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K-Ar dates of 1986 dacite from Mount St. Helens are very old (Talk.Origins)

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Response Article
This article (K-Ar dates of 1986 dacite from Mount St. Helens are very old (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 CD013.1:

The conventional K-Ar dating method was applied to the 1986 dacite flow from the new lava dome at Mount St. Helens, Washington. The whole-rock age was 0.35 +/- 0.05 million years (Mya). Ages for component minerals varied from 0.34 +/- 0.06 Mya to 2.8 +/- 0.6 Mya. These ages show that the K-Ar method is invalid.

Source: Austin, Steven A., 1996. Excess argon within mineral concentrates from the New Dacite Lava Dome at Mount St. Helens volcano. Creation Ex Nihilo Technical Journal 10(3): 335-343.


CreationWiki response: (Talk.Origins quotes in blue)

1. Austin sent his samples to a laboratory that clearly states that their equipment cannot accurately measure samples less than two million years old. All of the measured ages but one fall well under the stated limit of accuracy, so the method applied to them is obviously inapplicable. Since Austin misused the measurement technique, he should expect inaccurate results, but the fault is his, not the technique's. Experimental error is a possible explanation for the older date.

First of all Geochron Laboratories no longer does K-Ar dating, and so Talk Origins' claim in this regard cannot be checked from their web site, Talk Origins' source is actually another web site that is as dedicated to attacking creationists as Talk Origins is, as such they are clearly a biased source.

However when this source "quotes" Geochron Laboratories it does not say that "their equipment cannot accurately measure samples" but only that they cannot analyze samples expected to be less than 2,000,000 years old. This does not seem to represent a limitation of the equipment because all of the margins of error cited above are less than a million years. It seems to be more of a difficulty of determining the quality of the dates according to Uniformitarian Geology rather than the actual measurements. If that is the case then it really has no bearing on Austin's results.

Furthermore, AiG replied to this criticism on a "Counter The Critic" article:

One critic said that Dr Austin should not have sent young samples to the dating laboratory because it potentially puts ‘large error-bars on the data’. By this reasoning, the method could not be used on any rocks, since, if we did not see the rocks form, how would we know whether they are young? Anyway, the analytical error is reported by the laboratory (see ± values on Table 1), and in every case the error is much less than the supposed age of the sample.
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2. Austin's samples were not homogeneous, as he himself admitted. Any xenocrysts in the samples would make the samples appear older (because the xenocrysts themselves would be old). A K-Ar analysis of impure fractions of the sample, as Austin's were, is meaningless.

Accord to Austin's paper he dealt with this by removing the xenocrysts before the sample was sent to Geochron Laboratories. In addition the individual minerals were separated out for separate analysis. So Austin is not the incompetent idiot Talk Origins is portraying him as. He did send properly prepared samples to Geochron Laboratories.

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