The Fission-Track Method of Dating

Uranium is composed of three naturally occurring radioactive isotopes having the mass numbers 238, 235, and 234 all of which decay by emitting alpha particles from their nuclei. All of the naturally occurring isotopes of uranium can also decay by spontaneous fission, but virtually all spontaneous fission events in a uranium-bearing mineral are due to which is by far the most abundant isotope of uranium at 99.2745% by number. 

The temperature is an important variable because uranium-bearing minerals anneal fission tracks at elevated temperatures and retain them quantitatively only after the temperature has decreased below the level at which all tracks are preserved. Therefore, the fission track date of a mineral or glass is the time that has elapsed since the specimen cooled through the track-retention temperature for the last time. In other words, fission track dates are equal to the age of a specimen of mineral or glass only in cases when the specimen cooled to the track-retention temperature immediately after it was formed. The fission-track method appears to be straightforward in principle but is, in fact, quite labor intensive and demanding (Faure and Mensing 2005). 

Adams CJ (1986) Geochronological studies of the Swanson Formation of Marie Byrd Land, West Antarctica, and correlation with northern Victoria Land, East Antarctica, and South Island, New Zealand. New Zealand J Geol Geophys 29 354—358 

Adams CJ, Gabites JE, Wodzicki A, Laird MG, Bradshaw JD (1982) Potassium-argon geochronology of the Precambrian-Cambrian Wilson and Robertson Bay Groups and Bowers Supergroup, northern Victoria Land, Antarctica. In Craddock C (ed) Antarctic geoscience. University of Wisconsin Press, Madison, WI, pp 543-548 

Adams CJ, Seward D, Weaver SD (1995) Geochronology of Cretaceous granites and metasedimentary basement on Edward VII Peninsula (Ross maigin), Marie Byrd Land, West Antarctica. Antarctic Sci 7 265-277 

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