Mining giant Gold Fields Limited is getting ready to fire up the rigs again at Great Southern Mining’s vast Edinburgh Park project in north Queensland, with drilling set to restart after the north Queensland wet season.
In particular, near-term excitement is building around the Mt Dillon prospect, where IP geophysical surveys have outlined a large, high-chargeability anomaly sitting a few hundred metres below surface.
Prior to Gold Fields farming into the project, Great Southern had already identified more than 25 high priority targets across the extensive 1560-square-kilometre land package.
However, it was Mt Dillon that stood head and shoulders above the other prospects, with the company believing the anomaly might be linked to sulphides in a preserved intrusive system.
And now, the great day to put its theory to the test, is close at hand.
Mt Dillon is a topographic high featuring a silicified lithocap – a resistant cap that has protected the peak from erosion – coupled with intense alteration, exactly the kind of geological lid that has been identified above major gold-copper systems elsewhere in the world.
Drilling is due to kick off after the north Queensland wet season, likely around March or April, and initial plans are to punch at least two deep diamond holes straight through the heart of the IP anomaly and below it.
When Gold Fields farmed into the project two years ago, Great Southern agreed to allow the major to earn a 75 per cent stake in its land in exchange for up to A$15 million in expenditure over six years. So far, it has already spent the minimum $2 million hurdle.
The partnership was formed specifically to chase large-scale epithermal and intrusion-related gold systems (IRGS) - the sort that can rapidly grow from a fleeting, easily missed indication on a map into a massive gold operation.
Great Southern Mining managing director Matthew Keane said: “2026 is shaping up to be another exciting year for the Edinburgh Park JV. We are highly encouraged by the evidence of large-scale epithermal systems present in at least two of the target areas drilled to date. Multiple targets within Edinburgh Park display the attributes required for large-scale gold systems, including deep seated structures with pervasive hydrothermal alteration from surface and coincident geochemical anomalies.”
The massive project sits in elite geological company, rubbing shoulders with heavyweights like the 4-million-ounce Ravenswood operation, the legendary multi-million-ounce Mt Leyshon deposit, and Evolution Mining’s former Mt Carlton gold mine just down the road.
This latest planned diamond drilling campaign marks a second crack at Edinburgh by the partners following last year’s field season that saw six diamond holes drilled across three key targets - Leichhardt Creek, Molongle and Megan Veins - for a total of 2955.6 metres.
While the first assays from Leichhardt Creek didn’t deliver economic grades, the thick zones of quartz-sulphide veining and strong hydrothermal alteration that were intercepted are arguably just as important at this early stage.
Such characteristics indicate classic plumbing for a big mineralised system and are a solid hint that the geologists are homing in on a material target, potentially an intrusion-related gold system (IRGS).
These are large-scale gold deposits genetically linked to felsic igneous intrusions, which typically exhibit specific metal fingerprints including bismuth, tellurium, arsenic, molybdenum and tungsten. Edinburgh Park is prospective for high and low epithermal gold-silver systems, as well as porphyry-related gold-copper systems.
The three holes at Leichardt successfully intercepted a variety of supportive mineralisation indicators, including quartz-pyrite veining, intense hydrothermal alteration, molybdenum, and elevated silver and base-metal signatures.
Those signatures strongly support the company’s modelling, which it views as encouraging for other proposed targets in the north of the project area.
Importantly, assays are still pending from the remaining three drill holes at the company’s Molongle and Megan Veins targets.
Molongle already features surface rock chip results grading up to 5.27g/t gold and sits in strongly altered volcanic rocks typical of epithermal systems, while shallow drilling in 1989 yielded runs of 24m at 9.36g/t gold from surface and 18m at 0.34g/t gold from 12m.
Megan Veins has also yielded historic rock chips with up to 10.55g/t gold and shows classic gold-silver-base-metal veining and strong signature alteration, suggesting a nearby gold-silver late-stage epithermal system or an expression of a porphyry system lying a bit further away.
If assays from either Molongle or Megan Veins come good in the lab, the market could start paying much closer attention.
With more geophysics and geochemistry underway to generate fresh targets across the broader project, Edinburgh Park is still in what management calls its infancy.
When a project shows the kind of geological signals that hint at multi-million-ounce potential, like Edinburgh Park is starting to do, patience becomes part of the investment thesis.
The market often wants instant discovery holes and overnight re-rates, but the truth is these giant systems usually reveal themselves slowly - through multiple drill campaigns, plenty of metres in the ground and a growing understanding of the geology with each hole.
However, with Gold Fields funding the heavy lifting and several large-scale mineral systems already emerging, Great Southern has the luxury of time to do the exploration properly — exactly what’s needed to give a genuine province-scale hunt the thorough work it deserves.
Is your ASX-listed company doing something interesting? Contact: matt.birney@businessnews.com.au
By Doug Bright
