Internal U, Th and Rb concentrations of alkali-feldspar grains: Implications for luminescence dating



Smedley, RK ORCID: 0000-0001-7773-5193 and Pearce, NJG
(2016) Internal U, Th and Rb concentrations of alkali-feldspar grains: Implications for luminescence dating. QUATERNARY GEOCHRONOLOGY, 35. pp. 16-25.

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Abstract

This study assesses whether internal U, Th and Rb concentrations of single grains of alkali-feldspar can impact upon luminescence dating. Internal alpha dose-rates determined for two sedimentary samples calculated from mean U and Th concentrations accounted for ~10% of the total dose-rates, while internal beta dose-rates from mean Rb concentrations accounted for ~2%. Depth profiles of measurements penetrating into each grain show that internal U and Th concentrations varied between grains, where some grains had effective internal alpha dose-rates up to 1.8 Gy/ka (32% of the total dose-rate). K concentrations inferred from Rb (KRb) for individual grains suggest that internal U and Th concentrations are related to the feldspar composition. Grains with KRb > 6% had low U and Th, and grains with KRb < 6% had higher U and Th concentrations. Internal alpha and beta dose-rates of the perthitic and Na-rich grains contaminating the density-separated K-feldspar fractions had a significant impact upon the single-grain De distributions, which was estimated to be equivalent to overdispersion values of ~10 - 15%. The scatter in the De distributions arising from internal alpha and beta dose-rates for both samples could be reduced by selecting only the brightest 20% of grains for luminescence dating.

Item Type: Article
Uncontrolled Keywords: Luminescence dating, Alkali-feldspar, Internal dose-rate, Uranium, Thorium, Rubidium
Depositing User: Symplectic Admin
Date Deposited: 24 Jan 2018 07:51
Last Modified: 19 Jan 2023 06:42
DOI: 10.1016/j.quageo.2016.05.002
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3016721