Very high-grade copper mineralisation identified at ARC is associated with the Minik Anomaly, a coincident magnetic-electromagnetic-gravity feature in an area where there is a change in oxidation state and widespread native copper in stream sediments.
These features are presented as the footprint of a large-scale hydrothermal system. The frequency and size of native copper clasts and high grade of the copper-silver sulphides that are exposed at the surface, signify the potential for world-class discovery.
There are multiple additional identified targets and favourable geological settings to be tested within the ARC project area, including:
- the highly anomalous basalt is a high priority target that has not previously been the focus of commercial exploration. These basalts are the source of the native copper.
- the sulphide mineralised faults passing through these basalts into the overlying sediments have been subject to first pass exploration and shown to be rich in copper and silver. The high-grade sulphides in these faults will be the focus of further exploration.
- the permeable coarse-grained sandstone within the Jyske Ås Fm has high grade copper that is effectively unexplored. This stratiform mineralisation adds the potential for significant lateral extension of the known mineralisation exposed in the faults of the Discovery Zone.
As such, the extensive ARC mineral system is known to be prospective for basalt, fault, and sedimentary rock-hosted (‘sediment-hosted’) mineralisation that despite the attractive grades, is virtually unexplored.
The most advanced prospect within ARC is the copper-silver bearing Discovery Zone, located at the northern end of Neergaard Dal. The Discovery Zone is comprised of at least three parallel breccia faults trending northwest-southeast, with the furthest faults being around 2km apart. The faults are traced for a minimum of 2km along strike before they disappear underneath moraine. The Discovery Zone is open in both directions.
The width of the fault breccias is variable, ranging from 1m to 25m thick. The host lithology is red sandstones of the lower Jyske Ås Fm, and they are proximal to outcrops of Zig-Zag Fm. The breccias have copper sulphide and copper oxide mineralisation. The copper-bearing species include chalcocite, brochantite, bornite, chalcopyrite, and malachite.
The mineralisation is expressed in two main forms, within which there are two sub-forms:
- Breccia bound. Mineralisation occurs in thin quartz-dominated veining within the fault breccia and contains disseminated copper sulphides. Assays from this material grades up to 53.8% Cu and 2,480g/t Ag. Within the breccia-bound mineralisation are intensely potassic, unconsolidated materials known as ‘Black Earth’. The multiple but discontinuous 0.7m to 3m horizons have lengths between 2m to 50m. The Black Earth material contains high grades of copper and silver, with reported true widths of 4.5m grading 2.15% Cu and 35.5g/t Ag.
- Stratiform. Mineralisation occurs immediately adjacent to the faults and comprises lenses and blebs of chalcocite and bornite measuring from mm-scale to 15cm long.
Within the stratiform mineralisation is a poorly consolidated sandstone that is identified as a potentially vast target horizon within the Jyske Ås Fm. The outcrop shows pervasive interstitial chalcocite, bornite and chalcopyrite.