Helium diffusion dating

Helium diffusion is one type of nuclear decay dealing with the old (the age which conventional dating gives assuming a constant decay rate).
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These techniques can also be applied to other minerals such as titanate and apatite. Farley and Reiners and have developed the sophisticated laboratory equipment needed to accurately analyze microscopic crystals for the different isotopes of concern. To make any predictions about diffusion of helium out of crystals, one needs a diffusion rate at the temperature of concern.

That data is reproduced in Figure 1 , below. The diffusion rates are plotted on semilog axes against the reciprocal of the temperature in degrees Kelvin. The result is a line with a negative slope, which is typical of the Arrhenius Law behavior of a thermally activated process. Note that at lower temperatures the line breaks into a shallower slope. That indicates a different diffusion activation energy and hence that a different diffusion process is rate controlling.

Helium dating

While such behavior is more typical in polycrystals where grain boundary diffusion becomes rate controlling at lower temperatures, there is apparently some structural factor in these monocrystals that promotes low temperature diffusion. In any case, the low temperature diffusion rates are critical for this discussion.


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Figure 2 shows the diffusion rate data for the four lowest temperatures evaluated in that study , , and E C. The data points definitely form a straight line. Extrapolating these data can be a little risky so I will not try to extend the trend line much farther than the range of abscissa values covered by the four existing data points.

Professor Timothy H. Heaton

That extrapolation will extend nearly to a value of 0. The next step of this analysis is to estimate the rate at which helium would diffuse out of a zircon crystal at E C. For that calculation I used the degassing formula that estimates the average helium level left in the crystal after some diffusion time. That formula is given as an infinite series of the following expression. To estimate the remaining helium levels at various times I calculated the first 20 terms of the series higher order terms are so small as to be irrelevant to the total.

That radius is typical of the zircons studied by the RATE group and others and the diffusion rate is extrapolated from their data. The figure shows that the helium concentration needs nearly 50, years to drop to approximately 0.

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There are several studies in the literature that report such data. The first was published by Reiners, Farley and Hickes [7]. In that work, zircon specimens were obtained from the Gold Butte formation in southeastern Nevada near Lake Mead. That is an unusual formation which geologists interpret as having formed vertically about 1.


  • Numerous Fallacies Based on Bad Assumptions and Questionable Data.
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  • Helium dating - Wikipedia.

After the formation had tilted the deeper rock quickly cooled. The authors reasoned that the rock closest to the surface before tilting would have probably cooled sooner that the deeper rock. To estimate the time of cooling they measured the age as indicated by the uranium, thorium and helium contents for zircons from different locations along the now tilting rock formation. Keep in mind that the helium dating method gives the time at which the rock cooled to low temperature, not its total age. According to Laughlin et al.

Due to the uncertainties associated with the helium measurements of samples 5 and 6, Gentry et al. Although Humphreys et al. The semiquantitative at best nature of the helium Q results for samples 5 and 6 must also be remembered when evaluating Humphreys et al. Rather than treating both samples 5 and 6 as contamination during analysis, unreliable instrument noise, minor helium background concentrations, or in another consistent manner, Humphreys et al.


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At the same time, they show unjustified bias and fail to apply the same standards to sample 5. As part of their efforts to remove sample 6 from their models, Humphreys et al. Then as diffusion proceeds, C would decrease in the zircon and increase in the biotite, until the concentration was the same throughout the two materials. After that C would remain essentially constant, at about 0. First of all, what is meant by "disk-like volume"? How can Humphreys et al. That is, cubed and not squared dimensions. If Humphreys et al. Perhaps, Humphreys et al. If so, the volume of this biotite feature is not times the volume of Humphreys et al.

The typical width [ h ] of a biotite cleavage is about 3. Using a b value of 1, microns as argued by Humphreys et al. So, the vague arguments about "two-dimensional" volumes in Humphreys et al.

Helium diffusion - CreationWiki, the encyclopedia of creation science

In another attempt to justify the elimination of sample 6 from the creation model, Humphreys et al. Taking into account the difference in density of biotite and zircon 3. That suggests the zircon and biotite were near equilibrium in sample 6, thus supporting our hypothesis. In the above statements, Humphreys et al. They then illogically concluded that the biotites from sample 6 must have the same helium concentration as the biotites from the meter sample.

Certainly, the helium concentrations of the zircons and biotites in both samples 5 and 6 may be in equilibrium with extraneous background helium; however, how can anyone argue that the helium concentrations of the zircons and biotites in sample 6 are essentially the same on the basis of comparing the amount of helium in the sample 6 zircons at meters depth with the helium concentration of an impure biotite sample from a different lithology at only meters depth? Again, this approach utterly contradicts the admission in Humphreys et al. Humphreys needs to actually measure the helium concentration in the sample 6 biotites to confirm that they are not even lower.

Rather than deal with the irrational statements in Humphreys et al.

Dr. Humphreys' Young-Earth Helium Diffusion "Dates"

Besides invalidly comparing the helium content of a biotite with the content of the sample 6 zircons at much greater depth, the helium measurements for the biotite and the zircons are far too unreliable to support the efforts in Humphreys et al. As previously discussed, Gentry et al. Furthermore, information in Appendix B of Humphreys et al. The scientist that performed the helium diffusion measurements for Humphreys et al. I have no obvious explanation for this phenomenon.

It appears to be, i. It is possible that we are dealing with more than one He source multiple grain sizes or multiple minerals? The other source would be the helium diffused out of larger zircons no longer attached to the flakes. Since the biotite probably contained zircon impurities that produced excess helium and since Gentry et al. As discussed above, the comparison in the following paragraph from Humphreys et al. A scientist that peer-reviewed this essay decided to perform the calculations and verify Dr.

Humphreys' conclusion that the amount of helium in the Fenton Hill biotite at a depth of meters and the amount in the zircons of R. Gentry's sample 6 from a depth of meters were "almost exactly the same. Before multiplying, the Q values from Humphreys et al. The numbers are off by over an order of magnitude!

I cannot find any mistake in my math, but then again, if Humphreys meant something else, he should have elaborated on his argument in the first place. What is worse, for Humphreys, is the fact that the biotite value is higher than the zircon value which cannot happen through out-diffusion , which goes back to your point that one cannot claim that the biotite was in equilibrium with the zircon when the two minerals were separated by 3. Again, the scientist obtained the Q values for the Fenton Hill biotite and R.

Gentry's sample 6 zircons from an ICR copy of Humphreys et al. However, this is not the original version of Humphreys et al. It turns out that there are two versions of Humphreys et al. This earlier version had the original and uncorrected Q values from Gentry et al. When this original Q value is used, Dr.

Humphreys' calculation in Humphreys et al. Although it's a completely invalid and meaningless calculation as described above , the amount of helium in the Fenton Hill biotite at a depth of meters and the amount in the zircons of R. Humphreys changed the Q values in Humphreys et al.

Humphreys' "corrected" the Q values in Humphreys et al. As shown above in the scientist's calculations, the results now vary by an order of magnitude.