Mineralization
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.

Deposit Type
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 h ........

Open Pit Mining at Billabong is at Hermes Complex, which is about 65 kilometres from Plutonic. The Hermes Complex consists of two project areas – • Hermes Project – It has following four open pit cutbacks – o Trapper o Klinger o Hawkeye o Winchester. • Hermes South Project – It has following one open pit – o Wilgeena. The Hermes Project commenced being mined in December-2017 and paused in May-2019, as below – • Trapper Pit started in December-2017 & paused in April-2019. Trapper was mined in four stages • Hawkeye Pit started in December-2017 & paused in January-2019 • Klinger Pit started in April-2018 & paused in December-2018 • Winchester Pit ran for a month in May-2019, contour mining near surface deposit only. The Hermes South Project is about 20 kilometres south of Hermes Project. Historically, prior to Billabong takeover, contour mining very near to surface is done in Wilgeena Pit. All four pits in the Hermes Project area 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 being stockpiled adjacent to each pit exit before being loaded onto road trains for transport along the haul road to Plutonic for processing through the existing mineral processing configuration.

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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