What is a cemantation in geology ?

Cemantation : definition

The cemantation zone is the zone immediately below the hydrostatic level. It marks the return to more reducing conditions after the oxidizing environment of the surface part. This change in geochemical climate causes precipitation of dissolved elements in the overlying oxidation zone.

The cementation zone of the metalliferous deposits is frequently a very important enrichment site, often the richest in the deposit, because the metals dissolved in the surface fringe reprecipitate and concentrate there. It is in this cementation zone that native copper and silver usually appear.