Low temperature thermochronology using thermoluminescence signals from quartz

Abstract

Isothermal thermoluminescence (ITL) and thermoluminescence (TL) signals from quartz were studied. A single aliquot regenerative dose protocol has been applied for ITL De determination (SAR-ITL). In the SAR-ITL protocol, the preheat condition was a cutheat to 10 °C higher than measurement temperature. The test dose was approximate to the expected De, and a 450 °C heat was given at end of each cycle to minimize signal build-up. Based on signals strength and dose recovery test, temperatures of 235 and 255 °C were selected for the ITL De measurement. A multiple aliquots regenerative protocol has been applied for TL De determination (MAR-TL). The preheat procedure was a cutheat of 235 °C and a second glow TL of 175 Gy was used for normalization. The sensitivity change of first heating to 450 °C was negligible, supported by comparison between additive and regenerative dose growth curves. Based on the natural TL signal and preheat condition studies, De values at temperatures of 250–330 °C were used for thermochronological study. These two protocols were applied to rock samples collected at different elevations from Nujiang River (also called Salween River) valley slope. The SAR-ITL gave De results consistent with the MAR-TL at temperatures of 40–50 °C higher. The results clearly demonstrate the differences in the thermal histories between the analyzed samples. The SAR-ITL and MAR-TL protocols were both found to be suitable for application in thermochronology.