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GEOREF RECORD

Microstructure, mineralogy and chemistry of Cambrian glauconite pellets and glauconite, central U.S.A.

I. E. Odom
Microstructure, mineralogy and chemistry of Cambrian glauconite pellets and glauconite, central U.S.A.
Clays and Clay Minerals (October 1976) 24 (5): 232-238

Abstract

Glauconite pellets in the Cambrian of the central U.S.A. frequently contain two textural forms of glauconite-aggregate and oriented-which differ in both mineralogy and chemistry. The aggregate glauconite composes the bulk of most pellets and consists of crystals in a nearly random arrangement. The oriented glauconite occurs primarily as rims on the periphery of pellets. It has a honeycomb-like structure-the crystals are oriented with their c-axes tangent to the aggregate-textured cores. Scanning electron photomicrographs show that the aggregate and oriented textures grade one into the other. The aggregate glauconite has a 1 M structure and less than 5% expandable layers, whereas the oriented form has a 1 Md structure and approximately 10% expandable layers. The aggregate glauconite contains 5-8% more total iron oxides and 2-3% less Al (sub 2) O (sub 3) than the oriented glauconite. The b-cell dimension of individual samples increases nearly linearly with increasing octahedral Fe (super 3+) + F (super 2+) + Mg content. Chemical and crystallographic variations among various samples are, for the most part, related to the ratio of aggregate to oriented glauconite. The transition between the texture of the aggregate and oriented glauconite suggests that some glauconite pellets may form by concretionary growth. It is proposed that Cambrian glauconite pellets grew through the repetitive development of a smectite-like clay at the margin of pellets. The smectite was later altered, both chemically and texturally, first to the oriented and then to the aggregate-textured glauconite.


ISSN: 0009-8604
Coden: CLCMAB
Serial Title: Clays and Clay Minerals
Serial Volume: 24
Serial Issue: 5
Title: Microstructure, mineralogy and chemistry of Cambrian glauconite pellets and glauconite, central U.S.A.
Author(s): Odom, I. E.
Affiliation: North. Ill. Univ., De Kalb, Ill., United States
Pages: 232-238
Published: 197610
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 14
Accession Number: 1977-032079
Categories: Mineralogy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. tables, plates
N34°00'00" - N37°00'00", W92°00'00" - W88°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
Update Code: 1977
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