The SKO is located within the Eastern Goldfields Superterrane and the 842sqkm tenement package traverses across the Coolgardie, Ora Banda, Kambalda and Boorara Domains. Mineralisation is associated with the greenstone sequence that consists of a mafic to ultramafic volcanic succession that is overlain by an intermediate to felsic volcano-sedimentary sequence.

The structural architecture is dominated by NNW-trending crustal scale shear zones including the Boulder-Lefroy, Zuleika, Abattoir, Boorara, Kunanulling, Binduli and Spargoville structural corridors. These structural corridors are the key influencers of mineralisation in the greater Kalgoorlie district and to date have yielded a mineral endowment of over 100Moz.

Mineralisation styles within the district is a combination of Orogenic and Paleoplacer style deposits. Mineralisation is controlled by Brittle-Ductile shear zones, 1st and 2nd order structures that act as Lithostratigraphic contacts (as fluid conduits) through late stage brittle structures. Mineralisation is also associated with fertile sulphidised intrusive porphyries and layered mafic intrusions with chemically reactive lithologies that provide a rheological contrast.

Stratigraphy for the Ora Banda and Kalgoorlie Domains is relatively well-known and comprises (from stratigraphically lowest) a lower basalt unit, komatiitic to high-magnesian basaltic rocks, an upper basalt unit and overlying felsic volcanic-sedimentary units. Con ........

The South Kalgoorlie Operation (SKO) includes the HBJ underground mines (HBJ).

The HBJ gold deposit is mined by a top down long hole open stoping (LHOS) method. This mining method was selected to minimise the impact of mining induced stress on the underground operations through the use of geotechnical driven mining sequences at the same time as increasing the extraction rates.

The orebody is accessed through the hanging wall by a central access from which north and south drives are developed.

An initial porphyry ore lode is encountered and developed. Further out in the footwall there is an ore unit sitting against an ultra-mafic contact. Development of the 2401 (ultra-mafic) lodes are delayed as late as possible but just in time for stoping extraction. The priority is placed on developing the western lode followed by a step over to the eastern lode for both the northern and southern extents. Once the stoping panels are mined back towards the main access, development from the access to the north and south can be completed thus completing development.

The stoping front retreats from both northern and southern extents towards the access following a top down LHOS method leaving rib pillars. Additional sill pillars are also planned on the eastern lodes where the ultra-mafic contact is present to ensure the safe extraction of the ore whilst minimizing the potential for footwall failure. The dimensions of the stopes vary depending on what ........

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