Relative and k0-standardized INAA to assess the internal (Th, U) radiation dose rate in the “quartz coarse-grain protocol” for OSL dating of sediments: Unexpected observations

This paper reports on the unexpected observations in a study of the importance of the internal alpha contribution to the total dose rate in the quartz coarse-grain technique for the optical dating of sediments. INAA yielded the Th and U concentrations in the bulk material (B) and the etched quartz fraction (Q) of 8 sediments of various types/origins. The investigations were extended to residual mineral grains (QR) manually extracted from the etched quartz and to the thus obtained purified quartz (QQ). All these fractions (B, Q, QQ, QR) were analyzed via multi-element (relative and k0-standardized) INAA, and minerals were identified via microscopy and X-ray diffraction. Correlations were found between element concentrations and the presence of certain minerals, and between Th–U and some major elements of the minerals. A preliminary investigation was made of the ratio of infrared/blue light stimulated luminescence for the Q, QQ and QR fractions of 2 of the sediments. No unambigous conclusions could be drawn from the results of our experiments, thus pointing at the need for further optimized investigations.