OZ Minerals and Cassini Resources have reported the results of a prefeasibility study (PFS) of development of mining operations on the Nebo and Babel deposits on their West Musgrave property in the far east of Western Australia. The project is a joint venture between OZ (70%) and Cassini (30%).

The PFS has demonstrated positive potential for long-life, open-pit copper and nickel sulphide mining opera-
tions. It is the first development opportunity within the broader West Musgrave province, which includes a number of additional highly prospective opportunities, including the nearby Succoth copper deposit.

An initial probable ore reserve of 220 million metric tons (mt) grading 0.36% copper and 0.33% nickel supports about 22 years of mine life in the PFS analysis. The balance of the estimated 26-year mine life is underpinned by a combination of indicated and inferred mineral resources.

Processing capacity to produce separate copper and nickel concentrates is planned at 10 million mt per year (mt/y). Life-of-mine annual production of contained metals would average about 28,000 mt/y of copper and 22,000 mt/y of nickel. Preproduction capital costs are estimated at about A$995 million. Project payback from a decision to mine is estimated at about six years.

Mining is modeled to be conventional drill, blast, load, and haul and is assumed to be contractor operated during the first five years of operation, transitioning to owner operation in year six. The haulage fleet will comprise up to 25 220-mt haul trucks, and optionality is being maintained to allow for these trucks to be fully autonomous in the future.

An innovative mineral processing plant will be built on site. The grinding circuit consists of two stages of crushing followed by two parallel vertical roller mills treating nominally 5 million mt/y each.

Vertical roller mills are widely used in the grinding of cement plant feeds and products, slag, coal, and other industrial minerals. Benefits in using the mills at West Musgrave include reducing power consumption by about 15%, no requirement for ball charge grinding media, higher flotation recovery, and flexibility in throughput in response to the availability of low-cost renewable energy.

The project will operate as a fly-in/fly-out operation. An airstrip and 400-person-accommodation village will be constructed at the site. Approximately 60 staff will be employed in operations monitoring, control, and planning functions in an off-site integrated operations center.

Critical path activities are continuing while the West Musgrave project is being assessed under OZ Minerals’ capital allocation framework. The PFS provides a solid platform for discussions with potential lenders and advisors on how best to fund and structure the project prior to moving to the next phase.

OZ Minerals CEO Andrew Cole commented, “The PFS is now complete and has confirmed that the project can be a low-carbon, low-cost, long-life mine … During this study, we have partnered with the traditional owners, government agencies, and industry experts to design a project to meet our objectives in relation to low carbon intensity, innovation and adding value for our key stakeholders. We thank them all for their contribution and look forward to their ongoing support.”