Exploring IRSL 50 fading variability in bedrock feldspars and implications for OSL thermochronometryReportar como inadecuado

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1 ETH Zurich 2 Institute of Geology 3 Research School of Earth Sciences 4 ETH - Geological Institute 5 GR - Géosciences Rennes

Abstract : Optically Stimulated Luminescence OSL is a well-established Quaternary dating method, which has recently been adapted to application in low-temperature thermochronometry. The Infra-Red Stimulated Luminescence IRSL of feldspar, which so far is the most promising target signal in thermochronometry, is unfortunately prone to anomalous fading. The fading of feldspar IRSL is at times not only challenging to measure, but also laborious to incorporate within luminescence growth models. Quantification of IRSL fading is therefore a crucial step in OSL thermochronometry, raising questions regarding i reproducibility and reliability of laboratory measurements of fading, as well as ii the applicability of existing fading models to quantitatively predict the level of IRSL field saturation in nature. Here we investigate the natural luminescence signal and anomalous fading of IRSL measured at 50 °C IRSL50 in 32 bedrock samples collected from a variety of lithologies and exhumation settings Alaska and Norway. We report a large span of IRSL50 fading rates between samples g2days ranging from ∼0.5 to ∼45%-decade, which further demonstrates i a good reproducibility between two common fading measurement protocols, and ii the ability of tunnelling models to predict the level of feldspar IRSL50 field saturation in nature. We observe higher IRSL50 fading in feldspar with increasing Ca content, although other factors cannot be dismissed at present. Finally, our dataset confirms that the applicability of feldspar IRSL50 in OSL thermochronometry is limited to rapidly-exhuming settings or warm subsurface environments.

Keywords : OSL thermochronometry Feldspar IRSL Anomalous fading Luminescence

Autor: Pierre Valla - Sally Lowick - Frédéric Herman - Jean-Daniel Champagnac - Philippe Steer - Benny Guralnik -

Fuente: https://hal.archives-ouvertes.fr/


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