Studies of thermal stability of trapped charges associated with OSL from quartz

h i g h l i g h t sDiscrepancy between quartz SAR-OSL ages obtained on fine and coarse grains. Dose response curve adequately fitted by a sum of two saturating exponentials. Isothermal decay fitted by a single exponential. Clear dependency between the saturation characteristics (D 0 s) and the quartz grain size. No correlation between the 2 D 0 value and the maximum attainable accurate equivalent dose. a r t i c l e i n f o a b s t r a c tThere are two major problems commonly encountered when applying Optically Stimulated Luminescence (OSL) dating in the high dose range: (i) age discrepancy between different grain sizes, and (ii) age underestimation. A marked and systematic discrepancy between fine-grain (4e11 mm) and coarse-grain (63e90 mm) quartz single aliquot regeneration protocol (SAR) ages has been reported previously for Romanian and Serbian loess >40 ka (D e of~100 Gy), generally with fine-grain ages underestimating the depositional age. In this paper, we show a similar age pattern for two grain size fractions from Chinese loess, thus pointing to a potential worldwide phenomenon. While age underestimation is often attributed to signal saturation problems, this is not the case for fine grain material, which saturates at higher doses than coarse grains, yet begins to underestimate true ages earlier. Here we examine the dose response curves of quartz from different sedimentary contexts around the world, using a range of grain sizes (diameters of 4e11 mm, 11e30 mm, 35e50 mm, 63e90 mm, 90e125 mm, 125e180 mm, and 180 e250 mm). All dose response curves can be adequately described by a sum of two saturating exponential functions, whose saturation characteristics (D 0 values) are clearly anticorrelated with grain diameter (4) through an inverse square root relationship, D 0 ¼ A/√4, where A is a scaling factor. While the mechanism behind this grain-size dependency of saturation characteristics still needs to be understood, our results show that the observation of an extended SAR laboratory dose response curve does not necessarily enable high doses to be recorded accurately, or provide a corresponding extended age range.

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“…1.66 ± 0.03 13.0 ± 0.3~110 1.14 ± 0.14 9.5 ± 1.5 0.0004 1.75 ± 0.15 13.4 ± 1.5 1500 Li and Chen, 2001.…”

Section: Referencementioning

confidence: 98%

On the importance of grain size in luminescence dating using quartz

Timar-Gabor

Buylaert

Guralnik

et al. 2017

Radiation Measurements

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“…The lifetime (τ) is based on the activation energy (E) and frequency factor (s), which can be determined by various methods in kinetic studies, e.g pulse annealing and isothermal tests on the samples examined (e.g. Li and Chen, 2001;Li et al, 1997;Murray and Wintle, 1999 based on eq. 8 and eq.…”

Section: Numerical Simulation Resultsmentioning

confidence: 99%

“…Secondly, the thermal behaviour of the main OSL signal of quartz usually follows the first-order kinetics and its kinetic parameters have been well studied (e.g. Spooner and Questiaux, 2001;Li and Chen, 2001;Murray and Wintle, 1999;Singarayer and Bailey, 2003). Thirdly, the quartz OSL traps are deep (E=~1.6 eV) and hence sufficiently stable so that it can be applied to a time scale beyond ~100 ka.…”

Section: Discussionmentioning

confidence: 99%

“…Firstly, it has been shown that it is mainly associated with a single group of traps (e.g. Li and Chen, 2001;Murray and Wintle, 1999). Secondly, the thermal behaviour of the main OSL signal of quartz usually follows the first-order kinetics and its kinetic parameters have been well studied (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…These parameters were chosen as they are close to the experimental values for natural quartz OSL signals, so that the results are representative for typical quartz samples (e.g. Li and Chen, 2001;Murray and Wintle, 1999). The changes of apparent OSL age with time (or true age) for this 'quartz sample' under a dose rate of =3 Gy/ka at different environmental temperatures ranging from 10 to 50 °C is shown in Fig.…”

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Determining the cooling age using luminescence-thermochronology

2012

Tectonophysics

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Luminescence technique has been shown to have great potential in low-temperature (< 100 °C) themochronology. This study investigates the kinetic process of luminescence in a cooling system. We present a new formula that can be used for determining the cooling age based on luminescence-thermochronology. The cooling rate can be obtained directly from a plot of luminescence age versus the present temperature. We show that the application and capacity of luminescence-thermochronology are significantly controlled by the saturation of luminescence and environmental dose rate. AbstractLuminescence technique has been shown to have great potential in low-temperature (<100 °C) themochronology. This study investigates the kinetic process of luminescence in a cooling system. We present a new formula that can be used for determining the cooling age based on luminescence-thermochronology.The cooling rate can be obtained directly from a plot of luminescence age versus the present temperature. We show that the application and capacity of luminescence-thermochronology are significantly controlled by the saturation of luminescence and environmental dose rate.Keywords: luminescence, thermochronology, cooling age, closure temperature IntroductionThermochronology refers to determining or constraining the thermal history of a specific rock, mineral, or geologic unit using various dating techniques. Different techniques in thermochronology have been developed using various dating techniques, such as fission track dating of zircon and apatite, K-Ar and Ar-Ar dating of K-feldspars, (U-Th)/He dating of zircon and apatite and 4 He/ 3 He dating, etc. A full review of thermochronology has been provided by Reiners et al (2005). In terms of low-temperature thermochronology, radiation damage dating techniques, such as electron spin resonance (ESR) dating (Grün et al., 1999) and thermoluminescence (TL), are applied (Johnson 1966). Recently, in the study of the relief evolution and exhumation rates within the last glacial cycle in the Southern Alps of New Zealand, a new low-temperature 2 thermochronology has been introduced using the technique of optically stimulated luminescence (OSL) dating of quartz (Herman et al., 2010) .Luminescence refers to the light emitted by irradiated crystal materials in response to external stimulus, such as heat (TL), visible light (OSL) and infrared (IRSL). During the geological processes, the minerals contained in geological materials (e.g. rocks and sediments) are exposed to ionization radiation (alpha and beta particles and gamma rays) emitted by the decay of radioactive isotopes within the minerals themselves and the surrounding matrix. The high-energy ionizing radiation can create free electrons and holes which may be subsequently trapped at the structural defects and chemical impurities inside the crystal lattice. When the minerals are stimulated by heat or light, the trapped electrons are ejected and recombined with holes. The evicted electrons diffuse around the crystal lattice and some of them ma...

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2011

Thermally and Optically Stimulated Luminescence

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Studies of thermal stability of trapped charges associated with OSL from quartz

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On the importance of grain size in luminescence dating using quartz

On the importance of grain size in luminescence dating using quartz

Determining the cooling age using luminescence-thermochronology

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