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

Mass fraction and the isotopic anomalies of xenon and krypton in ordinary chondrites

The abundance and isotopic composition of all noble gases are reported in the Wellman chondrite, and the abundance and isotopic composition of xenon and krypton are reported in the gases released by stepwise heating of the Tell and Scurry chondrites. Major changes in the isotopic composition of xenon result from the presence of radiogenic Xe¹²⁹ and from isotopic mass fractionation. The isotopic composition of trapped krypton in the different temperature fractions of the Tell and Scurry chondrites also shows the effect of isotopic fractionation, and there is a covariance in the isotopic composition of xenon with krypton in the manner expected from mass dependent fractionation. The results from this study indicate that simple isotopic fractionation is responsible for many isotopic anomalies which have previously been attributed to nuclear reactions --Abstract, page ii

¹²⁹I in Iodyrite and Marshite

The concentrations of 129I incorporated in iodyrite (AgI) and marshite (CuI) are determined by measurements of radiogenic 129Xe. In addition to radiogenic 129Xe, some of these iodine-rich minerals contain excesses of 128Xe, 126Xe and 124Xe which are assigned to (n, γβ-), (n, 2nβ-) and spallation reactions on 127I, respectively. The concentrations of radiogenic 129Xe indicate that the initial isotopic composition of iodine in iodyrite was (1.48±0.33)10-14 ≤ 129I127I ≤ (9.8±2.2)10-14 and in marshite it was (0.32±0.24)10-14 ≤ 129I127I

Noble Gases in an Hawaiian Xenolith

The noble gas record in meteorites and lunar samples has been the subject of many investigations aimed at determining their age, the history of their exposure to cosmic rays and to the solar wind, and the early chronology of events in the Solar System (see review in ref. 1). Information on the latter is contained primarily in the isotopes of xenon, where the decay products of extinct 129I and 244Pu provide a record of the synthesis of elements and the early history of planetary solids (see review in ref. 2). The occurrence of radiogenic xenon in CO2 well gas from Harding County, New Mexico is the only clear evidence that extinct radioactivities were present in the early history of the Earth3,4, but the suggestion that this radiogenic xenon had been brought near the Earth\u27s surface in hot magmas was not confirmed by recent analyses of xenon in lava rock from this region 5

Argon, Krypton and Xenon in Iron Meteorites

The isotopic compositions of Ar, Kr and Xe trapped in iron meteorites appear to be a complementary component to the unusual noble gas component found in carbon-rich residues of stone meteorites. The isotopic compositions of noble gases in the earth, the moon, the sun and other classes of meteorites may represent mixtures of these two planetary components

Noble Gases in CO₂ Well Gas, Harding County, New Mexico

The abundance and isotopic composition of noble gases were determined in samples of CO2 well gas from Harding County, New Mexico. Our results confirm the presence of radiogenic 129Xe and fissiogenic 131-136Xe. Relative to noble gases in air, the CO2 gas is selectively depleted in the lighter weight, nonradiogenic noble gases, except at neon. It is suggested that loss of atmospheric neon into space could account for an apparent excess of neon in juvenile gases

A Comparison of the Noble Gases in Three Meteorite Specimens Labeled Springfield

The abundance and isotopic composition of the noble gases were measured in three Springfield specimens identified by the Denver Museum of Natural History with numbers 7029, 379.13 and 6040. The latter specimen contains more cosmogenic noble gas isotopes than the other two specimens and the abundance pattern of trapped noble gases in specimen 6040 is distinct from that in the other two specimens. Specimen 7029 contains about seven times as much radiogenic 40Ar and about four times as much radiogenic 129Xe as does specimen 379.13. These results indicate that the three specimens did not come from a single meteoroid

Mass Fractionation and the Isotopic Anomalies of Xenon and Krypton in Ordinary Chondrites

The abundance and isotopic composition of all noble gases are reported in the Wellman chondrite, and the abundance and isotopic composition of xenon and krypton are reported in the gases released by stepwise heating of the Tell and Scurry chondrites. Major changes in the isotopic composition of Xe result from radiogenic Xe129 and from variations in the isotopic mass fractionation pattern in the different temperature fractions. The isotopic composition of trapped krypton in the different temperature fractions of the Tell and Scurry chondrites displays smaller fractional changes than xenon, but the isotopic composition of these two gases covary in the manner expected from mass dependent fractionation

Fission Xenon in Wausau, Wisconsin Granite

Mass spectrometric analyses of xenon released by stepwise heating of large granite samples from Wausau, Wisconsin reveal (i) a low temperature, xenon-rich fraction which is slightly enriched in the light isotopes in the manner expected from mass fractionation of atmospheric xenon, and (ii) a high temperature fraction which is enriched in the heavy isotopes of xenon in the manner expected from the spontaneous fission of 238U. These analyses reveal no evidence of the anomalous fission yields which would be produced in spontaneous chain reactions

Double beta decay of ¹²⁸Te

The half-life of 128Te relative to the half-life of 130Te has been found to be t12128t12130=(1.59±0.05)×103 by measurement of the ββ-decay products, 128Xe and 130Xe, in a geologically old (2.4×109 yr) telluride ore. These results yield an upper limit on the lepton nonconservation parameter, η≤0.8×10-4. RADIOACTIVITY ββ-decay 128Te; measured T1/2=1.5×1024 yr; deduced η≤0.8×10-4. Detected excess 128Xe in old Te ore