Great Southern Copper PLC (LSE:GSCU) has extended high-grade copper and silver mineralisation at its Cerro Negro project in Chile, with new drilling pointing to a larger and more complex system than previously mapped.
The work suggests the presence of stacked mineralised lenses, a geological pattern in which several lens-shaped pockets of ore sit above or beside one another.
Systems of this kind can prove more substantial because each lens offers a separate zone of mineralisation that can be mined if continuous enough.
The latest holes intersected fresh chalcocite-rich zones in the Mostaza Lens 2 area.
Chalcocite is a copper sulphide mineral that forms some of the highest grade copper ores, so its presence typically strengthens the economic case for a project.
Early assays included 0.69 metres at 9.76% copper and 716 grams per tonne silver in hole DD029, within a broader 6.32-metre interval grading 1.39% copper and 98.2 grams per tonne silver.
Hole DD031 cut 1.78 metres at 4.02% copper and 271 grams per tonne silver, alongside a separate 1.1-metre section at 8.92% copper and 715.3 grams per tonne silver, all within wider mineralised zones up to 7.2 metres thick.
Another lens carrying anomalous silver, lead and zinc has also emerged in this area.
Drilling farther south in the Lens 3–5 zone confirmed the structure continues along trend, with narrow but consistently mineralised intersections that fit the pattern seen at Mostaza.
Scout drilling a kilometre beyond that encountered visual oxide and sulphide mineralisation, hinting at a system with far greater reach along the Mostaza Fault Zone.
The company has now completed about 3,000 metres of Phase III drilling. Petrographic work shows the system is high-level epithermal, meaning it formed relatively close to surface where hot fluids can repeatedly deposit metals as they circulate.
The drill core contains fragments of older copper-rich silica, which suggests more than one mineralising event and raises the possibility of additional mineralisation at depth.
Metallurgical testing, which determines how easily metals can be separated from the rock, is already in progress.
Sam Garrett, chief executive, said the results demonstrate the strength and continuity of the copper-silver system, while the discovery of new lenses “materially enhances the potential scale of the deposit”.
He added that signs of continuity to the south and a sharper geological picture were increasing confidence in the broader Cerro Negro trend.