ESR Dating of Marine Barite in Chimneys Deposited from Hydrothermal Vents

Abstract

Electron Spin Resonance (ESR) dating of marine barite in chimneys deposited from hydrothermal vents was attempted to determine the time since hydrothermal activity occurred. In this study, we used Barite (BaSO 4 ) precipitated in icroenvironments in the chimneys deposited from the hydrothermal vents at the Archaean site in South Mariana spreading centre (12°56.4'N, 143°37.9'E) and at Hakurei site in the Izena caldron (27°15'N, 127°04'E) for ESR measurements. ESR spectrum of marine barite is characterized by an electron-type centre with g values of 2.0034, 2.0022 and 1.9995 attributed to SO 3 -. The signal intensity increased with gamma ray dose. The dose rates of hydrothermal chimneys from the Archaean site and from the Hakurei site were calculated using a model that assumed a grain size and that incorporation of radionuclides after 226 Ra in U series into the chimney, and assuming the efficiency of the defect formation by alpha particles to be the same as that for OSL. The ESR ages were estimated to be 470 years old for barite from the Archaean site and 5670 years old for one from the Hakurei site, although there is a considerable difference between the present ESR ages and the 210 Pb/ 226 Ra disequilibrium ages previously reported.

230Th/238U dating of hydrothermal sulfides from Duanqiao hydrothermal field, Southwest Indian Ridge

“…Other U-Th disequilibrium methods such as 226 Ra/ 210 Pb,228 Ra/ 228 Th and 210 Pb/Pb were used to determine the age of deposits\150 years (Lalou et al 1986;Jamieson et al 2013). While the ESR (electron spin resonance) dating of barite ( 226 Ra/ 228 Ra) in seafloor hydrothermal fields can obtain ages of 300-3620 years (Kasuya et al 1991;Okumura et al 2010). So far, the 230 Th/ 238 U dating was used to obtain the ages of seafloor massive sulfide deposits from the East Pacific Ridge (EPR), the Mid-Atlantic Ridge (MAR) and the Central Indian Ridge (CIR) (Lalou and Brichet 1982, 1988, 1998aYou and Bickle 1998;Kuznetsov et al 2006Kuznetsov et al , 2007Kuznetsov et al , 2011Kuznetsov et al , 2013Kuznetsov et al , 2015Münch et al 1999;Wang et al 2012).…”

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

“…Assuming that Ra is populated only in barite as confirmed by Okumura et al (2010), the internal and external dose rates of alpha, beta and gamma rays given to the barite minerals were calculated (Toyoda et al 2014). The alpha effectiveness of 0.043 was adopted (Toyoda et al 2012).…”

“…It is the most important feature of hydrothermal barite in the aspect of dose rate estimation that the only source of the radiation is internal radium (Okumura et al 2010;Toyoda et al 2014). The dose rate was calculated from the concentrations of radium and its daughter nuclei as the following.…”

“…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.…”

Dating of Hydrothermal Mineralization in Active Hydrothermal Fields in the Southern Mariana Trough

“…The ESR dating is based on the idea that paramagnetic defects with unpaired electrons are created by natural radiation and accumulates with time since mineral precipitation. Okumura et al (2010) first practically applied this technique to barite in samples collected from the seafloor, by determining signal intensities of the paramagnetic defects with SO 3 À radical. Toyoda et al (2011) estimated an age range of application of the ESR dating for barite from 10 2 to 10 5 years based on estimation for stability of paramagnetic defects.…”