Editing Radiometric dating (section)

===Fission track dating method===
{{Main|fission track dating}}
[[File:Apatite Canada.jpg|thumb|[[Apatite]] crystals are widely used in fission track dating.]]
This involves inspection of a polished slice of a material to determine the density of "track" markings left in it by the [[spontaneous fission]] of uranium-238 impurities. The uranium content of the sample has to be known, but that can be determined by placing a plastic film over the polished slice of the material, and bombarding it with [[thermal neutrons|slow neutrons]]. This causes induced fission of <sup>235</sup>U, as opposed to the spontaneous fission of <sup>238</sup>U. The fission tracks produced by this process are recorded in the plastic film. The uranium content of the material can then be calculated from the number of tracks and the [[neutron flux]].<ref>{{Cite book |last1=Fleischer |first1=Robert L. |url=http://www.jstor.org/stable/jj.13167934 |title=Nuclear Tracks in Solids: Principles and Applications |last2=Price |first2=P. Buford |last3=Walker |first3=Robert M. |date=2024-03-29 |publisher=University of California Press |isbn=978-0-520-32023-9 |edition=1 |doi=10.2307/jj.13167934}}</ref>

This scheme has application over a wide range of geologic dates. For dates up to a few million years [[mica]]s, [[tektite]]s (glass fragments from volcanic eruptions), and meteorites are best used. Older materials can be dated using [[zircon]], [[apatite]], [[titanite]], [[epidote]] and [[garnet]] which have a variable amount of uranium content.<ref>{{cite journal|doi=10.1016/S0899-5362(01)80066-X |title=A titanite fission track profile across the southeastern Archæan Kaapvaal Craton and the Mesoproterozoic Natal Metamorphic Province, South Africa: evidence for differential cryptic Meso- to Neoproterozoic tectonism |date=August 2001 |first=J. |last=Jacobs |author2=R. J. Thomas |journal=Journal of African Earth Sciences |volume=33 |issue=2 |pages=323–333|bibcode = 2001JAfES..33..323J }}</ref> Because the fission tracks are healed by temperatures over about 200&nbsp;°C the technique has limitations as well as benefits. The technique has potential applications for detailing the thermal history of a deposit.<ref name="Naeser-McCulloh1989">{{cite book |last1=Naeser |first1=Nancy |last2=Naeser |first2=Charles |last3=McCulloh |first3=Thane |editor1-last=Naeser |editor1-first=Nancy |editor2-last=McCulloh |editor2-first=Thane |title=Thermal History of Sedimentary Basins |date=1989 |publisher=Springer New York|isbn=978-1-4612-8124-5|pages=157–180|chapter=The Application of Fission-Track Dating to the Depositional and Thermal History of Rocks in Sedimentary Basins|doi=10.1007/978-1-4612-3492-0_10 |chapter-url=https://link.springer.com/chapter/10.1007/978-1-4612-3492-0_10}}</ref>