Bellevue Gold Project

The Bellevue Gold Project

High Grade Gold Discovery- 2.3 Moz @ 10.0 g/t gold Global resources, including 0.86 Moz @ 11.6 g/t gold of Indicated Category resources

The Bellevue Gold Project (Bellevue Gold 100%) A Forgotten Treasure

The Bellevue Gold Project is situated 400km north west of Kalgoorlie in Western Australia and sits within a high-grade gold and nickel district on the prolific Wiluna-Norseman gold belt. Bellevue is within 100km of numerous producing goldmines and in close proximity to world-class nickel mines. The Leinster area is a world class mining district host to with in excess of 40 Moz of endowment.

The Bellevue Project covers new discoveries adjacent from the mine that historically produced 800,000 ounces at 15 g/t, closing in 1997. The new discoveries are from surface and have significantly extended the footprint of the Bellevue system both along strike and at depth.

Bellevue Gold Project High-Grade Resource Inventory

 

Included in the Indicated Resource is a spectacular higher-grade core of mineralisation totalling 480,000oz at 15.5g/t gold Indicated hosted in the Viago and Deacon Main Resource areas. This mineralisation is within a few hundred metres of existing underground development and contains consistent high-grade mineralisation that will be targeted in the early mine life at the project. This area is summarised in figure 1. Over half of the current Indicated and global Resource is contained in the Viago and Deacon Lodes with both lodes open for Resource growth in Indicated and Inferred categories with further drilling.

Figure  – Inspecting the decline at Bellevue in advance of re-entry and refurbishment June 2020

The Bellevue System is metallurgically very simple with exceptional conventional gravity and CIL recoveries both from the historic mine and recent testwork completed by Bellevue Gold Ltd on the new discovery areas. Total conventional leach recoveries averaged 97.8% with a gravity component up to 91.7%.

Bellevue Gold is currently re-establishing access to the historic underground which has been dewatered and will provide a platform for future underground drilling and  access to new development. The existing decline is within a few hundred metres of the high grade core at Viago and Deacon.

There is significant potential to expand the global resource with further exploration drilling from both surface and from underground and the company is committed to an aggressive exploration budget at the project.

High Grade Gold at the Bellevue Gold Project

Since restarting exploration at project, three significant new high-grade gold discoveries have been made, all close to existing historical development.

Deacon Lode

The Deacon Lode is a significant and new discovery located 400 m to the east of the Bellevue Lode. The discovery has been tested for 2.2 km of strike length and remains open in every direction. Previous results from Deacon include:

 

1refer ASX 27th of May 2020, 2refer ASX 10th of September 2019, 3refer ASX 5th of August 2019, 4refer ASX 24th of February 2020, 5refer ASX 2nd of October 2019. The Company confirms that it is not aware of any new information or data that materially affects the information included in the relevant announcements.

Figure  – High-grade drill core from the Deacon Lode at the Bellevue Gold Project- Interval assayed 4m @ 62.4 g/t gold

Viago High Grade Lode

Since restarting exploration at project, three significant new high-grade gold discoveries have been made, all close to existing historical development.

The Viago Deposit was discovered in June 2018 during drilling targeting offset lode positions of the Bellevue Mine. High-grade gold mineralisation in the Viago Lode has now been extended to a total strike length of 1,500 metres representing a doubling of the previous resource envelope (750 metres of strike length). The Viago Lode mineralisation remains completely open along strike in both directions.

1refer ASX 18th of February 2020, 2refer ASX 19th of November 2019, 3refer ASX 21st of May 2019, 4refer ASX 9th of October 2018, 5refer ASX 2nd of October 2019, 6refer ASX 17th of July 2019, 7refer ASX 2nd of October 2019, 8refer ASX 30th of May 2018.  The Company confirms that it is not aware of any new information or data that materially affects the information included in the relevant announcements.

Tribune Lode High Grade Discovery

The Tribune Lode was discovered by Bellevue Gold in late 2017 in shallow RC drilling. The lode is located 400m west of the Bellevue Mine and strike has now been tested for 1,300m and remains open along strike and at depth.

1refer ASX 18th of February 2020, 2refer ASX 7th of February 2018, 3refer ASX 21st of May 2019, 4refer ASX 23rd of March 2018, 5refer ASX 26th of August 2018, 6refer ASX 14th of March 2019, 7refer ASX 21st of May 2019, 8refer ASX 15th of July 2019.  The Company confirms that it is not aware of any new information or data that materially affects the information included in the relevant announcements.

Regional Geology

The BGP sits within the Yakabindie domain of the Agnew-Wiluna Greenstone Belt of the Eastern Goldfields Super Terrane, on the Sir Samuel 1:250,000 map sheet. The Yakabindie domain consists of the layered Kathleen Valley gabbro (dated at 2.736Ga – Black et al 2003) overlain by the tholeiitic Mt Goode basalt sequence. A mixed sequence of metamorphosed ultra-mafics and felsic volcanics overly the Mt Goode basalts and in turn sit underneath the unconformable boundary of a late basin conglomeratic sequence (the Jones Creek conglomerates). A simplified stratigraphic column of the Bellevue area is shown in Figure 2. The domain is bounded to the east by the crustal scale Keith-Kilkenny Shear (Perseverance Fault) and bounded by the Ida Lineament to the West (Figure 2). The Bellevue Gold Deposit is proximal to the Keith-Kilkenny Shear and the regional scale Waroonga and Miranda shear zones.

The Bellevue area stratigraphy broadly correlates to that of the Kalgoorlie terrane, with a lower mafic sequence (Kambalda sequence), an upper metasedimentary sequence (Kalgoorlie sequence) which is unconformable to the  mafics below, and a late basin sequence, which is separated from the Kalgoorlie sequence with an unconformity. The Mt Goode mafic sequence is part of the lower mafic sequence of the Eastern Goldfields super terrane and equivalent to the Kambalda sequence of the Kalgoorlie Terrane (Black et al 2003).

The belt has a complex deformation history with structural reactivation and switching kinematics, best summarised by Jones et al 2019:

  • D1: Progressive extension and basin formation. Ongoing extension leads to exhumation of granites and creation of unconformable sub-basins with recumbent folding proximal to sheared margins.
  • D2: Largely E-W compression, reactivates extensional structures and establishes thrust and fold architecture with NNW striking shear zones and fold axis
  • D3: Progressive NW-SE compression leading to the development of sinistral lateral escape structures, often nucleating on the D2 fold axis. Continued compression leading to the locking up of lateral escape structures and the establishment of a conjugate architecture of thrust faults which cross-cut earlier sinistral structures. These structures are coincident with mineralisation in the Bellevue area and are possibly coeval with the regional 2.645 –2.63Ga Gold Event (Czarnotta et al 2010).
  • D4: Progressive NE-SW compression leads to post-mineralisation SE and NW dipping planar faults and minor shears.
  • D5: Orogenic collapse, planar faults with steep slickenlines.

Figure  – Regional Geology of the Bellevue area (left) with a simplified stratigraphic column on the right.

Figure  – Geology of the Bellevue area

Local Geology

The Bellevue gold deposit lies to the west of the Miranda shear, a dextral strike-slip shear with an eastern block-down component. It separates the Mt Goode sequence from the younger felsic volcaniclastics and ultra mafics and also appears to be a Riedel splay between the transpressional Keith-Kilkenny and the Ida Lineaments.  The Project is located in an area of greenstone belt constriction, and associated structural complexities, with evidence of multi-scale shear zones and controlling faults coupled with a long and complex intrusion history. To the west, lie high-Ca granites and granitic gneiss. The major geological features in the Bellevue area are shown in Figure 3.

The surface geology of the Bellevue Project area is readily separated into two areas; subcrop to outcrop in the north and transported alluvium/colluvium in the south. The outcrop consists of Archean mafic lithologies in a range of low hills with thin residual soils that have a depth of weathering between 10 to 30 metres. Shallow Tertiary and Quaternary colluvium and alluvium can be found along the project area which sits immediately north of Lake Miranda to the south, as part of the paleo-drainage system. Lake Miranda is a playa lake system dominated by gypisferous dunes, lunettes and sandy, clayey, evaporitic lake floor deposits.  Pleistocene red sand sheets and dunes form remnant deposits to a few metres thickness on the lower, western flanks of the hills. This sand/silt material has been reworked into the lake floor deposits with the evaporites.

The main Bellevue lode can be traced at surface along a strike length of over 1,500 metres. The hosting shear zone strikes north-south and dips from 45° to 85° west. Further gold mineralisation occurs in hanging wall and footwall structures both sub-parallel to the Bellevue Lode and in conjugate low angle mineralised shears. The Archean geology around the mine is dominated by Mt Goode sequence, a suite of tholeiitic mafic basalts and dolerites which range in grain size from fine to coarse. Pillow and flow-top breccias have often been recognized by geologists. Minor basalt with megacrystic plagioclase has been mapped locally, with minor sediments and felsic intrusives (felsic porphyry and granite dykes). The tholeiites strike north to north-east and dip steeply to the west and north west. Stratigraphy at Bellevue is overturned, and the direction of younging is to the south east. 

Metamorphic grade of the area is upper greenschist to amphibolite grade however the strain distribution is heterogeneous with mylonites (greenschist-amphibolite facies metamorphism) developed within shear zones bounded by relatively undeformed tholeiites (greenschist facies metamorphism).

Local structure

Locally, a broad antiformal architecture was established under E-W compression during the D2 compressional event, in conjunction with the reactivation of earlier extensional structures. Ongoing, largely NW-SE compression in D3 established NNW striking sinistral shear structures, dipping steeply to the NE, including the Bellevue West, Highway and Yakabindie Shear Zones which are the most prominent mappable features in the project area.

It is thought that ongoing NW-SE compression under D3 lead to the ‘locking-up’ of these sinistral shear zones and the establishment of a conjugate architecture of thrust faults, which cross-cut the earlier sinistral structures. These structures are coincident with mineralisation in the Bellevue area and are possibly coeval with the regional 2.645 –2.63Ga gold event (Czarnota et al 2010). A later relaxation event has resulted in normal reactivation of the D3 shears. This event has important controls on mineralised shoot geometries. All structural features are cross-cut by later brittle faulting which segments mineralisation throughout the deposit area (Brotherton & Wilson, 1990).

In the Bellevue mine area, Bellevue geologists have subdivided the Mt Goode sequence into separate ‘panels’ referred to as, from west to east: the Waroonga Corridor, the Western Corridor, the Bellevue Corridor and the Vanguard Corridor. These corridors are separated by the north – north west trending, steeply north east dipping, D3 Sinistral Shear Zones, the West Shear, Highway Shear and Canberra Shear (refer to Figure 4 below)

Figure:  simplified geology of the BGP showing surface projections of lode geometries, major lithological subdivisions and major structural features.

Figure  – Diagrammatic representation of the Bellevue Structural Framework looking north.

Gold mineralisation in the area is structurally controlled and is generally associated with N-NNW trending, West dipping shear zones (dipping about 60 degrees), of 1 to 20 metre thickness. The exception is the Viago Lode, which is a low angle shear zone at 500 metres below surface which gently plunging to the South as well as the Westralia and Vanguard lodes, which dip about 45 degrees to the north east.

Locally, gold mineralisation is associated with three main structural orientations, most probably belonging to the same deformation event, including:

  • 50-85° west dipping north south striking high angle reverse mineralised shears containing a fabric indicative of ductile deformation, e.g. Bellevue, Southern Belle, Tribune and Deacon Lodes.
  • 50-70° east dipping north north-west striking mineralised ductile shears e.g. Westralia and Vanguard reefs.
  • Shallowly east dipping (10-20o), shallowly (20o) southern plunging ductile shear zones eg: Viago, Vlad and Mavis Lodes

The mineralisation at the Bellevue Mine was characterised by bonanza grade mineralised shoots that contained the bulk of the mined metal within the overall lode system These shoots generally had an up-dip component of approximately 20-40 metres and a significant greater down plunge component of several hundred metres. Ore shoots occur within dilational zones of the shear structure, with gold mineralisation being present within massive or disseminated sulphides in quartz breccias. An example of these shoot geometries, repeatability and predictability are shown on the Tribune long section

The established shear lodes and veins have been deformed by a post-mineralisation, normal re-activation of the mineralised structures, resulting in the mineralised veins being folded and boudinaged into 10-20 metre wide shoots. Lineations and fold axes plunge between 10 to 20 degrees to the south, parallel to the orientation of the high-grade shoots. Semi-massive to massive sulphide minerals (predominantly pyrrhotite and chalcopyrite) have been remobilised under normal reactivation of the structures to the boudin interstices and fold hinges. It is common that gold concentrates in these lower strain domains. The Bellevue structural framework is represented in the Figure 6 below, showing the post mineralisation folding of the shear structures under normal re-activation, which governs the high-grade shoot geometries.

Mineralisation has been segmented by later brittle-ductile structures of which the most prominent within the mine area are:

  • An un-mineralised shallow easterly dipping strike slip array, e.g. Bellevue Fault which terminates the Bellevue Main Lode at the 13th level underground
  • A series of east-west striking normal faults e.g. ‘A’ and ‘C’ faults.

Alteration

At the BGP, all lithologies have been metamorphosed to upper greenschist/lower amphibolite facies. Alteration is typically narrow, focused in and around shears. Observed alteration minerals include:

  • Chlorite – both early (shear foliation parallel) and late (shear foliation overprinting).
  • Amphibole – both early (shear foliation parallel) and late (shear foliation overprinting). Amphibole Intensity often has a negative association to gold mineralisation.
  • Biotite – an early phase, dark – foliation parallel (Figure 7) and a very late phase (light brown, matted, unoriented, overprints late chlorite). Biotite intensity has a positive association to gold mineralisation.
  • Albite/Silica – often observed in the Tribune and Bellevue lodes, but absent in the Viago lode.
  • Late alteration – a sericite-epidote-FeCO3 retrograde assemblage.

Of these, the early dark, foliation parallel biotite is the most effective vector to mineralisation, but often on a limited scale (20-50cm around mineralised intercepts and associated with shear intensity).The late biotite is often observed as ‘clots’ of 1-2 mm randomly oriented flakes overprinting the late coarse, matted chlorite-amphibole veins giving paragenetic timing. It exploits all existing fluid pathways giving a patchy to pervasive overprint of pre-existing vein networks and shear fabrics. Biotite alteration intensity is controlled by folding within shear zones, resulting in higher intensity biotite alteration corresponding to fold plunge orientations. It is observed that significant gold intercepts do not always have biotite alteration, however, the better intercepts nearly always have moderate to strong biotite alteration.

Pervasive biotite alteration does not correspond to higher grades which may be more a function of degree of shearing, namely stronger developed shears are pervasively altered but have sheared out mineralized veins.

Figure  – Dark biotite altered shear fabric folded around F7 fold axis with fabric picked out by remobilized pyrrhotite and chalcopyrite.

Mineralisation and Gold Characteristics

Pyrrhotite (po) and Chalcopyrite (cpy) mineralisation are observed in multiple settings:

  • Foliation parallel sulphides: discontinuous foliation parallel sulphides in zones of higher strain
  • Foliation cross cutting.
  • Fracture fill in veins: networks of po+/-cpy often hosted in sheared quartz veins.
  • Boudin interstices: Around the margins and in the interstices of boudinaged (often auriferous) quartz veins (Figure 9).
  • Basalt pillow rims.
  • Cataclastically remobilized
  • Extension veins: late tension veins (Quartz, Quartz-Carbonate, Quartz-Epidote gangue) –post deformation.
  • Pillow margins.
  • Disseminated – rarely observed – up to 20% of the host rock and intergrown with po and cpy are remobilised late into the paragenesis and so are found across multiple settings.

At Bellevue, gold grades have a strong association to remobilised pyrrhotite (and lesser chalcopyrite) in and around the shear structures and associated veins, making DHEM an effective targeting tool. Remobilised massive to semi-massive sulphide exploited vein margins and internal fractures and often contain cataclastic breccia fragments of quartz (Figure 8). Pyrrhotite and chalcopyrite display evidence of ductile remobilisation by mechanical processes such as cataclastic flow and dislocation flow rather than diffusive mass, liquid state or magmatic transfer. Arsenopyrite is late, euhedral, with no obvious gold association, although it is also often observed in late fractures. Pyrite replacement of pyrrhotite is mainly observed in the top 100 metres of the Tribune and Bellevue lodes or proximal to workings and is interpreted to be a result of low temperature retrograde processes.

Visible gold occurs with quartz fragments and within late (open) fractures in veins. There are two types of mineralised veins observed within 1-20 metre-wide zones of high strain:

  • Type 1: Smokey grey, highly strained, often highly folded and boudinaged with po and cpy remobilised to boudin interstices. Visible gold is observed in late fractures (Figure 9).
  • Type 2: Opaque (sometimes partially recrystalised) quartz veins, frequently observed cross-cutting Type 1 veins. Po and cpy observed as fracture fill in opaque veins with visible gold is observed in late fractures.