Experimental study of the stability and phase relations of clays at high temperature in a thermal gradient
Vidal, O. (Université Joseph Fourier)
Baldeyrou, A. (Université de Strasbourg)
Beaufort, Daniel (Université Poitiers)
Fritz, B. (Université de Strasbourg)
Geoffroy, N. (Université Joseph Fourier)
Lanson, Bruno (Université Joseph Fourier)

Data:	2012
Resum:	Clays are involved in a variety of natural and managed processes, and calculation of their stability conditions is important. Such calculations are still fraught with large uncertainties owing to the lack of experimental constraints on the thermodynamic properties of clays, and bracketing of equilibrium reactions at low temperature is barely possible. Experiments aimed at studying the thermal stabilities of, and composition-temperature relations among, smectite, illite, kaolinite, pyrophyllite, mica, and chlorite at different levels of SiO , K O, MgO, and Al O species in solution were conducted under a strong thermal gradient in the simple K O-Al O -SiO -H O (KASH), MgO-Al O -SiO -H O (MASH), and KMASH systems. The crystallization series observed in the different experiments match to some degree those observed in active geothermal systems where clay minerals precipitate from oversaturated solutions. Smectite and/or ordered mixed-layer materials, smectite-donbassite, or possibly pyrophyllite-donbassite were observed to crystallize in both KASH and MASH experiments. Similar crystallization sequences and clay composition variations with temperature were observed in most cases when the relative positions of the starting solids were switched. The experimental results were used to refine the thermodynamic properties of K- and Mg-smectite. Stability diagrams calculated by energy minimization and activity-activity diagrams are consistent with the experimental mineral variations, suggesting that smectite is thermodynamically stable at temperatures as high as 300°C in the presence of diluted water and quartz and K-feldspar-free systems.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Experimental Study ; Phase Relations ; Smectite ; Thermodynamic
Publicat a:	Clays and Clay Minerals, Vol. 60, Núm. 2 (2012) , p. 200-225, ISSN 1552-8367

DOI: 10.1346/CCMN.2012.0600209

26 p, 3.8 MB  Accés restringit a la UAB

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