GOLD PROCESSES: from mountains to ingots

Emeritus Professor Dave Craw (Otago University)

New Zealand is geologically active and some of these active processes are naturally concentrating gold in the rocks. Deep and shallow hot water systems dissolve trace amounts of gold from some rocks and concentrate it in other rocks, in the North Island and in the Southern Alps mountains. The same processes happened across Otago between 100 and 150 million years ago, to be mined now at Macraes in east Otago and possibly at Bendigo near Wanaka. Rivers eroding Otago’s golden rocks have also concentrated some of this gold in their gravels over the past 100 million years as various river systems came and went. Mining activity in Otago over the past 160 years has imitated all these gold concentration processes, leading to production of gold bars in a significant Otago industry.

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