Castillo Copper Ltd (ASX:CCZ) continues to improve the exploration upside at the Mt Oxide copper pillar in northwest Queensland with the potential for shear-hosted copper-zinc-lead mineralisation verified at Johnnies prospect.
Fresh evidence has been also uncovered that highlights the potential for Johnnies to host supergene mineralisation.
At Mt Oxide in the Mt Isa copper-belt district, there are now two prospects with supergene mineralisation potential along with four IOCG, two Mt Isa-style and several other targets.
Castillo Copper’s London-based director Gerrard Hall said: “Like a good novel, the Mt Oxide pillar story continues to get better and better as another piece of positive news from the prospect review is uncovered.”
Mt Oxide is one of three key pillars that Castillo Copper is pursuing as part of a strategic transformation to morph into a mid-tier copper group.
The others are four high-quality prospective assets across Zambia’s copper-belt which is Africa’s second-largest copper producer, and Cangai Copper Mine in northern NSW, one of Australia’s highest grading historic copper mines.
In addition, Castillo Copper is progressing a dual listing on the Standard Board of the London Stock Exchange.
Mt Oxide “taking shape”
The company’s managing director Simon Paull said: “The ongoing review of the Mt Oxide pillar continues to uncover excellent news, with verification there is potential for supergene ore at the Johnnies prospect which complements known shear-hosted copper mineralisation.
"CCZ’s current objective for the Mt Oxide pillar, which is to map out an extensive set of walk-up drill-test targets across eight prospects, is rapidly taking shape.”
At Johnnies, a historic induced polarisation survey identified two anomalies - a low phase response that is potentially sulphide mineralisation continuing down plunge; and a north-trending downwards plunging anomaly.
Across this prospect, strongly anomalous assayed surface samples have been associated with shear-hosted copper-lead-zinc mineralisation.
Moreover, the interpreted shear zone, which is circa 1,550 metres by 400 metres and orientated north-east, includes:
- Rock chips: up to 59,100ppm copper, 45,000ppm lead and 9,500ppm zinc; and
- Stream sediment: up to 90ppm copper, 87ppm lead and 225ppm zinc.
In addition, sub-surface mineralisation analysis was conducted from two 16-metre long costeans (A and B) dug either side of historical workings in Johnnies southwest quadrant.
These delivered highly encouraging assays, consistent with the rock chip results, including:
- Costean A: anomalous values from one sample – 63,000ppm zinc, 21,700ppm lead and 1,750ppm copper; and
- Costean A: a 5-metre composite sample along the length of the trench – 16,532ppm zinc, 5,658ppm lead and 782ppm copper.
Analysing the high-grade geochemical data and findings from the costeans determined there is potential for shear-hosted copper-zinc-lead mineralisation to be apparent in a north-east trending zone.
Preliminary drill targets
Furthermore, reconciling these findings with results from the IP surveys has enabled preliminary drill-test targets to be determined, pending further fieldwork.
Incrementally, there is potential for Johnnies to host supergene mineralisation associated with porphyry dyke intrusions, as these were noted in historic exploration reports.
Notably, the underlying mineralisation at Johnnies is comparable to the high-grade Big One deposit where historic RC drilling in the early 1990s intersected up to 28.4% copper.
Review of prospects
An independent geological consultant has been commissioned to review all eight prospects at Mt Oxide pillar, since they all have potential to deliver high-grade, near-surface deposits suitable for multiple open-pit operations that could provide feedstock ore for third party processors.
To date, of the reviews conducted, there has been sufficient historical geochemical and geophysical data to determine preliminary test-drill targets.
Hall added: "Based on the review’s current trajectory, a significant forward pipeline of drilling work is set to materialise.”
CCZ will continue the current review with further drilled down analysis on the remaining prospects within the Mt Oxide pillar and finalising the identification of preliminary drill targets.