Emission properties of thermoluminescence from natural quartz-blue and red TL response to absorbed dose

Abstract

The TL spectrometry of natural quartz exposed to 8.8 kGy proved that the red TL, mainly from volcanically originated quartz, has a broad emission band with a peak around 620 nm, while the blue TL from plutonically originated quartz also has a broad emission band giving a peak around 470 nm. These typical red or blue intrinsic colours were also confirmed on the thermoluminescence colour images (abbreviated to TLCI by the authors) to the lowest observable dose region in quartz grains of different origins. Exceptionally, a pegmatite quartz changed its TLCI colour from red to blue when the absorbed dose was increased. By using colour filter assemblies, all these quartz samples were ascertained to emit more or less blue and red TLs, which have distinctly different TL responses to the absorbed dose; the blue invariably showed a supralinearity relation between 1 and 10 kGy dose. For the purpose of dating, the use of red TL, passed through red-filter assemblies, is preferable if the specimens contain red TL quartz grains as attributed from their origin or from the TLCI observation. The red TL component was verified to be correlated with the impurity Eu content in quartz minerals.