Luminescence thermochronometry of feldspar minerals: Optimisation of measurement conditions for the derivation of thermal kinetic parameters using isothermal holding experiments

Luminescence thermochronometry is sensitive to very low temperatures (below -120 degrees C), and enables the resolution of thermal histories over sub-Quaternary timescales. Here we apply a multi-elevated-temperature post-infrared infrared-stimulated luminescence (MET-pIR-IRSL) measurement protocol to feldspar minerals to extract thermal histories. These thermal histories depend on the thermal stability of the MET signal, and are based on the thermal kinetic parameters extracted from isothermal decay experiments. However, the derived thermal kinetic parameters vary with experimental conditions, specifically with the isothermal holding temperatures (ITL) used. We analyse samples with independently known thermal histories, together with synthetic thermal history samples and samples with unknown thermal histories to test the validity of thermal kinetic parameters obtained from different combinations of isothermal holding data. This approach is tested on feldspars of different mineralogies and lithologies. We find that the temperatures inferred from inverting the data change, depending both on the number and on the highest ITL temperature used for thermal kinetic parameter derivation. Analysed samples validate the MET-pIR-IRSL protocol for extracting thermal histories, and we suggest that four isothermal holding temperatures between 190 and 250 degrees C are used for appropriate thermal kinetic parameter derivation.

Automated summary

Luminescence thermochronometry is used to resolve thermal histories over sub-Quaternary timescales by applying a MET-pIR-IRSL protocol to feldspar minerals. The thermal histories are dependent on the stability of the MET signal and vary with experimental conditions, specifically the isothermal holding temperatures. Through analysis of samples with known and unknown thermal histories, the study validates the protocol and suggests using four isothermal holding temperatures between 190 and 250 degrees C for appropriate thermal kinetic parameter derivation.