Tritium, argon 37, and argon 39 in the Bruderheim meteorite
Tritium and Ar/sup 39/ were measured in whole rock samples and in separated phases of the Bruderheim meteorite. Ar/sup 37/ was measured in a Bruderheim whole rock sample. There were 260 plus or minus 30 tritium decays/ kg min, 10 plus or minus 1 Ar//sup 39/ decays/kg min, and 23 plus or minus 4 Ar/sup 37/ decays/kg min in the whole rock samples. The tritium/Ar/sup 39/ ratio was 26 plus or minus 5, and the Ar/sup 37/ Ar/sup 39/ ratio was 2.2 plus or minus 0.4; these ratios are identical to those measured in the Hamlet meteorite. In the nonmagnetic (silicate) phase, there were 290 plus or minus 30 tritium decays/kg min and 4.8 plus or minus 0.6 Ar/sup 39/ decays/kg min. The tritium/ Ar/sup 39/ ratio of 60 plus or minus 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 plus or minus 20 tritium decays/Kg min and 36 plus or minus 6 Ar/sup 39/ decays/kg min. The high Ar/sup 39/ content of the metallic phase proves that the Ar/sup 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 Ar/sup 39/ ratio of 2.5 plus or minus 0.5 in the metallic phase shows that much of she tritium is lost from this phase; however, since less than 10% of the meteorite is in the metallic phase, the tritium loss from the metal does not introduce a serious error in the tritium-He/sup 3/ exposure age. An exposure age of 40 plus or minus 10 million years was obtained by combining our tritium value for the whole rock sample with a He/sup 3/ value of 50 x 10/sup -8/ sec/g. An exposure age of 36 plus or minus 4 m.y. w-as obtained by combining our Ar/ sup 39/ value with an Ar/sup 38/ value of 1.4 x 10/sup -8/ sec/g.
- Research Organization:
- Smithsonian Astrophysical Observatory, Cambridge, Mass.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-16-000916
- OSTI ID:
- 4836288
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: 10 Vol. 66; ISSN 0148-0227
- Publisher:
- American Geophysical Union
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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