D Craw & D Chappell, Geology Department, University of Otago.
Research funded by Public Good Science Fund
Hot spring system deposit high concentrations of metals (including gold) at and near the surface of the Earth. These metal deposits can become significant point sources for heavy metal pollution of streams (e.g. arsenic, mercury, cadmium, zinc, lead). Mining, e.g. for gold, can accelerate the release of these metals by exposing (e.g. in tailings or mine walls) large amounts of metallic minerals to atmospheric oxygen, causing rapid decay. High metal contents in streams can be toxic to plant and animal life, including humans.
The figure below is a reconstructed cross section through a 4 million year old hot spring system in Northland (modern analogue). Click inside the circles to see more information.