Distribution of trace elements in fracture fillings from the “Mina Fe” uranium deposit (Spain) by sequential leaching: implications for the retention processes

After a careful characterisation of the samples, the analytical data from each leaching step were statistically analysed and then interpreted in light of the mineralogical and geochemical features of the samples. Precise knowledge of the mineralogical distribution of trace elements by sequential leaching methods is quite complex, mainly due to cross-contamination throughout the different steps of the experiments. Thus, the results obtained suggest that U is retained as U-minerals, mainly oxides, closely associated with crystalline Fe-oxyhydroxides. Though Ce and La also form independent compounds, such as Ce oxides and La-Nd phosphates, they are mainly retained by the amorphous Mn-oxyhydroxides. However, the crystalline Mn-oxyhydroxides are the main sink for Ni and crystalline Fe-oxyhydroxides mainly retain P.