Summary:
The Warrawoona Project leases lie within the Warrawoona Group, one of the oldest greenstone belts within the Pilbara Craton. Composed largely of high-Mg basaltic lavas with lesser tholeiite, andesite, sodic dacite, potassic rhyolite, chert and banded iron formation (BIF), all metamorphosed to greenschist facies, the Warrawoona Group is sandwiched between the Mount Edgar batholith to the north and the Corunna Downs batholith to the south.
Gold occursin quartz veins and stringersin the Klondyke, Copenhagen and Fieldings Gully Shears and mineralisation is associated with quartz-carbonate-sericite-pyrite alteration. Quartz veins and stringers are generally approximately parallel to the predominant shear direction. The bulk of the gold mineralisation is hosted in strongly sericitised and sheared mafic units with thin chert bands marking probable stratigraphic breaks.
Over some abandoned workings gold mineralisation is associated with copper as indicated by the presence of malachite and other copper carbonates.
The Warrawoona Project is located within the East Pilbara Terrane of the Archean Pilbara Craton in Western Australia. The East Pilbara Terrane is characterised by large, dome-shaped composite granitic complexes wrapped by greenstone belts. The granite-greenstone terrane is unconformably overlain by little-deformed volcanic and sedimentary rocks of the Hamersley Province. The Klondyke deposit is hosted within the Warrawoona Group, a package of high-Mg basalt, komatiite and felsic volcanic units, that outcrops throughout much of the East Pilbara Terrane and is one of the more important hosts to Au mineralisation.
The Warrawoona Project mining leases lie within the Warrawoona greenstone belt, a highly tectonised package of rocks sandwiched between the Mount Edgar batholith to the north and the Corunna Downs batholith to the south. Episodic and long-lived diapirism during intrusion of the batholiths has resulted in pervasive deformation throughout the greenstone belt. In the eastern part of the tenement package between the batholiths, the greenstone belt is as narrow as 1.5km wide. To the west, the belt fans out to form a series of narrow, widely spaced mylonite zones with comparatively undeformed rocks between. Gold mineralisation is closely associated with the mylonite zones and with thin chert layers (such as Kopcke’s leader at Klondyke) which are interpreted to represent stratigraphic breaks and appear to have acted as a focus for mylonite development, hydrothermal alteration and gold mineralisation.
Klondyke Mineralisation
Gold mineralisation at Klondyke is concentrated around the Klondyke shear and is associated with quartz-carbonate- pyrite veins within sericite/fuchsite-carbonate-altered and intensely deformed mafic schists. The shear, and the veins, are sub-vertical or dip very steeply to the south-southwest and strike at about 110°. A 10–50cm-wide black chert band, referred to as Kopcke’s leader by the early miners, is exposed within the altered mafic schists. Kopcke's leader is persistent both laterally and at depth and provides a good indication as to the location of mineralisation along strike and down dip. Rock units and quartz-carbonate veins display strong egg-carton boudinage and are marked by a very strong sub-vertical mineral/intersection lineation.
One of the most prominent features of the sections through the ore zone is the profound asymmetry of the alteration, with fuchsite alteration in the footwall (northern side) and sericite alteration in the hangingwall. The alteration asymmetry implies that Kopcke’s leader is located at the contact between two different mafic units: a high-Cr (high-Mg) mafic unit below the chert in which fuchsite is developed and a low-Cr mafic unit above the chert in which sericite is developed. This contact marks an erosion surface with subsequent clastic deposition during a hiatus in volcanism. The Kopcke’s leader chert unit has a remarkable strike and depth continuity over the resource area, providing a strong marker unit to guide exploration and resource drilling.
Dimensions
At Klondyke (KL), mineralisation has a sub-vertical dip as and ranges from 2m to 20m thick. The resource extends over approximately 5.1 km of strike and extends to a vertical depth of over 500 metres. The St George Trend mineralisation has a sub-vertical dip and ranges from approximately 1 m to 10 m thick with an approximate strike of 1.6 km extending to a vertical depth of approximately 200 m.
The Resource is currently considered open along strike and down dip. Copenhagen Mineral Resources have a strike length of approximately 250 m with a steep southeasterly plunge and a steep northerly dip. Mineralised lodes range from 2m to 10m thick and extend to a vertical depth of 200m. Fieldings Gully mineralisation has a sub-vertical dip and ranges from 2m to 10m thick. The resource extends over approximately 440m of strike and extends to a vertical depth of 140m.