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.

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.

Current Open Pit Mining at Billabong occurs at Area 4, Perch and Plutonic Main Pit. Open pit mining was paused at the Hermes Complex in May 2019, which is about 65 kilometres from Plutonic. The Hermes Complex consists of two project areas, namely the Hermes Gold Mine and the Hermes South project.
• Area 4 – It has one open pit cutbacks
• Perch – It has two open pit cutbacks, A and B
• Main Pit Deeps – It has following one open pit

The Area 4 open pit commenced being mined in April 2021 and completed in August 2021. During this period, total saleable gold produced was 9,252 ounces.

The Perch open pit commenced being mined in September 2021 and completed in April, 2022.

During this period, total saleable gold produced was 6,334 ounces.

The Main Pit Deeps open pit is scheduled to commence being mined in 2022.

All pits are mined as a conventional open pit excavator-truck mining operation. A mining contractor was engaged for drilling, blasting, loading, hauling, and dumping, as well as civil services for general site maintenance works. The material mined from each pit is transported along the site haul road to the ROM pad for processing through the existing mineral processing configuration.

Areas disturbed by mining activities have been stripped of vegetation, topsoil, subsoil, and potentially hardpan duricrust material and stockpiled within designated storage areas for later use in rehabilitation. Laterite waste rock is being used to construct haul roads, erect windrows and sheet ore pads, with surplus material stockpiled in an accessible location for use in haul road maintenance. All other waste rock is being hauled directly to the waste dump, and sequenced so that any potential acid forming or hazardous material is encapsulated within the dump.

Some near surface weathered material is free-dig, but 100% of transitional material and fresh rock is blasted. Blast-hole drilling is undertaken using surface top hammer drill-rigs on 5 m benches using hole sizes up to 115 mm diameter. Drill burden, spacing and sub-drill design is a function of material types and powder factor. Drill and blast of 10 m benches in the upper waste sections of each pit is reviewed. Explosive selection depends on the presence of groundwater and the success of dewatering. For pit optimisation, ammonium nitrate fuel oil (ANFO) is assumed in the oxide material and emulsion for the remainder of the deposit.

CAT 777F Haul trucks with a load capacity of 90 t is used in conjunction with 120 t class hydraulic excavators in a backhoe configuration to achieve the required waste extraction ratio and selectively mine the ore. In general, 5 m benches are mined on two 2.5 to 3.5 m fitches (allowing for heave after blasting). In harder material, where extensive heaving of blasts occurs, the heave is mined separately down to bench level, followed by two 2.5 m fitches to minimise ore dilution. Ancillary services to support the production fleet include graders and water trucks for haul road maintenance and dozers for maintenance of pit benches, preparation of blasted benches, along with waste dump management.

The mining operation excavate and load ore and waste in accordance with marked ore and waste boundaries to ensure minimum dilution and maximum recovery of ore, with a geologist present during all ore mining. Standard practice to minimise dilution include mining along the strike of ore blocks, mining from hanging wall to footwall contacts, and grader or dozer clean-ups restricted to along strike in the ore zones. Ore and waste boundaries delineated based on grade control sampling results and bench and face mapping. Blocks are marked out by flagging tape and paint for excavation. Blast monitors are installed prior to blasting and surveyed post blast to determine ore movement. Blast design software (such as Shotplus) is used for all blast tie-ins ensuring ore shots are fired in a direction along strike. Ore above cutoff grade is transported to the Plutonic ROM pad and stockpiled separately by material type and grade. The frontend loader (FEL) on the Plutonic ROM pad maintains stockpiles. A rock breaker is maintained at the Plutonic ROM pad to break stockpiled
oversize ore.

A dedicated fleet of a grader, watercart, and roller maintain the haul road to the Plutonic ROM pad. Low-grade material may be stockpiled for possible processing later in the mine life.

Waste rock dump sides are progressively battered down to the final design slope at the completion of each segment. Topsoil is placed using the ancillary equipment on the crest of these walls in readiness for spreading over the slopes. At the completion of mining, stockpiled topsoil will be re-spread over all other remaining disturbed areas. These areas will then be contoured, ripped and seeded with plants native to the area or appropriate to the prevailing conditions. The mining contractor will decommission and demobilise all plant and infrastructure making good all disturbed areas for rehabilitation. The mine abandonment bund has been designed in accordance with DMP guidelines "Mining Abandonment Bunds" and will be constructed with competent mine waste material towards the end of operations.

Site layout
The office and workshop area are near the mine administration building to be outside the expected blast exclusion zone of 500 m. Traffic management controls include haul road layouts designed to manage heavy vehicle and light vehicle segregation, right angle intersections, dedicated parking areas, and one-way flow of traffic. The explosive magazines and explosive compounds are located to be outside the blast exclusion zone and comply with licensing separation distances from infrastructure areas.

Crushing
Run of Mine (ROM) ore is trucked to the ROM pad from the underground mine. The ore is classified and stockpiled according to gold grade, arsenopyrite content, pyrrhotite content, and graphitic content so that blending can be undertaken to maintain an optimal feed to the processing plant. Oversize ore and tramp metal are sorted from stockpiles and broken on the ROM pad using a loader or excavator. Any oversize that cannot pass through the primary crusher grizzly is broken by a rock breaker mounted at the grizzly.

The PP1 crushing circuit has a nameplate capacity of 2.5 Mtpa and consists of three stages of crushing:
A 60 x 48 Jacques primary double-toggle jaw crusher,
A Symons 7’ SXHD secondary standard head cone crusher, and
Two Symons 7’ SXHD tertiary short-head cone crushers.

In addition, there are separate surge bins that are operated in closed circuit with two Nordberg 7.1 m x 2.4 m double deck vibrating banana screens. Crushed ore exits the pro duct screen with a top size of 10 mm and is stored in the fine ore bin. The fine ore bin has a live capacity of 3,000t.

PP1 crushing circuit contains 2 x Thermo Scientific Ramsey 10-17 belt scales (CV07 and CV13) for measuring mass of circuit ore.

The now decommissioned PP2 oxide crushing circuit consists of a 48 x 42 Kemco double toggle jaw crusher with a nameplate capacity of 1.2 Mtpa, a product conveyor and a coarse ore stockpile with a live capacity of 2,200 tonnes. Crushed oxide ore was transferred to PP2 grinding mills using two variable speed belt feeders.

Grinding
Crushed ore is withdrawn from the Fine Ore Bin via two belt feeders (CV 14/15), which transfer ore onto the mill feed conveyor (CV04) that feeds into the primary grinding mill (ML01). Mill feed can also be fed via an emergency feed hopper (CV02) which is fed via the oxide coarse ore feed slots. Quicklime is discharged onto CV04 via a variable speed, manually controlled rotary valve from a 200t lime silo. Liquid lead nitrate (40% w/w) is discharged directly into CV04 head chute into the grinding circuit.

The grinding circuit comprises a Svenson 4.5m diameter by 5.63m long primary mill and two Svenson 4.2m diameter by 5.63m long secondary ball mills. The primary mill has a grate discharge and is rubber lined. Its speed is fixed at 14.6 rev/min (72 per cent of critical) and the installed power is 1,600kW (1,350kW drawn). 78mm diameter forged steel grinding media is used in the primary mill.

The secondary mills are rubber lined overflow mills run at 15.8 rev/min (75% of critical), also with 1,600 kW power (1,450 kW drawn). The grinding circuit throughput is currently operated at 165 tph with a primary mill and one ball mill configuration; this however can be increased to 230 tph by running the stand-by ball mill. 40 mm High Chromium steel grinding media is used in the secondary mills.

The primary mill discharge slurry is screened on a 6 mm aperture scalping screen and oversize is returned to the primary mill. Screen undersize reports to the ball mill discharge hopper. ML01 mill undersize and ML02/ML03 mill discharge is pumped to a hydrocyclone cluster consisting of 18 x 250 mm Cavex cyclones. Operating pressure is 130 to 150 kPa. Each cyclone contains 90 mm ceramic vortex finders and 75 mm ceramic spigots. Coarser cyclone underflow is returned to the operating secondary ball mill for further size reduction. Cyclone overflow (approximately 80% passing 75µm) discharges over a trash screen (1mm) with screen undersize reporting to the leaching circuit.

The primary sections of the processing plant that are currently in use are:

• Crushing and conveying
• Ore reclaim and grinding
• Leaching and carbon adsorption
• Carbon stripping, electrowinning, refining and carbon regeneration
• Tailings thickening
• Tailings deposition and storage
• Reagent mixing and handling
• Plant services.

Leaching and adsorption
The leach and adsorption circuit consists of two leach tanks and six CIL carbon adsorption tanks, all with a 1,020m3 capacity. All tanks mechanically agitated with dual, open, down- pumping impellor systems powered by 55kW drives. Facilities are currently available to inject oxygen into tanks #1, #2, #3, #4 and #6, with a high shear MMS oxygen injector feeding into Tank #1. Gold in solution is recovered and concentrated by adsorption onto activated carbon in the adsorption tanks. Leach tank 1 is used as a pre-oxidation (oxygen sparged) conditioning tank, to oxidise reactive ........