Albite feldspar dissolution kinetics as a function of the Gibbs free energy at high pCO2

Roland Hellmann (1) , Damien Daval (2) , Delphine Tisserand (1) , François Renard (1, 3)

1 LGIT - Laboratoire de Géophysique Interne et Tectonophysique
2 LGENS - Laboratoire de géologie de l'ENS
3 PGP - Physics of Geological Processes [Oslo]

We are currently measuring the dissolution kinetics of albite feldspar at 100 °C in the presence of high levels of dissolved CO2 (pCO2 = 9 MPa) as a function of the saturation state of the feldspar (Gibbs free energy of reaction, ∃G). The experiments are conducted using a flow through reactor, thereby allowing the dissolution reactions to occur at a fixed pH and at constant, but variable saturation states. Preliminary results indicate that at far-from-equilibrium conditions, the dissolution kinetics of albite are defined by a rate plateau, with R ≈ 5.0 x 10-10 mol m-2 s-1 at -70 < ∃G < -40 kJ mol-1. At ∃G > -40 kJ mol-1, the rates decrease sharply, revealing a strong inverse relation between the dissolution rate and free energy. Based on the experiments carried out to date, the dissolution rate-free energy data correspond to a highly non-linear and sigmoidal relation, in accord with recent studies.

Domaines: Géophysique [physics.geo-ph]; Géophysique [physics.geo-ph]; Géochimie

Roland Hellmann, Damien Daval, Delphine Tisserand, François Renard. Albite feldspar dissolution kinetics as a function of the Gibbs free energy at high pCO2. T. D. Bullen and Y. Wang. Water-rock Interaction, Taylor and Francis, pp.591-595, 2007. ⟨hal-00201799⟩