After working at Olympic Dam for many years I can say your right...

After working at Olympic Dam for many years I can say your right about its complexity. But you have to remember that for every ton of ore mined a ton has to go back in, that's one of the biggest costs of the whole operation Backfill. Stabilised sand back into the stopes so mining can continue. So back fill CAF (cement aggregate fill) containing underground mullock, quarry limestone and Stabilised tailing sand (and all the iron ore) are poured back into the stopes. No backfill no mine. Iron ore cheaper ( when mine set up) than mining more backfill.
Block mining doesn't need back fill. Heap leaching has been proven up by BHP and uranium can be leached out before the flotation process. If FMG set up the mine as block mining with heap leaching uranium, iron ore could be viable. But that's a long bow to draw hey!