Roger Phillimore and Tony Lea, Minorco's joint managing directors, have been replaced with a single chief executive, Hank Slack, and two new directors have been appointed to the board.
Mr Slack, son-in-law of the patriarch Harry Oppenheimer, has been president of Minorco since 1985. Mr Phillimore is leaving 'to pursue his own interests' while Mr Lea will be returning to South Africa to work at Anglo.
The new directors are Peter Burnell, who spent nine years as managing director of Anglo's South American operations, and Peter Wilmot-Sitwell, a vice-chairman of the bankers SG Warburg.
Robert Davies, a mining analyst with Lehman Brothers, said the reshuffle would aggravate concerns about whether Minorco would use some of its dollars 1bn cash mountain to assist Anglo's troubled De Beers diamond mining operation.
In November Minorco gave assurances to Lehman's US banking arm that none of its cash had been lent to De Beers.
Minorco's cash mountain is, however, thought to be shrinking as acquisitions and hefty operational investments have coincided with weak metal prices.
Mr Davies calculates investment income contributed dollars 165m to cash flow last year, compared with only dollars 37m for trading operations. This year he expects the figures to drop to around dollars 110m and dollars 2m respectively.