En mikroskopisk undersøkelse av en del av Røros-malmene.

Abstract

A microscopic examination of a collection of polished sections from some of the ores in the Røros area was carried out and the different ore minerals were described. The replacement processes and the age sequences of some of the ore minerals are described for each of the examined ore occurrence, and the different occurrences are compared. The frequent occurences of valleriite and cubanite gives a minimum temperature for the crystallisation of the copper minerals in most of the ores. Chalcopyrite often can be seen to replace pyrrhotite and furthermore, frequently the chalcopyrite occurs as thin veins in cataclastic minerals, both ore minerals and silikates. These observations lead to the conclusion that in most of the ores in the Røros area, the solutions containing copper came through cracks and cataclastically deformed parts of the pyrrhotite-sphalerite ores; and that the copper minerals, at least to some extent, were precipitated by the reactions of these solutions with the pyrrhotite. The finding of pentlandite in the ores in the Lossius mine fields indicates that these ores are of liquidmagmatic origin, thus differentiating these ores from the oter examined ores in the Røros area.