Lead isotope behaviour in a polyphased Pb-Zn ore deposit: Les Malines (Cévennes,France)

Les Malines Mine (Cévennes, France) provides an example of Pb-Zn ore bodies that underwent a polyphased evolution. On the Pb-Pb diagram, experimental points of the Les Malines ore types always plot in the central part of the field defined for the Cévennes metallogenic province. This homogeneity, the similarities with the Pb isotopic compositions of the surrounding rocks and the comparison with Pb isotopes evolution of whole rocks and minerals of the neighbouring continental lands, which emerged during Triassic and Liassic times, rule out the participation of extraneous Pb during the successive concentration stages and agree with an initial metal stock transformed and mobilized in a Pb closed system. Hercynian K-feldspars are the main source of the Pb preconcentrated during Triassic times. Most of the Cévennes Pb-Zn ore bodies could derive from this Triassic metal stock; nevertheless, local Pb isotopic anomalies suggest hydrothermal sources for some Pb-Zn ore bodies located along the Cévennes fault.