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A comparative study of the luminescence characteristics of polymineral fine grains and coarse grained K-, Na- and Ca-rich feldspars

Recently, the elevated temperature post-IR IRSL signal measured at 290°C (pIRIR290) has been found to show little or no anomalous fading in both K-feldspar and polymineral fine grains (Thiel et al., 2011, submitted ; Thomsen et al., 2011 ; Buylaert et al., submitted ; Schmidt et al., submitted). A preheat of 320°C (60s) and the pIRIR stimulation temperature of 290°C were chosen because the IRSL signal at 50°C from K-feldspar may be associated with a trap at 410°C (Murray et al., 2009). However, polymineral fine grains are a mixture of different kinds of feldspars, and little is known about the origins of the IRSL and pIRIR signals. In this study the luminescence characteristics of six polymineral fine grain samples are compared with those of coarse-grained K-, Na- and Ca-rich feldspar extracts ; the samples are taken from different regions of the world. The measurements of thermal stability and TL signal loss after illumination for both IRSL and post-IR IRSL are combined with time-resolved measurements (Jain and Ankjærgaard, 2011) to understand the nature of the IR dosimetric trap and recombination processes in these different samples. The comparison of coarsegrained mineral extracts with the fine grains will enable understanding of the origins of the luminescence signals in the polymineral fine grained samples ; the implications resulting from these measurements will be discussed.

feldspar; polymineral; IRSL; pIRIR; thermal stability; time resolved IRSL

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