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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.

Radioactive disequilibrium of thorium series nuclides in hot spring deposits

Takashi Okubo, Masanobu Sakanoue
Geochemical Journal, Vol. 9, No. 4, P. 221-226, 1975


The concentrations of radium isotopes (226Ra and 228Ra) and thorium isotopes (232Th, 230Th and 228Th) in a calcium carbonate sinter cone and hokutolites were determined. These nuclides were analyzed either by non-destructive γ-ray spectrometry or by α-ray sepctrometry after radiochemical separation. The concentrations of 232Th, 228Ra and 228Th (thorium series nuclides) in a sinter cone were 2.4 × 10-2, 4.3 × 10-1 and 7.1 × 10-1 dpm/g, respectively. It was confirmed that thorium series nuclides in this sample were not in radioactive equilibrium with their parent, 232Th. Hokutolite samples collected recently showed higher radioactivities of 228Ra, ranging from 9.6 × 104 to 2.8 × 104dpm/g BaSO4. These values give a rate of deposition and an initial composition of the radionuclides in the hokutolite.

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