This is the thermite reaction aka aluminothermic reaction:
Fe2O3 + 2 Al → 2 Fe + Al2O3

As someone said it would happen in space or in a total vacuum, so oxygen is not needed at all. Regarding your point of perfect balance, well it's the thermite mix itself, if you respect these proportions it will burn completely.
One possible source of explosion would be dihydrogen which is highly explosive (it's what pretty much destroyed the Chernobyl nuclear reactor), I just don't see how it could get created in these conditions. Sublimination of water or even ice is a much more likely.