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:
Geological Setting
The Wiluna Gold Mine is located in the northeastern Goldfields region of Western Australia. The geology of the mine consists of a complex structural regime that has resulted in multiple mineralization styles, including orogenic gold deposits.
The main mineralized structures at Wiluna include the Wiluna Main, East and Bulletin shear zones, which have been 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.
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.
Deposit 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 (Lambert-Smith, n.d.).
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 (Apex Gold PTY LTD, 2011).
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 (Apex Gold PTY LTD, 2011). 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 (Apex Gold PTY LTD, 2011).
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 (Lambert-Smith, n.d.).