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GEOREF RECORD

The structure and diagenetic transformation of illite-smectite and chlorite-smectite from North Sea Cretaceous-Tertiary chalk

H. Lindgreen, V. A. Drits, B. A. Sakharov, H. J. Jakobsen, A. L. Salyn, L. G. Dainyak and H. Kroyer
The structure and diagenetic transformation of illite-smectite and chlorite-smectite from North Sea Cretaceous-Tertiary chalk
Clay Minerals (September 2002) 37 (3): 429-450

Abstract

Illite-smectite (I-S) mixed-layer minerals from North Sea oil fields and a Danish outcrop were investigated to determine the detailed structure and the diagenetic clay transformation. Clay layers in the chalk and residues obtained by dissolution of the chalk matrix at pH 5 were investigated. The phase compositions and layer sequences were determined by X-ray diffraction (XRD) including simulation with a multicomponent program. The structural formulae were determined from chemical analysis, infrared (IR) and (super 27) Al NMR spectroscopies and XRD, and the particle shape by atomic force microscopy (AFM). A high-smectitic (HS) I-S phase and a low-smectitic (LS) illite-smectite-chlorite (I-S-Ch) phase, both dioctahedral, together constitute 80-90% of each sample. However, two samples contain significant amounts of tosudite and of Ch-Serpentine (Sr), respectively. Most of the clay layers have in well Baron 2 may have a sedimentary origin. The HS and LS minerals are probably of detrital origin. Early diagenesis has taken place through a fixation of Mg in brucite interlayers in the LS phase, this solid-state process forming di-trioctahedral chlorite layers. During later diagenesis involving dissolution of the HS phase, neoformation of a tosudite or of a random mixed-layer trioctahedral chlorite-berthierine took place. In the tosudite, brucite-like sheets are regularly interstratified with smectite interlayers between dioctahedral 2:1 layers, resulting in di-trioctahedral chlorite layers.


ISSN: 0009-8558
EISSN: 1471-8030
Coden: CLMIAF
Serial Title: Clay Minerals
Serial Volume: 37
Serial Issue: 3
Title: The structure and diagenetic transformation of illite-smectite and chlorite-smectite from North Sea Cretaceous-Tertiary chalk
Affiliation: Geological Survey of Denmark and Greenland, Clay Mineralogical Laboratory, Copenhagen, Denmark
Pages: 429-450
Published: 200209
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 40
Accession Number: 2003-060393
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch map
N51°00'00" - N61°10'00", W04°00'00" - E11°00'00"
Secondary Affiliation: Russian Academy of Science, RUS, Russian FederationUniversity of Aarhus, DNK, Denmark
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200319
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