Epigenetic graphitization in the basement of the Siberian craton - evidence of the migration of hydrocarbon-enriched fluids in the paleoproterozoic

Abstract

For the first time, diagnostics and structural studies of the сarbonaceous material (СM) of quartz-muscovite dinamoschists from schistase zones in biotite migmatites, pegmatites and diabases of the southern part of the Baikal ledge of the Siberian craton were performed. The сarbonaceous material is represented by clearly and microcrystalline graphite with residual hydrocarbon radicals. Native Ni, Sn, zincous Cu, intermetallic compounds of Fe-Ni composition, copper sulfides, rutile, monazite, and zircon were found in intergrowths with СM. The carbon isotopic composition is from -29.19 to -31.58‰, with the exception of CM from schistated diabase with δ13C = -24.93 ‰. The 40Ar/39Ar-dating of muscovite gave an age of 1947 ± 7.8 Ma, indicating a relationship between dynamometamorphism and the accretion of the Akitkan folded system with ancient craton complexes. It is concluded that the deposition of native carbon and metals is caused by the migration of essentially hydrocarbon fluid in the upper crustal formations.