Cobre Confirms Copper Mineralisation at Depth in First Diamond Hole
Key Takeaways
- Hole SA_CBR_DD001 reached 986.9m depth and logged two visually estimated mineralised intervals — 3.57m at 4% chalcopyrite and 0.60m at 6% chalcopyrite — in previously untested ground below the existing Sierra Atacama operation.
- The deep intersection of Devonian sedimentary host rocks opens the door to manto-style copper deposits, a potentially larger-scale opportunity than the existing vein-hosted system, with a comparable analogue at Marimarca's Pampa Medina project 20km to the northeast.
- Laboratory assay results from SA_CBR_DD001 are anticipated in October 2026 — the immediate next news event that will confirm or refine the significance of the visually logged mineralisation.
- Four drill rigs are now operating simultaneously across a ~40,000m surface and underground programme, with 11 RC holes already completed and underground drilling targeting the high-grade mixed zone underway.
- The programme is designed to convert the existing historical NI 43-101 resource into a maiden JORC-compliant resource estimate — the foundational near-term catalyst for Cobre on the ASX.
First deep diamond hole confirms mineralisation at depth at Sierra Atacama
Cobre Limited has reported preliminary results from the first diamond core hole drilled at its Sierra Atacama Copper Project in Chile since 2021, with hole SACBRDD001 successfully reaching 986.9m depth and intersecting copper mineralisation in previously untested ground below the existing operation.
The hole was drilled at a dip of -45° towards 255° azimuth and logged two mineralised intervals based on visual estimation (not laboratory assays). The first runs from 784.90m to 788.47m downhole, a 3.57m interval with visually estimated abundances of 4% chalcopyrite and 2% pyrite developed at the contact with a magnetite-bearing hydrothermal breccia. The second is a 0.60m interval from 798.20m to 798.80m downhole, with visually estimated abundances of 6% chalcopyrite and 3% pyrite hosted in massive magnetite breccia.
These figures are downhole lengths, not true widths, given the hole’s orientation relative to the steeply dipping mineralised system. Importantly, they are derived from visual mineralisation logging only. The announcement is explicit that visual estimates should never be treated as a proxy for laboratory analysis, and no grades are confirmed until assay results, which are anticipated in October 2026, are returned.
Adam Wooldridge, Chief Executive Officer
“We’re very pleased to see the extension of mineralisation at depth confirming the scale and size of the mineralising system below the existing operation. Additionally, the alteration system and favourable mineralised sedimentary host rocks intersected offer significant opportunity for manto-style deposits where thicker mineralisation is expected. Having a great result like this from our first deep hole adds tremendous value to our understanding of the bigger mineralised system and opportunity.
With 4 drill rigs in operation, the Company is breaking significant ground on our pathway to convert the NI43-101 resource into maiden JORC compliant resource estimate…”
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What diamond drilling reveals — and why it matters for investors
Not all drilling is equal. Understanding the distinction between the two main methods helps explain why this result is a meaningful programme milestone.
Reverse Circulation (RC) drilling uses compressed air or fluid to return rock chips to surface. It is fast and cost-effective for bulk sampling over large areas, but the chips are fragmented. Diamond drilling, by contrast, recovers a continuous cylindrical core of intact rock. That core allows geologists to examine the precise nature of mineralisation, its relationship to host rocks, structural controls, and alteration patterns in a level of detail that chip samples simply cannot provide.
Here is why that matters for Cobre’s programme at Sierra Atacama:
- Continuous core enables detailed geological logging — geologists can log lithology, mineralisation style, alteration, and structural features metre by metre, building a three-dimensional picture of the deposit system.
- Visual logging provides early directional data — before laboratory assays confirm grade, geologists can assess whether mineralisation is present, what minerals are visible, and how they relate to host rock contacts. This shapes where the programme drills next.
- Depth extensions open the door to a different deposit style — the mineralised Devonian sedimentary units intersected in SACBRDD001 are noted in the announcement as an ideal host rock for manto-type deposits, similar to neighbouring Marimarca’s Pampa Medina project located 20km to the northeast. Manto-style deposits tend to be laterally extensive and can carry thicker mineralised horizons, representing a different scale opportunity to the existing vein-hosted system.
- NI 43-101 vs JORC — Sierra Atacama holds a historical resource estimated under the NI 43-101 standard, a Canadian reporting code. For an ASX-listed company, converting that into a JORC-compliant resource estimate (the Australian standard under the 2012 edition of the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves) is essential. Australian investors and institutions require JORC compliance for a resource to be formally recognised on the ASX. A maiden JORC resource is therefore the foundational near-term catalyst for Cobre on this project.
Programme scale — four rigs operating across surface and underground
The SACBRDD001 result is one data point within a substantially larger field programme. Cobre announced a ~40,000m surface and underground drilling programme on 1 July 2026, designed to validate historical drilling, provide infill data for resource modelling, and test both depth extensions and brownfield targets adjacent to current mining operations.
The current state of that programme:
- 11 RC holes completed to date, with a second rig and crew arriving to accelerate surface drilling
- 4 drill rigs now operating simultaneously across the project
- Underground drilling commenced, targeting the high-grade mixed zone at the base of the current mining operation
- Additional diamond drilling in progress, targeting extensions below the northern underground working
- Assay results from SACBRDD001 anticipated October 2026, with further results to be announced as the programme progresses
The three key geological findings logged in SACBRDD001 are summarised below.
| Depth Zone | Key Observation | Significance |
|---|---|---|
| Shallow (upper hole) | Shallow oxide copper mineralisation logged, supporting 3D vein model | Demonstrates continuity of mineralisation from surface as expected |
| Mid-hole (~402m to ~788m) | Hydrothermal breccias with chalcopyrite and chalcocite mineralisation transitioning into magnetite-rich feeder zone | Demonstrates continuity from overlying oxide system into deeper primary mineralisation |
| Deep (~784m to ~799m) | Granodiorite hosting chalcopyrite-pyrite in magnetite-cemented hydrothermal breccia | Ideal host rock for manto-style deposits; opens potential for multiple deposit styles within the mineralising system |
Four rigs running simultaneously signals an aggressive pace toward the maiden JORC resource, which represents the central near-term catalyst for the stock.
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Path to maiden JORC resource — what comes next
The announcement sets out a clear near-term sequence of events for investors to track:
- October 2026 — Assay results from SACBRDD001 anticipated, providing the first laboratory-confirmed grade data from this deep hole
- Ongoing RC and diamond drilling — Further results to be announced as received across both surface and underground programmes
- Resource modelling infill — The programme is designed to deliver the infill data required to support a maiden JORC-compliant resource estimate, converting the existing historical NI 43-101 resource
- Brownfield target testing — Adjacent targets near current mining operations are being tested in parallel
- Site visit completed 19 September 2026 — Management hosted investors and stakeholders on site at Sierra Atacama, providing direct access to the project and visibility over progress since acquisition
The October assay results are the immediate next news event the market is watching. They will either confirm or refine the significance of the visually logged mineralisation reported here.
Sierra Atacama is an active, funded drilling programme with multiple news catalysts approaching across an ongoing ~40,000m drill campaign — one well advanced toward the maiden JORC resource that underpins the company’s near-term investment case.
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