Exploration for porphyry-style copper/gold deposits with their potential for big and long- lived production is normally the preserve of the major miners. And more often than not their exploration effort is in far-flung places like the Andes and the Gobi.
That’s not to say Australia’s rocks don’t stack up. Newcrest’s collection of porphyry discoveries which have gone on to be world-class mines near Orange in NSW’s Cadia Valley and Rio Tinto’s Northparkes operation, also in NSW and now owned by China’s CMOC, prove the point.
Porphyry systems host most of the world’s copper and as the Cadia and Northparkes examples demonstrate, they are on the big side of things in copper with the gold coming along as a project sweetener.
Where next in Australia for the next big porphyry to get the pulses racing? Don’t look to one of the mining states, look to the Mount Stavely volcanic belt near Ararat in western Victoria where the hunt for a big porphyry has been an on and off affair since the 1960s, involving the likes of WMC, Pennzoil, North Ltd and CRA, the latter two now part of Rio Tinto.
But for a little more than three years now it has been veteran geologist Chris Cairns at Stavely Minerals (SVY) who has taken up the challenge of finding a big porphyry beneath flat wheat and canola country on the Stavely tablelands.
Cairns knows what porphyry rocks look like courtesy of a stint in the Philippines back in his early years. The topography there means it is possible to view a porphyry system created from deep within the bowels of the earth at creek level, then climb to the top of the mountain to view the high level of alteration sitting on top.
Roll the clock forward to 2013 and Cairns found himself on site in the Stavely region at the 1970s discovery, Thursday’s Gossan, which had been put up for sale by the former owner BCD Resources.
Hosting a near-surface blanket of secondary enriched mineralisation with a resource estimate of 28 million tonnes grading 0.4 per cent copper for 110,000 tonnes of contained copper, Thursday’s Gossan went on to be a key asset in Stavely’s 2014 float.
Plus, the alluring combination of borate and lithium fuels demand for new float. Read more here.
