Title: Tritium, argon 37, and argon 39 in the Bruderheim meteorite
Abstract: Tritium and argon 39 were measured in whole rock samples and in separated phases of the Bruderheim meteorite. Argon 37 was measured in a Bruderheim whole rock sample. There were 260± 0 tritium decays/kg min, 10±1 argon 39 decays/kg min, and 23±4 argon 37 decays/kg min in the whole rock samples. The tritium/argon 39 ratio was 26±5, and the argon 37/argon 39 ratio was 2.2±0.4; these ratios are identical to those measured in the Hamlet meteorite. In the nonmagnetic (silicate) phase, there were 290±30 tritium decays/kg min and 4.8±0.6 argon 39 decays/kg min. The tritium/argon 39 ratio of 60±10 for this phase agrees with that expected from the chemical composition and the high-energy production cross sections. In the magnetic (metallic) phase, there were 90±20 tritium decays/kg min and 36±6 argon 39 decays/kg min. The high argon 39 content of the metallic phase proves that the argon 39 is produced chiefly from the element iron and that chondritic meteorites are in general less shielded from cosmic rays than metallic meteorites. The tritium to argon 39 ratio of 2.5±0.5 in the metallic phase shows that much of the tritium is lost from this phase; however, since less than 10 per cent of the meteorite is in the metallic phase, the tritium loss from the metal does not introduce a serious error in the tritium-helium 3 exposure age. An exposure age of 40±10 million years was obtained by combining our tritium value for the whole rock sample with a helium 3 value of 50×10−8 scc/g. An exposure age of 36±4 m.y. was obtained by combining our argon 39 value with an argon 38 value of 1.4×10−8 scc/g.
Publication Year: 1961
Publication Date: 1961-10-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 19
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