By analogy with the behaviour of Ra, Th and U it can be suggested that Pb, owing to its large mobility, was also fed to the magma by fluids. Many of the above authors attempt to explain these "fictitious" ages by resorting to the mixing of several sources of magma containing different amounts of Rb, Sr, and Sr immediately before the formation hardens. Geologists have tried various zircon treatments, including abrading the outer surfaces of the crystals, which are typically a tenth of a millimeter across, or leaching the crystals with strong acid.
Some are much shorter. Geologists extract the appropriate minerals from the rock in this case, zircon crystals and use a technique called mass spectrometry to figure out the relative amounts of uranium and lead in the zircon. Thus its radiometric age would tend to decrease rapidly with time, and lava emitted later would tend to look younger.