Some copper sulphideparageneses from the Raipas formation of Northern Norway.

Abstract

The Precambrian Raipas formation of Northern Norway contains copper deposits showing two distinct paraeneses. The first is a type common in the Scandinavian Precambrian and Caledonian ores, i.e. chalcopyrite-pyrite-pyrrhotite (the \"pytitic paragenesis\"). The other is much less common and consists of the association bornite-chalcopyrite-neodigenite-(chalcocite). This is termed the \"copper paragenesis\". The mineralogies of deposits showing these paragenetical types from Raipas areas in Vest-Finnmark are described, with the greatest emphasis on two deposits showing the \"copper paragenesis\". Especial attention is given to the question of the origin of the Cu2s mineral. It is concluded that this is mainly neodigenite and most probably of hypogene origin, an important point when considering the continuation of the ores in depth. The relations between the two paragenesis are briefly discussed, and different origins are suggested. The occurence of a cobalt sulphide in the ore at Raipas mine, Alta, indicates that the ores of the copper paragenesis belong to the world-wide group of Cu-Co-U ores and it is suggested that the possible occurence of the third metal should not be overlooked.