Radioactive series disequilibria in underground uranium deposits of the Singhbhum Shear Zone, Eastern India

Radionuclides of the 238U series (226Ra, 210Pb, 234Th and 234U), 235U series (227Ac and 231Pa) and 232Th series (228Th and 228Ra) series were measured by High Resolution Gamma Spectrometry system in twenty-five uranium ore samples from underground uranium deposits in the Singhbhum Shear Zone of Eastern India. The activity concentrations were observed to vary within a wide range in most of the deposits, as is the case in most rocks of crustal origin. The uranium ore from these deposits were not of high ore grade (U concentrations ranged from 0.015 to 0.082%). Activity ratios of key daughter–parent pairs from the decay chains, viz. 226Ra/238U, 226Ra/210Pb, 231Pa/235U, 227Ac/235U, 230Th/238U, 234U/238U, 226Ra/230Th and 228Th/228Ra indicated migration/accumulation of uranium and radium in some samples. The 226Ra/230Th ARs suggested that the deposits were not closed to groundwater movement for a maximum time period of 8ky. Thiel plot of the 234U/238U vs. 230Th/238U activity ratios indicated uranium accumulation and complex processes of uranium redistribution.