A vast new gold province, covering thousands of square kilometres of central South Australia, is being gradually unveiled with the help of a revolutionary geological exploration technique.

The Minister for Industry, Science and Tourism, John Moore, has congratulated the scientific team whose work helped to identify the new sources of wealth.

Mr Moore said the mining industry has quickly adopted the calcrete geochemistry method for finding gold deposits developed by Dr Charles Butt, Mr Melvyn Lintern and Dr David Gray from CSIRO Exploration and Mining and the Co-operative Research Centre for Landscape Evolution and Mineral Exploration (CRC LEME).

The team has been awarded the Association of Mining and Exploration Companies (AMEC) inaugural Science and Technology Award "in recognition of outstanding research, contributing to the development and growth of the Australian mineral exploration and mining industry".

Mineral companies are now racing to explore a huge region extending almost from Eucla in the West to Port Augusta in the east, and the SA coast to Coober Pedy in the north, a vast 2.4 billion year-old block of granitic rock known as the Gawler Craton.

Aeromagnetic surveys by the SA Government identified numerous promising geological structures and magnetic anomalies buried tens of metres deep under the layer of weathered rock and eroded sand which blankets much of the State and hampered previous exploration efforts.

Some of these structures certainly contain buried mineral deposits - the big question was: which ones? The calcrete geochemistry method pioneered by Dr Butt and his colleagues has had a spectacular impact on the rate of success in identifying gold-rich deposits. Using the technique, one explorer struck gold at 36 out of 38 sites drilled.

"That's an amazing strike rate," Dr Butt says. "Things like that just don't happen!"

Drilling results from this and other companies indicate the Gawler Craton harbours a gold province as large as any yet found in Australia, though the extent and richness of individual deposits is still being determined. It is expected many deposits also contain copper, zinc, lead, silver and other minerals.

If the gold discoveries have come rapidly, the science underpinning them did not. It was hammered out by Dr Butt and his colleagues over a ten year period of meticulous research, starting in 1986.

The CSIRO scientists began working on Kalgoorlie's Golden Mile and elsewhere in the enormous 3-billion year old Yilgarn Craton which makes up a substantial part of southern WA, tying together a suspected link between soil materials known as calcretes and gold deposits.

Calcretes are carbonates, deposited in weathered soils in the landscape largely by evaporative processes in regions where rainfall is very low - less than 600mm a year. They are widely distributed in the upper layers of both the Yilgarn and Gawler cratons.

The calcretes themselves are not gold-rich, but even early prospectors noted that the two were often associated, and gold nuggets were to be found in calcareous deposits.

The team began to observe a strong correlation between the concentrations of calcium and magnesium in the calcretes and concentrations of gold. This came as a surprise - as there is no direct chemical relationship between the two.

However, they found that the gold and calcrete had accumulated under exactly the same set of climatic conditions -- dissolving in water and then precipitating as the soil dried out under arid conditions. In other words, the presence of very small amounts of gold (commonly only 5 to 100 parts per billion) in calcrete can be used as a reliable indicator for concealed gold deposits.

"Collecting samples of calcrete for analysis is a relatively simple matter, as the layer can be easily recognised," Dr Butt says. "Obviously there are some areas where the technique works, and others where it is inappropriate. It is not a panacea to the problems of finding gold. But we are dealing with a material such that, if there is any gold in the system, you are likely to find it."

The team's discovery led to a series of recommendations to exploration and mining companies which, together with other methods such as aeromagnetics, have greatly increased the precision of their discovery activities, the chances of success and reduced the cost of exploration.

The result has been what mining journals are now describing as a new gold rush, targetting a region of Australia that was previously difficult, costly and unproductive to explore.

Gold discoveries made so far with the help of the scientists' technique include the Challenger prospect, several finds in the Tarcoola region, and the Nuckulla Hill, Birthday and Acacia deposits.

More information:
Dr Charles Butt, CSIRO Exploration & Mining, CRCLEME, Perth 08 9333 6750
Mr Melvyn Lintern, CSIRO & CRC LEME, Adelaide 08 8274 7742
Dr David Gray, CSIRO & CRCLEME, Perth 08 9333 6751
Mr Chris Priday, CSIRO Exploration & Mining 02 9490 8247