Although
hosted within an Ordovician magmatic arc, the Peak Hill high sulphidation system
displays features typical of youngerPacific Rim high sulphidation epithermal gold deposits.
Regional NW trending transfer structures are inferred to localise the magmatic
source at their intersection of the NS trending arc. Fluids have migrated from
the magmatic source along NW structures and thence exploited permeable horizons,
which have become silicified. Alteration displays typical zonation from
silicification through assemblages characterised by alunite, pyrophyllite and
kaolinite and is followed by breccia/fracture controlled sulphide and gold
deposition. Sinistral rotation on the NS arc has dilated NW trending fractures
to produce the WNW to EW dilational fractures which host the higher grade ore.
Mineral assemblages are typical of formation distal to the magmatic source in an
epithermal environment. The combination of alteration and mineralisation
zonation with structure provide fluid vectors which target a magmatic source to
the SE of Peak Hill.