Source : THE AGE NEWS
By Craig Nolan
Marmota Limited has achieved up to an impressive 93 per cent in gold recoveries from metallurgical testwork on ore from its flagship Aurora Tank project in South Australia’s renowned Gawler Craton region.
The results from column leach testing present the company with an opportunity to pursue a low-cost, low-capex heap leach operation at the site.
Drilling activities previously undertaken at Marmota Limited’s Aurora Tank gold project in the Gawler Craton region of South Australia.
Management believes the results confirm the viability of a low-cost option for gold extraction at Aurora Tank, rather than the prohibitive cost of building and operating a mill and constructing a tailings dam.
The cheaper and simpler heap leaching process usually comes with a trade-off, however, of lower recovery levels of gold compared to the capital cost of a conventional processing mill and carbon-in-leach plant.
‘Aurora Tank features multiple bonanza grades, predominantly close to surface, with soft ground and now confirmed outstanding metallurgy amenable to low-cost low-capex heap leach recovery. More generally, Marmota is extremely fortunate to own all the gold deposits within a 10,000 square kilometre gold hub of the Gawler Craton, just as gold is booming to record highs.’
Marmota Limited chairman Dr Colin Rose
Marmota Limited chairman Dr Colin Rose said: “Aurora Tank features multiple bonanza grades, predominantly close to surface, with soft ground and now confirmed outstanding metallurgy amenable to low-cost low-capex heap leach recovery. More generally, Marmota is extremely fortunate to own all the gold deposits within a 10,000 square kilometre gold hub of the Gawler Craton, just as gold is booming to record highs.”
Column leach metallurgical testing is used to estimate gold recoveries from a heap leach process. The testwork was performed by Australian Minmet Metallurgical Laboratories. The program was designed and managed by leading heap leach firm Kappes Cassiday and Associates.
Various composite samples from Aurora Tank were tested, distinguished by different weathering profiles, crush sizes and leach durations. The program included 31 drill core sub composites representing 197 metres of drill core.
Rapid leaching was observed, which achieved more than 55 per cent gold extraction within the first 10 days.
The best result came from testing a moderately weathered master composite sample, which returned the eyebrow-raising 93 per cent recovery across 59 days at an 8 millimetre crush size.
Testing of a partially weathered master composite sample achieved an impressive 83 per cent recovery level across 87 days of leaching on a 12.5mm crush size and 86 per cent on an 8mm crush size over 159 days.
The test program included head assays, sizing analyses with fraction assays, ground ore diagnostic leach tests, 10-day two-stage intermittent bottle roll tests at 12.5mm and 8mm and agglomeration/percolation testing.
Column tests were conducted in 100mm diameter columns on charges of 25 kilograms for all samples, with 2.5m targeted bed depths.
Management says the weathered materials are easy to crush with low abrasion and it expects to undertake further testing. Marmota believes coarser crush sizes than the largest 12.5mm tested are likely to provide similar outcomes for weathered materials.
The company expects silver, which averaged below 0.5 grams per tonne in samples, will have only a minor impact on the recovery plant design. Nor should the low copper-mercury values affect plant design or production operations of the Aurora Tank ore.
Marmota also recently identified the high-value titanium mineral leucoxene in historical drilling across its Muckanippie project in South Australia, stretching the heavy mineral discovery’s potential strike to 9km. Leucoxene is a high-value, fine-grained, high titanium content titanium dioxide.
The samples were collected from a drilling program at the western edge of Marmota’s tenement boundary and immediately west of the tenement ground where the company made a heavy mineral discovery last November.
The company revealed the head-turning discovery after it drilled a fenceline of four holes across part of a magnetic anomaly identified at Muckanippie.
Every hole yielded thick titanium dioxide hits with stellar numbers including 28m running 10.1 per cent, 36m going 6.2 per cent, 39m at 4.6 per cent and a solid 24m section grading 7.5 per cent titanium dioxide. All the hits extend from surface.
In a January follow-up announcement, management said all the fenceline discovery holes had returned bonanza heavy mineral grades, with 28m at 19.2 per cent heavy minerals and 36m going 13.5 per cent heavy minerals. The 36m intercept included 4m grading an eye-opening 27.8 per cent heavy minerals.
The results from both holes showed mineralisation starting from surface and the discovery remains open in all directions and at depth.
The historical samples from the west of the discovery zone potentially extend mineralisation at the site to an impressive 9km and confirm the presence of titanium in the western ground. However, further drill testing will be required to validate that it runs the full 9km strike length.
Marmota could be on to two projects that may eventually work their way into operation. The metallurgical testwork at Aurora Tank yielded outstanding gold recoveries and confirmed the potential for a low-cost, low-capex heap leach operation. Avoiding a high capital cost for the standard gold mill might offer an alternative pathway to production for the company.
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