There’s no doubt that one of Australia’s greatest economic resources is mineral ores. However, finding ore bodies is an expensive and sometimes environmentally destructive process but, as Paul Willis finds out, scientists are now learning a lot about what lies beneath, by studying what thrives above – trees; termites and even kangaroo poo.

TRANSCRIPT

Narration: Hidden under the surface of our vast continent lie some of the biggest mineral deposits in the world - iron ore, copper, lead, zinc, uranium and gold have helped generate great wealth, but before the nation can profit from them, they need to be found.

Dr Paul Willis: When you walk through a landscape like this you might wonder how you could work out what mineral wealth there could be 50 metres or 100 metres under your feet. Well the answer could very well lie within the trees, or the termite mounds or even the kangaroo poo.

Narration: Scientists are learning a lot about what lies beneath, by studying what thrives above.

Paul: So what do you see Steve when you look at a landscape like that?

Dr Steve Hill: For a geologist like me, my job is to look at this landscape and then start to read it…when you look at the surface you start to find things that have a very close connection to what’s happening at depth. The obvious one here are some of these really old trees.

Narration: Some trees have tap root systems so deep that they penetrate 10, 20, up to 30 metres or more through the weathered rock to reach the ground water below.

Once there, they can suck up nutrients - and a diverse array of metals.

Dr Ravi Anand:
We see they can take up gold copper zinc lead arsenic uranium you name it. 30;14

Narration: Some native plants like Spinifex, eucalypts and acacia are known to absorb these precious metals

Paul: So if there are any minerals in the waters around here this tree will have taken them up and we will find them in the leaves.

Dr Anand: Yes they will be distributed in different organs of the tree.

Narration: To get an accurate picture of the metal concentrations, Dr Anand needs samples of the leaves, stems, litter and bark.

But nature doesn’t just have its own hydraulic pumps, as Steve Hill knows it also has its own diggers.

Paul: So, termite mounds. They work the same for you as trees do for Ravi?

Dr Hill: Very similar. Yeah that’s right. The termites burrow down,, just like the plant roots sink through the soils.

They burrow down in dry conditions until they hit a groundwater table and its around there that they’ll start finding little pieces of gold and that will be brought up as they are digging their burrows and the great thing about this is that the gold nuggets when we look at them, are a perfect fit within the jaws or mandibles of the termites.

We call it passive mineral exploration if you like. It’s instead of bringing in big trucks and digging things up we can just walk through the landscape and tap away at termite mounds pick leaves off the trees…

Narration: So this is an environmentally friendly way of actually finding mineral deposits.

Dr Hill: The damage that we have done here lasts for about maximum of an hour. Within minutes the termites are closing off their galleries so that ants can’t attack them, and within an hour its all nicely bedded down.

INarration: t’s not the termites themselves, but the mounds made from their digestive material, that are analysed for trace metals.

In plants, it can even be possible to see those metals with an electron microscope.

Paul: So what are we looking at here Ravi?

Dr Anand: What we are seeing in here is 2, 3, 4 micron size gold grains sitting within the plant material itself.

Paul: But they’re so small and finely distributed that you are not going to make a fortune panning for gold in a gum tree?

Dr Anand: No Paul but .what it is telling us is that plants are taking up gold and they can concentrate gold.

Paul: That’s remarkable

Narration: Plants and termite mounds are telling geologists what minerals lie directly below the surface, but bounding kangaroos can tell them about much larger areas.

Paul: Jeez you’ve got a nice job

Dr Hill: It’s fantastic isn’t it Paul.

Paul: Why roo poo?

Narration: Kangaroos, they’re the squadron of geochemical samplers. What’s going on here is kangaroos will be grazing plants from a well-known home range and as they are grazing those plants that are sucking up geochemical signals from deep down in the soils and regolith, that then gets secreted in their droppings like this and what I can do then is // take it along to the laboratory and that will give me an environmental signature from a large area.

Dr Hill: It’s a little bit like Skippy finds an ore body.

Paul: So kangaroos just poo anywhere don’t they?

Dr Hill: Well, the sad thing is Paul, the longer you start doing this the more you start thinking like a roo that needs to poo. And sure enough as you get good at thinking about where kangaroos might want to go poo, you’ll find them!

Narration: And the results of roo poo analysis are very clear.

Dr Hill: We’ve done sampling of these out at Broken Hill and // roo poo that’s near the ore body that has hundreds of parts per million of lead and zinc and silver // 30;20 and then as we move away it drops back to background levels. 20;24

Narration: And, amazingly, by analysing roo poo and trees around Broken Hill, the scientists found the largest new mineral discovery in the area for over 100 years.

Dr Anand: And that ore body was sitting there and has never been discovered before now. With this technique we were able to find that ore body quite easily

Paul: The good thing about Steve and Ravi’s work is that it’s cheap and environmentally friendly. And it will reduce the need for expensive drilling like this.

Narration: While traditional exploration methods will never be fully replaced by nature’s little prospectors, some 14 mining exploration companies are already using the new techniques. Hopefully they will not only save money, but may leave fewer holes in the ground and more landscapes relatively unharmed.

Related Info

Native trees give clues to mineral deposits

Dr Steve Hill

Dr Ravi Anand

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