The hunt is on for the next big porphyry hit in the Lachlan Fold Belt — and these small caps are leading the charge
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The Lachlan Fold Belt (LFB) in New South Wales is regarded as one of the hottest mining addresses in Australia thanks in no small part to it hosting the giant Cadia copper-gold mine.
Newcrest Mining (ASX:NCM) produced nearly 913,000oz of gold and 91,000 tonnes of copper from Cadia at a tiny all-in sustaining cost of just $132/oz in the 2019 financial year.
That makes for very attractive margins given that gold currently commands a price of more than $2,300 per ounce.
However, much of the recent attention is due to Alkane Resources’ (ASX:ALK) discovery of thick porphyry copper-gold at the Boda prospect about 110km north of Cadia.
After all, it is hard to go past drill results such as 689m grading 0.46 grams per tonne (g/t) gold and 0.19 per cent copper from a depth of 402m, and 502m at 0.48g/t gold and 0.2 per cent copper from 211m.
We’re often told “grade is king” (which isn’t really true by the way; just look at the grades of some of the biggest, most profitable mines in the world), but because of their easy-mining large volumes, porphyry orebodies can be economic from copper concentrations as low as 0.15 per cent.
Speaking to Stockhead, well-known mining identity and Kaiser Reef executive director Jonathan Downes says the Boda discovery is significant as it proves that there are other copper-gold porphyries to be found within the LFB.
“This is very exciting because they form the largest type of gold deposit, and in Cadia’s case, probably the most profitable and largest in Australia,” he noted.
“The discovery of deposits like Boda are normally the domain of the majors but the prize is huge if a junior can discover one.
“With recent support from the Stavely discovery, also part of a porphyry system on the LFB, there is clearly strong investor support and interest.”
The LFB also benefits from well developed infrastructure and multiple regional processing facilities.
So just who are some of the explorers looking to make the next big find in the LFB?
Impact Minerals (ASX:IPT) is currently awaiting assays from rock chip samples taken from four targets at its Commonwealth project that are on trend from and close to Alkane’s Boda discovery.
The Boda South, Apsley, Spicers Creek and Greenobbys targets along with the newly identified Gladstone all have characteristics suggesting they are parts of large porphyry or other intrusive-related copper-gold systems.
These include significant copper and/or gold with associated pathfinder metals in recent rock chip assays and an association with unexplained magnetic anomalies, which like Boda, could be a direct indication of significant copper-gold mineralisation.
The project includes the Commonwealth mine that was discovered in 1900 and mined intermittently until the 1930s, producing about 470oz of gold.
Further south, Krakatoa Resources (ASX:KTA) will kick off an aircore drilling in late February targeting the Bella, Lara 1 and Lara 2 porphyry prospects in the Bell Valley area within its Belgravia project.
Drilling will also be carried out at the Lee prospect.
The three porphyry prospects lie within the same rocks that host the Cadia mine 35km to the south and the Boda discovery 65km to the north.
Aircore drilling is often used in first-pass exploration programs and typically aids in the prioritisation of prospects within a broader project.
Belgravia is adjacent to Golden Cross Resources’ (ASX:GCR) Copper Hill project, which has a resource of 87 million tonnes grading 0.32 per cent copper and 0.27g/t gold.
Meanwhile, Kaiser Reef is gearing up to commence trading on the ASX in late February following a heavily oversubscribed IPO to fund exploration over its Stuart Town gold project.
“Kaiser Reef is fortunate to hold a position on strike and in between Cadia and the new Boda discovery,” Downes told Stockhead.
“The project has been covered by what are interpreted to be shallow and younger rocks of the Hill End syncline and over 80 historic gold mines and significant gold production is modelled to be minor leaking from an underlying basement.”
Kaiser Reef will target the shallow modelled intrusions speculated but untested by earlier explorers such as MIM, with Downes explaining that soil sampling had returned large-scale gold anomalism and encouraging volcanic rocks hosting gold rich veins.
He added that the company was not looking at the historical mines but rather their source, which remains a mystery.
“The underlying basement is modelled to have been thrust up and comes to within 200m of surface — and may even be shallower.”
Meanwhile, Magmatic Resources (ASX:MAG) recently raised $5m to progress its exploration activities in the LFB, particularly the Lady Ilse porphyry target about 6km southwest of the Boda discovery.
The recent receipt of the remaining three out of four lines of a geophysical survey indicated that the Lady Ilse target had grown significantly relative to the previous interpretation and that it remained open to the south.