New Century Resources Ltd (ASX:NCZ) is making positive progress with a study assessing a potential restart of the past-producing Mt Lyell Copper Mine in Tasmania.
This study is a key component of an option agreement to acquire the historic project on the island's west coast.
Since entering this agreement in November 2021, New Century's study team has continued to verify the potential for restarting Mt Lyell as a substantial copper project with best-in-class environmental credentials.
Existing resource base
Supporting the study and the company's intentions is the project's mineral resource base of 1.1 million tonnes of copper and 940,000 ounces of gold.
There are multiple potential development pathways that are underpinned by a low-cost, carbon-free power supply and potential multi-decade production of high-quality, low-impurity copper concentrate based on historical performance.
Positive results to date
Among the positive results of the restart study to date are:
- Confirmed suitability of the sub-level caving mining method for future underground operations. This method has been successfully utilised at Mt Lyell since 1995;
- Existing underground workings allow direct access to ore; and
- Confirmation of the suitability of the existing flowsheet that historically delivered better than 90% copper recovery with gold credits.
Prior to the forced closure of the mine in 2014, Mt Lyell had more than 100,000 tonnes of copper metal in ore reserves and New Century is confident that the previous recovery rate can be further enhanced through the use of modern equipment that could improve power consumption, maintenance workload and process control.
Processing intentions
The study identifies several benefits of building a partial new processing plant. Work to date shows that a new plant can be accommodated without requiring upfront demolition of the old plant, leaving room for future expansion.
With an annual nameplate capacity of 2.4 million tonnes, the existing plant consists of four stages of crushing and two stages of grinding to present material with a P80 of 110µm in the flotation circuit.
Historically, copper flotation had three circuits - a rougher, middlings and scavenger circuit - as well as two cleaner circuits, with a copper product yield of more than 26% and recovery rates of more than 90%.
This flowsheet has been proven robust over years of production and will be used to aid in designing a new plant, with only minor changes expected to produce incremental benefits.
New Century plans to partially modernise the plant with new flotation and comminution circuits. Most existing auxiliary facilities would be able to continue operation.
Further resource potential
The restart study has initially focused on Prince Lyell and Western Tharsis deposits while additional underground resources are available at Copper Chert and Green Horn/Cape Horn for further study and potential mine life extension.
Mineralisation at Western Tharsis and Green Horn/Cape Horn remains open at depth.
An experienced local contractor has been engaged to conduct infill drilling from existing underground drives and this work aimed at near-term partial conversion of existing measured and indicated mineral resources to ore reserves is expected to start later this month.
New Century plans to define ore reserves in the coming months with a further upgrade of mineral resources and ore reserves expected in late 2022.
The drill program includes infill drill holes within the upper inferred resource of the Prince Lyell ore body. The aim of this work to further add measured and/or indicated resources that will be used for the study, and to demonstrate a significant life of mine for resumed operations.
It is the study team's goal to capitalise on the extensive mineral resource base to accelerate time to first ore while maximising production with the measured and indicated resources.
Renewable power
Access to low-cost, renewable hydroelectric power on the Tasmanian grid is a major advantage of the project's location. According to the company, the Mt Lyell copper concentrate has the potential to have one of the lowest carbon intensities available on the global market, due to its established grid connection.
There are also established rail transport and shipping facilities at Burnie Port, which provide a strong logistics network from mine to port.
From its mine to Burnie Port, New Century Resources has established a logistics network to facilitate copper exports.
For restarted operations, it has ensured that 100% renewable, low-cost hydroelectric power is available.
By taking advantage of the brownfield nature of the Mt Lyell mine, available site infrastructure is being assessed for condition and suitability for inclusion into the restart planning process.
Clear opportunity
The placement of Mt Lyell on care and maintenance in 2014 with substantial ore reserves in place suggests the possibility of first reinstating ore reserves in the short term, and then expanding from the existing, substantial material resources.
Previous operators, Copper Mines of Tasmania, switched from crown and pillar mining to longitudinal, then transverse, sub-level caving (SLC) in 1995 and employed this method successfully for more than 20 years, said New Century Resources.
Due to their vertical nature and expansive mineralisation footprint, the Prince Lyell and Western Tharsis deposits, which are being targeted for the restart, are good candidates for employing the SLC mining method.
About New Century
New Century is a mining, tailings management and economic rehabilitation company dedicated to producing metal from resource assets in a sustainable manner.
It is a top-15 global zinc producer, operating Australia’s largest hydraulic mine at the Century Mine in Queensland; extracting, processing and marketing zinc recovered from historical tailings.
New Century is also actively progressing organic growth opportunities through in-situ projects at the Century Mine and is exploring the potential to restart copper production at the historically significant Mt Lyell Mine in Tasmania using 100% renewable energy.