Chapter 17 



The Role of Microbes in Genesis and 

 Weathering of Sulfur Deposits'' 



S. I. KUSNETZOV 



A, 



^boiit 90 per cent of sulfur deposits of the earth are of sedi- 

 mentary origin. Very often their genesis is connected with the 

 activity of microbes of the sulfur cycle in nature under marine 

 conditions. Epigenetic and syngenetic genesis of sulfur deposits 

 take place also under recent conditions. We have studied their 

 microbiology in the USSR (6a). 



SYNGENETIC GENESIS (Fig. 1) 

 The sediments of Balkasch sea and of the sea of Tambukan 

 contain quartz sand, Calcite and Dolomite with elementary sulfur 

 up to 0.25 per cent (Table 1) which originates mostly from 

 desulfurication. 



02 

 i_l q \ Precipitotion of CoCOs 



"2^ 1 from photosynthesis and 



f. 



desulfurication 



-X 



Desulfurication within 

 the sediment 



xxxxxxxxxxx 



[:-':V.":;".| Oxidation of H2S and precipitotion 



of elementory sulfur by Th. thioparum 



Fig. 1. Sulfur beds of syngenetic origin (scheme). 



The sulfates are transformed to carbonates which are settled 

 together with sulfur and other sedimentary materials. Desulfur- 

 izing bacteria are very common in saltwater lakes, especially in 

 the surface layers of the mud (Table 2). 



Experiments with sulfur isotopes have shown that in Solenoje 



* Translated from German into English and presented by W. Schwartz. 



172 



