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Castillo Copper announces copper discovery at Big One Deposit

Published by , Editor
Global Mining Review,

Castillo Copper Ltd (CCZ) has announced that final assays have been received for the 200 series and six drill-holes (301 – 306RC) for the 300 series at Big One Deposit within the core Mt Oxide Project (Appendix A).


  • Game changing assays as two 40 – 44 m wide potentially economic intercepts from surface, with up to 16.65%, significantly extends known mineralisation at the high-grade Big One Deposit.
  • The best apparent intercepts comprise:
    • 303RC: 40 m at 1.64% from surface including: 11 m at 4.4% from 24 m, 5 m at 7.34% from 28 m and 1 m at 16.65% from 29 m.
    • 301RC: 44 m at 1.19% copper (Cu) from surface including: 14 m at 3.55% from 27 m, 3 m at 10.88% from 37 m and 1 m at 12.6% from 37 m.
    • 213RC: 12 m at 0.79% Cu from 52 m including: 8 m at 1.06% Cu from 57 m, 3 m at 2.03% Cu from 58 m, 1 m at 4.27% Cu from 59 m and 1 m at 1.46% Cu from 62 m.
    • 207RC: 8 m at 0.47% from 84 m including: 2 m at 1.1% Cu from 85 m and 1 m at 1.49% from 86 m.
    • 306RC: 8 m at 0.41% Cu from 16 m and 4 m at 0.97% from 96 m including: 2 m at 1.3% from 96 m.
    • 206RC: 8 m at 0.42% Cu from 54 m including: 3 m at 1.02% Cu from 59 m, 1 m at 1.75% Cu from 60 m.
    • 302RC: 5 m at 0.66% Cu from 35 m including: 1 m at 1.3% from 37 m.
    • 305RC: 5 m at 0.53% Cu from 34 m including: 1 m at 1.19% Cu from 38 m.
  • Encouragingly, the latest assays clearly make the case for potential scaling at Big One Deposit more compelling, especially as the results build materially on early high-grade findings, including:
    • B07: 3 m at 12.25% Cu from 42 m including: 2 m at 17.87% Cu from 43 m and 1 m at 28.4% Cu from 44 m.
    • B05: 8 m at 2.33% Cu from 44 m including: 6 m at 3% Cu from 45 m and 5 m at 3.28% Cu from 45 m.
    • B06: 4 m at 2.2% Cu from 44 m including: 2 m at 3.19% Cu from 46 m.
    • B25: 6 m at 1.55% Cu from 66 m including: 5 m at 1.79% Cu from 66 m B02: 4m at 1.45% Cu from 36 m including: 1 m at 2.48% Cu from 37 m.
    • B26: 3 m at 1.36% Cu from 73 m including: 2 m at 2.29% Cu from 73 m.
  • Key observations CCZ’s geology team garnered from interpreting drill-holes 301RC and 303RC include:
    • The mineralisation is spread out which is significant given the trachyte to diorite dyke is generally 4 – 6 m wide.
    • Secondary enrichment is apparent with several samples >10% Cu, likely due to intersected mineralisation occurring in the transitional zone between the oxide and sulfide domains.
    • High cobalt (Co) grades with 12 m at 912 ppm Co from 29 m including: 1 m at 1435 ppm Co from 30 m (301RC).
  • Further potential upside should become apparent when assays for drill-holes 307 – 14RC are received, as visible, shallow copper oxides and sulfides were intersected, comprising:
    • 307RC: 10 m from 18 – 28 m – Quartz veining, pyrite and chalcocite.
    • 308RC: 10 m cumulative – 7 m from 20 – 27 m and 3 m from 28 – 31 m – Quartz veining, pyrite and chalcocite.
    • 313RC: 8.5 m from 9.5 – 18m – Malachite and chalcocite.
  • Development plans for the Big One Deposit are being actively accelerated, with a geophysics campaign being formulated and the modelling of a JORC compliant resource has commenced.

Castillo Copper’s Managing Director, Simon Paull, commented: “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.”

Key observations

The latest assay results have extended original lengths of visually logged mineralised intersections (refer CCZ ASX Releases – 30 November 2020 and 14 December 2020), while laboratory analyses confirmed the presence of high-grade, shallow copper mineralisation in eight drill-holes at Big One Deposit. As a result of analysing the results in depth, CCZ’s geology team made the following key interpretations:

  • The full assay results, which included the entire seven drill-holes completed in the first tranche (201 – 213RC), confirm the presence of at least two mineralised lenses and a low-grade halo around the main ore body.
  • For drill-holes 301RC, 303RC and 213RC, the mineralisation is spread out which is significant given the trachyte to diorite dyke is generally 4 – 6 m wide.
  • There is likely secondary enrichment apparent within drill-holes 301RC and 303RC, as several 1 m samples >10% Cu possibly intersected mineralisation occurring in the transitional zone between the oxide and sulfide domains. Note, this is consistent with earlier observations that confirmed visible malachite (oxide) and chalcocite (sulfide) in RC chips, though more data points are required.
  • Surprisingly, ore grade cobalt readings were noted in 301RC – 12 m at 912 ppm Co from 29 m including: 1 m at 1435 ppm Co.
  • While further work is required to determine the extent of mineralisation, there is potential for significant cobalt credits.
  • Within the high-grade copper zone, there were anomalous readings for silver-arsenic-bismuth and very minor gold readings.

Accelerating development plans

With a game changing discovery of this nature at Big One Deposit, the board is now actively accelerating forward development plans. While there is a pause in drilling activities, due to the commencement of the wet season across northern Australia, a geophysics campaign is being formulated to identify new bedrock conductors (and potential test-drill targets). In addition, the board has instructed the geology team to commence modelling a JORC compliant resource based on available historic and fresh data. If the outcome of the geological modelling is positive, then the board expects to commence applying for a fresh mining lease.

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Australian mining news Copper mining news