Aim-listed mineral exploration and development company Tertiary Minerals has outlined a higher-grade, shallow silver/copper/zinc mineralised zone at its Target A1 prospect at the Mushima North project, in Zambia.

The company has reported assay results from 29 of the 39 holes drilled during its Phase 4 programme, which covered 3 639 m, with results from a further eight holes awaited and two holes yet to be submitted for analysis.

Target A1 is a polymetallic silver/copper/zinc prospect for which Tertiary has previously reported a near-surface exploration target of 15-million to 30-million tonnes grading between 40 g/t and 60 g/t silver-equivalent.

Some highlights from the prospect discovery include the higher-grade zone extending about 400 m along strike and 150 m wide, trending north-west, and key intersections include 52 m at 99 g/t silver, 0.41% copper and 0.43% zinc and 22 m at 90 g/t silver, 0.13% copper and 0.44% zinc from 64 m.

The company adds that the discovery and higher-grade zone remain open at depth, with several holes ending in mineralisation extending beyond the exploration target boundary, which measures about 500 m long, 350 m wide and 75 m thick.

Tertiary also highlights that the drilling activity has returned higher-grade copper intersections, including 10 m at 1.01% copper, 165 g/t silver and 0.78% zinc from 80 m, equal to 238 g/t silver or 3.97% copper and 5 m at 1.01% copper, 164 g/t silver and 0.15% zinc from 101 m, equal to 227 g/t silver and 3.79% copper.

The company adds that potential critical mineral content has not yet been evaluated, although certified laboratory assays have returned grades of up to 0.53% bismuth, 0.22% antimony and 0.39% cobalt.

Meanwhile, a new shallow copper discovery has been made in the western zone of the prospect area, about 900 m west-southwest of the discovery zone, with initial portable X-ray fluorescence results including 25 m at 0.38% copper from 19 m and 26 m at 0.13% copper from 23 m.

Accessory minerals, including bismuth, antimony and cobalt, have also been intersected in the latest holes, as well as in holes drilled during previous phases.

“We are delighted with the analytical results received to date from our recent Phase 4 drill programme which have allowed us to delineate a substantial higher-grade mineralised zone within the current exploration target.

“Notably, the mineralisation within the higher-grade zone remains open at depth, with numerous holes ending in mineralisation beyond the current modelled exploration target boundary,” says Tertiary Minerals MD Richard Belcher.

Mushima North is located within Zambia's prospective iron-oxide/copper/gold region, about 28 km east of the historic Kalengwa copper/silver mine, which is currently being redeveloped.

The potential of these metals has yet to be evaluated, but they are classified as critical and, in some cases, strategic raw materials by the European Commission.

If economically recoverable alongside the main silver/copper mineralisation, these accessory minerals could potentially enhance the future economics of the project.