A small team of researchers with members from institutions in the U.S. and New Zealand (3 of the 4 are GRC Members) has found that there are large deposits of gold and silver in at least six reservoirs beneath several volcanoes in New Zealand. In their paper published in the journal Geothermics, the team describes their investigation into geothermal systems in the V-shaped Taupo Volcanic Zone on New Zealand's North Island and just how much of the precious metal they believe is hiding down there.
As part of their study, the team found that magma heating water in the volcanic zone had been breaking down rocks for quite some time, releasing the gold and silver in them. Those metal particles then fell to the floor of reservoirs that are hundreds of meters deep. The natural process is similar to the way modern precious metals are obtained—lode bearing rock is crushed and then sifted using water—the heavier metals land at the bottom where they are retrieved. In their studies, the team found examples of gold at over 20 parts per billion, and silver at 2,000 ppb.
Gold and silver resources in Taupo Volcanic Zone geothermal systems, Geothermics, Available online 14 August 2015.