How do residual mineral deposits form in warm tropical regions?

Residual mineral deposits form in warm, tropical regions through a process known as laterization, which is driven by intense weathering and high rainfall. In these climates, rainwater leaches away soluble materials from the soil, leaving behind an insoluble residue composed primarily of iron and aluminum hydroxide minerals. These resulting soils are called laterites.12

While many laterites are mixtures of iron and aluminum, specific conditions can lead to economically viable ore deposits:

• Bauxites: These are aluminum-rich laterites that form when iron is either absent or rendered soluble by organic matter, allowing it to be separated from the aluminum minerals.1
• Nickeliferous Laterites: When mafic igneous rocks undergo this weathering, nickel released from primary silicate minerals can be redeposited at or below the water table as the mineral garnierite.1

Essentially, these deposits are created not by the transport of ore, but by the selective removal of valueless material, which concentrates the remaining, less-soluble minerals into a residual ore body.2