Epithermal vein and breccia hosted Au mineralisation at the Kerimenge prospect, in the Wau district, Papua New Guinea, occurs within a block of multiply fractured dacite porphyry of Pliocene age, and is localised on intersecting regional fault structures, marginal to the eroded vent of a Late Pliocene-Pleistocene maar volcano (diatreme)._x000D_
Au mineralisation is primarily controlled by the steeply dipping Kerimenge Fault zone, which hosts a basal zone of silicified breccias, transitional laterally and vertically to networks of fracture controlled veins._x000D_
Early quartz+pyrite veins, deposited from CO2 rich, NaCl saturated, boiling fluids pre-date the main phase of Au mineralisation. Four stages of Au bearing vein mineralisation have been recognised. Quartz+sulphide veins (stage 1) and partially coeval quartz+sulphide+carbonate+ adularia veins (stage 2) occur marginal to silicified breccias, and are associated with quartz+sericite+pyrite wallrock alteration._x000D_
Similar depositional conditions prevailed for stage 1 and stage 2 mineralisation. Mineralising fluids underwent two stage boiling at temperatures of 145 to 2300 C. Boiling resulted in the loss of approximately 3 wt.% CO to the vapour phase. 2 Fluid salinity was probably I wt.% NaCl or less.