Announcement • 8h
South32 Limited Announces Updated Ore Reserve and Mineral Resource Estimates for Sierra Gorda Copper Mine
South32 Limited announced updated Ore Reserve and Mineral Resource estimates for the Sierra Gorda copper mine in accordance with the JORC Code (2012) guidelines. These updates reflect enhanced orebody definition following successful infill drilling programs, with approximately 85,000 metres from 200 drillholes completed between 2023 and 2025. The updated estimates as at 31 July 2026 reflect a 61% increase in the Ore Reserve estimate to 1,100 million tonnes, averaging 0.39% total copper, 0.016% total molybdenum and 0.06 g/t gold, at a total copper equivalent grade of 0.46%. An extension of the initial reserve life by approximately five years to 2045. A Mineral Resource estimate of 1,870 million tonnes, averaging 0.37% total copper, 0.016% total molybdenum and 0.06 g/t gold, at a total copper equivalent grade of 0.44%. South32 acquired a 45% interest in Sierra Gorda in February 2022 and has joint control alongside 55% joint venture partner KGHM Polska Miedz. Sierra Gorda is a large, conventional, open pit copper mine located in the Antofagasta region of northern Chile. Sierra Gorda benefits from high quality, modern processing equipment, with significant historical capital investment. The operation is serviced by established infrastructure, including renewable power and a seawater pipeline, with freight rail and a national highway. The copper concentrate produced at the operation is transported by truck and rail to the ports of Antofagasta and Angamos for international export to end markets. Table A: Ore Reserve estimate for the Sierra Gorda deposit as at 31 July 2026 in 100% terms. Ore Type: Sulphide, Proved Ore Reserves: 444 million tonnes, 0.41% total copper, 0.021% total molybdenum, 0.06 g/t gold; Probable Ore Reserves: 594 million tonnes, 0.39% total copper, 0.014% total molybdenum, 0.06 g/t gold; Total Ore Reserves: 1,040 million tonnes, 0.40% total copper, 0.017% total molybdenum, 0.06 g/t gold. Stockpile: Proved Ore Reserves: 45 million tonnes, 0.27% total copper, 0.012% total molybdenum, 0.05 g/t gold; Probable Ore Reserves: 56 million tonnes, 0.27% total copper, 0.012% total molybdenum, 0.05 g/t gold. Million dry metric tonnes, % TCu- per cent total copper; % Mo- per cent total molybdenum; g/t Au- grams/tonne of gold; Kt- Kilo tonnes; Mt - Million tonnes; Moz - Million ounces. Cut-off grade: Net Smelter Return (NSR) of >0 USD/t. Input parameters for the NSR calculation are based on long term price forecasts for copper, molybdenum and gold; mining, haulage, processing, shipping, handling and G&A charges. Metallurgical recovery assumptions differ for geological domains with an average of 83% copper, 54% for molybdenum and 47% for gold. All tonnes and grade information have been rounded to reflect the relative uncertainty of the estimate; hence small differences may be present in the totals. All volumes are reported as dry metric tonnes. Ore delivered to process plant. Table B: Mineral Resource estimate for the Sierra Gorda Deposit as at 31 July 2026 in 100% terms. Ore Type: Sulphide, Measured Mineral Resources: 498 million tonnes, 0.39% total copper, 0.020% total molybdenum, 0.06 g/t gold; Indicated Mineral Resources: 853 million tonnes, 0.36% total copper, 0.014% total molybdenum, 0.06 g/t gold; Inferred Mineral Resources: 466 million tonnes, 0.35% total copper, 0.015% total molybdenum, 0.06 g/t gold; Total Mineral Resources: 1,820 million tonnes, 0.37% total copper, 0.016% total molybdenum, 0.06 g/t gold. Stockpile: Measured Mineral Resources: 56 million tonnes, 0.27% total copper, 0.012% total molybdenum, 0.05 g/t gold; Indicated Mineral Resources: 56 million tonnes, 0.27% total copper, 0.012% total molybdenum, 0.05 g/t gold. Million dry metric tonnes, % TCu - per cent total copper; % Mo - per cent total molybdenum; g/t Au - grams/tonne of gold; Kt - Kilo tonnes; Mt - Million tonnes; Moz - Million ounces. Cut-off grade: NSR of >0 USD/t. Input parameters for the NSR calculation are based on long term price forecasts for copper, molybdenum and gold; mining, haulage, processing, shipping, handling and G&A charges. Metallurgical recovery assumptions differ for geological domains with an average of 83% copper, 54% for molybdenum and 47% for gold. All tonnes and grade information have been rounded to reflect the relative uncertainty of the estimate; hence small differences may be present in the totals. All volumes are reported as dry metric tonnes. South32 confirms an update to the Mineral Resource estimate for the Sierra Gorda copper mine as at 31 July 2026. This update is based on infill drilling of approximately 85,000 metres from approximately 200 drillholes completed during 2023 and 2025. The update represents an 8% increase to the reported Total Mineral Resource as at 30 June 2026. The estimate of Mineral Resource is reported in accordance with the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves, 2012 (JORC Code) and the Australian Securities Exchange Listing (ASX) Rules. The breakdown of the estimate of Mineral Resources into the specific JORC Code categories is contained in Table B. The Sierra Gorda deposit is in the plain of the intermediate valleys between the Cordillera de la Costa and the source of the Cordillera de Los Andes. Exploration and research identified three metallogenic belts from different ages related to hydrothermal systems, with copper, molybdenum and gold mineralisation. Most of the world-class copper porphyries that exist in northern Chile are located within the three belts. Sierra Gorda is located in the central belt. Regionally, a sequence of Early Cretaceous volcanic rocks that was intruded by a granitic complex of Palaeocene age and a series of smaller younger intrusions have served as host rock for numerous hydrothermal mineralisation systems of copper, molybdenum and gold. The main structural systems are defined by regional faults in north-south and northwest directions, which control and serve as flow channels for systems of alteration and economic mineralisation. A total of 2,514 diamond drill holes (DD) (722.5km) with HQ core (hole diameter of 63.5mm), 1,366 reverse circulation (RC) drill holes (261.1km) with a hole diameter of 139.7mm and 366 holes with RC pre-collar to cover the supergene zone, followed by diamond drilling (173.2km) have been included in the database. Deviation measurements are made using North-Seeking Gyroscope methods. The Mineral Resource estimate for the Sierra Gorda deposit was completed using a total of 2,293 diamond drill holes (DD) and reverse circulation (RC) drill holes, corresponding to 674,210m, considering the limits of the model. Until 2021, drill half cores were sampled at 2m intervals.