Sentinel Metals Delivers Broad High-Grade Gold Hit in Maiden Columbia Hole

Sentinel Metals (ASX: SNM) has delivered a 46.8-metre intersection grading 5.5 grams per tonne gold from its maiden diamond drill hole at the Columbia gold-silver project in Montana, including a higher-grade 13.5m section at 16.6g/t gold.

The broader intercept began from 88.2m and also contained 21.4m at 11.1g/t gold, while mineralisation above and below the high-grade core returned 17.3m at 1.1g/t gold and 16.0m at 1.0g/t gold respectively.

Gold was also confirmed in fresh rock beneath the redox boundary at about 135m down-hole, extending across four discrete intervals to 218m and showing the mineralised system persists below the oxide zone historically targeted by previous operators.

The strongest results carry an important sampling caveat because core recovery through the 105.5m to 119.0m interval averaged just 20%, with Sentinel planning to re-drill the zone using triple-tube equipment.

Fresh Rock Extends System

Core recovery improved to between 95% and 100% below the oxide boundary, where Sentinel intersected fresh-rock gold mineralisation over four separate intervals to 218m down-hole, including a peak individual sample of 4.3g/t gold at 183.5m.

The company considers the result evidence that the Columbia system continues into fresh rock at this location, although further drilling is required to determine the continuity, geometry, and grade of mineralisation in the fresh sulphide domain.

The maiden hole was drilled down-dip through the existing mineral resource to test continuity beneath the historical oxide zone and provide Sentinel with its first comparison between diamond-drill assays and historical reverse circulation drilling in this part of the deposit.

A deeper hydrothermal breccia intersected from about 288m returned anomalous but sub-economic gold values, prompting Sentinel to deprioritise follow-up work on that interval while retaining plans to test other deeper structural and geophysical targets during the current program.

Recovery Re-Drill Planned

Sentinel found no systematic relationship between low recovery and grade elsewhere in the hole, with five comparable friable and gouge-bearing intervals recording recoveries of 27% to 50% but returning gold at or below detection limits or at low grade.

However, sampling bias in the high-grade interval cannot be discounted, the reported grades are regarded as indicative and the company plans to re-drill the 105.5m to 119.0m section irrespective of the outcome.

Gold grades were generated by PhotonAssay and remain preliminary pending fire-assay checks expected later this month, while silver and multi-element assays are also pending and may provide further information on the mineralised system.

“The program has already enhanced our understanding of the oxide profile and ground conditions, allowing us to further refine drilling techniques,” managing director Matt Herbert said.

“We have now transitioned to triple-tube drilling to optimise core recovery as we progress the program and, importantly, there is no indication at this stage that recovery characteristics have adversely impacted the reported gold grades.”

Columbia Program Continuing

Drilling is continuing across Sentinel’s 21-hole maiden program, with assays pending for the next four completed holes and the broader campaign targeting deeper structural zones, down-dip continuity of known veins and undrilled geophysical features.

Follow-up drilling will target the fresh sulphide horizon between the redox boundary and about 218m, while the company has already transitioned to triple-tube drilling to improve core recovery as the program progresses.

The existing Columbia Mineral Resource comprises an inferred 21.4 million tonnes at 1.3g/t gold and 4.6g/t silver, reported within a US$2,200-per-ounce optimised shell and above a 0.4865g/t gold cut-off.

Sentinel expects additional assays over the coming weeks as drilling continues, providing further tests of both the oxide mineralisation and the extent of the fresh-rock system beneath it.