Resource Dictionary

Supergene Enrichment

This occurs after the primary copper porphyry deposit has formed. Weathering processes leach copper out of the upper parts of the deposit; the copper bearing solution travels downward through fractures and pore spaces until it meets the water table. Because the copper is no longer in contact with the air, it is no longer stable in solution and so precipitates, forming very copper-rich minerals like bornite, chalcocite, and cuprite and even native copper. This enriched zone can have substantially higher ore grades than the primary mineralization.