Metalliferous mineral deposits of the southeastern Pacific region include: (1) hydrothermal, magmatic, and sedimentary deposits of the Andean region, one of the great mineral belts of the world; (2) scattered hydrothermal deposits in the Antarctic Peninsula; and (3) metal-enriched pelagic sediments and ferromanganese nodules on the seafloor. Andean metalliferous deposits, the chief topic of this report, are for the most part spatially and genetically related to calc-alkaline plutons, subvolcanic intrusions, and volcanic rocks emplaced during the Andean orogeny of Late Triassic to Quaternary age. They are components of a single metallogenic province superimposed on two or more pre-Andean metallogenic provinces of Paleozoic and Precambrian(?) age. Deposits in the Antarctic eninsula are similar in age and origin to the deposits in the Andes and are considered to belong to the Andean province.

The Andean metallogenic province may be divided into several subprovinces, each parallel with the Andes and the continental margin and each having a dominant metal or suite of metals. The central Andes of Peru, northern Chile, and Bolivia, which contain the greatest concentration of exploitable deposits and the greatest variety of ore types, have as many as five linear, partly overlapping subprovinces. These subprovinces, from west to east (Pacific coast to the eastern Andean front), are characterized, respectively, by deposits of iron, copper, polymetallic base metals, tin, and gold.

Calc-alkaline plutonic and volcanic rocks of the Andes, which probably originated by partial melting in the Benioff zone, show a general, though nonuniform progression of decreasing age from west to east. Igneous rocks of Jurassic and Cretaceous age are most abundant near the coast, whereas those of Tertiary and Quaternary age dominate in the Andes. Locally, intrusive rocks and associated ore deposits of widely different ages are juxtaposed. Several sources of the metals are probable; they include oceanic crust and pelagic sediments in the Benioff zone, some of which may have been enriched previously in certain metals at the ancestral East Pacific Rise, and metal-rich zones in the overlying mantle and continental crust.