The Strong Thermally and Optically Stimulated Luminescence of Solonópole (Ceará, Brazil) Natural Quartz: Comparing Records and Proposing New Insights

Abstract

Quartz plays a crucial role in retrospective dosimetry and dating inquiries in Quaternary Science. The success of thermally and optically stimulated luminescence (TL, OSL) methods depends on the signal repeatability and the signal intensity of quartz grains. Among numerous crystals investigated in the last 20 years, few pieces collected from pegmatitic deposits located near the Solonópole municipality (Ceará State) have shown a notable brightness after being sensitized with a method combining high dose γ radiation and moderate heat treatments. To examine this trend, this paper reviews TL and OSL records measured in six single crystals with different sensitivities by means of different equipment setups and a wide range of γ and β radiation doses. TL emission spectra and trace-element analyses are shown and used to further discuss the complex problem involving electron traps, luminescence centers, and impurity-related point defects into the lattice of quartz. Electron–hole transferring in association with Li⁺ motion through trapping and recombination centers related to Ge and Al impurities appear to be the basis for a model to explain the brightness of Solonópole samples. This study shows the importance of adopting samples in the single crystal form to further investigate TL and OSL signal properties in quartz.