Porphyry copper deposits are
copper orebodies that are formed from hydrothermal fluids that originate from a voluminous magma chamber several kilometers below the deposit itself. Predating or associated with those fluids are vertical dikes of
porphyritic intrusive rocks from which this deposit type derives its name. In later stages, circulating
meteoric fluids may interact with the
magmatic fluids. Successive envelopes of
hydrothermal alteration typically enclose a core of disseminated ore minerals in often
stockwork-forming hairline fractures and veins. Because of their large volume, porphyry orebodies can be economic from copper concentrations as low as 0.15%
copper and can have economic amounts of by-products such as
molybdenum,
silver and
gold. In some mines, those metals are the main product.