minerals Article Carbon Sources and the Graphitization of Carbonaceous Matter in Precambrian Rocks of the Keivy Terrane (Kola Peninsula, Russia) Ekaterina Fomina 1,* , Evgeniy Kozlov 1 , Kirill Lokhov 2, Olga Lokhova 3 and Vladimir Bocharov 4 1 Geological Institute, Kola Science Centre, Russian Academy of Sciences, 14, Fersmana Street, 184209 Apatity, Russia;
[email protected] 2 Institute of Earth Sciences, Saint-Petersburg State University, 7/9, Universitetskaya Emb., 199034 St. Petersburg, Russia;
[email protected] 3 Institute for the History of Material Culture, Russian Academy of Sciences, 18, Dvortsovaya Emb., 191186 St.-Petersburg, Russia;
[email protected] 4 Resource Center for Geo-Environmental Research and Modeling (GEOMODEL), Saint-Petersburg State University, 1, Ulyanovskaya Street, 198504 St. Petersburg, Russia;
[email protected] * Correspondence:
[email protected]; Tel.: +7-921-276-2996 Received: 15 December 2018; Accepted: 3 February 2019; Published: 8 February 2019 Abstract: The Precambrian rocks of the Keivy Terrane reveal five types of carbonaceous matter (CM): Fine-grained, flaky, nest, vein, and spherulitic. These types differ in their distribution character, carbon isotope composition, and graphitization temperatures calculated by the Raman spectra of carbonaceous material (RSCM) geothermometry. Supracrustal rocks of the Keivy Terrane 13 contain extremely isotopically light (δ CPDB = –43 ± 3‰) carbon. Presumably, its source was a methane–aqueous fluid. According to temperature calculations, this carbon matter and the host strata underwent at least two stages of metamorphism in the west of the Keivy Terrane and one stage in 13 the east. The CM isotope signatures of several samples of kyanite schists (δ CPDB = –33 ± 5‰) are close to those of oils and oil source rocks, and they indicate an additional carbon reservoir.