AEON METALS LIMITED
Aeon Managing Director and CEO, Dr
Background
On
Providing further geotechnical data to support mine design.
Completing in-fill drilling within the existing resource where appropriate to enhance confidence in mineralisation and mineral grade continuity.
Conducting exploration of the Vardy Deeps concept as detailed in ASX release dated
All 2021 drilling was completed within, or adjacent to, the Vardy and Marley zones, while the Amy zone was excluded. The program commenced with a single, multi-purpose drill rig operating on double shift from
Independent geological consultants,
The 2021 drilling was primarily aimed at producing metallurgical sample and geotechnical data to support the PFS. Holes were designed where possible to also provide infill data for the resource estimate. An improvement in the confidence for the MRE, highlighted by the increase in Measured and Indicated Resource, was achieved through this additional drilling data.
Amy Zone Exploration Target
Mineralised domains
The massive pyrite hosted high-grade copper/cobalt core tends to be surrounded or encased by a substantial tonnage of massive pyrite mineralisation which hosts cobalt and lower grade chalcopyrite (Cu) mineralisation along with substantial accumulations of argentiferous galena (Pb) and sphalerite (Zn). The PY1 and the DOL units have been combined and modelled together in this resource estimation work.
Sampling, sub-sampling techniques and Sample analysis method
Sampling was generally at 1m intervals under geological control with a minimum sampling width of 0.5m and a nominal maximum of 2m. Barren zones, particularly at the top of hole and within the green siltstone, were sampled either for 1m every 5m (diamond drilling) or on 5, 10 or 20m composite intervals (RC drilling). Where drillholes encountered the FRF, sampling continued past the fault for a nominal 5m.
During diamond drilling, predominantly HQ core was obtained from which 1m sawn half-core samples were collected and weighed, dried, crushed and pulverised at a commercial laboratory (dominantly ALS and Genalysis/
All above grade (termed
Estimation Methodology and Classification Criteria
Grade estimation was undertaken with commercially available
Only the sulphide mineralisation was estimated. The mineral wireframes acted as hard boundary domains for the grade interpolation. An additional hard boundary density domain was introduced for the PY1/DOL unit to prevent over-smoothing of density at the massive pyrite/pyritic dolomite boundary, essentially the PY1 and DOL unit segregation boundary. Domaining was achieved by using the lithostratigraphic interpretation, which had defined an upper massive pyrite zone for the PY1/DOL unit and a subsidiary massive pyrite zone towards the base of the PY1/DOL unit (in the old PY2 position). Metal grade interpolation used Ordinary Kriging with the dynamic interpolation technique. A total of 20,074 1m composites for the mineralisation were extracted from the drillhole database constrained by the mineral wireframes. Elements modelled included Cu, Pb, Zn, Ag, Co, Ni, Fe, S, Ca, Mg, Mn, Na, Tl and a calculated pyrite value from the base metal and sulphur assay data. No top cuts were applied to the data and there are no obvious correlations between any of the potentially economic elements. The dynamic interpolation technique aligns the search ellipse and variogram model to parallel the locally undulating mineral-defined surfaces, reflecting the subtle changes in strike and dip of the relatively flat-lying mineralisation.
Maximum extrapolation was 50m beyond the limiting drillholes for the Mineral Resource. Block size for Vardy and Marley was 10m by 5m by 5m with no sub-blocking. A 3 pass search strategy was employed for all deposits with an initial search of 30m by 20m by 7.5m with a minimum number of 12 data, a maximum of 8 data per sector (4 sectors) and a maximum of 8 data per drillhole, expanded to 60m by 40m by 15m with a minimum of 6 data. For Vardy and Marley, a 4th search pass, 90m by 60m by 20m with a minimum of 6 data, was used for interpolating grades for any unfilled blocks within the mineral wireframes and was treated as exploration potential (relatively a very small amount of low grade material).
A density weighting factor was applied to the composites based on a regression equation utilising 5,512 fresh rock samples from a total density database of 10,662 samples. Thus density was assigned to every 1m composite and modelled in conjunction with the other elements. The oxidation zones had densities assigned via the Inverse Distance Squared method using relevant density data for each oxidation zone with a flat lying search domain. Four sub-divisions were created with hard boundaries, namely surface cover, complete oxidation, partial oxidation, fresh Fish River Fault footwall. Several search passes were used with expanding search radii and decreasing number of data points in order to interpolate density grades for the three deposits. Remaining blocks with a metal grade within the mineral wireframes but with no density value were allocated default values derived from a density data analysis of stratigraphy. All metal composite grades were density weighted prior to the grade interpolation. Some minor post modelling processing was required to complete the density data for the mineral zones and the surrounding waste rock. No check models were completed. It should be noted that over the past nine years H&SC have completed five resource estimates for Walford Creek with all changes in the estimates consistent with the additional drilling and the geological interpretation.
This has included using static and dynamic OK interpolation methods along with varying the mineral constraining (and grade interpolation) wireframes and density weighted/unweighted composite metal grades. Allocation of the classification of the Mineral Resources is derived from the search pass number associated with each block, which essentially is a function of the drillhole data point distribution. Additional considerations were included in the assessment of the classification, in particular the geological understanding, continuity and complexity of the deposit, variography, sample recovery, quality of the QAQC sampling and outcomes, density data, block model validation and potential mining method
Mining and metallurgical methods and parameters
The proposed mining method will be a combination of open pit and underground mining scenarios consisting of a truck shovel operation for the upper mineralization, and conventional underground rubber tired methods incorporating a transverse retreat up hole bench stoping method for bulk ore mining of the PY3 mineral zone. Geotechnical studies for both open pit mining and the selected underground mining method are currently at a PFS level. Geotechnical and mine planning take into account the open hydrology investigations that have been carried out. The polymetallic nature of Walford Creek and the presence a wide range of metals, equate to increasing complexity of metallurgical treatment.
Metallurgical test work relating to be production of a bulk concentrate for downstream hydrometallurgical treatment has been conducted on 5 master composites. Composites relating to Upper Vardy, Vardy PY1 Fresh, Vardy PY3 and Marley PY3 are considered representative of the resource. The Vardy DOL composite is not considered representative of that area of the resource due to the limited spread of samples. No bulk flotation test work has been conducted on Amy material. No detailed variability or mine blend bulk flotation tests have been conducted. Comminution tests were completed by ALS Metallurgy, Balcatta, WA. Comminution variability samples were subjected to SMC, Bond Ball Mill Work Index (BWI) and Bond Abrasion Index tests. Copper samples had an average BWI of 13.4 kWh/t with minor variability. Lead-zinc samples had an average BWI of 11.5 kWh/t with minor variability. Only one sample was classified as transition material and reported a moderately high BWI value of 17.5 kWh/t.
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