OZ Minerals will spend nearly $100 million exploring for copper and gold in SA this year, hoping to build on the two deposits it already owns.

Australian shares have fallen to levels not seen since the GFC as investors reacted to the carnage on Wall St and European markets overnight. The local market shed more than $50 billion on Friday, and around $100 billion in the week, the worst performance since November 2008. RBS Morgans private client adviser Bill Bishop said developed economies had reached a point where there appeared no clear way to avoid an economic downturn.

Marathon Resources shares have fallen more than 38 per cent after coming out of a trading halt. The company's stock was placed in a trading halt on Friday last week when the State Government announced it would ban all mining in the Arkaroola Wilderness.

REX Minerals has forecast more copper from its Hillside project in SA, releasing a blueprint for a 12-year mine to almost rival Olympic Dam in size. "The conceptual study supports our view that Hillside is one of Australia's largest copper development opportunities," managing director Steven Olsen said.

It has been brewing for some time, but the revelation that Chinese state-owned company Shenhua Watermark Coal had spent about $200 million buying up 43 farms on prime agricultural land near Gunnedah in New South Wales has led to calls to halt the so-called foreign "land grab".