Special Report: Castillo Copper has intersected visible copper oxide and sulphide mineralisation during early drilling at the Big One deposit, within its Mt Oxide copper project in North West Queensland.

Inspecting samples from the first seven drill holes completed at the Big One deposit, Castillo (ASX:CCZ) observed visible copper oxide (otherwise known as malachite) and sulphide (chalcocite) mineralisation in intercepts of up to 13 metres at shallow depths.

The intercepts included:

  • 13m of metasediments/quartzite, chalcocite, malachite and quartz veining from 55 metres in RC_211
  • 12m of altered trachyte, chalcocite, chlorite and quartz veining from 53 metres in RC_206; and
  • 9 metres of altered metasediment/trachyte, chalcocite, pyrite and haematite from 78 metres in RC_207.

Castillo’s geology team said the results revealed promising insight into the mineral composition of Big One, from which 4400t of supergene ore was mined by previous owners in 1997 with an average achieved grade of 3.5% copper.

Castillo Copper
Drilling underway at Big One.

The team noted that the chalcocite and malachite evident at RC_211 meant the hole was drilled in a transitional/supergene zone below the oxide layer which sits proximal to historical working.

RC_207 is also thought to be drilled in that transitional zone, while the presence of haematite and quartz alteration in the results is significant, as this mineralisation is typically linked to copper in the Mt Isa Block region where the project sits.

Assay results are now being pushed through, but the company said the initial observations potentially extended the known copper mineralisation at depth and suggested there were underlying sulphides in the transitional/supergene zone.

Castillo managing director Simon Paull said the early results were outstanding for the company, which still has a further 28 drill holes to complete at the Big One deposit.

“Hitting visible copper oxide and sulphide mineralisation at shallow depths in the first phase of an extensive drilling campaign is exceptional,” he said.

“More encouraging, however, is the indicative size of the intercepts at Big One deposit, which range from 9 metres to 13 metres in work undertaken to date.

“The board is delighted with this early success and looks forward to receiving the assay results.”

Castillo’s UK-based director Ged Hall said the early signs indicated a strong mineral presence at Big One.

“The team is off to a flying start, especially hitting copper sulphide mineralisation at this early stage of the campaign,” he said.

“The is a lead indicator which highlights the potential scalability of the Big One deposit, as our knowledge of the underlying ore body expands in tandem with the drilling campaign’s progress.”

Castillo said the remainder of the drilling campaign would be reorientated to account for the underlying mineralisation, which is believed to be more steeply aligned than previously modelled.

The visible mineralisation is the latest in the positive newsflow out of Mt Oxide, where historical data uncovered in an attic by Castillo in January revealed some serious numbers recorded during drilling by a previous project owner in 1993.

The company intends to drill the Arya prospect at Mt Oxide following the current campaign at Big One.

A copper-pillared approach

Mt Oxide is one of the copper pillars which makes up dual-listed Castillo’s copper strategy across Australia and Zambia.

The project, located in the prospective Mt Isa copper belt district which has seen a resurgence of interest since 2019, offers significant exploration upside with a number of high-grade targets.

The company also holds four high quality prospective assets across Zambia’s copper belt – potentially rich pickings within the boundaries of Africa’s second-largest copper producer.

The final pillar is the Cangai copper mine in Northern New South Wales, one of Australia’s highest grading historic copper mines with a JORC inferred resource of 3.2 million tonnes at 3.35% copper.

Castillo also holds a large tenure footprint near Broken Hill’s world-class deposit which is said to be prospective for zinc-silver-lead-copper and gold.

Castillo Copper
The Mt Oxide project in Queensland.


This article was developed in collaboration with Castillo Copper, a Stockhead advertiser at the time of publishing.

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.