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GEOREF RECORD

Three-dimensional crystal structures of illite-smectite minerals in Paleozoic K-bentonites from the Appalachian Basin

Douglas K. McCarty and Robert C. Reynolds
Three-dimensional crystal structures of illite-smectite minerals in Paleozoic K-bentonites from the Appalachian Basin
Clays and Clay Minerals (February 2001) 49 (1): 24-35

Abstract

The three-dimensional crystal structures of illite-smectite (I-S) in K-bentonite samples from the Appalachian Basin are characterized by rotational disorder in the stacking sequence of 2:1 illite layers, different proportions of n60 degrees rotations (as opposed to n120 degrees ) in the rotated layers, and layers with centrosymmetric trans-vacant (tv) octahedral sites that are randomly interstratified with noncentric cis-vacant (cv) layers. The proportion of cv interstratification in the I-S increases with tetrahedral Al and decreases with octahedral Mg and Fe content. The I-S minerals in the northern Appalachian basin K-bentonites are characterized by high (79% average) proportions of cv (Pcv) layers. In contrast, I-S from equivalent K-bentonites from the southern Appalachian basin has low Pcv values (38% average). These values do not correlate with expandability or rotational disorder. The geographic distribution of these I-S structural parameters may have resulted from possibly short-term, hot, and advective fluid migrations that differed in Mg concentrations and/or other physical and chemical parameters.


ISSN: 0009-8604
Coden: CLCMAB
Serial Title: Clays and Clay Minerals
Serial Volume: 49
Serial Issue: 1
Title: Three-dimensional crystal structures of illite-smectite minerals in Paleozoic K-bentonites from the Appalachian Basin
Affiliation: Texaco Upstream Technology, Houston, TX, United States
Pages: 24-35
Published: 200102
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 48
Accession Number: 2001-041951
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch map
Secondary Affiliation: Dartmouth College, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200113
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