| Abstract: | Results of two routine 40Ar/39Ar stepwise heating experiments on a biotite and a basanite are interpreted in terms of Fick‘s and Arrhenius‘ laws. Both patterns represent a saddle-shaped 39Ar release. Argon isotope spectra are suggested to be controlled by the activation energy of diffusion E and the frequency factor D(o). The activation energy of 39Ar is lower than the one of 40Ar. This results in a preferable release of 40Ar relatively to 39Ar at high-temperature steps and an increasing high-temperature wing in the saddle-shaped age spectrum. At low temperatures, considerable losses and irregularities in release of mainly 39Ar are observed, which cause the decreasing low-temperature wing in the ‘saddle‘. The suggestion of argon losses (mainly of 39Ar) from a loose, ‘unstable‘ zone of the mineral structures becomes justified. The n-irradiation of the samples and the shift of E of 39Ar towards lower values seems to explain the saddle-shaped age-spectra often encountered in 40Ar/39Ar-geochronometry. |
| Genre: | Article |
| ProdID: | 70019355 |
| Citation Author: | Brandt, S. B.; Rasskazov, S. V.; Brandt, I. S.; Ivanov, A. V.; Kunk, M. J. |
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| Citation End Page: | 409 |
| Citation Issue: | 4 |
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| Citation Language: | English |
| Citation Larger Work Title: | Isotopes in Environmental and Health Studies |
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| Citation Number Of Pages: | 11 |
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| Citation Search Results Text: | The inverse problem of argon diffusion from minerals: Determination of kinetic parameters from stepwise-heating experiments; 1997; Article; Journal; Isotopes in Environmental and Health Studies; Brandt, S. B.; Rasskazov, S. V.; Brandt, I. S.; Ivanov, A. V.; Kunk, M. J. |
| Citation Start Page: | 399 |
| Citation Volume: | 33 |
| Citation Year: | 1997 |
| Type: | citation/reference |
| Text: | The inverse problem of argon diffusion from minerals: Determination of kinetic parameters from stepwise-heating experiments; 1997; Article; Journal; Isotopes in Environmental and Health Studies; Brandt, S. B.; Rasskazov, S. V.; Brandt, I. S.; Ivanov, A. V.; Kunk, M. J. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 1997 00:00 -0600 |
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