True North Copper uncovers signs of major IOCG system at Salebury in Queensland

• TNC maiden drilling strikes large copper-gold system spanning over 1km at Salebury in Queensland
• Three holes hit strong alteration 30km south of giant Ernest Henry mine
• Results suggest potentially large-scale discovery completing high-grade finds at other projects

Special Report: True North Copper’s maiden drilling has identified a large, high-potential iron oxide copper-gold system at its Salebury project in the northwest Queensland’s Cloncurry region.

Three holes drilled at The Gully, Raleigh’s and Salebury Main prospects intersected strong alteration and copper sulphide mineralisation with geochemistry consistent with halos of major IOCG systems such as Ernest Henry.

All three prospects feature induced polarisation chargeability, magnetic and gravity anomalies that are coincident with favourable structures.

True North Copper (ASX:TNC) notes the results confirm alteration and mineralisation over a zone of >1km, a find that extends the interpreted IOCG system along a major structural corridor which is prospective for large-scale mineralisation.

This includes a large zone of IOCG alteration over 120m with discrete higher-grade intervals that confirms depth extension of the historical JORC 2004 resource and demonstrates potential for resource growth.

Adding interest, the ~100m of anomalous copper with increasing pathfinder geochemistry at depth indicates a copper-endowed system consistent with the vertical zoning of major IOCG deposits.

“Salebury is a great result for True North, confirming favourable structures and an extended IOCG system with strong potential,” managing director Andrew Mooney said.

“While still early, it’s encouraging to see Salebury emerging as a potentially large-scale system that complements the high-grade discoveries ongoing at our Mt Oxide and Cloncurry copper projects.”

He added the discovery is aligned with the company’s strategy of building a strong copper growth pipeline across the short, medium and long term through its asset portfolio.

“Our three-stage strategy is to extend mine resources for a near-term restart, advance district-scale discoveries, and systematically test our regional targets.”

Salebury project

Salebury is 20km east of the Great Australia Mine and 30km south of the giant Ernest Henry copper-gold mine.

It sits within the same regional north-northeast structural corridor that hosts the Ernest Henry and E1 deposits and along a major north-northwest structural zone that potentially controls the Monakoff deposits.

The Monakoff and Monakoff East deposits on the north limb of the Pumpkin Syncline are ~8km north of the Salebury System, which is situated on the south limb.

Surface mineralisation at Salebury is known to be hosted at the northern east-west contact of the folded thrust sheet within veins and veinlet zones.

However, recent mapping and relogging of drilling also observed mineralisation associated with high-energy phreatomagmatic breccias.

These breccias are believed to be resulting from the near-paleosurface intrusions of the Williams-Naraku Suite that have been identified as synchronous with mineralisation in the Cloncurry district.

TNC has prioritised greenfields exploration at the project as it has the elements for a transformational copper-gold IOCG-style discovery.

Drill results

The Salebury Main Zone prospect is a mapped mineralised breccia with a large IP anomaly and gravity low interpreted as a mineralised breccia pipe extending to at least 300m depth below surface.

Its geological footprint indicates that hole SBRC001 has pierced the altered margins of a large breccia-centred system.

Laboratory assays define a broad background of copper anomalism across the central part of the hole, with an average of ~170ppm copper between 140m and 285m.

Discrete higher-grade peaks of 1m at 0.11% copper from 154m and 1m at 0.10% copper and 0.02g/t gold from 288m were also noted.

The isolated >0.1% copper spikes suggest vein or crack-seal events within a broader low-grade envelope and the potential for a feeder zone to be developed at depth.

Meanwhile, hole TGRC001 targeted coincident gravity and magnetic highs supported by IP anomalies at The Gully prospect.

Assays returned a broad ~100m interval of anomalous copper from ~285–385m.

This includes discrete higher-grade bands such as 1m at 0.85% copper and 0.21g/t gold from 320m, 1m at 0.30% copper and 0.13g/t gold from 344m and 1m at 0.12% copper and 0.14g/t gold from 365m.

The close match between copper anomalism and the gravity–magnetic high supports the targeting model and suggests TGRC001 has intercepted the outer to mid-level parts of the system above or adjacent to a denser, magnetite–hematite-rich core.

Notably, the results indicate that The Gully hosts geochemical and alteration mineral assemblages typically encountered above or adjacent to a denser, magnetite–hematite-rich core.

Over at Raleigh’s prospect, hole RLRC001 tested a gravity high coincident with an IP chargeability anomaly and mapped hydrothermal breccias at surface.

Assays defined a 2m wide zone at an average 0.89% copper and 0.22g/t gold from 98m including a peak 1m at 1.42% copper and 0.2g/t gold.

This is surrounded by broader low-grade halos such as a 45–50m interval averaging 361ppm copper.

The coupling of shallow high-grade vein-style copper with deeper arsenic anomalies within the gravity/IP response is consistent with a vertically zoned system.

As such, deeper drilling is warranted to test the gravity core for thicker, higher-grade sulphide accumulations.

Watch: Andrew Mooney to drive QLD copper-gold growth

Looking ahead

TNC plans to infill and expand the IP survey across the Salebury Main and Raleigh’s prospects as well as expanding coverage of the coincident magnetic and gravity responses at The Gully.

It will then optimise geophysical modelling with results from preliminary drilling and any infill or expanded surveys.

The company will also carry out drill planning for Salebury Main to target an increase in resource confidence and compliance with the current JORC 2012 reporting standard.

Other work includes expanded field reconnaissance targeting the Pumpkin Syncline and Crows Nest IOCG prospects proximal to The Gully and drilling at The Gully targeting the core of the coincident gravity, chargeability and magnetic anomaly.

This article was developed in collaboration with True North Copper, a Stockhead advertiser at the time of publishing.

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.