An investigation was carried out concerning the origin of carbon in the following pre-Cambrian materials from Finland: graphite, carbon-bearing schists, carbonaceous accumulations in phyllites including the suggested fossil Corycium enigmaticum Sederholm; shungite from Karelo-Finnish S.S.R. Geological and petrological descriptions of the materials investigated are given. CuO, V2O5, and MoO3 contents of the samples and the isotope ratios C12/C13 in carbon extracted from same are presented. Geological evidence and trace-element determinations make probable the division of carbon in these samples into organic and inorganic groups; the mass spectrometric C12/C13 determinations furnish definite proof of this and also final proof of the organic nature of the Corycium which thus is a real fossil of the Late Archean time, the oldest ever recorded with definite certainty.

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