Abstract Porphyry Cu deposits commonly contain critical and precious metal by-products, including the chalcophile and siderophile elements, Au, Pd, Pt, Ag, Te, Se, and Bi. These elements partition into residual sulfides during the partial melting of mantle wedge peridotite during subduction, potentially depleting the source magma for subduction-related porphyry Cu deposits. The chalcophile-rich residual sulfides in subduction-modified subcontinental lithosphere are thought to be the source of metals in postsubduction porphyry Cu deposits, and as such these deposits may be more enriched in chalcophile and siderophile elements than subduction-related porphyry deposits, although many postsubduction deposits have low Au grades. We test this by presenting whole-rock assay and PGE data with in situ LA-ICP-MS trace element data from sulfide minerals from three porphyry Cu deposits. The Skouries Cu-Au-(PGE) porphyry deposit, Greece, and the Muratdere Cu-Au-Mo porphyry deposit, Turkey are both postsubduction; these are contrasted with the El Teniente Cu-Mo porphyry deposit, Chile, which is a classic subduction-related system. By comparing these results with a newly compiled global dataset of trace element concentrations in sulfides from 18 other porphyry Cu deposits we show that postsubduction porphyry Cu deposit sulfides are relatively enriched in Bi, Sb, Te, and Se compared to sulfide minerals from subduction-related deposits. However, although some critical and precious metals (Ag, Bi, and Se) mainly reside in primary sulfide ore minerals, others (Au, Te, Pd, and Pt) are predominantly hosted in minor accessory minerals. Whole-rock data from mineralized samples show that although the Skouries and Muratdere deposits are enriched in Au compared with El Teniente, globally both subduction-related and postsubduction deposits can be precious and critical metal enriched, with metal endowment independent of tectonic setting. PGE-enriched porphyry Cu deposits are also enriched in Bi, Te, and Au, and semimetal melts are suggested to play an important role in PGE transport and concentration in porphyry Cu deposits.

Abstract The northern limb of the Bushveld Complex of South Africa contains a diverse array of Cr, Ni-Cu-platinum group element (PGE), Fe-V mineralization in mafic-ultramafic rocks and Sn mineralization hosted in granites. The limb has historically been underexplored compared to other parts of the Bushveld Complex and currently represents one of the world’s most interesting exploration frontiers. Successful low-cost open-pit mining of the thick Platreef Ni-Cu-PGE deposit, coupled with rising costs and limited scope for mechanization associated with narrow reef-type deposits in the eastern and western Bushveld, have driven efforts to locate similarly wide magmatic sulfide orebodies at surface or at reasonably shallow depths elsewhere in the northern limb, including recent discoveries of the Flatreef- and Main zone-hosted PGE deposits in the troctolite unit, at Aurora, and in the lower (F) and upper (T) mineralized zones at Waterberg. The Flatreef is hosted within a more consistent series of stratigraphic units than the more varied Platreef located updip, and while it shows similarities in terms of rock types and some geochemical features with the upper Critical zone of the eastern and western Bushveld, strict time equivalence remains to be proven. The various styles of Main zone-hosted PGE mineralization, on the other hand, have no known equivalents in the other limbs of the Bushveld Complex and seem to represent processes and events confined to the northern limb. Potential links based on similar rock types and metal budgets between Aurora and the Waterberg T zone and between the troctolite unit and the Waterberg F zone are attractive but must remain speculative until it becomes clearer whether the northernmost compartment that contains the Waterberg mineralization is linked to the remainder of the northern limb. If both the Flatreef and the Waterberg deposits enter production as planned over the coming decade, they will have dramatic effects on the South African platinum industry and dramatically increase the amount of Pd relative to Pt produced by South Africa due to the Pd-rich nature of all of the northern limb PGE orebodies.

Abstract Ore deposits form by a variety of natural processes that concentrate elements into a small volume that can be economically mined. Their type, character and abundance reflect the environment in which they formed and thus they preserve key evidence for the evolution of magmatic and tectonic processes, the state of the atmosphere and hydrosphere, and the evolution of life over geological time. This volume presents 13 papers on topical subjects in ore deposit research viewed in the context of Earth evolution. These diverse, yet interlinked, papers cover topics including: controls on the temporal and spatial distribution of ore deposits; the sources of fluid, gold and other components in orogenic gold deposits; the degree of oxygenation in the Neoproterozoic ocean; bacterial immobilization of gold in the semi-arid near-surface environment; and mineral resources for the future, including issues of resource estimation, sustainability of supply and the criticality of certain elements to society.