Epigenetic Graphitization in the Basement of the Siberian Craton as Evidence of the Migration of Hydrocarbon-enriched Fluids in the Paleoproterozoic

Resumo

This paper reports on diagnostic and structural studies that were first carried out for carbonaceous material of quartz–muscovite dynamoschists from the schistosity zone in biotite migmatites, pegmatites, and diabases of the southern part of the Baikal ledge of the Siberian craton. The carbonaceous material is represented by phanerocrystalline and microcrystalline graphite with residual hydrocarbon radicals. Native Ni, Sn, zincous Cu, Fe–Ni compounds, sulfides of Cu, rutile, monazite, and zircon were revealed in the intergrowths with carbonaceous material. The carbon isotopic composition ranges from –29.19‰ to –31.58‰, except for carbonaceous material from the schistocity diabase, where δ¹³C = –24.93‰. ⁴⁰Ar–³⁹Ar dating of muscovite gave an age of 1947 ± 7.8 Ma pointing to the relation between dynamic metamorphism with accretion of the Akitkan fold system and the ancient complexes of the craton. It was concluded that the deposition of native carbon and metals was caused by migration of essentially hydrocarbonate fluid in the formations of the upper crust (Fig. 4, Table 1).