Altair Copper-Zinc Prospect
The Altair Copper Prospect is interpreted to be Volcanic-Hosted Massive Sulphide (VHMS) style copper mineralisation associated with black shales and intermediate volcanics (Figure 1). The Company interprets the geological setting of the mineralisation at Altair to be that of a VHMS / SEDEX environment. Evidence for this interpretation includes:
- Restrictive black shale depositional environment, overlying an interpreted volcanic exhalative chert horizon;
- Extensive chlorite alteration and pyrite development in footwall intermediate volcanics;
- Evidence for mineralisation to have formed pre-deformation, and possibly syn-deposition; and
- Anomalous geochemical pathfinder elements characteristic of VHMS / SEDEX systems.
Volcanic-associated mineral deposits tend to occur in district-scale “camps”, with individual deposits occurring in favourable stratigraphic positions over many kilometres. In this respect, the Company considers the Teutonic Bore group of deposits, located approximately 200km southeast of Altair, to be a relevant analogy. Teutonic Bore contains three former or operating mines (Teutonic Bore, Bentley, Jaguar), that host current Resources totalling 6.5Mt @ 5.6% Zn, 0.9% Cu, 85g/t Ag and 0.4g/t Au (refer to Independence Group NL announcement dated 23 October 2017).
Figure 1: Geological plan of the central Gum Creek project area showing the location of Altair and Mensa Prospects
Limited drilling in the 1990’s by Goldfields Exploration intersected broad zones of copper mineralisation at Altair, including the following assay results:
- 44m @ 1.2% Cu from 56m (ALAC005);
- 24m @ 1.0% Cu from 64m (ALRC007);
- 20m @ 1.1% Cu from 52m (ALRC002); and
- 20m @ 0.9% Cu from 64m (ALRC006).
In 2018 and 2019 Horizon Gold Limited drilled 23 RC and diamond holes for 7,269m beneath the Goldfields Exploration intercepts returning the following significant zinc-copper intercepts from the base of a black shale sequence (refer to Horizon Gold Limited ASX Announcements dated 13 February 2019, 26 March 2019 and 2 April 2019). Significant assay results included:
- 55.0m @ 3.32% Zn, 0.52% Cu, 9.4g/t Ag from 184.0m incl. 9.0m @ 6.69% Zn, 1.00% Cu, 17.0g/t Ag from 213.0m (ALDD002)
- 44.4m @ 2.93% Zn, 0.49% Cu, 8.3g/t Ag from 274.2m incl. 2.0m @ 7.05% Zn, 0.92% Cu, 16.8g/t Ag from 306.0 (ALDD012)
- 78.0m @ 1.90% Zn, 0.32% Cu, 5.4g/t Ag from 288.0 incl. 14.0m @ 2.34% Zn, 0.51% Cu, 7.4g/t Ag from 342.0 (ALDD014)
- 62.6m @ 2.45% Zn, 0.42% Cu, 7.0g/t Ag from 262.0m incl. 19.0m @ 3.09% Zn, 0.53% Cu, 9.2g/t Ag from 297.0m (ALDD019)
- 38.0m @ 1.89% Zn and 0.64% Cu from 97.0m incl. 21.0m @ 2.47% Zn and 0.55% Cu from 106.0m (ALDD007)
- 36.0m @ 2.58% Zn and 0.41% Cu from 344.0m incl. 21.0m @ 3.10% Zn and 0.55% Cu from 358.0m (ALDD017)
- 32.0m @ 1.90% Zn and 0.37% Cu from 154.0m incl. 14.3m @ 2.59% Zn and 0.55% Cu from 166.0m (ALDD009)
- 35.6m @ 2.44% Zn and 0.43% Cu from 120.0m incl. 19.0m @ 3.42% Zn and 0.54% Cu from 129.0m (ALDD016)
- 30.0m @ 1.89% Zn and 0.34% Cu from 135.0m incl. 13.0m @ 2.30% Zn and 0.43% Cu from 150.0m (ALDD022)
- 18.0m @ 2.41% Zn and 0.52% Cu from 97.0m incl. 8.0m @ 3.00 % Zn and 0.88% Cu from 107.0m (ALDD008)
- 15.2m @ 2.33% Zn and 0.27% Cu from 136.0m incl. 5.4m @ 3.84% Zn and 0.23% Cu from 137.0m (ALDD011)
The Altair primary zinc-copper mineralisation forms a broad continuous lens of polymetallic (zinc-copper-silver+/-gold) mineralisation with a strike of more than 450 metres, down dip extent of 350m and average thickness of 25m (Figures 2 to 7). The average density (SG) of all assay intercepts within the lens was estimated at 3.1 tonnes per cubic metre. Mineralisation remains open down plunge to the east and at shallow depths along strike to the north.
Refer to Horizon Gold Ltd ASX Announcement titled “Altair Exploration Update” dated 16 July 2019. CP J Hicks.
The zinc-copper-silver mineralisation defined at Altair is coincident with anomalous multi-element surface geochemistry, magnetic highs visible in regional aeromagnetic surveys, and electromagnetic conductivity highs defined in both helicopter-borne Transient Electromagnetic (TEM) and ground moving loop electromagnetic (MLEM) surveys.
The Altair mineralisation is located at the base of a black shale sequence and occurs as fine to very fine grained red/brown sphalerite associated with semi-massive magnetic pyrrhotite in folded sub-millimetre stratiform layers interpreted to reflect original bedding plane deposition.
It is important to note that base-metal geochemistry at Altair (and potentially more regionally) is strongly depleted to around 50m depth. As can be seen in Figures 3 to 5, the supergene copper mineralisation occurs below 50m depth, and was not intersected in the initial vertical RAB and air-core holes drilled in the early 1990’s. This suggests that the historical wide-spaced and shallow drilling conducted in the Gum Creek Greenstone Belt may not have been an effective test for this style of mineralisation.
Resource Potentials Pty Ltd completed a full geochemical and geophysical review of the Altair / Mensa area. Surface geochemistry samples were gridded and imaged, including ternary images to compare concentrations of Au, Pb, Zn and Cu. Multiple geochemical anomalies were identified, including over the Altair, Central and Mensa prospect areas, however multi-element anomalies including elevated gold are the priority targets for Altair style mineralisation.
High frequency helicopter-borne TEM data was also reviewed by Resource Potentials to identify electrical conductors over the Altair-Mensa area. Ground based MLEM data collected using a lower transmitter frequency was then used to determine the strongest electrical conductors, and 3D conductor plate modelling of the MLEM data was then completed using lithological and structural measurements from detailed field mapping and the TEM decay data to help constrain the interpreted conductor plate orientations (Figure 7).
Two RC pre-collared diamond holes at Altair have been designed to test the strong gravity and conductivity highs at depth beneath and down plunge of the currently defined Zn-Cu-Ag mineralisation (Figure 7). Both RC pre-collars have been completed with diamond drilling to commence mid-June 2022.
Figure 2: Altair Prospect – drill hole location plan
Figure 3: Altair Prospect – long section (7006480N)
Figure 4: Altair Prospect – long section (7006420N)
Figure 5: Altair Prospect – long section (7006360N)
Figure 6: Altair Prospect – cross section (731350E)
Figure 7: Modelled 3D conductor plates, historic drillhole collars (coloured by hole type), and proposed drill holes (large black dots) over a greyscale derivative aeromagnetic image.
Mensa Copper-Zinc Prospect
Regional mapping and geophysical interpretation at Gum Creek suggests the target stratigraphy hosting the Altair prospect may extend at least 5km to the north to the Mensa Prospect (Figures 1 & 7).
At Mensa, shallow RC drilling by exploration companies in the 1990’s intersected zinc mineralisation beneath anomalous surface geochemistry in a similar geological setting to Altair. The results included 6m @ 0.22% Zn from 50.0m in GMRC001; and 24m @ 0.19% Zn from 20m in GMRC002.
Refer to Horizon Gold Ltd ASX Announcement titled “Significant Zinc-Copper Intersection at Gum Creek” dated 4 October 2018. CP J Hicks
RC drilling to intersect the strongest electromagnetic conductor plates that coincide with elevated magnetics and anomalous geochemistry has been completed at Mensa (Figure 7). Results are awaited.