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Ancient link gives fillip to explorers

Thursday, 14th July, 2011

ONCE JOINED: A map of the land between Broken Hill and Mt Isa shows the boundaries where the rock formations appear to have been separated. PICTURE: Geoscience Australia ONCE JOINED: A map of the land between Broken Hill and Mt Isa shows the boundaries where the rock formations appear to have been separated. PICTURE: Geoscience Australia

A newly-discovered link between Mt Isa and Broken Hill could influence mineral exploration in the region.

New research by Geoscience Australia (GA) shows that Broken Hill and Mt Isa were once joined by the same rock formation.

The two rich mineral provinces were believed to be connected until around 600 million years ago, when a stretching of the earth’s crustn forced a divide between the two areas, and in turn created the Cooper Basin.

The Government agency made the discovery by chance while conducting research in South Australia under its unrelated On-Shore Energy Security Program.

“It was a bit of a side benefit really, the relationships became evident when looking particularly at gravity data, which maps rock density,” said Dr James Johnson, Deputy CEO on GA.

“There was a definite pattern of north-south trending rock correlations, and if you remove that stretched part, it all fits neatly.”

Dr Johnson said the new data could prove invaluable to mining companies as they explore the region in search of new mineral deposits.

“It just so happens there’s a lot of important ore in there, and it really helps in a predictive capacity where exploring is concerned.

“One of the big roles we and other organisations try to do is provide industry with pre-competitive data.

“What we’re doing is indicating tenements to explore; it’s more of a broad address rather than a house on a street... it’s still up to them to put an X on the map.”

Geologist and CBH Director Dr Ian Plimer said the new data confirms long-held beliefs about a previous link between Broken Hill and Mt Isa.

Although Dr Plimer didn’t predict an exploration boom in the area on the basis of the finding, he said many exploration companies would find the information reassuring.

“There is a belief that there is a Mt Isa-type deposit to the north or north-west of Broken Hill, and there’s been a lot of exploration on that basis in the past,” he said.

“What this is likely to do is stimulate people and make them say ‘I thought I was on the right track!’

“When you’ve got rocks that are the same age, and formed by the same process, then you’re likely to find similar mineral deposits - but its up to the explorers to find those minerals.”

Dr Johnson said previous studies had shown similarities in mineralisation between the two regions, but this was first time such a tangible geographical link had been established.

“It was really fascinating. We’re always interested in understanding better how the country has evolved, how the pieces were put together and when they were put together.

“When you understand those processes you can better identify where mineral deposits might be. That contributes to the wealth of the nation, and that’s what gets us out of bed every morning.”

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