Castillo Copper Ltd (LSE:CCZ, FRA:7OR, ASX:CCZ) has returned up to 9% copper in assays from Big One Deposit at Mt Oxide Project within the Mt Isa copper-belt in northwest Queensland while visible mineralisation up to 26 metres thick in ongoing drilling demonstrates that copper is potentially structural as it extends beyond the trachyte/dacite dyke.

The best assay results from holes BO_315-317RC are:

  • 9 metres at 1.42% copper from 88 metres, including 4 metres at 3.06% copper from 92 metres and 1-metre at 9.19% copper from 92 metres;
  • 5 metres at 1.06% copper from 141 metres; and
  • 3 metres at 1.22% copper from 65 metres.

Assays for samples from priority holes BO_318RC1 and BO_326RC, which exhibited visual copper intercepts up to 34 metres and 26 metres respectively, will be returned shortly as the laboratory is fast-tracking the analysis.

Larger than expectations

Castillo managing director Simon Paull said: “It is encouraging there is a strong correlation between visual mineralisation and the assays, as the board optimistically looks forward to receiving further results.

“Otherwise, the progress of the drilling campaign is taking shape, especially verification the underlying copper system at the Big One Deposit is likely to be larger than our geology team’s initial expectations.”

Cross-section of drill holes at the Big One Deposit.

Drilling down, the assay results verify there is a relatively strong correlation to the visual estimates of sulphides and alteration minerals.

A closer examination of the initial assay results by CCZ’s geology team highlights the following interpretations:

  • Factoring the new data points into the preliminary geological model for the Big One Deposit suggests the underlying system is larger than initially envisaged;
  • There is now increasing evidence that copper mineralisation is potentially structural as it extends beyond the trachyte/dacite dyke; and
  • Using geophysics has enabled significantly better targeting and, in turn, optimised the results of the drilling campaign so far.

Next steps

There are several ongoing steps, including:

  • Reporting of the assay results for BO_318-27RC which are due back from the laboratory; and
  • Finalise logistics, access, cultural heritage, and targets for the drilling campaign at the Arya prospect.