Kalpini - Emu Lake nickel sulphide and gold prospect
Emu Lake is part of the Kalpini group of tenements and located 70km north-east of Kalgoorlie. The Kalpini group is home to significant lateritic nickel resources of the KNP (75Mt at 0.73% Ni and 0.044% Co, for contained metal of 476.1kt nickel and 28.8kt cobalt) (Ardea ASX announcement, 16 June 2021). There are multiple historic nickel sulphide drill hole intersections exceeding 1% nickel. Previous explorers include Jubilee Mines, Emu Nickel, Xstrata and Pioneer Nickel. The komatiite belt is known to be fertile for nickel sulphide, with previous explorers recording significant drilling results, such as 2m @ 6.2% nickel in historic core drilling (Heron Resources Limited ASX release, 26 November 2013. ELD015, 2m at 6.2% Ni, 1.78% Cu, and 2.17g/t PGEs). Results of this tenor confirm unequivocal nickel sulphide endowment and prospectivity.
The leading Ardea nickel sulphide target at Kalpini, Emu Lake, is located 70km north-east of Kalgoorlie. This strategic tenement package contains an East and West Ultramafic belt each with 20km of strike of prospective nickel sulphide ultramafic stratigraphy held 100% by Ardea and mostly within granted mining leases. The project is located 35km east of the Black Swan Nickel Project, owned by Poseidon Nickel Ltd, within a comparable parallel komatiite volcanic belt.
Recent Ardea drilling (Ardea ASX release, 10 June and 13 July 2021) has intersected a semi-massive basal contact nickel sulphide occurrence in diamond drillhole AELD0002 and returned assays of:
- 1.1m @ 4.78% Ni, 0.16% Cu, 0.47g/t Pt, 0.20g/t Pd from 366.9m downhole consisting of semi-massive and matrix-style nickel sulphides, within a broader zone of:
- 4.8m @ 1.44% Ni and 0.09% Cu, 0.20g/t Pt, 0.09g/t Pd from 365.9m depth
This represents one of the better nickel sulphide intercepts historically at Emu Lake and demonstrates the prospectivity of this new more westerly ultramafic position that has received little attention in the past. Most previous drilling has been concentrated on the Binti Main zone to the north and east and which has intersected often remobilised stringers of nickel sulphide.
DHEM surveys on AELD0002 generated a strong off-hole response directly south and below the nickel sulphide intercept, however, it was unclear from the DHEM the up-dip extent of the sulphide horizon.
Ardea’s geophysical consultants, therefore, designed a Mise a la Masse (MALM) and downhole magnetometric resistivity (DHMMR) survey to better define the conductive horizon. The survey was undertaken in mid-June and results recently processed and interpreted. The MALM survey measured the surface potential generated from a downhole electrode over an area of 400m x 300m and produced a broad 550mV anomaly above and slightly south-west of the known nickel sulphide mineralisation.
The data are interpreted to indicate the sulphide body is steeply dipping to the east with a relatively short strike length (approximately 80m) and potentially comes to within 150m of surface. The strike of the body is northwest to southeast and is interpreted to extend to the southeast beyond AELD0001.
The DHMMR data supported the MALM interpretation with currents flowing in a NW-SE direction along at least four different pathways creating a more complex situation to model reliably. However, the source has been interpreted as a north plunging and steeply dipping sulphide lens with a rectangular shape consistent with a lava channel morphology as distinct from a more extensive interflow sediment.
Drilling will be planned to test the up-dip position.
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.
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, located 150km northeast of Kalgoorlie Boulder and 96km east northeast of Goongarrie, is wholly owned by Ardea. 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.
Bardoc Tectonic Zone Nickel Sulphide
Exploration to unlock the nickel sulphide potential throughout Ardea’s ground holding in the Bardoc Tectonic Zone (BTZ) continued during March-June 2021 with the assistance of a dedicated nickel sulphide expert.
The Company also accelerated research work with the CSIRO to further assess the ultramafic sequences of the KNP, where nickel sulphide mineralisation, if it exists, would be located in undrilled fresh rock beneath the lateritic deposits.
Using various geochemical markers and re-evaluating historical geophysical data, new targets are being developed for potential drill testing.