Big One copper deposit

Castillo Copper unveils thick, high-grade intercepts up to 16.65% Cu at Mt Oxide

Australian miner Castillo Copper (ASX: CCZ) reported that the final assay results from the Big One Deposit at Mt Oxide project in north-west Queensland delivered broad, high-grade copper results.

CCZ said that two 40-44m wide potentially economic intercepts from surface, with up to 16.65%, have significantly extended known mineralisation at the Big One Deposit.

Best intercepts included 40m @ 1.64% from surface incl: 11m @ 4.40% from 24m, 5m @ 7.34% from 28m & 1m @ 16.65% from 29m; and 44m @ 1.19% Cu from surface incl: 14m @ 3.55% from 27m, 3m @ 10.88% from 37m & 1m @ 12.6% from 37m.

The company noted that the latest assays make the case for potential scaling at Big One Deposit more compelling since the results build materially on early high-grade findings.

CCZ’s geology team made several key interpretations on analysing the results in depth. The company said that further potential upside is expected when assays for drill-holes 307-14RC are received.

CCZ said that the development plans for the Big One Deposit have been accelerated, with the formulation of a geophysics campaign and the commencement of modelling of a JORC compliant resource.

Mt Oxide project

The Mt Oxide project is located in Mt Isa’s copper-belt in north-west Queensland and is prospective for Iron oxide copper gold mineralisation according to Geoscience Australia.

Significant deposits include Big One deposit, Arya prospect, Wall & Pancake prospects, and Boomerang Mine.

Historic intercepts at Big One

Early high-grade findings at Big One desposit included B07: 3m @ 12.25% Cu from 42m incl: 2m @ 17.87% Cu from 43m & 1m @ 28.4% Cu from 44m; B05: 8m @ 2.33% Cu from 44m incl: 6m @ 3.00% Cu from 45m & 5m @ 3.28% Cu from 45m; B06: 4m @ 2.20% Cu from 44m incl: 2m @ 3.19% Cu from 46m; B25: 6m @ 1.55% Cu from 66m incl: 5m @ 1.79% Cu from 66m; B02: 4m @ 1.45% Cu from 36m incl: 1m @ 2.48% Cu from 37m; and B26: 3m @ 1.36% Cu from 73m incl: 2m @ 2.29% Cu from 73m.

Drilling at the Big One deposit

The company had recently commenced a Reverse Circulation drilling program at the Big One deposit.

CCZ said that final assays have been received for the 200 series and six drill-holes (301-306RC) for the 300 series at Big One Deposit.

High-grade assays

The company said that high-grade assays were reported from the RC drilling at the Big One deposit. CCZ said that assays comprised two 40-44m wide potentially economic intercepts from surface, with up to 16.65% Cu from drill holes 303RC, and 301RC.

Intercepts included 303RC: 40m @ 1.64% from surface including 11m @ 4.40% from 24m, 5m @ 7.34% from 28m & 1m @ 16.65% from 29m; and 301RC: 44m @ 1.19% Cu from surface including 14m @ 3.55% from 27m, 3m @ 10.88% from 37m & 1m @ 12.6% from 37m.

Scalable copper system

The company said that the results confirm that there is a high-grade, shallow scalable copper system apparent at Big One Deposit.

CCZ noted that the latest assays significantly extend known mineralisation and build on high-grade historic potentially economic intercepts which had produced stellar intercepts from supergene copper mineralisation up to 28.4% Cu.

Key observations from geology team

CCZ’s geology team made some key interpretations on analysing the assay results in depth.

The team said that the mineralisation is spread out which is significant given the trachyte to diorite dyke is generally 4-6m wide; secondary enrichment is apparent with several samples >10% Cu, likely due to intersected mineralisation occurring in the transitional zone between the oxide and sulphide domains; and high cobalt grades were noted with 12m @ 912ppm Co from 29m incl: 1m @ 1,435ppm Co from 30m.

Updates and next steps

The company said that a geophysics campaign is being formulated to identify new bedrock conductors and the geology team has commenced modelling a JORC compliant resource based on available historic and fresh data.

CCZ said that the next batch of assay results would be reported from the 15 drill-holes 307-314RC that are pending to be completed along the 600m strike.

The drill holes 307-314RC had intersected visible, shallow copper oxides & sulphides comprising 307RC: 10m from 18-28m – Quartz veining, pyrite & chalcocite; 308RC: 10m cumulative – 7m from 20-27m & 3m from 28-31m – Quartz veining, pyrite & chalcocite; and 313RC: 8.5m from 9.5-18m – Malachite & chalcocite.

Management comments

Managing Director Simon Paull said: “We are delighted to receive assays of this calibre, especially with global copper supplies tight. There is now compelling evidence Big One Deposit is a shallow, high-grade copper-cobalt system that can potentially scale further. The Board is now ramping up forward development work and the modelling of a maiden JORC compliant resource.”

Written By Jonathan Norris
Jonathan is a founder of and has been covering the resources industry since 2018. With over 17 years experience in print, broadcast and online media, Jonathan has seen first hand the transformative effect of online niche media.