- 01Cu near-surface at Caribou Dome: up to 9.8% over 24.8m.
- 02Deeper extension ~170m below previous deepest.
- 03Twin holes outperformed historical assays; reassay planned.
PolarX Limited (ASX: PXX) has reported near-surface copper grades approaching 10% from its 2026 diamond drilling campaign at the Caribou Dome deposit in Alaska, alongside evidence that mineralisation extends substantially below the existing resource.
The strongest returned interval measured 24.8 metres at 9.8% copper and 14.5 grams per tonne silver from 2.4m, including narrower zones grading above 13% copper.
A second near-surface intersection returned 22.6m at 8.1% copper and 13.5g/t silver from 3.7m, while deeper drilling extended known copper mineralisation by approximately 170m vertically beneath the previously deepest mineralisation.
PolarX plans to re-assay available historical pulps after the modern twin holes returned materially higher grades and greater drilled widths than adjacent drilling completed between 1964 and 1970, creating potential for an uplift to the current mineral resource estimate.
Historical Grades Challenged
The twin-hole results were designed to test mineralisation already represented in the resource and produced significantly stronger copper grades than the historical holes they were drilled alongside.
PolarX considers the difference may reflect limitations in historical assaying, potentially introducing a conservative bias into the deposit grade, and will undertake systematic re-assaying of available historical sample pulps using current analytical methods.
The work will be combined with information from the current drilling campaign in future MRE updates, while further drilling will be required where historical pulps are unavailable.
Drilling of the two twin holes ended earlier than planned after historical survey inaccuracies led both to unexpectedly intersect old underground exploration adits, with one hole finishing in high-grade copper mineralisation on the northern hanging-wall boundary.
PolarX has deferred further evaluation of that deeper zone during the current season while prioritising western extension targets where thick zones of visual sulphides were recently encountered.
Mineralisation at Greater Depth
Separate drilling has pushed known mineralisation to a potential depth of approximately 500m from surface after intersecting 0.3m at 3.5% copper and 4g/t silver from 453.7m.
Although the intercept is narrow, PolarX considers its presence and grade evidence that high-grade copper mineralisation continues well below the current resource footprint, with additional drilling needed to determine whether wider zones occur at depth.
Caribou Dome currently contains 224,375t of copper within a MRE of 7.2Mt at 3.1% copper and 6.5g/t silver, using a 0.5% copper cut-off grade.
The deposit forms part of the Alaska Range joint venture with Northern Star Resources (ASX: NST), which is fully funding the 2026 exploration program after contributing US$6 million for the second year of activities and has earned a 30% project interest to date.
Approximately 1,700m of drilling remains scheduled before the campaign concludes at the end of September, with the program continuing to test extensions to the Caribou Dome mineralised system.
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