Radioisotopic dating with isotopes of different masses

[Astronuc]

An oversight in a radioisotope dating technique used to date everything from meteorites to geologic samples means that scientists have likely overestimated the age of many samples, according to new research from North Carolina State University.
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The ratios of strontium-86 to rubidium and strontium-87 are thought to only be influenced by the radioactive decay of the rubidium-87 into strontium-87. The current model of radioisotope dating is based on that idea.

But that model doesn't account for differential mass diffusion – the tendency of different atoms to diffuse though a material at different rates. And atoms of strontium-86 can diffuse more readily than atoms of strontium-87 or rubidium, simply because atoms of strontium-86 are smaller.

Read more at: https://phys.org/news/2017-01-paper-spotlights-key-flaw-widely.html#jCp

Robert B. Hayes. Some Mathematical and Geophysical Considerations in Radioisotope Dating Applications, Nuclear Technology (2017). DOI: 10.13182/NT16-98 (Requires purchase or subscription)

 

[mfb]

It's worth noting that the issues raised here do not apply to carbon dating, which does not utilize isotopic ratios."

What? It uses the C14/C12 ratio. But diffusion of carbon over timescales relevant for carbon dating would be very odd, and you just have the smaller isotope difference instead of a chemical difference.