Red Metal’s first scout diamond drill hole at its Bluebush silver-lead-zinc prospect in northwest Queensland has pointed the company towards new target opportunities in the same geology that hosts two of northern Australia’s biggest silver-lead-zinc mines.
The drill hole delivered a 73-metre hit at 9 grams per tonne (g/t) silver, including a 12m intercept at 19g/t silver. The silver runs also include base metal hits, with the 73m interval assaying 990 parts per million (ppm) lead and 256ppm zinc from 301m and the 12m run assaying 2446ppm lead and 780ppm zinc from 362m.
The drillhole bored through a further 33.6m assaying 4916ppm zinc and 304ppm lead from 538m.
Red Metal says results from its first drill hole at the prospect, within its Lawn Hill project, targeted a stand-out stratigraphic gravity anomaly, tagged BB01.
It successfully intersected a dense, heavily pyritic, dolomitic and carbonaceous siltstone over a true width of 119m.
The company considers the extensive pyritization as characteristic of the Barney Creek Formation and Urquhart Shale sequences, which host the River McArthur River and Teena silver-lead-zinc mineralisation in the Northern Territory.
Interpreted Riversleigh Siltstones in Red Metal’s core mark the time equivalence of the Barney Creek Formation.
The McArthur River mineralisation comprises a giant sediment-hosted zinc-lead-silver deposit characterised by eight ore lenses within the Barney Creek Formation, separated by breccias and dolomitic siltstones.
It is one of the world's biggest and most studied sediment-hosted base metal deposits, owing to its lack of deformation and preservation of sedimentary and ore textures.
Anomalous trace elements associated with lead and zinc mineralisation include silver, thallium, antimony, arsenic, copper and cobalt.
The accompanying and largely coincident anomalous thallium levels - over an intercept of 153m assaying 66ppm thallium - and high silver-to-lead ratios in the analyses point to a likely “near miss” setting, where the drill hole is likely to have pierced the margins of a more highly mineralised zone.
This interpretation has led the company to propose additional holes to target priority gravity targets.
Specific gravity measurements on the dense pyritic sequences are very high and range from greater than 3 grams per cubic centimetre to 4.62 grams per cubic centimetre, which provides a clear explanation of the source of the targeted gravity anomaly.
Heavily pyritic sequences lying close to other big strata-bound silver-lead-zinc deposits often demonstrate anomalous thallium values accompanied by high silver-to-lead ratios.
The new drillhole confirms that the company’s Bluebush prospect occurs within key McArthur River equivalent stratigraphy.
The prospect contains more than 88 historic drill holes within a 15 kilometre by 13km area, 40 of which produce broad intercepts of low-grade zinc and lead mineralisation.
Gravity surveying by Red Metal has identified several high-priority, stratigraphic targets along the trend of and adjacent to historic mineralised drilling.
Imbued with new enthusiasm after this first batch of results, the company’s maiden drill hole will comprise the vanguard assault on the prospect and it has new holes lined up to test the new targets.
Future exploration on Bluebush will prioritise gravity targets closer to the interpreted growth faults where the potential for higher-grade mineralisation is speculated.
The fact that such clear geochemical and lithological coincidence has been defined in Red Metal’s first drill hole aimed at a largely conceptual target has to be taken as a proof-of-concept from a very bold first hole, especially considering its depth.
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By Doug Bright
