Mineral explorer Ardea Resources has teamed up with Australia’s national science agency, CSIRO, to investigate the unlikely discovery of gold in its nickel-cobalt laterite deposits at the Goongarrie project in Western Australia.
The Goldfields of Western Australia has long been the state’s thriving gold region.
Just 80 kilometres north of Kalgoorlie in the world-class mineral province is Ardea Resources’ flagship Goongarrie nickel-cobalt project.
Forming a small part of the company’s larger Kalgoorlie nickel project (773 million tonnes at 0.7 per cent nickel and 0.05 per cent cobalt), Ardea has set its sights on developing the 216 million tonne Goongarrie resource, which comprises 0.71 per cent nickel and 0.06 per cent cobalt.
“We focussed on Goongarrie as our main tender because it has high-quality, laterally continuous nickel-cobalt mineralisation,” Ardea general manager exploration Matt Painter tells Australian Mining.
Goongarrie and the broader Kalgoorlie project both have a nickel-cobalt resource that covers a sequence of orogenic gold targets.
Ardea is already exploring the gold potential within the Kalgoorlie region’s Bardoc tectonic zone (BTZ) with the BTZ gold project, but it’s the company’s nickel prospects that may also be hiding a significant precious metals discovery.
“One thing that we noticed when we were pulling the data together for Goongarrie is that there’s a lot of gold anomalism in various parts of the laterite profile,” Painter explains.
“A lot of the drilling in Goongarrie doesn’t penetrate the fresh rock. It goes deep enough to fully intercept the nickel laterite mineralisation but not the fresh rock below.”
While gold isn’t the key focus of Goongarrie, it has certainly raised some eyebrows at Ardea and CSIRO.
In August, Ardea commenced a research project with CSIRO to explore the potential that the traces of gold at Goongarrie may be hinting towards.
CSIRO’s Regolith Geosciences team is working with Ardea to study gold behaviour within the Goongarrie project’s critical mineral deposits.
“What we strongly suspect is the gold that we see in the laterite profile is related to gold mineralisation in the fresh rock beneath,” Painter says.
Ardea and CSIRO aim to determine whether the gold anomalism in the nickel-cobalt laterite profile is residual or gold migrated by saline groundwater from a different source area in the region.
“We also want to get an idea of what’s happening in the laterite profile itself, relative to the nickel and the cobalt,” he says.
“The more we understand about how they interact, the better we’ll have an idea of how to go hunting for gold.”
CSIRO senior research scientist Walid Salama is leading the team working with Ardea.
Salama says the discovery of gold mineralisation in a nickel-cobalt deposit is uncommon.
“It is unusual to find gold enrichment in nickel-cobalt laterite deposits,” he says.
According to Salama, the minerology and geochemistry will determine if the gold anomalism in the nickel-cobalt laterite is residual and related to the same ultramafic rock underneath or the anomalism is brought from a different source rock within the Goongarrie project area
“At this stage, the goal is to understand the nature of the gold itself and its pathfinders in the weathering profile,” he says. “Our understanding of the mechanism of gold mobility or enrichment during weathering will have significant implications for gold exploration and targeting.
“(We) would also like to understand if the high salinity of the ground water in the project area can affect the mobility of gold because gold is mobile under acidic and highly saline conditions.”
CSIRO will adopt its rapid spectroscopic logging and imaging system, HyLogger technology, to study the mineralogy of the Goongarrie nickel-cobalt laterite. This will be followed by a separation of the gold grains from the weathering profile to map out trace element distribution in gold using a number of microanalytical techniques, including laser ablation ICPMS .
This will allow the CSIRO Regolith team to determine the chemical composition of the gold grains to work out if gold is forming alloys with other pathfinder elements or if it exists in a pure form. The presence of gold alloys in the weathering profile indicates that gold is residual and possibly exists in the underlying rocks, whereas the pure gold is considered secondary and possibly derived from a different source.
Painter believes Ardea will be the first miner to systematically explore for gold underneath the region’s nickel laterite sites if the project reveals gold beneath Goongarrie’s laterite.
“It’s a very interesting play for us particularly because we’re on such a major gold-bearing structure and it’s particularly important that we realise the potential that could be down there,” he says.
“We’re very proud of our association with CSIRO. Working with them and having that connection is absolutely brilliant. It’s certainly looking very promising so far.”
Ardea Resources’ project is supported by the Department of Industry, Science, Energy and Resources’ Entrepreneur’s Programme. Its Innovation Connections service unlocks innovation potential in Australian small- to medium-sized enterprises (SMEs) by developing a deep understanding of the business’ needs, matching SMEs with relevant experts from across Australia’s research sector and offering grants.