Australia

Eva Project

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Overview

Mine TypeOpen Pit
StagePermitting
Commodities
  • Copper
  • Gold
Mining Method
  • Truck & Shovel / Loader
Production StartH1 2027
Mine Life15 years (as of Jan 1, 2020)
ShapshotThe Eva Copper Project is in a feasibility update phase, project is located in the highly prospective Mt Isa Inlier region and will involve mining native copper and copper sulphide ore from six open pits and processing through a copper concentrator.

Finalisation of the updated feasibility study for approval by the board in calender year 2024.

Owners

SourceSource
CompanyInterestOwnership
Harmony Gold Mining Company Ltd. 100 % Indirect
On December 16, 2022, Harmony acquired full ownership of the Eva Copper Project.

Contractors

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Deposit type

  • IOCG
  • Hydrothermal
  • Vein / narrow vein
  • Stratabound

Summary:

Copper deposits of the Eva Copper Project are of two types. The most significant are those of the IOCG type, which are hydrothermal copper-gold deposits associated with relatively high contents of iron oxide minerals (magnetite or hematite), a general lack of quartz, and extensive sodic alteration. The hydrothermal fluids are believed to be sourced from, and/or driven by, magmatic systems with possible addition of basin brines; however, mineralization is commonly distal (or spatially distinct) from the causative plutonic rocks. Mineralization can take many forms, but the dominant ones are vein networks, breccias, dissemination, and replacement. Both structure (fault or fracture systems) and lithology (chemistry and rheology) are key features in localization of mineralization. The second type of copper deposit is termed copper-only; these deposits do not contain significant gold, and are typically hosted within deformed and metamorphosed calcareous sedimentary rocks as stratabound mineralization. One deposit, Turkey Creek, is a stratabound copper-only deposit within volcanic rocks, and has processing characteristics similar to those for the copper-gold deposits.

There are twelve known mineral deposits in the Project area, of which seven have been included in the current mine plan. Mineral deposits are grouped into two types: copper-gold, and copper only. There are five of the copper-gold deposits, all of which are in the mine plan. These deposits are classified as iron oxide copper-gold (IOCG) deposits, where mineralization is associated with regional-scale hematite and albite alteration (red-rock alteration), and localized magnetite alteration. Copper sulphide mineralization, primarily chalcopyrite with lesser bornite, occurs as veins, breccias, fracture fill, and disseminations in mafic to intermediate volcanic or intrusive rocks. Gold is generally correlated with copper, and is recovered in the copper concentrate. Mineralization appears to be localized and/or bounded by faults and other deformation-related structures.

The copper-only deposits hosted within calcareous metasedimentary rocks have additional zones of weathering and/or acid leaching, which has removed carbonate, reducing rock strength and density in addition to changing sulphide mineralogy. In the two such deposits, Blackard and Scanlan, a supergene zone termed native copper occurs below the oxide zone, and contains abundant native copper in addition to chalcocite, cuprite, and other low-sulphur copper species. Extensive metallurgical testing has been carried out on these deposits, with appropriate processing design and estimation of recoveries. Within these deposits a narrow transition zone occurs between the copper zone and underlying sulphide zone.

All of the deposits have a 10 m to 25 m thick overlying zone of oxidation, where the rock is extensively weathered, and copper sulphide minerals have been leached or converted to various oxide minerals that cannot be recovered by flotation. The oxide zones are treated as waste, but tonnages and copper grades have been estimated. With the exception of the Turkey Creek deposit, the copper-only deposits commonly have a significant thickness of supergene material, where carbonate has been leached from the rock, reducing hardness and density, and the copper occurs as native-copper, chalcocite, and other low-sulphur copper species. The carbonate-leached zone is separated from the underlying sulphide zone by a thin transition zone. Each of these mineralogical zones has been modelled so that resources can be estimated for each and the appropriate metallurgical recoveries can be applied for reserve estimation.

Little Eva
The Little Eva deposit is a significant hydrothermal iron-oxidecopper gold (IOCG) deposit within the Eva Copper Project area, and is the largest single copper deposit in the project, sharing similarities with the Ernest Henry copper-gold deposit nearby. Spanning 1.4km in length, varying from 20m to 370m in width, the deposit's mineralisation is open below 350m (165mRL) vertically and extends beyond the current drilling extents, with additional potential both to the north and south.

The mineralisation is hosted by faulted subvolcanic porphyritic and amygdaloidal intermediate volcanic or intrusive rocks within intercalated folded calc-silicate, marble, quartzite, and biotitescapolite schists. The mineralisation is structurally controlled, occurring within breccias, fracture fill, and veinlet stock works.

Turkey Creek
The Turkey Creek deposit is located 1.5km east of the Little Eva deposit. The deposit is sub-cropping in a relatively flat, gently undulating area with thin (<0.5m) in-situ soils and alluvium cover. The deposit is over 1.8km in length, with mineralisation is open at depth extending from surface to drilled depths of 150m. The deposit displays excellent continuity along strike and down-dip with true widths varying from 10m to 30m at the southern end, to 30m to 50m at the northern end. The main part of the deposit strikes north and dips 60 degrees to the east. At the northern end, the mineralisation and host stratigraphy are folded sharply eastwards into a curved synform that dips steeply south. The northern zone is slightly offset by faulting from the main southern zone.

Blackard and Scanlan
The Blackard and Scanlan deposits are located approximately 5km and 17km, respectively, south of the Eva deposit and form a 7km long trend of mineralisation that follows the stratigraphy as it curves around the east side of the Knapdale Quartzite. The Blackard deposit morphology is a function of folded stratigraphy and/or faulting having a strike length of 3.5km, a maximum plan width of 350m, and a stratigraphic width of only 60m to 90m. A series of parasitic folds and/or fault repetitions result in a much wider deposit. The Scanlan deposit has a strike length of 1 500m and a maximum width in plan of 500m. Scanlan comprises a 10m to 50m thick horizon in the southern half, with the thicker part folded into a ‘V’ shaped synform on the eastern side and the thinner part forming a nearly flat antiform to the east.

Reserves

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Mining Methods

  • Truck & Shovel / Loader

Summary:

Conventional open pit mining methods, which include drilling, blasting, loading, and hauling, will be employed at the Eva Copper Project open pits. The Eva Copper Project is estimated to have a two- year construction period, one of which is pre-production mining. Mining activities are based on open pit mining of the Little Eva deposit at a rate of 31,200 t/d of ore. This primary pit at Little Eva will be supplemented by progressively mining six satellite pit areas at Blackard, Scanlan, Turkey Creek, Bedford North and South, Lady Clayre, and Ivy Ann, to achieve a minimum 11.4 Mt/a mill feed rate.

The mining method involves a 13.4 Mt pre-strip of a starter pit at Little Eva, which includes 1.2 Mt of ore. To sustain a 31,200 t/d production rate during the mine life, stripping will continue at slightly elevated rates for several months after production commences. There will be three pushback pits in Little Eva, three pushbacks at Blackard, and two pushback pits in Turkey Creek, while Bedford, Scanlan, Lady Clayre, and Ivy Ann will have one phase of mining.

Drilling will be carried out using conventional drill and blast (D&B) blasthole drills with diesel-powered front shovel excavation, and off-highway dump truck haulage. The initial main mining fleet consists of two front shovels with 22-m3 buckets and an operating weight of 400-tonnes each, matched to fourteen (Year -2 and Year -1) 141-tonne off-highway rear dump trucks. This fleet is supplemented by the standard support equipment composed of, but not limited to, track dozers, water trucks, graders, front-end loaders (FELs), light vehicles, and service equipment. Ore haulage from the Scanlan and Lady Clayre satellite pits will be accomplished with the same mining fleet as discussed above.

Approximately 381 Mt of mine waste will be transported to dumps adjacent to each of the pits, or to the TSF for construction. The TSF is expected to require approximately 65 Mt of mine waste. Waste will also be used to construct an engineered creek diversion channel and flood protection bund around the Little Eva pit, known as the Cabbage Tree Creek (CTC) Bund. The channel and bund will redirect wet season water flows in Cabbage Tree Creek away from the Little Eva pit. Diversion bunds and ditches will also be built around the other open pits, where needed.

The ROM ore will be delivered to the ROM pad, where there will be the capability to direct feed from mine trucks to a gyratory crusher with 600 kW of installed power capable of accepting 1-m diameter rock at a rate of 1,733 t/h (75% crusher availability).

The current mining schedule then prioritizes the mining of ore sequentially from Little Eva, Blackard, Scanlan, and Turkey Creek. The other satellite deposits (Lady Clayre, Bedford, and Ivy Ann), which only account for 5% of the Mineral Reserves, will commence mining towards the middle to end of the mine life. The proximity of Turkey Creek to the mill makes it preferable to mine it early in the mining schedule. Further investigation and rescheduling will be carried out prior to project commencement.

Mining of ore from the Bedford pits (North and South) is scheduled to commence in Year 4 and Year 5. Lady Clayre pits are scheduled to be mined in years six to eight, and Ivy Ann in Year 5 through Year 6. As noted previously, three of the satellite pits are quite small compared to the Little Eva and Blackard pits.

Dewatering of the open pits will be required. A plan of dewatering wells, horizontal drains, and sumps is envisioned. A detailed plan will be developed during the Project’s development period. It has been estimated that the Little Eva pit dewatering will discharge approximately 4,000 m3/d, and the Blackard pit dewatering approximately 2,000 m3/d. This water is slated to be used as make-up water in the processing plant.

Comminution

Crushers and Mills

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Processing

  • Jig plant
  • Gravity separation
  • Crush & Screen plant
  • Centrifugal concentrator
  • Flotation
  • Dewatering
  • Filter press

Summary:

The Eva Copper Project, comprising Little Eva, Blackard, and other satellite deposits, has been developed based on the mine plan for a nominal combined mining rate of approximately 31,200 t/d copper ore, equivalent to 11.4 Mt/a, with direct feeding of the ore to the processing plant. The processing plant was designed to produce a marketable concentrate with a grade of 28% Cu (and 3 g/t Au when treating gold-bearing ores) using conventional recovery methods, including crushing, grinding, gravity concentration, flotation, and tailings disposal.

The throughput of 31,200 t/d of copper ore was developed for a feed blend consisting of 75% sulphide ores and 25% native copper ores.

The process description that follows is based on the nominal throughput of 31,200 t/d. The key
process units are the following:
- Primary, secondary and tertiary crushing.
- Ball milling in closed-circuit with cyclones, which includes a jigging circuit.
- Rougher flotation circuit.
- Rougher concentrate regrind mill in closed circuit with cyclones and a gravity circuit
- Cleaner, recleaner, and cleaner-scavenger DFR circuit.
- Gravity concentrate dewatering and sun-drying paddock.
- Flotation concentrate thickening, filtration, and storage.
- Gravity and flotation concentrate dispatch.
- Tailings thickening and disposal.
- Process and fresh water circuits.

Jigging
The two blanks are dedicated to feed the rougher jigs (1 blank per rougher jig). A portion of the cyclone cluster feed (typically 15%) gravitates to the rougher jigs, which consist of two IPJ3500 inline pressure jigs. The rougher jigs produce a concentrate that requires further upgrading, and reports to the cleaner jig. The cleaner jig is a single IPJ2400 inline pressure jig. The cleaner gravity concentrate gravitates to the recleaner jig. Both rougher and cleaner jig tailings gravitate to the cyclone feed pump box.

The recleaner jig consists of a single IPJ1000 inline pressure jig. Tailings from the recleaner jig report to the recleaner jig tailings tank, from where they are pumped and recirculated to the cleaner jig. Concentrate from the recleaner jig reports to the gravity concentrate dewatering cone.

Flotation and Flotation Concentrate Regrind Circuits
The flotation circuit consists of conventional rougher flotation followed by rougher concentrate regrind, and a cleaner, recleaner, and cleaner-scavenger DFR circuit to produce a final flotation concentrate. The flotation area of the plant will include the following:
- Conventional rougher flotation followed by rougher concentrate regrind, and a cleaner, recleaner, and cleaner-scavenger DFR circuit to produce a final flotation concentrate.
- Six conventional forced-air addition 300 m3 rougher flotation tank cells. The rougher concentrate flows by gravity to the regrind circuit, and the rougher tailings reports to the tailings thickener via a metallurgical sampler.
- Rougher concentrate is directed to a regrind tower mill operating with circulating load of 150% in closed circuit with a cyclone cluster.
- The regrind cyclone cluster has six ports, with four 400 mm diameter operating cyclones and two in standby. The cyclones operate at 80 kPa, producing a cyclone overflow particle size of P80 48 µm. The regrind cyclone overflow reports to the cleaner flotation head tank.
- A continuous gravity concentrator has been included in the rougher concentrate regrind circuit. The gravity concentrator, treating 25 t/h of solids, has been sized for this application, and processes approximately 16% of the regrind cyclone underflow stream. The resulting concentrate reports directly to the gravity concentrate dewatering cone.
- The cleaner circuit consists of two 18 m3 DFRs. The cleaner DFRs produce a high-grade concentrate that reports to the final flotation concentrate pump box, while the tailings flow to the cleaner-scavenger DFRs.
- The cleaner-scavenger circuit consists of six 18 m3 DFRs. Concentrate from the cleaner-scavenger DFRs is pumped to the recleaner DFRs, while the tailings are pumped to the tailings thickener via a metallurgical sampler.
- The recleaner circuit consists of three 6 m3 DFRs. The recleaner concentrate reports to the final flotation concentrate pump box, and tailings are pumped to the regrind cyclone feed pump box.
- An on-stream analyzer (OSA) and associated multiplexer is included for online process control and sampling.
- Flotation collector (PAX) is added to the ball mill and rougher and cleaner flotation. Frother (MIBC or Polyfroth H27) is added to the rougher, cleaner, and cleaner-scavenger flotation as required. Sulphidizer (NaHS) is added to the two last rougher flotation cells.

Gravity Concentrate Handling
The gravity concentrate handling area of the plant is summarized as follows:
- A 1.8 m diameter gravity concentrate dewatering cone receives the concentrate from the recleaner jig and Knelson concentrator. The dewatering cone overflow solution is recovered and sent to the flotation concentrate thickener. Gravity concentrate solids settle for collection at the underflow cone at a density of 70% solids.
- The dewatering cone underflow gravity flows to the gravity concentrate paddock, where the remaining moisture will evaporate.

Flotation Concentrate Handling
The flotation concentrate handling area of the plant is summarized as follows:
- A 16 m diameter high-rate concentrate thickener, including a Frothbuster system to minimize foam and concentrate loss, is included in the design. The concentrate thickener underflow density has been specified as 65% solids. Flocculant is added to facilitate settling and limit suspended solids in the supernatant solution. Overflow solution from the concentrate thickener is recycled as process water to the primary cyclone pump box to utilize the presence of residual flotation reagents.
- The design specification is for an automatic pressure filter (horizontal filter press) with a filtration area of 140 m2 (using sixty-two 1.5 x 1.5 m plates) and air drying, to achieve a concentrate filter cake with 9% moisture, operating at an availability of 65%, with a cycle time of 12.5 minutes.

Concentrate Storage and Load-Out
Gravity and flotation concentrates will be stored and transported separately:
- A covered building provides storage for up to 2,400 tonnes of flotation concentrate (equivalent to three to four days of production at design rates) and a FEL is used to optimize concentrate storage within the building. Flotation concentrate is loaded into trucks by FELs. Trucks are positioned on a scale prior to loading. The scale provides feedback to the FEL operators as the trucks are filled. When trucks are full, they drive through a wheel wash, and then the concentrate is transported to an off-site facility in half-height sealed containers.
- The gravity concentrate paddock provides storage of up to 200 tonnes of gravity concentrate. The gravity concentrate paddock has two compartments, each with capacity of 100 tonnes. While concentrate fills one compartment during a period of 11 days, the gravity concentrate in the other compartment dries out and is loaded into a truck by a FEL, similarly to the procedure described for the flotation concentrate. The proportion of copper production as gravity concentrate is anticipated to vary significantly over the life of mine; therefore, the residence time provided by the drying paddocks is estimated based on the nominal mill feed blend composition and corresponding testwork results.

Recoveries & Grades:

CommodityParameterAvg. LOM
Copper Recovery Rate, % 87
Copper Head Grade, % 0.46
Copper Concentrate Grade, % 28
Gold Recovery Rate, % 78
Gold Head Grade, g/t 0.05
Gold Concentrate Grade, g/t 3

Production

CommodityProductUnitsAvg. AnnualLOM
Copper Payable metal M lbs 1,437
Copper Metal in concentrate M lbs 991,497
Copper Concentrate kt 1632,425
Gold Payable metal koz 192
Gold Metal in copper conc. koz 14203

Operational metrics

Metrics
Daily mining rate 98,200 t *
Daily ore mining rate 31,200 t *
Daily processing rate 31,200 t *
Annual ore mining rate 11.4 Mt *
Annual production capacity 194 dmt of copper concentrate *
Annual processing rate 11.4 Mt *
Annual processing capacity 12 Mt *
Stripping / waste ratio 2.2 *
Waste tonnes, LOM 380,574 kt *
Ore tonnes mined, LOM 170,386 kt *
Total tonnes mined, LOM 550,959 kt *
Tonnes processed, LOM 170,386 kt *
* According to 2020 study.

Production Costs

CommodityUnitsAverage
All-in sustaining costs (AISC) Copper USD 0000000
C1 cash costs Copper USD 0000000
Assumed price Copper USD 000
Assumed price Gold USD 0000
* According to 2020 study / presentation.
Net of By-Product.

Operating Costs

Currency2020
OP mining costs ($/t mined) USD 1.66 *  
OP mining costs ($/t milled) USD 5.26 *  
Processing costs ($/t milled) USD 5.14 *  
G&A ($/t milled) USD 0.56 *  
Total operating costs ($/t milled) USD 11.4 *  
* According to 2020 study.

Project Costs

MetricsUnitsLOM Total
Initial CapEx $M USD 443.4
Sustaining CapEx $M USD 34
Closure costs $M USD 14.1
Total CapEx $M USD 491.5
OP OpEx $M USD 888.7
Processing OpEx $M USD 868.3
G&A costs $M USD 95
Total OpEx $M USD 1,925
Total Taxes $M USD 447
Royalty payments $M USD 199.9
Net revenue (LOM) $M USD 4,311
After-tax Cash Flow (LOM) $M USD 1,091
Pre-tax NPV @ 8% $M USD 648
After-tax NPV @ 8% $M USD 437
Pre-tax IRR, % 37
After-tax IRR, % 29
After-tax payback period, years 2.5

Heavy Mobile Equipment

Ref. Date: January 31, 2020

SourceSource
HME TypeModelSizeQuantity
Compactor Komatsu WF450-T 1
Crane 250 t 1
Crane 80 t 1
Dozer (crawler) Komatsu D375A 4
Dozer (rubber tire) Komatsu WA600-5 1
Drill Epiroc PV271 2
Drill (blasthole) Epiroc DM45 1
Excavator Komatsu PC850-8 1
Grader Komatsu 825A-2 2
Loader Komatsu WA200PZ-6 1
Loader Komatsu WA600-5 6.5 m3 2
Loader (FEL) Caterpillar IT 28 1
Loader (FEL) Caterpillar 930G 1
Loader (FEL) Komatsu WA900 13 m3 2
Scraper 24 cu. yd 1
Shovel Komatsu PC4000 22 m3 3
Tire manipulator Komatsu WA600 1
Truck (dump) Komatsu HD1500-7 144 t 22
Truck (dump) Komatsu HM400-3MO 5
Truck (fuel / lube) Komatsu HD605-7 1
Truck (fuel / lube) Caterpillar 775B 1
Truck (water) Komatsu HD605 63 t 2

Personnel

Mine Management

Source Source
Job TitleNameProfileRef. Date
Consultant - Recovery Methods Paul Staples LinkedIn May 7, 2020
Environmental Manager Sarah Watson LinkedIn Nov 6, 2023
Procurement Manager Robert Blyth LinkedIn Nov 6, 2023
Project Executive Bryan Bailie LinkedIn Nov 6, 2023
Site Senior Executive & Mine Manager Iain Sturgeon LinkedIn Dec 24, 2023

Total WorkforceYear
280 2020

Aerial view:

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