Structural and thermoluminescence properties of quartz from different geological locations in Botswana.

Thermoluminescence and structural characteristics of volcanic, hydrothermal and metamorphic quartz from three different geological locations in Botswana are reported. The glow curves of the volcanic, hydrothermal and metamorphic quartz showed three (near 82, 201, and 295°C), two (near 80 and 247°C) and two (near 83 and 367°C) clear peaks respectively. All the samples exhibited the "110 °C", which is fairly isolated, around 82°C. The high temperature peaks overlap one another with a degree of overlapping that varies from sample to sample. The TL response of the "110°C" peak in the three samples increased linearly with dose for doses below 16Gy. Above 16Gy, TL responses of volcanic and metamorphic quartz became sublinear while that for hydrothermal became supralinear with dose. Volcanic quartz had the least minimum detectable dose of 0.4mGy. The higher the crystallinity index of quartz samples the higher the TL sensitivity. Metamorphic with the highest peak intensity of 26.62° peak in the XRD spectrum. The higher the intensity of 26.62° peak in the XRD spectrum of quartz, the lower the minimum detectable dose. The decrease in TL response of the "110°C" with increase in duration of optical bleaching showed no dependence on the origin of quartz. The activation energy of thermal quenching for the "110°C" peak in the volcanic, hydrothermal and metamorphic quartz are 0.71. 1.06 and 0.92 ev respectively. The possibility of using crystallinity index for characterization of some TL properties of quartz is presented.