ASX- and JSE-listed Orion Minerals has reported robust assay results from the confirmation diamond drilling programme in the Flat Mines area at its Okiep Copper Project (OCP) in the Northern Cape.

The latest results build on initial findings reported in April and June, including a notable intersection of 49.34 m at 5.05% copper at Flat Mine East (FME), among other high-grade intersections.

“Following our success in confirming the potential for high-grade copper mineralisation at FME over the past month, the first assay results from Flat Mine South (FMS), located about 3 km to the south-west of FME, have delivered further outstanding copper intercepts. These results show that the Flat Mines complex contains very high-grade copper sulphide mineralisation contained within wider zones of moderate-grade intrusive.

“We are encouraged by the potential to rapidly add high-grade tonnes from near-surface bodies such as at Flat Mine Nababeep (FMNb), and also down-dip and along the trend of the blocks being included in the current mine plan,” Orion MD Errol Smart said on July 9.

The OCP ground holdings span 641 km2, covering most of the area where a total of 105-million tonnes have been mined over the past 100 years. The Flat Mines area and the current drilling programme fall within an executed mining right.

The results from the first two of four planned holes at FMS have confirmed historical drilling information from Newmont and Gold Fields in the 1980s and 1990s, used in the mineral resource update, which reported 9.4- million tonnes at 1.3% copper for the Flat Mines, including 3.4- million tonnes at 1.4% copper at FMS.

“Our initial bankable feasibility study (BFS) that is nearing completion has only focused on immediately available Joint Ore Reserves Committee- (Jorc-) compliant mineral resources from Flat Mine North (FMN), FME and FMS. However, the potential to expand scale and extend the mine life lies at the core of why Orion invested in the Okiep district.

“Our aspirational target is to restore our Okiep properties to their historical production levels of 20 000 t/y to 50 000 t/y of copper production, which previous owners maintained for over five decades. Our ongoing drilling results underscore this potential,” Smart noted.

The diamond drilling programme, which started in February, includes 11 diamond core drill holes planned at FME, FMS and FMN, comprising a total of about 5 800 m. This total includes a nondirectional deflection for each hole. The programme is designed to confirm historical drilling information, provide geotechnical information, and deliver additional material for confirmatory metallurgical testwork for the FMN, FME and FMS blocks included in the initial BFS mine schedule.

Drill hole OFMSD076 returned 6 m at 0.9% copper from 454 m within a broad zone of elevated copper of 32.32 m at 0.63% copper from 427.68 m. Historical hole FMS012, located about 20 m away from OFMSD076, intersected 34.8 m at 0.74% copper from 447.9 m.

Historical hole FMS046, located about 20 m away from OFMSD076, intersected 31.82 m at 1.14% copper from 377.18 m. Drill hole OFMSD077 returned an outstanding intercept of 20.5 m at 4.99% copper from 549.5 m within 43 m at 3.41% copper from 527 m. This is all within a broad zone of elevated copper, but inclusive of wider zones of internal waste and lower grade, of 62 m at 2.51% copper from 508 m.

Historical hole FMS053D1, located about 10 m away from OFMSD077, intersected 38.98 m at 2.16% copper from 574.44 m.

Orion said significant widths of waste granitic material are included within the reported intersection widths, providing opportunities for upgrading material through modern X-ray flourescence (XRF) ore sorting techniques to reject internal waste before milling. This allows for optimised metal extraction with larger stopes operated at lower mining costs, while limiting concentrator capital and operating costs, the company said.

On completion of the drilling programme, the geological and mineralisation envelope interpretations will be reviewed and adjusted where necessary, followed by an update of the mineral resource estimate including the new information. New geotechnical information will be used for input to mine design.

Planned confirmatory metallurgical testwork includes XRF sorting, comminution, flotation optimisation and tailings characterisation. Detailed geotechnical assessment will also be undertaken on all intersections.

Orion said three of the five drilling rigs have been retained on site to test for an increase in classification of Jorc resource blocks not yet included in the mine plan and to test for extensions of high-grade mineralisation beyond the margins of the current Jorc resource blocks.

At FMS, historical Gold Fields holes and Orion hole OFMSD077 indicate that high-grade mineralisation remains open down-dip for up to 200 m within an untested area encompassing a strike length of 300 m.

Confirmatory drilling is also under way at FMNb, where an inferred mineral resource of one-million tonnes at 1.4% copper was previously reported. Original drilling over the main zone of mineralisation was carried out by the Cape Copper Company in the 1940s, with 141 000 t at 2.72% copper reported as being subsequently mined in the 1950s.

Six holes totalling about 480 m are initially planned to test and confirm the near-surface mineralisation at FMNb, Orion said. Highly mineralised intrusive, similar to that intersected and reporting high grades at FME and FMS, has already been intersected from 6 m to 52 m in the first drill hole completed at FMNb.

Outcropping exposure and drill intersections indicate that FMNb is likely to have a high internal waste content, suitable for bulk extraction with the application of ore sorting to remove the granitic waste before milling the higher-grade mafic intrusive rock fraction.