The move is intended to finance investments and provide the parent company with funds to expand in other core areas, sources say.
The new rules, due to be enforced in December 2018, aim to capture 95% of smelter emissions.
Copper, gold, zinc, tin, iron ore and molybdenum exports all rose in February as companies increased shipments and benefitted from the ongoing price rally.
Will copper be at US$5,000/t or US$7,000/t in 2020? Expert opinions vary.
The uptick in copper and iron ore prices helped offset the decline in output as a result of the 43-day strike that affected BHP Billiton's Escondida mine.