Transformation of Chlorites by Primary Biological Agents—A Synthesis of X-ray Diffraction Studies

Abstract

Chlorites in the bio interaction zone (or rhizosphere soils) are transformed by bacteria, fungi and mosses into expanding 2:1 minerals with different cation fixation capacities. Some of the new clays are smectitic, expanding with glycol treatment in the Ca-saturated state, while others have a high intensity 001 peak unchanged by glycol treatment. Most of all, potassium saturation results in different hydration states in mixed layered phases or as individual illitic units or minerals indicating dissimilarity in charge site and intensity on the 2:1 layers of the original chlorites. However, the overall pattern is that of the transformation of high temperature chlorite to expanding clay minerals with high exchange capacities. Biotic processes appear to modify chlorites in a rather homogeneous manner compared to the formation of interstratified minerals common in the water-rock interaction pathway. These high charge expanding clays left after the biologically mediated reactions with chlorites are strong potential sites for cation (e.g., magnesium and potassium) capture and storage to supply the nutritional requirements of plants and organisms.