Young-earth advocate Robert Gentry and a handful of other creationists have claimed that the presence of polonium radiohalos in certain rocks demonstrates that they are "primordial rocks" created almost instantaneously (within about 3 minutes) on day one of a literal creation week only several thousand years ago.(Gentry, 1986) However, mainstream workers and even many creationists have noted serious problems in Gentry's methods and interpretations, including the following:
1. Failure to document the precise geologic setting of many of his samples.
2. Some of Gentry's samples are known to have been taken from Precambrian metamorphic rocks and pegmatite veins that are intruded into, or occur on top of sedimentary rocks - sometimes even fossil-bearing rocks (Wakefield, 1998, 1990). Logically, such veins must be younger than the sedimentary layers, and thus cannot be "primordial rocks."
3. Radio halos occur in many other parts of the geologic column, including Paleozoic and Mesozoic strata underlain by extensive sequences of fossiliferous rocks (DeYoung, 2006), again precluding a "primordial rocks" interpretation.
4. Several credible alternate hypotheses have been advanced for the origin of the supposedly anomalous Po-halos, including erasure or modification of inner halos by Alpha radiation from other isotopes, migration of uranium-series elements through rocks by fluid migration or diffusion, and modification of halos during geologic metamorphism (Baillieul, 2005; Brawley, 2007). Gentry has disputed but not effectively refuted these explanations.
5. Difficulties with Po-halo identification include coloration reverals due to saturation effects, attenuation of alpha particle ranges by the radioactive inclusion, dose dependence of halo radii, lack of adequate data on the relation between energy and distance in various mineral types, and the effects of crystal imperfections and chemical impurities (Dalrymple, 1985).
6. Issues have been raised about the difficulty in distinguishing between certain Po halos and radon halos (Wakefield, 1990), which like uranium can be precursors of polonium isotopes. Radon is a gas which can permiate the smallest pores or cleavages in rocks or be incorporated into them during crystalization (Collins, 1988).
7. Thin sections of Po-halos show that they are often concentrated along fractures and cleavage planes, in rocks containing uranium or other radioactive elements, strongly suggesting a secondary source of the halos (Baillieul, 2005).
8. Creationists who examined Po halos in diamonds similarly concluded that the halos can be explained by hydrothermal fluid transport. They further conclude that they formed after emplacement of their host kimberlite/lamproite pipes at or near the earth’s surface (Armitage and Snelling, 2009).
9. Even if Gentry could demonstrate that rocks containing Po-halos were created instantaneously, it would not demonstrate when the rocks were created. Instantaneous creation does not necessarily imply young age.
The existence of reasonable alternate explanations would alone be sufficient to undermine Gentry's claim that rocks bearing Po-halos require an instanteneous creation interpretation. One of the most convincing explanations was put forth by Collins (2000, 1988), who described evidence that in uranium rich rocks, radon gas can diffuse into host rocks during crystalization, whereupon the radon (222Rn) decays, Po isotopes nucleate the biotite (and fluorite) crystals, and Po-halos are formed. However, whatever the process involved, it is clear from the geologic setting evidence that Po-halos do not necessarily imply primordial, instantaneously created rocks, and in many cases, that the primordial interpretation is well refuted by the geologic context.
Neither Gentry's website nor his book deals substantially with the critical geologic setting data fatal to his interpretations. Gentry suggests, without convincing evidence, that the geologic evidence is erroneous and based on "uniformitarian assumptions." He also intimates that God could have created complex geologic (even fossiliferous layers?) instantaneously. The first explanation is untenable in that the intrusive nature of the host rocks containing some of Gentry' halo specimens and presence of Po halos in post Phanerozoic rocks has been well documented and acknowledged even by strict creationists workers such as Wise (1989), Snelling,(2002, 2003) and DeYoung (2006) and Tas Walker (2001). Snelling bluntly stated that it was wrong for Gentry "to go on denying and rejecting the many impeccable observational evidences...". Likewise, in reviewing evidence that many of the holos occur in intrusive dikes, Brown et al(1988) state: "...it would be safe to say that the majority of halo-containing minerals are younger than the host rock and therefore do not represent primordial material."
Gentry's second suggestion, implying that God might create evidence of geologic events (or even life forms) which appeared to take many years to form, but which (according to Gentry) never occurred or happened almost instantaneously, is reminiscent of suggestions by some creationists that light from distant stars (even when showing events such as stellar explosions) were created en route to earth by God. Since this interpretation appears to make God a deceiver, even many creationists are uncomfortable with it. Furthermore, in regards to post-Phanerozoic halos, it implies that a large portion of fossil-bearing rocks would be "primordial" which conflicts with not only extensive geologic evidence, but also virtually all YEC/Flood models.
At times Gentry seems to deliberately obscure the extent of contrary evidence. For example, the introduction at his website states "Have you heard that, decades later, this evidence still stands unrefuted by the scientific community?" Yet not only does Gentry not deal fully with the unsupportive geologic evidence, his website does not even reference some of the most extensive and compelling critiques, including those of Wakefield, ( 1998, 1990), Collins (1988), and Hunt et al (1992). Thus, while claiming to be open to counter evidence and refutations, he displays virtually the opposite attitude, and even boldly proclaims "Creation's Tiny Mystery will stand as the Rock of Gibraltar against the tide of evolution."
Gentry claims also include serious logical errors. For example, he argues that unless scientists can artifically form a hand-held piece of granite, it demonstrates that God created granite by fiat. However, whether or not humans can dupicate a piece of granite has no logical bearing whatsoever on whether God and/or natural processes did so in the past. Indeed, since there are many post-Phanerozoic granitic rocks, which are acknolwedged by all to be non-primordial, Gentry's syllogism is already disproven. Moreover, although most diamonds are Pre-cambrian, humans already have created artifical diamonds. By Gentry's logic, this implies (contrary to his claims) that Pre-cambrian rocks are not primordial. Other problems and inconsistencies with Gentry's callenge are discussed by Dalrymple (1985).
Although most major creationist groups seem to be abandoning Gentry's claims that Po halos imply primoridal rocks, they are now trying to fit the same evidence into a Flood Geology scenario. Some suggest that the halos are evidence that uranium bearing minerals were incorporated into the host rock by a rapid geologic process (Snelling, 2003). Even if this were the case, it does not indicate that any significant part of the geologic column, let alone most post-Phanerozoic rock, was formed quickly or during the Flood. Moreover it not only refutes Gentry's contention that radio halos indicate primordial rocks created virtually instantaneously, and undermines the idea that the halos-bearing minerals need to be created by direct or supernatural fiat at any time.