Base metals are heading into the northern summer’s final quarter with an unusual mix of stress signals. Copper has printed repeated records this year, zinc concentrate is so scarce that smelters are effectively paying miners to take their ore, and the Middle East conflict is still reshaping aluminium flows. For Australian investors, the timing matters because LME Week kicked off on 19 October, and the commentary coming out of London is feeding straight into how the market prices ASX-listed producers.
Prices and the record-low treatment charge story
Three-month LME copper hit an intraday record of US$14,875 a tonne on 10 September, driven in part by fears of US Section 232 tariffs on refined copper that have pulled metal into America and tightened LME spreads. The more telling indicator sits further up the supply chain. The Asia Pacific copper concentrate treatment charge index has fallen to around negative US$272 a tonne in early October, from negative US$70 at the start of the year, while spot zinc concentrate treatment charges in China touched a record low of roughly negative US$115 to US$150 a tonne.
Negative treatment charges mean miners hold the pricing power and smelters are squeezed. It also explains why our earlier coverage of the zinc four-year high and weak lead market has aged well: tight concentrate supply has persisted and deepened rather than eased.
South32 repositions as an upstream base metals company
The biggest ASX corporate story in the sector is South32. Shareholders backed the sale of its aluminium value chain to Alcoa at the 15 October AGM with 99.18 per cent approval. The deal is valued at up to US$5.6 billion and is expected to complete in the June 2027 half, subject to regulatory approvals. The original portfolio update was lodged on the ASX announcements platform in July, and management has since leaned hard into the message that South32 is becoming a copper, zinc and manganese-focused producer.
Its September quarter report, released on 19 October, kept FY2027 guidance intact. Payable copper equivalent output at Sierra Gorda in Chile rose 11 per cent on higher grades, and the mine paid a record quarterly distribution of US$153 million. A fourth grinding line has moved into execution and is expected to lift processing capacity by about 25 per cent. At Hermosa in Arizona, the Taylor zinc-lead-silver project is under construction with its expected life extended by five years to 33 years. Net cash edged up to US$297 million.
Supply disruption is the common thread
Global copper mine output slipped about one per cent year on year across January to July, according to Fastmarkets, with Chile down around seven per cent after storms. Operational setbacks have piled on, including a fatal accident and suspension at Escondida, a fatality at Codelco’s Radomiro Tomic, a strike at Centinela and an avalanche at El Teniente. Our recent piece on copper’s record run and the Escondida strike vote covers the early part of that sequence.
In zinc, weather is the next risk. El Nino-related disruptions are expected to peak between November 2026 and February 2027. Meanwhile Nyrstar has launched a strategic review of its 300,000 tonne a year Budel smelter in the Netherlands, with a conclusion due by the end of 2026, a sign that low treatment charges are already forcing hard decisions downstream.
Aluminium, nickel and tin on the periphery
Aluminium remains a premium story rather than a pure price story. The Rotterdam duty-unpaid premium sat around US$550 to US$585 a tonne in mid-October, while Gulf smelter output is expected to recover to 75 to 80 per cent of pre-war levels by the first quarter of 2027. The alumina index for Australian FOB cargoes rose to roughly US$368 a tonne, a positive for refiners exposed to Western Australia and Queensland.
Nickel is the laggard. It is the second most heavily stocked metal on both the LME and Shanghai Futures Exchange because of Indonesian oversupply, although quota uncertainty continues to create sharp spikes, as discussed in our look at Indonesian quota cut reports and what they mean for Nickel Industries, BHP and IGO. Tin, meanwhile, has traded above US$50,000 a tonne since late June on tight supply and AI-linked soldering demand.
What it means for ASX investors
The setup favours producers with concentrate to sell and punishes those reliant on toll treatment margins. Diversified names with copper and zinc exposure benefit from by-product credits, a theme also visible in the Aurelia Metals dividend story. Government forecasts are worth cross-checking too, and the Department of Industry’s Resources and Energy Quarterly provides export value and volume outlooks for Australian base metals. For background on zinc’s global supply base, the US Geological Survey zinc statistics are a useful reference.
What to watch next
- Outcome of 2027 copper and zinc concentrate treatment charge negotiations, which will show how far the miner-friendly shift extends.
- Any formal US decision on Section 232 tariffs for refined copper, which could redirect metal flows again.
- Operational restarts at Escondida, Centinela and El Teniente, and whether Chilean output recovers into year end.
- Regulatory progress on the South32 and Alcoa transaction ahead of the June 2027 half completion target.
Frequently Asked Questions
What does a negative treatment charge mean?
Treatment charges are fees miners pay smelters to process concentrate. When they turn negative, smelters are paying for scarce concentrate, which signals a tight raw material market and favours miners.
Which ASX companies have base metals exposure?
South32 is the clearest large-cap example, with copper, zinc and manganese operations. Smaller producers such as Aurelia Metals offer zinc and copper exposure, while diversified majors also carry base metals earnings. Always check each company’s latest announcements.
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