FEATURE-Hunt for ever-deeper S.Africa gold still costs lives

* Mponeng is world's deepest mine * Fatality rate dropping but miner killed there last week

By Ed Stoddard

CARLETONVILLE, South Africa, June 3 (Reuters) - The massive drill is deafening as it bores into the rock of the world's deepest mine, where heat and humidity sap the strength of gold miners who never know when the next rock fall might kill or maim.

At 3.8 km (2.4 miles) underground, it feels like the bottom of the world.

Toil and blood have brought humans to this spot, the lowest in AngloGold Ashanti's Mponeng mine, 60 kms (35 miles) southwest of Johannesburg.

At such depths it is impossible to ignore the thousands of tonnes of rock overhead -- unnerving in a region prone to seismic activity.

"Sometimes you feel a tremor down here. You get used to them," said section manager Geert Jacobs, clad in overalls and hard hat as he directed journalists through a tunnel.

But tremors can be fatal and the following day a rock fall in the mine killed a worker -- the first death in 2011 at Mponeng.

Mining was halted while it was investigated, which has become standard procedure since South Africa set out to cut the heavy death toll in mines, chiefly among black workers, that the authorities tolerated before white minority rule ended in 1994.