Overview

Deposit type

• Breccia pipe / Stockwork
• Porphyry
• Vein / narrow vein

Summary:

The Northparkes deposits occur within the Ordovician Goonumbla Volcanics of the Goonumbla Volcanic Complex and Wombin Volcanics. The Goonumbla Volcanics form part of the Junee-Narromine Volcanic Belt of the Lachlan Orogen and consist of a folded sequence of trachyandesitic to trachytic volcanics and volcaniclastic sediments that are interpreted to have been deposited in a submarine environment.

The Goonumbla Volcanics at Northparkes have undergone little deformation, with gentle to moderate bedding dips as a result of regional folding. The dominant structure observed to date in the Northparkes area is the Altona Fault, an east-dipping thrust fault, which truncates the top of E48 and GRP314 and is known to extend from east of E26 north through E27.

Resources at Northparkes are associated with alkalic porphyry copper-gold deposits. Copper and gold mineralisation occurs as quartz-sulphide veins, breccia-fill and disseminations developed in and around clusters of pencil-shaped magmatic intrusions of quartz monzonite composition. Copper occurs as bornite (Cu5FeS4 ) and chalcopyrite (CuFeS2 ), while gold occurs as microscopic native gold grains within and around the copper sulphides.

The porphyries form narrow, typically less than 50 m in diameter, but vertically extensive (greater than 1,000 m) pipes. Mineralisation extends from the porphyries into their host lithology. The current life of mine plan is focused on five porphyries, referred to as E26, E48, E22, E31 and GRP314; in addition to these zones numerous other mineralised porphyries exist across the district. The deposits are hosted within both the Goonumbla and Wombin Volcanics, with mineralisation related intrusive rocks effectively forming part of the latter.

Sulphide mineralisation occurs in quartz stockwork veins, as disseminations and fracture coatings. Highest grades are generally associated with the most intense stockwork veining. Sulphide species in the systems are zoned from bornite-dominant cores, centred on the quartz monzonite porphyries, outwards through a chalcopyrite-dominant zone to distal pyrite. As the copper grade increases (approximately > 1.2 per cent copper), the content of covellite, digenite and chalcocite associated with the bornite mineralisation also increases. Gold normally occurs as fine inclusions within the bornite; due to the intimate relationship with bornite, visible gold tends to occur within the highest-grade zones of the central portion of the deposit. A small portion of gold mineralisation does not appear to be directly associated with copper sulphide minerals. Silver is associated with copper sulphide minerals and is present in solid solution and as inclusions of silver-bearing tellurides and electrum. Copper-to-gold ratios differ between the different deposits and within individual deposits.

All of the Northparkes deposits are cross-cut by late faults/veins filled with quartz carbonate and minor gypsum, anhydrite, pyrite, tennantite chalcopyrite, sphalerite and galena, the associated sericite alteration can extend up to 10 m from the faults. Tennantite, which contributes arsenic to the final copper concentrate, is present in higher concentrations in the E48 deposit.

Oxide mineralisation blankets were well developed over the E22 and E27 deposits. The upper blanket was gold-rich and copper-poor. The lower blanket was enriched in copper by supergene processes. The dominant copper oxide minerals at E22 and E27 were copper carbonates (malachite and azurite) and phosphates (pseudomalachite and libethenite) with lesser chalcocite, native copper, cuprite and chrysocolla. A gold-poor, less well developed, supergene copper blanket was also developed over the E26 deposit. At E26 the oxide copper minerals included atacamite, clinoatacamite and sampleite, in addition to those copper minerals observed in E22 and E27.

The Northparkes deposits are typical porphyry copper systems, in that the mineralisation and alteration are zoned around multiphase quartz monzonite porphyries. As described by Pacey et al (2019) mineralization was caused by the forcible, periodic escape of low-viscosity, crystal and volatile-rich magmas. These exploited pre-existing structural intersections and focused the discharge of large quantities of magmatic fluids from the underlying chamber. The fluids circulated in intricate fracture networks to produce K-feldspar-sulphide veinlets and quartz sulphide stockwork veins, surrounded by K-feldspar–dominated alteration. Ore grades are exclusively located within the potassic alteration zones, although some have been sericitically overprinted.

Mining Methods

• Truck & Shovel / Loader
• Sub-level caving
• Block caving

Summary:

Mining methods at Northparkes include (underground) block-caving and sub-level caving of the low grade massive and reasonably large rock masses with suitable (caveability) properties. Open cut mining has been used in past and is underway on several small resources.

Underground Operations
Operations in 2023 included the mining of the E26 L1N block cave, E48 block cave, development of the E26 SLC level 5 and level 6, and the initial production from the E26 SLC level 5.

* E48
- First lift (E48L1) completed December 2023
- Sub level cave (SLC) due to be executed from FY25, benefitting from existing infrastructure
- First fully automated underground mining operation

* E26
- E26 mining areas comprised of L1, L2, L1N block caves and the E26SLC
- Current mining is focused on E26L1N block cave (commenced 2022) and E26SLC (commenced 2016)
- E26 L1N block cave expected to operate thru 2032
- E26SLC consists of 6 sub levels, 4 mined to date

Block cave mining accounts for the majority of ore production at Northparkes, with minor contributions from surface stockpile reclamation and open pit mining. Preproduction mining development work consists of establishing two working levels, the undercut level and extraction level, at the base of each ore block, as well as the development to support the associated material handling system. Northparkes has developed its own unique extraction level layout that locates the material handling system, including crusher, to the side of the extraction level, thereby alleviating the need to construct a third level dedicated to haulage. Similarly, it has established the extraction level as the primary ventilation level, thereby eliminating development to support mine ventilation. The undercut level, which is used to initiate caving, is 14 - 20 m vertically above the extraction level, the height being dependent on the undercutting method. Undercutting, which involves sequential firings of overlapping fans of blastholes to create the initial void for caving, is the rate controlling step for production ramp-up, controlling both the rate of undercutting ore and the start of production from drawpoints.

The Northparkes rock mass, including the E48 and E26 deposits, is a highly jointed rock mass with fracture frequencies of between three and 20/m and fracture density that increases with copper grade.

Mine access for all personnel and equipment is provided by surface portal and decline. The decline has a standard 5 m wide by 5.5 m high arched profile. The hoisting shaft represents the second means of egress and the ore skips can be fitted with a man-riding cage in the event that personnel cannot egress the mine via the decline. The mining process involves recovery of broken rock from the drawpoints by 14 t capacity electric LHDs, which tram the ore to a primary crushing station, consisting of plate feeder and jaw gyratory crusher, located on the margin of the extraction level. Typically, four to five LHDs operate on a continuous basis. E48 Lift 1 is highly automated, utilising driverless loaders. Crushed ore is fed onto high-speed inclined conveyors via an ore pass that also provides storage capacity. Ore is conveyed to the underground loading station, which consists of three ore passes feeding the hoisting system. The hoisting system consists of a ground mounted friction winder with integrated drum and rotor, servicing two 18 t payload skips in counterbalance, running on rope guides in the 6 m diameter concrete lined shaft. Hoisted ore is transferred via an overland conveyor to crushing cicuit.

Northparkes has developed a comprehensive cave management system based on its experiences with operating the E26 block caves. These management systems are designed to manage the specific catastrophic safety risks particular to block caves; namely airblast, surface subsidence and inrush and large-scale rock falls. The system is also designed to support maximising reserve recovery and optimising mine production. The system is based on a large number of monitoring systems, including real-time microseismic event monitoring, open hole surveys using probes and video cameras, time domain reflectometers installed in grouted boreholes, convergence monitoring using extensometers and manual measurements of mine openings on the extraction level and in key underground infrastructure, drawpoint fragmentation and geology mapping, drawpoint grade sampling, subsidence zone volume surveys and water inflow measurements.

The mine ventilation system consists of two primary exhaust shafts (E26 and E48) each with two fans mounted on surface above a system of vertical and lateral return airways. The primary air intakes are the main decline, the hoisting shaft and E48 intake shaft. The ventilation system typically operates at airflows of 600 - 650 m3 per second, which are shared across the various work areas.

Operations in 2023 included the mining of the E26 L1N block cave, E48 block cave, development of the E26 SLC level 5 and level 6, and the initial production from the E26 SLC level 5.

Underground mining activities are currently undertaken in the E26 ore body. The E26 L1N mine is operated as a block cave as the primary method of resource extraction. Block caving is an underground hard rock mining method that involves undermining an ore body, allowing it to progressively collapse under its own weight (see Figure 4 Block Cave Mining Method). The E26 SLC mine is a sublevel caving operation involving construction of the sub level horizon followed by retreat drill and blast of that horizon, with the material above allowed to freely cave to fill the opened voids.

The E26 SLC project commenced construction in April 2015 and went into production in 2016. The mine design aimed to extract a remnant wedge of high-grade material adjacent to the E26 Lift 2 block cave. The operations at E26 SLC had ceased in 2021, having completed production from the first four levels at approximately 20m vertical spacing. The remaining two levels were deferred due to less favourable economics. The development of the remaining levels commenced in 2023 with 25m vertical spacings. Production has commenced from level 5, with level 6 coming online early in 2024. Production in the SLC is expected to continue until early 2026.

Mining development is planned for 2024 for the purpose of accessing the E22 ore body, however, pending approval of proposed Modification, other development may occur under other orebodies.

Open cut
Current open cut mines are E31 and E31N.

Open-pit mining operations re-commenced at Northparkes in late 2022, following a period of only underground mining for more than ten years.

In the first half of 2023, the E31 Project continued providing waste for the construction of the adjacent Rosedale TSF until the facility was completed.

In July 2023, the approved mining contractor commenced production, with the two pits being mined concurrently to obtain greater operational flexibility. The estimated open pit mine life was approximately 18 months at a mining rate of approximately 400,000 bank cubic metres (BCM) per month.

During the open pit lifespan, approximately 3.9Mt of higher-grade sulphide ore will be added to the Northparkes production plan, as well as an additional 1.7Mt lower-grade sulphide and 1.9Mt of transitional ore, which will be stockpiled for future processing.

Over the life of the open cuts, a combined total of approximately 13.5 million tonnes of material is to be mined as either waste or ore, of which approximately 3.6 million tonnes were mined in 2023. This comprised of roughly 400,000 tonnes of sulphide ore, 935,000 tonnes of oxide ore, and 3.1 million tonnes of waste material.

Approximately three 10m benches were mined in each pit in 2023; E31N progressing from 290mRL to the 270mRL bench, while E31S was mined from 275mRL to the 255mRL bench.

Comminution

Crushers and Mills

Summary:

Ore is fed to the plant from two sources; via the underground operations and the winder, or from open cut material via a surface crushers. New surface secondary crushing and screening facility installed with Sandvik crushers.

Underground Crushing
The first BK 63-75 crusher was commissioned underground at Northparkes in 2003 followed by a second installation in 2009.

2019 - Northparkes is installing a third BK 63-75 at the new E26L1N block cavern underground crushing station.

The first two crushers installed are of a single mouth design with the latest crusher being a double mouth design.

The latest crusher is noteworthy as the world’s first “double-mouth” jaw-gyratory crusher, developed by thyssenkrupp Industrial Solutions in consultation with Northparkes to meet its specific operating objectives. It is based on the proven BK 63-75 design but has a new, patented, spider to give the opportunity to feed the crusher from both sides – the double mouth jaw configuration – thus removing the need for a primary crusher feed (buffer) hopper and primary apron feeder.

Grinding
The comminution process consists of two parallel grinding modules and a single line flotation plant consisting of a SAG, ball and tertiary mills:

•Module 1: 2.9MW SAG mill with a pebble crushing circuit followed by a 2.9MW primary ball mill and 1.3MW tertiary ball mill; throughput rates vary between 280tph and 430tph depending on feed size, with a final product grindsize (P80) of between 90-140um; and

• Module 2: 4.9MW SAG mill with two pebble crushers followed by a 4.9MW primary ball mill and a 1.6MW tertiary ball mill; throughput rates vary between 450tph and 680tph depending on SAG mill feed size, with a final product grindsize of between 100-160um.

Processing

• Crush & Screen plant
• Jameson Cell Flotation
• Flotation
• Dewatering

Summary:

The plant was designed to process both copper gold oxide and sulphide ore; the cyanide / oxide processing circuity was decommissioned.

Ore processing includes several defined stages that include crushing, grinding, flotation and dewatering. Ore is sourced from either underground mines, surface stockpiles or open pits, where it is first primary crushed, followed by passing through a secondary and tertiary crushing circuit before being stockpiled into two separate stockpiles. From the stockpiles, material is fed to the grinding circuit, compromising of two parallel modules (Mod 1 and Mod 2), each incorporating a Semi Autogenous Grinding (SAG) mill, oversize pebble crushing, two stages of ball milling, flotation (rougher-scavenger with cleaning stage) and thickeners for concentrate and tails streams.

From grinding, the material flows through a single line flotation circuit; initially through a series of rougher/scavenger flotation cells, before entering the cleaner circuit, comprised of Jameson Cells and mechanical cleaner-scavengers. Copper and Gold bearing sulfide minerals are recovered using Hostaflot 26293 as the primary flotation collector and Flotanol 16319 as the frother as well as Sodium.

Hydrosulphide (NaHS) as a sulphidizing agent. Concentrate produced from the flotation circuit is thickened and filtered to produce a final concentrate, with a moisture content of 8-10%.

Air and agitation to produce bubbles in combination with a suite of regents, to enable attachment of particles (minerals) are captured and recovered in the flotation process to produce a sulphide-rich concentrate containing Copper and Gold bearing minerals. After flotation, the concentrate is first thickened through thickeners and filtered through ceramic disc filters to produce a low moisture concentrate ready for loading and transportation to the port.

The recent expansion project comprised of: (1) the installation of a closed loop secondary & tertiary crushing circuit to replace the existing open circuit secondary crusher; (2) upgrading of the feed conveyors, discharge screens, hoppers, cyclone clusters and pumps; and (3) Relocation of existing pre flotation cell, installing a new flotation cell and refurbishing the cleaner scavenger cells.

Commissioning of the new secondary and tertiary crushing facility was completed in 2021 allowing the concentrator to achieve a nominal throughput rate of 7.6Mtpa.

The tailings component is pumped from the final flotation stage to a tails thickener for dewatering followed by additional pumping to the tailing’s storage facilities.

Pipelines and Water Supply

Summary:

Northparkes sources water from numerous locations including imported water from various licences. Water recycled from the on-site ore processing facility and tailings dam reclamation system is collected through existing on-site infrastructure. Effective water management is crucial to the long-term success of Northparkes operations as it is essential in the processing of ore through the concentrator to produce copper concentrate. The water management system aims to collect efficiently and economically, store and re-use water onsite to minimise external water supply inputs and supplement supply during periods of high consumption.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Commercial Manager	Glenn Pearson		Oct 23, 2024
General Manager Operations	Rob Cunningham		Oct 27, 2024
Mining Manager	Johan Ferreira		Oct 23, 2024
Processing Manager	Mitch Garside		Oct 23, 2024
Superintendent Logistics	Gabe (Rosser) Albert		Oct 23, 2024
Technical Services Manager	Sergio Melloni		Oct 23, 2024
Technical Services Superintendent	Riek Muller		Oct 23, 2024