Thermoluminescence as a palaeothermometer

Abstract

Chondritic meteorites are widely regarded as a unique source of information on the chemical and physical processes that occurred in the early Solar System. An important phase in their history is a period of metamorphism¹ and thermoluminescence (TL) has proved a powerful technique for exploring this aspect, especially at the low end of the metamorphic spectrum². The ordinary chondrites as a whole display a 10⁵-fold range in TL sensitivity, while the least metamorphosed, or type 3, ordinary chondrites display a 10³-fold range. Associated with this 10³-fold range in TL sensitivity are variations in the temperature at which the maximum TL emission occurs, and in the temperature range over which emission occurs^3,4. We report here the results of annealing experiments on a little-metamorphosed (type 3.5) ordinary chondrite. The TL emission characteristics of the annealed samples show trends very similar to those observed in meteorites which have naturally been metamorphosed to various extents. The trends are also similar to those observed in annealing experiments on terrestrial albite^5–7 where the changes are associated with the low-to high-temperature transformation. These data suggest that the TL phosphor in meteorites is feldspar and that TL can be used to estimate palaeotemperatures for little-metamorphosed and highly-unequilibrated meteorites.