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

Abstract

Electron spin resonance (ESR) dating of barite has been recently developed and is now practically applied to barite extracted from sea-floor hydrothermal deposits. The evolution of the accumulated dose to barite is simulated for an actual sample of barite in sea-floor hydrothermal sulfide deposit to find that the contribution of radioactive nuclei of 228Ra series can be important for the samples younger than 300 years old. Currently, any date over 50 years should be considered a maximum value when the 228Ra content is not obtained. The method to estimate the contribution from 228Ra series has to be developed in future for those in which 228Ra is not detected. The age limit of ESR dating of barite would be 5000 to 6000 years due to the decay of 226Ra, which is also found by simulation of the accumulated dose.