[ASC-media] Media release: secret of gold nuggets
crca-media at starclass.com.au
Tue Jan 27 03:36:00 EST 2004
Cooperative Research Centres Association Media Release - 04/04
January 27, 2004
THE SECRET OF NUGGETS
Gold nuggets may grow underground 'like potatoes', according to a dramatic scientific discovery by researchers in Australia's Co-operative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME).
The prized pieces of bullion have long puzzled prospectors and geologists because they show up in places where there is no obvious local gold concentration from which a large piece of pure metal could have come.
An investigation by CRC LEME doctoral researcher Frank Reith has yielded evidence that the formation of gold nuggets may be the product of generations of soil microbes hard at work. This could lead to significant enhancements in gold discovery and exploitation in Australia.
Mr Reith was studying some microscopic "bubbly" formations on the surface of naturally-occurring flakes of alluvial gold, thought by researchers to be microfossils - the eons-old remnants of bacteria.
"I found some areas on gold flakes that were covered with apparent biofilms
- traces of bacterial action. I stained for DNA, and got a positive result, which was suggestive, although this could have come from recent organisms," he explains.
But the test came when Frank tried to grow his own gold nuggets in the lab, and showed that certain tiny soil organisms - both fungi and bacteria - readily deposit gold, building it up in layers "like a miniature coral reef". They did this within a matter of days, piling up the gold atom by atom.
Researchers have long known certain microbes can dissolve gold out of rock. Mr Reith's work indicates they can also transport and precipitate it, or lay it down in a steadily-growing lump, which expands over a long period of time from a tiny flake to a prospector's delight.
The Chief Executive of CRC LEME, Dr Dennis Gee, says Mr Reith's work opens up a new way of thinking about Australian and other landscapes, and may lead to better ways to both find and extract gold and other minerals.
"The gold originated a few billion years ago, several kilometres down in the earth's crust. Over time erosion brought it to the surface and weathering distributed it across the landscape.
"Traditionally we tend to think of gold as a noble element, an inert metal that is mobilised mainly by chemical action. This research opens up the possibility that living organisms are involved in the whole process of mobilising, transporting and re-concentrating alluvial and elluvial (up-slope) gold."
The discovery of signs of bacterial action on gold flakes was made on material from the Tomakin Park gold mine in southeast NSW, and Palmer River in North Queensland but Dr Gee considers that a similar process may apply to all the main alluvial goldfields in Victoria, at Bathurst in NSW, in the Northern Territory and possibly at Coolgardie in WA.
"At Fly Flat, Coolgardie, the early prospectors saw gold nuggets lying on the surface, sparkling in the sun.
"We think these nuggets were formed metres down in the soil by microbial action, and were then gradually exposed by wind erosion and deflation (shrinking) of the surface sediments.
"Possibly these secondary nuggets grew like potatoes in the soil - although it may take millions of years to form a really large one."
"Frank has managed to reconstruct this biological process in the laboratory - making it a very strong probability that this is one gold nuggets may be formed."
The discovery could have significant commercial implications for gold discovery and exploitation in Australia.
Dr Gee says that the new information may help guide gold exploration in future - by geologists searching for traces of the right microbes in soil.
Mr Reith considers it could also be used to develop an economic and environmentally-friendly biological method for gold extraction and concentration.
Dr Gee adds it could also help improve the "biox" process used to extract gold from the 'refractory' (hard to dissolve) ores, which make up a third of Australia's gold reserves, including some that cannot be economically exploited with present technology.
In this way, the research addresses two of four Australia's National Research priorities - frontier technologies for industry and sustainability.
The discovery also illustrates how much we still have to learn about what lives in the continent of Australia - more than 99 per cent of our soil microbes remain undescribed by science, Dr Gee says.
Mr Frank Reith, ANU / CRC LEME 02 6125 2064 or 0409 974 658
Dr Dennis Gee, CRC LEME 08 6436 8786
Prof. Julian Cribb, CRCA media, 0418 639 245
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