Periodic Reporting for period 1 - RECREATE (Reducing empiricism in luminescence models to measure rates of Earth surface processes)
Reporting period: 2023-10-01 to 2025-09-30
The interdisciplinary project “Reducing Empiricism in luminesCence models to measuRE rATes of Earth surface processes” (RECREATE) combined solid state physics and geosciences to enhance our understanding of the physical processes governing luminescence thermochronometry. Luminescence thermochronometry is used to constrain rock cooling and exhumation rates. Feldspar luminescence signals function as low-temperature thermochronometers. With a closure temperature <100 °C, they can constrain rock cooling histories over timescales from 0.1-0.4 Myr, dependent on cooling, dose and fading rate.
Luminescence thermochronometry relies upon numerical models that describe the build-up of luminescence due to ionising radiation and its decay due to thermal and athermal depletion. Several numerical models with different underlying physics exist, and it is challenging to evaluate their performance against geological data. Although the model parameters describe physical constants related to defects or the crystal lattice, we observe that the parameter values are strongly dependent on the model chosen to estimate them, potentially leading to an erroneous understanding of past landscape evolution. Whilst a combination of different luminescence signals, models and model parameters may adequately describe the laboratory kinetic data, each combination can yield divergent results over geological time scales. Consequently, the purpose of this project was to eliminate this subjectivity, and thus to reduce the uncertainty and empiricism in the feldspar luminescence thermochronometry to derive rates of Earth surface processes.
Luminescence thermochronometry relies upon numerical models that describe the build-up of luminescence due to ionising radiation and its decay due to thermal and athermal depletion. Several numerical models with different underlying physics exist, and it is challenging to evaluate their performance against geological data. Although the model parameters describe physical constants related to defects or the crystal lattice, we observe that the parameter values are strongly dependent on the model chosen to estimate them, potentially leading to an erroneous understanding of past landscape evolution. Whilst a combination of different luminescence signals, models and model parameters may adequately describe the laboratory kinetic data, each combination can yield divergent results over geological time scales. Consequently, the purpose of this project was to eliminate this subjectivity, and thus to reduce the uncertainty and empiricism in the feldspar luminescence thermochronometry to derive rates of Earth surface processes.
As part of this project, we carried out both experimental and computational research to deepen our understanding of the processes and factors influencing luminescence thermochronometry. A key achievement was the development of an entirely new laboratory experiment that simulates rock exhumation and cooling, enabling the creation of four independent calibration datasets for use in luminescence thermochronometry.
We also made considerable progress in improving the accessibility and transparency of existing luminescence thermochronometry modelling tools. This was achieved by translating code originally written in Matlab into the open-source language R, aligning with the FAIR data principles.
Additionally, we investigated the luminescence characteristics of various feldspar samples, focusing on how these properties may impact measurements and outcomes in thermochronometry. Specifically, we conducted experiments to determine whether fading results from ground state or excited state tunnelling, and examined variations in low-temperature thermoluminescence peaks to assess the distribution of band-tail states in feldspars. As part of a supervised BSc thesis, we further explored the thermal quenching behaviour of three radioluminescence emissions using temperature-controlled spectroscopy.
We also made considerable progress in improving the accessibility and transparency of existing luminescence thermochronometry modelling tools. This was achieved by translating code originally written in Matlab into the open-source language R, aligning with the FAIR data principles.
Additionally, we investigated the luminescence characteristics of various feldspar samples, focusing on how these properties may impact measurements and outcomes in thermochronometry. Specifically, we conducted experiments to determine whether fading results from ground state or excited state tunnelling, and examined variations in low-temperature thermoluminescence peaks to assess the distribution of band-tail states in feldspars. As part of a supervised BSc thesis, we further explored the thermal quenching behaviour of three radioluminescence emissions using temperature-controlled spectroscopy.
From all results gathered during this project, four main results are particularly noteworthy:
(i) Novel experiment to emulate exhumation: The novel laboratory experiment developed during the course of this project allows for reproducible and controlled simulation of rock cooling in the laboratory, significantly improving calibration accuracy in luminescence thermochronometry. With this experiment, we created four independent calibration datasets for the use in luminescence thermochronometry.
(ii) New insights into fading: We obtained the first experimental evidence for the identification of excited state tunnelling as the cause of fading in feldspars, challenging longstanding assumptions and advancing the theoretical understanding of luminescence processes.
(iii) Determination of kinetic parameters: Luminescence-based experiments re revealed the complexity of feldspar luminescence, thus supporting previous findings. Additionally, newly designed experiments enabled an enhanced understanding of luminescence processes in feldspars and thus inform on theoretical and applied luminescence-based research in Earth sciences.
(iv) Open-source modelling tools: By translating Matlab-based models into R and integrating them into the open-access R Luminescence package, the project expanded accessibility and reproducibility in luminescence modelling, aligning with FAIR data principles.
(i) Novel experiment to emulate exhumation: The novel laboratory experiment developed during the course of this project allows for reproducible and controlled simulation of rock cooling in the laboratory, significantly improving calibration accuracy in luminescence thermochronometry. With this experiment, we created four independent calibration datasets for the use in luminescence thermochronometry.
(ii) New insights into fading: We obtained the first experimental evidence for the identification of excited state tunnelling as the cause of fading in feldspars, challenging longstanding assumptions and advancing the theoretical understanding of luminescence processes.
(iii) Determination of kinetic parameters: Luminescence-based experiments re revealed the complexity of feldspar luminescence, thus supporting previous findings. Additionally, newly designed experiments enabled an enhanced understanding of luminescence processes in feldspars and thus inform on theoretical and applied luminescence-based research in Earth sciences.
(iv) Open-source modelling tools: By translating Matlab-based models into R and integrating them into the open-access R Luminescence package, the project expanded accessibility and reproducibility in luminescence modelling, aligning with FAIR data principles.