Metherion NGC said something similar. From U238 to Lb206 is 8 radioisotopes. The rocks contain 3 halos. They start 5/8 of the way down the decay chain. Even if there was 4 Rn222's half life is only ~4days so.... But your saying its from a completely seperate decay chain? Its still unrebutted in journals and i have to believe they would lurrrvvvvvv to explain it away but they cant?
I'm saying that other elements and other isotopes of uranium have their own decay chains. These other decay chains contain polonium. Therefore, these other decay chains SHOULD make halos. But they don't. This means it cannot be the polonium causing the halos, or the OTHER elements and isotopes would ALSO have their OWN halos.
I've seen other ideas on how it happens involving radon (another element in the decay chain) migrating through cracks in the rock when there are halos, but it's a bit too... geology for me. However, the fact is, there are nowhere near the number of halos there SHOULD be if what Gentry said happened happened, and that's just one problem, not all of them.
U-238's decay chain contains 3 isotopes of polonium. U-235's decay chain contains 2 instances of polonium. Thorium-232's decay chain also contains 2 instances. This means that every instance of U-235 should have 2 halos, as should every instance of Thorium-232. Furthermore, some of the Uranium halos should be stronger because you don't find just U-238 or U-235, you have to purify/separate them (hence the terms 'enriched uranium' and 'depleted uranium'). But this isn't seen.
Now, according to
Collins, Lorence G., 1997, "Polonium Halos and Myrmekite in Pegmatite and Granite,"
www.csun.edu/~vcgeo005/revised8.htm, 9 pgs.
the rings are generally along microfractures in the minerals. Furthermore, the isotopes of radon produced in U-238, U-235, and Th-232 have different half-lives. U-238 gives rise to Rn-222, U-235 gives rise to Rn-219, and Th-232 gives rise to Rn-220. Rn-222 is the only one with a half life longer than 1 minute (3.8 days versus 3.92 seconds and 51.5 seconds), so it would make sense that the radon accumulating in the fractures would have something to do with the halos, and it explains why there aren't halos around U-235 or Th-232. Not confirmed, but explains more evidence than 'pure polonium was poofed into various types of granite, but only around U-238 and not U-235 or Th-232 and then it decayed, and God had to do it, and there is NO OTHER POSSIBLE EXPLANATION SO WE SHOULD STOP LOOKING.' The worst part is the THERE IS NO OTHER POSSIBLE EXPLANATION SO WE SHOULD STOP LOOKING. We should *never* stop looking for a better way to explain what we know, a better model, a better whatever. Saying what Gentry has said is just... bad.
Metherion