By James Macharia

ELANDSRAND MINE, South Africa, Oct 4 (Reuters) - South Africa's mining minister said she aimed to crack down on old mines that may threaten workers after an accident stranded thousands of miners underground.

Minerals and Energy Minister Buyelwa Sonjica told Reuters on Thursday she would step up a campaign to boost mine safety after ordering a six-week closure of Harmony's <HARJ.J> Elandsrand mine, where 3,200 miners were trapped after a power failure.

"I'm worried about the obsolete infrastructure," Sonjica said in an interview at the mine southwest of Johannesburg.

"The boom in the commodity prices has led to new mines that are not really new, but are built on old sites and have old infrastructure that has not been maintained over time."

The Elandsrand mine is around three decades old and was purchased by Harmony in 2001 from AngloGold Ashanti <ANGJ.J>, which had planned to close it down.

Sonjica said she would seek sharp improvements in safety through an existing process that involves companies, unions and government, including a meeting that had already been planned for Friday.

"I can't allow them (companies) to sacrifice workers in pursuit of profits."

WORLD'S DEEPEST MINES

Part of the problem was that South Africa's mines were the deepest in the world and the gold industry was a labour intensive sector, she said. But she was also struggling against an apartheid legacy that failed to respect workers.

"Mine workers have been extremely exploited by the industry because of apartheid. There was no culture of human rights, the mine workers are uneducated ... and are vulnerable to exploitation."

Last week, four miners were killed in a rock fall at the Mponeng mine owned by AngloGold Ashanti, the deepest in the world.

The government has been long seeking to boost mine safety in South Africa, where around 200 workers are killed in mine accidents each year.

Workers at Elandsrand were stranded 2.2 km (1.4 miles) underground on Wednesday when the electricity cable of the mine's main lift was severed in an accident.

Rescuers at Harmony, the world's fifth biggest gold producer, were bringing up batches of miners during the day on Thursday in a small lift.

Sonjica said she had ordered the closure of the mine for six weeks to make sure it was safe when it reopened.

"It will be closed for six weeks and we will monitor the kind of repair before it can reopen," she said.

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