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 occu ........

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.

• 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 su ........

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.

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