Mobilisation features and environmental mobility of gold across New Zealand

Abstract

Gold from localities across New Zealand; including Southland, Central Otago, the West Coast, and the South Coast, were studied using scanning electron microscopy. Sites were chosen based on contrasting relationships of environments to compare and contrast the fine micrometer and nanometer scale features present on the gold. Using the latest equipment for subsurface imaging, that included a focused ion beam scanning electron microscope, gold mobilisation features were indentified. Features include gold precipitation and aggregation structures, dissolution and fluvial transport damage, as well as nano-particulate formation seen on samples from every site. Secondary features are present on all of the sampled gold grains and are the result of remobilisation, aggregation and dispersion of the samples while in the supergene environment and not the result of prior processes. Nano-particulate dispersion is discussed as the possible source for gold precipitation and aggregation due to its high reactivity and gold’s natural affinity towards itself. Nano-particulates are also identified as the gold form resulting from the etching of underlying gold and the principle feature by which gold nano-particulates are created and subsequently dispersed.