Gold Fields turns to autonomous mining at South Deep Mine

August 25, 2014

Gold Fields announced that it will launch two new mining techniques at its South Deep Mine, the company’s last property in South Africa.
Chief Executive Nick Holland said at an earnings presentation that the new methods at South Deep in a fully-mechanized operation and are being used as the company attempts to meet a target of producing 700,000 oa/year there by around 2018.

Currently, Gold Fields is using a system called "destress mining" in which horizontal cuts are made into the rock in such a way that a lot of the "stress" that can cause rock bursts underground are removed.

But it also means opening up vast areas which require a lot of support, so much time and money can be spent before any bullion is extracted, Reuters reported.

Holland said the company was experimenting with a variation of destress mining as well as an entirely new way of doing things called the inclined slot method, which has been employed at its Australian operations.

The inclined slot method is a faster process in which ore is extracted and then backfilled without support structures. It is done mechanically without miners being put in harms way.

"It is much quicker, easier and probably will be cheaper," Holland said.

"It's going to be a year for us to pilot it, assimilate all the results and determine the way forward," he said.

South Deep descends to 3 km (2 miles) and South Africa, with the world's deepest mines, has more than a century of experience when it comes to extracting ore far below the surface with a large, unskilled workforce.

But heavily mechanized mining is relatively virgin territory in South Africa's gold reefs, from which a third of the bullion ever mined in recorded history has been produced.

South Deep, which sits atop a mammoth 40-million ounce reserve worth around $50 billion at current spot prices, is one of the few gold mines in South Africa where sophisticated mechanization is possible because the seam is so big - 120 metres wide in some places, making it suitable for big machines.

Gold Fields has brought in a top Australian engineering team to help overcome the technical and geological challenges at South Deep, where delays and shifting production targets have annoyed investors.

In the most recent setback, production has been curtailed by maintenance and a safety review though Gold Fields insists this "will make the mine safer and position the mine for an improved performance in 2015."

It is also a long-term project which is seen producing gold for several decades to come and the company's stable of global mines are generating a steady cash flow at the moment.

 

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