60 V. A. SOKOLOV 



for example, o °C. For example, the reaction between NO and 0> to form NO2 

 goes 100 times faster at -184 C than at o C [17]. 



To the next group of gases, which are given off proportionately to the rise 

 in temperature, belong CF4, Xe, CoHi, C'Hc, NjO (boiling points of from 

 — 83-6 C for N2O to —128 °C for CF4). Within this range of temperature a 

 number of other compounds also go over to the gaseous state but they are not 

 very stable chemically. 



With a further rise in temperature CO2, HoS, C3H8, CO, NH3 etc. will have 

 been given off. Later still, when the temperature rose still further, water vapour 

 was given off and underwent various chemical reactions. 



Among these reactions we may mention the formation of hydrogen by the 

 action of water on rock formations and, in particular, on the more reduced 

 compounds of iron and other metals. The reactions whereby the hydrocarbons, 

 C1-C4 and higher, are synthesized by the interaction of hydrogen with CO2 and 

 CO are extremely important. 



The interaction between CO2 and the silicates, which leads to the formation 

 of carbonates, has played a great part in the history of the CO2 in the atmosphere. 



Like the temperatures, so the conditions under which gases were given oflF, 

 were different for the crust of the Earth and the deeper layers. At the time when 

 gases which had previously been condensed were being given off from the 

 superficial layers, the temperature was so high in the deep layers that water 

 vapour was already under considerable pressure. However, if there was to be 

 any large-scale migration of gases from such great depths, suitable vents had to 

 be formed in the crust of the Earth to serve as paths for this migration. This 

 could only occur after heating of the deeper-lying layers had allowed the 

 development of tectonic processes. 



Volcanic gases provide visible evidence of the way in which chemical processes 

 of gas formation in the deep zones of the crust of the Earth are going on at 

 present. Apart from water vapour, the main substances composing these and 

 other gases given off by magmatic formations are CO2, N2, CO, Ho and CH4 

 as well as other gases (HjS, SO2, CI2, HCl, NH3 etc.). 



Study of the composition of gases contained in cooling magmatic formations, 

 without heating them, has shown that they contain mainly CO2 and N2. In 

 some cases, however, CH4 and heavier hydrocarbons have been found, and also 

 H2 and other gases. In this connection, considerable interest attaches to the 

 emissions of gas recently discovered in the Khibin massif in the Kola peninsula. 

 Studies of the composition and distribution of the eruptive formations found 

 here (by A. Kravtsov, V. A. Sokolov, M. G. Gurevich, M. M. Elinson, L A. 

 Petersilé, A. S. Fridman, workers in the apatite mines and others), have demon- 

 strated the presence of methane and heavier hydrocarbons and also hydrogen. 

 The emission of jets of hot gases (CH4, H2, etc.) is sometimes observed in these 

 parts. CH4, C2H(„ C3H8 and H2 are also very often met with in low concen- 

 trations in the eruptive formations of the neighbourhood. In some specimens 

 small quantities of bituminous substances were observed. A consideration of 

 the physico-chemical and geochemical conditions prevailing argues in favour of 

 the magmatic origin of these gases. 



