Great Southern Mining and farm-in partner Gold Fields Ltd have unearthed a huge, 2km-wide induced polarisation anomaly, potentially a big porphyry gold-copper system, lurking at depth at Great Southern’s Edinburgh Park project in Queensland.
The buried structural geological feature is coincident with a grab bag of other exciting geological indicators including positive soil samples, rock chips going over 10 grams per tonne gold and importantly, the interpreted anomaly already has sulphides outcropping at surface above it.
Great Southern says the geophysical anomaly has the potential to host a large-scale intrusive related gold-copper and/or epithermal gold deposit at the project which sits about 100km south-east of Townsville in Queensland.
While the project is owned by Great Southern Mining, mega-miner Gold Fields Ltd has been busy exploring the ground as part of its right to earn 75 per cent of it by spending $15m on exploration over 6 years.
Surface mapping and geochemical sampling over the interpreted anomaly stretches across 4kms by 1km and has kicked up high concentrations of gold, silver, copper and particularly molybdenum, a typical marker of a porphyry deposit.
Rock chip samples taken from surface veins in the southwest zone returned impressive gold levels, reaching up to 10.5 grams per tonne (g/t).
Field mapping also found sulphides in the outcropping rocks above the anomaly together with an already-mapped zone of vein-like stockwork directly below the surface, filled with quartz and pyrite sulphides.
The presence of sulphides can be a strong indicator of nearby mineralisation and Great Southern says the geophysical signature of the IP anomaly could be interpreted as a sulphide “halo” around a preserved porphyry system. The alternative interpretation according to management is an intrusion related gold system similar to the more than 3 million ounce Mount Leyshon gold-silver mine about 120kms to the west.
In fact, the entire region around Great Southern’s Edinburgh Park project is littered with big discoveries – mostly due west of Great Southern’s Ground.
They include the revered 16.6m ounce Charters Towers mine, the 2.3m ounce Pajingo gold mine, the 10m ounce Ravenswood gold mine and the 1.3m ounce Mount Wright gold mine – all of which sets the scene well for a potentially new big discovery at Edinburgh Park which the company says is likely to be drilled in early 2025.
In the meantime, helicopter-borne geophysical IP and aeromagnetic surveys and on-ground mapping by Gold Fields has continued in efforts to generate additional similar sized targets.
Great Southern Mining managing director Matthew Keane said: “The scale of this IP anomaly, combined with coincident geochemical anomalism, favourable surface geology, and inferred structural trends, marks it as a prime target for a significant intrusion-related or epithermal gold copper system.”
The story of Great Southern Mining stretches back to 2011 when its now chairman John Terpu first picked up the Edinburgh Park ground in the name of ASX-listed Forte Consolidated. The ground pretty much surrounds the nearby 2m ounce gold equivalent Mt Carlton gold mine.
While working at Conquest Mining, Terpu led the team that made and developed the Mt Carlton discovery. Conquest later merged with Catalpa Resources, paving the way for the creation of Evolution Mining, now a $10b ASX-listed company. Notably, Gold Fields Ltd had climbed up the Conquest register back in those days to hold a little under 20 per cent of the company, showing its early confidence in the region.
In 2018 Forte then changed its name to Great Southern Mining and also took the opportunity on the back of a refreshed image to pick up the Mon Ami gold mining licence directly south of Laverton in Western Australia.
During the past seven years, the West Australian portfolio has grown further to encompass two more significant exploration areas around Laverton, including the East Laverton gold-nickel project and the promising Duketon gold project.
Mon Ami, which the company sees as the most prospective for early development, comprises of a 1.5 million tonne deposit for 55,000 ounces of gold grading 1.1g/t. The mineralisation sits on a mining licence with all relevant permits and an existing pit design in place and is essentially shovel ready for a potentially toll treating operation.
Given the current rampant gold price, currently trading at AU$4064 per ounce, Mon Ami represents a potentially quick and easy pathway to early cashflows for the company.
And there are various potential options for toll treating the ore in the area too including Gold Fields’ Granny Smith plant which has spare capacity just 10km away and the Genesis Minerals-owned Mt Morgan plant which is about to reopen albeit a little further away.
To the north west of Mon Ami Great Southern also has the Duketon gold project. Duketon spans 178 square kilometres covering 13 virtually contiguous leases on the north south trending Duketon Greenstone Belt which it shares with Regis Resources’ eight-million-ounce Garden Well gold project.
The project is in an up-market geological address just 40km north of the massive Gold Fields-owned Granny Smith gold mine. The Ashanti gold-owned Sunrise Dam gold operations are also just a little further south.
Remarkably, with Regis’s multi-million-ounce discoveries to its north and more than 10 million ounces unearthed to the south, the company’s leases, which stretch across 75km of the greenstone belt, have been left relatively under explored.
Within Duketon, there are three advanced target areas. At the southern end and just 3km from Regis’s 400,000-ounce satellite Ben Hur gold deposit is the Southern Star prospect.
With 11km of prospective strike across a granted mining lease, 700m of strike has already been defined as contiguously mineralised. Only relatively shallow drilling to 160m has been conducted so far however according to the company, it is open in almost every direction.
A recent hit of 13m grading 2.2g/t on the lease’s northern boundary and just 1.6km south of Regis’ Ben Hur has opened the possibility of further mineralisation between it and the Southern Star deposit.
Seven kilometres to the north of Southern Star, Great Southern has recently been busy plunging the drill bit into the Golden Boulder prospect where it has more than 4km of anomalous strike across three parallel mineralised trends called Main, East and Ogalvie’s.
Most notably there is evidence of almost 50 historic workings in the area with some previous drill hits coming in at 8m grading 3.9g/t from 44m and 5m running 3.3g/t from 49m.
The latest eight-hole drilling program did not disappoint either with intercepts including 4m grading 5.64g/t from 63m, 3m at 4.8g/t for 18m and 2m running at 3.44g/t from 141m.
The Amy Clarke prospect, the company’s third target area within the Duketon project, sits five kilometres further north again from Golden Boulder and is a stone’s throw from Regis’s 320,000-ounce Erlistoun pit.
Five kilometres of anomalous ground has been identified from geochemical surveys. When coupled with some limited but successful shallow air core drilling and an 8m hit grading 6.7g/t from 33m from a 2021 drill program, the current data is pointing towards a strong target worthy of a more detailed campaign in the future.
The East Laverton leases with early-stage nickel prospects complete Great Southern’s portfolio.
Great Southern was always going to be in danger of biting off more than it could chew with a belt-scale porphyry play such as Edinburgh Park in Queensland. Porphyry’s are often massive and take serious amounts of money to drill out. The rewards however can also be massive despite what most would consider modest in-ground grades. The sheer scale of the mineralisation in a porphyry can even make grades such as 0.4 per cent gold plus a tiny bit of copper economic and there are plenty of examples around the world of successful porphyries being mined at similar or even lower grades.
However, with the backing of a deep-pocketed top ten global gold producer, if there really is something lurking at depth out there around the latest IP anomaly at Edinburgh Park, Gold Fields has both the skill and deep enough pockets to find it.
Meanwhile in the best gold environment the world has ever seen Great Southern has plenty to go on within Laverton with some rapidly advancing gold plays, however Edinburgh Park just might produce that one-in-a-hundred Hail Mary pass mid-game that could lead to Great Southern owning 25 per cent of a rolled gold geological touch down.
Is your ASX-listed company doing something interesting? Contact: matt.birney@businessnews.com.au
By James Pearson
