Legend Mining is preparing the diamond drill bit after identifying six important electromagnetic geophysical nickel-copper conductors at its Octagonal prospect within Western Australia’s Fraser Range.
The company believes its newly-discovered conductors relate to and potentially extend the mineralised eastern margin of the Octagonal intrusive – part of its Rockford project – where previous drilling has already delivered multiple nickel-copper sulphide intercepts.
Management says its high-power fixed-loop transient electromagnetic (HPFLTEM) geophysical survey data indicates that the sulphide mineralisation could extend not only to the predominantly untested eastern contact zone of the intrusive body, but also beyond it.
Most significantly, the likely eastwards extension of sulphide mineralisation at Octagonal appears to be confirmed by results from two diamond drillholes put into the eastern margins of the intrusive that intercepted nickel-copper sulphides in ultramafic sills close to the new conductors.
Legend Mining executive chairman Mark Wilson said: “We are pleased to be able to announce positive news from the Rockford project with a series of conductors from the recent high-power fixed-loop EM survey at the Octagonal prospect. The conductors are along the Eastern flank of the prospect which we have identified as a mineralised area from earlier drilling.”
The company says the style of mineralisation at Octagonal is the same as that described at IGO’s 100 per cent-owned Nova-Bollinger operation, which is also located in the Fraser Range, about 160km east/north-east of Norseman in WA – and, intriguingly, just 185km south-west of the Rockford project area.
The Nova deposit was discovered in July 2012, with development of the current operation kicking off in January 2015. In the 2023 financial year, Nova produced 22,915 tonnes of nickel, 10,266 tonnes of copper and 803 tonnes of cobalt.
Legend’s 2532-square-kilometre Rockford project and IGO’s Nova-Bollinger operations both lie within the Fraser Zone of the highly-prospective tectonic zone known as the Albany-Fraser Belt (AFB).
The AFB is a major arcuate tectonic belt that extends – as its name implies – from WA’s south-western coast at Albany and through Esperance, before trending north-eastwards inland for more than 1200km. The belt is characterised by a series of distinct mineralising events throughout its history, with the Nova nickel-copper-cobalt deposit hosted by mafic intrusions being dated at about 1.3 billion years old.
Nova is a prime example of the incidence of magmatic sulphide melts being emplaced into the deep crust during the major ancient tectonic event known as the Albany-Fraser Orogen. IGO has previously expressed its view that the magmatic processes that gave rise to its Nova style of massive sulphide nickel mineralisation could have occurred in multiple locations along the tectonic belt.
The HPFLTEM survey extension at the Octagonal prospect started mid-last month after considerable weather-related access delays, but Highpower EM Geophysical Services has now completed the extension survey at Octagonal.
Highpower has already moved on to undertake a maiden HPFLTEM survey at Legend’s Magnus prospect, about 25km north-east of Octagonal, where management has defined another interesting lensoid “eye-shaped” feature that bears similarity to the one that led to the Nova discovery.
Aeromagnetics imagery depicts the 5.4km by 1.2km-sized lensoid body as an intrusive entity that has displaced the country rocks around it in a characteristic arcuate outline around both flanks of the body. A remarkably similar and potentially analogous feature is also being investigated by Terrain Minerals at its Lort River project that sits about 300km south-west of the Nova-Bollinger operation.
Legend says its immediate future work will be to compile and interpret reprocessed seismic data, AI-machine learning and its HPFLTEM datasets across Octagonal and generate targets at the prospect for diamond drilling after securing heritage clearance. The company is also planning to process and interpret the results of the Magnus HPFLTEM survey, which is expected to be done and dusted in just 24 days.
So, could Legend’s Octagonal prospect be one such example of IGO’s surmised repetition of potentially-mineralised intrusives in the Albany Fraser Belt? And could Legend’s Magnus target be another? And what can be learned from Terrain’s similar lensoid example further to the south?
The work to come from both of those companies will create a tantalising watch.
Is your ASX-listed company doing something interesting? Contact: matt.birney@businessnews.com.au
By Doug Bright
