via Brittanicca.com - Supergene Enrichment

A good article discussing the meaning of Supergene Enrichment:

"The ore thus enriched forms the secondary, or supergene sulfide, zone and overlies the primary, or hypogene, zone. The phenomenon is most common in arid or semi-arid regions. As erosion extends the oxidized, or weathered, zone deeper, the primary (unaltered) zone is enriched by the metal from the oxidized supergene sulfides; in this way the primary ore may be enriched as much as tenfold: rich ores are made even richer, lean ores are made more valuable, and some ores too lean to be economic are upgraded enough to be workable."

This is what they're trying to hide underneath the EP Zone.

http://www.britannica.com/science/supergene-sulfide-enrichment

-F6