Empire Metals Limited (LON: EEE), the AIM-quoted resource exploration and development company, is pleased to provide an analysis of the historical geochemical sampling that has been compiled to date on the Pitfield Copper Project (‘Pitfield’), located in Western Australia.
The mapping shows extensive copper, silver and other base metals anomalism over a 40km strike length, giving further confidence in the potential to discover a “Giant” copper mineralised system at Pitfield.
- An exceptionally large magnetic anomaly extending over 40km N-S has been identified in the Airborne Magnetic- (AM) survey data, likely caused by a basin-scale alteration event.
- A subsequent Airborne Electro-Magnetic (AEM) survey identified a suite of highly conductive rocks within the Mt Scratch siltstone surrounding the magnetic feature.
- Historical geochemical sampling by CRA Limited (“CRA”) in the vicinity of the magnetic anomaly indicates high background values for copper (Cu), silver (Ag), zinc (Zn) and nickel (Ni) including up to 2.3% Cu and 20.8g/t Ag from surface rock chip sampling.
- Pitfield has the potential to contain multiple sediment-hosted stratabound copper (SSC) deposits lying within what may be a “Giant” copper mineralised system.
- Exploration field work to commence by Q1 2023 ahead of an intended drill programme to evaluate the economic significance of any SSC deposit.
Shaun Bunn, Managing Director, said: “I am delighted to provide an update on our emerging Giant copper exploration project at Pitfield, where geochemical mapping has confirmed high background values of copper, silver and other base metals across almost our entire licence area.
“Since significantly expanding the exploration camps within our portfolio from 3.1km2 to 1,728km2 earlier this year, thanks largely to the acquisition of three highly prospective large-scale copper-gold projects, we have focused on successfully building up the prerequisite assay databases and geological, geophysical and geochemical maps initially for the Pitfield Copper Project. This information has underpinned our hypothesis that Pitfield is potentially a newly discovered Giant copper system rmed with this historical geochemical sampling data and the analysis of the AM and AEM survey, we will plan our next phase of surface exploration work before moving on to the evaluation of the economic significance of any SSC deposits through drilling.
“I look forward to being able to provide further updates over the coming months as we continue to develop our understanding of the exciting opportunity that Pitfield has to offer.”
The favourable geology of the Yandanooka basin for large-scale copper deposits has previously attracted major mining companies which carried out exploration within the area, including: Kennecott Corporation (“Kennecott”), MIM Holdings (“MIM”), BHP Group Limited (“BHP”) and CRA. Widespread copper, silver, nickel and zinc anomalism has been identified over large parts of the Yandanooka basin by these previous explorers, particularly in association with magnetite-altered rocks.
CRA (1992) completed IP geophysics and auger sampling defining a +7km Cu-in-auger anomaly (plus Ag) over what is now the western flank of the Pitfield project, and remains open to the east and south. CRA followed up with two diamond holes, the southern hole on Pitfield recording copper anomalism with a maximum value of 570ppm (from 4m chip samples of drillcore) associated with fracture-controlled malachite and minor native copper.
CRA also carried out soil sampling at Mt Scratch towards the north of the project area which shows a direct correlation between more strongly anomalous copper-in-soils with magnetic units within the stratigraphy. Rock chip samples taken by CRA from surface exposures returned very encouraging Cu-Ag values (up to 2.3% Cu and 20.8 g/t Ag) within the magnetic units highlighting a large, highly prospective SSC target (Figure 1).
Pitfield remains an early phase exploration project and as such requires further surface exploration work to effectively define geochemical (soils, auger and AC drilling) and geophysical anomalies (electrical surveys such as IP) prior to evaluating their economic significance through drilling.
Figure 1. Surface sampling by CRA highlighting Cu anomalism.
Extensive Ag, Zn and Ni anomalies were also highlighted within the surface sampling. In the context of sedimentary rock sequences, copper values >100ppm, nickel >50ppm and silver >0.5ppm are considered highly anomalous and may indicate the presence of significant SSC mineral systems. Such values are widespread within the sampled portions of the project. The Cu-Ag-Ni-Zn anomalous areas require further surface geochemical exploration to fully define their extent with field work set to commence by the first quarter of 2023.
The co-existence of Cu and Ag (Figure 2) is extremely encouraging as SSC deposits are an important source of other metals, ranking first among all deposit types in the world for cobalt (Co) production and fourth among all deposit types in silver (Ag) production. However, those that contain by-product Ag do not contain by-product Co and vice versa.
Figure 2. Surface sampling by CRA highlighting Ag anomalism.
The high Ni values (Figure 3). Are also significant in that they act as a good pathfinder in these highly weathered conditions as Ni is more stable in the laterites in comparison to more mobile elements such as Cu-Ag-Zn.
Figure 3. Surface sampling by CRA highlighting Ni anomalism
Geophysical surveying, geochemical sampling and geology work show that the Yandanooka basin contains coincident favourable features that make this an attractive sediment-hosted copper exploration target.
The AEM survey identified significant variations in rock conductivity including a suite of anomalous conductive features within the Mt Scratch siltstone, which indicates the presence of reductants such as graphite. The presence of reduced carbonaceous rocks (containing organic matter, graphite or hydrocarbons) stratigraphically higher in the sequence may provide a redox trap to allow for the precipitation of copper.
The AMG survey has distinguished a widespread, stratabound, regional magnetic anomaly (magnetite-bearing alteration) over 40km long. This massive magnetic anomaly, extending over 40km north-south indicates that the project area has been impacted by a large alteration event compatible with the influx of warm, oxidized, metals-transporting, sedimentary brines.
BHP (1984), who drilled four stratigraphic diamond holes focussed along the western contact of the Yandanooka basin within the basement Mullingarra gneiss, confirmed that the basement rock was depleted in Cu, indicating that the base metals have been leached and mobilised by the fluids passing through and this most likely explains the Cu anomalies identified within the upper zones of siltstone/sandstone.
Market Abuse Regulation (MAR) Disclosure
Certain information contained in this announcement would have been deemed inside information for the purposes of Article 7 of Regulation (EU) No 596/2014, as incorporated into UK law by the European Union (Withdrawal) Act 2018, until the release of this announcement.
For further information please visit www.empiremetals.co.uk or contact:
Empire Metals Ltd
Shaun Bunn / Greg Kuenzel
Tel: 020 7907 9327
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