Geochemical behavior of gold and critical metals in the Goongarrie Ni-laterites, Western Australia

The Goongarrie Ni–Co laterite deposit, developed on serpentinized komatiites of the Walter Williams Formation in the Eastern Goldfields Superterrane in Western Australia, comprises a thick lateritic weathering profile marked by a lower Mg-silicate-rich saprolite and an upper ferruginous saprolite (Fe-oxide zone enriched in Ni and Co). Structural controls, particularly NW–SE and NNW–SSE shear zones, and paleochannels have influenced the profile thickness (up to 125 m) and the localization of metal enrichment. Mineralogical and geochemical data reveal that nickel and cobalt are hosted primarily in Fe- and Mn-oxides (goethite, asbolane), with scandium and REE enriched in Fe-rich zones and clay minerals. Heavy mineral concentrates show that primary and secondary Ni–Co–Cu–As sulfides, PGE-bearing phases, and Au-Ag electrum are variably preserved or remobilized, especially along redox boundaries such as the Mg-discontinuity.

Hydrothermal overprints have contributed to the formation of Ni–Co–As sulfides and PGE in chromite and chlorite-rich zones, particularly in the lower saprolite. Ruthenium content in chromite varies systematically, providing a proxy for sulfide saturation in different parts of the profile. Laser ablation ICP-MS and geochemical correlations indicate that Fe- and Mn-oxides play a central role in the enrichment and redistribution of trace and critical metals (e.g., Sc, REE, Au, Ag, PGE). Gold enrichment is associated with redox gradients, a change in pH near the Mg-discontinuity and structurally controlled pathways, with evidence for halide complex transport under acidic and oxidizing conditions, and precipitation in lateritic and paleochannel settings. The integration of stratigraphic, mineralogical, and geochemical data highlights the interplay between lithology, structure, weathering, and fluid flow in concentrating Ni, Co, Sc, REE, and Au in the Goongarrie laterite profile.