Tenor variation within komatiite-associated nickel sulphide deposits: insights from the Wannaway Deposit, Widgiemooltha Dome, Western Australia

Abstract

Detailed geological evaluation yields insights into the relative influence of post-volcanic structural and metamorphic processes on Ni tenor (Ni concentration in 100 wt% sulphides) variation within the Wannaway N02 ore body, Western Australia. The ore body is characterised by highly variable geometrical configuration and ore zone morphology, and predominance of massive sulphides. Polyphase deformation and metamorphism to mid-amphibolite facies have modified the ore continuity, mineralogy, textures and fabrics. The up-dip and down-dip parts of the ore body are distinct from the central part, with significant structural relocation of massive ores, abundance of pyrrhotite-rich massive ores that lack mineralogical layering, and breccia ores. Massive sulphides plot within the field of Fe–Ni–S monosulphide solid solution (MSS) at 600 °C and form separate low, and medium- to high-tenor populations. Nickel tenor in massive ores varies from 6.1% to 18.8% within the ore body. Moreover, massive ore tenor is highly variable (>8 wt%) over distances of ∼20 m, and the lowest tenor massive ores occur at the down-dip and up-dip parts of the ore body.