View source for Geochronology/Argon–argon dating

The age of a sample is given by the age equation:
:<math>t=\frac{1}{\lambda} \ln (J \times R+1)</math>
where λ is the radioactive decay constant of <sup>40</sup>K (approximately 5.5 x 10<sup>−10</sup> year<sup>−1</sup>, corresponding to a half-life of approximately 1.25 billion years), J is the J-factor (parameter associated with the irradiation process), and R is the <sup>40</sup>Ar*/<sup>39</sup>Ar ratio. The J factor relates to the fluence of the neutron bombardment during the irradiation process; a denser flow of neutron particles will convert more atoms of <sup>39</sup>K to <sup>39</sup>Ar than a less dense one.

One problem with argon-argon dating has been a slight discrepancy with other methods of dating.<ref name=Renne>{{cite journal |last1=Renne |first1=P. R. |title=Absolute Ages Aren't Exactly |journal=Science |date=1998 |volume=282 |issue=5395 |pages=1840–1841 |doi=10.1126/science.282.5395.1840}}</ref> A correction of 0.65% is needed.<ref name=Kuiper>{{cite journal |last1=Kuiper |first1=K. F. |last2=Deino |first2=A. |last3=Hilgen |first3=F. J. |last4=Krijgsman |first4=W. |last5=Renne |first5=P. R. |last6=Wijbrans |first6=J. R. |title=Synchronizing Rock Clocks of Earth History |journal=Science |date=2008 |volume=320 |issue=5875 |pages=500–504 |doi=10.1126/science.1154339}}</ref>

==See also==
{{div col|colwidth=20em}}
* [[Geochronology/Potassium–argon dating|Potassium–argon dating]]
* [[Geochronology/Radiocarbon dating|Radiocarbon dating]]
* [[Geochronology/Uranium–lead dating|Uranium–lead dating]]
* [[Geochronology/Uranium-thorium dating|Uranium-thorium dating]]
{{Div col end}}

==References==
{{reflist|2}}

==External links==
* [http://geochronology.geoscience.wisc.edu/ WiscAr Geochronology Laboratory, University of Wisconsin-Madison]
* UC Berkeley press release: "[http://www.berkeley.edu/news/media/releases/97legacy/pompeii.html Precise dating of the destruction of Pompeii proves argon-argon method can reliably date rocks as young as 2,000 years]"
* [http://www.gla.ac.uk/departments/suerc/nercfacilities/argonisotopefacility/ Argon Isotope Facility] of the Scottish Universities Environmental Research Council
* [http://www8.open.ac.uk/science/argon-noble-gas-research Open University Ar/Ar and Noble Gas Laboratory]
* [http://argon.anu.edu.au Argon Laboratory / Australian National University]

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