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100 Reasons to Choose Biblical Creation Over Evolution
76. Helium and Lead Diffusion
Helium and lead are both the products of radioactive decay. That is, they are produced as certain elements lose their mass over time. Uranium, for example, will decay into lead, changing into and producing various other substances along the way. Helium and lead are both part of this decay chain.
It is a well-known fact that both decay products, helium and lead, will diffuse (leak) out of zircon crystals at a rate that increases with pressure and heat. It was assumed therefore, that zircons in supposedly ancient rock layers buried deep within the earth where the pressure and heat is greatly increased, would show less helium and lead than those at higher levels. The fact that no discernable difference was found in the amount of helium or lead throughout the first 4000 meters of the earth's crustA is a good indicator that the earth's crust is only thousands - not millions - of years old.
76. Helium and Lead Diffusion - Notes and References
A. In a personal e-mail from Astronomer Barry Setterfield (14 Feb. 2003), Mr. Setterfield offered the following data, relevant to this topic:
"In 1999, an assessment of data collected in 1997 indicated that the bottom 1000km of the earth's mantle contained anomalous reservoirs of heat producing elements ["Researchers propose a new model for earth mantle convection", MIT News Release 31 March, 1999]…In other words, there is a layer in the earth's interior where the radioactive materials were concentrated, and from which some have come to reside in the crust as a result of ongoing geologic processes. This means that the majority of helium must still be within the earth's mantle, not having enough time to work its way to the surface.
However, that does not account for the radioactive material which has come to reside in the crust of the earth. Where is the helium emitted by radioactive decay from that source? The possible answer is a surprise. It has been noted by R.E. Zartman in a Los Alamos Science Laboratory New Mexico gave an age for the granitic basement complex there about 1.5 billion atomic years. However, when zircons from this complex were analyzed by Gentry et al in 1982, they were found to contain very large percentages of helium, despite the hot conditions [R.V. Gentry, G.L. Glish and E.H. McBay "Differential helium retention in zircons…" Geophysical Research Letters Vol. 9 (1982), p. 1129]. The zircons were surrounded by a matrix of mica which prevented the helium from escaping. In other words, these zircons crystals had retained within them the radioactive decay products of almost 1.5 billion atomic years, without very much diffusing out. Work must still be done on the diffusion rate of helium through mica (in this case biotite), and Humphreys has made a creationist prediction about this compared with the diffusion rate expected from the evolutionist position [op. cit., p. 344, 350]. I find myself in agreement with this assessment."
Therefore the answer to your question on these assessments is that (1) radiogenic helium is trapped in the interior of the earth, not having sufficient time to be brought to the surface from the radioactive layer that exists at a depth of 1700 km, while (2) much of that which was brought up to the crust has not diffused out of the host rocks, again because of insufficient time and also because of much lower diffusion rates than previously anticipated. This position has at least some experimental data to support it."
Robert V. Gentry, "Creation's Tiny Mystery", Earth Science Associates, Knoxville TN, 4th Ed., 2003, p. 170