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Abstract
A part of the North-Karelian uranium ores occurs in a certain quartzite horizon. The cementing material of quartzite contains locally goethite in abundance, and in addition pitchblende, fine-grained hematite, quartz, and sericite. These ores are clearly of sedimentary origin. A part of uranium ores occur within the zones of contact between quartzites (or conglomerates) and cutting dikes of uralite diabases. Pitchblende fills fractures in the rocks mentioned, and it is evidently mobilized from the sedimentary uranium ores.
The Jussarö ore field is characterized by abundance of granites, granodiorites, and quartz diorites. The iron ores contain 22–26% magnetite iron, 1.6–2.2% Mn, 0.12–0.25% TiO2 and 0.024–0.046% P. The structure of the ores is often schlieric, and they are surrounded by peculiar schlieric or banded rocks. Evidently the ores have been directly segregated from acid magmas, and they could be called late liquid magmatic.
The chromite ores in Kemi region are intimately related to ultrabasic rocks in the lowermost part of a great sheet-like basic and ultrabasic intrusion. They are clearly early liquid magmatic. The ores are strongly brecciated and auto-metasomatically altered. They contain 20% Cr2O3, and the ratio Cr: Fe = 0.81-1.87.