Name
Mount Isa Mines Complex

Location
In the North West Minerals Province, in Queensland, Australia.

Mine Owner/s
Glencore.

Brief Description
Mount Isa Mines Complex is one of the world's largest mining complexes and the hub of Glencore’s operations in Queensland.

Brief History
In February 1923, prospector John Campbell Miles discovered one of the richest-known zinc/lead seams in the world. He pegged out the lease area, claiming 17 ha, and named the larger outcrop ‘Mount Isa’. On January 19, 1924, Mount Isa Mines was established.

The region maintained production and provided consistent work during the Great Depression, focusing on zinc, lead and silver production. The mine briefly prioritised copper production in the late 1930s until the 1940s to contribute to Australia’s World War Two effort. Parallel production of zinc, lead, silver and copper did not begin until 1953.

The Isa Process Technology was developed in 1978, revolutionising the copper refining. It replaced copper cathode starter sheets with stainless steel sheets, transforming an extremely labour-intensive process through mechanisation for the first time.

Glencore acquired Mount Isa Mines in May 2013.

Primary Metals/Minerals
Lead, zinc and silver.

Secondary Metals/Minerals
Copper.

Geology and Mineralisation
The Mount Isa lead/zinc/silver/copper deposits are hosted within the Mesoproterozoic Urquhart Shale.

The copper mineralisation occurs in extensive zones of silica-dolomite alteration, while the lead/zinc/silver mineralisation occurs in a series of over 30 stratiform lenses occurring to the north of, and above the copper orebodies.

The Sustainable Minerals Institute notes that the Mount Isa copper orebody covers an extent of more than 4 km and a vertical extent of 1 800 m.

The lead/zinc/silver orebodies are broadly stratiform, with a 60° to 65° westerly dip parallel to bedding in the host Urquhart Shale. The main stacked group of orebodies are an en-echelon group of north-plunging lenses bounded to the south by the silica-dolomite alteration zone associated with the copper orebodies, and to the north by the north-northwest-plunging Mount Isa fold.

Reserves
As at December 31, 2022, Mount Isa’s total zinc-bearing ore reserve amounted to 67-million tonnes grading 7% zinc, 3.56% lead and 64 g/t silver. The total copper-bearing ore reserve amounted to 17.2-million tonnes grading 1.84% copper.

Resources
As at December 31, 2022, Mount Isa had a measured and indicated copper-bearing resource of 157-million tonnes grading at 1.70% copper, as well as a measured and indicated zinc-bearing resource of 391-million tonnes grading at 6.90% zinc, 3.51% lead and 69 g/t silver.

Type of Mine
Underground.

Mining Method
Underground. 

Major Infrastructure/Equipment
A copper concentrator, zinc/lead concentrator and filter plant, as well as copper and lead smelters.

Prospects
Glencore announced In October 2023 that, after more than 60 years of copper mining, the Mount Isa underground copper operations – including Enterprise, X41 and Black Rock – the copper concentrator, in Queensland, and the Lady Loretta zinc mine, would close in the second half of 2025.

Glencore said Mount Isa Mines’ other metal assets, including the copper smelter, George Fisher mine, zinc/lead concentrator and lead smelter (in Mount Isa), as well as the copper refinery, in Townsville, would continue operating. 

The decision to close the underground operation and copper concentrator followed a range of studies and reviews by Glencore to further extend the life of the underground copper mines. The studies revealed that the remaining mineral resources were not economically viable, owing to low ore grades and areas where the geological conditions were not conducive to the safe extraction of ore using current technology.

“Our focus over the coming months will be to work closely with our people and contractors, our suppliers, and the Mount Isa community to provide support as we move towards closure of these assets. 

“Glencore will continue to invest in the long-term future of Mount Isa Mines, including the George Fisher mine, with a current life of mine to 2036, and our zinc/lead concentrator and lead smelter,” Glencore Australian zinc asset COO Sam Strohmayr has said.

He has added that the copper smelter and refinery are expected to continue operating to 2030, subject to approval of additional capital investment.

Contact Details
Glencore Australia
Tel +61 2 8247 6300
Email communications@glencore.com.au

Sources
Glencore. Website https://www.glencore.com
Glencore. 2022 Annual Report.
Glencore Australia. Website https://www.glencore.com.au
Glencore Australia. Operations: Mount Isa Mines.

Mining Weekly. Website https://www.miningweekly.com
Mining Weekly. Curtain falls on Mt Isa underground copper mine (October 18, 2023).

Sustainable Minerals Institute. Website https://smi.uq.edu.au
Sustainable Minerals Institute. Northwest Mineral Province Deposit Atlas Prototype Chapter 2 (January 2018).