Mass transfer around the Uzer fault: a proximal source for the Cevenole Pb-Zn mineralisation.

Studies have been carried out of microstructures and related fluid inclusions in the MM1 and BA1 boreholes along the Azer fault in France. The results show that during the Triassic, the Cevenole margin was flushed by diluted waters with remaining circulating fluids at BA1 being halite-contaminated. The development of fluid-assisted structures in sediments shows that the fault was an avenue for fluids. Also, hot saline fluids partly originating from the deep basin percolated upward through cracks. At the base of BA1, the replacement of anhydrite by dolomite during burial marks the thermal reduction of sulphates by CH4 flowing up from Stephanian sediments. The dolomitised and silicified evaporites observed at BA1 and MM1, along with related sulphides, are geochemically similar to the Cevenole mineralisation. The source rocks for Pb-Zn ores can be found on continental margins, particularly along growth faults.
Studies have been carried out of microstructures and related fluid inclusions in the MM1 and BA1 boreholes along the Azer fault in France. The results show that during the Triassic, the Cevenole margin was flushed by diluted waters with remaining circulating fluids at BA1 being halite-contaminated. The development of fluid-assisted structures in sediments shows that the fault was an avenue for fluids. Also, hot saline fluids partly originating from the deep basin percolated upward through cracks. At the base of BA1, the replacement of anhydrite by dolomite during burial marks the thermal reduction of sulphates by CH4 flowing up from Stephanian sediments. The dolomitised and silicified evaporites observed at BA1 and MM1, along with related sulphides, are geochemically similar to the Cevenole mineralisation. The source rocks for Pb-Zn ores can be found on continental margins, particularly along growth faults.