The Discovery of the Olympic Dam Deposit

The discovery of the giant Olympic Dam Copper-Uranium-Gold Deposit by Western Mining Corporation (WMC) in mid 1975 resulted from the application of good geoscience backed by a supportive management and a measure of good luck. Geoff Hudson (pictured) came to Adelaide from Kalgoorlie in 1977 to head up the exploration team and was with the project through the joint venture process, after which he managed the Stuart Shelf Joint Venture for a number of years.

WMC had been exploring for sediment-hosted copper deposits in Western Australia with little success and the focus moved to South Australia which has a long history of copper mining at Moonta and Burra. Model-based exploration draws together the characteristics of the deposit type being sought and the Stuart Shelf region met many of the those associated with sediment-hosted copper deposits such as the famous Zambian Copper Belt. As the prospective area is covered by unrelated sedimentary rocks, magnetic and gravity surveys provided the only method of focussing the exploration interest.

Two diamond drill holes were scheduled to determine the thickness of the sedimentary cover and the nature of the underlying prospective rocks. RD1 was drilled near Olympic Dam, so named because it was constructed during the Melbourne Olympic Games, and passed through 325m of barren cover before entering brecciated, hematite-rich rocks that appeared to be of little interest The drilling rig moved 22km to the SW to drill ACD1 at Appendicitis Dam, now called the Acropolis prospect.

 

The drill core from RD1 was routinely sampled and returned assays of 35m at 1% copper. Not economic at that depth, but very encouraging. In the following 2 years 8 more drill hoes were completed that contained minor copper, but then RD10 demonstrated the true potential of the area with an intersection of 145m at 2.2% copper together with uranium and gold. The geology was baffling and did not fit any known ore deposit model.