The findings imply that nanoparticles of gold and copper
maymigrate through the transported cover to the surface. Uraniumis converted to uranyl ions [UO2
2+] under oxidizing
conditions when migrating from ore bodies to the surface. The uranyl ions are absorbed on clay minerals,
because clay layers have a net negative charge,which needs to be balanced by interlayer cations. Nanoparticles of
Au and Cu and ion complexes of U are more readily absorbed onto fine fractions of soils containing clays, colloids,
oxides and organic matters. Thus, fine-grained soils enriched with clays, oxides and colloids are useful media for
regional geochemical surveys in regolith-covered terrains and in sedimentary basins