<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><p>Plagioclase feldspar is the major luminescent mineral in meteorites. Thermoluminescence (TL) characteristics, peak temperature (Tm), full width at half maximum (FWHM), ratio of high (HT) to low temperature (LT) peak, and TL sensitivity (TL/dose/mass) to an extent reflect degree of crystallinity of the mineral. The present study explores and establishes a correlation between quantum mechanical anomalous (athermal) fading and structural state by examining TL of individual chondrules. Chondrules were separated using freeze-thaw technique from a single fragment of Dhajala meteorite. The results show large variation in Tm (155−230°C), FWHM (80−210°C) and HT/LT (0.07–0.47) and seem to be positively correlated. TL sensitivity (ranging from 14 to 554 counts/s/Gy/mg) decreases with increasing Tm and FWHM. Large variations in TL parameters (Tm, FWHM, HT/LT, and Sensitivty) suggest that individual chondrules had different degree of crystallization. Thermal annealing experiments suggest that comparatively ordered form of feldspar can be converted to a disordered form by annealing the sample at high temperatures (1000°C) for long time (10 hr) in vacuum (1 mbar pressure) condition and rapidly cooling it. Measured anomalous fading suggest that fading rate increases as the crystal form changes from an ordered state to a disordered state. However, the fading rate becomes nearly negligible for the most disordered feldspars.</p></abstract>

Plagioclase feldspar is the major luminescent mineral in meteorites. Thermoluminescence (TL) characteristics, peak temperature (Tm), full width at half maximum (FWHM), ratio of high (HT) to low temperature (LT) peak, and TL sensitivity (TL/dose/mass) to an extent reflect degree of crystallinity of the mineral. The present study explores and establishes a correlation between quantum mechanical anomalous (athermal) fading and structural state by examining TL of individual chondrules. Chondrules were separated using freeze-thaw technique from a single fragment of Dhajala meteorite. The results show large variation in Tm (155−230°C), FWHM (80−210°C) and HT/LT (0.07–0.47) and seem to be positively correlated. TL sensitivity (ranging from 14 to 554 counts/s/Gy/mg) decreases with increasing Tm and FWHM. Large variations in TL parameters (Tm, FWHM, HT/LT, and Sensitivty) suggest that individual chondrules had different degree of crystallization. Thermal annealing experiments suggest that comparatively ordered form of feldspar can be converted to a disordered form by annealing the sample at high temperatures (1000°C) for long time (10 hr) in vacuum (1 mbar pressure) condition and rapidly cooling it. Measured anomalous fading suggest that fading rate increases as the crystal form changes from an ordered state to a disordered state. However, the fading rate becomes nearly negligible for the most disordered feldspars.

Anomalous fading and crystalline structure: Studies on individual chondrules from the same parent body

Geosciences Division, Physical Research Laboratory, Ahmedabad, 380009, India

Geochronometria

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Plagioclase feldspar is the major luminescent mineral in meteorites. Thermoluminescence (TL) characteristics, peak temperature (Tm), full width at half maximum...

Anomalous fading and crystalline structure: Studies on individual chondrules from the same parent body

Published Online: Sep 27, 2013

Page range: 250 - 257

DOI: https://doi.org/10.2478/s13386-013-0114-9

Keywords
TL of chondrules, anomalous fading, degree of crystallinity, thermal metamorphism, thermal annealing

© 2013 Silesian University of Technology, Gliwice, Poland

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Anomalous fading and crystalline structure: Studies on individual chondrules from the same parent body

Published Online: Sep 27, 2013

Page range: 250 - 257

DOI: https://doi.org/10.2478/s13386-013-0114-9

KeywordsTL of chondrules, anomalous fading, degree of crystallinity, thermal metamorphism, thermal annealing

© 2013 Silesian University of Technology, Gliwice, Poland

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
TL of chondrules, anomalous fading, degree of crystallinity, thermal metamorphism, thermal annealing