Conditions for Appearance of Life on Earth 69 



methods of analysis, is constantly being found in small amounts (sometimes to 

 10%) in combustible gases [29, 30]. 'By no means always', — wrote V. I. Ver- 

 nadskii, 'are hydrocarbons connected with life. There exists methane, which 

 rises from the deeper sections of the Earth's crust ... It is in regard to 

 methane, in particular, that the exclusive connection with hfe is doubtful, since 

 this light gas has properties similar to those of hydrogen. Its known syntheses 

 in the laboratory are extraordinarily varied and often independent of organic 

 compounds. There must be analogous processes in magmas'. ([31], p. 133). 



Lately, thanks to the investigations carried on by V. A. Sokolov, the magni- 

 tude of incessant addition of methane from the depths of the Earth into the atmos- 

 phere has become known. V. A. Sokolov has estimated the annual addition of 

 methane to the atmosphere from oil and gas deposits and volcanoes to be about 

 100 million tons [32]. Even if we were to take a figure ten times less, it would 

 appear that, during a very short geological period of 100,000 years, the atmos- 

 phere has received an amoimt of hydrocarbons many times more than the known 

 and estimated oil resources on the Earth. In this aspect, the accumulation of 

 oil appears to be a secondary resulting effect of the grandiose process of ascen- 

 sion of gaseous hydrocarbons, together with other gases, from the depths of the 

 Earth. 



THE THERMAL CONDITIONS FOR THE FORMATION OF 



OIL AND THE CHANGE IN ITS COMPOSITION 



IN THE EARTH'S CRUST 



Thus, the tectonic regularities of oil and gas distribution (in area) in the 

 Earth's crust, the wide vertical range of hydrocarbon migration, and, finally, 

 the geochemical association of petroleimi with gaseous hydrocarbons, hydrogen, 

 nitrogen and heUum, throw Hght on the origin of oil and gas. The hydrocarbons 

 rising up out of the depths of the Earth are of a primary inorganic origin. 

 Together with methane, the hydrocarbon stream contains heavier, composi- 

 tionally more complex hydrocarbons which are detained in the porous rock of 

 the sedimentary cover, accumulating in the form of the pecuhar gas mixture of 

 the so-called condensate pools (see above) and in the form of methane petroleum, 

 i.e., petroleum composed almost exclusively of saturated hydrocarbons. Judging 

 by the physical-chemical equilibrium of hydrocarbons studied by S. P. Obryad- 

 chikov and A. V. Frost, methane petroleimi forms at a temperature of 200-350° 

 [33, 34]. The further change in the composition of petroleum in the Earth's crust 

 consists chiefly in the differentiation of hydrocarbons and removal of the lightest 

 fractions, which are the richest in hydrogen; correspondingly, the petroleum is 

 enriched with naphthenes, isoparaffins, and heavy components. Together with 

 the differentiation, a certain oxidation of the petroleum takes place (the appear- 

 ance of naphthene acids, bases, resin), and also its sulphuration in connection 

 with the Ufe activity of bacteria and the dissolution in petroleum of the products, 

 mostly of plant origin (such as porphyrins and phytosterol), contained in pet- 

 roliferous rocks [35]. Porphyrins, to which such great importance was attached 

 by the advocates of the biogenic origin of petroleum, are practically absent in 



