Explosive properties of superheated aqueous solutions in volcanic and hydrothermal systems

Régis Thiery (1) , Sébastien Loock (1, 2) , Lionel Mercury (3)

1 LMV - Laboratoire Magmas et Volcans
2 GEOAZUR 6526 - Géoazur
3 ISTO - Institut des Sciences de la Terre d'Orléans

Superheated aqueous solutions in volcanic and hydrothermal environments are known to reequilibrate violently through explosive boilings and gas exsolutions. While these phenomena are purely kinetic problems in essence, the explosivity conditions of these demixion processes can be investigated by following a thermodynamic approach based on spinodal curves. In a first part, we recall briefly the concepts of mechanical and diffusion spinodals. Then, we propose to differentiate superspinodal (explosive) transformations from subspinodal (non-explosive) ones. Finally, a quantitative study of spinodal curves is attempted on the binary systems H2O-CO2 and H2O-NaCl with equations of state with solid theoretical basis. It is shown that dissolved gaseous components and electrolytes have an antagonist effect: dissolved volatiles tend to shift the superspinodal region towards lower temperatures, whereas electrolytes tend to extend the metastable field towards higher temperatures. This study may give some clues to understand the explosive destabilization conditions of aqueous solutions in phreatic, phreato-magmatic and hydrothermal eruptions

Mots clés: metastability; equation of state; spinodal; explosivity; aqueous solution; carbon dioxide; sodium chloride; supersaturation; natural systems

Domaines: Volcanologie; Milieux et Changements globaux

Régis Thiery, Sébastien Loock, Lionel Mercury. Explosive properties of superheated aqueous solutions in volcanic and hydrothermal systems. Metastable Systems under Pressure, Springer, pp.293-310, 2010. ⟨insu-00460799⟩