Lead


Lay summary
This proposal deals with the role of phyllosilicates namely clay and mica, and their interaction with quartz during rock deformation. During the last 30 months we carried out a systematic experimental investigation on the quartz-muscovite system and illite-rich shale at elevated pressure and temperature, as proposed in the initial submission. The results opened several challenging windows of study, particularly for an interacting binary (solid- fluid) system, which has wide applications for the physical and chemical behaviour of the deep crust. For the first time in the rock deformation community, we have been able to deform synthetic quartz-muscovite aggregates up to a finite shear strain of 15 and the rheology and phase relations of the deforming material were established in the light of mechanical data obtained during our experiments coupled with evolving microstructures. This allowed extrapolating the rheology, associated flow law and its high stress transition to geological strain rates. We also focused on the dynamics of shear localization in melt-generating metapelites at syn-tectonic conditions. This work leads to at least six papers; one has already been published, one is under revision and two are ready for submission and rests are under preparation. In addition, seismic anisotropy, i.e. the directional dependency of the elastic properties of a rock, is being investigated in a series of synthetic quartz-muscovite aggregates as function of confining pressure and temperature. Results being acquired at the time this project-continuation is written will predictably be matter of more publications.The primary aim of the project continuation is to study the link between deformation and metamorphism in the quartz-muscovite system at different conditions with reference to the KASH system. Clay minerals and muscovite dehydrate with temperature, resulting in local pore pressure build up and normal stress lowering. This project will also characterize the in-situ pore pressure increase during high strain torsion as a function of shear heating and mechanical weakening. As the laboratory is specialized in measuring seismic anisotropy of mono- and polycrystalline rocks at high pressure and temperature, and from plastically deformed individual crystals, this study will focus on the influence of different deformation mechanisms on the development of seismic anisotropy at the crustal scale.