birdman Birdman. Iron formationss have NOTHING in common with intrusive rocks. That's why I don't like trying to explain things in here. I gave the differences between IF's and Porphyry deposits and some how you are trying to marry the two together. They are not related. I know that you are an eager learner and are trying to understand the geology, but without some basic training or undertsanding you are going to arrive at conclusions that have no merit. As I have suggested in the past, you need to read a lot more literature to get a better understanding of geology, the different rock units, how deposits are formed, etc. perhaps the local college or univeristy near you has some self study courses you can sign up for.