Séminaire ISTeP - Lucie Tajcmanova

(ETHZ)

Grain-scale Pressure Variations in Metamorphic Rocks: Implications for the Interpretation of Petrographic Observations

Recent work on mineral reactions and microstructures in metamorphic rocks has focused on forward modelling of phase equilibria and on their description through chemical potential relationships which control mass transfer in rocks. The available thermodynamic databases and computer programs for phase equilibria modelling have significantly improved the quantification and understanding of geodynamic processes. Therefore, our current methodological framework seems to be satisfactory. However, the quantification approaches in petrology focus on chemical processes with oversimplified mechanics. A review of the recent literature shows that mechanical effects in rocks may result in the development of pressure variations even on a hand specimen or grain scale. Such variations are critical for interpreting microstructural and mineral composition observations in rocks. Mechanical effects may influence element transport and mineral assemblage in rocks. Considering the interplay of mechanical properties and metamorphic reactions is therefore crucial for a correct interpretation of microstructural observations in metamorphic rocks as well as for quantification of processes. In the talk, the new quantification approach for phase equilibria modeling as well as diffusion modeling will be introduced. The impact of ignoring grain-scale pressure variations on geodynamic modeling and our understanding of the processes in the Earth’s interior will be discussed.

23/01/2015 à 12h30, Salle Fourcade (Tour 55/56, 4ème étage)