ARGON-39 AND TRITIUM IN METEORITES
The radioactive isotopes Ar/sup 39/ and tritium are measured in a number of Fe and stone meteorites. The stable isotope He/sup 3/ is also measured and the Ar/sup 38/ content is estimated from the He/sup 3/ content. The cosmic ray exposure ages obtained from the Ar/sup 39/ and Ar/sup 38/ are: 4.2 x 10/sup 8/ years for the Siknote-Alin Fe meteorite, 4.5 x 10/sup 8/ years for the Treysa Fe meteorite, 0.3 x 10/sup 8/ years for the Pitts Fe meteorite, 5 x 10/sup 8/ years for the Norton County achondrite, and 0.8 x 10/sup 8/ years for the St. Michel chondrite. The ratio of tritium to Ar/sup 39/ radioactivities at the time of fall is 140 combination rat 20 for the Norton County meteonite, 56 combination rat 15 for the St. Michel meteorite, 6 combination rat 1 for the Treysa meteorite, and less than 1/2 for the Siknote-Alin meteorite. For the stone meteorites this ratio is consistent with the production probabilities and the hypothesis of the constancy of cosmic rays. For the Fe meteorites this is lower than expected from the production probabilities. Either the cosmic-ray bombardment is not constant or tritium loss from diffusion occurs for the Fe meteorites. Also reported is the lack of Ar/sup 39/ and tritium in a number of undated Fe meteorite falls, which indicates that they fell more than 1,500 years ago. Only 1 undated Fe meteorite fall, Washington County, gave a small trace of Ar/sup 39/, indicating that it fell about 1,000 years ago. Possible interpretations of the cosmic ray exposure ages are discussed. (GeoScience Abstr. 2, No. 5, 1960)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-14-019670
- OSTI ID:
- 4187665
- Journal Information:
- Geochim. et Cosmochim. Acta, Journal Name: Geochim. et Cosmochim. Acta Vol. Vol: 18
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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