Constraints on Conceptual and Quantitative Modeling of Early Diagenetic Sediment-Hosted Stratiform Copper Mineralization

Early diagenetic sediment-hosted stratiform copper (eSSC) mineralization results from low-temperature cuprous chloride complexes carried by saline aqueous solution circulating through footwall aquifers. Favorable copper solubilities are attained in moderately oxidizing, near-neutral pH solutions. That specific oxidation level is not determined by co-existence with hematite, with its near-indiscriminant control over Eh. Instead, redbed footwall aquifers are signatures of diagenetic oxidation. Relentless in-situ oxidation of ferrous minerals in redbeds produces pore waters too reduced to transport copper, thus eliminating compaction waters as ore solutions. Continuous early influxes of descending oxygen-rich meteoric waters which have assimilated evaporitic salts may redden aquifers and still retain oxidation levels capable of carrying copper to form downstream eSSCs.