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Compositional and structural features of the octahedral sheet in mixed-layer illite/smectite from bentonites

Javier Cuadros and Stephen P. Altaner
Compositional and structural features of the octahedral sheet in mixed-layer illite/smectite from bentonites
European Journal of Mineralogy (February 1998) 10 (1): 111-124

Abstract

XRD, EPMA, TG and IR techniques were used to study mixed I/S from 28 bentonite samples from Ordovician to Pliocene age in the USA and Europe, in order to identify the structural and chemical evolution of the octahedral sheet during the reaction of smectite to illite. Al and Fe exchange occurs in the octahedral sheet; with increasing illite, the I/S octahedral sheet becomes more Al-rich and Fe-poor, and Mg approaches a value of 0.5 per O (sub 20) (OH) (sub 4) . These trends are attributed to a balance of electrostatic and structural controls. Smectite I/S tends to be cis-vacant and becomes increasingly trans-vacant with increasing illitization. Cis-vacant I/S dehydroxylates at a higher T (650 degrees C) compared to trans-vacant I/S (550 degrees C). Octahedral Fe shows a tendency towards segregation; Fe segregation increases with increasing development of trans-vacancies.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 10
Serial Issue: 1
Title: Compositional and structural features of the octahedral sheet in mixed-layer illite/smectite from bentonites
Affiliation: University of Illinois, Department of Geology, Urbana, IL, United States
Pages: 111-124
Published: 199802
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 42
Accession Number: 1999-014521
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 5 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199906
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