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New applications of electron spin resonance dating dosimetry and microscopy

In this study, modern river bed sediments and bedrock samples were collected at sites S1–S7and R1– R5, respectively, from the Kizu River basin, western Japan (Fig. The total length of the Kizu River is 89 km, and the basin covers an area of 1663 km Location map showing sample sites for the present-day river bed sediments and the possible source rocks around the Kizu River, Japan.

new applications of electron spin resonance dating dosimetry and microscopy-7new applications of electron spin resonance dating dosimetry and microscopy-33

Samples S6–S7 and R4–R5 were collected along the main course of the Kizu River.The Al and Ti-Li center signals from the quartz samples were measured at 77 K (–196°C) using a microwave power of 5 m W, a sweep time of 2 min, a time constant of 0.03 s, an amplitude of field modulation of 0.1 m T, and a modulation frequency of 100 k Hz. Given that the peroxy center signal at g = 2.067 overlaps the Al center signal, Toyoda and Falguères (2003) suggested taking the peak height between g = 2.018 and 1.993 as the Al center signal intensity to avoid the contribution from the peroxy center signal.To calculate the g values of the ESR signals, and to further check the sensitivity of the ESR spectrometer, we used the intensity of a standard Mn O marker inside the cavity.The results indicate that the dose-saturated Al and Ti-Li center ESR intensities can be used to quantitatively estimate the provenance of the sediments deposited by the Kizu River.’ center signal intensity, which corresponds to the number of oxygen vacancies in natural volcanic and granitic quartz, is correlated with age, with higher values found in the quartz of older source rocks (Toyoda and Hattori, 2000; Toyoda and Naruse, 2002). The Al center is an electron hole trapped at the bond between oxygen atoms and Al impurity atoms (the latter having replaced Si in the quartz crystal; O’Brien, 1955).The Ti-Li center is an electron trapped at Ti, which can also replace Si in the quartz crystal, together with an accompanying Li ion (Wright ., 1963).The Al and Ti-Li center signal intensities obtained from the quartz of the metamudstone with sandstone sample R2 and the river sediment sample S4 increased with the gamma ray dose, becoming almost saturated above 2.5 k Gy (Fig. The intensities obtained from the quartz in the granitic samples (R3) were almost saturated with gamma ray doses above 2 k Gy (Fig. Different samples may have received different accumulated natural doses that cause the signal intensities to differ; therefore, to erase the effect of different natural radiation doses, we used a dose of 2.5 k Gy in order to reach the saturation for all samples.

Each sample was divided into five aliquots and then each aliquot was measured five times to investigate variations in the Al and Ti-Li center signal intensity of the quartz in the same sample.

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(2015) showed that the method using ESR signals makes it possible to discriminate quartz grains of different geological sources from one another.

In this study, we investigate the relationships among ESR signals of quartz in modern river bed sediments and bedrocks of the Kizu River basin using the dose-saturated signal intensities of the Al and Ti-Li centers.

Each sample was measured five times, and the sample tube was rotated in the cavity to average the angular dependence of the ESR signals.