By Emily Lehmann
While money doesn’t grow on trees per se, we’ve found that precious gold does.
Our scientists have revealed that gum trees from the Western Australian goldfields draw up tiny particles of gold via their roots and it ends up in their leaves and branches.
The study published in Nature Communications today provides the first evidence of gold growing in trees.
“The eucalypt acts as a hydraulic pump – its roots extend tens of metres into the ground and draw up water containing the gold. As the gold is likely to be toxic to the plant, it’s moved to the leaves and branches where it can be released or shed to the ground,” CSIRO geochemist, Dr Mel Lintern says.
Prospectors be warned – the discovery is unlikely to start an old-time gold rush – the ‘nuggets’ are just one-fifth the diameter of a human hair and invisible to the eye.
Yet, it could provide a golden opportunity for mineral exploration, as the leaves or soil underneath the trees where they have fallen could indicate gold ore deposits buried up to tens of metres underground and under sediments that are up to 60 million years old.
“The leaves could be used in combination with other tools to get an idea of what’s happening below the surface without the need to drill. It could enhance gold exploration in a way that’s more targeted and environmentally friendly,” says Dr Lintern.
The research team used the powerful x-ray elemental imaging equipment at the Australian Synchrotron to locate and see the gold in the leaves.
Read more on our media page.
Media: Emily Lehmann, P: +61 419 271 822, Emily.Lehmann@csiro.au
By James Tickner, Office of the Chief Executive Science Leader
Globally, the minerals industry is operating in an increasingly challenging environment. Lower and more volatile metal prices, declining ore grades, increasing production costs, environmental pressures and mounting global competition all affect the sector.
At CSIRO we are working with the minerals industry to develop new technologies that will help maintain global competitiveness – and we recently announced a new X-ray technology to do just this.
It has the potential to boost productivity and save the Australian gold industry hundreds of millions of dollars a year.
The challenges of producing gold
Gold in Australia is normally mined at very low grades – as little as one gram of gold for every tonne of rock. Explorers looking for new gold deposits, and the people running mines or monitoring extraction plants, need a really sensitive detection method.
The industry standard analysis, fire-assay, is complex, laborious and destroys samples by fusing them at temperatures up to 1,200C.
The process is normally carried out in centralised laboratories. This can lead to turn-around times of several days, particularly if materials are sent in from remote locations. Running a large processing plant is like trying to drive a truck looking only in the rear view mirror.
The lack of real-time feedback is one of the factors contributing to a typical gold plant only extracting 65-85% of the gold present in mined rock. And with Australia producing around A$10 billion worth of gold last year, billions of dollars worth of gold is potentially going to waste.
Even a 5% improvement in recovery efficiency would be worth half a billion dollars a year. Huge amounts of water and energy are required to extract gold, so this would also pay dividends in reducing the resources embedded in every ounce of metal.
Our X-ray method
The X-rays force nuclei at the heart of any gold atoms present into an excited state and this results in the gold atoms becoming weakly radioactive for just a few seconds.
A highly sensitive detector picks up the radiation emitted by the gold and reads out the level of the precious metal.
The big benefits of the method are simplicity, speed and accuracy. Up to half a kilogram of material is packed into a plastic jar and fed into the analyser. A few minutes later, the analysis is complete and the sample is returned unchanged.
As the method is completely non-destructive, the sample can be subjected to further testing if required.
Measuring a large mass of material improves accuracy. This is especially true for gold, as distribution can be very patchy even in a rich ore deposit.
One of the great advantages of using nuclear analysis is that it is sensitive to all forms of gold. It doesn’t matter what chemical or physical form the gold takes, or whether the sample is a solid or a liquid. If gold atoms are there, they will be seen and counted.
Proving the new technology
While the science behind using X-rays to find gold has been known for decades, achieving the necessary sensitivity was a major challenge. CSIRO combined the latest developments in high-power X-ray sources and radiation detectors with advanced computer modelling. This led to an analyser capable of detecting gold at levels nearly ten times lower than previous systems.
We have recently completed tests in collaboration with the Canadian technology company Mevex which showed that our prototype analyser is capable of measuring gold two to three times more accurately than commercial laboratory fire-assay. We are now exploring how to bring the technology to market with Australian and international partners.
An X-ray based analysis system would probably be first used in a commercial assay laboratory. But things get really exciting when you think what might be possible beyond that. A complete, fully automated system could be packaged into a couple of shipping containers. This could be trucked out and dropped down for real-time, on-the-spot analysis in remote locations.
Some of the prospects for the technology include speeding up the exploration for gold and three-dimensional mapping of deposits by monitoring the spoil produced as bore-holes are being drilled. Helping to control the billion-dollar concentrator plants used to process gold ore would be another important application.
Any new technology is a jigsaw puzzle built around what starts out as just a crazy idea. The most satisfying part of working as an applied scientist is nurturing some of those ideas into the real world.
Rapid X-ray analysis is set to make a huge difference to the productivity and competitiveness of the gold industry.
Powerful x-rays can now be used to rapidly and accurately detect gold in ore samples, thanks to a fancy new technique our scientists have developed.
We’re pretty excited about this, because it means mining companies will be able to recover small traces of gold that would otherwise be discarded.
Given that a gold processing plant may only recover between 65 and 85 per cent of gold present in mined rock, these wasted traces of gold add up pretty quickly – to the tune of hundreds of millions of dollars each year.
The new technique, known as gamma activation analysis, works by blasting mineral samples using high-energy x-rays similar to those used to treat patients in hospitals. The x-rays activate any gold in the sample, which is then picked up using a sensitive detector.
You can read all about it in this media release.
Small-scale fault systems in the Earth’s crust have a strong correlation with the location of gold, a recent study of the St Ives Goldfields in Western Australia has found.
The research, published in science journal Ore Geology Reviews, found that all major gold deposits are controlled by faults, but small fault systems are more likely to lead to gold than larger ones.
Researcher Dr Carsten Laukamp says the relationship between fault systems and gold traces is key to understanding the genesis of gold and could be used to help locate any commodity.
“Determining the spatial relationship between geological features such as fault lines, and gold traces, is not only important to understand how deposits form, it can also guide mineral exploration because we can use this information to develop predictive mineral maps,” he says.
Dr Laukamp and the team developed a predictive mineral map of the St Ives Goldfields that shows new prospective areas where there is a high likelihood that gold could be located.
“We used information such as rock type, colour, shape and size and geological boundaries – all information we can gather from drilling samples – to develop the map,” Dr Laukamp says.
“This research is one step in the development of predictive mineral maps that integrate various types of geological data.
“Next, we’ll incorporate data collected from aircrafts and satellites, such as geophysical and spectroscopic data, which will improve the information value and accuracy of the predictive mineral map.”
This research was carried out by a collaborative team of researchers from Curtin University of Technology, the ARC Centre of Excellence for Core to Crust Fluid Systems and CSIRO.
Learn more about our research in mineral exploration.
Media enquiries: Liz Greenbank | 03 9545 8563 | firstname.lastname@example.org
Ant and termite nests could lead to hidden treasure according to research conducted by CSIRO.
Research published in science journals PLoS ONE and Geochemistry: Exploration, Environment, Analysis, found that at a test site in the West Australian goldfields termite mounds contained high concentrations of gold. This gold indicates there is a larger deposit underneath.
“We’re using insects to help find new gold and other mineral deposits. These resources are becoming increasingly hard to find because much of the Australian landscape is covered by a layer of eroded material that masks what’s going on deeper underground,” Dr Aaron Stewart, CSIRO entomologist said.
Termites and ants burrow into this layer of material where a fingerprint of the underlying gold deposit is found, and bring traces of this fingerprint to the surface.
“The insects bring up small particles that contain gold from the deposit’s fingerprint, or halo, and effectively stockpile it in their mounds,” Dr Stewart said.
“Our recent research has shown that small ant and termite mounds that may not look like much on the surface, are just as valuable in finding gold as the large African mounds are that stand several metres tall.”
Mineral resources make up $86.7 billion of Australia’s exports and new discoveries in many commodities are required to sustain production. After 150 years of mining, gold and other mineral deposits near the surface have been discovered and miners need new tools to explore deeper underground.
Insects could provide a new, cost effective and environmentally friendly way of exploring for new mineral deposits, avoiding the traditional method of expensive and often inaccurate drilling.
Dr Stewart’s work has also found that insects carry metals in their bodies.
“We’ve found that metals accumulate in excretory systems of termites,” he said.
“Although the insects may not concentrate metals in their bodies, they actively rid their bodies of excess metals. This process shows up as little stones, much like kidney stones in people. This finding is important because these excretions are a driving force in redistribution of metals near the surface.”
Dr Stewart was selected as a finalist in this year’s Fresh Science Awards.
Media: Liz Greenbank. Mb: 0408 778 189. E: email@example.com