lew@ihuxr.UUCP (Lew Mammel, Jr.) (02/19/84)
I promised Paul Dubuc a long time ago that I would post my assesment of Gentry's polonium haloes. I did post a summary of Gentry's claim along with a summary of an independent assesment which concluded that Gentry's evidence wasn't very strong. Paul wasn't satisfied with this, commenting that I hadn't "answered" Gentry, which I hadn't intended to do. Here is my judgement of the situation. Radioactive haloes are due to small (~2 micron) inclusions of radioactive material, usually uranium, in various rocks. The uranium decays through a series of intermediate products into lead, and each decay has a fixed energy. this results in the alpha paricles emitted accumulating at a fixed distance (for a given decay) from the inclusion where they cause enough dislocation to cause coloration in the rock. An "overexposed" ring will form a disk. Sometimes there are even "reversing effects" due to multiple exposures by different decays. These rings range from about 5 to 20 microns in radius. Polonium is one of these intermediate decay products, which itself decays in a matter of minutes, leaving its own characteristic rings along with the others. The so-called polonium haloes seem to show only the polonium signature, without the other products. WOW! They must be due to inclusions of polonium by itself! How could it have gotten there? As Gentry noted, the problem "seems to defy reason". But wait, how come the other guys aren't impressed? Well, all the other rings lie within the innermost of three polonium rings, and this innermost ring is an overexposed disk which would obscure them if present. So the other guys say, "Hey no problem, they're in there." But wait again! Gentry has done all kinds of detailed assays of the inclusion itself, and concludes that the uranium isn't there (in "sufficient quantities", that is) However, he is working at the limits of the several techniques he applied due to the small size of the haloes. So where does that leave you? You can believe Gentry, or you can say "phooey" ... or somebody could check it out independently. The independent check I mentioned was just visual, and didn't attempt to reproduce any of Gentry's exquisite assays. Here's the rub. Gentry makes quite a point of the tremendous effort he's sunk into this, so nobody feels like taking the bait and spending all that time on what is surely a bunch of nonsense anyway. Yes, it is just like refusing to look through Galileo's telescope! Except that that was a little easier, I should think. The one telling point against Gentry's interpretation that I can think of is his failure to find any polonium haloes WITHOUT THE INNER RING OVEREXPOSED. As I mentioned, these things come in all varieties. Gentry has one amazing figure which crowds about twenty different types into a montage, with labels a through r (including h' and r'). He spends a long time making his case that the polonium haloes can be distinguished from all the varieties of uranium haloes. So with all this variety, including plenty of underexposed uranium haloes, you'd think you might see a polonium halo with a nice blank spot where the other uranium rings should be. That doesn't prove he's wrong mind you, but I think it saves conventional geology from going down the tubes for the time being at least. References on request. Lew Mammel, Jr. ihnp4!ihuxr!lew