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Characterization of illitization of smectite in bentonite beds at Kinnekulle, Sweden

Atsuyuki Inoue, Takashi Watanabe, Norihiko Kohyama and Ann Marie Brusewitz
Characterization of illitization of smectite in bentonite beds at Kinnekulle, Sweden
Clays and Clay Minerals (June 1990) 38 (3): 241-249


Structure, morphology, and chemical composition of illite/smectite (I/S) containing 30-50% smectite layers (% S) from Kinnekulle bentonites, Sweden, of diagenetic origin were examined using X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Interlayer arrangements of I/S changed from random interstratification to short-range ordered at about 40% S. The transition from random to ordered structure proceeded continuously as reflected by the gradual decrease in probability of two smectite neighbors (P (sub ss) ) towards zero. TEM observations of water-dispersed samples that had not been cation-exchanged showed that the I/S consisted dominantly of flakes coexisting with laths having a length/width ratio of about 4, regardless of % S. The thickness of the I/S particles ranged from 30 to 100 Aa, and no systematic variation in thickness was detected with decreasing % S. The chemical composition of the I/S also changed continuously with decreasing % S. These observations suggest no dissolution of smectite layers and no recrystallization of illite layers during the formation of the I/S in these bentonites; rather, cationic substitutions occurred within a smectite precursor (termed a solid-state transformation mechanism). A comparison of interlayer order, particle texture, and chemistry of the I/S from various types of rocks suggests that the mechanism of smectite-to-illite conversion in the range 100% S-30% S was related to the porosity and permeability of original rocks. The solid-state transformation mechanism appears to have predominated in rocks of low porosity and permeability.

ISSN: 0009-8604
Serial Title: Clays and Clay Minerals
Serial Volume: 38
Serial Issue: 3
Title: Characterization of illitization of smectite in bentonite beds at Kinnekulle, Sweden
Affiliation: Chiba Univ., Geol. Inst., Chiba, Japan
Pages: 241-249
Published: 199006
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 38
Accession Number: 1990-038187
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N55°15'00" - N69°15'00", E11°00'00" - E24°15'00"
Secondary Affiliation: Johetsu Univ. Educ., JPN, JapanMinist. Labor at Kawasaki, JPN, JapanGeol. Surv. Swed., SWE, Sweden
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
Update Code: 1990
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