REE Concentrations in Zircon and the Origin of Uranium in the Unconformity-related U Deposits in the Athabasca Basin,

Summary Rare Earth elements (REE) in zircons from the Athabasca Basin sandstone and its crystalline basement and in uraninites from basement- and sandstone-hosted unconformity-type uranium deposits were analyzed using laser ablation inductively-coupled plasma mass spectrometer. Considering that REE and uranium have similar geochemical properties, the purpose of this study was to distinguish the initial uranium source for the deposits in the basement. The REE patterns of sandstone- and of basement-hosted zircons are similar, showing strong enrichment in heavy REE, whereas the uraninite patterns are more variable and typically are “hump”shaped, which reflects the greater incompatibility of the heavy REE into the uraninite structure. The REE concentrations in basement-hosted zircons are significantly higher that those in sandstone-hosted zircons, typically by one order of magnitude. The concentrations of REE in uraninites are similar to those in sandstone-hosted zircons, which appear to be the most likely source of uranium.