03 January 2017
Kate Ravilious
Termite mounds, such as this one at the Bee Hive formations at Purnululu National Park in Western Australia, and acacia trees churn soil and minuscule chunks of gold up from below. John Crux Photography / Getty Images.
It’s no good heading to the hills to look for gold these days. Instead, modern prospectors might do better to sample termite mounds and acacia trees, according to a new study carried out in Western Australia.
Most of the easy gold spilling out at the Earth’s surface has been found, but there are still undiscovered veins of riches, hidden beneath sediments deposited over the past few million years. But how can a modern gold hunter work out where to start digging?
To answer this question, Ravi Anand from the Commonwealth Scientific Industrial Research Organisation [CSIRO] in Western Australia and colleagues gathered hundreds of samples of sediment, soil and acacia leaves from Moolart Well gold deposit, 400 kilometres northeast of Kalgoorlie in Western Australia.
After analysing the samples’ gold content, they discovered that regions were gold-poor, while others contained clusters of nanometre-sized spheres and rods of the precious metal.
The sediments where gold clustered were rich in organic carbon (carbon made from once-living material). “This gold is derived from the decay of the biomass created by the past vegetation in humid conditions,” Anand explains, whose findings were published in the journal Geology.
Better still, the areas containing clusters of gold may hint at deeper riches. Anand and his colleagues believe that the gold they found near to the surface had gone through several stages of recycling.
First, physical, chemical and biological processes moved gold from gold veins in the underlying bedrock into iron-rich sediments during humid climate conditions, more than 10 million years ago.
These little flakes of gold were transferred upwards again into younger sediments by the action of burrowing creatures, erosion and flooding, during the dry phase of the past few million years.
Finally, acacia trees and termites that thrive in the arid climate conditions continue to shuffle tiny flakes of gold around, diluting and dispersing the gold further still.
Any mounds or trees that are unusually rich in gold are likely to be lying above gold rich sediments, which in turn may well be hiding a valuable vein of gold. In other parts of the world, with different environmental processes and history, the recycling stages will differ.
Nonetheless, the clues are there for those who know what to look for, Anand says: “By studying soil and sediment formation, organisms and landscape evolution we can determine how gold has been dispersed, to help us narrow down the best places for mineral exploration.”
See the full article here .
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