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An interstratified illite-smectite from Denchworth series soil in weathered Oxford Clay

Published online by Cambridge University Press:  09 July 2018

A. H. Weir  and
J. H. Rayner
A. H. Weir
Affiliation:
Rothamsted Experimental Station, Harpenden, Herts
J. H. Rayner
Affiliation:
Rothamsted Experimental Station, Harpenden, Herts
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Abstract

The very fine (<0·04 µm) clay fraction of a Denchworth series subsoil in weathered Oxford Clay has been investigated in detail. It contains a layer silicate mineral, almost free from impurities, that is a randomly interstratified mixture of approximately 45% expanding and 55% non-expanding interlayers with the following unit formula: Na0.33K0.29(Al1.41Fe0.34Mg0.26)(Si3.60Al0.40)O11. Computer-simulated diffraction patterns showed that experimental patterns are best matched when an average diffracting packet consists of between 4 and 5 2:1 layer silicate units. Correction of the chemical composition for external exchangeable ions associated with such small packets gives non-expanding interlayers a charge density of 0·69K/Si4O11 and expanding interlayers one of 0·57M+/Si4O11. The relationship between these values and those of mica and regularly expanding minerals is briefly discussed.

Type
Research Article
Information
Clay Minerals , Volume 10 , Issue 3 , July 1974 , pp. 173 - 187
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1974

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