Geochemical exploration research in regolith-covered terrains in
China has made great progress both in migration mechanisms and
methods during the latest 20 years. Nanoparticles of Cu and Au were
widely observed in gases, soils and ores, because these metals occur as
native forms whereas U occurs as complex uranyl ions in regolith. This
implies that the migration mechanism for different metal elements may
be different. Nano-crystals of Cu and Au, formed and liberated from the
ore bodies, may migrate with an ascending flow of gases upward to the
surface. On arriving at the surface, some of the particles persist in the
soil gases and other particles are trapped by soil geochemical barriers
such as clays, oxide coatings and colloids. Uranium occurs as complex
uranyl ions under oxidizing conditions while migrating from ore bodies
to the surface and the ion complexes are absorbed onto clay minerals