Geophysical response of alteration and mineralisation in the WafiGolpu porphyry system, Papua New Guinea

The Wafi-Golpu porphyry system in Papua New Guinea is about 2km in diameter and contains the Golpu and Nambonga porphyry deposits and the Wafi epithermal deposit. Several ground and airborne geophysical surveys have been undertaken over the deposits and related alteration. The Nambonga porphyry produces a discrete magnetic anomaly due to magnetite associated with potassic alteration. Magnetite has been destroyed in the upper part of the Golpu porphyry and occurs at depth with preserved potassic alteration. Alteration, apart from the potassic, is magnetite destructive. Induced Polarisation surveys map the extensive pyrite-sericite alteration associated with the system as demonstrated by high chargeability and low resistivities. Electromagnetic surveys map the system and detect the upper parts of the Golpu porphyry which is a good conductor, mainly due to secondary copper and sulphide veining.