The significance of microbiological processes in lakustrine manganese ore formation

Summary

The role of microorganisms in the formation of lakustrine manganese ore is manifested both in reducing processes of Mn⁴⁺ into Mn²⁺ and in oxidizing the latter into Mn⁴⁺.

Oxidizing processes with participation of microorganisms, mainly Metallogenium, take place under physico-chemical conditions corresponding to manganese stability against chemical oxidation. The use of methods of selective culture technique elective media, quantitative determination on membrane filters and electron microscopic analysis of the ore from Punnus-Järvi Lake have shown direct participation of manganese oxidizing microorganisms in the formation of concretions. Peculiar morphology of these organisms contributes to retention and binding of manganese oxides on the surface of concretions. Data on ore-forming role have been experimentally confirmed: with the use of Metallogenium concretions of manganese oxides were obtained in laboratory which had a size of 2–5 mm. In tests with chemical reaction with a solution in the absence of microorganisms no formation of concretions took place.

The data considered show that ore-forming activity of microorganisms is substantially manifested at principal geochemical stages of ore-formation, namely, in sedimentation and diagenesis.