Western Mining's faith in geologists' theories leads to lucky copper find at Olympic Dam in South Australia in 1975
A monument to RD1, the first exploration hole sunk by Western Minining Company from a theory-based search at Olympic Dam on Roxby Downs pastoral station in South Australia in mid 1975.
Image courtesy Wikipedia
The initial discovery in 1975 pointing to the copper, gold and uranium riches on Tom Allison’s Roxby Downs pastoral station, more than 500 kilometres north of Adelaide, came from the calculated luck of the Western Mining Company executives backing their young unconventional geologists.
Western Mining, whose executives included Arvo Parbo, an Estonian migrant from South Australia, was founded in 1933 by The Age business editor turned stockbroker W.S. Robinson, who became the London-base managing director of the Broken Hill Associated Smelters in Port Pirie, South Australia. In London, Robinson convinced several big mining companies to form syndicates to develop gold mines in Australia. This led to the start of Western Mining Company, based on a principle of innovation.
Western Mining Company recruited internationally for the best geologists, who were mocked (Western Mining being nicknamed “Wasting Money Corporation”) because they used aerial photos to scan entire regions – an unorthodox method in the days before the 1950s when mining companies didn’t employ geologists.
Western Mining had made extraordinary discoveries in the 1950s, 1960s and early 1970s by defying conventional thinking and going with the science but finding copper from 1957 eluded them.
Western Mining’s small team of geoscientists was guided to Olympic Dam purely by scientific ideas when its focus moved to South Australia with its long history of copper mining at Moonta and Burra. Drawing on theories developed by young scientist Douglas Haynes, they had developed world-first thinking about where to search for copper in some of the oldest rocks in the world in South Australia’s Stuart Shelf.
The first exploration hole, RD1, sunk from a theory-based search at Olympic Dam on Roxby Downs in mid 1975 did yield copper but not at economic levels and in hard rock at a depth of 350 metres. That rock, formed by ancient geological mega turmoil 1.6 billion years ago, was mostly the jagged fragments of a granite that had later soaked in iron-rich volcanic fluids at up to 400°C.
After the initial excitement, Western Mining’s faith in its geologists was tested as drill ing continued on more holes with a diamond-studded bit to cut a 36.5mm core of rock, at 10 to 12 metres a day, to depths of around half a kilometre. It took until November 1976, and the 10th exploration hole, Roxby Diamond 10 (RD10), for a discovery of copper at an economic and stunning 2.2% level. Even them, the venture could have missed hitting the mother lode by metres.
Gold and uranium were also found in the RD10 hole but the geology continued to be baffling and didn't fit any known ore deposit model.
Millions more dollars yet had to be spent to proving the presence of massive amounts of copper, gold, uranium and other minerals in the areas. Competitors from around the world rushed to explore any available ground near Western Mining’s mineral licences after the RD10 results were announced. But they didn’t realise – and Western Mining kept it secret for a while – that its pay dirt was the hard rocks in the geological basement at depths below 350 metres. The depth and complex metallurgy of that pay dirt would continue to be bugbear of the Olympic Dam mine story.
The sheer immensity of the Olympic Dam mineral lode would seem to make finding it inevitable. But it was confined to a deep definite guitar-shaped area. The world’s biggest miners had all departed the region by the end of the 1980s without finding economic amounts of copper. It was 20 years after the Olympic Dam discovery before another economic find of copper was made at Prominent Hill.
