Unusually high sub-microscopic gold and arsenic contents of pyrite from the Emperor gold deposit, Fiji

摘要

Gold is found in three different forms in the Emperor gold deposit: "invisible" or sub-micron gold in arsenian pyrite, native gold/electrum, and as tellurides (calaverite, krennerite, sylvanite, and petzite). Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and secondary ion mass spec-troscopy (SIMS) show that pyrite is among the most gold-(up to 11,057 ppm Au), tellurium-(up to 5,796 ppm Te), and arsenic-rich (up to 16.60 wt. % As) yet reported in the literature. Arsenian pyrite manifests itself as uniformly distributed grains, as arsenic-rich rims on preexisting grains, or as arsenic-rich cores. Although the preponderance of visible gold-bearing minerals is in the form of tellurides, in particular sylvanite, the majority of gold at Emperor occurs as "invisible gold."