Gold mineralisation at Porgera is inferred to have been derived from a deep differentiated magmatic source which is capped
by a series of (now tilted) inward dipping sills and stocks, which comprise the Porgera Intrusive Complex. An arc normal
transfer structure provides a conduit, at the intersection with an arc parallel structure, into which basic magma derived from
the deep melting of mantle material has been emplaced. Two phases of mineralisation display an association with late stage
feldspar porphyry intrusives. Stage I carbonate-base metal-style gold mineralisation occurs as early quartz-sericite, then
massive sulphide and late zoned Mn-Fe-Mg-Ca carbonate vein/breccias. Magmatic fluids derived from the deep magma
source, are interpreted to have migrated along the margin of a feeder stock to the sills, and south to Waruwari. Stage II
epithermal Au-Ag quartz-style gold mineralisation occurs as early fluidised breccias and carbonate veining, followed by
zoned quartz-roscoelite-carbonate-gold vein/breccias, and late carbonate and/or sulphate open space infill. Magmatic fluids
are interpreted to have utilised the same plumbing system as the late stage feldspar porphyry intrusive, and then migrated
into the Roamane Fault which was dilated by; dextral rotation on elements of the transfer structure, normal faulting, and
refraction around the competent footwall hornblende diorite. Bonanza gold is localised in a jog in the Roamane Fault,
hangingwall splits and at intersections with cross structures. Bulk low grade Stage I gold has been deposited by the mixing
of magmatic fluids with cool gas condensate waters, whereas high grade Stage II gold mineralisation resulted from the rapid
quenching of mineralised magmatic fluids by oxygenated groundwaters.