Metal provinces of contrasting sizes and shapes in the Cordilleran region of western North America include deposits of many ages and appear to be no more than vaguely related to major elements of crustal tectonics. When considered in terms of respective structural and petrologic associations, apparent ages, and inferred genesis, however, the known deposits can be assigned to metallogenic provinces with a geologically systematic pattern. Five principal kinds of metal concentrations are especially useful in this connection: (1) relatively massive sulfide deposits associated with thick sections of subaqueous volcanic rocks; (2) strata-bound deposits in marine sedimentary rocks; (3) strata-bound deposits in continental sedimentary rocks; (4) deposits in various host rocks of ontinental orogens; and (5) deposits associated with major volcanic accumulations of continental affinities.

The volcanogenic sulfide associations, which provide a complex and long-term clue to crustal concentration processes, include (1) Fe-Cu-Zn-Au-Ag deposits of Precambrian age that may well reflect repeated contributions from a primitive mantle, (2) Fe-Cu-Pb-Zn-Ag deposits of younger Precambrian to Mesozoic ages in less mafic volcanic rocks and associated eugeosynclinal strata, and (3) post-Paleozoic Fe-Cu-Au deposits of the ophiolitic type that evidently represent mantle contributions along divergent boundaries between crustal plates. The mantle also appears to have been the principal source of Fe, Cu, Mn, and other metallic accumulations in pelagic sediments of deep ocean basins during Cenozoic time.

In marked contrast are other deposits that bespeak early separation into the earth's sialic crust of metals such as Mo, W, Sn, U, and V, and continuing differentiation in this direction for Ag, Pb, Zn, and other metals. Unlike those of more direct mantle derivation, these deposits evidently have required recycling of metals through various combinations of sedimentation, metamorphism, crustal melting, fluid transport, and new additions from the mantle to explain their present levels of concentration. Thus current models of metallization along zones of continental rifting, seafloor spreading, island-arc development, and subduction of oceanic crust can account directly for the formation of some deposits, but they must include at least partly related processes of concentration within the ontinental crust to explain all of the recognized metallogenic provinces. The copper province of Arizona and adjacent areas is perhaps the best example of such complicated interplay over a very long period of geologic time.