(Converted for HTML using
FrontPage 97 in March of 1997, colour images are for this
(Originally published in the May 1988 Issue of the Journal of Geological Education)
The unusual polonium halos described by Robert Gentry have been a problem for some years now. Gentry claimed that the polonium halos show that the Precambrian granite they are hosted in were 'instantly created.'
Some research on the halos has been carried our by other scientists, but most of it has been aimed at solving the problems of the peculiar configuration of these halos. Fortunately, Gentry provided two specific site locations in the Canadian Shield where his samples came from. The geological setting of these sites shows conclusively that Gentrys notion of an 'instantly created' earth composed of granite is false. Specifically the samples came from crystallized rocks which can be shown to crosscut several sedimentary and other plutonic rocks. Some of the sedimentary rocks contain stromatolites. The geology of the sites shows that the uranium, and most likely the polonium, were deposited via postmagmatic hydrothermal fluids. Besides ignoring the geology at his collection areas, Gentry also makes numerous grossly erroneous generalizations about the origin of plutonic rocks.
Gentry's Basic Premise
Geology of the Canadian Sites
Precambrian Geology and Instantaneous Creation
Crystal Sizes and Pegmatite Dikes
Sequence of Rock Formation
Gentry Pays a Visit! [future]
Reply to Gentry's Reply [future]