Summary:
The Mandilla Gold Project (Mandilla), is includes the satellite Feysville deposits, located near Kalgoorlie in the Eastern Goldfields.
Astral now holds of the Spargoville Project, which includes approximately 144km2 of primarily contiguous tenure to Mandilla. The PFS does not contemplate any contribution of ore from Spargoville but does utilise the Spargoville tenure for locating infrastructure and the associated operational footprint.
Mandilla
The Mandilla project is located within the south-west of the Lefroy Map Sheet 3235. It is situated in the Coolgardie Domain, on the western margin of the Kalgoorlie Terrain within the Wiluna-Norseman Greenstone Belt, Archaean Yilgarn Block.
The Mandilla project is located along the southern margin of M15/96 extending into M15/633 and E15/1404 further to the southeast. It comprises an east and west zone, both of which are dominated by supergene mineralisation between 20 and 50 metres depth below surface. Only the east zone shows any significant evidence of primary mineralisation, generally within coarse granular felsic rocks likely to be part of the granite outcropping to the east. Minor primary mineralisation occurs in sediments.
Gold mineralisation appears as a series of narrow, high grade quartz veins with relatively common visible gold and grades over the width of the vein of up to several hundreds of grams per tonne. Surrounding these veins are lower grade alteration haloes. In places, these haloes can coalesce to form quite thick zones of lower grades (tens of metres). The mineralisation manifests itself as large zones of lower grade mineralisation from ~0.5 – 1.5 g/t Au with occasional high grades of +5 g/t Au over one or two metres.
Vein density increases from 1 per metre to 2-3 per metre in the core of the mineralised zones, with individual veins up to 15 cm thick, but typically 1-10 cm in thickness. Visible gold is commonly observed within and on the margin of quartz veins, and rarely observed in wall rock. Individual grains of gold, or small aggregates of grains are observed and can be coarse grained over 1 mm in size.
In addition to the granite-hosted mineralisation, a paleochannel situated above the granite/sediment contact contains significant gold mineralisation. The channel is about two kilometres in length, up to 50 metres wide, but only a few metres thick. Gold is contained within quartz sands and gravels, although is not consistently distributed throughout the paleochannel.
The Project contains four discrete deposits that are separated spatially and with differing geological characteristics:
• Theia is the main deposit and contains 80% of the gold ounces. It extends over a strike length of 1600 mN, is about 150 to 250 mE wide and extends to 350 m below the surface. The overall mineralisation at Theia strikes to the north-west at about 330°, with a sub-vertical dip. However, extensive structural logging from diamond core drilling of the quartz veins within the mineralised zones shows that majority dip gently (20° to 30°) towards SE to SSE (130° to 160°).
• The Iris deposit contains approximately 9% of the gold ounces of the Project and has a similar trend and orientation as Theia. The mineralisation extends over a strike length of 600 mN, is about 200 mE wide and extends to 200 m below the surface.
• Eos, representing approximately 3% of the total gold ounces, is at the southern boundary of the project and comprises paleochannel mineralisation that extends over a strike length of 300 m, is about 75m wide and up to 20 m thick and is 40 to 50 m below surface. Recent deeper drilling has also defined a zone of fresh rock mineralisation at Eos.
• Hestia is on the western edge of the Project and contains approximately 8% of the total gold ounces - the mineralisation extends over a strike length of 800 m and up to 200 m below surface. The stacked lodes are between 2 m and 10 m thick, and dip steeply (75°) towards the WSW (250°). The mineralisation style is very different to the other deposits and is associated with a shear zone adjacent to a mafic/sediment contact.
Feysville
Gold mineralisation within the area is strongly associated with sheared contacts between porphyry units and the mafic country rock with multiple mineralisation styles present over the project. There are a number of historical gold workings on the Project.
Geology is a subvertical feldspar porphyry swarm intruding into volcaniclastically derived andesitic conglomerates, trending NW with a hanging wall ultramafic (UM) unit. Contacts between conglomerates and porphyries are intrusive however structures have preferentially sheared the contacts possibly a result of rheological contrast between the units. The sheared contacts dip steeply to the west.
Mineralisation at Think Big is predominantly found within the volcaniclastic derived conglomerate hosts between sheared porphyry bodies. The strongest tenor is on margins of porphyries between closely spaced porphyries - where the conglomerate is moderately to intensely sericitised and albitised. Porphyries appear to be completely barren - no sulphides present or even anomalous mineralisation.
A series of stacked lodes have been interpreted steeply dipping to the south-west at approximately 70° toward 230° with a total strike length of 500m. The average width of each lode is between 2 – 8 m, with a total width approximately 110m. These are overlain by a supergene blanket. The wireframes generally envelope 0.4 ppm Au but are allowed to 0.20 ppm Au in many areas to connect the interpreted continuity of the sub-vertical lodes.
At Kamperman, the mineralisation appears to be in proximity to a NE trending fault, first interpreted by aerial magnetics (truncation of a strongly magnetic ultramafic body), and later supported by drillhole log interpretation and multi-element lithogeochemistry. The fault also happens to mark a boundary between different styles of mineralisation. The fault could either be offsetting mineralisation or primarily related to gold mineralization. Literature suggests the fault may be related to D4 deformation and hence synchronous with gold mineralisation.
Drilling at Kamperman has delineated gold mineralisation over 450m of strike length. Gold occurs within several different styles of mineralisation through the prospect including the following:
• Pyrite+-pyrrhotite+-chalcopyrite+-magnetite rich zone hosted in chloritic “mafic” unit (Southern Lode),
• High grade gold occurring along lithological contacts,
• Quartz veining (Northern Lodes),
• Pyrite bearing silicified feldspar porphyry,
• Mineralized minor sheared zones and
• Supergene blanket at saprock-joint oxidised horizon.
Spargoville
Granitoid intrusions associated with syntectonic domains are found in the Spargoville area, including the Depot Granite and the Widgiemooltha Dome. Domed structures associated with granitoid emplacement are observed in the St Ives camp, with deposition of the Merougil Beds and emplacement of porphyry intrusions occurring during extensional deformation. Gold occurrences associated with the Zuleika and Spargoville. The Spargoville project consists of the Wattle Dam, Eagles Nest, Larkinville, Hilditch and 5B projects.