Mixed-layer illite-smectite in the Kinne

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• journal_title：Clay Minerals
• Contributor：P. Somelar ; K. Kirsimäe ; J. Środoń
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2009-
• Format：text/html
• Language：en
• Identifier：10.1180/claymin.2009.044.4.455
• journal_abbrev：Clay Minerals
• issn：0009-8558
• volume：44
• issue：4
• firstpage：455
• section：Articles

摘要

<p id="p-1">The composition and particle morphology of diagenetic mixed-layer illite-smectite (I-S) in the shallow buried Ordovician Kinnekulle K-bentonite were studied to understand the process of illitization in the Baltic Basin. The same K-bentonite bed from 12 different locations in the Basin was sampled and analysed by means of X-ray diffraction (XRD), atomic-force microscopy (AFM) and K-Ar dating. Illite-smectite in the samples was identified as a highly illitic R1 type illite-smectite vermiculite (high-charge smectite) mixed-layer mineral with 63–78% illitic layers. Illitesmectite was characterized by log-normally distributed thin particles with an area-weighted mean thickness varying from 1.9 to 3.6 nm and 2.1 to 3.8 nm by XRD-PVP and AFM analysis, respectively. The K-Ar diagenetic ages of the mixed-layer minerals suggest an illitization age of 370 to 420 Ma that agrees with the latest phase of the Caledonian orogeny. Illitization of the Kinnekulle bentonite was probably driven by the intrusion of K-rich fluids. p>