The Lihir deposit is considered to be an example of an epithermal gold deposit. Lihir Island is part of a 155 mile (250-kilometers) long, northwest-trending, alkalic volcanic island chain that sits within an area where several micro-plates (Solomon Sea Plate, South Bismarck Plate and North Bismarck Plate) developed between the converging Australian and South Pacific plates. Lihir Island comprises two Plio–Pleistocene volcanic blocks, Londolovit Block and Wurtol Wedge and three Pleistocene volcanic edifices, Huniho, Kinami, and Luise.
Features of the Lihir deposit that classifies it as an alkalic epithermal gold deposit include:
- Island arc association;
- Hosted in a sector-collapse amphitheatre developed in oxidised alkaline igneous rocks;
- Mineralisation hosted in vein stockworks, disseminated zones and breccias;
- Gold association with pyrite; often refractory;
- Low temperature/low salinity fluids.
Intense alteration was intimately associated with ore-forming events. Early-stage potassic alteration occurred as porphyry-style alteration associated with the emplacement of alkalic stocks within the volcanic edifice, with peripheral and broadly contemporaneous propylitic alteration. Sudden collapse of the volcanic edifice is interpreted to have resulted in the rapid depressurising of the system and subsequent telescoping of epithermal alteration and associated gold mineralisation upon the porphyry environment. Argillic and advan ........