Reliability of K-Ar Dating of Clays and Silicifications Associated with vein Mineralizations in Western Europe

K-Ar ages were determined on fine fractions and one massive silicification associated with vein mineralizations in uranium, barium, fluorine and related base metals in Western Europe. The reliability of the potassic materials analysed, once the mineralogical and geochemical relationships to the low-temperature mineralization have been established, is demonstrated. The isotopic ages are concentrated between nearly 190 and 170 MA. This epoch corresponds to that of the rifting of the future Atlantic and Tethys oceans. This type of low-temperature mineralization thus seems to be better explained by extensional phenomena.