ARGON DETERMINATION IN POTASSIUM MINERALS. XII. NOBLE GAS DIFFUSION MEASUREMENTS IN STONE AND IRON METEORITES (in German)
The diffusion of noble gases (He, Ne, Ar) was measured on some stone meteorites of very different K-Ar ages and on one iron meteorite. Both artificially produced radioactive Ar/sup 37/ and the natural radiogenic and cosmogenic stable Ar isotopes were used to investigate the argon diffusion; radiogenic He/sup 4/ and the cosmogenic He and Ne isotopes were also measured. With isothermal diffusion a decrease of D/a/sup 2/ (D = diffusion constant, a = grain radius) was observed and interpreted as successive degassing of the meteorite crystals of different sizes. The influence of this effect on the temperature dependence of D/a/sup 2/ can be eliminated. On the stone meteorites activation energies of about 45 kcal/ mole were obtained for the diffusion of pile produced Ar/sup 37/, radioactive and stable spallation argon, and radiogenic Ar/sup 40/; for helium and neon the values obtained were about 35 to 40 kcal/mole. On the iron meteorite the activation energies for cosmogenic He, Ne, and Ar were about 60 kcal/mole. At room temperature D/a/sup 2/ is so small (<10/sup -23/ sec/ sup -1/ for argon, <10/sup -17/ sec/sup -1/ for helium and neon) that no diffusion losses are possible after the fall of the meteorite. The temperatures occurring on meteorites in space outside the orbit of the earth do not suffice to explnin differences in the radiogenic ages by diffusion losses. Additional heating-up, possibly caused by collisions, has to be taken into consideration. (auth)
- Research Organization:
- Max-Planck-Institut fur Kernphysik, Heidelberg
- NSA Number:
- NSA-18-005486
- OSTI ID:
- 4121070
- Journal Information:
- Geochimica et Cosmochimica Acta (England), Journal Name: Geochimica et Cosmochimica Acta (England) Vol. Vol: 27; ISSN GCACA
- Country of Publication:
- Country unknown/Code not available
- Language:
- German
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Related Subjects
AGE ESTIMATION
ARGON
ARGON 37
ARGON 40
COSMIC RADIATION
CRYSTALS
DECAY
DEGASSING
DIFFUSION
EARTH
ENERGY
FISSION
GEOLOGY AND MINERALOGY
HELIUM
HELIUM 4
IRON
MEASURED VALUES
METEORITES
MINERALS
NEON
ORBITS
POTASSIUM
QUANTITATIVE ANALYSIS
RADIOACTIVITY
RADIOISOTOPES
RARE GASES
REACTORS
SILICATES
TEMPERATURE