Determining the K-content of single-grains of feldspar for luminescence dating

Feldspars form a solid-solution series whereby the K-content may range from 0 to 14%. LA-ICP-MS measurements for density-separated single-grains of feldspar yielded realistic concentrations of K within the range of those naturally occurring, and also highlighted the difficulty in isolating the pure end members during density-separation. No direct relationship was found between the thermal stability of the infrared-stimulated luminescence (IRSL) signal and measured K-content of individual grains. However, the brightest IRSL and post-IR IRSL signals originated from grains with ∼12% K-content. All grains giving a measurable signal had K-content between 6 and 13%, therefore it is suggested that an internal K-content of 10 ± 2% can be assumed for routine single-grain dating of density-separated K-feldspars.

► Measure range of K for single-grains of density separated feldspar using LA-ICP-MS.
► Single-grain thermal stability and brightness do not directly relate to K-content.
► Brightest 3 grains measured ∼12% K and provided the majority of the IRSL signals.