The noble gas record of terrestrial and meteoritic samples

Analyses of tellurium and xenon in a telluride ore from Kalgoorlie, Australia resulted in the following conclusions: The ratio of the double beta-decay half-life of 128Te relative to that of 130Te is 1.6 x 103 The double beta-decay half-life of 130Te is 1.0 x 1021 years. The measured half-lives are consistent with values predicted for a second order process of ordinary beta-decay that occurs with the emission of two neutrinos. A study of noble gases in Thailand tektites provided the following information on the history of these objects: The isotopic compositions of nonradiogenic Ne, Ar, Kr, and Xe are atmospheric. The abundance pattern of noble gases relative to cosmic abundances shows a selective depletion of the light-weight gases, except at neon. The amounts of excess neon in the tektites and the diffusion coefficient of neon in tektite glass yield a neon diffusion age in agreement with ages estimated by K-Ar and fission track methods. Analyses of the abundance and isotopic composition of noble gases in lava rock from the Mt. Capulin crater cone, New Mexico resulted in the following conclusions: The abundance pattern of noble gases in the lava rock cannot be accounted for by equilibration with atmospheric noble gases. There is a large excess of \u27\u27parentless\u27\u27 40Ar trapped from the hot magma. The isotopic composition of xenon is consistent with a mixture of 90% atmospheric and 10% solar xenon. The absence of excess 129Xe does not support an earlier suggestion that radiogenic 129Xe, found in CO2 gas wells from this region of New Mexico, had been transported to the Earth\u27s surface in hot magmas. The abundance and isotopic composition of noble gases were determined in CO2 well gas from Harding County, New Mexico. The results can be summarized as follows: The presence of relatively large isotopic anomalies of xenon because of radiogenic 129Xe and fissio-genic 131-136Xe is confirmed. The abundance pattern of Ar, Kr, and Xe can be understood in terms of fractionation effects in the release of noble gases to the atmosphere or the adsorption of gases from the atmosphere. An apparent excess of neon results from selective leakage of light weight noble gases into the CO2 gas, or perhaps is an indication that atmospheric neon has escaped from the exosphere. A study of noble gases in an Hawaiian xenolith, a deep-seated magnesium silicate with inclusions of liquid CO2, provided the following information on the interior of the Earth: An excess of 129Xe from the decay of primordial 129I indicates that the formation of the Earth did not appreciably postdate the formation of meteorites. The relative abundances of nonradiogenic Ne, Ar, and Kr are those expected in a melt which equilibrated with a gas reservoir containing atmospheric abundances of these noble gases. The nonradiogenic Xe is ten times higher than expected from equilibration of atmospheric noble gases with a melt, confirming an earlier suggestion that the atmosphere is selectively depleted in Xe relative to the total terrestrial inventory of noble gases. A study of noble gases in a 3.3 x 109 year old anorthosite from Greenland revealed isotopic anomalies of krypton and xenon which could be accounted for by a combination of two effects, a selective enrichment of the heavy isotopes by mass fractionation, and an enrichment of the proton- rich isotopes of Kr and Xe from spallation reactions on Sr and Ba, respectively. The Greenland anorthosite appears to have received an average of about 1.7 kg cm-2 more shielding from cosmic rays than have rocks on the lunar surface, and the bulk of this difference in shielding can be accounted for by the Earth\u27s atmosphere. Analyses of noble gases in three Springfield specimens, identified by the Denver Museum of Natural History with numbers 7029, 379.13 and 6040, revealed different noble gas records for each specimen. These results suggest that the three specimens were separate entities in space and thus represent different meteorites. A review of the isotopic composition of xenon released from carbonaceous chondrites at extraction temperatures of ≈ 600⁰-1000⁰C resulted in the following conclusions: There is a positive correlation in the release of excess proton-rich xenon isotopes and excess neutron-rich xenon isotopes which cannot be explained by the occurrence of nuclear or fractionation processes within the meteorites. Possible sources suggested for this anomalous xenon cornponent are (i) xenon from a supernova explosion, (ii) a mixture of severely mass fractionated xenon with xenon isotopes produced by neutron-induced fission of transbisrnuth elements during the early deuterium burning stage of the sun or (iii) parts of a differentiated planetary body that were enriched in uranium acted as a natural assemblage producing a thermal neutron flux ≈ 3 x 1013 n cm-2 sec-1. The isotopic composition of trapped meteoritic xenon, calculated by subtraction of this anomalous component, is 124Xe: 126Xe: 128Xe: 130Xe: 131Xe: 132Xe: 134Xe: 136Xe = 0.0276: 0.0248: 0.501:1.00: 5.04: 6.19: 2.31: 1.90. --Abstract, pages iii-vii