Depth, Crack-Haloes, and Radon Self-Migration
If Radon(222) migration is happening, evidence should exist countering other means of Uranium daughter element transport.
Haloes cannot form when the mineral constituents are still in hydrothermal fluid solution.
Once the mineral has crystallized, hydrothermal fluid should be excluded from it.
If no cracks or distortions of crystal planes are present, then there should be no means of daughter element transport available except Radon gas diffusion/migration.
In other words, if I can find haloing in the mica, which appears to be contained within otherwise unbroken, uncracked surrounding mica, this should be strongly suggestive that only Radon could have done the haloing.
I here present two samples from my first biotite mica, obtained from Mike Fix of the University of Missouri. (It is unfortunate that the source mines of this mica cannot be known with certainty; Mike told me they were probably from South Dakota.)
Both samples involve sequential splitting. That is, in the one, both halves of the piece of mica are shown, and in the other, a complete sequence of slices, from below the haloing to above it, are shown.
First, my "bullet" sample:
(Each image is a link to its larger parent image; backbutton yourself back here, please....)
Note that in this, no cracks are visible around the inclusion. The "connecting rod" between the dark, fuzzy blob and the decent "polonium"-type halo, is apparently hollow.
The crack you see in the image is caused by the splitting process. (In other words, I did that.)
I at first suspected this of being evidence of large-scale fission of an Uranium-235 particle, but have since changed my mind.
And, second, my "spider" :
(Likewise, each section is a link; images are 500x300, 16 megacolors....)
Images 1 and 7 show little to no evidence of darkening from the inclusion shown in image 4.
Image 5 shows the hole left by the actual inclusion (probably a zircon crystal; see its closeup), which stuck in the piece in image 4.
Images 2 and 6 show a darkened area. They are just below and just above the inclusion.
The center images show the cracks along which whatever-it-was (Radon222?) travelled as it left the immediate area around the (zircon?) inclusion.
I have the 1024x768 originals of these, in which it is seen that all of the radiating crack-haloes
terminate within the field of view. (In other words, the cracks that run out the edges of these images, do not run out into other cracks. This is all there is; what you see is what you get.)
Here is an image (link) of the very amateurish, but functional, "carrier" in which the above samples are permanently mounted: