The Lihir deposit is considered to be an example of an epithermal gold deposit.
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 advanced argillic alteration assemblages developed through continued geothermal activity, driven by post mineralisation magmatism. Geothermal activity continues to this day.
Three alteration styles are recognised:
-Clay zone: equates to argillic ± advanced argillic alteration, about 250 m thick, and subparallel to basal topography of amphitheatre; represents the modern geothermal system;
-Sulphide–adularia zone: equates to epithermal-style low s ........
