Inventories of copper in LME-registered warehouses have surged 141% in the past three months.

Nearly 90% of union members voted to approve the agreement.

Copper and silver are often skipped over in discussions of metals needed for the green economy, with battery metals like lithium, graphite, cobalt and nickel hogging the limelight.

Both the Tia Maria project and the Las Bambas copper mine have been heavily opposed by local communities.

The union says BHP is looking to reduce benefits and production bonuses while extending working hours.

The collaboration will aim to increase Fortune's cobalt and bismuth refining operations to process co-product streams of the minerals recovered from the Kennecott smelter.

The Chinese official manufacturing gauge is expected to signal expansion for the first time since March.