What is an oxidation zone in geology ?

Oxidation zone : definition

In geology, the oxidation zone is the superficial part of the terrain in which interactions with the oxygen in the air, surface waters and bioreactions take place.

Many secondary minerals, called supergenes, are formed in this zone by dissolution of primary minerals, combination and precipitation of the elements in solution. Most of the clay minerals generally appear in this zone by hydrolysis of primary silicates (feldspars, biotite, amphiboles, etc...).

The oxidation zone is particularly spectacular in the case of sulfide mineral concentrations, the sulfides altering into a host of secondary minerals : carbonates, sulphatesphosphates and arsenates in particular. This oxidation phenomenon can lead to the genesis of very iron-rich zones (gossans) and exploitable mineral concentrations (bauxites, laterites, etc...).