The Kanowna Belle mine and associated infrastructure is located on Mining Leases M27/92 and M27/103. The Mining Leases and most of the surrounding tenement holdings are 100% owned by Northern Star (Kanowna) Pty Limited, a wholly owned subsidiary of Northern Star Resources Limited.
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Summary:
Kanowna Belle is located within the Kalgoorlie Terrane, one of a number of elongate, broadly NNW-SSE striking structural-stratigraphic late Archaean greenstone terranes of the Eastern Goldfields of Western Australia. The Kanowna Belle gold mine is located close to the centre of the NNW-SSE trending, greenstone-dominated Boorara Domain, the eastern most subdivision of the Kalgoorlie Terrane.
The Kanowna Belle deposit can be categorised as a refractory, Archean lode-gold type deposit. The orebody is comprised of several ore shoots, including the large Lowes Shoot, and several smaller lodes including Troy, Sims, Hilder, Hangingwall and Footwall shoots controlled by sets of structures of various orientations oblique to Lowes. 600m west of the main Lowes lode, are the Velvet and Joplin lodes, that are considered to be part of the KB mineralised system.
Mineralisation is mainly hosted within a large porphyritic granodiorite body (Kanowna Belle Porphyry) that has intruded a sequence of sedimentary and volcaniclastic rocks. A zone of intense structural disruption (Fitzroy Shear Zone) separates the deposit into hangingwall and footwall structural domains and is the primary control on gold distribution. Gold mineralisation is locally associated with quartz-carbonate stockwork veins, breccia zones, sulphide-quartz-carbonate stringers and sheeted vein arrays. The generally tabular enveloping surface to mineralisation dips steeply to the south, has a high plunge to strike ratio and remains open at depth.
Lowes contains some 80% of known gold mineralisation and strikes ENE, dips steeply SSW and plunges steeply SW. The Lowes shoot has a strike length of 500m, width between 5 m and 50 m and down-plunge extent greater than 1,250 m. The overall steep SE plunge is interpreted to reflect the intersection of D1 (ENE) and D2 (NW) structures.
Kanowna Belle is one of the few known refractory pyritic orebodies in the Yilgarn Craton. Gold in the Kanowna Belle deposit occurs mostly as fine-grained (<10 µm) inclusions in pyrite or as very fine-grained gold located in arsenic-rich growth zones in pyrite. Typical ore assemblages contain 0.5% S to 1.5% S and 40 ppm As.
The Kanowna Belle deposit is hosted by sedimentary volcanoclastic and conglomeratic rocks which are separated into hangingwall and footwall sequences by a major, steeply SSE dipping zone of structural disruption. This structure represents the product of at least three distinct stages of deformation, comprising the Fitzroy Mylonite, the Fitzroy Shear Zone and the Fitzroy Fault, which have produced clear structural overprinting relations. Importantly, this structure has localised emplacement of the Kanowna Belle porphyry which hosts at least 70% of known mineralisation. Localisation of high grade mineralisation and most intense alteration around the composite structure emphasises its importance for acting as the major plumbing system for fluids.
Formation of the Fitzroy Mylonite and Fitzroy Shear Zone are interpreted to have occurred during regional south-to-north D1 thrusting. A switch in far-field stress axes to the approximately ENE-WSW D2 orientation caused reactivation of the Fitzroy Shear Zone, resulting in sigmoidal folding of pre-existing structures and formation of a shallow lineation associated with sinistral transcurrent shearing. The Kanowna Belle porphyry crosscuts fabrics associated with the D1 Fitzroy Mylonite and Fitzroy Shear Zone and is in turn overprinted by S2.
In the vicinity of the Velvet and Joplin lodes, five types of intrusions have been identified - two types with Kanowna Belle Porphyry-like compositions, the Panglo Porphyry, hornblende porphyry and a lamprophyre dyke of intermediate composition. The latter is the principal host to gold mineralisation at Velvet, with Joplin mineralisation focused along structural features at the contact or within the Panglo Porphyry. The intrusions, intrude the thick-bedded, dacitic volcaniclastic breccia known as the Grave Dam Grit. Both lithological domains and the hanging wall intrusions are truncated to the west by an erosional unconformity at the base of the Panglo Basin. Polymictic conglomerate and coarse-grained lithic arenite units of the Panglo Basin are correlated with the ~2650 Ma Kurrawang Formation.
Dimensions
The near-surface weathered portion of the Kanowna Belle deposit shows significant gold depletion to at least 35 m above an undulating supergene “blanket” horizon. This mineralised supergene “blanket” had pre-mining plan dimensions of 600m strike x 250m across strike and a thickness of between 1 m and 10 m.
The main Lowes shoot has a strike length of 500 m, width of 5 m to 50 m, and a down-plunge extent greater than 1,250 m.
Hanging wall shoots have a maximum strike of 240 m, width of 2 m to 10 m and a current down plunge extent of no more than 800 m.
Footwall shoots have a maximum strike of 240 m, width of 2 m to 20 m and a current down plunge extent of no more than 700 m.
Velvet lodes have a strike length of 50-400 m, width of 2-30 m, and a down-plunge extent of approximately 500 m.
Joplin lodes have a strike length of 50-800 m, width of 0.5 m to 5m and a known down dip extent of 150-350 m.