Diffusion Creep of Sodic Amphibole-Bearing Blueschist Limited by Microboudinage by Tokle et al.
Researchers at the RMPLab use rock deformation experiments and microstructural analyses to better understand the mechanical properties of amphibole-bearing rocks.
Deformation experiments were conducted on a powdered natural blueschist consisting of primarily Na-amphibole and epidote to constrain the mechanical properties of blueschist rocks. Blueschists are high-pressure rocks that form along the subduction zone interface and their mechanical properties are important for understanding a number of geodynamic processes. From the deformation experiments we see Na amphibole, the most abundant mineral in our samples, deforms by a process called microboudinage, where the Na-amphibole fractures and a compositionally new amphibole simultaneously diffuses into the fracture, allowing the sample to accommodate strain. Using existing theory on microboudinage and our mechanical data from the deformation experiments, we develope a mechanical relationship (e.g., flow law) that can be extrapolated to geologic conditions to provide constraints on blueschist deformation. We also showed that microboudinage is widely observed in naturally deformed amphiboles from paleosubduction zone environments, supporting the application of our flow law to estimate amphibole rheology in modern subduction zones.