Source controls on mineralisation: Regional geology and magmatic evolution of Fiji

There is a well-established link between world-class gold telluride mineral deposits and alkalic magmatic host rocks, often emplaced post-subduction in arc terranes. Fiji home to two such deposits, provides an ideal location study the relationship (shoshonitic) their geodynamic context, potential roles metal enrichment. A total of 93 new geochemical analyses rocks from across are presented, alongside detailed petrography mineralogy compilation literature data. Despite relatively similar syn- samples, there differences them, with latter displaying elevated concentrations Ba (<2137 ppm), Rb (<218 Sr (<2648 ppm) K2O (<10.18 wt%), depletions Nb Ta. Multi-element trends suggest exaggerations ‘typical’ patterns shoshonites. Geochemical data that whilst fluxing fluids sediment melts subducted slab may play role producing distinctive magmas, they likely insufficient drive strong trends. Instead, biotite or possibly phlogopite lithosphere suggested as being key ‘ingredient’. Earlier subduction can modify through addition hydrous phases, both by metasomatism lithospheric mantle, formation residual minerals during fractional crystallisation. Remelting these phases could liberate trace elements metals. Biotite particular facilitate some observed large ion lithophile (LILE) enrichments alkali-rich (potassic) nature magmas.