Overview

Deposit type

• Skarn
• Vein / narrow vein
• Porphyry
• Volcanic hosted

Summary:

The alkalic porphyry gold–copper deposits of the Cadia district are located in the eastern Lachlan Fold Belt of New South Wales. The district comprises four porphyry deposits, Ridgeway, Cadia Extended (Cadia Quarry), Cadia Hill and Cadia East, and two related iron-skarn deposits, Big Cadia and Little Cadia.

The mineralisation within the Project area occurs within a 6 km-long west–northwestoriented corridor.

Six mineralisation styles are known in the district:
• Cadia Hill: Intrusion and volcanic-hosted, sheeted quartz vein mineralisation;
• Cadia East: Volcanic-hosted, disseminated and sheeted quartz vein mineralisation;
• Cadia Far East: Volcanic and intrusion hosted mainly sheeted quartz vein mineralisation;
• Cadia Quarry: intrusion hosted mainly sheeted quartz vein mineralisation;
• Ridgeway: intrusion and volcanic hosted quartz stockwork vein mineralisation;
• Big Cadia, Little Cadia: iron-rich skarns.

Mineralisation in the porphyry deposits occurs as sheeted and stockwork quartz–sulphide veins, and locally as broadly stratabound disseminated mineralisation (Cadia East) and skarn (Big Cadia and Little Cadia).

The Cadia district porphyry deposits have recorded a sequence of alteration and mineralisation events that evolved from early-stage magnetite-stable sodic, potassic and calc-potassic alteration with locally significant gold–copper mineralisation, through a period of transitional stage potassic alteration that introduced most of the gold–copper mineralisation. Propylitic and calc-silicate alteration were developed in the deposit peripheries at this time and a late stage of feldspathic alteration developed irregularly around the deposit margins and locally destroyed mineralisation.

All of the porphyry deposits show a close spatial association with shoshonitic monzodiorite to quartz monzonite dykes and stocks of the CIC. Gold–copper mineralisation is hosted by these intrusions and also by the enclosing FRV wall rocks. Field evidence (e.g., cross-cutting intrusive and vein relationships, vein dykes, intermineral comb quartz layers) strongly supports the hypothesis of deposit formation at the same time as the emplacement of the intrusive rocks that host mineralisation.

Wilson (2003) divided the Cadia porphyry deposits into two types:

• Intrusive wall rock deposits. Monzonitic intrusions in these deposits were interpreted to be country rock, upon which porphyry-style mineralisation was superimposed (e.g., Cadia Quarry and Cadia Hill). These deposits display no field evidence for a temporal relationship between intrusion and mineralisation;
• Intrusive-centred deposits. The intrusions in this deposit class display textural evidence to indicate the existence of a temporal and genetic link between the monzonitic intrusive complexes and hydrothermal alteration and mineralisation (e.g., Ridgeway, Cadia Far East).

The two types have distinctive alteration and mineralisation characteristics, but share a number of paragenetic features.

Cadia East
The Cadia East–Far East deposit occupies a mineralised zone 2.5 km in strike length, 600 m in width and over 1,900 m in vertical extent. It is located below and to the east of the Cadia Hill deposit.

Ridgeway
The deposit is a subvertical body of quartz–sulphide vein stockwork mineralisation with an elliptical, pipe-like geometry, elongated along a northwest-striking axis. Stockwork dimensions are approximately 400 m east–west, 250 m north–south and the deposit extends to a depth in excess of 1,000 m.

Mineralisation is spatially and temporally associated with a composite intrusive plug consisting of multiple mafic monzonite to quartz monzonite phases that intruded the FRV. The earliest phase is a mafic monzonite, which is a northwest striking, subvertical body with horizontal dimensions of 200 x 50 m wide and a vertical extent of at least 500 m. It occurs as a subvertical plug along the southern side of the Ridgeway deposit.

Three phases of porphyritic intrusion (early-mineral monzonite, and inter- and latemineral quartz monzonite) post-date the mafic monzonite, and form a composite pipe along the northeastern margin of the mafic monzonite. This pipe has a horizontal footprint of about 130 x 40 m, oriented along a west–northwest trending axis. The pipe has been recognised over a vertical interval of >650 m and remains open at depth.

Mineralisation at Ridgeway and Ridgeway Deeps occurs in dense quartz vein stockworks and sheeted arrays localised in and around the small (50–100 m diameter) composite diorite to quartz–monzonite intrusive complex. The most strongly developed quartz stockwork veining and alteration, and the highest copper and gold grades, occur immediately adjacent to the monzonite.

The Cadia Hill deposit was mined out in 2012 and the open pit is currently being used for tailings backfill. The Cadia Hill deposit was about 900 m long. Quartz vein-hosted mineralisation extended down dip for over 600 m, although the vein system continued for at least 350 m beyond the base of significant gold and copper mineralisation.

The Big Cadia iron–copper–gold skarn deposit lies about 600 m north of the Cadia Quarry deposit and is hosted by calcareous volcanic sandstone and limestone units (lithofacies 3) of the FRV. These units occupy a reasonably high stratigraphic position within the FRV. The fault-bounded magnetite (epidote) skarn deposit dips to the southeast, and strikes west–northwest.

Below the skarn, pyroxene-phyric volcanic rocks are dominant, including basaltic lavas, peperites, pillow basalts and monomict porphyritic basalt clast conglomerates.

A polymictic rounded cobble conglomerate overlies the skarn. This unit is mostly restricted to the footwall (southern side) of the PC40 fault.

Skarn mineralisation is hosted in an intensely-altered, bedded, calcareous volcaniclastic unit. It is most conspicuously altered to bladed magnetite after hematite + calcite ± pyrite ± chalcopyrite. Magnetite and sulphides can also be seen replacing fossils. The magnetite rich skarn core varies between massive, banded, and wrigglite-bedded textures. Zones of massive magnetite skarn contain up to 70% magnetite, with the remaining rock being composed of sulphides (mostly pyrite), calcite, and black chlorite. Wrigglite-bedded skarn zones contain 20–50% magnetite, and compositional banding is preserved. Banded texture is intermediate between the massive and wrigglite-bedded skarn in magnetite proportion and appearance. Chlorite-rich, magnetite-poor volcaniclastic sandstone interbeds are present in some intervals within the skarn, and are typically <1 m wide.

The massive magnetite skarn is surrounded by a transitional, or peripheral skarn zone envelope containing typically <5% magnetite. This envelope has higher gold grades than the massive magnetite skarn.

The Big Cadia deposit has dimensions of 1,000 x 200 m, and a drill-tested depth extent of about 400 m. It consists of an oxide lens, and sulphide mineralisation at depth.

Chalcopyrite and minor gold are closely associated with bladed hematite, magnetite and epidote (with lesser chlorite–quartz–calcite) replacements.

The Little Cadia deposit has dimensions of 0.8 km x 300 m, and extends to about 150 m depth. The Little Cadia deposit is hosted by bedded, calcareous volcanic-derived sandstones that correlate to the same skarn host at Big Cadia (Packham et al., 1999). Gold and chalcopyrite are associated with epidote ± quartz in the interstices of bladed hematite–magnetite aggregates that have replaced the calcareous sandstone (Forster et al., 2004).

Mining Methods

• Block caving
• Sub-level caving
• Panel caving

Summary:

The Cadia Operations include Cadia East underground mine, Cadia Hill open pit mine, Ridgeway underground mine.

Operations at the Cadia Hill open pit ceased by 2014 and, subsequently, the pit has been used for tailings storage. The Ridgeway Deeps and Ridgeway underground mine was also placed into care and maintenance by 2018.

Production mining is an underground panel cave mining from Cadia East with underground crushing and conveyor to surface. Mine development at Cadia East commenced in 2012 with commercial production following in 2013 and is now a very large-scale underground mining operation adjacent to the Cadia Hill open pit.

Current mining operations in production at Cadia East consist of three mature panel caves and two developing panel caves.

Caves in production
PC1-1, PC2-1 (PC2-West), and PC2-2 (PC2-East) are in production and have been for some time.

Cadia East is accessed via two declines, the main access decline, and the conveyor decline.

Extracting ore by panel caving involves a series of steps:
* development of an access decline to the bottom of the orebody, an undercut level (to blast the ore), an extraction level (to remove the ore) and drawbells (through which ore gravitates from the undercut level to the extraction level);
* undercutting a block of ore to induce caving of the rock mass (which results in “fragmentation” or breaking of the ore);
* removal of the broken ore from the extraction level via load-haul-dump fleet to underground crushing stations; and
* transportation of the crushed ore via conveyor to a coarse ore stockpile at surface. Waste rock is hauled to the surface via the access decline.

The mining method involves inducing caving of the rock mass by undercutting a block of ore. Mining proceeds by progressively advancing an undercut level beneath the block of ore. Above the undercut level, the overlying rocks are pre-conditioned by blasting and/or hydraulic fracturing resulting in consistent progression of the fracturing of the caving ore block as it is mined.

Following pre-conditioning, broken rock is removed through an extraction level, which is developed below the undercut level. The extraction level is connected to the undercut level by draw-bells that open into draw-points from which the broken rock is removed. Load-haul-dump (LHD) units load the broken ore at the draw-point and dump the material into underground crushing stations.

At each crushing station, ore is tipped into a coarse ore bin, which then feeds the crusher. Crushed rock is then fed to a surge-bin which regulates the flow of crushed rock onto collection conveyor belts. The collection belts then feed crushed rock onto the main trunk belt system, which transports ore to the surface at a rate of between 4,600 to 5,150 tonnes per hour. The main trunk belt extends approximately 7,500 m to the surface, depositing material on the concentrator coarse ore stockpile. The coarse ore is then gravity fed into the surface ore processing system.

Waste rock is removed from the underground workings by truck via the decline and dumped at the South Waste Rock Facility.

PC1-1 is the original caving front for Cadia East and is located at 4,650 mRL (approximately 1,180 m below surface). It is now automated with minimal access to the cave footprint to manage caving subsidence and in-rush hazards. Production from PC1-1 is forecast to be completed by FY29 with a relatively consistent average annual production rate of approximately 5.2 Mtpa until the end of life. The extraction level is designed on an El Teniente layout. Production ore is loaded from seven extraction drives through four tipples into a single crusher. Ore is transported to surface via the Materials Handling System (MHS).

PC2-1 and PC2-2 are located 200 m deeper, at 4,450 mRL, with PC2-1 having a breakthrough connection to the eastern portion of PC1-1 ensuring caving fronts merge. Both PC2-1 and PC2- 2 are mined on an El Teniente mining layout each with their own independent crusher, supplied via a four-way tipple. The two caves support seven independent extraction drives with one additional common extraction drive in the middle.

PC2-1 is forecast to finish mining in FY29 with a peak production of approximately 14 Mtpa in 2023, tapering to closure. PC2-2 is forecast to finish in FY28 with an equivalent peak of approximately 14 Mtpa with a shorter taper to closure. The eastern extent of PC2-2 adjoins the future caving front PC2-3 discussed below.

Caves under development
Cadia East has two developing caves; PC2-3 and PC1-2. These assets are the next production zones required to supply ore to the mill.

PC2-3 is being developed as a post undercut cave utilizing blast pre-conditioning as well as hydrofracking to facilitate caving. Total production from the cave is 146 Mt with an annual production capacity of 15Mtpa. Ore is mined from 154 drawbells and a 98,000 m² footprint.

Construction of the underground materials handling system for PC2-3 was finalised in FY23 and first ore was delivered to the mill in the March 2023 quarter.

PC1-2 is a post-undercut cave utilizing blast pre-conditioning as well as hydrofracking to facilitate caving. Total production from the cave is 280 Mt with an annual production capacity of 24 Mtpa from 146 draw bells and a 115,600 m² footprint. The cave requires approximately 32 km of lateral development. It contains common capital development that enables PC1-3 to take place in future. Main works development has commenced, with development forecast to be completed in January 2027. PC1-2 adjoins PC1 (to the East) and consists of nine extraction drives, the most eastern of which breaks into PC1. PC1-2 is supported by two crushers on the north and south of the footprint. The design throughput for the MHS is 36 Mtpa including support for the deferred PC1-3 to be mined concurrently. Production is forecast to commence in FY26.

Ridgeway underground mine has been under care and maintenance since 2018.
Ridgeway is a vertical porphyry copper/gold deposit located within the Cadia Valley and approximately 5 km from the ore treatment facility and adjacent to the Cadia Hill deposit. The upper portion of the deposit down to 5040 Level (approximately 800 m below surface) has been mined using Sub-level caving (SLC) methods, resulting in a column of caved material that extends to the surface to form a subsidence zone. An underground crusher was installed at the base of the SLC area and crushed ore was conveyed out of the mine via an inclined conveyor system. SLC mining is now complete.

The Ridgeway Deeps Lift 1 block cave operation was mined between 2007 and 2015 and was Newcrest’s first block cave operation. The change to block caving was introduced after the identification that the grade profile for Ridgeway was declining to the point where subsequent SLC levels below the 5040 mRL were uneconomic. It was also recognised that experience with techniques and methods of cave establishment were required for the then future Cadia East operations. As a result of extensive reviews and study it was proposed that a 5.6 Mt/a block cave mine be established 250 m downdip of the base of the SLC at the 4786 mRL. Subsequent to establishment and ramp-up, the mine was debottlenecked to the point of achieving a total of 9.6 Mt/a. A total of 17 Mt grading 0.57g/t Au and 0.29% Cu remains in the Lift 1 level.

The majority of the Mineral Reserves for Ridgeway are located in the Ridgeway Deeps Lift 2 block cave. This cave is similar in nature to the original Lift 1 cave with a similar downdip extension depth, similar layout and establishment method, and operational targets for 8 Mt/a.

Comminution

Crushers and Mills

Summary:

Concentrator 1:

• Primary crushing in a 60-inch x 113-inch gyratory crusher. This was the main primary crusher for the original Cadia concentrator and now primarily used for surface stockpile reclaim;
• Coarse ore stockpile (COS) to a live capacity of 40,000 t and subsequent reclaim facilities;
• Distribution bin and double-deck vibrating screens for feed size preparation;
• Secondary crushing, treating screen oversize, using MP1000 cone crushers;
• High pressure grinding rolls (HPGR) unit treating screen undersize prior to the SAG mill;
• Primary open circuit milling in a single 40-ft SAG mill fitted with a 20 MW motor. The motor will be upgraded to 22 MW. Oversize pebbles from the SAG mill are returned to the distribution bin;
• Secondary milling in three ball mills, with the two original mills fitted with 8.7 MW motors, and a more recently installed third ball mill with a 16 MW motor. The mills are in closed circuit with cyclone classification for a target grind size of P80 of 150–190 µm.

Concentrator 2:

• Reclaim and conveying system to transfer ore from Concentrator 1 COS to Concentrator 2 facilities;
• Secondary and tertiary crushing using MP800 cone crushers and open circuit prescreening;
• Dedicated coarse (crushed) ore stockpile (COS) and apron feeder reclaim facilities;
• Primary open circuit milling in a single SAG mill fitted with a 7.5 MW motor;
• Secondary milling using a 7.5 MW ball mill and parallel Vertimill VTM1250, in closed circuit with classifying cyclones.
• Tertiary milling using a Vertimill VTM 3000.

Processing

• Jameson Cell Flotation
• Centrifugal concentrator
• Gravity separation
• Smelting
• Flotation

Summary:

Cadia operates two adjacent concentrators, Concentrator 1 and Concentrator 2, currently treating ore from Cadia East mine. Both concentrators have undergone throughput upgrades, including operational improvements, over the years. The processing plant infrastructure includes high-pressure grinding rolls, SAG mills, ball mills, flotation, coarse ore flotation, gravity concentrator and a molybdenum plant to produce copper and gold concentrate, gold doré and molybdenum concentrate.

Mined ore recovered from the extraction level at the bottom of each cave is crushed in an underground crusher. It is then transported by conveyor to the surface for processing at one of Cadia’s two concentrators, which produce both gold doré (via gravity recovery) and copper concentrate. The gold doré is delivered to a gold refinery in Australia to produce refined gold and silver, while the copper concentrate is slurried and pumped along a dedicated pipeline to the Blayney dewatering facility for filtering before being transported by rail to Port Kembla for export to international smelters particularly in Japan and South Korea. The copper concentrates have final mineral grades of 23-26% copper and 28-66 g/t gold as well as trace levels of deleterious materials such as fluorine and molybdenum. A new molybdenum processing plant was commissioned in 2022 to recover molybdenum into a separate molybdenum concentrate, providing an additional revenue stream and reducing the penalties that would otherwise result from excessive molybdenum content in the copper concentrate.

Concentrator 1 has undergone several upgrades since commissioning in 1998 and currently processes around 26 Mtpa ore using a conventional SABC circuit (SAG mill and ball mill with single stage pebble crusher). The inclusion of high-pressure grinding rolls and third train of flotation cells enables the circuit to treat ore from the Cadia East mine. Increasing throughput has required a coarser primary grind size (over with 80% < 150 microns) and in order to treat the increased tonnage, as well as upgrading and including additional equipment into two of the three flotation trains.

Concentrator 2 was commissioned in 2002, and had a target rate of 4 Mt/a. Concentrator 2 with several upgrades has almost doubled its original capacity and now processes 9 Mtpa. In mid-2008, the facilities were upgraded to suit predictions of harder and fines-deficient ore from Ridgeway Deeps block cave mine. The upgrade included installation of a secondary crushing circuit and additional regrind mill power. A 2.24 MW Vertimill was installed in 2011 to reduce flotation feed size and improve metal recoveries.

Concentrator 1 has historically been referred to as the low-grade process facility, or the Cadia concentrator. Concentrator 2 has historically been referred to as the high-grade process facility, or the Ridgeway concentrator.

Concentrator 1 Design
The key unit operations in the processing plant are:

- Flash flotation cells and gravity concentrators for processing a component of the hydrocyclone underflow streams.
- Three flotation trains comprised of conventional Outokumpu flotation cells in rougherscavenger duties and a combination of Jameson cells and conventional cells in cleaner duties, and cleaner-scavenger and recleaner duties.
- HydroFloatTM cells for coarse tailings flotation, with cross flow classifier made by Eriez.
- 2 x Vertimills made by Metso for regrinding.
- Tailings thickeners made by EIMCO 53 m and FLSmidth 40 m diameter.
- Concentrate thickener made by Outokumpu Superflo 12 m diameter.

Concentrator 2 includes the following processes:

- Flash flotation cell.
- One Jameson cell operating in a rougher duty.
- One bank of conventional rougher and scavenger cells with and a combination of Outotec conventional cleaner, cleaner-scavenger and recleaner cells float cells, complementing Jameson final cleaner cells.
- 2 x Vertimills made by Metso (0.93 MW) in regrinding duties.
- Tailings thickeners made by Outokumpu Superflo 29 m diameter.
- Concentrate thickener made by Outokumpu Superflo 20 m diameter.

The final copper concentrate slurry with a grade of around 25% copper is pumped to the town of Blayney where it is filtered and exported using the same filtration facilities as used by Concentrator 1.

Approximately 15% of the gold in feed ore is recovered as gravity concentrate and then smelted on site to produce gold doré for sale.

The two-stage plant expansion project at Cadia is now complete. First ore was delivered to the mill in the March 2023 quarter.

Pipelines and Water Supply

Summary:

The water requirements are proportional to the amount of mineral processing occurring and therefore as throughput increases so too will the daily water requirements. The water supply system has been designed to recycle as much of the on-site water as possible, with make-up water from local sources as required.

Most water on-site is recycled from the TSF and return water from Blayney Dewatering Facility. Make-up water is extracted from the Belubula River, Cadiangullong Dam, Flyers Creek Weir, Cadia Creek Weir, Orange, and Blayney Sewage Treatment Plant treated effluent, on-site groundwater extraction bores, and site runoff.

Agreements are in place with the City of Orange and the annualised license agreement with Newcrest is reviewed annually. The Newcrest LOMP assumes that between 65% to 70% of water used is recycled, however Cadia continue to work on further water saving initiatives. To address the additional water required for an expansion to 35Mtpa, in the context of a history of periodic drought, Cadia has included a new South Water Storage Dam in the EIS. In addition, Cadia is pursuing various other projects to secure future water supplies.

The water management system at Cadia includes separate management systems for clean, mixed and site captured water. The surface water management system at Cadia involves a number of interlinked dams and their catchments, tailings storage facilities, Cadia Hill open pit, the underground mining operations and the water pumping systems. The majority of the site water requirement is for minerals processing, with minor amounts used in mining, dust suppression and for ancillary / maintenance purposes.

Process water is suitable for reuse without treatment. CVO aims to maximise the reuse of process water with the balance of the water requirements made up from raw water stored on site. CVO captures and collects raw water from a diverse range of sources including extraction from creeks and rivers, treated sewage effluent, groundwater inflow to mining areas and bore extraction. Stormwater from disturbed areas is collected in a series of dams and seepage from large mining related infrastructure (tailings storage facilities, waste rock dumps) is captured and collected for re-use and supplements the site’s water supply. To manage the variability in water supply over extended time-frames, CVO stores water on site in two main water storages, Cadiangullong Dam (on stream) and Rodds Creek Dam (primarily off stream).

Water security, flood risk and operational management decisions at CVO are actively managed via a committee comprising key internal stakeholders. The water committee sitsonce per quarter to forecast and plan water demand, supply, transfer and storage requirements and to identify and manage water related risks that arise from changing site and climatic conditions.

The largest consumer of water required by the operation is for processing of ore to produce a mineral concentrate (Section 3.4), using up to 5,000 ML/month. Tailings from the process plant is currently deposited in the Southern Tailings Storage Facility (STSF) and in the Cadia Hill Pit Tailings Storage Facility (PTSF) from which water is reclaimed. The Northern Tailings Storage Facility (NTSF) is under care and maintenance during repair of its southern embankment following a failure in March 2018. The majority of the water demand is supplied by recycling water within the ore processing plant and recycling tailings water from the PTSF and the STSF (via Rodds Creek Dam).

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Development Manager	Nicholas Fryer		Apr 16, 2024
Development Superintendent	Owen Wells		Apr 16, 2024
Electrical Maintenance Superintendent	Shehan Fernando		Apr 16, 2024
Fixed Plant Maintenance Manager	Johan Botha		Apr 16, 2024
Fixed Plant Maintenance Superintendent	Jarrad Haynes		Apr 16, 2024
General Manager Operations	Tom Lukeman		Apr 16, 2024
Health, Safety & Environment Manager	Greg Taylor-Adams		Apr 16, 2024
Metallurgical Superintendent	Campbell Haines		Apr 16, 2024
Processing Manager	Rami Ghattas		Apr 16, 2024
Technology Manager	Jason Nitz		Apr 16, 2024