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Mineralogical stability of phyllosilicates in hyperalkaline fluids; influence of layer nature, octahedral occupation and presence of tetrahedral Al

Ana I. Becerro, Marco Mantovani and Alberto Escudero
Mineralogical stability of phyllosilicates in hyperalkaline fluids; influence of layer nature, octahedral occupation and presence of tetrahedral Al
American Mineralogist (August 2009) 94 (8-9): 1187-1197

Abstract

Mineralogical changes in a set of phyllosilicates, differing in their layer nature, chemical composition, octahedral character, and Al content of the tetrahedral sheet, were analyzed after hydrothermal reaction in an alkaline solution. The composition of the alkaline solution was selected to simulate the first stage of cement degradation [NaOH-KOH-Ca(OH) (sub 2) ]. The reaction products have been analyzed by XRD, (super 29) Si and (super 27) Al MAS NMR spectroscopy, SEM/EDX, and TEM. The results indicate that the main factor influencing the stability of the clays is the occupation of the octahedral sheet such that all trioctahedral members withstand the alkaline attack, whereas most of the dioctahedral clays suffer a complete dissolution and crystallization of new phases. Second, clays with Al in the tetrahedral sheet of their layers are shown to be less stable than those with a pure Si tetrahedral sheet.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 94
Serial Issue: 8-9
Title: Mineralogical stability of phyllosilicates in hyperalkaline fluids; influence of layer nature, octahedral occupation and presence of tetrahedral Al
Affiliation: Instituto de Ciencia de Materiales de Sevilla, Department of Inorganic Chemistry, Seville, Spain
Pages: 1187-1197
Published: 200908
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 39
Accession Number: 2009-085395
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
Secondary Affiliation: Universitaet Bayreuth, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200946
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