Askari on trail of potential Pilbara copper-silver porphyry

Askari Metals has revealed some tantalising high-grade copper-silver mineralisation in rock chip sampling at its Callawa project in Western Australia’s Pilbara region, jagging a top hit of 6.78 per cent copper with 2.34 grams per tonne silver.

The headline result is supported by a second sample that produced 4.35 per cent copper with 8.25g/t silver and a third offering of 2.02 per cent copper with 6.42g/t silver. There is also a fourth sample giving up a lower copper value at 1.85 per cent, but it has a surprising 11.1g/t silver hit.

Only trace gold was identified in the range of 11 parts per billion to 48ppb for the four samples, while molybdenum ran 1.3ppm to 5ppm across the suite. The results are somewhat comparable with two previous samples collected at the project, which gave up 9.35 per cent copper with 25.9g/t silver and 7.63 per cent copper with 15.7g/t silver.

Initial element correlation indicates that copper and silver are mutually complementary, but the company says it will undertake petrographic analysis to confirm the nature of their apparent association.

Askari Metals managing director Gino D'Anna said: "Callawa represents an underexplored opportunity and includes some spectacular historical results identifying high-grade copper and silver mineralisation which indicate the significant exploration potential of the project area. The strike extent of the mineralisation remains open and follow-up work is planned to map out areas of interest and potentially extend the strike beyond the area identified by surface outcrop.”

The company's 100 per cent-owned Callawa project lies about 90km north-east of Marble Bar in WA’s East Pilbara region. It consists of a single granted exploration licence and an adjacent exploration licence application.

The project embraces more than 167 square kilometres and sits over part of what the company describes as a “ring structure” that appears to have the characteristics of a potential porphyry terrane. The regional geological setting places Callawa over a large area of the Warrawagine Granitoid Complex on the north-eastern margin of the Pilbara Craton, which is described as a poorly exposed sequence of various granitoid plutons and gneisses.

Management says copper occurs in quartz veining and is associated with elevated gold values in several places, which could indicate possibly porphyry-related origins to the copper. Secondary supergene surface copper staining can be ubiquitous in such environments, with hand-specimen mineralisation featuring malachite – a copper carbonate that can be a low-grade copper ore mineral – within highly-altered quartz-mineralised and sheared/brecciated host rock.

The company believes the extent of alteration in the surface samples could indicate the potential for the presence of a bigger mineralised system at depth – possibly a high-grade epithermal copper system fed by a copper-porphyry intrusive at depth.

Rock chip samples were taken from areas of good rock outcrop and included sampling around the Du Valles workings. After initial reconnaissance work identified high-grade copper mineralisation at the surface, the company undertook a high-definition airborne magnetic drone survey over the Du Valles prospect.

The survey covered about 19sq km at 50m line spacings for 408 line kilometres in a bid to correlate magnetics with mineralisation. The company plans to have geophysical consultants review and interpret the magnetic data to identify possible primary targets.

Future work will also likely include a second phase of more closely-spaced soil sampling to better define the mineralised area and potential targets and a follow-up infill soil auger program across the current 200m-by-100m grid pattern to home in on targets.

The company will also undertake a remote sensing study with the use of Sentinel data, which may be able to define the alteration styles and possibly the variations in the regional intrusive granitoid bodies in the area.

In addition to advancing its exploration activities, Askari is also progressing the grant of its adjacent exploration licence application. But it is clear that the results of the upcoming work will help determine future activities at Callawa.

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