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

Natalia Boeva,Anatoly Slukin,Nikolay Bortnikov,Elena Shipilova,Philimon Melnikov,Marina Makarova

doi:10.3390/min11111184

Abstract

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.

Highlights

All processes of destruction of parent rocks and formation of supergene minerals occur in close interaction with living and dead organic matter
Biofilms were studied by electron microscope, and minerals were identified by morphological features formed by biofilms
Laterites are the products of the complex cumulative effects of a variety of physical, chemical and biochemical forces

Summary

Introduction

All processes of destruction of parent rocks and formation of supergene minerals occur in close interaction with living and dead organic matter. The formation of minerals through biomineral films are material traces of the work done by the biota in the process of bauxite formation. In the process of lateritization, the parent and associated rocks containing an increased amount of certain chemical elements and minerals are concentrated and become economically profitable [1]. Bauxite is the ultimate weathering product of aluminosilicate rocks of all composition and genesis. Preserved in situ, it is called lateritic bauxite [1]. Lateritic bauxites crown the zonal profiles of the weathering crust. In the upper part of the profile under the soil layer, lateritic bauxites are affected by chemically active rainwater penetrating through the living foliage of the vegetation cover, soil, mortmass, and root system. An amorphous mass is formed, saturated with biota, from which biofilms of various compositions are formed [1]

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