Reaction kinetics and plastic deformation in mantle rocks

• Applicant: Dr. Florian Heidelbach
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2012 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 221259457

We propose to study three garnet-forming reactions experimentally under dynamic conditions, i.e. under deviatoric stresses and while accumulating significant amounts of plastic strain. With this approach we want to investigate the interaction between metamorphic reactions and concurrent deformation. In particular, we are interested how deformation microstructures influence the progress of metamorphic reactions and in turn, how the phase change affects the rheological behaviour and deformation mechanisms. We chose garnet as the main mineral of interest since its rheological behaviour plays a crucial role for the understanding of the rheology of subducting slabs and the mantle transition zone. The three reactions we would like to investigate closely are 1) the formation of garnet peridotite from spinel peridotite, 2) the formation of eclogite from gabbro and 3) the formation of majoritic garnet from pyroxenes under high pressure up to 15 GPa. The results of this project will give an improved insight into the plastic deformation mechanisms of garnet, yield a quantitative relationship between reaction progress and plastic strain and contribute to the understanding ofthe role of metamorphic reactions during mantle flow. Within this project we will also apply a new method of measuring deviatoric stresses in multianvil deformation experiments with piezoelectric crystals, which is a critical step for performing quantitative rheological experiments at high pressure.

• DFG Programme: Research Grants