Just thought it interesting that Ar40 Ar36 might be diffusing into rocks
Nobody cares about your "might". We have plenty of evidence that it's not a problem. Call back when you have some evidence that it actually happens.
Interesting lecture, diffusion Ar40 Ar36 is cause of great concern
Not according to the link you posted (which is part of an excellent though highly technical series available at
Earth & Atmospheric Sciences 656).