Not sure if it is reported somewhere but I was doing some testing and regarding the fire (and I guess other enchantments) this is what I got:

Item lvl 1-3? : 5% added resist
Item lvl 4-6 : 10% added resist
Item lvl 7-9 : 15% resist

At some point it gets to 20 and 25% but I do not own item levels in this range presently.