Xenon isotope anomalies

A related problem is the conspicuous xenon isotope anomalies in various meteorites. The heavy fraction [79-87] enriched in Xe was originally [79, 80] ascribed to y-ray or neutron-induced fission of Pu (half-life 83 million years, only 0.08 percent probability of spontaneous fission otherwise, He emitter) and a controversy maintained about plutonium(IV) occupying sites in (quite scarce mineral fractions) and forming xenon or the noble gas directly incorporated from the protoplanetary cloud. Some of the most remarkable components of the... 

Clayton DD (1989) Origin of heavy xenon in meteoritic diamonds. Astrophys J 340 613-619 Clayton DD, Dwek E, Woosley SE (1977a) Isotopic anomalies and proton irradiation in the early solar system. Astrophys J 214 300-315... 

Swindle TD, Podosek FA (1988) Iodine-Xenon dating. In Meteorites and the Early Solar System. Kerridge JF and Matthews MS (eds) University of Arizona Press, Tucson, p 1114-1146 Tang M, Lewis RS, Anders E (1988) Isotopic anomalies of Ne, Xe, and C in meteorites. I. Separation of carriers by density and chemical resistance. Geochim Cosmochim Acta 52 1221-1234 Tera F, Eugster O, Burnett DS, Wasserburg GJ (1970) Comparative study of Li, Na, K, Rb, Cs, Ca, Sr and Ba abundances in achondrites and in Apollo 11 lunar samples. Geochim Cosmochim Acta Suppl 1 1637-1657... 

Kuroda, P. K., Sherill, R. D. (1977) Xenon and krypton isotope anomalies in the Besner Mine, Ontario, thucolite. Geochem. J., 11, 9-19. 

Krummenacher D., Merrihue C. M., Pepin R. O., and Reynolds J. H. (1962) Meteoritic krypton and barium versus the general isotopic anomalies in meteoritic xenon. Geochim. Cosmochim. Acta 26, 231 —249. 

Besides neon, xenon has turned out to be the element most diagnostic in its isotopic composition. An important role has been played by Xenon-HL, which was the first of the nucleosynthetic isotope anomalies to be discovered (Reynolds and Turner 1964). The HL component has received its name for the simultaneous overabundance of the heavy xenon isotopes (= Xe-H) and the light xenon isotopes (= Xe-L). Because the H part originally was more reliably determined, Xenon-HL was first believed to be associated with fission, possibly of a superheavy element (e.g., Anders et al. 1975), but in the end the search for its host phase led to the discovery of the existence of grains of presolar origin in primitive meteorites (Lewis et al. 1987). 

There are no reports of krypton isotope anomalies in arc-related terrains— the small number of krypton isotopic analyses (e.g., Patterson et al. 1994) reveal only atmospheric-like ratios. For the most part, the situation is similar for xenon—atmospheric-like ratios dominate the few analyses reported. An exception is found in the work of Nakai et al. (1997) which reports two samples from the vicinity of Mt. Etna with enrichments in both Xe and Xe relative to air. The anomalies are correlated such that they appear to reflect mixing between air and an enriched source with a xenon isotope signature similar to MORE. 

The first isotopic anomaly was discovered in 1960 in the noble gas Xe. The anomalies were of a dual nature - the so-called special anomaly in which was shown to be caused by the presence of the extinct radionuclide and the general anomalies which occurred in most of the other isotopes (Figure 2). The pattern of enrichment in the heavy isotopes 136,134,132,131,which is particularly pronounced in carbonaceous chondrites, became known as carbonaceous chondrite fission xenon, because it was hypothesized that these anomalies were produced by the spontaneous fission of a super-heavy element. Isotopic anomalies in Xe, and also Ne, made little impression on the cosmochemical community because the systematics of the noble gases were poorly understood and other explanations for the anomalies were forthcoming. It was not until isotopic variations were found in the abundant element oxygen in 1973 that the reality of isotopically anomalous material in meteorites was fully accepted. 

Takaoka, N. (1972) An interpretation of general anomalies of xenon and the isotopic composition of primitive xenon. Mass Spectrometry, 20, 287-302. 

CFF-Xe. Isotopic Xe anomalies, characterized by enriched Xe, Xe and Xe relative to fission Xe, were identified within minerals from the natural nuclear reactor no.2 in the Oklo uranium mine, Gabon (Shukolyukov et al. 1976). Although early theories focused on a nuclear process to account for this observation, it later became apparent that this was a chemical fractionation effect (Meshik and Shukolyokov 1986 Meshik 1988). CFF-Xe, or Chemically Fractionated Fission-Xenon is created when fast... 

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