Ardea Resources’ Big Four gold prospect north of Kalgoorlie is starting to bear some serious fruit, with preliminary metallurgical test work showing outstanding recoveries of gold mineralisation. Four bulk samples from the deposit were submitted to Bureau Veritas in Perth for test work, with simple gravity and leaching returning a stunning average of 97.7 per cent recovery of the contained gold.
The Big Four deposit forms part of Ardea’s Goongarrie West project north of Kalgoorlie and overlies the gold-rich Bardoc Tectonic Zone. Big Four has a rich history of gold mining dating back to the 1920s and 30s. And while the historical tonnage produced may seem modest by modern standards, the grades recovered certainly merit attention averaging an impressive 18.4 g/t gold.
Ardea’s work over the deposit indicates that whilst the prospectors exploited the outcropping mineralisation it seems likely the remaining strike extends over several kilometres. The auriferous structure that hosts the deposit is largely covered by alluvial sands and lateritic development, masking its geochemical signature suggesting Big Four still has plenty more to offer.
Recent drilling by the company at the deposit has returned a swag of exceptional shallow drill hits including 18m at 3.38 g/t gold with 6m at 6.03 g/t gold from only 18m and 14m at 2.4 g/t gold with 4m at 5.73 g/t gold from only 38m down-hole.
Excellent results from the first ever metallurgical test work at the Big Four Gold project mark another significant step towards development of Ardea’s evolving gold assets. High recoveries and a lack of deleterious elements are exactly what any miner would want, and we have achieved that here at Big Four Gold. It also shows what can be achieved in WA during these difficult times, with Ardea’s drilling, resource modelling, and now metallurgical testing of the Big Four Gold project all being completed since commencement in February 2020.
The four bulk samples submitted for the metallurgical test work were put together from Ardea’s previous drilling. These samples were compiled to assess the characteristics of the Big Four ores at various grades and stages of weathering and oxidation.
The samples consisted of more than 85kg of material each which were homogenised and ground down to sizing of less than 1mm before being split into sub-samples for testing. The 10kg subsamples were put through a Knelson jig to simulate gravity recoveries of the gold, with the gravity residue then submitted to conventional cyanide leaching.
The gravity recoveries of the samples varied, with the semi-oxidised ores giving up around 42.6 per cent of their gold content whilst the fresh, high-grade ores, weighing in at over 7 g/t gold, yielded 87.9 per cent recovery of gold mineralisation.
The real surprise for Ardea came following the application of a cyanide leach to the residues from the gravity work. All of the Big Four samples returned total recoveries in excess of 95.8 per cent, with the high-grade samples once again outperforming the pack and tipping the scales at a near-perfect 99.8 per cent gold recovery.
The stunning gold recoveries demonstrate the Big Four deposit, and potentially others within Ardea’s portfolio could easily be processed via a cheap and simple gold circuit at either an existing operation or if the critical tonnage could be put together, a central processing operation constructed by the company.
Ardea’s has already estimated a small, shallow resource over the Big Four deposit, despite its limited exploration over the area, by utilising both its drill data and historical exploration. The current JORC resource is estimated at a modest 178,000 tonnes at a healthy 2.7 g/t gold. However, with the company’s recent work identifying the strike extensions of the deposit, and the mineralisation extending to depth, the existing Big Four resource may just be the tip of the iceberg.
Work remains to be done at Big Four Gold, but these excellent results mean that, should the deposit be developed, several options will be available. This will be strongly influenced by our ongoing drill programs at several targets in the GNCP, including the Aphrodite North area and follow-up drilling at Lady Charlotte. Ardea’s gold programs aim to assess individual targets in their own right. They also mark the first pass systematic assessment of a modelled gold camp, potentially comparable to the Paddington mining centre to the south or the Menzies mining centre to the north, hidden beneath transported cover within Ardea’s expansive mining and exploration tenure.
Ardea continues to show its exploration prowess, and with a range of gold and nickel targets across WA’s Eastern Goldfields the company looks set to continue its tour-de-force across the fertile terrane. The company’s recent work programs are uncovering a wealth of gold mineralisation in the covered terrane north of Kalgoorlie with targets at Aphrodite North, Grafters, Big Four and Lady Charlotte already looking the goods with strong gold intercepts and the metallurgical results to match.
With drilling currently underway north of Kalgoorlie at the Lady Charlotte prospect, and the highly prospective Windanya next on the company’s hit list, it may not be long until Ardea starts stacking up a serious book of gold resources for potential development.
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