Single and multiple weathering-erosion cycles in supergene ore genesis

Supergene ore deposits form when the relative tempo between weathering and erosion favors the formation and preservation of deep chemically stratified weathering profiles. If erosion outpaces weathering, weathering profiles are incipient or the surface is stripped to bedrock, and no supergene metal concentration occurs. If erosion and weathering occurs at comparable rates, metals chemically enriched at the Earth's surface are physically eroded, preventing the formation of supergene deposits. When chemical weathering is fast but chemical erosion slow, shallow weathering profiles devoid of enrichment blankets form because undesirable elements are not removed fast enough. Therefore, the ideal conditions for the formation and preservation of supergene ore deposits are relatively fast chemical weathering and erosion but slow physical erosion at the local scale, and relatively fast physical erosion, drainage incision, and lowering of the water table at the regional scale. Determining absolute ages of weathering profiles and rates of chemical and physical weathering and erosion for landsurfaces at local and regional scales is one of the primary challenges in quantifying supergene ore genesis and a necessary approach for identifying areas likely to host significant supergene ore deposits.