Evidence for Solution Collapse of a Magmatic-Hydrothermal Breccia Complex at the Lihir Gold Deposit, Papua New Guinea

The Lihir deposit is the largest known alkalic gold deposit in the world, and the one of the best examples of a telescoped epithermal-porphyry system. Lihir contains volcanic, magmatic and hydrothermal breccia complexes in the core of a sector-collapsed volcanic edifice, however, their relationships to porphyry and overprinting epithermal mineralization remains enigmatic. Detailed pit mapping has revealed a deep-seated, biotite-anhydrite-cemented, matrix-rich magmatic-hydrothermal breccia complex in the Lienetz ore zone. This study on the internal textures and external geometry reveals a history of early magmatic-hydrothermal brecciation and veining, followed by solution collapse promoted by anhydrite dissolution. Near the upper-levels of the breccia complex, open-space cavities were created by solution collapse and partly sealed by high-grade epithermal-style gold mineralization with associated bladed anhydrite and quartz.