IOCG deposits are usually associated with distal zones of particular large-scale igneous events, for instance a particular Suite or Supersuite of granites, intermediate mafic intrusives of a particular age.
IOCG mineralisation may accumulate within metasomatised wall rocks, within brecciated maar or caldera structures, faults or shears, or the aureole of an intrusive event (possibly as a skarn) and is typically accompanied by a substantial enrichment in iron oxide minerals (hematite, magnetite).