Mineral parageneses of the massive sulfide ore bodies of the Caledonides of Norway

Abstract

Two types are distinguished in the massive sulfide ores of the Caledonian mountain chain in Norway, characterized respectively by the dominance of pyrite and pyrrhotite. The pyritic type, containing some sphalerite and chalcopyrite (galena and pyrrhotite minor or absent), commonly occurs as concordant bodies in schists of the same general metamorphic grade (epidote-amphibolite or amphibolite facies), exhibits coarser textures and directed fabrics in areas of higher metamorphism, and is believed to be pre- or synorogenic, with the present composition and texture reflecting the effects of Caledonian regional metamorphism. The pyrrhotite type, containing variable amounts of chalcopyrite with subordinate sphalerite (pyrite minor or lacking), is essentially a breccia ore occurring as flat irregular plates generally concordant with the layering of the enclosing schists but in detail exhibiting cross-cutting features, and may have been formed by late or post-orogenic palingenic processes.