Sensitisation of OSL Signals in Quartz and Provenance Implications: Insights from Multi-Spectroscopic Analysis of Quartz from Multiple Geological Settings

Quartz optically stimulated luminescence (OSL) sensitivity and electron spin resonance (ESR) signals have been empirically proposed as indicators for sediment provenance. OSL sensitivity is defined as luminescence produced per unit dose (Gray: Gy) per unit mass (mg). The mechanisms driving OSL sensitisation during weathering from source rocks remain an open question in the luminescence community. Most previous work has focused solely on sink sediments, while recent studies highlight the role of lattice defects in the source rocks in the OSL sensitisation process. The present study investigates diverse source rocks from around the world, including granites, sandstones, volcanic rocks, metamorphic rocks, and, in some cases, their derived sediments, with ages ranging from millions (Ma) to billions (Ga) of years. We combine thermoluminescence (TL), OSL, ESR, cathodoluminescence (CL) and Raman spectroscopy, with geochemical data obtained through laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Only those quartzes that exhibited the [TiO4-Li+]0 paramagnetic centre in ESR, had notably high concentration of titanium and lithium impurities and had high blue emission in SEM-CL, showed sensitisation following repeated cycles of laboratory dosing and bleaching. Samples lacking these centres did not show any laboratory OSL sensitisation by dosing and bleaching. We find a strong correlation of the degree of laboratory OSL sensitisation with the [TiO4-Li+]0 electron centre from ESR signal, and the titanium and lithium concentrations measured by LA-ICPMS. Our data on rocks of various ages and regions reinforce the idea that the potential for OSL sensitisation originates from specific lattice defect structures acquired by quartz during crystallisation.