Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Dariusz Malczewski, Agnieszka Grabias, Maria Dziurowicz

Activation energy of annealed, partially metamict davidite by 57Fe Mössbauer spectroscopy

Journal of Geosciences, volume 65 (2020), issue 1, 37 - 44

DOI: http://dx.doi.org/10.3190/jgeosci.298



This study used 57Fe Mössbauer spectroscopy to determine the activation energy for thermal recrystallization of partially metamict davidite [multiple oxide, (La,Ce,Ca,Th)(Y,U)(Ti,Fe3+)20O38]. Radioactive elements in metamict minerals damage crystal structure primarily due to recoil nuclei from α-decay of 238U, 232Th, 235U, and their daughter products. Metamict minerals are widely used in geochronology and can serve as natural analogues for the study of radiation effects in high-level nuclear waste. Analysis was performed on fragments of a davidite sample collected from the Bektau-Ata alkaline granitoid massif (Kazakhstan). Electron-microprobe analysis showed that the sample may be classified as a davidite-(La) due to its La concentration of 3.14 wt. %, relatively low U of 0.88 wt. %, and Th of 0.25 wt. %. The calculated total absorbed α-dose was 8.1 × 1015 α-decay mg-1. The concentration of Fe was 15 wt. % (2.1 % Fe2+ and 12.9 % Fe3+). 57Fe Mössbauer spectroscopy was carried out on fragments of the davidite sample after one-hour annealing under an argon atmosphere from 673 to 1373 K. A Fe2+ component was observed up to 1173 K. Variation in the ratio of amplitudes for the main absorption peaks in the Mössbauer spectra vs. annealing temperature appeared to be a sensitive indicator of thermally-induced recrystallization. The activation energy, EA = 0.45 eV, for recrystallization was determined based on the exponential dependence of the amplitudes’ ratio upon temperature and using an Arrhenius plot.

Journal of Geosciences, Published by © Czech Geological Society, with support from the Czech Geological Survey.
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SNIP (Scopus, 2019): 0.914

IF (ISI, 2019): 1.279

5 YEAR IF (ISI, 2019): 1.45

Policy: Open Access

ISSN: 1802-6222

E-ISSN: 1803-1943