On 29 June 2023, Catalyst Metals acquired 100% of the ordinary shares of Superior Gold Inc., a Canadian-based gold producer that owns 100% of the Plutonic Gold Operations located in Western Australia, through its wholly-owned subsidiary Billabong Gold Pty Ltd.
- subscription is required.
Summary:
Deposit Type
The Plutonic Gold Mine deposits are Archean Greenstone gold deposits. The gold mineralisation is predominantly structurally controlled occurring in a variety of stratigraphic settings, mainly associated with replacement-style lodes and stockwork veining within a wide variety of host rocks ranging from ultramafic and mafic volcanic rocks, metasediments, felsic intrusive, volcanoclastic units, and banded iron formations.
In the Hermes Gold Mine and BBJV Projects there are two broad mineralisation styles (Outhwaite, 2013) referred to here as the Peak Hill Type and the Bryah Type.
The Peak Hill Type gold deposits are hosted in rocks that are generally highly deformed (four or more fold events) and metamorphosed (up to amphibolite facies), generally represented by the Peak Hill Schist Formation. Mineralisation is early in the paragenesis, (syn- to post-D1 isoclinal folding) with folded mineralisation commonly observed. Previously mined examples include Peak Hill Main/Five-Ways, Mt Pleasant, Jubilee, Wilgeena and St Crispin. The Hermes deposits may be examples of mineralisation that belongs in this category.
The local controls on this deposit class are difficult to identify, because of the effects of strong, postmineralisation deformation, and probable remobilisation of Au.
Mineralisation
Plutonic
The Plutonic Gold Mine Mineral Resources mined and unmined lie with a surface area of approximately 10 km east-west by 5 km north-south. The historical Plutonic Main Pit is approximately 1.5 km long by 800 m wide by 200 m deep. Current Mineral Resources being mined at the Plutonic Gold Mine including the Main Pit, Indian, Indian Extension, Baltic and Baltic Extension lies in a semi-continuous mineralised trend that extends from the base of the open pit 1.7 km down plunge (880 m in elevation) and mineralisation is 1-3 m thick but individual mineralised pods have a short range (generally <30 m).
The Cortez-Area 134-Timor zone extends approximately 1.2 km north-south, by 1.0 km east-west.
The main style of gold mineralisation (Plutonic brown-lode) typically occurs as thin (~1 – 3 m wide) lodes that consist predominantly of quartz-biotite-amphibole-titanite-epidote-carbonate-tourmaline-arsenopyritepyrrhotite ± chalcopyrite ± scheelite ± gold. Visible gold is considered to have occurred at a late-stage during the evolution of the deposit as it is largely undeformed and overprints most, if not all, of the minerals and fabrics. It is typically associated with thin, discontinuous quartz-calc-silicate veins within the brown-lodes. Where these gold-bearing zones are well developed, they tend to be near-parallel to the stratigraphy as marked by the rare metasedimentary horizons and to the dominant foliation, which is also typically parallel to metasediment horizons. Geochemistry suggests that these lodes developed on the boundary between mafic units or are focused along or adjacent to minor metasedimentary units within the Mine Mafic unit. Lodes may be rich in arsenopyrite or pyrrhotite, and while arsenopyrite is a good indicator of mineralisation, it may not be present in all mineralisation.
Mineralisation at Plutonic is separated into four distinct styles:
• Replacement “brown” or “Plutonic” lodes (which contain the bulk of the gold)
• Replacement “green lodes”
• “Invisible lodes”
• Dilation high angle quartz veins
The Plutonic “Brown lodes” are characterised by a series of moderately-dipping to very flat-lying, stacked, banded replacement-style lodes, individually up to five metres wide, that are hosted within ductile mylonitic shear zones, oriented slightly oblique to the main stratigraphic contacts. Hydrothermal alteration during midto lower-amphibolite facies conditions has resulted in a zoned hydrothermal assemblage consisting of plagioclase–biotite-quartz-amphibole-titanite-carbonate-arsenopyrite-pyrrhotite-tourmaline-muscovite-pyritescheelite-gold-sphalerite. The replacement style lodes are restricted within the Mine Mafic unit, preferentially within the Upper Mine Mafic unit, sub-parallel to primary lithological contacts. Arsenopyrite associated with gold mineralisation at Plutonic is subtly zoned with respect to gold, antimony, and arsenic abundance. Within individual grains of arsenopyrite there is a negative correlation between gold and antimony (core). Arsenic abundance generally increases from core to rims, indicating increasing temperature. There is a conspicuous lack of quartz veining associated with mineralisation except where the ductile shear zones have intersected early quartz veins subsequently deforming them. Wall rock alteration adjacent to the lodes is very narrow, often confined to 20 cm to 30 cm. Mass balancing of the lodes against the host amphibolite indicates a general SiO2 loss of seven to ten percent and volume decreases of up to 30%.
Plutonic “Invisible Lodes” are less common than the Plutonic Brown and Green lodes. These are more abundant in the Zone 19 area. They do not occur within ductile shear zones but are developed predominantly within the upper five metres of the Upper Mine Mafic unit within the hornblende amphibolite. Gold is finely disseminated throughout an apparently unaltered groundmass in which minor pyrrhotite and pyrite are associated. There is no biotite, albite or arsenopyrite alteration. In higher-grade examples, free gold is sited within quartz-carbonate veins oriented parallel to overprinting local penetrative fabrics with no associated sulphides or visible alteration halo.
Quartz vein hosted mineralisation is the least abundant form of mineralisation and is mainly located close to the Quartz Hill Thrust which separate the Overthrust mafic to the Hangingwall Ultramafic or proximal to high angle dolerite dykes where the dykes cut replacement lodes. Above the Quartz Hill Thrust, gold is associated with pyrrhotite-pyrite-sphalerite-galena in quartz veins and unlike the shear zone-related gold mineralisation at Plutonic there is an absence of arsenic. Immediately below the Quartz Hill Thrust, high grade gold mineralisation is present in close proximity to Brown lode mineralisation. Coarse gold is observed within quartz veining and silica flooding. The gold overprints the Brown lode layer parallel fabric, possibly indicating a remobilised origin for this coarse free gold.
The mineralisation of the Plutonic Gold Mine is truncated to the south by a local structure called the MPS Fault, a minor fault splay off the major regional structure known as the MMR Fault.
Hermes
At Hermes the Hawkeye, Trapper, Klinger, Winchester & Blake deposits are sub-parallel, northeast trending, mineralised zones. Mineralisation at all deposits is typically associated with quartz veins at or near the sheared contact of mafic amphibolite footwall and hangingwall quartz-biotite-sericite schists. Graphitic schist occurs to a minor extent on the hangingwall and footwall sides of the mineralisation at Trapper, Klinger and Blake. The base of strong oxidation varies from 20-30 m vertically below surface at Hawkeye & Winchester, and from 25-45 m at Trapper, Klinger & Blake. Transition to fresh rock occurs at approximately 30-50 m and 40-65 m, respectively.
In general, the mineralised quartz veins, foliation and relict bedding are steeply NW-dipping to sub-vertical in both the Hawkeye and Trapper deposits and high-grade shoots are interpreted to plunge shallowly to the north within the mineralised plane.
Hermes South
Gold mineralisation occurs within a predominantly metasedimentary sequence of the Proterozoic Peak Hill Schist and mafic units. The Peak Hill Schist comprises quartz-sericite schist and quartz-muscovite schist and is located on the south-western extreme of the Marymia Inlier.
Mineralisation at Hermes South is associated with the development of strong linear fabrics and quartz veining dipping at 65 degrees to the south in fairly predictable and consistent zones.