Investigating signal evolution: A comparison of red and UV/blue TL, and UV OSL emissions from the same quartz sample

Samples from plutonic geological settings emit strong and stable UV, blue and red luminescence. These samples provide a unique opportunity to investigate the evolution of luminescence emissions by comparing their origin, intensity, trapping and recombination characteristics. In addition, the De derived from certain techniques can be used to investigate De consistency. Thus, UV and red signals emitted by the same sample of grantic quartz have been compared according to the strength and shape of the emissions, response to annealing and dose, growth characteristics and the resulting De derived from single-aliquot regeneration (SAR – UV emissions) and the dual-aliquot protocol for red TL (DAP – red emissions). This comparison of UV and red De values can be used as an alternative measure of accuracy for depositional situations where independent age control is not available. Furthermore, this comparison has been extended to a single-grain level to determine if UV and red signals are emitted by the same quartz grain. The resulting comparisons demonstrate that both signals are strong, reproducible, are suitable for dating, and a comparison of De is a valid internal check of consistency. The single-grain analysis demonstrates that the grains contain UV and red recombination centres rather than the typical characteristics of just beta or alpha quartz. Thus it has been suggested that the emissions relate to post-origin modifications of the signal rather than its thermal origin. This type of comparative analysis provides clues as to the source and evolution of the signals, provides a greater understanding of the complexities of the luminescence signal and a possible solution for accuracy testing in challenging depositional contexts.

► Granitic quartz emits strong red and blue emissions, both are reliable and reproducible.
► Emissions can be compared to check De consistency.
► Red and blue emissions from the same quartz grain.
► Emissions relate to post-origin modifications rather than temperature of mineralisation.