It is now almost two decades since the then Assistant Chief Geologist
of the US Geological Survey, Dr. G. Brent Dalrymple, described
polonium radiohalos as "a very tiny mystery."¹ An expert
geochronologist, Dalrymple was being cross-examined in the Federal
District Court in Little Rock at the Arkansas "creation trial"
of December 1981.

Radiohalos (or radioactive halos) are minute spherical zones
of color or darkening surrounding tiny mineral crystals, all included
in larger grains or crystals of host minerals in certain rocks.
Alpha-particles produced by radioactive decay of U, Th, and their
decay products in the tiny mineral inclusions penetrate the surrounding
host minerals, damaging their crystal lattices and discoloring
them. The distances traveled by the a-particles are related to
their energies, and where the a-particles stop they do the most
damage, leaving spherical shells of intense discoloration. Because
the a-particles emitted by the radionuclides in the U and Th decay
chains have different energies, it is therefore possible to identify
which radionuclides were responsible for producing the radiohalos.
The minerals containing these radiohalos are usually studied in
thin sections, so the radiohalos are viewed in cross-sections
and thus exhibit ring structures.

Radiohalos produced by the ²³⁸U and ²³²Th
decay chains are thus easily explained. However, there are also
radiohalos found that only exhibit rings produced by the three
Po (polonium) radionuclides of the ²³⁸U decay chain
(Figure 1), and it is these Po radiohalos that are enigmatic.³
Examination of the tiny central mineral inclusions (or radiocenters)
in these Po radiohalos reveals that only the respective Po radionuclides
were present at the time the Po radiohalos formed, but their half-lives
are very short—²¹⁸Po (3.1 minutes), ²¹⁴Po
(164 micro-seconds) and ²¹⁰Po (138 days). After 10
half-lives of decay the original quantities of radionuclides are
essentially exhausted, so these Po radiohalos rings would seem
to have formed very quickly, in approximately 31 minutes (²¹⁸Po),
1.64 milli-seconds (²¹⁴Po) and 1,380 days (²¹⁰Po).

Now these Po radiohalos have been found primarily in the mineral
biotite, a mica—at 20 out of 22 reported localities.⁴
The rocks hosting these Po-radiohalo-bearing biotites at 17 of
the 20 localities are probably granites or granitic pegmatites.
According to conventional uniformitarian geology, such granitic
rocks formed over millions of years by cooling from hot magmas
intruded into the upper levels of the earth's crust.⁵
However, the radiohalos could only have formed after the biotites
had crystallized around the tiny Po-bearing inclusions and cooled.
Thus, assuming the Po was in the tiny inclusions when they first
crystallized, it can be concluded that the biotites, and therefore
the granites, had to crystallize and cool in less time than it
would have taken for the Po radiohalo rings to form⁶—1.64
milli-seconds for the ²¹⁴Po radiohalo rings! If this
implies that these granitic rocks were instantly created, then
it is no wonder that the conventional geologist Dalrymple relegated
Po radiohalos to being "a very tiny mystery"!

Of course, such incredible implications have not gone unopposed.
Some observers have claimed that many Po radiohalos occur along
cracks and cleavage planes in biotites, and that fluids may therefore
have transported the Po into the biotites after the granitic rocks
had formed.⁷ In a relatively few instances this is
obviously true, but only ²¹⁰Po radiohalos are found
along such cracks, which are sometimes also bordered by discoloration
with a width equivalent to the ring diameter of ²¹⁰Po.
This implies that only the longer-lived ²¹⁰Po was transported
in the fluids. Secondary ²¹⁰Po radiohalos have also
been found in coalified wood associated with sandstone-hosted
U orebodies formed by groundwater flow.⁸ The Po was
concentrated from the U-transporting fluids into the Se-rich radiocenters
because of the geochemical affinity of Po with Se.

Critics also point to the apparent association between the occurrence
of Po radiohalos and concentrations of U—16 out of 20 Po-radiohalo-bearing
biotite localities have reported U in the rock or in an orebody.⁹
Thus it has been suggested that the fluids responsible for concentrating
the U may have also transported the Po and concentrated it in
the tiny radiocenters. ²¹⁰Po is present in groundwaters,¹⁰
and in volcanic gases¹¹ and fluids,¹² and
has been reported in submarine hydrothermal vent fluids and chimney
deposits on the East Pacific Rise,¹³ where the ²¹⁰Po
appears to have been transported over distances of up to several
kilometers in 20-30 days.

However, if Po radiohalos formed secondarily from fluid-transported
U-decay products, the expected amounts of the ²¹⁸Po,
²¹⁴Po and ²¹⁰Po radiohalos would be directly
proportional to their different half-lives.¹⁴ Thus,
for example, there should be 67,000 ²¹⁰Po radiohalos
for each ²¹⁸Po radiohalo. Yet in a Norwegian biotite
there are more than 1,000 ²¹⁰Po radiohalos, 90 ²¹⁸Po
radiohalos and only one ²¹⁴Po radiohalo,¹⁵
but in other biotites the abundance ratios are ²¹⁸Po>²¹⁰Po>²¹⁴
Po, and even ²¹⁴Po>²¹⁸Po or ²¹⁰Po.¹⁶
Also, there may be as many as 20,000-30,000 ²¹⁸Po and
²¹⁰Po radiohalos per cubic centimeter,¹⁷
or 5,000-10,000 ²¹⁸Po and ²¹⁴Po radiohalos
per cubic centimeter.¹⁸ The seeming impossibility of
this secondary transport explanation is highlighted by the fact
that the 5 x 10⁹ atoms of ²¹⁸Po initially
needed to produce each very dark ²¹⁸Po radiohalo had
to be concentrated in the tiny radiocenters in less than the ²¹⁸Po's
three minute half-life.¹⁹ But experimentally-measured
diffusion rates are just too slow,²⁰ and close to radiocenters
there is no large excess of a-recoil tracks left by decay of the
fluid-transported Po and Po-precursors.²¹

Another puzzle is that at five of the 20 Po-radiohalo-bearing
biotite localities the host granitic rocks intrude apparently
older rocks arguably produced during the Flood.²² If
these granitic rocks therefore also formed during the Flood, then
how were the Po radiohalos produced in them? On the other hand,
most of the Po radiohalos occur in Precambrian granitic rocks,
many of which might be related to the events of the Creation Week,
as might the one occurrence of Po radiohalos in a Precambrian
high-grade metamorphic rock.

Thus the Po radiohalos still remain "a very tiny mystery." There
can be no doubt, though, that they are significant as clues for
unraveling earth history within the Biblical framework, so further
research is warranted. If the Po radiohalos are indeed "fingerprints
of creation," ²³ then they provide the means of identifying
Creation Week rocks. Similarly, they may indicate accelerated
radioactive decay in the past and/or suspension of normal geological
processes and process rates, including fluid transport, during
the Flood. Whatever these Po radiohalos are "telling us," we are
only going to find out by further "reading the rocks" to seek
a better understanding of the geological distribution and occurrences
of these Po radiohalos at both known and new localities. Such
research is now being pursued.²⁴

Figure 1. Composite schematic drawing of (a) a 218Po halo, (b) a 238U halo, (c) a 214Po halo and (d) a 210Po halo with radii proportional to the ranges of a-particles in air. The nuclides responsible for the a-particles and their energies are listed for the different halo rings [after Gentry2].

Figure 2. 218Po radiohalo. Photo by Mark Armitage.

References

¹ Gentry, R.V., Creation's Tiny Mystery
(Knoxville, TN: Earth Science Associates, 1988), p.122.

² Gentry, R.V., "Radioactive Halos," Annual Review
of Nuclear Science 23 (1973):

347-362. R.V. Gentry, "Radiohalos in a Radiochronological and
Cosmological Perspective," Science 184 (1974): 62-66.

³ Gentry, Ref.2. R.V. Gentry, "Radioactive Halos in
a Radiochronological and Cosmological Perspective," Proceedings
of the 63rd Annual Meeting, Pacific Division, American Association
for the Advancement of Science 1, no. 3 (1984): 38-65.

⁴ Wise, K.P., "Radioactive Halos: Geological Concerns,"
Creation Research Society Quarterly 25 (1989): 171-176.


⁵ Snelling, A.A., and J. Woodmorappe, "The Cooling
of Thick Igneous Bodies on a Young Earth," in Proceedings of
the Fourth International Conference on Creationism, edited
by R.E. Walsh (Pittsburgh, PA: Creation Science Fellowship, 1998),
pp.527-545, however, have demonstrated that only tens to a few
thousands of years are necessary for the intrusion and cooling
of granitic rocks.

⁶ Gentry, R.V., "Radioactive Halos: Implications for
Creation," in Proceedings of the First International Conference
on Creationism, vol. 2, edited by R.E. Walsh, C.L. Brooks,
and R.S. Crowell (Pittsburgh, PA: Creation Science Fellowship,
1986), pp.89-100. Gentry, Ref.1.

⁷ Henderson, G.H., and F.W. Sparks, "A Quantitative
Study of Pleochroic Haloes—IV. New Types of Haloes," Proceedings
of the Royal Society of London, Series A, 173 (1939): 238-239.
H. Meier and W. Hecker, "Radioactive Halos as Possible Indicators
for Geochemical Processes in Magmatites," Geochemical Journal
10 (1976): 185-195.

⁸ Gentry, R.V., W.H. Christie, D.H. Smith, J.F. Emery,
S.A. Reynolds, R. Walker, S.S. Christy, and P.A. Gentry, "Radiohalos
in Coalified Wood: New Evidence Relating to the Time of Uranium
Introduction and Coalification," Science 194(1976): 315-318.


⁹ Wise, Ref.4.

¹⁰ Harada, K., W.C. Burnett, P.A. LaRock, and J.B.
Cowart, "Polonium in Florida Groundwater and its Possible Relationship
to the Sulfur Cycle and Bacteria," Geochimica et Cosmochimica
Acta 53 (1989): 143-150.

¹¹ Kuroda, P.K., J.C.H. Liou, A.D. Banavali, J.D.
Akridge, and L.A. Burchfield, "Polonium-210 Fallout from the 1980
Eruption of Mount St Helens and the Mystery Cloud of 1982," Geochemical
Journal 18 (1984): 55-60.

¹² LeCloarec, M.F., M. Pennisi, E. Corazza, and G.
Lambert, "Origin of Fumarolic Fluids Emitted from a Nonerupting
Volcano: Radionuclide Constraints at Vulcano (Aeolian Islands,
Italy)," Geochimica et Cosmochimica Acta 58 (1994): 4401-4410.


¹³ Hussain, N., and T.M. Church, "²¹⁰Po
and ²¹⁰Pb Disequilibrium in the Hydrothermal Vent Fluids
and Chimney Deposits from Juan de Fuca Ridge," Geophysical
Research Letters 22 (1995): 3175-3178.

¹⁴ Gentry, R.V., "Radiohalos in Diamonds," Creation
Ex Nihilo Technical Journal 12 (1998): 287-290.

¹⁵ Meier and Hecker, Ref.7.

¹⁶ Feather, N., "The Unsolved Problem of the Po-Haloes
in Precambrian Biotite and Other Old Minerals," Communications
to the Royal Society of Edinburgh 11 (1978): 147-158.

¹⁷ Gentry, R.V., "Fossil Alpha-Recoil Analysis of Certain
Variant Radioactive Halos," Science 160 (1968): 1228-1230.


¹⁸ Gentry, R.V., "Spectacle Haloes," Nature
258 (1975): 269-270.

¹⁹ Gentry, Ref.2.

²⁰ Gentry, Ref.18. S.R. Hashemi-Nezhad, J.H. Fremlin,
and S.A. Durrani, "Polonium Haloes in Mica," Nature 278
(1979): 333-335.

²¹ Gentry, Refs.17, 18.

²² Wise, Ref.4.

²³ Fingerprints of Creation (Thousand Oaks,
CA: Adventist Media Center, 1993), videocassette.

²⁴ Vardiman, L., "RATE Group Prepares Status Report"
(El Cajon, CA: Institute for Creation Research Impact
No. 314, 1999), pp. i-iv.

* Dr. Snelling is Professor of Geology for the ICR Graduate
School.