South32’s 61% Sierra Gorda reserve lift: life-of-mine and plant planning notes
Reviewed by Joe Ashwell

First reported on MINING.com
30 Second Briefing
South32 has lifted the Sierra Gorda ore reserve in Chile by 61% to 1.1 billion tonnes at 0.39% total copper, 0.016% molybdenum and 0.06 g/t gold (0.46% CuEq), extending reserve life by about five years to 2045 after 85,000 metres of infill drilling from 200 holes. The updated MRE now stands at 1.87 billion tonnes at 0.37% copper (0.44% CuEq), with the orebody remaining open at depth and additional potential at the Catabela Northeast target. A fourth grinding line, approved in July, is expected to lift copper output by roughly 30% from 2031, reinforcing long-term concentrator planning and infrastructure requirements.
Technical Brief
- Infill drilling totalled ~85,000 m from 200 holes between 2023–2025, materially tightening orebody definition.
- Updated estimates are reported as at 31 July 2026, anchoring mine planning assumptions to current data.
- Sierra Gorda operates as a large, conventional open pit in Chile’s Antofagasta region with modern concentrator facilities.
- Copper concentrate is hauled by truck then rail to Antofagasta and Angamos ports for export logistics.
- South32 holds 45% and joint-controls the operation with 55% partner KGHM Polska Miedź.
- Catabela Northeast exploration holes have intersected significant copper mineralisation, flagged as a future life-extension target.
- Approval for the fourth grinding line was granted in July, moving that debottlenecking project into execution.
Our Take
South32’s enlarged copper, gold and molybdenum reserve at Sierra Gorda aligns with its broader portfolio shift towards base metals noted in our July 20, 2026 coverage, suggesting this Chilean asset is now one of the key levers underpinning its move away from aluminium.
With copper prices recently trading near record levels and Sierra Gorda explicitly cited alongside Codelco, Freeport-McMoRan and others in our July 20, 2026 copper market piece, a longer mine life to 2045 positions the South32–KGHM JV to benefit from any sustained tightness in concentrate supply from Latin America.
The 30% copper production uplift targeted from the fourth grinding line project from 2031, combined with relatively modest reserve grades, signals that Sierra Gorda will rely heavily on throughput and processing efficiency rather than grade, similar to how South32 is deploying advanced concentrator technology at its Hermosa critical minerals project in Arizona.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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