A recent collaboration between scientists from Monash University, Mineral Resources Tasmania, the University of Queensland, University of WA, RMIT and Germany’s Federal Institute for Geosciences and Natural Resources has uncovered the important role of specialist bacteria in the formation and movement of platinum and related metals in surface environments.
Project leader Dr Frank Reith said the research has important implications for the future exploration of platinum group metals.
“These platinum group elements are strategically important metals, but finding new deposits is becoming increasingly difficult due to our limited understanding of the processes that affect the way they are cycled through surface environments,” Dr Reith said.
“This research reveals the key role of bacteria in these processes. This improved bio geochemical understanding is not only important from a scientific perspective but we hope will also lead to new and better ways of exploring for these metals.”
Platinum group metals, especially platinum and palladium, are highly prized ‘noble’ metals used in a wide range of industrial processes, and Dr Reith said that ensuring adequate supplies was considered a global priority.
“Traditionally it was thought that these platinum group metals only formed under high pressure and temperature systems deep underground, and that when they were brought to the surface through weathering and uplift, they just sat there and nothing further happened to them,” he said.
“We’ve shown that that is far from the case. We’ve linked specialised bacterial communities, found in biofilms on the grains of platinum group minerals at three separate locations around the world, with the dispersion and re-concentration of these elements in surface environments. We’ve shown that nuggets of platinum and related metals can be reformed at the surface through bacterial processes.”
The study, which was published in the journal Nature Geoscience, has investigated platinum group elements from Brazil, Colombia and the Australian state of Tasmania.
“We needed to find fresh grains of platinum group minerals and extract them from soils and sediments in a manner that preserves fragile biofilms and tell-tale DNA. These grains are incredibly rare, and the chase took us all over the world, from Tasmania to Brazil,” said Monash University Professor Joël Brugger.
By using scanning electron microscopy, the researchers were able to find for the first time live bacterial biofilms on mineral grains from all three sites. According to Dr Reith, they had been suggested previously but never before shown to exist.
He said they also showed that the mineral grains found at the Brazil site were bio-organic in origin, further supporting the role of the bacteria in the secondary formation of platinum grains.
“We’ve shown the biofilms occur across a range of platinum-group-metal grains and in different locations,” Dr Reith added.
“And we’ve shown, that at the Brazil site at least, the entire process of formation of platinum and palladium was mediated by microbes.”