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Nickel Sulphide Exploration

Ardea’s extensive and strategic land holding in the Eastern Goldfields of WA covers ~3,500km². In addition to the globally significant nickel-cobalt-scandium KNP resource, the tenure represents unrivalled Battery and Critical Minerals exploration potential.

Ardea Nickel Sulphide Strategy

The Company’s priority continues to be the development of the KNP, commencing with the Goongarrie Hub nickel laterite deposits. However, Ardea’s strategic tenure in the heart of the Eastern Goldfields of Western Australia is also highly prospective for nickel sulphide which is mined extensively throughout the region. Ardea’s nickel sulphide strategy complements the development of the KNP. The KNP nickel sulphide targets are a valuable asset in a region of multiple nickel sulphide concentrators, with most constrained by insufficient sulphide feed availability.

Ardea’s KNP tenure covers extensive zones of ultramafic stratigraphy which hosts the KNP nickel laterite resources. This same tenure is highly prospective for both Kambalda style komatiite lava flow and Nova-Julimar style intrusive related nickel sulphide mineralisation. It is important to note that any nickel sulphide discovery has the potential to be processed supplementary to laterite mineralisation through the autoclaves planned for Goongarrie.

Emu Lake Nickel Sulphide Prospect

Ardea’s Kalpini Project is located 70km north-east of the City of Kalgoorlie-Boulder and covers 121km² on contiguous granted Mining Lease tenure 100% owned by Ardea.

Regionally there are two distinct Kalpini ultramafic units each with 20-25km strike within Ardea tenure:

  • The Kalpini Eastern Komatiite Belt hosts the Wellington East and Acra North nickel laterite deposits containing 75Mt at 0.73% nickel and 0.04% cobalt, for 549.7kt nickel and 32.6kt cobalt (Ardea ASX release 16 June 2021). Aeromagnetic data indicates a uniform sheet of ultramafics (lacking discrete volcanic centres). The ultramafics are typical of the Walter Williams Formation style, consisting of a thick 200-600m sheet with olivine orthocumulate upper and lower contacts with middle olivine meso to adcumulate which weathers to nickel laterite (Dunitic Sheet Flows-Layered Lava Lakes, “DSF-LLS”). The Eastern Komatiite sits on the Kurnalpi Dome granitoid basement and is presumably an older lava flow sequence.
  • The Kalpini Western Komatiite Belt hosts the Emu Lake Nickel Sulphide Camp. There are three documented and well-defined fertile nickel sulphide surfaces at Emu Lake (Dunitic Channelised Sheet Flows, “DCSF”). The volcanics are characterised by a bi-modal co-magmatic suite, with each cycle having a footwall dacite volcanic overlain by ultramafic volcanic flows. Aeromagnetics indicate multiple discrete ultramafic centres. The ultramafic component of the flows is typically 10-40m thick, with dacite the lower flow component and komatiite the upper flow component. Massive nickel sulphide typically occurs in the upper dacite and grades stratigraphically up into disseminated nickel sulphide in the basal komatiite. The volcanic morphology is typical of a komatiite thermal erosion setting (as per Silver Swan) in a channelised flow (Huppert & Sparks 1989, Dowling et al. 2004). The Western Komatiite Belt overlies a thick felsic volcanic sequence (Black Flag Group equivalent) and is presumably a younger flow sequence.

The 2021-2022 drill testing of the Western Ultramafic at Binti discovered significant komatiite-hosted massive Ni-CuPGE sulphides ie AELD0003: 2.72m at 5.42% Ni and 0.85% Cu from 391.04m including 1.23m at 8.22% Ni and 0.56% Cu from 391.04m (ARL ASX 3 Dec 2021 and ARL ASX 14 Jan 2022). During 2023, regional technical targeting using detailed geochemical ratios, geophysical data, geological and structural interpretation was completed, which generated twelve nickel sulphide exploration targets in the ~20km strike Western Komatiite sequence. An RC drill program was designed with 52 RC holes for 11,200m. In addition, a diamond drill program comprising six holes for 3,210m was planned, with four holes in the Binti area. The plan for the Kalpini Hub is to postpone the exploration activities proposed above until the current Goongarrie Hub feasibility programs are completed. Low cost/low impact work such as field mapping and rock chip sampling of the fertile Western Ultramafic continues.

Emu Lake Nickel Sulphide Discovery confirmed with 2.72m at 5.42% Ni

  • In 2022, Emu Lake core holes AELD0002 and 3 at the Binti South Prospect confirmed a high-grade massive nickel-copper-PGE sulphide discovery within an intact felsic footwall contact of the Western Ultramafic (WM):
    • AELD0003: 2.72m at 5.42% Ni and 0.85% Cu from 391.04m including 1.23m at 8.22% Ni and 0.56% Cu from 391.04m (ARL ASX 14 Jan 2022)
    • AELD0003 is showing increased massive nickel and copper sulphide grade and thickness on an intact, basal dacite contact
    • AELD0002: 4.8m at 1.44% Ni and 0.16% Cu from 365.9m including 1.10m at 4.78% Ni and 0.16% Cu from 366.9m (ARL ASX 10 Jun 2021)
    • Discovery confirmed on an intact felsic footwall demonstrating thermal erosion textures analogous with the Silver Swan nickel deposit 35km west.
  • Historic exploration at the Binti Gossan Prospect located 1km northwest along strike from Binti South within an intact felsic footwall contact of the Central Ultramafic (CU):
    • ELD015: 2.0m at 6.08% Ni and 1.82% Cu from 336.0m including 0.6m at 18.82% Ni and 5.57% Cu from 336.3m (HRR ASX 26 Nov 2013)
  • Regionally there are two distinct Kalpini ultramafic units each with a 20km strike within Ardea granted Mining Lease tenure:
    • The Kalpini Eastern Komatiite Belt hosts the Wellington East and Acra North nickel laterite deposits.
    • The Kalpini Western Komatiite Belt hosts the Emu Lake Nickel Sulphide Camp. There are three well-defined fertile nickel sulphide surfaces at Emu Lake which are characterised by dacite footwalls to the ultramafic flows with aeromagnetics indicating discrete “string of pearls” ultramafic centres (“channels”).
  • The drilling completed by Ardea at Emu Lake since the AELD0003 discovery hole (ARL ASX 14 Jan 2022) has comprised 11 diamond core holes drilled for 5,122.3 metres. All drill holes have intersected nickel sulphide mineralisation and demonstrated the potential for both high grade massive nickel sulphides and disseminated nickel sulphides and reinforced the prospectivity of the underexplored ultramafic sequences within Ardea’s tenure in the Kurnalpi terrane.
  • Assay results and downhole electromagnetic (DHEM) surveys from recent diamond drilling at the Binti Prospect at Emu Lake identified three offhole anomalies with conductivities consistent with massive sulphides and aligned with defined mineralised channel positions.
  • Completed 3D modelling at the Binti Prospect (Emu Lake Project) based on results from the recent drilling and DHEM, with current interpretation indicating prospective mineralised channels are still open.
  • Emu Lake Project aircore drill program of 24 holes for 1,077m completed and intersected various thicknesses of prospective ultramafics within the Western Ultramafic sequence, with assay results expected next March 2023 quarter.
  • For more information, see ARL ASX announcement 22 Nov 2022 and ARL Quarterly Report for Dec 2022

Ardea’s Managing Director, Andrew Penkethman, said:

“The focus of historic Emu Lake exploration has been the Binti Gossan prospect area, 1km north of Ardea’s Western Ultramafic channel discovery.

The Western Ultramafic is a separate and distict high-magnesium ultramafic flow that was not prioritised by past explorers, presumably due to an absence of surface gossans as seen at the Binti Gossan.

With the assay results from core hole AELD0003 confirming high grade nickel sulphides located on an intact basal dacite contact with komatiite, we now have three adjoining drill holes with nickel sulphide mineralisation on the same contact which conclusively confirms that a discovery has been made.

Importantly, the interpreted 3D geometry of the AELD0003 discovery suggests the mineralisation is open in all directions for further drill exploration.

With Ardea holding 20km of fertile komatiite strike at Emu Lake, there is significant scope to extend this nickel sulphide discovery and make additional discoveries.

I acknowledge the Ardea team and partners such as CSIRO and Newexco for their input which has assisted in developing the Emu Lake “Thermal Erosion” nickel sulphide model which is a major exploration breakthrough for the Company, as it has opened up a new search space.”

Bulong Nickel Sulphide Prospect

Ardea has non-gold mineral rights for the Bulong tenements, located approximately 30km east of the City of Kalgoorlie Boulder.

Ardea's focus on the Bulong tenements has been on high grade laterite hosted nickel-cobalt mineralisation (54.1Mt at 0.88% Ni and 0.05% Co, for contained metal of 476.1kt nickel and 28.8kt cobalt) as part of the KNP resource base.

In addition to the significant nickel-cobalt resources hosted at Bulong, 36 exploration targets have been defined. These range from gold, PGEs and base metals (nickel, copper, lead and zinc).

Limited historic nickel-cobalt laterite drill holes have been located over some of the targets and a search for the historic pulps within Ardea’s West Kalgoorlie sample archive facilities has been completed and samples submitted for multi-element assay. This is a low impact and much cheaper form of exploration, as it removes the need to redrill holes.

During March 2022 quarter, six RC holes were drilled for 798m, with three holes drilled on each line to test a layered mafic complex (LMC) target defined by anomalous PGE soil geochemistry, limited subcrop and magnetic geophysical data. The concept was to test for nickel-copper-PGE mineralisation proximal to a norite (orthopyroxene gabbro) and pyroxenite contact in a similar setting to the Nova or Julimar LMC. The data collected is currently being interpreted and assay results are awaited.

Bardoc Tectonic Zone Nickel Sulphide

Exploration to unlock the nickel sulphide potential throughout Ardea’s strategic ground holding in the Bardoc Tectonic Zone continues. This work is assessing the ultramafic sequences of the KNP, where nickel sulphide mineralisation, if it exists, would be located in undrilled fresh rock beneath the laterite deposits. Using various geochemical markers, detailed petrographic studies, and re-evaluating historical geophysical data, new targets are being developed for potential drill testing.

In particular, interesting targets are evolving along the western basal contact of the Walter Williams Formation komatiite at Goongarrie South, Highway and Ghost Rocks.

Highway Nickel Prospect

The Highway Prospect, located 110km north of Kalgoorlie Boulder and 30km north of Goongarrie, is within a wholly owned and granted mining lease which hosts the Company’s Highway nickel laterite resource (92Mt at 0.69% nickel and 0.038% cobalt, for 633kt nickel and 35kt cobalt) (Ardea ASX release, 16 June 2021).

Magmatic nickel sulphide has been identified in historic RC drilling near the basal contact of the Walter Williams Formation (WWF). A MLEM survey in 2009 identified two subtle conductors along strike from the disseminated sulphide occurrence, however, drilling did not intersect massive sulphides. The fact that this portion of the Walter Williams Formation is fertile for nickel sulphides is significant with little or no focus on such occurrences over the last 20 years. It also raises the possibility of nickel sulphide occurrences beneath the Goongarrie tenements to the south.

During March to June 2021, RC hole AHIR0001 was completed to a depth of 259m testing an IP-chargeability anomaly near the basal (western) contact of the WWF near where historical CRA drilling recorded disseminated sulphides in the ultramafic units of the WWF. Assay results are awaited.

The prize of finding economic nickel sulphides in the WWF is significant, as it immediately opens up a large new search space, of which Ardea is overwhelmingly the major ground holder, controlling 40km of cumulative strike.

In 2023, a single diamond drillhole, AHID0024, was made at the Highway Project testing the nickel sulphide prospectivity of the Walter Williams Formation ultramafic and to also further understand alteration of the ultramafics by felsic hydrothermal events. The drillhole was part funded by the Geological Survey of Western Australia’s Exploration Incentive Scheme (EIS), targeting the western basal contact of the Walter Williams Formation.

AHID0024 returned the following results:

  • Pentlandite mineralisation confirms fertile ultramafic at Highway
    • Petrological studies confirm the key nickel sulphide mineral pentlandite is present in AHID0024. The Walter Williams Formation (WWF) komatiite ultramafic within the Goongarrie Hub is demonstrated to be fertile for nickel sulphide mineralisation.
  • Lithium-caesium intrusives with very high rubidium were identified in the EIS drill hole. Along with historic drill holes at Highway, a highly fractionated fertile Lithium-Caesium-Tantalum (LCT) mineral system is confirmed.
    Significant intersections in AHID0024 include:
    • 21.2m @ 0.23% Li₂O, 945ppm Cs, 1,237ppm Rb from 406.8m
      including 3.45m @ 0.34% Li₂O, 4,108ppm Cs, 4,772ppm Rb from 409.1m
    • 0.85m @ 0.34% Li₂O, 3,392ppm Cs, 4,222ppm Rb from 368.75m
    • 0.95m @ 0.15% Li₂O, 3,000ppm Cs, 4,830ppm Rb from 390.85m
  • Multiple fertile intrusives identified at Highway
    Based on the geological model generated from the EIS hole:
    • The lithium-caesium-rubidium style anomalism discovered in the AHID0024 fresh drill core has now been identified in intermediate-felsic porphyries within the weathered regolith throughout the Highway Project, with highest-grade zones on the biotite-rich intrusion margins.
    • Review of historic drill holes at Highway identified eleven holes with intersections >0.1% Li₂O, with the highest intersection 2m @ 0.68% Li₂O, 1.43% Rb, all within the oxidised weathered profile.
    • Recent Ardea mapping at Highway and Ghost Rocks has identified and sampled numerous prospective LCT intrusive outcrops including pegmatites, with assay results from Highway pending.

For details see ASX release 21 August 2023 and ASX release 15 December 2023.

Ghost Rocks Project

The Ghost Rocks Project, located 140km north of Kalgoorlie and 60km north of Goongarrie contains a mixed package of mafic and ultramafic stratigraphy associated with the WWF and hosts Ardea’s Ghost Rocks laterite resource (47.3Mt at 0.66% nickel and 0.042% cobalt, for 312.9kt nickel and 19.9kt cobalt) (Ardea Annual Report, 24 October 2019). It was extensively prospected for nickel and copper sulphide deposits in the late 1960s and early 1970s where copper gossan zones were mapped in the mafic/ultramafic package. Drilling of these gossan zones by Newmont in the early 1970s returned a best result in the oxide zone of 3.3m (10 foot) grading 2.14% copper to end of hole from 12m depth.

Work by Heron Resources in 2008/09 identified several MLEM anomalies that were drilled and intersected broad zones of “cloud nickel sulphides” in ultramafic rocks and copper assays up to 0.53% over 2m in a differentiated mafic unit. No follow-up was completed at the time.

During March-June 2021, re-assessing historic MLEM anomalies and the effectiveness of past drilling has continued, along with the completion of a modern MLEM survey. A compelling MLEM conductor has been defined which is associated with a copper anomaly in a historic Heron RC hole (GRRC0215). Deepening this hole would test this anomaly and this target has been added to the exploration target pipeline and will be considered for inclusion in future exploration drilling programs.

Black Range Project

The Black Range Project is located 65km north-west of Kalgoorlie Boulder and contains a 5km zone of the Ora Banda Sill mafic/ultramafic complex enriched in nickel, cobalt, copper, scandium and PGE metals. The Ardea Black Range resource comprises 19.2Mt at 0.68% nickel and 0.09% cobalt, for 130.7kt nickel and 17.8kt cobalt, as well as 8.70Mt at 65.6g/t scandium for 570,000kg scandium, and 6.55Mt at 0.33g/t Pt and 0.21g/t Pd for 70,300oz platinum and 44,000oz palladium (Ardea ASX release, 31 October 2017).

Past Ardea drilling programs have delineated a zoned lateritic distribution of nickel, cobalt, copper, scandium and PGE metals, including:

  • ABR0001/4-20m 16m at 0.24% Ni, 0.11% Cu, 0.29g/t Pd, 0.38g/t Pt
  • ABR0016/2-18m 16m at 0.45% Ni, 0.17% Cu, 0.15g/t Pd, 0.26g/t Pt
  • ABR0021/4-24m 20m at 0.18% Ni, 0.09% Cu, 0.29g/t Pd, 0.36g/t Pt

This geochemical signature is consistent with a sulphidic nickel metal source and is different to the usual KNP nickel laterite geochemistry. The target zone is located at a specific rock unit contact within the Ora Banda Sill layered mafic complex (LMC) with potential for Nova or Julimar style intrusion-related nickel-copper-PGE sulphides.

During March-June 2021, RC drillhole ABR0028 was completed to 271m testing coincident IP-chargeability and surface EM anomalies. The hole intersected the middle portion of the Ora Banda Sill with mafic intrusive rocks (gabbro/dolerite) to 90 metres followed by mixed peridotite and pyroxenite intrusive rocks with traces of pyritic sulphides to 271m. Traces of disseminated pyritic sulphides were observed through much of the hole, but this is not considered sufficient to explain the IP anomaly. The hole steepened from -63° to -69° when it was expected to lift and this resulted in it passing to one edge of the anomaly, rather than in the centre. The hole has been sampled with samples despatched in early June and results are awaited.

Jump-Up Dam – Nickel Sulphide Target

The Jump-Up Dam Project is located 150km northeast of Kalgoorlie Boulder and 96km east northeast of Goongarrie. Ardea holds non-gold mineral rights. It contains a nickel laterite resource of 64Mt at 0.75% nickel and 0.04% cobalt for 479kt nickel and 26.1kt cobalt associated with an Archaean ultramafic complex. Drilling on the eastern side of the ultramafic has defined a 400m long, north-south trending, zone of copper-nickel enrichment in the regolith profile and in places extending into the upper saprolite. The anomalous zone includes an intercept of 18m at 0.10% copper and 0.52% nickel from 18m to end of hole in hole JDRC0127. Interestingly, gold is also anomalous in this intercept – up to 0.21g/t Au over 2m. To further follow-up on this strong geochemical anomaly, a MLEM survey was completed during the Quarter over the eastern margin of the ultramafic complex. No specific conductors were identified in this survey, however, a broad increase in conductivity was recorded across the ultramafic contact. Further work will be undertaken to assess these results and determine the potential for disseminated nickel/copper sulphides in this area.