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Thermodynamic properties of chlorite and berthierine derived from calorimetric measurements |
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| Authors: | Philippe Blanc Hélène Gailhanou Jacques Rogez Georges Mikaelian Hitoshi Kawaji Fabienne Warmont Stéphane Gaboreau Sylvain Grangeon Jean-Marc Grenèche Philippe Vieillard Claire I Fialips Eric Giffaut Eric C Gaucher F Claret |
| Institution: | 1. BRGM, 3 Av. Claude Guillemin, BP 6009, 45060, Orléans, France 2. IM2NP-CNRS Aix Marseille Université, FST Saint-Jér?me, 13397, Marseille Cedex 20, France 3. Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan 4. CRMD-CNRS, 1b Rue de la Ferollerie, 45071, Orléans, France 5. IMMM UMR CNRS 6283, Institut des Molécules et Matériaux du Mans, LUNAM, Université du Maine, 72085, Le Mans Cedex 9, France 6. CNRS-IC2MP-UMR-7285-Hydrasa, 5 Av. Albert Turpain, 86022, Poitiers-Cedex, France 7. Andra, 92298, Chatenay-Malabry Cedex, France |
| Abstract: | In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois USA; (Al0.975FeIII0.182FeII1.422Mg0.157Li0.035Mn0.002)(Si1.332Al0.668)O5(OH)4] and chlorite CCa-2 from Flagstaff Hill, California USA; (Si2.633Al1.367)(Al1.116FeIII0.215Mg2.952FeII1.712Mn0.012Ca0.011)O10(OH)8]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738–4749, 2009) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature. |
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