Hi Perry,
I didn't want to comment specifically on the Polonium Halos in my first post, since it has been awhile since I've read material on this. I just re-read this article: http://www.talkorigins.org/faqs/po-halos/violences.html
The author, John Brawley, is an amateur scientist, however I was impressed by the length he went to study this issue and produce a report. It takes awhile to read the report, so if you stop before reaching the end, you'll miss a funny bit about him trying to get people to let him on their land to get samples. To quote him: "[some from a] high-security mining operation and could not wait to get me the hell off their property."
After his research and examining several examples his conclusion was the Polonium Halos are mostly likely formed by Radon-222. This is consistent with other reports I have read about this. In any regards, it is telling that Dr. Gentry is trying to hang so much on one thing, without considering many lines of evidence that contradict the Genesis creation account and Noah's flood. I mentioned a few above, but there are many -- even simple things like asking would enough population be available after the flood to build Stonehenge, The Great Wall of China and the Pyramids of Egypt? Or why don't we find evidence of lemurs outside of Madagascar?
I think the best approach to these things is to accept the theories that are most encompasing of all lines of evidence. Yet at the same time appreciate there will always be outliers wherein some small bits of data doesn't seem to fit. Such might indicate a refinement in our theories is required, but jumping to some wild conclusion that is opposed to mountains of other evidence based on an unexplained anomaly is not productive.
Here is John Brawley's conclusions. If you feel inclined to comment it would be appreciated, but in any regards I enjoy the opportunity these threads create to discuss such things.
"In Conclusion, I believe that Radon-222 is the most likely candidate for the source of certain "Polonium-218" halos in biotite mica. The process envisioned is most consistent with the data (including some observational data not mentioned by previous researchers), and providentially is unique in its characteristics: Radon is an inert gas, the only gas in the Uranium-238 decay chain, having the thermodynamic ability and more than enough time to migrate about in the mica, a few atoms at a time. Also significant is the apparent impossibility of distinguishing Radon-222 halos from Polonium-218 halos under the microscope."
Cheers,
-Randy