Investigating feldspar compositions and kinetic responses in TL onset methods for thermal history analysis

, , , and . UK meeting on luminescence and ESR dating, University of Liverpool, Liverpool, (11th-13th July 2016)


Stimulated luminescence methods have recognised potential for recording thermal histories in archaeological, geological, geo-environmental and engineering applications. Yet the dependences of luminescence behaviour on specific mineral composition, and geological, radiation and thermal histories are potentially complex, and need to be monitored and compensated for by calibration procedures. Recent work on OSL and IRSL thermochronology methods have focussed on the use of isothermal decay analysis to estimate kinetic parameters, used in combination with dose response curves and fading tests to account for the partial filling of natural systems in response to their recent thermal histories (Guralnik, 2014). By contrast TL onset temperature methods utilise the properties of systems containing distributions of traps, whose least stable surviving components can be rapidly and precisely registered on the rise of a natural TL curve. The feldspar system is well suited to this approach. More recently TL onset methods have been shown to respond to geothermal temperatures in the range from 10-40°C in the 2.5 km deep Outokumpu borehole (Sanderson et al 2014), and to register thermal gradients in shallow boreholes in Scottish Granites (Mooney et al, 2014). The procedures included regenerative calibration to account for sample specific behavioural changes within variable lithology. However it was notable that the relationship between onset temperature in the natural cycle and external controls was more precisely reproduced, than the overall uncertainty following regenerative calibration. In this poster a combination of SEM characterisation and luminescence analysis is used to look at the extent to which the calibration data dispersion observed can be related to feldspar composition within the samples. The potential for improving temperature resolution of calibrated data to the 1-2 degree resolution of onset temperature measurements by selecting individual feldspar components is assessed.

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