A geological factory powered by weather
The nickel ore deposits in Sekong Province are a type of mineral accumulation known as a laterite. These deposits form from the intense, prolonged chemical weathering of specific parent rocks, in this case, ultramafic rocks rich in the mineral olivine. This region of Laos is part of an ancient block of continental crust called the Kontum Massif, which contains rocks that are hundreds of millions of years old. Over millions of years, the consistent heavy rainfall of a tropical climate has slowly broken down these parent rocks.
The process is a massive natural filtration. Rainwater, which is slightly acidic, percolates through the ground and dissolves the more mobile elements in the rock, primarily magnesium and silica. These elements are carried away by groundwater, leaving behind a thick, residual layer enriched in less-soluble elements like iron and aluminum. Nickel, originally present in the parent rock's olivine at concentrations around 0.3%, is also released. The nickel is not washed away. Instead, it is redeposited and concentrated at specific depths within the weathered rock profile, creating an economically valuable ore body. This entire process can take as little as one million years to develop a complete laterite profile.