Polycomponent Interstratified Phyllosilicates in Dolomite Residuum and Sandy Till of Central Wisconsin
1980
Lim, C. H. | Jackson, M. L.
Clay minerals of four central Wisconsin soil parent materials containing highly interstratified layer silicates were difficult to identify in conventional Mg-glycerol X-ray diffraction (XRD) patterns. One group was from dolomite residuum (65% clay); another from sandy till (6% clay, with only small resolved XRD peaks). The Mg-saturated, glycerol-solvated clays of the former gave X-ray diffractograms with diffuse and continuous low-angle scatter ending with a dropoff at the (001) spacing of 7Å. Potassium saturation and heating at 400°C yielded an intense, sharp 10Å peak, identifying coincidence of XRD peaks for mica + vermiculite + smectite. Shoulders extending from the sharpened 10Å peak to the 7Å peak and toward low-angle spacings indicated the presence of chlorite. Incomplete collapse of interlayers at 550°C and the production of a 14.2Å peak following fusion in LiNO₃ at 300°C confirmed the presence of chlorite. Discrete kaolinite occurring in association with other phyllosilicates was revealed by the 11.2Å peak after Li saturation and DMSO intercalation. The X-ray diffractograms indicated short-range order in irregularly interstratified phyllosilicates occurring in ternary (3-component), quaternary (4-component), and quinary (5-component) mixtures. The quantitative mineralogy, as assessed by K content, cation exchange capacity (CEC), selective dissolution, and thermal methods, averaged 15% mica, 10% vermiculite, 25% montmorillonite, 5% chlorite, and 30% kaolinite.
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