Protocol for TL dating with zircon: Computer simulation of temperature and dose rate effects

J. Phys. D: Appl. Phys.

et al. 2004

After exposure to ionizing irradiation, mineral zircon exhibits thermoluminescence (TL), which can be used to calculate the irradiation dose and the age of natural samples. Different aspects of the dating procedure based on zircon TL, including laboratory added irradiation at room and elevated temperatures, fading and preheat processes, have been considered within the framework of the kinetic model developed by our group earlier. It is shown that dose rate effects arising due to the difference between natural and laboratory irradiation can be removed by a suitable preheat treatment of the laboratory irradiated samples prior to the TL measurements. We demonstrate that the TL behaviour of zircon which has been irradiated under natural conditions can be reproduced by means of laboratory irradiation at some elevated temperature. This opens a promising possibility of (i) getting rid of dose rate effects and anomalous fading and (ii) reconstructing the dose dependence of the total TL signal emitted by samples irradiated under natural conditions. The model has been checked by simulating the dating procedures used for our coastal dune sand samples from Ameland (NL), the age of which is known from historical records; the results agree well with the available experimental data. The results of this investigation demonstrate the utility of the kinetic model for planning dating experiments and for development of new and innovative TL dating methods.

Section: Introductionsupporting

confidence: 56%

Simulation of the effects of the dose rate and temperature on zircon thermoluminescence

J. Phys. D: Appl. Phys.

et al. 2004

“…In a short communication[22] we have presented the results of a successful application of kinetic modelling to simulate the processes relevant for dating.…”

mentioning

confidence: 99%

Thermoluminescence of zircon: a kinetic model

J. Phys.: Condens. Matter

et al. 2003

The mineral zircon, ZrSiO 4 , belongs to a class of promising materials for geochronometry by means of thermoluminescence (TL) dating. The development of a reliable and reproducible method for TL dating with zircon requires detailed knowledge of the processes taking place during exposure to ionizing radiation, long-term storage, annealing at moderate temperatures and heating at a constant rate (TL measurements). To understand these processes one needs a kinetic model of TL. This paper is devoted to the construction of such a model. The goal is to study the qualitative behaviour of the system and to determine the parameters and processes controlling TL phenomena of zircon. The model considers the following processes: (i) Filling of electron and hole traps at the excitation stage as a function of the dose rate and the dose for both (low dose rate) natural and (high dose rate) laboratory irradiation. (ii) Time dependence of TL fading in samples irradiated under laboratory conditions. (iii) Short time annealing at a given temperature. (iv) Heating of the irradiated sample to simulate TL experiments both after laboratory and natural irradiation. The input parameters of the model, such as the types and concentrations of the TL centres and the energy distributions of the hole and electron traps, were obtained by analysing the experimental data on fading of the TL-emission spectra of samples from different geological locations. Electron paramagnetic resonance (EPR) data were used to establish the nature of the TL centres. Glow curves and 3D TL emission spectra are simulated and compared with the experimental data on time-dependent TL fading. The saturation and annealing behaviour of filled trap concentrations has been considered in the framework of the proposed kinetic model and compared with the EPR data associated with the rare-earth ions Tb 3+ and Dy 3+ , which play a crucial role as hole traps and recombination centres. In addition, the behaviour of some of the SiO n− m centres has been compared with simulation results.

“…This suggests that only the deep traps associated to the broad 420 °C TL peak contribute directly to the Tb 3+ related OSL emission. For stimulation wavelengths of 875nm OSL has been detected only in the 380-390 nm range of the [SiO 4 ] 4-luminescent emission [4]. Pulse annealing experiments have shown that this OSL signal can be thermally bleached at about 400 °C (Fig.…”

Section: -mentioning

confidence: 96%

“…1(a), dotted curve). The treatment is equivalent with the storage in the dark for long periods of time [4]. The OSL decay curves recorded in the 350-450 nm range and at wavelengths 550 and 583 nm using IR light stimulation (above 700 nm) are presented in the Fig.…”

Section: Temperature ( O C)mentioning

confidence: 99%

Thermoluminescence and optically stimulated luminescence of gamma‐irradiated mineral zircon

Secu

Phys. Status Solidi (c)

et al. 2007

Self Cite

Thermoluminescence (TL) manifested by gamma-irradiated mineral zircon has shown a strong TL peak at about 165 °C which is due to recombination of electrons and Dy 3+ related shallow hole traps. After they have been removed by a short preheat we have observed two TL peaks at 300-320 °C and ≈420 °C, which are mainly due to recombination of electrons and 1 Introduction The luminescence dating methods, TL and OSL might be useful to fill an important time gap in geochronometry, because often the last 500 ky, turn out to be inaccessible through other methods. The minerals used most frequently for luminescence dating are quartz and feldspars, because of their ubiquity and the ease to separate these minerals from sediments. In the 1970's investigators have established that mineral zircon (ZrSiO 4 ) can in principle be used for TL geochronometry (see e.g. [1]). Zircon has an advantage over other minerals, which are used for luminescence dating (quartz and feldspars), because they contain radioactive U and Th impurities, which irradiate the mineral internally at dose rates much higher than those from external environmental sources. In this way the major source of variability observed in e.g. quartz-based luminescence dating, which is due to the heterogeneity of the external irradiation field, is eliminated. However it was recognized at the same time that serious problems associated with anomalous fading and the inhomogenities of zircon (due to e.g. zoning and metamictization) exist, which are responsible for intra-grain variations of the luminescence properties. Recently, these problems have been overcome by introducing a special selection procedure to obtain the most homogeneous grains of high optical quality [2]. In this way TL dating of young sediments using zircon has been successfully performed [2,3], which leads the question whether zircon can also be used for OSL dating.In the present paper the OSL properties of mineral zircon have been studied in relationship with TL by performing OSL measurements after repeated preheats to successively higher temperatures, i.e. pulse annealing experiments and TL after OSL bleaching measurements.