Ardea Resources says a deep diamond drillhole into its Kalgoorlie nickel project nailed a tasty trifecta, yielding nickel sulphides at depth, surface lateritic nickel and strong lithium-related mineralisation in a 21m intercept grading 0.23 per cent lithium oxide.
The company says its diamond-core hole intersected the Walter Williams Formation (WWF) from 132.25m to the end of the hole at 499.1m. But most significantly, it identified blebs of nickel sulphide between 441.7m and 442.7m, which have since been confirmed by petrography and assayed 1m at 0.35 per cent nickel.
Petrological studies show the key nickel sulphide mineral pentlandite is present in the drill core, confirming that fertile komatiite ultramafic rocks exist in the WWF at Ardea’s Highway project within its Goongarrie Hub complex, about 30km north of Kalgoorlie in Western Australia’s renowned Goldfields region.
In addition to the nickel intercepts, the hole intersected anomalous lithium-caesium-rubidium results at considerable depth, with the headline intercept of 21.2m running 0.23 per cent lithium oxide, 945 parts per million caesium and 1237ppm rubidium from 406.8m including 3.45m going 0.34 per cent lithium, 4108ppm caesium and 4772ppm rubidium from 409.1m.
It also jagged 0.85m at 0.34 per cent lithium, 3392ppm caesium and 4222ppm rubidium from 368.75m, with a further 0.95m going 0.15 per cent lithium oxide, 3000ppm caesium and 4830ppm rubidium from 390.85m.
The drilling was jointly-funded by the WA Government through its exploration incentive scheme (EIS) that has been designed to encourage mineral exploration within the State. The company was granted $112,000 by the WA Government to help meet direct drilling costs under the EIS terms.
Whilst Ardea is entirely focussed on concluding the Kalgoorlie Nickel Project Goongarrie Hub Strategic partner process, the company considers that its broader Kalgoorlie Nickel project tenements have significant battery and critical mineral exploration potential. The results from the EIS diamond core hole at Highway confirm the prospectivity of the Walter Williams Formation for nickel sulphide mineralisation at depth, and the extensive surface nickel laterite development. Ardea Resources managing director and chief executive officer Andrew Penkethman
Penkethman said the lithium-caesium-rubidium-bearing intrusives into the WWF had prompted a broader assessment of the company’s Goongarrie Hub tenure that meets the State Government’s EIS hole exploration model, in a bid to demonstrate that significant grades exist and to justify ranking for future exploration.
The EIS drillhole was designed to explore the WWF, a succession of komatiitic ultramafic rocks previously demonstrated by petrographic studies of chip samples from earlier reverse-circulation (RC) drilling that revealed minor nickel sulphides consisting of pentlandite and millerite.
The hole also sought to test the bottom of the WWF for nickel sulphides and to understand alteration of the ultramafics by hydrothermal events and any relationships that could explain not only the minor millerite connection, but also those associated with alkaline felsic intrusive rocks identified in earlier shallow RC drillholes.
Ardea says that while only minor nickel sulphides were intersected, their presence further confirms that the WWF achieved a degree of sulphur saturation and is fertile for nickel sulphide mineralisation.
Additionally, management says recent research in collaboration with Australia’s national science agency, the CSIRO, as part of the “Indicator Minerals for Nickel Sulphide” project, identified low ruthenium signatures of less than 150ppb in chromite and nickel and copper depletion in olivine – both of which suggest possible sulphur saturation and hence, nickel sulphide prospectivity within the WWF.
The intrusive felsic rocks intercepted by previous shallow RC drilling in the near surface laterites are represented by a distinctive pallid alteration clay. The company has identified it as sepiolite, which assigns a characteristic cobalt-manganese-nickel signature to the laterites. It indicates that the project area may contain potentially economic lateritic nickel mineralisation that needs to be further tested.
Management says the characteristic lithium-caesium-tantalum (LCT) signature, which may include other elements such as gallium, hafnium, rubidium, niobium and tin, among others, has now also been identified in intermediate-felsic porphyries within the weathered regolith throughout the Highway project, with highest-grade zones on the biotite-rich intrusion margins.
Moreover, it says 11 old drillholes at Highway also hit LCT mineralisation in the weathered profile, running greater than 0.1 per cent lithium and with a best result of 2m going 0.68 per cent lithium oxide and 1.43 per cent rubidium.
The growing awareness of potentially economic LCT mineralisation in the area has been reinforced by the results of recent mapping of pegmatites at Highway and Ghost Rocks, although assays are not yet available.
The prize for finding economic nickel sulphides in the WWF is significant – especially when spiced up with potentially economic LCT mineralisation and surface lateritic nickel deposits – as it immediately opens up an extensive new exploration area where Ardea is by far the major ground holder, controlling about 40km of cumulative strike in prospective terrain.
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