1st polymetalic result, page-2

Hi Zachary

IOCG deposits are not volcanic mate, they are magmatic.

Where volcanogenic deposits (e.g. VMS, SEDEX etc.) are created at, on, or near, the earth's surface or the surface of the seabed by lava, ashfall or some other volcanic-derived sedimentary material.

Magmatic deposits are created subsurface by magmas ascending from the mantle and crystallising. Here the magma does not reach the surface. Examples include IOCG and porphyry deposits amongst others.

All of these style can be very complex in geometry as you rightly pointed out.