A giant Palaeoproterozoic deposit of shungite in NW Russia: genesis and practical applications

Mineral-templated growth of natural graphite films

“…Numerous veins consisting largely of pyrobitumen or containing also quartz and carbonate can be observed throughout the Zaonega Formation as well as in overlying sedimentary and volcanic rocks (Melezhik et al, 2009;Melezhik et al, 1999). Pyrobitumen-rich intervals that are in places rich in silicates (Melezhik et al, 2004), are found in the contact zones of magmatic bodies, but also occur as layers within sedimentary successions. CM in the Zaonega Formation display a large overall range in δ 13 C org (-45 to -17 ‰) and a low average H/C-ratio (0.005-0.2), indicating various precursor materials and 6 a complex history of oil generation, migration, and subsequent thermal alteration (Buseck et al, 1997;Fillipov, 1994;Khavari-Khorasani, 1979;Melezhik et al, 1999).…”

“…Isolated pyrobitumen-rich intervals that do not associate with magmatic bodies are typically massive exhibiting cryptic fluidal textures and signs of multiphase, syndepositional micro-brecciation. These intervals appear to represent organic-rich sediment masses generated during the course of hydrocarbon migration that have been injected into the host sediment or expelled onto the sea-floor as mud-volcanos (Melezhik et al, 2004). The highsilica content (quartz, feldspars) of some pyrobitumen-rich rocks is likely related to wide-scale hydrothermal circulation and silica-leaching during hydrocarbon formation and migration.…”

7.6 Enhanced Accumulation of Organic Matter: The Shunga Event

“…Hanski, Michael M. Filippov, and Victor A. Melezhik The Shunga Event is defined as an episode of enhanced accumulation of organic matter that is inferred to be global and synchronous (Melezhik et al 1999a;Melezhik et al 2004). Numerous sedimentary formations that were all deposited broadly around 2000 Ma ago are characterised by high abundances of organic carbon (Table 7.3; Fig.…”

“…In the following text, this microstructural pattern is referred to as "maksovite-type matrix". Because the two major constituents of the rocks are quartz and pyrobitumen, such rocks were earlier termed the "organosiliceous rocks" (Melezhik et al 2004). Although currently a tendency exists to apply the term maksovite to any massive rock rich in organic matter, the rocks with the above-mentioned structural, textural, geochemical and mineralogical characteristics have been reported so far only from the middle part of the Zaonega Formation (Figs.…”

“…original meaning of this term has been frequently and arbitrarily modified, thus leading to misunderstandings and confusion (reviewed in Filippov 2000;Melezhik et al 2004;Filippov and Melezhik 2007). Most of the confusion resulted from Borisov's (1956) classification, which served industrial purposes, was solely based on the organic carbon content in any Palaeoproterozoic C org -bearing rocks known from the Onega Basin, and considered neither the nature of the host lithology nor the nature of the organic matter itself.…”