explains the formation of some much younger gold deposits during the Phanerozoic period (approximately 650 million years ago). It suggests that as the Earth's oceans became richer in oxygen during the Phanerozoic period, gold got trapped within another mineral known as pyrite (often called fool's gold) as microscopic particles. Later, geological processes – like continental growth (accretion) and heat or pressure changes (metamorphism) released this gold – forming deposits that could be mined.
Most gold production and reserves in west Africa are found within the west African craton. This is one of the world's oldest geological formations, consisting of ancient, continental crust that has remained largely unchanged for billions of years.
The craton underlies much of west Africa, spanning parts of Mali, Ghana, Burkina Faso, Côte d'Ivoire, Guinea, Senegal and Mauritania. In fact, most west African countries that have significant gold deposits have close to 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 receive so much attention from gold prospectors.
Gold deposits were formed within west Africa's craton rocks during a major tectonic event, known as the Eburnean Orogeny, 2.2 billion to 2.08 billion years ago. This event was accompanied by the temperature, pressure and tectonic conditions which promote gold mineralisation events. Most of the gold resources in the west African craton are found within ancient geological formations formed by volcanic and tectonic processes about 2.3 billion to 2.05 billion years ago. These are known as the Rhyacian Birimian granitoid-greenstone belts.
These gold-bearing belts in Ghana and Mali are by far the most endowed when compared with other countries in the region. Ghana and Mali currently, cumulatively account for over 57% of the combined past production and resources of the entire west Africa sub-region.
Ghana is thought to be home to 1,000 metric tonnes of gold. The country produces 90 metric tonnes each year – or 7% of global production. Gold production in Mali reached around 67.7 tonnes in 2023. Mali has an estimated 800 tons of gold deposits.
By comparison, the world's two largest gold producers are China (which mined approximately 370 metric tonnes of gold in 2023) and Australia (which had an output of around 310 metric tonnes in 2023).
Gold was traditionally found by panning in riverbeds, where miners swirled sediment in water to separate the heavy gold particles, or by digging shallow pits to extract gold-rich ores. Over time, methods have evolved to include geochemical exploration techniques, advanced geophysical surveys, and chemical extraction techniques, like cyanide leaching.
Geological mapping techniques are always evolving, and at the moment, there is a lot of interest in combining remote sensing data with cutting-edge data analytics methods, like machine learning. By combining these two methods, geologists can get around some of the problems caused by traditional methods, like the reliance on subjective judgement to create reliable maps and the need to spend money prospecting in areas with low chances of success.
In recent years, deep learning computer techniques have made significant progress. They examine various geological data-sets to reduce uncertainty and increase the chances of finding gold mineralisation through advanced artificial intelligence techniques. These methods have proved highly beneficial in identifying specific features and discovering new mineral deposits when applied to remote sensing data.
Another method, which I've researched and which could serve as a complementary gold exploration tool, is the use of stable isotopes. Stable isotopes are elements – like carbon, hydrogen and oxygen – that do not decay over time. Some are responsible for helping to carry gold, in fluids, through rocks to form the deposits. As the gold-bearing fluids interact with the rocks, they transfer the stable isotopes to the rocks, thereby imbuing them with their unique signature. The thinking here is to identify the signature and then use it as a proxy for finding gold, since gold itself is hard to identify directly.
Advancements in analytical techniques have reduced the cost, volume, and time involved. This makes it a viable alternative to geochemical approaches – the most widely used and relatively efficient method.
This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Raymond Kazapoe, University for Development Studies
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Ghana's urban strategies neglect the needs of street vendors: policy must catch up with reality
Raymond Kazapoe receives funding from the African Union and Pan African University to carry out some of the research referenced in this article
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Nighttime temperatures plummeted to half the day's 125-degree high. Insects attracted by our bizarre desert light show retired before midnight. All told, we would pack out two tons of Ouranosaurus fossils in just three days. Gadoufaoua hides its secrets under drifting, shifting sand: You might walk right past a hidden skull one year only to spot it the next. On an earlier visit, we had discovered a patiolike stretch of exposed sandstone that was packed, to a jaw-dropping degree, with the embedded bones of raptors, turtles, fish, and more—what paleontologists call a microsite. As I returned to Gadoufaoua, among the foremost questions on my mind was whether the microsite would be buried under deep sand, and if it wasn't, how we might carve it up and collect it. I held my breath as I neared the spot and saw a towering dune. But miraculously, just yards away from it, the microsite was exposed. And soon it was surrounded by awestruck paleontologists on their hands and knees, marveling at the sandstone-bound menagerie. We used a rock saw with the largest diamond-covered blade we could find to slice down, about six inches, into the bone patio, hoping to cut it into bricks we could carry out in our usual field jackets. But would the slabs separate cleanly? When the first one did, with little more than the tap of a chisel, my team whooped. I felt like Michelangelo at first, then like Darwin aboard the H.M.S. Beagle, knowing a million bones of unknown species were ours for the collecting. Painstakingly removing rock or sediment from around fossil treasures like these might require years of lab time. But there at Gadoufaoua, one of my team members submerged a block from the microsite in water, and we discovered to our amazement that the sandstone matrix softened instantly—meaning this trove could be freed with minimal effort back at the Fossil Lab. The thrill of that realization helped power us through six long days transforming the bone patio into 10 tons of jacketed slabs. We headed to our final site with only two weeks left in the field, feeling the pressure. Three years before, we'd come to this place, some 120 miles east of Agadez, after investigating a passage I'd read in a 1950s monograph. Its author, French geologist Hugues Faure, described an isolated site where he had found saber-shaped teeth, like those of the T. rex-esque Egyptian predator Carcharodontosaurus. With some effort, we had found his site and, along with it, plenty more teeth, confirming Faure's understanding of the beds as late Cretaceous, some 95 million years old. We might have left with nothing more than teeth if not for a serendipitous visitor to our camp. He wore a black trench coat, cheche head wrap, and sunglasses, with a Tuareg sword slung over his shoulder. His name was Abdul Nasser, and he offered to take us to a bigger bone field. As he led us deep into one of the Sahara's great ergs, or sand seas, over and between dunes, our Land Rover struggled to keep pace with his Honda motorbike. It was feeling like a fool's errand until Abdul pulled up alongside a thigh bone as long as I am tall. It clearly belonged to a skeleton; in every direction, there was more bone. Grace Kinney-Broderick, then a field assistant and a former fossil preparator in Sereno's University of Chicago Fossil Lab, brushes off a sauropod tailbone while members of the team's security detail look on. Truck-mounted guns were a precaution against bandits. With little daylight and fuel, we were able only to note the GPS coordinates of the place, called Jenguebi, and grab a few jaw pieces we assumed were from Carcharodontosaurus. But assembling the jaw back in Chicago, I realized the teeth and tooth sockets were all wrong. They belonged instead to the sail-backed predator Spinosaurus. It was the first record of one of these water-loving beasts found so far inland—and I suspected it was a new species. Our return trip to Jenguebi took us back across the erg. We hopscotched among rocky areas, each smaller than the last, as we traveled deeper into it. We set up camp near where we found the jaw pieces, and we'd been there no more than an hour when my colleague Dan Vidal, a seasoned paleontologist from Spain, came running toward me, eyes gleaming. 'It's here!' he said. 'The skull!' (What dinosaur has 500 teeth? This prehistoric jaw was one-of-a-kind.) I found much of my team gathered around a toothy snout jutting up from the rock. These were the first Spinosaurus skull bones found in place in more than a century. My colleagues stood, mesmerized, as the significance of the find sank in. Some even wept. A few hours later, Dan found me again. This time he held an unfamiliar, boomerang-shaped bone. It was a head crest, we realized, but a strange one, projecting upward to a degree never seen in predatory dinosaurs. And where the crest of an Egyptian Spinosaurus is a ridge, this one was shaped like a scimitar. While team members Jahan Ramezani (at left) and Vincent Reneleau handle lunch dishes, Sereno finds a patch of elusive shade alongside the kitchen tent. On coals made from kindling, the team's Tuareg guides boiled water for tea in the evenings. Knowledgeable local guides were key to the expedition's success. While the team excavated the skull, Dan, our photogrammetry expert, documented the emerging skeleton with digital photos—a much faster process than in my early career, when we'd have photographed a few key fossils and I'd have stood over others, doing shaded drawings. That evening, on a laptop in the tent, he presented us with a 3D image, made from the stitched-together photos, of the skull of our new tall-crested Spinosaurus. The team was awestruck. It wasn't our last spectacular find at Jenguebi. A few days later, an 11-year-old boy from a Tuareg family camped nearby offered to show us fossils he'd seen while wandering with his goats. Navigating complex terrain he knew by heart, he led us to site after site, some with little more than a lonely bone fragment. At the last site, however, was an impressive set of bones and teeth. The latter's saber-like shape left no doubt we had found Africa's first partial skeleton of a carcharodontosaurid. After cleaning and assembly, it will provide the first detailed look at Africa's line of these colossal predators. We returned to Agadez haggard, dirty, and triumphant, with fossils filling two 40-foot containers. On a truck scale, the results of our efforts weighed in at 55 tons, twice what many of us had estimated. I, meanwhile, was 32 pounds lighter. I was also elated, leaving Niger for Chicago and knowing that, in a matter of months, our fossils would soon make the same trip. Then one last hurdle arose, suddenly and unexpectedly, a few months after our return. A military coup toppled the elected government of Niger, putting the shipment of the fossils on hold. (How a trip through the Sahara reflects Niger's fragile state.) Veteran fossil hunter Agali Bazo, curator of a small natural history museum in the oasis town of Ingall, visits the site that the team nicknamed Sauropod Island. For nearly two years, the fossils from our expedition remained in limbo. Then this spring, I traveled to Niamey, Niger's capital, where I signed an agreement that will at last bring the fossils to Chicago. It also provides for their staged repatriation, and it establishes a blueprint to develop two new Nigerien museums to house them, along with an institute to train the country's next generation of museologists, archaeologists, and paleontologists. These initiatives will be overseen by NigerHeritage, a foundation I established in 2016. I first came to Niger for its fossils, for high adventure, and for the stark beauty of its landscapes and sunsets. But I've returned again and again because of my deeper motivations as a paleontologist—because I know that the significance of my work isn't ultimately measured in new species but by the impact those discoveries can have on the future of a nation. On the eve of our expedition, I had goaded my young team members by telling them this would be their chance to write a new chapter in Earth's history, something they'd have few opportunities to do in a lifetime. We now have troves of images, video, and data from the field, and we have presented findings to conferences and journals, including a paper on the remarkable tall-crested Spinosaurus species. Soon we will have the bones for close study, along with geologic samples to reveal their age. Next will come an outpouring of discoveries related to the Carcharodontosaurus, a dozen new sauropods, a digging raptor, an armorless croc, a giant 'SuperFish,' and other new species. We are poised to write that chapter, introducing others to Africa's lost dinosaur worlds, daring them to imagine what still lies beneath the surface. A version of this story appears in the August 2025 issue of National Geographic magazine. An Explorer since 1983, paleontologist Paul Sereno writes this month about the most ambitious expedition of his career. He is a professor of organismal biology and anatomy at the University of Chicago and runs the university's Fossil Lab, a research and education center.
