On the relationship between K concentration, grain size and dose in feldspar. (15th December 2018)

• Record Type: Journal Article
• Authors: Buylaert, J.-P.; Újvári, G.; Murray, A.S.; Smedley, R.K.; Kook, M.
• Is Part Of: Radiation measurements. Volume 120(2019:Jan.)
• Page Start: 181
• Page End: 187
• Publication Date: 2018-12-15
• Subjects: Feldspar -- Potassium -- Rubidium -- Dose -- Isochron; Nuclear emulsions -- Periodicals; Particle tracks (Nuclear physics) -- Periodicals; Thermoluminescence -- Periodicals; Cosmic rays -- Periodicals; Radiation -- Measurement -- Periodicals; Radiometry -- Periodicals; Radiation Monitoring -- Periodicals; Émulsions nucléaires -- Périodiques; Particules (Physique nucléaire) -- Traces -- Périodiques; Thermoluminescence -- Périodiques; Rayonnement cosmique -- Périodiques; Radiométrie -- Périodiques; 539.77
• DOI: 10.1016/j.radmeas.2018.06.003
• Languages: English
• ISSNs: 1350-4487

Abstract

Abstract: Previous work has been unable to establish a relationship between K concentration and De in single-grains of feldspar. Here we use four well-bleached sediments with low external dose rate (typically ≤1.5 Gy ka −1 ) to investigate this relationship. Single and multi-grain pIRIR measurements and μ-XRF analyses are made on Na- and K-rich extracts; μ-XRF is directly applied to grains sitting in single-grain discs to minimise uncertainty in grain identification. Micro-XRF is shown to be sufficiently precise and accurate and luminescence instrument reproducibility is confirmed using dose recovery measurements on heated feldspar. We are again unable to establish any correlation between single-grain De and K concentration, even in feldspar grains for which the internal dose rate should dominate. We also measure highly variable Rb concentrations in these grains and are unable to detect, at the single-grain level, the correlation between K and Rb previously observed in multi-grain investigations. Nevertheless, these results are unable to explain the lack of De correlation with K. Finally, we investigate the dependence of De on grain size (isochrons). Linear correlations are observed but slopes are inconsistent with model prediction. We conclude that this surprising absence of the expected relationships between dose and K concentration and grain size does not arise from analytical precision, incomplete bleaching, sediment mixing or fading. It appears that we cannot measure feldspar doses in these samples as accurately as we thought. Highlights: Unable to establish any correlation between single-grain pIRIR De and K concentration. Slopes of IR50 and pIRIR isochrons (De as a function of grain size) not consistent with model predictions. Rb content in individual feldspar grains highly variable.