Xenon is a heavy rare gas with nine stable isotopes, 124Xe,
126Xe, 128Xe, 129Xe, 130Xe,
131Xe, 132Xe, 134Xe and 136Xe,
five of which are radiogenic. 129Xe is produced by beta decay
of 129I (half-life = 16 Myr); 131Xe, 132Xe,
134Xe and 136Xe are fission products of both 238U
and the extinct nuclide 244Pu. Because Xe is a tracer for two
extinct nuclides, Xe isotopic ratios in meteorites are a powerful tool
for studying the condensation of the solar system (Reynolds, 1963). The
129I-129Xe decay scheme has been used as a geochronometer
based on the time-dependent decrease of the ratio of the radioactive 129I
to stable 127I in the solar nebula. The I-Xe method of dating
gives the time elapsed between nucleosynthesis and the condensation of
a solid object from the solar nebula. Xenon isotopes are also a powerful
tool for understanding terrestrial differentiation. Excess 129Xe
found in CO2 well gases from New Mexico (Butler et al., 1963)
was believed to have been derived by decay of mantle-derived gases soon
after the formation of the Earth. Additional evidence for xenon isotopic
evolution of mantle reservoirs has been obtained from MORBs (Staudacher
and Allegre, 1982) and diamonds (Ozima and Zashu, 1991).
Source of text: This review was assembled by Eric Caldwell,
primarily from Dicken (1995) and Faure (1986).
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