AnEXTENDED ABSTRACTis available for download._x000D_
A full-length paper was notprepared for this presentation._x000D_
Shoshonite suite (absarokite-shoshonite-banakite) and adakite-hosted epithermal Au deposits are a feature of circum-Pacific magmatism._x000D_
Fijian examples include Tavua (Emperor) and Tuvatu on Viti Levu. New discoveries of shoshonite suite and adakite-hosted epithermal Au mineralisation have been made in the southern Yasawa Islands and in central-northern and central-western Viti Levu. The Fijian shoshonites define four NE-SW trending suites. The oldest is the northern 7.9-5.0 Ma Yasawa suite, followed by the 4.7-3.5 Ma Sabeto-Tavua-Rakiraki suite in northern Viti Levu, the 4.7-4.2 Ma Yanuca-Vatulele suite approximately 20 km south of Viti Levu and the 3.4 Ma Astrolabe suite approximately 75 km further south. Shoshonite suite lithologies with 3.8-3.0 Ma ages also occur in the Lomaiviti islands between Vatu-Cake and Moala, to the east of Viti Levu, defining a trend oblique to the NE-SW shoshonite belts. Seatura, a 3.3-2.8 Ma ocean island basalt (OIB) volcano, sits at the northern end of the Lomaiviti trend shoshonites. Trace element/isotopic chemistries indicate that shoshonite arc magma genesis involved the melting of a hydrated supra-subduction zone mantle wedge and also a lower mantle-derived plume (OIB) component. The upwelling plume provided heat for melting and possibly Au enrichment. Accessing the melt generation zone associated with the plume required a slab conduit or window. Such slab windows form by tearing during subduction or occur at slab edges. Adakites form by plume-induced slab melting. The four NE-SW Fijian shoshonite suites are interpreted to occur in back-arc extensional zones above a slab window (tear) that migrated southward during rollback of the New Hebrides-Vanuatu subduction zone. The plume (Seatura OIB) that is interpreted to have caused mantle wedge melting and formation of the Lomaviti trend shoshonites was focused along the interface between the north-dipping Vanuatu-New Hebrides subduction zone and the west-dipping Tonga subduction zone, which we have seismically imaged at approximately 400 km depth._x000D_
Our model cracks the metallogenetic code' for shoshonites and adakites and has regional and global implications for Au exploration.CITATION:Collerson, K, Lal, S, Williams, Q and Rost, S, 2015._x000D_
Cracking the metallogenetic code for Fijian epithermal gold mineralisation , in Proceedings PACRIM 2015 Congress, pp 219-226 (The Australasian Institute of Mining and Metallurgy: Melbourne).