Sphere Minerals has changed its board after a takeover offer by Xstrata became unconditional.
Sphere says directors Alexander Burns, Marcello Cardaci and Peter Donkin and company secretary Lexton Graefe have resigned.
They are being replaced by Peter Freyberg, Mark Eames, Earl Melamed, Damian Hogue and Anthony Clark.
Nicholas Talintyre and Matthew Conroy had been appointed company secretaries, Sphere said in a statement.
Michael Paine had been made public officer.
On November 11, Xstrata claimed success in its $514 million bid for iron ore junior Sphere Minerals.
Xstrata said it had received acceptances for another 32.13 per cent of the company in addition to its 18.99 stake, which pushed its interest to just above 51 per cent.
The Swiss mining giant had offered investors $3.00 per Sphere share but had warned bid would expire mid-month if it did not secure at least a 50 per cent stake in Sphere by last Friday.
Sphere has three large-scale iron ore projects in Mauritania in north-western Africa.
