and fumeroles, and associated with mid-ocean ridge hydrothermal vents and chimney deposits (Hussain et al. 1995; LeCloarec et al. 1994; Rubin 1997), as well as in ground waters (Harada et al. 1989; LaRock et al. 1996). The distances involved in this fluid transport of the Po are several kilometers (and more), so there is increasing evidence of the potential viability of the secondary transport of Po by hydrothermal fluids during pluton emplacement, perhaps in the waning stages of the crystallization and cooling of granitic magmas (Snelling and Woodmorappe 1998; Snelling 2000b, 2008a). Consequently, Snelling and Armitage (2003) investigated the Po radiohalo occurrences in three Phanerozoic granitic plutons and logically argued for a model of Po radiohalo formation involving secondary transport of Po by hydrothermal fluids during crystallization and cooling of the granitic magmas. Their data and details of this hydrothermal fluid transport model were initially published by Snelling et al. (2003), but full details encompassing these results were elaborated upon in Snelling (2005a). He proposed that hydrothermal fluids infiltrating along the cleavage planes within biotite flakes dissolved 226Ra, 222Rn and the Po isotopes emanating from 238U decay within the zircon radiocenters of the 238U radiohalos. At conducive sites down flow within the same biotite flakes the Po isotopes were deposited and concentrated in what became the radiocenters for 218Po, 214Po and 210Po radiohalos as the Po isotopes decayed. Hydrothermal fluids are typically Cl-rich and are known to be capable of dissolving 226Ra, 222Rn and the Po isotopes, the latter particularly bonding with Cl (Bagnall 1957). Hydrothermal fluids also carry S, and because Po behaves geochemically the same as Pb it also bonds with S (Bagnall 1957). Furthermore, the mica sheets making up the biotite structure are weakly bonded by K, OH, and F ions, so S and Cl ions can occasionally substitute at point loci within the cleavage planes. It was thus postulated by Snelling (2005a) that as the hydrothermal fluids carrying 222Rn and the Po along the cleavage planes between the biotite sheets, Po atoms were attracted to those point loci where they decayed, only to be replaced by more Po atoms attracted to the same S or Cl point loci. The Po radiocenters were thus formed surrounded by Po radiohalos. Whereas Po radiohalos would appear to indicate extremely rapid geological processes were responsible for their production (because of the extremely short half-lifes of the Po isotopes responsible), 238U and 232Th radiohalos appear to be evidence of long periods of radioactive decay, assuming decay rates have been constant at today’s rates throughout earth history. Indeed, it has been estimated that dark, fully-formed U and Th radiohalos require around 100 million years’ worth of radioactive decay at today’s rates to form (Gentry 1973, 1974; Humphreys 2000; Snelling 2000b). Thus, the presence of mature U and Th radiohalos in granitic rocks globally throughout the geological record would indicate that at least 100 million years’ worth of radioactive decay at today’s rates had occurred during earth history. Therefore, the requirement of grossly accelerated 238U decay is essential to this hydrothermal fluid model for the transport of the Po isotopes from the decay of 238U in the radiocenters of 238U radiohalos (Snelling 2005a). Vardiman et al. (2005) found that the greater the half-life of a radioisotope the greater the decay rate acceleration. Thus, whereas 238U decay would have been grossly accelerated during some past geologically catastrophic event such as the Flood, the very short half-life Po radioisotopes would not have been affected. Several lines of evidence suggest that during the Flood when much of the fossil-bearing sedimentary rock record was accumulating, and when biotite-bearing granites were intruded into those sedimentary rocks, the decay rate of 238U was grossly accelerated (Vardiman et al. 2005). These include systematicallydifferent radioisotope ages for the same rock units dated by multiple methods, helium diffusion in zircons, the quantities of fission tracks matching conventional Phanerozoic stratigraphic ages in tuff beds deposited during the Flood year, and radiocarbon in Phanerozoic coal beds and other organic materials, as elaborated in detail by Vardiman et al. (2005). Thus, whereas today’s very slow 238U decay rate produces only a few Ra, Rn and Po atoms very slowly, that grossly accelerated decay rate would have produced huge numbers of Ra, Rn and Po atoms very rapidly, which were then easily transported the short distances within the host biotite flakes to precipitate in the adjacent Po radiocenters and produce the Po radiohalos. As proposed by Humphreys (2000) and Vardiman et al. (2005), these observable data require that within the Biblical young-earth time framework radioisotope decay therefore had to have been accelerated, but just by how much needs to be determined. If, for example, mature U and Th radiohalos were found in granitic rocks that were demonstrated to have formed during the Flood year, then that would imply at least 100 million years’ worth of radioisotope decay at today’s rates had occurred at an accelerated rate during the Flood year (Baumgardner 2000; Snelling 2000b, 2005a). Vardiman et al. (2005) postulated the 238U decay rate was accelerated by five orders of magnitude, so it could then be supposed the Po isotopes’ decay rates were similarly accelerated, which could make their existence so fleeting there wouldn’t be sufficient time for hydrothermal transport to form radiocenters. However, as already noted, Vardiman et al. (2005) also found that the amount of acceleration was related to the present half-lives of the parent radioisotopes, the slower the present decay rate (or the longer the current half-life) resulting in the most acceleration. Thus, with such fast decay rates (short half-lives) today, the Po isotopes would virtually have not been accelerated. Furthermore, the accelerated decay rates would not have resulted in much larger radii for 238U radiohalos, as ring radii are not affected by the decay rates but are related to the energies of the emitted α-particles (Gentry 1973, 1974). In this hydrothermal model, therefore, the Po accumulated in the radiocenters by time integration as Po atoms were progressively deposited from the passing hydrothermal fluids (Snelling and Armitage 2003; Snelling 2005a). So, instead of the Po radiohalos forming virtually instantaneously as proposed by Gentry (1988), the Po radiohalos formed over hours and days. However, whereas granitic magmas are intruded at 650-730°C, the radiohalos cannot form until the magma has crystallized and the temperature has fallen below 150°C, because above that temperature radiohalos are annealed (Laney and Laughlin 1981). This still has drastic time implications for the formation of granites (Snelling 2008a). Whereas Gentry (1988) concluded that granites were created instantaneously by divine fiat, Snelling (2005a, 2008a, 2014) postulated that granite magmas crystallized and cooled within days, which is still very radical compared to the uniformitarian timescale. Furthermore, if Po SNELLING Radiohalos through earth history 2023 ICC 543
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