Mineralogical constraints on the genesis of an alkalic-type epithermal Au-Te deposit: Tuvatu, Fiji

To study the characteristics and genetic constraints on alkalic-type epithermal Au mineralisation, here we use example of Tuvatu Au-Ag deposit in Fiji, with an emphasis detailed, quantitative mineralogy. mineralisation is hosted a weakly altered potassic monzonite parallel sided-veins K-feldspar, biotite, sericite, calcite, quartz, epidote-bearing propylitic or sericite-rich selvages. Petrographic core automated SEM-based mineralogical mapping thin sections have been utilised to update previous parageneses deposit. Automated SEM techniques enable identification small amounts obscure minerals that form minuscule grains, which would otherwise be very difficult identify measure. As result, our data show gold fineness extremely high, mean median content native-Au alloy being 96.7% 100% respectively, yet precious-metal tellurides make up majority deportment. Tellurides evidence multiple phases zoning depth. For first time at Tuvatu, Pt- Pd-tellurides identified. has number features common alkalic systems elsewhere, including quartz-poor, carbonate-rich veins alteration, abundant varied telluride minerals, high grades, Pt-Pd occurrences. We suggest these are result relatively temperature (250–300 °C) fluids immiscible semi-metal melts fluxing into shallow environment. High pH lead quartz-poor but mildly acidic conditions dominate areas fluid flux, where lower causes precipitation quartz. Boiling produces zonation depth leaves subtle textural compared boiling most systems, other quartz poor, deposits around world.