- The Whim Creek Project located 120 km southwest of Port Hedland, is an 80/20 joint venture between Anax Metals Limited and Develop Global Limited
- Oxide ore was mined from Whim Creek and Mons Cupri volcanic-hosted massive sulphide (VMS) deposits by Straits Resources Limited (now Aeris Resources) in the mid-2000s. Ore was processed through a heap leach and SX/EW plant to produce around 15,000 tpa of copper cathode
- Sulphide resources are undeveloped
- Anax acquired its 80% interest in the Project in late 2020 and has been focussed on advancing the Project through the completion of resource development, feasibility studies and exploration
- Refurbished and new stormwater infrastructure completed by Anax has significantly reduced legacy environmental harm and future risk
- Project Reserve of 4.6 Mt @ 1.36% Cu and 2.30% Zn (April 2023 DFS) will produce 10,000 to 12,000t of copper equivalent metal per year
- A technically and economically robust polymetallic project and strategic processing hub development in the Pilbara
- Numerous opportunities for consolidation in the area actively being assessed and pursued
- Anax is working with the Ngarluma people to refurbish the iconic Whim Creek Hotel complex which will provide benefits to the greater Pilbara community
Anax has signed a binding royalty agreement with Anglo American whereby Anglo American receives a 1% Net Smelter Return for Anax’s copper and zinc production at Whim Creek. Anglo American have paid Anax US$2M towards capital expenditure, as well as providing a project funding package of up to US$20M.
Anax’s 80/20 joint venture agreement with Develop Global Limited enables Anax to develop the Whim Creek Project in the Pilbara region of Western Australia. Anax is conducting a feasibility study at Whim Creek, including smart sorting testwork, to enable the project development.
The Whim Creek Copper-Zinc Project is located approximately 120km south-west of Port Hedland in the Central Pilbara Region of Western Australia. The map illustrates the location of the project in relation to neighbouring tenure and local infrastructure, including Port Hedland, Karratha and the Great Northern Highway.
Whim Creek Project Location Map
Regional GSWA Geology and tenure at Whim Creek Project
Within the Project are four main prospects, namely Whim Creek, Mons Cupri, Salt Creek and Evelyn, where structurally controlled, volcanic hosted massive sulphide (VHMS) style, copper-zinc-lead mineralisation have defined JORC-2012 Resources. Salt Creek, Whim Creek and Mons Cupri occur within volcanicastics and sediments of the Bookingarra Group, part of the Archean Whim Creek Basin. The Evelyn deposit, 25km to the south, occupies the contact between sandstones and ultramafics of the De Grey Group in the Croydon Anticline structure of the Mallina Basin, considered to be laterally equivalent to the Whim Creek Greenstones. All four resources have potential for extensions at depth.
The Archean granite-greenstones of the Whim Creek tenure are highly prospective for gold, lithium, nickel-cobalt and platinum group elements, as well as new VMS style polymetallic deposits. Deep seated, mineralising structures bound the tenure to the north-east and south-west providing 10,000 Ha of prospective ground for exploration.
Since acquiring the Project in 2020, Anax has increased defined JORC 2012 resources by over 57%. The Mineral Resources that underpin the reserves and production targets declared in the April 2023 DFS, have been prepared by Competent Persons in accordance with the 2012 edition of the JORC Code, and were first published by the Company in the following ASX releases:
- Mons Cupri: Re-compliance Prospectus (18 Sep 2020)
- Whim Creek: Whim Creek Resource (25 May 2021)
- Evelyn: Evelyn extended with excellent Cu, Zn & Au intersection (4 Oct 2022)
- Salt Creek: Significant increase for Salt Creek Resource (12 September 2022)
The 2023 April Feasibility Study identified a Life of Mine (LOM) Production Schedule that underpins an overall mine life of 8 years, which includes 7.5 years of open pit and underground mining. The DFS LOM Production Schedule is made up of Ore Reserves and Inferred Mineral Resources that were modified using the same factors as the Ore Reserve.
2023 DFS LOM Mining Schedule
Mons Cupri Pit Design
A key feature of the Whim Creek operation will be pre-concentrating ore through the use of X-ray transmission ore sorters that will upgrade the ore extracting the particles with the highest sulphide content thereby removing dilution maximising feed grades prior to milling and flotation. This has numerous environmental and cost benefits, resulting in substantial savings in power, water, reagents and a reduction in tailings deposition.
Whim Creek will use a two-stage ore sorting circuit for >8mm and an in-line pressure jig (IPJ) for <8mm crushed ore as shown below. The bulk of contained copper, zinc, lead and precious metals will report to the high-grade pre-concentrates generated in the first stage of ore sorting. These pre-concentrates (as well as gravity-upgraded -8mm fines) will then be treated in the concentrator to produce saleable concentrates.
Primary sort rejects will contain residual copper and zinc that will be processed through the second stage ore sorter to produce medium grade ore (middlings) that will be stockpiled for processing through either the concentrator or the heap. Secondary sort rejects may also be treated on the heap if their residual copper and zinc content is above the marginal cut-off grade for production through the heap leach circuit.
2023 Definitive Feasibility Study
The Whim Creek Definitive Feasibility Study (DFS) completed in April 2023 demonstrates the potential for a technically and economically robust polymetallic project and strategic processing hub development in the Pilbara.
Mons Cupri and Whim Creek are proposed to be mined using conventional open cut mining techniques, while the high-grade Evelyn and Salt Creek deposits are proposed to be mined using underground techniques.
The processing route considered for the Whim Creek DFS is the construction of a new modular 400 Kilo-tonne per annum (Ktpa) polymetallic concentrator that will be fed with ore pre-concentrated using a combination of ore sorters (for >8mm material) and gravity separation (for <8mm material).
Key findings from the Feasibility Study are summarised below:
- Project free cash of $340 million (M) with a pre-tax NPV (7%) of $224M and an IRR of 54%
- Pre-production Capex of $71M including contingency and owner’s costs.
- Working capital of $14M with maximum drawdown of $85M
- Ore Reserves of 4.6 Mt @ 1.36% Cu, 2.30% Zn and 0.68% Pb supporting average annual concentrate production of ~55ktpa (containing Cu, Zn, Pb) over the life of the project.
- An initial 8-year mine life based on Ore Reserves
- Open pits and processing infrastructure are fully permitted as of August 2023
The Feasibility Study identified a combined Ore Reserve estimate for the Mons Cupri and Whim Creek pits, and the proposed Salt Creek Underground Evelyn underground operation.
Simplified crushing, sorting and jigging flow sheet
Crushing, classification and sorting circuit
2023 Heap Leach Scoping Study
In June 2023, Anax announced highly encouraging results from bioleaching test work undertaken at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Bentley, Western Australia. The column leach test work, which achieved copper extraction of 80% and zinc extraction of 90%, form the basis for the heap leach scoping study released in September 2023 that considers processing of oxide, transitional and low-grade sulphide ore using the recently refurbished and fully permitted heap leach infrastructure located at Whim Creek. The heap leach operation is proposed to operate in parallel with the concentrator.
The heap leach circuit will produce copper cathode and zinc sulphate and is anticipated to operate for a period of approximately 6 years. The heap leach feed sources will primarily consist of:
- Ore sorter and IPJ rejects.
- A sulphide ore domain with high zinc at the Whim Creek deposit that will be more profitable to process through the heap leach circuit due to the ability to recover both zinc and copper.
- Additional ore identified from new pit optimisations completed at the Mons Cupri and Whim Creek deposits.
- Transitional ore domains from the Whim Creek and Evelyn deposits excluded from the 2023 DFS.
- Tailings with high residual metal content.
Conventional SX-EW will be utilised to produce a copper cathode in conjunction with production of zinc sulphate via solvent extraction (SX) and crystallisation. Cathode copper will be produced from the processing of leach solutions in the Solvent Extraction and Electrowinning (SX-EW) plant. Saleable zinc products will be recovered from a zinc sulphate production circuit which will be a new addition to the plant. The zinc circuit will involve neutralisation for iron removal, solvent extraction followed by precipitation of a zinc sulphate product.
Heap Leach flow sheet
The Scoping Study has identified a heap leach Production Target of 2.19 Mt of ore at an average grade of 0.54% Cu and 0.71% Zn. The heap leach operation is anticipated to produce 8,875 tonnes of copper cathode and 13,325 tonnes of zinc as zinc sulphate. Key financial results from the modelling are shown in the Table below.
The discovery of gold and copper in the Whim Creek area in the early 1880s led to a period of underground, artisanal mining until 1912, during which high grade copper-gold ore shoots were targeted.
Systematic exploration by various companies in the 1960s, including Texasgulf, defined the known VHMS deposits of the Whim Creek Greenstone Belt, namely Whim Creek, Mons Cupri and Salt Creek.
Straits Resources acquired the Project in 1996 and commenced mining in 2005. Oxide copper ore mined from the Whim Creek and Mons Cupri open pits was crushed and placed on a purpose-built heap leach facility located 3km north east of the Mons Cupri pit. Approximately 67,000t of copper cathode was produced through an SX-EW treatment facility until 2009.
Venturex acquired the Whim Creek Project from Straits Resources in 2010, intending to use Whim Creek as a central processing hub for their existing Evelyn and Sulphur Springs deposits. The 2012 Sulphur Springs Feasibility Study, 2012, proposed locating the central processing plant at Sulphur Springs and transporting ore from the satellite deposits such as Mons Cupri and Salt Creek. This became Venturex’s preferred development proposal. However, Venturex has continued to develop the Whim Creek project, defining JORC 2012 compliant resources at Mons Cupri and Salt Creek, updated in 2018.
In March 2014, Venturex entered into an agreement with a private company, Blackrock Metals Pty Ltd (“Blackrock”), for the reprocessing of existing heap leach pads to recover copper metal through a small, refurbished, 5,000 tonne per annum, SX-EW treatment facility which operated until October 2019.
The Whim Creek Project tenure consists of seven mining leases, two exploration licences and one miscellaneous licence encompassing an area of approximately 175km2 of fertile volcanic and sedimentary units of the Whim Creek Greenstone Belt and geologically contemporaneous Mallina Formation.
The semi-arid climate of the west Pilbara has extremely variable annual rainfall of between 250 and 400mm, largely dependent on the formation of seasonal tropical cyclones offshore between December and April. Summer maximum temperatures reach 40˚ to 45˚, while mild winter temperatures average 25˚ by day, and 12˚ at night.
The vegetation of the West Pilbara is closely related to topography, soil type and proximity to the coast. In the Whim Creek area, broad floodplains are dominated by short grass savanna mixed with spinifex and dotted with dwarf acacia shrubs. Ephemeral streams are lined with eucalypts and the rocky hill slopes are sparsely vegetated.