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Mixed-layer kaolinite-illite-vermiculite in North Sea shales

Published online by Cambridge University Press:  09 July 2018

B. A. Sakharov
Affiliation:
Institute of Geology, Russian Academy of Sciences, Pyzhevsky per D.7, 109017 Moscow, Russia
H. Lindgreen
Affiliation:
Clay Mineralogical Laboratory, Geological Survey of Denmark and Greenland, Thoravej 8, DK2400 Copenhagen NV, Denmark
A. L. Salyn
Affiliation:
Institute of Geology, Russian Academy of Sciences, Pyzhevsky per D.7, 109017 Moscow, Russia
V. A. Drits
Affiliation:
Institute of Geology, Russian Academy of Sciences, Pyzhevsky per D.7, 109017 Moscow, Russia

Abstract

The finest fractions of Upper Jurassic shales from the North Sea and onshore Denmark contain 80–90% of an illite-smectite-vermiculite (I-S-V) mixed-layer mineral and, in addition a phase which has X-ray diffraction (XRD) peaks at 7.20–7.26 Å and 3.56–3.58 Å in air- dried and glycolated specimens. This phase may be a fine kaolinite with a small thickness of coherent scattering domains (CSDs) or alternatively a mixed-layer mineral which has kaolinite as the dominant component. For one sample from the Norwegian well 9/4-3, these alternatives are investigated using the multi-specimen method by which agreement between the experimental pattern and the pattern calculated for one and the same structure is obtained for each of several specimens saturated with different cations and with/without glycolation. It is demonstrated that the modelled XRD patterns for a kaolinite-illite-vermiculite (K-I-V) structure having 0.94 kaolinite, 0.03 illite and 0.03 vermiculite layers and random alternation fit the experimental patterns.

Information

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1999

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