The geological features of the destructive plate margins of the southwest Pacific favour the formation of porphyry type
deposits. The major controlling factor favouring the formation of gold-rich deposits of this type is a dense crust. This
results in shallow intrusion of large magma bodies beneath andesite stratovolcanoes. Where the intrusives have near
vertical sides, the comparatively low temperature of transfer of volatiles from the solidifying melt favours the partitioning
of gold into bubbles of volatiles. They reduce the viscosity and density of the melt, resulting in the upward movement of a
mineralised melt. With the drop of pressure with upward movement the bubbles separate into a two phase mixture,
triggering freezing of the mineralised melt and the formation of a gold mineralised stockwork.