Comment on gchron-2023-14

Le résumé fourni par la source

Abstract. During ionising irradiation, potassium (K)-rich feldspar grains emit infrared (IR) light, which is used for infrared-radiofluorescence (IR-RF) dating. The late-saturating IR-RF emission centred at ~880 nm represents a promising tool to date Quaternary sediments. However, in the present work, we report the presence of individual grains of K-feldspar displaying an aberrant IR-RF signal shape, whose combined intensity contaminates the sum signal of an aliquot composed of dozens of grains. Our experiments were carried out at the National Synchrotron Light Source (NSLS-II) on coarse (> 90 µm) K-feldspar grains of five samples of different ages, nature and origin in order to characterise the composition of grains yielding the desired or contaminated IR-RF emission. Using micro-X-ray-fluorescence (µXRF), we successfully acquired element distribution maps of fifteen elements (<1 µm resolution) of the surface of grains previously used for luminescence dating. In keeping with current theories of IR-RF signal production, we observed a correlation between the relative proportions of Pb and Fe and the shape of the luminescence signal: most grains with the desired IR-RF signal shape had high Pb and low Fe contents. Interestingly, these grains were also defined by high Ba and low Ca contents. Additionally, this study represents a proof-of-concept for mapping the oxidation states of Fe-ions using micro-X-ray absorption near-edge structure spectroscopy (µXANES) on individual grains. The high spatial resolution enabled by synchrotron spectroscopy makes it a powerful tool for future experiments to elucidate long-standing issues concerning the nature and type of defect(s) associated with the main dosimetric trap in feldspar.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.