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Alma Metals soil sampling expands Queensland copper anomaly

Alma Metals soil sampling efforts have grown its copper anomaly in Queensland. Credit: File

Soil sampling by WA-based explorer Alma Metals at its Briggs project in Queensland has expanded its soil copper anomaly out to 2300m long and 1000m wide, with readings of more than 500 parts per million copper.

Management says the work has allowed it to revise its target of 480 million tonnes to 880 million tonnes at between 0.20 per cent and 0.30 per cent copper and 25ppm to 40ppm molybdenum.

Earlier this month, Alma unveiled a global resource estimate for the project, which comprised an inferred 415 million tonnes going 0.25 per cent copper and 31ppm molybdenum, with a copper cut-off grade of 0.20 per cent. It extends from surface to a depth of about 650m and the company believes it correlates closely, where it has been tested by drilling, to the 500ppm copper contour.

Management says several clusters of more than 1000ppm and going up to 4710ppm within the anomaly, reflect the known mineralised centres across several targets. Its sampling program also highlighted anomalous molybdenum up to 84ppm, associated with the porphyry system.

The company is expecting to see dust clouds from a hard-working drill rig rising again over the project soon, with a 2500m campaign of 11 diamond drillholes in the works.

The program will include four holes that will aim to validate the exploration target, with the remaining seven looking to test higher-grade zones at its Briggs Central prospect.

Alma says its Briggs project has now clawed its way into the top 10 biggest undeveloped copper plays in Australia, in terms of contained metal.

The project is a porphyry copper deposit, the type of which are generally known for containing hundreds of millions of tonnes of ore, but average a fraction of a percent of copper. Despite their low-grade, the deposits constitute important sources of copper because they can be worked on a large scale at relatively low cost.

In fact, porphyry copper deposits account for more than 60 percent of the annual world copper production and about 65 percent of the known total copper resource.

The International Copper Association argues that global supply is expected to jump 26 per cent to 38.5 million tonnes annually by 2035. But even then, it will still likely fall 1.7 per cent short of demand, despite increased recycling.

Copper is open to supply chain issues brought on by political instability, with 75 per cent of the biggest copper mines in the tinderbox of South America. Chile is the globe’s top producer (27 per cent), followed by Peru (10 per cent).

Recent political disarray has threatened 30 per cent of Peru’s copper supply, with heavyweight mines such as Glencore’s Antapaccay and MMG’s Las Bamba, which account for 2.5 per cent of global copper output, having been closed or restricted by protester action.

While it is only early days for Alma at Briggs, the company will be hoping its rapidly-expanding project nestled in the heart of a tier-one mining jurisdiction will one day be helping sate the growing global appetite for copper.

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