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Textures and polytypes in vermiform kaolins diagenetically formed in a sandstone reservoir; a FIB-TEM investigation

Jun Kameda, Kazuko Saruwatari, Daniel Beaufort and Toshihiro Kogure
Textures and polytypes in vermiform kaolins diagenetically formed in a sandstone reservoir; a FIB-TEM investigation
European Journal of Mineralogy (May 2008) 20 (2): 199-204

Abstract

Focused ion beam (FIB) sample preparation was applied to vermiform kaolin minerals to investigate by TEM the morphological evolution and mechanisms of kaolinite-to-dickite transformation during burial diagenesis. A core sample of a K-feldspar bearing arkosic sandstone, collected from the Brent Group sediments of the Froy hydrocarbon reservoir, Norwegian continental shelf, North Sea, was studied. Two types of vermiform aggregates were analyzed: 1) porous aggregates of fine lamellar crystals or intercalations of blocky and lamellar crystals, and 2) aggregates of densely packed hexagonal crystals. Electron diffraction (ED) revealed that aggregates of the first type are composed of pure one-layer kaolinite, whereas those of the second type consist of pure two-layer dickite. The two polytypes never coexist within the same aggregate. Furthermore, ED patterns of kaolinite and dickite are almost streak free, indicating a very low density of stacking faults. These observations suggest that the kaolinite-to-dickite transition in the pores of sandstone reservoir during burial diagenesis takes place by a dissolution-precipitation process rather than by a solid-state process. Blocky kaolinite, grown epitaxially on the (001) surface of muscovite, was also found in the specimen.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 20
Serial Issue: 2
Title: Textures and polytypes in vermiform kaolins diagenetically formed in a sandstone reservoir; a FIB-TEM investigation
Affiliation: University of Tokyo, Tokyo, Japan
Pages: 199-204
Published: 200805
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 20
Accession Number: 2008-086479
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N51°00'00" - N61°10'00", W04°00'00" - E11°00'00"
N58°00'00" - N71°00'00", E04°00'00" - E31°00'00"
Secondary Affiliation: Universite de Poitiers, FRA, France
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200826
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