Prehistoric volcanoes to prospect for metals

The remains of volcanoes from billions of years ago are helping scientists identify both bygone continental boundaries and new places to find mineral resources in Australia.

Volcanoes often form where continental plates collide. Small amounts of water and carbon dioxide in an ocean crust forced under another continent can cause the mantle—the solid interior of the planet—to melt at several hundred degrees lower than normal. When these melts move to the surface, they erupt as volcanoes.

“Specific types of volcanoes have specific mineral resources associated with them. For example, gold is strongly associated with volcanoes in island arcs,” says Professor Stephen Foley, a petrologist and geochemist at the ARC Centre of Excellence for Core to Crust Fluid Systems.

Stephen studies the melts that move around the Earth’s mantle at depths of up to 200 kilometres below the crust. By looking at the volcanoes and melt compositions that occur on modern Earth, he can identify where rift valleys and volcanoes used to be, and predict the kinds of rocks and resources that may be found there.

“Many of the mineral resources and metals we’re looking for in Australia, such as nickel or gold, were formed in the first half of Earth’s history, about 2.5 to three billion years ago,” Stephen says.

“We’re looking for evidence of fault lines and former rift valleys where volcanoes or particular types of melts would be concentrated.

“The volcano may be long gone because of erosion, but we can still find the feeder dykes that took the melts up to the surface. These feeder dykes and their composition help us know where to look for which mineral resources.”

For more information:

ARC Centre of Excellence for Core to Crust Fluid Systems
Macquarie University
Stephen Foley
+61 2 9850 9452