Conclusions Regional tectonic uplift since the Miocene has exposed paleoplacer gold deposits and orogenicgold deposits in the underlying basement in the Otago Schist belt of southern New Zealand. Rise of higher mountains to the west has caused a semiarid rain shadow zone to develop over the area. Erosion and sedimentary recycling during on-going uplift in this rain shadow has yielded gold-bearing Late Pleistocene to Holocene alluvial fans (Figure 10a) in which biologically-mediated gold mobility has occurred in groundwater. Resultant micron-scale authigenic gold overgrowths on detrital gold particles are widespread (Figures 5–9). The products of this short-term and small scale gold mobility are different from long-term supergene enrichment of gold in the basement that has been enhancing gold particle sizes via inorganic processes since the Cretaceous, with some centimetre scale nugget formation (Figure 2a).