Cobre Limited (CBE.ASX) Signs Agreement with ENAMI: Unlocking Low-Cast Copper Ahead of Sierra Atacama Expansion
Cobre Limited (ASX:CBE) is advancing two complementary strategies to increase utilisation of Sierra Atacama's existing leach and solvent extraction-electrowinning (SX-EW) infrastructure: securing low-cost regional feed from ENAMI, and progressing an on-site copper recovery programme across historical leach pads and ponds. Together, these programmes support the Company's regional processing hub strategy and target additional copper production during the underground ramp-up and planned open-pit expansion.
HIGHLIGHTS
- Low-cost ENAMI feed secured: Approximately 150,000t of crushed-leached copper oxide material at an average grade of ~0.65% CuT secured for purchase and delivery to Sierra Atacama from Empresa Nacional de Mineria (ENAMI) for ~US$9/t including delivery to site.
- On-site copper recovery programme under way: Two new workstreams targeting additional low-cost, pregnant leach solution (PLS) from Sierra Atacama for the existing SX-EW:
1. Reprocessing of copper-rich material contained within historical lixiviant ponds has commenced, providing a potentially low-cost supplementary source of PLS for the existing SX-EW circuit; and
2. Re-leaching trials have commenced on the extensive historical stacked leach pads with initial irrigation trials generating PLS grading containing 2 g/L Cu.
- Together, these initiatives increase utilisation of the existing SX-EW plant during the underground ramp-up and planned open-pit expansion; and
- Importantly, all the initiatives are expected to have relatively low acid requirements, providing an additional advantage in the current high acid-price environment.
Commenting on these two complementary strategies to increase utilisation of Sierra Atacama's SX-EW infrastructure, Cobre's Chief Executive Officer, Adam Wooldridge, said:
" Sierra Atacama provides Cobre with a unique opportunity to establish a regional copper processing hub in an established mining district with limited electrowinning capacity.
Securing approximately 150,000 tonnes of low-cost ENAMI material, while simultaneously recovering copper from historical ponds and re-leaching historical pads, gives us three potential sources of incremental copper that can utilise infrastructure already in place.
These initiatives have been identified and moved rapidly into implementation by the Sierra Atacama metallurgy team and have the potential to support increased copper production as we ramp up underground mining and progress toward open-pit operations."
OPPORTUNITIES IN DETAIL
Low-cost ENAMI feed supports regional processing hub strategy
Cobre has entered into an agreement to purchase approximately 150,000 tonnes grading approximately 0.65% Cu, of crushedleached copper oxide ore from a stockpile held by ENAMI. The material is already crushed and located within 55km by road from Sierra Atacama, providing an attractive source of supplementary feed for the Company's existing leach and SX-EW facilities.
Cobre plans to transport approximately 30,000 tonnes per month to Sierra Atacama, where the ENAMI material will be blended with ore produced from the Company's underground mining operations. The additional feed is expected to assist Cobre in maintaining high utilisation of its processing infrastructure as underground production continues to ramp up and the Company progresses development of its planned open-pit operations.
Metallurgical column leaching testwork undertaken on the ENAMI material has returned 58% copper recovery, with laboratory acid consumption of approximately 45 kg/t. For planning purposes, Cobre is applying a more conservative ~50% recovery assumption at industrial scale with bulk acid consumption of 30 kg/t. These results indicate the material is well suited to processing through Sierra Atacama's existing leach circuit.
On-site copper recovery programme
Cobre's on-site copper recovery programme comprises two workstreams: (1) Re-leaching material on historical stacked leach pads, and (2) Reprocessing copper-rich material in historical leach-solution ponds. Both workstreams target additional lowcost copper from material already on site, using existing processing infrastructure. The programme complements regional feed sourcing by assessing additional copper-bearing solution sources within Sierra Atacama.
(1) Re-leaching material on historical stacked leach pads:
Historical mining operations at Sierra Atacama utilised large 30m high stacked leach pads. Available historical operating records indicate copper recoveries of approximately 50-55%, compared with recoveries of approximately 72-82% currently achieved by Cobre through finer crushing, lower stack heights and dynamic leaching practices (see June 2026 Quarterly Report released to ASX on 29 July 2026). The difference in historical recovery performance indicates that potentially significant residual copper remains within the historical leach pads. This result is supported by limited historical drilling and sampling undertaken by the previous operator which returned residual copper grades supporting the presence of further leachable copper. Simple volumetric estimates from LIDAR data indicate that the historical pads may contain in excess of 10 million tonnes of material using a nominal density of 1.6 t/m3.
Cobre has commenced a staged programme to assess the economic potential of the historical pads. The initial programme involves surface irrigation using recycled ILS from the existing operation. Early trials have successfully generated copper-rich PLS, demonstrating that residual copper can be remobilised from the historical material. The Company intends to progressively optimise irrigation rates and solution chemistry before assessing additional recovery techniques, including injection leaching, during the December 2026 quarter.
The historical pads represent a particularly attractive opportunity because the material has already been mined, crushed and stacked and can potentially be reprocessed using existing leach and SX-EW infrastructure. Subject to the results of the current programme, Cobre will assess the potential to progressively scale up re-leaching of the historical pads as a supplementary source of copper production. In the interim, the current leaching programme continues to provide a copper-rich (2g/l Cu) PLS which is being fed into the existing operation.
(2) Reprocessing copper-rich material in historical leach-solution ponds
Historical lixiviant ponds at Sierra Atacama contain accumulations of copper-rich precipitates and sediments supported by sampling.
Cobre has commenced a programme to recover this copper by circulating water through the accumulated material, dissolving readily soluble copper sulphates and generating copper-rich solution that can be filtered and introduced directly into Sierra Atacama's existing PLS circuit.
Importantly, the initiative utilises existing site infrastructure and requires minimal additional capital.
Recovery activities have commenced, with first copper production from the programme targeted by the end of the quarter.
*To view tables and figures included in the announcement, please visit:
https://abnnewswire.net/lnk/1BCH0W19
Cobre Limited Martin Holland E: info@cobre.com.au WWW: www.cobre.com.au
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