Layer charge of expandable 2:1 phyllosilicates in selected parent materials of some Canadian soils

Abstract

We investigated the nature of the layer charge of the different expandable 2:1 phyllosilicates present in glacial till, marine sediment, beach sand, loess, weathered sandstone and acid shale parent materials of selected soils from the arctic, alpine and interior plateau regions of Canada. Detailed characterization of 2:1 clay minerals, using the layer charge, was done by intercalation of the clay fractions with different chains (nc = 6 to 18) of n-alkylammonium cations (AC).Results indicated that AC were able to detect a mixture of smectite and vermiculite that was not detected by previous studies, using the glycerol (GLY) and ethylene glycol (EG) solvation techniques. The mean unit cell layer charge [in mol(+)/Si,Al)4O10)] varies from 0.30 to 0.39 for the smectite and from 0.71 to 0.74 for vermiculite. Vermiculite from the beach sand is trioctahedral in which most of the charge is located in the tetrahedral sheet, while vermiculite in the weathered sandstone is dioctahedral in which part of the charge originates from the octahedral layers. The presence of smectite, associated with the weathering of chlorite and an expanding component associated with the degradation of biotite, was also observed. Key words:n-alkylammonium cations, mean layer charge, 2:1 phyllosilicates