Overview

Deposit type

• Vein / narrow vein
• Porphyry
• Orogenic

Summary:

Mineralisation
Gruyere
Gold mineralisation at the Gruyere gold deposit is developed in the monzonite porphyry in response to a complex structural event. The monzonite porphyry, which is more competent and brittle with respect to the more ductile host rocks, suffered increased cracking and fracturing compared to the adjacent rock types. This created increased permeability allowing gold bearing mineralising fluids to flow through the rock mass and deposit gold.

Multiple quartz vein sets are mapped through the deposit. These fall into three broad orientations: consistent tabular quartz veins with a shallow dip to the southeast varying from 1 cm - 100 cm in thickness; irregular quartz veins with a moderate dip to the northwest; and quartz-carbonate shear veins parallel to the shear foliation.

The entire Gruyere quartz monzonite is altered with the alteration intensity ranging from very weak to very strong intensity. Early-stage alteration comprises a brick-red haematite-magnetite assemblage associated with background (<0.3 g/t Au) gold mineralisation. Weak to strong gold mineralisation is increasingly associated with sericite, sericite- chlorite, chlorite-muscovite, chlorite-muscovite-albite, and strong albite alteration. The mineralised strike is 2,200 m with a known vertical extent of over 1,100 m.

Sulphides are commonly associated with the gold mineralisation, with pyrite dominant in the upper areas and pyrrhotite increasing with depth. Arsenopyrite is commonly associated with quartz veining in areas of highest grade gold mineralisation.

A persistent 1 m to 5 m wide steeply dipping mafic dyke (Main Dyke) is located proximal to the hangingwall zone. Multiple thin sub-parallel, intensely sheared, predominantly mafic rocks occur internal to the monzonite porphyry and are interpreted to be rafts of the initial shear zone caught up in the monzonite porphyry during the intrusion of the unit and post mineralisation dykes.

Yam14
The YAM14 deposit is located 8 km south of Gruyere within a flexure of the Dorothy Hills Shear Zone. Host rocks to the gold mineralisation at YAM14 are dominated by a felsic volcanoclastic sedimentary package (felsic tuff) and a sequence of intercalated mafic and intermediate sediments.

Primary mineralisation occurs sub-parallel to lithology and dips moderately to steeply (55 ° - 75 °) to the east. Elevated gold grades are associated with intense shearing, increased quartz veining, sulphide content (pyrite-pyrrhotite) and sericite-chlorite-albite alteration. Visible gold occurs within the quartz veining.

Mineralisation transects the felsic tuff in the footwall to the south and the hangingwall to the north. Two major faults are interpreted from aeromagnetic and induced polarisation (IP) geophysical data; the Monocot to the south and the Breakaway in the north. The faults appear to define the strike extent of mineralisation; however, the area north of the Breakaway Fault has not been thoroughly tested.

The weathering profile is of moderate thickness with the transition to fresh rock occurring at a depth of 50 m to 60 m.

Attila – Alaric trend
Gold mineralisation within Yamarna Greenstone Belt is associated with a northwest trending structural corridor termed the Attila – Alaric trend defined over a ~17 km strike length.

Mineralisation at Attila is hosted in a sequence of mafic and felsic volcanic intrusives and sediments on the western margin of the Yamarna Greenstone Belt. The deposit is located on a flexure of the northwest striking Yamarna Shear Zone. The sequence strikes northwest, dips steeply to the east, is metamorphosed to amphibolite facies and is strongly foliated.

Gold mineralisation is hosted in shear zones parallel to the stratigraphy characterised by laminated quartz-micaamphibolite schists. Gold deposition has both a lithological and structural control. Mineralisation is associated with the presence of sulphides and quartz veining and within iron-rich mafic units. The trend of the main zone of mineralisation is steeply dipping (65 º - 75 º) to the east with either gently north-plunging or horizontal shoots developed.

The Alaric deposit is located on a flexure of the northwest striking Yamarna Shear Zone, within a ~1.5 km wide zone of mylonitic mafic and felsic volcanics and sediments.

Gold mineralisation at Alaric is typically located on or near to contacts of interpreted dolerites hosted within intermediate and dacitic volcanic sediments. The Main Shear is hosted within a dolerite with a characteristic chromerich base traced along the length of the deposit. Mineralisation is hosted within northwest striking, steeply east-dipping shear zones conformable to stratigraphy and characterised by laminated quartz-mica-amphibole units. The trend of the main mineralisation is interpreted to be steeply dipping (65° - 75°) to the east and associated with the presence of sulphides and quartz veining. Several cross-cutting linear faults are interpreted from the magnetics and distribution of lithologies and appear to limit the strike extent of the mineralisation.

The stratigraphy at Montagne is dominated by sheared intercalated mafic and intermediate sediments. Occasional mafic intrusives including biotite ± amphibole altered melanodolerites are common in the hangingwall above the main mineralised shear. Chloritic shale and tuff, which are two unique stratigraphic hangingwall marker units traceable over several kilometres of the Attila-Alaric trend, are both present at Montagne.

Gold mineralisation is hosted within north-striking (Attila local grid), steeply east-dipping shear zones characterised by laminated pyrite-biotite units ± thin quartz veins. High-grade mineralisation occurs as 2 m to 15 m wide zones proximal to the core of the shears associated with increased pyrite alteration.

The thickness of transported cover at Montagne is minimal, comprising 2 m to 5 m of aeolian sand, with weathering typically ranging in depth from 25 m to 70 m.

Gold mineralisation at Argos trends parallel to the local foliation in more mafic units within a sequence of mafic to intermediate volcanics and sediments. Multiple narrow (2 m -7 m), parallel zones of gold mineralisation are common and exhibit good continuity along strike and downdip.

The mineralisation is associated with shearing and early amphibole-albite-biotite-sericite-quartz alteration. The principal sulphide is pyrite, with rare disseminated pyrrhotite and arsenopyrite also present. A later stage haematitequartz alteration on either side of the main shear zone is interpreted to be associated with oxidised fluids introduced by late-stage, northeast trending faults which cut the Attila-Alaric trend stratigraphy.

The regolith profile at Argos is stripped, with the recent cover sequence ranging from 1 m to 3 m thick in the north and 15 m to 20 m in the south of the deposit.

Mineralisation at Orleans is hosted by intermediate sediments with gold associated with an increase in shearing and biotite-sulphide alteration. The footwall position of coarse intermediate sediments is higher up the stratigraphic profile than seen at Argos and Montagne.

The Central Bore deposit is located 3 km east of the Orleans deposit. The geology at Central Bore consists of northwest trending, sub-vertical andesitic volcanics and porphyries (tuffs). Gold mineralisation is also sub-vertical, restricted to a single, narrow shear zone (1 m to 2 m wide) characterized by carbonate veinlets, alteration, and fine-grained sulphides (molybdenite in particular). Visible gold is common in these intersections, but it is generally fine grained.

Deposit types
Gruyere and other deposits on the property are Archean orogenic type gold deposits. They are typically associated with flexures in regional-scale structures, shearing, increased quartz veining and albite-chlorite-pyrite-arsenopyrite alteration.

Mining Methods

• Truck & Shovel / Loader

Summary:

The Gruyere mine utilises mining contractors to mine the open pit using conventional drill, blast, load and haul activities. The Gruyere pit mined oxide and fresh rock material in 2023, allowing validation and optimisation of the geotechnical parameters. The pit is designed to be mined in stages over the LOM. Material was mined from stages two, three and four during 2023. The new LOM expands the pit from stages three to seven.

The Gruyere JV Mineral Reserve comprises five open pits plus ore stockpiles. The Mineral Resource includes seven open pits and one underground deposit.

During 2023, mining consisted of predominantly fresh rock material mined, which is harder and more abrasive than oxide material previously processed.

The pit is designed to be mined in five stages over the LoM. The mining methods include:
• Drilling and blasting of ore, associated internal waste and bulk waste outside of the ore envelope on 10 m benches. Trim blasts and pre-splits are used to provide wall control in fresh rock as required. The majority of explosives usage is bulk emulsion and the remainder is ANFO.
• Loading and hauling utilising excavators and 225 t haul trucks mining on 3 m to 4 m high flitches. Ore is marked out by paint or tapes on the ground, supported by dedicated ore spotters as required. Ore is direct fed to the crusher or placed on stockpiles for future rehandle as required.
• Waste dumps are developed in 10 m lifts and progressively rehabilitated. TSF embankment raises are constructed with waste material from the mine as required.
• Ancillary plant support for floor control, haul road construction and maintenance, rehabilitation, drill support, waste dump battering are provided by a fleet of dozers, graders and water carts.
• Pit dewatering is minimal and is managed by the collection of water from in-pit sumps for use in the mining operation.
• Crusher feed is provided by a combination of direct tip from the mine (45 % of crusher feed) and rehandle from RoM or long-term stockpiles using either a front-end loader only or a front-end loader and 135 t capacity haul trucks (dependent on the haul distance).
• RC grade control drilling services to a 25 m by 25 m pattern are provided either by the mining contractor or an externally contracted drilling company.

Comminution

Crushers and Mills

Summary:

Primary Crushing
The crushing circuit will be a single stage, open circuit gyratory crusher. Product from the crushing circuit will be conveyed to the coarse ore stockpile. The circuit will crush 1,300 dtph to a product size P80 of 135 mm. The crushing plant will operate with utilisation range of 66% to 78%, depending on ore type being crushed.

ROM ore will be trucked from the mine to a ROM pad and will either be tipped directly into the primary crusher dump pocket or stockpiled on the ROM pad for reclaim at a later stage by FEL. Any oversize material fed into the dump pocket bridging the opening to the gyratory crusher will be fragmented by a fixed rock breaker to permit it to pass into the primary crusher. The FEL will be supplied and operated by the mining contractor.

The primary crusher will be a 1.370 metres by 1.905 metres (54 to 75 inch) gyratory crusher with a 650 kW motor. It will be operated with an open side setting of 160 mm and a 37 mm throw. The primary crusher will discharge onto a 1.2 metre wide by 6.5 metres long apron feeder (55 kW drive) that will, in turn, discharge onto the crusher discharge conveyor. The crusher discharge conveyor (71 metres in length, 1,500 mm wide, 200 kW drive) will feed onto the stockpile feed conveyor (156 metres in length, 1,500 mm wide, 300 kW drive). A selfcleaning magnet located at the crusher discharge conveyor head chute will remove magnetic tramp metal from the ore stream and discharge it into a tramp metal bin. The stockpile feed conveyor will discharge onto the coarse ore stockpile.

To minimise dust emissions, the primary crusher discharge chamber will be serviced by a dust extraction system comprising a filter bag unit with reverse air pulse cleaning. The dust collected by the system will be discharged onto the crusher product conveyor.

Grinding and Classification
The mill feed conveyor (178 metres in length, 1,500 mm wide, 220 kW drive) will feed the two stage grinding circuit. The first stage will be a grate discharge SAG mill in open circuit with pebble crushing and the second stage will be an overflow discharge ball mill in closed circuit. The circuit will grind 1,100 dtph of Oxide ore, 1,000 dtph of transitional ore and 937 dtph of Fresh ore to a product size P80 of 125 µm. The comminution circuit will operate with utilisation of 91.3%.

The SAG mill will have an inside shell diameter of 10.97 metres and effective grinding length (EGL) of 5.79 metres. The mill will have a grate discharge configuration and dual pinion variable speed drive with 7,700 kW low speed synchronous motors (15.4 MW installed motor power combined). The SAG mill will be charged with 125 mm grinding media and will be designed to operate with a 15% ball charge. The ball charge and mill speed will be adjusted to suit the ore type. The mill discharge grate will have 15 mm apertures and 65 mm pebble ports. SAG mill discharge will be screened on a 3.6 metres wide by 5.8 metres long, double deck, horizontal, wet vibrating screen with top and bottom deck apertures of 50 mm by 50 mm and 8 mm by 16 mm respectively. The screen oversize from both screen decks will be conveyed to the pebble crushing circuit. A twin deck screen is required for screening capacity and to ensure clean product to the pebble crushing circuit. The screen undersize will produce a slurry transfer size of approximately 1 mm which will be transferred to the ball mill discharge hopper.

The pebble crushing circuit will consist of a feed bin fitted with dual vibrating plate feeders, feeding two 1.12 metre diameter short head cone crushers fitted with 220 kW motors (HP300 or equivalent). Both feeders and crushers will be duty units. The pebble crushers will be operated with a 15 mm closed side setting. Pebble crusher discharge will be returned to the SAG mill via the mill feed conveyor. To protect the pebble crushers from damage by grinding media, a self-cleaning magnet will be fitted on the head chute of the pebble transfer conveyor. Grinding media removed by the magnet will discharge into the pebble crusher magnet bunker for reuse in the ball mill or reject (broken balls or miss-shaped steel scats). In addition, a metal detector will be fitted to the pebble crusher feed conveyor. In the event of a metal detection signal, a flop gate at the head chute of the conveyor will be activated to temporarily divert feed directly back onto the mill feed conveyor for return to the SAG mill. The pebbles will be directed to ground by a flop gate to bypass the crushers should this be required. Dual pebble crushers have been selected to provide a degree of redundancy which may be required for certain ore types.

The SAG mill discharge screen undersize will flow by gravity into the mill discharge hopper. The SAG mill discharge screen undersize will combine with the ball mill discharge pulp in the mill discharge hopper. One of two centrifugal slurry pumps (20 by 18 inch) with 1,500 kW drives, arranged in a duty/ standby configuration, will pump the combined mill discharge pulp to a cyclone cluster for classification.

The cyclone cluster will consist of 12 mm by 650 mm diameter cyclones, eight to ten duty cyclones and two to four standby cyclones, depending on ore type. Cyclone overflow will gravitate to the trash screens. Cyclone underflow will be split between the ball mill and the gravity circuit and this will be accomplished by partitioning the cyclone underflow launder into three compartments. One compartment will be fed by the underflow from six cyclones and will be directed to the ball mill. The other two compartments will be fed by the underflow from three cyclones each and both will be directed to the gravity circuit. The arrangement will provide the ability to adjust the proportion of the underflow treated by the gravity circuit and will suit varying circulating loads that may result from treating the different ore types or blended feed.

The ball mill will be a 7.93 metre (Inside Shell) diameter by 11.58 metres EGL overflow discharge with a dual pinion variable speed drive with 7,700 kW low speed synchronous motors (15.4 MW installed motor power combined). It will be charged with 65 mm grinding media. The ball mill speed and ball charge will be adjusted to suit the ore type. The ball mill will discharge onto a 5.4 metre diameter by 4m long trommel screen with 8 mm by 16 mm apertures. Trommel screen oversize will discharge into the ball mill scats bunker whilst trommel screen undersize will discharge into the mill discharge hopper.

The grinding area will be serviced by three vertical spindle centrifugal sump pumps (150 mm pump size) for clean-up, with floor slopes appropriately graded to the relevant sumps to facilitate ease of cleaning.

Grinding media will be delivered in bulk and stored in ball bunkers (one bunker for each media size). The SAG mill will be charged via a ball loader and the mill feed conveyor and the ball mill will be charged via an electromagnet hoist.

Ongoing plant improvement work includes the installation of a new larger pebble crusher, which was scheduled to be commissioned by Q1 2024.

Processing

• Gravity separation
• Centrifugal concentrator
• Smelting
• Carbon re-activation kiln
• Crush & Screen plant
• Agitated tank (VAT) leaching
• Concentrate leach
• Inline Leach Reactor (ILR)
• Carbon in leach (CIL)
• Carbon adsorption-desorption-recovery (ADR)
• AARL elution
• Solvent Extraction & Electrowinning
• Cyanide (reagent)

Summary:

All ore mined is processed in the Gruyere plant, which consists of primary crushing, semi-autogenous grind (SAG)/ball milling, gravity and carbon in leach (CIL) circuits. The processing plant was originally designed with a capacity of 7.5Mtpa for treating the deeper fresh (harder) ores. However, subsequent optimisation work and upgrades - the installation of a new larger pebble crusher - increased actual and planned throughputs to range between approximately 9.5Mtpa to 9.8Mtpa.

The current processing facility consists of a primary crushing circuit, a semi-autogenous ball mill crusher (SABC) grinding circuit, leach feed and tailings thickeners and a standard CIL circuit. RoM ore is trucked and direct tipped into a primary gyratory crusher or stockpiled on the RoM pad before processing. Ore from the future Golden Highway deposits will be transported to the process plant and blended with Gruyere ore.

Discharge from the primary crusher is transferred via conveyors onto a coarse ore stockpile (COS). The COS capacity is approximately 75,000 tonnes. Apron feeders under the COS stockpile reclaim and transfer crushed ore to the SAG mill feed conveyor which feeds the two-stage grinding circuit. The first stage is a grate discharge SAG mill in open circuit (with closed circuit pebble crushing) and the second stage is an overflow discharge ball mill in closed circuit. Each grinding mill is installed with 15,000 kW motors. This is followed by a gravity concentration circuit and in-line leach reactor and a hybrid CIL recovery circuit, consisting of 1 leach tank, 6 adsorption tanks and an elution circuit (consisting of carbon acid washing, cyanide elution, higher temperature regeneration).

The gold in pregnant solution from the intensive leaching and elution circuit is recovered via electrowinning in the gold room. The recovered gold is smelted in a furnace to produce the final gold product (doré bars). Gold bars are poured from sludge from both the gravity and CIL electrowinning circuits. Gold is refined on-site to crude doré at 75- 90 % gold purity. Doré is dispatched to the Perth Mint refinery for further processing.

PLANT
Gravity Recovery
The gravity circuit will consist of four centrifugal concentrators treating a portion of the cyclone underflow. Gravity concentrate will be leached using a vendor supplied intensive leach reactor to yield a pregnant solution from which precious metals will be recovered by electrowinning.

The cyclone underflow launder will have three separate compartments. Two of these compartments will feed the gravity circuit. The number of cyclones servicing each gravity compartment can be adjusted as required. Each of the two gravity feed compartments will feed a dedicated 2.4 metres wide by 6 metres long, horizontal, wet vibrating screen. The screen deck panels will have alternating rows of 2.4 mm by 6 mm and 2.4 mm by 18 mm slots. Screen oversize will return to the ball mill feed. Screen undersize will feed the centrifugal gravity concentrators. Each screen will supply two 1.219 metre (48 inch) diameter centrifugal concentrators. The concentrators will operate in a staggered discharge cycle so that while one unit is flushing the other units are collecting concentrate. The gravity circuit has been designed for a 40-minute collection cycle followed by a standard flushing cycle.

The tailings from the gravity concentrators will return to the ball mill feed. Concentrate from the gravity concentrators will discharge to the intensive leach reactor. The batch leach process will be initiated on a daily basis. The leaching sequence will be controlled by a programmable logic controller (PLC). After leaching, the residue will be returned to the mill discharge hopper by a centrifugal slurry pump and the pregnant solution will be forwarded to electrowinning located in the gold room.

Electrowinning will be carried out in a dedicated 800 mm by 800 mm electrowinning cell fitted with 12 cathodes and 13 anodes. Electrical current will be supplied from a 1,200 A rectifier. The cathodes will be stainless steel and the precious metal precipitate will be removed by washing loaded cathodes in a cathode washing station and filtering the resulting sludge. The filter cake will be dried in an oven and then combined with fluxes and smelted to produce gold doré.

Leaching and Adsorption
After screening to remove trash, the cyclone overflow from the grinding circuit will be thickened using a 38 metre diameter Hi-rate thickener and then leached with cyanide in a hybrid CIL circuit that consists of a singlestage of leaching and six stages of leaching and adsorption. The total nominal pulp residence time in the hybrid CIL circuit will be 24 hours.

Pre-leach thickener feed will be dosed with flocculant and thickened in the 38 metre diameter Hi-rate thickener to 50% solids (w/w). The thickener underflow (leach feed) will be pumped by one of two centrifugal slurry pumps (14 by 12 inch) with 315 kW drives, arranged in a duty/ standby configuration, to the CIL tanks. Cyanide will be dosed into the suction of the duty thickener underflow pump, and oxygen will be injected into the leach feed line. The thickener overflow will gravitate to the process water pond via a sedimentation pond.

The leaching and adsorption circuit will consist of a 5,000 m³ leaching tank with a nominal pulp residence time for Fresh ore of four hours and six 4,200 m³ CIL tanks with a nominal 20 hour pulp residence time (leaching and CIL). For Oxide ore the residence time will be a total of 20.4 hours, for the Transition it will be 22.7 hours and for Fresh ore it will be 24 hours. The design will include the ability to bypass any tank in the train should this be required.

Each CIL tank will have two 20 m² mechanically wiped, inter-tank screens with 1 mm aperture stainless steel wedge wire to retain carbon. The design carbon concentration will be 9 g/L. Carbon will be advanced through the CIL circuit counter current to the pulp, on a batch basis, by recessed impeller pumps. Loaded carbon from the first stage of the CIL will be pumped to the loaded carbon screen. The loaded carbon screen will be a 1.5 metres wide by 3.6 metreslong, horizontal, wet vibrating screen. Loaded carbon from the loaded carbon screen will gravitate into the acid wash column. The design advance rate for the circuit is 15 t/d. Barren carbon from the kiln (or directly from the elution column) will be returned to the circuit via the barren carbon screen. The barren carbon screen will be a 1.5 metres wide by 3.6 metres long, horizontal, wet vibrating screen.

Elution and Gold Recovery
The carbon handling and gold recovery system will comprise the following:
- 18 t mild steel, rubber lined, acid wash column;
- 18 t stainless steel elution column;
- 6,500 kW elution heater;
- A split AARL elution system with two 249 m³ pregnant solution tanks and a 249 m³ barren solution tank;
- 1.5 tph carbon regeneration kiln and its associated quench tank;
- An eduction water system for carbon transfer including a recycle system with a settling cone to remove carbon fines from the circuit for bagging and subsequent treatment (by others);
- An electrowinning circuit with four 800 mm by 800 mm electrowinning cells with each cell fitted with 12 cathodes and 13 anodes and supplied by a 1,200 A rectifier;
- A cathode washing station and filter to recover precious metal precipitate;
- An A300 smelting furnace and crucible to produce gold doré;
- A secure gold room with a vault and safe for the storage of bullion.

Water Supply

Summary:

All water used at Gruyere is sourced from groundwater. The primary and largest use of groundwater is for the processing of ore, followed by dust suppression with a small proportion processed for potable water. Mine dewatering is reused for dust suppression and to supplement process water.

Eight bores were commissioned at the Anne Beadell borefield which provides most of the water required for the accommodation village. Potable water is processed via a reverse osmosis (RO) plant and disinfected using ultra-violet light filtration systems. The Anne Beadell borefield is in a shallow paleochannel 23 km southeast of the mine site. Water extracted from the borefield is classed as brackish-saline water.

A water supply of up to 20,500 kL/day was developed at the Yeo borefield for mineral processing and ancillary services such as dust suppression. The Yeo borefield is approximately 28 km west of the process plant and comprises northern and southern borefield branches. Water is also be recycled from the TSF and returned to the process plant.

The Gruyere water management strategy will be continually improved to better utilise and conserve the groundwater resources at Gruyere and identify new water sources to enhance water security. Water use is minimised through return of TSF supernatant water and interception and recovery bores around the perimeter of the facility.

The water demand is only around 60 % of the water availability with the current Ground Water Licence sufficient to provide substantially more water.

Water recovered from dewatering of the Gruyere open pit is used for dust suppression and is supplemented by raw water from the borefields. Water requirements for dust suppression are estimated 0.6 GL/a. Any excess water from the pit or storm events is pumped to the process plant. Discharge from the ex- pit boreholes and horizontal seep wells is pumped to the raw water storage dam and utilised for dust suppression. Wastewater and treated wastewater from the sewage plant are discharged via a spray field at both the village and site.

Most of the water at Gruyere is reused within the mining and processing circuits. Storage is largely in settling and storage ponds. The key operational areas are supported with tanks that contain enough surge volume to ensure minimal interruption in the event of a pump failure at one of the ponds.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Occupational Health & Safety Manager	Zoe Green		Apr 22, 2024
Open Pit Project Engineer	Kiran Bandla		Apr 22, 2024
Processing Manager	Tristan Freemantle		Apr 22, 2024
Supply Chain Manager	Mark Dominy		Apr 22, 2024