Boreskov

PP‐64BIOMARKERS IN PRECAMBRIAN KARELIAN SHUNGITESShanina S.N., Golubev Ye.A., Burdelnaya N.S.Institute of Geology, 54, Pervomaiskaya st., 167982, Syktyvkar, RussiaThe results of elemental analysis, composition of normal and iso‐alkanes, polycyclichydrocarbon biomarkers in Karelian shungite rocks with various content of organic carbonand PT‐conditions of organic substance formation are presented. Earlier similar researcheswere carried out basically for low‐carbon shungite rocks (Сorg < 35 %) [1‐3]. Thus, bitumoid’sfrom high‐carbon shungites (Сorg > 60 %), owing to their low concentrations, were studiedonly by magnetic resonance and infrared spectrometry [4].It was established, that distribution of n‐alkanes differs for various types of deposits. Forexample bimodal distribution of n‐alkanes with C 17 ‐C 19 and C 21 ‐C 23 maximum was fixed forthe higher anthraxolite from Shunga deposit. Similar distribution was established in lidite,shungite rock with lower organic carbon content (3 %) where dominated С 17 and С 21 n‐alkanes. Obtained data confirm a similarity source of organic substance in various types ofshungite rocks within the Shunga deposit [4, 5].In samples from Zazhogino and Chebolaksha deposits domination of С 21 ‐С 23 n‐alkaneswas not established. It is connected with accumulation of small molecular weight n‐alkanesduring thermal destruction of their high‐molecular homologs, since the temperaturesinfluenced on organic substance of Zazhogino and Chebolaksha deposits, were considerablygreater, than in Shunga deposit.The low contents of iso‐alkanes in the higher anthraxolites were observed. The(Pr+Ph)/(n‐C 17 +n‐C 18 ) coefficient is about 0.5 in the higher anthraxolites, and in III‐type ofshungite it increased up to 1. The iso‐alkanes content increase in comparison with normalalkanes also confirm to a high thermal degree of shungite carbon from Zazhogino andChebolaksha deposits and/or theirs bacterial oxidation.The results of alkanes researches indicate a significant change of initial hydrocarboncomposition under heating. It does not allow using their distribution for determine ofshungite substance source.Among polycyclic biomarkers steranes and hopanes were identified [5]. It wasestablished, that biomarkers composition of organic substance in various types of shungite is247