Lihir Island is on the Rim of Fire. Not much chance of an eruption, although earthquakes are par for the course in that region. My fear would be a tsunami that rolled up the shores and took out LGL's facilities.
Aside from that, in the gold mining game a greater risk is a team of turkeys at the helm, such as befell Croesus and the mob in WA that had the gold/tantalum mine (forgot their name- sorry).