Imaging and measurement of red-infrared stimulated luminescence (R-IRSL) from feldspar samples

Abstract

When the infrared light was illuminated on granites and feldspar slices irradiated with X-rays, luminescence color images (abbreviated to IRSLCI) showed three color patterns, separable into intense yellow, red and faint violet portions. The yellow and faint violet parts were assignable to plagioclase and potassium feldspars and quartz constituent, respectively. The red color parts appeared on both potassium and albite feldspars. From spectrometry of the IRSL, two main emission peaks in the middle wavelength region, consisting of 550 nm (yellow) and 580 nm (orange), were revealed besides intense emission both in wavelengths shorter than 450 nm (violet region) and in wavelengths longer than 600 nm (red region) on every feldspar sample. The red IRSL (R-IRSL) of as-received feldspars was significantly enhanced after annealing treatment in oxidative conditions, rather than in reductive annealing conditions for 3hrs at 900oC. The dose response of R-IRSL offered slower saturation of microcline in comparison with rapid saturation tendency of albite. The results are suggestive of a preferable application of R-IRSL to dating of burnt archaeological materials.