A copper-zinc mineralization in Trolldalen, Lofoten, Northern Norway.

Abstract

From the previous it is most likely that even separated the various mineralizations in Trolldalen are related and contemporary. Allthough different minerals appear in the different veins, pyrrhotite, chalcopyrite and sphalerite are always present. It may also be noted that pyrite, a very common mineral in this paragenesis, is no where observed as a primary constituent. Due to replacement textures the following succession of crystallization is suggested. Appearing as sub. to euhedrale grains, partly replaced by the other sulphides the arsenopyrite seems to be the first mineral in the sequence. It is followed by a simultaneous crystallization of pyrrhotite and chalcopyrite. The pyrrhotite shows two mode of occurrence, as a massive variety with internal lamellae appear at one locality, while a granular type, but for one occasion without lamellae is seen elsewhere. Also a difference in magnetic properties seems to follow this division. The chalcopyrite contain frequent exsolution lamellae of cubanite. The latter appear as granular aggregates in the chalcopyrite fields. It is suggested that the formation of this granular cubanite started from solution formed when the chalcopyrite was corroded by pyrrhotite. Later on both the chalcopyrite and the cubanite have been replaced by pyrrhotite.