South32 has reported a 61% increase in ore reserves at its Sierra Gorda copper mine in Chile, bringing the total reserve estimate to 1,100 million tonnes as of July 31, 2026. This significant upgrade reflects the success of infill drilling campaigns totaling approximately 85,000 metres across 200 drillholes completed between 2023 and 2025. The expanded reserve base provides the company with an extended operational runway, now projecting mine life through to 2045, representing an approximate five-year extension from previous guidance.
The ore reserve upgrade carries particular relevance for South32’s shareholders given the company’s 45% stake in Sierra Gorda alongside joint venture partner KGHM Polska Miedź. The updated reserves contain an average total copper grade of 0.39%, accompanied by molybdenum at 0.016% and gold at 0.06 grams per tonne. When expressed in copper equivalent terms, the deposit grades 0.46%, demonstrating the multi-metal nature of the resource. These grades remain consistent with the operation’s historical performance and support the economic viability of the asset over the extended reserve life.
The timing of this announcement coincides with South32’s recent approval of a fourth grinding line project at Sierra Gorda, expected to boost copper production by approximately 30% from 2031 onwards. This production expansion combined with the reserve life extension positions the mine as a sustained source of supply through the mid-2040s. The combination of reserve growth and processing capacity enhancement suggests management confidence in Sierra Gorda’s ability to compete in global copper markets during a period when demand for the metal is anticipated to remain robust, particularly given energy transition requirements and increased electrification trends.
From an operational perspective, Sierra Gorda benefits from established infrastructure that supports cost-effective production. The mine operates as a conventional open pit facility in Chile’s Antofagasta region, with access to renewable power and established logistics networks including a seawater pipeline, freight rail, and proximity to international ports. This infrastructure base reduces execution risk around the planned production increases and supports the mine’s economics across various copper price scenarios.
The announcement also highlights exploration upside potential, with copper mineralization identified at the Catabela Northeast project within the broader concession area. South32 Chief Executive Officer Matt Daley noted that the orebody remains open at depth, suggesting scope for additional reserve additions beyond the current update. Management indicated that the company continues to work with KGHM to drive growth, which may present opportunities for further reserve or resource increases through future exploration and delineation drilling.
Investors should monitor the execution of the fourth grinding line project, which represents a material capital deployment to realize the production benefits outlined. Reserve realization and the pace of production ramp-up will be key indicators to track through FY2031 and beyond. This announcement is price sensitive and has been flagged as material by the ASX.
View the full ASX announcement (PDF)
About South32 Limited (ASX: S32)
South32 Limited is a diversified metals and mining company headquartered in Perth, Australia. The company produces bauxite, alumina, aluminum, copper, silver, lead, zinc, and manganese through operations across multiple segments including Worsley Alumina, Brazil Alumina, Sierra Gorda, Cannington, and others. It operates globally with assets in Australia, South Africa, Brazil, Chile, Mozambique, Colombia, and the United States.
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