Why is Great Oxidation Event associated with Iron oxidation but not Aluminum or Silicon?
Because Al and Si were already oxidised to begin with.

When the Earth formed, it had some amount of metals (Fe, Si, Mg, Al, Ca, etc) and a fixed amount of oxygen to bond with those metals. Certain metals with bond with oxygen preferentially. Mg and Ca are usually the first to take up oxygen, followed by Al, Si, and then Fe comes last (out of the short list I just provided). Turns out that there is not enough oxygen left for all of the Fe!

As you probably know, Fe oxides come in two states, ferrous iron (Fe2+) and ferric iron (Fe3+). So to put it simply, the amount of oxygen left in the Earth after being used up in the other more-easily-oxidised metals was enough to oxidise just a small part of the Fe0 to Fe2+. That's why Earth has a metal core - that's where all of the Fe0 is. The crust, however, had only Fe2+ in it. Once you start pumping out oxygen to the atmosphere, this Fe2+ starts oxidising to Fe3+, which is the stable form of iron in the Earth's surface in the presence of oxygen (as you can tell by iron rusting everywhere quite rapidly). This buffers the amount of oxygen you had in the atmosphere until you run out of Fe2+ and then oxygen can really increase.

Some corrections:
Al2O3 is not clay. It is an important component of clay minerals, but it is definitely not clay. Clay minerals have both Al2O3 and SiO2 in it.