Thermoluminescence in tektites

Thermoluminescence (TL) in tektites has been studied with a view to dating tektites. Powdered samples, both natural and after irradiation by Co60 γ rays, are heated in a nitrogen atmosphere at a rate of 30°C/sec, the glow being examined as a function of temperature by a specially selected photomultiplier. The structure of glow curves is found to be constant and reproducible, showing several distinct peaks besides some unresolved ones. In several samples, the lowest peaks up to 212°C, or perhaps even 231°C, are found to be either missing or considerably drained, probably because of heating at ambient temperatures for prolonged periods of time. Irradiation of natural samples reinforces, and that of heated samples reinstates, the peaks at their normal positions within experimental errors. Heating seems, however, to enhance the dose-response sensitivity of samples markedly. Exposure to UV light results in a severe bleaching of the TL glow within a few hours. Isothermal annealing of various glow peaks is studied in detail, and an attempt is made to derive from these observations the half-lives and energy depths of electron traps responsible for the glow. Thermoluminescence from surface versus core is not significantly different, thus indicating that the times of formation and of fall were probably fairly close to each other. Some tentative age estimates are made (a few times 105 years for an indochinite) subject to certain assumptions discussed in the text.