The conversion of montmorillonite to interstratified halloysite-smectite by weathering in the Omi acid clay deposit, Japan
| Autor: | Y. Sawada, W. J. McHardy, J. D. Russell, M. J. Wilson, T. Watanabe |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
geography
geography.geographical_feature_category Andesite Geochemistry Mineralogy 020101 civil engineering Context (language use) Weathering 02 engineering and technology engineering.material 010502 geochemistry & geophysics 01 natural sciences Halloysite 0201 civil engineering Volcanic rock chemistry.chemical_compound Montmorillonite chemistry Geochemistry and Petrology Clastic rock engineering Clay minerals Geology 0105 earth and related environmental sciences |
| Zdroj: | Clay Minerals. 27:159-173 |
| ISSN: | 1471-8030 0009-8558 |
| DOI: | 10.1180/claymin.1992.027.2.02 |
| Popis: | A B S T R A C T: The weathering of montmorillonite in the acid clay deposit at Itoigawa, Japan has been investigated by X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). In the lower, least weathered part of the deposit, weathering has occurred by the formation of minor amounts of halloysite with concomitant precipitation of a silica phase identified as opal C-T. A relatively rapid transition occurs to the most weathered, upper part of the deposit where the mineralogy is dominated by interstratified halloysite-smectite. Computer simulations of XRD profiles indicate that the interstratified arrangement is random with a probable composition of 70% halloysite and 30% smectite, a composition supported by the 75-85% and 15-25% of the phases, respectively, calculated from the IR spectra. The early development of clay mineralogy in Japan was stimulated by the discovery of the so-called "acid clays" in Niigata Prefecture by Kobayashi in 1899 (Sudo, 1978). These clays were found to have a strong bleaching effect in addition to a number of absorptive and catalytic properties of great commercial, industrial and academic interest. Acid clays in Japan are associated with volcanic rocks and volcanigenic sediments of Miocene and Oligocene age and occur as thick lenticular intercalations or as massive deposits with lateral extensions (Takeshi, 1978). Typically, their mineralogy is dominated by montmorillonite, but certain specimens from weathered zones yield XRD patterns resembling both montmorillonite and halloysite (Sudo & Hayashi, 1956). It has been suggested by Takeshi et al. (1969) that these clays represent an intermediate stage in the transformation of montmorillonite to halloysite via a randomly interstratified structure with further confirmatory evidence being compiled by Takeshi (1978). Often, however, acid clays are described as interstratifications of montmorillonite and kaolin components, with the nature of the latter being unspecified. Interstratified kaolin-smectite (K-S) is now becoming more widely recognized in soils, and indeed where these derive from volcanic material it may be a major component. An early finding of K-S was in brown earths developed on glacial till derived from andesite in Scotland (Wilson & Cradwick, 1972) and more recently in a British context it has been identified as a major component of the clay fraction of basalt-derived soils in Northern |
| Databáze: | OpenAIRE |
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