The Leigh Creek copper mine is an open-pit copper project located in the North Flinders Ranges of South Australia. It is owned and operated by Strategic Minerals, a mineral production and development company based in the UK.
The Leigh Creek project was brought back into production in April 2019, after a gap of seven years since its previous owner Phoenix Copper put the mine under care and maintenance in early-2012.
The project area is spreads over 1,250km² of mining and exploration leases on three sites, namely ML 5467 Mountain of Light (MOL), ML 5498 Lorna Doone (Lyndhurst), and ML 5741 Mount Coffin.
Strategic Minerals plans to develop the Leigh Creek project in three phases, with phase one involving the development of MOL resources with a target of producing 300 tonnes (t) of saleable copper a month.
Leigh Creek copper mine history
Copper mining in the North Flinders Ranges dates back to the late-1800s, while open-pit mining on the Lorna Doone deposit was carried out for a brief period in the late-1960s.
Leigh Creek Copper Mine (LCCM), a private syndicate, began open-pit mining at Rosmann East on the MOL lease in 2006.
Phoenix Copper acquired LCCM in July 2010 and produced approximately 425t of copper before putting the mine under care and maintenance in early-2012 due to high operating cost, as well as issues pertaining to the leach pad design and processing recovery.
Resilience Mining Australia (RMA) acquired the mine from Phoenix Copper in 2015. Further, Strategic Minerals acquired the Leigh Creek copper property from RMA in a cash-cum-stock deal in January 2018.
Strategic Minerals received approval from the South Australian government for restarting the Mountain of Light processing facility in August 2018.
The company completed a feasibility study for the Paltridge North and the Rosmann East deposits at the MOL site in November 2019. In the same month, it updated a feasibility study for the Lynda and Lorna Doone deposits.
Location, geology and mineralisation
The Leigh Creek copper mine is situated within the northern Adelaide Geosyncline sedimentary basin, approximately 500km north of Adelaide.
The MOL site comprises three near-surface deposits namely, Paltridge North, Paltridge South and Rosmann East, within 1km distance from each other in a star-shaped geological structure known as the Copley Diapir.
The Lyndhurst project site comprises Lorna Doone and Lynda copper oxide deposits that are located roughly 70km north to the MOL project site, while the Mount Coffin lease area hosts the Elsie Adair and West Jubilee copper deposits.
Each deposit of the Leigh Creek copper project is hosted by siliceous siltstones and is closely associated with diapiric breccia structures of the Callanna Group sedimentary formations.
Leigh Creek copper reserves
The Leigh Creek project is estimated to hold 5.4 million tonnes (Mt) of ore resources grading 0.7% Cu and containing 36,400t of saleable copper.
The Lynda, Lorna Doone, and Paltridge North deposits account for a total of 3.6Mt of ore resources with 24,900t of contained copper.
Leigh Creek copper project development plan
The first phase development of the project involves ore extraction from the Paltridge and Rosmann deposits, as well as the restarting and refurbishment of the Mountain of Light processing plant for a sustainable monthly production of up to 300t of marketable copper.
Phase two will involve mining and processing of ore from the Lynda and Lorna Doone deposits, while phase three targets the development of other copper deposits in the North Flinders Ranges to extend the mine life of Leigh Creek beyond 15 years.
Mining and ore processing
Open-pit mining method involving free-digging of ore material is employed for the Leigh Creek mine. The ore extraction process does not require any blasting.
The pit design for the Paltridge North deposit involves 4m safety berm, 10m bench height, and a 17m-wide ramp, while the nominal mining rate is anticipated to be 7,000 tonnes a day.
The proposed mining fleet includes a 120t capacity excavator, five Caterpillar 740B or similar 40t capacity trucks, one Cat D11R or similar dozer, one Cat 12H or similar grader, one water truck, one service truck, and a front-end loader.
The run-of-the-mine (ROM) oxide ore is sent to the existing MOL processing facility, where it is crushed to less than 35mm size before being subject to wet-scrubbing, screening, and heap leaching.
Copper from the heap-leach solution is recovered through reaction with iron scrap in two Kennecott cones.
The resultant copper cement containing minimum 70% copper is filtered and dried before being packed in one tonne bulk bags for export.
The Leigh Creek project is supported by an off-take agreement with Adchem, a chemical company based in Melbourne that specialises in cupric oxide and copper carbonate production.
Adchem received an initial shipment of five tonnes of copper cement containing 70% Cu from the Mount of Light processing facility in May 2019.
Leigh Creek copper project infrastructure
The Leigh Creek project sites are accessed by gravel tracks connecting the Leigh Creek-Lyndhurst sealed road. The nearest airport is the Leigh Creek Airport, which has an all-weather sealed air strip.
The project area is located near existing power grid, while portable water supply is provided by South Australia (SW) Water.
Mining One was engaged as the main consultant for undertaking the feasibility study for the development of the Paltridge North deposit.
PPM Global was engaged by Phoenix Copper for the refurbishment and re-commissioning of the Mountain of Light processing plant in 2010.