3:30 PM - 3:45 PM
[HQR05-01] ESR Dating of barite with the regeneration protocol: advantages and issues
Keywords:ESR Dating, barite, hydrothermal
The potential of ESR (electron spin resonance) dating of barite (BaSO4) was first shown by Kasuya et al. [1] while the first practical application using SO3- radical was reported on barite formed by sea-floor hydrothermal activities [2]. The main natural radiation source is Ra contained in barite replacing Ba ions. It is possible to obtain young ages as several years when the natural dose rate is high in the order of Gy/y. The development of the dating method has involved specific issues such as radioactive disequilibrium of Ra [3] and alpha effectiveness, which is a factor relative to gamma rays to form the radical.
The precision and correctness of the estimated natural accumulated doses (denote as the equivalent doses in the procedure) are those of the key factors in order to improve the dating method. While the additive dose method has been employed in the dating procedure, the regenerative method has an advantage in the aspect of precision and correctness. In the present paper, a new regenerative protocol was developed, and applied to two samples taken from Yoron (70-150 yrs) and Gondo (2500-3300 yrs) sea-floor hydrothermal fields for which ESR ages have been obtained [5] and to one from Ieyama of unknown age.
In the regenerative protocol, the dating signal is first erased by heating, where the possible sensitivity (the rate of radical formation per unit of absorbed dose) change has to be checked. A method has been developed to check the sensitivity change for quartz [6] based on previously developed for luminescence dating, which is SARA (single aliquot regenerative additive) [7]. However, this method works when the dose response is linear. In the present case, it was found that the dose response of SO3- radical in barite is well fitted to a function of sum of saturating exponential and linear. In the present paper, we have developed a protocol to fit the additive dose response to the regenerative response with two parameters, shift of the dose axis and the factor to multiply the signal intensity. The results applied to the actual samples will be reported.
References
[1] Kasuya, M., Kato, M., Ikeya, M. (1991) In Essay in Geology, Prof. Nakagawa Commemorative Volume, 95-98.
[2] Okumura, T., Toyoda, S., Sato, F., Uchida, A., Ishibashi, J., Nakai, S. (2010) Geochronometria, 37, 57-61.
[3] Fujiwara, T., Toyoda, S., Uchida, A., Ishibashi, J., Nakai, S., and Takamasa, A. (2015) In Subseafloor Biosphere Linked to Global Hydrothermal Systems; TAIGA Concept, Springer, Tokyo, 369-386.
[4] Fujiwara, T., Toyoda, S., Uchida, A., Nishido, H., and Ishibashi, J. (2016) Geochronometria, 43, 174-178.
[5] Fujiwara, T. (2018), Ph.D Thesis, Okayama University of Science.
[6] Toyoda, S., Miura, H., Tissoux, H. (2009) Radiation Measurements, 44, 483-487.
[7] Mejdahl, V. and Botter-Jensen, L. (1994) Quaternary Science Reviews, 7, 551-554.
The precision and correctness of the estimated natural accumulated doses (denote as the equivalent doses in the procedure) are those of the key factors in order to improve the dating method. While the additive dose method has been employed in the dating procedure, the regenerative method has an advantage in the aspect of precision and correctness. In the present paper, a new regenerative protocol was developed, and applied to two samples taken from Yoron (70-150 yrs) and Gondo (2500-3300 yrs) sea-floor hydrothermal fields for which ESR ages have been obtained [5] and to one from Ieyama of unknown age.
In the regenerative protocol, the dating signal is first erased by heating, where the possible sensitivity (the rate of radical formation per unit of absorbed dose) change has to be checked. A method has been developed to check the sensitivity change for quartz [6] based on previously developed for luminescence dating, which is SARA (single aliquot regenerative additive) [7]. However, this method works when the dose response is linear. In the present case, it was found that the dose response of SO3- radical in barite is well fitted to a function of sum of saturating exponential and linear. In the present paper, we have developed a protocol to fit the additive dose response to the regenerative response with two parameters, shift of the dose axis and the factor to multiply the signal intensity. The results applied to the actual samples will be reported.
References
[1] Kasuya, M., Kato, M., Ikeya, M. (1991) In Essay in Geology, Prof. Nakagawa Commemorative Volume, 95-98.
[2] Okumura, T., Toyoda, S., Sato, F., Uchida, A., Ishibashi, J., Nakai, S. (2010) Geochronometria, 37, 57-61.
[3] Fujiwara, T., Toyoda, S., Uchida, A., Ishibashi, J., Nakai, S., and Takamasa, A. (2015) In Subseafloor Biosphere Linked to Global Hydrothermal Systems; TAIGA Concept, Springer, Tokyo, 369-386.
[4] Fujiwara, T., Toyoda, S., Uchida, A., Nishido, H., and Ishibashi, J. (2016) Geochronometria, 43, 174-178.
[5] Fujiwara, T. (2018), Ph.D Thesis, Okayama University of Science.
[6] Toyoda, S., Miura, H., Tissoux, H. (2009) Radiation Measurements, 44, 483-487.
[7] Mejdahl, V. and Botter-Jensen, L. (1994) Quaternary Science Reviews, 7, 551-554.