Sea floor dating
The sample is a portion of sulfide deposit including barite crystals.The analysis was made according to the procedures described in Fujiwara . A piece of a block cut out of the deposit was soaked in water for 3 days and its mass was measured.For the present test sample, a simulation indicates that the age will be estimated to be 90 years at age of 50 years when the contribution is not taken into account, while it will still be 360 years, 20% overestimates, at age of 300 year, where the overestimate is comparable as the typical variation, 20%, of the ESR ages from a same portion (Fujiwara Ra series nuclei have decayed out, but still necessary to be considered according to the above discussion.In summary, the ages of the samples for which the ESR ages have been estimated to be less than 300 years without considering the doses from Ra concentrations and the ESR age, which is equivalent to virtually equilibrated Th/U ratio (in ppm) of 10.7.This ratio would be a little high but in the reasonable range as material in the crust.
They showed that the ESR ages are roughly consistent with the U-Th ages. (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.An XRF measurement was made to confirm that the extracted crystals are pure barite.