Some Aspects of the Mineralisation of the Wainaleka Massive Sulphide Prospect, Fiji

Abstract

The pyritic Zn-Cu Wainaleka massive sulphide prospect, southern Viti Levu, Fiji, is associated with Early Miocene dacitic volcanism. The prospect occurs within altered dacitic pyroclastics occurring in the upper parts of the volcanic complex. The mineralisation was emplaced during the final stages of a dacitic phase of volcanism. The mineralisation consists of a lens-shaped, massive sulphide body with minor stringer mineralisation. In the massive zone, pyrite and sphalerite are the dominant minerals with ubiquitous but minor chalcopyrite. Also occurring in the zone are minor amounts of tetrahedrite - tennantite, galena, bornite, enargite group minerals and supergene covellite. Pyrite and chalcopyrite are the dominant minerals in the stringer zone. Quartz and sericite occur as the common gangue minerals along with minor calcite, gypsum and barite. The ores are polymetallic in nature, enriched in Cu and Zn and a number of other minor elements such as Ag, As, Ba and Pb. The prospect appears to have been formed at the discharge site of a submarine hydrothermal system.