ESR Dating of Barite in Sea-Floor Hydrothermal Sulfide Deposits in the Okinawa Trough

Abstract

ESR (electron spin resonance) ages were determined for barite crystals extracted from hydrothermal sulfide deposits taken at Daiyon-Yonaguni Knoll field, Hatoma Knoll field, Iheya North Knoll field, Hakurei Site of Izena Hole field, Yoron Hole field of the Okinawa Trough. The ages range from 4.1 to 16,000 years, being consistent with detection of 228 Ra in younger samples and radioactive equilibrium/disequilibrium between radium and daughter nuclei. The variation of the ages within each sample is mostly within the statistical error range. The relative order of the ages is consistent with the result of 226 Pb method, but the determining absolute ages is still an issue. The order of ages of the 5 hydrothermal fields would be arranged, from young to old as follows; Yoron Hole field, Daiyon-Yonaguni Knoll field, Hatoma Knoll field, being nearly equal to Iheya North Knoll field. KeywordsBarite Dating Electron spin resonance Hydrothermal activities IntroductionThere have been many scientific efforts devoted for studies on active sea-floor hydrothermal fields found in Okinawa Trough (Ishibashi et al. Chap. 23). The evolution of these hydrothermal fields is one of the important issues. Dating methods have been employed for hydrothermal sulfide deposits, such as the U-Th disequilibrium method (e.g. You and Bickle 1998) applicable for the age range more than several thousand years, and 226 Pb and 228 Th method (e.g. Noguchi et al. 2011) for the range less than 150 years. The age range of several hundred years is essential to estimate the life time of hydrothermal activities. However, dating methods for the age range are lacking. Okumura et al. (2010) made the first practical application of ESR dating technique to a sample of seafloor hydrothermal barite to obtain ages of 300 and 3,620 years, while Kasuya et al. (1991) first pointed out that barite can be used for ESR dating. Toyoda et al. (2011) determined the optimum ESR condition while Sato et al. (2011) confirmed that the signal is thermally stable enough for an age range of several thousand years.Seafloor massive sulfide deposits are composed of sulfide minerals such as pyrite, sphalerite, chalcopyrite and galena, and also include sulfate minerals such as anhydrite and barite. The sulfate minerals precipitate by mixing of hydrothermal fluid and seawater, while the sulfide minerals precipitate from the hydrothermal fluid mainly by cooling (Hannington et al. 1995). It is generally considered that a combination and/or switch of these two modes of hydrothermal precipitation lead to growth of sulfide structures such as a chimney and mound and that of large hydrothermal T. Fujiwara S. Toyoda (*) A. Uchida Okayama University of Science, Okayama, Japan e-mail: toyoda@dap.ous.ac.jp deposits (e.g. Tivey 2007). Takamasa et al. (2013) determined ESR ages for barite in sulfide deposits in the South Mariana Trough hydrothermal field, and concluded that the ages are consistent with U-Th ages. In this study, the ages of various hydrothermal sulfides in the Okinawa Trough a...

Genetic population structure of four hydrothermal vent shrimp species (Alvinocarididae) in the Okinawa Trough, Northwest Pacific

“…In the present study, high haplotype diversity was observed for each local population of S. leurokolos (haplotype diversity: 0.98 to 1.00) and no genetic differentiation was detected among the local populations. S. leurokolos is assumed to have a high colonisation ability compared to the other 3 alvinocaridids because this species (1) is broadly distributed both spatially and bathymetrically and (2) rapidly colonised a newly developed hydrothermal vent site at Yoron Hole, where all of the collected chimneys and ores are < 400 yr in age (Fujiwara et al 2015). Another dominant decapod species in the Okinawa Trough, Shinkaia crosnieri, also has high genetic diversity (Kumagai et al 2015).…”

ESR dating of sea-floor hydrothermal barite: contribution of ²²⁸Ra to the accumulated dose

“…The barite crystals occur in sulfide chimneys and in deposits, incorporating radium ions that are in the hydrothermal fluid. As a radium ion has an ionic radius similar with barium, radium ions easily replace barium in barite to have high concentration up to several tens Bq/g of 226 Ra (Fujiwara et al, 2015).…”

“…They showed that the ESR ages are roughly consistent with the U-Th ages. While Toyoda et al (2014) discussed several detailed technical issues such as the dose rate conversion factors, the sample edge effect for gamma ray dose, and the correction for the decay of 226 Ra, Fujiwara et al (2015) made the first practical systematic dating work with ESR on barite of sea-floor hydrothermal sulfide deposits taken at Okinawa Trough on total of 18 samples (60 subsamples) with new formulas which take the radioactive disequilibrium of Ra daughter nuclei into account. The obtained ages range 4 to 16000 years, showing that the ESR method has a wide application age range.…”

“…The obtained ages range 4 to 16000 years, showing that the ESR method has a wide application age range. Uchida et al (2015) obtained 226 Ra-210 Pb and 228 Ra-228 Th ages for the same samples as Fujiwara et al (2015) analyzed and attributed the differences of the ages among these three dating methods to possible multiple formation stages of the sulfide deposits.…”

OSL Dating of Sea Floor Sediments at the Okinawa Trough

“…Various dating techniques have been employed, such as U-Th method on sulfide minerals (Takamasa et al 2013), ESR method on barite (Takamasa et al 2013;Fujiwara et al (2014), Chap. 34), and 226 Pb,228 Th method on barite (Noguchi et al 2004;Uchida et al (2014), Chap.…”