Cobre Limited is progressing a major upgrade of its Sierra Atacama copper project in Chile, aiming to convert a large foreign resource estimate into a JORC-compliant Mineral Resource Estimate while launching a 40,000-metre drilling program targeting near-mine expansion and deeper sulphide mineralisation.
- JORC resource conversion underway with WSP Australia
- 40,000m drilling targets resource validation and expansion
- New geophysical surveys identify priority exploration targets
- Near-surface oxide zones offer supplementary feed potential
- High-grade sulphide system remains open at depth
JORC Compliance Drive Underpins Asset Value
Cobre Limited (ASX:CBE) is methodically unlocking the potential of its Sierra Atacama copper project by converting an existing NI 43-101 resource estimate; approximately 110 million tonnes at 0.67% total copper; into a JORC-compliant Mineral Resource Estimate (MRE). This conversion is critical for the company to formally recognise and leverage the resource under Australian securities standards.
To achieve this, Cobre has engaged WSP Australia as an independent consultant to lead geological modelling and resource estimation. A comprehensive validation program has re-assayed intervals from 23 historical drill holes, integrated detailed structural mapping, and developed a 3D geological model that reveals a broader mineralised system than previously understood. Concurrently, an underground 3D void mapping initiative is underway to accurately define historical mining volumes, supporting a robust resource base.
Expanding the Resource Footprint with Targeted Drilling and Surveys
Beyond compliance, the company is aggressively pursuing resource growth. A high-resolution drone magnetic survey and Titan™ IP/DC and magnetotelluric (MT) geophysical surveys by Quantec have delineated multiple priority targets, including new mineralised corridors that could support larger-scale open pit mining.
Surface and underground mapping have identified multiple parallel and splaying vein structures between the main mineralised zones, suggesting a more extensive copper system than historical mining footprints indicate. This structural complexity opens avenues for bulk-scale open pit scenarios.
To capitalise on these opportunities, Cobre has commenced a 40,000-metre drilling program designed to validate historical data, support the JORC resource conversion, and test near-mine expansion targets. Notably, near-surface oxide copper zones at the Valentina and Triunfo prospects offer near-term potential to supplement feed to the existing solvent extraction-electrowinning (SX-EW) operation, pending environmental permitting.
Deeper High-Grade Sulphide Potential Offers Transformational Upside
While current operations focus on oxide mineralisation, Sierra Atacama hosts a high-grade sulphide system at depth that remains open and largely unexplored. Samples from the base of existing mines like Cecelia and Nicolasa have returned significant copper grades, indicating a substantial sulphide resource beneath the oxide zone.
Quantec's preliminary Titan™ IP/DC and MT survey results have successfully imaged these primary mineralised corridors and intriguingly suggest an additional mineralised corridor west of known zones. These geophysical insights will guide future deep drilling campaigns targeting this transformational sulphide upside.
Strategic Location and Infrastructure Support Development
Situated roughly 50 kilometres northeast of Antofagasta, a major mining hub in northern Chile, Sierra Atacama benefits from excellent infrastructure, including road access, power (currently generator-based), and proximity to ports for export. The project spans 65 mining concessions over approximately 15,000 hectares, encompassing multiple structurally controlled copper systems within a complex Jurassic geological setting.
The deposit's structural controls, including the Atacama Fault System and associated vein corridors, underpin its mineralisation style. The company’s detailed 3D geological modelling highlights the importance of these structures in controlling copper distribution, which will inform ongoing resource estimation and mine planning.
Operational and Financial Steps Ahead
Cobre’s CEO Adam Wooldridge emphasised the dual focus of the current programs: "While converting the resource to JORC compliance, our technical work is already revealing meaningful near-mine growth opportunities." He highlighted the synergy of new geophysics, mapping, and modelling in building a foundation for a larger, longer-life operation.
The company’s staged strategy includes underpinning asset value with JORC-compliant resources, optimising underground mining to return to cash-positive operations, and advancing near-mine expansions through supplementary starter pits and eventual large-scale open pit development. Refinancing and cleaning the debt structure form part of the broader plan to position Sierra Atacama for sustainable growth.
Environmental permitting remains a key milestone, particularly for near-surface oxide targets like Valentina, where historical open pit mining licenses exist but require reinstatement. Metallurgical studies on deeper sulphide mineralisation are also planned to assess processing options beyond the current SX-EW plant’s capabilities.
Bottom Line?
Cobre’s comprehensive validation and expansion efforts at Sierra Atacama set the stage for a significant resource upgrade, but the transition to JORC compliance and environmental approvals will be pivotal milestones to watch.
Questions in the middle?
- How will upcoming drilling results affect the timing and scale of Sierra Atacama’s open pit development?
- What progress will Cobre make on environmental permitting for near-surface oxide zones like Valentina?
- To what extent can the deeper sulphide mineralisation be economically integrated into Sierra Atacama’s production profile?