Dual-listed Orion Minerals says it has received “highly encouraging” initial assay results from an in-fill drilling programme designed to upgrade the existing shallow inferred resource in the +105 Level Crown Pillar area at its flagship Prieska copper/zinc project, in South Africa’s Northern Cape province.

Fourteen in-fill holes were completed for a total of 917.87 m, designed to upgrade the existing inferred supergene resource of 630 000 t at 2.2% copper and 1.8% zinc to the higher-confidence indicated category as part of ongoing feasibility studies on the early production strategy.

This supergene inferred resource forms part of the overall resource of 1.76-million tonnes at 1.5 % copper and 2% zinc for the +105 Level Crown Pillar area.

The ASX- and JSE-listed company reports that drilling intersected higher-than-expected copper grades in several of the holes.

Once final results are received, the orebody model will be updated and the resource re-estimated.

The sampling density achieved is anticipated to allow an indicated classification, adding to the existing indicated resource of 620 000 t at 1.54% copper and 3.05% zinc.

The drilling programme was designed to in-fill an inferred resource area in the +105 Level Crown Pillar supergene mineralised zone to upgrade it to indicated resource classification.

Fourteen holes successfully intersected the mineralised zone, while five holes were abandoned owing to poor ground conditions and unacceptable core loss.

Assay results have been received for 13 of the 14 holes, with final assays for the last intersection expected shortly.

Results received to date have confirmed the presence of enriched copper and gold mineralisation in the previously drilled supergene mineralisation, which is currently classified as an inferred resource owing to the wider-spaced drilling.

The zinc grades confirm that zinc is depleted in the supergene zone.

The orebody model is currently being updated and the resource will be re-estimated and re-classified where appropriate.

An area of geotechnical collapse into underlying mining voids was also confirmed as being confined to a small zone with less than 10% of the mineralised strike affected.

“The in-fill drilling has confirmed and exceeded our expectations, returning outstanding widths and grades of high-grade copper sulphide mineralisation within the +105 Level Crown Pillar.

“This is a great result for our team. At face value, the grades intersected to date mostly exceed that of the average grade of the standing inferred resource estimate, making the early start of mining via an openpit an increasingly attractive opportunity,” CEO and MD Errol Smart says.

Orion’s early production strategy aims to target the openpit and remnant pillars while dewatering is undertaken on Prieska Deeps.

“These results provide strong support for that strategy, with the higher-than-expected grades also opening up the possibility that we may be able to undertake shallow underground mining in the early phases of the development, further optimising financial returns.

“Work is continuing as part of the ongoing feasibility studies to determine the optimal approach,” he adds.