Transformation sequences of copper sulfides at Vielsalm, Stavelot Massif, Belgium

Bornite, chalcopyrite, idaite, covellite, yarrowite, spionkopite, anilite, digenite, djurleite, and chalcocite have been identified in quartz veins from the Vielsalm area. Stavelot Massif, Belgium. The identification of these copper sulfides is confirmed by electron-microprobe analyses. The association of primary sulfides indicates that the bornite-bearing quartz veins crystallized above 300-350 degrees C, whereas the chalcocite-bearing quartz veins crystallized below 200 degrees C. Relations among sulfides indicate the occurrence of two sequences of transformation, responsible of the formation of secondary sulfides: chalcocite-H double right arrow chalcocite-M double right arrow djurleite double right arrow low digenite or (anilite + djurleite) double right arrow yarrowite + spionkopite double right arrow covellite + oxidation minerals, and bornite double right arrow idaite + chalcopyrite double right arrow covellite + oxidation minerals. The crystallization of chalcocite-M, djurleite, and low digenite or (anilite + djurleite) took place between 103.5 and 72 degrees C. The associations idaite + chalcopyrite, yarrowite + spionkopite, and covellite + oxidation minerals, were produced under meteoric conditions. The source of Cu and of the other elements present in the quartz veins must be sought in the host chloritoid-bearing schists.