Mt Marion $490m expansion: design and risk notes for lithium project teams
Reviewed by Tom Sullivan

First reported on Australian Mining
30 Second Briefing
Mineral Resources and Jiangxi Ganfeng Lithium have approved a A$490 million brownfield expansion at the Mt Marion lithium operation in Western Australia, adding an underground mine and new flotation plant to increase recoveries and throughput. The final investment decision covers transitioning from a purely open-pit operation to a combined open-pit/underground layout, with flotation enabling higher-grade concentrate production from existing ore types. The partners expect the upgrade to materially extend Mt Marion’s mine life by decades, with implications for long-term tailings, water balance and underground geotechnical design.
Technical Brief
- Brownfield nature constrains underground access design around existing pits, waste dumps and plant footprint.
- Combined open-pit/underground layout will require revised geotechnical domains and updated slope/underground interaction assessments.
- Flotation tailings stream introduces new tailings storage design requirements and potential thickening/filtration options.
- Process water demand and recycle ratios must be rebalanced to accommodate flotation circuits in arid WA conditions.
- Transition to underground haulage will alter power demand, ventilation sizing and heat-load management at depth.
- Long mine-life scenario drives need for staged TSF lifts, closure landform design and progressive rehabilitation planning.
Our Take
In our database, MinRes’ decision to expand Mt Marion comes alongside multiple pieces on the restart of its Bald Hill lithium mine, signalling a coordinated push to lift Western Australian hard‑rock lithium output as prices recover.
The presence of Ganfeng/Jiangxi Ganfeng Lithium in this JV gives Mt Marion direct exposure to downstream Chinese conversion capacity, which typically improves offtake certainty compared with standalone Australian producers such as Core Lithium at Finniss.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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