Biofilms and Biominerals in the Lateritic Weathering Crust as Exemplified by the Central Bauxite Deposit (Siberian Platform, Russia)

The study of lateritic bauxite by electron microscopy revealed abundant products of interaction between organic matter and minerals. Abundant biomineral films of different genesis and composition were found, including Al, Fe, Al-Fe, Al-Si, Al-Fe-Si, sorbed rare and rare-earth elements (REE). The evolution of these films from amorphous to crystallized and the conversion into druse crystals of gibbsite, hematite, kaolinite etc. was traced. New data were obtained on mineralization of deposits of wood, roots, biofilms and bacteria in tropical conditions. Mono- and multilayer films were identified. Different composition biofilms occurred before and after seasonal monsoon rains. The mineral composition of the films is influenced by micro-local conditions and the introduction of chemical elements, including rare and rare-earth elements, with capillary water during the dry seasons. The products of biomineralization are microscopic in size, but are of universal and global importance to all weathered rocks and associated bauxite deposits.