The mobility of the REE, U and Th in geological environments in Idaho and their relevance to radioactive waste disposal

Investigation of natural analogues of radioactive waste disposal environments in eastern central Idaho generally reveals minimal mobility of the elements Th, U and REE. The mineral allanite, containing Th and REE, is altered by hydrothermal solutions, but these elements are retained in secondary phases. The contents of U, Th and REE in present-day thermal waters in the area are low (ng l-1 range). However, the apparent high mobility of Th and REE during the formation of the Lemhi Pass Th-REE deposits indicates that conditions may exist where REE and actinides can be mobilized by aqueous fluids in the Earth's crust. (orig.)