Application of reflection-seismic method to leached cap exploration over porphyry copper deposits

Leached caps that formed over disseminated sulfide bodies are typical of large copper deposits mined throughout the western United States, Chile and Peru. The caps result from the weathering of rock containing an appreciable amount of sulfide mineralization. This weathering process results in the formation of an upper layer of leached rock at the paleosurface and an underlying layer of rock with an elevated content of metal. Additional weathering cycles may account for additional layers. Such a complex of horizontal to near-horizontal layers is amenable to detection using the reflection seismic geophysical method. At North Silver Bell, AZ, drilling data confirmed the presence of layers of leached and enriched rock that were originally identified in a reflection seismic survey.