There are obvious distinctions between various interpretations of the term “Big Hits” – and some of this week’s featured intersections show why that is the case.
When looking at gold, for example, keen students are often hoping to see an intercept running at least 10m at more than 10 grams per tonne.
Looking at a different commodity, the thickness and grade of a niobium hit reported by Encounter Resources may not seem spectacular, but it is notable in a unique target. And for Future Battery Minerals, both intercept and grade in a highlight slice reported last week are only moderate, but they are consistent and extend the footprint of a single target.
Meanwhile, Riversgold’s numbers are dominated by big intercepts, but with gold grades many would consider “low”. However, at today’s gold prices, more life is breathing into the economies of scale due to the company’s potential for big tonnage.
Lastly, Spartan Resources’ latest work highlights solid sub-20m intercepts with excellent gold grades and strong lateral and vertical persistence of recently-discovered mineralisation that looks like it might head below 1000m vertical depth.
Each company almost certainly views its own set of “Big Hit” numbers through different lenses.
So, let’s dive in.
Encounter Resources
Aileron project – West Arunta, Western Australia
Hit: 46m at 3.1 per cent niobium pentoxide from 60m to end-of-hole at 106m.
Encounter’s open-ended headline hit amplifies previously-reported air-core (AC) results from the Crean carbonatite and drives the point home emphatically with a 4m run going 6.4 per cent niobium from 84m.
And the intercept is not just a one-hit-wonder, as an adjacent step-back hole also delivered with 18m going 3.2 per cent niobium from 76m including 2m running a stunning 17 per cent.
This year’s drilling at Crean has unveiled persistent, near-surface, carbonatite-hosted niobium mineralisation across four north-south lines spaced 200m apart, with drillholes spaced between about 13m and 50m apart. The holes attain depths ranging between about 90m and 120m and intercept what appears to be an east-west-trending, steeply north-dipping carbonatite dike interpreted to be a uniform 115m thick in current sections.
The headline hole lies 200m east of Encounter’s previously-reported 52m going 3 per cent niobium from 81m including 16m at 6 per cent niobium on an adjacent section drilled during the company’s first-phase program. Three other complementary adjacent intercepts also bracket the hole.
Given the distribution of robust values, commonality of depths and along-strike continuity, there seems little doubt the current mineralised entity is real. So, now the question becomes, how much bigger can it be?
Well, the niobium intercepts appear to improve towards the west – which remains open – and Encounter has already returned the rig to Crean to put in additional drillholes on 200m-spaced lines in a bid to extend the discovery in that direction.
While there is still a lot of detective work left to do as the mineralised entity is traced out along strike and in depth, it looks like the story will make for some interesting reading.
Future Battery Minerals
Kangaroo Hills project – Goldfields region, WA
Hit: 27m at 1.04 per cent lithium oxide from 118m
Future Battery scored the notable hit that also includes 15m at 1.53 per cent lithium oxide from 122m in its latest run of six reverse-circulation (RC) drill assays from the Big Red pegmatite at its Kangaroo Hills project.
The company’s phase-4B program involved 19 holes for 3109m of drilling, which met its objective in stepping out to the north-east from the Big Red mineralisation and extending it for a further 250m. The six holes track from the known centre axis of the pegmatite towards the north-east, exposing a strongly-mineralised trend.
Intercepts within the trend test about 250m of the Big Red pegmatite strike, with the geology looking like it remains open to the north-east beyond the current limit of drilling. It means that when the south-western holes in Big Red are included, the pegmatite has now been defined through a total strike of about 600m and it still looks like it has more to offer in the north-east.
However, just 250m of Big Red’s strike remains to be tested to the north-east before the company may be limited by tenement boundary constraints. In that context, it is significant that with the shallowing dip of Big Red to the north-east – about 20 degrees at the deepest and most north-easterly hole – it results in the deepest intercept sitting at just 100m vertical depth.
It also means Big Red could trend out of the tenement while remaining a shallow, thick, well-mineralised structure that is still open to the north-east.
Any strike extension of Big Red to the north-east of the tenement boundary would have about 1670m to run before re-entering the company’s Miriam project, in which it holds an 85 per cent interest.
Including the overlapping Potoroo pegmatite discovery and the underlying Rocky trend in phase-4A drilling, the entire surface-projected lithium footprint in the Big Red zone now extends for a strike distance of about 900m. The south-western extremity of the trend has only been thinly drilled and further shallow drilling perpendicular to strike has the potential to pick up near-surface extensions in that direction.
Riversgold
Northern Zone project – 25km east of Kalgoorlie, WA
Hit: 18m at 4.14 grams per tonne gold from 36m
Riversgold nailed the 18m hit in its most recent results from RC drilling of the porphyry intrusive-hosted Northern Zone gold project, 25km east of Kalgoorlie in WA, where it is working to secure an 80 per cent interest following an earn-in deal last year with Oracle Power.
The program sought to further define shallow, up-dip gold mineralisation the company encountered in its maiden diamond drilling program in August last year and in this year’s subsequent RC and AC drilling programs.
The headline hit was accompanied by a second, longer interval of 54m running 0.38g/t gold from 158m depth and 14m going 0.76g/t from 226m to end-of-hole, just 185m to the south-east.
In May last year, Riversgold confirmed that Northern Zone enclosed an estimated exploration target of between 200 and 250 million tonnes at grades ranging between 0.4g/t gold and 0.6g/t for between 2.5 and 4.8 million ounces. Those numbers came from London-based Oracle following that company’s successful 2021 drilling undertaken to validate historical drilling between 1998 and 2012.
In that campaign, Oracle encountered multiple porphyry intrusives striking more than 350m up to 150m thick and extending to depths attaining 250m. A handful of Oracle’s drilling results from its 2021 and prior RC drilling showed spectacularly long intervals of gold in the range of 0.4g/t to 1g/t gold.
Riversgold was drawn to the numbers that highlight potential for a big tonnage, low-grade intrusive-related gold system (IRGS), with a possible width of more than 100m. Following the latest results, the company is now planning further exploration drilling to the north-east to follow the open direction of the mineralisation defined to date.
Management says it takes inspiration from Saturn Metals’ Apollo Hill project near Leonora that features a mineral resource estimate of 105 million tonnes at a grade of 0.54g/t gold for a total of about 1.84 million ounces of contained gold.
Riversgold is musing on the possibility of emulating Saturn, which has a preliminary economic assessment (PEA) contemplating a big open pit bulk mining operation coupled with conventional heap leach processing to produce gold doré on site.
Naturally, at the Northern Zone’s current level of development, further pondering along such lines will have to wait until further drilling demonstrates mineralisation scale and depths of oxidation, free-dig and drill-blast-crush limits or … if the numbers reflect a big underground resource lurking below.
Spartan Resources
Dalgaranga project – Murchison region, WA
Hit: 10.14m at 11.26g/t gold from 996.9m
After our previous look at Spartan in this column, the company has come back with another serve of golden goodness from the near-1000m depths of its Never Never deposit, about 275m below the floor of its inferred mineral resource estimate.
The headline intercept includes 0.77m going 126.45g/t gold, piercing Never Never about 100m above the deepest intercept through the zone reported to date and further confirming robust mineralisation at depth.
That confirmation is reinforced by two supportive intercepts from the same program higher up the structure of 9.07m at 17.81g/t gold from 760.55m downhole including 1.52m going 99.45g/t and 10.66m running 6.55g/t from 798.02m including 0.49m at 126.00g/t.
The drilling was undertaken ahead of an imminent resource estimate update and management says the intercepts highlight “the incredible potential” that until recently lay undiscovered just in front of the company’s processing plant. That discovery is largely attributable to a change in mindset regarding the dominant structural controls that has also led to the discovery of the adjacent high-grade Pepper deposit where the latest drilling hit 13.5m at 4.47g/t gold from 679.50m including 0.5m going 73.04g/t.
Drilling at the more recently-discovered Pepper zone has not yet reached the same level of density as at Never Never, but it appears to be fast catching up. Both Never Never and Pepper remain open at about 1000m and 700m below surface, respectively.
Spartan is now finalising approvals and support activities for its underground exploration drill drive. The current mineral resource estimate for Never Never contains just under 1 million ounces of gold at a grade of 5.74g/t.
Development is slated to kick off in the third quarter of this year and the numbers are likely to be something to look forward to, as will be the next intercepts when they start coming in from below the magic 1000m depth.
Is your ASX-listed company doing something interesting? Contact: matt.birneyatbusinessnews.com.au
By Doug Bright
