Porphyry deposits are large, low- to medium-grade deposits in which hypogene ore minerals are primarily structurally controlled and which are spatially and genetically related to felsic to intermediate porphyritic intrusions (Kirkham, 1972). The large size and structural control (e.g., veins, vein sets, stockworks, fractures, ‘crackled zones’, and breccia pipes) serve to separate porphyry deposits from genetically-related (e.g., some skarns, high-temperature mantos, breccia pipes, peripheral mesothermal (“intermediate”�, “transitional”�) veins, epithermal precious-metal deposits) and unrelated deposit types.

Supergene minerals may be developed in enriched zones in porphyry deposits by weathering of primary sulphides. Such zones typically have much higher copper grades, thereby enhancing the possibility of economic exploitation. Oxidization of porphyry deposits can also reduce sulphide contents of gold zones, thus improving extraction of gold by heap-leach methods.