ANR METROLOGY

Summary of the projet

Any combination of minerals (in an alloy, a solid battery or a rock) brought out of its equilibrium field tends to react to regain stability. The changes in strength, volume and latent heat associated with such transformations can have a significant impact on the material’s properties and mechanical behavior (i.e. its rheology). In geosciences, recent studies are beginning to point to the major role of transformations (metamorphic or hydrothermal) on the dynamics of the lithosphere in the short (seismicity) and long term (geodynamics). Yet, quantifying the impact of these reactions on force and energy balances on large time and space scales remains a challenge in the absence of adequate modeling tools. The majority of current thermo-mechanical models are still unable to properly account for these processes, as they are based on two strong assumptions: (1) they incorporate density changes using the Boussinesq approximation, which ignores rock compressibility, and (2) phase changes are not implemented in strength calculations.

The aim of METROLOGY is to develop a new generation of thermo-mechanical models incorporating the changes in volume, mechanical properties and latent heat associated with these transformations.

These models will be compared with a test series of laboratory experiments carried out in a Griggs press, which enables reactive systems to be studied under selected conditions. The two key Earth Science reactions on which this project will focus are the quartz-coesite reaction and the serpentinization of peridotite. With this new numerical tool, it will then be possible to elucidate the feedbacks between metamorphic reactions and thermomechanical processes, and identify the mechanisms that really have an impact on the mechanics of rocks undergoing transformation.

List of LGL-TPE participants:

Muriel Andréani