ABSTRACT
Numerous small, noneconomic copper deposits are associated with syn-tectonic sandstones of Tertiary age in the south Pyrenean foreland basin. Copper, primarily as sulphides or oxides, replaces woody organic debris and earlier formed pyrite. Sulphide sulphur and organic carbon concentrations are generally low (<2 wt. %) and δ34S values are compatible with bacteriogenic derivation from Pyrenean evaporites, which suggests that Cu-rich fluids were introduced into reduced sediments during diagenesis. Mineralizing processes took place in two different periods: the first one related to the filling of the Jaca basin during erosion of Pyrenean basement and the second one related to the emplacement of a thrust ramp which provoked the erosion of the previously formed cupriferous sandstones.
