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Zircons retain too much helium for an old earth (Talk.Origins)

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Response Article
This article (Zircons retain too much helium for an old earth (Talk.Origins)) is a response to a rebuttal of a creationist claim published by Talk.Origins Archive under the title Index to Creationist Claims.


Claim CD015:

Uranium and thorium in zircons produce helium as a by-product of their radioactive decay. This helium seeps out the the (sic) zircons quickly over a wide range of temperatures. If the zircons really are about 1.5 billion years old (the age which conventional dating gives assuming a constant decay rate), almost all of the helium should have dissipated from the zircons long ago. But there is a significant amount of helium still inside the zircons, showing their ages to be 6000 +/- 2000 years. Accelerated decay must have produced a billion years worth of helium in that short amount of time.

Source:


CreationWiki response:

For a more detailed rebuttal, please read Response to criticism of RATE’s helium diffusion dates (Talk.Origins quotes in blue)

1. Subsurface pressure and temperature conditions affect how quickly the helium diffuses out of zircons.

Humphreys' experiments dealt with variable temperatures so that factor is considered in the results. He also considered the problem of pressure, and after researching it he found that in the case of zircons the difference in pressure would affect the diffusion rates by less than 1%, placing it within the margin of error. The affect on the biotite mica would be about one order of magnitude, and Humphreys corrected for it.

The onus here seems to be more properly placed on TalkOrgins & Henke. As Humphreys points out in the conclusion of his response:

If Henke wishes to make a real contribution to science, instead of to polemics, he could commission an experiment to determine the effect of pressure on the diffusion rates of helium in zircon. He could contact Ken Farley, a world expert on measuring helium diffusion in minerals (including zircons) at Cal Tech, and pay him to do such an experiment. Farley might even do it for free, since I know from personal experience that he has been searching for an alternative interpretation to our helium data for years. It is a bit suggestive that Farley, an expert, hasn’t resorted to the rather obvious “pressure” argument used by Henke, a non-expert. But if experiments were to yield a significant pressure effect in zircons, Farley would be overjoyed to publish the results in the prestigious journal Earth and Planetary Science Letters, of which he is editor-in-chief.

Indeed.

D. R. Humphreys et al. selected a rock core sample from the Fenton Hill site, which Los Alamos National Laboratory evaluated in the 1970s for geothermal energy production. The area is within a few kilometers of the Valles Caldera, which has gone through several periods of faulting and volcanism. The rocks of the Fenton Hill core have been fractured, brecciated, and intruded by hydrothermal veins. Excess helium is present in the rocks of the Valles Caldera (Goff and Gardner 1994). The helium may have contaminated the gneiss that Humphreys et al. studied. In short, the entire region has had a very complex thermal history. Based on oil industry experience, it is essentially impossible to make accurate statements about the helium-diffusion history of such a system.

WRONG! The possibility of contamination was studied, and Talk Origins' would know that if they actually took the time to read the scientific papers. The concentrations of He in the zircons is about 200 times that of biotite, which eliminates the possibility of contamination. The laws of diffusion say that diffusion goes from the greater amount to the lesser, and not the other way around.

In addition the helium diffusion rate fits creation model's predicted values exactly, thus making contamination unlikely.

2. Scientific studies, especially those with radical implications, do not mean much until the results have been replicated by others. Many scientific claims have disappeared entirely when others could not get the same results.

Duplicate experiments including other locations are planned. Getting duplicate results is just a matter of time.

Also, RATE's zircon data matches that of a site called Fish Canyon Tuff.

P. W. Reiners, K. A. Farley, and H. J. Hickes, "He diffusion and (U-Th)/He thermochronometry of zircon: Initial results from Fish Canyon Tuff and Gold Butte, Nevada," Tectonophysics 349(1-4):297-308, 2002.

Confidence in this particular paper is reduced by certain points:
  • Most measurement errors and variabilities are not reported. Therefore, we do not know how accurate the results are.
That is because they are not large enough to be relevant. For there to be an error large enough to salvage the 1.5 billion year date it would have to reduce the measurements by a factor of 100,000.
  • Humphreys et al. claimed that they studied zircons and biotites from depths of 750 and 1,490 meters in the Jemez Granodiorite. However, Sasada (1989) showed that at those depths, the samples came from a gneiss, an entirely different rock type.
Talk Origins must have based this on the wrong location.
  • Because of math errors, the Q/Q0 values (fraction of helium retained), used by Humphreys et al. to derive their dates, are too high.
This is a baseless claim. What math errors? Besides, the retention level predicted by the uniformitarian model would be so small that it would be at equilibrium with the biotite instead of 200 times the levels of the biotite.
  • Humphreys et al. (2003) failed properly to total their data in Appendix C, which means that they grossly underestimated the total amount of helium released by their 750-meter-deep zircons. The amount of helium in the zircons greatly exceeds the amount that would be expected from the radioactive decay of uranium over 1.5 billion years. The high helium concentration may be due to samples that were abnormally high in uranium and/or to the presence of excess helium.
If they did, they clearly corrected it in the 2004 paper, since the total yield was 42% of what would result from nuclear decay.
  • Much is made of the fact that samples five and six retained the same amount of helium, even though the amounts are probably at the limit of what could be measured. The possibility of measurement error accounting for the results is never mentioned.
On pg. 3 they do suggest the possibility of measurement error and account for it. The fact is that sample 5 is right where it is predicted to be, suggesting that the measurement is not in error. It turns out that sample 6 is at equilibrium with the biotite around it. Its predicted diffusion rate is consistent with this.
  • If one discounts sample five, which is likely at the limit of measurable precision, the conclusions of Humphreys et al. (2004) rest on just three samples. Such a small data set may be the basis for further research, but not for drawing firm conclusions.
First, this assumes that sample 5 is a result of measurement error despite the fact that it fits the curve perfectly. Secondly, it assumes that the four data points used in calculating the date are the only samples. There are 28 data points that were used to calculate the diffusion rates. They back up the calculated date.
  • Humphreys et al. (2003, note 9) referred to correcting "apparent typographical errors" in the raw data, casting suspicion on the validity of all the data.
The two typographical errors were found and corrected and as such were not part of the calculations. This was done by checking with the original source.
The helium results could easily be due to an aberrant sample. They could be an artifact of the experimental or collecting method (e.g., defects in the zircons caused by rapid cooling) or from just plain sloppiness. We cannot know for sure until others have looked at the issue, too.

This is a very small possibility, considering that the data fits the creation model perfectly, while not being even close to the uniformitarian model. This is particularly the case given the insufficiency of the above objections.

3. Producing a billion years of radioactive decay in a "Creation week" or year-long flood would have produced a billion years worth of heat from radioactive decay as well. This would pretty much vaporize the earth. Since the earth apparently has not been vaporized recently, we can be confident that the accelerated decay did not occur. (Humphreys recognizes this "heat problem" but is currently unable to provide a solution.)

Actually he does have a possible solution involving the expansion of space.[1] Humphreys indicates that it is not fully developed, but that progress is being made.

4. If helium concentrations stay high around the rocks, it is possible for helium to diffuse into voids and fractures in the zircons, or at least high helium pressures could reduce the rate at which helium diffuses out. Either of these scenarios would invalidate the helium diffusion calculations in Humphreys et al. (2003, 2004). Helium concentrations within the earth become high enough for commercial mining. The sample measured by Humphreys et al. came from an area that is probably helium enriched. Helium deposits are common in New Mexico, and excess helium has been found just a few miles from where the sample was taken (Goff and Gardner 1994). To test for the presence of excess helium in their zircons, Humphreys et al. should look for 3He.

While checking for 3He is a good suggestion, the simple fact is that the Helium (He) concentration of the zircons is 200 times that of the surrounding biotite. This fact invalidates both possibilities.

5. Uranium does not decay directly to lead; rather, it proceeds through a series of multiple intermediate radioactive elements (Faure 1986, 284-287). It takes about ten half-lives of the longest lived intermediate to achieve secular equilibrium (i.e., each intermediate having the same activity). The uranium decay series contains elements with half-lives well over 10,000 years. If the decay rates changed suddenly, we would not expect the various elements to be in a secular equilibrium. Humphreys et al. should test for this in their zircons. Other uranium ores are at secular equilibrium, indicating a constant decay rate for at least the last two million years.

All that is necessary for this equilibrium to be maintained is for the change to be proportional in each element.

For related information go to Radiometric dating falsely assumes rates are constant (Talk.Origins)

References

  1. Humphreys, D.R. 2000. Accelerated nuclear decay: a viable hypothesis? In Vardiman et al. (2000), Chapter 7, pp. 333-379.
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