Global miner Rio Tinto (RIO.AX) has shelved a $229 million plan to extend its Northparkes copper mine in Australia, the firm said on Tuesday, as it slashes capital spending and seeks to rein in nearly $40 billion of debt.

The world's fourth-biggest miner by market value took the decision in response to weaker copper prices, which have plunged about 60 percent since July as demand for the metal in building and electronics products has evaporated.

The project aimed to extend the mine's life to at least 2016.

In the nine months to Sept. 30, Northparkes produced 13,800 tonnes of copper and 20,000 ounces of gold.

Rio Tinto said 26 Northparkes staff would lose their jobs and a further 320 contractors would be laid off.

As well, the group has delayed its $371 million plan to automate train operations on a rail network that services its iron ore mines in western Australia's Pilbara region. It blamed slowing demand for iron ore as global economic growth stalls.

The group approved the automated-trains project last July to improve efficiency as Pilbara infrastructure was expanded beyond its current annual production capacity of 220 million tonnes.

Japan's Komatsu (6301.T) was working with Rio Tinto on the project which, according to Rinto Tinto, had made great strides towards its 2012 implementation.

On Monday, Rio Tinto confirmed it had shelved a planned $2.15 billion expansion of its Corumba iron ore project in Brazil.

Last month, it announced it would slash capital expenditure by $5 billion this year and sell assets in response to the market downturn and to cut debt.

(Reporting by Bruce Hextall; Editing by Mark Bendeich)

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