Wiluna Mining Corporation Limited (formerly Blackham Resources Limited) is a Western Australian based gold mining company that owns and operates the Wiluna Mining Operation.
On 20 July 2022, Michael Ryan, Kathryn Warwick, Daniel Woodhouse and Ian Francis, all Senior Managing Directors of FTI Consulting, were appointed as Voluntary Administrators of Wiluna Mining Corporation Limited.
The Deed of Company Arrangement (“DOCA”) was signed by the Company and the Deed Administrators on 28 July 2023. This agreement with creditors is an important milestone to advance the broader strategic turnaround plan and recapitalisation of the Group.
Subsequent to the conclusion of the audit and lodgement of Wiluna’s annual report for FY22, RSM Australian Partners resigned as Wiluna’s auditor and Wiluna appointed Grant Thornton Audit Pty Ltd as its auditor in January 2024.
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Summary:
The Wiluna Gold Mine, situated in the northeastern Goldfields region of Western Australia, exhibits a geologically complex setting characterized by a variety of mineralisation styles. The Archean-aged Wiluna greenstone belt, hosts key mineralised structures such as the Wiluna Main, East, and Bulletin shear zones, folded and faulted over time. These structures are hosted in the Archeanaged Wiluna greenstone belt, a sequence of volcanic and sedimentary rocks that formed over 2.7 billion years ago.
Deposit Type
The gold deposits are categorized as orogenic gold deposits, with similarities to most other gold deposits in the Yilgarn region. The deposits are hosted within the Wiluna Domain of the Wiluna greenstone belt.
The Wiluna Main shear zone is the most significant mineralized structure at the mine and hosts the majority of the gold resources. It comprises a series of interrelated, east-northeast trending shears and folds that have been steeply dipping, and contain multiple generations of quartz veins and sulfide mineralization.
The East shear zone is a parallel structure to the Wiluna Main and hosts both gold and nickel mineralization. The Bulletin shear zone, located to the east of the Wiluna Main, is a broad, northeast-trending structure that contains significant gold mineralization.
The Wiluna Main shear zone, crucial for gold resources, features interrelated east-northeast trending shears and folds with multiple generations of quartz veins and sulfide mineralisation. The East shear zone, parallel to Wiluna Main, hosts gold and nickel, while the Bulletin shear zone to the east contains significant gold mineralisation.
Mineralisation
Mineralization at Wiluna is both hosted and controlled by a north- and northeast-trending, steeply east and west-dipping sets of dextral strike-slip faults that runs through the area (interpreted to be a subsidiary structure of the larger Perseverance Fault). Formation of this structure may be due to the emplacement of the nearby granitoid bodies.
Gold mineralization is comprised of two main types. Firstly, an earlier non-refractory quartz reef hosted style and a refractory lode style. The quartz vein hosted mineralization is hosted in stratigraphic reefs emplaced along discontinuities within the stratigraphy.
The refractory mineralization is controlled by the Wiluna Fault System. The ore shoots generally plunge to the north, within an overall trend to the south with the stratigraphy. Mineralization is localized along faults at dilational bends or jogs, fault intersections, horsetail splays and within subsidiary overstepping faults. The wall rock is altered, along with the structural deformation and mineralization is asymmetric in relation to the main fault planes due to the dextral fault movement post mineralization. This forms a distinct sequential wall-rock alteration around the faults. Alteration assemblages can vary depending on the host rock, but two major alteration zones can be defined in general which include a distal chlorite-calcite and proximal sericite-silica-albite-dolomite/ankerite-arsenopyrite-pyrite zone. Stibnite is also present in a few deposits such as Moonlight, West Lode and Happy Jack.
Gold occurs at sub-microscopic particles within or in solid solution with sulfide minerals such as pyrite and arsenopyrite. Gold is not particularly associated with pyrite mineralization at Wiluna and large volume percentages do not always indicate good grade.
Arsenopyrite occurs as fine-grained (<1 mm) silver coloured rhombs, which are mostly disseminated throughout the groundmass of the wall rock. It is closely associated with Au mineralization, with high Au grade generally coinciding with high arsenic (As) concentrations. Au occurs as both solid solution and as sub microscopic particulate inclusions within the crystals.
The mineralisation at Wiluna is controlled by north- and northeast-trending dextral strike-slip faults associated with the Perseverance Fault. Gold mineralisation includes non-refractory quartz reef-hosted and refractory lode styles. The latter is governed by the Wiluna Fault System, with ore shoots plunging north and localized along faults at dilational bends, intersections, horsetail splays, and subsidiary overstepping faults.
The rock has rock undergone alteration, forming distinct sequential wall-rock alteration zones. Gold is found as submicroscopic particles within or in solid solution with sulfide minerals like pyrite and arsenopyrite. Arsenopyrite, closely associated with gold, occurs in fine-grained rhombs and indicates high gold concentrations.
Dimensions
TheWiluna deposits occur along aNS strike extent of greaterthan 3.6kmfrom9,220Nto 12,835N (local grid) and are encompassed within a 1.6km wide corridor from 9,270E to 10,900E. Drilling extends to a vertical depth of approximately 1,600m and the mineralisation has been modelled from surface to a depth of approximately 1,200m below surface.
Lodes vary in strike between 330 and 045 degrees, with most lodes striking between 000 and 015 degrees. The dip of each lode varies from 60° to sub-vertical.
Wiluna Tailings
The Wiluna tailings consist of tailings produced during previous operations that are stored in pit voids or tailings storage facilities. This included all the pit voids as well as TSF West, TSF H, TSF C Upper and TSF C Lower.