Bounty Gold Deposit, Western Australia: Magnetic and Electromagnetic Responses

Mineralisation at the Bounty gold deposit is in a steeply plunging zone within a sheared iron-formation in the Archaean Forrestania greenstone belt. The gold was deposited together with pyrrhotite, replacing magnetite, but later dyke intrusion has converted pyrrhotite to magnetite adjacent to the dyke. Geophysical surveys have included magnetic and transient electromagnetic measurements. Magnetic data show the Bounty mineralisation is highly magnetic. The magnetic information has mainly been used to help map stratigraphy and structure, seeking favourable sites for mineralisation. An orientation transient electromagnetic survey showed that the Bounty orebody is a good conductor. More extensive surveys delineated an anomaly over the North Bounty deposit also, and discovered several other conductive zones which, so far, have been found only to be barren sulphidic shale and chert horizons.