Gentry's Basis Premise
"The basement rocks of the continents, the Precambrian granites, would be classed among the primordial Genesis rocks of our planet." (Gentry, 1986, p. 33)
". .. the primordial Earth being called into existence on Day 1 of creation week about 6000 years ago. ...other primordial rocks could include sedimentary rocks (without fossils) as well as some non-Precambrian granites and metamorphic rocks."
(Gentry. 1986. p. 184)
(Po214 in biotite, from Creation's Tiny
Mystery, by R.V. Gentry)
Gentry has described his work on halos and his interpretations of the significance of the halos in a series at papers and in a recent book Creations Tiny Mystery (Gentry 1986). How these halos form is not difficult to understand. They are formed by alpha particles released during the decay of radioactive nuclides. As an alpha particle nears the end of its path and slows, it causes disruption of the crystal structure and leaves a small damage track. Over time, repeated decays from the parent nuclide will leave a spherical halo of discolouration. The distance that an alpha particle travels depends on the energy of the decay and that, in turn, is a function of the particular nuclide that decays. Theoretically, then, the radii of a series of halos that surround a radioactive inclusion permit identification of the specific decaying nuclides.
Gentry has claimed that certain of his halos indicate that the "basement rocks" of the earth are "the primordial Genesis rocks" and were created instantaneously about 6,000 years ago. Essentially, Gentry has found that in certain samples of Precambrian biotite the inner halos of uranium and other nuclides in the decay chain, which should be producing 210Po, 214Po, and 218Po, are missing: only the polonium rings for these three isotopes are present. In addition, Gentry observed little or no uranium in the radioactive inclusion. He concluded that the polonium must have been primordial and, because of the short half-lives of the Po isotopes (138.4 days, .000164 seconds, and 3.04 minutes respectively), the granite, therefore, must have been created in the solid state in "... only a brief period between nucleosynthesis' and crystallization of the host rock." (Gentry in Fremlin, 1975, p. 270)
In the papers he has published in scientific journals, Gently has avoided making creationist statements, but his other publications on the matter give the distinct impression that he is trying to link the rocks of the Precambrian to the rocks that existed right after Earth's formation (or creation). For example, Gentry states in one publication (1974, p. 63) that.
"It is also apparent that Po halos do pose contradictions to currently held views of Earth history."
"The Question is, can they be explained by presently accepted cosmological and geological concepts of the origin and development of Earth?" (1974, pĚ 56)
"Do Po halos imply unknown processes were operative during the formative periods of the Earth?" (Gentry and others, 1974, p. 564)
Gentrys book, however, is far more bold and less cryptic than his refereed papers. Comments like
"Were tiny polonium halos God's fingerprint in Earth's primordial rocks? Could it be that the Precambrian granites were the Genesis rocks of our planet." (Gentry, 1986, p. 32)
"...polonium halos in Precambrian granites identify these rocks as some of the Genesis rocks of our planet - created in such a way that they cannot be duplicated without intervention of the Creator." (p. 133)
In the young-earth creationist perspective, this puts Gentry in agreement with John Whitcomb and Henry Morris (Whitcomb and Morris. 1961, p. 228) in claiming that the Precambrian consists of created rock of granitic composition. To any geologist this is such an overly simplified view of the complex Precambrian terrains of the world as to be ludicrous. Precambrian rocks formed by the same or similar processes that formed the Phanerozoic rocks. The only significant differences are that
- Fossils are rarer in Precambrian rocks, and
- Many Precambrian rocks have had more complex histories because they are much older.
Gentry was called as a witness at the 1981 Arkansas trial to present his work and interpretation. However, a number of alternative explanations have been advanced to explain Gentrys halos (for example, see Feather, 1978; Meier and Hecker, 1976; Moazed and others, 1973; or Chaudhuri and lyer, 1980), and the alternatives were discussed by geologist G. Brent Dalrymple at the trial in some detail, but Gentry has disputed the validity of the alternative origins.
Scientifically, they were confronted with evidence far creation, and they didn't even try to refute it. Make no mistake - if the ACLU had found a flaw in that evidence they certainly would have brought it out during my cross-examination (Gentry, 1986, p. 143)
I do not intend to discuss the physics of halos in this paper. What I will describe here is the geology of three of the locations where some of Gentrys biotite samples came from - the Fission Mine, the Silver Crater Mine and the Faraday Mine, all near Bancroft in southern Ontario (see Figure 1). On the basis of the geology of the sample sites. I will hypothesize that the uranium, and hence the polonium, were deposited by precipitation from circulating fluids.