Skip to Main Content
GEOREF RECORD

Experimental study of the thermal stability of pyrophyllite, paragonite, and clays in a thermal gradient

Olivier Vidal
Experimental study of the thermal stability of pyrophyllite, paragonite, and clays in a thermal gradient
European Journal of Mineralogy (February 1997) 9 (1): 123-140

Abstract

Tube-in-tube experiments involving a strong thermal gradient have been conducted in the system Na (sub 2) O-Al (sub 2) O (sub 3) -SiO (sub 2) -H (sub 2) O, using a starting mixture of quartz + paragonite + pyrophyllite. Whatever the proportions of the these ingredients, new clay minerals crystallized along the thermal profile; the new phases were beidellite + or - quartz at the cold end and, depending on the paragonite:pyrophyllite:quartz starting ratios, mica or pyrophyllite + or - diaspore crystallized at the hot end. Rectorite crystallized at an intermediate position. SEM and microdiffraction data indicate that Na-beidellite broke down to rectorite at approximately 360 degrees C, and rectorite broke down to pyrophyllite + paragonite at approximately 420 degrees C. Attempts to reverse these reactions by isothermal, isobaric experiments failed or gave contradictory results. The experimental results are consistent with thermodynamic calculations and indicate that local solid solution heterogeneous equilibria control the composition of solids that crystallized as well as their distribution along the thermal profile.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 9
Serial Issue: 1
Title: Experimental study of the thermal stability of pyrophyllite, paragonite, and clays in a thermal gradient
Author(s): Vidal, Olivier
Affiliation: Ecole Nationale Superieure, Laboratoire de Geologie, Paris, France
Pages: 123-140
Published: 199702
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 35
Accession Number: 1997-030097
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 4 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199710
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal